3 bool "64-bit kernel" if ARCH = "x86"
6 Say yes to build a 64-bit kernel - formerly known as x86_64
7 Say no to build a 32-bit kernel - formerly known as i386
12 # Options that are inherently 32-bit kernel only:
13 select ARCH_WANT_IPC_PARSE_VERSION
15 select CLONE_BACKWARDS
17 select HAVE_GENERIC_DMA_COHERENT
18 select MODULES_USE_ELF_REL
24 # Options that are inherently 64-bit kernel only:
25 select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
26 select ARCH_SUPPORTS_INT128
27 select ARCH_USE_CMPXCHG_LOCKREF
28 select HAVE_ARCH_SOFT_DIRTY
29 select MODULES_USE_ELF_RELA
30 select X86_DEV_DMA_OPS
35 # ( Note that options that are marked 'if X86_64' could in principle be
36 # ported to 32-bit as well. )
41 # Note: keep this list sorted alphabetically
43 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
44 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
46 select ARCH_CLOCKSOURCE_DATA
47 select ARCH_DISCARD_MEMBLOCK
48 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
49 select ARCH_HAS_DEBUG_VIRTUAL
50 select ARCH_HAS_DEVMEM_IS_ALLOWED
51 select ARCH_HAS_ELF_RANDOMIZE
52 select ARCH_HAS_FAST_MULTIPLIER
53 select ARCH_HAS_FORTIFY_SOURCE
54 select ARCH_HAS_GCOV_PROFILE_ALL
55 select ARCH_HAS_KCOV if X86_64
56 select ARCH_HAS_MMIO_FLUSH
57 select ARCH_HAS_PMEM_API if X86_64
58 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
59 select ARCH_HAS_SET_MEMORY
60 select ARCH_HAS_SG_CHAIN
61 select ARCH_HAS_STRICT_KERNEL_RWX
62 select ARCH_HAS_STRICT_MODULE_RWX
63 select ARCH_HAS_UBSAN_SANITIZE_ALL
64 select ARCH_HAS_ZONE_DEVICE if X86_64
65 select ARCH_HAVE_NMI_SAFE_CMPXCHG
66 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
67 select ARCH_MIGHT_HAVE_PC_PARPORT
68 select ARCH_MIGHT_HAVE_PC_SERIO
69 select ARCH_SUPPORTS_ATOMIC_RMW
70 select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
71 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
72 select ARCH_USE_BUILTIN_BSWAP
73 select ARCH_USE_QUEUED_RWLOCKS
74 select ARCH_USE_QUEUED_SPINLOCKS
75 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
76 select ARCH_WANT_FRAME_POINTERS
77 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
78 select ARCH_WANTS_THP_SWAP if X86_64
79 select BUILDTIME_EXTABLE_SORT
81 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
82 select CLOCKSOURCE_WATCHDOG
83 select DCACHE_WORD_ACCESS
84 select EDAC_ATOMIC_SCRUB
86 select GENERIC_CLOCKEVENTS
87 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
88 select GENERIC_CLOCKEVENTS_MIN_ADJUST
89 select GENERIC_CMOS_UPDATE
90 select GENERIC_CPU_AUTOPROBE
91 select GENERIC_EARLY_IOREMAP
92 select GENERIC_FIND_FIRST_BIT
94 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
95 select GENERIC_IRQ_MIGRATION if SMP
96 select GENERIC_IRQ_PROBE
97 select GENERIC_IRQ_SHOW
98 select GENERIC_PENDING_IRQ if SMP
99 select GENERIC_SMP_IDLE_THREAD
100 select GENERIC_STRNCPY_FROM_USER
101 select GENERIC_STRNLEN_USER
102 select GENERIC_TIME_VSYSCALL
103 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
104 select HAVE_ACPI_APEI if ACPI
105 select HAVE_ACPI_APEI_NMI if ACPI
106 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
107 select HAVE_ARCH_AUDITSYSCALL
108 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
109 select HAVE_ARCH_JUMP_LABEL
110 select HAVE_ARCH_KASAN if X86_64 && SPARSEMEM_VMEMMAP
111 select HAVE_ARCH_KGDB
112 select HAVE_ARCH_KMEMCHECK
113 select HAVE_ARCH_MMAP_RND_BITS if MMU
114 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
115 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
116 select HAVE_ARCH_SECCOMP_FILTER
117 select HAVE_ARCH_TRACEHOOK
118 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
119 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
120 select HAVE_ARCH_VMAP_STACK if X86_64
121 select HAVE_ARCH_WITHIN_STACK_FRAMES
122 select HAVE_CC_STACKPROTECTOR
123 select HAVE_CMPXCHG_DOUBLE
124 select HAVE_CMPXCHG_LOCAL
125 select HAVE_CONTEXT_TRACKING if X86_64
126 select HAVE_COPY_THREAD_TLS
127 select HAVE_C_RECORDMCOUNT
128 select HAVE_DEBUG_KMEMLEAK
129 select HAVE_DEBUG_STACKOVERFLOW
130 select HAVE_DMA_API_DEBUG
131 select HAVE_DMA_CONTIGUOUS
132 select HAVE_DYNAMIC_FTRACE
133 select HAVE_DYNAMIC_FTRACE_WITH_REGS
134 select HAVE_EBPF_JIT if X86_64
135 select HAVE_EFFICIENT_UNALIGNED_ACCESS
136 select HAVE_EXIT_THREAD
137 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
138 select HAVE_FTRACE_MCOUNT_RECORD
139 select HAVE_FUNCTION_GRAPH_TRACER
140 select HAVE_FUNCTION_TRACER
141 select HAVE_GCC_PLUGINS
142 select HAVE_HW_BREAKPOINT
144 select HAVE_IOREMAP_PROT
145 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
146 select HAVE_IRQ_TIME_ACCOUNTING
147 select HAVE_KERNEL_BZIP2
148 select HAVE_KERNEL_GZIP
149 select HAVE_KERNEL_LZ4
150 select HAVE_KERNEL_LZMA
151 select HAVE_KERNEL_LZO
152 select HAVE_KERNEL_XZ
154 select HAVE_KPROBES_ON_FTRACE
155 select HAVE_KRETPROBES
157 select HAVE_LIVEPATCH if X86_64
159 select HAVE_MEMBLOCK_NODE_MAP
160 select HAVE_MIXED_BREAKPOINTS_REGS
163 select HAVE_OPTPROBES
164 select HAVE_PCSPKR_PLATFORM
165 select HAVE_PERF_EVENTS
166 select HAVE_PERF_EVENTS_NMI
167 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
168 select HAVE_PERF_REGS
169 select HAVE_PERF_USER_STACK_DUMP
170 select HAVE_REGS_AND_STACK_ACCESS_API
171 select HAVE_RELIABLE_STACKTRACE if X86_64 && FRAME_POINTER && STACK_VALIDATION
172 select HAVE_STACK_VALIDATION if X86_64
173 select HAVE_SYSCALL_TRACEPOINTS
174 select HAVE_UNSTABLE_SCHED_CLOCK
175 select HAVE_USER_RETURN_NOTIFIER
176 select IRQ_FORCED_THREADING
177 select PCI_LOCKLESS_CONFIG
180 select RTC_MC146818_LIB
183 select SYSCTL_EXCEPTION_TRACE
184 select THREAD_INFO_IN_TASK
185 select USER_STACKTRACE_SUPPORT
187 select X86_FEATURE_NAMES if PROC_FS
189 config INSTRUCTION_DECODER
191 depends on KPROBES || PERF_EVENTS || UPROBES
195 default "elf32-i386" if X86_32
196 default "elf64-x86-64" if X86_64
198 config ARCH_DEFCONFIG
200 default "arch/x86/configs/i386_defconfig" if X86_32
201 default "arch/x86/configs/x86_64_defconfig" if X86_64
203 config LOCKDEP_SUPPORT
206 config STACKTRACE_SUPPORT
212 config ARCH_MMAP_RND_BITS_MIN
216 config ARCH_MMAP_RND_BITS_MAX
220 config ARCH_MMAP_RND_COMPAT_BITS_MIN
223 config ARCH_MMAP_RND_COMPAT_BITS_MAX
229 config NEED_DMA_MAP_STATE
231 depends on X86_64 || INTEL_IOMMU || DMA_API_DEBUG || SWIOTLB
233 config NEED_SG_DMA_LENGTH
236 config GENERIC_ISA_DMA
238 depends on ISA_DMA_API
243 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
245 config GENERIC_BUG_RELATIVE_POINTERS
248 config GENERIC_HWEIGHT
251 config ARCH_MAY_HAVE_PC_FDC
253 depends on ISA_DMA_API
255 config RWSEM_XCHGADD_ALGORITHM
258 config GENERIC_CALIBRATE_DELAY
261 config ARCH_HAS_CPU_RELAX
264 config ARCH_HAS_CACHE_LINE_SIZE
267 config HAVE_SETUP_PER_CPU_AREA
270 config NEED_PER_CPU_EMBED_FIRST_CHUNK
273 config NEED_PER_CPU_PAGE_FIRST_CHUNK
276 config ARCH_HIBERNATION_POSSIBLE
279 config ARCH_SUSPEND_POSSIBLE
282 config ARCH_WANT_HUGE_PMD_SHARE
285 config ARCH_WANT_GENERAL_HUGETLB
294 config ARCH_SUPPORTS_OPTIMIZED_INLINING
297 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
300 config KASAN_SHADOW_OFFSET
303 default 0xdff8000000000000 if X86_5LEVEL
304 default 0xdffffc0000000000
306 config HAVE_INTEL_TXT
308 depends on INTEL_IOMMU && ACPI
312 depends on X86_32 && SMP
316 depends on X86_64 && SMP
318 config X86_32_LAZY_GS
320 depends on X86_32 && !CC_STACKPROTECTOR
322 config ARCH_SUPPORTS_UPROBES
325 config FIX_EARLYCON_MEM
328 config PGTABLE_LEVELS
334 source "init/Kconfig"
335 source "kernel/Kconfig.freezer"
337 menu "Processor type and features"
340 bool "DMA memory allocation support" if EXPERT
343 DMA memory allocation support allows devices with less than 32-bit
344 addressing to allocate within the first 16MB of address space.
345 Disable if no such devices will be used.
350 bool "Symmetric multi-processing support"
352 This enables support for systems with more than one CPU. If you have
353 a system with only one CPU, say N. If you have a system with more
356 If you say N here, the kernel will run on uni- and multiprocessor
357 machines, but will use only one CPU of a multiprocessor machine. If
358 you say Y here, the kernel will run on many, but not all,
359 uniprocessor machines. On a uniprocessor machine, the kernel
360 will run faster if you say N here.
362 Note that if you say Y here and choose architecture "586" or
363 "Pentium" under "Processor family", the kernel will not work on 486
364 architectures. Similarly, multiprocessor kernels for the "PPro"
365 architecture may not work on all Pentium based boards.
367 People using multiprocessor machines who say Y here should also say
368 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
369 Management" code will be disabled if you say Y here.
371 See also <file:Documentation/x86/i386/IO-APIC.txt>,
372 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
373 <http://www.tldp.org/docs.html#howto>.
375 If you don't know what to do here, say N.
377 config X86_FEATURE_NAMES
378 bool "Processor feature human-readable names" if EMBEDDED
381 This option compiles in a table of x86 feature bits and corresponding
382 names. This is required to support /proc/cpuinfo and a few kernel
383 messages. You can disable this to save space, at the expense of
384 making those few kernel messages show numeric feature bits instead.
388 config X86_FAST_FEATURE_TESTS
389 bool "Fast CPU feature tests" if EMBEDDED
392 Some fast-paths in the kernel depend on the capabilities of the CPU.
393 Say Y here for the kernel to patch in the appropriate code at runtime
394 based on the capabilities of the CPU. The infrastructure for patching
395 code at runtime takes up some additional space; space-constrained
396 embedded systems may wish to say N here to produce smaller, slightly
400 bool "Support x2apic"
401 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
403 This enables x2apic support on CPUs that have this feature.
405 This allows 32-bit apic IDs (so it can support very large systems),
406 and accesses the local apic via MSRs not via mmio.
408 If you don't know what to do here, say N.
411 bool "Enable MPS table" if ACPI || SFI
413 depends on X86_LOCAL_APIC
415 For old smp systems that do not have proper acpi support. Newer systems
416 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
419 bool "Support for big SMP systems with more than 8 CPUs"
420 depends on X86_32 && SMP
422 This option is needed for the systems that have more than 8 CPUs
426 depends on X86_GOLDFISH
429 bool "Intel Resource Director Technology Allocation support"
431 depends on X86 && CPU_SUP_INTEL
434 Select to enable resource allocation which is a sub-feature of
435 Intel Resource Director Technology(RDT). More information about
436 RDT can be found in the Intel x86 Architecture Software
442 config X86_EXTENDED_PLATFORM
443 bool "Support for extended (non-PC) x86 platforms"
446 If you disable this option then the kernel will only support
447 standard PC platforms. (which covers the vast majority of
450 If you enable this option then you'll be able to select support
451 for the following (non-PC) 32 bit x86 platforms:
452 Goldfish (Android emulator)
455 SGI 320/540 (Visual Workstation)
456 STA2X11-based (e.g. Northville)
457 Moorestown MID devices
459 If you have one of these systems, or if you want to build a
460 generic distribution kernel, say Y here - otherwise say N.
464 config X86_EXTENDED_PLATFORM
465 bool "Support for extended (non-PC) x86 platforms"
468 If you disable this option then the kernel will only support
469 standard PC platforms. (which covers the vast majority of
472 If you enable this option then you'll be able to select support
473 for the following (non-PC) 64 bit x86 platforms:
478 If you have one of these systems, or if you want to build a
479 generic distribution kernel, say Y here - otherwise say N.
481 # This is an alphabetically sorted list of 64 bit extended platforms
482 # Please maintain the alphabetic order if and when there are additions
484 bool "Numascale NumaChip"
486 depends on X86_EXTENDED_PLATFORM
489 depends on X86_X2APIC
490 depends on PCI_MMCONFIG
492 Adds support for Numascale NumaChip large-SMP systems. Needed to
493 enable more than ~168 cores.
494 If you don't have one of these, you should say N here.
498 select HYPERVISOR_GUEST
500 depends on X86_64 && PCI
501 depends on X86_EXTENDED_PLATFORM
504 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
505 supposed to run on these EM64T-based machines. Only choose this option
506 if you have one of these machines.
509 bool "SGI Ultraviolet"
511 depends on X86_EXTENDED_PLATFORM
514 depends on X86_X2APIC
517 This option is needed in order to support SGI Ultraviolet systems.
518 If you don't have one of these, you should say N here.
520 # Following is an alphabetically sorted list of 32 bit extended platforms
521 # Please maintain the alphabetic order if and when there are additions
524 bool "Goldfish (Virtual Platform)"
525 depends on X86_EXTENDED_PLATFORM
527 Enable support for the Goldfish virtual platform used primarily
528 for Android development. Unless you are building for the Android
529 Goldfish emulator say N here.
532 bool "CE4100 TV platform"
534 depends on PCI_GODIRECT
535 depends on X86_IO_APIC
537 depends on X86_EXTENDED_PLATFORM
538 select X86_REBOOTFIXUPS
540 select OF_EARLY_FLATTREE
542 Select for the Intel CE media processor (CE4100) SOC.
543 This option compiles in support for the CE4100 SOC for settop
544 boxes and media devices.
547 bool "Intel MID platform support"
548 depends on X86_EXTENDED_PLATFORM
549 depends on X86_PLATFORM_DEVICES
551 depends on X86_64 || (PCI_GOANY && X86_32)
552 depends on X86_IO_APIC
558 select MFD_INTEL_MSIC
560 Select to build a kernel capable of supporting Intel MID (Mobile
561 Internet Device) platform systems which do not have the PCI legacy
562 interfaces. If you are building for a PC class system say N here.
564 Intel MID platforms are based on an Intel processor and chipset which
565 consume less power than most of the x86 derivatives.
567 config X86_INTEL_QUARK
568 bool "Intel Quark platform support"
570 depends on X86_EXTENDED_PLATFORM
571 depends on X86_PLATFORM_DEVICES
575 depends on X86_IO_APIC
580 Select to include support for Quark X1000 SoC.
581 Say Y here if you have a Quark based system such as the Arduino
582 compatible Intel Galileo.
584 config X86_INTEL_LPSS
585 bool "Intel Low Power Subsystem Support"
586 depends on X86 && ACPI
591 Select to build support for Intel Low Power Subsystem such as
592 found on Intel Lynxpoint PCH. Selecting this option enables
593 things like clock tree (common clock framework) and pincontrol
594 which are needed by the LPSS peripheral drivers.
596 config X86_AMD_PLATFORM_DEVICE
597 bool "AMD ACPI2Platform devices support"
602 Select to interpret AMD specific ACPI device to platform device
603 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
604 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
605 implemented under PINCTRL subsystem.
608 tristate "Intel SoC IOSF Sideband support for SoC platforms"
611 This option enables sideband register access support for Intel SoC
612 platforms. On these platforms the IOSF sideband is used in lieu of
613 MSR's for some register accesses, mostly but not limited to thermal
614 and power. Drivers may query the availability of this device to
615 determine if they need the sideband in order to work on these
616 platforms. The sideband is available on the following SoC products.
617 This list is not meant to be exclusive.
622 You should say Y if you are running a kernel on one of these SoC's.
624 config IOSF_MBI_DEBUG
625 bool "Enable IOSF sideband access through debugfs"
626 depends on IOSF_MBI && DEBUG_FS
628 Select this option to expose the IOSF sideband access registers (MCR,
629 MDR, MCRX) through debugfs to write and read register information from
630 different units on the SoC. This is most useful for obtaining device
631 state information for debug and analysis. As this is a general access
632 mechanism, users of this option would have specific knowledge of the
633 device they want to access.
635 If you don't require the option or are in doubt, say N.
638 bool "RDC R-321x SoC"
640 depends on X86_EXTENDED_PLATFORM
642 select X86_REBOOTFIXUPS
644 This option is needed for RDC R-321x system-on-chip, also known
646 If you don't have one of these chips, you should say N here.
648 config X86_32_NON_STANDARD
649 bool "Support non-standard 32-bit SMP architectures"
650 depends on X86_32 && SMP
651 depends on X86_EXTENDED_PLATFORM
653 This option compiles in the bigsmp and STA2X11 default
654 subarchitectures. It is intended for a generic binary
655 kernel. If you select them all, kernel will probe it one by
656 one and will fallback to default.
658 # Alphabetically sorted list of Non standard 32 bit platforms
660 config X86_SUPPORTS_MEMORY_FAILURE
662 # MCE code calls memory_failure():
664 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
665 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
666 depends on X86_64 || !SPARSEMEM
667 select ARCH_SUPPORTS_MEMORY_FAILURE
670 bool "STA2X11 Companion Chip Support"
671 depends on X86_32_NON_STANDARD && PCI
672 select X86_DEV_DMA_OPS
679 This adds support for boards based on the STA2X11 IO-Hub,
680 a.k.a. "ConneXt". The chip is used in place of the standard
681 PC chipset, so all "standard" peripherals are missing. If this
682 option is selected the kernel will still be able to boot on
683 standard PC machines.
686 tristate "Eurobraille/Iris poweroff module"
689 The Iris machines from EuroBraille do not have APM or ACPI support
690 to shut themselves down properly. A special I/O sequence is
691 needed to do so, which is what this module does at
694 This is only for Iris machines from EuroBraille.
698 config SCHED_OMIT_FRAME_POINTER
700 prompt "Single-depth WCHAN output"
703 Calculate simpler /proc/<PID>/wchan values. If this option
704 is disabled then wchan values will recurse back to the
705 caller function. This provides more accurate wchan values,
706 at the expense of slightly more scheduling overhead.
708 If in doubt, say "Y".
710 menuconfig HYPERVISOR_GUEST
711 bool "Linux guest support"
713 Say Y here to enable options for running Linux under various hyper-
714 visors. This option enables basic hypervisor detection and platform
717 If you say N, all options in this submenu will be skipped and
718 disabled, and Linux guest support won't be built in.
723 bool "Enable paravirtualization code"
725 This changes the kernel so it can modify itself when it is run
726 under a hypervisor, potentially improving performance significantly
727 over full virtualization. However, when run without a hypervisor
728 the kernel is theoretically slower and slightly larger.
730 config PARAVIRT_DEBUG
731 bool "paravirt-ops debugging"
732 depends on PARAVIRT && DEBUG_KERNEL
734 Enable to debug paravirt_ops internals. Specifically, BUG if
735 a paravirt_op is missing when it is called.
737 config PARAVIRT_SPINLOCKS
738 bool "Paravirtualization layer for spinlocks"
739 depends on PARAVIRT && SMP
741 Paravirtualized spinlocks allow a pvops backend to replace the
742 spinlock implementation with something virtualization-friendly
743 (for example, block the virtual CPU rather than spinning).
745 It has a minimal impact on native kernels and gives a nice performance
746 benefit on paravirtualized KVM / Xen kernels.
748 If you are unsure how to answer this question, answer Y.
750 config QUEUED_LOCK_STAT
751 bool "Paravirt queued spinlock statistics"
752 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
754 Enable the collection of statistical data on the slowpath
755 behavior of paravirtualized queued spinlocks and report
758 source "arch/x86/xen/Kconfig"
761 bool "KVM Guest support (including kvmclock)"
763 select PARAVIRT_CLOCK
766 This option enables various optimizations for running under the KVM
767 hypervisor. It includes a paravirtualized clock, so that instead
768 of relying on a PIT (or probably other) emulation by the
769 underlying device model, the host provides the guest with
770 timing infrastructure such as time of day, and system time
773 bool "Enable debug information for KVM Guests in debugfs"
774 depends on KVM_GUEST && DEBUG_FS
777 This option enables collection of various statistics for KVM guest.
778 Statistics are displayed in debugfs filesystem. Enabling this option
779 may incur significant overhead.
781 source "arch/x86/lguest/Kconfig"
783 config PARAVIRT_TIME_ACCOUNTING
784 bool "Paravirtual steal time accounting"
788 Select this option to enable fine granularity task steal time
789 accounting. Time spent executing other tasks in parallel with
790 the current vCPU is discounted from the vCPU power. To account for
791 that, there can be a small performance impact.
793 If in doubt, say N here.
795 config PARAVIRT_CLOCK
798 endif #HYPERVISOR_GUEST
803 source "arch/x86/Kconfig.cpu"
807 prompt "HPET Timer Support" if X86_32
809 Use the IA-PC HPET (High Precision Event Timer) to manage
810 time in preference to the PIT and RTC, if a HPET is
812 HPET is the next generation timer replacing legacy 8254s.
813 The HPET provides a stable time base on SMP
814 systems, unlike the TSC, but it is more expensive to access,
815 as it is off-chip. The interface used is documented
816 in the HPET spec, revision 1.
818 You can safely choose Y here. However, HPET will only be
819 activated if the platform and the BIOS support this feature.
820 Otherwise the 8254 will be used for timing services.
822 Choose N to continue using the legacy 8254 timer.
824 config HPET_EMULATE_RTC
826 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
829 def_bool y if X86_INTEL_MID
830 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
832 depends on X86_INTEL_MID && SFI
834 APB timer is the replacement for 8254, HPET on X86 MID platforms.
835 The APBT provides a stable time base on SMP
836 systems, unlike the TSC, but it is more expensive to access,
837 as it is off-chip. APB timers are always running regardless of CPU
838 C states, they are used as per CPU clockevent device when possible.
840 # Mark as expert because too many people got it wrong.
841 # The code disables itself when not needed.
844 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
845 bool "Enable DMI scanning" if EXPERT
847 Enabled scanning of DMI to identify machine quirks. Say Y
848 here unless you have verified that your setup is not
849 affected by entries in the DMI blacklist. Required by PNP
853 bool "Old AMD GART IOMMU support"
855 depends on X86_64 && PCI && AMD_NB
857 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
858 GART based hardware IOMMUs.
860 The GART supports full DMA access for devices with 32-bit access
861 limitations, on systems with more than 3 GB. This is usually needed
862 for USB, sound, many IDE/SATA chipsets and some other devices.
864 Newer systems typically have a modern AMD IOMMU, supported via
865 the CONFIG_AMD_IOMMU=y config option.
867 In normal configurations this driver is only active when needed:
868 there's more than 3 GB of memory and the system contains a
869 32-bit limited device.
874 bool "IBM Calgary IOMMU support"
876 depends on X86_64 && PCI
878 Support for hardware IOMMUs in IBM's xSeries x366 and x460
879 systems. Needed to run systems with more than 3GB of memory
880 properly with 32-bit PCI devices that do not support DAC
881 (Double Address Cycle). Calgary also supports bus level
882 isolation, where all DMAs pass through the IOMMU. This
883 prevents them from going anywhere except their intended
884 destination. This catches hard-to-find kernel bugs and
885 mis-behaving drivers and devices that do not use the DMA-API
886 properly to set up their DMA buffers. The IOMMU can be
887 turned off at boot time with the iommu=off parameter.
888 Normally the kernel will make the right choice by itself.
891 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
893 prompt "Should Calgary be enabled by default?"
894 depends on CALGARY_IOMMU
896 Should Calgary be enabled by default? if you choose 'y', Calgary
897 will be used (if it exists). If you choose 'n', Calgary will not be
898 used even if it exists. If you choose 'n' and would like to use
899 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
902 # need this always selected by IOMMU for the VIA workaround
906 Support for software bounce buffers used on x86-64 systems
907 which don't have a hardware IOMMU. Using this PCI devices
908 which can only access 32-bits of memory can be used on systems
909 with more than 3 GB of memory.
914 depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU
917 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
918 depends on X86_64 && SMP && DEBUG_KERNEL
919 select CPUMASK_OFFSTACK
921 Enable maximum number of CPUS and NUMA Nodes for this architecture.
925 int "Maximum number of CPUs" if SMP && !MAXSMP
926 range 2 8 if SMP && X86_32 && !X86_BIGSMP
927 range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK
928 range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
930 default "8192" if MAXSMP
931 default "32" if SMP && X86_BIGSMP
932 default "8" if SMP && X86_32
935 This allows you to specify the maximum number of CPUs which this
936 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
937 supported value is 8192, otherwise the maximum value is 512. The
938 minimum value which makes sense is 2.
940 This is purely to save memory - each supported CPU adds
941 approximately eight kilobytes to the kernel image.
944 bool "SMT (Hyperthreading) scheduler support"
947 SMT scheduler support improves the CPU scheduler's decision making
948 when dealing with Intel Pentium 4 chips with HyperThreading at a
949 cost of slightly increased overhead in some places. If unsure say
954 prompt "Multi-core scheduler support"
957 Multi-core scheduler support improves the CPU scheduler's decision
958 making when dealing with multi-core CPU chips at a cost of slightly
959 increased overhead in some places. If unsure say N here.
962 bool "CPU core priorities scheduler support"
963 depends on SCHED_MC && CPU_SUP_INTEL
964 select X86_INTEL_PSTATE
968 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
969 core ordering determined at manufacturing time, which allows
970 certain cores to reach higher turbo frequencies (when running
971 single threaded workloads) than others.
973 Enabling this kernel feature teaches the scheduler about
974 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
975 scheduler's CPU selection logic accordingly, so that higher
976 overall system performance can be achieved.
978 This feature will have no effect on CPUs without this feature.
980 If unsure say Y here.
982 source "kernel/Kconfig.preempt"
986 depends on !SMP && X86_LOCAL_APIC
989 bool "Local APIC support on uniprocessors" if !PCI_MSI
991 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
993 A local APIC (Advanced Programmable Interrupt Controller) is an
994 integrated interrupt controller in the CPU. If you have a single-CPU
995 system which has a processor with a local APIC, you can say Y here to
996 enable and use it. If you say Y here even though your machine doesn't
997 have a local APIC, then the kernel will still run with no slowdown at
998 all. The local APIC supports CPU-generated self-interrupts (timer,
999 performance counters), and the NMI watchdog which detects hard
1002 config X86_UP_IOAPIC
1003 bool "IO-APIC support on uniprocessors"
1004 depends on X86_UP_APIC
1006 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1007 SMP-capable replacement for PC-style interrupt controllers. Most
1008 SMP systems and many recent uniprocessor systems have one.
1010 If you have a single-CPU system with an IO-APIC, you can say Y here
1011 to use it. If you say Y here even though your machine doesn't have
1012 an IO-APIC, then the kernel will still run with no slowdown at all.
1014 config X86_LOCAL_APIC
1016 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1017 select IRQ_DOMAIN_HIERARCHY
1018 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1022 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1024 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1025 bool "Reroute for broken boot IRQs"
1026 depends on X86_IO_APIC
1028 This option enables a workaround that fixes a source of
1029 spurious interrupts. This is recommended when threaded
1030 interrupt handling is used on systems where the generation of
1031 superfluous "boot interrupts" cannot be disabled.
1033 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1034 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1035 kernel does during interrupt handling). On chipsets where this
1036 boot IRQ generation cannot be disabled, this workaround keeps
1037 the original IRQ line masked so that only the equivalent "boot
1038 IRQ" is delivered to the CPUs. The workaround also tells the
1039 kernel to set up the IRQ handler on the boot IRQ line. In this
1040 way only one interrupt is delivered to the kernel. Otherwise
1041 the spurious second interrupt may cause the kernel to bring
1042 down (vital) interrupt lines.
1044 Only affects "broken" chipsets. Interrupt sharing may be
1045 increased on these systems.
1048 bool "Machine Check / overheating reporting"
1049 select GENERIC_ALLOCATOR
1052 Machine Check support allows the processor to notify the
1053 kernel if it detects a problem (e.g. overheating, data corruption).
1054 The action the kernel takes depends on the severity of the problem,
1055 ranging from warning messages to halting the machine.
1057 config X86_MCELOG_LEGACY
1058 bool "Support for deprecated /dev/mcelog character device"
1061 Enable support for /dev/mcelog which is needed by the old mcelog
1062 userspace logging daemon. Consider switching to the new generation
1065 config X86_MCE_INTEL
1067 prompt "Intel MCE features"
1068 depends on X86_MCE && X86_LOCAL_APIC
1070 Additional support for intel specific MCE features such as
1071 the thermal monitor.
1075 prompt "AMD MCE features"
1076 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1078 Additional support for AMD specific MCE features such as
1079 the DRAM Error Threshold.
1081 config X86_ANCIENT_MCE
1082 bool "Support for old Pentium 5 / WinChip machine checks"
1083 depends on X86_32 && X86_MCE
1085 Include support for machine check handling on old Pentium 5 or WinChip
1086 systems. These typically need to be enabled explicitly on the command
1089 config X86_MCE_THRESHOLD
1090 depends on X86_MCE_AMD || X86_MCE_INTEL
1093 config X86_MCE_INJECT
1094 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1095 tristate "Machine check injector support"
1097 Provide support for injecting machine checks for testing purposes.
1098 If you don't know what a machine check is and you don't do kernel
1099 QA it is safe to say n.
1101 config X86_THERMAL_VECTOR
1103 depends on X86_MCE_INTEL
1105 source "arch/x86/events/Kconfig"
1107 config X86_LEGACY_VM86
1108 bool "Legacy VM86 support"
1112 This option allows user programs to put the CPU into V8086
1113 mode, which is an 80286-era approximation of 16-bit real mode.
1115 Some very old versions of X and/or vbetool require this option
1116 for user mode setting. Similarly, DOSEMU will use it if
1117 available to accelerate real mode DOS programs. However, any
1118 recent version of DOSEMU, X, or vbetool should be fully
1119 functional even without kernel VM86 support, as they will all
1120 fall back to software emulation. Nevertheless, if you are using
1121 a 16-bit DOS program where 16-bit performance matters, vm86
1122 mode might be faster than emulation and you might want to
1125 Note that any app that works on a 64-bit kernel is unlikely to
1126 need this option, as 64-bit kernels don't, and can't, support
1127 V8086 mode. This option is also unrelated to 16-bit protected
1128 mode and is not needed to run most 16-bit programs under Wine.
1130 Enabling this option increases the complexity of the kernel
1131 and slows down exception handling a tiny bit.
1133 If unsure, say N here.
1137 default X86_LEGACY_VM86
1140 bool "Enable support for 16-bit segments" if EXPERT
1142 depends on MODIFY_LDT_SYSCALL
1144 This option is required by programs like Wine to run 16-bit
1145 protected mode legacy code on x86 processors. Disabling
1146 this option saves about 300 bytes on i386, or around 6K text
1147 plus 16K runtime memory on x86-64,
1151 depends on X86_16BIT && X86_32
1155 depends on X86_16BIT && X86_64
1157 config X86_VSYSCALL_EMULATION
1158 bool "Enable vsyscall emulation" if EXPERT
1162 This enables emulation of the legacy vsyscall page. Disabling
1163 it is roughly equivalent to booting with vsyscall=none, except
1164 that it will also disable the helpful warning if a program
1165 tries to use a vsyscall. With this option set to N, offending
1166 programs will just segfault, citing addresses of the form
1169 This option is required by many programs built before 2013, and
1170 care should be used even with newer programs if set to N.
1172 Disabling this option saves about 7K of kernel size and
1173 possibly 4K of additional runtime pagetable memory.
1176 tristate "Toshiba Laptop support"
1179 This adds a driver to safely access the System Management Mode of
1180 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1181 not work on models with a Phoenix BIOS. The System Management Mode
1182 is used to set the BIOS and power saving options on Toshiba portables.
1184 For information on utilities to make use of this driver see the
1185 Toshiba Linux utilities web site at:
1186 <http://www.buzzard.org.uk/toshiba/>.
1188 Say Y if you intend to run this kernel on a Toshiba portable.
1192 tristate "Dell i8k legacy laptop support"
1194 select SENSORS_DELL_SMM
1196 This option enables legacy /proc/i8k userspace interface in hwmon
1197 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1198 temperature and allows controlling fan speeds of Dell laptops via
1199 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1200 it reports also power and hotkey status. For fan speed control is
1201 needed userspace package i8kutils.
1203 Say Y if you intend to run this kernel on old Dell laptops or want to
1204 use userspace package i8kutils.
1207 config X86_REBOOTFIXUPS
1208 bool "Enable X86 board specific fixups for reboot"
1211 This enables chipset and/or board specific fixups to be done
1212 in order to get reboot to work correctly. This is only needed on
1213 some combinations of hardware and BIOS. The symptom, for which
1214 this config is intended, is when reboot ends with a stalled/hung
1217 Currently, the only fixup is for the Geode machines using
1218 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1220 Say Y if you want to enable the fixup. Currently, it's safe to
1221 enable this option even if you don't need it.
1225 bool "CPU microcode loading support"
1227 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1230 If you say Y here, you will be able to update the microcode on
1231 Intel and AMD processors. The Intel support is for the IA32 family,
1232 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1233 AMD support is for families 0x10 and later. You will obviously need
1234 the actual microcode binary data itself which is not shipped with
1237 The preferred method to load microcode from a detached initrd is described
1238 in Documentation/x86/early-microcode.txt. For that you need to enable
1239 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1240 initrd for microcode blobs.
1242 In addition, you can build-in the microcode into the kernel. For that you
1243 need to enable FIRMWARE_IN_KERNEL and add the vendor-supplied microcode
1244 to the CONFIG_EXTRA_FIRMWARE config option.
1246 config MICROCODE_INTEL
1247 bool "Intel microcode loading support"
1248 depends on MICROCODE
1252 This options enables microcode patch loading support for Intel
1255 For the current Intel microcode data package go to
1256 <https://downloadcenter.intel.com> and search for
1257 'Linux Processor Microcode Data File'.
1259 config MICROCODE_AMD
1260 bool "AMD microcode loading support"
1261 depends on MICROCODE
1264 If you select this option, microcode patch loading support for AMD
1265 processors will be enabled.
1267 config MICROCODE_OLD_INTERFACE
1269 depends on MICROCODE
1272 tristate "/dev/cpu/*/msr - Model-specific register support"
1274 This device gives privileged processes access to the x86
1275 Model-Specific Registers (MSRs). It is a character device with
1276 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1277 MSR accesses are directed to a specific CPU on multi-processor
1281 tristate "/dev/cpu/*/cpuid - CPU information support"
1283 This device gives processes access to the x86 CPUID instruction to
1284 be executed on a specific processor. It is a character device
1285 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1289 prompt "High Memory Support"
1296 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1297 However, the address space of 32-bit x86 processors is only 4
1298 Gigabytes large. That means that, if you have a large amount of
1299 physical memory, not all of it can be "permanently mapped" by the
1300 kernel. The physical memory that's not permanently mapped is called
1303 If you are compiling a kernel which will never run on a machine with
1304 more than 1 Gigabyte total physical RAM, answer "off" here (default
1305 choice and suitable for most users). This will result in a "3GB/1GB"
1306 split: 3GB are mapped so that each process sees a 3GB virtual memory
1307 space and the remaining part of the 4GB virtual memory space is used
1308 by the kernel to permanently map as much physical memory as
1311 If the machine has between 1 and 4 Gigabytes physical RAM, then
1314 If more than 4 Gigabytes is used then answer "64GB" here. This
1315 selection turns Intel PAE (Physical Address Extension) mode on.
1316 PAE implements 3-level paging on IA32 processors. PAE is fully
1317 supported by Linux, PAE mode is implemented on all recent Intel
1318 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1319 then the kernel will not boot on CPUs that don't support PAE!
1321 The actual amount of total physical memory will either be
1322 auto detected or can be forced by using a kernel command line option
1323 such as "mem=256M". (Try "man bootparam" or see the documentation of
1324 your boot loader (lilo or loadlin) about how to pass options to the
1325 kernel at boot time.)
1327 If unsure, say "off".
1332 Select this if you have a 32-bit processor and between 1 and 4
1333 gigabytes of physical RAM.
1340 Select this if you have a 32-bit processor and more than 4
1341 gigabytes of physical RAM.
1346 prompt "Memory split" if EXPERT
1350 Select the desired split between kernel and user memory.
1352 If the address range available to the kernel is less than the
1353 physical memory installed, the remaining memory will be available
1354 as "high memory". Accessing high memory is a little more costly
1355 than low memory, as it needs to be mapped into the kernel first.
1356 Note that increasing the kernel address space limits the range
1357 available to user programs, making the address space there
1358 tighter. Selecting anything other than the default 3G/1G split
1359 will also likely make your kernel incompatible with binary-only
1362 If you are not absolutely sure what you are doing, leave this
1366 bool "3G/1G user/kernel split"
1367 config VMSPLIT_3G_OPT
1369 bool "3G/1G user/kernel split (for full 1G low memory)"
1371 bool "2G/2G user/kernel split"
1372 config VMSPLIT_2G_OPT
1374 bool "2G/2G user/kernel split (for full 2G low memory)"
1376 bool "1G/3G user/kernel split"
1381 default 0xB0000000 if VMSPLIT_3G_OPT
1382 default 0x80000000 if VMSPLIT_2G
1383 default 0x78000000 if VMSPLIT_2G_OPT
1384 default 0x40000000 if VMSPLIT_1G
1390 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1393 bool "PAE (Physical Address Extension) Support"
1394 depends on X86_32 && !HIGHMEM4G
1397 PAE is required for NX support, and furthermore enables
1398 larger swapspace support for non-overcommit purposes. It
1399 has the cost of more pagetable lookup overhead, and also
1400 consumes more pagetable space per process.
1402 config ARCH_PHYS_ADDR_T_64BIT
1404 depends on X86_64 || X86_PAE
1406 config ARCH_DMA_ADDR_T_64BIT
1408 depends on X86_64 || HIGHMEM64G
1410 config X86_DIRECT_GBPAGES
1412 depends on X86_64 && !DEBUG_PAGEALLOC && !KMEMCHECK
1414 Certain kernel features effectively disable kernel
1415 linear 1 GB mappings (even if the CPU otherwise
1416 supports them), so don't confuse the user by printing
1417 that we have them enabled.
1419 # Common NUMA Features
1421 bool "Numa Memory Allocation and Scheduler Support"
1423 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1424 default y if X86_BIGSMP
1426 Enable NUMA (Non Uniform Memory Access) support.
1428 The kernel will try to allocate memory used by a CPU on the
1429 local memory controller of the CPU and add some more
1430 NUMA awareness to the kernel.
1432 For 64-bit this is recommended if the system is Intel Core i7
1433 (or later), AMD Opteron, or EM64T NUMA.
1435 For 32-bit this is only needed if you boot a 32-bit
1436 kernel on a 64-bit NUMA platform.
1438 Otherwise, you should say N.
1442 prompt "Old style AMD Opteron NUMA detection"
1443 depends on X86_64 && NUMA && PCI
1445 Enable AMD NUMA node topology detection. You should say Y here if
1446 you have a multi processor AMD system. This uses an old method to
1447 read the NUMA configuration directly from the builtin Northbridge
1448 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1449 which also takes priority if both are compiled in.
1451 config X86_64_ACPI_NUMA
1453 prompt "ACPI NUMA detection"
1454 depends on X86_64 && NUMA && ACPI && PCI
1457 Enable ACPI SRAT based node topology detection.
1459 # Some NUMA nodes have memory ranges that span
1460 # other nodes. Even though a pfn is valid and
1461 # between a node's start and end pfns, it may not
1462 # reside on that node. See memmap_init_zone()
1464 config NODES_SPAN_OTHER_NODES
1466 depends on X86_64_ACPI_NUMA
1469 bool "NUMA emulation"
1472 Enable NUMA emulation. A flat machine will be split
1473 into virtual nodes when booted with "numa=fake=N", where N is the
1474 number of nodes. This is only useful for debugging.
1477 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1479 default "10" if MAXSMP
1480 default "6" if X86_64
1482 depends on NEED_MULTIPLE_NODES
1484 Specify the maximum number of NUMA Nodes available on the target
1485 system. Increases memory reserved to accommodate various tables.
1487 config ARCH_HAVE_MEMORY_PRESENT
1489 depends on X86_32 && DISCONTIGMEM
1491 config NEED_NODE_MEMMAP_SIZE
1493 depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
1495 config ARCH_FLATMEM_ENABLE
1497 depends on X86_32 && !NUMA
1499 config ARCH_DISCONTIGMEM_ENABLE
1501 depends on NUMA && X86_32
1503 config ARCH_DISCONTIGMEM_DEFAULT
1505 depends on NUMA && X86_32
1507 config ARCH_SPARSEMEM_ENABLE
1509 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1510 select SPARSEMEM_STATIC if X86_32
1511 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1513 config ARCH_SPARSEMEM_DEFAULT
1517 config ARCH_SELECT_MEMORY_MODEL
1519 depends on ARCH_SPARSEMEM_ENABLE
1521 config ARCH_MEMORY_PROBE
1522 bool "Enable sysfs memory/probe interface"
1523 depends on X86_64 && MEMORY_HOTPLUG
1525 This option enables a sysfs memory/probe interface for testing.
1526 See Documentation/memory-hotplug.txt for more information.
1527 If you are unsure how to answer this question, answer N.
1529 config ARCH_PROC_KCORE_TEXT
1531 depends on X86_64 && PROC_KCORE
1533 config ILLEGAL_POINTER_VALUE
1536 default 0xdead000000000000 if X86_64
1540 config X86_PMEM_LEGACY_DEVICE
1543 config X86_PMEM_LEGACY
1544 tristate "Support non-standard NVDIMMs and ADR protected memory"
1545 depends on PHYS_ADDR_T_64BIT
1547 select X86_PMEM_LEGACY_DEVICE
1550 Treat memory marked using the non-standard e820 type of 12 as used
1551 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1552 The kernel will offer these regions to the 'pmem' driver so
1553 they can be used for persistent storage.
1558 bool "Allocate 3rd-level pagetables from highmem"
1561 The VM uses one page table entry for each page of physical memory.
1562 For systems with a lot of RAM, this can be wasteful of precious
1563 low memory. Setting this option will put user-space page table
1564 entries in high memory.
1566 config X86_CHECK_BIOS_CORRUPTION
1567 bool "Check for low memory corruption"
1569 Periodically check for memory corruption in low memory, which
1570 is suspected to be caused by BIOS. Even when enabled in the
1571 configuration, it is disabled at runtime. Enable it by
1572 setting "memory_corruption_check=1" on the kernel command
1573 line. By default it scans the low 64k of memory every 60
1574 seconds; see the memory_corruption_check_size and
1575 memory_corruption_check_period parameters in
1576 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1578 When enabled with the default parameters, this option has
1579 almost no overhead, as it reserves a relatively small amount
1580 of memory and scans it infrequently. It both detects corruption
1581 and prevents it from affecting the running system.
1583 It is, however, intended as a diagnostic tool; if repeatable
1584 BIOS-originated corruption always affects the same memory,
1585 you can use memmap= to prevent the kernel from using that
1588 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1589 bool "Set the default setting of memory_corruption_check"
1590 depends on X86_CHECK_BIOS_CORRUPTION
1593 Set whether the default state of memory_corruption_check is
1596 config X86_RESERVE_LOW
1597 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1601 Specify the amount of low memory to reserve for the BIOS.
1603 The first page contains BIOS data structures that the kernel
1604 must not use, so that page must always be reserved.
1606 By default we reserve the first 64K of physical RAM, as a
1607 number of BIOSes are known to corrupt that memory range
1608 during events such as suspend/resume or monitor cable
1609 insertion, so it must not be used by the kernel.
1611 You can set this to 4 if you are absolutely sure that you
1612 trust the BIOS to get all its memory reservations and usages
1613 right. If you know your BIOS have problems beyond the
1614 default 64K area, you can set this to 640 to avoid using the
1615 entire low memory range.
1617 If you have doubts about the BIOS (e.g. suspend/resume does
1618 not work or there's kernel crashes after certain hardware
1619 hotplug events) then you might want to enable
1620 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1621 typical corruption patterns.
1623 Leave this to the default value of 64 if you are unsure.
1625 config MATH_EMULATION
1627 depends on MODIFY_LDT_SYSCALL
1628 prompt "Math emulation" if X86_32
1630 Linux can emulate a math coprocessor (used for floating point
1631 operations) if you don't have one. 486DX and Pentium processors have
1632 a math coprocessor built in, 486SX and 386 do not, unless you added
1633 a 487DX or 387, respectively. (The messages during boot time can
1634 give you some hints here ["man dmesg"].) Everyone needs either a
1635 coprocessor or this emulation.
1637 If you don't have a math coprocessor, you need to say Y here; if you
1638 say Y here even though you have a coprocessor, the coprocessor will
1639 be used nevertheless. (This behavior can be changed with the kernel
1640 command line option "no387", which comes handy if your coprocessor
1641 is broken. Try "man bootparam" or see the documentation of your boot
1642 loader (lilo or loadlin) about how to pass options to the kernel at
1643 boot time.) This means that it is a good idea to say Y here if you
1644 intend to use this kernel on different machines.
1646 More information about the internals of the Linux math coprocessor
1647 emulation can be found in <file:arch/x86/math-emu/README>.
1649 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1650 kernel, it won't hurt.
1654 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1656 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1657 the Memory Type Range Registers (MTRRs) may be used to control
1658 processor access to memory ranges. This is most useful if you have
1659 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1660 allows bus write transfers to be combined into a larger transfer
1661 before bursting over the PCI/AGP bus. This can increase performance
1662 of image write operations 2.5 times or more. Saying Y here creates a
1663 /proc/mtrr file which may be used to manipulate your processor's
1664 MTRRs. Typically the X server should use this.
1666 This code has a reasonably generic interface so that similar
1667 control registers on other processors can be easily supported
1670 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1671 Registers (ARRs) which provide a similar functionality to MTRRs. For
1672 these, the ARRs are used to emulate the MTRRs.
1673 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1674 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1675 write-combining. All of these processors are supported by this code
1676 and it makes sense to say Y here if you have one of them.
1678 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1679 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1680 can lead to all sorts of problems, so it's good to say Y here.
1682 You can safely say Y even if your machine doesn't have MTRRs, you'll
1683 just add about 9 KB to your kernel.
1685 See <file:Documentation/x86/mtrr.txt> for more information.
1687 config MTRR_SANITIZER
1689 prompt "MTRR cleanup support"
1692 Convert MTRR layout from continuous to discrete, so X drivers can
1693 add writeback entries.
1695 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1696 The largest mtrr entry size for a continuous block can be set with
1701 config MTRR_SANITIZER_ENABLE_DEFAULT
1702 int "MTRR cleanup enable value (0-1)"
1705 depends on MTRR_SANITIZER
1707 Enable mtrr cleanup default value
1709 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1710 int "MTRR cleanup spare reg num (0-7)"
1713 depends on MTRR_SANITIZER
1715 mtrr cleanup spare entries default, it can be changed via
1716 mtrr_spare_reg_nr=N on the kernel command line.
1720 prompt "x86 PAT support" if EXPERT
1723 Use PAT attributes to setup page level cache control.
1725 PATs are the modern equivalents of MTRRs and are much more
1726 flexible than MTRRs.
1728 Say N here if you see bootup problems (boot crash, boot hang,
1729 spontaneous reboots) or a non-working video driver.
1733 config ARCH_USES_PG_UNCACHED
1739 prompt "x86 architectural random number generator" if EXPERT
1741 Enable the x86 architectural RDRAND instruction
1742 (Intel Bull Mountain technology) to generate random numbers.
1743 If supported, this is a high bandwidth, cryptographically
1744 secure hardware random number generator.
1748 prompt "Supervisor Mode Access Prevention" if EXPERT
1750 Supervisor Mode Access Prevention (SMAP) is a security
1751 feature in newer Intel processors. There is a small
1752 performance cost if this enabled and turned on; there is
1753 also a small increase in the kernel size if this is enabled.
1757 config X86_INTEL_MPX
1758 prompt "Intel MPX (Memory Protection Extensions)"
1760 depends on CPU_SUP_INTEL
1762 MPX provides hardware features that can be used in
1763 conjunction with compiler-instrumented code to check
1764 memory references. It is designed to detect buffer
1765 overflow or underflow bugs.
1767 This option enables running applications which are
1768 instrumented or otherwise use MPX. It does not use MPX
1769 itself inside the kernel or to protect the kernel
1770 against bad memory references.
1772 Enabling this option will make the kernel larger:
1773 ~8k of kernel text and 36 bytes of data on a 64-bit
1774 defconfig. It adds a long to the 'mm_struct' which
1775 will increase the kernel memory overhead of each
1776 process and adds some branches to paths used during
1777 exec() and munmap().
1779 For details, see Documentation/x86/intel_mpx.txt
1783 config X86_INTEL_MEMORY_PROTECTION_KEYS
1784 prompt "Intel Memory Protection Keys"
1786 # Note: only available in 64-bit mode
1787 depends on CPU_SUP_INTEL && X86_64
1788 select ARCH_USES_HIGH_VMA_FLAGS
1789 select ARCH_HAS_PKEYS
1791 Memory Protection Keys provides a mechanism for enforcing
1792 page-based protections, but without requiring modification of the
1793 page tables when an application changes protection domains.
1795 For details, see Documentation/x86/protection-keys.txt
1800 bool "EFI runtime service support"
1803 select EFI_RUNTIME_WRAPPERS
1805 This enables the kernel to use EFI runtime services that are
1806 available (such as the EFI variable services).
1808 This option is only useful on systems that have EFI firmware.
1809 In addition, you should use the latest ELILO loader available
1810 at <http://elilo.sourceforge.net> in order to take advantage
1811 of EFI runtime services. However, even with this option, the
1812 resultant kernel should continue to boot on existing non-EFI
1816 bool "EFI stub support"
1817 depends on EFI && !X86_USE_3DNOW
1820 This kernel feature allows a bzImage to be loaded directly
1821 by EFI firmware without the use of a bootloader.
1823 See Documentation/efi-stub.txt for more information.
1826 bool "EFI mixed-mode support"
1827 depends on EFI_STUB && X86_64
1829 Enabling this feature allows a 64-bit kernel to be booted
1830 on a 32-bit firmware, provided that your CPU supports 64-bit
1833 Note that it is not possible to boot a mixed-mode enabled
1834 kernel via the EFI boot stub - a bootloader that supports
1835 the EFI handover protocol must be used.
1841 prompt "Enable seccomp to safely compute untrusted bytecode"
1843 This kernel feature is useful for number crunching applications
1844 that may need to compute untrusted bytecode during their
1845 execution. By using pipes or other transports made available to
1846 the process as file descriptors supporting the read/write
1847 syscalls, it's possible to isolate those applications in
1848 their own address space using seccomp. Once seccomp is
1849 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1850 and the task is only allowed to execute a few safe syscalls
1851 defined by each seccomp mode.
1853 If unsure, say Y. Only embedded should say N here.
1855 source kernel/Kconfig.hz
1858 bool "kexec system call"
1861 kexec is a system call that implements the ability to shutdown your
1862 current kernel, and to start another kernel. It is like a reboot
1863 but it is independent of the system firmware. And like a reboot
1864 you can start any kernel with it, not just Linux.
1866 The name comes from the similarity to the exec system call.
1868 It is an ongoing process to be certain the hardware in a machine
1869 is properly shutdown, so do not be surprised if this code does not
1870 initially work for you. As of this writing the exact hardware
1871 interface is strongly in flux, so no good recommendation can be
1875 bool "kexec file based system call"
1880 depends on CRYPTO_SHA256=y
1882 This is new version of kexec system call. This system call is
1883 file based and takes file descriptors as system call argument
1884 for kernel and initramfs as opposed to list of segments as
1885 accepted by previous system call.
1887 config KEXEC_VERIFY_SIG
1888 bool "Verify kernel signature during kexec_file_load() syscall"
1889 depends on KEXEC_FILE
1891 This option makes kernel signature verification mandatory for
1892 the kexec_file_load() syscall.
1894 In addition to that option, you need to enable signature
1895 verification for the corresponding kernel image type being
1896 loaded in order for this to work.
1898 config KEXEC_BZIMAGE_VERIFY_SIG
1899 bool "Enable bzImage signature verification support"
1900 depends on KEXEC_VERIFY_SIG
1901 depends on SIGNED_PE_FILE_VERIFICATION
1902 select SYSTEM_TRUSTED_KEYRING
1904 Enable bzImage signature verification support.
1907 bool "kernel crash dumps"
1908 depends on X86_64 || (X86_32 && HIGHMEM)
1910 Generate crash dump after being started by kexec.
1911 This should be normally only set in special crash dump kernels
1912 which are loaded in the main kernel with kexec-tools into
1913 a specially reserved region and then later executed after
1914 a crash by kdump/kexec. The crash dump kernel must be compiled
1915 to a memory address not used by the main kernel or BIOS using
1916 PHYSICAL_START, or it must be built as a relocatable image
1917 (CONFIG_RELOCATABLE=y).
1918 For more details see Documentation/kdump/kdump.txt
1922 depends on KEXEC && HIBERNATION
1924 Jump between original kernel and kexeced kernel and invoke
1925 code in physical address mode via KEXEC
1927 config PHYSICAL_START
1928 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
1931 This gives the physical address where the kernel is loaded.
1933 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
1934 bzImage will decompress itself to above physical address and
1935 run from there. Otherwise, bzImage will run from the address where
1936 it has been loaded by the boot loader and will ignore above physical
1939 In normal kdump cases one does not have to set/change this option
1940 as now bzImage can be compiled as a completely relocatable image
1941 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
1942 address. This option is mainly useful for the folks who don't want
1943 to use a bzImage for capturing the crash dump and want to use a
1944 vmlinux instead. vmlinux is not relocatable hence a kernel needs
1945 to be specifically compiled to run from a specific memory area
1946 (normally a reserved region) and this option comes handy.
1948 So if you are using bzImage for capturing the crash dump,
1949 leave the value here unchanged to 0x1000000 and set
1950 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
1951 for capturing the crash dump change this value to start of
1952 the reserved region. In other words, it can be set based on
1953 the "X" value as specified in the "crashkernel=YM@XM"
1954 command line boot parameter passed to the panic-ed
1955 kernel. Please take a look at Documentation/kdump/kdump.txt
1956 for more details about crash dumps.
1958 Usage of bzImage for capturing the crash dump is recommended as
1959 one does not have to build two kernels. Same kernel can be used
1960 as production kernel and capture kernel. Above option should have
1961 gone away after relocatable bzImage support is introduced. But it
1962 is present because there are users out there who continue to use
1963 vmlinux for dump capture. This option should go away down the
1966 Don't change this unless you know what you are doing.
1969 bool "Build a relocatable kernel"
1972 This builds a kernel image that retains relocation information
1973 so it can be loaded someplace besides the default 1MB.
1974 The relocations tend to make the kernel binary about 10% larger,
1975 but are discarded at runtime.
1977 One use is for the kexec on panic case where the recovery kernel
1978 must live at a different physical address than the primary
1981 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
1982 it has been loaded at and the compile time physical address
1983 (CONFIG_PHYSICAL_START) is used as the minimum location.
1985 config RANDOMIZE_BASE
1986 bool "Randomize the address of the kernel image (KASLR)"
1987 depends on RELOCATABLE
1990 In support of Kernel Address Space Layout Randomization (KASLR),
1991 this randomizes the physical address at which the kernel image
1992 is decompressed and the virtual address where the kernel
1993 image is mapped, as a security feature that deters exploit
1994 attempts relying on knowledge of the location of kernel
1997 On 64-bit, the kernel physical and virtual addresses are
1998 randomized separately. The physical address will be anywhere
1999 between 16MB and the top of physical memory (up to 64TB). The
2000 virtual address will be randomized from 16MB up to 1GB (9 bits
2001 of entropy). Note that this also reduces the memory space
2002 available to kernel modules from 1.5GB to 1GB.
2004 On 32-bit, the kernel physical and virtual addresses are
2005 randomized together. They will be randomized from 16MB up to
2006 512MB (8 bits of entropy).
2008 Entropy is generated using the RDRAND instruction if it is
2009 supported. If RDTSC is supported, its value is mixed into
2010 the entropy pool as well. If neither RDRAND nor RDTSC are
2011 supported, then entropy is read from the i8254 timer. The
2012 usable entropy is limited by the kernel being built using
2013 2GB addressing, and that PHYSICAL_ALIGN must be at a
2014 minimum of 2MB. As a result, only 10 bits of entropy are
2015 theoretically possible, but the implementations are further
2016 limited due to memory layouts.
2020 # Relocation on x86 needs some additional build support
2021 config X86_NEED_RELOCS
2023 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2025 config PHYSICAL_ALIGN
2026 hex "Alignment value to which kernel should be aligned"
2028 range 0x2000 0x1000000 if X86_32
2029 range 0x200000 0x1000000 if X86_64
2031 This value puts the alignment restrictions on physical address
2032 where kernel is loaded and run from. Kernel is compiled for an
2033 address which meets above alignment restriction.
2035 If bootloader loads the kernel at a non-aligned address and
2036 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2037 address aligned to above value and run from there.
2039 If bootloader loads the kernel at a non-aligned address and
2040 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2041 load address and decompress itself to the address it has been
2042 compiled for and run from there. The address for which kernel is
2043 compiled already meets above alignment restrictions. Hence the
2044 end result is that kernel runs from a physical address meeting
2045 above alignment restrictions.
2047 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2048 this value must be a multiple of 0x200000.
2050 Don't change this unless you know what you are doing.
2052 config RANDOMIZE_MEMORY
2053 bool "Randomize the kernel memory sections"
2055 depends on RANDOMIZE_BASE
2056 default RANDOMIZE_BASE
2058 Randomizes the base virtual address of kernel memory sections
2059 (physical memory mapping, vmalloc & vmemmap). This security feature
2060 makes exploits relying on predictable memory locations less reliable.
2062 The order of allocations remains unchanged. Entropy is generated in
2063 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2064 configuration have in average 30,000 different possible virtual
2065 addresses for each memory section.
2069 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2070 hex "Physical memory mapping padding" if EXPERT
2071 depends on RANDOMIZE_MEMORY
2072 default "0xa" if MEMORY_HOTPLUG
2074 range 0x1 0x40 if MEMORY_HOTPLUG
2077 Define the padding in terabytes added to the existing physical
2078 memory size during kernel memory randomization. It is useful
2079 for memory hotplug support but reduces the entropy available for
2080 address randomization.
2082 If unsure, leave at the default value.
2085 bool "Support for hot-pluggable CPUs"
2088 Say Y here to allow turning CPUs off and on. CPUs can be
2089 controlled through /sys/devices/system/cpu.
2090 ( Note: power management support will enable this option
2091 automatically on SMP systems. )
2092 Say N if you want to disable CPU hotplug.
2094 config BOOTPARAM_HOTPLUG_CPU0
2095 bool "Set default setting of cpu0_hotpluggable"
2097 depends on HOTPLUG_CPU
2099 Set whether default state of cpu0_hotpluggable is on or off.
2101 Say Y here to enable CPU0 hotplug by default. If this switch
2102 is turned on, there is no need to give cpu0_hotplug kernel
2103 parameter and the CPU0 hotplug feature is enabled by default.
2105 Please note: there are two known CPU0 dependencies if you want
2106 to enable the CPU0 hotplug feature either by this switch or by
2107 cpu0_hotplug kernel parameter.
2109 First, resume from hibernate or suspend always starts from CPU0.
2110 So hibernate and suspend are prevented if CPU0 is offline.
2112 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2113 offline if any interrupt can not migrate out of CPU0. There may
2114 be other CPU0 dependencies.
2116 Please make sure the dependencies are under your control before
2117 you enable this feature.
2119 Say N if you don't want to enable CPU0 hotplug feature by default.
2120 You still can enable the CPU0 hotplug feature at boot by kernel
2121 parameter cpu0_hotplug.
2123 config DEBUG_HOTPLUG_CPU0
2125 prompt "Debug CPU0 hotplug"
2126 depends on HOTPLUG_CPU
2128 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2129 soon as possible and boots up userspace with CPU0 offlined. User
2130 can online CPU0 back after boot time.
2132 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2133 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2134 compilation or giving cpu0_hotplug kernel parameter at boot.
2140 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2141 depends on COMPAT_32
2143 Certain buggy versions of glibc will crash if they are
2144 presented with a 32-bit vDSO that is not mapped at the address
2145 indicated in its segment table.
2147 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2148 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2149 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2150 the only released version with the bug, but OpenSUSE 9
2151 contains a buggy "glibc 2.3.2".
2153 The symptom of the bug is that everything crashes on startup, saying:
2154 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2156 Saying Y here changes the default value of the vdso32 boot
2157 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2158 This works around the glibc bug but hurts performance.
2160 If unsure, say N: if you are compiling your own kernel, you
2161 are unlikely to be using a buggy version of glibc.
2164 prompt "vsyscall table for legacy applications"
2166 default LEGACY_VSYSCALL_EMULATE
2168 Legacy user code that does not know how to find the vDSO expects
2169 to be able to issue three syscalls by calling fixed addresses in
2170 kernel space. Since this location is not randomized with ASLR,
2171 it can be used to assist security vulnerability exploitation.
2173 This setting can be changed at boot time via the kernel command
2174 line parameter vsyscall=[native|emulate|none].
2176 On a system with recent enough glibc (2.14 or newer) and no
2177 static binaries, you can say None without a performance penalty
2178 to improve security.
2180 If unsure, select "Emulate".
2182 config LEGACY_VSYSCALL_NATIVE
2185 Actual executable code is located in the fixed vsyscall
2186 address mapping, implementing time() efficiently. Since
2187 this makes the mapping executable, it can be used during
2188 security vulnerability exploitation (traditionally as
2189 ROP gadgets). This configuration is not recommended.
2191 config LEGACY_VSYSCALL_EMULATE
2194 The kernel traps and emulates calls into the fixed
2195 vsyscall address mapping. This makes the mapping
2196 non-executable, but it still contains known contents,
2197 which could be used in certain rare security vulnerability
2198 exploits. This configuration is recommended when userspace
2199 still uses the vsyscall area.
2201 config LEGACY_VSYSCALL_NONE
2204 There will be no vsyscall mapping at all. This will
2205 eliminate any risk of ASLR bypass due to the vsyscall
2206 fixed address mapping. Attempts to use the vsyscalls
2207 will be reported to dmesg, so that either old or
2208 malicious userspace programs can be identified.
2213 bool "Built-in kernel command line"
2215 Allow for specifying boot arguments to the kernel at
2216 build time. On some systems (e.g. embedded ones), it is
2217 necessary or convenient to provide some or all of the
2218 kernel boot arguments with the kernel itself (that is,
2219 to not rely on the boot loader to provide them.)
2221 To compile command line arguments into the kernel,
2222 set this option to 'Y', then fill in the
2223 boot arguments in CONFIG_CMDLINE.
2225 Systems with fully functional boot loaders (i.e. non-embedded)
2226 should leave this option set to 'N'.
2229 string "Built-in kernel command string"
2230 depends on CMDLINE_BOOL
2233 Enter arguments here that should be compiled into the kernel
2234 image and used at boot time. If the boot loader provides a
2235 command line at boot time, it is appended to this string to
2236 form the full kernel command line, when the system boots.
2238 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2239 change this behavior.
2241 In most cases, the command line (whether built-in or provided
2242 by the boot loader) should specify the device for the root
2245 config CMDLINE_OVERRIDE
2246 bool "Built-in command line overrides boot loader arguments"
2247 depends on CMDLINE_BOOL
2249 Set this option to 'Y' to have the kernel ignore the boot loader
2250 command line, and use ONLY the built-in command line.
2252 This is used to work around broken boot loaders. This should
2253 be set to 'N' under normal conditions.
2255 config MODIFY_LDT_SYSCALL
2256 bool "Enable the LDT (local descriptor table)" if EXPERT
2259 Linux can allow user programs to install a per-process x86
2260 Local Descriptor Table (LDT) using the modify_ldt(2) system
2261 call. This is required to run 16-bit or segmented code such as
2262 DOSEMU or some Wine programs. It is also used by some very old
2263 threading libraries.
2265 Enabling this feature adds a small amount of overhead to
2266 context switches and increases the low-level kernel attack
2267 surface. Disabling it removes the modify_ldt(2) system call.
2269 Saying 'N' here may make sense for embedded or server kernels.
2271 source "kernel/livepatch/Kconfig"
2275 config ARCH_ENABLE_MEMORY_HOTPLUG
2277 depends on X86_64 || (X86_32 && HIGHMEM)
2279 config ARCH_ENABLE_MEMORY_HOTREMOVE
2281 depends on MEMORY_HOTPLUG
2283 config USE_PERCPU_NUMA_NODE_ID
2287 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2289 depends on X86_64 || X86_PAE
2291 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2293 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2295 menu "Power management and ACPI options"
2297 config ARCH_HIBERNATION_HEADER
2299 depends on X86_64 && HIBERNATION
2301 source "kernel/power/Kconfig"
2303 source "drivers/acpi/Kconfig"
2305 source "drivers/sfi/Kconfig"
2312 tristate "APM (Advanced Power Management) BIOS support"
2313 depends on X86_32 && PM_SLEEP
2315 APM is a BIOS specification for saving power using several different
2316 techniques. This is mostly useful for battery powered laptops with
2317 APM compliant BIOSes. If you say Y here, the system time will be
2318 reset after a RESUME operation, the /proc/apm device will provide
2319 battery status information, and user-space programs will receive
2320 notification of APM "events" (e.g. battery status change).
2322 If you select "Y" here, you can disable actual use of the APM
2323 BIOS by passing the "apm=off" option to the kernel at boot time.
2325 Note that the APM support is almost completely disabled for
2326 machines with more than one CPU.
2328 In order to use APM, you will need supporting software. For location
2329 and more information, read <file:Documentation/power/apm-acpi.txt>
2330 and the Battery Powered Linux mini-HOWTO, available from
2331 <http://www.tldp.org/docs.html#howto>.
2333 This driver does not spin down disk drives (see the hdparm(8)
2334 manpage ("man 8 hdparm") for that), and it doesn't turn off
2335 VESA-compliant "green" monitors.
2337 This driver does not support the TI 4000M TravelMate and the ACER
2338 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2339 desktop machines also don't have compliant BIOSes, and this driver
2340 may cause those machines to panic during the boot phase.
2342 Generally, if you don't have a battery in your machine, there isn't
2343 much point in using this driver and you should say N. If you get
2344 random kernel OOPSes or reboots that don't seem to be related to
2345 anything, try disabling/enabling this option (or disabling/enabling
2348 Some other things you should try when experiencing seemingly random,
2351 1) make sure that you have enough swap space and that it is
2353 2) pass the "no-hlt" option to the kernel
2354 3) switch on floating point emulation in the kernel and pass
2355 the "no387" option to the kernel
2356 4) pass the "floppy=nodma" option to the kernel
2357 5) pass the "mem=4M" option to the kernel (thereby disabling
2358 all but the first 4 MB of RAM)
2359 6) make sure that the CPU is not over clocked.
2360 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2361 8) disable the cache from your BIOS settings
2362 9) install a fan for the video card or exchange video RAM
2363 10) install a better fan for the CPU
2364 11) exchange RAM chips
2365 12) exchange the motherboard.
2367 To compile this driver as a module, choose M here: the
2368 module will be called apm.
2372 config APM_IGNORE_USER_SUSPEND
2373 bool "Ignore USER SUSPEND"
2375 This option will ignore USER SUSPEND requests. On machines with a
2376 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2377 series notebooks, it is necessary to say Y because of a BIOS bug.
2379 config APM_DO_ENABLE
2380 bool "Enable PM at boot time"
2382 Enable APM features at boot time. From page 36 of the APM BIOS
2383 specification: "When disabled, the APM BIOS does not automatically
2384 power manage devices, enter the Standby State, enter the Suspend
2385 State, or take power saving steps in response to CPU Idle calls."
2386 This driver will make CPU Idle calls when Linux is idle (unless this
2387 feature is turned off -- see "Do CPU IDLE calls", below). This
2388 should always save battery power, but more complicated APM features
2389 will be dependent on your BIOS implementation. You may need to turn
2390 this option off if your computer hangs at boot time when using APM
2391 support, or if it beeps continuously instead of suspending. Turn
2392 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2393 T400CDT. This is off by default since most machines do fine without
2398 bool "Make CPU Idle calls when idle"
2400 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2401 On some machines, this can activate improved power savings, such as
2402 a slowed CPU clock rate, when the machine is idle. These idle calls
2403 are made after the idle loop has run for some length of time (e.g.,
2404 333 mS). On some machines, this will cause a hang at boot time or
2405 whenever the CPU becomes idle. (On machines with more than one CPU,
2406 this option does nothing.)
2408 config APM_DISPLAY_BLANK
2409 bool "Enable console blanking using APM"
2411 Enable console blanking using the APM. Some laptops can use this to
2412 turn off the LCD backlight when the screen blanker of the Linux
2413 virtual console blanks the screen. Note that this is only used by
2414 the virtual console screen blanker, and won't turn off the backlight
2415 when using the X Window system. This also doesn't have anything to
2416 do with your VESA-compliant power-saving monitor. Further, this
2417 option doesn't work for all laptops -- it might not turn off your
2418 backlight at all, or it might print a lot of errors to the console,
2419 especially if you are using gpm.
2421 config APM_ALLOW_INTS
2422 bool "Allow interrupts during APM BIOS calls"
2424 Normally we disable external interrupts while we are making calls to
2425 the APM BIOS as a measure to lessen the effects of a badly behaving
2426 BIOS implementation. The BIOS should reenable interrupts if it
2427 needs to. Unfortunately, some BIOSes do not -- especially those in
2428 many of the newer IBM Thinkpads. If you experience hangs when you
2429 suspend, try setting this to Y. Otherwise, say N.
2433 source "drivers/cpufreq/Kconfig"
2435 source "drivers/cpuidle/Kconfig"
2437 source "drivers/idle/Kconfig"
2442 menu "Bus options (PCI etc.)"
2448 Find out whether you have a PCI motherboard. PCI is the name of a
2449 bus system, i.e. the way the CPU talks to the other stuff inside
2450 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2451 VESA. If you have PCI, say Y, otherwise N.
2454 prompt "PCI access mode"
2455 depends on X86_32 && PCI
2458 On PCI systems, the BIOS can be used to detect the PCI devices and
2459 determine their configuration. However, some old PCI motherboards
2460 have BIOS bugs and may crash if this is done. Also, some embedded
2461 PCI-based systems don't have any BIOS at all. Linux can also try to
2462 detect the PCI hardware directly without using the BIOS.
2464 With this option, you can specify how Linux should detect the
2465 PCI devices. If you choose "BIOS", the BIOS will be used,
2466 if you choose "Direct", the BIOS won't be used, and if you
2467 choose "MMConfig", then PCI Express MMCONFIG will be used.
2468 If you choose "Any", the kernel will try MMCONFIG, then the
2469 direct access method and falls back to the BIOS if that doesn't
2470 work. If unsure, go with the default, which is "Any".
2475 config PCI_GOMMCONFIG
2492 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2494 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2497 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2501 depends on X86_32 && PCI && (ACPI || SFI) && (PCI_GOMMCONFIG || PCI_GOANY)
2505 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2509 depends on PCI && XEN
2517 bool "Support mmconfig PCI config space access"
2518 depends on X86_64 && PCI && ACPI
2520 config PCI_CNB20LE_QUIRK
2521 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2524 Read the PCI windows out of the CNB20LE host bridge. This allows
2525 PCI hotplug to work on systems with the CNB20LE chipset which do
2528 There's no public spec for this chipset, and this functionality
2529 is known to be incomplete.
2531 You should say N unless you know you need this.
2533 source "drivers/pci/Kconfig"
2536 bool "ISA-style bus support on modern systems" if EXPERT
2539 Enables ISA-style drivers on modern systems. This is necessary to
2540 support PC/104 devices on X86_64 platforms.
2544 # x86_64 have no ISA slots, but can have ISA-style DMA.
2546 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2549 Enables ISA-style DMA support for devices requiring such controllers.
2557 Find out whether you have ISA slots on your motherboard. ISA is the
2558 name of a bus system, i.e. the way the CPU talks to the other stuff
2559 inside your box. Other bus systems are PCI, EISA, MicroChannel
2560 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2561 newer boards don't support it. If you have ISA, say Y, otherwise N.
2567 The Extended Industry Standard Architecture (EISA) bus was
2568 developed as an open alternative to the IBM MicroChannel bus.
2570 The EISA bus provided some of the features of the IBM MicroChannel
2571 bus while maintaining backward compatibility with cards made for
2572 the older ISA bus. The EISA bus saw limited use between 1988 and
2573 1995 when it was made obsolete by the PCI bus.
2575 Say Y here if you are building a kernel for an EISA-based machine.
2579 source "drivers/eisa/Kconfig"
2582 tristate "NatSemi SCx200 support"
2584 This provides basic support for National Semiconductor's
2585 (now AMD's) Geode processors. The driver probes for the
2586 PCI-IDs of several on-chip devices, so its a good dependency
2587 for other scx200_* drivers.
2589 If compiled as a module, the driver is named scx200.
2591 config SCx200HR_TIMER
2592 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2596 This driver provides a clocksource built upon the on-chip
2597 27MHz high-resolution timer. Its also a workaround for
2598 NSC Geode SC-1100's buggy TSC, which loses time when the
2599 processor goes idle (as is done by the scheduler). The
2600 other workaround is idle=poll boot option.
2603 bool "One Laptop Per Child support"
2610 Add support for detecting the unique features of the OLPC
2614 bool "OLPC XO-1 Power Management"
2615 depends on OLPC && MFD_CS5535 && PM_SLEEP
2618 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2621 bool "OLPC XO-1 Real Time Clock"
2622 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2624 Add support for the XO-1 real time clock, which can be used as a
2625 programmable wakeup source.
2628 bool "OLPC XO-1 SCI extras"
2629 depends on OLPC && OLPC_XO1_PM
2635 Add support for SCI-based features of the OLPC XO-1 laptop:
2636 - EC-driven system wakeups
2640 - AC adapter status updates
2641 - Battery status updates
2643 config OLPC_XO15_SCI
2644 bool "OLPC XO-1.5 SCI extras"
2645 depends on OLPC && ACPI
2648 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2649 - EC-driven system wakeups
2650 - AC adapter status updates
2651 - Battery status updates
2654 bool "PCEngines ALIX System Support (LED setup)"
2657 This option enables system support for the PCEngines ALIX.
2658 At present this just sets up LEDs for GPIO control on
2659 ALIX2/3/6 boards. However, other system specific setup should
2662 Note: You must still enable the drivers for GPIO and LED support
2663 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2665 Note: You have to set alix.force=1 for boards with Award BIOS.
2668 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2671 This option enables system support for the Soekris Engineering net5501.
2674 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2678 This option enables system support for the Traverse Technologies GEOS.
2681 bool "Technologic Systems TS-5500 platform support"
2683 select CHECK_SIGNATURE
2687 This option enables system support for the Technologic Systems TS-5500.
2693 depends on CPU_SUP_AMD && PCI
2695 source "drivers/pcmcia/Kconfig"
2698 tristate "RapidIO support"
2702 If enabled this option will include drivers and the core
2703 infrastructure code to support RapidIO interconnect devices.
2705 source "drivers/rapidio/Kconfig"
2708 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2710 Firmwares often provide initial graphics framebuffers so the BIOS,
2711 bootloader or kernel can show basic video-output during boot for
2712 user-guidance and debugging. Historically, x86 used the VESA BIOS
2713 Extensions and EFI-framebuffers for this, which are mostly limited
2715 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2716 framebuffers so the new generic system-framebuffer drivers can be
2717 used on x86. If the framebuffer is not compatible with the generic
2718 modes, it is adverticed as fallback platform framebuffer so legacy
2719 drivers like efifb, vesafb and uvesafb can pick it up.
2720 If this option is not selected, all system framebuffers are always
2721 marked as fallback platform framebuffers as usual.
2723 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2724 not be able to pick up generic system framebuffers if this option
2725 is selected. You are highly encouraged to enable simplefb as
2726 replacement if you select this option. simplefb can correctly deal
2727 with generic system framebuffers. But you should still keep vesafb
2728 and others enabled as fallback if a system framebuffer is
2729 incompatible with simplefb.
2736 menu "Executable file formats / Emulations"
2738 source "fs/Kconfig.binfmt"
2740 config IA32_EMULATION
2741 bool "IA32 Emulation"
2743 select ARCH_WANT_OLD_COMPAT_IPC
2745 select COMPAT_BINFMT_ELF
2746 select COMPAT_OLD_SIGACTION
2748 Include code to run legacy 32-bit programs under a
2749 64-bit kernel. You should likely turn this on, unless you're
2750 100% sure that you don't have any 32-bit programs left.
2753 tristate "IA32 a.out support"
2754 depends on IA32_EMULATION
2756 Support old a.out binaries in the 32bit emulation.
2759 bool "x32 ABI for 64-bit mode"
2762 Include code to run binaries for the x32 native 32-bit ABI
2763 for 64-bit processors. An x32 process gets access to the
2764 full 64-bit register file and wide data path while leaving
2765 pointers at 32 bits for smaller memory footprint.
2767 You will need a recent binutils (2.22 or later) with
2768 elf32_x86_64 support enabled to compile a kernel with this
2773 depends on IA32_EMULATION || X86_32
2775 select OLD_SIGSUSPEND3
2779 depends on IA32_EMULATION || X86_X32
2782 config COMPAT_FOR_U64_ALIGNMENT
2785 config SYSVIPC_COMPAT
2793 config HAVE_ATOMIC_IOMAP
2797 config X86_DEV_DMA_OPS
2799 depends on X86_64 || STA2X11
2801 config X86_DMA_REMAP
2805 config HAVE_GENERIC_GUP
2808 source "net/Kconfig"
2810 source "drivers/Kconfig"
2812 source "drivers/firmware/Kconfig"
2816 source "arch/x86/Kconfig.debug"
2818 source "security/Kconfig"
2820 source "crypto/Kconfig"
2822 source "arch/x86/kvm/Kconfig"
2824 source "lib/Kconfig"