1 # SPDX-License-Identifier: GPL-2.0
4 bool "64-bit kernel" if ARCH = "x86"
7 Say yes to build a 64-bit kernel - formerly known as x86_64
8 Say no to build a 32-bit kernel - formerly known as i386
13 # Options that are inherently 32-bit kernel only:
14 select ARCH_WANT_IPC_PARSE_VERSION
16 select CLONE_BACKWARDS
18 select HAVE_GENERIC_DMA_COHERENT
19 select MODULES_USE_ELF_REL
25 # Options that are inherently 64-bit kernel only:
26 select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
27 select ARCH_SUPPORTS_INT128
28 select ARCH_USE_CMPXCHG_LOCKREF
29 select HAVE_ARCH_SOFT_DIRTY
30 select MODULES_USE_ELF_RELA
31 select X86_DEV_DMA_OPS
36 # ( Note that options that are marked 'if X86_64' could in principle be
37 # ported to 32-bit as well. )
42 # Note: keep this list sorted alphabetically
44 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
45 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
47 select ARCH_CLOCKSOURCE_DATA
48 select ARCH_DISCARD_MEMBLOCK
49 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
50 select ARCH_HAS_DEBUG_VIRTUAL
51 select ARCH_HAS_DEVMEM_IS_ALLOWED
52 select ARCH_HAS_ELF_RANDOMIZE
53 select ARCH_HAS_FAST_MULTIPLIER
54 select ARCH_HAS_FORTIFY_SOURCE
55 select ARCH_HAS_GCOV_PROFILE_ALL
56 select ARCH_HAS_KCOV if X86_64
57 select ARCH_HAS_PMEM_API if X86_64
58 # Causing hangs/crashes, see the commit that added this change for details.
59 select ARCH_HAS_REFCOUNT
60 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
61 select ARCH_HAS_SET_MEMORY
62 select ARCH_HAS_SG_CHAIN
63 select ARCH_HAS_STRICT_KERNEL_RWX
64 select ARCH_HAS_STRICT_MODULE_RWX
65 select ARCH_HAS_UBSAN_SANITIZE_ALL
66 select ARCH_HAS_ZONE_DEVICE if X86_64
67 select ARCH_HAVE_NMI_SAFE_CMPXCHG
68 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
69 select ARCH_MIGHT_HAVE_PC_PARPORT
70 select ARCH_MIGHT_HAVE_PC_SERIO
71 select ARCH_SUPPORTS_ATOMIC_RMW
72 select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
73 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
74 select ARCH_USE_BUILTIN_BSWAP
75 select ARCH_USE_QUEUED_RWLOCKS
76 select ARCH_USE_QUEUED_SPINLOCKS
77 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
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_MATRIX_ALLOCATOR if X86_LOCAL_APIC
97 select GENERIC_IRQ_MIGRATION if SMP
98 select GENERIC_IRQ_PROBE
99 select GENERIC_IRQ_RESERVATION_MODE
100 select GENERIC_IRQ_SHOW
101 select GENERIC_PENDING_IRQ if SMP
102 select GENERIC_SMP_IDLE_THREAD
103 select GENERIC_STRNCPY_FROM_USER
104 select GENERIC_STRNLEN_USER
105 select GENERIC_TIME_VSYSCALL
106 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
107 select HAVE_ACPI_APEI if ACPI
108 select HAVE_ACPI_APEI_NMI if ACPI
109 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
110 select HAVE_ARCH_AUDITSYSCALL
111 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
112 select HAVE_ARCH_JUMP_LABEL
113 select HAVE_ARCH_KASAN if X86_64 && SPARSEMEM_VMEMMAP
114 select HAVE_ARCH_KGDB
115 select HAVE_ARCH_KMEMCHECK
116 select HAVE_ARCH_MMAP_RND_BITS if MMU
117 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
118 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
119 select HAVE_ARCH_SECCOMP_FILTER
120 select HAVE_ARCH_TRACEHOOK
121 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
122 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
123 select HAVE_ARCH_VMAP_STACK if X86_64
124 select HAVE_ARCH_WITHIN_STACK_FRAMES
125 select HAVE_CC_STACKPROTECTOR
126 select HAVE_CMPXCHG_DOUBLE
127 select HAVE_CMPXCHG_LOCAL
128 select HAVE_CONTEXT_TRACKING if X86_64
129 select HAVE_COPY_THREAD_TLS
130 select HAVE_C_RECORDMCOUNT
131 select HAVE_DEBUG_KMEMLEAK
132 select HAVE_DEBUG_STACKOVERFLOW
133 select HAVE_DMA_API_DEBUG
134 select HAVE_DMA_CONTIGUOUS
135 select HAVE_DYNAMIC_FTRACE
136 select HAVE_DYNAMIC_FTRACE_WITH_REGS
137 select HAVE_EBPF_JIT if X86_64
138 select HAVE_EFFICIENT_UNALIGNED_ACCESS
139 select HAVE_EXIT_THREAD
140 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
141 select HAVE_FTRACE_MCOUNT_RECORD
142 select HAVE_FUNCTION_GRAPH_TRACER
143 select HAVE_FUNCTION_TRACER
144 select HAVE_GCC_PLUGINS
145 select HAVE_HW_BREAKPOINT
147 select HAVE_IOREMAP_PROT
148 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
149 select HAVE_IRQ_TIME_ACCOUNTING
150 select HAVE_KERNEL_BZIP2
151 select HAVE_KERNEL_GZIP
152 select HAVE_KERNEL_LZ4
153 select HAVE_KERNEL_LZMA
154 select HAVE_KERNEL_LZO
155 select HAVE_KERNEL_XZ
157 select HAVE_KPROBES_ON_FTRACE
158 select HAVE_KRETPROBES
160 select HAVE_LIVEPATCH if X86_64
162 select HAVE_MEMBLOCK_NODE_MAP
163 select HAVE_MIXED_BREAKPOINTS_REGS
164 select HAVE_MOD_ARCH_SPECIFIC
167 select HAVE_OPTPROBES
168 select HAVE_PCSPKR_PLATFORM
169 select HAVE_PERF_EVENTS
170 select HAVE_PERF_EVENTS_NMI
171 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
172 select HAVE_PERF_REGS
173 select HAVE_PERF_USER_STACK_DUMP
174 select HAVE_RCU_TABLE_FREE
175 select HAVE_REGS_AND_STACK_ACCESS_API
176 select HAVE_RELIABLE_STACKTRACE if X86_64 && UNWINDER_FRAME_POINTER && STACK_VALIDATION
177 select HAVE_STACK_VALIDATION if X86_64
178 select HAVE_SYSCALL_TRACEPOINTS
179 select HAVE_UNSTABLE_SCHED_CLOCK
180 select HAVE_USER_RETURN_NOTIFIER
181 select IRQ_FORCED_THREADING
182 select PCI_LOCKLESS_CONFIG
185 select RTC_MC146818_LIB
188 select SYSCTL_EXCEPTION_TRACE
189 select THREAD_INFO_IN_TASK
190 select USER_STACKTRACE_SUPPORT
192 select X86_FEATURE_NAMES if PROC_FS
194 config INSTRUCTION_DECODER
196 depends on KPROBES || PERF_EVENTS || UPROBES
200 default "elf32-i386" if X86_32
201 default "elf64-x86-64" if X86_64
203 config ARCH_DEFCONFIG
205 default "arch/x86/configs/i386_defconfig" if X86_32
206 default "arch/x86/configs/x86_64_defconfig" if X86_64
208 config LOCKDEP_SUPPORT
211 config STACKTRACE_SUPPORT
217 config ARCH_MMAP_RND_BITS_MIN
221 config ARCH_MMAP_RND_BITS_MAX
225 config ARCH_MMAP_RND_COMPAT_BITS_MIN
228 config ARCH_MMAP_RND_COMPAT_BITS_MAX
234 config NEED_DMA_MAP_STATE
236 depends on X86_64 || INTEL_IOMMU || DMA_API_DEBUG || SWIOTLB
238 config NEED_SG_DMA_LENGTH
241 config GENERIC_ISA_DMA
243 depends on ISA_DMA_API
248 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
250 config GENERIC_BUG_RELATIVE_POINTERS
253 config GENERIC_HWEIGHT
256 config ARCH_MAY_HAVE_PC_FDC
258 depends on ISA_DMA_API
260 config RWSEM_XCHGADD_ALGORITHM
263 config GENERIC_CALIBRATE_DELAY
266 config ARCH_HAS_CPU_RELAX
269 config ARCH_HAS_CACHE_LINE_SIZE
272 config HAVE_SETUP_PER_CPU_AREA
275 config NEED_PER_CPU_EMBED_FIRST_CHUNK
278 config NEED_PER_CPU_PAGE_FIRST_CHUNK
281 config ARCH_HIBERNATION_POSSIBLE
284 config ARCH_SUSPEND_POSSIBLE
287 config ARCH_WANT_HUGE_PMD_SHARE
290 config ARCH_WANT_GENERAL_HUGETLB
299 config ARCH_SUPPORTS_OPTIMIZED_INLINING
302 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
305 config KASAN_SHADOW_OFFSET
308 default 0xdffffc0000000000
310 config HAVE_INTEL_TXT
312 depends on INTEL_IOMMU && ACPI
316 depends on X86_32 && SMP
320 depends on X86_64 && SMP
322 config X86_32_LAZY_GS
324 depends on X86_32 && !CC_STACKPROTECTOR
326 config ARCH_SUPPORTS_UPROBES
329 config FIX_EARLYCON_MEM
332 config PGTABLE_LEVELS
334 default 5 if X86_5LEVEL
339 source "init/Kconfig"
340 source "kernel/Kconfig.freezer"
342 menu "Processor type and features"
345 bool "DMA memory allocation support" if EXPERT
348 DMA memory allocation support allows devices with less than 32-bit
349 addressing to allocate within the first 16MB of address space.
350 Disable if no such devices will be used.
355 bool "Symmetric multi-processing support"
357 This enables support for systems with more than one CPU. If you have
358 a system with only one CPU, say N. If you have a system with more
361 If you say N here, the kernel will run on uni- and multiprocessor
362 machines, but will use only one CPU of a multiprocessor machine. If
363 you say Y here, the kernel will run on many, but not all,
364 uniprocessor machines. On a uniprocessor machine, the kernel
365 will run faster if you say N here.
367 Note that if you say Y here and choose architecture "586" or
368 "Pentium" under "Processor family", the kernel will not work on 486
369 architectures. Similarly, multiprocessor kernels for the "PPro"
370 architecture may not work on all Pentium based boards.
372 People using multiprocessor machines who say Y here should also say
373 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
374 Management" code will be disabled if you say Y here.
376 See also <file:Documentation/x86/i386/IO-APIC.txt>,
377 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
378 <http://www.tldp.org/docs.html#howto>.
380 If you don't know what to do here, say N.
382 config X86_FEATURE_NAMES
383 bool "Processor feature human-readable names" if EMBEDDED
386 This option compiles in a table of x86 feature bits and corresponding
387 names. This is required to support /proc/cpuinfo and a few kernel
388 messages. You can disable this to save space, at the expense of
389 making those few kernel messages show numeric feature bits instead.
393 config X86_FAST_FEATURE_TESTS
394 bool "Fast CPU feature tests" if EMBEDDED
397 Some fast-paths in the kernel depend on the capabilities of the CPU.
398 Say Y here for the kernel to patch in the appropriate code at runtime
399 based on the capabilities of the CPU. The infrastructure for patching
400 code at runtime takes up some additional space; space-constrained
401 embedded systems may wish to say N here to produce smaller, slightly
405 bool "Support x2apic"
406 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
408 This enables x2apic support on CPUs that have this feature.
410 This allows 32-bit apic IDs (so it can support very large systems),
411 and accesses the local apic via MSRs not via mmio.
413 If you don't know what to do here, say N.
416 bool "Enable MPS table" if ACPI || SFI
418 depends on X86_LOCAL_APIC
420 For old smp systems that do not have proper acpi support. Newer systems
421 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
424 bool "Support for big SMP systems with more than 8 CPUs"
425 depends on X86_32 && SMP
427 This option is needed for the systems that have more than 8 CPUs
431 depends on X86_GOLDFISH
434 bool "Intel Resource Director Technology support"
436 depends on X86 && CPU_SUP_INTEL
439 Select to enable resource allocation and monitoring which are
440 sub-features of Intel Resource Director Technology(RDT). More
441 information about RDT can be found in the Intel x86
442 Architecture Software Developer Manual.
447 config X86_EXTENDED_PLATFORM
448 bool "Support for extended (non-PC) x86 platforms"
451 If you disable this option then the kernel will only support
452 standard PC platforms. (which covers the vast majority of
455 If you enable this option then you'll be able to select support
456 for the following (non-PC) 32 bit x86 platforms:
457 Goldfish (Android emulator)
460 SGI 320/540 (Visual Workstation)
461 STA2X11-based (e.g. Northville)
462 Moorestown MID devices
464 If you have one of these systems, or if you want to build a
465 generic distribution kernel, say Y here - otherwise say N.
469 config X86_EXTENDED_PLATFORM
470 bool "Support for extended (non-PC) x86 platforms"
473 If you disable this option then the kernel will only support
474 standard PC platforms. (which covers the vast majority of
477 If you enable this option then you'll be able to select support
478 for the following (non-PC) 64 bit x86 platforms:
483 If you have one of these systems, or if you want to build a
484 generic distribution kernel, say Y here - otherwise say N.
486 # This is an alphabetically sorted list of 64 bit extended platforms
487 # Please maintain the alphabetic order if and when there are additions
489 bool "Numascale NumaChip"
491 depends on X86_EXTENDED_PLATFORM
494 depends on X86_X2APIC
495 depends on PCI_MMCONFIG
497 Adds support for Numascale NumaChip large-SMP systems. Needed to
498 enable more than ~168 cores.
499 If you don't have one of these, you should say N here.
503 select HYPERVISOR_GUEST
505 depends on X86_64 && PCI
506 depends on X86_EXTENDED_PLATFORM
509 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
510 supposed to run on these EM64T-based machines. Only choose this option
511 if you have one of these machines.
514 bool "SGI Ultraviolet"
516 depends on X86_EXTENDED_PLATFORM
519 depends on X86_X2APIC
522 This option is needed in order to support SGI Ultraviolet systems.
523 If you don't have one of these, you should say N here.
525 # Following is an alphabetically sorted list of 32 bit extended platforms
526 # Please maintain the alphabetic order if and when there are additions
529 bool "Goldfish (Virtual Platform)"
530 depends on X86_EXTENDED_PLATFORM
532 Enable support for the Goldfish virtual platform used primarily
533 for Android development. Unless you are building for the Android
534 Goldfish emulator say N here.
537 bool "CE4100 TV platform"
539 depends on PCI_GODIRECT
540 depends on X86_IO_APIC
542 depends on X86_EXTENDED_PLATFORM
543 select X86_REBOOTFIXUPS
545 select OF_EARLY_FLATTREE
547 Select for the Intel CE media processor (CE4100) SOC.
548 This option compiles in support for the CE4100 SOC for settop
549 boxes and media devices.
552 bool "Intel MID platform support"
553 depends on X86_EXTENDED_PLATFORM
554 depends on X86_PLATFORM_DEVICES
556 depends on X86_64 || (PCI_GOANY && X86_32)
557 depends on X86_IO_APIC
563 select MFD_INTEL_MSIC
565 Select to build a kernel capable of supporting Intel MID (Mobile
566 Internet Device) platform systems which do not have the PCI legacy
567 interfaces. If you are building for a PC class system say N here.
569 Intel MID platforms are based on an Intel processor and chipset which
570 consume less power than most of the x86 derivatives.
572 config X86_INTEL_QUARK
573 bool "Intel Quark platform support"
575 depends on X86_EXTENDED_PLATFORM
576 depends on X86_PLATFORM_DEVICES
580 depends on X86_IO_APIC
585 Select to include support for Quark X1000 SoC.
586 Say Y here if you have a Quark based system such as the Arduino
587 compatible Intel Galileo.
589 config X86_INTEL_LPSS
590 bool "Intel Low Power Subsystem Support"
591 depends on X86 && ACPI
596 Select to build support for Intel Low Power Subsystem such as
597 found on Intel Lynxpoint PCH. Selecting this option enables
598 things like clock tree (common clock framework) and pincontrol
599 which are needed by the LPSS peripheral drivers.
601 config X86_AMD_PLATFORM_DEVICE
602 bool "AMD ACPI2Platform devices support"
607 Select to interpret AMD specific ACPI device to platform device
608 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
609 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
610 implemented under PINCTRL subsystem.
613 tristate "Intel SoC IOSF Sideband support for SoC platforms"
616 This option enables sideband register access support for Intel SoC
617 platforms. On these platforms the IOSF sideband is used in lieu of
618 MSR's for some register accesses, mostly but not limited to thermal
619 and power. Drivers may query the availability of this device to
620 determine if they need the sideband in order to work on these
621 platforms. The sideband is available on the following SoC products.
622 This list is not meant to be exclusive.
627 You should say Y if you are running a kernel on one of these SoC's.
629 config IOSF_MBI_DEBUG
630 bool "Enable IOSF sideband access through debugfs"
631 depends on IOSF_MBI && DEBUG_FS
633 Select this option to expose the IOSF sideband access registers (MCR,
634 MDR, MCRX) through debugfs to write and read register information from
635 different units on the SoC. This is most useful for obtaining device
636 state information for debug and analysis. As this is a general access
637 mechanism, users of this option would have specific knowledge of the
638 device they want to access.
640 If you don't require the option or are in doubt, say N.
643 bool "RDC R-321x SoC"
645 depends on X86_EXTENDED_PLATFORM
647 select X86_REBOOTFIXUPS
649 This option is needed for RDC R-321x system-on-chip, also known
651 If you don't have one of these chips, you should say N here.
653 config X86_32_NON_STANDARD
654 bool "Support non-standard 32-bit SMP architectures"
655 depends on X86_32 && SMP
656 depends on X86_EXTENDED_PLATFORM
658 This option compiles in the bigsmp and STA2X11 default
659 subarchitectures. It is intended for a generic binary
660 kernel. If you select them all, kernel will probe it one by
661 one and will fallback to default.
663 # Alphabetically sorted list of Non standard 32 bit platforms
665 config X86_SUPPORTS_MEMORY_FAILURE
667 # MCE code calls memory_failure():
669 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
670 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
671 depends on X86_64 || !SPARSEMEM
672 select ARCH_SUPPORTS_MEMORY_FAILURE
675 bool "STA2X11 Companion Chip Support"
676 depends on X86_32_NON_STANDARD && PCI
677 select X86_DEV_DMA_OPS
684 This adds support for boards based on the STA2X11 IO-Hub,
685 a.k.a. "ConneXt". The chip is used in place of the standard
686 PC chipset, so all "standard" peripherals are missing. If this
687 option is selected the kernel will still be able to boot on
688 standard PC machines.
691 tristate "Eurobraille/Iris poweroff module"
694 The Iris machines from EuroBraille do not have APM or ACPI support
695 to shut themselves down properly. A special I/O sequence is
696 needed to do so, which is what this module does at
699 This is only for Iris machines from EuroBraille.
703 config SCHED_OMIT_FRAME_POINTER
705 prompt "Single-depth WCHAN output"
708 Calculate simpler /proc/<PID>/wchan values. If this option
709 is disabled then wchan values will recurse back to the
710 caller function. This provides more accurate wchan values,
711 at the expense of slightly more scheduling overhead.
713 If in doubt, say "Y".
715 menuconfig HYPERVISOR_GUEST
716 bool "Linux guest support"
718 Say Y here to enable options for running Linux under various hyper-
719 visors. This option enables basic hypervisor detection and platform
722 If you say N, all options in this submenu will be skipped and
723 disabled, and Linux guest support won't be built in.
728 bool "Enable paravirtualization code"
730 This changes the kernel so it can modify itself when it is run
731 under a hypervisor, potentially improving performance significantly
732 over full virtualization. However, when run without a hypervisor
733 the kernel is theoretically slower and slightly larger.
735 config PARAVIRT_DEBUG
736 bool "paravirt-ops debugging"
737 depends on PARAVIRT && DEBUG_KERNEL
739 Enable to debug paravirt_ops internals. Specifically, BUG if
740 a paravirt_op is missing when it is called.
742 config PARAVIRT_SPINLOCKS
743 bool "Paravirtualization layer for spinlocks"
744 depends on PARAVIRT && SMP
746 Paravirtualized spinlocks allow a pvops backend to replace the
747 spinlock implementation with something virtualization-friendly
748 (for example, block the virtual CPU rather than spinning).
750 It has a minimal impact on native kernels and gives a nice performance
751 benefit on paravirtualized KVM / Xen kernels.
753 If you are unsure how to answer this question, answer Y.
755 config QUEUED_LOCK_STAT
756 bool "Paravirt queued spinlock statistics"
757 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
759 Enable the collection of statistical data on the slowpath
760 behavior of paravirtualized queued spinlocks and report
763 source "arch/x86/xen/Kconfig"
766 bool "KVM Guest support (including kvmclock)"
768 select PARAVIRT_CLOCK
771 This option enables various optimizations for running under the KVM
772 hypervisor. It includes a paravirtualized clock, so that instead
773 of relying on a PIT (or probably other) emulation by the
774 underlying device model, the host provides the guest with
775 timing infrastructure such as time of day, and system time
778 bool "Enable debug information for KVM Guests in debugfs"
779 depends on KVM_GUEST && DEBUG_FS
782 This option enables collection of various statistics for KVM guest.
783 Statistics are displayed in debugfs filesystem. Enabling this option
784 may incur significant overhead.
786 config PARAVIRT_TIME_ACCOUNTING
787 bool "Paravirtual steal time accounting"
791 Select this option to enable fine granularity task steal time
792 accounting. Time spent executing other tasks in parallel with
793 the current vCPU is discounted from the vCPU power. To account for
794 that, there can be a small performance impact.
796 If in doubt, say N here.
798 config PARAVIRT_CLOCK
801 endif #HYPERVISOR_GUEST
806 source "arch/x86/Kconfig.cpu"
810 prompt "HPET Timer Support" if X86_32
812 Use the IA-PC HPET (High Precision Event Timer) to manage
813 time in preference to the PIT and RTC, if a HPET is
815 HPET is the next generation timer replacing legacy 8254s.
816 The HPET provides a stable time base on SMP
817 systems, unlike the TSC, but it is more expensive to access,
818 as it is off-chip. The interface used is documented
819 in the HPET spec, revision 1.
821 You can safely choose Y here. However, HPET will only be
822 activated if the platform and the BIOS support this feature.
823 Otherwise the 8254 will be used for timing services.
825 Choose N to continue using the legacy 8254 timer.
827 config HPET_EMULATE_RTC
829 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
832 def_bool y if X86_INTEL_MID
833 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
835 depends on X86_INTEL_MID && SFI
837 APB timer is the replacement for 8254, HPET on X86 MID platforms.
838 The APBT provides a stable time base on SMP
839 systems, unlike the TSC, but it is more expensive to access,
840 as it is off-chip. APB timers are always running regardless of CPU
841 C states, they are used as per CPU clockevent device when possible.
843 # Mark as expert because too many people got it wrong.
844 # The code disables itself when not needed.
847 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
848 bool "Enable DMI scanning" if EXPERT
850 Enabled scanning of DMI to identify machine quirks. Say Y
851 here unless you have verified that your setup is not
852 affected by entries in the DMI blacklist. Required by PNP
856 bool "Old AMD GART IOMMU support"
858 depends on X86_64 && PCI && AMD_NB
860 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
861 GART based hardware IOMMUs.
863 The GART supports full DMA access for devices with 32-bit access
864 limitations, on systems with more than 3 GB. This is usually needed
865 for USB, sound, many IDE/SATA chipsets and some other devices.
867 Newer systems typically have a modern AMD IOMMU, supported via
868 the CONFIG_AMD_IOMMU=y config option.
870 In normal configurations this driver is only active when needed:
871 there's more than 3 GB of memory and the system contains a
872 32-bit limited device.
877 bool "IBM Calgary IOMMU support"
879 depends on X86_64 && PCI
881 Support for hardware IOMMUs in IBM's xSeries x366 and x460
882 systems. Needed to run systems with more than 3GB of memory
883 properly with 32-bit PCI devices that do not support DAC
884 (Double Address Cycle). Calgary also supports bus level
885 isolation, where all DMAs pass through the IOMMU. This
886 prevents them from going anywhere except their intended
887 destination. This catches hard-to-find kernel bugs and
888 mis-behaving drivers and devices that do not use the DMA-API
889 properly to set up their DMA buffers. The IOMMU can be
890 turned off at boot time with the iommu=off parameter.
891 Normally the kernel will make the right choice by itself.
894 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
896 prompt "Should Calgary be enabled by default?"
897 depends on CALGARY_IOMMU
899 Should Calgary be enabled by default? if you choose 'y', Calgary
900 will be used (if it exists). If you choose 'n', Calgary will not be
901 used even if it exists. If you choose 'n' and would like to use
902 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
905 # need this always selected by IOMMU for the VIA workaround
909 Support for software bounce buffers used on x86-64 systems
910 which don't have a hardware IOMMU. Using this PCI devices
911 which can only access 32-bits of memory can be used on systems
912 with more than 3 GB of memory.
917 depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU
920 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
921 depends on X86_64 && SMP && DEBUG_KERNEL
922 select CPUMASK_OFFSTACK
924 Enable maximum number of CPUS and NUMA Nodes for this architecture.
928 int "Maximum number of CPUs" if SMP && !MAXSMP
929 range 2 8 if SMP && X86_32 && !X86_BIGSMP
930 range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK
931 range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
933 default "8192" if MAXSMP
934 default "32" if SMP && X86_BIGSMP
935 default "8" if SMP && X86_32
938 This allows you to specify the maximum number of CPUs which this
939 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
940 supported value is 8192, otherwise the maximum value is 512. The
941 minimum value which makes sense is 2.
943 This is purely to save memory - each supported CPU adds
944 approximately eight kilobytes to the kernel image.
947 bool "SMT (Hyperthreading) scheduler support"
950 SMT scheduler support improves the CPU scheduler's decision making
951 when dealing with Intel Pentium 4 chips with HyperThreading at a
952 cost of slightly increased overhead in some places. If unsure say
957 prompt "Multi-core scheduler support"
960 Multi-core scheduler support improves the CPU scheduler's decision
961 making when dealing with multi-core CPU chips at a cost of slightly
962 increased overhead in some places. If unsure say N here.
965 bool "CPU core priorities scheduler support"
966 depends on SCHED_MC && CPU_SUP_INTEL
967 select X86_INTEL_PSTATE
971 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
972 core ordering determined at manufacturing time, which allows
973 certain cores to reach higher turbo frequencies (when running
974 single threaded workloads) than others.
976 Enabling this kernel feature teaches the scheduler about
977 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
978 scheduler's CPU selection logic accordingly, so that higher
979 overall system performance can be achieved.
981 This feature will have no effect on CPUs without this feature.
983 If unsure say Y here.
985 source "kernel/Kconfig.preempt"
989 depends on !SMP && X86_LOCAL_APIC
992 bool "Local APIC support on uniprocessors" if !PCI_MSI
994 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
996 A local APIC (Advanced Programmable Interrupt Controller) is an
997 integrated interrupt controller in the CPU. If you have a single-CPU
998 system which has a processor with a local APIC, you can say Y here to
999 enable and use it. If you say Y here even though your machine doesn't
1000 have a local APIC, then the kernel will still run with no slowdown at
1001 all. The local APIC supports CPU-generated self-interrupts (timer,
1002 performance counters), and the NMI watchdog which detects hard
1005 config X86_UP_IOAPIC
1006 bool "IO-APIC support on uniprocessors"
1007 depends on X86_UP_APIC
1009 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1010 SMP-capable replacement for PC-style interrupt controllers. Most
1011 SMP systems and many recent uniprocessor systems have one.
1013 If you have a single-CPU system with an IO-APIC, you can say Y here
1014 to use it. If you say Y here even though your machine doesn't have
1015 an IO-APIC, then the kernel will still run with no slowdown at all.
1017 config X86_LOCAL_APIC
1019 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1020 select IRQ_DOMAIN_HIERARCHY
1021 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1025 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1027 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1028 bool "Reroute for broken boot IRQs"
1029 depends on X86_IO_APIC
1031 This option enables a workaround that fixes a source of
1032 spurious interrupts. This is recommended when threaded
1033 interrupt handling is used on systems where the generation of
1034 superfluous "boot interrupts" cannot be disabled.
1036 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1037 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1038 kernel does during interrupt handling). On chipsets where this
1039 boot IRQ generation cannot be disabled, this workaround keeps
1040 the original IRQ line masked so that only the equivalent "boot
1041 IRQ" is delivered to the CPUs. The workaround also tells the
1042 kernel to set up the IRQ handler on the boot IRQ line. In this
1043 way only one interrupt is delivered to the kernel. Otherwise
1044 the spurious second interrupt may cause the kernel to bring
1045 down (vital) interrupt lines.
1047 Only affects "broken" chipsets. Interrupt sharing may be
1048 increased on these systems.
1051 bool "Machine Check / overheating reporting"
1052 select GENERIC_ALLOCATOR
1055 Machine Check support allows the processor to notify the
1056 kernel if it detects a problem (e.g. overheating, data corruption).
1057 The action the kernel takes depends on the severity of the problem,
1058 ranging from warning messages to halting the machine.
1060 config X86_MCELOG_LEGACY
1061 bool "Support for deprecated /dev/mcelog character device"
1064 Enable support for /dev/mcelog which is needed by the old mcelog
1065 userspace logging daemon. Consider switching to the new generation
1068 config X86_MCE_INTEL
1070 prompt "Intel MCE features"
1071 depends on X86_MCE && X86_LOCAL_APIC
1073 Additional support for intel specific MCE features such as
1074 the thermal monitor.
1078 prompt "AMD MCE features"
1079 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1081 Additional support for AMD specific MCE features such as
1082 the DRAM Error Threshold.
1084 config X86_ANCIENT_MCE
1085 bool "Support for old Pentium 5 / WinChip machine checks"
1086 depends on X86_32 && X86_MCE
1088 Include support for machine check handling on old Pentium 5 or WinChip
1089 systems. These typically need to be enabled explicitly on the command
1092 config X86_MCE_THRESHOLD
1093 depends on X86_MCE_AMD || X86_MCE_INTEL
1096 config X86_MCE_INJECT
1097 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1098 tristate "Machine check injector support"
1100 Provide support for injecting machine checks for testing purposes.
1101 If you don't know what a machine check is and you don't do kernel
1102 QA it is safe to say n.
1104 config X86_THERMAL_VECTOR
1106 depends on X86_MCE_INTEL
1108 source "arch/x86/events/Kconfig"
1110 config X86_LEGACY_VM86
1111 bool "Legacy VM86 support"
1115 This option allows user programs to put the CPU into V8086
1116 mode, which is an 80286-era approximation of 16-bit real mode.
1118 Some very old versions of X and/or vbetool require this option
1119 for user mode setting. Similarly, DOSEMU will use it if
1120 available to accelerate real mode DOS programs. However, any
1121 recent version of DOSEMU, X, or vbetool should be fully
1122 functional even without kernel VM86 support, as they will all
1123 fall back to software emulation. Nevertheless, if you are using
1124 a 16-bit DOS program where 16-bit performance matters, vm86
1125 mode might be faster than emulation and you might want to
1128 Note that any app that works on a 64-bit kernel is unlikely to
1129 need this option, as 64-bit kernels don't, and can't, support
1130 V8086 mode. This option is also unrelated to 16-bit protected
1131 mode and is not needed to run most 16-bit programs under Wine.
1133 Enabling this option increases the complexity of the kernel
1134 and slows down exception handling a tiny bit.
1136 If unsure, say N here.
1140 default X86_LEGACY_VM86
1143 bool "Enable support for 16-bit segments" if EXPERT
1145 depends on MODIFY_LDT_SYSCALL
1147 This option is required by programs like Wine to run 16-bit
1148 protected mode legacy code on x86 processors. Disabling
1149 this option saves about 300 bytes on i386, or around 6K text
1150 plus 16K runtime memory on x86-64,
1154 depends on X86_16BIT && X86_32
1158 depends on X86_16BIT && X86_64
1160 config X86_VSYSCALL_EMULATION
1161 bool "Enable vsyscall emulation" if EXPERT
1165 This enables emulation of the legacy vsyscall page. Disabling
1166 it is roughly equivalent to booting with vsyscall=none, except
1167 that it will also disable the helpful warning if a program
1168 tries to use a vsyscall. With this option set to N, offending
1169 programs will just segfault, citing addresses of the form
1172 This option is required by many programs built before 2013, and
1173 care should be used even with newer programs if set to N.
1175 Disabling this option saves about 7K of kernel size and
1176 possibly 4K of additional runtime pagetable memory.
1179 tristate "Toshiba Laptop support"
1182 This adds a driver to safely access the System Management Mode of
1183 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1184 not work on models with a Phoenix BIOS. The System Management Mode
1185 is used to set the BIOS and power saving options on Toshiba portables.
1187 For information on utilities to make use of this driver see the
1188 Toshiba Linux utilities web site at:
1189 <http://www.buzzard.org.uk/toshiba/>.
1191 Say Y if you intend to run this kernel on a Toshiba portable.
1195 tristate "Dell i8k legacy laptop support"
1197 select SENSORS_DELL_SMM
1199 This option enables legacy /proc/i8k userspace interface in hwmon
1200 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1201 temperature and allows controlling fan speeds of Dell laptops via
1202 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1203 it reports also power and hotkey status. For fan speed control is
1204 needed userspace package i8kutils.
1206 Say Y if you intend to run this kernel on old Dell laptops or want to
1207 use userspace package i8kutils.
1210 config X86_REBOOTFIXUPS
1211 bool "Enable X86 board specific fixups for reboot"
1214 This enables chipset and/or board specific fixups to be done
1215 in order to get reboot to work correctly. This is only needed on
1216 some combinations of hardware and BIOS. The symptom, for which
1217 this config is intended, is when reboot ends with a stalled/hung
1220 Currently, the only fixup is for the Geode machines using
1221 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1223 Say Y if you want to enable the fixup. Currently, it's safe to
1224 enable this option even if you don't need it.
1228 bool "CPU microcode loading support"
1230 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1233 If you say Y here, you will be able to update the microcode on
1234 Intel and AMD processors. The Intel support is for the IA32 family,
1235 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1236 AMD support is for families 0x10 and later. You will obviously need
1237 the actual microcode binary data itself which is not shipped with
1240 The preferred method to load microcode from a detached initrd is described
1241 in Documentation/x86/early-microcode.txt. For that you need to enable
1242 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1243 initrd for microcode blobs.
1245 In addition, you can build-in the microcode into the kernel. For that you
1246 need to enable FIRMWARE_IN_KERNEL and add the vendor-supplied microcode
1247 to the CONFIG_EXTRA_FIRMWARE config option.
1249 config MICROCODE_INTEL
1250 bool "Intel microcode loading support"
1251 depends on MICROCODE
1255 This options enables microcode patch loading support for Intel
1258 For the current Intel microcode data package go to
1259 <https://downloadcenter.intel.com> and search for
1260 'Linux Processor Microcode Data File'.
1262 config MICROCODE_AMD
1263 bool "AMD microcode loading support"
1264 depends on MICROCODE
1267 If you select this option, microcode patch loading support for AMD
1268 processors will be enabled.
1270 config MICROCODE_OLD_INTERFACE
1272 depends on MICROCODE
1275 tristate "/dev/cpu/*/msr - Model-specific register support"
1277 This device gives privileged processes access to the x86
1278 Model-Specific Registers (MSRs). It is a character device with
1279 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1280 MSR accesses are directed to a specific CPU on multi-processor
1284 tristate "/dev/cpu/*/cpuid - CPU information support"
1286 This device gives processes access to the x86 CPUID instruction to
1287 be executed on a specific processor. It is a character device
1288 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1292 prompt "High Memory Support"
1299 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1300 However, the address space of 32-bit x86 processors is only 4
1301 Gigabytes large. That means that, if you have a large amount of
1302 physical memory, not all of it can be "permanently mapped" by the
1303 kernel. The physical memory that's not permanently mapped is called
1306 If you are compiling a kernel which will never run on a machine with
1307 more than 1 Gigabyte total physical RAM, answer "off" here (default
1308 choice and suitable for most users). This will result in a "3GB/1GB"
1309 split: 3GB are mapped so that each process sees a 3GB virtual memory
1310 space and the remaining part of the 4GB virtual memory space is used
1311 by the kernel to permanently map as much physical memory as
1314 If the machine has between 1 and 4 Gigabytes physical RAM, then
1317 If more than 4 Gigabytes is used then answer "64GB" here. This
1318 selection turns Intel PAE (Physical Address Extension) mode on.
1319 PAE implements 3-level paging on IA32 processors. PAE is fully
1320 supported by Linux, PAE mode is implemented on all recent Intel
1321 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1322 then the kernel will not boot on CPUs that don't support PAE!
1324 The actual amount of total physical memory will either be
1325 auto detected or can be forced by using a kernel command line option
1326 such as "mem=256M". (Try "man bootparam" or see the documentation of
1327 your boot loader (lilo or loadlin) about how to pass options to the
1328 kernel at boot time.)
1330 If unsure, say "off".
1335 Select this if you have a 32-bit processor and between 1 and 4
1336 gigabytes of physical RAM.
1343 Select this if you have a 32-bit processor and more than 4
1344 gigabytes of physical RAM.
1349 prompt "Memory split" if EXPERT
1353 Select the desired split between kernel and user memory.
1355 If the address range available to the kernel is less than the
1356 physical memory installed, the remaining memory will be available
1357 as "high memory". Accessing high memory is a little more costly
1358 than low memory, as it needs to be mapped into the kernel first.
1359 Note that increasing the kernel address space limits the range
1360 available to user programs, making the address space there
1361 tighter. Selecting anything other than the default 3G/1G split
1362 will also likely make your kernel incompatible with binary-only
1365 If you are not absolutely sure what you are doing, leave this
1369 bool "3G/1G user/kernel split"
1370 config VMSPLIT_3G_OPT
1372 bool "3G/1G user/kernel split (for full 1G low memory)"
1374 bool "2G/2G user/kernel split"
1375 config VMSPLIT_2G_OPT
1377 bool "2G/2G user/kernel split (for full 2G low memory)"
1379 bool "1G/3G user/kernel split"
1384 default 0xB0000000 if VMSPLIT_3G_OPT
1385 default 0x80000000 if VMSPLIT_2G
1386 default 0x78000000 if VMSPLIT_2G_OPT
1387 default 0x40000000 if VMSPLIT_1G
1393 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1396 bool "PAE (Physical Address Extension) Support"
1397 depends on X86_32 && !HIGHMEM4G
1400 PAE is required for NX support, and furthermore enables
1401 larger swapspace support for non-overcommit purposes. It
1402 has the cost of more pagetable lookup overhead, and also
1403 consumes more pagetable space per process.
1406 bool "Enable 5-level page tables support"
1409 5-level paging enables access to larger address space:
1410 upto 128 PiB of virtual address space and 4 PiB of
1411 physical address space.
1413 It will be supported by future Intel CPUs.
1415 Note: a kernel with this option enabled can only be booted
1416 on machines that support the feature.
1418 See Documentation/x86/x86_64/5level-paging.txt for more
1423 config ARCH_PHYS_ADDR_T_64BIT
1425 depends on X86_64 || X86_PAE
1427 config ARCH_DMA_ADDR_T_64BIT
1429 depends on X86_64 || HIGHMEM64G
1431 config X86_DIRECT_GBPAGES
1433 depends on X86_64 && !DEBUG_PAGEALLOC && !KMEMCHECK
1435 Certain kernel features effectively disable kernel
1436 linear 1 GB mappings (even if the CPU otherwise
1437 supports them), so don't confuse the user by printing
1438 that we have them enabled.
1440 config ARCH_HAS_MEM_ENCRYPT
1443 config AMD_MEM_ENCRYPT
1444 bool "AMD Secure Memory Encryption (SME) support"
1445 depends on X86_64 && CPU_SUP_AMD
1447 Say yes to enable support for the encryption of system memory.
1448 This requires an AMD processor that supports Secure Memory
1451 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1452 bool "Activate AMD Secure Memory Encryption (SME) by default"
1454 depends on AMD_MEM_ENCRYPT
1456 Say yes to have system memory encrypted by default if running on
1457 an AMD processor that supports Secure Memory Encryption (SME).
1459 If set to Y, then the encryption of system memory can be
1460 deactivated with the mem_encrypt=off command line option.
1462 If set to N, then the encryption of system memory can be
1463 activated with the mem_encrypt=on command line option.
1465 config ARCH_USE_MEMREMAP_PROT
1467 depends on AMD_MEM_ENCRYPT
1469 # Common NUMA Features
1471 bool "Numa Memory Allocation and Scheduler Support"
1473 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1474 default y if X86_BIGSMP
1476 Enable NUMA (Non Uniform Memory Access) support.
1478 The kernel will try to allocate memory used by a CPU on the
1479 local memory controller of the CPU and add some more
1480 NUMA awareness to the kernel.
1482 For 64-bit this is recommended if the system is Intel Core i7
1483 (or later), AMD Opteron, or EM64T NUMA.
1485 For 32-bit this is only needed if you boot a 32-bit
1486 kernel on a 64-bit NUMA platform.
1488 Otherwise, you should say N.
1492 prompt "Old style AMD Opteron NUMA detection"
1493 depends on X86_64 && NUMA && PCI
1495 Enable AMD NUMA node topology detection. You should say Y here if
1496 you have a multi processor AMD system. This uses an old method to
1497 read the NUMA configuration directly from the builtin Northbridge
1498 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1499 which also takes priority if both are compiled in.
1501 config X86_64_ACPI_NUMA
1503 prompt "ACPI NUMA detection"
1504 depends on X86_64 && NUMA && ACPI && PCI
1507 Enable ACPI SRAT based node topology detection.
1509 # Some NUMA nodes have memory ranges that span
1510 # other nodes. Even though a pfn is valid and
1511 # between a node's start and end pfns, it may not
1512 # reside on that node. See memmap_init_zone()
1514 config NODES_SPAN_OTHER_NODES
1516 depends on X86_64_ACPI_NUMA
1519 bool "NUMA emulation"
1522 Enable NUMA emulation. A flat machine will be split
1523 into virtual nodes when booted with "numa=fake=N", where N is the
1524 number of nodes. This is only useful for debugging.
1527 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1529 default "10" if MAXSMP
1530 default "6" if X86_64
1532 depends on NEED_MULTIPLE_NODES
1534 Specify the maximum number of NUMA Nodes available on the target
1535 system. Increases memory reserved to accommodate various tables.
1537 config ARCH_HAVE_MEMORY_PRESENT
1539 depends on X86_32 && DISCONTIGMEM
1541 config NEED_NODE_MEMMAP_SIZE
1543 depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
1545 config ARCH_FLATMEM_ENABLE
1547 depends on X86_32 && !NUMA
1549 config ARCH_DISCONTIGMEM_ENABLE
1551 depends on NUMA && X86_32
1553 config ARCH_DISCONTIGMEM_DEFAULT
1555 depends on NUMA && X86_32
1557 config ARCH_SPARSEMEM_ENABLE
1559 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1560 select SPARSEMEM_STATIC if X86_32
1561 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1563 config ARCH_SPARSEMEM_DEFAULT
1567 config ARCH_SELECT_MEMORY_MODEL
1569 depends on ARCH_SPARSEMEM_ENABLE
1571 config ARCH_MEMORY_PROBE
1572 bool "Enable sysfs memory/probe interface"
1573 depends on X86_64 && MEMORY_HOTPLUG
1575 This option enables a sysfs memory/probe interface for testing.
1576 See Documentation/memory-hotplug.txt for more information.
1577 If you are unsure how to answer this question, answer N.
1579 config ARCH_PROC_KCORE_TEXT
1581 depends on X86_64 && PROC_KCORE
1583 config ILLEGAL_POINTER_VALUE
1586 default 0xdead000000000000 if X86_64
1590 config X86_PMEM_LEGACY_DEVICE
1593 config X86_PMEM_LEGACY
1594 tristate "Support non-standard NVDIMMs and ADR protected memory"
1595 depends on PHYS_ADDR_T_64BIT
1597 select X86_PMEM_LEGACY_DEVICE
1600 Treat memory marked using the non-standard e820 type of 12 as used
1601 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1602 The kernel will offer these regions to the 'pmem' driver so
1603 they can be used for persistent storage.
1608 bool "Allocate 3rd-level pagetables from highmem"
1611 The VM uses one page table entry for each page of physical memory.
1612 For systems with a lot of RAM, this can be wasteful of precious
1613 low memory. Setting this option will put user-space page table
1614 entries in high memory.
1616 config X86_CHECK_BIOS_CORRUPTION
1617 bool "Check for low memory corruption"
1619 Periodically check for memory corruption in low memory, which
1620 is suspected to be caused by BIOS. Even when enabled in the
1621 configuration, it is disabled at runtime. Enable it by
1622 setting "memory_corruption_check=1" on the kernel command
1623 line. By default it scans the low 64k of memory every 60
1624 seconds; see the memory_corruption_check_size and
1625 memory_corruption_check_period parameters in
1626 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1628 When enabled with the default parameters, this option has
1629 almost no overhead, as it reserves a relatively small amount
1630 of memory and scans it infrequently. It both detects corruption
1631 and prevents it from affecting the running system.
1633 It is, however, intended as a diagnostic tool; if repeatable
1634 BIOS-originated corruption always affects the same memory,
1635 you can use memmap= to prevent the kernel from using that
1638 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1639 bool "Set the default setting of memory_corruption_check"
1640 depends on X86_CHECK_BIOS_CORRUPTION
1643 Set whether the default state of memory_corruption_check is
1646 config X86_RESERVE_LOW
1647 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1651 Specify the amount of low memory to reserve for the BIOS.
1653 The first page contains BIOS data structures that the kernel
1654 must not use, so that page must always be reserved.
1656 By default we reserve the first 64K of physical RAM, as a
1657 number of BIOSes are known to corrupt that memory range
1658 during events such as suspend/resume or monitor cable
1659 insertion, so it must not be used by the kernel.
1661 You can set this to 4 if you are absolutely sure that you
1662 trust the BIOS to get all its memory reservations and usages
1663 right. If you know your BIOS have problems beyond the
1664 default 64K area, you can set this to 640 to avoid using the
1665 entire low memory range.
1667 If you have doubts about the BIOS (e.g. suspend/resume does
1668 not work or there's kernel crashes after certain hardware
1669 hotplug events) then you might want to enable
1670 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1671 typical corruption patterns.
1673 Leave this to the default value of 64 if you are unsure.
1675 config MATH_EMULATION
1677 depends on MODIFY_LDT_SYSCALL
1678 prompt "Math emulation" if X86_32
1680 Linux can emulate a math coprocessor (used for floating point
1681 operations) if you don't have one. 486DX and Pentium processors have
1682 a math coprocessor built in, 486SX and 386 do not, unless you added
1683 a 487DX or 387, respectively. (The messages during boot time can
1684 give you some hints here ["man dmesg"].) Everyone needs either a
1685 coprocessor or this emulation.
1687 If you don't have a math coprocessor, you need to say Y here; if you
1688 say Y here even though you have a coprocessor, the coprocessor will
1689 be used nevertheless. (This behavior can be changed with the kernel
1690 command line option "no387", which comes handy if your coprocessor
1691 is broken. Try "man bootparam" or see the documentation of your boot
1692 loader (lilo or loadlin) about how to pass options to the kernel at
1693 boot time.) This means that it is a good idea to say Y here if you
1694 intend to use this kernel on different machines.
1696 More information about the internals of the Linux math coprocessor
1697 emulation can be found in <file:arch/x86/math-emu/README>.
1699 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1700 kernel, it won't hurt.
1704 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1706 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1707 the Memory Type Range Registers (MTRRs) may be used to control
1708 processor access to memory ranges. This is most useful if you have
1709 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1710 allows bus write transfers to be combined into a larger transfer
1711 before bursting over the PCI/AGP bus. This can increase performance
1712 of image write operations 2.5 times or more. Saying Y here creates a
1713 /proc/mtrr file which may be used to manipulate your processor's
1714 MTRRs. Typically the X server should use this.
1716 This code has a reasonably generic interface so that similar
1717 control registers on other processors can be easily supported
1720 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1721 Registers (ARRs) which provide a similar functionality to MTRRs. For
1722 these, the ARRs are used to emulate the MTRRs.
1723 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1724 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1725 write-combining. All of these processors are supported by this code
1726 and it makes sense to say Y here if you have one of them.
1728 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1729 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1730 can lead to all sorts of problems, so it's good to say Y here.
1732 You can safely say Y even if your machine doesn't have MTRRs, you'll
1733 just add about 9 KB to your kernel.
1735 See <file:Documentation/x86/mtrr.txt> for more information.
1737 config MTRR_SANITIZER
1739 prompt "MTRR cleanup support"
1742 Convert MTRR layout from continuous to discrete, so X drivers can
1743 add writeback entries.
1745 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1746 The largest mtrr entry size for a continuous block can be set with
1751 config MTRR_SANITIZER_ENABLE_DEFAULT
1752 int "MTRR cleanup enable value (0-1)"
1755 depends on MTRR_SANITIZER
1757 Enable mtrr cleanup default value
1759 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1760 int "MTRR cleanup spare reg num (0-7)"
1763 depends on MTRR_SANITIZER
1765 mtrr cleanup spare entries default, it can be changed via
1766 mtrr_spare_reg_nr=N on the kernel command line.
1770 prompt "x86 PAT support" if EXPERT
1773 Use PAT attributes to setup page level cache control.
1775 PATs are the modern equivalents of MTRRs and are much more
1776 flexible than MTRRs.
1778 Say N here if you see bootup problems (boot crash, boot hang,
1779 spontaneous reboots) or a non-working video driver.
1783 config ARCH_USES_PG_UNCACHED
1789 prompt "x86 architectural random number generator" if EXPERT
1791 Enable the x86 architectural RDRAND instruction
1792 (Intel Bull Mountain technology) to generate random numbers.
1793 If supported, this is a high bandwidth, cryptographically
1794 secure hardware random number generator.
1798 prompt "Supervisor Mode Access Prevention" if EXPERT
1800 Supervisor Mode Access Prevention (SMAP) is a security
1801 feature in newer Intel processors. There is a small
1802 performance cost if this enabled and turned on; there is
1803 also a small increase in the kernel size if this is enabled.
1807 config X86_INTEL_UMIP
1809 depends on CPU_SUP_INTEL
1810 prompt "Intel User Mode Instruction Prevention" if EXPERT
1812 The User Mode Instruction Prevention (UMIP) is a security
1813 feature in newer Intel processors. If enabled, a general
1814 protection fault is issued if the instructions SGDT, SLDT,
1815 SIDT, SMSW and STR are executed in user mode.
1817 config X86_INTEL_MPX
1818 prompt "Intel MPX (Memory Protection Extensions)"
1820 # Note: only available in 64-bit mode due to VMA flags shortage
1821 depends on CPU_SUP_INTEL && X86_64
1822 select ARCH_USES_HIGH_VMA_FLAGS
1824 MPX provides hardware features that can be used in
1825 conjunction with compiler-instrumented code to check
1826 memory references. It is designed to detect buffer
1827 overflow or underflow bugs.
1829 This option enables running applications which are
1830 instrumented or otherwise use MPX. It does not use MPX
1831 itself inside the kernel or to protect the kernel
1832 against bad memory references.
1834 Enabling this option will make the kernel larger:
1835 ~8k of kernel text and 36 bytes of data on a 64-bit
1836 defconfig. It adds a long to the 'mm_struct' which
1837 will increase the kernel memory overhead of each
1838 process and adds some branches to paths used during
1839 exec() and munmap().
1841 For details, see Documentation/x86/intel_mpx.txt
1845 config X86_INTEL_MEMORY_PROTECTION_KEYS
1846 prompt "Intel Memory Protection Keys"
1848 # Note: only available in 64-bit mode
1849 depends on CPU_SUP_INTEL && X86_64
1850 select ARCH_USES_HIGH_VMA_FLAGS
1851 select ARCH_HAS_PKEYS
1853 Memory Protection Keys provides a mechanism for enforcing
1854 page-based protections, but without requiring modification of the
1855 page tables when an application changes protection domains.
1857 For details, see Documentation/x86/protection-keys.txt
1862 bool "EFI runtime service support"
1865 select EFI_RUNTIME_WRAPPERS
1867 This enables the kernel to use EFI runtime services that are
1868 available (such as the EFI variable services).
1870 This option is only useful on systems that have EFI firmware.
1871 In addition, you should use the latest ELILO loader available
1872 at <http://elilo.sourceforge.net> in order to take advantage
1873 of EFI runtime services. However, even with this option, the
1874 resultant kernel should continue to boot on existing non-EFI
1878 bool "EFI stub support"
1879 depends on EFI && !X86_USE_3DNOW
1882 This kernel feature allows a bzImage to be loaded directly
1883 by EFI firmware without the use of a bootloader.
1885 See Documentation/efi-stub.txt for more information.
1888 bool "EFI mixed-mode support"
1889 depends on EFI_STUB && X86_64
1891 Enabling this feature allows a 64-bit kernel to be booted
1892 on a 32-bit firmware, provided that your CPU supports 64-bit
1895 Note that it is not possible to boot a mixed-mode enabled
1896 kernel via the EFI boot stub - a bootloader that supports
1897 the EFI handover protocol must be used.
1903 prompt "Enable seccomp to safely compute untrusted bytecode"
1905 This kernel feature is useful for number crunching applications
1906 that may need to compute untrusted bytecode during their
1907 execution. By using pipes or other transports made available to
1908 the process as file descriptors supporting the read/write
1909 syscalls, it's possible to isolate those applications in
1910 their own address space using seccomp. Once seccomp is
1911 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1912 and the task is only allowed to execute a few safe syscalls
1913 defined by each seccomp mode.
1915 If unsure, say Y. Only embedded should say N here.
1917 source kernel/Kconfig.hz
1920 bool "kexec system call"
1923 kexec is a system call that implements the ability to shutdown your
1924 current kernel, and to start another kernel. It is like a reboot
1925 but it is independent of the system firmware. And like a reboot
1926 you can start any kernel with it, not just Linux.
1928 The name comes from the similarity to the exec system call.
1930 It is an ongoing process to be certain the hardware in a machine
1931 is properly shutdown, so do not be surprised if this code does not
1932 initially work for you. As of this writing the exact hardware
1933 interface is strongly in flux, so no good recommendation can be
1937 bool "kexec file based system call"
1942 depends on CRYPTO_SHA256=y
1944 This is new version of kexec system call. This system call is
1945 file based and takes file descriptors as system call argument
1946 for kernel and initramfs as opposed to list of segments as
1947 accepted by previous system call.
1949 config KEXEC_VERIFY_SIG
1950 bool "Verify kernel signature during kexec_file_load() syscall"
1951 depends on KEXEC_FILE
1953 This option makes kernel signature verification mandatory for
1954 the kexec_file_load() syscall.
1956 In addition to that option, you need to enable signature
1957 verification for the corresponding kernel image type being
1958 loaded in order for this to work.
1960 config KEXEC_BZIMAGE_VERIFY_SIG
1961 bool "Enable bzImage signature verification support"
1962 depends on KEXEC_VERIFY_SIG
1963 depends on SIGNED_PE_FILE_VERIFICATION
1964 select SYSTEM_TRUSTED_KEYRING
1966 Enable bzImage signature verification support.
1969 bool "kernel crash dumps"
1970 depends on X86_64 || (X86_32 && HIGHMEM)
1972 Generate crash dump after being started by kexec.
1973 This should be normally only set in special crash dump kernels
1974 which are loaded in the main kernel with kexec-tools into
1975 a specially reserved region and then later executed after
1976 a crash by kdump/kexec. The crash dump kernel must be compiled
1977 to a memory address not used by the main kernel or BIOS using
1978 PHYSICAL_START, or it must be built as a relocatable image
1979 (CONFIG_RELOCATABLE=y).
1980 For more details see Documentation/kdump/kdump.txt
1984 depends on KEXEC && HIBERNATION
1986 Jump between original kernel and kexeced kernel and invoke
1987 code in physical address mode via KEXEC
1989 config PHYSICAL_START
1990 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
1993 This gives the physical address where the kernel is loaded.
1995 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
1996 bzImage will decompress itself to above physical address and
1997 run from there. Otherwise, bzImage will run from the address where
1998 it has been loaded by the boot loader and will ignore above physical
2001 In normal kdump cases one does not have to set/change this option
2002 as now bzImage can be compiled as a completely relocatable image
2003 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2004 address. This option is mainly useful for the folks who don't want
2005 to use a bzImage for capturing the crash dump and want to use a
2006 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2007 to be specifically compiled to run from a specific memory area
2008 (normally a reserved region) and this option comes handy.
2010 So if you are using bzImage for capturing the crash dump,
2011 leave the value here unchanged to 0x1000000 and set
2012 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2013 for capturing the crash dump change this value to start of
2014 the reserved region. In other words, it can be set based on
2015 the "X" value as specified in the "crashkernel=YM@XM"
2016 command line boot parameter passed to the panic-ed
2017 kernel. Please take a look at Documentation/kdump/kdump.txt
2018 for more details about crash dumps.
2020 Usage of bzImage for capturing the crash dump is recommended as
2021 one does not have to build two kernels. Same kernel can be used
2022 as production kernel and capture kernel. Above option should have
2023 gone away after relocatable bzImage support is introduced. But it
2024 is present because there are users out there who continue to use
2025 vmlinux for dump capture. This option should go away down the
2028 Don't change this unless you know what you are doing.
2031 bool "Build a relocatable kernel"
2034 This builds a kernel image that retains relocation information
2035 so it can be loaded someplace besides the default 1MB.
2036 The relocations tend to make the kernel binary about 10% larger,
2037 but are discarded at runtime.
2039 One use is for the kexec on panic case where the recovery kernel
2040 must live at a different physical address than the primary
2043 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2044 it has been loaded at and the compile time physical address
2045 (CONFIG_PHYSICAL_START) is used as the minimum location.
2047 config RANDOMIZE_BASE
2048 bool "Randomize the address of the kernel image (KASLR)"
2049 depends on RELOCATABLE
2052 In support of Kernel Address Space Layout Randomization (KASLR),
2053 this randomizes the physical address at which the kernel image
2054 is decompressed and the virtual address where the kernel
2055 image is mapped, as a security feature that deters exploit
2056 attempts relying on knowledge of the location of kernel
2059 On 64-bit, the kernel physical and virtual addresses are
2060 randomized separately. The physical address will be anywhere
2061 between 16MB and the top of physical memory (up to 64TB). The
2062 virtual address will be randomized from 16MB up to 1GB (9 bits
2063 of entropy). Note that this also reduces the memory space
2064 available to kernel modules from 1.5GB to 1GB.
2066 On 32-bit, the kernel physical and virtual addresses are
2067 randomized together. They will be randomized from 16MB up to
2068 512MB (8 bits of entropy).
2070 Entropy is generated using the RDRAND instruction if it is
2071 supported. If RDTSC is supported, its value is mixed into
2072 the entropy pool as well. If neither RDRAND nor RDTSC are
2073 supported, then entropy is read from the i8254 timer. The
2074 usable entropy is limited by the kernel being built using
2075 2GB addressing, and that PHYSICAL_ALIGN must be at a
2076 minimum of 2MB. As a result, only 10 bits of entropy are
2077 theoretically possible, but the implementations are further
2078 limited due to memory layouts.
2082 # Relocation on x86 needs some additional build support
2083 config X86_NEED_RELOCS
2085 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2087 config PHYSICAL_ALIGN
2088 hex "Alignment value to which kernel should be aligned"
2090 range 0x2000 0x1000000 if X86_32
2091 range 0x200000 0x1000000 if X86_64
2093 This value puts the alignment restrictions on physical address
2094 where kernel is loaded and run from. Kernel is compiled for an
2095 address which meets above alignment restriction.
2097 If bootloader loads the kernel at a non-aligned address and
2098 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2099 address aligned to above value and run from there.
2101 If bootloader loads the kernel at a non-aligned address and
2102 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2103 load address and decompress itself to the address it has been
2104 compiled for and run from there. The address for which kernel is
2105 compiled already meets above alignment restrictions. Hence the
2106 end result is that kernel runs from a physical address meeting
2107 above alignment restrictions.
2109 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2110 this value must be a multiple of 0x200000.
2112 Don't change this unless you know what you are doing.
2114 config RANDOMIZE_MEMORY
2115 bool "Randomize the kernel memory sections"
2117 depends on RANDOMIZE_BASE
2118 default RANDOMIZE_BASE
2120 Randomizes the base virtual address of kernel memory sections
2121 (physical memory mapping, vmalloc & vmemmap). This security feature
2122 makes exploits relying on predictable memory locations less reliable.
2124 The order of allocations remains unchanged. Entropy is generated in
2125 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2126 configuration have in average 30,000 different possible virtual
2127 addresses for each memory section.
2131 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2132 hex "Physical memory mapping padding" if EXPERT
2133 depends on RANDOMIZE_MEMORY
2134 default "0xa" if MEMORY_HOTPLUG
2136 range 0x1 0x40 if MEMORY_HOTPLUG
2139 Define the padding in terabytes added to the existing physical
2140 memory size during kernel memory randomization. It is useful
2141 for memory hotplug support but reduces the entropy available for
2142 address randomization.
2144 If unsure, leave at the default value.
2147 bool "Support for hot-pluggable CPUs"
2150 Say Y here to allow turning CPUs off and on. CPUs can be
2151 controlled through /sys/devices/system/cpu.
2152 ( Note: power management support will enable this option
2153 automatically on SMP systems. )
2154 Say N if you want to disable CPU hotplug.
2156 config BOOTPARAM_HOTPLUG_CPU0
2157 bool "Set default setting of cpu0_hotpluggable"
2159 depends on HOTPLUG_CPU
2161 Set whether default state of cpu0_hotpluggable is on or off.
2163 Say Y here to enable CPU0 hotplug by default. If this switch
2164 is turned on, there is no need to give cpu0_hotplug kernel
2165 parameter and the CPU0 hotplug feature is enabled by default.
2167 Please note: there are two known CPU0 dependencies if you want
2168 to enable the CPU0 hotplug feature either by this switch or by
2169 cpu0_hotplug kernel parameter.
2171 First, resume from hibernate or suspend always starts from CPU0.
2172 So hibernate and suspend are prevented if CPU0 is offline.
2174 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2175 offline if any interrupt can not migrate out of CPU0. There may
2176 be other CPU0 dependencies.
2178 Please make sure the dependencies are under your control before
2179 you enable this feature.
2181 Say N if you don't want to enable CPU0 hotplug feature by default.
2182 You still can enable the CPU0 hotplug feature at boot by kernel
2183 parameter cpu0_hotplug.
2185 config DEBUG_HOTPLUG_CPU0
2187 prompt "Debug CPU0 hotplug"
2188 depends on HOTPLUG_CPU
2190 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2191 soon as possible and boots up userspace with CPU0 offlined. User
2192 can online CPU0 back after boot time.
2194 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2195 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2196 compilation or giving cpu0_hotplug kernel parameter at boot.
2202 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2203 depends on COMPAT_32
2205 Certain buggy versions of glibc will crash if they are
2206 presented with a 32-bit vDSO that is not mapped at the address
2207 indicated in its segment table.
2209 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2210 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2211 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2212 the only released version with the bug, but OpenSUSE 9
2213 contains a buggy "glibc 2.3.2".
2215 The symptom of the bug is that everything crashes on startup, saying:
2216 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2218 Saying Y here changes the default value of the vdso32 boot
2219 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2220 This works around the glibc bug but hurts performance.
2222 If unsure, say N: if you are compiling your own kernel, you
2223 are unlikely to be using a buggy version of glibc.
2226 prompt "vsyscall table for legacy applications"
2228 default LEGACY_VSYSCALL_EMULATE
2230 Legacy user code that does not know how to find the vDSO expects
2231 to be able to issue three syscalls by calling fixed addresses in
2232 kernel space. Since this location is not randomized with ASLR,
2233 it can be used to assist security vulnerability exploitation.
2235 This setting can be changed at boot time via the kernel command
2236 line parameter vsyscall=[native|emulate|none].
2238 On a system with recent enough glibc (2.14 or newer) and no
2239 static binaries, you can say None without a performance penalty
2240 to improve security.
2242 If unsure, select "Emulate".
2244 config LEGACY_VSYSCALL_NATIVE
2247 Actual executable code is located in the fixed vsyscall
2248 address mapping, implementing time() efficiently. Since
2249 this makes the mapping executable, it can be used during
2250 security vulnerability exploitation (traditionally as
2251 ROP gadgets). This configuration is not recommended.
2253 config LEGACY_VSYSCALL_EMULATE
2256 The kernel traps and emulates calls into the fixed
2257 vsyscall address mapping. This makes the mapping
2258 non-executable, but it still contains known contents,
2259 which could be used in certain rare security vulnerability
2260 exploits. This configuration is recommended when userspace
2261 still uses the vsyscall area.
2263 config LEGACY_VSYSCALL_NONE
2266 There will be no vsyscall mapping at all. This will
2267 eliminate any risk of ASLR bypass due to the vsyscall
2268 fixed address mapping. Attempts to use the vsyscalls
2269 will be reported to dmesg, so that either old or
2270 malicious userspace programs can be identified.
2275 bool "Built-in kernel command line"
2277 Allow for specifying boot arguments to the kernel at
2278 build time. On some systems (e.g. embedded ones), it is
2279 necessary or convenient to provide some or all of the
2280 kernel boot arguments with the kernel itself (that is,
2281 to not rely on the boot loader to provide them.)
2283 To compile command line arguments into the kernel,
2284 set this option to 'Y', then fill in the
2285 boot arguments in CONFIG_CMDLINE.
2287 Systems with fully functional boot loaders (i.e. non-embedded)
2288 should leave this option set to 'N'.
2291 string "Built-in kernel command string"
2292 depends on CMDLINE_BOOL
2295 Enter arguments here that should be compiled into the kernel
2296 image and used at boot time. If the boot loader provides a
2297 command line at boot time, it is appended to this string to
2298 form the full kernel command line, when the system boots.
2300 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2301 change this behavior.
2303 In most cases, the command line (whether built-in or provided
2304 by the boot loader) should specify the device for the root
2307 config CMDLINE_OVERRIDE
2308 bool "Built-in command line overrides boot loader arguments"
2309 depends on CMDLINE_BOOL
2311 Set this option to 'Y' to have the kernel ignore the boot loader
2312 command line, and use ONLY the built-in command line.
2314 This is used to work around broken boot loaders. This should
2315 be set to 'N' under normal conditions.
2317 config MODIFY_LDT_SYSCALL
2318 bool "Enable the LDT (local descriptor table)" if EXPERT
2321 Linux can allow user programs to install a per-process x86
2322 Local Descriptor Table (LDT) using the modify_ldt(2) system
2323 call. This is required to run 16-bit or segmented code such as
2324 DOSEMU or some Wine programs. It is also used by some very old
2325 threading libraries.
2327 Enabling this feature adds a small amount of overhead to
2328 context switches and increases the low-level kernel attack
2329 surface. Disabling it removes the modify_ldt(2) system call.
2331 Saying 'N' here may make sense for embedded or server kernels.
2333 source "kernel/livepatch/Kconfig"
2337 config ARCH_HAS_ADD_PAGES
2339 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2341 config ARCH_ENABLE_MEMORY_HOTPLUG
2343 depends on X86_64 || (X86_32 && HIGHMEM)
2345 config ARCH_ENABLE_MEMORY_HOTREMOVE
2347 depends on MEMORY_HOTPLUG
2349 config USE_PERCPU_NUMA_NODE_ID
2353 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2355 depends on X86_64 || X86_PAE
2357 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2359 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2361 config ARCH_ENABLE_THP_MIGRATION
2363 depends on X86_64 && TRANSPARENT_HUGEPAGE
2365 menu "Power management and ACPI options"
2367 config ARCH_HIBERNATION_HEADER
2369 depends on X86_64 && HIBERNATION
2371 source "kernel/power/Kconfig"
2373 source "drivers/acpi/Kconfig"
2375 source "drivers/sfi/Kconfig"
2382 tristate "APM (Advanced Power Management) BIOS support"
2383 depends on X86_32 && PM_SLEEP
2385 APM is a BIOS specification for saving power using several different
2386 techniques. This is mostly useful for battery powered laptops with
2387 APM compliant BIOSes. If you say Y here, the system time will be
2388 reset after a RESUME operation, the /proc/apm device will provide
2389 battery status information, and user-space programs will receive
2390 notification of APM "events" (e.g. battery status change).
2392 If you select "Y" here, you can disable actual use of the APM
2393 BIOS by passing the "apm=off" option to the kernel at boot time.
2395 Note that the APM support is almost completely disabled for
2396 machines with more than one CPU.
2398 In order to use APM, you will need supporting software. For location
2399 and more information, read <file:Documentation/power/apm-acpi.txt>
2400 and the Battery Powered Linux mini-HOWTO, available from
2401 <http://www.tldp.org/docs.html#howto>.
2403 This driver does not spin down disk drives (see the hdparm(8)
2404 manpage ("man 8 hdparm") for that), and it doesn't turn off
2405 VESA-compliant "green" monitors.
2407 This driver does not support the TI 4000M TravelMate and the ACER
2408 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2409 desktop machines also don't have compliant BIOSes, and this driver
2410 may cause those machines to panic during the boot phase.
2412 Generally, if you don't have a battery in your machine, there isn't
2413 much point in using this driver and you should say N. If you get
2414 random kernel OOPSes or reboots that don't seem to be related to
2415 anything, try disabling/enabling this option (or disabling/enabling
2418 Some other things you should try when experiencing seemingly random,
2421 1) make sure that you have enough swap space and that it is
2423 2) pass the "no-hlt" option to the kernel
2424 3) switch on floating point emulation in the kernel and pass
2425 the "no387" option to the kernel
2426 4) pass the "floppy=nodma" option to the kernel
2427 5) pass the "mem=4M" option to the kernel (thereby disabling
2428 all but the first 4 MB of RAM)
2429 6) make sure that the CPU is not over clocked.
2430 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2431 8) disable the cache from your BIOS settings
2432 9) install a fan for the video card or exchange video RAM
2433 10) install a better fan for the CPU
2434 11) exchange RAM chips
2435 12) exchange the motherboard.
2437 To compile this driver as a module, choose M here: the
2438 module will be called apm.
2442 config APM_IGNORE_USER_SUSPEND
2443 bool "Ignore USER SUSPEND"
2445 This option will ignore USER SUSPEND requests. On machines with a
2446 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2447 series notebooks, it is necessary to say Y because of a BIOS bug.
2449 config APM_DO_ENABLE
2450 bool "Enable PM at boot time"
2452 Enable APM features at boot time. From page 36 of the APM BIOS
2453 specification: "When disabled, the APM BIOS does not automatically
2454 power manage devices, enter the Standby State, enter the Suspend
2455 State, or take power saving steps in response to CPU Idle calls."
2456 This driver will make CPU Idle calls when Linux is idle (unless this
2457 feature is turned off -- see "Do CPU IDLE calls", below). This
2458 should always save battery power, but more complicated APM features
2459 will be dependent on your BIOS implementation. You may need to turn
2460 this option off if your computer hangs at boot time when using APM
2461 support, or if it beeps continuously instead of suspending. Turn
2462 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2463 T400CDT. This is off by default since most machines do fine without
2468 bool "Make CPU Idle calls when idle"
2470 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2471 On some machines, this can activate improved power savings, such as
2472 a slowed CPU clock rate, when the machine is idle. These idle calls
2473 are made after the idle loop has run for some length of time (e.g.,
2474 333 mS). On some machines, this will cause a hang at boot time or
2475 whenever the CPU becomes idle. (On machines with more than one CPU,
2476 this option does nothing.)
2478 config APM_DISPLAY_BLANK
2479 bool "Enable console blanking using APM"
2481 Enable console blanking using the APM. Some laptops can use this to
2482 turn off the LCD backlight when the screen blanker of the Linux
2483 virtual console blanks the screen. Note that this is only used by
2484 the virtual console screen blanker, and won't turn off the backlight
2485 when using the X Window system. This also doesn't have anything to
2486 do with your VESA-compliant power-saving monitor. Further, this
2487 option doesn't work for all laptops -- it might not turn off your
2488 backlight at all, or it might print a lot of errors to the console,
2489 especially if you are using gpm.
2491 config APM_ALLOW_INTS
2492 bool "Allow interrupts during APM BIOS calls"
2494 Normally we disable external interrupts while we are making calls to
2495 the APM BIOS as a measure to lessen the effects of a badly behaving
2496 BIOS implementation. The BIOS should reenable interrupts if it
2497 needs to. Unfortunately, some BIOSes do not -- especially those in
2498 many of the newer IBM Thinkpads. If you experience hangs when you
2499 suspend, try setting this to Y. Otherwise, say N.
2503 source "drivers/cpufreq/Kconfig"
2505 source "drivers/cpuidle/Kconfig"
2507 source "drivers/idle/Kconfig"
2512 menu "Bus options (PCI etc.)"
2518 Find out whether you have a PCI motherboard. PCI is the name of a
2519 bus system, i.e. the way the CPU talks to the other stuff inside
2520 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2521 VESA. If you have PCI, say Y, otherwise N.
2524 prompt "PCI access mode"
2525 depends on X86_32 && PCI
2528 On PCI systems, the BIOS can be used to detect the PCI devices and
2529 determine their configuration. However, some old PCI motherboards
2530 have BIOS bugs and may crash if this is done. Also, some embedded
2531 PCI-based systems don't have any BIOS at all. Linux can also try to
2532 detect the PCI hardware directly without using the BIOS.
2534 With this option, you can specify how Linux should detect the
2535 PCI devices. If you choose "BIOS", the BIOS will be used,
2536 if you choose "Direct", the BIOS won't be used, and if you
2537 choose "MMConfig", then PCI Express MMCONFIG will be used.
2538 If you choose "Any", the kernel will try MMCONFIG, then the
2539 direct access method and falls back to the BIOS if that doesn't
2540 work. If unsure, go with the default, which is "Any".
2545 config PCI_GOMMCONFIG
2562 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2564 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2567 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2571 depends on X86_32 && PCI && (ACPI || SFI) && (PCI_GOMMCONFIG || PCI_GOANY)
2575 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2579 depends on PCI && XEN
2587 bool "Support mmconfig PCI config space access"
2588 depends on X86_64 && PCI && ACPI
2590 config PCI_CNB20LE_QUIRK
2591 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2594 Read the PCI windows out of the CNB20LE host bridge. This allows
2595 PCI hotplug to work on systems with the CNB20LE chipset which do
2598 There's no public spec for this chipset, and this functionality
2599 is known to be incomplete.
2601 You should say N unless you know you need this.
2603 source "drivers/pci/Kconfig"
2606 bool "ISA-style bus support on modern systems" if EXPERT
2609 Enables ISA-style drivers on modern systems. This is necessary to
2610 support PC/104 devices on X86_64 platforms.
2614 # x86_64 have no ISA slots, but can have ISA-style DMA.
2616 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2619 Enables ISA-style DMA support for devices requiring such controllers.
2627 Find out whether you have ISA slots on your motherboard. ISA is the
2628 name of a bus system, i.e. the way the CPU talks to the other stuff
2629 inside your box. Other bus systems are PCI, EISA, MicroChannel
2630 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2631 newer boards don't support it. If you have ISA, say Y, otherwise N.
2637 The Extended Industry Standard Architecture (EISA) bus was
2638 developed as an open alternative to the IBM MicroChannel bus.
2640 The EISA bus provided some of the features of the IBM MicroChannel
2641 bus while maintaining backward compatibility with cards made for
2642 the older ISA bus. The EISA bus saw limited use between 1988 and
2643 1995 when it was made obsolete by the PCI bus.
2645 Say Y here if you are building a kernel for an EISA-based machine.
2649 source "drivers/eisa/Kconfig"
2652 tristate "NatSemi SCx200 support"
2654 This provides basic support for National Semiconductor's
2655 (now AMD's) Geode processors. The driver probes for the
2656 PCI-IDs of several on-chip devices, so its a good dependency
2657 for other scx200_* drivers.
2659 If compiled as a module, the driver is named scx200.
2661 config SCx200HR_TIMER
2662 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2666 This driver provides a clocksource built upon the on-chip
2667 27MHz high-resolution timer. Its also a workaround for
2668 NSC Geode SC-1100's buggy TSC, which loses time when the
2669 processor goes idle (as is done by the scheduler). The
2670 other workaround is idle=poll boot option.
2673 bool "One Laptop Per Child support"
2680 Add support for detecting the unique features of the OLPC
2684 bool "OLPC XO-1 Power Management"
2685 depends on OLPC && MFD_CS5535 && PM_SLEEP
2688 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2691 bool "OLPC XO-1 Real Time Clock"
2692 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2694 Add support for the XO-1 real time clock, which can be used as a
2695 programmable wakeup source.
2698 bool "OLPC XO-1 SCI extras"
2699 depends on OLPC && OLPC_XO1_PM
2705 Add support for SCI-based features of the OLPC XO-1 laptop:
2706 - EC-driven system wakeups
2710 - AC adapter status updates
2711 - Battery status updates
2713 config OLPC_XO15_SCI
2714 bool "OLPC XO-1.5 SCI extras"
2715 depends on OLPC && ACPI
2718 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2719 - EC-driven system wakeups
2720 - AC adapter status updates
2721 - Battery status updates
2724 bool "PCEngines ALIX System Support (LED setup)"
2727 This option enables system support for the PCEngines ALIX.
2728 At present this just sets up LEDs for GPIO control on
2729 ALIX2/3/6 boards. However, other system specific setup should
2732 Note: You must still enable the drivers for GPIO and LED support
2733 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2735 Note: You have to set alix.force=1 for boards with Award BIOS.
2738 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2741 This option enables system support for the Soekris Engineering net5501.
2744 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2748 This option enables system support for the Traverse Technologies GEOS.
2751 bool "Technologic Systems TS-5500 platform support"
2753 select CHECK_SIGNATURE
2757 This option enables system support for the Technologic Systems TS-5500.
2763 depends on CPU_SUP_AMD && PCI
2765 source "drivers/pcmcia/Kconfig"
2768 tristate "RapidIO support"
2772 If enabled this option will include drivers and the core
2773 infrastructure code to support RapidIO interconnect devices.
2775 source "drivers/rapidio/Kconfig"
2778 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2780 Firmwares often provide initial graphics framebuffers so the BIOS,
2781 bootloader or kernel can show basic video-output during boot for
2782 user-guidance and debugging. Historically, x86 used the VESA BIOS
2783 Extensions and EFI-framebuffers for this, which are mostly limited
2785 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2786 framebuffers so the new generic system-framebuffer drivers can be
2787 used on x86. If the framebuffer is not compatible with the generic
2788 modes, it is adverticed as fallback platform framebuffer so legacy
2789 drivers like efifb, vesafb and uvesafb can pick it up.
2790 If this option is not selected, all system framebuffers are always
2791 marked as fallback platform framebuffers as usual.
2793 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2794 not be able to pick up generic system framebuffers if this option
2795 is selected. You are highly encouraged to enable simplefb as
2796 replacement if you select this option. simplefb can correctly deal
2797 with generic system framebuffers. But you should still keep vesafb
2798 and others enabled as fallback if a system framebuffer is
2799 incompatible with simplefb.
2806 menu "Executable file formats / Emulations"
2808 source "fs/Kconfig.binfmt"
2810 config IA32_EMULATION
2811 bool "IA32 Emulation"
2813 select ARCH_WANT_OLD_COMPAT_IPC
2815 select COMPAT_BINFMT_ELF
2816 select COMPAT_OLD_SIGACTION
2818 Include code to run legacy 32-bit programs under a
2819 64-bit kernel. You should likely turn this on, unless you're
2820 100% sure that you don't have any 32-bit programs left.
2823 tristate "IA32 a.out support"
2824 depends on IA32_EMULATION
2826 Support old a.out binaries in the 32bit emulation.
2829 bool "x32 ABI for 64-bit mode"
2832 Include code to run binaries for the x32 native 32-bit ABI
2833 for 64-bit processors. An x32 process gets access to the
2834 full 64-bit register file and wide data path while leaving
2835 pointers at 32 bits for smaller memory footprint.
2837 You will need a recent binutils (2.22 or later) with
2838 elf32_x86_64 support enabled to compile a kernel with this
2843 depends on IA32_EMULATION || X86_32
2845 select OLD_SIGSUSPEND3
2849 depends on IA32_EMULATION || X86_X32
2852 config COMPAT_FOR_U64_ALIGNMENT
2855 config SYSVIPC_COMPAT
2863 config HAVE_ATOMIC_IOMAP
2867 config X86_DEV_DMA_OPS
2869 depends on X86_64 || STA2X11
2871 config X86_DMA_REMAP
2875 config HAVE_GENERIC_GUP
2878 source "net/Kconfig"
2880 source "drivers/Kconfig"
2882 source "drivers/firmware/Kconfig"
2886 source "arch/x86/Kconfig.debug"
2888 source "security/Kconfig"
2890 source "crypto/Kconfig"
2892 source "arch/x86/kvm/Kconfig"
2894 source "lib/Kconfig"