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Commit | Line | Data |
---|---|---|
b10d79f7 | 1 | acpi= [HW,ACPI,X86,ARM64] |
03d926f8 | 2 | Advanced Configuration and Power Interface |
6a1f5471 | 3 | Format: { force | on | off | strict | noirq | rsdt | |
e58d154b | 4 | copy_dsdt } |
1da177e4 | 5 | force -- enable ACPI if default was off |
6a1f5471 | 6 | on -- enable ACPI but allow fallback to DT [arm64] |
1da177e4 LT |
7 | off -- disable ACPI if default was on |
8 | noirq -- do not use ACPI for IRQ routing | |
a9913044 | 9 | strict -- Be less tolerant of platforms that are not |
1da177e4 | 10 | strictly ACPI specification compliant. |
237889bf | 11 | rsdt -- prefer RSDT over (default) XSDT |
aa2110cb | 12 | copy_dsdt -- copy DSDT to memory |
6a1f5471 AB |
13 | For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force" |
14 | are available | |
1da177e4 | 15 | |
151f4e2b | 16 | See also Documentation/power/runtime_pm.rst, pci=noacpi |
1da177e4 | 17 | |
a1fdcc0d LB |
18 | acpi_apic_instance= [ACPI, IOAPIC] |
19 | Format: <int> | |
20 | 2: use 2nd APIC table, if available | |
21 | 1,0: use 1st APIC table | |
4e381a4f | 22 | default: 0 |
a1fdcc0d | 23 | |
c3d6de69 | 24 | acpi_backlight= [HW,ACPI] |
5fd769c2 RD |
25 | { vendor | video | native | none } |
26 | If set to vendor, prefer vendor-specific driver | |
c3d6de69 TR |
27 | (e.g. thinkpad_acpi, sony_acpi, etc.) instead |
28 | of the ACPI video.ko driver. | |
5fd769c2 RD |
29 | If set to video, use the ACPI video.ko driver. |
30 | If set to native, use the device's native backlight mode. | |
31 | If set to none, disable the ACPI backlight interface. | |
c3d6de69 | 32 | |
b2ca5dae CIK |
33 | acpi_force_32bit_fadt_addr |
34 | force FADT to use 32 bit addresses rather than the | |
35 | 64 bit X_* addresses. Some firmware have broken 64 | |
36 | bit addresses for force ACPI ignore these and use | |
37 | the older legacy 32 bit addresses. | |
38 | ||
ef69449b DB |
39 | acpica_no_return_repair [HW, ACPI] |
40 | Disable AML predefined validation mechanism | |
41 | This mechanism can repair the evaluation result to make | |
42 | the return objects more ACPI specification compliant. | |
43 | This option is useful for developers to identify the | |
44 | root cause of an AML interpreter issue when the issue | |
45 | has something to do with the repair mechanism. | |
46 | ||
a0d84a92 BH |
47 | acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] |
48 | acpi.debug_level= [HW,ACPI,ACPI_DEBUG] | |
1da177e4 | 49 | Format: <int> |
a0d84a92 BH |
50 | CONFIG_ACPI_DEBUG must be enabled to produce any ACPI |
51 | debug output. Bits in debug_layer correspond to a | |
52 | _COMPONENT in an ACPI source file, e.g., | |
53 | #define _COMPONENT ACPI_PCI_COMPONENT | |
54 | Bits in debug_level correspond to a level in | |
55 | ACPI_DEBUG_PRINT statements, e.g., | |
56 | ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... | |
e76f4276 | 57 | The debug_level mask defaults to "info". See |
cb1aaebe | 58 | Documentation/firmware-guide/acpi/debug.rst for more information about |
e76f4276 | 59 | debug layers and levels. |
a0d84a92 | 60 | |
e76f4276 BH |
61 | Enable processor driver info messages: |
62 | acpi.debug_layer=0x20000000 | |
63 | Enable PCI/PCI interrupt routing info messages: | |
64 | acpi.debug_layer=0x400000 | |
a0d84a92 BH |
65 | Enable AML "Debug" output, i.e., stores to the Debug |
66 | object while interpreting AML: | |
67 | acpi.debug_layer=0xffffffff acpi.debug_level=0x2 | |
a0d84a92 BH |
68 | Enable all messages related to ACPI hardware: |
69 | acpi.debug_layer=0x2 acpi.debug_level=0xffffffff | |
70 | ||
71 | Some values produce so much output that the system is | |
72 | unusable. The "log_buf_len" parameter may be useful | |
73 | if you need to capture more output. | |
f989106c | 74 | |
ef69449b DB |
75 | acpi_enforce_resources= [ACPI] |
76 | { strict | lax | no } | |
77 | Check for resource conflicts between native drivers | |
78 | and ACPI OperationRegions (SystemIO and SystemMemory | |
79 | only). IO ports and memory declared in ACPI might be | |
80 | used by the ACPI subsystem in arbitrary AML code and | |
81 | can interfere with legacy drivers. | |
82 | strict (default): access to resources claimed by ACPI | |
83 | is denied; legacy drivers trying to access reserved | |
84 | resources will fail to bind to device using them. | |
85 | lax: access to resources claimed by ACPI is allowed; | |
86 | legacy drivers trying to access reserved resources | |
87 | will bind successfully but a warning message is logged. | |
88 | no: ACPI OperationRegions are not marked as reserved, | |
89 | no further checks are performed. | |
90 | ||
4fc0a7e8 LZ |
91 | acpi_force_table_verification [HW,ACPI] |
92 | Enable table checksum verification during early stage. | |
93 | By default, this is disabled due to x86 early mapping | |
94 | size limitation. | |
95 | ||
0cb55ad2 RD |
96 | acpi_irq_balance [HW,ACPI] |
97 | ACPI will balance active IRQs | |
98 | default in APIC mode | |
99 | ||
100 | acpi_irq_nobalance [HW,ACPI] | |
101 | ACPI will not move active IRQs (default) | |
102 | default in PIC mode | |
103 | ||
104 | acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA | |
105 | Format: <irq>,<irq>... | |
106 | ||
107 | acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for | |
108 | use by PCI | |
109 | Format: <irq>,<irq>... | |
110 | ||
6dddd7a7 | 111 | acpi_mask_gpe= [HW,ACPI] |
9c4aa1ee LZ |
112 | Due to the existence of _Lxx/_Exx, some GPEs triggered |
113 | by unsupported hardware/firmware features can result in | |
6dddd7a7 TB |
114 | GPE floodings that cannot be automatically disabled by |
115 | the GPE dispatcher. | |
9c4aa1ee LZ |
116 | This facility can be used to prevent such uncontrolled |
117 | GPE floodings. | |
a7583e72 | 118 | Format: <byte> |
9c4aa1ee | 119 | |
08e1d7c0 LZ |
120 | acpi_no_auto_serialize [HW,ACPI] |
121 | Disable auto-serialization of AML methods | |
22b5afce BM |
122 | AML control methods that contain the opcodes to create |
123 | named objects will be marked as "Serialized" by the | |
124 | auto-serialization feature. | |
08e1d7c0 LZ |
125 | This feature is enabled by default. |
126 | This option allows to turn off the feature. | |
22b5afce | 127 | |
ef69449b DB |
128 | acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump |
129 | kernels. | |
130 | ||
a94e88cd LZ |
131 | acpi_no_static_ssdt [HW,ACPI] |
132 | Disable installation of static SSDTs at early boot time | |
133 | By default, SSDTs contained in the RSDT/XSDT will be | |
134 | installed automatically and they will appear under | |
135 | /sys/firmware/acpi/tables. | |
136 | This option turns off this feature. | |
137 | Note that specifying this option does not affect | |
138 | dynamic table installation which will install SSDT | |
139 | tables to /sys/firmware/acpi/tables/dynamic. | |
0cb55ad2 | 140 | |
3f9e12e0 JD |
141 | acpi_no_watchdog [HW,ACPI,WDT] |
142 | Ignore the ACPI-based watchdog interface (WDAT) and let | |
143 | a native driver control the watchdog device instead. | |
144 | ||
ef69449b DB |
145 | acpi_rsdp= [ACPI,EFI,KEXEC] |
146 | Pass the RSDP address to the kernel, mostly used | |
147 | on machines running EFI runtime service to boot the | |
148 | second kernel for kdump. | |
4dde507f | 149 | |
0cb55ad2 RD |
150 | acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS |
151 | Format: To spoof as Windows 98: ="Microsoft Windows" | |
152 | ||
18d78b64 RW |
153 | acpi_rev_override [ACPI] Override the _REV object to return 5 (instead |
154 | of 2 which is mandated by ACPI 6) as the supported ACPI | |
155 | specification revision (when using this switch, it may | |
156 | be necessary to carry out a cold reboot _twice_ in a | |
157 | row to make it take effect on the platform firmware). | |
158 | ||
0cb55ad2 | 159 | acpi_osi= [HW,ACPI] Modify list of supported OS interface strings |
5dc17986 LZ |
160 | acpi_osi="string1" # add string1 |
161 | acpi_osi="!string2" # remove string2 | |
741d8128 | 162 | acpi_osi=!* # remove all strings |
5dc17986 LZ |
163 | acpi_osi=! # disable all built-in OS vendor |
164 | strings | |
a707edeb LZ |
165 | acpi_osi=!! # enable all built-in OS vendor |
166 | strings | |
0cb55ad2 RD |
167 | acpi_osi= # disable all strings |
168 | ||
5dc17986 LZ |
169 | 'acpi_osi=!' can be used in combination with single or |
170 | multiple 'acpi_osi="string1"' to support specific OS | |
171 | vendor string(s). Note that such command can only | |
172 | affect the default state of the OS vendor strings, thus | |
173 | it cannot affect the default state of the feature group | |
174 | strings and the current state of the OS vendor strings, | |
175 | specifying it multiple times through kernel command line | |
741d8128 LZ |
176 | is meaningless. This command is useful when one do not |
177 | care about the state of the feature group strings which | |
178 | should be controlled by the OSPM. | |
5dc17986 LZ |
179 | Examples: |
180 | 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent | |
181 | to 'acpi_osi="Windows 2000" acpi_osi=!', they all | |
182 | can make '_OSI("Windows 2000")' TRUE. | |
183 | ||
184 | 'acpi_osi=' cannot be used in combination with other | |
185 | 'acpi_osi=' command lines, the _OSI method will not | |
186 | exist in the ACPI namespace. NOTE that such command can | |
187 | only affect the _OSI support state, thus specifying it | |
188 | multiple times through kernel command line is also | |
189 | meaningless. | |
190 | Examples: | |
191 | 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' | |
192 | FALSE. | |
193 | ||
741d8128 LZ |
194 | 'acpi_osi=!*' can be used in combination with single or |
195 | multiple 'acpi_osi="string1"' to support specific | |
196 | string(s). Note that such command can affect the | |
197 | current state of both the OS vendor strings and the | |
198 | feature group strings, thus specifying it multiple times | |
199 | through kernel command line is meaningful. But it may | |
200 | still not able to affect the final state of a string if | |
201 | there are quirks related to this string. This command | |
202 | is useful when one want to control the state of the | |
203 | feature group strings to debug BIOS issues related to | |
204 | the OSPM features. | |
205 | Examples: | |
206 | 1. 'acpi_osi="Module Device" acpi_osi=!*' can make | |
207 | '_OSI("Module Device")' FALSE. | |
208 | 2. 'acpi_osi=!* acpi_osi="Module Device"' can make | |
209 | '_OSI("Module Device")' TRUE. | |
210 | 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is | |
211 | equivalent to | |
212 | 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' | |
213 | and | |
214 | 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', | |
215 | they all will make '_OSI("Windows 2000")' TRUE. | |
216 | ||
6cececfc | 217 | acpi_pm_good [X86] |
0cb55ad2 RD |
218 | Override the pmtimer bug detection: force the kernel |
219 | to assume that this machine's pmtimer latches its value | |
220 | and always returns good values. | |
221 | ||
4af94f39 RD |
222 | acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode |
223 | Format: { level | edge | high | low } | |
224 | ||
4af94f39 RD |
225 | acpi_skip_timer_override [HW,ACPI] |
226 | Recognize and ignore IRQ0/pin2 Interrupt Override. | |
227 | For broken nForce2 BIOS resulting in XT-PIC timer. | |
228 | ||
229 | acpi_sleep= [HW,ACPI] Sleep options | |
230 | Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, | |
57044031 | 231 | old_ordering, nonvs, sci_force_enable, nobl } |
151f4e2b | 232 | See Documentation/power/video.rst for information on |
4af94f39 RD |
233 | s3_bios and s3_mode. |
234 | s3_beep is for debugging; it makes the PC's speaker beep | |
235 | as soon as the kernel's real-mode entry point is called. | |
236 | s4_nohwsig prevents ACPI hardware signature from being | |
237 | used during resume from hibernation. | |
238 | old_ordering causes the ACPI 1.0 ordering of the _PTS | |
239 | control method, with respect to putting devices into | |
240 | low power states, to be enforced (the ACPI 2.0 ordering | |
241 | of _PTS is used by default). | |
72ad5d77 RW |
242 | nonvs prevents the kernel from saving/restoring the |
243 | ACPI NVS memory during suspend/hibernation and resume. | |
d7f0eea9 ZR |
244 | sci_force_enable causes the kernel to set SCI_EN directly |
245 | on resume from S1/S3 (which is against the ACPI spec, | |
246 | but some broken systems don't work without it). | |
57044031 RW |
247 | nobl causes the internal blacklist of systems known to |
248 | behave incorrectly in some ways with respect to system | |
249 | suspend and resume to be ignored (use wisely). | |
4af94f39 RD |
250 | |
251 | acpi_use_timer_override [HW,ACPI] | |
252 | Use timer override. For some broken Nvidia NF5 boards | |
253 | that require a timer override, but don't have HPET | |
254 | ||
4af94f39 RD |
255 | add_efi_memmap [EFI; X86] Include EFI memory map in |
256 | kernel's map of available physical RAM. | |
257 | ||
0cb55ad2 RD |
258 | agp= [AGP] |
259 | { off | try_unsupported } | |
260 | off: disable AGP support | |
261 | try_unsupported: try to drive unsupported chipsets | |
262 | (may crash computer or cause data corruption) | |
263 | ||
bcfde334 | 264 | ALSA [HW,ALSA] |
1ca2c806 | 265 | See Documentation/sound/alsa-configuration.rst |
bcfde334 | 266 | |
d944d549 RK |
267 | alignment= [KNL,ARM] |
268 | Allow the default userspace alignment fault handler | |
269 | behaviour to be specified. Bit 0 enables warnings, | |
270 | bit 1 enables fixups, and bit 2 sends a segfault. | |
271 | ||
dfb09f9b BP |
272 | align_va_addr= [X86-64] |
273 | Align virtual addresses by clearing slice [14:12] when | |
274 | allocating a VMA at process creation time. This option | |
275 | gives you up to 3% performance improvement on AMD F15h | |
276 | machines (where it is enabled by default) for a | |
277 | CPU-intensive style benchmark, and it can vary highly in | |
278 | a microbenchmark depending on workload and compiler. | |
279 | ||
8360ee2f BP |
280 | 32: only for 32-bit processes |
281 | 64: only for 64-bit processes | |
dfb09f9b BP |
282 | on: enable for both 32- and 64-bit processes |
283 | off: disable for both 32- and 64-bit processes | |
284 | ||
55034cd6 SRRH |
285 | alloc_snapshot [FTRACE] |
286 | Allocate the ftrace snapshot buffer on boot up when the | |
287 | main buffer is allocated. This is handy if debugging | |
288 | and you need to use tracing_snapshot() on boot up, and | |
289 | do not want to use tracing_snapshot_alloc() as it needs | |
290 | to be done where GFP_KERNEL allocations are allowed. | |
291 | ||
89e0b9a3 | 292 | amd_iommu= [HW,X86-64] |
54b4cbd2 JR |
293 | Pass parameters to the AMD IOMMU driver in the system. |
294 | Possible values are: | |
afa9fdc2 FT |
295 | fullflush - enable flushing of IO/TLB entries when |
296 | they are unmapped. Otherwise they are | |
297 | flushed before they will be reused, which | |
298 | is a lot of faster | |
a5235725 JR |
299 | off - do not initialize any AMD IOMMU found in |
300 | the system | |
5abcdba4 JR |
301 | force_isolation - Force device isolation for all |
302 | devices. The IOMMU driver is not | |
303 | allowed anymore to lift isolation | |
304 | requirements as needed. This option | |
305 | does not override iommu=pt | |
afa9fdc2 | 306 | |
c099cf17 SK |
307 | amd_iommu_dump= [HW,X86-64] |
308 | Enable AMD IOMMU driver option to dump the ACPI table | |
309 | for AMD IOMMU. With this option enabled, AMD IOMMU | |
310 | driver will print ACPI tables for AMD IOMMU during | |
311 | IOMMU initialization. | |
312 | ||
3928aa3f SS |
313 | amd_iommu_intr= [HW,X86-64] |
314 | Specifies one of the following AMD IOMMU interrupt | |
315 | remapping modes: | |
316 | legacy - Use legacy interrupt remapping mode. | |
317 | vapic - Use virtual APIC mode, which allows IOMMU | |
318 | to inject interrupts directly into guest. | |
319 | This mode requires kvm-amd.avic=1. | |
320 | (Default when IOMMU HW support is present.) | |
321 | ||
1da177e4 LT |
322 | amijoy.map= [HW,JOY] Amiga joystick support |
323 | Map of devices attached to JOY0DAT and JOY1DAT | |
324 | Format: <a>,<b> | |
1752118d | 325 | See also Documentation/input/joydev/joystick.rst |
1da177e4 LT |
326 | |
327 | analog.map= [HW,JOY] Analog joystick and gamepad support | |
328 | Specifies type or capabilities of an analog joystick | |
329 | connected to one of 16 gameports | |
330 | Format: <type1>,<type2>,..<type16> | |
331 | ||
a9913044 RD |
332 | apc= [HW,SPARC] |
333 | Power management functions (SPARCstation-4/5 + deriv.) | |
1da177e4 LT |
334 | Format: noidle |
335 | Disable APC CPU standby support. SPARCstation-Fox does | |
336 | not play well with APC CPU idle - disable it if you have | |
337 | APC and your system crashes randomly. | |
338 | ||
64e05d11 | 339 | apic= [APIC,X86] Advanced Programmable Interrupt Controller |
806654a9 | 340 | Change the output verbosity while booting |
1da177e4 LT |
341 | Format: { quiet (default) | verbose | debug } |
342 | Change the amount of debugging information output | |
343 | when initialising the APIC and IO-APIC components. | |
64e05d11 DL |
344 | For X86-32, this can also be used to specify an APIC |
345 | driver name. | |
346 | Format: apic=driver_name | |
347 | Examples: apic=bigsmp | |
a9913044 | 348 | |
b7c4948e HK |
349 | apic_extnmi= [APIC,X86] External NMI delivery setting |
350 | Format: { bsp (default) | all | none } | |
351 | bsp: External NMI is delivered only to CPU 0 | |
352 | all: External NMIs are broadcast to all CPUs as a | |
353 | backup of CPU 0 | |
354 | none: External NMI is masked for all CPUs. This is | |
355 | useful so that a dump capture kernel won't be | |
356 | shot down by NMI | |
357 | ||
b0f83b28 | 358 | autoconf= [IPV6] |
19093313 | 359 | See Documentation/networking/ipv6.rst. |
b0f83b28 | 360 | |
9636bc05 CG |
361 | show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller |
362 | Limit apic dumping. The parameter defines the maximal | |
363 | number of local apics being dumped. Also it is possible | |
364 | to set it to "all" by meaning -- no limit here. | |
365 | Format: { 1 (default) | 2 | ... | all }. | |
366 | The parameter valid if only apic=debug or | |
367 | apic=verbose is specified. | |
368 | Example: apic=debug show_lapic=all | |
369 | ||
1da177e4 | 370 | apm= [APM] Advanced Power Management |
71f77055 | 371 | See header of arch/x86/kernel/apm_32.c. |
1da177e4 | 372 | |
1da177e4 LT |
373 | arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards |
374 | Format: <io>,<irq>,<nodeID> | |
375 | ||
376 | ataflop= [HW,M68k] | |
377 | ||
378 | atarimouse= [HW,MOUSE] Atari Mouse | |
379 | ||
1da177e4 LT |
380 | atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, |
381 | EzKey and similar keyboards | |
382 | ||
383 | atkbd.reset= [HW] Reset keyboard during initialization | |
384 | ||
a9913044 RD |
385 | atkbd.set= [HW] Select keyboard code set |
386 | Format: <int> (2 = AT (default), 3 = PS/2) | |
1da177e4 LT |
387 | |
388 | atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar | |
389 | keyboards | |
390 | ||
391 | atkbd.softraw= [HW] Choose between synthetic and real raw mode | |
392 | Format: <bool> (0 = real, 1 = synthetic (default)) | |
a9913044 RD |
393 | |
394 | atkbd.softrepeat= [HW] | |
395 | Use software keyboard repeat | |
1da177e4 | 396 | |
a106fb0c | 397 | audit= [KNL] Enable the audit sub-system |
11dd2666 GE |
398 | Format: { "0" | "1" | "off" | "on" } |
399 | 0 | off - kernel audit is disabled and can not be | |
400 | enabled until the next reboot | |
d7961148 EP |
401 | unset - kernel audit is initialized but disabled and |
402 | will be fully enabled by the userspace auditd. | |
11dd2666 GE |
403 | 1 | on - kernel audit is initialized and partially |
404 | enabled, storing at most audit_backlog_limit | |
405 | messages in RAM until it is fully enabled by the | |
406 | userspace auditd. | |
a106fb0c | 407 | Default: unset |
f3411cb2 | 408 | |
f910fde7 RGB |
409 | audit_backlog_limit= [KNL] Set the audit queue size limit. |
410 | Format: <int> (must be >=0) | |
411 | Default: 64 | |
412 | ||
1c532e00 AT |
413 | bau= [X86_UV] Enable the BAU on SGI UV. The default |
414 | behavior is to disable the BAU (i.e. bau=0). | |
415 | Format: { "0" | "1" } | |
416 | 0 - Disable the BAU. | |
417 | 1 - Enable the BAU. | |
418 | unset - Disable the BAU. | |
419 | ||
1da177e4 LT |
420 | baycom_epp= [HW,AX25] |
421 | Format: <io>,<mode> | |
a9913044 | 422 | |
1da177e4 LT |
423 | baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem |
424 | Format: <io>,<mode> | |
425 | See header of drivers/net/hamradio/baycom_par.c. | |
426 | ||
a9913044 RD |
427 | baycom_ser_fdx= [HW,AX25] |
428 | BayCom Serial Port AX.25 Modem (Full Duplex Mode) | |
1da177e4 LT |
429 | Format: <io>,<irq>,<mode>[,<baud>] |
430 | See header of drivers/net/hamradio/baycom_ser_fdx.c. | |
431 | ||
a9913044 RD |
432 | baycom_ser_hdx= [HW,AX25] |
433 | BayCom Serial Port AX.25 Modem (Half Duplex Mode) | |
1da177e4 LT |
434 | Format: <io>,<irq>,<mode> |
435 | See header of drivers/net/hamradio/baycom_ser_hdx.c. | |
436 | ||
080506ad PG |
437 | blkdevparts= Manual partition parsing of block device(s) for |
438 | embedded devices based on command line input. | |
898bd37a | 439 | See Documentation/block/cmdline-partition.rst |
080506ad | 440 | |
bfe8df3d RD |
441 | boot_delay= Milliseconds to delay each printk during boot. |
442 | Values larger than 10 seconds (10000) are changed to | |
443 | no delay (0). | |
444 | Format: integer | |
445 | ||
7495e092 SRV |
446 | bootconfig [KNL] |
447 | Extended command line options can be added to an initrd | |
448 | and this will cause the kernel to look for it. | |
449 | ||
450 | See Documentation/admin-guide/bootconfig.rst | |
451 | ||
a3e2acc5 HY |
452 | bert_disable [ACPI] |
453 | Disable BERT OS support on buggy BIOSes. | |
454 | ||
1ffb8d03 AH |
455 | bgrt_disable [ACPI][X86] |
456 | Disable BGRT to avoid flickering OEM logo. | |
457 | ||
1da177e4 | 458 | bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) |
a9913044 RD |
459 | bttv.radio= Most important insmod options are available as |
460 | kernel args too. | |
32e2eae2 | 461 | bttv.pll= See Documentation/admin-guide/media/bttv.rst |
395cf969 | 462 | bttv.tuner= |
1da177e4 | 463 | |
4e89a2d8 WS |
464 | bulk_remove=off [PPC] This parameter disables the use of the pSeries |
465 | firmware feature for flushing multiple hpte entries | |
466 | at a time. | |
467 | ||
1da177e4 LT |
468 | c101= [NET] Moxa C101 synchronous serial card |
469 | ||
cd4f0ef7 | 470 | cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. |
1da177e4 LT |
471 | Sometimes CPU hardware bugs make them report the cache |
472 | size incorrectly. The kernel will attempt work arounds | |
473 | to fix known problems, but for some CPUs it is not | |
474 | possible to determine what the correct size should be. | |
475 | This option provides an override for these situations. | |
476 | ||
3fc46fc9 MK |
477 | carrier_timeout= |
478 | [NET] Specifies amount of time (in seconds) that | |
479 | the kernel should wait for a network carrier. By default | |
480 | it waits 120 seconds. | |
481 | ||
ffb70f61 DK |
482 | ca_keys= [KEYS] This parameter identifies a specific key(s) on |
483 | the system trusted keyring to be used for certificate | |
484 | trust validation. | |
32c4741c | 485 | format: { id:<keyid> | builtin } |
ffb70f61 | 486 | |
fd1bb4c9 FF |
487 | cca= [MIPS] Override the kernel pages' cache coherency |
488 | algorithm. Accepted values range from 0 to 7 | |
489 | inclusive. See arch/mips/include/asm/pgtable-bits.h | |
490 | for platform specific values (SB1, Loongson3 and | |
491 | others). | |
492 | ||
6dddd7a7 | 493 | ccw_timeout_log [S390] |
8b4a503d | 494 | See Documentation/s390/common_io.rst for details. |
1da177e4 | 495 | |
6dddd7a7 | 496 | cgroup_disable= [KNL] Disable a particular controller |
8bab8dde | 497 | Format: {name of the controller(s) to disable} |
ca0bdbb5 QH |
498 | The effects of cgroup_disable=foo are: |
499 | - foo isn't auto-mounted if you mount all cgroups in | |
500 | a single hierarchy | |
501 | - foo isn't visible as an individually mountable | |
502 | subsystem | |
503 | {Currently only "memory" controller deal with this and | |
504 | cut the overhead, others just disable the usage. So | |
505 | only cgroup_disable=memory is actually worthy} | |
8bab8dde | 506 | |
3fc9c12d TH |
507 | cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1 |
508 | Format: { { controller | "all" | "named" } | |
509 | [,{ controller | "all" | "named" }...] } | |
1619b6d4 JW |
510 | Like cgroup_disable, but only applies to cgroup v1; |
511 | the blacklisted controllers remain available in cgroup2. | |
3fc9c12d TH |
512 | "all" blacklists all controllers and "named" disables |
513 | named mounts. Specifying both "all" and "named" disables | |
514 | all v1 hierarchies. | |
1619b6d4 | 515 | |
f7e1cb6e JW |
516 | cgroup.memory= [KNL] Pass options to the cgroup memory controller. |
517 | Format: <string> | |
518 | nosocket -- Disable socket memory accounting. | |
04823c83 | 519 | nokmem -- Disable kernel memory accounting. |
f7e1cb6e | 520 | |
1da177e4 LT |
521 | checkreqprot [SELINUX] Set initial checkreqprot flag value. |
522 | Format: { "0" | "1" } | |
523 | See security/selinux/Kconfig help text. | |
a9913044 RD |
524 | 0 -- check protection applied by kernel (includes |
525 | any implied execute protection). | |
1da177e4 LT |
526 | 1 -- check protection requested by application. |
527 | Default value is set via a kernel config option. | |
a9913044 | 528 | Value can be changed at runtime via |
d41415eb | 529 | /sys/fs/selinux/checkreqprot. |
e9c38f9f | 530 | Setting checkreqprot to 1 is deprecated. |
a9913044 | 531 | |
661ca0da | 532 | cio_ignore= [S390] |
8b4a503d | 533 | See Documentation/s390/common_io.rst for details. |
1e435256 OJ |
534 | clk_ignore_unused |
535 | [CLK] | |
e156ee56 MT |
536 | Prevents the clock framework from automatically gating |
537 | clocks that have not been explicitly enabled by a Linux | |
538 | device driver but are enabled in hardware at reset or | |
539 | by the bootloader/firmware. Note that this does not | |
540 | force such clocks to be always-on nor does it reserve | |
541 | those clocks in any way. This parameter is useful for | |
542 | debug and development, but should not be needed on a | |
543 | platform with proper driver support. For more | |
18bcaa4e | 544 | information, see Documentation/driver-api/clk.rst. |
661ca0da | 545 | |
cd4f0ef7 | 546 | clock= [BUGS=X86-32, HW] gettimeofday clocksource override. |
734efb46 | 547 | [Deprecated] |
3f6dee9b | 548 | Forces specified clocksource (if available) to be used |
734efb46 | 549 | when calculating gettimeofday(). If specified |
3f6dee9b | 550 | clocksource is not available, it defaults to PIT. |
1da177e4 LT |
551 | Format: { pit | tsc | cyclone | pmtmr } |
552 | ||
592913ec | 553 | clocksource= Override the default clocksource |
3d6ac984 RD |
554 | Format: <string> |
555 | Override the default clocksource and use the clocksource | |
556 | with the name specified. | |
557 | Some clocksource names to choose from, depending on | |
558 | the platform: | |
559 | [all] jiffies (this is the base, fallback clocksource) | |
560 | [ACPI] acpi_pm | |
561 | [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, | |
562 | pxa_timer,timer3,32k_counter,timer0_1 | |
9863c90f | 563 | [X86-32] pit,hpet,tsc; |
3d6ac984 RD |
564 | scx200_hrt on Geode; cyclone on IBM x440 |
565 | [MIPS] MIPS | |
566 | [PARISC] cr16 | |
567 | [S390] tod | |
568 | [SH] SuperH | |
569 | [SPARC64] tick | |
570 | [X86-64] hpet,tsc | |
571 | ||
46fd5c6b WD |
572 | clocksource.arm_arch_timer.evtstrm= |
573 | [ARM,ARM64] | |
574 | Format: <bool> | |
575 | Enable/disable the eventstream feature of the ARM | |
576 | architected timer so that code using WFE-based polling | |
577 | loops can be debugged more effectively on production | |
578 | systems. | |
579 | ||
ac72e788 AK |
580 | clearcpuid=BITNUM [X86] |
581 | Disable CPUID feature X for the kernel. See | |
cd4d09ec | 582 | arch/x86/include/asm/cpufeatures.h for the valid bit |
07983f0e | 583 | numbers. Note the Linux specific bits are not necessarily |
ac72e788 AK |
584 | stable over kernel options, but the vendor specific |
585 | ones should be. | |
586 | Also note that user programs calling CPUID directly | |
587 | or using the feature without checking anything | |
588 | will still see it. This just prevents it from | |
589 | being used by the kernel or shown in /proc/cpuinfo. | |
590 | Also note the kernel might malfunction if you disable | |
591 | some critical bits. | |
592 | ||
5ea3b1b2 AM |
593 | cma=nn[MG]@[start[MG][-end[MG]]] |
594 | [ARM,X86,KNL] | |
595 | Sets the size of kernel global memory area for | |
596 | contiguous memory allocations and optionally the | |
597 | placement constraint by the physical address range of | |
f0d6d1f6 JD |
598 | memory allocations. A value of 0 disables CMA |
599 | altogether. For more information, see | |
c64be2bb MS |
600 | include/linux/dma-contiguous.h |
601 | ||
14f966e7 RJ |
602 | cmo_free_hint= [PPC] Format: { yes | no } |
603 | Specify whether pages are marked as being inactive | |
604 | when they are freed. This is used in CMO environments | |
605 | to determine OS memory pressure for page stealing by | |
606 | a hypervisor. | |
607 | Default: yes | |
608 | ||
c7909509 MS |
609 | coherent_pool=nn[KMG] [ARM,KNL] |
610 | Sets the size of memory pool for coherent, atomic dma | |
e9da6e99 | 611 | allocations, by default set to 256K. |
c7909509 | 612 | |
1da177e4 | 613 | com20020= [HW,NET] ARCnet - COM20020 chipset |
a9913044 RD |
614 | Format: |
615 | <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] | |
1da177e4 LT |
616 | |
617 | com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) | |
618 | Format: <io>[,<irq>] | |
619 | ||
a9913044 RD |
620 | com90xx= [HW,NET] |
621 | ARCnet - COM90xx chipset (memory-mapped buffers) | |
1da177e4 LT |
622 | Format: <io>[,<irq>[,<memstart>]] |
623 | ||
624 | condev= [HW,S390] console device | |
625 | conmode= | |
a9913044 | 626 | |
1da177e4 LT |
627 | console= [KNL] Output console device and options. |
628 | ||
629 | tty<n> Use the virtual console device <n>. | |
630 | ||
631 | ttyS<n>[,options] | |
f1a1c2dc | 632 | ttyUSB0[,options] |
1da177e4 | 633 | Use the specified serial port. The options are of |
f1a1c2dc RD |
634 | the form "bbbbpnf", where "bbbb" is the baud rate, |
635 | "p" is parity ("n", "o", or "e"), "n" is number of | |
636 | bits, and "f" is flow control ("r" for RTS or | |
637 | omit it). Default is "9600n8". | |
638 | ||
e52347bd | 639 | See Documentation/admin-guide/serial-console.rst for more |
f1a1c2dc | 640 | information. See |
d9d6ef25 | 641 | Documentation/networking/netconsole.rst for an |
f1a1c2dc | 642 | alternative. |
1da177e4 | 643 | |
18a8bd94 YL |
644 | uart[8250],io,<addr>[,options] |
645 | uart[8250],mmio,<addr>[,options] | |
bd94c407 | 646 | uart[8250],mmio16,<addr>[,options] |
ca782f16 PH |
647 | uart[8250],mmio32,<addr>[,options] |
648 | uart[8250],0x<addr>[,options] | |
1da177e4 LT |
649 | Start an early, polled-mode console on the 8250/16550 |
650 | UART at the specified I/O port or MMIO address, | |
ca782f16 PH |
651 | switching to the matching ttyS device later. |
652 | MMIO inter-register address stride is either 8-bit | |
bd94c407 MY |
653 | (mmio), 16-bit (mmio16), or 32-bit (mmio32). |
654 | If none of [io|mmio|mmio16|mmio32], <addr> is assumed | |
655 | to be equivalent to 'mmio'. 'options' are specified in | |
656 | the same format described for ttyS above; if unspecified, | |
ca782f16 PH |
657 | the h/w is not re-initialized. |
658 | ||
a2fd6419 KRW |
659 | hvc<n> Use the hypervisor console device <n>. This is for |
660 | both Xen and PowerPC hypervisors. | |
1da177e4 | 661 | |
6dddd7a7 TB |
662 | If the device connected to the port is not a TTY but a braille |
663 | device, prepend "brl," before the device type, for instance | |
f7511d5f ST |
664 | console=brl,ttyS0 |
665 | For now, only VisioBraille is supported. | |
666 | ||
cca10d58 SS |
667 | console_msg_format= |
668 | [KNL] Change console messages format | |
669 | default | |
670 | By default we print messages on consoles in | |
671 | "[time stamp] text\n" format (time stamp may not be | |
672 | printed, depending on CONFIG_PRINTK_TIME or | |
673 | `printk_time' param). | |
674 | syslog | |
675 | Switch to syslog format: "<%u>[time stamp] text\n" | |
676 | IOW, each message will have a facility and loglevel | |
677 | prefix. The format is similar to one used by syslog() | |
678 | syscall, or to executing "dmesg -S --raw" or to reading | |
679 | from /proc/kmsg. | |
680 | ||
f324edc8 | 681 | consoleblank= [KNL] The console blank (screen saver) timeout in |
ac0a314c | 682 | seconds. A value of 0 disables the blank timer. |
6dddd7a7 | 683 | Defaults to 0. |
f324edc8 | 684 | |
4cb0e11b HK |
685 | coredump_filter= |
686 | [KNL] Change the default value for | |
687 | /proc/<pid>/coredump_filter. | |
cd4ca341 | 688 | See also Documentation/filesystems/proc.rst. |
4cb0e11b | 689 | |
62a31ce1 LY |
690 | coresight_cpu_debug.enable |
691 | [ARM,ARM64] | |
692 | Format: <bool> | |
693 | Enable/disable the CPU sampling based debugging. | |
694 | 0: default value, disable debugging | |
695 | 1: enable debugging at boot time | |
696 | ||
62027aea LB |
697 | cpuidle.off=1 [CPU_IDLE] |
698 | disable the cpuidle sub-system | |
699 | ||
61cb5758 RW |
700 | cpuidle.governor= |
701 | [CPU_IDLE] Name of the cpuidle governor to use. | |
702 | ||
d82f2692 LB |
703 | cpufreq.off=1 [CPU_FREQ] |
704 | disable the cpufreq sub-system | |
705 | ||
d68921f9 LB |
706 | cpu_init_udelay=N |
707 | [X86] Delay for N microsec between assert and de-assert | |
708 | of APIC INIT to start processors. This delay occurs | |
709 | on every CPU online, such as boot, and resume from suspend. | |
710 | Default: 10000 | |
711 | ||
1da177e4 | 712 | cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver |
a9913044 RD |
713 | Format: |
714 | <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] | |
1da177e4 | 715 | |
6f21e646 AD |
716 | crashkernel=size[KMG][@offset[KMG]] |
717 | [KNL] Using kexec, Linux can switch to a 'crash kernel' | |
718 | upon panic. This parameter reserves the physical | |
719 | memory region [offset, offset + size] for that kernel | |
720 | image. If '@offset' is omitted, then a suitable offset | |
b9ac3849 DY |
721 | is selected automatically. |
722 | [KNL, x86_64] select a region under 4G first, and | |
723 | fall back to reserve region above 4G when '@offset' | |
724 | hasn't been specified. | |
330d4810 | 725 | See Documentation/admin-guide/kdump/kdump.rst for further details. |
dc009d92 | 726 | |
fb391599 BW |
727 | crashkernel=range1:size1[,range2:size2,...][@offset] |
728 | [KNL] Same as above, but depends on the memory | |
729 | in the running system. The syntax of range is | |
730 | start-[end] where start and end are both | |
731 | a memory unit (amount[KMG]). See also | |
330d4810 | 732 | Documentation/admin-guide/kdump/kdump.rst for an example. |
fb391599 | 733 | |
adbc742b | 734 | crashkernel=size[KMG],high |
55a20ee7 YL |
735 | [KNL, x86_64] range could be above 4G. Allow kernel |
736 | to allocate physical memory region from top, so could | |
737 | be above 4G if system have more than 4G ram installed. | |
738 | Otherwise memory region will be allocated below 4G, if | |
739 | available. | |
740 | It will be ignored if crashkernel=X is specified. | |
adbc742b YL |
741 | crashkernel=size[KMG],low |
742 | [KNL, x86_64] range under 4G. When crashkernel=X,high | |
743 | is passed, kernel could allocate physical memory region | |
c729de8f YL |
744 | above 4G, that cause second kernel crash on system |
745 | that require some amount of low memory, e.g. swiotlb | |
c6045031 BH |
746 | requires at least 64M+32K low memory, also enough extra |
747 | low memory is needed to make sure DMA buffers for 32-bit | |
748 | devices won't run out. Kernel would try to allocate at | |
749 | at least 256M below 4G automatically. | |
c729de8f YL |
750 | This one let user to specify own low range under 4G |
751 | for second kernel instead. | |
752 | 0: to disable low allocation. | |
adbc742b | 753 | It will be ignored when crashkernel=X,high is not used |
55a20ee7 | 754 | or memory reserved is below 4G. |
c729de8f | 755 | |
9e5c9fe4 | 756 | cryptomgr.notests |
6dddd7a7 | 757 | [KNL] Disable crypto self-tests |
9e5c9fe4 | 758 | |
1da177e4 LT |
759 | cs89x0_dma= [HW,NET] |
760 | Format: <dma> | |
761 | ||
762 | cs89x0_media= [HW,NET] | |
763 | Format: { rj45 | aui | bnc } | |
a9913044 | 764 | |
a9913044 | 765 | dasd= [HW,NET] |
1da177e4 LT |
766 | See header of drivers/s390/block/dasd_devmap.c. |
767 | ||
768 | db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port | |
769 | (one device per port) | |
770 | Format: <port#>,<type> | |
1752118d | 771 | See also Documentation/input/devices/joystick-parport.rst |
1da177e4 | 772 | |
6dddd7a7 | 773 | ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot |
787e3075 SM |
774 | time. See |
775 | Documentation/admin-guide/dynamic-debug-howto.rst for | |
29e36c9f | 776 | details. Deprecated, see dyndbg. |
a648ec05 | 777 | |
1da177e4 LT |
778 | debug [KNL] Enable kernel debugging (events log level). |
779 | ||
3672476e TH |
780 | debug_boot_weak_hash |
781 | [KNL] Enable printing [hashed] pointers early in the | |
782 | boot sequence. If enabled, we use a weak hash instead | |
783 | of siphash to hash pointers. Use this option if you are | |
784 | seeing instances of '(___ptrval___)') and need to see a | |
785 | value (hashed pointer) instead. Cryptographically | |
786 | insecure, please do not use on production kernels. | |
787 | ||
cae2ed9a IM |
788 | debug_locks_verbose= |
789 | [KNL] verbose self-tests | |
790 | Format=<0|1> | |
791 | Print debugging info while doing the locking API | |
792 | self-tests. | |
793 | We default to 0 (no extra messages), setting it to | |
794 | 1 will print _a lot_ more information - normally | |
795 | only useful to kernel developers. | |
796 | ||
3ac7fe5a TG |
797 | debug_objects [KNL] Enable object debugging |
798 | ||
3e8ebb5c KM |
799 | no_debug_objects |
800 | [KNL] Disable object debugging | |
801 | ||
c0a32fc5 SG |
802 | debug_guardpage_minorder= |
803 | [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this | |
804 | parameter allows control of the order of pages that will | |
805 | be intentionally kept free (and hence protected) by the | |
806 | buddy allocator. Bigger value increase the probability | |
807 | of catching random memory corruption, but reduce the | |
808 | amount of memory for normal system use. The maximum | |
809 | possible value is MAX_ORDER/2. Setting this parameter | |
810 | to 1 or 2 should be enough to identify most random | |
811 | memory corruption problems caused by bugs in kernel or | |
812 | driver code when a CPU writes to (or reads from) a | |
813 | random memory location. Note that there exists a class | |
814 | of memory corruptions problems caused by buggy H/W or | |
815 | F/W or by drivers badly programing DMA (basically when | |
816 | memory is written at bus level and the CPU MMU is | |
817 | bypassed) which are not detectable by | |
818 | CONFIG_DEBUG_PAGEALLOC, hence this option will not help | |
819 | tracking down these problems. | |
820 | ||
031bc574 | 821 | debug_pagealloc= |
3972f6bb VB |
822 | [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter |
823 | enables the feature at boot time. By default, it is | |
824 | disabled and the system will work mostly the same as a | |
825 | kernel built without CONFIG_DEBUG_PAGEALLOC. | |
8974558f VB |
826 | Note: to get most of debug_pagealloc error reports, it's |
827 | useful to also enable the page_owner functionality. | |
031bc574 JK |
828 | on: enable the feature |
829 | ||
d3af01f1 TG |
830 | debugpat [X86] Enable PAT debugging |
831 | ||
2d27a966 | 832 | decnet.addr= [HW,NET] |
1da177e4 | 833 | Format: <area>[,<node>] |
9a69fb9c | 834 | See also Documentation/networking/decnet.rst. |
1da177e4 | 835 | |
0cb55ad2 | 836 | default_hugepagesz= |
282f4214 MK |
837 | [HW] The size of the default HugeTLB page. This is |
838 | the size represented by the legacy /proc/ hugepages | |
839 | APIs. In addition, this is the default hugetlb size | |
840 | used for shmget(), mmap() and mounting hugetlbfs | |
841 | filesystems. If not specified, defaults to the | |
842 | architecture's default huge page size. Huge page | |
843 | sizes are architecture dependent. See also | |
844 | Documentation/admin-guide/mm/hugetlbpage.rst. | |
845 | Format: size[KMG] | |
55ff9780 | 846 | |
25b4e70d RH |
847 | deferred_probe_timeout= |
848 | [KNL] Debugging option to set a timeout in seconds for | |
849 | deferred probe to give up waiting on dependencies to | |
850 | probe. Only specific dependencies (subsystems or | |
851 | drivers) that have opted in will be ignored. A timeout of 0 | |
852 | will timeout at the end of initcalls. This option will also | |
853 | dump out devices still on the deferred probe list after | |
854 | retrying. | |
855 | ||
c65e6815 MZ |
856 | dfltcc= [HW,S390] |
857 | Format: { on | off | def_only | inf_only | always } | |
858 | on: s390 zlib hardware support for compression on | |
859 | level 1 and decompression (default) | |
860 | off: No s390 zlib hardware support | |
861 | def_only: s390 zlib hardware support for deflate | |
862 | only (compression on level 1) | |
863 | inf_only: s390 zlib hardware support for inflate | |
864 | only (decompression) | |
865 | always: Same as 'on' but ignores the selected compression | |
866 | level always using hardware support (used for debugging) | |
867 | ||
1da177e4 LT |
868 | dhash_entries= [KNL] |
869 | Set number of hash buckets for dentry cache. | |
a9913044 | 870 | |
faf78829 OH |
871 | disable_1tb_segments [PPC] |
872 | Disables the use of 1TB hash page table segments. This | |
873 | causes the kernel to fall back to 256MB segments which | |
874 | can be useful when debugging issues that require an SLB | |
875 | miss to occur. | |
876 | ||
82a1b8ed NP |
877 | stress_slb [PPC] |
878 | Limits the number of kernel SLB entries, and flushes | |
879 | them frequently to increase the rate of SLB faults | |
880 | on kernel addresses. | |
881 | ||
b0f83b28 | 882 | disable= [IPV6] |
19093313 | 883 | See Documentation/networking/ipv6.rst. |
b0f83b28 | 884 | |
b5cb15d9 CR |
885 | hardened_usercopy= |
886 | [KNL] Under CONFIG_HARDENED_USERCOPY, whether | |
887 | hardening is enabled for this boot. Hardened | |
888 | usercopy checking is used to protect the kernel | |
889 | from reading or writing beyond known memory | |
890 | allocation boundaries as a proactive defense | |
891 | against bounds-checking flaws in the kernel's | |
892 | copy_to_user()/copy_from_user() interface. | |
893 | on Perform hardened usercopy checks (default). | |
894 | off Disable hardened usercopy checks. | |
895 | ||
b275bfb2 AK |
896 | disable_radix [PPC] |
897 | Disable RADIX MMU mode on POWER9 | |
898 | ||
2275d7b5 NP |
899 | disable_tlbie [PPC] |
900 | Disable TLBIE instruction. Currently does not work | |
901 | with KVM, with HASH MMU, or with coherent accelerators. | |
902 | ||
151e0c7d HD |
903 | disable_cpu_apicid= [X86,APIC,SMP] |
904 | Format: <int> | |
905 | The number of initial APIC ID for the | |
906 | corresponding CPU to be disabled at boot, | |
907 | mostly used for the kdump 2nd kernel to | |
908 | disable BSP to wake up multiple CPUs without | |
909 | causing system reset or hang due to sending | |
910 | INIT from AP to BSP. | |
911 | ||
2a5bf23d PZ |
912 | perf_v4_pmi= [X86,INTEL] |
913 | Format: <bool> | |
af3bdb99 AK |
914 | Disable Intel PMU counter freezing feature. |
915 | The feature only exists starting from | |
916 | Arch Perfmon v4 (Skylake and newer). | |
917 | ||
6dddd7a7 | 918 | disable_ddw [PPC/PSERIES] |
4e8b0cf4 NA |
919 | Disable Dynamic DMA Window support. Use this if |
920 | to workaround buggy firmware. | |
921 | ||
b0f83b28 | 922 | disable_ipv6= [IPV6] |
19093313 | 923 | See Documentation/networking/ipv6.rst. |
b0f83b28 | 924 | |
95ffa243 | 925 | disable_mtrr_cleanup [X86] |
95ffa243 YL |
926 | The kernel tries to adjust MTRR layout from continuous |
927 | to discrete, to make X server driver able to add WB | |
0cb55ad2 | 928 | entry later. This parameter disables that. |
95ffa243 | 929 | |
093af8d7 | 930 | disable_mtrr_trim [X86, Intel and AMD only] |
99fc8d42 JB |
931 | By default the kernel will trim any uncacheable |
932 | memory out of your available memory pool based on | |
933 | MTRR settings. This parameter disables that behavior, | |
934 | possibly causing your machine to run very slowly. | |
935 | ||
6cececfc | 936 | disable_timer_pin_1 [X86] |
0cb55ad2 RD |
937 | Disable PIN 1 of APIC timer |
938 | Can be useful to work around chipset bugs. | |
939 | ||
ce14c583 PB |
940 | dis_ucode_ldr [X86] Disable the microcode loader. |
941 | ||
0cb55ad2 RD |
942 | dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, |
943 | this option disables the debugging code at boot. | |
944 | ||
945 | dma_debug_entries=<number> | |
946 | This option allows to tune the number of preallocated | |
947 | entries for DMA-API debugging code. One entry is | |
948 | required per DMA-API allocation. Use this if the | |
949 | DMA-API debugging code disables itself because the | |
950 | architectural default is too low. | |
951 | ||
1745de5e JR |
952 | dma_debug_driver=<driver_name> |
953 | With this option the DMA-API debugging driver | |
954 | filter feature can be enabled at boot time. Just | |
955 | pass the driver to filter for as the parameter. | |
956 | The filter can be disabled or changed to another | |
957 | driver later using sysfs. | |
958 | ||
1ea61b68 FT |
959 | driver_async_probe= [KNL] |
960 | List of driver names to be probed asynchronously. | |
961 | Format: <driver_name1>,<driver_name2>... | |
962 | ||
53fd40a9 | 963 | drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] |
96206e29 BP |
964 | Broken monitors, graphic adapters, KVMs and EDIDless |
965 | panels may send no or incorrect EDID data sets. | |
966 | This parameter allows to specify an EDID data sets | |
967 | in the /lib/firmware directory that are used instead. | |
da0df92b CE |
968 | Generic built-in EDID data sets are used, if one of |
969 | edid/1024x768.bin, edid/1280x1024.bin, | |
970 | edid/1680x1050.bin, or edid/1920x1080.bin is given | |
971 | and no file with the same name exists. Details and | |
972 | instructions how to build your own EDID data are | |
cd4ca341 | 973 | available in Documentation/admin-guide/edid.rst. An EDID |
da0df92b CE |
974 | data set will only be used for a particular connector, |
975 | if its name and a colon are prepended to the EDID | |
96206e29 BP |
976 | name. Each connector may use a unique EDID data |
977 | set by separating the files with a comma. An EDID | |
978 | data set with no connector name will be used for | |
979 | any connectors not explicitly specified. | |
da0df92b | 980 | |
1da177e4 LT |
981 | dscc4.setup= [NET] |
982 | ||
a2b05b7a NP |
983 | dt_cpu_ftrs= [PPC] |
984 | Format: {"off" | "known"} | |
985 | Control how the dt_cpu_ftrs device-tree binding is | |
986 | used for CPU feature discovery and setup (if it | |
987 | exists). | |
988 | off: Do not use it, fall back to legacy cpu table. | |
989 | known: Do not pass through unknown features to guests | |
990 | or userspace, only those that the kernel is aware of. | |
991 | ||
58c5475a LW |
992 | dump_apple_properties [X86] |
993 | Dump name and content of EFI device properties on | |
994 | x86 Macs. Useful for driver authors to determine | |
995 | what data is available or for reverse-engineering. | |
996 | ||
29e36c9f JC |
997 | dyndbg[="val"] [KNL,DYNAMIC_DEBUG] |
998 | module.dyndbg[="val"] | |
999 | Enable debug messages at boot time. See | |
787e3075 SM |
1000 | Documentation/admin-guide/dynamic-debug-howto.rst |
1001 | for details. | |
29e36c9f | 1002 | |
06976945 DH |
1003 | nopku [X86] Disable Memory Protection Keys CPU feature found |
1004 | in some Intel CPUs. | |
1005 | ||
f2411da7 LR |
1006 | module.async_probe [KNL] |
1007 | Enable asynchronous probe on this module. | |
1008 | ||
56aeeba8 MS |
1009 | early_ioremap_debug [KNL] |
1010 | Enable debug messages in early_ioremap support. This | |
1011 | is useful for tracking down temporary early mappings | |
1012 | which are not unmapped. | |
1013 | ||
0cb55ad2 | 1014 | earlycon= [KNL] Output early console device and options. |
0d3c673e | 1015 | |
e18409c0 CH |
1016 | When used with no options, the early console is |
1017 | determined by stdout-path property in device tree's | |
1018 | chosen node or the ACPI SPCR table if supported by | |
1019 | the platform. | |
5664f764 | 1020 | |
c41251b1 ST |
1021 | cdns,<addr>[,options] |
1022 | Start an early, polled-mode console on a Cadence | |
1023 | (xuartps) serial port at the specified address. Only | |
1024 | supported option is baud rate. If baud rate is not | |
1025 | specified, the serial port must already be setup and | |
1026 | configured. | |
6fa62fc4 | 1027 | |
0cb55ad2 RD |
1028 | uart[8250],io,<addr>[,options] |
1029 | uart[8250],mmio,<addr>[,options] | |
1917ac76 | 1030 | uart[8250],mmio32,<addr>[,options] |
6e63be3f | 1031 | uart[8250],mmio32be,<addr>[,options] |
ca782f16 | 1032 | uart[8250],0x<addr>[,options] |
0cb55ad2 RD |
1033 | Start an early, polled-mode console on the 8250/16550 |
1034 | UART at the specified I/O port or MMIO address. | |
16290246 | 1035 | MMIO inter-register address stride is either 8-bit |
6e63be3f NC |
1036 | (mmio) or 32-bit (mmio32 or mmio32be). |
1037 | If none of [io|mmio|mmio32|mmio32be], <addr> is assumed | |
1038 | to be equivalent to 'mmio'. 'options' are specified | |
1039 | in the same format described for "console=ttyS<n>"; if | |
ca782f16 | 1040 | unspecified, the h/w is not initialized. |
0cb55ad2 | 1041 | |
0d3c673e | 1042 | pl011,<addr> |
3b78fae7 | 1043 | pl011,mmio32,<addr> |
0d3c673e RH |
1044 | Start an early, polled-mode console on a pl011 serial |
1045 | port at the specified address. The pl011 serial port | |
1046 | must already be setup and configured. Options are not | |
3b78fae7 TT |
1047 | yet supported. If 'mmio32' is specified, then only |
1048 | the driver will use only 32-bit accessors to read/write | |
1049 | the device registers. | |
0d3c673e | 1050 | |
736d5538 AF |
1051 | meson,<addr> |
1052 | Start an early, polled-mode console on a meson serial | |
1053 | port at the specified address. The serial port must | |
1054 | already be setup and configured. Options are not yet | |
1055 | supported. | |
1056 | ||
0efe7296 SB |
1057 | msm_serial,<addr> |
1058 | Start an early, polled-mode console on an msm serial | |
1059 | port at the specified address. The serial port | |
1060 | must already be setup and configured. Options are not | |
1061 | yet supported. | |
1062 | ||
1063 | msm_serial_dm,<addr> | |
1064 | Start an early, polled-mode console on an msm serial | |
1065 | dm port at the specified address. The serial port | |
1066 | must already be setup and configured. Options are not | |
1067 | yet supported. | |
1068 | ||
e36361d7 AF |
1069 | owl,<addr> |
1070 | Start an early, polled-mode console on a serial port | |
1071 | of an Actions Semi SoC, such as S500 or S900, at the | |
1072 | specified address. The serial port must already be | |
1073 | setup and configured. Options are not yet supported. | |
1074 | ||
c10b1332 MS |
1075 | rda,<addr> |
1076 | Start an early, polled-mode console on a serial port | |
1077 | of an RDA Micro SoC, such as RDA8810PL, at the | |
1078 | specified address. The serial port must already be | |
e36361d7 AF |
1079 | setup and configured. Options are not yet supported. |
1080 | ||
82f12ab3 PD |
1081 | sbi |
1082 | Use RISC-V SBI (Supervisor Binary Interface) for early | |
1083 | console. | |
1084 | ||
d50d7269 RH |
1085 | smh Use ARM semihosting calls for early console. |
1086 | ||
b94ba032 TF |
1087 | s3c2410,<addr> |
1088 | s3c2412,<addr> | |
1089 | s3c2440,<addr> | |
1090 | s3c6400,<addr> | |
1091 | s5pv210,<addr> | |
1092 | exynos4210,<addr> | |
1093 | Use early console provided by serial driver available | |
1094 | on Samsung SoCs, requires selecting proper type and | |
1095 | a correct base address of the selected UART port. The | |
1096 | serial port must already be setup and configured. | |
1097 | Options are not yet supported. | |
1098 | ||
ec84aa0a MB |
1099 | lantiq,<addr> |
1100 | Start an early, polled-mode console on a lantiq serial | |
1101 | (lqasc) port at the specified address. The serial port | |
1102 | must already be setup and configured. Options are not | |
1103 | yet supported. | |
1104 | ||
1d59b382 SA |
1105 | lpuart,<addr> |
1106 | lpuart32,<addr> | |
1107 | Use early console provided by Freescale LP UART driver | |
1108 | found on Freescale Vybrid and QorIQ LS1021A processors. | |
1109 | A valid base address must be provided, and the serial | |
1110 | port must already be setup and configured. | |
1111 | ||
7fe068db JN |
1112 | ec_imx21,<addr> |
1113 | ec_imx6q,<addr> | |
1114 | Start an early, polled-mode, output-only console on the | |
1115 | Freescale i.MX UART at the specified address. The UART | |
1116 | must already be setup and configured. | |
1117 | ||
f7c864e7 | 1118 | ar3700_uart,<addr> |
30530791 WD |
1119 | Start an early, polled-mode console on the |
1120 | Armada 3700 serial port at the specified | |
1121 | address. The serial port must already be setup | |
1122 | and configured. Options are not yet supported. | |
1123 | ||
43f1831b KR |
1124 | qcom_geni,<addr> |
1125 | Start an early, polled-mode console on a Qualcomm | |
1126 | Generic Interface (GENI) based serial port at the | |
1127 | specified address. The serial port must already be | |
1128 | setup and configured. Options are not yet supported. | |
1129 | ||
69c1f396 AB |
1130 | efifb,[options] |
1131 | Start an early, unaccelerated console on the EFI | |
1132 | memory mapped framebuffer (if available). On cache | |
1133 | coherent non-x86 systems that use system memory for | |
1134 | the framebuffer, pass the 'ram' option so that it is | |
1135 | mapped with the correct attributes. | |
1136 | ||
09864c1c | 1137 | linflex,<addr> |
9905f32a | 1138 | Use early console provided by Freescale LINFlexD UART |
09864c1c SM |
1139 | serial driver for NXP S32V234 SoCs. A valid base |
1140 | address must be provided, and the serial port must | |
1141 | already be setup and configured. | |
1142 | ||
4ba66a97 | 1143 | earlyprintk= [X86,SH,ARM,M68k,S390] |
1da177e4 | 1144 | earlyprintk=vga |
89175cf7 | 1145 | earlyprintk=sclp |
2482a92e | 1146 | earlyprintk=xen |
1da177e4 | 1147 | earlyprintk=serial[,ttySn[,baudrate]] |
147ea091 | 1148 | earlyprintk=serial[,0x...[,baudrate]] |
ea3acb19 | 1149 | earlyprintk=ttySn[,baudrate] |
9780bc41 | 1150 | earlyprintk=dbgp[debugController#] |
d2266bbf | 1151 | earlyprintk=pciserial[,force],bus:device.function[,baudrate] |
1b5aeebf | 1152 | earlyprintk=xdbc[xhciController#] |
1da177e4 | 1153 | |
147ea091 DH |
1154 | earlyprintk is useful when the kernel crashes before |
1155 | the normal console is initialized. It is not enabled by | |
1156 | default because it has some cosmetic problems. | |
1157 | ||
a9913044 | 1158 | Append ",keep" to not disable it when the real console |
1da177e4 LT |
1159 | takes over. |
1160 | ||
72548e83 MF |
1161 | Only one of vga, efi, serial, or usb debug port can |
1162 | be used at a time. | |
1da177e4 | 1163 | |
147ea091 DH |
1164 | Currently only ttyS0 and ttyS1 may be specified by |
1165 | name. Other I/O ports may be explicitly specified | |
1166 | on some architectures (x86 and arm at least) by | |
1167 | replacing ttySn with an I/O port address, like this: | |
1168 | earlyprintk=serial,0x1008,115200 | |
1169 | You can find the port for a given device in | |
1170 | /proc/tty/driver/serial: | |
1171 | 2: uart:ST16650V2 port:00001008 irq:18 ... | |
1da177e4 LT |
1172 | |
1173 | Interaction with the standard serial driver is not | |
1174 | very good. | |
1175 | ||
72548e83 MF |
1176 | The VGA and EFI output is eventually overwritten by |
1177 | the real console. | |
1da177e4 | 1178 | |
2482a92e KRW |
1179 | The xen output can only be used by Xen PV guests. |
1180 | ||
89175cf7 HC |
1181 | The sclp output can only be used on s390. |
1182 | ||
d2266bbf FT |
1183 | The optional "force" to "pciserial" enables use of a |
1184 | PCI device even when its classcode is not of the | |
1185 | UART class. | |
1186 | ||
c700f013 CG |
1187 | edac_report= [HW,EDAC] Control how to report EDAC event |
1188 | Format: {"on" | "off" | "force"} | |
1189 | on: enable EDAC to report H/W event. May be overridden | |
1190 | by other higher priority error reporting module. | |
1191 | off: disable H/W event reporting through EDAC. | |
1192 | force: enforce the use of EDAC to report H/W event. | |
1193 | default: on. | |
1194 | ||
9731191f JW |
1195 | ekgdboc= [X86,KGDB] Allow early kernel console debugging |
1196 | ekgdboc=kbd | |
1197 | ||
25985edc | 1198 | This is designed to be used in conjunction with |
9731191f JW |
1199 | the boot argument: earlyprintk=vga |
1200 | ||
f71fc3bc DA |
1201 | This parameter works in place of the kgdboc parameter |
1202 | but can only be used if the backing tty is available | |
1203 | very early in the boot process. For early debugging | |
1204 | via a serial port see kgdboc_earlycon instead. | |
1205 | ||
1da177e4 | 1206 | edd= [EDD] |
8c4dd606 | 1207 | Format: {"off" | "on" | "skip[mbr]"} |
1da177e4 | 1208 | |
d2f7cbe7 | 1209 | efi= [EFI] |
b617c526 | 1210 | Format: { "old_map", "nochunk", "noruntime", "debug", |
4444f854 MG |
1211 | "nosoftreserve", "disable_early_pci_dma", |
1212 | "no_disable_early_pci_dma" } | |
d2f7cbe7 | 1213 | old_map [X86-64]: switch to the old ioremap-based EFI |
1f299fad | 1214 | runtime services mapping. [Needs CONFIG_X86_UV=y] |
5a17dae4 MF |
1215 | nochunk: disable reading files in "chunks" in the EFI |
1216 | boot stub, as chunking can cause problems with some | |
1217 | firmware implementations. | |
5ae3683c | 1218 | noruntime : disable EFI runtime services support |
fed6cefe | 1219 | debug: enable misc debug output |
b617c526 DW |
1220 | nosoftreserve: The EFI_MEMORY_SP (Specific Purpose) |
1221 | attribute may cause the kernel to reserve the | |
1222 | memory range for a memory mapping driver to | |
1223 | claim. Specify efi=nosoftreserve to disable this | |
1224 | reservation and treat the memory by its base type | |
1225 | (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM"). | |
4444f854 MG |
1226 | disable_early_pci_dma: Disable the busmaster bit on all |
1227 | PCI bridges while in the EFI boot stub | |
1228 | no_disable_early_pci_dma: Leave the busmaster bit set | |
1229 | on all PCI bridges while in the EFI boot stub | |
d2f7cbe7 | 1230 | |
8c58bf3e RW |
1231 | efi_no_storage_paranoia [EFI; X86] |
1232 | Using this parameter you can use more than 50% of | |
1233 | your efi variable storage. Use this parameter only if | |
1234 | you are really sure that your UEFI does sane gc and | |
1235 | fulfills the spec otherwise your board may brick. | |
1236 | ||
0f96a99d TI |
1237 | efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] |
1238 | Add arbitrary attribute to specific memory range by | |
1239 | updating original EFI memory map. | |
1240 | Region of memory which aa attribute is added to is | |
1241 | from ss to ss+nn. | |
199c8471 | 1242 | |
0f96a99d TI |
1243 | If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 |
1244 | is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) | |
1245 | attribute is added to range 0x100000000-0x180000000 and | |
1246 | 0x10a0000000-0x1120000000. | |
1247 | ||
199c8471 DW |
1248 | If efi_fake_mem=8G@9G:0x40000 is specified, the |
1249 | EFI_MEMORY_SP(0x40000) attribute is added to | |
1250 | range 0x240000000-0x43fffffff. | |
1251 | ||
0f96a99d | 1252 | Using this parameter you can do debugging of EFI memmap |
199c8471 | 1253 | related features. For example, you can do debugging of |
0f96a99d | 1254 | Address Range Mirroring feature even if your box |
199c8471 DW |
1255 | doesn't support it, or mark specific memory as |
1256 | "soft reserved". | |
0f96a99d | 1257 | |
475fb4e8 OP |
1258 | efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT |
1259 | that is to be dynamically loaded by Linux. If there are | |
1260 | multiple variables with the same name but with different | |
1261 | vendor GUIDs, all of them will be loaded. See | |
cb1aaebe | 1262 | Documentation/admin-guide/acpi/ssdt-overlays.rst for details. |
475fb4e8 OP |
1263 | |
1264 | ||
1da177e4 LT |
1265 | eisa_irq_edge= [PARISC,HW] |
1266 | See header of drivers/parisc/eisa.c. | |
1267 | ||
cd4f0ef7 | 1268 | elanfreq= [X86-32] |
1da177e4 | 1269 | See comment before function elanfreq_setup() in |
71f77055 | 1270 | arch/x86/kernel/cpu/cpufreq/elanfreq.c. |
1da177e4 | 1271 | |
d3bf3795 | 1272 | elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] |
a9913044 | 1273 | Specifies physical address of start of kernel core |
d3bf3795 MH |
1274 | image elf header and optionally the size. Generally |
1275 | kexec loader will pass this option to capture kernel. | |
330d4810 | 1276 | See Documentation/admin-guide/kdump/kdump.rst for details. |
1da177e4 | 1277 | |
0cb55ad2 RD |
1278 | enable_mtrr_cleanup [X86] |
1279 | The kernel tries to adjust MTRR layout from continuous | |
1280 | to discrete, to make X server driver able to add WB | |
1281 | entry later. This parameter enables that. | |
1282 | ||
ca1eda2d | 1283 | enable_timer_pin_1 [X86] |
0cb55ad2 RD |
1284 | Enable PIN 1 of APIC timer |
1285 | Can be useful to work around chipset bugs | |
1286 | (in particular on some ATI chipsets). | |
1287 | The kernel tries to set a reasonable default. | |
1288 | ||
1da177e4 LT |
1289 | enforcing [SELINUX] Set initial enforcing status. |
1290 | Format: {"0" | "1"} | |
1291 | See security/selinux/Kconfig help text. | |
1292 | 0 -- permissive (log only, no denials). | |
1293 | 1 -- enforcing (deny and log). | |
1294 | Default value is 0. | |
d41415eb SS |
1295 | Value can be changed at runtime via |
1296 | /sys/fs/selinux/enforce. | |
1da177e4 | 1297 | |
a08f82d0 HY |
1298 | erst_disable [ACPI] |
1299 | Disable Error Record Serialization Table (ERST) | |
1300 | support. | |
1301 | ||
1da177e4 LT |
1302 | ether= [HW,NET] Ethernet cards parameters |
1303 | This option is obsoleted by the "netdev=" option, which | |
1304 | has equivalent usage. See its documentation for details. | |
1305 | ||
7102ebcd MZ |
1306 | evm= [EVM] |
1307 | Format: { "fix" } | |
1308 | Permit 'security.evm' to be updated regardless of | |
1309 | current integrity status. | |
1310 | ||
de1ba09b AM |
1311 | failslab= |
1312 | fail_page_alloc= | |
1313 | fail_make_request=[KNL] | |
1314 | General fault injection mechanism. | |
1315 | Format: <interval>,<probability>,<space>,<times> | |
395cf969 | 1316 | See also Documentation/fault-injection/. |
de1ba09b | 1317 | |
1da177e4 | 1318 | floppy= [HW] |
e7751617 | 1319 | See Documentation/admin-guide/blockdev/floppy.rst. |
1da177e4 | 1320 | |
f13ae30e AC |
1321 | force_pal_cache_flush |
1322 | [IA-64] Avoid check_sal_cache_flush which may hang on | |
1323 | buggy SAL_CACHE_FLUSH implementations. Using this | |
1324 | parameter will force ia64_sal_cache_flush to call | |
1325 | ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. | |
1326 | ||
6dddd7a7 | 1327 | forcepae [X86-32] |
69f2366c CB |
1328 | Forcefully enable Physical Address Extension (PAE). |
1329 | Many Pentium M systems disable PAE but may have a | |
1330 | functionally usable PAE implementation. | |
1331 | Warning: use of this parameter will taint the kernel | |
1332 | and may cause unknown problems. | |
1333 | ||
d9e54076 | 1334 | ftrace=[tracer] |
2af15d6a | 1335 | [FTRACE] will set and start the specified tracer |
d9e54076 PZ |
1336 | as early as possible in order to facilitate early |
1337 | boot debugging. | |
1338 | ||
cecbca96 | 1339 | ftrace_dump_on_oops[=orig_cpu] |
2af15d6a | 1340 | [FTRACE] will dump the trace buffers on oops. |
cecbca96 FW |
1341 | If no parameter is passed, ftrace will dump |
1342 | buffers of all CPUs, but if you pass orig_cpu, it will | |
1343 | dump only the buffer of the CPU that triggered the | |
1344 | oops. | |
2af15d6a SR |
1345 | |
1346 | ftrace_filter=[function-list] | |
1347 | [FTRACE] Limit the functions traced by the function | |
1348 | tracer at boot up. function-list is a comma separated | |
1349 | list of functions. This list can be changed at run | |
1350 | time by the set_ftrace_filter file in the debugfs | |
16290246 | 1351 | tracing directory. |
2af15d6a SR |
1352 | |
1353 | ftrace_notrace=[function-list] | |
1354 | [FTRACE] Do not trace the functions specified in | |
1355 | function-list. This list can be changed at run time | |
1356 | by the set_ftrace_notrace file in the debugfs | |
1357 | tracing directory. | |
d9e54076 | 1358 | |
369bc18f SA |
1359 | ftrace_graph_filter=[function-list] |
1360 | [FTRACE] Limit the top level callers functions traced | |
1361 | by the function graph tracer at boot up. | |
1362 | function-list is a comma separated list of functions | |
1363 | that can be changed at run time by the | |
1364 | set_graph_function file in the debugfs tracing directory. | |
1365 | ||
0d7d9a16 NK |
1366 | ftrace_graph_notrace=[function-list] |
1367 | [FTRACE] Do not trace from the functions specified in | |
1368 | function-list. This list is a comma separated list of | |
1369 | functions that can be changed at run time by the | |
1370 | set_graph_notrace file in the debugfs tracing directory. | |
1371 | ||
65a50c65 TB |
1372 | ftrace_graph_max_depth=<uint> |
1373 | [FTRACE] Used with the function graph tracer. This is | |
1374 | the max depth it will trace into a function. This value | |
1375 | can be changed at run time by the max_graph_depth file | |
1376 | in the tracefs tracing directory. default: 0 (no limit) | |
1377 | ||
8375e74f SK |
1378 | fw_devlink= [KNL] Create device links between consumer and supplier |
1379 | devices by scanning the firmware to infer the | |
1380 | consumer/supplier relationships. This feature is | |
1381 | especially useful when drivers are loaded as modules as | |
1382 | it ensures proper ordering of tasks like device probing | |
1383 | (suppliers first, then consumers), supplier boot state | |
1384 | clean up (only after all consumers have probed), | |
1385 | suspend/resume & runtime PM (consumers first, then | |
1386 | suppliers). | |
1387 | Format: { off | permissive | on | rpm } | |
1388 | off -- Don't create device links from firmware info. | |
1389 | permissive -- Create device links from firmware info | |
1390 | but use it only for ordering boot state clean | |
1391 | up (sync_state() calls). | |
1392 | on -- Create device links from firmware info and use it | |
1393 | to enforce probe and suspend/resume ordering. | |
1394 | rpm -- Like "on", but also use to order runtime PM. | |
1395 | ||
1da177e4 LT |
1396 | gamecon.map[2|3]= |
1397 | [HW,JOY] Multisystem joystick and NES/SNES/PSX pad | |
1398 | support via parallel port (up to 5 devices per port) | |
1399 | Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> | |
1752118d | 1400 | See also Documentation/input/devices/joystick-parport.rst |
1da177e4 LT |
1401 | |
1402 | gamma= [HW,DRM] | |
1403 | ||
6dddd7a7 | 1404 | gart_fix_e820= [X86_64] disable the fix e820 for K8 GART |
aaf23042 YL |
1405 | Format: off | on |
1406 | default: on | |
1407 | ||
2521f2c2 PO |
1408 | gcov_persist= [GCOV] When non-zero (default), profiling data for |
1409 | kernel modules is saved and remains accessible via | |
1410 | debugfs, even when the module is unloaded/reloaded. | |
1411 | When zero, profiling data is discarded and associated | |
1412 | debugfs files are removed at module unload time. | |
1413 | ||
47512cfd TG |
1414 | goldfish [X86] Enable the goldfish android emulator platform. |
1415 | Don't use this when you are not running on the | |
1416 | android emulator | |
1417 | ||
1da177e4 | 1418 | gpt [EFI] Forces disk with valid GPT signature but |
6c5de79b DB |
1419 | invalid Protective MBR to be treated as GPT. If the |
1420 | primary GPT is corrupted, it enables the backup/alternate | |
1421 | GPT to be used instead. | |
1da177e4 | 1422 | |
6cec9b07 AL |
1423 | grcan.enable0= [HW] Configuration of physical interface 0. Determines |
1424 | the "Enable 0" bit of the configuration register. | |
1425 | Format: 0 | 1 | |
1426 | Default: 0 | |
1427 | grcan.enable1= [HW] Configuration of physical interface 1. Determines | |
1428 | the "Enable 0" bit of the configuration register. | |
1429 | Format: 0 | 1 | |
1430 | Default: 0 | |
1431 | grcan.select= [HW] Select which physical interface to use. | |
1432 | Format: 0 | 1 | |
1433 | Default: 0 | |
1434 | grcan.txsize= [HW] Sets the size of the tx buffer. | |
1435 | Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0. | |
1436 | Default: 1024 | |
1437 | grcan.rxsize= [HW] Sets the size of the rx buffer. | |
1438 | Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. | |
1439 | Default: 1024 | |
1440 | ||
0f98dd1b BJZ |
1441 | gpio-mockup.gpio_mockup_ranges |
1442 | [HW] Sets the ranges of gpiochip of for this device. | |
1443 | Format: <start1>,<end1>,<start2>,<end2>... | |
1444 | ||
55537871 JK |
1445 | hardlockup_all_cpu_backtrace= |
1446 | [KNL] Should the hard-lockup detector generate | |
1447 | backtraces on all cpus. | |
1448 | Format: <integer> | |
1449 | ||
1da177e4 LT |
1450 | hashdist= [KNL,NUMA] Large hashes allocated during boot |
1451 | are distributed across NUMA nodes. Defaults on | |
16290246 | 1452 | for 64-bit NUMA, off otherwise. |
a9913044 | 1453 | Format: 0 | 1 (for off | on) |
1da177e4 LT |
1454 | |
1455 | hcl= [IA-64] SGI's Hardware Graph compatibility layer | |
1456 | ||
1457 | hd= [EIDE] (E)IDE hard drive subsystem geometry | |
1458 | Format: <cyl>,<head>,<sect> | |
1459 | ||
ea8c071c HY |
1460 | hest_disable [ACPI] |
1461 | Disable Hardware Error Source Table (HEST) support; | |
1462 | corresponding firmware-first mode error processing | |
1463 | logic will be disabled. | |
1464 | ||
1da177e4 LT |
1465 | highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact |
1466 | size of <nn>. This works even on boxes that have no | |
1467 | highmem otherwise. This also works to reduce highmem | |
1468 | size on bigger boxes. | |
1469 | ||
54cdfdb4 TG |
1470 | highres= [KNL] Enable/disable high resolution timer mode. |
1471 | Valid parameters: "on", "off" | |
1472 | Default: "on" | |
1473 | ||
0cb55ad2 RD |
1474 | hlt [BUGS=ARM,SH] |
1475 | ||
1476 | hpet= [X86-32,HPET] option to control HPET usage | |
1477 | Format: { enable (default) | disable | force | | |
1478 | verbose } | |
1479 | disable: disable HPET and use PIT instead | |
1480 | force: allow force enabled of undocumented chips (ICH4, | |
1481 | VIA, nVidia) | |
1482 | verbose: show contents of HPET registers during setup | |
1483 | ||
3d035f58 PB |
1484 | hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET |
1485 | registers. Default set by CONFIG_HPET_MMAP_DEFAULT. | |
1486 | ||
cf11e85f RG |
1487 | hugetlb_cma= [HW] The size of a cma area used for allocation |
1488 | of gigantic hugepages. | |
1489 | Format: nn[KMGTPE] | |
1490 | ||
1491 | Reserve a cma area of given size and allocate gigantic | |
1492 | hugepages using the cma allocator. If enabled, the | |
1493 | boot-time allocation of gigantic hugepages is skipped. | |
1494 | ||
282f4214 MK |
1495 | hugepages= [HW] Number of HugeTLB pages to allocate at boot. |
1496 | If this follows hugepagesz (below), it specifies | |
1497 | the number of pages of hugepagesz to be allocated. | |
1498 | If this is the first HugeTLB parameter on the command | |
1499 | line, it specifies the number of pages to allocate for | |
1500 | the default huge page size. See also | |
1501 | Documentation/admin-guide/mm/hugetlbpage.rst. | |
1502 | Format: <integer> | |
1503 | ||
1504 | hugepagesz= | |
1505 | [HW] The size of the HugeTLB pages. This is used in | |
1506 | conjunction with hugepages (above) to allocate huge | |
1507 | pages of a specific size at boot. The pair | |
1508 | hugepagesz=X hugepages=Y can be specified once for | |
1509 | each supported huge page size. Huge page sizes are | |
1510 | architecture dependent. See also | |
1511 | Documentation/admin-guide/mm/hugetlbpage.rst. | |
1512 | Format: size[KMG] | |
6902aa84 | 1513 | |
a49d9c0a OS |
1514 | hung_task_panic= |
1515 | [KNL] Should the hung task detector generate panics. | |
1516 | Format: <integer> | |
cef7125d | 1517 | |
a49d9c0a OS |
1518 | A nonzero value instructs the kernel to panic when a |
1519 | hung task is detected. The default value is controlled | |
1520 | by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time | |
1521 | option. The value selected by this boot parameter can | |
1522 | be changed later by the kernel.hung_task_panic sysctl. | |
1523 | ||
6dddd7a7 TB |
1524 | hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) |
1525 | terminal devices. Valid values: 0..8 | |
1526 | hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. | |
1527 | If specified, z/VM IUCV HVC accepts connections | |
1528 | from listed z/VM user IDs only. | |
3a025de6 YS |
1529 | |
1530 | hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations | |
1531 | which allow the hypervisor to 'idle' the | |
1532 | guest on lock contention. | |
1533 | ||
7bf69395 FDN |
1534 | keep_bootcon [KNL] |
1535 | Do not unregister boot console at start. This is only | |
1536 | useful for debugging when something happens in the window | |
1537 | between unregistering the boot console and initializing | |
1538 | the real console. | |
1539 | ||
6dddd7a7 TB |
1540 | i2c_bus= [HW] Override the default board specific I2C bus speed |
1541 | or register an additional I2C bus that is not | |
1542 | registered from board initialization code. | |
1543 | Format: | |
1544 | <bus_id>,<clkrate> | |
3a853fb9 | 1545 | |
36d95739 | 1546 | i8042.debug [HW] Toggle i8042 debug mode |
e1443d28 SCP |
1547 | i8042.unmask_kbd_data |
1548 | [HW] Enable printing of interrupt data from the KBD port | |
1549 | (disabled by default, and as a pre-condition | |
1550 | requires that i8042.debug=1 be enabled) | |
1da177e4 | 1551 | i8042.direct [HW] Put keyboard port into non-translated mode |
84eb8d06 ML |
1552 | i8042.dumbkbd [HW] Pretend that controller can only read data from |
1553 | keyboard and cannot control its state | |
1da177e4 LT |
1554 | (Don't attempt to blink the leds) |
1555 | i8042.noaux [HW] Don't check for auxiliary (== mouse) port | |
945ef0d4 | 1556 | i8042.nokbd [HW] Don't check/create keyboard port |
75d08c78 JK |
1557 | i8042.noloop [HW] Disable the AUX Loopback command while probing |
1558 | for the AUX port | |
1da177e4 | 1559 | i8042.nomux [HW] Don't check presence of an active multiplexing |
e55a3366 | 1560 | controller |
1da177e4 LT |
1561 | i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX |
1562 | controllers | |
24775d65 | 1563 | i8042.notimeout [HW] Ignore timeout condition signalled by controller |
930e1924 MPS |
1564 | i8042.reset [HW] Reset the controller during init, cleanup and |
1565 | suspend-to-ram transitions, only during s2r | |
1566 | transitions, or never reset | |
1567 | Format: { 1 | Y | y | 0 | N | n } | |
1568 | 1, Y, y: always reset controller | |
1569 | 0, N, n: don't ever reset controller | |
1570 | Default: only on s2r transitions on x86; most other | |
1571 | architectures force reset to be always executed | |
1da177e4 | 1572 | i8042.unlock [HW] Unlock (ignore) the keylock |
6dddd7a7 | 1573 | i8042.kbdreset [HW] Reset device connected to KBD port |
1da177e4 LT |
1574 | |
1575 | i810= [HW,DRM] | |
1576 | ||
e70c9d5e DT |
1577 | i8k.ignore_dmi [HW] Continue probing hardware even if DMI data |
1578 | indicates that the driver is running on unsupported | |
1579 | hardware. | |
1da177e4 LT |
1580 | i8k.force [HW] Activate i8k driver even if SMM BIOS signature |
1581 | does not match list of supported models. | |
1582 | i8k.power_status | |
1583 | [HW] Report power status in /proc/i8k | |
1584 | (disabled by default) | |
1585 | i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN | |
1586 | capability is set. | |
1587 | ||
4dca20ef | 1588 | i915.invert_brightness= |
7bd90909 CE |
1589 | [DRM] Invert the sense of the variable that is used to |
1590 | set the brightness of the panel backlight. Normally a | |
4dca20ef CE |
1591 | brightness value of 0 indicates backlight switched off, |
1592 | and the maximum of the brightness value sets the backlight | |
1593 | to maximum brightness. If this parameter is set to 0 | |
1594 | (default) and the machine requires it, or this parameter | |
1595 | is set to 1, a brightness value of 0 sets the backlight | |
1596 | to maximum brightness, and the maximum of the brightness | |
1597 | value switches the backlight off. | |
1598 | -1 -- never invert brightness | |
1599 | 0 -- machine default | |
1600 | 1 -- force brightness inversion | |
7bd90909 | 1601 | |
1da177e4 LT |
1602 | icn= [HW,ISDN] |
1603 | Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] | |
1604 | ||
0af80c04 DF |
1605 | ide-core.nodma= [HW] (E)IDE subsystem |
1606 | Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc | |
075affcb BZ |
1607 | .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr |
1608 | .cdrom .chs .ignore_cable are additional options | |
d7b461c5 | 1609 | See Documentation/ide/ide.rst. |
1da177e4 | 1610 | |
0f8b7f5d MR |
1611 | ide-generic.probe-mask= [HW] (E)IDE subsystem |
1612 | Format: <int> | |
1613 | Probe mask for legacy ISA IDE ports. Depending on | |
1614 | platform up to 6 ports are supported, enabled by | |
1615 | setting corresponding bits in the mask to 1. The | |
1616 | default value is 0x0, which has a special meaning. | |
1617 | On systems that have PCI, it triggers scanning the | |
1618 | PCI bus for the first and the second port, which | |
1619 | are then probed. On systems without PCI the value | |
1620 | of 0x0 enables probing the two first ports as if it | |
1621 | was 0x3. | |
1622 | ||
0cb55ad2 RD |
1623 | ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem |
1624 | Claim all unknown PCI IDE storage controllers. | |
1625 | ||
f039b754 | 1626 | idle= [X86] |
69fb3676 | 1627 | Format: idle=poll, idle=halt, idle=nomwait |
ada9cfdd RD |
1628 | Poll forces a polling idle loop that can slightly |
1629 | improve the performance of waking up a idle CPU, but | |
1630 | will use a lot of power and make the system run hot. | |
1631 | Not recommended. | |
ada9cfdd | 1632 | idle=halt: Halt is forced to be used for CPU idle. |
c1e3b377 | 1633 | In such case C2/C3 won't be used again. |
ada9cfdd | 1634 | idle=nomwait: Disable mwait for CPU C-states |
a9913044 | 1635 | |
503943e0 MR |
1636 | ieee754= [MIPS] Select IEEE Std 754 conformance mode |
1637 | Format: { strict | legacy | 2008 | relaxed } | |
1638 | Default: strict | |
1639 | ||
1640 | Choose which programs will be accepted for execution | |
1641 | based on the IEEE 754 NaN encoding(s) supported by | |
1642 | the FPU and the NaN encoding requested with the value | |
1643 | of an ELF file header flag individually set by each | |
1644 | binary. Hardware implementations are permitted to | |
1645 | support either or both of the legacy and the 2008 NaN | |
1646 | encoding mode. | |
1647 | ||
1648 | Available settings are as follows: | |
1649 | strict accept binaries that request a NaN encoding | |
1650 | supported by the FPU | |
1651 | legacy only accept legacy-NaN binaries, if supported | |
1652 | by the FPU | |
1653 | 2008 only accept 2008-NaN binaries, if supported | |
1654 | by the FPU | |
1655 | relaxed accept any binaries regardless of whether | |
1656 | supported by the FPU | |
1657 | ||
1658 | The FPU emulator is always able to support both NaN | |
1659 | encodings, so if no FPU hardware is present or it has | |
1660 | been disabled with 'nofpu', then the settings of | |
1661 | 'legacy' and '2008' strap the emulator accordingly, | |
1662 | 'relaxed' straps the emulator for both legacy-NaN and | |
1663 | 2008-NaN, whereas 'strict' enables legacy-NaN only on | |
1664 | legacy processors and both NaN encodings on MIPS32 or | |
1665 | MIPS64 CPUs. | |
1666 | ||
1667 | The setting for ABS.fmt/NEG.fmt instruction execution | |
1668 | mode generally follows that for the NaN encoding, | |
1669 | except where unsupported by hardware. | |
1670 | ||
79290822 IM |
1671 | ignore_loglevel [KNL] |
1672 | Ignore loglevel setting - this will print /all/ | |
1673 | kernel messages to the console. Useful for debugging. | |
0eca6b7c YZ |
1674 | We also add it as printk module parameter, so users |
1675 | could change it dynamically, usually by | |
1676 | /sys/module/printk/parameters/ignore_loglevel. | |
79290822 | 1677 | |
d977d56c KK |
1678 | ignore_rlimit_data |
1679 | Ignore RLIMIT_DATA setting for data mappings, | |
1680 | print warning at first misuse. Can be changed via | |
1681 | /sys/module/kernel/parameters/ignore_rlimit_data. | |
1682 | ||
1da177e4 LT |
1683 | ihash_entries= [KNL] |
1684 | Set number of hash buckets for inode cache. | |
1685 | ||
2fe5d6de | 1686 | ima_appraise= [IMA] appraise integrity measurements |
2faa6ef3 | 1687 | Format: { "off" | "enforce" | "fix" | "log" } |
2fe5d6de MZ |
1688 | default: "enforce" |
1689 | ||
41475a3e | 1690 | ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead. |
07f6a794 MZ |
1691 | The builtin appraise policy appraises all files |
1692 | owned by uid=0. | |
1693 | ||
d68a6fe9 MZ |
1694 | ima_canonical_fmt [IMA] |
1695 | Use the canonical format for the binary runtime | |
1696 | measurements, instead of host native format. | |
1697 | ||
3323eec9 | 1698 | ima_hash= [IMA] |
e7a2ad7e MZ |
1699 | Format: { md5 | sha1 | rmd160 | sha256 | sha384 |
1700 | | sha512 | ... } | |
3323eec9 MZ |
1701 | default: "sha1" |
1702 | ||
e7a2ad7e MZ |
1703 | The list of supported hash algorithms is defined |
1704 | in crypto/hash_info.h. | |
1705 | ||
24fd03c8 | 1706 | ima_policy= [IMA] |
33ce9549 | 1707 | The builtin policies to load during IMA setup. |
9e67028e MZ |
1708 | Format: "tcb | appraise_tcb | secure_boot | |
1709 | fail_securely" | |
33ce9549 MZ |
1710 | |
1711 | The "tcb" policy measures all programs exec'd, files | |
1712 | mmap'd for exec, and all files opened with the read | |
1713 | mode bit set by either the effective uid (euid=0) or | |
1714 | uid=0. | |
1715 | ||
1716 | The "appraise_tcb" policy appraises the integrity of | |
41475a3e | 1717 | all files owned by root. |
24fd03c8 | 1718 | |
503ceaef MZ |
1719 | The "secure_boot" policy appraises the integrity |
1720 | of files (eg. kexec kernel image, kernel modules, | |
1721 | firmware, policy, etc) based on file signatures. | |
24fd03c8 | 1722 | |
9e67028e MZ |
1723 | The "fail_securely" policy forces file signature |
1724 | verification failure also on privileged mounted | |
1725 | filesystems with the SB_I_UNVERIFIABLE_SIGNATURE | |
1726 | flag. | |
1727 | ||
24fd03c8 | 1728 | ima_tcb [IMA] Deprecated. Use ima_policy= instead. |
5789ba3b EP |
1729 | Load a policy which meets the needs of the Trusted |
1730 | Computing Base. This means IMA will measure all | |
1731 | programs exec'd, files mmap'd for exec, and all files | |
1732 | opened for read by uid=0. | |
1733 | ||
6dddd7a7 | 1734 | ima_template= [IMA] |
9b9d4ce5 | 1735 | Select one of defined IMA measurements template formats. |
8265a2f8 | 1736 | Formats: { "ima" | "ima-ng" | "ima-sig" } |
9b9d4ce5 RS |
1737 | Default: "ima-ng" |
1738 | ||
c2426d2a | 1739 | ima_template_fmt= |
6dddd7a7 | 1740 | [IMA] Define a custom template format. |
c2426d2a RS |
1741 | Format: { "field1|...|fieldN" } |
1742 | ||
3bcced39 DK |
1743 | ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage |
1744 | Format: <min_file_size> | |
1745 | Set the minimal file size for using asynchronous hash. | |
1746 | If left unspecified, ahash usage is disabled. | |
1747 | ||
1748 | ahash performance varies for different data sizes on | |
1749 | different crypto accelerators. This option can be used | |
1750 | to achieve the best performance for a particular HW. | |
1751 | ||
6edf7a89 DK |
1752 | ima.ahash_bufsize= [IMA] Asynchronous hash buffer size |
1753 | Format: <bufsize> | |
1754 | Set hashing buffer size. Default: 4k. | |
1755 | ||
1756 | ahash performance varies for different chunk sizes on | |
1757 | different crypto accelerators. This option can be used | |
1758 | to achieve best performance for particular HW. | |
1759 | ||
1da177e4 LT |
1760 | init= [KNL] |
1761 | Format: <full_path> | |
1762 | Run specified binary instead of /sbin/init as init | |
1763 | process. | |
1764 | ||
1765 | initcall_debug [KNL] Trace initcalls as they are executed. Useful | |
1766 | for working out where the kernel is dying during | |
1767 | startup. | |
1768 | ||
7b0b73d7 PB |
1769 | initcall_blacklist= [KNL] Do not execute a comma-separated list of |
1770 | initcall functions. Useful for debugging built-in | |
1771 | modules and initcalls. | |
1772 | ||
1da177e4 LT |
1773 | initrd= [BOOT] Specify the location of the initial ramdisk |
1774 | ||
694cfd87 RM |
1775 | initrdmem= [KNL] Specify a physical address and size from which to |
1776 | load the initrd. If an initrd is compiled in or | |
1777 | specified in the bootparams, it takes priority over this | |
1778 | setting. | |
1779 | Format: ss[KMG],nn[KMG] | |
1780 | Default is 0, 0 | |
1781 | ||
6471384a AP |
1782 | init_on_alloc= [MM] Fill newly allocated pages and heap objects with |
1783 | zeroes. | |
1784 | Format: 0 | 1 | |
1785 | Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON. | |
1786 | ||
1787 | init_on_free= [MM] Fill freed pages and heap objects with zeroes. | |
1788 | Format: 0 | 1 | |
1789 | Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON. | |
1790 | ||
acd547b2 DH |
1791 | init_pkru= [x86] Specify the default memory protection keys rights |
1792 | register contents for all processes. 0x55555554 by | |
1793 | default (disallow access to all but pkey 0). Can | |
1794 | override in debugfs after boot. | |
1795 | ||
1da177e4 LT |
1796 | inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver |
1797 | Format: <irq> | |
1798 | ||
6dddd7a7 | 1799 | int_pln_enable [x86] Enable power limit notification interrupt |
6bb2ff84 | 1800 | |
d726d8d7 MZ |
1801 | integrity_audit=[IMA] |
1802 | Format: { "0" | "1" } | |
1803 | 0 -- basic integrity auditing messages. (Default) | |
1804 | 1 -- additional integrity auditing messages. | |
1805 | ||
ba395927 | 1806 | intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option |
0cd5c3c8 KM |
1807 | on |
1808 | Enable intel iommu driver. | |
ba395927 KA |
1809 | off |
1810 | Disable intel iommu driver. | |
1811 | igfx_off [Default Off] | |
1812 | By default, gfx is mapped as normal device. If a gfx | |
1813 | device has a dedicated DMAR unit, the DMAR unit is | |
1814 | bypassed by not enabling DMAR with this option. In | |
1815 | this case, gfx device will use physical address for | |
1816 | DMA. | |
7d3b03ce KA |
1817 | forcedac [x86_64] |
1818 | With this option iommu will not optimize to look | |
16290246 | 1819 | for io virtual address below 32-bit forcing dual |
7d3b03ce | 1820 | address cycle on pci bus for cards supporting greater |
16290246 RD |
1821 | than 32-bit addressing. The default is to look |
1822 | for translation below 32-bit and if not available | |
7d3b03ce | 1823 | then look in the higher range. |
5e0d2a6f | 1824 | strict [Default Off] |
1825 | With this option on every unmap_single operation will | |
1826 | result in a hardware IOTLB flush operation as opposed | |
1827 | to batching them for performance. | |
6dd9a7c7 YS |
1828 | sp_off [Default Off] |
1829 | By default, super page will be supported if Intel IOMMU | |
1830 | has the capability. With this option, super page will | |
1831 | not be supported. | |
8950dcd8 LB |
1832 | sm_on [Default Off] |
1833 | By default, scalable mode will be disabled even if the | |
765b6a98 LB |
1834 | hardware advertises that it has support for the scalable |
1835 | mode translation. With this option set, scalable mode | |
8950dcd8 | 1836 | will be used on hardware which claims to support it. |
bfd20f1c SL |
1837 | tboot_noforce [Default Off] |
1838 | Do not force the Intel IOMMU enabled under tboot. | |
1839 | By default, tboot will force Intel IOMMU on, which | |
1840 | could harm performance of some high-throughput | |
1841 | devices like 40GBit network cards, even if identity | |
1842 | mapping is enabled. | |
1843 | Note that using this option lowers the security | |
1844 | provided by tboot because it makes the system | |
1845 | vulnerable to DMA attacks. | |
e5e04d05 | 1846 | nobounce [Default off] |
bf347b9d | 1847 | Disable bounce buffer for untrusted devices such as |
e5e04d05 LB |
1848 | the Thunderbolt devices. This will treat the untrusted |
1849 | devices as the trusted ones, hence might expose security | |
1850 | risks of DMA attacks. | |
2e92c7ad MI |
1851 | |
1852 | intel_idle.max_cstate= [KNL,HW,ACPI,X86] | |
1853 | 0 disables intel_idle and fall back on acpi_idle. | |
22c6bbe4 | 1854 | 1 to 9 specify maximum depth of C-state. |
2e92c7ad | 1855 | |
6dddd7a7 TB |
1856 | intel_pstate= [X86] |
1857 | disable | |
1858 | Do not enable intel_pstate as the default | |
1859 | scaling driver for the supported processors | |
1860 | passive | |
1861 | Use intel_pstate as a scaling driver, but configure it | |
1862 | to work with generic cpufreq governors (instead of | |
1863 | enabling its internal governor). This mode cannot be | |
1864 | used along with the hardware-managed P-states (HWP) | |
1865 | feature. | |
1866 | force | |
1867 | Enable intel_pstate on systems that prohibit it by default | |
1868 | in favor of acpi-cpufreq. Forcing the intel_pstate driver | |
1869 | instead of acpi-cpufreq may disable platform features, such | |
1870 | as thermal controls and power capping, that rely on ACPI | |
1871 | P-States information being indicated to OSPM and therefore | |
1872 | should be used with caution. This option does not work with | |
1873 | processors that aren't supported by the intel_pstate driver | |
1874 | or on platforms that use pcc-cpufreq instead of acpi-cpufreq. | |
1875 | no_hwp | |
1876 | Do not enable hardware P state control (HWP) | |
1877 | if available. | |
1878 | hwp_only | |
1879 | Only load intel_pstate on systems which support | |
1880 | hardware P state control (HWP) if available. | |
1881 | support_acpi_ppc | |
1882 | Enforce ACPI _PPC performance limits. If the Fixed ACPI | |
1883 | Description Table, specifies preferred power management | |
1884 | profile as "Enterprise Server" or "Performance Server", | |
1885 | then this feature is turned on by default. | |
1886 | per_cpu_perf_limits | |
1887 | Allow per-logical-CPU P-State performance control limits using | |
1888 | cpufreq sysfs interface | |
6be26498 | 1889 | |
d1423d56 | 1890 | intremap= [X86-64, Intel-IOMMU] |
d1423d56 CW |
1891 | on enable Interrupt Remapping (default) |
1892 | off disable Interrupt Remapping | |
1893 | nosid disable Source ID checking | |
41750d31 SS |
1894 | no_x2apic_optout |
1895 | BIOS x2APIC opt-out request will be ignored | |
b7d20631 | 1896 | nopost disable Interrupt Posting |
d1423d56 | 1897 | |
0cb55ad2 RD |
1898 | iomem= Disable strict checking of access to MMIO memory |
1899 | strict regions from userspace. | |
1900 | relaxed | |
1901 | ||
1902 | iommu= [x86] | |
1903 | off | |
1904 | force | |
1905 | noforce | |
1906 | biomerge | |
1907 | panic | |
1908 | nopanic | |
1909 | merge | |
1910 | nomerge | |
0cb55ad2 | 1911 | soft |
58d11317 OJ |
1912 | pt [x86] |
1913 | nopt [x86] | |
4e287840 TLSC |
1914 | nobypass [PPC/POWERNV] |
1915 | Disable IOMMU bypass, using IOMMU for PCI devices. | |
bcb71abe | 1916 | |
68a6efe8 ZL |
1917 | iommu.strict= [ARM64] Configure TLB invalidation behaviour |
1918 | Format: { "0" | "1" } | |
1919 | 0 - Lazy mode. | |
1920 | Request that DMA unmap operations use deferred | |
1921 | invalidation of hardware TLBs, for increased | |
1922 | throughput at the cost of reduced device isolation. | |
1923 | Will fall back to strict mode if not supported by | |
1924 | the relevant IOMMU driver. | |
1925 | 1 - Strict mode (default). | |
1926 | DMA unmap operations invalidate IOMMU hardware TLBs | |
1927 | synchronously. | |
1928 | ||
fccb4e3b | 1929 | iommu.passthrough= |
c8fb436b | 1930 | [ARM64, X86] Configure DMA to bypass the IOMMU by default. |
fccb4e3b WD |
1931 | Format: { "0" | "1" } |
1932 | 0 - Use IOMMU translation for DMA. | |
1933 | 1 - Bypass the IOMMU for DMA. | |
9d723b4c | 1934 | unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. |
0cb55ad2 RD |
1935 | |
1936 | io7= [HW] IO7 for Marvel based alpha systems | |
1937 | See comment before marvel_specify_io7 in | |
1938 | arch/alpha/kernel/core_marvel.c. | |
1939 | ||
6cececfc | 1940 | io_delay= [X86] I/O delay method |
6e7c4025 IM |
1941 | 0x80 |
1942 | Standard port 0x80 based delay | |
1943 | 0xed | |
1944 | Alternate port 0xed based delay (needed on some systems) | |
b02aae9c | 1945 | udelay |
6e7c4025 IM |
1946 | Simple two microseconds delay |
1947 | none | |
1948 | No delay | |
b02aae9c | 1949 | |
1da177e4 | 1950 | ip= [IP_PNP] |
3eb30c51 | 1951 | See Documentation/admin-guide/nfs/nfsroot.rst. |
1da177e4 | 1952 | |
5ac893b8 WL |
1953 | ipcmni_extend [KNL] Extend the maximum number of unique System V |
1954 | IPC identifiers from 32,768 to 16,777,216. | |
1955 | ||
fbf19803 | 1956 | irqaffinity= [SMP] Set the default irq affinity mask |
2d13e6ca | 1957 | The argument is a cpu list, as described above. |
fbf19803 | 1958 | |
0962289b MZ |
1959 | irqchip.gicv2_force_probe= |
1960 | [ARM, ARM64] | |
1961 | Format: <bool> | |
1962 | Force the kernel to look for the second 4kB page | |
1963 | of a GICv2 controller even if the memory range | |
1964 | exposed by the device tree is too small. | |
1965 | ||
f736d65d MZ |
1966 | irqchip.gicv3_nolpi= |
1967 | [ARM, ARM64] | |
1968 | Force the kernel to ignore the availability of | |
1969 | LPIs (and by consequence ITSs). Intended for system | |
1970 | that use the kernel as a bootloader, and thus want | |
1971 | to let secondary kernels in charge of setting up | |
1972 | LPIs. | |
1973 | ||
bc3c03cc JT |
1974 | irqchip.gicv3_pseudo_nmi= [ARM64] |
1975 | Enables support for pseudo-NMIs in the kernel. This | |
1976 | requires the kernel to be built with | |
1977 | CONFIG_ARM64_PSEUDO_NMI. | |
1978 | ||
200803df AC |
1979 | irqfixup [HW] |
1980 | When an interrupt is not handled search all handlers | |
1981 | for it. Intended to get systems with badly broken | |
1982 | firmware running. | |
1983 | ||
1984 | irqpoll [HW] | |
1985 | When an interrupt is not handled search all handlers | |
1986 | for it. Also check all handlers each timer | |
1987 | interrupt. Intended to get systems with badly broken | |
1988 | firmware running. | |
1989 | ||
1da177e4 | 1990 | isapnp= [ISAPNP] |
a9913044 | 1991 | Format: <RDP>,<reset>,<pci_scan>,<verbosity> |
1da177e4 | 1992 | |
d94d1053 | 1993 | isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance. |
b0d40d2b FW |
1994 | [Deprecated - use cpusets instead] |
1995 | Format: [flag-list,]<cpu-list> | |
1996 | ||
1997 | Specify one or more CPUs to isolate from disturbances | |
1998 | specified in the flag list (default: domain): | |
1999 | ||
2000 | nohz | |
2001 | Disable the tick when a single task runs. | |
083c6eea FW |
2002 | |
2003 | A residual 1Hz tick is offloaded to workqueues, which you | |
2004 | need to affine to housekeeping through the global | |
2005 | workqueue's affinity configured via the | |
2006 | /sys/devices/virtual/workqueue/cpumask sysfs file, or | |
2007 | by using the 'domain' flag described below. | |
2008 | ||
2009 | NOTE: by default the global workqueue runs on all CPUs, | |
2010 | so to protect individual CPUs the 'cpumask' file has to | |
2011 | be configured manually after bootup. | |
2012 | ||
b0d40d2b FW |
2013 | domain |
2014 | Isolate from the general SMP balancing and scheduling | |
2015 | algorithms. Note that performing domain isolation this way | |
2016 | is irreversible: it's not possible to bring back a CPU to | |
2017 | the domains once isolated through isolcpus. It's strongly | |
2018 | advised to use cpusets instead to disable scheduler load | |
2019 | balancing through the "cpuset.sched_load_balance" file. | |
2020 | It offers a much more flexible interface where CPUs can | |
2021 | move in and out of an isolated set anytime. | |
2022 | ||
2023 | You can move a process onto or off an "isolated" CPU via | |
2024 | the CPU affinity syscalls or cpuset. | |
2025 | <cpu number> begins at 0 and the maximum value is | |
2026 | "number of CPUs in system - 1". | |
2027 | ||
11ea68f5 ML |
2028 | managed_irq |
2029 | ||
2030 | Isolate from being targeted by managed interrupts | |
2031 | which have an interrupt mask containing isolated | |
2032 | CPUs. The affinity of managed interrupts is | |
2033 | handled by the kernel and cannot be changed via | |
2034 | the /proc/irq/* interfaces. | |
2035 | ||
2036 | This isolation is best effort and only effective | |
2037 | if the automatically assigned interrupt mask of a | |
2038 | device queue contains isolated and housekeeping | |
2039 | CPUs. If housekeeping CPUs are online then such | |
2040 | interrupts are directed to the housekeeping CPU | |
2041 | so that IO submitted on the housekeeping CPU | |
2042 | cannot disturb the isolated CPU. | |
2043 | ||
2044 | If a queue's affinity mask contains only isolated | |
2045 | CPUs then this parameter has no effect on the | |
2046 | interrupt routing decision, though interrupts are | |
2047 | only delivered when tasks running on those | |
2048 | isolated CPUs submit IO. IO submitted on | |
2049 | housekeeping CPUs has no influence on those | |
2050 | queues. | |
1da177e4 | 2051 | |
11ea68f5 | 2052 | The format of <cpu-list> is described above. |
1da177e4 | 2053 | |
a9913044 | 2054 | iucv= [HW,NET] |
1da177e4 | 2055 | |
7d8bfa26 JR |
2056 | ivrs_ioapic [HW,X86_64] |
2057 | Provide an override to the IOAPIC-ID<->DEVICE-ID | |
2058 | mapping provided in the IVRS ACPI table. For | |
2059 | example, to map IOAPIC-ID decimal 10 to | |
2060 | PCI device 00:14.0 write the parameter as: | |
2061 | ivrs_ioapic[10]=00:14.0 | |
2062 | ||
2063 | ivrs_hpet [HW,X86_64] | |
2064 | Provide an override to the HPET-ID<->DEVICE-ID | |
2065 | mapping provided in the IVRS ACPI table. For | |
2066 | example, to map HPET-ID decimal 0 to | |
2067 | PCI device 00:14.0 write the parameter as: | |
2068 | ivrs_hpet[0]=00:14.0 | |
2069 | ||
ca3bf5d4 SS |
2070 | ivrs_acpihid [HW,X86_64] |
2071 | Provide an override to the ACPI-HID:UID<->DEVICE-ID | |
2072 | mapping provided in the IVRS ACPI table. For | |
2073 | example, to map UART-HID:UID AMD0020:0 to | |
2074 | PCI device 00:14.5 write the parameter as: | |
2075 | ivrs_acpihid[00:14.5]=AMD0020:0 | |
2076 | ||
1da177e4 | 2077 | js= [HW,JOY] Analog joystick |
1752118d | 2078 | See Documentation/input/joydev/joystick.rst. |
1da177e4 | 2079 | |
65fe935d KC |
2080 | nokaslr [KNL] |
2081 | When CONFIG_RANDOMIZE_BASE is set, this disables | |
2082 | kernel and module base offset ASLR (Address Space | |
2083 | Layout Randomization). | |
24f2e027 | 2084 | |
b0845ce5 MR |
2085 | kasan_multi_shot |
2086 | [KNL] Enforce KASAN (Kernel Address Sanitizer) to print | |
2087 | report on every invalid memory access. Without this | |
2088 | parameter KASAN will print report only for the first | |
2089 | invalid access. | |
2090 | ||
0cb55ad2 RD |
2091 | keepinitrd [HW,ARM] |
2092 | ||
342332e6 | 2093 | kernelcore= [KNL,X86,IA-64,PPC] |
a5c6d650 DR |
2094 | Format: nn[KMGTPE] | nn% | "mirror" |
2095 | This parameter specifies the amount of memory usable by | |
2096 | the kernel for non-movable allocations. The requested | |
2097 | amount is spread evenly throughout all nodes in the | |
2098 | system as ZONE_NORMAL. The remaining memory is used for | |
2099 | movable memory in its own zone, ZONE_MOVABLE. In the | |
2100 | event, a node is too small to have both ZONE_NORMAL and | |
2101 | ZONE_MOVABLE, kernelcore memory will take priority and | |
2102 | other nodes will have a larger ZONE_MOVABLE. | |
2103 | ||
2104 | ZONE_MOVABLE is used for the allocation of pages that | |
2105 | may be reclaimed or moved by the page migration | |
2106 | subsystem. Note that allocations like PTEs-from-HighMem | |
2107 | still use the HighMem zone if it exists, and the Normal | |
ed7ed365 MG |
2108 | zone if it does not. |
2109 | ||
a5c6d650 DR |
2110 | It is possible to specify the exact amount of memory in |
2111 | the form of "nn[KMGTPE]", a percentage of total system | |
2112 | memory in the form of "nn%", or "mirror". If "mirror" | |
342332e6 TI |
2113 | option is specified, mirrored (reliable) memory is used |
2114 | for non-movable allocations and remaining memory is used | |
a5c6d650 DR |
2115 | for Movable pages. "nn[KMGTPE]", "nn%", and "mirror" |
2116 | are exclusive, so you cannot specify multiple forms. | |
ed7ed365 | 2117 | |
4fe1da4e JW |
2118 | kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. |
2119 | Format: <Controller#>[,poll interval] | |
2120 | The controller # is the number of the ehci usb debug | |
2121 | port as it is probed via PCI. The poll interval is | |
2122 | optional and is the number seconds in between | |
2123 | each poll cycle to the debug port in case you need | |
2124 | the functionality for interrupting the kernel with | |
2125 | gdb or control-c on the dbgp connection. When | |
2126 | not using this parameter you use sysrq-g to break into | |
2127 | the kernel debugger. | |
2128 | ||
84c08fd6 | 2129 | kgdboc= [KGDB,HW] kgdb over consoles. |
ada64e4c JW |
2130 | Requires a tty driver that supports console polling, |
2131 | or a supported polling keyboard driver (non-usb). | |
65b5ac14 JW |
2132 | Serial only format: <serial_device>[,baud] |
2133 | keyboard only format: kbd | |
2134 | keyboard and serial format: kbd,<serial_device>[,baud] | |
2135 | Optional Kernel mode setting: | |
2136 | kms, kbd format: kms,kbd | |
2137 | kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] | |
6cdf6e06 | 2138 | |
f71fc3bc DA |
2139 | kgdboc_earlycon= [KGDB,HW] |
2140 | If the boot console provides the ability to read | |
2141 | characters and can work in polling mode, you can use | |
2142 | this parameter to tell kgdb to use it as a backend | |
2143 | until the normal console is registered. Intended to | |
2144 | be used together with the kgdboc parameter which | |
2145 | specifies the normal console to transition to. | |
2146 | ||
2147 | The name of the early console should be specified | |
2148 | as the value of this parameter. Note that the name of | |
2149 | the early console might be different than the tty | |
2150 | name passed to kgdboc. It's OK to leave the value | |
2151 | blank and the first boot console that implements | |
2152 | read() will be picked. | |
2153 | ||
84c08fd6 JW |
2154 | kgdbwait [KGDB] Stop kernel execution and enter the |
2155 | kernel debugger at the earliest opportunity. | |
2156 | ||
9bed90c6 FF |
2157 | kmac= [MIPS] korina ethernet MAC address. |
2158 | Configure the RouterBoard 532 series on-chip | |
2159 | Ethernet adapter MAC address. | |
2160 | ||
04f70336 CM |
2161 | kmemleak= [KNL] Boot-time kmemleak enable/disable |
2162 | Valid arguments: on, off | |
2163 | Default: on | |
47aeeddc MI |
2164 | Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, |
2165 | the default is off. | |
04f70336 | 2166 | |
970988e1 MH |
2167 | kprobe_event=[probe-list] |
2168 | [FTRACE] Add kprobe events and enable at boot time. | |
2169 | The probe-list is a semicolon delimited list of probe | |
2170 | definitions. Each definition is same as kprobe_events | |
2171 | interface, but the parameters are comma delimited. | |
2172 | For example, to add a kprobe event on vfs_read with | |
2173 | arg1 and arg2, add to the command line; | |
2174 | ||
2175 | kprobe_event=p,vfs_read,$arg1,$arg2 | |
2176 | ||
2177 | See also Documentation/trace/kprobetrace.rst "Kernel | |
2178 | Boot Parameter" section. | |
2179 | ||
de190555 JL |
2180 | kpti= [ARM64] Control page table isolation of user |
2181 | and kernel address spaces. | |
2182 | Default: enabled on cores which need mitigation. | |
2183 | 0: force disabled | |
2184 | 1: force enabled | |
2185 | ||
fef07aae AP |
2186 | kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. |
2187 | Default is 0 (don't ignore, but inject #GP) | |
2188 | ||
c4ae60e4 LA |
2189 | kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface. |
2190 | Default is false (don't support). | |
2191 | ||
a182d873 XG |
2192 | kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit |
2193 | KVM MMU at runtime. | |
fef07aae AP |
2194 | Default is 0 (off) |
2195 | ||
b8e8c830 PB |
2196 | kvm.nx_huge_pages= |
2197 | [KVM] Controls the software workaround for the | |
2198 | X86_BUG_ITLB_MULTIHIT bug. | |
2199 | force : Always deploy workaround. | |
2200 | off : Never deploy workaround. | |
2201 | auto : Deploy workaround based on the presence of | |
2202 | X86_BUG_ITLB_MULTIHIT. | |
2203 | ||
2204 | Default is 'auto'. | |
2205 | ||
2206 | If the software workaround is enabled for the host, | |
2207 | guests do need not to enable it for nested guests. | |
2208 | ||
1aa9b957 JS |
2209 | kvm.nx_huge_pages_recovery_ratio= |
2210 | [KVM] Controls how many 4KiB pages are periodically zapped | |
2211 | back to huge pages. 0 disables the recovery, otherwise if | |
2212 | the value is N KVM will zap 1/Nth of the 4KiB pages every | |
2213 | minute. The default is 60. | |
2214 | ||
fef07aae | 2215 | kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. |
8475f94a | 2216 | Default is 1 (enabled) |
fef07aae AP |
2217 | |
2218 | kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) | |
2219 | for all guests. | |
16290246 | 2220 | Default is 1 (enabled) if in 64-bit or 32-bit PAE mode. |
fef07aae | 2221 | |
e23f62f7 MZ |
2222 | kvm-arm.vgic_v3_group0_trap= |
2223 | [KVM,ARM] Trap guest accesses to GICv3 group-0 | |
2224 | system registers | |
2225 | ||
182936ee MZ |
2226 | kvm-arm.vgic_v3_group1_trap= |
2227 | [KVM,ARM] Trap guest accesses to GICv3 group-1 | |
2228 | system registers | |
2229 | ||
ff89511e MZ |
2230 | kvm-arm.vgic_v3_common_trap= |
2231 | [KVM,ARM] Trap guest accesses to GICv3 common | |
2232 | system registers | |
2233 | ||
a7546054 MZ |
2234 | kvm-arm.vgic_v4_enable= |
2235 | [KVM,ARM] Allow use of GICv4 for direct injection of | |
2236 | LPIs. | |
2237 | ||
fef07aae AP |
2238 | kvm-intel.ept= [KVM,Intel] Disable extended page tables |
2239 | (virtualized MMU) support on capable Intel chips. | |
2240 | Default is 1 (enabled) | |
2241 | ||
2242 | kvm-intel.emulate_invalid_guest_state= | |
2243 | [KVM,Intel] Enable emulation of invalid guest states | |
2244 | Default is 0 (disabled) | |
2245 | ||
2246 | kvm-intel.flexpriority= | |
2247 | [KVM,Intel] Disable FlexPriority feature (TPR shadow). | |
2248 | Default is 1 (enabled) | |
2249 | ||
e1a72ae2 SL |
2250 | kvm-intel.nested= |
2251 | [KVM,Intel] Enable VMX nesting (nVMX). | |
2252 | Default is 0 (disabled) | |
2253 | ||
fef07aae AP |
2254 | kvm-intel.unrestricted_guest= |
2255 | [KVM,Intel] Disable unrestricted guest feature | |
2256 | (virtualized real and unpaged mode) on capable | |
2257 | Intel chips. Default is 1 (enabled) | |
2258 | ||
a399477e KRW |
2259 | kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault |
2260 | CVE-2018-3620. | |
2261 | ||
2262 | Valid arguments: never, cond, always | |
2263 | ||
2264 | always: L1D cache flush on every VMENTER. | |
2265 | cond: Flush L1D on VMENTER only when the code between | |
2266 | VMEXIT and VMENTER can leak host memory. | |
2267 | never: Disables the mitigation | |
2268 | ||
2269 | Default is cond (do L1 cache flush in specific instances) | |
2270 | ||
fef07aae AP |
2271 | kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification |
2272 | feature (tagged TLBs) on capable Intel chips. | |
2273 | Default is 1 (enabled) | |
2274 | ||
d90a7a0e JK |
2275 | l1tf= [X86] Control mitigation of the L1TF vulnerability on |
2276 | affected CPUs | |
2277 | ||
2278 | The kernel PTE inversion protection is unconditionally | |
2279 | enabled and cannot be disabled. | |
2280 | ||
2281 | full | |
2282 | Provides all available mitigations for the | |
2283 | L1TF vulnerability. Disables SMT and | |
2284 | enables all mitigations in the | |
2285 | hypervisors, i.e. unconditional L1D flush. | |
2286 | ||
2287 | SMT control and L1D flush control via the | |
2288 | sysfs interface is still possible after | |
2289 | boot. Hypervisors will issue a warning | |
2290 | when the first VM is started in a | |
2291 | potentially insecure configuration, | |
2292 | i.e. SMT enabled or L1D flush disabled. | |
2293 | ||
2294 | full,force | |
2295 | Same as 'full', but disables SMT and L1D | |
2296 | flush runtime control. Implies the | |
2297 | 'nosmt=force' command line option. | |
2298 | (i.e. sysfs control of SMT is disabled.) | |
2299 | ||
2300 | flush | |
2301 | Leaves SMT enabled and enables the default | |
2302 | hypervisor mitigation, i.e. conditional | |
2303 | L1D flush. | |
2304 | ||
2305 | SMT control and L1D flush control via the | |
2306 | sysfs interface is still possible after | |
2307 | boot. Hypervisors will issue a warning | |
2308 | when the first VM is started in a | |
2309 | potentially insecure configuration, | |
2310 | i.e. SMT enabled or L1D flush disabled. | |
2311 | ||
2312 | flush,nosmt | |
2313 | ||
2314 | Disables SMT and enables the default | |
2315 | hypervisor mitigation. | |
2316 | ||
2317 | SMT control and L1D flush control via the | |
2318 | sysfs interface is still possible after | |
2319 | boot. Hypervisors will issue a warning | |
2320 | when the first VM is started in a | |
2321 | potentially insecure configuration, | |
2322 | i.e. SMT enabled or L1D flush disabled. | |
2323 | ||
2324 | flush,nowarn | |
2325 | Same as 'flush', but hypervisors will not | |
2326 | warn when a VM is started in a potentially | |
2327 | insecure configuration. | |
2328 | ||
2329 | off | |
2330 | Disables hypervisor mitigations and doesn't | |
2331 | emit any warnings. | |
5b5e4d62 MH |
2332 | It also drops the swap size and available |
2333 | RAM limit restriction on both hypervisor and | |
2334 | bare metal. | |
d90a7a0e JK |
2335 | |
2336 | Default is 'flush'. | |
2337 | ||
65fd4cb6 | 2338 | For details see: Documentation/admin-guide/hw-vuln/l1tf.rst |
d90a7a0e | 2339 | |
1da177e4 LT |
2340 | l2cr= [PPC] |
2341 | ||
a78bfbfc RB |
2342 | l3cr= [PPC] |
2343 | ||
cd4f0ef7 | 2344 | lapic [X86-32,APIC] Enable the local APIC even if BIOS |
a9913044 | 2345 | disabled it. |
1da177e4 | 2346 | |
279f1461 SS |
2347 | lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline |
2348 | value for LAPIC timer one-shot implementation. Default | |
2349 | back to the programmable timer unit in the LAPIC. | |
2350 | ||
6cececfc | 2351 | lapic_timer_c2_ok [X86,APIC] trust the local apic timer |
ada9cfdd | 2352 | in C2 power state. |
e585bef8 | 2353 | |
fcb71f6f FC |
2354 | libata.dma= [LIBATA] DMA control |
2355 | libata.dma=0 Disable all PATA and SATA DMA | |
2356 | libata.dma=1 PATA and SATA Disk DMA only | |
2357 | libata.dma=2 ATAPI (CDROM) DMA only | |
16290246 | 2358 | libata.dma=4 Compact Flash DMA only |
fcb71f6f FC |
2359 | Combinations also work, so libata.dma=3 enables DMA |
2360 | for disks and CDROMs, but not CFs. | |
16290246 | 2361 | |
20308871 MP |
2362 | libata.ignore_hpa= [LIBATA] Ignore HPA limit |
2363 | libata.ignore_hpa=0 keep BIOS limits (default) | |
2364 | libata.ignore_hpa=1 ignore limits, using full disk | |
fcb71f6f | 2365 | |
78e70c23 DJ |
2366 | libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume |
2367 | when set. | |
2368 | Format: <int> | |
2369 | ||
33267325 TH |
2370 | libata.force= [LIBATA] Force configurations. The format is comma |
2371 | separated list of "[ID:]VAL" where ID is | |
4c44f309 | 2372 | PORT[.DEVICE]. PORT and DEVICE are decimal numbers |
33267325 TH |
2373 | matching port, link or device. Basically, it matches |
2374 | the ATA ID string printed on console by libata. If | |
2375 | the whole ID part is omitted, the last PORT and DEVICE | |
2376 | values are used. If ID hasn't been specified yet, the | |
2377 | configuration applies to all ports, links and devices. | |
2378 | ||
2379 | If only DEVICE is omitted, the parameter applies to | |
2380 | the port and all links and devices behind it. DEVICE | |
2381 | number of 0 either selects the first device or the | |
2382 | first fan-out link behind PMP device. It does not | |
2383 | select the host link. DEVICE number of 15 selects the | |
2384 | host link and device attached to it. | |
2385 | ||
2386 | The VAL specifies the configuration to force. As long | |
2387 | as there's no ambiguity shortcut notation is allowed. | |
2388 | For example, both 1.5 and 1.5G would work for 1.5Gbps. | |
2389 | The following configurations can be forced. | |
2390 | ||
2391 | * Cable type: 40c, 80c, short40c, unk, ign or sata. | |
2392 | Any ID with matching PORT is used. | |
2393 | ||
2394 | * SATA link speed limit: 1.5Gbps or 3.0Gbps. | |
2395 | ||
2396 | * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. | |
2397 | udma[/][16,25,33,44,66,100,133] notation is also | |
2398 | allowed. | |
2399 | ||
2400 | * [no]ncq: Turn on or off NCQ. | |
2401 | ||
d7b16e4f MP |
2402 | * [no]ncqtrim: Turn off queued DSM TRIM. |
2403 | ||
05944bdf | 2404 | * nohrst, nosrst, norst: suppress hard, soft |
6dddd7a7 | 2405 | and both resets. |
05944bdf | 2406 | |
ca6d43b0 DW |
2407 | * rstonce: only attempt one reset during |
2408 | hot-unplug link recovery | |
2409 | ||
43c9c591 TH |
2410 | * dump_id: dump IDENTIFY data. |
2411 | ||
966fbe19 VP |
2412 | * atapi_dmadir: Enable ATAPI DMADIR bridge support |
2413 | ||
b8bd6dc3 RJ |
2414 | * disable: Disable this device. |
2415 | ||
33267325 TH |
2416 | If there are multiple matching configurations changing |
2417 | the same attribute, the last one is used. | |
2418 | ||
95f72d1e | 2419 | memblock=debug [KNL] Enable memblock debug messages. |
7c4be253 | 2420 | |
1da177e4 | 2421 | load_ramdisk= [RAM] List of ramdisks to load from floppy |
e7751617 | 2422 | See Documentation/admin-guide/blockdev/ramdisk.rst. |
1da177e4 | 2423 | |
a6b25b67 RD |
2424 | lockd.nlm_grace_period=P [NFS] Assign grace period. |
2425 | Format: <integer> | |
1da177e4 | 2426 | |
a6b25b67 RD |
2427 | lockd.nlm_tcpport=N [NFS] Assign TCP port. |
2428 | Format: <integer> | |
2429 | ||
2430 | lockd.nlm_timeout=T [NFS] Assign timeout value. | |
2431 | Format: <integer> | |
2432 | ||
2433 | lockd.nlm_udpport=M [NFS] Assign UDP port. | |
2434 | Format: <integer> | |
1da177e4 | 2435 | |
000d388e MG |
2436 | lockdown= [SECURITY] |
2437 | { integrity | confidentiality } | |
2438 | Enable the kernel lockdown feature. If set to | |
2439 | integrity, kernel features that allow userland to | |
2440 | modify the running kernel are disabled. If set to | |
2441 | confidentiality, kernel features that allow userland | |
2442 | to extract confidential information from the kernel | |
2443 | are also disabled. | |
2444 | ||
ec4518aa PM |
2445 | locktorture.nreaders_stress= [KNL] |
2446 | Set the number of locking read-acquisition kthreads. | |
2447 | Defaults to being automatically set based on the | |
2448 | number of online CPUs. | |
2449 | ||
2450 | locktorture.nwriters_stress= [KNL] | |
2451 | Set the number of locking write-acquisition kthreads. | |
2452 | ||
2453 | locktorture.onoff_holdoff= [KNL] | |
2454 | Set time (s) after boot for CPU-hotplug testing. | |
2455 | ||
2456 | locktorture.onoff_interval= [KNL] | |
2457 | Set time (s) between CPU-hotplug operations, or | |
2458 | zero to disable CPU-hotplug testing. | |
2459 | ||
2460 | locktorture.shuffle_interval= [KNL] | |
2461 | Set task-shuffle interval (jiffies). Shuffling | |
2462 | tasks allows some CPUs to go into dyntick-idle | |
2463 | mode during the locktorture test. | |
2464 | ||
2465 | locktorture.shutdown_secs= [KNL] | |
2466 | Set time (s) after boot system shutdown. This | |
2467 | is useful for hands-off automated testing. | |
2468 | ||
2469 | locktorture.stat_interval= [KNL] | |
2470 | Time (s) between statistics printk()s. | |
2471 | ||
2472 | locktorture.stutter= [KNL] | |
2473 | Time (s) to stutter testing, for example, | |
2474 | specifying five seconds causes the test to run for | |
2475 | five seconds, wait for five seconds, and so on. | |
2476 | This tests the locking primitive's ability to | |
2477 | transition abruptly to and from idle. | |
2478 | ||
ec4518aa PM |
2479 | locktorture.torture_type= [KNL] |
2480 | Specify the locking implementation to test. | |
2481 | ||
2482 | locktorture.verbose= [KNL] | |
2483 | Enable additional printk() statements. | |
2484 | ||
1da177e4 LT |
2485 | logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver |
2486 | Format: <irq> | |
2487 | ||
2488 | loglevel= All Kernel Messages with a loglevel smaller than the | |
2489 | console loglevel will be printed to the console. It can | |
2490 | also be changed with klogd or other programs. The | |
2491 | loglevels are defined as follows: | |
2492 | ||
2493 | 0 (KERN_EMERG) system is unusable | |
2494 | 1 (KERN_ALERT) action must be taken immediately | |
2495 | 2 (KERN_CRIT) critical conditions | |
2496 | 3 (KERN_ERR) error conditions | |
2497 | 4 (KERN_WARNING) warning conditions | |
2498 | 5 (KERN_NOTICE) normal but significant condition | |
2499 | 6 (KERN_INFO) informational | |
2500 | 7 (KERN_DEBUG) debug-level messages | |
2501 | ||
c756d08a | 2502 | log_buf_len=n[KMG] Sets the size of the printk ring buffer, |
23b2899f LR |
2503 | in bytes. n must be a power of two and greater |
2504 | than the minimal size. The minimal size is defined | |
2505 | by LOG_BUF_SHIFT kernel config parameter. There is | |
2506 | also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter | |
2507 | that allows to increase the default size depending on | |
2508 | the number of CPUs. See init/Kconfig for more details. | |
1da177e4 | 2509 | |
accaa24c RD |
2510 | logo.nologo [FB] Disables display of the built-in Linux logo. |
2511 | This may be used to provide more screen space for | |
2512 | kernel log messages and is useful when debugging | |
2513 | kernel boot problems. | |
2514 | ||
1da177e4 LT |
2515 | lp=0 [LP] Specify parallel ports to use, e.g, |
2516 | lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses | |
2517 | lp=reset first parallel port). 'lp=0' disables the | |
2518 | lp=auto printer driver. 'lp=reset' (which can be | |
2519 | specified in addition to the ports) causes | |
2520 | attached printers to be reset. Using | |
2521 | lp=port1,port2,... specifies the parallel ports | |
2522 | to associate lp devices with, starting with | |
2523 | lp0. A port specification may be 'none' to skip | |
2524 | that lp device, or a parport name such as | |
2525 | 'parport0'. Specifying 'lp=auto' instead of a | |
2526 | port specification list means that device IDs | |
2527 | from each port should be examined, to see if | |
2528 | an IEEE 1284-compliant printer is attached; if | |
2529 | so, the driver will manage that printer. | |
2530 | See also header of drivers/char/lp.c. | |
2531 | ||
2532 | lpj=n [KNL] | |
2533 | Sets loops_per_jiffy to given constant, thus avoiding | |
2534 | time-consuming boot-time autodetection (up to 250 ms per | |
2535 | CPU). 0 enables autodetection (default). To determine | |
2536 | the correct value for your kernel, boot with normal | |
2537 | autodetection and see what value is printed. Note that | |
2538 | on SMP systems the preset will be applied to all CPUs, | |
2539 | which is likely to cause problems if your CPUs need | |
2540 | significantly divergent settings. An incorrect value | |
2541 | will cause delays in the kernel to be wrong, leading to | |
2542 | unpredictable I/O errors and other breakage. Although | |
2543 | unlikely, in the extreme case this might damage your | |
2544 | hardware. | |
2545 | ||
2546 | ltpc= [NET] | |
2547 | Format: <io>,<irq>,<dma> | |
2548 | ||
9b8c7c14 KC |
2549 | lsm.debug [SECURITY] Enable LSM initialization debugging output. |
2550 | ||
79f7865d KC |
2551 | lsm=lsm1,...,lsmN |
2552 | [SECURITY] Choose order of LSM initialization. This | |
89a9684e | 2553 | overrides CONFIG_LSM, and the "security=" parameter. |
79f7865d | 2554 | |
16290246 | 2555 | machvec= [IA-64] Force the use of a particular machine-vector |
a9913044 | 2556 | (machvec) in a generic kernel. |
df43acac | 2557 | Example: machvec=hpzx1 |
1da177e4 | 2558 | |
3209e70e WZ |
2559 | machtype= [Loongson] Share the same kernel image file between different |
2560 | yeeloong laptop. | |
2561 | Example: machtype=lemote-yeeloong-2f-7inch | |
2562 | ||
0cb55ad2 RD |
2563 | max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater |
2564 | than or equal to this physical address is ignored. | |
1da177e4 LT |
2565 | |
2566 | maxcpus= [SMP] Maximum number of processors that an SMP kernel | |
7c142bfe BH |
2567 | will bring up during bootup. maxcpus=n : n >= 0 limits |
2568 | the kernel to bring up 'n' processors. Surely after | |
2569 | bootup you can bring up the other plugged cpu by executing | |
2570 | "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus | |
2571 | only takes effect during system bootup. | |
2572 | While n=0 is a special case, it is equivalent to "nosmp", | |
2573 | which also disables the IO APIC. | |
1da177e4 | 2574 | |
d134b00b KS |
2575 | max_loop= [LOOP] The number of loop block devices that get |
2576 | (loop.max_loop) unconditionally pre-created at init time. The default | |
2577 | number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead | |
2578 | of statically allocating a predefined number, loop | |
2579 | devices can be requested on-demand with the | |
2580 | /dev/loop-control interface. | |
2b2c3750 | 2581 | |
cd4f0ef7 | 2582 | mce [X86-32] Machine Check Exception |
1da177e4 | 2583 | |
cb1aaebe | 2584 | mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst |
909dd324 | 2585 | |
1da177e4 | 2586 | md= [HW] RAID subsystems devices and level |
e52347bd | 2587 | See Documentation/admin-guide/md.rst. |
a9913044 | 2588 | |
1da177e4 LT |
2589 | mdacon= [MDA] |
2590 | Format: <first>,<last> | |
2591 | Specifies range of consoles to be captured by the MDA. | |
a9913044 | 2592 | |
bc124170 TG |
2593 | mds= [X86,INTEL] |
2594 | Control mitigation for the Micro-architectural Data | |
2595 | Sampling (MDS) vulnerability. | |
2596 | ||
2597 | Certain CPUs are vulnerable to an exploit against CPU | |
2598 | internal buffers which can forward information to a | |
2599 | disclosure gadget under certain conditions. | |
2600 | ||
2601 | In vulnerable processors, the speculatively | |
2602 | forwarded data can be used in a cache side channel | |
2603 | attack, to access data to which the attacker does | |
2604 | not have direct access. | |
2605 | ||
2606 | This parameter controls the MDS mitigation. The | |
2607 | options are: | |
2608 | ||
d71eb0ce JP |
2609 | full - Enable MDS mitigation on vulnerable CPUs |
2610 | full,nosmt - Enable MDS mitigation and disable | |
2611 | SMT on vulnerable CPUs | |
2612 | off - Unconditionally disable MDS mitigation | |
bc124170 | 2613 | |
64870ed1 WL |
2614 | On TAA-affected machines, mds=off can be prevented by |
2615 | an active TAA mitigation as both vulnerabilities are | |
2616 | mitigated with the same mechanism so in order to disable | |
2617 | this mitigation, you need to specify tsx_async_abort=off | |
2618 | too. | |
2619 | ||
bc124170 TG |
2620 | Not specifying this option is equivalent to |
2621 | mds=full. | |
2622 | ||
5999bbe7 TG |
2623 | For details see: Documentation/admin-guide/hw-vuln/mds.rst |
2624 | ||
1da177e4 | 2625 | mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory |
f3cd4c86 BH |
2626 | Amount of memory to be used in cases as follows: |
2627 | ||
2628 | 1 for test; | |
2629 | 2 when the kernel is not able to see the whole system memory; | |
2630 | 3 memory that lies after 'mem=' boundary is excluded from | |
2631 | the hypervisor, then assigned to KVM guests. | |
2632 | ||
fbb97d87 WC |
2633 | [X86] Work as limiting max address. Use together |
2634 | with memmap= to avoid physical address space collisions. | |
2635 | Without memmap= PCI devices could be placed at addresses | |
2636 | belonging to unused RAM. | |
1da177e4 | 2637 | |
f3cd4c86 BH |
2638 | Note that this only takes effects during boot time since |
2639 | in above case 3, memory may need be hot added after boot | |
2640 | if system memory of hypervisor is not sufficient. | |
2641 | ||
cd4f0ef7 | 2642 | mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel |
1da177e4 LT |
2643 | memory. |
2644 | ||
6902aa84 PM |
2645 | memchunk=nn[KMG] |
2646 | [KNL,SH] Allow user to override the default size for | |
2647 | per-device physically contiguous DMA buffers. | |
2648 | ||
6dddd7a7 | 2649 | memhp_default_state=online/offline |
86dd995d VK |
2650 | [KNL] Set the initial state for the memory hotplug |
2651 | onlining policy. If not specified, the default value is | |
2652 | set according to the | |
2653 | CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config | |
2654 | option. | |
cb1aaebe | 2655 | See Documentation/admin-guide/mm/memory-hotplug.rst. |
86dd995d | 2656 | |
6cececfc | 2657 | memmap=exactmap [KNL,X86] Enable setting of an exact |
1da177e4 LT |
2658 | E820 memory map, as specified by the user. |
2659 | Such memmap=exactmap lines can be constructed based on | |
2660 | BIOS output or other requirements. See the memmap=nn@ss | |
2661 | option description. | |
2662 | ||
2663 | memmap=nn[KMG]@ss[KMG] | |
277cba1d RD |
2664 | [KNL] Force usage of a specific region of memory. |
2665 | Region of memory to be used is from ss to ss+nn. | |
8fcc9bc3 BH |
2666 | If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG], |
2667 | which limits max address to nn[KMG]. | |
2668 | Multiple different regions can be specified, | |
2669 | comma delimited. | |
2670 | Example: | |
2671 | memmap=100M@2G,100M#3G,1G!1024G | |
1da177e4 LT |
2672 | |
2673 | memmap=nn[KMG]#ss[KMG] | |
2674 | [KNL,ACPI] Mark specific memory as ACPI data. | |
277cba1d | 2675 | Region of memory to be marked is from ss to ss+nn. |
1da177e4 LT |
2676 | |
2677 | memmap=nn[KMG]$ss[KMG] | |
2678 | [KNL,ACPI] Mark specific memory as reserved. | |
277cba1d | 2679 | Region of memory to be reserved is from ss to ss+nn. |
1312848e PM |
2680 | Example: Exclude memory from 0x18690000-0x1869ffff |
2681 | memmap=64K$0x18690000 | |
2682 | or | |
2683 | memmap=0x10000$0x18690000 | |
8fcc9bc3 BH |
2684 | Some bootloaders may need an escape character before '$', |
2685 | like Grub2, otherwise '$' and the following number | |
2686 | will be eaten. | |
1da177e4 | 2687 | |
ec776ef6 CH |
2688 | memmap=nn[KMG]!ss[KMG] |
2689 | [KNL,X86] Mark specific memory as protected. | |
2690 | Region of memory to be used, from ss to ss+nn. | |
2691 | The memory region may be marked as e820 type 12 (0xc) | |
2692 | and is NVDIMM or ADR memory. | |
2693 | ||
ef61f8a3 JS |
2694 | memmap=<size>%<offset>-<oldtype>+<newtype> |
2695 | [KNL,ACPI] Convert memory within the specified region | |
2696 | from <oldtype> to <newtype>. If "-<oldtype>" is left | |
2697 | out, the whole region will be marked as <newtype>, | |
2698 | even if previously unavailable. If "+<newtype>" is left | |
2699 | out, matching memory will be removed. Types are | |
2700 | specified as e820 types, e.g., 1 = RAM, 2 = reserved, | |
2701 | 3 = ACPI, 12 = PRAM. | |
2702 | ||
9f077871 JF |
2703 | memory_corruption_check=0/1 [X86] |
2704 | Some BIOSes seem to corrupt the first 64k of | |
2705 | memory when doing things like suspend/resume. | |
2706 | Setting this option will scan the memory | |
2707 | looking for corruption. Enabling this will | |
2708 | both detect corruption and prevent the kernel | |
2709 | from using the memory being corrupted. | |
2710 | However, its intended as a diagnostic tool; if | |
2711 | repeatable BIOS-originated corruption always | |
2712 | affects the same memory, you can use memmap= | |
2713 | to prevent the kernel from using that memory. | |
2714 | ||
2715 | memory_corruption_check_size=size [X86] | |
2716 | By default it checks for corruption in the low | |
2717 | 64k, making this memory unavailable for normal | |
2718 | use. Use this parameter to scan for | |
2719 | corruption in more or less memory. | |
2720 | ||
2721 | memory_corruption_check_period=seconds [X86] | |
2722 | By default it checks for corruption every 60 | |
2723 | seconds. Use this parameter to check at some | |
2724 | other rate. 0 disables periodic checking. | |
2725 | ||
d90fe2ac | 2726 | memtest= [KNL,X86,ARM,PPC] Enable memtest |
c64df707 | 2727 | Format: <integer> |
c64df707 | 2728 | default : 0 <disable> |
9e5f6cf5 AH |
2729 | Specifies the number of memtest passes to be |
2730 | performed. Each pass selects another test | |
2731 | pattern from a given set of patterns. Memtest | |
2732 | fills the memory with this pattern, validates | |
2733 | memory contents and reserves bad memory | |
2734 | regions that are detected. | |
c64df707 | 2735 | |
c262f3b9 TL |
2736 | mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control |
2737 | Valid arguments: on, off | |
2738 | Default (depends on kernel configuration option): | |
2739 | on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y) | |
2740 | off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n) | |
2741 | mem_encrypt=on: Activate SME | |
2742 | mem_encrypt=off: Do not activate SME | |
2743 | ||
2f5947df | 2744 | Refer to Documentation/virt/kvm/amd-memory-encryption.rst |
c262f3b9 TL |
2745 | for details on when memory encryption can be activated. |
2746 | ||
406e7938 RW |
2747 | mem_sleep_default= [SUSPEND] Default system suspend mode: |
2748 | s2idle - Suspend-To-Idle | |
2749 | shallow - Power-On Suspend or equivalent (if supported) | |
2750 | deep - Suspend-To-RAM or equivalent (if supported) | |
58e7cb9e | 2751 | See Documentation/admin-guide/pm/sleep-states.rst. |
406e7938 | 2752 | |
1da177e4 | 2753 | meye.*= [HW] Set MotionEye Camera parameters |
32e2eae2 | 2754 | See Documentation/admin-guide/media/meye.rst. |
1da177e4 | 2755 | |
8f36881b AS |
2756 | mfgpt_irq= [IA-32] Specify the IRQ to use for the |
2757 | Multi-Function General Purpose Timers on AMD Geode | |
2758 | platforms. | |
2759 | ||
e6c4dc6c WT |
2760 | mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when |
2761 | the BIOS has incorrectly applied a workaround. TinyBIOS | |
2762 | version 0.98 is known to be affected, 0.99 fixes the | |
2763 | problem by letting the user disable the workaround. | |
2764 | ||
1da177e4 LT |
2765 | mga= [HW,DRM] |
2766 | ||
1c207f95 RD |
2767 | min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this |
2768 | physical address is ignored. | |
2769 | ||
39f45d7b MP |
2770 | mini2440= [ARM,HW,KNL] |
2771 | Format:[0..2][b][c][t] | |
2772 | Default: "0tb" | |
2773 | MINI2440 configuration specification: | |
2774 | 0 - The attached screen is the 3.5" TFT | |
2775 | 1 - The attached screen is the 7" TFT | |
2776 | 2 - The VGA Shield is attached (1024x768) | |
2777 | Leaving out the screen size parameter will not load | |
2778 | the TFT driver, and the framebuffer will be left | |
2779 | unconfigured. | |
2780 | b - Enable backlight. The TFT backlight pin will be | |
2781 | linked to the kernel VESA blanking code and a GPIO | |
2782 | LED. This parameter is not necessary when using the | |
2783 | VGA shield. | |
2784 | c - Enable the s3c camera interface. | |
2785 | t - Reserved for enabling touchscreen support. The | |
2786 | touchscreen support is not enabled in the mainstream | |
2787 | kernel as of 2.6.30, a preliminary port can be found | |
2788 | in the "bleeding edge" mini2440 support kernel at | |
2789 | http://repo.or.cz/w/linux-2.6/mini2440.git | |
2790 | ||
98af8452 | 2791 | mitigations= |
a111b7c0 JP |
2792 | [X86,PPC,S390,ARM64] Control optional mitigations for |
2793 | CPU vulnerabilities. This is a set of curated, | |
d68be4c4 JP |
2794 | arch-independent options, each of which is an |
2795 | aggregation of existing arch-specific options. | |
98af8452 JP |
2796 | |
2797 | off | |
2798 | Disable all optional CPU mitigations. This | |
2799 | improves system performance, but it may also | |
2800 | expose users to several CPU vulnerabilities. | |
782e69ef | 2801 | Equivalent to: nopti [X86,PPC] |
a111b7c0 | 2802 | kpti=0 [ARM64] |
a2059825 | 2803 | nospectre_v1 [X86,PPC] |
0336e04a | 2804 | nobp=0 [S390] |
a111b7c0 | 2805 | nospectre_v2 [X86,PPC,S390,ARM64] |
d68be4c4 | 2806 | spectre_v2_user=off [X86] |
782e69ef | 2807 | spec_store_bypass_disable=off [X86,PPC] |
a111b7c0 | 2808 | ssbd=force-off [ARM64] |
d68be4c4 | 2809 | l1tf=off [X86] |
5c14068f | 2810 | mds=off [X86] |
a7a248c5 | 2811 | tsx_async_abort=off [X86] |
b8e8c830 PB |
2812 | kvm.nx_huge_pages=off [X86] |
2813 | ||
2814 | Exceptions: | |
2815 | This does not have any effect on | |
2816 | kvm.nx_huge_pages when | |
2817 | kvm.nx_huge_pages=force. | |
98af8452 JP |
2818 | |
2819 | auto (default) | |
2820 | Mitigate all CPU vulnerabilities, but leave SMT | |
2821 | enabled, even if it's vulnerable. This is for | |
2822 | users who don't want to be surprised by SMT | |
2823 | getting disabled across kernel upgrades, or who | |
2824 | have other ways of avoiding SMT-based attacks. | |
d68be4c4 | 2825 | Equivalent to: (default behavior) |
98af8452 JP |
2826 | |
2827 | auto,nosmt | |
2828 | Mitigate all CPU vulnerabilities, disabling SMT | |
2829 | if needed. This is for users who always want to | |
2830 | be fully mitigated, even if it means losing SMT. | |
d68be4c4 | 2831 | Equivalent to: l1tf=flush,nosmt [X86] |
5c14068f | 2832 | mds=full,nosmt [X86] |
a7a248c5 | 2833 | tsx_async_abort=full,nosmt [X86] |
98af8452 | 2834 | |
6b74ab97 MG |
2835 | mminit_loglevel= |
2836 | [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this | |
2837 | parameter allows control of the logging verbosity for | |
2838 | the additional memory initialisation checks. A value | |
2839 | of 0 disables mminit logging and a level of 4 will | |
2840 | log everything. Information is printed at KERN_DEBUG | |
2841 | so loglevel=8 may also need to be specified. | |
2842 | ||
106a4ee2 RR |
2843 | module.sig_enforce |
2844 | [KNL] When CONFIG_MODULE_SIG is set, this means that | |
2845 | modules without (valid) signatures will fail to load. | |
2a039be7 | 2846 | Note that if CONFIG_MODULE_SIG_FORCE is set, that |
106a4ee2 RR |
2847 | is always true, so this option does nothing. |
2848 | ||
be7de5f9 PB |
2849 | module_blacklist= [KNL] Do not load a comma-separated list of |
2850 | modules. Useful for debugging problem modules. | |
2851 | ||
1da177e4 LT |
2852 | mousedev.tap_time= |
2853 | [MOUSE] Maximum time between finger touching and | |
2854 | leaving touchpad surface for touch to be considered | |
2855 | a tap and be reported as a left button click (for | |
2856 | touchpads working in absolute mode only). | |
2857 | Format: <msecs> | |
2858 | mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices | |
2859 | reporting absolute coordinates, such as tablets | |
2860 | mousedev.yres= [MOUSE] Vertical screen resolution, used for devices | |
2861 | reporting absolute coordinates, such as tablets | |
2862 | ||
a5c6d650 DR |
2863 | movablecore= [KNL,X86,IA-64,PPC] |
2864 | Format: nn[KMGTPE] | nn% | |
2865 | This parameter is the complement to kernelcore=, it | |
2866 | specifies the amount of memory used for migratable | |
2867 | allocations. If both kernelcore and movablecore is | |
2868 | specified, then kernelcore will be at *least* the | |
2869 | specified value but may be more. If movablecore on its | |
2870 | own is specified, the administrator must be careful | |
0cb55ad2 RD |
2871 | that the amount of memory usable for all allocations |
2872 | is not too small. | |
2873 | ||
f70029bb MH |
2874 | movable_node [KNL] Boot-time switch to make hotplugable memory |
2875 | NUMA nodes to be movable. This means that the memory | |
2876 | of such nodes will be usable only for movable | |
2877 | allocations which rules out almost all kernel | |
2878 | allocations. Use with caution! | |
c5320926 | 2879 | |
1da177e4 LT |
2880 | MTD_Partition= [MTD] |
2881 | Format: <name>,<region-number>,<size>,<offset> | |
2882 | ||
a9913044 RD |
2883 | MTD_Region= [MTD] Format: |
2884 | <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] | |
1da177e4 LT |
2885 | |
2886 | mtdparts= [MTD] | |
fb251124 | 2887 | See drivers/mtd/parsers/cmdlinepart.c |
1da177e4 | 2888 | |
4e89a2d8 WS |
2889 | multitce=off [PPC] This parameter disables the use of the pSeries |
2890 | firmware feature for updating multiple TCE entries | |
2891 | at a time. | |
2892 | ||
5988af23 RH |
2893 | onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration |
2894 | ||
2895 | Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] | |
2896 | ||
2897 | boundary - index of last SLC block on Flex-OneNAND. | |
2898 | The remaining blocks are configured as MLC blocks. | |
2899 | lock - Configure if Flex-OneNAND boundary should be locked. | |
2900 | Once locked, the boundary cannot be changed. | |
2901 | 1 indicates lock status, 0 indicates unlock status. | |
2902 | ||
9db829f4 BD |
2903 | mtdset= [ARM] |
2904 | ARM/S3C2412 JIVE boot control | |
2905 | ||
2906 | See arch/arm/mach-s3c2412/mach-jive.c | |
2907 | ||
1da177e4 | 2908 | mtouchusb.raw_coordinates= |
a9913044 RD |
2909 | [HW] Make the MicroTouch USB driver use raw coordinates |
2910 | ('y', default) or cooked coordinates ('n') | |
1da177e4 | 2911 | |
0cb55ad2 | 2912 | mtrr_chunk_size=nn[KMG] [X86] |
19f59460 | 2913 | used for mtrr cleanup. It is largest continuous chunk |
0cb55ad2 RD |
2914 | that could hold holes aka. UC entries. |
2915 | ||
2916 | mtrr_gran_size=nn[KMG] [X86] | |
2917 | Used for mtrr cleanup. It is granularity of mtrr block. | |
2918 | Default is 1. | |
2919 | Large value could prevent small alignment from | |
2920 | using up MTRRs. | |
2921 | ||
2922 | mtrr_spare_reg_nr=n [X86] | |
2923 | Format: <integer> | |
2924 | Range: 0,7 : spare reg number | |
2925 | Default : 1 | |
2926 | Used for mtrr cleanup. It is spare mtrr entries number. | |
2927 | Set to 2 or more if your graphical card needs more. | |
2928 | ||
1da177e4 LT |
2929 | n2= [NET] SDL Inc. RISCom/N2 synchronous serial card |
2930 | ||
1da177e4 LT |
2931 | netdev= [NET] Network devices parameters |
2932 | Format: <irq>,<io>,<mem_start>,<mem_end>,<name> | |
2933 | Note that mem_start is often overloaded to mean | |
2934 | something different and driver-specific. | |
a9913044 RD |
2935 | This usage is only documented in each driver source |
2936 | file if at all. | |
2937 | ||
58401572 KPO |
2938 | nf_conntrack.acct= |
2939 | [NETFILTER] Enable connection tracking flow accounting | |
2940 | 0 to disable accounting | |
2941 | 1 to enable accounting | |
d70a011d | 2942 | Default value is 0. |
58401572 | 2943 | |
306a0753 | 2944 | nfsaddrs= [NFS] Deprecated. Use ip= instead. |
3eb30c51 | 2945 | See Documentation/admin-guide/nfs/nfsroot.rst. |
1da177e4 LT |
2946 | |
2947 | nfsroot= [NFS] nfs root filesystem for disk-less boxes. | |
3eb30c51 | 2948 | See Documentation/admin-guide/nfs/nfsroot.rst. |
1da177e4 | 2949 | |
306a0753 | 2950 | nfsrootdebug [NFS] enable nfsroot debugging messages. |
3eb30c51 | 2951 | See Documentation/admin-guide/nfs/nfsroot.rst. |
306a0753 | 2952 | |
5405fc44 TM |
2953 | nfs.callback_nr_threads= |
2954 | [NFSv4] set the total number of threads that the | |
2955 | NFS client will assign to service NFSv4 callback | |
2956 | requests. | |
2957 | ||
a72b4422 TM |
2958 | nfs.callback_tcpport= |
2959 | [NFS] set the TCP port on which the NFSv4 callback | |
2960 | channel should listen. | |
2961 | ||
e571cbf1 TM |
2962 | nfs.cache_getent= |
2963 | [NFS] sets the pathname to the program which is used | |
2964 | to update the NFS client cache entries. | |
2965 | ||
2966 | nfs.cache_getent_timeout= | |
2967 | [NFS] sets the timeout after which an attempt to | |
2968 | update a cache entry is deemed to have failed. | |
2969 | ||
58df095b TM |
2970 | nfs.idmap_cache_timeout= |
2971 | [NFS] set the maximum lifetime for idmapper cache | |
2972 | entries. | |
2973 | ||
f43bf0be TM |
2974 | nfs.enable_ino64= |
2975 | [NFS] enable 64-bit inode numbers. | |
2976 | If zero, the NFS client will fake up a 32-bit inode | |
2977 | number for the readdir() and stat() syscalls instead | |
2978 | of returning the full 64-bit number. | |
2979 | The default is to return 64-bit inode numbers. | |
2980 | ||
5405fc44 TM |
2981 | nfs.max_session_cb_slots= |
2982 | [NFSv4.1] Sets the maximum number of session | |
2983 | slots the client will assign to the callback | |
2984 | channel. This determines the maximum number of | |
2985 | callbacks the client will process in parallel for | |
2986 | a particular server. | |
2987 | ||
ef159e91 TM |
2988 | nfs.max_session_slots= |
2989 | [NFSv4.1] Sets the maximum number of session slots | |
2990 | the client will attempt to negotiate with the server. | |
2991 | This limits the number of simultaneous RPC requests | |
2992 | that the client can send to the NFSv4.1 server. | |
2993 | Note that there is little point in setting this | |
2994 | value higher than the max_tcp_slot_table_limit. | |
2995 | ||
b064eca2 | 2996 | nfs.nfs4_disable_idmapping= |
074b1d12 TM |
2997 | [NFSv4] When set to the default of '1', this option |
2998 | ensures that both the RPC level authentication | |
2999 | scheme and the NFS level operations agree to use | |
3000 | numeric uids/gids if the mount is using the | |
3001 | 'sec=sys' security flavour. In effect it is | |
3002 | disabling idmapping, which can make migration from | |
3003 | legacy NFSv2/v3 systems to NFSv4 easier. | |
3004 | Servers that do not support this mode of operation | |
3005 | will be autodetected by the client, and it will fall | |
3006 | back to using the idmapper. | |
3007 | To turn off this behaviour, set the value to '0'. | |
6f2ea7f2 CL |
3008 | nfs.nfs4_unique_id= |
3009 | [NFS4] Specify an additional fixed unique ident- | |
3010 | ification string that NFSv4 clients can insert into | |
3011 | their nfs_client_id4 string. This is typically a | |
3012 | UUID that is generated at system install time. | |
b064eca2 | 3013 | |
db8ac8ba WAA |
3014 | nfs.send_implementation_id = |
3015 | [NFSv4.1] Send client implementation identification | |
3016 | information in exchange_id requests. | |
3017 | If zero, no implementation identification information | |
3018 | will be sent. | |
3019 | The default is to send the implementation identification | |
3020 | information. | |
e52347bd | 3021 | |
f6de7a39 TM |
3022 | nfs.recover_lost_locks = |
3023 | [NFSv4] Attempt to recover locks that were lost due | |
3024 | to a lease timeout on the server. Please note that | |
3025 | doing this risks data corruption, since there are | |
3026 | no guarantees that the file will remain unchanged | |
3027 | after the locks are lost. | |
3028 | If you want to enable the kernel legacy behaviour of | |
3029 | attempting to recover these locks, then set this | |
3030 | parameter to '1'. | |
3031 | The default parameter value of '0' causes the kernel | |
3032 | not to attempt recovery of lost locks. | |
db8ac8ba | 3033 | |
bbf58bf3 TM |
3034 | nfs4.layoutstats_timer = |
3035 | [NFSv4.2] Change the rate at which the kernel sends | |
3036 | layoutstats to the pNFS metadata server. | |
3037 | ||
3038 | Setting this to value to 0 causes the kernel to use | |
3039 | whatever value is the default set by the layout | |
3040 | driver. A non-zero value sets the minimum interval | |
3041 | in seconds between layoutstats transmissions. | |
3042 | ||
e9541ce8 BF |
3043 | nfsd.nfs4_disable_idmapping= |
3044 | [NFSv4] When set to the default of '1', the NFSv4 | |
3045 | server will return only numeric uids and gids to | |
3046 | clients using auth_sys, and will accept numeric uids | |
3047 | and gids from such clients. This is intended to ease | |
3048 | migration from NFSv2/v3. | |
db8ac8ba | 3049 | |
c0c74acb | 3050 | nmi_debug= [KNL,SH] Specify one or more actions to take |
e7ba176b HS |
3051 | when a NMI is triggered. |
3052 | Format: [state][,regs][,debounce][,die] | |
3053 | ||
6cececfc | 3054 | nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels |
fef2c9bc | 3055 | Format: [panic,][nopanic,][num] |
195daf66 | 3056 | Valid num: 0 or 1 |
334bb79c PK |
3057 | 0 - turn hardlockup detector in nmi_watchdog off |
3058 | 1 - turn hardlockup detector in nmi_watchdog on | |
0cb55ad2 | 3059 | When panic is specified, panic when an NMI watchdog |
93285c01 ZD |
3060 | timeout occurs (or 'nopanic' to not panic on an NMI |
3061 | watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) | |
3062 | To disable both hard and soft lockup detectors, | |
334bb79c | 3063 | please see 'nowatchdog'. |
0cb55ad2 RD |
3064 | This is useful when you use a panic=... timeout and |
3065 | need the box quickly up again. | |
1da177e4 | 3066 | |
d22881dc SW |
3067 | These settings can be accessed at runtime via |
3068 | the nmi_watchdog and hardlockup_panic sysctls. | |
3069 | ||
bff38771 AV |
3070 | netpoll.carrier_timeout= |
3071 | [NET] Specifies amount of time (in seconds) that | |
3072 | netpoll should wait for a carrier. By default netpoll | |
3073 | waits 4 seconds. | |
3074 | ||
cd4f0ef7 | 3075 | no387 [BUGS=X86-32] Tells the kernel to use the 387 maths |
1da177e4 LT |
3076 | emulation library even if a 387 maths coprocessor |
3077 | is present. | |
3078 | ||
372fddf7 KS |
3079 | no5lvl [X86-64] Disable 5-level paging mode. Forces |
3080 | kernel to use 4-level paging instead. | |
3081 | ||
0cb55ad2 RD |
3082 | no_console_suspend |
3083 | [HW] Never suspend the console | |
3084 | Disable suspending of consoles during suspend and | |
3085 | hibernate operations. Once disabled, debugging | |
3086 | messages can reach various consoles while the rest | |
3087 | of the system is being put to sleep (ie, while | |
3088 | debugging driver suspend/resume hooks). This may | |
3089 | not work reliably with all consoles, but is known | |
3090 | to work with serial and VGA consoles. | |
134620f7 YZ |
3091 | To facilitate more flexible debugging, we also add |
3092 | console_suspend, a printk module parameter to control | |
3093 | it. Users could use console_suspend (usually | |
3094 | /sys/module/printk/parameters/console_suspend) to | |
3095 | turn on/off it dynamically. | |
0cb55ad2 | 3096 | |
c6c40533 KS |
3097 | novmcoredd [KNL,KDUMP] |
3098 | Disable device dump. Device dump allows drivers to | |
3099 | append dump data to vmcore so you can collect driver | |
3100 | specified debug info. Drivers can append the data | |
3101 | without any limit and this data is stored in memory, | |
3102 | so this may cause significant memory stress. Disabling | |
3103 | device dump can help save memory but the driver debug | |
3104 | data will be no longer available. This parameter | |
3105 | is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP | |
3106 | is set. | |
3107 | ||
c1aee215 CL |
3108 | noaliencache [MM, NUMA, SLAB] Disables the allocation of alien |
3109 | caches in the slab allocator. Saves per-node memory, | |
3110 | but will impact performance. | |
3395ee05 | 3111 | |
a9913044 RD |
3112 | noalign [KNL,ARM] |
3113 | ||
686140a1 VG |
3114 | noaltinstr [S390] Disables alternative instructions patching |
3115 | (CPU alternatives feature). | |
3116 | ||
1da177e4 LT |
3117 | noapic [SMP,APIC] Tells the kernel to not make use of any |
3118 | IOAPICs that may be present in the system. | |
3119 | ||
5091faa4 MG |
3120 | noautogroup Disable scheduler automatic task group creation. |
3121 | ||
1da177e4 LT |
3122 | nobats [PPC] Do not use BATs for mapping kernel lowmem |
3123 | on "Classic" PPC cores. | |
3124 | ||
3125 | nocache [ARM] | |
a9913044 | 3126 | |
0cb55ad2 RD |
3127 | noclflush [BUGS=X86] Don't use the CLFLUSH instruction |
3128 | ||
163ecdff SN |
3129 | nodelayacct [KNL] Disable per-task delay accounting |
3130 | ||
6902aa84 PM |
3131 | nodsp [SH] Disable hardware DSP at boot time. |
3132 | ||
b2e0a54a | 3133 | noefi Disable EFI runtime services support. |
8b2cb7a8 | 3134 | |
1da177e4 LT |
3135 | noexec [IA-64] |
3136 | ||
6cececfc | 3137 | noexec [X86] |
f5a1b191 | 3138 | On X86-32 available only on PAE configured kernels. |
1da177e4 | 3139 | noexec=on: enable non-executable mappings (default) |
f5a1b191 JS |
3140 | noexec=off: disable non-executable mappings |
3141 | ||
de78a9c4 | 3142 | nosmap [X86,PPC] |
52b6179a PA |
3143 | Disable SMAP (Supervisor Mode Access Prevention) |
3144 | even if it is supported by processor. | |
3145 | ||
0fb1c25a | 3146 | nosmep [X86,PPC] |
52b6179a | 3147 | Disable SMEP (Supervisor Mode Execution Prevention) |
de5397ad FY |
3148 | even if it is supported by processor. |
3149 | ||
f5a1b191 JS |
3150 | noexec32 [X86-64] |
3151 | This affects only 32-bit executables. | |
3152 | noexec32=on: enable non-executable mappings (default) | |
3153 | read doesn't imply executable mappings | |
3154 | noexec32=off: disable non-executable mappings | |
3155 | read implies executable mappings | |
1da177e4 | 3156 | |
fab43ef4 | 3157 | nofpu [MIPS,SH] Disable hardware FPU at boot time. |
6902aa84 | 3158 | |
cd4f0ef7 | 3159 | nofxsr [BUGS=X86-32] Disables x86 floating point extended |
4f886511 CE |
3160 | register save and restore. The kernel will only save |
3161 | legacy floating-point registers on task switch. | |
1da177e4 | 3162 | |
d909f910 | 3163 | nohugeiomap [KNL,x86,PPC] Disable kernel huge I/O mappings. |
0ddab1d2 | 3164 | |
52c48c51 SS |
3165 | nosmt [KNL,S390] Disable symmetric multithreading (SMT). |
3166 | Equivalent to smt=1. | |
3167 | ||
05736e4a | 3168 | [KNL,x86] Disable symmetric multithreading (SMT). |
506a66f3 TG |
3169 | nosmt=force: Force disable SMT, cannot be undone |
3170 | via the sysfs control file. | |
5e2d059b | 3171 | |
a2059825 JP |
3172 | nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1 |
3173 | (bounds check bypass). With this option data leaks are | |
3174 | possible in the system. | |
05736e4a | 3175 | |
e5ce5e72 JL |
3176 | nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for |
3177 | the Spectre variant 2 (indirect branch prediction) | |
3178 | vulnerability. System may allow data leaks with this | |
3179 | option. | |
da285121 | 3180 | |
24f7fc83 KRW |
3181 | nospec_store_bypass_disable |
3182 | [HW] Disable all mitigations for the Speculative Store Bypass vulnerability | |
3183 | ||
0c752a93 SS |
3184 | noxsave [BUGS=X86] Disables x86 extended register state save |
3185 | and restore using xsave. The kernel will fallback to | |
3186 | enabling legacy floating-point and sse state. | |
3187 | ||
b6f42a4a FY |
3188 | noxsaveopt [X86] Disables xsaveopt used in saving x86 extended |
3189 | register states. The kernel will fall back to use | |
3190 | xsave to save the states. By using this parameter, | |
3191 | performance of saving the states is degraded because | |
3192 | xsave doesn't support modified optimization while | |
3193 | xsaveopt supports it on xsaveopt enabled systems. | |
3194 | ||
3195 | noxsaves [X86] Disables xsaves and xrstors used in saving and | |
3196 | restoring x86 extended register state in compacted | |
3197 | form of xsave area. The kernel will fall back to use | |
3198 | xsaveopt and xrstor to save and restore the states | |
3199 | in standard form of xsave area. By using this | |
3200 | parameter, xsave area per process might occupy more | |
3201 | memory on xsaves enabled systems. | |
3202 | ||
01a24d2b PZ |
3203 | nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or |
3204 | wfi(ARM) instruction doesn't work correctly and not to | |
3205 | use it. This is also useful when using JTAG debugger. | |
a9913044 | 3206 | |
1f29fae2 SH |
3207 | no_file_caps Tells the kernel not to honor file capabilities. The |
3208 | only way then for a file to be executed with privilege | |
3209 | is to be setuid root or executed by root. | |
3210 | ||
1da177e4 LT |
3211 | nohalt [IA-64] Tells the kernel not to use the power saving |
3212 | function PAL_HALT_LIGHT when idle. This increases | |
3213 | power-consumption. On the positive side, it reduces | |
3214 | interrupt wake-up latency, which may improve performance | |
3215 | in certain environments such as networked servers or | |
3216 | real-time systems. | |
3217 | ||
a6e15a39 KC |
3218 | nohibernate [HIBERNATION] Disable hibernation and resume. |
3219 | ||
79bf2bb3 TG |
3220 | nohz= [KNL] Boottime enable/disable dynamic ticks |
3221 | Valid arguments: on, off | |
3222 | Default: on | |
3223 | ||
d94d1053 | 3224 | nohz_full= [KNL,BOOT,SMP,ISOL] |
2d13e6ca | 3225 | The argument is a cpu list, as described above. |
c5bfece2 | 3226 | In kernels built with CONFIG_NO_HZ_FULL=y, set |
a831881b | 3227 | the specified list of CPUs whose tick will be stopped |
0453b435 | 3228 | whenever possible. The boot CPU will be forced outside |
f99bcb2c PM |
3229 | the range to maintain the timekeeping. Any CPUs |
3230 | in this list will have their RCU callbacks offloaded, | |
3231 | just as if they had also been called out in the | |
3232 | rcu_nocbs= boot parameter. | |
a831881b | 3233 | |
eeee7853 PM |
3234 | noiotrap [SH] Disables trapped I/O port accesses. |
3235 | ||
cd4f0ef7 | 3236 | noirqdebug [X86-32] Disables the code which attempts to detect and |
1da177e4 LT |
3237 | disable unhandled interrupt sources. |
3238 | ||
6cececfc | 3239 | no_timer_check [X86,APIC] Disables the code which tests for |
8542b200 ZA |
3240 | broken timer IRQ sources. |
3241 | ||
1da177e4 LT |
3242 | noisapnp [ISAPNP] Disables ISA PnP code. |
3243 | ||
3244 | noinitrd [RAM] Tells the kernel not to load any configured | |
3245 | initial RAM disk. | |
3246 | ||
03ea8155 WH |
3247 | nointremap [X86-64, Intel-IOMMU] Do not enable interrupt |
3248 | remapping. | |
d1423d56 | 3249 | [Deprecated - use intremap=off] |
03ea8155 | 3250 | |
1da177e4 LT |
3251 | nointroute [IA-64] |
3252 | ||
d12a72b8 AL |
3253 | noinvpcid [X86] Disable the INVPCID cpu feature. |
3254 | ||
16290246 | 3255 | nojitter [IA-64] Disables jitter checking for ITC timers. |
0aa366f3 | 3256 | |
9cf4c4fc JK |
3257 | no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver |
3258 | ||
fd10cde9 GN |
3259 | no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page |
3260 | fault handling. | |
3261 | ||
80e9a4f2 AM |
3262 | no-vmw-sched-clock |
3263 | [X86,PV_OPS] Disable paravirtualized VMware scheduler | |
3264 | clock and use the default one. | |
3265 | ||
e73a8f38 | 3266 | no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time |
e0685fa2 SP |
3267 | accounting. steal time is computed, but won't |
3268 | influence scheduler behaviour | |
d910f5c1 | 3269 | |
cd4f0ef7 | 3270 | nolapic [X86-32,APIC] Do not enable or use the local APIC. |
1da177e4 | 3271 | |
cd4f0ef7 | 3272 | nolapic_timer [X86-32,APIC] Do not use the local APIC timer. |
ad62ca2b | 3273 | |
1da177e4 | 3274 | noltlbs [PPC] Do not use large page/tlb entries for kernel |
f15eea66 | 3275 | lowmem mapping on PPC40x and PPC8xx |
1da177e4 | 3276 | |
312f1f01 H |
3277 | nomca [IA-64] Disable machine check abort handling |
3278 | ||
13696e0a | 3279 | nomce [X86-32] Disable Machine Check Exception |
abe37e5a | 3280 | |
83d7384f AS |
3281 | nomfgpt [X86-32] Disable Multi-Function General Purpose |
3282 | Timer usage (for AMD Geode machines). | |
3283 | ||
bda62633 DZ |
3284 | nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to |
3285 | shutdown the other cpus. Instead use the REBOOT_VECTOR | |
3286 | irq. | |
3287 | ||
02608bef DY |
3288 | nomodule Disable module load |
3289 | ||
016ddd9b JK |
3290 | nopat [X86] Disable PAT (page attribute table extension of |
3291 | pagetables) support. | |
3292 | ||
0790c9aa AL |
3293 | nopcid [X86-64] Disable the PCID cpu feature. |
3294 | ||
0cb55ad2 RD |
3295 | norandmaps Don't use address space randomization. Equivalent to |
3296 | echo 0 > /proc/sys/kernel/randomize_va_space | |
3297 | ||
cd4f0ef7 | 3298 | noreplace-smp [X86-32,SMP] Don't replace SMP instructions |
b7fb4af0 JF |
3299 | with UP alternatives |
3300 | ||
7a5091d5 PA |
3301 | nordrand [X86] Disable kernel use of the RDRAND and |
3302 | RDSEED instructions even if they are supported | |
3303 | by the processor. RDRAND and RDSEED are still | |
3304 | available to user space applications. | |
49d859d7 | 3305 | |
a9913044 RD |
3306 | noresume [SWSUSP] Disables resume and restores original swap |
3307 | space. | |
3308 | ||
1da177e4 LT |
3309 | no-scroll [VGA] Disables scrollback. |
3310 | This is required for the Braillex ib80-piezo Braille | |
3311 | reader made by F.H. Papenmeier (Germany). | |
3312 | ||
3313 | nosbagart [IA-64] | |
3314 | ||
cd4f0ef7 | 3315 | nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. |
4f886511 | 3316 | |
61ec7567 LB |
3317 | nosmp [SMP] Tells an SMP kernel to act as a UP kernel, |
3318 | and disable the IO APIC. legacy for "maxcpus=0". | |
1da177e4 | 3319 | |
97842216 DJ |
3320 | nosoftlockup [KNL] Disable the soft-lockup detector. |
3321 | ||
1da177e4 LT |
3322 | nosync [HW,M68K] Disables sync negotiation for all devices. |
3323 | ||
195daf66 | 3324 | nowatchdog [KNL] Disable both lockup detectors, i.e. |
6dddd7a7 | 3325 | soft-lockup and NMI watchdog (hard-lockup). |
58687acb | 3326 | |
1da177e4 | 3327 | nowb [ARM] |
a9913044 | 3328 | |
2b2fd87a WH |
3329 | nox2apic [X86-64,APIC] Do not enable x2APIC mode. |
3330 | ||
f78cff48 FY |
3331 | cpu0_hotplug [X86] Turn on CPU0 hotplug feature when |
3332 | CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. | |
3333 | Some features depend on CPU0. Known dependencies are: | |
3334 | 1. Resume from suspend/hibernate depends on CPU0. | |
3335 | Suspend/hibernate will fail if CPU0 is offline and you | |
3336 | need to online CPU0 before suspend/hibernate. | |
3337 | 2. PIC interrupts also depend on CPU0. CPU0 can't be | |
3338 | removed if a PIC interrupt is detected. | |
3339 | It's said poweroff/reboot may depend on CPU0 on some | |
3340 | machines although I haven't seen such issues so far | |
3341 | after CPU0 is offline on a few tested machines. | |
3342 | If the dependencies are under your control, you can | |
3343 | turn on cpu0_hotplug. | |
3344 | ||
6dddd7a7 | 3345 | nps_mtm_hs_ctr= [KNL,ARC] |
35b55ef2 NC |
3346 | This parameter sets the maximum duration, in |
3347 | cycles, each HW thread of the CTOP can run | |
3348 | without interruptions, before HW switches it. | |
3349 | The actual maximum duration is 16 times this | |
3350 | parameter's value. | |
3351 | Format: integer between 1 and 255 | |
3352 | Default: 255 | |
3353 | ||
16290246 | 3354 | nptcg= [IA-64] Override max number of concurrent global TLB |
a6c75b86 FY |
3355 | purges which is reported from either PAL_VM_SUMMARY or |
3356 | SAL PALO. | |
3357 | ||
2b633e3f YL |
3358 | nr_cpus= [SMP] Maximum number of processors that an SMP kernel |
3359 | could support. nr_cpus=n : n >= 1 limits the kernel to | |
7c142bfe BH |
3360 | support 'n' processors. It could be larger than the |
3361 | number of already plugged CPU during bootup, later in | |
3362 | runtime you can physically add extra cpu until it reaches | |
3363 | n. So during boot up some boot time memory for per-cpu | |
3364 | variables need be pre-allocated for later physical cpu | |
3365 | hot plugging. | |
2b633e3f | 3366 | |
0cb55ad2 RD |
3367 | nr_uarts= [SERIAL] maximum number of UARTs to be registered. |
3368 | ||
1a687c2e MG |
3369 | numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing. |
3370 | Allowed values are enable and disable | |
3371 | ||
f0c0b2b8 | 3372 | numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. |
c9bff3ee | 3373 | 'node', 'default' can be specified |
f0c0b2b8 | 3374 | This can be set from sysctl after boot. |
57043247 | 3375 | See Documentation/admin-guide/sysctl/vm.rst for details. |
f0c0b2b8 | 3376 | |
7c4be253 | 3377 | ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. |
a74e2a22 | 3378 | See Documentation/core-api/debugging-via-ohci1394.rst for more |
7c4be253 RD |
3379 | info. |
3380 | ||
3ef0e1f8 AS |
3381 | olpc_ec_timeout= [OLPC] ms delay when issuing EC commands |
3382 | Rather than timing out after 20 ms if an EC | |
3383 | command is not properly ACKed, override the length | |
3384 | of the timeout. We have interrupts disabled while | |
3385 | waiting for the ACK, so if this is set too high | |
3386 | interrupts *may* be lost! | |
3387 | ||
15ac7afe TL |
3388 | omap_mux= [OMAP] Override bootloader pin multiplexing. |
3389 | Format: <mux_mode0.mode_name=value>... | |
3390 | For example, to override I2C bus2: | |
3391 | omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 | |
3392 | ||
1da177e4 LT |
3393 | oprofile.timer= [HW] |
3394 | Use timer interrupt instead of performance counters | |
3395 | ||
7e4e0bd5 RR |
3396 | oprofile.cpu_type= Force an oprofile cpu type |
3397 | This might be useful if you have an older oprofile | |
3398 | userland or if you want common events. | |
8d7ff4f2 RR |
3399 | Format: { arch_perfmon } |
3400 | arch_perfmon: [X86] Force use of architectural | |
7e4e0bd5 RR |
3401 | perfmon on Intel CPUs instead of the |
3402 | CPU specific event set. | |
159a80b2 RR |
3403 | timer: [X86] Force use of architectural NMI |
3404 | timer mode (see also oprofile.timer | |
3405 | for generic hr timer mode) | |
1dcdb5a9 | 3406 | |
44a4dcf7 RD |
3407 | oops=panic Always panic on oopses. Default is to just kill the |
3408 | process, but there is a small probability of | |
3409 | deadlocking the machine. | |
d404ab0a OH |
3410 | This will also cause panics on machine check exceptions. |
3411 | Useful together with panic=30 to trigger a reboot. | |
3412 | ||
e900a918 DW |
3413 | page_alloc.shuffle= |
3414 | [KNL] Boolean flag to control whether the page allocator | |
3415 | should randomize its free lists. The randomization may | |
3416 | be automatically enabled if the kernel detects it is | |
3417 | running on a platform with a direct-mapped memory-side | |
3418 | cache, and this parameter can be used to | |
3419 | override/disable that behavior. The state of the flag | |
3420 | can be read from sysfs at: | |
3421 | /sys/module/page_alloc/parameters/shuffle. | |
3422 | ||
48c96a36 JK |
3423 | page_owner= [KNL] Boot-time page_owner enabling option. |
3424 | Storage of the information about who allocated | |
3425 | each page is disabled in default. With this switch, | |
3426 | we can turn it on. | |
3427 | on: enable the feature | |
3428 | ||
8823b1db | 3429 | page_poison= [KNL] Boot-time parameter changing the state of |
8c9a134c KC |
3430 | poisoning on the buddy allocator, available with |
3431 | CONFIG_PAGE_POISONING=y. | |
3432 | off: turn off poisoning (default) | |
8823b1db LA |
3433 | on: turn on poisoning |
3434 | ||
44a4dcf7 | 3435 | panic= [KNL] Kernel behaviour on panic: delay <timeout> |
4302fbc8 HD |
3436 | timeout > 0: seconds before rebooting |
3437 | timeout = 0: wait forever | |
3438 | timeout < 0: reboot immediately | |
1da177e4 LT |
3439 | Format: <timeout> |
3440 | ||
d999bd93 FT |
3441 | panic_print= Bitmask for printing system info when panic happens. |
3442 | User can chose combination of the following bits: | |
3443 | bit 0: print all tasks info | |
3444 | bit 1: print system memory info | |
3445 | bit 2: print timer info | |
3446 | bit 3: print locks info if CONFIG_LOCKDEP is on | |
3447 | bit 4: print ftrace buffer | |
de6da1e8 | 3448 | bit 5: print all printk messages in buffer |
d999bd93 | 3449 | |
db38d5c1 RA |
3450 | panic_on_taint= Bitmask for conditionally calling panic() in add_taint() |
3451 | Format: <hex>[,nousertaint] | |
3452 | Hexadecimal bitmask representing the set of TAINT flags | |
3453 | that will cause the kernel to panic when add_taint() is | |
3454 | called with any of the flags in this set. | |
3455 | The optional switch "nousertaint" can be utilized to | |
3456 | prevent userspace forced crashes by writing to sysctl | |
3457 | /proc/sys/kernel/tainted any flagset matching with the | |
3458 | bitmask set on panic_on_taint. | |
3459 | See Documentation/admin-guide/tainted-kernels.rst for | |
3460 | extra details on the taint flags that users can pick | |
3461 | to compose the bitmask to assign to panic_on_taint. | |
3462 | ||
9e3961a0 PB |
3463 | panic_on_warn panic() instead of WARN(). Useful to cause kdump |
3464 | on a WARN(). | |
3465 | ||
f06e5153 MH |
3466 | crash_kexec_post_notifiers |
3467 | Run kdump after running panic-notifiers and dumping | |
3468 | kmsg. This only for the users who doubt kdump always | |
3469 | succeeds in any situation. | |
3470 | Note that this also increases risks of kdump failure, | |
3471 | because some panic notifiers can make the crashed | |
3472 | kernel more unstable. | |
3473 | ||
1da177e4 LT |
3474 | parkbd.port= [HW] Parallel port number the keyboard adapter is |
3475 | connected to, default is 0. | |
3476 | Format: <parport#> | |
3477 | parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, | |
3478 | 0 for XT, 1 for AT (default is AT). | |
a9913044 RD |
3479 | Format: <mode> |
3480 | ||
3481 | parport= [HW,PPT] Specify parallel ports. 0 disables. | |
3482 | Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } | |
3483 | Use 'auto' to force the driver to use any | |
3484 | IRQ/DMA settings detected (the default is to | |
3485 | ignore detected IRQ/DMA settings because of | |
3486 | possible conflicts). You can specify the base | |
3487 | address, IRQ, and DMA settings; IRQ and DMA | |
3488 | should be numbers, or 'auto' (for using detected | |
3489 | settings on that particular port), or 'nofifo' | |
3490 | (to avoid using a FIFO even if it is detected). | |
3491 | Parallel ports are assigned in the order they | |
3492 | are specified on the command line, starting | |
3493 | with parport0. | |
3494 | ||
3495 | parport_init_mode= [HW,PPT] | |
3496 | Configure VIA parallel port to operate in | |
3497 | a specific mode. This is necessary on Pegasos | |
3498 | computer where firmware has no options for setting | |
3499 | up parallel port mode and sets it to spp. | |
3500 | Currently this function knows 686a and 8231 chips. | |
1da177e4 LT |
3501 | Format: [spp|ps2|epp|ecp|ecpepp] |
3502 | ||
dd287796 AM |
3503 | pause_on_oops= |
3504 | Halt all CPUs after the first oops has been printed for | |
3505 | the specified number of seconds. This is to be used if | |
3506 | your oopses keep scrolling off the screen. | |
3507 | ||
1da177e4 LT |
3508 | pcbit= [HW,ISDN] |
3509 | ||
3510 | pcd. [PARIDE] | |
3511 | See header of drivers/block/paride/pcd.c. | |
e7751617 | 3512 | See also Documentation/admin-guide/blockdev/paride.rst. |
1da177e4 | 3513 | |
07d8d7e5 LG |
3514 | pci=option[,option...] [PCI] various PCI subsystem options. |
3515 | ||
3516 | Some options herein operate on a specific device | |
3517 | or a set of devices (<pci_dev>). These are | |
3518 | specified in one of the following formats: | |
3519 | ||
45db3370 | 3520 | [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]* |
07d8d7e5 LG |
3521 | pci:<vendor>:<device>[:<subvendor>:<subdevice>] |
3522 | ||
3523 | Note: the first format specifies a PCI | |
3524 | bus/device/function address which may change | |
3525 | if new hardware is inserted, if motherboard | |
3526 | firmware changes, or due to changes caused | |
3527 | by other kernel parameters. If the | |
3528 | domain is left unspecified, it is | |
45db3370 LG |
3529 | taken to be zero. Optionally, a path |
3530 | to a device through multiple device/function | |
3531 | addresses can be specified after the base | |
3532 | address (this is more robust against | |
3533 | renumbering issues). The second format | |
07d8d7e5 LG |
3534 | selects devices using IDs from the |
3535 | configuration space which may match multiple | |
3536 | devices in the system. | |
3537 | ||
11eb0e0e | 3538 | earlydump dump PCI config space before the kernel |
6dddd7a7 | 3539 | changes anything |
c0115606 | 3540 | off [X86] don't probe for the PCI bus |
cd4f0ef7 | 3541 | bios [X86-32] force use of PCI BIOS, don't access |
a9913044 RD |
3542 | the hardware directly. Use this if your machine |
3543 | has a non-standard PCI host bridge. | |
cd4f0ef7 | 3544 | nobios [X86-32] disallow use of PCI BIOS, only direct |
a9913044 RD |
3545 | hardware access methods are allowed. Use this |
3546 | if you experience crashes upon bootup and you | |
3547 | suspect they are caused by the BIOS. | |
afd8c084 BP |
3548 | conf1 [X86] Force use of PCI Configuration Access |
3549 | Mechanism 1 (config address in IO port 0xCF8, | |
3550 | data in IO port 0xCFC, both 32-bit). | |
3551 | conf2 [X86] Force use of PCI Configuration Access | |
3552 | Mechanism 2 (IO port 0xCF8 is an 8-bit port for | |
3553 | the function, IO port 0xCFA, also 8-bit, sets | |
3554 | bus number. The config space is then accessed | |
3555 | through ports 0xC000-0xCFFF). | |
3556 | See http://wiki.osdev.org/PCI for more info | |
3557 | on the configuration access mechanisms. | |
7f785763 RD |
3558 | noaer [PCIE] If the PCIEAER kernel config parameter is |
3559 | enabled, this kernel boot option can be used to | |
3560 | disable the use of PCIE advanced error reporting. | |
32a2eea7 JG |
3561 | nodomains [PCI] Disable support for multiple PCI |
3562 | root domains (aka PCI segments, in ACPI-speak). | |
6cececfc | 3563 | nommconf [X86] Disable use of MMCONFIG for PCI |
61be6d66 | 3564 | Configuration |
12983077 AH |
3565 | check_enable_amd_mmconf [X86] check for and enable |
3566 | properly configured MMIO access to PCI | |
3567 | config space on AMD family 10h CPU | |
309e57df MW |
3568 | nomsi [MSI] If the PCI_MSI kernel config parameter is |
3569 | enabled, this kernel boot option can be used to | |
3570 | disable the use of MSI interrupts system-wide. | |
a9322f64 SA |
3571 | noioapicquirk [APIC] Disable all boot interrupt quirks. |
3572 | Safety option to keep boot IRQs enabled. This | |
3573 | should never be necessary. | |
9197979b SA |
3574 | ioapicreroute [APIC] Enable rerouting of boot IRQs to the |
3575 | primary IO-APIC for bridges that cannot disable | |
3576 | boot IRQs. This fixes a source of spurious IRQs | |
3577 | when the system masks IRQs. | |
41b9eb26 SA |
3578 | noioapicreroute [APIC] Disable workaround that uses the |
3579 | boot IRQ equivalent of an IRQ that connects to | |
3580 | a chipset where boot IRQs cannot be disabled. | |
3581 | The opposite of ioapicreroute. | |
cd4f0ef7 | 3582 | biosirq [X86-32] Use PCI BIOS calls to get the interrupt |
a9913044 RD |
3583 | routing table. These calls are known to be buggy |
3584 | on several machines and they hang the machine | |
3585 | when used, but on other computers it's the only | |
3586 | way to get the interrupt routing table. Try | |
3587 | this option if the kernel is unable to allocate | |
3588 | IRQs or discover secondary PCI buses on your | |
3589 | motherboard. | |
c0115606 | 3590 | rom [X86] Assign address space to expansion ROMs. |
a9913044 RD |
3591 | Use with caution as certain devices share |
3592 | address decoders between ROMs and other | |
3593 | resources. | |
c0115606 | 3594 | norom [X86] Do not assign address space to |
bb71ad88 GH |
3595 | expansion ROMs that do not already have |
3596 | BIOS assigned address ranges. | |
7bd1c365 MH |
3597 | nobar [X86] Do not assign address space to the |
3598 | BARs that weren't assigned by the BIOS. | |
c0115606 | 3599 | irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be |
a9913044 RD |
3600 | assigned automatically to PCI devices. You can |
3601 | make the kernel exclude IRQs of your ISA cards | |
3602 | this way. | |
c0115606 | 3603 | pirqaddr=0xAAAAA [X86] Specify the physical address |
a9913044 RD |
3604 | of the PIRQ table (normally generated |
3605 | by the BIOS) if it is outside the | |
3606 | F0000h-100000h range. | |
c0115606 | 3607 | lastbus=N [X86] Scan all buses thru bus #N. Can be |
a9913044 RD |
3608 | useful if the kernel is unable to find your |
3609 | secondary buses and you want to tell it | |
3610 | explicitly which ones they are. | |
c0115606 | 3611 | assign-busses [X86] Always assign all PCI bus |
a9913044 RD |
3612 | numbers ourselves, overriding |
3613 | whatever the firmware may have done. | |
c0115606 | 3614 | usepirqmask [X86] Honor the possible IRQ mask stored |
a9913044 RD |
3615 | in the BIOS $PIR table. This is needed on |
3616 | some systems with broken BIOSes, notably | |
3617 | some HP Pavilion N5400 and Omnibook XE3 | |
3618 | notebooks. This will have no effect if ACPI | |
3619 | IRQ routing is enabled. | |
c0115606 | 3620 | noacpi [X86] Do not use ACPI for IRQ routing |
a9913044 | 3621 | or for PCI scanning. |
7bc5e3f2 BH |
3622 | use_crs [X86] Use PCI host bridge window information |
3623 | from ACPI. On BIOSes from 2008 or later, this | |
3624 | is enabled by default. If you need to use this, | |
3625 | please report a bug. | |
3626 | nocrs [X86] Ignore PCI host bridge windows from ACPI. | |
6dddd7a7 | 3627 | If you need to use this, please report a bug. |
a9913044 RD |
3628 | routeirq Do IRQ routing for all PCI devices. |
3629 | This is normally done in pci_enable_device(), | |
3630 | so this option is a temporary workaround | |
3631 | for broken drivers that don't call it. | |
13a6ddb0 YL |
3632 | skip_isa_align [X86] do not align io start addr, so can |
3633 | handle more pci cards | |
0637a70a AK |
3634 | noearly [X86] Don't do any early type 1 scanning. |
3635 | This might help on some broken boards which | |
3636 | machine check when some devices' config space | |
3637 | is read. But various workarounds are disabled | |
3638 | and some IOMMU drivers will not work. | |
6b4b78fe MD |
3639 | bfsort Sort PCI devices into breadth-first order. |
3640 | This sorting is done to get a device | |
3641 | order compatible with older (<= 2.4) kernels. | |
3642 | nobfsort Don't sort PCI devices into breadth-first order. | |
fa238712 YW |
3643 | pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) |
3644 | tuning and use the BIOS-configured MPS defaults. | |
3645 | pcie_bus_safe Set every device's MPS to the largest value | |
3646 | supported by all devices below the root complex. | |
3647 | pcie_bus_perf Set device MPS to the largest allowable MPS | |
3648 | based on its parent bus. Also set MRRS (Max | |
3649 | Read Request Size) to the largest supported | |
3650 | value (no larger than the MPS that the device | |
3651 | or bus can support) for best performance. | |
3652 | pcie_bus_peer2peer Set every device's MPS to 128B, which | |
3653 | every device is guaranteed to support. This | |
3654 | configuration allows peer-to-peer DMA between | |
3655 | any pair of devices, possibly at the cost of | |
3656 | reduced performance. This also guarantees | |
3657 | that hot-added devices will work. | |
4516a618 AN |
3658 | cbiosize=nn[KMG] The fixed amount of bus space which is |
3659 | reserved for the CardBus bridge's IO window. | |
3660 | The default value is 256 bytes. | |
3661 | cbmemsize=nn[KMG] The fixed amount of bus space which is | |
3662 | reserved for the CardBus bridge's memory | |
3663 | window. The default value is 64 megabytes. | |
32a9a682 YS |
3664 | resource_alignment= |
3665 | Format: | |
07d8d7e5 | 3666 | [<order of align>@]<pci_dev>[; ...] |
32a9a682 | 3667 | Specifies alignment and device to reassign |
07d8d7e5 LG |
3668 | aligned memory resources. How to |
3669 | specify the device is described above. | |
32a9a682 YS |
3670 | If <order of align> is not specified, |
3671 | PAGE_SIZE is used as alignment. | |
3b1b1ce3 | 3672 | A PCI-PCI bridge can be specified if resource |
32a9a682 | 3673 | windows need to be expanded. |
8b078c60 MK |
3674 | To specify the alignment for several |
3675 | instances of a device, the PCI vendor, | |
3676 | device, subvendor, and subdevice may be | |
3b1b1ce3 AK |
3677 | specified, e.g., 12@pci:8086:9c22:103c:198f |
3678 | for 4096-byte alignment. | |
43c16408 AP |
3679 | ecrc= Enable/disable PCIe ECRC (transaction layer |
3680 | end-to-end CRC checking). | |
3681 | bios: Use BIOS/firmware settings. This is the | |
3682 | the default. | |
3683 | off: Turn ECRC off | |
3684 | on: Turn ECRC on. | |
8c8803c5 YW |
3685 | hpiosize=nn[KMG] The fixed amount of bus space which is |
3686 | reserved for hotplug bridge's IO window. | |
3687 | Default size is 256 bytes. | |
d7b8a217 NJ |
3688 | hpmmiosize=nn[KMG] The fixed amount of bus space which is |
3689 | reserved for hotplug bridge's MMIO window. | |
3690 | Default size is 2 megabytes. | |
3691 | hpmmioprefsize=nn[KMG] The fixed amount of bus space which is | |
3692 | reserved for hotplug bridge's MMIO_PREF window. | |
3693 | Default size is 2 megabytes. | |
8c8803c5 | 3694 | hpmemsize=nn[KMG] The fixed amount of bus space which is |
d7b8a217 NJ |
3695 | reserved for hotplug bridge's MMIO and |
3696 | MMIO_PREF window. | |
8c8803c5 | 3697 | Default size is 2 megabytes. |
e16b4660 KB |
3698 | hpbussize=nn The minimum amount of additional bus numbers |
3699 | reserved for buses below a hotplug bridge. | |
3700 | Default is 1. | |
b55438fd YL |
3701 | realloc= Enable/disable reallocating PCI bridge resources |
3702 | if allocations done by BIOS are too small to | |
3703 | accommodate resources required by all child | |
3704 | devices. | |
3705 | off: Turn realloc off | |
3706 | on: Turn realloc on | |
3707 | realloc same as realloc=on | |
6748dcc2 | 3708 | noari do not use PCIe ARI. |
cef74409 GK |
3709 | noats [PCIE, Intel-IOMMU, AMD-IOMMU] |
3710 | do not use PCIe ATS (and IOMMU device IOTLB). | |
284f5f9d BH |
3711 | pcie_scan_all Scan all possible PCIe devices. Otherwise we |
3712 | only look for one device below a PCIe downstream | |
3713 | port. | |
f32ab754 UCCB |
3714 | big_root_window Try to add a big 64bit memory window to the PCIe |
3715 | root complex on AMD CPUs. Some GFX hardware | |
3716 | can resize a BAR to allow access to all VRAM. | |
3717 | Adding the window is slightly risky (it may | |
3718 | conflict with unreported devices), so this | |
3719 | taints the kernel. | |
aaca43fd LG |
3720 | disable_acs_redir=<pci_dev>[; ...] |
3721 | Specify one or more PCI devices (in the format | |
3722 | specified above) separated by semicolons. | |
3723 | Each device specified will have the PCI ACS | |
3724 | redirect capabilities forced off which will | |
3725 | allow P2P traffic between devices through | |
3726 | bridges without forcing it upstream. Note: | |
3727 | this removes isolation between devices and | |
3728 | may put more devices in an IOMMU group. | |
fbfe07d4 | 3729 | force_floating [S390] Force usage of floating interrupts. |
56271303 | 3730 | nomio [S390] Do not use MIO instructions. |
6b4b78fe | 3731 | |
e5665a45 CE |
3732 | pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power |
3733 | Management. | |
3734 | off Disable ASPM. | |
3735 | force Enable ASPM even on devices that claim not to support it. | |
3736 | WARNING: Forcing ASPM on may cause system lockups. | |
3737 | ||
4c0fd764 BH |
3738 | pcie_ports= [PCIE] PCIe port services handling: |
3739 | native Use native PCIe services (PME, AER, DPC, PCIe hotplug) | |
3740 | even if the platform doesn't give the OS permission to | |
3741 | use them. This may cause conflicts if the platform | |
3742 | also tries to use these services. | |
35a0b237 OJ |
3743 | dpc-native Use native PCIe service for DPC only. May |
3744 | cause conflicts if firmware uses AER or DPC. | |
4c0fd764 BH |
3745 | compat Disable native PCIe services (PME, AER, DPC, PCIe |
3746 | hotplug). | |
79dd9182 | 3747 | |
9d26d3a8 MW |
3748 | pcie_port_pm= [PCIE] PCIe port power management handling: |
3749 | off Disable power management of all PCIe ports | |
3750 | force Forcibly enable power management of all PCIe ports | |
3751 | ||
c7f48656 | 3752 | pcie_pme= [PCIE,PM] Native PCIe PME signaling options: |
c39fae14 | 3753 | nomsi Do not use MSI for native PCIe PME signaling (this makes |
28eb5f27 | 3754 | all PCIe root ports use INTx for all services). |
c7f48656 | 3755 | |
1da177e4 LT |
3756 | pcmv= [HW,PCMCIA] BadgePAD 4 |
3757 | ||
39ac5ba5 TB |
3758 | pd_ignore_unused |
3759 | [PM] | |
3760 | Keep all power-domains already enabled by bootloader on, | |
3761 | even if no driver has claimed them. This is useful | |
3762 | for debug and development, but should not be | |
3763 | needed on a platform with proper driver support. | |
3764 | ||
1da177e4 | 3765 | pd. [PARIDE] |
e7751617 | 3766 | See Documentation/admin-guide/blockdev/paride.rst. |
1da177e4 LT |
3767 | |
3768 | pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at | |
3769 | boot time. | |
3770 | Format: { 0 | 1 } | |
3771 | See arch/parisc/kernel/pdc_chassis.c | |
3772 | ||
f58dc01b | 3773 | percpu_alloc= Select which percpu first chunk allocator to use. |
e933a73f TH |
3774 | Currently supported values are "embed" and "page". |
3775 | Archs may support subset or none of the selections. | |
3776 | See comments in mm/percpu.c for details on each | |
3777 | allocator. This parameter is primarily for debugging | |
3778 | and performance comparison. | |
fa8a7094 | 3779 | |
1da177e4 | 3780 | pf. [PARIDE] |
e7751617 | 3781 | See Documentation/admin-guide/blockdev/paride.rst. |
1da177e4 LT |
3782 | |
3783 | pg. [PARIDE] | |
e7751617 | 3784 | See Documentation/admin-guide/blockdev/paride.rst. |
1da177e4 LT |
3785 | |
3786 | pirq= [SMP,APIC] Manual mp-table setup | |
cb1aaebe | 3787 | See Documentation/x86/i386/IO-APIC.rst. |
1da177e4 LT |
3788 | |
3789 | plip= [PPT,NET] Parallel port network link | |
3790 | Format: { parport<nr> | timid | 0 } | |
3ba9b1b8 | 3791 | See also Documentation/admin-guide/parport.rst. |
1da177e4 | 3792 | |
16290246 | 3793 | pmtmr= [X86] Manual setup of pmtmr I/O Port. |
de32a243 TG |
3794 | Override pmtimer IOPort with a hex value. |
3795 | e.g. pmtmr=0x508 | |
3796 | ||
db96a759 CY |
3797 | pm_debug_messages [SUSPEND,KNL] |
3798 | Enable suspend/resume debug messages during boot up. | |
3799 | ||
96242116 BH |
3800 | pnp.debug=1 [PNP] |
3801 | Enable PNP debug messages (depends on the | |
3802 | CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time | |
3803 | via /sys/module/pnp/parameters/debug. We always show | |
3804 | current resource usage; turning this on also shows | |
3805 | possible settings and some assignment information. | |
97ef062b | 3806 | |
1da177e4 LT |
3807 | pnpacpi= [ACPI] |
3808 | { off } | |
3809 | ||
3810 | pnpbios= [ISAPNP] | |
3811 | { on | off | curr | res | no-curr | no-res } | |
3812 | ||
3813 | pnp_reserve_irq= | |
3814 | [ISAPNP] Exclude IRQs for the autoconfiguration | |
3815 | ||
3816 | pnp_reserve_dma= | |
3817 | [ISAPNP] Exclude DMAs for the autoconfiguration | |
3818 | ||
3819 | pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration | |
a9913044 | 3820 | Ranges are in pairs (I/O port base and size). |
1da177e4 LT |
3821 | |
3822 | pnp_reserve_mem= | |
a9913044 RD |
3823 | [ISAPNP] Exclude memory regions for the |
3824 | autoconfiguration. | |
1da177e4 LT |
3825 | Ranges are in pairs (memory base and size). |
3826 | ||
4af94f39 RD |
3827 | ports= [IP_VS_FTP] IPVS ftp helper module |
3828 | Default is 21. | |
3829 | Up to 8 (IP_VS_APP_MAX_PORTS) ports | |
3830 | may be specified. | |
3831 | Format: <port>,<port>.... | |
3832 | ||
c3cbd075 BS |
3833 | powersave=off [PPC] This option disables power saving features. |
3834 | It specifically disables cpuidle and sets the | |
3835 | platform machine description specific power_save | |
3836 | function to NULL. On Idle the CPU just reduces | |
3837 | execution priority. | |
3838 | ||
3eb5d588 AB |
3839 | ppc_strict_facility_enable |
3840 | [PPC] This option catches any kernel floating point, | |
3841 | Altivec, VSX and SPE outside of regions specifically | |
3842 | allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). | |
3843 | There is some performance impact when enabling this. | |
3844 | ||
07fd1761 CB |
3845 | ppc_tm= [PPC] |
3846 | Format: {"off"} | |
3847 | Disable Hardware Transactional Memory | |
3848 | ||
45807a1d IM |
3849 | print-fatal-signals= |
3850 | [KNL] debug: print fatal signals | |
f84d49b2 NO |
3851 | |
3852 | If enabled, warn about various signal handling | |
3853 | related application anomalies: too many signals, | |
3854 | too many POSIX.1 timers, fatal signals causing a | |
3855 | coredump - etc. | |
3856 | ||
3857 | If you hit the warning due to signal overflow, | |
3858 | you might want to try "ulimit -i unlimited". | |
3859 | ||
45807a1d IM |
3860 | default: off. |
3861 | ||
c22ab332 MG |
3862 | printk.always_kmsg_dump= |
3863 | Trigger kmsg_dump for cases other than kernel oops or | |
3864 | panics | |
3865 | Format: <bool> (1/Y/y=enable, 0/N/n=disable) | |
3866 | default: disabled | |
3867 | ||
750afe7b BP |
3868 | printk.devkmsg={on,off,ratelimit} |
3869 | Control writing to /dev/kmsg. | |
3870 | on - unlimited logging to /dev/kmsg from userspace | |
3871 | off - logging to /dev/kmsg disabled | |
3872 | ratelimit - ratelimit the logging | |
3873 | Default: ratelimit | |
3874 | ||
e84845c4 RD |
3875 | printk.time= Show timing data prefixed to each printk message line |
3876 | Format: <bool> (1/Y/y=enable, 0/N/n=disable) | |
3877 | ||
0cb55ad2 RD |
3878 | processor.max_cstate= [HW,ACPI] |
3879 | Limit processor to maximum C-state | |
3880 | max_cstate=9 overrides any DMI blacklist limit. | |
3881 | ||
3882 | processor.nocst [HW,ACPI] | |
3883 | Ignore the _CST method to determine C-states, | |
3884 | instead using the legacy FADT method | |
3885 | ||
1da177e4 | 3886 | profile= [KNL] Enable kernel profiling via /proc/profile |
e7e61fc0 RD |
3887 | Format: [<profiletype>,]<number> |
3888 | Param: <profiletype>: "schedule", "sleep", or "kvm" | |
3889 | [defaults to kernel profiling] | |
a9913044 | 3890 | Param: "schedule" - profile schedule points. |
b3da2a73 MG |
3891 | Param: "sleep" - profile D-state sleeping (millisecs). |
3892 | Requires CONFIG_SCHEDSTATS | |
c0fe2e69 | 3893 | Param: "kvm" - profile VM exits. |
e7e61fc0 RD |
3894 | Param: <number> - step/bucket size as a power of 2 for |
3895 | statistical time based profiling. | |
1da177e4 | 3896 | |
1da177e4 LT |
3897 | prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk |
3898 | before loading. | |
e7751617 | 3899 | See Documentation/admin-guide/blockdev/ramdisk.rst. |
1da177e4 | 3900 | |
ecdc5d84 VG |
3901 | prot_virt= [S390] enable hosting protected virtual machines |
3902 | isolated from the hypervisor (if hardware supports | |
3903 | that). | |
3904 | Format: <bool> | |
3905 | ||
e0c27447 JW |
3906 | psi= [KNL] Enable or disable pressure stall information |
3907 | tracking. | |
3908 | Format: <bool> | |
3909 | ||
a9913044 RD |
3910 | psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to |
3911 | probe for; one of (bare|imps|exps|lifebook|any). | |
1da177e4 LT |
3912 | psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports |
3913 | per second. | |
a9913044 RD |
3914 | psmouse.resetafter= [HW,MOUSE] |
3915 | Try to reset the device after so many bad packets | |
1da177e4 LT |
3916 | (0 = never). |
3917 | psmouse.resolution= | |
3918 | [HW,MOUSE] Set desired mouse resolution, in dpi. | |
3919 | psmouse.smartscroll= | |
a9913044 | 3920 | [HW,MOUSE] Controls Logitech smartscroll autorepeat. |
1da177e4 LT |
3921 | 0 = disabled, 1 = enabled (default). |
3922 | ||
dee28e72 MG |
3923 | pstore.backend= Specify the name of the pstore backend to use |
3924 | ||
1da177e4 | 3925 | pt. [PARIDE] |
e7751617 | 3926 | See Documentation/admin-guide/blockdev/paride.rst. |
1da177e4 | 3927 | |
01c9b17b DH |
3928 | pti= [X86_64] Control Page Table Isolation of user and |
3929 | kernel address spaces. Disabling this feature | |
3930 | removes hardening, but improves performance of | |
3931 | system calls and interrupts. | |
3932 | ||
3933 | on - unconditionally enable | |
3934 | off - unconditionally disable | |
3935 | auto - kernel detects whether your CPU model is | |
3936 | vulnerable to issues that PTI mitigates | |
3937 | ||
3938 | Not specifying this option is equivalent to pti=auto. | |
3939 | ||
3940 | nopti [X86_64] | |
3941 | Equivalent to pti=off | |
41f4c20b | 3942 | |
dc8c8587 KS |
3943 | pty.legacy_count= |
3944 | [KNL] Number of legacy pty's. Overwrites compiled-in | |
3945 | default number. | |
3946 | ||
7d2c502f | 3947 | quiet [KNL] Disable most log messages |
a9913044 | 3948 | |
1da177e4 LT |
3949 | r128= [HW,DRM] |
3950 | ||
3951 | raid= [HW,RAID] | |
e52347bd | 3952 | See Documentation/admin-guide/md.rst. |
1da177e4 | 3953 | |
1da177e4 | 3954 | ramdisk_size= [RAM] Sizes of RAM disks in kilobytes |
e7751617 | 3955 | See Documentation/admin-guide/blockdev/ramdisk.rst. |
1da177e4 | 3956 | |
9b254366 KC |
3957 | random.trust_cpu={on,off} |
3958 | [KNL] Enable or disable trusting the use of the | |
3959 | CPU's random number generator (if available) to | |
3960 | fully seed the kernel's CRNG. Default is controlled | |
3961 | by CONFIG_RANDOM_TRUST_CPU. | |
3962 | ||
011d8261 BP |
3963 | ras=option[,option,...] [KNL] RAS-specific options |
3964 | ||
3965 | cec_disable [X86] | |
3966 | Disable the Correctable Errors Collector, | |
3967 | see CONFIG_RAS_CEC help text. | |
3968 | ||
4102adab | 3969 | rcu_nocbs= [KNL] |
da8739f2 PM |
3970 | The argument is a cpu list, as described above, |
3971 | except that the string "all" can be used to | |
3972 | specify every CPU on the system. | |
2d13e6ca | 3973 | |
3fbfbf7a PM |
3974 | In kernels built with CONFIG_RCU_NOCB_CPU=y, set |
3975 | the specified list of CPUs to be no-callback CPUs. | |
77095901 PM |
3976 | Invocation of these CPUs' RCU callbacks will be |
3977 | offloaded to "rcuox/N" kthreads created for that | |
3978 | purpose, where "x" is "p" for RCU-preempt, and | |
3979 | "s" for RCU-sched, and "N" is the CPU number. | |
3980 | This reduces OS jitter on the offloaded CPUs, | |
3981 | which can be useful for HPC and real-time | |
3982 | workloads. It can also improve energy efficiency | |
3983 | for asymmetric multiprocessors. | |
3fbfbf7a | 3984 | |
4102adab | 3985 | rcu_nocb_poll [KNL] |
3fbfbf7a PM |
3986 | Rather than requiring that offloaded CPUs |
3987 | (specified by rcu_nocbs= above) explicitly | |
3988 | awaken the corresponding "rcuoN" kthreads, | |
3989 | make these kthreads poll for callbacks. | |
3990 | This improves the real-time response for the | |
3991 | offloaded CPUs by relieving them of the need to | |
3992 | wake up the corresponding kthread, but degrades | |
3993 | energy efficiency by requiring that the kthreads | |
3994 | periodically wake up to do the polling. | |
3995 | ||
4102adab | 3996 | rcutree.blimit= [KNL] |
97e63f0c PM |
3997 | Set maximum number of finished RCU callbacks to |
3998 | process in one batch. | |
21a1ea9e | 3999 | |
a3dc2948 PM |
4000 | rcutree.dump_tree= [KNL] |
4001 | Dump the structure of the rcu_node combining tree | |
4002 | out at early boot. This is used for diagnostic | |
4003 | purposes, to verify correct tree setup. | |
4004 | ||
0f41c0dd PM |
4005 | rcutree.gp_cleanup_delay= [KNL] |
4006 | Set the number of jiffies to delay each step of | |
90040c9e | 4007 | RCU grace-period cleanup. |
0f41c0dd | 4008 | |
37745d28 PM |
4009 | rcutree.gp_init_delay= [KNL] |
4010 | Set the number of jiffies to delay each step of | |
90040c9e | 4011 | RCU grace-period initialization. |
0f41c0dd PM |
4012 | |
4013 | rcutree.gp_preinit_delay= [KNL] | |
4014 | Set the number of jiffies to delay each step of | |
4015 | RCU grace-period pre-initialization, that is, | |
4016 | the propagation of recent CPU-hotplug changes up | |
90040c9e | 4017 | the rcu_node combining tree. |
37745d28 | 4018 | |
48d07c04 SAS |
4019 | rcutree.use_softirq= [KNL] |
4020 | If set to zero, move all RCU_SOFTIRQ processing to | |
4021 | per-CPU rcuc kthreads. Defaults to a non-zero | |
4022 | value, meaning that RCU_SOFTIRQ is used by default. | |
4023 | Specify rcutree.use_softirq=0 to use rcuc kthreads. | |
4024 | ||
7fa27001 PM |
4025 | rcutree.rcu_fanout_exact= [KNL] |
4026 | Disable autobalancing of the rcu_node combining | |
4027 | tree. This is used by rcutorture, and might | |
4028 | possibly be useful for architectures having high | |
4029 | cache-to-cache transfer latencies. | |
37745d28 | 4030 | |
4102adab | 4031 | rcutree.rcu_fanout_leaf= [KNL] |
ee968ac6 PM |
4032 | Change the number of CPUs assigned to each |
4033 | leaf rcu_node structure. Useful for very | |
4034 | large systems, which will choose the value 64, | |
4035 | and for NUMA systems with large remote-access | |
4036 | latencies, which will choose a value aligned | |
4037 | with the appropriate hardware boundaries. | |
f885b7f2 | 4038 | |
4102adab | 4039 | rcutree.jiffies_till_first_fqs= [KNL] |
c0f4dfd4 PM |
4040 | Set delay from grace-period initialization to |
4041 | first attempt to force quiescent states. | |
4042 | Units are jiffies, minimum value is zero, | |
4043 | and maximum value is HZ. | |
4044 | ||
4102adab | 4045 | rcutree.jiffies_till_next_fqs= [KNL] |
c0f4dfd4 PM |
4046 | Set delay between subsequent attempts to force |
4047 | quiescent states. Units are jiffies, minimum | |
4048 | value is one, and maximum value is HZ. | |
4049 | ||
1a4762b9 PM |
4050 | rcutree.jiffies_till_sched_qs= [KNL] |
4051 | Set required age in jiffies for a | |
4052 | given grace period before RCU starts | |
4053 | soliciting quiescent-state help from | |
4054 | rcu_note_context_switch() and cond_resched(). | |
4055 | If not specified, the kernel will calculate | |
4056 | a value based on the most recent settings | |
4057 | of rcutree.jiffies_till_first_fqs | |
4058 | and rcutree.jiffies_till_next_fqs. | |
4059 | This calculated value may be viewed in | |
4060 | rcutree.jiffies_to_sched_qs. Any attempt to set | |
4061 | rcutree.jiffies_to_sched_qs will be cheerfully | |
4062 | overwritten. | |
4063 | ||
21871d7e | 4064 | rcutree.kthread_prio= [KNL,BOOT] |
d2af1ad7 PM |
4065 | Set the SCHED_FIFO priority of the RCU per-CPU |
4066 | kthreads (rcuc/N). This value is also used for | |
4067 | the priority of the RCU boost threads (rcub/N) | |
4068 | and for the RCU grace-period kthreads (rcu_bh, | |
4069 | rcu_preempt, and rcu_sched). If RCU_BOOST is | |
4070 | set, valid values are 1-99 and the default is 1 | |
4071 | (the least-favored priority). Otherwise, when | |
4072 | RCU_BOOST is not set, valid values are 0-99 and | |
4073 | the default is zero (non-realtime operation). | |
21871d7e | 4074 | |
f7c612b0 PM |
4075 | rcutree.rcu_nocb_gp_stride= [KNL] |
4076 | Set the number of NOCB callback kthreads in | |
4077 | each group, which defaults to the square root | |
4078 | of the number of CPUs. Larger numbers reduce | |
4079 | the wakeup overhead on the global grace-period | |
4080 | kthread, but increases that same overhead on | |
4081 | each group's NOCB grace-period kthread. | |
fbce7497 | 4082 | |
4102adab | 4083 | rcutree.qhimark= [KNL] |
97e63f0c PM |
4084 | Set threshold of queued RCU callbacks beyond which |
4085 | batch limiting is disabled. | |
21a1ea9e | 4086 | |
4102adab | 4087 | rcutree.qlowmark= [KNL] |
24aaef8d RD |
4088 | Set threshold of queued RCU callbacks below which |
4089 | batch limiting is re-enabled. | |
21a1ea9e | 4090 | |
b2b00ddf PM |
4091 | rcutree.qovld= [KNL] |
4092 | Set threshold of queued RCU callbacks beyond which | |
4093 | RCU's force-quiescent-state scan will aggressively | |
4094 | enlist help from cond_resched() and sched IPIs to | |
4095 | help CPUs more quickly reach quiescent states. | |
4096 | Set to less than zero to make this be set based | |
4097 | on rcutree.qhimark at boot time and to zero to | |
4098 | disable more aggressive help enlistment. | |
4099 | ||
4102adab | 4100 | rcutree.rcu_idle_gp_delay= [KNL] |
c0f4dfd4 PM |
4101 | Set wakeup interval for idle CPUs that have |
4102 | RCU callbacks (RCU_FAST_NO_HZ=y). | |
d40011f6 | 4103 | |
4102adab | 4104 | rcutree.rcu_idle_lazy_gp_delay= [KNL] |
c0f4dfd4 PM |
4105 | Set wakeup interval for idle CPUs that have |
4106 | only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y). | |
4107 | Lazy RCU callbacks are those which RCU can | |
4108 | prove do nothing more than free memory. | |
d40011f6 | 4109 | |
e3c50dfb PM |
4110 | rcutree.rcu_kick_kthreads= [KNL] |
4111 | Cause the grace-period kthread to get an extra | |
4112 | wake_up() if it sleeps three times longer than | |
4113 | it should at force-quiescent-state time. | |
4114 | This wake_up() will be accompanied by a | |
4115 | WARN_ONCE() splat and an ftrace_dump(). | |
4116 | ||
2ccaff10 PM |
4117 | rcutree.sysrq_rcu= [KNL] |
4118 | Commandeer a sysrq key to dump out Tree RCU's | |
4119 | rcu_node tree with an eye towards determining | |
4120 | why a new grace period has not yet started. | |
4121 | ||
881ed593 PM |
4122 | rcuperf.gp_async= [KNL] |
4123 | Measure performance of asynchronous | |
4124 | grace-period primitives such as call_rcu(). | |
4125 | ||
4126 | rcuperf.gp_async_max= [KNL] | |
4127 | Specify the maximum number of outstanding | |
4128 | callbacks per writer thread. When a writer | |
4129 | thread exceeds this limit, it invokes the | |
4130 | corresponding flavor of rcu_barrier() to allow | |
4131 | previously posted callbacks to drain. | |
4132 | ||
bdea9e34 PM |
4133 | rcuperf.gp_exp= [KNL] |
4134 | Measure performance of expedited synchronous | |
4135 | grace-period primitives. | |
4136 | ||
df37e66b PM |
4137 | rcuperf.holdoff= [KNL] |
4138 | Set test-start holdoff period. The purpose of | |
4139 | this parameter is to delay the start of the | |
4140 | test until boot completes in order to avoid | |
4141 | interference. | |
4142 | ||
e6e78b00 JFG |
4143 | rcuperf.kfree_rcu_test= [KNL] |
4144 | Set to measure performance of kfree_rcu() flooding. | |
4145 | ||
4146 | rcuperf.kfree_nthreads= [KNL] | |
4147 | The number of threads running loops of kfree_rcu(). | |
4148 | ||
4149 | rcuperf.kfree_alloc_num= [KNL] | |
4150 | Number of allocations and frees done in an iteration. | |
4151 | ||
4152 | rcuperf.kfree_loops= [KNL] | |
4153 | Number of loops doing rcuperf.kfree_alloc_num number | |
4154 | of allocations and frees. | |
4155 | ||
bdea9e34 PM |
4156 | rcuperf.nreaders= [KNL] |
4157 | Set number of RCU readers. The value -1 selects | |
4158 | N, where N is the number of CPUs. A value | |
4159 | "n" less than -1 selects N-n+1, where N is again | |
4160 | the number of CPUs. For example, -2 selects N | |
4161 | (the number of CPUs), -3 selects N+1, and so on. | |
4162 | A value of "n" less than or equal to -N selects | |
4163 | a single reader. | |
4164 | ||
4165 | rcuperf.nwriters= [KNL] | |
4166 | Set number of RCU writers. The values operate | |
4167 | the same as for rcuperf.nreaders. | |
4168 | N, where N is the number of CPUs | |
4169 | ||
820687a7 PM |
4170 | rcuperf.perf_type= [KNL] |
4171 | Specify the RCU implementation to test. | |
4172 | ||
bdea9e34 PM |
4173 | rcuperf.shutdown= [KNL] |
4174 | Shut the system down after performance tests | |
4175 | complete. This is useful for hands-off automated | |
4176 | testing. | |
4177 | ||
bdea9e34 PM |
4178 | rcuperf.verbose= [KNL] |
4179 | Enable additional printk() statements. | |
4180 | ||
820687a7 PM |
4181 | rcuperf.writer_holdoff= [KNL] |
4182 | Write-side holdoff between grace periods, | |
4183 | in microseconds. The default of zero says | |
4184 | no holdoff. | |
4185 | ||
4102adab | 4186 | rcutorture.fqs_duration= [KNL] |
21b05de4 PM |
4187 | Set duration of force_quiescent_state bursts |
4188 | in microseconds. | |
dabb8aa9 | 4189 | |
4102adab | 4190 | rcutorture.fqs_holdoff= [KNL] |
21b05de4 PM |
4191 | Set holdoff time within force_quiescent_state bursts |
4192 | in microseconds. | |
dabb8aa9 | 4193 | |
4102adab | 4194 | rcutorture.fqs_stutter= [KNL] |
21b05de4 PM |
4195 | Set wait time between force_quiescent_state bursts |
4196 | in seconds. | |
4197 | ||
ed8f6fb2 PM |
4198 | rcutorture.fwd_progress= [KNL] |
4199 | Enable RCU grace-period forward-progress testing | |
4200 | for the types of RCU supporting this notion. | |
4201 | ||
4202 | rcutorture.fwd_progress_div= [KNL] | |
4203 | Specify the fraction of a CPU-stall-warning | |
4204 | period to do tight-loop forward-progress testing. | |
4205 | ||
4206 | rcutorture.fwd_progress_holdoff= [KNL] | |
4207 | Number of seconds to wait between successive | |
4208 | forward-progress tests. | |
4209 | ||
4210 | rcutorture.fwd_progress_need_resched= [KNL] | |
4211 | Enclose cond_resched() calls within checks for | |
4212 | need_resched() during tight-loop forward-progress | |
4213 | testing. | |
4214 | ||
21b05de4 PM |
4215 | rcutorture.gp_cond= [KNL] |
4216 | Use conditional/asynchronous update-side | |
4217 | primitives, if available. | |
dabb8aa9 | 4218 | |
4102adab | 4219 | rcutorture.gp_exp= [KNL] |
21b05de4 | 4220 | Use expedited update-side primitives, if available. |
4102adab PM |
4221 | |
4222 | rcutorture.gp_normal= [KNL] | |
21b05de4 PM |
4223 | Use normal (non-expedited) asynchronous |
4224 | update-side primitives, if available. | |
4225 | ||
4226 | rcutorture.gp_sync= [KNL] | |
4227 | Use normal (non-expedited) synchronous | |
4228 | update-side primitives, if available. If all | |
4229 | of rcutorture.gp_cond=, rcutorture.gp_exp=, | |
4230 | rcutorture.gp_normal=, and rcutorture.gp_sync= | |
4231 | are zero, rcutorture acts as if is interpreted | |
4232 | they are all non-zero. | |
dabb8aa9 | 4233 | |
4102adab | 4234 | rcutorture.n_barrier_cbs= [KNL] |
dabb8aa9 PM |
4235 | Set callbacks/threads for rcu_barrier() testing. |
4236 | ||
4102adab | 4237 | rcutorture.nfakewriters= [KNL] |
dabb8aa9 PM |
4238 | Set number of concurrent RCU writers. These just |
4239 | stress RCU, they don't participate in the actual | |
4240 | test, hence the "fake". | |
4241 | ||
4102adab | 4242 | rcutorture.nreaders= [KNL] |
3838cc18 PM |
4243 | Set number of RCU readers. The value -1 selects |
4244 | N-1, where N is the number of CPUs. A value | |
4245 | "n" less than -1 selects N-n-2, where N is again | |
4246 | the number of CPUs. For example, -2 selects N | |
4247 | (the number of CPUs), -3 selects N+1, and so on. | |
dabb8aa9 | 4248 | |
4102adab PM |
4249 | rcutorture.object_debug= [KNL] |
4250 | Enable debug-object double-call_rcu() testing. | |
4251 | ||
4252 | rcutorture.onoff_holdoff= [KNL] | |
dabb8aa9 PM |
4253 | Set time (s) after boot for CPU-hotplug testing. |
4254 | ||
4102adab | 4255 | rcutorture.onoff_interval= [KNL] |
028be12b PM |
4256 | Set time (jiffies) between CPU-hotplug operations, |
4257 | or zero to disable CPU-hotplug testing. | |
dabb8aa9 | 4258 | |
4102adab | 4259 | rcutorture.shuffle_interval= [KNL] |
dabb8aa9 PM |
4260 | Set task-shuffle interval (s). Shuffling tasks |
4261 | allows some CPUs to go into dyntick-idle mode | |
4262 | during the rcutorture test. | |
4263 | ||
4102adab | 4264 | rcutorture.shutdown_secs= [KNL] |
dabb8aa9 PM |
4265 | Set time (s) after boot system shutdown. This |
4266 | is useful for hands-off automated testing. | |
4267 | ||
4102adab | 4268 | rcutorture.stall_cpu= [KNL] |
dabb8aa9 PM |
4269 | Duration of CPU stall (s) to test RCU CPU stall |
4270 | warnings, zero to disable. | |
4271 | ||
19a8ff95 PM |
4272 | rcutorture.stall_cpu_block= [KNL] |
4273 | Sleep while stalling if set. This will result | |
4274 | in warnings from preemptible RCU in addition | |
4275 | to any other stall-related activity. | |
4276 | ||
4102adab | 4277 | rcutorture.stall_cpu_holdoff= [KNL] |
dabb8aa9 PM |
4278 | Time to wait (s) after boot before inducing stall. |
4279 | ||
2b1516e5 PM |
4280 | rcutorture.stall_cpu_irqsoff= [KNL] |
4281 | Disable interrupts while stalling if set. | |
4282 | ||
55b2dcf5 PM |
4283 | rcutorture.stall_gp_kthread= [KNL] |
4284 | Duration (s) of forced sleep within RCU | |
4285 | grace-period kthread to test RCU CPU stall | |
4286 | warnings, zero to disable. If both stall_cpu | |
4287 | and stall_gp_kthread are specified, the | |
4288 | kthread is starved first, then the CPU. | |
4289 | ||
4102adab | 4290 | rcutorture.stat_interval= [KNL] |
dabb8aa9 PM |
4291 | Time (s) between statistics printk()s. |
4292 | ||
4102adab | 4293 | rcutorture.stutter= [KNL] |
dabb8aa9 PM |
4294 | Time (s) to stutter testing, for example, specifying |
4295 | five seconds causes the test to run for five seconds, | |
4296 | wait for five seconds, and so on. This tests RCU's | |
4297 | ability to transition abruptly to and from idle. | |
4298 | ||
4102adab | 4299 | rcutorture.test_boost= [KNL] |
dabb8aa9 PM |
4300 | Test RCU priority boosting? 0=no, 1=maybe, 2=yes. |
4301 | "Maybe" means test if the RCU implementation | |
4302 | under test support RCU priority boosting. | |
4303 | ||
4102adab | 4304 | rcutorture.test_boost_duration= [KNL] |
dabb8aa9 PM |
4305 | Duration (s) of each individual boost test. |
4306 | ||
4102adab | 4307 | rcutorture.test_boost_interval= [KNL] |
dabb8aa9 PM |
4308 | Interval (s) between each boost test. |
4309 | ||
4102adab | 4310 | rcutorture.test_no_idle_hz= [KNL] |
dabb8aa9 PM |
4311 | Test RCU's dyntick-idle handling. See also the |
4312 | rcutorture.shuffle_interval parameter. | |
4313 | ||
4102adab | 4314 | rcutorture.torture_type= [KNL] |
dabb8aa9 PM |
4315 | Specify the RCU implementation to test. |
4316 | ||
4102adab | 4317 | rcutorture.verbose= [KNL] |
dabb8aa9 PM |
4318 | Enable additional printk() statements. |
4319 | ||
cdc694b2 PM |
4320 | rcupdate.rcu_cpu_stall_ftrace_dump= [KNL] |
4321 | Dump ftrace buffer after reporting RCU CPU | |
4322 | stall warning. | |
4323 | ||
5a9be7c6 PM |
4324 | rcupdate.rcu_cpu_stall_suppress= [KNL] |
4325 | Suppress RCU CPU stall warning messages. | |
4326 | ||
58c53360 PM |
4327 | rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL] |
4328 | Suppress RCU CPU stall warning messages and | |
4329 | rcutorture writer stall warnings that occur | |
4330 | during early boot, that is, during the time | |
4331 | before the init task is spawned. | |
4332 | ||
5a9be7c6 PM |
4333 | rcupdate.rcu_cpu_stall_timeout= [KNL] |
4334 | Set timeout for RCU CPU stall warning messages. | |
4335 | ||
4102adab PM |
4336 | rcupdate.rcu_expedited= [KNL] |
4337 | Use expedited grace-period primitives, for | |
4338 | example, synchronize_rcu_expedited() instead | |
4339 | of synchronize_rcu(). This reduces latency, | |
4340 | but can increase CPU utilization, degrade | |
4341 | real-time latency, and degrade energy efficiency. | |
79cfea02 | 4342 | No effect on CONFIG_TINY_RCU kernels. |
4102adab | 4343 | |
5a9be7c6 PM |
4344 | rcupdate.rcu_normal= [KNL] |
4345 | Use only normal grace-period primitives, | |
4346 | for example, synchronize_rcu() instead of | |
4347 | synchronize_rcu_expedited(). This improves | |
79cfea02 PM |
4348 | real-time latency, CPU utilization, and |
4349 | energy efficiency, but can expose users to | |
4350 | increased grace-period latency. This parameter | |
4351 | overrides rcupdate.rcu_expedited. No effect on | |
4352 | CONFIG_TINY_RCU kernels. | |
4102adab | 4353 | |
3e42ec1a PM |
4354 | rcupdate.rcu_normal_after_boot= [KNL] |
4355 | Once boot has completed (that is, after | |
4356 | rcu_end_inkernel_boot() has been invoked), use | |
79cfea02 PM |
4357 | only normal grace-period primitives. No effect |
4358 | on CONFIG_TINY_RCU kernels. | |
3e42ec1a | 4359 | |
b0afa0f0 PM |
4360 | rcupdate.rcu_task_ipi_delay= [KNL] |
4361 | Set time in jiffies during which RCU tasks will | |
4362 | avoid sending IPIs, starting with the beginning | |
4363 | of a given grace period. Setting a large | |
4364 | number avoids disturbing real-time workloads, | |
4365 | but lengthens grace periods. | |
4366 | ||
52db30ab PM |
4367 | rcupdate.rcu_task_stall_timeout= [KNL] |
4368 | Set timeout in jiffies for RCU task stall warning | |
4369 | messages. Disable with a value less than or equal | |
4370 | to zero. | |
4371 | ||
74860fee PK |
4372 | rcupdate.rcu_self_test= [KNL] |
4373 | Run the RCU early boot self tests | |
4374 | ||
ffdfc409 OJ |
4375 | rdinit= [KNL] |
4376 | Format: <full_path> | |
4377 | Run specified binary instead of /init from the ramdisk, | |
4378 | used for early userspace startup. See initrd. | |
4379 | ||
c49a0a80 TL |
4380 | rdrand= [X86] |
4381 | force - Override the decision by the kernel to hide the | |
4382 | advertisement of RDRAND support (this affects | |
4383 | certain AMD processors because of buggy BIOS | |
4384 | support, specifically around the suspend/resume | |
4385 | path). | |
4386 | ||
1d9807fc TL |
4387 | rdt= [HW,X86,RDT] |
4388 | Turn on/off individual RDT features. List is: | |
31516de3 FY |
4389 | cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp, |
4390 | mba. | |
1d9807fc TL |
4391 | E.g. to turn on cmt and turn off mba use: |
4392 | rdt=cmt,!mba | |
4393 | ||
1b3a5d02 RH |
4394 | reboot= [KNL] |
4395 | Format (x86 or x86_64): | |
4396 | [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \ | |
4397 | [[,]s[mp]#### \ | |
4398 | [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ | |
4399 | [[,]f[orce] | |
b287a25a AK |
4400 | Where reboot_mode is one of warm (soft) or cold (hard) or gpio |
4401 | (prefix with 'panic_' to set mode for panic | |
4402 | reboot only), | |
1b3a5d02 RH |
4403 | reboot_type is one of bios, acpi, kbd, triple, efi, or pci, |
4404 | reboot_force is either force or not specified, | |
4405 | reboot_cpu is s[mp]#### with #### being the processor | |
4406 | to be used for rebooting. | |
1da177e4 | 4407 | |
46b6d94e PJ |
4408 | relax_domain_level= |
4409 | [KNL, SMP] Set scheduler's default relax_domain_level. | |
da82c92f | 4410 | See Documentation/admin-guide/cgroup-v1/cpusets.rst. |
46b6d94e | 4411 | |
ffd2e8df BH |
4412 | reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory |
4413 | Format: <base1>,<size1>[,<base2>,<size2>,...] | |
4414 | Reserve I/O ports or memory so the kernel won't use | |
4415 | them. If <base> is less than 0x10000, the region | |
4416 | is assumed to be I/O ports; otherwise it is memory. | |
1da177e4 | 4417 | |
cd4f0ef7 | 4418 | reservetop= [X86-32] |
461a9aff ZA |
4419 | Format: nn[KMG] |
4420 | Reserves a hole at the top of the kernel virtual | |
4421 | address space. | |
4422 | ||
9ea77bdb PA |
4423 | reservelow= [X86] |
4424 | Format: nn[K] | |
4425 | Set the amount of memory to reserve for BIOS at | |
4426 | the bottom of the address space. | |
4427 | ||
7e96287d VG |
4428 | reset_devices [KNL] Force drivers to reset the underlying device |
4429 | during initialization. | |
4430 | ||
a9913044 RD |
4431 | resume= [SWSUSP] |
4432 | Specify the partition device for software suspend | |
2df83fa4 MB |
4433 | Format: |
4434 | {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>} | |
1da177e4 | 4435 | |
ecbd0da1 RW |
4436 | resume_offset= [SWSUSP] |
4437 | Specify the offset from the beginning of the partition | |
4438 | given by "resume=" at which the swap header is located, | |
4439 | in <PAGE_SIZE> units (needed only for swap files). | |
151f4e2b | 4440 | See Documentation/power/swsusp-and-swap-files.rst |
ecbd0da1 | 4441 | |
f126f733 BS |
4442 | resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to |
4443 | read the resume files | |
4444 | ||
6f8d7022 BS |
4445 | resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up. |
4446 | Useful for devices that are detected asynchronously | |
4447 | (e.g. USB and MMC devices). | |
4448 | ||
f996fc96 BS |
4449 | hibernate= [HIBERNATION] |
4450 | noresume Don't check if there's a hibernation image | |
4451 | present during boot. | |
4452 | nocompress Don't compress/decompress hibernation images. | |
a6e15a39 | 4453 | no Disable hibernation and resume. |
4c0b6c10 RW |
4454 | protect_image Turn on image protection during restoration |
4455 | (that will set all pages holding image data | |
4456 | during restoration read-only). | |
f996fc96 | 4457 | |
0a7b35cb MN |
4458 | retain_initrd [RAM] Keep initrd memory after extraction |
4459 | ||
0efbb786 AC |
4460 | rfkill.default_state= |
4461 | 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, | |
4462 | etc. communication is blocked by default. | |
4463 | 1 Unblocked. | |
4464 | ||
4465 | rfkill.master_switch_mode= | |
4466 | 0 The "airplane mode" button does nothing. | |
4467 | 1 The "airplane mode" button toggles between everything | |
4468 | blocked and the previous configuration. | |
4469 | 2 The "airplane mode" button toggles between everything | |
4470 | blocked and everything unblocked. | |
4471 | ||
1da177e4 LT |
4472 | rhash_entries= [KNL,NET] |
4473 | Set number of hash buckets for route cache | |
4474 | ||
e16fd002 GA |
4475 | ring3mwait=disable |
4476 | [KNL] Disable ring 3 MONITOR/MWAIT feature on supported | |
4477 | CPUs. | |
4478 | ||
1da177e4 LT |
4479 | ro [KNL] Mount root device read-only on boot |
4480 | ||
d2aa1aca KC |
4481 | rodata= [KNL] |
4482 | on Mark read-only kernel memory as read-only (default). | |
4483 | off Leave read-only kernel memory writable for debugging. | |
4484 | ||
605df8af HS |
4485 | rockchip.usb_uart |
4486 | Enable the uart passthrough on the designated usb port | |
4487 | on Rockchip SoCs. When active, the signals of the | |
4488 | debug-uart get routed to the D+ and D- pins of the usb | |
4489 | port and the regular usb controller gets disabled. | |
4490 | ||
1da177e4 | 4491 | root= [KNL] Root filesystem |
f2d34fd9 | 4492 | See name_to_dev_t comment in init/do_mounts.c. |
1da177e4 LT |
4493 | |
4494 | rootdelay= [KNL] Delay (in seconds) to pause before attempting to | |
4495 | mount the root filesystem | |
4496 | ||
4497 | rootflags= [KNL] Set root filesystem mount option string | |
4498 | ||
4499 | rootfstype= [KNL] Set root filesystem type | |
4500 | ||
cc1ed754 PO |
4501 | rootwait [KNL] Wait (indefinitely) for root device to show up. |
4502 | Useful for devices that are detected asynchronously | |
4503 | (e.g. USB and MMC devices). | |
4504 | ||
5c71d618 RT |
4505 | rproc_mem=nn[KMG][@address] |
4506 | [KNL,ARM,CMA] Remoteproc physical memory block. | |
4507 | Memory area to be used by remote processor image, | |
4508 | managed by CMA. | |
4509 | ||
1da177e4 LT |
4510 | rw [KNL] Mount root device read-write on boot |
4511 | ||
4512 | S [KNL] Run init in single mode | |
4513 | ||
c60d1ae4 GS |
4514 | s390_iommu= [HW,S390] |
4515 | Set s390 IOTLB flushing mode | |
4516 | strict | |
4517 | With strict flushing every unmap operation will result in | |
4518 | an IOTLB flush. Default is lazy flushing before reuse, | |
4519 | which is faster. | |
4520 | ||
1da177e4 LT |
4521 | sa1100ir [NET] |
4522 | See drivers/net/irda/sa1100_ir.c. | |
4523 | ||
1da177e4 | 4524 | sbni= [NET] Granch SBNI12 leased line adapter |
a9913044 | 4525 | |
f6630114 MT |
4526 | sched_debug [KNL] Enables verbose scheduler debug messages. |
4527 | ||
cb251765 MG |
4528 | schedstats= [KNL,X86] Enable or disable scheduled statistics. |
4529 | Allowed values are enable and disable. This feature | |
4530 | incurs a small amount of overhead in the scheduler | |
4531 | but is useful for debugging and performance tuning. | |
f6630114 | 4532 | |
05289b90 TG |
4533 | sched_thermal_decay_shift= |
4534 | [KNL, SMP] Set a decay shift for scheduler thermal | |
4535 | pressure signal. Thermal pressure signal follows the | |
4536 | default decay period of other scheduler pelt | |
4537 | signals(usually 32 ms but configurable). Setting | |
4538 | sched_thermal_decay_shift will left shift the decay | |
4539 | period for the thermal pressure signal by the shift | |
4540 | value. | |
4541 | i.e. with the default pelt decay period of 32 ms | |
4542 | sched_thermal_decay_shift thermal pressure decay pr | |
4543 | 1 64 ms | |
4544 | 2 128 ms | |
4545 | and so on. | |
4546 | Format: integer between 0 and 10 | |
4547 | Default is 0. | |
4548 | ||
5307c955 MG |
4549 | skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate |
4550 | xtime_lock contention on larger systems, and/or RCU lock | |
4551 | contention on all systems with CONFIG_MAXSMP set. | |
4552 | Format: { "0" | "1" } | |
4553 | 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1" | |
4554 | 1 -- enable. | |
4555 | Note: increases power consumption, thus should only be | |
4556 | enabled if running jitter sensitive (HPC/RT) workloads. | |
4557 | ||
89a9684e KC |
4558 | security= [SECURITY] Choose a legacy "major" security module to |
4559 | enable at boot. This has been deprecated by the | |
4560 | "lsm=" parameter. | |
0cb55ad2 RD |
4561 | |
4562 | selinux= [SELINUX] Disable or enable SELinux at boot time. | |
1da177e4 LT |
4563 | Format: { "0" | "1" } |
4564 | See security/selinux/Kconfig help text. | |
4565 | 0 -- disable. | |
4566 | 1 -- enable. | |
d41415eb | 4567 | Default value is 1. |
1da177e4 | 4568 | |
c1c124e9 JJ |
4569 | apparmor= [APPARMOR] Disable or enable AppArmor at boot time |
4570 | Format: { "0" | "1" } | |
4571 | See security/apparmor/Kconfig help text | |
4572 | 0 -- disable. | |
4573 | 1 -- enable. | |
4574 | Default value is set via kernel config option. | |
4575 | ||
cd4f0ef7 | 4576 | serialnumber [BUGS=X86-32] |
1da177e4 | 4577 | |
1da177e4 LT |
4578 | shapers= [NET] |
4579 | Maximal number of shapers. | |
a9913044 | 4580 | |
1da177e4 LT |
4581 | simeth= [IA-64] |
4582 | simscsi= | |
a9913044 | 4583 | |
1da177e4 LT |
4584 | slram= [HW,MTD] |
4585 | ||
423c929c JK |
4586 | slab_nomerge [MM] |
4587 | Disable merging of slabs with similar size. May be | |
4588 | necessary if there is some reason to distinguish | |
7660a6fd KC |
4589 | allocs to different slabs, especially in hardened |
4590 | environments where the risk of heap overflows and | |
4591 | layout control by attackers can usually be | |
4592 | frustrated by disabling merging. This will reduce | |
4593 | most of the exposure of a heap attack to a single | |
4594 | cache (risks via metadata attacks are mostly | |
4595 | unchanged). Debug options disable merging on their | |
4596 | own. | |
ad56b738 | 4597 | For more information see Documentation/vm/slub.rst. |
423c929c | 4598 | |
3df1cccd DR |
4599 | slab_max_order= [MM, SLAB] |
4600 | Determines the maximum allowed order for slabs. | |
4601 | A high setting may cause OOMs due to memory | |
4602 | fragmentation. Defaults to 1 for systems with | |
4603 | more than 32MB of RAM, 0 otherwise. | |
4604 | ||
f0630fff CL |
4605 | slub_debug[=options[,slabs]] [MM, SLUB] |
4606 | Enabling slub_debug allows one to determine the | |
4607 | culprit if slab objects become corrupted. Enabling | |
4608 | slub_debug can create guard zones around objects and | |
4609 | may poison objects when not in use. Also tracks the | |
4610 | last alloc / free. For more information see | |
ad56b738 | 4611 | Documentation/vm/slub.rst. |
c1aee215 | 4612 | |
1663f26d TH |
4613 | slub_memcg_sysfs= [MM, SLUB] |
4614 | Determines whether to enable sysfs directories for | |
4615 | memory cgroup sub-caches. 1 to enable, 0 to disable. | |
4616 | The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON. | |
4617 | Enabling this can lead to a very high number of debug | |
4618 | directories and files being created under | |
4619 | /sys/kernel/slub. | |
4620 | ||
c1aee215 | 4621 | slub_max_order= [MM, SLUB] |
f0630fff CL |
4622 | Determines the maximum allowed order for slabs. |
4623 | A high setting may cause OOMs due to memory | |
4624 | fragmentation. For more information see | |
ad56b738 | 4625 | Documentation/vm/slub.rst. |
c1aee215 CL |
4626 | |
4627 | slub_min_objects= [MM, SLUB] | |
f0630fff CL |
4628 | The minimum number of objects per slab. SLUB will |
4629 | increase the slab order up to slub_max_order to | |
4630 | generate a sufficiently large slab able to contain | |
4631 | the number of objects indicated. The higher the number | |
4632 | of objects the smaller the overhead of tracking slabs | |
4633 | and the less frequently locks need to be acquired. | |
ad56b738 | 4634 | For more information see Documentation/vm/slub.rst. |
c1aee215 CL |
4635 | |
4636 | slub_min_order= [MM, SLUB] | |
24775d65 | 4637 | Determines the minimum page order for slabs. Must be |
f0630fff | 4638 | lower than slub_max_order. |
ad56b738 | 4639 | For more information see Documentation/vm/slub.rst. |
c1aee215 CL |
4640 | |
4641 | slub_nomerge [MM, SLUB] | |
423c929c JK |
4642 | Same with slab_nomerge. This is supported for legacy. |
4643 | See slab_nomerge for more information. | |
c1aee215 | 4644 | |
1da177e4 LT |
4645 | smart2= [HW] |
4646 | Format: <io1>[,<io2>[,...,<io8>]] | |
4647 | ||
d0d4f69b BH |
4648 | smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices |
4649 | smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port | |
4650 | smsc-ircc2.ircc_sir= [HW] SIR base I/O port | |
4651 | smsc-ircc2.ircc_fir= [HW] FIR base I/O port | |
4652 | smsc-ircc2.ircc_irq= [HW] IRQ line | |
4653 | smsc-ircc2.ircc_dma= [HW] DMA channel | |
4654 | smsc-ircc2.ircc_transceiver= [HW] Transceiver type: | |
4655 | 0: Toshiba Satellite 1800 (GP data pin select) | |
4656 | 1: Fast pin select (default) | |
4657 | 2: ATC IRMode | |
4658 | ||
52c48c51 SS |
4659 | smt [KNL,S390] Set the maximum number of threads (logical |
4660 | CPUs) to use per physical CPU on systems capable of | |
4661 | symmetric multithreading (SMT). Will be capped to the | |
4662 | actual hardware limit. | |
4663 | Format: <integer> | |
4664 | Default: -1 (no limit) | |
4665 | ||
9c44bc03 IM |
4666 | softlockup_panic= |
4667 | [KNL] Should the soft-lockup detector generate panics. | |
44a4dcf7 | 4668 | Format: <integer> |
9c44bc03 | 4669 | |
3ce62385 | 4670 | A nonzero value instructs the soft-lockup detector |
0a07bef6 GP |
4671 | to panic the machine when a soft-lockup occurs. It is |
4672 | also controlled by the kernel.softlockup_panic sysctl | |
4673 | and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the | |
4674 | respective build-time switch to that functionality. | |
3ce62385 | 4675 | |
ed235875 AT |
4676 | softlockup_all_cpu_backtrace= |
4677 | [KNL] Should the soft-lockup detector generate | |
4678 | backtraces on all cpus. | |
4679 | Format: <integer> | |
4680 | ||
1da177e4 | 4681 | sonypi.*= [HW] Sony Programmable I/O Control Device driver |
9e1cbede | 4682 | See Documentation/admin-guide/laptops/sonypi.rst |
1da177e4 | 4683 | |
da285121 DW |
4684 | spectre_v2= [X86] Control mitigation of Spectre variant 2 |
4685 | (indirect branch speculation) vulnerability. | |
fa1202ef TG |
4686 | The default operation protects the kernel from |
4687 | user space attacks. | |
da285121 | 4688 | |
fa1202ef TG |
4689 | on - unconditionally enable, implies |
4690 | spectre_v2_user=on | |
4691 | off - unconditionally disable, implies | |
4692 | spectre_v2_user=off | |
da285121 DW |
4693 | auto - kernel detects whether your CPU model is |
4694 | vulnerable | |
4695 | ||
4696 | Selecting 'on' will, and 'auto' may, choose a | |
4697 | mitigation method at run time according to the | |
4698 | CPU, the available microcode, the setting of the | |
4699 | CONFIG_RETPOLINE configuration option, and the | |
4700 | compiler with which the kernel was built. | |
4701 | ||
fa1202ef TG |
4702 | Selecting 'on' will also enable the mitigation |
4703 | against user space to user space task attacks. | |
4704 | ||
4705 | Selecting 'off' will disable both the kernel and | |
4706 | the user space protections. | |
4707 | ||
da285121 DW |
4708 | Specific mitigations can also be selected manually: |
4709 | ||
4710 | retpoline - replace indirect branches | |
4711 | retpoline,generic - google's original retpoline | |
4712 | retpoline,amd - AMD-specific minimal thunk | |
4713 | ||
4714 | Not specifying this option is equivalent to | |
4715 | spectre_v2=auto. | |
4716 | ||
fa1202ef TG |
4717 | spectre_v2_user= |
4718 | [X86] Control mitigation of Spectre variant 2 | |
4719 | (indirect branch speculation) vulnerability between | |
4720 | user space tasks | |
4721 | ||
4722 | on - Unconditionally enable mitigations. Is | |
4723 | enforced by spectre_v2=on | |
4724 | ||
4725 | off - Unconditionally disable mitigations. Is | |
4726 | enforced by spectre_v2=off | |
4727 | ||
7cc765a6 TG |
4728 | prctl - Indirect branch speculation is enabled, |
4729 | but mitigation can be enabled via prctl | |
4730 | per thread. The mitigation control state | |
4731 | is inherited on fork. | |
4732 | ||
55a97402 TG |
4733 | prctl,ibpb |
4734 | - Like "prctl" above, but only STIBP is | |
4735 | controlled per thread. IBPB is issued | |
4736 | always when switching between different user | |
4737 | space processes. | |
4738 | ||
6b3e64c2 TG |
4739 | seccomp |
4740 | - Same as "prctl" above, but all seccomp | |
4741 | threads will enable the mitigation unless | |
4742 | they explicitly opt out. | |
4743 | ||
55a97402 TG |
4744 | seccomp,ibpb |
4745 | - Like "seccomp" above, but only STIBP is | |
4746 | controlled per thread. IBPB is issued | |
4747 | always when switching between different | |
4748 | user space processes. | |
4749 | ||
fa1202ef TG |
4750 | auto - Kernel selects the mitigation depending on |
4751 | the available CPU features and vulnerability. | |
6b3e64c2 TG |
4752 | |
4753 | Default mitigation: | |
4754 | If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl" | |
fa1202ef TG |
4755 | |
4756 | Not specifying this option is equivalent to | |
4757 | spectre_v2_user=auto. | |
4758 | ||
24f7fc83 KRW |
4759 | spec_store_bypass_disable= |
4760 | [HW] Control Speculative Store Bypass (SSB) Disable mitigation | |
4761 | (Speculative Store Bypass vulnerability) | |
4762 | ||
4763 | Certain CPUs are vulnerable to an exploit against a | |
4764 | a common industry wide performance optimization known | |
4765 | as "Speculative Store Bypass" in which recent stores | |
4766 | to the same memory location may not be observed by | |
4767 | later loads during speculative execution. The idea | |
4768 | is that such stores are unlikely and that they can | |
4769 | be detected prior to instruction retirement at the | |
4770 | end of a particular speculation execution window. | |
4771 | ||
4772 | In vulnerable processors, the speculatively forwarded | |
4773 | store can be used in a cache side channel attack, for | |
4774 | example to read memory to which the attacker does not | |
4775 | directly have access (e.g. inside sandboxed code). | |
4776 | ||
4777 | This parameter controls whether the Speculative Store | |
4778 | Bypass optimization is used. | |
4779 | ||
6b4c1360 ME |
4780 | On x86 the options are: |
4781 | ||
f21b53b2 KC |
4782 | on - Unconditionally disable Speculative Store Bypass |
4783 | off - Unconditionally enable Speculative Store Bypass | |
4784 | auto - Kernel detects whether the CPU model contains an | |
4785 | implementation of Speculative Store Bypass and | |
4786 | picks the most appropriate mitigation. If the | |
4787 | CPU is not vulnerable, "off" is selected. If the | |
4788 | CPU is vulnerable the default mitigation is | |
4789 | architecture and Kconfig dependent. See below. | |
4790 | prctl - Control Speculative Store Bypass per thread | |
4791 | via prctl. Speculative Store Bypass is enabled | |
4792 | for a process by default. The state of the control | |
4793 | is inherited on fork. | |
4794 | seccomp - Same as "prctl" above, but all seccomp threads | |
4795 | will disable SSB unless they explicitly opt out. | |
24f7fc83 | 4796 | |
f21b53b2 KC |
4797 | Default mitigations: |
4798 | X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl" | |
4799 | ||
6b4c1360 ME |
4800 | On powerpc the options are: |
4801 | ||
4802 | on,auto - On Power8 and Power9 insert a store-forwarding | |
4803 | barrier on kernel entry and exit. On Power7 | |
4804 | perform a software flush on kernel entry and | |
4805 | exit. | |
4806 | off - No action. | |
4807 | ||
4808 | Not specifying this option is equivalent to | |
4809 | spec_store_bypass_disable=auto. | |
4810 | ||
1da177e4 LT |
4811 | spia_io_base= [HW,MTD] |
4812 | spia_fio_base= | |
4813 | spia_pedr= | |
4814 | spia_peddr= | |
4815 | ||
6650cdd9 PZI |
4816 | split_lock_detect= |
4817 | [X86] Enable split lock detection | |
4818 | ||
4819 | When enabled (and if hardware support is present), atomic | |
4820 | instructions that access data across cache line | |
4821 | boundaries will result in an alignment check exception. | |
4822 | ||
4823 | off - not enabled | |
4824 | ||
4825 | warn - the kernel will emit rate limited warnings | |
4826 | about applications triggering the #AC | |
4827 | exception. This mode is the default on CPUs | |
4828 | that supports split lock detection. | |
4829 | ||
4830 | fatal - the kernel will send SIGBUS to applications | |
4831 | that trigger the #AC exception. | |
4832 | ||
4833 | If an #AC exception is hit in the kernel or in | |
4834 | firmware (i.e. not while executing in user mode) | |
4835 | the kernel will oops in either "warn" or "fatal" | |
4836 | mode. | |
4837 | ||
c350c008 PM |
4838 | srcutree.counter_wrap_check [KNL] |
4839 | Specifies how frequently to check for | |
4840 | grace-period sequence counter wrap for the | |
4841 | srcu_data structure's ->srcu_gp_seq_needed field. | |
4842 | The greater the number of bits set in this kernel | |
4843 | parameter, the less frequently counter wrap will | |
4844 | be checked for. Note that the bottom two bits | |
4845 | are ignored. | |
4846 | ||
22607d66 PM |
4847 | srcutree.exp_holdoff [KNL] |
4848 | Specifies how many nanoseconds must elapse | |
4849 | since the end of the last SRCU grace period for | |
4850 | a given srcu_struct until the next normal SRCU | |
4851 | grace period will be considered for automatic | |
4852 | expediting. Set to zero to disable automatic | |
4853 | expediting. | |
4854 | ||
a43ae4df MZ |
4855 | ssbd= [ARM64,HW] |
4856 | Speculative Store Bypass Disable control | |
4857 | ||
4858 | On CPUs that are vulnerable to the Speculative | |
4859 | Store Bypass vulnerability and offer a | |
4860 | firmware based mitigation, this parameter | |
4861 | indicates how the mitigation should be used: | |
4862 | ||
4863 | force-on: Unconditionally enable mitigation for | |
4864 | for both kernel and userspace | |
4865 | force-off: Unconditionally disable mitigation for | |
4866 | for both kernel and userspace | |
4867 | kernel: Always enable mitigation in the | |
4868 | kernel, and offer a prctl interface | |
4869 | to allow userspace to register its | |
4870 | interest in being mitigated too. | |
4871 | ||
1be7107f HD |
4872 | stack_guard_gap= [MM] |
4873 | override the default stack gap protection. The value | |
4874 | is in page units and it defines how many pages prior | |
4875 | to (for stacks growing down) resp. after (for stacks | |
4876 | growing up) the main stack are reserved for no other | |
4877 | mapping. Default value is 256 pages. | |
4878 | ||
f38f1d2a SR |
4879 | stacktrace [FTRACE] |
4880 | Enabled the stack tracer on boot up. | |
4881 | ||
762e1207 SR |
4882 | stacktrace_filter=[function-list] |
4883 | [FTRACE] Limit the functions that the stack tracer | |
4884 | will trace at boot up. function-list is a comma separated | |
4885 | list of functions. This list can be changed at run | |
4886 | time by the stack_trace_filter file in the debugfs | |
4887 | tracing directory. Note, this enables stack tracing | |
4888 | and the stacktrace above is not needed. | |
4889 | ||
1da177e4 LT |
4890 | sti= [PARISC,HW] |
4891 | Format: <num> | |
4892 | Set the STI (builtin display/keyboard on the HP-PARISC | |
4893 | machines) console (graphic card) which should be used | |
4894 | as the initial boot-console. | |
4895 | See also comment in drivers/video/console/sticore.c. | |
4896 | ||
4897 | sti_font= [HW] | |
4898 | See comment in drivers/video/console/sticore.c. | |
4899 | ||
4900 | stifb= [HW] | |
4901 | Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] | |
4902 | ||
cbf11071 TM |
4903 | sunrpc.min_resvport= |
4904 | sunrpc.max_resvport= | |
4905 | [NFS,SUNRPC] | |
4906 | SunRPC servers often require that client requests | |
4907 | originate from a privileged port (i.e. a port in the | |
4908 | range 0 < portnr < 1024). | |
4909 | An administrator who wishes to reserve some of these | |
4910 | ports for other uses may adjust the range that the | |
4911 | kernel's sunrpc client considers to be privileged | |
4912 | using these two parameters to set the minimum and | |
4913 | maximum port values. | |
4914 | ||
ff3ac5c3 TM |
4915 | sunrpc.svc_rpc_per_connection_limit= |
4916 | [NFS,SUNRPC] | |
4917 | Limit the number of requests that the server will | |
4918 | process in parallel from a single connection. | |
4919 | The default value is 0 (no limit). | |
4920 | ||
42a7fc4a GB |
4921 | sunrpc.pool_mode= |
4922 | [NFS] | |
4923 | Control how the NFS server code allocates CPUs to | |
4924 | service thread pools. Depending on how many NICs | |
4925 | you have and where their interrupts are bound, this | |
4926 | option will affect which CPUs will do NFS serving. | |
4927 | Note: this parameter cannot be changed while the | |
4928 | NFS server is running. | |
4929 | ||
4930 | auto the server chooses an appropriate mode | |
4931 | automatically using heuristics | |
4932 | global a single global pool contains all CPUs | |
4933 | percpu one pool for each CPU | |
4934 | pernode one pool for each NUMA node (equivalent | |
4935 | to global on non-NUMA machines) | |
4936 | ||
cbf11071 TM |
4937 | sunrpc.tcp_slot_table_entries= |
4938 | sunrpc.udp_slot_table_entries= | |
4939 | [NFS,SUNRPC] | |
4940 | Sets the upper limit on the number of simultaneous | |
4941 | RPC calls that can be sent from the client to a | |
4942 | server. Increasing these values may allow you to | |
4943 | improve throughput, but will also increase the | |
4944 | amount of memory reserved for use by the client. | |
4945 | ||
1d4a9c17 BN |
4946 | suspend.pm_test_delay= |
4947 | [SUSPEND] | |
4948 | Sets the number of seconds to remain in a suspend test | |
4949 | mode before resuming the system (see | |
4950 | /sys/power/pm_test). Only available when CONFIG_PM_DEBUG | |
4951 | is set. Default value is 5. | |
4952 | ||
6a9c930b RP |
4953 | svm= [PPC] |
4954 | Format: { on | off | y | n | 1 | 0 } | |
4955 | This parameter controls use of the Protected | |
4956 | Execution Facility on pSeries. | |
4957 | ||
07555ac1 | 4958 | swapaccount=[0|1] |
a42c390c MH |
4959 | [KNL] Enable accounting of swap in memory resource |
4960 | controller if no parameter or 1 is given or disable | |
da82c92f | 4961 | it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst) |
a42c390c | 4962 | |
91fec0f5 | 4963 | swiotlb= [ARM,IA-64,PPC,MIPS,X86] |
fff5d992 | 4964 | Format: { <int> | force | noforce } |
91fec0f5 JK |
4965 | <int> -- Number of I/O TLB slabs |
4966 | force -- force using of bounce buffers even if they | |
4967 | wouldn't be automatically used by the kernel | |
fff5d992 | 4968 | noforce -- Never use bounce buffers (for debugging) |
a9913044 | 4969 | |
1da177e4 LT |
4970 | switches= [HW,M68k] |
4971 | ||
e52eec13 AK |
4972 | sysfs.deprecated=0|1 [KNL] |
4973 | Enable/disable old style sysfs layout for old udev | |
4974 | on older distributions. When this option is enabled | |
4975 | very new udev will not work anymore. When this option | |
4976 | is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) | |
4977 | in older udev will not work anymore. | |
4978 | Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in | |
4979 | the kernel configuration. | |
4980 | ||
5d6f647f IM |
4981 | sysrq_always_enabled |
4982 | [KNL] | |
4983 | Ignore sysrq setting - this boot parameter will | |
4984 | neutralize any effect of /proc/sys/kernel/sysrq. | |
4985 | Useful for debugging. | |
4986 | ||
747029a5 FF |
4987 | tcpmhash_entries= [KNL,NET] |
4988 | Set the number of tcp_metrics_hash slots. | |
4989 | Default value is 8192 or 16384 depending on total | |
4990 | ram pages. This is used to specify the TCP metrics | |
1cec2cac | 4991 | cache size. See Documentation/networking/ip-sysctl.rst |
747029a5 FF |
4992 | "tcp_no_metrics_save" section for more details. |
4993 | ||
1da177e4 LT |
4994 | tdfx= [HW,DRM] |
4995 | ||
acc82342 | 4996 | test_suspend= [SUSPEND][,N] |
77437fd4 | 4997 | Specify "mem" (for Suspend-to-RAM) or "standby" (for |
acc82342 SP |
4998 | standby suspend) or "freeze" (for suspend type freeze) |
4999 | as the system sleep state during system startup with | |
5000 | the optional capability to repeat N number of times. | |
5001 | The system is woken from this state using a | |
5002 | wakeup-capable RTC alarm. | |
77437fd4 | 5003 | |
1da177e4 LT |
5004 | thash_entries= [KNL,NET] |
5005 | Set number of hash buckets for TCP connection | |
5006 | ||
f8707ec9 LB |
5007 | thermal.act= [HW,ACPI] |
5008 | -1: disable all active trip points in all thermal zones | |
5009 | <degrees C>: override all lowest active trip points | |
5010 | ||
c52a7419 LB |
5011 | thermal.crt= [HW,ACPI] |
5012 | -1: disable all critical trip points in all thermal zones | |
22a94d79 | 5013 | <degrees C>: override all critical trip points |
c52a7419 | 5014 | |
f5487145 LB |
5015 | thermal.nocrt= [HW,ACPI] |
5016 | Set to disable actions on ACPI thermal zone | |
5017 | critical and hot trip points. | |
5018 | ||
72b33ef8 LB |
5019 | thermal.off= [HW,ACPI] |
5020 | 1: disable ACPI thermal control | |
5021 | ||
a70cdc52 LB |
5022 | thermal.psv= [HW,ACPI] |
5023 | -1: disable all passive trip points | |
ada9cfdd RD |
5024 | <degrees C>: override all passive trip points to this |
5025 | value | |
a70cdc52 | 5026 | |
730ff34d LB |
5027 | thermal.tzp= [HW,ACPI] |
5028 | Specify global default ACPI thermal zone polling rate | |
5029 | <deci-seconds>: poll all this frequency | |
5030 | 0: no polling (default) | |
5031 | ||
8d32a307 TG |
5032 | threadirqs [KNL] |
5033 | Force threading of all interrupt handlers except those | |
24775d65 | 5034 | marked explicitly IRQF_NO_THREAD. |
8d32a307 | 5035 | |
2b1a61f0 HC |
5036 | topology= [S390] |
5037 | Format: {off | on} | |
5038 | Specify if the kernel should make use of the cpu | |
f65e51d7 SL |
5039 | topology information if the hardware supports this. |
5040 | The scheduler will make use of this information and | |
2b1a61f0 | 5041 | e.g. base its process migration decisions on it. |
c9af3fa9 | 5042 | Default is on. |
2b1a61f0 | 5043 | |
2d73bae1 NA |
5044 | topology_updates= [KNL, PPC, NUMA] |
5045 | Format: {off} | |
5046 | Specify if the kernel should ignore (off) | |
5047 | topology updates sent by the hypervisor to this | |
5048 | LPAR. | |
5049 | ||
8171d3e0 PM |
5050 | torture.disable_onoff_at_boot= [KNL] |
5051 | Prevent the CPU-hotplug component of torturing | |
5052 | until after init has spawned. | |
5053 | ||
1da177e4 LT |
5054 | tp720= [HW,PS2] |
5055 | ||
225a9be2 RA |
5056 | tpm_suspend_pcr=[HW,TPM] |
5057 | Format: integer pcr id | |
5058 | Specify that at suspend time, the tpm driver | |
5059 | should extend the specified pcr with zeros, | |
5060 | as a workaround for some chips which fail to | |
5061 | flush the last written pcr on TPM_SaveState. | |
5062 | This will guarantee that all the other pcrs | |
5063 | are saved. | |
5064 | ||
9d612bef | 5065 | trace_buf_size=nn[KMG] |
3e6fb8e9 | 5066 | [FTRACE] will set tracing buffer size on each cpu. |
631595fb | 5067 | |
020e5f85 LZ |
5068 | trace_event=[event-list] |
5069 | [FTRACE] Set and start specified trace events in order | |
d81749ea BN |
5070 | to facilitate early boot debugging. The event-list is a |
5071 | comma separated list of trace events to enable. See | |
5fb94e9c | 5072 | also Documentation/trace/events.rst |
020e5f85 | 5073 | |
7bcfaf54 SR |
5074 | trace_options=[option-list] |
5075 | [FTRACE] Enable or disable tracer options at boot. | |
5076 | The option-list is a comma delimited list of options | |
5077 | that can be enabled or disabled just as if you were | |
5078 | to echo the option name into | |
5079 | ||
5080 | /sys/kernel/debug/tracing/trace_options | |
5081 | ||
5082 | For example, to enable stacktrace option (to dump the | |
5083 | stack trace of each event), add to the command line: | |
5084 | ||
5085 | trace_options=stacktrace | |
5086 | ||
5fb94e9c | 5087 | See also Documentation/trace/ftrace.rst "trace options" |
7bcfaf54 SR |
5088 | section. |
5089 | ||
0daa2302 SRRH |
5090 | tp_printk[FTRACE] |
5091 | Have the tracepoints sent to printk as well as the | |
5092 | tracing ring buffer. This is useful for early boot up | |
5093 | where the system hangs or reboots and does not give the | |
5094 | option for reading the tracing buffer or performing a | |
5095 | ftrace_dump_on_oops. | |
5096 | ||
5097 | To turn off having tracepoints sent to printk, | |
5098 | echo 0 > /proc/sys/kernel/tracepoint_printk | |
5099 | Note, echoing 1 into this file without the | |
5100 | tracepoint_printk kernel cmdline option has no effect. | |
5101 | ||
5102 | ** CAUTION ** | |
5103 | ||
5104 | Having tracepoints sent to printk() and activating high | |
5105 | frequency tracepoints such as irq or sched, can cause | |
5106 | the system to live lock. | |
5107 | ||
de7edd31 SRRH |
5108 | traceoff_on_warning |
5109 | [FTRACE] enable this option to disable tracing when a | |
5110 | warning is hit. This turns off "tracing_on". Tracing can | |
5111 | be enabled again by echoing '1' into the "tracing_on" | |
5112 | file located in /sys/kernel/debug/tracing/ | |
5113 | ||
5114 | This option is useful, as it disables the trace before | |
5115 | the WARNING dump is called, which prevents the trace to | |
5116 | be filled with content caused by the warning output. | |
5117 | ||
5118 | This option can also be set at run time via the sysctl | |
5119 | option: kernel/traceoff_on_warning | |
5120 | ||
fcf4d821 JK |
5121 | transparent_hugepage= |
5122 | [KNL] | |
5123 | Format: [always|madvise|never] | |
5124 | Can be used to control the default behavior of the system | |
5125 | with respect to transparent hugepages. | |
45c9a74f MR |
5126 | See Documentation/admin-guide/mm/transhuge.rst |
5127 | for more details. | |
fcf4d821 | 5128 | |
d3b8f889 | 5129 | tsc= Disable clocksource stability checks for TSC. |
395628ef AK |
5130 | Format: <string> |
5131 | [x86] reliable: mark tsc clocksource as reliable, this | |
d3b8f889 JS |
5132 | disables clocksource verification at runtime, as well |
5133 | as the stability checks done at bootup. Used to enable | |
5134 | high-resolution timer mode on older hardware, and in | |
5135 | virtualized environment. | |
e82b8e4e VP |
5136 | [x86] noirqtime: Do not use TSC to do irq accounting. |
5137 | Used to run time disable IRQ_TIME_ACCOUNTING on any | |
5138 | platforms where RDTSC is slow and this accounting | |
5139 | can add overhead. | |
6be53520 DL |
5140 | [x86] unstable: mark the TSC clocksource as unstable, this |
5141 | marks the TSC unconditionally unstable at bootup and | |
5142 | avoids any further wobbles once the TSC watchdog notices. | |
0f0b7e1c JL |
5143 | [x86] nowatchdog: disable clocksource watchdog. Used |
5144 | in situations with strict latency requirements (where | |
5145 | interruptions from clocksource watchdog are not | |
5146 | acceptable). | |
395628ef | 5147 | |
bd35c77e KP |
5148 | tsc_early_khz= [X86] Skip early TSC calibration and use the given |
5149 | value instead. Useful when the early TSC frequency discovery | |
5150 | procedure is not reliable, such as on overclocked systems | |
5151 | with CPUID.16h support and partial CPUID.15h support. | |
5152 | Format: <unsigned int> | |
5153 | ||
95c5824f PG |
5154 | tsx= [X86] Control Transactional Synchronization |
5155 | Extensions (TSX) feature in Intel processors that | |
5156 | support TSX control. | |
5157 | ||
5158 | This parameter controls the TSX feature. The options are: | |
5159 | ||
5160 | on - Enable TSX on the system. Although there are | |
5161 | mitigations for all known security vulnerabilities, | |
5162 | TSX has been known to be an accelerator for | |
5163 | several previous speculation-related CVEs, and | |
5164 | so there may be unknown security risks associated | |
5165 | with leaving it enabled. | |
5166 | ||
5167 | off - Disable TSX on the system. (Note that this | |
5168 | option takes effect only on newer CPUs which are | |
5169 | not vulnerable to MDS, i.e., have | |
5170 | MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get | |
5171 | the new IA32_TSX_CTRL MSR through a microcode | |
5172 | update. This new MSR allows for the reliable | |
5173 | deactivation of the TSX functionality.) | |
5174 | ||
7531a359 PG |
5175 | auto - Disable TSX if X86_BUG_TAA is present, |
5176 | otherwise enable TSX on the system. | |
5177 | ||
95c5824f PG |
5178 | Not specifying this option is equivalent to tsx=off. |
5179 | ||
5180 | See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst | |
5181 | for more details. | |
5182 | ||
a7a248c5 PG |
5183 | tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async |
5184 | Abort (TAA) vulnerability. | |
5185 | ||
5186 | Similar to Micro-architectural Data Sampling (MDS) | |
5187 | certain CPUs that support Transactional | |
5188 | Synchronization Extensions (TSX) are vulnerable to an | |
5189 | exploit against CPU internal buffers which can forward | |
5190 | information to a disclosure gadget under certain | |
5191 | conditions. | |
5192 | ||
5193 | In vulnerable processors, the speculatively forwarded | |
5194 | data can be used in a cache side channel attack, to | |
5195 | access data to which the attacker does not have direct | |
5196 | access. | |
5197 | ||
5198 | This parameter controls the TAA mitigation. The | |
5199 | options are: | |
5200 | ||
5201 | full - Enable TAA mitigation on vulnerable CPUs | |
5202 | if TSX is enabled. | |
5203 | ||
5204 | full,nosmt - Enable TAA mitigation and disable SMT on | |
5205 | vulnerable CPUs. If TSX is disabled, SMT | |
5206 | is not disabled because CPU is not | |
5207 | vulnerable to cross-thread TAA attacks. | |
5208 | off - Unconditionally disable TAA mitigation | |
5209 | ||
64870ed1 WL |
5210 | On MDS-affected machines, tsx_async_abort=off can be |
5211 | prevented by an active MDS mitigation as both vulnerabilities | |
5212 | are mitigated with the same mechanism so in order to disable | |
5213 | this mitigation, you need to specify mds=off too. | |
5214 | ||
a7a248c5 PG |
5215 | Not specifying this option is equivalent to |
5216 | tsx_async_abort=full. On CPUs which are MDS affected | |
5217 | and deploy MDS mitigation, TAA mitigation is not | |
5218 | required and doesn't provide any additional | |
5219 | mitigation. | |
5220 | ||
5221 | For details see: | |
5222 | Documentation/admin-guide/hw-vuln/tsx_async_abort.rst | |
5223 | ||
a9913044 RD |
5224 | turbografx.map[2|3]= [HW,JOY] |
5225 | TurboGraFX parallel port interface | |
5226 | Format: | |
5227 | <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> | |
1752118d | 5228 | See also Documentation/input/devices/joystick-parport.rst |
1da177e4 | 5229 | |
b6935f8c | 5230 | udbg-immortal [PPC] When debugging early kernel crashes that |
e52347bd | 5231 | happen after console_init() and before a proper |
b6935f8c CK |
5232 | console driver takes over, this boot options might |
5233 | help "seeing" what's going on. | |
5234 | ||
f86dcc5a ED |
5235 | uhash_entries= [KNL,NET] |
5236 | Set number of hash buckets for UDP/UDP-Lite connections | |
5237 | ||
5f8364b7 AS |
5238 | uhci-hcd.ignore_oc= |
5239 | [USB] Ignore overcurrent events (default N). | |
5240 | Some badly-designed motherboards generate lots of | |
5241 | bogus events, for ports that aren't wired to | |
5242 | anything. Set this parameter to avoid log spamming. | |
5243 | Note that genuine overcurrent events won't be | |
5244 | reported either. | |
5245 | ||
e3a61b0a | 5246 | unknown_nmi_panic |
44a4dcf7 | 5247 | [X86] Cause panic on unknown NMI. |
e3a61b0a | 5248 | |
c4fc2342 CDH |
5249 | usbcore.authorized_default= |
5250 | [USB] Default USB device authorization: | |
5251 | (default -1 = authorized except for wireless USB, | |
7bae0432 DT |
5252 | 0 = not authorized, 1 = authorized, 2 = authorized |
5253 | if device connected to internal port) | |
c4fc2342 | 5254 | |
b5e795f8 AS |
5255 | usbcore.autosuspend= |
5256 | [USB] The autosuspend time delay (in seconds) used | |
5257 | for newly-detected USB devices (default 2). This | |
5258 | is the time required before an idle device will be | |
5259 | autosuspended. Devices for which the delay is set | |
eaafbc3a | 5260 | to a negative value won't be autosuspended at all. |
b5e795f8 | 5261 | |
fd7c519d JK |
5262 | usbcore.usbfs_snoop= |
5263 | [USB] Set to log all usbfs traffic (default 0 = off). | |
5264 | ||
0290cc9f AS |
5265 | usbcore.usbfs_snoop_max= |
5266 | [USB] Maximum number of bytes to snoop in each URB | |
5267 | (default = 65536). | |
5268 | ||
fd7c519d JK |
5269 | usbcore.blinkenlights= |
5270 | [USB] Set to cycle leds on hubs (default 0 = off). | |
5271 | ||
5272 | usbcore.old_scheme_first= | |
5273 | [USB] Start with the old device initialization | |
3155f4f4 | 5274 | scheme (default 0 = off). |
fd7c519d | 5275 | |
3f5eb8d5 AS |
5276 | usbcore.usbfs_memory_mb= |
5277 | [USB] Memory limit (in MB) for buffers allocated by | |
5278 | usbfs (default = 16, 0 = max = 2047). | |
5279 | ||
fd7c519d JK |
5280 | usbcore.use_both_schemes= |
5281 | [USB] Try the other device initialization scheme | |
5282 | if the first one fails (default 1 = enabled). | |
5283 | ||
5284 | usbcore.initial_descriptor_timeout= | |
5285 | [USB] Specifies timeout for the initial 64-byte | |
6dddd7a7 | 5286 | USB_REQ_GET_DESCRIPTOR request in milliseconds |
fd7c519d JK |
5287 | (default 5000 = 5.0 seconds). |
5288 | ||
40d58148 ON |
5289 | usbcore.nousb [USB] Disable the USB subsystem |
5290 | ||
027bd6ca KHF |
5291 | usbcore.quirks= |
5292 | [USB] A list of quirk entries to augment the built-in | |
5293 | usb core quirk list. List entries are separated by | |
5294 | commas. Each entry has the form | |
5295 | VendorID:ProductID:Flags. The IDs are 4-digit hex | |
5296 | numbers and Flags is a set of letters. Each letter | |
5297 | will change the built-in quirk; setting it if it is | |
5298 | clear and clearing it if it is set. The letters have | |
5299 | the following meanings: | |
5300 | a = USB_QUIRK_STRING_FETCH_255 (string | |
5301 | descriptors must not be fetched using | |
5302 | a 255-byte read); | |
5303 | b = USB_QUIRK_RESET_RESUME (device can't resume | |
5304 | correctly so reset it instead); | |
5305 | c = USB_QUIRK_NO_SET_INTF (device can't handle | |
5306 | Set-Interface requests); | |
5307 | d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't | |
5308 | handle its Configuration or Interface | |
5309 | strings); | |
5310 | e = USB_QUIRK_RESET (device can't be reset | |
5311 | (e.g morph devices), don't use reset); | |
5312 | f = USB_QUIRK_HONOR_BNUMINTERFACES (device has | |
5313 | more interface descriptions than the | |
5314 | bNumInterfaces count, and can't handle | |
5315 | talking to these interfaces); | |
5316 | g = USB_QUIRK_DELAY_INIT (device needs a pause | |
5317 | during initialization, after we read | |
5318 | the device descriptor); | |
5319 | h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For | |
5320 | high speed and super speed interrupt | |
5321 | endpoints, the USB 2.0 and USB 3.0 spec | |
5322 | require the interval in microframes (1 | |
5323 | microframe = 125 microseconds) to be | |
5324 | calculated as interval = 2 ^ | |
5325 | (bInterval-1). | |
5326 | Devices with this quirk report their | |
5327 | bInterval as the result of this | |
5328 | calculation instead of the exponent | |
5329 | variable used in the calculation); | |
5330 | i = USB_QUIRK_DEVICE_QUALIFIER (device can't | |
5331 | handle device_qualifier descriptor | |
5332 | requests); | |
5333 | j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device | |
5334 | generates spurious wakeup, ignore | |
5335 | remote wakeup capability); | |
5336 | k = USB_QUIRK_NO_LPM (device can't handle Link | |
5337 | Power Management); | |
5338 | l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL | |
5339 | (Device reports its bInterval as linear | |
5340 | frames instead of the USB 2.0 | |
5341 | calculation); | |
5342 | m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs | |
5343 | to be disconnected before suspend to | |
4d8d5a39 KHF |
5344 | prevent spurious wakeup); |
5345 | n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a | |
5346 | pause after every control message); | |
781f0766 KHF |
5347 | o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra |
5348 | delay after resetting its port); | |
027bd6ca KHF |
5349 | Example: quirks=0781:5580:bk,0a5c:5834:gij |
5350 | ||
1da177e4 LT |
5351 | usbhid.mousepoll= |
5352 | [USBHID] The interval which mice are to be polled at. | |
a9913044 | 5353 | |
933bfe4d TJ |
5354 | usbhid.jspoll= |
5355 | [USBHID] The interval which joysticks are to be polled at. | |
5356 | ||
2ddc8e2d FA |
5357 | usbhid.kbpoll= |
5358 | [USBHID] The interval which keyboards are to be polled at. | |
5359 | ||
d4f373e5 AS |
5360 | usb-storage.delay_use= |
5361 | [UMS] The delay in seconds before a new device is | |
19101954 | 5362 | scanned for Logical Units (default 1). |
d4f373e5 AS |
5363 | |
5364 | usb-storage.quirks= | |
5365 | [UMS] A list of quirks entries to supplement or | |
5366 | override the built-in unusual_devs list. List | |
5367 | entries are separated by commas. Each entry has | |
5368 | the form VID:PID:Flags where VID and PID are Vendor | |
5369 | and Product ID values (4-digit hex numbers) and | |
5370 | Flags is a set of characters, each corresponding | |
5371 | to a common usb-storage quirk flag as follows: | |
c838ea46 | 5372 | a = SANE_SENSE (collect more than 18 bytes |
65cc8bf9 | 5373 | of sense data, not on uas); |
a0bb1081 | 5374 | b = BAD_SENSE (don't collect more than 18 |
65cc8bf9 | 5375 | bytes of sense data, not on uas); |
d4f373e5 AS |
5376 | c = FIX_CAPACITY (decrease the reported |
5377 | device capacity by one sector); | |
5116901d | 5378 | d = NO_READ_DISC_INFO (don't use |
65cc8bf9 | 5379 | READ_DISC_INFO command, not on uas); |
5116901d KR |
5380 | e = NO_READ_CAPACITY_16 (don't use |
5381 | READ_CAPACITY_16 command); | |
734016b0 HG |
5382 | f = NO_REPORT_OPCODES (don't use report opcodes |
5383 | command, uas only); | |
ee136af4 HG |
5384 | g = MAX_SECTORS_240 (don't transfer more than |
5385 | 240 sectors at a time, uas only); | |
c838ea46 AS |
5386 | h = CAPACITY_HEURISTICS (decrease the |
5387 | reported device capacity by one | |
5388 | sector if the number is odd); | |
d4f373e5 AS |
5389 | i = IGNORE_DEVICE (don't bind to this |
5390 | device); | |
13630746 HG |
5391 | j = NO_REPORT_LUNS (don't use report luns |
5392 | command, uas only); | |
d4f373e5 | 5393 | l = NOT_LOCKABLE (don't try to lock and |
65cc8bf9 | 5394 | unlock ejectable media, not on uas); |
d4f373e5 | 5395 | m = MAX_SECTORS_64 (don't transfer more |
65cc8bf9 ON |
5396 | than 64 sectors = 32 KB at a time, |
5397 | not on uas); | |
21c13a4f | 5398 | n = INITIAL_READ10 (force a retry of the |
65cc8bf9 | 5399 | initial READ(10) command, not on uas); |
c838ea46 | 5400 | o = CAPACITY_OK (accept the capacity |
65cc8bf9 | 5401 | reported by the device, not on uas); |
eaa05dfc | 5402 | p = WRITE_CACHE (the device cache is ON |
65cc8bf9 | 5403 | by default, not on uas); |
d4f373e5 | 5404 | r = IGNORE_RESIDUE (the device reports |
65cc8bf9 | 5405 | bogus residue values, not on uas); |
d4f373e5 AS |
5406 | s = SINGLE_LUN (the device has only one |
5407 | Logical Unit); | |
59307852 HG |
5408 | t = NO_ATA_1X (don't allow ATA(12) and ATA(16) |
5409 | commands, uas only); | |
b6089f19 | 5410 | u = IGNORE_UAS (don't bind to the uas driver); |
d4f373e5 AS |
5411 | w = NO_WP_DETECT (don't test whether the |
5412 | medium is write-protected). | |
050bc4e8 | 5413 | y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE |
65cc8bf9 ON |
5414 | even if the device claims no cache, |
5415 | not on uas) | |
d4f373e5 AS |
5416 | Example: quirks=0419:aaf5:rl,0421:0433:rc |
5417 | ||
ac1667db SB |
5418 | user_debug= [KNL,ARM] |
5419 | Format: <int> | |
5420 | See arch/arm/Kconfig.debug help text. | |
5421 | 1 - undefined instruction events | |
5422 | 2 - system calls | |
5423 | 4 - invalid data aborts | |
5424 | 8 - SIGSEGV faults | |
5425 | 16 - SIGBUS faults | |
5426 | Example: user_debug=31 | |
5427 | ||
14315592 IC |
5428 | userpte= |
5429 | [X86] Flags controlling user PTE allocations. | |
5430 | ||
5431 | nohigh = do not allocate PTE pages in | |
5432 | HIGHMEM regardless of setting | |
5433 | of CONFIG_HIGHPTE. | |
5434 | ||
6cececfc | 5435 | vdso= [X86,SH] |
b0b49f26 AL |
5436 | On X86_32, this is an alias for vdso32=. Otherwise: |
5437 | ||
5438 | vdso=1: enable VDSO (the default) | |
e6e5494c IM |
5439 | vdso=0: disable VDSO mapping |
5440 | ||
b0b49f26 AL |
5441 | vdso32= [X86] Control the 32-bit vDSO |
5442 | vdso32=1: enable 32-bit VDSO | |
5443 | vdso32=0 or vdso32=2: disable 32-bit VDSO | |
5444 | ||
5445 | See the help text for CONFIG_COMPAT_VDSO for more | |
5446 | details. If CONFIG_COMPAT_VDSO is set, the default is | |
5447 | vdso32=0; otherwise, the default is vdso32=1. | |
5448 | ||
5449 | For compatibility with older kernels, vdso32=2 is an | |
5450 | alias for vdso32=0. | |
5451 | ||
5452 | Try vdso32=0 if you encounter an error that says: | |
5453 | dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! | |
af65d648 | 5454 | |
d080d397 YI |
5455 | vector= [IA-64,SMP] |
5456 | vector=percpu: enable percpu vector domain | |
5457 | ||
1da177e4 | 5458 | video= [FB] Frame buffer configuration |
ab42b818 | 5459 | See Documentation/fb/modedb.rst. |
1da177e4 | 5460 | |
3afe6dab AL |
5461 | video.brightness_switch_enabled= [0,1] |
5462 | If set to 1, on receiving an ACPI notify event | |
5463 | generated by hotkey, video driver will adjust brightness | |
5464 | level and then send out the event to user space through | |
5465 | the allocated input device; If set to 0, video driver | |
5466 | will only send out the event without touching backlight | |
5467 | brightness level. | |
2843768b | 5468 | default: 1 |
3afe6dab | 5469 | |
81a054ce PM |
5470 | virtio_mmio.device= |
5471 | [VMMIO] Memory mapped virtio (platform) device. | |
5472 | ||
5473 | <size>@<baseaddr>:<irq>[:<id>] | |
5474 | where: | |
5475 | <size> := size (can use standard suffixes | |
5476 | like K, M and G) | |
5477 | <baseaddr> := physical base address | |
5478 | <irq> := interrupt number (as passed to | |
5479 | request_irq()) | |
5480 | <id> := (optional) platform device id | |
5481 | example: | |
5482 | virtio_mmio.device=1K@0x100b0000:48:7 | |
5483 | ||
5484 | Can be used multiple times for multiple devices. | |
5485 | ||
cd4f0ef7 | 5486 | vga= [BOOT,X86-32] Select a particular video mode |
cb1aaebe | 5487 | See Documentation/x86/boot.rst and |
4f4cfa6c | 5488 | Documentation/admin-guide/svga.rst. |
1da177e4 LT |
5489 | Use vga=ask for menu. |
5490 | This is actually a boot loader parameter; the value is | |
5491 | passed to the kernel using a special protocol. | |
5492 | ||
f682a97a AD |
5493 | vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y. |
5494 | May slow down system boot speed, especially when | |
5495 | enabled on systems with a large amount of memory. | |
5496 | All options are enabled by default, and this | |
5497 | interface is meant to allow for selectively | |
5498 | enabling or disabling specific virtual memory | |
5499 | debugging features. | |
5500 | ||
5501 | Available options are: | |
5502 | P Enable page structure init time poisoning | |
5503 | - Disable all of the above options | |
5504 | ||
a9913044 | 5505 | vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact |
1da177e4 LT |
5506 | size of <nn>. This can be used to increase the |
5507 | minimum size (128MB on x86). It can also be used to | |
5508 | decrease the size and leave more room for directly | |
5509 | mapped kernel RAM. | |
5510 | ||
3f429842 HC |
5511 | vmcp_cma=nn[MG] [KNL,S390] |
5512 | Sets the memory size reserved for contiguous memory | |
5513 | allocations for the vmcp device driver. | |
5514 | ||
585c3047 PO |
5515 | vmhalt= [KNL,S390] Perform z/VM CP command after system halt. |
5516 | Format: <command> | |
1da177e4 | 5517 | |
585c3047 PO |
5518 | vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. |
5519 | Format: <command> | |
5520 | ||
5521 | vmpoff= [KNL,S390] Perform z/VM CP command after power off. | |
5522 | Format: <command> | |
a9913044 | 5523 | |
3ae36655 AL |
5524 | vsyscall= [X86-64] |
5525 | Controls the behavior of vsyscalls (i.e. calls to | |
5526 | fixed addresses of 0xffffffffff600x00 from legacy | |
5527 | code). Most statically-linked binaries and older | |
5528 | versions of glibc use these calls. Because these | |
5529 | functions are at fixed addresses, they make nice | |
5530 | targets for exploits that can control RIP. | |
5531 | ||
2e57ae05 | 5532 | emulate [default] Vsyscalls turn into traps and are |
bd49e16e AL |
5533 | emulated reasonably safely. The vsyscall |
5534 | page is readable. | |
3ae36655 | 5535 | |
bd49e16e AL |
5536 | xonly Vsyscalls turn into traps and are |
5537 | emulated reasonably safely. The vsyscall | |
5538 | page is not readable. | |
3ae36655 AL |
5539 | |
5540 | none Vsyscalls don't work at all. This makes | |
5541 | them quite hard to use for exploits but | |
5542 | might break your system. | |
5543 | ||
3855ae1c CL |
5544 | vt.color= [VT] Default text color. |
5545 | Format: 0xYX, X = foreground, Y = background. | |
5546 | Default: 0x07 = light gray on black. | |
5547 | ||
9ea9a886 CL |
5548 | vt.cur_default= [VT] Default cursor shape. |
5549 | Format: 0xCCBBAA, where AA, BB, and CC are the same as | |
5550 | the parameters of the <Esc>[?A;B;Cc escape sequence; | |
5551 | see VGA-softcursor.txt. Default: 2 = underline. | |
5552 | ||
0cb55ad2 RD |
5553 | vt.default_blu= [VT] |
5554 | Format: <blue0>,<blue1>,<blue2>,...,<blue15> | |
5555 | Change the default blue palette of the console. | |
5556 | This is a 16-member array composed of values | |
5557 | ranging from 0-255. | |
5558 | ||
5559 | vt.default_grn= [VT] | |
5560 | Format: <green0>,<green1>,<green2>,...,<green15> | |
5561 | Change the default green palette of the console. | |
5562 | This is a 16-member array composed of values | |
5563 | ranging from 0-255. | |
5564 | ||
5565 | vt.default_red= [VT] | |
5566 | Format: <red0>,<red1>,<red2>,...,<red15> | |
5567 | Change the default red palette of the console. | |
5568 | This is a 16-member array composed of values | |
5569 | ranging from 0-255. | |
5570 | ||
5571 | vt.default_utf8= | |
5572 | [VT] | |
5573 | Format=<0|1> | |
5574 | Set system-wide default UTF-8 mode for all tty's. | |
5575 | Default is 1, i.e. UTF-8 mode is enabled for all | |
5576 | newly opened terminals. | |
5577 | ||
f6c06b68 MG |
5578 | vt.global_cursor_default= |
5579 | [VT] | |
5580 | Format=<-1|0|1> | |
5581 | Set system-wide default for whether a cursor | |
5582 | is shown on new VTs. Default is -1, | |
5583 | i.e. cursors will be created by default unless | |
5584 | overridden by individual drivers. 0 will hide | |
5585 | cursors, 1 will display them. | |
5586 | ||
3855ae1c CL |
5587 | vt.italic= [VT] Default color for italic text; 0-15. |
5588 | Default: 2 = green. | |
5589 | ||
5590 | vt.underline= [VT] Default color for underlined text; 0-15. | |
5591 | Default: 3 = cyan. | |
5592 | ||
4724ba57 | 5593 | watchdog timers [HW,WDT] For information on watchdog timers, |
cc2a2d19 | 5594 | see Documentation/watchdog/watchdog-parameters.rst |
4724ba57 RD |
5595 | or other driver-specific files in the |
5596 | Documentation/watchdog/ directory. | |
1da177e4 | 5597 | |
11295055 LO |
5598 | watchdog_thresh= |
5599 | [KNL] | |
5600 | Set the hard lockup detector stall duration | |
5601 | threshold in seconds. The soft lockup detector | |
5602 | threshold is set to twice the value. A value of 0 | |
5603 | disables both lockup detectors. Default is 10 | |
5604 | seconds. | |
5605 | ||
82607adc TH |
5606 | workqueue.watchdog_thresh= |
5607 | If CONFIG_WQ_WATCHDOG is configured, workqueue can | |
5608 | warn stall conditions and dump internal state to | |
5609 | help debugging. 0 disables workqueue stall | |
5610 | detection; otherwise, it's the stall threshold | |
5611 | duration in seconds. The default value is 30 and | |
5612 | it can be updated at runtime by writing to the | |
5613 | corresponding sysfs file. | |
5614 | ||
d55262c4 TH |
5615 | workqueue.disable_numa |
5616 | By default, all work items queued to unbound | |
5617 | workqueues are affine to the NUMA nodes they're | |
5618 | issued on, which results in better behavior in | |
5619 | general. If NUMA affinity needs to be disabled for | |
5620 | whatever reason, this option can be used. Note | |
5621 | that this also can be controlled per-workqueue for | |
5622 | workqueues visible under /sys/bus/workqueue/. | |
5623 | ||
cee22a15 VK |
5624 | workqueue.power_efficient |
5625 | Per-cpu workqueues are generally preferred because | |
5626 | they show better performance thanks to cache | |
5627 | locality; unfortunately, per-cpu workqueues tend to | |
5628 | be more power hungry than unbound workqueues. | |
5629 | ||
5630 | Enabling this makes the per-cpu workqueues which | |
5631 | were observed to contribute significantly to power | |
5632 | consumption unbound, leading to measurably lower | |
5633 | power usage at the cost of small performance | |
5634 | overhead. | |
5635 | ||
5636 | The default value of this parameter is determined by | |
5637 | the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. | |
5638 | ||
f303fccb TH |
5639 | workqueue.debug_force_rr_cpu |
5640 | Workqueue used to implicitly guarantee that work | |
5641 | items queued without explicit CPU specified are put | |
5642 | on the local CPU. This guarantee is no longer true | |
5643 | and while local CPU is still preferred work items | |
5644 | may be put on foreign CPUs. This debug option | |
5645 | forces round-robin CPU selection to flush out | |
5646 | usages which depend on the now broken guarantee. | |
5647 | When enabled, memory and cache locality will be | |
5648 | impacted. | |
5649 | ||
0cb55ad2 RD |
5650 | x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of |
5651 | default x2apic cluster mode on platforms | |
5652 | supporting x2apic. | |
5653 | ||
712b6aa8 KS |
5654 | x86_intel_mid_timer= [X86-32,APBT] |
5655 | Choose timer option for x86 Intel MID platform. | |
bb24c471 JP |
5656 | Two valid options are apbt timer only and lapic timer |
5657 | plus one apbt timer for broadcast timer. | |
712b6aa8 | 5658 | x86_intel_mid_timer=apbt_only | lapic_and_apbt |
bb24c471 | 5659 | |
c70727a5 JG |
5660 | xen_512gb_limit [KNL,X86-64,XEN] |
5661 | Restricts the kernel running paravirtualized under Xen | |
5662 | to use only up to 512 GB of RAM. The reason to do so is | |
5663 | crash analysis tools and Xen tools for doing domain | |
5664 | save/restore/migration must be enabled to handle larger | |
5665 | domains. | |
5666 | ||
c1c5413a SS |
5667 | xen_emul_unplug= [HW,X86,XEN] |
5668 | Unplug Xen emulated devices | |
5669 | Format: [unplug0,][unplug1] | |
5670 | ide-disks -- unplug primary master IDE devices | |
5671 | aux-ide-disks -- unplug non-primary-master IDE devices | |
5672 | nics -- unplug network devices | |
5673 | all -- unplug all emulated devices (NICs and IDE disks) | |
1dc7ce99 IC |
5674 | unnecessary -- unplugging emulated devices is |
5675 | unnecessary even if the host did not respond to | |
5676 | the unplug protocol | |
c93a4dfb | 5677 | never -- do not unplug even if version check succeeds |
c1c5413a | 5678 | |
c6875f3a BO |
5679 | xen_legacy_crash [X86,XEN] |
5680 | Crash from Xen panic notifier, without executing late | |
5681 | panic() code such as dumping handler. | |
5682 | ||
15a3eac0 KRW |
5683 | xen_nopvspin [X86,XEN] |
5684 | Disables the ticketlock slowpath using Xen PV | |
5685 | optimizations. | |
5686 | ||
8d693b91 KRW |
5687 | xen_nopv [X86] |
5688 | Disables the PV optimizations forcing the HVM guest to | |
5689 | run as generic HVM guest with no PV drivers. | |
b39b0497 ZD |
5690 | This option is obsoleted by the "nopv" option, which |
5691 | has equivalent effect for XEN platform. | |
8d693b91 | 5692 | |
197ecb38 MMG |
5693 | xen_scrub_pages= [XEN] |
5694 | Boolean option to control scrubbing pages before giving them back | |
5695 | to Xen, for use by other domains. Can be also changed at runtime | |
5696 | with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. | |
5697 | Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. | |
5698 | ||
2ec16bc0 RT |
5699 | xen_timer_slop= [X86-64,XEN] |
5700 | Set the timer slop (in nanoseconds) for the virtual Xen | |
5701 | timers (default is 100000). This adjusts the minimum | |
5702 | delta of virtualized Xen timers, where lower values | |
5703 | improve timer resolution at the expense of processing | |
5704 | more timer interrupts. | |
5705 | ||
30978346 ZD |
5706 | nopv= [X86,XEN,KVM,HYPER_V,VMWARE] |
5707 | Disables the PV optimizations forcing the guest to run | |
5708 | as generic guest with no PV drivers. Currently support | |
5709 | XEN HVM, KVM, HYPER_V and VMWARE guest. | |
5710 | ||
1da177e4 | 5711 | xirc2ps_cs= [NET,PCMCIA] |
a9913044 RD |
5712 | Format: |
5713 | <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] | |
c0addc9a | 5714 | |
ba45cff6 MN |
5715 | xive= [PPC] |
5716 | By default on POWER9 and above, the kernel will | |
5717 | natively use the XIVE interrupt controller. This option | |
5718 | allows the fallback firmware mode to be used: | |
5719 | ||
5720 | off Fallback to firmware control of XIVE interrupt | |
5721 | controller on both pseries and powernv | |
5722 | platforms. Only useful on POWER9 and above. | |
5723 | ||
c0addc9a LT |
5724 | xhci-hcd.quirks [USB,KNL] |
5725 | A hex value specifying bitmask with supplemental xhci | |
5726 | host controller quirks. Meaning of each bit can be | |
5727 | consulted in header drivers/usb/host/xhci.h. | |
6278f55b GR |
5728 | |
5729 | xmon [PPC] | |
5730 | Format: { early | on | rw | ro | off } | |
5731 | Controls if xmon debugger is enabled. Default is off. | |
5732 | Passing only "xmon" is equivalent to "xmon=early". | |
5733 | early Call xmon as early as possible on boot; xmon | |
5734 | debugger is called from setup_arch(). | |
5735 | on xmon debugger hooks will be installed so xmon | |
5736 | is only called on a kernel crash. Default mode, | |
5737 | i.e. either "ro" or "rw" mode, is controlled | |
5738 | with CONFIG_XMON_DEFAULT_RO_MODE. | |
5739 | rw xmon debugger hooks will be installed so xmon | |
5740 | is called only on a kernel crash, mode is write, | |
5741 | meaning SPR registers, memory and, other data | |
5742 | can be written using xmon commands. | |
5743 | ro same as "rw" option above but SPR registers, | |
5744 | memory, and other data can't be written using | |
5745 | xmon commands. | |
5746 | off xmon is disabled. |