1 # SPDX-License-Identifier: GPL-2.0
4 bool "64-bit kernel" if "$(ARCH)" = "x86"
5 default "$(ARCH)" != "i386"
7 Say yes to build a 64-bit kernel - formerly known as x86_64
8 Say no to build a 32-bit kernel - formerly known as i386
13 # Options that are inherently 32-bit kernel only:
14 select ARCH_WANT_IPC_PARSE_VERSION
16 select CLONE_BACKWARDS
17 select GENERIC_VDSO_32
18 select HAVE_DEBUG_STACKOVERFLOW
20 select MODULES_USE_ELF_REL
22 select ARCH_SPLIT_ARG64
27 # Options that are inherently 64-bit kernel only:
28 select ARCH_HAS_GIGANTIC_PAGE
29 select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
30 select ARCH_USE_CMPXCHG_LOCKREF
31 select HAVE_ARCH_SOFT_DIRTY
32 select MODULES_USE_ELF_RELA
33 select NEED_DMA_MAP_STATE
35 select ARCH_HAS_ELFCORE_COMPAT
38 config FORCE_DYNAMIC_FTRACE
41 depends on FUNCTION_TRACER
44 We keep the static function tracing (!DYNAMIC_FTRACE) around
45 in order to test the non static function tracing in the
46 generic code, as other architectures still use it. But we
47 only need to keep it around for x86_64. No need to keep it
48 for x86_32. For x86_32, force DYNAMIC_FTRACE.
52 # ( Note that options that are marked 'if X86_64' could in principle be
53 # ported to 32-bit as well. )
58 # Note: keep this list sorted alphabetically
60 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
61 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
62 select ARCH_32BIT_OFF_T if X86_32
63 select ARCH_CLOCKSOURCE_INIT
64 select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
65 select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64 || (X86_32 && HIGHMEM)
66 select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
67 select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE)
68 select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
69 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
70 select ARCH_HAS_CACHE_LINE_SIZE
71 select ARCH_HAS_DEBUG_VIRTUAL
72 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
73 select ARCH_HAS_DEVMEM_IS_ALLOWED
74 select ARCH_HAS_EARLY_DEBUG if KGDB
75 select ARCH_HAS_ELF_RANDOMIZE
76 select ARCH_HAS_FAST_MULTIPLIER
77 select ARCH_HAS_FILTER_PGPROT
78 select ARCH_HAS_FORTIFY_SOURCE
79 select ARCH_HAS_GCOV_PROFILE_ALL
80 select ARCH_HAS_KCOV if X86_64 && STACK_VALIDATION
81 select ARCH_HAS_MEM_ENCRYPT
82 select ARCH_HAS_MEMBARRIER_SYNC_CORE
83 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
84 select ARCH_HAS_PMEM_API if X86_64
85 select ARCH_HAS_PTE_DEVMAP if X86_64
86 select ARCH_HAS_PTE_SPECIAL
87 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
88 select ARCH_HAS_COPY_MC if X86_64
89 select ARCH_HAS_SET_MEMORY
90 select ARCH_HAS_SET_DIRECT_MAP
91 select ARCH_HAS_STRICT_KERNEL_RWX
92 select ARCH_HAS_STRICT_MODULE_RWX
93 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
94 select ARCH_HAS_SYSCALL_WRAPPER
95 select ARCH_HAS_UBSAN_SANITIZE_ALL
96 select ARCH_HAS_DEBUG_WX
97 select ARCH_HAS_ZONE_DMA_SET if EXPERT
98 select ARCH_HAVE_NMI_SAFE_CMPXCHG
99 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
100 select ARCH_MIGHT_HAVE_PC_PARPORT
101 select ARCH_MIGHT_HAVE_PC_SERIO
102 select ARCH_STACKWALK
103 select ARCH_SUPPORTS_ACPI
104 select ARCH_SUPPORTS_ATOMIC_RMW
105 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
106 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
107 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
108 select ARCH_SUPPORTS_LTO_CLANG
109 select ARCH_SUPPORTS_LTO_CLANG_THIN
110 select ARCH_USE_BUILTIN_BSWAP
111 select ARCH_USE_MEMTEST
112 select ARCH_USE_QUEUED_RWLOCKS
113 select ARCH_USE_QUEUED_SPINLOCKS
114 select ARCH_USE_SYM_ANNOTATIONS
115 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
116 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
117 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
118 select ARCH_WANTS_NO_INSTR
119 select ARCH_WANT_HUGE_PMD_SHARE
120 select ARCH_WANT_LD_ORPHAN_WARN
121 select ARCH_WANTS_THP_SWAP if X86_64
122 select ARCH_HAS_PARANOID_L1D_FLUSH
123 select BUILDTIME_TABLE_SORT
125 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
126 select CLOCKSOURCE_WATCHDOG
127 select DCACHE_WORD_ACCESS
128 select EDAC_ATOMIC_SCRUB
130 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
131 select GENERIC_CLOCKEVENTS_MIN_ADJUST
132 select GENERIC_CMOS_UPDATE
133 select GENERIC_CPU_AUTOPROBE
134 select GENERIC_CPU_VULNERABILITIES
135 select GENERIC_EARLY_IOREMAP
137 select GENERIC_FIND_FIRST_BIT
139 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
140 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
141 select GENERIC_IRQ_MIGRATION if SMP
142 select GENERIC_IRQ_PROBE
143 select GENERIC_IRQ_RESERVATION_MODE
144 select GENERIC_IRQ_SHOW
145 select GENERIC_PENDING_IRQ if SMP
146 select GENERIC_PTDUMP
147 select GENERIC_SMP_IDLE_THREAD
148 select GENERIC_TIME_VSYSCALL
149 select GENERIC_GETTIMEOFDAY
150 select GENERIC_VDSO_TIME_NS
151 select GUP_GET_PTE_LOW_HIGH if X86_PAE
152 select HARDIRQS_SW_RESEND
153 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
154 select HAVE_ACPI_APEI if ACPI
155 select HAVE_ACPI_APEI_NMI if ACPI
156 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
157 select HAVE_ARCH_AUDITSYSCALL
158 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
159 select HAVE_ARCH_JUMP_LABEL
160 select HAVE_ARCH_JUMP_LABEL_RELATIVE
161 select HAVE_ARCH_KASAN if X86_64
162 select HAVE_ARCH_KASAN_VMALLOC if X86_64
163 select HAVE_ARCH_KFENCE
164 select HAVE_ARCH_KGDB
165 select HAVE_ARCH_MMAP_RND_BITS if MMU
166 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
167 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
168 select HAVE_ARCH_PREL32_RELOCATIONS
169 select HAVE_ARCH_SECCOMP_FILTER
170 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
171 select HAVE_ARCH_STACKLEAK
172 select HAVE_ARCH_TRACEHOOK
173 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
174 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
175 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
176 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
177 select HAVE_ARCH_VMAP_STACK if X86_64
178 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
179 select HAVE_ARCH_WITHIN_STACK_FRAMES
180 select HAVE_ASM_MODVERSIONS
181 select HAVE_CMPXCHG_DOUBLE
182 select HAVE_CMPXCHG_LOCAL
183 select HAVE_CONTEXT_TRACKING if X86_64
184 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
185 select HAVE_C_RECORDMCOUNT
186 select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION
187 select HAVE_DEBUG_KMEMLEAK
188 select HAVE_DMA_CONTIGUOUS
189 select HAVE_DYNAMIC_FTRACE
190 select HAVE_DYNAMIC_FTRACE_WITH_REGS
191 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
192 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
194 select HAVE_EFFICIENT_UNALIGNED_ACCESS
196 select HAVE_EXIT_THREAD
198 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
199 select HAVE_FTRACE_MCOUNT_RECORD
200 select HAVE_FUNCTION_GRAPH_TRACER
201 select HAVE_FUNCTION_TRACER
202 select HAVE_GCC_PLUGINS
203 select HAVE_HW_BREAKPOINT
204 select HAVE_IOREMAP_PROT
205 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
206 select HAVE_IRQ_TIME_ACCOUNTING
207 select HAVE_KERNEL_BZIP2
208 select HAVE_KERNEL_GZIP
209 select HAVE_KERNEL_LZ4
210 select HAVE_KERNEL_LZMA
211 select HAVE_KERNEL_LZO
212 select HAVE_KERNEL_XZ
213 select HAVE_KERNEL_ZSTD
215 select HAVE_KPROBES_ON_FTRACE
216 select HAVE_FUNCTION_ERROR_INJECTION
217 select HAVE_KRETPROBES
219 select HAVE_LIVEPATCH if X86_64
220 select HAVE_MIXED_BREAKPOINTS_REGS
221 select HAVE_MOD_ARCH_SPECIFIC
225 select HAVE_OPTPROBES
226 select HAVE_PCSPKR_PLATFORM
227 select HAVE_PERF_EVENTS
228 select HAVE_PERF_EVENTS_NMI
229 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
231 select HAVE_PERF_REGS
232 select HAVE_PERF_USER_STACK_DUMP
233 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
234 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
235 select HAVE_REGS_AND_STACK_ACCESS_API
236 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
237 select HAVE_FUNCTION_ARG_ACCESS_API
238 select HAVE_SOFTIRQ_ON_OWN_STACK
239 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
240 select HAVE_STACK_VALIDATION if X86_64
241 select HAVE_STATIC_CALL
242 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
243 select HAVE_PREEMPT_DYNAMIC
245 select HAVE_SYSCALL_TRACEPOINTS
246 select HAVE_UNSTABLE_SCHED_CLOCK
247 select HAVE_USER_RETURN_NOTIFIER
248 select HAVE_GENERIC_VDSO
249 select HOTPLUG_SMT if SMP
250 select IRQ_FORCED_THREADING
251 select NEED_SG_DMA_LENGTH
252 select PCI_DOMAINS if PCI
253 select PCI_LOCKLESS_CONFIG if PCI
256 select RTC_MC146818_LIB
259 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
260 select SYSCTL_EXCEPTION_TRACE
261 select THREAD_INFO_IN_TASK
262 select TRACE_IRQFLAGS_SUPPORT
263 select USER_STACKTRACE_SUPPORT
265 select HAVE_ARCH_KCSAN if X86_64
266 select X86_FEATURE_NAMES if PROC_FS
267 select PROC_PID_ARCH_STATUS if PROC_FS
268 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
270 config INSTRUCTION_DECODER
272 depends on KPROBES || PERF_EVENTS || UPROBES
276 default "elf32-i386" if X86_32
277 default "elf64-x86-64" if X86_64
279 config LOCKDEP_SUPPORT
282 config STACKTRACE_SUPPORT
288 config ARCH_MMAP_RND_BITS_MIN
292 config ARCH_MMAP_RND_BITS_MAX
296 config ARCH_MMAP_RND_COMPAT_BITS_MIN
299 config ARCH_MMAP_RND_COMPAT_BITS_MAX
305 config GENERIC_ISA_DMA
307 depends on ISA_DMA_API
312 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
314 config GENERIC_BUG_RELATIVE_POINTERS
317 config ARCH_MAY_HAVE_PC_FDC
319 depends on ISA_DMA_API
321 config GENERIC_CALIBRATE_DELAY
324 config ARCH_HAS_CPU_RELAX
327 config ARCH_HAS_FILTER_PGPROT
330 config HAVE_SETUP_PER_CPU_AREA
333 config NEED_PER_CPU_EMBED_FIRST_CHUNK
336 config NEED_PER_CPU_PAGE_FIRST_CHUNK
339 config ARCH_HIBERNATION_POSSIBLE
342 config ARCH_SUSPEND_POSSIBLE
345 config ARCH_WANT_GENERAL_HUGETLB
351 config KASAN_SHADOW_OFFSET
354 default 0xdffffc0000000000
356 config HAVE_INTEL_TXT
358 depends on INTEL_IOMMU && ACPI
362 depends on X86_32 && SMP
366 depends on X86_64 && SMP
368 config ARCH_SUPPORTS_UPROBES
371 config FIX_EARLYCON_MEM
374 config DYNAMIC_PHYSICAL_MASK
377 config PGTABLE_LEVELS
379 default 5 if X86_5LEVEL
384 config CC_HAS_SANE_STACKPROTECTOR
386 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
387 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
389 We have to make sure stack protector is unconditionally disabled if
390 the compiler produces broken code or if it does not let us control
391 the segment on 32-bit kernels.
393 menu "Processor type and features"
396 bool "Symmetric multi-processing support"
398 This enables support for systems with more than one CPU. If you have
399 a system with only one CPU, say N. If you have a system with more
402 If you say N here, the kernel will run on uni- and multiprocessor
403 machines, but will use only one CPU of a multiprocessor machine. If
404 you say Y here, the kernel will run on many, but not all,
405 uniprocessor machines. On a uniprocessor machine, the kernel
406 will run faster if you say N here.
408 Note that if you say Y here and choose architecture "586" or
409 "Pentium" under "Processor family", the kernel will not work on 486
410 architectures. Similarly, multiprocessor kernels for the "PPro"
411 architecture may not work on all Pentium based boards.
413 People using multiprocessor machines who say Y here should also say
414 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
415 Management" code will be disabled if you say Y here.
417 See also <file:Documentation/x86/i386/IO-APIC.rst>,
418 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
419 <http://www.tldp.org/docs.html#howto>.
421 If you don't know what to do here, say N.
423 config X86_FEATURE_NAMES
424 bool "Processor feature human-readable names" if EMBEDDED
427 This option compiles in a table of x86 feature bits and corresponding
428 names. This is required to support /proc/cpuinfo and a few kernel
429 messages. You can disable this to save space, at the expense of
430 making those few kernel messages show numeric feature bits instead.
435 bool "Support x2apic"
436 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
438 This enables x2apic support on CPUs that have this feature.
440 This allows 32-bit apic IDs (so it can support very large systems),
441 and accesses the local apic via MSRs not via mmio.
443 If you don't know what to do here, say N.
446 bool "Enable MPS table" if ACPI
448 depends on X86_LOCAL_APIC
450 For old smp systems that do not have proper acpi support. Newer systems
451 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
455 depends on X86_GOLDFISH
458 bool "Avoid speculative indirect branches in kernel"
461 Compile kernel with the retpoline compiler options to guard against
462 kernel-to-user data leaks by avoiding speculative indirect
463 branches. Requires a compiler with -mindirect-branch=thunk-extern
464 support for full protection. The kernel may run slower.
466 config X86_CPU_RESCTRL
467 bool "x86 CPU resource control support"
468 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
470 select PROC_CPU_RESCTRL if PROC_FS
472 Enable x86 CPU resource control support.
474 Provide support for the allocation and monitoring of system resources
477 Intel calls this Intel Resource Director Technology
478 (Intel(R) RDT). More information about RDT can be found in the
479 Intel x86 Architecture Software Developer Manual.
481 AMD calls this AMD Platform Quality of Service (AMD QoS).
482 More information about AMD QoS can be found in the AMD64 Technology
483 Platform Quality of Service Extensions manual.
489 bool "Support for big SMP systems with more than 8 CPUs"
492 This option is needed for the systems that have more than 8 CPUs.
494 config X86_EXTENDED_PLATFORM
495 bool "Support for extended (non-PC) x86 platforms"
498 If you disable this option then the kernel will only support
499 standard PC platforms. (which covers the vast majority of
502 If you enable this option then you'll be able to select support
503 for the following (non-PC) 32 bit x86 platforms:
504 Goldfish (Android emulator)
507 SGI 320/540 (Visual Workstation)
508 STA2X11-based (e.g. Northville)
509 Moorestown MID devices
511 If you have one of these systems, or if you want to build a
512 generic distribution kernel, say Y here - otherwise say N.
516 config X86_EXTENDED_PLATFORM
517 bool "Support for extended (non-PC) x86 platforms"
520 If you disable this option then the kernel will only support
521 standard PC platforms. (which covers the vast majority of
524 If you enable this option then you'll be able to select support
525 for the following (non-PC) 64 bit x86 platforms:
530 If you have one of these systems, or if you want to build a
531 generic distribution kernel, say Y here - otherwise say N.
533 # This is an alphabetically sorted list of 64 bit extended platforms
534 # Please maintain the alphabetic order if and when there are additions
536 bool "Numascale NumaChip"
538 depends on X86_EXTENDED_PLATFORM
541 depends on X86_X2APIC
542 depends on PCI_MMCONFIG
544 Adds support for Numascale NumaChip large-SMP systems. Needed to
545 enable more than ~168 cores.
546 If you don't have one of these, you should say N here.
550 select HYPERVISOR_GUEST
552 depends on X86_64 && PCI
553 depends on X86_EXTENDED_PLATFORM
556 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
557 supposed to run on these EM64T-based machines. Only choose this option
558 if you have one of these machines.
561 bool "SGI Ultraviolet"
563 depends on X86_EXTENDED_PLATFORM
566 depends on KEXEC_CORE
567 depends on X86_X2APIC
570 This option is needed in order to support SGI Ultraviolet systems.
571 If you don't have one of these, you should say N here.
573 # Following is an alphabetically sorted list of 32 bit extended platforms
574 # Please maintain the alphabetic order if and when there are additions
577 bool "Goldfish (Virtual Platform)"
578 depends on X86_EXTENDED_PLATFORM
580 Enable support for the Goldfish virtual platform used primarily
581 for Android development. Unless you are building for the Android
582 Goldfish emulator say N here.
585 bool "CE4100 TV platform"
587 depends on PCI_GODIRECT
588 depends on X86_IO_APIC
590 depends on X86_EXTENDED_PLATFORM
591 select X86_REBOOTFIXUPS
593 select OF_EARLY_FLATTREE
595 Select for the Intel CE media processor (CE4100) SOC.
596 This option compiles in support for the CE4100 SOC for settop
597 boxes and media devices.
600 bool "Intel MID platform support"
601 depends on X86_EXTENDED_PLATFORM
602 depends on X86_PLATFORM_DEVICES
604 depends on X86_64 || (PCI_GOANY && X86_32)
605 depends on X86_IO_APIC
610 select MFD_INTEL_MSIC
612 Select to build a kernel capable of supporting Intel MID (Mobile
613 Internet Device) platform systems which do not have the PCI legacy
614 interfaces. If you are building for a PC class system say N here.
616 Intel MID platforms are based on an Intel processor and chipset which
617 consume less power than most of the x86 derivatives.
619 config X86_INTEL_QUARK
620 bool "Intel Quark platform support"
622 depends on X86_EXTENDED_PLATFORM
623 depends on X86_PLATFORM_DEVICES
627 depends on X86_IO_APIC
632 Select to include support for Quark X1000 SoC.
633 Say Y here if you have a Quark based system such as the Arduino
634 compatible Intel Galileo.
636 config X86_INTEL_LPSS
637 bool "Intel Low Power Subsystem Support"
638 depends on X86 && ACPI && PCI
643 Select to build support for Intel Low Power Subsystem such as
644 found on Intel Lynxpoint PCH. Selecting this option enables
645 things like clock tree (common clock framework) and pincontrol
646 which are needed by the LPSS peripheral drivers.
648 config X86_AMD_PLATFORM_DEVICE
649 bool "AMD ACPI2Platform devices support"
654 Select to interpret AMD specific ACPI device to platform device
655 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
656 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
657 implemented under PINCTRL subsystem.
660 tristate "Intel SoC IOSF Sideband support for SoC platforms"
663 This option enables sideband register access support for Intel SoC
664 platforms. On these platforms the IOSF sideband is used in lieu of
665 MSR's for some register accesses, mostly but not limited to thermal
666 and power. Drivers may query the availability of this device to
667 determine if they need the sideband in order to work on these
668 platforms. The sideband is available on the following SoC products.
669 This list is not meant to be exclusive.
674 You should say Y if you are running a kernel on one of these SoC's.
676 config IOSF_MBI_DEBUG
677 bool "Enable IOSF sideband access through debugfs"
678 depends on IOSF_MBI && DEBUG_FS
680 Select this option to expose the IOSF sideband access registers (MCR,
681 MDR, MCRX) through debugfs to write and read register information from
682 different units on the SoC. This is most useful for obtaining device
683 state information for debug and analysis. As this is a general access
684 mechanism, users of this option would have specific knowledge of the
685 device they want to access.
687 If you don't require the option or are in doubt, say N.
690 bool "RDC R-321x SoC"
692 depends on X86_EXTENDED_PLATFORM
694 select X86_REBOOTFIXUPS
696 This option is needed for RDC R-321x system-on-chip, also known
698 If you don't have one of these chips, you should say N here.
700 config X86_32_NON_STANDARD
701 bool "Support non-standard 32-bit SMP architectures"
702 depends on X86_32 && SMP
703 depends on X86_EXTENDED_PLATFORM
705 This option compiles in the bigsmp and STA2X11 default
706 subarchitectures. It is intended for a generic binary
707 kernel. If you select them all, kernel will probe it one by
708 one and will fallback to default.
710 # Alphabetically sorted list of Non standard 32 bit platforms
712 config X86_SUPPORTS_MEMORY_FAILURE
714 # MCE code calls memory_failure():
716 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
717 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
718 depends on X86_64 || !SPARSEMEM
719 select ARCH_SUPPORTS_MEMORY_FAILURE
722 bool "STA2X11 Companion Chip Support"
723 depends on X86_32_NON_STANDARD && PCI
728 This adds support for boards based on the STA2X11 IO-Hub,
729 a.k.a. "ConneXt". The chip is used in place of the standard
730 PC chipset, so all "standard" peripherals are missing. If this
731 option is selected the kernel will still be able to boot on
732 standard PC machines.
735 tristate "Eurobraille/Iris poweroff module"
738 The Iris machines from EuroBraille do not have APM or ACPI support
739 to shut themselves down properly. A special I/O sequence is
740 needed to do so, which is what this module does at
743 This is only for Iris machines from EuroBraille.
747 config SCHED_OMIT_FRAME_POINTER
749 prompt "Single-depth WCHAN output"
752 Calculate simpler /proc/<PID>/wchan values. If this option
753 is disabled then wchan values will recurse back to the
754 caller function. This provides more accurate wchan values,
755 at the expense of slightly more scheduling overhead.
757 If in doubt, say "Y".
759 menuconfig HYPERVISOR_GUEST
760 bool "Linux guest support"
762 Say Y here to enable options for running Linux under various hyper-
763 visors. This option enables basic hypervisor detection and platform
766 If you say N, all options in this submenu will be skipped and
767 disabled, and Linux guest support won't be built in.
772 bool "Enable paravirtualization code"
773 depends on HAVE_STATIC_CALL
775 This changes the kernel so it can modify itself when it is run
776 under a hypervisor, potentially improving performance significantly
777 over full virtualization. However, when run without a hypervisor
778 the kernel is theoretically slower and slightly larger.
783 config PARAVIRT_DEBUG
784 bool "paravirt-ops debugging"
785 depends on PARAVIRT && DEBUG_KERNEL
787 Enable to debug paravirt_ops internals. Specifically, BUG if
788 a paravirt_op is missing when it is called.
790 config PARAVIRT_SPINLOCKS
791 bool "Paravirtualization layer for spinlocks"
792 depends on PARAVIRT && SMP
794 Paravirtualized spinlocks allow a pvops backend to replace the
795 spinlock implementation with something virtualization-friendly
796 (for example, block the virtual CPU rather than spinning).
798 It has a minimal impact on native kernels and gives a nice performance
799 benefit on paravirtualized KVM / Xen kernels.
801 If you are unsure how to answer this question, answer Y.
803 config X86_HV_CALLBACK_VECTOR
806 source "arch/x86/xen/Kconfig"
809 bool "KVM Guest support (including kvmclock)"
811 select PARAVIRT_CLOCK
812 select ARCH_CPUIDLE_HALTPOLL
813 select X86_HV_CALLBACK_VECTOR
816 This option enables various optimizations for running under the KVM
817 hypervisor. It includes a paravirtualized clock, so that instead
818 of relying on a PIT (or probably other) emulation by the
819 underlying device model, the host provides the guest with
820 timing infrastructure such as time of day, and system time
822 config ARCH_CPUIDLE_HALTPOLL
824 prompt "Disable host haltpoll when loading haltpoll driver"
826 If virtualized under KVM, disable host haltpoll.
829 bool "Support for running PVH guests"
831 This option enables the PVH entry point for guest virtual machines
832 as specified in the x86/HVM direct boot ABI.
834 config PARAVIRT_TIME_ACCOUNTING
835 bool "Paravirtual steal time accounting"
838 Select this option to enable fine granularity task steal time
839 accounting. Time spent executing other tasks in parallel with
840 the current vCPU is discounted from the vCPU power. To account for
841 that, there can be a small performance impact.
843 If in doubt, say N here.
845 config PARAVIRT_CLOCK
848 config JAILHOUSE_GUEST
849 bool "Jailhouse non-root cell support"
850 depends on X86_64 && PCI
853 This option allows to run Linux as guest in a Jailhouse non-root
854 cell. You can leave this option disabled if you only want to start
855 Jailhouse and run Linux afterwards in the root cell.
858 bool "ACRN Guest support"
860 select X86_HV_CALLBACK_VECTOR
862 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
863 a flexible, lightweight reference open-source hypervisor, built with
864 real-time and safety-criticality in mind. It is built for embedded
865 IOT with small footprint and real-time features. More details can be
866 found in https://projectacrn.org/.
868 endif #HYPERVISOR_GUEST
870 source "arch/x86/Kconfig.cpu"
874 prompt "HPET Timer Support" if X86_32
876 Use the IA-PC HPET (High Precision Event Timer) to manage
877 time in preference to the PIT and RTC, if a HPET is
879 HPET is the next generation timer replacing legacy 8254s.
880 The HPET provides a stable time base on SMP
881 systems, unlike the TSC, but it is more expensive to access,
882 as it is off-chip. The interface used is documented
883 in the HPET spec, revision 1.
885 You can safely choose Y here. However, HPET will only be
886 activated if the platform and the BIOS support this feature.
887 Otherwise the 8254 will be used for timing services.
889 Choose N to continue using the legacy 8254 timer.
891 config HPET_EMULATE_RTC
893 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
895 # Mark as expert because too many people got it wrong.
896 # The code disables itself when not needed.
899 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
900 bool "Enable DMI scanning" if EXPERT
902 Enabled scanning of DMI to identify machine quirks. Say Y
903 here unless you have verified that your setup is not
904 affected by entries in the DMI blacklist. Required by PNP
908 bool "Old AMD GART IOMMU support"
912 depends on X86_64 && PCI && AMD_NB
914 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
915 GART based hardware IOMMUs.
917 The GART supports full DMA access for devices with 32-bit access
918 limitations, on systems with more than 3 GB. This is usually needed
919 for USB, sound, many IDE/SATA chipsets and some other devices.
921 Newer systems typically have a modern AMD IOMMU, supported via
922 the CONFIG_AMD_IOMMU=y config option.
924 In normal configurations this driver is only active when needed:
925 there's more than 3 GB of memory and the system contains a
926 32-bit limited device.
931 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
932 depends on X86_64 && SMP && DEBUG_KERNEL
933 select CPUMASK_OFFSTACK
935 Enable maximum number of CPUS and NUMA Nodes for this architecture.
939 # The maximum number of CPUs supported:
941 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
942 # and which can be configured interactively in the
943 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
945 # The ranges are different on 32-bit and 64-bit kernels, depending on
946 # hardware capabilities and scalability features of the kernel.
948 # ( If MAXSMP is enabled we just use the highest possible value and disable
949 # interactive configuration. )
952 config NR_CPUS_RANGE_BEGIN
954 default NR_CPUS_RANGE_END if MAXSMP
958 config NR_CPUS_RANGE_END
961 default 64 if SMP && X86_BIGSMP
962 default 8 if SMP && !X86_BIGSMP
965 config NR_CPUS_RANGE_END
968 default 8192 if SMP && CPUMASK_OFFSTACK
969 default 512 if SMP && !CPUMASK_OFFSTACK
972 config NR_CPUS_DEFAULT
975 default 32 if X86_BIGSMP
979 config NR_CPUS_DEFAULT
982 default 8192 if MAXSMP
987 int "Maximum number of CPUs" if SMP && !MAXSMP
988 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
989 default NR_CPUS_DEFAULT
991 This allows you to specify the maximum number of CPUs which this
992 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
993 supported value is 8192, otherwise the maximum value is 512. The
994 minimum value which makes sense is 2.
996 This is purely to save memory: each supported CPU adds about 8KB
1004 prompt "Multi-core scheduler support"
1007 Multi-core scheduler support improves the CPU scheduler's decision
1008 making when dealing with multi-core CPU chips at a cost of slightly
1009 increased overhead in some places. If unsure say N here.
1011 config SCHED_MC_PRIO
1012 bool "CPU core priorities scheduler support"
1013 depends on SCHED_MC && CPU_SUP_INTEL
1014 select X86_INTEL_PSTATE
1018 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1019 core ordering determined at manufacturing time, which allows
1020 certain cores to reach higher turbo frequencies (when running
1021 single threaded workloads) than others.
1023 Enabling this kernel feature teaches the scheduler about
1024 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1025 scheduler's CPU selection logic accordingly, so that higher
1026 overall system performance can be achieved.
1028 This feature will have no effect on CPUs without this feature.
1030 If unsure say Y here.
1034 depends on !SMP && X86_LOCAL_APIC
1037 bool "Local APIC support on uniprocessors" if !PCI_MSI
1039 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1041 A local APIC (Advanced Programmable Interrupt Controller) is an
1042 integrated interrupt controller in the CPU. If you have a single-CPU
1043 system which has a processor with a local APIC, you can say Y here to
1044 enable and use it. If you say Y here even though your machine doesn't
1045 have a local APIC, then the kernel will still run with no slowdown at
1046 all. The local APIC supports CPU-generated self-interrupts (timer,
1047 performance counters), and the NMI watchdog which detects hard
1050 config X86_UP_IOAPIC
1051 bool "IO-APIC support on uniprocessors"
1052 depends on X86_UP_APIC
1054 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1055 SMP-capable replacement for PC-style interrupt controllers. Most
1056 SMP systems and many recent uniprocessor systems have one.
1058 If you have a single-CPU system with an IO-APIC, you can say Y here
1059 to use it. If you say Y here even though your machine doesn't have
1060 an IO-APIC, then the kernel will still run with no slowdown at all.
1062 config X86_LOCAL_APIC
1064 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1065 select IRQ_DOMAIN_HIERARCHY
1066 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1070 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1072 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1073 bool "Reroute for broken boot IRQs"
1074 depends on X86_IO_APIC
1076 This option enables a workaround that fixes a source of
1077 spurious interrupts. This is recommended when threaded
1078 interrupt handling is used on systems where the generation of
1079 superfluous "boot interrupts" cannot be disabled.
1081 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1082 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1083 kernel does during interrupt handling). On chipsets where this
1084 boot IRQ generation cannot be disabled, this workaround keeps
1085 the original IRQ line masked so that only the equivalent "boot
1086 IRQ" is delivered to the CPUs. The workaround also tells the
1087 kernel to set up the IRQ handler on the boot IRQ line. In this
1088 way only one interrupt is delivered to the kernel. Otherwise
1089 the spurious second interrupt may cause the kernel to bring
1090 down (vital) interrupt lines.
1092 Only affects "broken" chipsets. Interrupt sharing may be
1093 increased on these systems.
1096 bool "Machine Check / overheating reporting"
1097 select GENERIC_ALLOCATOR
1100 Machine Check support allows the processor to notify the
1101 kernel if it detects a problem (e.g. overheating, data corruption).
1102 The action the kernel takes depends on the severity of the problem,
1103 ranging from warning messages to halting the machine.
1105 config X86_MCELOG_LEGACY
1106 bool "Support for deprecated /dev/mcelog character device"
1109 Enable support for /dev/mcelog which is needed by the old mcelog
1110 userspace logging daemon. Consider switching to the new generation
1113 config X86_MCE_INTEL
1115 prompt "Intel MCE features"
1116 depends on X86_MCE && X86_LOCAL_APIC
1118 Additional support for intel specific MCE features such as
1119 the thermal monitor.
1123 prompt "AMD MCE features"
1124 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1126 Additional support for AMD specific MCE features such as
1127 the DRAM Error Threshold.
1129 config X86_ANCIENT_MCE
1130 bool "Support for old Pentium 5 / WinChip machine checks"
1131 depends on X86_32 && X86_MCE
1133 Include support for machine check handling on old Pentium 5 or WinChip
1134 systems. These typically need to be enabled explicitly on the command
1137 config X86_MCE_THRESHOLD
1138 depends on X86_MCE_AMD || X86_MCE_INTEL
1141 config X86_MCE_INJECT
1142 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1143 tristate "Machine check injector support"
1145 Provide support for injecting machine checks for testing purposes.
1146 If you don't know what a machine check is and you don't do kernel
1147 QA it is safe to say n.
1149 source "arch/x86/events/Kconfig"
1151 config X86_LEGACY_VM86
1152 bool "Legacy VM86 support"
1155 This option allows user programs to put the CPU into V8086
1156 mode, which is an 80286-era approximation of 16-bit real mode.
1158 Some very old versions of X and/or vbetool require this option
1159 for user mode setting. Similarly, DOSEMU will use it if
1160 available to accelerate real mode DOS programs. However, any
1161 recent version of DOSEMU, X, or vbetool should be fully
1162 functional even without kernel VM86 support, as they will all
1163 fall back to software emulation. Nevertheless, if you are using
1164 a 16-bit DOS program where 16-bit performance matters, vm86
1165 mode might be faster than emulation and you might want to
1168 Note that any app that works on a 64-bit kernel is unlikely to
1169 need this option, as 64-bit kernels don't, and can't, support
1170 V8086 mode. This option is also unrelated to 16-bit protected
1171 mode and is not needed to run most 16-bit programs under Wine.
1173 Enabling this option increases the complexity of the kernel
1174 and slows down exception handling a tiny bit.
1176 If unsure, say N here.
1180 default X86_LEGACY_VM86
1183 bool "Enable support for 16-bit segments" if EXPERT
1185 depends on MODIFY_LDT_SYSCALL
1187 This option is required by programs like Wine to run 16-bit
1188 protected mode legacy code on x86 processors. Disabling
1189 this option saves about 300 bytes on i386, or around 6K text
1190 plus 16K runtime memory on x86-64,
1194 depends on X86_16BIT && X86_32
1198 depends on X86_16BIT && X86_64
1200 config X86_VSYSCALL_EMULATION
1201 bool "Enable vsyscall emulation" if EXPERT
1205 This enables emulation of the legacy vsyscall page. Disabling
1206 it is roughly equivalent to booting with vsyscall=none, except
1207 that it will also disable the helpful warning if a program
1208 tries to use a vsyscall. With this option set to N, offending
1209 programs will just segfault, citing addresses of the form
1212 This option is required by many programs built before 2013, and
1213 care should be used even with newer programs if set to N.
1215 Disabling this option saves about 7K of kernel size and
1216 possibly 4K of additional runtime pagetable memory.
1218 config X86_IOPL_IOPERM
1219 bool "IOPERM and IOPL Emulation"
1222 This enables the ioperm() and iopl() syscalls which are necessary
1223 for legacy applications.
1225 Legacy IOPL support is an overbroad mechanism which allows user
1226 space aside of accessing all 65536 I/O ports also to disable
1227 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1228 capabilities and permission from potentially active security
1231 The emulation restricts the functionality of the syscall to
1232 only allowing the full range I/O port access, but prevents the
1233 ability to disable interrupts from user space which would be
1234 granted if the hardware IOPL mechanism would be used.
1237 tristate "Toshiba Laptop support"
1240 This adds a driver to safely access the System Management Mode of
1241 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1242 not work on models with a Phoenix BIOS. The System Management Mode
1243 is used to set the BIOS and power saving options on Toshiba portables.
1245 For information on utilities to make use of this driver see the
1246 Toshiba Linux utilities web site at:
1247 <http://www.buzzard.org.uk/toshiba/>.
1249 Say Y if you intend to run this kernel on a Toshiba portable.
1253 tristate "Dell i8k legacy laptop support"
1255 select SENSORS_DELL_SMM
1257 This option enables legacy /proc/i8k userspace interface in hwmon
1258 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1259 temperature and allows controlling fan speeds of Dell laptops via
1260 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1261 it reports also power and hotkey status. For fan speed control is
1262 needed userspace package i8kutils.
1264 Say Y if you intend to run this kernel on old Dell laptops or want to
1265 use userspace package i8kutils.
1268 config X86_REBOOTFIXUPS
1269 bool "Enable X86 board specific fixups for reboot"
1272 This enables chipset and/or board specific fixups to be done
1273 in order to get reboot to work correctly. This is only needed on
1274 some combinations of hardware and BIOS. The symptom, for which
1275 this config is intended, is when reboot ends with a stalled/hung
1278 Currently, the only fixup is for the Geode machines using
1279 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1281 Say Y if you want to enable the fixup. Currently, it's safe to
1282 enable this option even if you don't need it.
1286 bool "CPU microcode loading support"
1288 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1290 If you say Y here, you will be able to update the microcode on
1291 Intel and AMD processors. The Intel support is for the IA32 family,
1292 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1293 AMD support is for families 0x10 and later. You will obviously need
1294 the actual microcode binary data itself which is not shipped with
1297 The preferred method to load microcode from a detached initrd is described
1298 in Documentation/x86/microcode.rst. For that you need to enable
1299 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1300 initrd for microcode blobs.
1302 In addition, you can build the microcode into the kernel. For that you
1303 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1306 config MICROCODE_INTEL
1307 bool "Intel microcode loading support"
1308 depends on MICROCODE
1311 This options enables microcode patch loading support for Intel
1314 For the current Intel microcode data package go to
1315 <https://downloadcenter.intel.com> and search for
1316 'Linux Processor Microcode Data File'.
1318 config MICROCODE_AMD
1319 bool "AMD microcode loading support"
1320 depends on MICROCODE
1322 If you select this option, microcode patch loading support for AMD
1323 processors will be enabled.
1325 config MICROCODE_OLD_INTERFACE
1326 bool "Ancient loading interface (DEPRECATED)"
1328 depends on MICROCODE
1330 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1331 which was used by userspace tools like iucode_tool and microcode.ctl.
1332 It is inadequate because it runs too late to be able to properly
1333 load microcode on a machine and it needs special tools. Instead, you
1334 should've switched to the early loading method with the initrd or
1335 builtin microcode by now: Documentation/x86/microcode.rst
1338 tristate "/dev/cpu/*/msr - Model-specific register support"
1340 This device gives privileged processes access to the x86
1341 Model-Specific Registers (MSRs). It is a character device with
1342 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1343 MSR accesses are directed to a specific CPU on multi-processor
1347 tristate "/dev/cpu/*/cpuid - CPU information support"
1349 This device gives processes access to the x86 CPUID instruction to
1350 be executed on a specific processor. It is a character device
1351 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1355 prompt "High Memory Support"
1362 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1363 However, the address space of 32-bit x86 processors is only 4
1364 Gigabytes large. That means that, if you have a large amount of
1365 physical memory, not all of it can be "permanently mapped" by the
1366 kernel. The physical memory that's not permanently mapped is called
1369 If you are compiling a kernel which will never run on a machine with
1370 more than 1 Gigabyte total physical RAM, answer "off" here (default
1371 choice and suitable for most users). This will result in a "3GB/1GB"
1372 split: 3GB are mapped so that each process sees a 3GB virtual memory
1373 space and the remaining part of the 4GB virtual memory space is used
1374 by the kernel to permanently map as much physical memory as
1377 If the machine has between 1 and 4 Gigabytes physical RAM, then
1380 If more than 4 Gigabytes is used then answer "64GB" here. This
1381 selection turns Intel PAE (Physical Address Extension) mode on.
1382 PAE implements 3-level paging on IA32 processors. PAE is fully
1383 supported by Linux, PAE mode is implemented on all recent Intel
1384 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1385 then the kernel will not boot on CPUs that don't support PAE!
1387 The actual amount of total physical memory will either be
1388 auto detected or can be forced by using a kernel command line option
1389 such as "mem=256M". (Try "man bootparam" or see the documentation of
1390 your boot loader (lilo or loadlin) about how to pass options to the
1391 kernel at boot time.)
1393 If unsure, say "off".
1398 Select this if you have a 32-bit processor and between 1 and 4
1399 gigabytes of physical RAM.
1403 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1406 Select this if you have a 32-bit processor and more than 4
1407 gigabytes of physical RAM.
1412 prompt "Memory split" if EXPERT
1416 Select the desired split between kernel and user memory.
1418 If the address range available to the kernel is less than the
1419 physical memory installed, the remaining memory will be available
1420 as "high memory". Accessing high memory is a little more costly
1421 than low memory, as it needs to be mapped into the kernel first.
1422 Note that increasing the kernel address space limits the range
1423 available to user programs, making the address space there
1424 tighter. Selecting anything other than the default 3G/1G split
1425 will also likely make your kernel incompatible with binary-only
1428 If you are not absolutely sure what you are doing, leave this
1432 bool "3G/1G user/kernel split"
1433 config VMSPLIT_3G_OPT
1435 bool "3G/1G user/kernel split (for full 1G low memory)"
1437 bool "2G/2G user/kernel split"
1438 config VMSPLIT_2G_OPT
1440 bool "2G/2G user/kernel split (for full 2G low memory)"
1442 bool "1G/3G user/kernel split"
1447 default 0xB0000000 if VMSPLIT_3G_OPT
1448 default 0x80000000 if VMSPLIT_2G
1449 default 0x78000000 if VMSPLIT_2G_OPT
1450 default 0x40000000 if VMSPLIT_1G
1456 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1459 bool "PAE (Physical Address Extension) Support"
1460 depends on X86_32 && !HIGHMEM4G
1461 select PHYS_ADDR_T_64BIT
1464 PAE is required for NX support, and furthermore enables
1465 larger swapspace support for non-overcommit purposes. It
1466 has the cost of more pagetable lookup overhead, and also
1467 consumes more pagetable space per process.
1470 bool "Enable 5-level page tables support"
1472 select DYNAMIC_MEMORY_LAYOUT
1473 select SPARSEMEM_VMEMMAP
1476 5-level paging enables access to larger address space:
1477 upto 128 PiB of virtual address space and 4 PiB of
1478 physical address space.
1480 It will be supported by future Intel CPUs.
1482 A kernel with the option enabled can be booted on machines that
1483 support 4- or 5-level paging.
1485 See Documentation/x86/x86_64/5level-paging.rst for more
1490 config X86_DIRECT_GBPAGES
1494 Certain kernel features effectively disable kernel
1495 linear 1 GB mappings (even if the CPU otherwise
1496 supports them), so don't confuse the user by printing
1497 that we have them enabled.
1499 config X86_CPA_STATISTICS
1500 bool "Enable statistic for Change Page Attribute"
1503 Expose statistics about the Change Page Attribute mechanism, which
1504 helps to determine the effectiveness of preserving large and huge
1505 page mappings when mapping protections are changed.
1507 config AMD_MEM_ENCRYPT
1508 bool "AMD Secure Memory Encryption (SME) support"
1509 depends on X86_64 && CPU_SUP_AMD
1510 select DMA_COHERENT_POOL
1511 select DYNAMIC_PHYSICAL_MASK
1512 select ARCH_USE_MEMREMAP_PROT
1513 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1514 select INSTRUCTION_DECODER
1515 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1517 Say yes to enable support for the encryption of system memory.
1518 This requires an AMD processor that supports Secure Memory
1521 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1522 bool "Activate AMD Secure Memory Encryption (SME) by default"
1524 depends on AMD_MEM_ENCRYPT
1526 Say yes to have system memory encrypted by default if running on
1527 an AMD processor that supports Secure Memory Encryption (SME).
1529 If set to Y, then the encryption of system memory can be
1530 deactivated with the mem_encrypt=off command line option.
1532 If set to N, then the encryption of system memory can be
1533 activated with the mem_encrypt=on command line option.
1535 # Common NUMA Features
1537 bool "NUMA Memory Allocation and Scheduler Support"
1539 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1540 default y if X86_BIGSMP
1542 Enable NUMA (Non-Uniform Memory Access) support.
1544 The kernel will try to allocate memory used by a CPU on the
1545 local memory controller of the CPU and add some more
1546 NUMA awareness to the kernel.
1548 For 64-bit this is recommended if the system is Intel Core i7
1549 (or later), AMD Opteron, or EM64T NUMA.
1551 For 32-bit this is only needed if you boot a 32-bit
1552 kernel on a 64-bit NUMA platform.
1554 Otherwise, you should say N.
1558 prompt "Old style AMD Opteron NUMA detection"
1559 depends on X86_64 && NUMA && PCI
1561 Enable AMD NUMA node topology detection. You should say Y here if
1562 you have a multi processor AMD system. This uses an old method to
1563 read the NUMA configuration directly from the builtin Northbridge
1564 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1565 which also takes priority if both are compiled in.
1567 config X86_64_ACPI_NUMA
1569 prompt "ACPI NUMA detection"
1570 depends on X86_64 && NUMA && ACPI && PCI
1573 Enable ACPI SRAT based node topology detection.
1576 bool "NUMA emulation"
1579 Enable NUMA emulation. A flat machine will be split
1580 into virtual nodes when booted with "numa=fake=N", where N is the
1581 number of nodes. This is only useful for debugging.
1584 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1586 default "10" if MAXSMP
1587 default "6" if X86_64
1591 Specify the maximum number of NUMA Nodes available on the target
1592 system. Increases memory reserved to accommodate various tables.
1594 config ARCH_FLATMEM_ENABLE
1596 depends on X86_32 && !NUMA
1598 config ARCH_SPARSEMEM_ENABLE
1600 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1601 select SPARSEMEM_STATIC if X86_32
1602 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1604 config ARCH_SPARSEMEM_DEFAULT
1605 def_bool X86_64 || (NUMA && X86_32)
1607 config ARCH_SELECT_MEMORY_MODEL
1609 depends on ARCH_SPARSEMEM_ENABLE
1611 config ARCH_MEMORY_PROBE
1612 bool "Enable sysfs memory/probe interface"
1613 depends on X86_64 && MEMORY_HOTPLUG
1615 This option enables a sysfs memory/probe interface for testing.
1616 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1617 If you are unsure how to answer this question, answer N.
1619 config ARCH_PROC_KCORE_TEXT
1621 depends on X86_64 && PROC_KCORE
1623 config ILLEGAL_POINTER_VALUE
1626 default 0xdead000000000000 if X86_64
1628 config X86_PMEM_LEGACY_DEVICE
1631 config X86_PMEM_LEGACY
1632 tristate "Support non-standard NVDIMMs and ADR protected memory"
1633 depends on PHYS_ADDR_T_64BIT
1635 select X86_PMEM_LEGACY_DEVICE
1636 select NUMA_KEEP_MEMINFO if NUMA
1639 Treat memory marked using the non-standard e820 type of 12 as used
1640 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1641 The kernel will offer these regions to the 'pmem' driver so
1642 they can be used for persistent storage.
1647 bool "Allocate 3rd-level pagetables from highmem"
1650 The VM uses one page table entry for each page of physical memory.
1651 For systems with a lot of RAM, this can be wasteful of precious
1652 low memory. Setting this option will put user-space page table
1653 entries in high memory.
1655 config X86_CHECK_BIOS_CORRUPTION
1656 bool "Check for low memory corruption"
1658 Periodically check for memory corruption in low memory, which
1659 is suspected to be caused by BIOS. Even when enabled in the
1660 configuration, it is disabled at runtime. Enable it by
1661 setting "memory_corruption_check=1" on the kernel command
1662 line. By default it scans the low 64k of memory every 60
1663 seconds; see the memory_corruption_check_size and
1664 memory_corruption_check_period parameters in
1665 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1667 When enabled with the default parameters, this option has
1668 almost no overhead, as it reserves a relatively small amount
1669 of memory and scans it infrequently. It both detects corruption
1670 and prevents it from affecting the running system.
1672 It is, however, intended as a diagnostic tool; if repeatable
1673 BIOS-originated corruption always affects the same memory,
1674 you can use memmap= to prevent the kernel from using that
1677 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1678 bool "Set the default setting of memory_corruption_check"
1679 depends on X86_CHECK_BIOS_CORRUPTION
1682 Set whether the default state of memory_corruption_check is
1685 config MATH_EMULATION
1687 depends on MODIFY_LDT_SYSCALL
1688 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1690 Linux can emulate a math coprocessor (used for floating point
1691 operations) if you don't have one. 486DX and Pentium processors have
1692 a math coprocessor built in, 486SX and 386 do not, unless you added
1693 a 487DX or 387, respectively. (The messages during boot time can
1694 give you some hints here ["man dmesg"].) Everyone needs either a
1695 coprocessor or this emulation.
1697 If you don't have a math coprocessor, you need to say Y here; if you
1698 say Y here even though you have a coprocessor, the coprocessor will
1699 be used nevertheless. (This behavior can be changed with the kernel
1700 command line option "no387", which comes handy if your coprocessor
1701 is broken. Try "man bootparam" or see the documentation of your boot
1702 loader (lilo or loadlin) about how to pass options to the kernel at
1703 boot time.) This means that it is a good idea to say Y here if you
1704 intend to use this kernel on different machines.
1706 More information about the internals of the Linux math coprocessor
1707 emulation can be found in <file:arch/x86/math-emu/README>.
1709 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1710 kernel, it won't hurt.
1714 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1716 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1717 the Memory Type Range Registers (MTRRs) may be used to control
1718 processor access to memory ranges. This is most useful if you have
1719 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1720 allows bus write transfers to be combined into a larger transfer
1721 before bursting over the PCI/AGP bus. This can increase performance
1722 of image write operations 2.5 times or more. Saying Y here creates a
1723 /proc/mtrr file which may be used to manipulate your processor's
1724 MTRRs. Typically the X server should use this.
1726 This code has a reasonably generic interface so that similar
1727 control registers on other processors can be easily supported
1730 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1731 Registers (ARRs) which provide a similar functionality to MTRRs. For
1732 these, the ARRs are used to emulate the MTRRs.
1733 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1734 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1735 write-combining. All of these processors are supported by this code
1736 and it makes sense to say Y here if you have one of them.
1738 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1739 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1740 can lead to all sorts of problems, so it's good to say Y here.
1742 You can safely say Y even if your machine doesn't have MTRRs, you'll
1743 just add about 9 KB to your kernel.
1745 See <file:Documentation/x86/mtrr.rst> for more information.
1747 config MTRR_SANITIZER
1749 prompt "MTRR cleanup support"
1752 Convert MTRR layout from continuous to discrete, so X drivers can
1753 add writeback entries.
1755 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1756 The largest mtrr entry size for a continuous block can be set with
1761 config MTRR_SANITIZER_ENABLE_DEFAULT
1762 int "MTRR cleanup enable value (0-1)"
1765 depends on MTRR_SANITIZER
1767 Enable mtrr cleanup default value
1769 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1770 int "MTRR cleanup spare reg num (0-7)"
1773 depends on MTRR_SANITIZER
1775 mtrr cleanup spare entries default, it can be changed via
1776 mtrr_spare_reg_nr=N on the kernel command line.
1780 prompt "x86 PAT support" if EXPERT
1783 Use PAT attributes to setup page level cache control.
1785 PATs are the modern equivalents of MTRRs and are much more
1786 flexible than MTRRs.
1788 Say N here if you see bootup problems (boot crash, boot hang,
1789 spontaneous reboots) or a non-working video driver.
1793 config ARCH_USES_PG_UNCACHED
1799 prompt "x86 architectural random number generator" if EXPERT
1801 Enable the x86 architectural RDRAND instruction
1802 (Intel Bull Mountain technology) to generate random numbers.
1803 If supported, this is a high bandwidth, cryptographically
1804 secure hardware random number generator.
1808 prompt "Supervisor Mode Access Prevention" if EXPERT
1810 Supervisor Mode Access Prevention (SMAP) is a security
1811 feature in newer Intel processors. There is a small
1812 performance cost if this enabled and turned on; there is
1813 also a small increase in the kernel size if this is enabled.
1819 prompt "User Mode Instruction Prevention" if EXPERT
1821 User Mode Instruction Prevention (UMIP) is a security feature in
1822 some x86 processors. If enabled, a general protection fault is
1823 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1824 executed in user mode. These instructions unnecessarily expose
1825 information about the hardware state.
1827 The vast majority of applications do not use these instructions.
1828 For the very few that do, software emulation is provided in
1829 specific cases in protected and virtual-8086 modes. Emulated
1832 config X86_INTEL_MEMORY_PROTECTION_KEYS
1833 prompt "Memory Protection Keys"
1835 # Note: only available in 64-bit mode
1836 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1837 select ARCH_USES_HIGH_VMA_FLAGS
1838 select ARCH_HAS_PKEYS
1840 Memory Protection Keys provides a mechanism for enforcing
1841 page-based protections, but without requiring modification of the
1842 page tables when an application changes protection domains.
1844 For details, see Documentation/core-api/protection-keys.rst
1849 prompt "TSX enable mode"
1850 depends on CPU_SUP_INTEL
1851 default X86_INTEL_TSX_MODE_OFF
1853 Intel's TSX (Transactional Synchronization Extensions) feature
1854 allows to optimize locking protocols through lock elision which
1855 can lead to a noticeable performance boost.
1857 On the other hand it has been shown that TSX can be exploited
1858 to form side channel attacks (e.g. TAA) and chances are there
1859 will be more of those attacks discovered in the future.
1861 Therefore TSX is not enabled by default (aka tsx=off). An admin
1862 might override this decision by tsx=on the command line parameter.
1863 Even with TSX enabled, the kernel will attempt to enable the best
1864 possible TAA mitigation setting depending on the microcode available
1865 for the particular machine.
1867 This option allows to set the default tsx mode between tsx=on, =off
1868 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1871 Say off if not sure, auto if TSX is in use but it should be used on safe
1872 platforms or on if TSX is in use and the security aspect of tsx is not
1875 config X86_INTEL_TSX_MODE_OFF
1878 TSX is disabled if possible - equals to tsx=off command line parameter.
1880 config X86_INTEL_TSX_MODE_ON
1883 TSX is always enabled on TSX capable HW - equals the tsx=on command
1886 config X86_INTEL_TSX_MODE_AUTO
1889 TSX is enabled on TSX capable HW that is believed to be safe against
1890 side channel attacks- equals the tsx=auto command line parameter.
1894 bool "Software Guard eXtensions (SGX)"
1895 depends on X86_64 && CPU_SUP_INTEL
1897 depends on CRYPTO_SHA256=y
1900 select NUMA_KEEP_MEMINFO if NUMA
1902 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1903 that can be used by applications to set aside private regions of code
1904 and data, referred to as enclaves. An enclave's private memory can
1905 only be accessed by code running within the enclave. Accesses from
1906 outside the enclave, including other enclaves, are disallowed by
1912 bool "EFI runtime service support"
1915 select EFI_RUNTIME_WRAPPERS
1917 This enables the kernel to use EFI runtime services that are
1918 available (such as the EFI variable services).
1920 This option is only useful on systems that have EFI firmware.
1921 In addition, you should use the latest ELILO loader available
1922 at <http://elilo.sourceforge.net> in order to take advantage
1923 of EFI runtime services. However, even with this option, the
1924 resultant kernel should continue to boot on existing non-EFI
1928 bool "EFI stub support"
1929 depends on EFI && !X86_USE_3DNOW
1930 depends on $(cc-option,-mabi=ms) || X86_32
1933 This kernel feature allows a bzImage to be loaded directly
1934 by EFI firmware without the use of a bootloader.
1936 See Documentation/admin-guide/efi-stub.rst for more information.
1939 bool "EFI mixed-mode support"
1940 depends on EFI_STUB && X86_64
1942 Enabling this feature allows a 64-bit kernel to be booted
1943 on a 32-bit firmware, provided that your CPU supports 64-bit
1946 Note that it is not possible to boot a mixed-mode enabled
1947 kernel via the EFI boot stub - a bootloader that supports
1948 the EFI handover protocol must be used.
1952 source "kernel/Kconfig.hz"
1955 bool "kexec system call"
1958 kexec is a system call that implements the ability to shutdown your
1959 current kernel, and to start another kernel. It is like a reboot
1960 but it is independent of the system firmware. And like a reboot
1961 you can start any kernel with it, not just Linux.
1963 The name comes from the similarity to the exec system call.
1965 It is an ongoing process to be certain the hardware in a machine
1966 is properly shutdown, so do not be surprised if this code does not
1967 initially work for you. As of this writing the exact hardware
1968 interface is strongly in flux, so no good recommendation can be
1972 bool "kexec file based system call"
1977 depends on CRYPTO_SHA256=y
1979 This is new version of kexec system call. This system call is
1980 file based and takes file descriptors as system call argument
1981 for kernel and initramfs as opposed to list of segments as
1982 accepted by previous system call.
1984 config ARCH_HAS_KEXEC_PURGATORY
1988 bool "Verify kernel signature during kexec_file_load() syscall"
1989 depends on KEXEC_FILE
1992 This option makes the kexec_file_load() syscall check for a valid
1993 signature of the kernel image. The image can still be loaded without
1994 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
1995 there's a signature that we can check, then it must be valid.
1997 In addition to this option, you need to enable signature
1998 verification for the corresponding kernel image type being
1999 loaded in order for this to work.
2001 config KEXEC_SIG_FORCE
2002 bool "Require a valid signature in kexec_file_load() syscall"
2003 depends on KEXEC_SIG
2005 This option makes kernel signature verification mandatory for
2006 the kexec_file_load() syscall.
2008 config KEXEC_BZIMAGE_VERIFY_SIG
2009 bool "Enable bzImage signature verification support"
2010 depends on KEXEC_SIG
2011 depends on SIGNED_PE_FILE_VERIFICATION
2012 select SYSTEM_TRUSTED_KEYRING
2014 Enable bzImage signature verification support.
2017 bool "kernel crash dumps"
2018 depends on X86_64 || (X86_32 && HIGHMEM)
2020 Generate crash dump after being started by kexec.
2021 This should be normally only set in special crash dump kernels
2022 which are loaded in the main kernel with kexec-tools into
2023 a specially reserved region and then later executed after
2024 a crash by kdump/kexec. The crash dump kernel must be compiled
2025 to a memory address not used by the main kernel or BIOS using
2026 PHYSICAL_START, or it must be built as a relocatable image
2027 (CONFIG_RELOCATABLE=y).
2028 For more details see Documentation/admin-guide/kdump/kdump.rst
2032 depends on KEXEC && HIBERNATION
2034 Jump between original kernel and kexeced kernel and invoke
2035 code in physical address mode via KEXEC
2037 config PHYSICAL_START
2038 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2041 This gives the physical address where the kernel is loaded.
2043 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2044 bzImage will decompress itself to above physical address and
2045 run from there. Otherwise, bzImage will run from the address where
2046 it has been loaded by the boot loader and will ignore above physical
2049 In normal kdump cases one does not have to set/change this option
2050 as now bzImage can be compiled as a completely relocatable image
2051 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2052 address. This option is mainly useful for the folks who don't want
2053 to use a bzImage for capturing the crash dump and want to use a
2054 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2055 to be specifically compiled to run from a specific memory area
2056 (normally a reserved region) and this option comes handy.
2058 So if you are using bzImage for capturing the crash dump,
2059 leave the value here unchanged to 0x1000000 and set
2060 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2061 for capturing the crash dump change this value to start of
2062 the reserved region. In other words, it can be set based on
2063 the "X" value as specified in the "crashkernel=YM@XM"
2064 command line boot parameter passed to the panic-ed
2065 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2066 for more details about crash dumps.
2068 Usage of bzImage for capturing the crash dump is recommended as
2069 one does not have to build two kernels. Same kernel can be used
2070 as production kernel and capture kernel. Above option should have
2071 gone away after relocatable bzImage support is introduced. But it
2072 is present because there are users out there who continue to use
2073 vmlinux for dump capture. This option should go away down the
2076 Don't change this unless you know what you are doing.
2079 bool "Build a relocatable kernel"
2082 This builds a kernel image that retains relocation information
2083 so it can be loaded someplace besides the default 1MB.
2084 The relocations tend to make the kernel binary about 10% larger,
2085 but are discarded at runtime.
2087 One use is for the kexec on panic case where the recovery kernel
2088 must live at a different physical address than the primary
2091 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2092 it has been loaded at and the compile time physical address
2093 (CONFIG_PHYSICAL_START) is used as the minimum location.
2095 config RANDOMIZE_BASE
2096 bool "Randomize the address of the kernel image (KASLR)"
2097 depends on RELOCATABLE
2100 In support of Kernel Address Space Layout Randomization (KASLR),
2101 this randomizes the physical address at which the kernel image
2102 is decompressed and the virtual address where the kernel
2103 image is mapped, as a security feature that deters exploit
2104 attempts relying on knowledge of the location of kernel
2107 On 64-bit, the kernel physical and virtual addresses are
2108 randomized separately. The physical address will be anywhere
2109 between 16MB and the top of physical memory (up to 64TB). The
2110 virtual address will be randomized from 16MB up to 1GB (9 bits
2111 of entropy). Note that this also reduces the memory space
2112 available to kernel modules from 1.5GB to 1GB.
2114 On 32-bit, the kernel physical and virtual addresses are
2115 randomized together. They will be randomized from 16MB up to
2116 512MB (8 bits of entropy).
2118 Entropy is generated using the RDRAND instruction if it is
2119 supported. If RDTSC is supported, its value is mixed into
2120 the entropy pool as well. If neither RDRAND nor RDTSC are
2121 supported, then entropy is read from the i8254 timer. The
2122 usable entropy is limited by the kernel being built using
2123 2GB addressing, and that PHYSICAL_ALIGN must be at a
2124 minimum of 2MB. As a result, only 10 bits of entropy are
2125 theoretically possible, but the implementations are further
2126 limited due to memory layouts.
2130 # Relocation on x86 needs some additional build support
2131 config X86_NEED_RELOCS
2133 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2135 config PHYSICAL_ALIGN
2136 hex "Alignment value to which kernel should be aligned"
2138 range 0x2000 0x1000000 if X86_32
2139 range 0x200000 0x1000000 if X86_64
2141 This value puts the alignment restrictions on physical address
2142 where kernel is loaded and run from. Kernel is compiled for an
2143 address which meets above alignment restriction.
2145 If bootloader loads the kernel at a non-aligned address and
2146 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2147 address aligned to above value and run from there.
2149 If bootloader loads the kernel at a non-aligned address and
2150 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2151 load address and decompress itself to the address it has been
2152 compiled for and run from there. The address for which kernel is
2153 compiled already meets above alignment restrictions. Hence the
2154 end result is that kernel runs from a physical address meeting
2155 above alignment restrictions.
2157 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2158 this value must be a multiple of 0x200000.
2160 Don't change this unless you know what you are doing.
2162 config DYNAMIC_MEMORY_LAYOUT
2165 This option makes base addresses of vmalloc and vmemmap as well as
2166 __PAGE_OFFSET movable during boot.
2168 config RANDOMIZE_MEMORY
2169 bool "Randomize the kernel memory sections"
2171 depends on RANDOMIZE_BASE
2172 select DYNAMIC_MEMORY_LAYOUT
2173 default RANDOMIZE_BASE
2175 Randomizes the base virtual address of kernel memory sections
2176 (physical memory mapping, vmalloc & vmemmap). This security feature
2177 makes exploits relying on predictable memory locations less reliable.
2179 The order of allocations remains unchanged. Entropy is generated in
2180 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2181 configuration have in average 30,000 different possible virtual
2182 addresses for each memory section.
2186 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2187 hex "Physical memory mapping padding" if EXPERT
2188 depends on RANDOMIZE_MEMORY
2189 default "0xa" if MEMORY_HOTPLUG
2191 range 0x1 0x40 if MEMORY_HOTPLUG
2194 Define the padding in terabytes added to the existing physical
2195 memory size during kernel memory randomization. It is useful
2196 for memory hotplug support but reduces the entropy available for
2197 address randomization.
2199 If unsure, leave at the default value.
2205 config BOOTPARAM_HOTPLUG_CPU0
2206 bool "Set default setting of cpu0_hotpluggable"
2207 depends on HOTPLUG_CPU
2209 Set whether default state of cpu0_hotpluggable is on or off.
2211 Say Y here to enable CPU0 hotplug by default. If this switch
2212 is turned on, there is no need to give cpu0_hotplug kernel
2213 parameter and the CPU0 hotplug feature is enabled by default.
2215 Please note: there are two known CPU0 dependencies if you want
2216 to enable the CPU0 hotplug feature either by this switch or by
2217 cpu0_hotplug kernel parameter.
2219 First, resume from hibernate or suspend always starts from CPU0.
2220 So hibernate and suspend are prevented if CPU0 is offline.
2222 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2223 offline if any interrupt can not migrate out of CPU0. There may
2224 be other CPU0 dependencies.
2226 Please make sure the dependencies are under your control before
2227 you enable this feature.
2229 Say N if you don't want to enable CPU0 hotplug feature by default.
2230 You still can enable the CPU0 hotplug feature at boot by kernel
2231 parameter cpu0_hotplug.
2233 config DEBUG_HOTPLUG_CPU0
2235 prompt "Debug CPU0 hotplug"
2236 depends on HOTPLUG_CPU
2238 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2239 soon as possible and boots up userspace with CPU0 offlined. User
2240 can online CPU0 back after boot time.
2242 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2243 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2244 compilation or giving cpu0_hotplug kernel parameter at boot.
2250 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2251 depends on COMPAT_32
2253 Certain buggy versions of glibc will crash if they are
2254 presented with a 32-bit vDSO that is not mapped at the address
2255 indicated in its segment table.
2257 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2258 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2259 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2260 the only released version with the bug, but OpenSUSE 9
2261 contains a buggy "glibc 2.3.2".
2263 The symptom of the bug is that everything crashes on startup, saying:
2264 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2266 Saying Y here changes the default value of the vdso32 boot
2267 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2268 This works around the glibc bug but hurts performance.
2270 If unsure, say N: if you are compiling your own kernel, you
2271 are unlikely to be using a buggy version of glibc.
2274 prompt "vsyscall table for legacy applications"
2276 default LEGACY_VSYSCALL_XONLY
2278 Legacy user code that does not know how to find the vDSO expects
2279 to be able to issue three syscalls by calling fixed addresses in
2280 kernel space. Since this location is not randomized with ASLR,
2281 it can be used to assist security vulnerability exploitation.
2283 This setting can be changed at boot time via the kernel command
2284 line parameter vsyscall=[emulate|xonly|none].
2286 On a system with recent enough glibc (2.14 or newer) and no
2287 static binaries, you can say None without a performance penalty
2288 to improve security.
2290 If unsure, select "Emulate execution only".
2292 config LEGACY_VSYSCALL_EMULATE
2293 bool "Full emulation"
2295 The kernel traps and emulates calls into the fixed vsyscall
2296 address mapping. This makes the mapping non-executable, but
2297 it still contains readable known contents, which could be
2298 used in certain rare security vulnerability exploits. This
2299 configuration is recommended when using legacy userspace
2300 that still uses vsyscalls along with legacy binary
2301 instrumentation tools that require code to be readable.
2303 An example of this type of legacy userspace is running
2304 Pin on an old binary that still uses vsyscalls.
2306 config LEGACY_VSYSCALL_XONLY
2307 bool "Emulate execution only"
2309 The kernel traps and emulates calls into the fixed vsyscall
2310 address mapping and does not allow reads. This
2311 configuration is recommended when userspace might use the
2312 legacy vsyscall area but support for legacy binary
2313 instrumentation of legacy code is not needed. It mitigates
2314 certain uses of the vsyscall area as an ASLR-bypassing
2317 config LEGACY_VSYSCALL_NONE
2320 There will be no vsyscall mapping at all. This will
2321 eliminate any risk of ASLR bypass due to the vsyscall
2322 fixed address mapping. Attempts to use the vsyscalls
2323 will be reported to dmesg, so that either old or
2324 malicious userspace programs can be identified.
2329 bool "Built-in kernel command line"
2331 Allow for specifying boot arguments to the kernel at
2332 build time. On some systems (e.g. embedded ones), it is
2333 necessary or convenient to provide some or all of the
2334 kernel boot arguments with the kernel itself (that is,
2335 to not rely on the boot loader to provide them.)
2337 To compile command line arguments into the kernel,
2338 set this option to 'Y', then fill in the
2339 boot arguments in CONFIG_CMDLINE.
2341 Systems with fully functional boot loaders (i.e. non-embedded)
2342 should leave this option set to 'N'.
2345 string "Built-in kernel command string"
2346 depends on CMDLINE_BOOL
2349 Enter arguments here that should be compiled into the kernel
2350 image and used at boot time. If the boot loader provides a
2351 command line at boot time, it is appended to this string to
2352 form the full kernel command line, when the system boots.
2354 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2355 change this behavior.
2357 In most cases, the command line (whether built-in or provided
2358 by the boot loader) should specify the device for the root
2361 config CMDLINE_OVERRIDE
2362 bool "Built-in command line overrides boot loader arguments"
2363 depends on CMDLINE_BOOL && CMDLINE != ""
2365 Set this option to 'Y' to have the kernel ignore the boot loader
2366 command line, and use ONLY the built-in command line.
2368 This is used to work around broken boot loaders. This should
2369 be set to 'N' under normal conditions.
2371 config MODIFY_LDT_SYSCALL
2372 bool "Enable the LDT (local descriptor table)" if EXPERT
2375 Linux can allow user programs to install a per-process x86
2376 Local Descriptor Table (LDT) using the modify_ldt(2) system
2377 call. This is required to run 16-bit or segmented code such as
2378 DOSEMU or some Wine programs. It is also used by some very old
2379 threading libraries.
2381 Enabling this feature adds a small amount of overhead to
2382 context switches and increases the low-level kernel attack
2383 surface. Disabling it removes the modify_ldt(2) system call.
2385 Saying 'N' here may make sense for embedded or server kernels.
2387 source "kernel/livepatch/Kconfig"
2391 config ARCH_HAS_ADD_PAGES
2393 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2395 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2398 config USE_PERCPU_NUMA_NODE_ID
2402 menu "Power management and ACPI options"
2404 config ARCH_HIBERNATION_HEADER
2406 depends on HIBERNATION
2408 source "kernel/power/Kconfig"
2410 source "drivers/acpi/Kconfig"
2417 tristate "APM (Advanced Power Management) BIOS support"
2418 depends on X86_32 && PM_SLEEP
2420 APM is a BIOS specification for saving power using several different
2421 techniques. This is mostly useful for battery powered laptops with
2422 APM compliant BIOSes. If you say Y here, the system time will be
2423 reset after a RESUME operation, the /proc/apm device will provide
2424 battery status information, and user-space programs will receive
2425 notification of APM "events" (e.g. battery status change).
2427 If you select "Y" here, you can disable actual use of the APM
2428 BIOS by passing the "apm=off" option to the kernel at boot time.
2430 Note that the APM support is almost completely disabled for
2431 machines with more than one CPU.
2433 In order to use APM, you will need supporting software. For location
2434 and more information, read <file:Documentation/power/apm-acpi.rst>
2435 and the Battery Powered Linux mini-HOWTO, available from
2436 <http://www.tldp.org/docs.html#howto>.
2438 This driver does not spin down disk drives (see the hdparm(8)
2439 manpage ("man 8 hdparm") for that), and it doesn't turn off
2440 VESA-compliant "green" monitors.
2442 This driver does not support the TI 4000M TravelMate and the ACER
2443 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2444 desktop machines also don't have compliant BIOSes, and this driver
2445 may cause those machines to panic during the boot phase.
2447 Generally, if you don't have a battery in your machine, there isn't
2448 much point in using this driver and you should say N. If you get
2449 random kernel OOPSes or reboots that don't seem to be related to
2450 anything, try disabling/enabling this option (or disabling/enabling
2453 Some other things you should try when experiencing seemingly random,
2456 1) make sure that you have enough swap space and that it is
2458 2) pass the "no-hlt" option to the kernel
2459 3) switch on floating point emulation in the kernel and pass
2460 the "no387" option to the kernel
2461 4) pass the "floppy=nodma" option to the kernel
2462 5) pass the "mem=4M" option to the kernel (thereby disabling
2463 all but the first 4 MB of RAM)
2464 6) make sure that the CPU is not over clocked.
2465 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2466 8) disable the cache from your BIOS settings
2467 9) install a fan for the video card or exchange video RAM
2468 10) install a better fan for the CPU
2469 11) exchange RAM chips
2470 12) exchange the motherboard.
2472 To compile this driver as a module, choose M here: the
2473 module will be called apm.
2477 config APM_IGNORE_USER_SUSPEND
2478 bool "Ignore USER SUSPEND"
2480 This option will ignore USER SUSPEND requests. On machines with a
2481 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2482 series notebooks, it is necessary to say Y because of a BIOS bug.
2484 config APM_DO_ENABLE
2485 bool "Enable PM at boot time"
2487 Enable APM features at boot time. From page 36 of the APM BIOS
2488 specification: "When disabled, the APM BIOS does not automatically
2489 power manage devices, enter the Standby State, enter the Suspend
2490 State, or take power saving steps in response to CPU Idle calls."
2491 This driver will make CPU Idle calls when Linux is idle (unless this
2492 feature is turned off -- see "Do CPU IDLE calls", below). This
2493 should always save battery power, but more complicated APM features
2494 will be dependent on your BIOS implementation. You may need to turn
2495 this option off if your computer hangs at boot time when using APM
2496 support, or if it beeps continuously instead of suspending. Turn
2497 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2498 T400CDT. This is off by default since most machines do fine without
2503 bool "Make CPU Idle calls when idle"
2505 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2506 On some machines, this can activate improved power savings, such as
2507 a slowed CPU clock rate, when the machine is idle. These idle calls
2508 are made after the idle loop has run for some length of time (e.g.,
2509 333 mS). On some machines, this will cause a hang at boot time or
2510 whenever the CPU becomes idle. (On machines with more than one CPU,
2511 this option does nothing.)
2513 config APM_DISPLAY_BLANK
2514 bool "Enable console blanking using APM"
2516 Enable console blanking using the APM. Some laptops can use this to
2517 turn off the LCD backlight when the screen blanker of the Linux
2518 virtual console blanks the screen. Note that this is only used by
2519 the virtual console screen blanker, and won't turn off the backlight
2520 when using the X Window system. This also doesn't have anything to
2521 do with your VESA-compliant power-saving monitor. Further, this
2522 option doesn't work for all laptops -- it might not turn off your
2523 backlight at all, or it might print a lot of errors to the console,
2524 especially if you are using gpm.
2526 config APM_ALLOW_INTS
2527 bool "Allow interrupts during APM BIOS calls"
2529 Normally we disable external interrupts while we are making calls to
2530 the APM BIOS as a measure to lessen the effects of a badly behaving
2531 BIOS implementation. The BIOS should reenable interrupts if it
2532 needs to. Unfortunately, some BIOSes do not -- especially those in
2533 many of the newer IBM Thinkpads. If you experience hangs when you
2534 suspend, try setting this to Y. Otherwise, say N.
2538 source "drivers/cpufreq/Kconfig"
2540 source "drivers/cpuidle/Kconfig"
2542 source "drivers/idle/Kconfig"
2547 menu "Bus options (PCI etc.)"
2550 prompt "PCI access mode"
2551 depends on X86_32 && PCI
2554 On PCI systems, the BIOS can be used to detect the PCI devices and
2555 determine their configuration. However, some old PCI motherboards
2556 have BIOS bugs and may crash if this is done. Also, some embedded
2557 PCI-based systems don't have any BIOS at all. Linux can also try to
2558 detect the PCI hardware directly without using the BIOS.
2560 With this option, you can specify how Linux should detect the
2561 PCI devices. If you choose "BIOS", the BIOS will be used,
2562 if you choose "Direct", the BIOS won't be used, and if you
2563 choose "MMConfig", then PCI Express MMCONFIG will be used.
2564 If you choose "Any", the kernel will try MMCONFIG, then the
2565 direct access method and falls back to the BIOS if that doesn't
2566 work. If unsure, go with the default, which is "Any".
2571 config PCI_GOMMCONFIG
2588 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2590 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2593 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2596 bool "Support mmconfig PCI config space access" if X86_64
2598 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2599 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2603 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2607 depends on PCI && XEN
2610 config MMCONF_FAM10H
2612 depends on X86_64 && PCI_MMCONFIG && ACPI
2614 config PCI_CNB20LE_QUIRK
2615 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2618 Read the PCI windows out of the CNB20LE host bridge. This allows
2619 PCI hotplug to work on systems with the CNB20LE chipset which do
2622 There's no public spec for this chipset, and this functionality
2623 is known to be incomplete.
2625 You should say N unless you know you need this.
2628 bool "ISA bus support on modern systems" if EXPERT
2630 Expose ISA bus device drivers and options available for selection and
2631 configuration. Enable this option if your target machine has an ISA
2632 bus. ISA is an older system, displaced by PCI and newer bus
2633 architectures -- if your target machine is modern, it probably does
2634 not have an ISA bus.
2638 # x86_64 have no ISA slots, but can have ISA-style DMA.
2640 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2643 Enables ISA-style DMA support for devices requiring such controllers.
2651 Find out whether you have ISA slots on your motherboard. ISA is the
2652 name of a bus system, i.e. the way the CPU talks to the other stuff
2653 inside your box. Other bus systems are PCI, EISA, MicroChannel
2654 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2655 newer boards don't support it. If you have ISA, say Y, otherwise N.
2658 tristate "NatSemi SCx200 support"
2660 This provides basic support for National Semiconductor's
2661 (now AMD's) Geode processors. The driver probes for the
2662 PCI-IDs of several on-chip devices, so its a good dependency
2663 for other scx200_* drivers.
2665 If compiled as a module, the driver is named scx200.
2667 config SCx200HR_TIMER
2668 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2672 This driver provides a clocksource built upon the on-chip
2673 27MHz high-resolution timer. Its also a workaround for
2674 NSC Geode SC-1100's buggy TSC, which loses time when the
2675 processor goes idle (as is done by the scheduler). The
2676 other workaround is idle=poll boot option.
2679 bool "One Laptop Per Child support"
2687 Add support for detecting the unique features of the OLPC
2691 bool "OLPC XO-1 Power Management"
2692 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2694 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2697 bool "OLPC XO-1 Real Time Clock"
2698 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2700 Add support for the XO-1 real time clock, which can be used as a
2701 programmable wakeup source.
2704 bool "OLPC XO-1 SCI extras"
2705 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2709 Add support for SCI-based features of the OLPC XO-1 laptop:
2710 - EC-driven system wakeups
2714 - AC adapter status updates
2715 - Battery status updates
2717 config OLPC_XO15_SCI
2718 bool "OLPC XO-1.5 SCI extras"
2719 depends on OLPC && ACPI
2722 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2723 - EC-driven system wakeups
2724 - AC adapter status updates
2725 - Battery status updates
2728 bool "PCEngines ALIX System Support (LED setup)"
2731 This option enables system support for the PCEngines ALIX.
2732 At present this just sets up LEDs for GPIO control on
2733 ALIX2/3/6 boards. However, other system specific setup should
2736 Note: You must still enable the drivers for GPIO and LED support
2737 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2739 Note: You have to set alix.force=1 for boards with Award BIOS.
2742 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2745 This option enables system support for the Soekris Engineering net5501.
2748 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2752 This option enables system support for the Traverse Technologies GEOS.
2755 bool "Technologic Systems TS-5500 platform support"
2757 select CHECK_SIGNATURE
2761 This option enables system support for the Technologic Systems TS-5500.
2767 depends on CPU_SUP_AMD && PCI
2772 menu "Binary Emulations"
2774 config IA32_EMULATION
2775 bool "IA32 Emulation"
2777 select ARCH_WANT_OLD_COMPAT_IPC
2779 select COMPAT_OLD_SIGACTION
2781 Include code to run legacy 32-bit programs under a
2782 64-bit kernel. You should likely turn this on, unless you're
2783 100% sure that you don't have any 32-bit programs left.
2786 tristate "IA32 a.out support"
2787 depends on IA32_EMULATION
2790 Support old a.out binaries in the 32bit emulation.
2793 bool "x32 ABI for 64-bit mode"
2796 Include code to run binaries for the x32 native 32-bit ABI
2797 for 64-bit processors. An x32 process gets access to the
2798 full 64-bit register file and wide data path while leaving
2799 pointers at 32 bits for smaller memory footprint.
2801 You will need a recent binutils (2.22 or later) with
2802 elf32_x86_64 support enabled to compile a kernel with this
2807 depends on IA32_EMULATION || X86_32
2809 select OLD_SIGSUSPEND3
2813 depends on IA32_EMULATION || X86_X32
2816 config COMPAT_FOR_U64_ALIGNMENT
2819 config SYSVIPC_COMPAT
2827 config HAVE_ATOMIC_IOMAP
2831 source "drivers/firmware/Kconfig"
2833 source "arch/x86/kvm/Kconfig"
2835 source "arch/x86/Kconfig.assembler"