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_REFCOUNT
59 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
60 select ARCH_HAS_SET_MEMORY
61 select ARCH_HAS_SG_CHAIN
62 select ARCH_HAS_STRICT_KERNEL_RWX
63 select ARCH_HAS_STRICT_MODULE_RWX
64 select ARCH_HAS_UBSAN_SANITIZE_ALL
65 select ARCH_HAS_ZONE_DEVICE if X86_64
66 select ARCH_HAVE_NMI_SAFE_CMPXCHG
67 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
68 select ARCH_MIGHT_HAVE_PC_PARPORT
69 select ARCH_MIGHT_HAVE_PC_SERIO
70 select ARCH_SUPPORTS_ATOMIC_RMW
71 select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
72 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
73 select ARCH_USE_BUILTIN_BSWAP
74 select ARCH_USE_QUEUED_RWLOCKS
75 select ARCH_USE_QUEUED_SPINLOCKS
76 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
77 select ARCH_WANT_FRAME_POINTERS
78 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
79 select ARCH_WANTS_THP_SWAP if X86_64
80 select BUILDTIME_EXTABLE_SORT
82 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
83 select CLOCKSOURCE_WATCHDOG
84 select DCACHE_WORD_ACCESS
85 select EDAC_ATOMIC_SCRUB
87 select GENERIC_CLOCKEVENTS
88 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
89 select GENERIC_CLOCKEVENTS_MIN_ADJUST
90 select GENERIC_CMOS_UPDATE
91 select GENERIC_CPU_AUTOPROBE
92 select GENERIC_EARLY_IOREMAP
93 select GENERIC_FIND_FIRST_BIT
95 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
96 select GENERIC_IRQ_MIGRATION if SMP
97 select GENERIC_IRQ_PROBE
98 select GENERIC_IRQ_SHOW
99 select GENERIC_PENDING_IRQ if SMP
100 select GENERIC_SMP_IDLE_THREAD
101 select GENERIC_STRNCPY_FROM_USER
102 select GENERIC_STRNLEN_USER
103 select GENERIC_TIME_VSYSCALL
104 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
105 select HAVE_ACPI_APEI if ACPI
106 select HAVE_ACPI_APEI_NMI if ACPI
107 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
108 select HAVE_ARCH_AUDITSYSCALL
109 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
110 select HAVE_ARCH_JUMP_LABEL
111 select HAVE_ARCH_KASAN if X86_64 && SPARSEMEM_VMEMMAP
112 select HAVE_ARCH_KGDB
113 select HAVE_ARCH_KMEMCHECK
114 select HAVE_ARCH_MMAP_RND_BITS if MMU
115 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
116 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
117 select HAVE_ARCH_SECCOMP_FILTER
118 select HAVE_ARCH_TRACEHOOK
119 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
120 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
121 select HAVE_ARCH_VMAP_STACK if X86_64
122 select HAVE_ARCH_WITHIN_STACK_FRAMES
123 select HAVE_CC_STACKPROTECTOR
124 select HAVE_CMPXCHG_DOUBLE
125 select HAVE_CMPXCHG_LOCAL
126 select HAVE_CONTEXT_TRACKING if X86_64
127 select HAVE_COPY_THREAD_TLS
128 select HAVE_C_RECORDMCOUNT
129 select HAVE_DEBUG_KMEMLEAK
130 select HAVE_DEBUG_STACKOVERFLOW
131 select HAVE_DMA_API_DEBUG
132 select HAVE_DMA_CONTIGUOUS
133 select HAVE_DYNAMIC_FTRACE
134 select HAVE_DYNAMIC_FTRACE_WITH_REGS
135 select HAVE_EBPF_JIT if X86_64
136 select HAVE_EFFICIENT_UNALIGNED_ACCESS
137 select HAVE_EXIT_THREAD
138 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
139 select HAVE_FTRACE_MCOUNT_RECORD
140 select HAVE_FUNCTION_GRAPH_TRACER
141 select HAVE_FUNCTION_TRACER
142 select HAVE_GCC_PLUGINS
143 select HAVE_HW_BREAKPOINT
145 select HAVE_IOREMAP_PROT
146 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
147 select HAVE_IRQ_TIME_ACCOUNTING
148 select HAVE_KERNEL_BZIP2
149 select HAVE_KERNEL_GZIP
150 select HAVE_KERNEL_LZ4
151 select HAVE_KERNEL_LZMA
152 select HAVE_KERNEL_LZO
153 select HAVE_KERNEL_XZ
155 select HAVE_KPROBES_ON_FTRACE
156 select HAVE_KRETPROBES
158 select HAVE_LIVEPATCH if X86_64
160 select HAVE_MEMBLOCK_NODE_MAP
161 select HAVE_MIXED_BREAKPOINTS_REGS
164 select HAVE_OPTPROBES
165 select HAVE_PCSPKR_PLATFORM
166 select HAVE_PERF_EVENTS
167 select HAVE_PERF_EVENTS_NMI
168 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
169 select HAVE_PERF_REGS
170 select HAVE_PERF_USER_STACK_DUMP
171 select HAVE_REGS_AND_STACK_ACCESS_API
172 select HAVE_RELIABLE_STACKTRACE if X86_64 && FRAME_POINTER && STACK_VALIDATION
173 select HAVE_STACK_VALIDATION if X86_64
174 select HAVE_SYSCALL_TRACEPOINTS
175 select HAVE_UNSTABLE_SCHED_CLOCK
176 select HAVE_USER_RETURN_NOTIFIER
177 select IRQ_FORCED_THREADING
178 select PCI_LOCKLESS_CONFIG
181 select RTC_MC146818_LIB
184 select SYSCTL_EXCEPTION_TRACE
185 select THREAD_INFO_IN_TASK
186 select USER_STACKTRACE_SUPPORT
188 select X86_FEATURE_NAMES if PROC_FS
190 config INSTRUCTION_DECODER
192 depends on KPROBES || PERF_EVENTS || UPROBES
196 default "elf32-i386" if X86_32
197 default "elf64-x86-64" if X86_64
199 config ARCH_DEFCONFIG
201 default "arch/x86/configs/i386_defconfig" if X86_32
202 default "arch/x86/configs/x86_64_defconfig" if X86_64
204 config LOCKDEP_SUPPORT
207 config STACKTRACE_SUPPORT
213 config ARCH_MMAP_RND_BITS_MIN
217 config ARCH_MMAP_RND_BITS_MAX
221 config ARCH_MMAP_RND_COMPAT_BITS_MIN
224 config ARCH_MMAP_RND_COMPAT_BITS_MAX
230 config NEED_DMA_MAP_STATE
232 depends on X86_64 || INTEL_IOMMU || DMA_API_DEBUG || SWIOTLB
234 config NEED_SG_DMA_LENGTH
237 config GENERIC_ISA_DMA
239 depends on ISA_DMA_API
244 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
246 config GENERIC_BUG_RELATIVE_POINTERS
249 config GENERIC_HWEIGHT
252 config ARCH_MAY_HAVE_PC_FDC
254 depends on ISA_DMA_API
256 config RWSEM_XCHGADD_ALGORITHM
259 config GENERIC_CALIBRATE_DELAY
262 config ARCH_HAS_CPU_RELAX
265 config ARCH_HAS_CACHE_LINE_SIZE
268 config HAVE_SETUP_PER_CPU_AREA
271 config NEED_PER_CPU_EMBED_FIRST_CHUNK
274 config NEED_PER_CPU_PAGE_FIRST_CHUNK
277 config ARCH_HIBERNATION_POSSIBLE
280 config ARCH_SUSPEND_POSSIBLE
283 config ARCH_WANT_HUGE_PMD_SHARE
286 config ARCH_WANT_GENERAL_HUGETLB
295 config ARCH_SUPPORTS_OPTIMIZED_INLINING
298 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
301 config KASAN_SHADOW_OFFSET
304 default 0xdff8000000000000 if X86_5LEVEL
305 default 0xdffffc0000000000
307 config HAVE_INTEL_TXT
309 depends on INTEL_IOMMU && ACPI
313 depends on X86_32 && SMP
317 depends on X86_64 && SMP
319 config X86_32_LAZY_GS
321 depends on X86_32 && !CC_STACKPROTECTOR
323 config ARCH_SUPPORTS_UPROBES
326 config FIX_EARLYCON_MEM
329 config PGTABLE_LEVELS
335 source "init/Kconfig"
336 source "kernel/Kconfig.freezer"
338 menu "Processor type and features"
341 bool "DMA memory allocation support" if EXPERT
344 DMA memory allocation support allows devices with less than 32-bit
345 addressing to allocate within the first 16MB of address space.
346 Disable if no such devices will be used.
351 bool "Symmetric multi-processing support"
353 This enables support for systems with more than one CPU. If you have
354 a system with only one CPU, say N. If you have a system with more
357 If you say N here, the kernel will run on uni- and multiprocessor
358 machines, but will use only one CPU of a multiprocessor machine. If
359 you say Y here, the kernel will run on many, but not all,
360 uniprocessor machines. On a uniprocessor machine, the kernel
361 will run faster if you say N here.
363 Note that if you say Y here and choose architecture "586" or
364 "Pentium" under "Processor family", the kernel will not work on 486
365 architectures. Similarly, multiprocessor kernels for the "PPro"
366 architecture may not work on all Pentium based boards.
368 People using multiprocessor machines who say Y here should also say
369 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
370 Management" code will be disabled if you say Y here.
372 See also <file:Documentation/x86/i386/IO-APIC.txt>,
373 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
374 <http://www.tldp.org/docs.html#howto>.
376 If you don't know what to do here, say N.
378 config X86_FEATURE_NAMES
379 bool "Processor feature human-readable names" if EMBEDDED
382 This option compiles in a table of x86 feature bits and corresponding
383 names. This is required to support /proc/cpuinfo and a few kernel
384 messages. You can disable this to save space, at the expense of
385 making those few kernel messages show numeric feature bits instead.
389 config X86_FAST_FEATURE_TESTS
390 bool "Fast CPU feature tests" if EMBEDDED
393 Some fast-paths in the kernel depend on the capabilities of the CPU.
394 Say Y here for the kernel to patch in the appropriate code at runtime
395 based on the capabilities of the CPU. The infrastructure for patching
396 code at runtime takes up some additional space; space-constrained
397 embedded systems may wish to say N here to produce smaller, slightly
401 bool "Support x2apic"
402 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
404 This enables x2apic support on CPUs that have this feature.
406 This allows 32-bit apic IDs (so it can support very large systems),
407 and accesses the local apic via MSRs not via mmio.
409 If you don't know what to do here, say N.
412 bool "Enable MPS table" if ACPI || SFI
414 depends on X86_LOCAL_APIC
416 For old smp systems that do not have proper acpi support. Newer systems
417 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
420 bool "Support for big SMP systems with more than 8 CPUs"
421 depends on X86_32 && SMP
423 This option is needed for the systems that have more than 8 CPUs
427 depends on X86_GOLDFISH
430 bool "Intel Resource Director Technology Allocation support"
432 depends on X86 && CPU_SUP_INTEL
435 Select to enable resource allocation which is a sub-feature of
436 Intel Resource Director Technology(RDT). More information about
437 RDT can be found in the Intel x86 Architecture Software
443 config X86_EXTENDED_PLATFORM
444 bool "Support for extended (non-PC) x86 platforms"
447 If you disable this option then the kernel will only support
448 standard PC platforms. (which covers the vast majority of
451 If you enable this option then you'll be able to select support
452 for the following (non-PC) 32 bit x86 platforms:
453 Goldfish (Android emulator)
456 SGI 320/540 (Visual Workstation)
457 STA2X11-based (e.g. Northville)
458 Moorestown MID devices
460 If you have one of these systems, or if you want to build a
461 generic distribution kernel, say Y here - otherwise say N.
465 config X86_EXTENDED_PLATFORM
466 bool "Support for extended (non-PC) x86 platforms"
469 If you disable this option then the kernel will only support
470 standard PC platforms. (which covers the vast majority of
473 If you enable this option then you'll be able to select support
474 for the following (non-PC) 64 bit x86 platforms:
479 If you have one of these systems, or if you want to build a
480 generic distribution kernel, say Y here - otherwise say N.
482 # This is an alphabetically sorted list of 64 bit extended platforms
483 # Please maintain the alphabetic order if and when there are additions
485 bool "Numascale NumaChip"
487 depends on X86_EXTENDED_PLATFORM
490 depends on X86_X2APIC
491 depends on PCI_MMCONFIG
493 Adds support for Numascale NumaChip large-SMP systems. Needed to
494 enable more than ~168 cores.
495 If you don't have one of these, you should say N here.
499 select HYPERVISOR_GUEST
501 depends on X86_64 && PCI
502 depends on X86_EXTENDED_PLATFORM
505 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
506 supposed to run on these EM64T-based machines. Only choose this option
507 if you have one of these machines.
510 bool "SGI Ultraviolet"
512 depends on X86_EXTENDED_PLATFORM
515 depends on X86_X2APIC
518 This option is needed in order to support SGI Ultraviolet systems.
519 If you don't have one of these, you should say N here.
521 # Following is an alphabetically sorted list of 32 bit extended platforms
522 # Please maintain the alphabetic order if and when there are additions
525 bool "Goldfish (Virtual Platform)"
526 depends on X86_EXTENDED_PLATFORM
528 Enable support for the Goldfish virtual platform used primarily
529 for Android development. Unless you are building for the Android
530 Goldfish emulator say N here.
533 bool "CE4100 TV platform"
535 depends on PCI_GODIRECT
536 depends on X86_IO_APIC
538 depends on X86_EXTENDED_PLATFORM
539 select X86_REBOOTFIXUPS
541 select OF_EARLY_FLATTREE
543 Select for the Intel CE media processor (CE4100) SOC.
544 This option compiles in support for the CE4100 SOC for settop
545 boxes and media devices.
548 bool "Intel MID platform support"
549 depends on X86_EXTENDED_PLATFORM
550 depends on X86_PLATFORM_DEVICES
552 depends on X86_64 || (PCI_GOANY && X86_32)
553 depends on X86_IO_APIC
559 select MFD_INTEL_MSIC
561 Select to build a kernel capable of supporting Intel MID (Mobile
562 Internet Device) platform systems which do not have the PCI legacy
563 interfaces. If you are building for a PC class system say N here.
565 Intel MID platforms are based on an Intel processor and chipset which
566 consume less power than most of the x86 derivatives.
568 config X86_INTEL_QUARK
569 bool "Intel Quark platform support"
571 depends on X86_EXTENDED_PLATFORM
572 depends on X86_PLATFORM_DEVICES
576 depends on X86_IO_APIC
581 Select to include support for Quark X1000 SoC.
582 Say Y here if you have a Quark based system such as the Arduino
583 compatible Intel Galileo.
585 config X86_INTEL_LPSS
586 bool "Intel Low Power Subsystem Support"
587 depends on X86 && ACPI
592 Select to build support for Intel Low Power Subsystem such as
593 found on Intel Lynxpoint PCH. Selecting this option enables
594 things like clock tree (common clock framework) and pincontrol
595 which are needed by the LPSS peripheral drivers.
597 config X86_AMD_PLATFORM_DEVICE
598 bool "AMD ACPI2Platform devices support"
603 Select to interpret AMD specific ACPI device to platform device
604 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
605 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
606 implemented under PINCTRL subsystem.
609 tristate "Intel SoC IOSF Sideband support for SoC platforms"
612 This option enables sideband register access support for Intel SoC
613 platforms. On these platforms the IOSF sideband is used in lieu of
614 MSR's for some register accesses, mostly but not limited to thermal
615 and power. Drivers may query the availability of this device to
616 determine if they need the sideband in order to work on these
617 platforms. The sideband is available on the following SoC products.
618 This list is not meant to be exclusive.
623 You should say Y if you are running a kernel on one of these SoC's.
625 config IOSF_MBI_DEBUG
626 bool "Enable IOSF sideband access through debugfs"
627 depends on IOSF_MBI && DEBUG_FS
629 Select this option to expose the IOSF sideband access registers (MCR,
630 MDR, MCRX) through debugfs to write and read register information from
631 different units on the SoC. This is most useful for obtaining device
632 state information for debug and analysis. As this is a general access
633 mechanism, users of this option would have specific knowledge of the
634 device they want to access.
636 If you don't require the option or are in doubt, say N.
639 bool "RDC R-321x SoC"
641 depends on X86_EXTENDED_PLATFORM
643 select X86_REBOOTFIXUPS
645 This option is needed for RDC R-321x system-on-chip, also known
647 If you don't have one of these chips, you should say N here.
649 config X86_32_NON_STANDARD
650 bool "Support non-standard 32-bit SMP architectures"
651 depends on X86_32 && SMP
652 depends on X86_EXTENDED_PLATFORM
654 This option compiles in the bigsmp and STA2X11 default
655 subarchitectures. It is intended for a generic binary
656 kernel. If you select them all, kernel will probe it one by
657 one and will fallback to default.
659 # Alphabetically sorted list of Non standard 32 bit platforms
661 config X86_SUPPORTS_MEMORY_FAILURE
663 # MCE code calls memory_failure():
665 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
666 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
667 depends on X86_64 || !SPARSEMEM
668 select ARCH_SUPPORTS_MEMORY_FAILURE
671 bool "STA2X11 Companion Chip Support"
672 depends on X86_32_NON_STANDARD && PCI
673 select X86_DEV_DMA_OPS
680 This adds support for boards based on the STA2X11 IO-Hub,
681 a.k.a. "ConneXt". The chip is used in place of the standard
682 PC chipset, so all "standard" peripherals are missing. If this
683 option is selected the kernel will still be able to boot on
684 standard PC machines.
687 tristate "Eurobraille/Iris poweroff module"
690 The Iris machines from EuroBraille do not have APM or ACPI support
691 to shut themselves down properly. A special I/O sequence is
692 needed to do so, which is what this module does at
695 This is only for Iris machines from EuroBraille.
699 config SCHED_OMIT_FRAME_POINTER
701 prompt "Single-depth WCHAN output"
704 Calculate simpler /proc/<PID>/wchan values. If this option
705 is disabled then wchan values will recurse back to the
706 caller function. This provides more accurate wchan values,
707 at the expense of slightly more scheduling overhead.
709 If in doubt, say "Y".
711 menuconfig HYPERVISOR_GUEST
712 bool "Linux guest support"
714 Say Y here to enable options for running Linux under various hyper-
715 visors. This option enables basic hypervisor detection and platform
718 If you say N, all options in this submenu will be skipped and
719 disabled, and Linux guest support won't be built in.
724 bool "Enable paravirtualization code"
726 This changes the kernel so it can modify itself when it is run
727 under a hypervisor, potentially improving performance significantly
728 over full virtualization. However, when run without a hypervisor
729 the kernel is theoretically slower and slightly larger.
731 config PARAVIRT_DEBUG
732 bool "paravirt-ops debugging"
733 depends on PARAVIRT && DEBUG_KERNEL
735 Enable to debug paravirt_ops internals. Specifically, BUG if
736 a paravirt_op is missing when it is called.
738 config PARAVIRT_SPINLOCKS
739 bool "Paravirtualization layer for spinlocks"
740 depends on PARAVIRT && SMP
742 Paravirtualized spinlocks allow a pvops backend to replace the
743 spinlock implementation with something virtualization-friendly
744 (for example, block the virtual CPU rather than spinning).
746 It has a minimal impact on native kernels and gives a nice performance
747 benefit on paravirtualized KVM / Xen kernels.
749 If you are unsure how to answer this question, answer Y.
751 config QUEUED_LOCK_STAT
752 bool "Paravirt queued spinlock statistics"
753 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
755 Enable the collection of statistical data on the slowpath
756 behavior of paravirtualized queued spinlocks and report
759 source "arch/x86/xen/Kconfig"
762 bool "KVM Guest support (including kvmclock)"
764 select PARAVIRT_CLOCK
767 This option enables various optimizations for running under the KVM
768 hypervisor. It includes a paravirtualized clock, so that instead
769 of relying on a PIT (or probably other) emulation by the
770 underlying device model, the host provides the guest with
771 timing infrastructure such as time of day, and system time
774 bool "Enable debug information for KVM Guests in debugfs"
775 depends on KVM_GUEST && DEBUG_FS
778 This option enables collection of various statistics for KVM guest.
779 Statistics are displayed in debugfs filesystem. Enabling this option
780 may incur significant overhead.
782 source "arch/x86/lguest/Kconfig"
784 config PARAVIRT_TIME_ACCOUNTING
785 bool "Paravirtual steal time accounting"
789 Select this option to enable fine granularity task steal time
790 accounting. Time spent executing other tasks in parallel with
791 the current vCPU is discounted from the vCPU power. To account for
792 that, there can be a small performance impact.
794 If in doubt, say N here.
796 config PARAVIRT_CLOCK
799 endif #HYPERVISOR_GUEST
804 source "arch/x86/Kconfig.cpu"
808 prompt "HPET Timer Support" if X86_32
810 Use the IA-PC HPET (High Precision Event Timer) to manage
811 time in preference to the PIT and RTC, if a HPET is
813 HPET is the next generation timer replacing legacy 8254s.
814 The HPET provides a stable time base on SMP
815 systems, unlike the TSC, but it is more expensive to access,
816 as it is off-chip. The interface used is documented
817 in the HPET spec, revision 1.
819 You can safely choose Y here. However, HPET will only be
820 activated if the platform and the BIOS support this feature.
821 Otherwise the 8254 will be used for timing services.
823 Choose N to continue using the legacy 8254 timer.
825 config HPET_EMULATE_RTC
827 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
830 def_bool y if X86_INTEL_MID
831 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
833 depends on X86_INTEL_MID && SFI
835 APB timer is the replacement for 8254, HPET on X86 MID platforms.
836 The APBT provides a stable time base on SMP
837 systems, unlike the TSC, but it is more expensive to access,
838 as it is off-chip. APB timers are always running regardless of CPU
839 C states, they are used as per CPU clockevent device when possible.
841 # Mark as expert because too many people got it wrong.
842 # The code disables itself when not needed.
845 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
846 bool "Enable DMI scanning" if EXPERT
848 Enabled scanning of DMI to identify machine quirks. Say Y
849 here unless you have verified that your setup is not
850 affected by entries in the DMI blacklist. Required by PNP
854 bool "Old AMD GART IOMMU support"
856 depends on X86_64 && PCI && AMD_NB
858 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
859 GART based hardware IOMMUs.
861 The GART supports full DMA access for devices with 32-bit access
862 limitations, on systems with more than 3 GB. This is usually needed
863 for USB, sound, many IDE/SATA chipsets and some other devices.
865 Newer systems typically have a modern AMD IOMMU, supported via
866 the CONFIG_AMD_IOMMU=y config option.
868 In normal configurations this driver is only active when needed:
869 there's more than 3 GB of memory and the system contains a
870 32-bit limited device.
875 bool "IBM Calgary IOMMU support"
877 depends on X86_64 && PCI
879 Support for hardware IOMMUs in IBM's xSeries x366 and x460
880 systems. Needed to run systems with more than 3GB of memory
881 properly with 32-bit PCI devices that do not support DAC
882 (Double Address Cycle). Calgary also supports bus level
883 isolation, where all DMAs pass through the IOMMU. This
884 prevents them from going anywhere except their intended
885 destination. This catches hard-to-find kernel bugs and
886 mis-behaving drivers and devices that do not use the DMA-API
887 properly to set up their DMA buffers. The IOMMU can be
888 turned off at boot time with the iommu=off parameter.
889 Normally the kernel will make the right choice by itself.
892 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
894 prompt "Should Calgary be enabled by default?"
895 depends on CALGARY_IOMMU
897 Should Calgary be enabled by default? if you choose 'y', Calgary
898 will be used (if it exists). If you choose 'n', Calgary will not be
899 used even if it exists. If you choose 'n' and would like to use
900 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
903 # need this always selected by IOMMU for the VIA workaround
907 Support for software bounce buffers used on x86-64 systems
908 which don't have a hardware IOMMU. Using this PCI devices
909 which can only access 32-bits of memory can be used on systems
910 with more than 3 GB of memory.
915 depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU
918 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
919 depends on X86_64 && SMP && DEBUG_KERNEL
920 select CPUMASK_OFFSTACK
922 Enable maximum number of CPUS and NUMA Nodes for this architecture.
926 int "Maximum number of CPUs" if SMP && !MAXSMP
927 range 2 8 if SMP && X86_32 && !X86_BIGSMP
928 range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK
929 range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
931 default "8192" if MAXSMP
932 default "32" if SMP && X86_BIGSMP
933 default "8" if SMP && X86_32
936 This allows you to specify the maximum number of CPUs which this
937 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
938 supported value is 8192, otherwise the maximum value is 512. The
939 minimum value which makes sense is 2.
941 This is purely to save memory - each supported CPU adds
942 approximately eight kilobytes to the kernel image.
945 bool "SMT (Hyperthreading) scheduler support"
948 SMT scheduler support improves the CPU scheduler's decision making
949 when dealing with Intel Pentium 4 chips with HyperThreading at a
950 cost of slightly increased overhead in some places. If unsure say
955 prompt "Multi-core scheduler support"
958 Multi-core scheduler support improves the CPU scheduler's decision
959 making when dealing with multi-core CPU chips at a cost of slightly
960 increased overhead in some places. If unsure say N here.
963 bool "CPU core priorities scheduler support"
964 depends on SCHED_MC && CPU_SUP_INTEL
965 select X86_INTEL_PSTATE
969 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
970 core ordering determined at manufacturing time, which allows
971 certain cores to reach higher turbo frequencies (when running
972 single threaded workloads) than others.
974 Enabling this kernel feature teaches the scheduler about
975 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
976 scheduler's CPU selection logic accordingly, so that higher
977 overall system performance can be achieved.
979 This feature will have no effect on CPUs without this feature.
981 If unsure say Y here.
983 source "kernel/Kconfig.preempt"
987 depends on !SMP && X86_LOCAL_APIC
990 bool "Local APIC support on uniprocessors" if !PCI_MSI
992 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
994 A local APIC (Advanced Programmable Interrupt Controller) is an
995 integrated interrupt controller in the CPU. If you have a single-CPU
996 system which has a processor with a local APIC, you can say Y here to
997 enable and use it. If you say Y here even though your machine doesn't
998 have a local APIC, then the kernel will still run with no slowdown at
999 all. The local APIC supports CPU-generated self-interrupts (timer,
1000 performance counters), and the NMI watchdog which detects hard
1003 config X86_UP_IOAPIC
1004 bool "IO-APIC support on uniprocessors"
1005 depends on X86_UP_APIC
1007 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1008 SMP-capable replacement for PC-style interrupt controllers. Most
1009 SMP systems and many recent uniprocessor systems have one.
1011 If you have a single-CPU system with an IO-APIC, you can say Y here
1012 to use it. If you say Y here even though your machine doesn't have
1013 an IO-APIC, then the kernel will still run with no slowdown at all.
1015 config X86_LOCAL_APIC
1017 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1018 select IRQ_DOMAIN_HIERARCHY
1019 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1023 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1025 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1026 bool "Reroute for broken boot IRQs"
1027 depends on X86_IO_APIC
1029 This option enables a workaround that fixes a source of
1030 spurious interrupts. This is recommended when threaded
1031 interrupt handling is used on systems where the generation of
1032 superfluous "boot interrupts" cannot be disabled.
1034 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1035 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1036 kernel does during interrupt handling). On chipsets where this
1037 boot IRQ generation cannot be disabled, this workaround keeps
1038 the original IRQ line masked so that only the equivalent "boot
1039 IRQ" is delivered to the CPUs. The workaround also tells the
1040 kernel to set up the IRQ handler on the boot IRQ line. In this
1041 way only one interrupt is delivered to the kernel. Otherwise
1042 the spurious second interrupt may cause the kernel to bring
1043 down (vital) interrupt lines.
1045 Only affects "broken" chipsets. Interrupt sharing may be
1046 increased on these systems.
1049 bool "Machine Check / overheating reporting"
1050 select GENERIC_ALLOCATOR
1053 Machine Check support allows the processor to notify the
1054 kernel if it detects a problem (e.g. overheating, data corruption).
1055 The action the kernel takes depends on the severity of the problem,
1056 ranging from warning messages to halting the machine.
1058 config X86_MCELOG_LEGACY
1059 bool "Support for deprecated /dev/mcelog character device"
1062 Enable support for /dev/mcelog which is needed by the old mcelog
1063 userspace logging daemon. Consider switching to the new generation
1066 config X86_MCE_INTEL
1068 prompt "Intel MCE features"
1069 depends on X86_MCE && X86_LOCAL_APIC
1071 Additional support for intel specific MCE features such as
1072 the thermal monitor.
1076 prompt "AMD MCE features"
1077 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1079 Additional support for AMD specific MCE features such as
1080 the DRAM Error Threshold.
1082 config X86_ANCIENT_MCE
1083 bool "Support for old Pentium 5 / WinChip machine checks"
1084 depends on X86_32 && X86_MCE
1086 Include support for machine check handling on old Pentium 5 or WinChip
1087 systems. These typically need to be enabled explicitly on the command
1090 config X86_MCE_THRESHOLD
1091 depends on X86_MCE_AMD || X86_MCE_INTEL
1094 config X86_MCE_INJECT
1095 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1096 tristate "Machine check injector support"
1098 Provide support for injecting machine checks for testing purposes.
1099 If you don't know what a machine check is and you don't do kernel
1100 QA it is safe to say n.
1102 config X86_THERMAL_VECTOR
1104 depends on X86_MCE_INTEL
1106 source "arch/x86/events/Kconfig"
1108 config X86_LEGACY_VM86
1109 bool "Legacy VM86 support"
1113 This option allows user programs to put the CPU into V8086
1114 mode, which is an 80286-era approximation of 16-bit real mode.
1116 Some very old versions of X and/or vbetool require this option
1117 for user mode setting. Similarly, DOSEMU will use it if
1118 available to accelerate real mode DOS programs. However, any
1119 recent version of DOSEMU, X, or vbetool should be fully
1120 functional even without kernel VM86 support, as they will all
1121 fall back to software emulation. Nevertheless, if you are using
1122 a 16-bit DOS program where 16-bit performance matters, vm86
1123 mode might be faster than emulation and you might want to
1126 Note that any app that works on a 64-bit kernel is unlikely to
1127 need this option, as 64-bit kernels don't, and can't, support
1128 V8086 mode. This option is also unrelated to 16-bit protected
1129 mode and is not needed to run most 16-bit programs under Wine.
1131 Enabling this option increases the complexity of the kernel
1132 and slows down exception handling a tiny bit.
1134 If unsure, say N here.
1138 default X86_LEGACY_VM86
1141 bool "Enable support for 16-bit segments" if EXPERT
1143 depends on MODIFY_LDT_SYSCALL
1145 This option is required by programs like Wine to run 16-bit
1146 protected mode legacy code on x86 processors. Disabling
1147 this option saves about 300 bytes on i386, or around 6K text
1148 plus 16K runtime memory on x86-64,
1152 depends on X86_16BIT && X86_32
1156 depends on X86_16BIT && X86_64
1158 config X86_VSYSCALL_EMULATION
1159 bool "Enable vsyscall emulation" if EXPERT
1163 This enables emulation of the legacy vsyscall page. Disabling
1164 it is roughly equivalent to booting with vsyscall=none, except
1165 that it will also disable the helpful warning if a program
1166 tries to use a vsyscall. With this option set to N, offending
1167 programs will just segfault, citing addresses of the form
1170 This option is required by many programs built before 2013, and
1171 care should be used even with newer programs if set to N.
1173 Disabling this option saves about 7K of kernel size and
1174 possibly 4K of additional runtime pagetable memory.
1177 tristate "Toshiba Laptop support"
1180 This adds a driver to safely access the System Management Mode of
1181 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1182 not work on models with a Phoenix BIOS. The System Management Mode
1183 is used to set the BIOS and power saving options on Toshiba portables.
1185 For information on utilities to make use of this driver see the
1186 Toshiba Linux utilities web site at:
1187 <http://www.buzzard.org.uk/toshiba/>.
1189 Say Y if you intend to run this kernel on a Toshiba portable.
1193 tristate "Dell i8k legacy laptop support"
1195 select SENSORS_DELL_SMM
1197 This option enables legacy /proc/i8k userspace interface in hwmon
1198 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1199 temperature and allows controlling fan speeds of Dell laptops via
1200 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1201 it reports also power and hotkey status. For fan speed control is
1202 needed userspace package i8kutils.
1204 Say Y if you intend to run this kernel on old Dell laptops or want to
1205 use userspace package i8kutils.
1208 config X86_REBOOTFIXUPS
1209 bool "Enable X86 board specific fixups for reboot"
1212 This enables chipset and/or board specific fixups to be done
1213 in order to get reboot to work correctly. This is only needed on
1214 some combinations of hardware and BIOS. The symptom, for which
1215 this config is intended, is when reboot ends with a stalled/hung
1218 Currently, the only fixup is for the Geode machines using
1219 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1221 Say Y if you want to enable the fixup. Currently, it's safe to
1222 enable this option even if you don't need it.
1226 bool "CPU microcode loading support"
1228 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1231 If you say Y here, you will be able to update the microcode on
1232 Intel and AMD processors. The Intel support is for the IA32 family,
1233 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1234 AMD support is for families 0x10 and later. You will obviously need
1235 the actual microcode binary data itself which is not shipped with
1238 The preferred method to load microcode from a detached initrd is described
1239 in Documentation/x86/early-microcode.txt. For that you need to enable
1240 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1241 initrd for microcode blobs.
1243 In addition, you can build-in the microcode into the kernel. For that you
1244 need to enable FIRMWARE_IN_KERNEL and add the vendor-supplied microcode
1245 to the CONFIG_EXTRA_FIRMWARE config option.
1247 config MICROCODE_INTEL
1248 bool "Intel microcode loading support"
1249 depends on MICROCODE
1253 This options enables microcode patch loading support for Intel
1256 For the current Intel microcode data package go to
1257 <https://downloadcenter.intel.com> and search for
1258 'Linux Processor Microcode Data File'.
1260 config MICROCODE_AMD
1261 bool "AMD microcode loading support"
1262 depends on MICROCODE
1265 If you select this option, microcode patch loading support for AMD
1266 processors will be enabled.
1268 config MICROCODE_OLD_INTERFACE
1270 depends on MICROCODE
1273 tristate "/dev/cpu/*/msr - Model-specific register support"
1275 This device gives privileged processes access to the x86
1276 Model-Specific Registers (MSRs). It is a character device with
1277 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1278 MSR accesses are directed to a specific CPU on multi-processor
1282 tristate "/dev/cpu/*/cpuid - CPU information support"
1284 This device gives processes access to the x86 CPUID instruction to
1285 be executed on a specific processor. It is a character device
1286 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1290 prompt "High Memory Support"
1297 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1298 However, the address space of 32-bit x86 processors is only 4
1299 Gigabytes large. That means that, if you have a large amount of
1300 physical memory, not all of it can be "permanently mapped" by the
1301 kernel. The physical memory that's not permanently mapped is called
1304 If you are compiling a kernel which will never run on a machine with
1305 more than 1 Gigabyte total physical RAM, answer "off" here (default
1306 choice and suitable for most users). This will result in a "3GB/1GB"
1307 split: 3GB are mapped so that each process sees a 3GB virtual memory
1308 space and the remaining part of the 4GB virtual memory space is used
1309 by the kernel to permanently map as much physical memory as
1312 If the machine has between 1 and 4 Gigabytes physical RAM, then
1315 If more than 4 Gigabytes is used then answer "64GB" here. This
1316 selection turns Intel PAE (Physical Address Extension) mode on.
1317 PAE implements 3-level paging on IA32 processors. PAE is fully
1318 supported by Linux, PAE mode is implemented on all recent Intel
1319 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1320 then the kernel will not boot on CPUs that don't support PAE!
1322 The actual amount of total physical memory will either be
1323 auto detected or can be forced by using a kernel command line option
1324 such as "mem=256M". (Try "man bootparam" or see the documentation of
1325 your boot loader (lilo or loadlin) about how to pass options to the
1326 kernel at boot time.)
1328 If unsure, say "off".
1333 Select this if you have a 32-bit processor and between 1 and 4
1334 gigabytes of physical RAM.
1341 Select this if you have a 32-bit processor and more than 4
1342 gigabytes of physical RAM.
1347 prompt "Memory split" if EXPERT
1351 Select the desired split between kernel and user memory.
1353 If the address range available to the kernel is less than the
1354 physical memory installed, the remaining memory will be available
1355 as "high memory". Accessing high memory is a little more costly
1356 than low memory, as it needs to be mapped into the kernel first.
1357 Note that increasing the kernel address space limits the range
1358 available to user programs, making the address space there
1359 tighter. Selecting anything other than the default 3G/1G split
1360 will also likely make your kernel incompatible with binary-only
1363 If you are not absolutely sure what you are doing, leave this
1367 bool "3G/1G user/kernel split"
1368 config VMSPLIT_3G_OPT
1370 bool "3G/1G user/kernel split (for full 1G low memory)"
1372 bool "2G/2G user/kernel split"
1373 config VMSPLIT_2G_OPT
1375 bool "2G/2G user/kernel split (for full 2G low memory)"
1377 bool "1G/3G user/kernel split"
1382 default 0xB0000000 if VMSPLIT_3G_OPT
1383 default 0x80000000 if VMSPLIT_2G
1384 default 0x78000000 if VMSPLIT_2G_OPT
1385 default 0x40000000 if VMSPLIT_1G
1391 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1394 bool "PAE (Physical Address Extension) Support"
1395 depends on X86_32 && !HIGHMEM4G
1398 PAE is required for NX support, and furthermore enables
1399 larger swapspace support for non-overcommit purposes. It
1400 has the cost of more pagetable lookup overhead, and also
1401 consumes more pagetable space per process.
1403 config ARCH_PHYS_ADDR_T_64BIT
1405 depends on X86_64 || X86_PAE
1407 config ARCH_DMA_ADDR_T_64BIT
1409 depends on X86_64 || HIGHMEM64G
1411 config X86_DIRECT_GBPAGES
1413 depends on X86_64 && !DEBUG_PAGEALLOC && !KMEMCHECK
1415 Certain kernel features effectively disable kernel
1416 linear 1 GB mappings (even if the CPU otherwise
1417 supports them), so don't confuse the user by printing
1418 that we have them enabled.
1420 # Common NUMA Features
1422 bool "Numa Memory Allocation and Scheduler Support"
1424 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1425 default y if X86_BIGSMP
1427 Enable NUMA (Non Uniform Memory Access) support.
1429 The kernel will try to allocate memory used by a CPU on the
1430 local memory controller of the CPU and add some more
1431 NUMA awareness to the kernel.
1433 For 64-bit this is recommended if the system is Intel Core i7
1434 (or later), AMD Opteron, or EM64T NUMA.
1436 For 32-bit this is only needed if you boot a 32-bit
1437 kernel on a 64-bit NUMA platform.
1439 Otherwise, you should say N.
1443 prompt "Old style AMD Opteron NUMA detection"
1444 depends on X86_64 && NUMA && PCI
1446 Enable AMD NUMA node topology detection. You should say Y here if
1447 you have a multi processor AMD system. This uses an old method to
1448 read the NUMA configuration directly from the builtin Northbridge
1449 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1450 which also takes priority if both are compiled in.
1452 config X86_64_ACPI_NUMA
1454 prompt "ACPI NUMA detection"
1455 depends on X86_64 && NUMA && ACPI && PCI
1458 Enable ACPI SRAT based node topology detection.
1460 # Some NUMA nodes have memory ranges that span
1461 # other nodes. Even though a pfn is valid and
1462 # between a node's start and end pfns, it may not
1463 # reside on that node. See memmap_init_zone()
1465 config NODES_SPAN_OTHER_NODES
1467 depends on X86_64_ACPI_NUMA
1470 bool "NUMA emulation"
1473 Enable NUMA emulation. A flat machine will be split
1474 into virtual nodes when booted with "numa=fake=N", where N is the
1475 number of nodes. This is only useful for debugging.
1478 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1480 default "10" if MAXSMP
1481 default "6" if X86_64
1483 depends on NEED_MULTIPLE_NODES
1485 Specify the maximum number of NUMA Nodes available on the target
1486 system. Increases memory reserved to accommodate various tables.
1488 config ARCH_HAVE_MEMORY_PRESENT
1490 depends on X86_32 && DISCONTIGMEM
1492 config NEED_NODE_MEMMAP_SIZE
1494 depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
1496 config ARCH_FLATMEM_ENABLE
1498 depends on X86_32 && !NUMA
1500 config ARCH_DISCONTIGMEM_ENABLE
1502 depends on NUMA && X86_32
1504 config ARCH_DISCONTIGMEM_DEFAULT
1506 depends on NUMA && X86_32
1508 config ARCH_SPARSEMEM_ENABLE
1510 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1511 select SPARSEMEM_STATIC if X86_32
1512 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1514 config ARCH_SPARSEMEM_DEFAULT
1518 config ARCH_SELECT_MEMORY_MODEL
1520 depends on ARCH_SPARSEMEM_ENABLE
1522 config ARCH_MEMORY_PROBE
1523 bool "Enable sysfs memory/probe interface"
1524 depends on X86_64 && MEMORY_HOTPLUG
1526 This option enables a sysfs memory/probe interface for testing.
1527 See Documentation/memory-hotplug.txt for more information.
1528 If you are unsure how to answer this question, answer N.
1530 config ARCH_PROC_KCORE_TEXT
1532 depends on X86_64 && PROC_KCORE
1534 config ILLEGAL_POINTER_VALUE
1537 default 0xdead000000000000 if X86_64
1541 config X86_PMEM_LEGACY_DEVICE
1544 config X86_PMEM_LEGACY
1545 tristate "Support non-standard NVDIMMs and ADR protected memory"
1546 depends on PHYS_ADDR_T_64BIT
1548 select X86_PMEM_LEGACY_DEVICE
1551 Treat memory marked using the non-standard e820 type of 12 as used
1552 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1553 The kernel will offer these regions to the 'pmem' driver so
1554 they can be used for persistent storage.
1559 bool "Allocate 3rd-level pagetables from highmem"
1562 The VM uses one page table entry for each page of physical memory.
1563 For systems with a lot of RAM, this can be wasteful of precious
1564 low memory. Setting this option will put user-space page table
1565 entries in high memory.
1567 config X86_CHECK_BIOS_CORRUPTION
1568 bool "Check for low memory corruption"
1570 Periodically check for memory corruption in low memory, which
1571 is suspected to be caused by BIOS. Even when enabled in the
1572 configuration, it is disabled at runtime. Enable it by
1573 setting "memory_corruption_check=1" on the kernel command
1574 line. By default it scans the low 64k of memory every 60
1575 seconds; see the memory_corruption_check_size and
1576 memory_corruption_check_period parameters in
1577 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1579 When enabled with the default parameters, this option has
1580 almost no overhead, as it reserves a relatively small amount
1581 of memory and scans it infrequently. It both detects corruption
1582 and prevents it from affecting the running system.
1584 It is, however, intended as a diagnostic tool; if repeatable
1585 BIOS-originated corruption always affects the same memory,
1586 you can use memmap= to prevent the kernel from using that
1589 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1590 bool "Set the default setting of memory_corruption_check"
1591 depends on X86_CHECK_BIOS_CORRUPTION
1594 Set whether the default state of memory_corruption_check is
1597 config X86_RESERVE_LOW
1598 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1602 Specify the amount of low memory to reserve for the BIOS.
1604 The first page contains BIOS data structures that the kernel
1605 must not use, so that page must always be reserved.
1607 By default we reserve the first 64K of physical RAM, as a
1608 number of BIOSes are known to corrupt that memory range
1609 during events such as suspend/resume or monitor cable
1610 insertion, so it must not be used by the kernel.
1612 You can set this to 4 if you are absolutely sure that you
1613 trust the BIOS to get all its memory reservations and usages
1614 right. If you know your BIOS have problems beyond the
1615 default 64K area, you can set this to 640 to avoid using the
1616 entire low memory range.
1618 If you have doubts about the BIOS (e.g. suspend/resume does
1619 not work or there's kernel crashes after certain hardware
1620 hotplug events) then you might want to enable
1621 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1622 typical corruption patterns.
1624 Leave this to the default value of 64 if you are unsure.
1626 config MATH_EMULATION
1628 depends on MODIFY_LDT_SYSCALL
1629 prompt "Math emulation" if X86_32
1631 Linux can emulate a math coprocessor (used for floating point
1632 operations) if you don't have one. 486DX and Pentium processors have
1633 a math coprocessor built in, 486SX and 386 do not, unless you added
1634 a 487DX or 387, respectively. (The messages during boot time can
1635 give you some hints here ["man dmesg"].) Everyone needs either a
1636 coprocessor or this emulation.
1638 If you don't have a math coprocessor, you need to say Y here; if you
1639 say Y here even though you have a coprocessor, the coprocessor will
1640 be used nevertheless. (This behavior can be changed with the kernel
1641 command line option "no387", which comes handy if your coprocessor
1642 is broken. Try "man bootparam" or see the documentation of your boot
1643 loader (lilo or loadlin) about how to pass options to the kernel at
1644 boot time.) This means that it is a good idea to say Y here if you
1645 intend to use this kernel on different machines.
1647 More information about the internals of the Linux math coprocessor
1648 emulation can be found in <file:arch/x86/math-emu/README>.
1650 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1651 kernel, it won't hurt.
1655 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1657 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1658 the Memory Type Range Registers (MTRRs) may be used to control
1659 processor access to memory ranges. This is most useful if you have
1660 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1661 allows bus write transfers to be combined into a larger transfer
1662 before bursting over the PCI/AGP bus. This can increase performance
1663 of image write operations 2.5 times or more. Saying Y here creates a
1664 /proc/mtrr file which may be used to manipulate your processor's
1665 MTRRs. Typically the X server should use this.
1667 This code has a reasonably generic interface so that similar
1668 control registers on other processors can be easily supported
1671 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1672 Registers (ARRs) which provide a similar functionality to MTRRs. For
1673 these, the ARRs are used to emulate the MTRRs.
1674 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1675 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1676 write-combining. All of these processors are supported by this code
1677 and it makes sense to say Y here if you have one of them.
1679 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1680 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1681 can lead to all sorts of problems, so it's good to say Y here.
1683 You can safely say Y even if your machine doesn't have MTRRs, you'll
1684 just add about 9 KB to your kernel.
1686 See <file:Documentation/x86/mtrr.txt> for more information.
1688 config MTRR_SANITIZER
1690 prompt "MTRR cleanup support"
1693 Convert MTRR layout from continuous to discrete, so X drivers can
1694 add writeback entries.
1696 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1697 The largest mtrr entry size for a continuous block can be set with
1702 config MTRR_SANITIZER_ENABLE_DEFAULT
1703 int "MTRR cleanup enable value (0-1)"
1706 depends on MTRR_SANITIZER
1708 Enable mtrr cleanup default value
1710 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1711 int "MTRR cleanup spare reg num (0-7)"
1714 depends on MTRR_SANITIZER
1716 mtrr cleanup spare entries default, it can be changed via
1717 mtrr_spare_reg_nr=N on the kernel command line.
1721 prompt "x86 PAT support" if EXPERT
1724 Use PAT attributes to setup page level cache control.
1726 PATs are the modern equivalents of MTRRs and are much more
1727 flexible than MTRRs.
1729 Say N here if you see bootup problems (boot crash, boot hang,
1730 spontaneous reboots) or a non-working video driver.
1734 config ARCH_USES_PG_UNCACHED
1740 prompt "x86 architectural random number generator" if EXPERT
1742 Enable the x86 architectural RDRAND instruction
1743 (Intel Bull Mountain technology) to generate random numbers.
1744 If supported, this is a high bandwidth, cryptographically
1745 secure hardware random number generator.
1749 prompt "Supervisor Mode Access Prevention" if EXPERT
1751 Supervisor Mode Access Prevention (SMAP) is a security
1752 feature in newer Intel processors. There is a small
1753 performance cost if this enabled and turned on; there is
1754 also a small increase in the kernel size if this is enabled.
1758 config X86_INTEL_MPX
1759 prompt "Intel MPX (Memory Protection Extensions)"
1761 depends on CPU_SUP_INTEL
1763 MPX provides hardware features that can be used in
1764 conjunction with compiler-instrumented code to check
1765 memory references. It is designed to detect buffer
1766 overflow or underflow bugs.
1768 This option enables running applications which are
1769 instrumented or otherwise use MPX. It does not use MPX
1770 itself inside the kernel or to protect the kernel
1771 against bad memory references.
1773 Enabling this option will make the kernel larger:
1774 ~8k of kernel text and 36 bytes of data on a 64-bit
1775 defconfig. It adds a long to the 'mm_struct' which
1776 will increase the kernel memory overhead of each
1777 process and adds some branches to paths used during
1778 exec() and munmap().
1780 For details, see Documentation/x86/intel_mpx.txt
1784 config X86_INTEL_MEMORY_PROTECTION_KEYS
1785 prompt "Intel Memory Protection Keys"
1787 # Note: only available in 64-bit mode
1788 depends on CPU_SUP_INTEL && X86_64
1789 select ARCH_USES_HIGH_VMA_FLAGS
1790 select ARCH_HAS_PKEYS
1792 Memory Protection Keys provides a mechanism for enforcing
1793 page-based protections, but without requiring modification of the
1794 page tables when an application changes protection domains.
1796 For details, see Documentation/x86/protection-keys.txt
1801 bool "EFI runtime service support"
1804 select EFI_RUNTIME_WRAPPERS
1806 This enables the kernel to use EFI runtime services that are
1807 available (such as the EFI variable services).
1809 This option is only useful on systems that have EFI firmware.
1810 In addition, you should use the latest ELILO loader available
1811 at <http://elilo.sourceforge.net> in order to take advantage
1812 of EFI runtime services. However, even with this option, the
1813 resultant kernel should continue to boot on existing non-EFI
1817 bool "EFI stub support"
1818 depends on EFI && !X86_USE_3DNOW
1821 This kernel feature allows a bzImage to be loaded directly
1822 by EFI firmware without the use of a bootloader.
1824 See Documentation/efi-stub.txt for more information.
1827 bool "EFI mixed-mode support"
1828 depends on EFI_STUB && X86_64
1830 Enabling this feature allows a 64-bit kernel to be booted
1831 on a 32-bit firmware, provided that your CPU supports 64-bit
1834 Note that it is not possible to boot a mixed-mode enabled
1835 kernel via the EFI boot stub - a bootloader that supports
1836 the EFI handover protocol must be used.
1842 prompt "Enable seccomp to safely compute untrusted bytecode"
1844 This kernel feature is useful for number crunching applications
1845 that may need to compute untrusted bytecode during their
1846 execution. By using pipes or other transports made available to
1847 the process as file descriptors supporting the read/write
1848 syscalls, it's possible to isolate those applications in
1849 their own address space using seccomp. Once seccomp is
1850 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1851 and the task is only allowed to execute a few safe syscalls
1852 defined by each seccomp mode.
1854 If unsure, say Y. Only embedded should say N here.
1856 source kernel/Kconfig.hz
1859 bool "kexec system call"
1862 kexec is a system call that implements the ability to shutdown your
1863 current kernel, and to start another kernel. It is like a reboot
1864 but it is independent of the system firmware. And like a reboot
1865 you can start any kernel with it, not just Linux.
1867 The name comes from the similarity to the exec system call.
1869 It is an ongoing process to be certain the hardware in a machine
1870 is properly shutdown, so do not be surprised if this code does not
1871 initially work for you. As of this writing the exact hardware
1872 interface is strongly in flux, so no good recommendation can be
1876 bool "kexec file based system call"
1881 depends on CRYPTO_SHA256=y
1883 This is new version of kexec system call. This system call is
1884 file based and takes file descriptors as system call argument
1885 for kernel and initramfs as opposed to list of segments as
1886 accepted by previous system call.
1888 config KEXEC_VERIFY_SIG
1889 bool "Verify kernel signature during kexec_file_load() syscall"
1890 depends on KEXEC_FILE
1892 This option makes kernel signature verification mandatory for
1893 the kexec_file_load() syscall.
1895 In addition to that option, you need to enable signature
1896 verification for the corresponding kernel image type being
1897 loaded in order for this to work.
1899 config KEXEC_BZIMAGE_VERIFY_SIG
1900 bool "Enable bzImage signature verification support"
1901 depends on KEXEC_VERIFY_SIG
1902 depends on SIGNED_PE_FILE_VERIFICATION
1903 select SYSTEM_TRUSTED_KEYRING
1905 Enable bzImage signature verification support.
1908 bool "kernel crash dumps"
1909 depends on X86_64 || (X86_32 && HIGHMEM)
1911 Generate crash dump after being started by kexec.
1912 This should be normally only set in special crash dump kernels
1913 which are loaded in the main kernel with kexec-tools into
1914 a specially reserved region and then later executed after
1915 a crash by kdump/kexec. The crash dump kernel must be compiled
1916 to a memory address not used by the main kernel or BIOS using
1917 PHYSICAL_START, or it must be built as a relocatable image
1918 (CONFIG_RELOCATABLE=y).
1919 For more details see Documentation/kdump/kdump.txt
1923 depends on KEXEC && HIBERNATION
1925 Jump between original kernel and kexeced kernel and invoke
1926 code in physical address mode via KEXEC
1928 config PHYSICAL_START
1929 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
1932 This gives the physical address where the kernel is loaded.
1934 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
1935 bzImage will decompress itself to above physical address and
1936 run from there. Otherwise, bzImage will run from the address where
1937 it has been loaded by the boot loader and will ignore above physical
1940 In normal kdump cases one does not have to set/change this option
1941 as now bzImage can be compiled as a completely relocatable image
1942 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
1943 address. This option is mainly useful for the folks who don't want
1944 to use a bzImage for capturing the crash dump and want to use a
1945 vmlinux instead. vmlinux is not relocatable hence a kernel needs
1946 to be specifically compiled to run from a specific memory area
1947 (normally a reserved region) and this option comes handy.
1949 So if you are using bzImage for capturing the crash dump,
1950 leave the value here unchanged to 0x1000000 and set
1951 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
1952 for capturing the crash dump change this value to start of
1953 the reserved region. In other words, it can be set based on
1954 the "X" value as specified in the "crashkernel=YM@XM"
1955 command line boot parameter passed to the panic-ed
1956 kernel. Please take a look at Documentation/kdump/kdump.txt
1957 for more details about crash dumps.
1959 Usage of bzImage for capturing the crash dump is recommended as
1960 one does not have to build two kernels. Same kernel can be used
1961 as production kernel and capture kernel. Above option should have
1962 gone away after relocatable bzImage support is introduced. But it
1963 is present because there are users out there who continue to use
1964 vmlinux for dump capture. This option should go away down the
1967 Don't change this unless you know what you are doing.
1970 bool "Build a relocatable kernel"
1973 This builds a kernel image that retains relocation information
1974 so it can be loaded someplace besides the default 1MB.
1975 The relocations tend to make the kernel binary about 10% larger,
1976 but are discarded at runtime.
1978 One use is for the kexec on panic case where the recovery kernel
1979 must live at a different physical address than the primary
1982 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
1983 it has been loaded at and the compile time physical address
1984 (CONFIG_PHYSICAL_START) is used as the minimum location.
1986 config RANDOMIZE_BASE
1987 bool "Randomize the address of the kernel image (KASLR)"
1988 depends on RELOCATABLE
1991 In support of Kernel Address Space Layout Randomization (KASLR),
1992 this randomizes the physical address at which the kernel image
1993 is decompressed and the virtual address where the kernel
1994 image is mapped, as a security feature that deters exploit
1995 attempts relying on knowledge of the location of kernel
1998 On 64-bit, the kernel physical and virtual addresses are
1999 randomized separately. The physical address will be anywhere
2000 between 16MB and the top of physical memory (up to 64TB). The
2001 virtual address will be randomized from 16MB up to 1GB (9 bits
2002 of entropy). Note that this also reduces the memory space
2003 available to kernel modules from 1.5GB to 1GB.
2005 On 32-bit, the kernel physical and virtual addresses are
2006 randomized together. They will be randomized from 16MB up to
2007 512MB (8 bits of entropy).
2009 Entropy is generated using the RDRAND instruction if it is
2010 supported. If RDTSC is supported, its value is mixed into
2011 the entropy pool as well. If neither RDRAND nor RDTSC are
2012 supported, then entropy is read from the i8254 timer. The
2013 usable entropy is limited by the kernel being built using
2014 2GB addressing, and that PHYSICAL_ALIGN must be at a
2015 minimum of 2MB. As a result, only 10 bits of entropy are
2016 theoretically possible, but the implementations are further
2017 limited due to memory layouts.
2021 # Relocation on x86 needs some additional build support
2022 config X86_NEED_RELOCS
2024 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2026 config PHYSICAL_ALIGN
2027 hex "Alignment value to which kernel should be aligned"
2029 range 0x2000 0x1000000 if X86_32
2030 range 0x200000 0x1000000 if X86_64
2032 This value puts the alignment restrictions on physical address
2033 where kernel is loaded and run from. Kernel is compiled for an
2034 address which meets above alignment restriction.
2036 If bootloader loads the kernel at a non-aligned address and
2037 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2038 address aligned to above value and run from there.
2040 If bootloader loads the kernel at a non-aligned address and
2041 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2042 load address and decompress itself to the address it has been
2043 compiled for and run from there. The address for which kernel is
2044 compiled already meets above alignment restrictions. Hence the
2045 end result is that kernel runs from a physical address meeting
2046 above alignment restrictions.
2048 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2049 this value must be a multiple of 0x200000.
2051 Don't change this unless you know what you are doing.
2053 config RANDOMIZE_MEMORY
2054 bool "Randomize the kernel memory sections"
2056 depends on RANDOMIZE_BASE
2057 default RANDOMIZE_BASE
2059 Randomizes the base virtual address of kernel memory sections
2060 (physical memory mapping, vmalloc & vmemmap). This security feature
2061 makes exploits relying on predictable memory locations less reliable.
2063 The order of allocations remains unchanged. Entropy is generated in
2064 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2065 configuration have in average 30,000 different possible virtual
2066 addresses for each memory section.
2070 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2071 hex "Physical memory mapping padding" if EXPERT
2072 depends on RANDOMIZE_MEMORY
2073 default "0xa" if MEMORY_HOTPLUG
2075 range 0x1 0x40 if MEMORY_HOTPLUG
2078 Define the padding in terabytes added to the existing physical
2079 memory size during kernel memory randomization. It is useful
2080 for memory hotplug support but reduces the entropy available for
2081 address randomization.
2083 If unsure, leave at the default value.
2086 bool "Support for hot-pluggable CPUs"
2089 Say Y here to allow turning CPUs off and on. CPUs can be
2090 controlled through /sys/devices/system/cpu.
2091 ( Note: power management support will enable this option
2092 automatically on SMP systems. )
2093 Say N if you want to disable CPU hotplug.
2095 config BOOTPARAM_HOTPLUG_CPU0
2096 bool "Set default setting of cpu0_hotpluggable"
2098 depends on HOTPLUG_CPU
2100 Set whether default state of cpu0_hotpluggable is on or off.
2102 Say Y here to enable CPU0 hotplug by default. If this switch
2103 is turned on, there is no need to give cpu0_hotplug kernel
2104 parameter and the CPU0 hotplug feature is enabled by default.
2106 Please note: there are two known CPU0 dependencies if you want
2107 to enable the CPU0 hotplug feature either by this switch or by
2108 cpu0_hotplug kernel parameter.
2110 First, resume from hibernate or suspend always starts from CPU0.
2111 So hibernate and suspend are prevented if CPU0 is offline.
2113 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2114 offline if any interrupt can not migrate out of CPU0. There may
2115 be other CPU0 dependencies.
2117 Please make sure the dependencies are under your control before
2118 you enable this feature.
2120 Say N if you don't want to enable CPU0 hotplug feature by default.
2121 You still can enable the CPU0 hotplug feature at boot by kernel
2122 parameter cpu0_hotplug.
2124 config DEBUG_HOTPLUG_CPU0
2126 prompt "Debug CPU0 hotplug"
2127 depends on HOTPLUG_CPU
2129 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2130 soon as possible and boots up userspace with CPU0 offlined. User
2131 can online CPU0 back after boot time.
2133 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2134 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2135 compilation or giving cpu0_hotplug kernel parameter at boot.
2141 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2142 depends on COMPAT_32
2144 Certain buggy versions of glibc will crash if they are
2145 presented with a 32-bit vDSO that is not mapped at the address
2146 indicated in its segment table.
2148 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2149 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2150 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2151 the only released version with the bug, but OpenSUSE 9
2152 contains a buggy "glibc 2.3.2".
2154 The symptom of the bug is that everything crashes on startup, saying:
2155 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2157 Saying Y here changes the default value of the vdso32 boot
2158 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2159 This works around the glibc bug but hurts performance.
2161 If unsure, say N: if you are compiling your own kernel, you
2162 are unlikely to be using a buggy version of glibc.
2165 prompt "vsyscall table for legacy applications"
2167 default LEGACY_VSYSCALL_EMULATE
2169 Legacy user code that does not know how to find the vDSO expects
2170 to be able to issue three syscalls by calling fixed addresses in
2171 kernel space. Since this location is not randomized with ASLR,
2172 it can be used to assist security vulnerability exploitation.
2174 This setting can be changed at boot time via the kernel command
2175 line parameter vsyscall=[native|emulate|none].
2177 On a system with recent enough glibc (2.14 or newer) and no
2178 static binaries, you can say None without a performance penalty
2179 to improve security.
2181 If unsure, select "Emulate".
2183 config LEGACY_VSYSCALL_NATIVE
2186 Actual executable code is located in the fixed vsyscall
2187 address mapping, implementing time() efficiently. Since
2188 this makes the mapping executable, it can be used during
2189 security vulnerability exploitation (traditionally as
2190 ROP gadgets). This configuration is not recommended.
2192 config LEGACY_VSYSCALL_EMULATE
2195 The kernel traps and emulates calls into the fixed
2196 vsyscall address mapping. This makes the mapping
2197 non-executable, but it still contains known contents,
2198 which could be used in certain rare security vulnerability
2199 exploits. This configuration is recommended when userspace
2200 still uses the vsyscall area.
2202 config LEGACY_VSYSCALL_NONE
2205 There will be no vsyscall mapping at all. This will
2206 eliminate any risk of ASLR bypass due to the vsyscall
2207 fixed address mapping. Attempts to use the vsyscalls
2208 will be reported to dmesg, so that either old or
2209 malicious userspace programs can be identified.
2214 bool "Built-in kernel command line"
2216 Allow for specifying boot arguments to the kernel at
2217 build time. On some systems (e.g. embedded ones), it is
2218 necessary or convenient to provide some or all of the
2219 kernel boot arguments with the kernel itself (that is,
2220 to not rely on the boot loader to provide them.)
2222 To compile command line arguments into the kernel,
2223 set this option to 'Y', then fill in the
2224 boot arguments in CONFIG_CMDLINE.
2226 Systems with fully functional boot loaders (i.e. non-embedded)
2227 should leave this option set to 'N'.
2230 string "Built-in kernel command string"
2231 depends on CMDLINE_BOOL
2234 Enter arguments here that should be compiled into the kernel
2235 image and used at boot time. If the boot loader provides a
2236 command line at boot time, it is appended to this string to
2237 form the full kernel command line, when the system boots.
2239 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2240 change this behavior.
2242 In most cases, the command line (whether built-in or provided
2243 by the boot loader) should specify the device for the root
2246 config CMDLINE_OVERRIDE
2247 bool "Built-in command line overrides boot loader arguments"
2248 depends on CMDLINE_BOOL
2250 Set this option to 'Y' to have the kernel ignore the boot loader
2251 command line, and use ONLY the built-in command line.
2253 This is used to work around broken boot loaders. This should
2254 be set to 'N' under normal conditions.
2256 config MODIFY_LDT_SYSCALL
2257 bool "Enable the LDT (local descriptor table)" if EXPERT
2260 Linux can allow user programs to install a per-process x86
2261 Local Descriptor Table (LDT) using the modify_ldt(2) system
2262 call. This is required to run 16-bit or segmented code such as
2263 DOSEMU or some Wine programs. It is also used by some very old
2264 threading libraries.
2266 Enabling this feature adds a small amount of overhead to
2267 context switches and increases the low-level kernel attack
2268 surface. Disabling it removes the modify_ldt(2) system call.
2270 Saying 'N' here may make sense for embedded or server kernels.
2272 source "kernel/livepatch/Kconfig"
2276 config ARCH_ENABLE_MEMORY_HOTPLUG
2278 depends on X86_64 || (X86_32 && HIGHMEM)
2280 config ARCH_ENABLE_MEMORY_HOTREMOVE
2282 depends on MEMORY_HOTPLUG
2284 config USE_PERCPU_NUMA_NODE_ID
2288 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2290 depends on X86_64 || X86_PAE
2292 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2294 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2296 menu "Power management and ACPI options"
2298 config ARCH_HIBERNATION_HEADER
2300 depends on X86_64 && HIBERNATION
2302 source "kernel/power/Kconfig"
2304 source "drivers/acpi/Kconfig"
2306 source "drivers/sfi/Kconfig"
2313 tristate "APM (Advanced Power Management) BIOS support"
2314 depends on X86_32 && PM_SLEEP
2316 APM is a BIOS specification for saving power using several different
2317 techniques. This is mostly useful for battery powered laptops with
2318 APM compliant BIOSes. If you say Y here, the system time will be
2319 reset after a RESUME operation, the /proc/apm device will provide
2320 battery status information, and user-space programs will receive
2321 notification of APM "events" (e.g. battery status change).
2323 If you select "Y" here, you can disable actual use of the APM
2324 BIOS by passing the "apm=off" option to the kernel at boot time.
2326 Note that the APM support is almost completely disabled for
2327 machines with more than one CPU.
2329 In order to use APM, you will need supporting software. For location
2330 and more information, read <file:Documentation/power/apm-acpi.txt>
2331 and the Battery Powered Linux mini-HOWTO, available from
2332 <http://www.tldp.org/docs.html#howto>.
2334 This driver does not spin down disk drives (see the hdparm(8)
2335 manpage ("man 8 hdparm") for that), and it doesn't turn off
2336 VESA-compliant "green" monitors.
2338 This driver does not support the TI 4000M TravelMate and the ACER
2339 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2340 desktop machines also don't have compliant BIOSes, and this driver
2341 may cause those machines to panic during the boot phase.
2343 Generally, if you don't have a battery in your machine, there isn't
2344 much point in using this driver and you should say N. If you get
2345 random kernel OOPSes or reboots that don't seem to be related to
2346 anything, try disabling/enabling this option (or disabling/enabling
2349 Some other things you should try when experiencing seemingly random,
2352 1) make sure that you have enough swap space and that it is
2354 2) pass the "no-hlt" option to the kernel
2355 3) switch on floating point emulation in the kernel and pass
2356 the "no387" option to the kernel
2357 4) pass the "floppy=nodma" option to the kernel
2358 5) pass the "mem=4M" option to the kernel (thereby disabling
2359 all but the first 4 MB of RAM)
2360 6) make sure that the CPU is not over clocked.
2361 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2362 8) disable the cache from your BIOS settings
2363 9) install a fan for the video card or exchange video RAM
2364 10) install a better fan for the CPU
2365 11) exchange RAM chips
2366 12) exchange the motherboard.
2368 To compile this driver as a module, choose M here: the
2369 module will be called apm.
2373 config APM_IGNORE_USER_SUSPEND
2374 bool "Ignore USER SUSPEND"
2376 This option will ignore USER SUSPEND requests. On machines with a
2377 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2378 series notebooks, it is necessary to say Y because of a BIOS bug.
2380 config APM_DO_ENABLE
2381 bool "Enable PM at boot time"
2383 Enable APM features at boot time. From page 36 of the APM BIOS
2384 specification: "When disabled, the APM BIOS does not automatically
2385 power manage devices, enter the Standby State, enter the Suspend
2386 State, or take power saving steps in response to CPU Idle calls."
2387 This driver will make CPU Idle calls when Linux is idle (unless this
2388 feature is turned off -- see "Do CPU IDLE calls", below). This
2389 should always save battery power, but more complicated APM features
2390 will be dependent on your BIOS implementation. You may need to turn
2391 this option off if your computer hangs at boot time when using APM
2392 support, or if it beeps continuously instead of suspending. Turn
2393 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2394 T400CDT. This is off by default since most machines do fine without
2399 bool "Make CPU Idle calls when idle"
2401 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2402 On some machines, this can activate improved power savings, such as
2403 a slowed CPU clock rate, when the machine is idle. These idle calls
2404 are made after the idle loop has run for some length of time (e.g.,
2405 333 mS). On some machines, this will cause a hang at boot time or
2406 whenever the CPU becomes idle. (On machines with more than one CPU,
2407 this option does nothing.)
2409 config APM_DISPLAY_BLANK
2410 bool "Enable console blanking using APM"
2412 Enable console blanking using the APM. Some laptops can use this to
2413 turn off the LCD backlight when the screen blanker of the Linux
2414 virtual console blanks the screen. Note that this is only used by
2415 the virtual console screen blanker, and won't turn off the backlight
2416 when using the X Window system. This also doesn't have anything to
2417 do with your VESA-compliant power-saving monitor. Further, this
2418 option doesn't work for all laptops -- it might not turn off your
2419 backlight at all, or it might print a lot of errors to the console,
2420 especially if you are using gpm.
2422 config APM_ALLOW_INTS
2423 bool "Allow interrupts during APM BIOS calls"
2425 Normally we disable external interrupts while we are making calls to
2426 the APM BIOS as a measure to lessen the effects of a badly behaving
2427 BIOS implementation. The BIOS should reenable interrupts if it
2428 needs to. Unfortunately, some BIOSes do not -- especially those in
2429 many of the newer IBM Thinkpads. If you experience hangs when you
2430 suspend, try setting this to Y. Otherwise, say N.
2434 source "drivers/cpufreq/Kconfig"
2436 source "drivers/cpuidle/Kconfig"
2438 source "drivers/idle/Kconfig"
2443 menu "Bus options (PCI etc.)"
2449 Find out whether you have a PCI motherboard. PCI is the name of a
2450 bus system, i.e. the way the CPU talks to the other stuff inside
2451 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2452 VESA. If you have PCI, say Y, otherwise N.
2455 prompt "PCI access mode"
2456 depends on X86_32 && PCI
2459 On PCI systems, the BIOS can be used to detect the PCI devices and
2460 determine their configuration. However, some old PCI motherboards
2461 have BIOS bugs and may crash if this is done. Also, some embedded
2462 PCI-based systems don't have any BIOS at all. Linux can also try to
2463 detect the PCI hardware directly without using the BIOS.
2465 With this option, you can specify how Linux should detect the
2466 PCI devices. If you choose "BIOS", the BIOS will be used,
2467 if you choose "Direct", the BIOS won't be used, and if you
2468 choose "MMConfig", then PCI Express MMCONFIG will be used.
2469 If you choose "Any", the kernel will try MMCONFIG, then the
2470 direct access method and falls back to the BIOS if that doesn't
2471 work. If unsure, go with the default, which is "Any".
2476 config PCI_GOMMCONFIG
2493 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2495 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2498 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2502 depends on X86_32 && PCI && (ACPI || SFI) && (PCI_GOMMCONFIG || PCI_GOANY)
2506 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2510 depends on PCI && XEN
2518 bool "Support mmconfig PCI config space access"
2519 depends on X86_64 && PCI && ACPI
2521 config PCI_CNB20LE_QUIRK
2522 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2525 Read the PCI windows out of the CNB20LE host bridge. This allows
2526 PCI hotplug to work on systems with the CNB20LE chipset which do
2529 There's no public spec for this chipset, and this functionality
2530 is known to be incomplete.
2532 You should say N unless you know you need this.
2534 source "drivers/pci/Kconfig"
2537 bool "ISA-style bus support on modern systems" if EXPERT
2540 Enables ISA-style drivers on modern systems. This is necessary to
2541 support PC/104 devices on X86_64 platforms.
2545 # x86_64 have no ISA slots, but can have ISA-style DMA.
2547 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2550 Enables ISA-style DMA support for devices requiring such controllers.
2558 Find out whether you have ISA slots on your motherboard. ISA is the
2559 name of a bus system, i.e. the way the CPU talks to the other stuff
2560 inside your box. Other bus systems are PCI, EISA, MicroChannel
2561 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2562 newer boards don't support it. If you have ISA, say Y, otherwise N.
2568 The Extended Industry Standard Architecture (EISA) bus was
2569 developed as an open alternative to the IBM MicroChannel bus.
2571 The EISA bus provided some of the features of the IBM MicroChannel
2572 bus while maintaining backward compatibility with cards made for
2573 the older ISA bus. The EISA bus saw limited use between 1988 and
2574 1995 when it was made obsolete by the PCI bus.
2576 Say Y here if you are building a kernel for an EISA-based machine.
2580 source "drivers/eisa/Kconfig"
2583 tristate "NatSemi SCx200 support"
2585 This provides basic support for National Semiconductor's
2586 (now AMD's) Geode processors. The driver probes for the
2587 PCI-IDs of several on-chip devices, so its a good dependency
2588 for other scx200_* drivers.
2590 If compiled as a module, the driver is named scx200.
2592 config SCx200HR_TIMER
2593 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2597 This driver provides a clocksource built upon the on-chip
2598 27MHz high-resolution timer. Its also a workaround for
2599 NSC Geode SC-1100's buggy TSC, which loses time when the
2600 processor goes idle (as is done by the scheduler). The
2601 other workaround is idle=poll boot option.
2604 bool "One Laptop Per Child support"
2611 Add support for detecting the unique features of the OLPC
2615 bool "OLPC XO-1 Power Management"
2616 depends on OLPC && MFD_CS5535 && PM_SLEEP
2619 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2622 bool "OLPC XO-1 Real Time Clock"
2623 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2625 Add support for the XO-1 real time clock, which can be used as a
2626 programmable wakeup source.
2629 bool "OLPC XO-1 SCI extras"
2630 depends on OLPC && OLPC_XO1_PM
2636 Add support for SCI-based features of the OLPC XO-1 laptop:
2637 - EC-driven system wakeups
2641 - AC adapter status updates
2642 - Battery status updates
2644 config OLPC_XO15_SCI
2645 bool "OLPC XO-1.5 SCI extras"
2646 depends on OLPC && ACPI
2649 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2650 - EC-driven system wakeups
2651 - AC adapter status updates
2652 - Battery status updates
2655 bool "PCEngines ALIX System Support (LED setup)"
2658 This option enables system support for the PCEngines ALIX.
2659 At present this just sets up LEDs for GPIO control on
2660 ALIX2/3/6 boards. However, other system specific setup should
2663 Note: You must still enable the drivers for GPIO and LED support
2664 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2666 Note: You have to set alix.force=1 for boards with Award BIOS.
2669 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2672 This option enables system support for the Soekris Engineering net5501.
2675 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2679 This option enables system support for the Traverse Technologies GEOS.
2682 bool "Technologic Systems TS-5500 platform support"
2684 select CHECK_SIGNATURE
2688 This option enables system support for the Technologic Systems TS-5500.
2694 depends on CPU_SUP_AMD && PCI
2696 source "drivers/pcmcia/Kconfig"
2699 tristate "RapidIO support"
2703 If enabled this option will include drivers and the core
2704 infrastructure code to support RapidIO interconnect devices.
2706 source "drivers/rapidio/Kconfig"
2709 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2711 Firmwares often provide initial graphics framebuffers so the BIOS,
2712 bootloader or kernel can show basic video-output during boot for
2713 user-guidance and debugging. Historically, x86 used the VESA BIOS
2714 Extensions and EFI-framebuffers for this, which are mostly limited
2716 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2717 framebuffers so the new generic system-framebuffer drivers can be
2718 used on x86. If the framebuffer is not compatible with the generic
2719 modes, it is adverticed as fallback platform framebuffer so legacy
2720 drivers like efifb, vesafb and uvesafb can pick it up.
2721 If this option is not selected, all system framebuffers are always
2722 marked as fallback platform framebuffers as usual.
2724 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2725 not be able to pick up generic system framebuffers if this option
2726 is selected. You are highly encouraged to enable simplefb as
2727 replacement if you select this option. simplefb can correctly deal
2728 with generic system framebuffers. But you should still keep vesafb
2729 and others enabled as fallback if a system framebuffer is
2730 incompatible with simplefb.
2737 menu "Executable file formats / Emulations"
2739 source "fs/Kconfig.binfmt"
2741 config IA32_EMULATION
2742 bool "IA32 Emulation"
2744 select ARCH_WANT_OLD_COMPAT_IPC
2746 select COMPAT_BINFMT_ELF
2747 select COMPAT_OLD_SIGACTION
2749 Include code to run legacy 32-bit programs under a
2750 64-bit kernel. You should likely turn this on, unless you're
2751 100% sure that you don't have any 32-bit programs left.
2754 tristate "IA32 a.out support"
2755 depends on IA32_EMULATION
2757 Support old a.out binaries in the 32bit emulation.
2760 bool "x32 ABI for 64-bit mode"
2763 Include code to run binaries for the x32 native 32-bit ABI
2764 for 64-bit processors. An x32 process gets access to the
2765 full 64-bit register file and wide data path while leaving
2766 pointers at 32 bits for smaller memory footprint.
2768 You will need a recent binutils (2.22 or later) with
2769 elf32_x86_64 support enabled to compile a kernel with this
2774 depends on IA32_EMULATION || X86_32
2776 select OLD_SIGSUSPEND3
2780 depends on IA32_EMULATION || X86_X32
2783 config COMPAT_FOR_U64_ALIGNMENT
2786 config SYSVIPC_COMPAT
2794 config HAVE_ATOMIC_IOMAP
2798 config X86_DEV_DMA_OPS
2800 depends on X86_64 || STA2X11
2802 config X86_DMA_REMAP
2806 config HAVE_GENERIC_GUP
2809 source "net/Kconfig"
2811 source "drivers/Kconfig"
2813 source "drivers/firmware/Kconfig"
2817 source "arch/x86/Kconfig.debug"
2819 source "security/Kconfig"
2821 source "crypto/Kconfig"
2823 source "arch/x86/kvm/Kconfig"
2825 source "lib/Kconfig"