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_PHYS_TO_DMA
58 select ARCH_HAS_PMEM_API if X86_64
59 # Causing hangs/crashes, see the commit that added this change for details.
60 select ARCH_HAS_REFCOUNT
61 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
62 select ARCH_HAS_SET_MEMORY
63 select ARCH_HAS_SG_CHAIN
64 select ARCH_HAS_STRICT_KERNEL_RWX
65 select ARCH_HAS_STRICT_MODULE_RWX
66 select ARCH_HAS_UBSAN_SANITIZE_ALL
67 select ARCH_HAS_ZONE_DEVICE if X86_64
68 select ARCH_HAVE_NMI_SAFE_CMPXCHG
69 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
70 select ARCH_MIGHT_HAVE_PC_PARPORT
71 select ARCH_MIGHT_HAVE_PC_SERIO
72 select ARCH_SUPPORTS_ATOMIC_RMW
73 select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
74 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
75 select ARCH_USE_BUILTIN_BSWAP
76 select ARCH_USE_QUEUED_RWLOCKS
77 select ARCH_USE_QUEUED_SPINLOCKS
78 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
79 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
80 select ARCH_WANTS_THP_SWAP if X86_64
81 select BUILDTIME_EXTABLE_SORT
83 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
84 select CLOCKSOURCE_WATCHDOG
85 select DCACHE_WORD_ACCESS
86 select EDAC_ATOMIC_SCRUB
88 select GENERIC_CLOCKEVENTS
89 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
90 select GENERIC_CLOCKEVENTS_MIN_ADJUST
91 select GENERIC_CMOS_UPDATE
92 select GENERIC_CPU_AUTOPROBE
93 select GENERIC_EARLY_IOREMAP
94 select GENERIC_FIND_FIRST_BIT
96 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
97 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
98 select GENERIC_IRQ_MIGRATION if SMP
99 select GENERIC_IRQ_PROBE
100 select GENERIC_IRQ_RESERVATION_MODE
101 select GENERIC_IRQ_SHOW
102 select GENERIC_PENDING_IRQ if SMP
103 select GENERIC_SMP_IDLE_THREAD
104 select GENERIC_STRNCPY_FROM_USER
105 select GENERIC_STRNLEN_USER
106 select GENERIC_TIME_VSYSCALL
107 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
108 select HAVE_ACPI_APEI if ACPI
109 select HAVE_ACPI_APEI_NMI if ACPI
110 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
111 select HAVE_ARCH_AUDITSYSCALL
112 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
113 select HAVE_ARCH_JUMP_LABEL
114 select HAVE_ARCH_KASAN if X86_64
115 select HAVE_ARCH_KGDB
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 64 if SMP && X86_32 && X86_BIGSMP
931 range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK && X86_64
932 range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
934 default "8192" if MAXSMP
935 default "32" if SMP && X86_BIGSMP
936 default "8" if SMP && X86_32
939 This allows you to specify the maximum number of CPUs which this
940 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
941 supported value is 8192, otherwise the maximum value is 512. The
942 minimum value which makes sense is 2.
944 This is purely to save memory - each supported CPU adds
945 approximately eight kilobytes to the kernel image.
948 bool "SMT (Hyperthreading) scheduler support"
951 SMT scheduler support improves the CPU scheduler's decision making
952 when dealing with Intel Pentium 4 chips with HyperThreading at a
953 cost of slightly increased overhead in some places. If unsure say
958 prompt "Multi-core scheduler support"
961 Multi-core scheduler support improves the CPU scheduler's decision
962 making when dealing with multi-core CPU chips at a cost of slightly
963 increased overhead in some places. If unsure say N here.
966 bool "CPU core priorities scheduler support"
967 depends on SCHED_MC && CPU_SUP_INTEL
968 select X86_INTEL_PSTATE
972 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
973 core ordering determined at manufacturing time, which allows
974 certain cores to reach higher turbo frequencies (when running
975 single threaded workloads) than others.
977 Enabling this kernel feature teaches the scheduler about
978 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
979 scheduler's CPU selection logic accordingly, so that higher
980 overall system performance can be achieved.
982 This feature will have no effect on CPUs without this feature.
984 If unsure say Y here.
986 source "kernel/Kconfig.preempt"
990 depends on !SMP && X86_LOCAL_APIC
993 bool "Local APIC support on uniprocessors" if !PCI_MSI
995 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
997 A local APIC (Advanced Programmable Interrupt Controller) is an
998 integrated interrupt controller in the CPU. If you have a single-CPU
999 system which has a processor with a local APIC, you can say Y here to
1000 enable and use it. If you say Y here even though your machine doesn't
1001 have a local APIC, then the kernel will still run with no slowdown at
1002 all. The local APIC supports CPU-generated self-interrupts (timer,
1003 performance counters), and the NMI watchdog which detects hard
1006 config X86_UP_IOAPIC
1007 bool "IO-APIC support on uniprocessors"
1008 depends on X86_UP_APIC
1010 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1011 SMP-capable replacement for PC-style interrupt controllers. Most
1012 SMP systems and many recent uniprocessor systems have one.
1014 If you have a single-CPU system with an IO-APIC, you can say Y here
1015 to use it. If you say Y here even though your machine doesn't have
1016 an IO-APIC, then the kernel will still run with no slowdown at all.
1018 config X86_LOCAL_APIC
1020 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1021 select IRQ_DOMAIN_HIERARCHY
1022 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1026 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1028 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1029 bool "Reroute for broken boot IRQs"
1030 depends on X86_IO_APIC
1032 This option enables a workaround that fixes a source of
1033 spurious interrupts. This is recommended when threaded
1034 interrupt handling is used on systems where the generation of
1035 superfluous "boot interrupts" cannot be disabled.
1037 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1038 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1039 kernel does during interrupt handling). On chipsets where this
1040 boot IRQ generation cannot be disabled, this workaround keeps
1041 the original IRQ line masked so that only the equivalent "boot
1042 IRQ" is delivered to the CPUs. The workaround also tells the
1043 kernel to set up the IRQ handler on the boot IRQ line. In this
1044 way only one interrupt is delivered to the kernel. Otherwise
1045 the spurious second interrupt may cause the kernel to bring
1046 down (vital) interrupt lines.
1048 Only affects "broken" chipsets. Interrupt sharing may be
1049 increased on these systems.
1052 bool "Machine Check / overheating reporting"
1053 select GENERIC_ALLOCATOR
1056 Machine Check support allows the processor to notify the
1057 kernel if it detects a problem (e.g. overheating, data corruption).
1058 The action the kernel takes depends on the severity of the problem,
1059 ranging from warning messages to halting the machine.
1061 config X86_MCELOG_LEGACY
1062 bool "Support for deprecated /dev/mcelog character device"
1065 Enable support for /dev/mcelog which is needed by the old mcelog
1066 userspace logging daemon. Consider switching to the new generation
1069 config X86_MCE_INTEL
1071 prompt "Intel MCE features"
1072 depends on X86_MCE && X86_LOCAL_APIC
1074 Additional support for intel specific MCE features such as
1075 the thermal monitor.
1079 prompt "AMD MCE features"
1080 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1082 Additional support for AMD specific MCE features such as
1083 the DRAM Error Threshold.
1085 config X86_ANCIENT_MCE
1086 bool "Support for old Pentium 5 / WinChip machine checks"
1087 depends on X86_32 && X86_MCE
1089 Include support for machine check handling on old Pentium 5 or WinChip
1090 systems. These typically need to be enabled explicitly on the command
1093 config X86_MCE_THRESHOLD
1094 depends on X86_MCE_AMD || X86_MCE_INTEL
1097 config X86_MCE_INJECT
1098 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1099 tristate "Machine check injector support"
1101 Provide support for injecting machine checks for testing purposes.
1102 If you don't know what a machine check is and you don't do kernel
1103 QA it is safe to say n.
1105 config X86_THERMAL_VECTOR
1107 depends on X86_MCE_INTEL
1109 source "arch/x86/events/Kconfig"
1111 config X86_LEGACY_VM86
1112 bool "Legacy VM86 support"
1116 This option allows user programs to put the CPU into V8086
1117 mode, which is an 80286-era approximation of 16-bit real mode.
1119 Some very old versions of X and/or vbetool require this option
1120 for user mode setting. Similarly, DOSEMU will use it if
1121 available to accelerate real mode DOS programs. However, any
1122 recent version of DOSEMU, X, or vbetool should be fully
1123 functional even without kernel VM86 support, as they will all
1124 fall back to software emulation. Nevertheless, if you are using
1125 a 16-bit DOS program where 16-bit performance matters, vm86
1126 mode might be faster than emulation and you might want to
1129 Note that any app that works on a 64-bit kernel is unlikely to
1130 need this option, as 64-bit kernels don't, and can't, support
1131 V8086 mode. This option is also unrelated to 16-bit protected
1132 mode and is not needed to run most 16-bit programs under Wine.
1134 Enabling this option increases the complexity of the kernel
1135 and slows down exception handling a tiny bit.
1137 If unsure, say N here.
1141 default X86_LEGACY_VM86
1144 bool "Enable support for 16-bit segments" if EXPERT
1146 depends on MODIFY_LDT_SYSCALL
1148 This option is required by programs like Wine to run 16-bit
1149 protected mode legacy code on x86 processors. Disabling
1150 this option saves about 300 bytes on i386, or around 6K text
1151 plus 16K runtime memory on x86-64,
1155 depends on X86_16BIT && X86_32
1159 depends on X86_16BIT && X86_64
1161 config X86_VSYSCALL_EMULATION
1162 bool "Enable vsyscall emulation" if EXPERT
1166 This enables emulation of the legacy vsyscall page. Disabling
1167 it is roughly equivalent to booting with vsyscall=none, except
1168 that it will also disable the helpful warning if a program
1169 tries to use a vsyscall. With this option set to N, offending
1170 programs will just segfault, citing addresses of the form
1173 This option is required by many programs built before 2013, and
1174 care should be used even with newer programs if set to N.
1176 Disabling this option saves about 7K of kernel size and
1177 possibly 4K of additional runtime pagetable memory.
1180 tristate "Toshiba Laptop support"
1183 This adds a driver to safely access the System Management Mode of
1184 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1185 not work on models with a Phoenix BIOS. The System Management Mode
1186 is used to set the BIOS and power saving options on Toshiba portables.
1188 For information on utilities to make use of this driver see the
1189 Toshiba Linux utilities web site at:
1190 <http://www.buzzard.org.uk/toshiba/>.
1192 Say Y if you intend to run this kernel on a Toshiba portable.
1196 tristate "Dell i8k legacy laptop support"
1198 select SENSORS_DELL_SMM
1200 This option enables legacy /proc/i8k userspace interface in hwmon
1201 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1202 temperature and allows controlling fan speeds of Dell laptops via
1203 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1204 it reports also power and hotkey status. For fan speed control is
1205 needed userspace package i8kutils.
1207 Say Y if you intend to run this kernel on old Dell laptops or want to
1208 use userspace package i8kutils.
1211 config X86_REBOOTFIXUPS
1212 bool "Enable X86 board specific fixups for reboot"
1215 This enables chipset and/or board specific fixups to be done
1216 in order to get reboot to work correctly. This is only needed on
1217 some combinations of hardware and BIOS. The symptom, for which
1218 this config is intended, is when reboot ends with a stalled/hung
1221 Currently, the only fixup is for the Geode machines using
1222 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1224 Say Y if you want to enable the fixup. Currently, it's safe to
1225 enable this option even if you don't need it.
1229 bool "CPU microcode loading support"
1231 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1234 If you say Y here, you will be able to update the microcode on
1235 Intel and AMD processors. The Intel support is for the IA32 family,
1236 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1237 AMD support is for families 0x10 and later. You will obviously need
1238 the actual microcode binary data itself which is not shipped with
1241 The preferred method to load microcode from a detached initrd is described
1242 in Documentation/x86/early-microcode.txt. For that you need to enable
1243 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1244 initrd for microcode blobs.
1246 In addition, you can build-in the microcode into the kernel. For that you
1247 need to enable FIRMWARE_IN_KERNEL and add the vendor-supplied microcode
1248 to the CONFIG_EXTRA_FIRMWARE config option.
1250 config MICROCODE_INTEL
1251 bool "Intel microcode loading support"
1252 depends on MICROCODE
1256 This options enables microcode patch loading support for Intel
1259 For the current Intel microcode data package go to
1260 <https://downloadcenter.intel.com> and search for
1261 'Linux Processor Microcode Data File'.
1263 config MICROCODE_AMD
1264 bool "AMD microcode loading support"
1265 depends on MICROCODE
1268 If you select this option, microcode patch loading support for AMD
1269 processors will be enabled.
1271 config MICROCODE_OLD_INTERFACE
1273 depends on MICROCODE
1276 tristate "/dev/cpu/*/msr - Model-specific register support"
1278 This device gives privileged processes access to the x86
1279 Model-Specific Registers (MSRs). It is a character device with
1280 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1281 MSR accesses are directed to a specific CPU on multi-processor
1285 tristate "/dev/cpu/*/cpuid - CPU information support"
1287 This device gives processes access to the x86 CPUID instruction to
1288 be executed on a specific processor. It is a character device
1289 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1293 prompt "High Memory Support"
1300 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1301 However, the address space of 32-bit x86 processors is only 4
1302 Gigabytes large. That means that, if you have a large amount of
1303 physical memory, not all of it can be "permanently mapped" by the
1304 kernel. The physical memory that's not permanently mapped is called
1307 If you are compiling a kernel which will never run on a machine with
1308 more than 1 Gigabyte total physical RAM, answer "off" here (default
1309 choice and suitable for most users). This will result in a "3GB/1GB"
1310 split: 3GB are mapped so that each process sees a 3GB virtual memory
1311 space and the remaining part of the 4GB virtual memory space is used
1312 by the kernel to permanently map as much physical memory as
1315 If the machine has between 1 and 4 Gigabytes physical RAM, then
1318 If more than 4 Gigabytes is used then answer "64GB" here. This
1319 selection turns Intel PAE (Physical Address Extension) mode on.
1320 PAE implements 3-level paging on IA32 processors. PAE is fully
1321 supported by Linux, PAE mode is implemented on all recent Intel
1322 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1323 then the kernel will not boot on CPUs that don't support PAE!
1325 The actual amount of total physical memory will either be
1326 auto detected or can be forced by using a kernel command line option
1327 such as "mem=256M". (Try "man bootparam" or see the documentation of
1328 your boot loader (lilo or loadlin) about how to pass options to the
1329 kernel at boot time.)
1331 If unsure, say "off".
1336 Select this if you have a 32-bit processor and between 1 and 4
1337 gigabytes of physical RAM.
1344 Select this if you have a 32-bit processor and more than 4
1345 gigabytes of physical RAM.
1350 prompt "Memory split" if EXPERT
1354 Select the desired split between kernel and user memory.
1356 If the address range available to the kernel is less than the
1357 physical memory installed, the remaining memory will be available
1358 as "high memory". Accessing high memory is a little more costly
1359 than low memory, as it needs to be mapped into the kernel first.
1360 Note that increasing the kernel address space limits the range
1361 available to user programs, making the address space there
1362 tighter. Selecting anything other than the default 3G/1G split
1363 will also likely make your kernel incompatible with binary-only
1366 If you are not absolutely sure what you are doing, leave this
1370 bool "3G/1G user/kernel split"
1371 config VMSPLIT_3G_OPT
1373 bool "3G/1G user/kernel split (for full 1G low memory)"
1375 bool "2G/2G user/kernel split"
1376 config VMSPLIT_2G_OPT
1378 bool "2G/2G user/kernel split (for full 2G low memory)"
1380 bool "1G/3G user/kernel split"
1385 default 0xB0000000 if VMSPLIT_3G_OPT
1386 default 0x80000000 if VMSPLIT_2G
1387 default 0x78000000 if VMSPLIT_2G_OPT
1388 default 0x40000000 if VMSPLIT_1G
1394 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1397 bool "PAE (Physical Address Extension) Support"
1398 depends on X86_32 && !HIGHMEM4G
1401 PAE is required for NX support, and furthermore enables
1402 larger swapspace support for non-overcommit purposes. It
1403 has the cost of more pagetable lookup overhead, and also
1404 consumes more pagetable space per process.
1407 bool "Enable 5-level page tables support"
1410 5-level paging enables access to larger address space:
1411 upto 128 PiB of virtual address space and 4 PiB of
1412 physical address space.
1414 It will be supported by future Intel CPUs.
1416 Note: a kernel with this option enabled can only be booted
1417 on machines that support the feature.
1419 See Documentation/x86/x86_64/5level-paging.txt for more
1424 config ARCH_PHYS_ADDR_T_64BIT
1426 depends on X86_64 || X86_PAE
1428 config ARCH_DMA_ADDR_T_64BIT
1430 depends on X86_64 || HIGHMEM64G
1432 config X86_DIRECT_GBPAGES
1434 depends on X86_64 && !DEBUG_PAGEALLOC
1436 Certain kernel features effectively disable kernel
1437 linear 1 GB mappings (even if the CPU otherwise
1438 supports them), so don't confuse the user by printing
1439 that we have them enabled.
1441 config ARCH_HAS_MEM_ENCRYPT
1444 config AMD_MEM_ENCRYPT
1445 bool "AMD Secure Memory Encryption (SME) support"
1446 depends on X86_64 && CPU_SUP_AMD
1448 Say yes to enable support for the encryption of system memory.
1449 This requires an AMD processor that supports Secure Memory
1452 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1453 bool "Activate AMD Secure Memory Encryption (SME) by default"
1455 depends on AMD_MEM_ENCRYPT
1457 Say yes to have system memory encrypted by default if running on
1458 an AMD processor that supports Secure Memory Encryption (SME).
1460 If set to Y, then the encryption of system memory can be
1461 deactivated with the mem_encrypt=off command line option.
1463 If set to N, then the encryption of system memory can be
1464 activated with the mem_encrypt=on command line option.
1466 config ARCH_USE_MEMREMAP_PROT
1468 depends on AMD_MEM_ENCRYPT
1470 # Common NUMA Features
1472 bool "Numa Memory Allocation and Scheduler Support"
1474 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1475 default y if X86_BIGSMP
1477 Enable NUMA (Non Uniform Memory Access) support.
1479 The kernel will try to allocate memory used by a CPU on the
1480 local memory controller of the CPU and add some more
1481 NUMA awareness to the kernel.
1483 For 64-bit this is recommended if the system is Intel Core i7
1484 (or later), AMD Opteron, or EM64T NUMA.
1486 For 32-bit this is only needed if you boot a 32-bit
1487 kernel on a 64-bit NUMA platform.
1489 Otherwise, you should say N.
1493 prompt "Old style AMD Opteron NUMA detection"
1494 depends on X86_64 && NUMA && PCI
1496 Enable AMD NUMA node topology detection. You should say Y here if
1497 you have a multi processor AMD system. This uses an old method to
1498 read the NUMA configuration directly from the builtin Northbridge
1499 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1500 which also takes priority if both are compiled in.
1502 config X86_64_ACPI_NUMA
1504 prompt "ACPI NUMA detection"
1505 depends on X86_64 && NUMA && ACPI && PCI
1508 Enable ACPI SRAT based node topology detection.
1510 # Some NUMA nodes have memory ranges that span
1511 # other nodes. Even though a pfn is valid and
1512 # between a node's start and end pfns, it may not
1513 # reside on that node. See memmap_init_zone()
1515 config NODES_SPAN_OTHER_NODES
1517 depends on X86_64_ACPI_NUMA
1520 bool "NUMA emulation"
1523 Enable NUMA emulation. A flat machine will be split
1524 into virtual nodes when booted with "numa=fake=N", where N is the
1525 number of nodes. This is only useful for debugging.
1528 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1530 default "10" if MAXSMP
1531 default "6" if X86_64
1533 depends on NEED_MULTIPLE_NODES
1535 Specify the maximum number of NUMA Nodes available on the target
1536 system. Increases memory reserved to accommodate various tables.
1538 config ARCH_HAVE_MEMORY_PRESENT
1540 depends on X86_32 && DISCONTIGMEM
1542 config NEED_NODE_MEMMAP_SIZE
1544 depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
1546 config ARCH_FLATMEM_ENABLE
1548 depends on X86_32 && !NUMA
1550 config ARCH_DISCONTIGMEM_ENABLE
1552 depends on NUMA && X86_32
1554 config ARCH_DISCONTIGMEM_DEFAULT
1556 depends on NUMA && X86_32
1558 config ARCH_SPARSEMEM_ENABLE
1560 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1561 select SPARSEMEM_STATIC if X86_32
1562 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1564 config ARCH_SPARSEMEM_DEFAULT
1568 config ARCH_SELECT_MEMORY_MODEL
1570 depends on ARCH_SPARSEMEM_ENABLE
1572 config ARCH_MEMORY_PROBE
1573 bool "Enable sysfs memory/probe interface"
1574 depends on X86_64 && MEMORY_HOTPLUG
1576 This option enables a sysfs memory/probe interface for testing.
1577 See Documentation/memory-hotplug.txt for more information.
1578 If you are unsure how to answer this question, answer N.
1580 config ARCH_PROC_KCORE_TEXT
1582 depends on X86_64 && PROC_KCORE
1584 config ILLEGAL_POINTER_VALUE
1587 default 0xdead000000000000 if X86_64
1591 config X86_PMEM_LEGACY_DEVICE
1594 config X86_PMEM_LEGACY
1595 tristate "Support non-standard NVDIMMs and ADR protected memory"
1596 depends on PHYS_ADDR_T_64BIT
1598 select X86_PMEM_LEGACY_DEVICE
1601 Treat memory marked using the non-standard e820 type of 12 as used
1602 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1603 The kernel will offer these regions to the 'pmem' driver so
1604 they can be used for persistent storage.
1609 bool "Allocate 3rd-level pagetables from highmem"
1612 The VM uses one page table entry for each page of physical memory.
1613 For systems with a lot of RAM, this can be wasteful of precious
1614 low memory. Setting this option will put user-space page table
1615 entries in high memory.
1617 config X86_CHECK_BIOS_CORRUPTION
1618 bool "Check for low memory corruption"
1620 Periodically check for memory corruption in low memory, which
1621 is suspected to be caused by BIOS. Even when enabled in the
1622 configuration, it is disabled at runtime. Enable it by
1623 setting "memory_corruption_check=1" on the kernel command
1624 line. By default it scans the low 64k of memory every 60
1625 seconds; see the memory_corruption_check_size and
1626 memory_corruption_check_period parameters in
1627 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1629 When enabled with the default parameters, this option has
1630 almost no overhead, as it reserves a relatively small amount
1631 of memory and scans it infrequently. It both detects corruption
1632 and prevents it from affecting the running system.
1634 It is, however, intended as a diagnostic tool; if repeatable
1635 BIOS-originated corruption always affects the same memory,
1636 you can use memmap= to prevent the kernel from using that
1639 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1640 bool "Set the default setting of memory_corruption_check"
1641 depends on X86_CHECK_BIOS_CORRUPTION
1644 Set whether the default state of memory_corruption_check is
1647 config X86_RESERVE_LOW
1648 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1652 Specify the amount of low memory to reserve for the BIOS.
1654 The first page contains BIOS data structures that the kernel
1655 must not use, so that page must always be reserved.
1657 By default we reserve the first 64K of physical RAM, as a
1658 number of BIOSes are known to corrupt that memory range
1659 during events such as suspend/resume or monitor cable
1660 insertion, so it must not be used by the kernel.
1662 You can set this to 4 if you are absolutely sure that you
1663 trust the BIOS to get all its memory reservations and usages
1664 right. If you know your BIOS have problems beyond the
1665 default 64K area, you can set this to 640 to avoid using the
1666 entire low memory range.
1668 If you have doubts about the BIOS (e.g. suspend/resume does
1669 not work or there's kernel crashes after certain hardware
1670 hotplug events) then you might want to enable
1671 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1672 typical corruption patterns.
1674 Leave this to the default value of 64 if you are unsure.
1676 config MATH_EMULATION
1678 depends on MODIFY_LDT_SYSCALL
1679 prompt "Math emulation" if X86_32
1681 Linux can emulate a math coprocessor (used for floating point
1682 operations) if you don't have one. 486DX and Pentium processors have
1683 a math coprocessor built in, 486SX and 386 do not, unless you added
1684 a 487DX or 387, respectively. (The messages during boot time can
1685 give you some hints here ["man dmesg"].) Everyone needs either a
1686 coprocessor or this emulation.
1688 If you don't have a math coprocessor, you need to say Y here; if you
1689 say Y here even though you have a coprocessor, the coprocessor will
1690 be used nevertheless. (This behavior can be changed with the kernel
1691 command line option "no387", which comes handy if your coprocessor
1692 is broken. Try "man bootparam" or see the documentation of your boot
1693 loader (lilo or loadlin) about how to pass options to the kernel at
1694 boot time.) This means that it is a good idea to say Y here if you
1695 intend to use this kernel on different machines.
1697 More information about the internals of the Linux math coprocessor
1698 emulation can be found in <file:arch/x86/math-emu/README>.
1700 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1701 kernel, it won't hurt.
1705 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1707 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1708 the Memory Type Range Registers (MTRRs) may be used to control
1709 processor access to memory ranges. This is most useful if you have
1710 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1711 allows bus write transfers to be combined into a larger transfer
1712 before bursting over the PCI/AGP bus. This can increase performance
1713 of image write operations 2.5 times or more. Saying Y here creates a
1714 /proc/mtrr file which may be used to manipulate your processor's
1715 MTRRs. Typically the X server should use this.
1717 This code has a reasonably generic interface so that similar
1718 control registers on other processors can be easily supported
1721 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1722 Registers (ARRs) which provide a similar functionality to MTRRs. For
1723 these, the ARRs are used to emulate the MTRRs.
1724 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1725 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1726 write-combining. All of these processors are supported by this code
1727 and it makes sense to say Y here if you have one of them.
1729 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1730 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1731 can lead to all sorts of problems, so it's good to say Y here.
1733 You can safely say Y even if your machine doesn't have MTRRs, you'll
1734 just add about 9 KB to your kernel.
1736 See <file:Documentation/x86/mtrr.txt> for more information.
1738 config MTRR_SANITIZER
1740 prompt "MTRR cleanup support"
1743 Convert MTRR layout from continuous to discrete, so X drivers can
1744 add writeback entries.
1746 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1747 The largest mtrr entry size for a continuous block can be set with
1752 config MTRR_SANITIZER_ENABLE_DEFAULT
1753 int "MTRR cleanup enable value (0-1)"
1756 depends on MTRR_SANITIZER
1758 Enable mtrr cleanup default value
1760 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1761 int "MTRR cleanup spare reg num (0-7)"
1764 depends on MTRR_SANITIZER
1766 mtrr cleanup spare entries default, it can be changed via
1767 mtrr_spare_reg_nr=N on the kernel command line.
1771 prompt "x86 PAT support" if EXPERT
1774 Use PAT attributes to setup page level cache control.
1776 PATs are the modern equivalents of MTRRs and are much more
1777 flexible than MTRRs.
1779 Say N here if you see bootup problems (boot crash, boot hang,
1780 spontaneous reboots) or a non-working video driver.
1784 config ARCH_USES_PG_UNCACHED
1790 prompt "x86 architectural random number generator" if EXPERT
1792 Enable the x86 architectural RDRAND instruction
1793 (Intel Bull Mountain technology) to generate random numbers.
1794 If supported, this is a high bandwidth, cryptographically
1795 secure hardware random number generator.
1799 prompt "Supervisor Mode Access Prevention" if EXPERT
1801 Supervisor Mode Access Prevention (SMAP) is a security
1802 feature in newer Intel processors. There is a small
1803 performance cost if this enabled and turned on; there is
1804 also a small increase in the kernel size if this is enabled.
1808 config X86_INTEL_UMIP
1810 depends on CPU_SUP_INTEL
1811 prompt "Intel User Mode Instruction Prevention" if EXPERT
1813 The User Mode Instruction Prevention (UMIP) is a security
1814 feature in newer Intel processors. If enabled, a general
1815 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1816 or STR instructions are executed in user mode. These instructions
1817 unnecessarily expose information about the hardware state.
1819 The vast majority of applications do not use these instructions.
1820 For the very few that do, software emulation is provided in
1821 specific cases in protected and virtual-8086 modes. Emulated
1824 config X86_INTEL_MPX
1825 prompt "Intel MPX (Memory Protection Extensions)"
1827 # Note: only available in 64-bit mode due to VMA flags shortage
1828 depends on CPU_SUP_INTEL && X86_64
1829 select ARCH_USES_HIGH_VMA_FLAGS
1831 MPX provides hardware features that can be used in
1832 conjunction with compiler-instrumented code to check
1833 memory references. It is designed to detect buffer
1834 overflow or underflow bugs.
1836 This option enables running applications which are
1837 instrumented or otherwise use MPX. It does not use MPX
1838 itself inside the kernel or to protect the kernel
1839 against bad memory references.
1841 Enabling this option will make the kernel larger:
1842 ~8k of kernel text and 36 bytes of data on a 64-bit
1843 defconfig. It adds a long to the 'mm_struct' which
1844 will increase the kernel memory overhead of each
1845 process and adds some branches to paths used during
1846 exec() and munmap().
1848 For details, see Documentation/x86/intel_mpx.txt
1852 config X86_INTEL_MEMORY_PROTECTION_KEYS
1853 prompt "Intel Memory Protection Keys"
1855 # Note: only available in 64-bit mode
1856 depends on CPU_SUP_INTEL && X86_64
1857 select ARCH_USES_HIGH_VMA_FLAGS
1858 select ARCH_HAS_PKEYS
1860 Memory Protection Keys provides a mechanism for enforcing
1861 page-based protections, but without requiring modification of the
1862 page tables when an application changes protection domains.
1864 For details, see Documentation/x86/protection-keys.txt
1869 bool "EFI runtime service support"
1872 select EFI_RUNTIME_WRAPPERS
1874 This enables the kernel to use EFI runtime services that are
1875 available (such as the EFI variable services).
1877 This option is only useful on systems that have EFI firmware.
1878 In addition, you should use the latest ELILO loader available
1879 at <http://elilo.sourceforge.net> in order to take advantage
1880 of EFI runtime services. However, even with this option, the
1881 resultant kernel should continue to boot on existing non-EFI
1885 bool "EFI stub support"
1886 depends on EFI && !X86_USE_3DNOW
1889 This kernel feature allows a bzImage to be loaded directly
1890 by EFI firmware without the use of a bootloader.
1892 See Documentation/efi-stub.txt for more information.
1895 bool "EFI mixed-mode support"
1896 depends on EFI_STUB && X86_64
1898 Enabling this feature allows a 64-bit kernel to be booted
1899 on a 32-bit firmware, provided that your CPU supports 64-bit
1902 Note that it is not possible to boot a mixed-mode enabled
1903 kernel via the EFI boot stub - a bootloader that supports
1904 the EFI handover protocol must be used.
1910 prompt "Enable seccomp to safely compute untrusted bytecode"
1912 This kernel feature is useful for number crunching applications
1913 that may need to compute untrusted bytecode during their
1914 execution. By using pipes or other transports made available to
1915 the process as file descriptors supporting the read/write
1916 syscalls, it's possible to isolate those applications in
1917 their own address space using seccomp. Once seccomp is
1918 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1919 and the task is only allowed to execute a few safe syscalls
1920 defined by each seccomp mode.
1922 If unsure, say Y. Only embedded should say N here.
1924 source kernel/Kconfig.hz
1927 bool "kexec system call"
1930 kexec is a system call that implements the ability to shutdown your
1931 current kernel, and to start another kernel. It is like a reboot
1932 but it is independent of the system firmware. And like a reboot
1933 you can start any kernel with it, not just Linux.
1935 The name comes from the similarity to the exec system call.
1937 It is an ongoing process to be certain the hardware in a machine
1938 is properly shutdown, so do not be surprised if this code does not
1939 initially work for you. As of this writing the exact hardware
1940 interface is strongly in flux, so no good recommendation can be
1944 bool "kexec file based system call"
1949 depends on CRYPTO_SHA256=y
1951 This is new version of kexec system call. This system call is
1952 file based and takes file descriptors as system call argument
1953 for kernel and initramfs as opposed to list of segments as
1954 accepted by previous system call.
1956 config KEXEC_VERIFY_SIG
1957 bool "Verify kernel signature during kexec_file_load() syscall"
1958 depends on KEXEC_FILE
1960 This option makes kernel signature verification mandatory for
1961 the kexec_file_load() syscall.
1963 In addition to that option, you need to enable signature
1964 verification for the corresponding kernel image type being
1965 loaded in order for this to work.
1967 config KEXEC_BZIMAGE_VERIFY_SIG
1968 bool "Enable bzImage signature verification support"
1969 depends on KEXEC_VERIFY_SIG
1970 depends on SIGNED_PE_FILE_VERIFICATION
1971 select SYSTEM_TRUSTED_KEYRING
1973 Enable bzImage signature verification support.
1976 bool "kernel crash dumps"
1977 depends on X86_64 || (X86_32 && HIGHMEM)
1979 Generate crash dump after being started by kexec.
1980 This should be normally only set in special crash dump kernels
1981 which are loaded in the main kernel with kexec-tools into
1982 a specially reserved region and then later executed after
1983 a crash by kdump/kexec. The crash dump kernel must be compiled
1984 to a memory address not used by the main kernel or BIOS using
1985 PHYSICAL_START, or it must be built as a relocatable image
1986 (CONFIG_RELOCATABLE=y).
1987 For more details see Documentation/kdump/kdump.txt
1991 depends on KEXEC && HIBERNATION
1993 Jump between original kernel and kexeced kernel and invoke
1994 code in physical address mode via KEXEC
1996 config PHYSICAL_START
1997 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2000 This gives the physical address where the kernel is loaded.
2002 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2003 bzImage will decompress itself to above physical address and
2004 run from there. Otherwise, bzImage will run from the address where
2005 it has been loaded by the boot loader and will ignore above physical
2008 In normal kdump cases one does not have to set/change this option
2009 as now bzImage can be compiled as a completely relocatable image
2010 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2011 address. This option is mainly useful for the folks who don't want
2012 to use a bzImage for capturing the crash dump and want to use a
2013 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2014 to be specifically compiled to run from a specific memory area
2015 (normally a reserved region) and this option comes handy.
2017 So if you are using bzImage for capturing the crash dump,
2018 leave the value here unchanged to 0x1000000 and set
2019 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2020 for capturing the crash dump change this value to start of
2021 the reserved region. In other words, it can be set based on
2022 the "X" value as specified in the "crashkernel=YM@XM"
2023 command line boot parameter passed to the panic-ed
2024 kernel. Please take a look at Documentation/kdump/kdump.txt
2025 for more details about crash dumps.
2027 Usage of bzImage for capturing the crash dump is recommended as
2028 one does not have to build two kernels. Same kernel can be used
2029 as production kernel and capture kernel. Above option should have
2030 gone away after relocatable bzImage support is introduced. But it
2031 is present because there are users out there who continue to use
2032 vmlinux for dump capture. This option should go away down the
2035 Don't change this unless you know what you are doing.
2038 bool "Build a relocatable kernel"
2041 This builds a kernel image that retains relocation information
2042 so it can be loaded someplace besides the default 1MB.
2043 The relocations tend to make the kernel binary about 10% larger,
2044 but are discarded at runtime.
2046 One use is for the kexec on panic case where the recovery kernel
2047 must live at a different physical address than the primary
2050 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2051 it has been loaded at and the compile time physical address
2052 (CONFIG_PHYSICAL_START) is used as the minimum location.
2054 config RANDOMIZE_BASE
2055 bool "Randomize the address of the kernel image (KASLR)"
2056 depends on RELOCATABLE
2059 In support of Kernel Address Space Layout Randomization (KASLR),
2060 this randomizes the physical address at which the kernel image
2061 is decompressed and the virtual address where the kernel
2062 image is mapped, as a security feature that deters exploit
2063 attempts relying on knowledge of the location of kernel
2066 On 64-bit, the kernel physical and virtual addresses are
2067 randomized separately. The physical address will be anywhere
2068 between 16MB and the top of physical memory (up to 64TB). The
2069 virtual address will be randomized from 16MB up to 1GB (9 bits
2070 of entropy). Note that this also reduces the memory space
2071 available to kernel modules from 1.5GB to 1GB.
2073 On 32-bit, the kernel physical and virtual addresses are
2074 randomized together. They will be randomized from 16MB up to
2075 512MB (8 bits of entropy).
2077 Entropy is generated using the RDRAND instruction if it is
2078 supported. If RDTSC is supported, its value is mixed into
2079 the entropy pool as well. If neither RDRAND nor RDTSC are
2080 supported, then entropy is read from the i8254 timer. The
2081 usable entropy is limited by the kernel being built using
2082 2GB addressing, and that PHYSICAL_ALIGN must be at a
2083 minimum of 2MB. As a result, only 10 bits of entropy are
2084 theoretically possible, but the implementations are further
2085 limited due to memory layouts.
2089 # Relocation on x86 needs some additional build support
2090 config X86_NEED_RELOCS
2092 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2094 config PHYSICAL_ALIGN
2095 hex "Alignment value to which kernel should be aligned"
2097 range 0x2000 0x1000000 if X86_32
2098 range 0x200000 0x1000000 if X86_64
2100 This value puts the alignment restrictions on physical address
2101 where kernel is loaded and run from. Kernel is compiled for an
2102 address which meets above alignment restriction.
2104 If bootloader loads the kernel at a non-aligned address and
2105 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2106 address aligned to above value and run from there.
2108 If bootloader loads the kernel at a non-aligned address and
2109 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2110 load address and decompress itself to the address it has been
2111 compiled for and run from there. The address for which kernel is
2112 compiled already meets above alignment restrictions. Hence the
2113 end result is that kernel runs from a physical address meeting
2114 above alignment restrictions.
2116 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2117 this value must be a multiple of 0x200000.
2119 Don't change this unless you know what you are doing.
2121 config RANDOMIZE_MEMORY
2122 bool "Randomize the kernel memory sections"
2124 depends on RANDOMIZE_BASE
2125 default RANDOMIZE_BASE
2127 Randomizes the base virtual address of kernel memory sections
2128 (physical memory mapping, vmalloc & vmemmap). This security feature
2129 makes exploits relying on predictable memory locations less reliable.
2131 The order of allocations remains unchanged. Entropy is generated in
2132 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2133 configuration have in average 30,000 different possible virtual
2134 addresses for each memory section.
2138 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2139 hex "Physical memory mapping padding" if EXPERT
2140 depends on RANDOMIZE_MEMORY
2141 default "0xa" if MEMORY_HOTPLUG
2143 range 0x1 0x40 if MEMORY_HOTPLUG
2146 Define the padding in terabytes added to the existing physical
2147 memory size during kernel memory randomization. It is useful
2148 for memory hotplug support but reduces the entropy available for
2149 address randomization.
2151 If unsure, leave at the default value.
2154 bool "Support for hot-pluggable CPUs"
2157 Say Y here to allow turning CPUs off and on. CPUs can be
2158 controlled through /sys/devices/system/cpu.
2159 ( Note: power management support will enable this option
2160 automatically on SMP systems. )
2161 Say N if you want to disable CPU hotplug.
2163 config BOOTPARAM_HOTPLUG_CPU0
2164 bool "Set default setting of cpu0_hotpluggable"
2166 depends on HOTPLUG_CPU
2168 Set whether default state of cpu0_hotpluggable is on or off.
2170 Say Y here to enable CPU0 hotplug by default. If this switch
2171 is turned on, there is no need to give cpu0_hotplug kernel
2172 parameter and the CPU0 hotplug feature is enabled by default.
2174 Please note: there are two known CPU0 dependencies if you want
2175 to enable the CPU0 hotplug feature either by this switch or by
2176 cpu0_hotplug kernel parameter.
2178 First, resume from hibernate or suspend always starts from CPU0.
2179 So hibernate and suspend are prevented if CPU0 is offline.
2181 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2182 offline if any interrupt can not migrate out of CPU0. There may
2183 be other CPU0 dependencies.
2185 Please make sure the dependencies are under your control before
2186 you enable this feature.
2188 Say N if you don't want to enable CPU0 hotplug feature by default.
2189 You still can enable the CPU0 hotplug feature at boot by kernel
2190 parameter cpu0_hotplug.
2192 config DEBUG_HOTPLUG_CPU0
2194 prompt "Debug CPU0 hotplug"
2195 depends on HOTPLUG_CPU
2197 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2198 soon as possible and boots up userspace with CPU0 offlined. User
2199 can online CPU0 back after boot time.
2201 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2202 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2203 compilation or giving cpu0_hotplug kernel parameter at boot.
2209 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2210 depends on COMPAT_32
2212 Certain buggy versions of glibc will crash if they are
2213 presented with a 32-bit vDSO that is not mapped at the address
2214 indicated in its segment table.
2216 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2217 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2218 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2219 the only released version with the bug, but OpenSUSE 9
2220 contains a buggy "glibc 2.3.2".
2222 The symptom of the bug is that everything crashes on startup, saying:
2223 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2225 Saying Y here changes the default value of the vdso32 boot
2226 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2227 This works around the glibc bug but hurts performance.
2229 If unsure, say N: if you are compiling your own kernel, you
2230 are unlikely to be using a buggy version of glibc.
2233 prompt "vsyscall table for legacy applications"
2235 default LEGACY_VSYSCALL_EMULATE
2237 Legacy user code that does not know how to find the vDSO expects
2238 to be able to issue three syscalls by calling fixed addresses in
2239 kernel space. Since this location is not randomized with ASLR,
2240 it can be used to assist security vulnerability exploitation.
2242 This setting can be changed at boot time via the kernel command
2243 line parameter vsyscall=[native|emulate|none].
2245 On a system with recent enough glibc (2.14 or newer) and no
2246 static binaries, you can say None without a performance penalty
2247 to improve security.
2249 If unsure, select "Emulate".
2251 config LEGACY_VSYSCALL_NATIVE
2254 Actual executable code is located in the fixed vsyscall
2255 address mapping, implementing time() efficiently. Since
2256 this makes the mapping executable, it can be used during
2257 security vulnerability exploitation (traditionally as
2258 ROP gadgets). This configuration is not recommended.
2260 config LEGACY_VSYSCALL_EMULATE
2263 The kernel traps and emulates calls into the fixed
2264 vsyscall address mapping. This makes the mapping
2265 non-executable, but it still contains known contents,
2266 which could be used in certain rare security vulnerability
2267 exploits. This configuration is recommended when userspace
2268 still uses the vsyscall area.
2270 config LEGACY_VSYSCALL_NONE
2273 There will be no vsyscall mapping at all. This will
2274 eliminate any risk of ASLR bypass due to the vsyscall
2275 fixed address mapping. Attempts to use the vsyscalls
2276 will be reported to dmesg, so that either old or
2277 malicious userspace programs can be identified.
2282 bool "Built-in kernel command line"
2284 Allow for specifying boot arguments to the kernel at
2285 build time. On some systems (e.g. embedded ones), it is
2286 necessary or convenient to provide some or all of the
2287 kernel boot arguments with the kernel itself (that is,
2288 to not rely on the boot loader to provide them.)
2290 To compile command line arguments into the kernel,
2291 set this option to 'Y', then fill in the
2292 boot arguments in CONFIG_CMDLINE.
2294 Systems with fully functional boot loaders (i.e. non-embedded)
2295 should leave this option set to 'N'.
2298 string "Built-in kernel command string"
2299 depends on CMDLINE_BOOL
2302 Enter arguments here that should be compiled into the kernel
2303 image and used at boot time. If the boot loader provides a
2304 command line at boot time, it is appended to this string to
2305 form the full kernel command line, when the system boots.
2307 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2308 change this behavior.
2310 In most cases, the command line (whether built-in or provided
2311 by the boot loader) should specify the device for the root
2314 config CMDLINE_OVERRIDE
2315 bool "Built-in command line overrides boot loader arguments"
2316 depends on CMDLINE_BOOL
2318 Set this option to 'Y' to have the kernel ignore the boot loader
2319 command line, and use ONLY the built-in command line.
2321 This is used to work around broken boot loaders. This should
2322 be set to 'N' under normal conditions.
2324 config MODIFY_LDT_SYSCALL
2325 bool "Enable the LDT (local descriptor table)" if EXPERT
2328 Linux can allow user programs to install a per-process x86
2329 Local Descriptor Table (LDT) using the modify_ldt(2) system
2330 call. This is required to run 16-bit or segmented code such as
2331 DOSEMU or some Wine programs. It is also used by some very old
2332 threading libraries.
2334 Enabling this feature adds a small amount of overhead to
2335 context switches and increases the low-level kernel attack
2336 surface. Disabling it removes the modify_ldt(2) system call.
2338 Saying 'N' here may make sense for embedded or server kernels.
2340 source "kernel/livepatch/Kconfig"
2344 config ARCH_HAS_ADD_PAGES
2346 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2348 config ARCH_ENABLE_MEMORY_HOTPLUG
2350 depends on X86_64 || (X86_32 && HIGHMEM)
2352 config ARCH_ENABLE_MEMORY_HOTREMOVE
2354 depends on MEMORY_HOTPLUG
2356 config USE_PERCPU_NUMA_NODE_ID
2360 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2362 depends on X86_64 || X86_PAE
2364 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2366 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2368 config ARCH_ENABLE_THP_MIGRATION
2370 depends on X86_64 && TRANSPARENT_HUGEPAGE
2372 menu "Power management and ACPI options"
2374 config ARCH_HIBERNATION_HEADER
2376 depends on X86_64 && HIBERNATION
2378 source "kernel/power/Kconfig"
2380 source "drivers/acpi/Kconfig"
2382 source "drivers/sfi/Kconfig"
2389 tristate "APM (Advanced Power Management) BIOS support"
2390 depends on X86_32 && PM_SLEEP
2392 APM is a BIOS specification for saving power using several different
2393 techniques. This is mostly useful for battery powered laptops with
2394 APM compliant BIOSes. If you say Y here, the system time will be
2395 reset after a RESUME operation, the /proc/apm device will provide
2396 battery status information, and user-space programs will receive
2397 notification of APM "events" (e.g. battery status change).
2399 If you select "Y" here, you can disable actual use of the APM
2400 BIOS by passing the "apm=off" option to the kernel at boot time.
2402 Note that the APM support is almost completely disabled for
2403 machines with more than one CPU.
2405 In order to use APM, you will need supporting software. For location
2406 and more information, read <file:Documentation/power/apm-acpi.txt>
2407 and the Battery Powered Linux mini-HOWTO, available from
2408 <http://www.tldp.org/docs.html#howto>.
2410 This driver does not spin down disk drives (see the hdparm(8)
2411 manpage ("man 8 hdparm") for that), and it doesn't turn off
2412 VESA-compliant "green" monitors.
2414 This driver does not support the TI 4000M TravelMate and the ACER
2415 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2416 desktop machines also don't have compliant BIOSes, and this driver
2417 may cause those machines to panic during the boot phase.
2419 Generally, if you don't have a battery in your machine, there isn't
2420 much point in using this driver and you should say N. If you get
2421 random kernel OOPSes or reboots that don't seem to be related to
2422 anything, try disabling/enabling this option (or disabling/enabling
2425 Some other things you should try when experiencing seemingly random,
2428 1) make sure that you have enough swap space and that it is
2430 2) pass the "no-hlt" option to the kernel
2431 3) switch on floating point emulation in the kernel and pass
2432 the "no387" option to the kernel
2433 4) pass the "floppy=nodma" option to the kernel
2434 5) pass the "mem=4M" option to the kernel (thereby disabling
2435 all but the first 4 MB of RAM)
2436 6) make sure that the CPU is not over clocked.
2437 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2438 8) disable the cache from your BIOS settings
2439 9) install a fan for the video card or exchange video RAM
2440 10) install a better fan for the CPU
2441 11) exchange RAM chips
2442 12) exchange the motherboard.
2444 To compile this driver as a module, choose M here: the
2445 module will be called apm.
2449 config APM_IGNORE_USER_SUSPEND
2450 bool "Ignore USER SUSPEND"
2452 This option will ignore USER SUSPEND requests. On machines with a
2453 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2454 series notebooks, it is necessary to say Y because of a BIOS bug.
2456 config APM_DO_ENABLE
2457 bool "Enable PM at boot time"
2459 Enable APM features at boot time. From page 36 of the APM BIOS
2460 specification: "When disabled, the APM BIOS does not automatically
2461 power manage devices, enter the Standby State, enter the Suspend
2462 State, or take power saving steps in response to CPU Idle calls."
2463 This driver will make CPU Idle calls when Linux is idle (unless this
2464 feature is turned off -- see "Do CPU IDLE calls", below). This
2465 should always save battery power, but more complicated APM features
2466 will be dependent on your BIOS implementation. You may need to turn
2467 this option off if your computer hangs at boot time when using APM
2468 support, or if it beeps continuously instead of suspending. Turn
2469 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2470 T400CDT. This is off by default since most machines do fine without
2475 bool "Make CPU Idle calls when idle"
2477 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2478 On some machines, this can activate improved power savings, such as
2479 a slowed CPU clock rate, when the machine is idle. These idle calls
2480 are made after the idle loop has run for some length of time (e.g.,
2481 333 mS). On some machines, this will cause a hang at boot time or
2482 whenever the CPU becomes idle. (On machines with more than one CPU,
2483 this option does nothing.)
2485 config APM_DISPLAY_BLANK
2486 bool "Enable console blanking using APM"
2488 Enable console blanking using the APM. Some laptops can use this to
2489 turn off the LCD backlight when the screen blanker of the Linux
2490 virtual console blanks the screen. Note that this is only used by
2491 the virtual console screen blanker, and won't turn off the backlight
2492 when using the X Window system. This also doesn't have anything to
2493 do with your VESA-compliant power-saving monitor. Further, this
2494 option doesn't work for all laptops -- it might not turn off your
2495 backlight at all, or it might print a lot of errors to the console,
2496 especially if you are using gpm.
2498 config APM_ALLOW_INTS
2499 bool "Allow interrupts during APM BIOS calls"
2501 Normally we disable external interrupts while we are making calls to
2502 the APM BIOS as a measure to lessen the effects of a badly behaving
2503 BIOS implementation. The BIOS should reenable interrupts if it
2504 needs to. Unfortunately, some BIOSes do not -- especially those in
2505 many of the newer IBM Thinkpads. If you experience hangs when you
2506 suspend, try setting this to Y. Otherwise, say N.
2510 source "drivers/cpufreq/Kconfig"
2512 source "drivers/cpuidle/Kconfig"
2514 source "drivers/idle/Kconfig"
2519 menu "Bus options (PCI etc.)"
2525 Find out whether you have a PCI motherboard. PCI is the name of a
2526 bus system, i.e. the way the CPU talks to the other stuff inside
2527 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2528 VESA. If you have PCI, say Y, otherwise N.
2531 prompt "PCI access mode"
2532 depends on X86_32 && PCI
2535 On PCI systems, the BIOS can be used to detect the PCI devices and
2536 determine their configuration. However, some old PCI motherboards
2537 have BIOS bugs and may crash if this is done. Also, some embedded
2538 PCI-based systems don't have any BIOS at all. Linux can also try to
2539 detect the PCI hardware directly without using the BIOS.
2541 With this option, you can specify how Linux should detect the
2542 PCI devices. If you choose "BIOS", the BIOS will be used,
2543 if you choose "Direct", the BIOS won't be used, and if you
2544 choose "MMConfig", then PCI Express MMCONFIG will be used.
2545 If you choose "Any", the kernel will try MMCONFIG, then the
2546 direct access method and falls back to the BIOS if that doesn't
2547 work. If unsure, go with the default, which is "Any".
2552 config PCI_GOMMCONFIG
2569 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2571 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2574 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2578 depends on X86_32 && PCI && (ACPI || SFI) && (PCI_GOMMCONFIG || PCI_GOANY)
2582 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2586 depends on PCI && XEN
2594 bool "Support mmconfig PCI config space access"
2595 depends on X86_64 && PCI && ACPI
2597 config PCI_CNB20LE_QUIRK
2598 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2601 Read the PCI windows out of the CNB20LE host bridge. This allows
2602 PCI hotplug to work on systems with the CNB20LE chipset which do
2605 There's no public spec for this chipset, and this functionality
2606 is known to be incomplete.
2608 You should say N unless you know you need this.
2610 source "drivers/pci/Kconfig"
2613 bool "ISA-style bus support on modern systems" if EXPERT
2616 Enables ISA-style drivers on modern systems. This is necessary to
2617 support PC/104 devices on X86_64 platforms.
2621 # x86_64 have no ISA slots, but can have ISA-style DMA.
2623 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2626 Enables ISA-style DMA support for devices requiring such controllers.
2634 Find out whether you have ISA slots on your motherboard. ISA is the
2635 name of a bus system, i.e. the way the CPU talks to the other stuff
2636 inside your box. Other bus systems are PCI, EISA, MicroChannel
2637 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2638 newer boards don't support it. If you have ISA, say Y, otherwise N.
2644 The Extended Industry Standard Architecture (EISA) bus was
2645 developed as an open alternative to the IBM MicroChannel bus.
2647 The EISA bus provided some of the features of the IBM MicroChannel
2648 bus while maintaining backward compatibility with cards made for
2649 the older ISA bus. The EISA bus saw limited use between 1988 and
2650 1995 when it was made obsolete by the PCI bus.
2652 Say Y here if you are building a kernel for an EISA-based machine.
2656 source "drivers/eisa/Kconfig"
2659 tristate "NatSemi SCx200 support"
2661 This provides basic support for National Semiconductor's
2662 (now AMD's) Geode processors. The driver probes for the
2663 PCI-IDs of several on-chip devices, so its a good dependency
2664 for other scx200_* drivers.
2666 If compiled as a module, the driver is named scx200.
2668 config SCx200HR_TIMER
2669 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2673 This driver provides a clocksource built upon the on-chip
2674 27MHz high-resolution timer. Its also a workaround for
2675 NSC Geode SC-1100's buggy TSC, which loses time when the
2676 processor goes idle (as is done by the scheduler). The
2677 other workaround is idle=poll boot option.
2680 bool "One Laptop Per Child support"
2687 Add support for detecting the unique features of the OLPC
2691 bool "OLPC XO-1 Power Management"
2692 depends on OLPC && MFD_CS5535 && PM_SLEEP
2695 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2698 bool "OLPC XO-1 Real Time Clock"
2699 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2701 Add support for the XO-1 real time clock, which can be used as a
2702 programmable wakeup source.
2705 bool "OLPC XO-1 SCI extras"
2706 depends on OLPC && OLPC_XO1_PM
2712 Add support for SCI-based features of the OLPC XO-1 laptop:
2713 - EC-driven system wakeups
2717 - AC adapter status updates
2718 - Battery status updates
2720 config OLPC_XO15_SCI
2721 bool "OLPC XO-1.5 SCI extras"
2722 depends on OLPC && ACPI
2725 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2726 - EC-driven system wakeups
2727 - AC adapter status updates
2728 - Battery status updates
2731 bool "PCEngines ALIX System Support (LED setup)"
2734 This option enables system support for the PCEngines ALIX.
2735 At present this just sets up LEDs for GPIO control on
2736 ALIX2/3/6 boards. However, other system specific setup should
2739 Note: You must still enable the drivers for GPIO and LED support
2740 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2742 Note: You have to set alix.force=1 for boards with Award BIOS.
2745 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2748 This option enables system support for the Soekris Engineering net5501.
2751 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2755 This option enables system support for the Traverse Technologies GEOS.
2758 bool "Technologic Systems TS-5500 platform support"
2760 select CHECK_SIGNATURE
2764 This option enables system support for the Technologic Systems TS-5500.
2770 depends on CPU_SUP_AMD && PCI
2772 source "drivers/pcmcia/Kconfig"
2775 tristate "RapidIO support"
2779 If enabled this option will include drivers and the core
2780 infrastructure code to support RapidIO interconnect devices.
2782 source "drivers/rapidio/Kconfig"
2785 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2787 Firmwares often provide initial graphics framebuffers so the BIOS,
2788 bootloader or kernel can show basic video-output during boot for
2789 user-guidance and debugging. Historically, x86 used the VESA BIOS
2790 Extensions and EFI-framebuffers for this, which are mostly limited
2792 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2793 framebuffers so the new generic system-framebuffer drivers can be
2794 used on x86. If the framebuffer is not compatible with the generic
2795 modes, it is adverticed as fallback platform framebuffer so legacy
2796 drivers like efifb, vesafb and uvesafb can pick it up.
2797 If this option is not selected, all system framebuffers are always
2798 marked as fallback platform framebuffers as usual.
2800 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2801 not be able to pick up generic system framebuffers if this option
2802 is selected. You are highly encouraged to enable simplefb as
2803 replacement if you select this option. simplefb can correctly deal
2804 with generic system framebuffers. But you should still keep vesafb
2805 and others enabled as fallback if a system framebuffer is
2806 incompatible with simplefb.
2813 menu "Executable file formats / Emulations"
2815 source "fs/Kconfig.binfmt"
2817 config IA32_EMULATION
2818 bool "IA32 Emulation"
2820 select ARCH_WANT_OLD_COMPAT_IPC
2822 select COMPAT_BINFMT_ELF
2823 select COMPAT_OLD_SIGACTION
2825 Include code to run legacy 32-bit programs under a
2826 64-bit kernel. You should likely turn this on, unless you're
2827 100% sure that you don't have any 32-bit programs left.
2830 tristate "IA32 a.out support"
2831 depends on IA32_EMULATION
2833 Support old a.out binaries in the 32bit emulation.
2836 bool "x32 ABI for 64-bit mode"
2839 Include code to run binaries for the x32 native 32-bit ABI
2840 for 64-bit processors. An x32 process gets access to the
2841 full 64-bit register file and wide data path while leaving
2842 pointers at 32 bits for smaller memory footprint.
2844 You will need a recent binutils (2.22 or later) with
2845 elf32_x86_64 support enabled to compile a kernel with this
2850 depends on IA32_EMULATION || X86_32
2852 select OLD_SIGSUSPEND3
2856 depends on IA32_EMULATION || X86_X32
2859 config COMPAT_FOR_U64_ALIGNMENT
2862 config SYSVIPC_COMPAT
2870 config HAVE_ATOMIC_IOMAP
2874 config X86_DEV_DMA_OPS
2876 depends on X86_64 || STA2X11
2878 config X86_DMA_REMAP
2882 config HAVE_GENERIC_GUP
2885 source "net/Kconfig"
2887 source "drivers/Kconfig"
2889 source "drivers/firmware/Kconfig"
2893 source "arch/x86/Kconfig.debug"
2895 source "security/Kconfig"
2897 source "crypto/Kconfig"
2899 source "arch/x86/kvm/Kconfig"
2901 source "lib/Kconfig"
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