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 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_NUMA_BALANCING if X86_64
73 select ARCH_USE_BUILTIN_BSWAP
74 select ARCH_USE_QUEUED_RWLOCKS
75 select ARCH_USE_QUEUED_SPINLOCKS
76 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
77 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
78 select ARCH_WANTS_THP_SWAP if X86_64
79 select BUILDTIME_EXTABLE_SORT
81 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
82 select CLOCKSOURCE_WATCHDOG
83 select DCACHE_WORD_ACCESS
84 select EDAC_ATOMIC_SCRUB
86 select GENERIC_CLOCKEVENTS
87 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
88 select GENERIC_CLOCKEVENTS_MIN_ADJUST
89 select GENERIC_CMOS_UPDATE
90 select GENERIC_CPU_AUTOPROBE
91 select GENERIC_CPU_VULNERABILITIES
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
114 select HAVE_ARCH_KGDB
115 select HAVE_ARCH_MMAP_RND_BITS if MMU
116 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
117 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
118 select HAVE_ARCH_SECCOMP_FILTER
119 select HAVE_ARCH_TRACEHOOK
120 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
121 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
122 select HAVE_ARCH_VMAP_STACK if X86_64
123 select HAVE_ARCH_WITHIN_STACK_FRAMES
124 select HAVE_CC_STACKPROTECTOR
125 select HAVE_CMPXCHG_DOUBLE
126 select HAVE_CMPXCHG_LOCAL
127 select HAVE_CONTEXT_TRACKING if X86_64
128 select HAVE_COPY_THREAD_TLS
129 select HAVE_C_RECORDMCOUNT
130 select HAVE_DEBUG_KMEMLEAK
131 select HAVE_DEBUG_STACKOVERFLOW
132 select HAVE_DMA_API_DEBUG
133 select HAVE_DMA_CONTIGUOUS
134 select HAVE_DYNAMIC_FTRACE
135 select HAVE_DYNAMIC_FTRACE_WITH_REGS
136 select HAVE_EBPF_JIT if X86_64
137 select HAVE_EFFICIENT_UNALIGNED_ACCESS
138 select HAVE_EXIT_THREAD
139 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
140 select HAVE_FTRACE_MCOUNT_RECORD
141 select HAVE_FUNCTION_GRAPH_TRACER
142 select HAVE_FUNCTION_TRACER
143 select HAVE_GCC_PLUGINS
144 select HAVE_HW_BREAKPOINT
146 select HAVE_IOREMAP_PROT
147 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
148 select HAVE_IRQ_TIME_ACCOUNTING
149 select HAVE_KERNEL_BZIP2
150 select HAVE_KERNEL_GZIP
151 select HAVE_KERNEL_LZ4
152 select HAVE_KERNEL_LZMA
153 select HAVE_KERNEL_LZO
154 select HAVE_KERNEL_XZ
156 select HAVE_KPROBES_ON_FTRACE
157 select HAVE_FUNCTION_ERROR_INJECTION
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 "Avoid speculative indirect branches in kernel"
437 Compile kernel with the retpoline compiler options to guard against
438 kernel-to-user data leaks by avoiding speculative indirect
439 branches. Requires a compiler with -mindirect-branch=thunk-extern
440 support for full protection. The kernel may run slower.
442 Without compiler support, at least indirect branches in assembler
443 code are eliminated. Since this includes the syscall entry path,
444 it is not entirely pointless.
447 bool "Intel Resource Director Technology support"
449 depends on X86 && CPU_SUP_INTEL
452 Select to enable resource allocation and monitoring which are
453 sub-features of Intel Resource Director Technology(RDT). More
454 information about RDT can be found in the Intel x86
455 Architecture Software Developer Manual.
460 config X86_EXTENDED_PLATFORM
461 bool "Support for extended (non-PC) x86 platforms"
464 If you disable this option then the kernel will only support
465 standard PC platforms. (which covers the vast majority of
468 If you enable this option then you'll be able to select support
469 for the following (non-PC) 32 bit x86 platforms:
470 Goldfish (Android emulator)
473 SGI 320/540 (Visual Workstation)
474 STA2X11-based (e.g. Northville)
475 Moorestown MID devices
477 If you have one of these systems, or if you want to build a
478 generic distribution kernel, say Y here - otherwise say N.
482 config X86_EXTENDED_PLATFORM
483 bool "Support for extended (non-PC) x86 platforms"
486 If you disable this option then the kernel will only support
487 standard PC platforms. (which covers the vast majority of
490 If you enable this option then you'll be able to select support
491 for the following (non-PC) 64 bit x86 platforms:
496 If you have one of these systems, or if you want to build a
497 generic distribution kernel, say Y here - otherwise say N.
499 # This is an alphabetically sorted list of 64 bit extended platforms
500 # Please maintain the alphabetic order if and when there are additions
502 bool "Numascale NumaChip"
504 depends on X86_EXTENDED_PLATFORM
507 depends on X86_X2APIC
508 depends on PCI_MMCONFIG
510 Adds support for Numascale NumaChip large-SMP systems. Needed to
511 enable more than ~168 cores.
512 If you don't have one of these, you should say N here.
516 select HYPERVISOR_GUEST
518 depends on X86_64 && PCI
519 depends on X86_EXTENDED_PLATFORM
522 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
523 supposed to run on these EM64T-based machines. Only choose this option
524 if you have one of these machines.
527 bool "SGI Ultraviolet"
529 depends on X86_EXTENDED_PLATFORM
532 depends on X86_X2APIC
535 This option is needed in order to support SGI Ultraviolet systems.
536 If you don't have one of these, you should say N here.
538 # Following is an alphabetically sorted list of 32 bit extended platforms
539 # Please maintain the alphabetic order if and when there are additions
542 bool "Goldfish (Virtual Platform)"
543 depends on X86_EXTENDED_PLATFORM
545 Enable support for the Goldfish virtual platform used primarily
546 for Android development. Unless you are building for the Android
547 Goldfish emulator say N here.
550 bool "CE4100 TV platform"
552 depends on PCI_GODIRECT
553 depends on X86_IO_APIC
555 depends on X86_EXTENDED_PLATFORM
556 select X86_REBOOTFIXUPS
558 select OF_EARLY_FLATTREE
560 Select for the Intel CE media processor (CE4100) SOC.
561 This option compiles in support for the CE4100 SOC for settop
562 boxes and media devices.
565 bool "Intel MID platform support"
566 depends on X86_EXTENDED_PLATFORM
567 depends on X86_PLATFORM_DEVICES
569 depends on X86_64 || (PCI_GOANY && X86_32)
570 depends on X86_IO_APIC
576 select MFD_INTEL_MSIC
578 Select to build a kernel capable of supporting Intel MID (Mobile
579 Internet Device) platform systems which do not have the PCI legacy
580 interfaces. If you are building for a PC class system say N here.
582 Intel MID platforms are based on an Intel processor and chipset which
583 consume less power than most of the x86 derivatives.
585 config X86_INTEL_QUARK
586 bool "Intel Quark platform support"
588 depends on X86_EXTENDED_PLATFORM
589 depends on X86_PLATFORM_DEVICES
593 depends on X86_IO_APIC
598 Select to include support for Quark X1000 SoC.
599 Say Y here if you have a Quark based system such as the Arduino
600 compatible Intel Galileo.
602 config X86_INTEL_LPSS
603 bool "Intel Low Power Subsystem Support"
604 depends on X86 && ACPI
609 Select to build support for Intel Low Power Subsystem such as
610 found on Intel Lynxpoint PCH. Selecting this option enables
611 things like clock tree (common clock framework) and pincontrol
612 which are needed by the LPSS peripheral drivers.
614 config X86_AMD_PLATFORM_DEVICE
615 bool "AMD ACPI2Platform devices support"
620 Select to interpret AMD specific ACPI device to platform device
621 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
622 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
623 implemented under PINCTRL subsystem.
626 tristate "Intel SoC IOSF Sideband support for SoC platforms"
629 This option enables sideband register access support for Intel SoC
630 platforms. On these platforms the IOSF sideband is used in lieu of
631 MSR's for some register accesses, mostly but not limited to thermal
632 and power. Drivers may query the availability of this device to
633 determine if they need the sideband in order to work on these
634 platforms. The sideband is available on the following SoC products.
635 This list is not meant to be exclusive.
640 You should say Y if you are running a kernel on one of these SoC's.
642 config IOSF_MBI_DEBUG
643 bool "Enable IOSF sideband access through debugfs"
644 depends on IOSF_MBI && DEBUG_FS
646 Select this option to expose the IOSF sideband access registers (MCR,
647 MDR, MCRX) through debugfs to write and read register information from
648 different units on the SoC. This is most useful for obtaining device
649 state information for debug and analysis. As this is a general access
650 mechanism, users of this option would have specific knowledge of the
651 device they want to access.
653 If you don't require the option or are in doubt, say N.
656 bool "RDC R-321x SoC"
658 depends on X86_EXTENDED_PLATFORM
660 select X86_REBOOTFIXUPS
662 This option is needed for RDC R-321x system-on-chip, also known
664 If you don't have one of these chips, you should say N here.
666 config X86_32_NON_STANDARD
667 bool "Support non-standard 32-bit SMP architectures"
668 depends on X86_32 && SMP
669 depends on X86_EXTENDED_PLATFORM
671 This option compiles in the bigsmp and STA2X11 default
672 subarchitectures. It is intended for a generic binary
673 kernel. If you select them all, kernel will probe it one by
674 one and will fallback to default.
676 # Alphabetically sorted list of Non standard 32 bit platforms
678 config X86_SUPPORTS_MEMORY_FAILURE
680 # MCE code calls memory_failure():
682 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
683 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
684 depends on X86_64 || !SPARSEMEM
685 select ARCH_SUPPORTS_MEMORY_FAILURE
688 bool "STA2X11 Companion Chip Support"
689 depends on X86_32_NON_STANDARD && PCI
690 select X86_DEV_DMA_OPS
697 This adds support for boards based on the STA2X11 IO-Hub,
698 a.k.a. "ConneXt". The chip is used in place of the standard
699 PC chipset, so all "standard" peripherals are missing. If this
700 option is selected the kernel will still be able to boot on
701 standard PC machines.
704 tristate "Eurobraille/Iris poweroff module"
707 The Iris machines from EuroBraille do not have APM or ACPI support
708 to shut themselves down properly. A special I/O sequence is
709 needed to do so, which is what this module does at
712 This is only for Iris machines from EuroBraille.
716 config SCHED_OMIT_FRAME_POINTER
718 prompt "Single-depth WCHAN output"
721 Calculate simpler /proc/<PID>/wchan values. If this option
722 is disabled then wchan values will recurse back to the
723 caller function. This provides more accurate wchan values,
724 at the expense of slightly more scheduling overhead.
726 If in doubt, say "Y".
728 menuconfig HYPERVISOR_GUEST
729 bool "Linux guest support"
731 Say Y here to enable options for running Linux under various hyper-
732 visors. This option enables basic hypervisor detection and platform
735 If you say N, all options in this submenu will be skipped and
736 disabled, and Linux guest support won't be built in.
741 bool "Enable paravirtualization code"
743 This changes the kernel so it can modify itself when it is run
744 under a hypervisor, potentially improving performance significantly
745 over full virtualization. However, when run without a hypervisor
746 the kernel is theoretically slower and slightly larger.
748 config PARAVIRT_DEBUG
749 bool "paravirt-ops debugging"
750 depends on PARAVIRT && DEBUG_KERNEL
752 Enable to debug paravirt_ops internals. Specifically, BUG if
753 a paravirt_op is missing when it is called.
755 config PARAVIRT_SPINLOCKS
756 bool "Paravirtualization layer for spinlocks"
757 depends on PARAVIRT && SMP
759 Paravirtualized spinlocks allow a pvops backend to replace the
760 spinlock implementation with something virtualization-friendly
761 (for example, block the virtual CPU rather than spinning).
763 It has a minimal impact on native kernels and gives a nice performance
764 benefit on paravirtualized KVM / Xen kernels.
766 If you are unsure how to answer this question, answer Y.
768 config QUEUED_LOCK_STAT
769 bool "Paravirt queued spinlock statistics"
770 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
772 Enable the collection of statistical data on the slowpath
773 behavior of paravirtualized queued spinlocks and report
776 source "arch/x86/xen/Kconfig"
779 bool "KVM Guest support (including kvmclock)"
781 select PARAVIRT_CLOCK
784 This option enables various optimizations for running under the KVM
785 hypervisor. It includes a paravirtualized clock, so that instead
786 of relying on a PIT (or probably other) emulation by the
787 underlying device model, the host provides the guest with
788 timing infrastructure such as time of day, and system time
791 bool "Enable debug information for KVM Guests in debugfs"
792 depends on KVM_GUEST && DEBUG_FS
795 This option enables collection of various statistics for KVM guest.
796 Statistics are displayed in debugfs filesystem. Enabling this option
797 may incur significant overhead.
799 config PARAVIRT_TIME_ACCOUNTING
800 bool "Paravirtual steal time accounting"
804 Select this option to enable fine granularity task steal time
805 accounting. Time spent executing other tasks in parallel with
806 the current vCPU is discounted from the vCPU power. To account for
807 that, there can be a small performance impact.
809 If in doubt, say N here.
811 config PARAVIRT_CLOCK
814 config JAILHOUSE_GUEST
815 bool "Jailhouse non-root cell support"
816 depends on X86_64 && PCI
819 This option allows to run Linux as guest in a Jailhouse non-root
820 cell. You can leave this option disabled if you only want to start
821 Jailhouse and run Linux afterwards in the root cell.
823 endif #HYPERVISOR_GUEST
828 source "arch/x86/Kconfig.cpu"
832 prompt "HPET Timer Support" if X86_32
834 Use the IA-PC HPET (High Precision Event Timer) to manage
835 time in preference to the PIT and RTC, if a HPET is
837 HPET is the next generation timer replacing legacy 8254s.
838 The HPET 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. The interface used is documented
841 in the HPET spec, revision 1.
843 You can safely choose Y here. However, HPET will only be
844 activated if the platform and the BIOS support this feature.
845 Otherwise the 8254 will be used for timing services.
847 Choose N to continue using the legacy 8254 timer.
849 config HPET_EMULATE_RTC
851 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
854 def_bool y if X86_INTEL_MID
855 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
857 depends on X86_INTEL_MID && SFI
859 APB timer is the replacement for 8254, HPET on X86 MID platforms.
860 The APBT provides a stable time base on SMP
861 systems, unlike the TSC, but it is more expensive to access,
862 as it is off-chip. APB timers are always running regardless of CPU
863 C states, they are used as per CPU clockevent device when possible.
865 # Mark as expert because too many people got it wrong.
866 # The code disables itself when not needed.
869 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
870 bool "Enable DMI scanning" if EXPERT
872 Enabled scanning of DMI to identify machine quirks. Say Y
873 here unless you have verified that your setup is not
874 affected by entries in the DMI blacklist. Required by PNP
878 bool "Old AMD GART IOMMU support"
880 depends on X86_64 && PCI && AMD_NB
882 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
883 GART based hardware IOMMUs.
885 The GART supports full DMA access for devices with 32-bit access
886 limitations, on systems with more than 3 GB. This is usually needed
887 for USB, sound, many IDE/SATA chipsets and some other devices.
889 Newer systems typically have a modern AMD IOMMU, supported via
890 the CONFIG_AMD_IOMMU=y config option.
892 In normal configurations this driver is only active when needed:
893 there's more than 3 GB of memory and the system contains a
894 32-bit limited device.
899 bool "IBM Calgary IOMMU support"
901 depends on X86_64 && PCI
903 Support for hardware IOMMUs in IBM's xSeries x366 and x460
904 systems. Needed to run systems with more than 3GB of memory
905 properly with 32-bit PCI devices that do not support DAC
906 (Double Address Cycle). Calgary also supports bus level
907 isolation, where all DMAs pass through the IOMMU. This
908 prevents them from going anywhere except their intended
909 destination. This catches hard-to-find kernel bugs and
910 mis-behaving drivers and devices that do not use the DMA-API
911 properly to set up their DMA buffers. The IOMMU can be
912 turned off at boot time with the iommu=off parameter.
913 Normally the kernel will make the right choice by itself.
916 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
918 prompt "Should Calgary be enabled by default?"
919 depends on CALGARY_IOMMU
921 Should Calgary be enabled by default? if you choose 'y', Calgary
922 will be used (if it exists). If you choose 'n', Calgary will not be
923 used even if it exists. If you choose 'n' and would like to use
924 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
927 # need this always selected by IOMMU for the VIA workaround
931 Support for software bounce buffers used on x86-64 systems
932 which don't have a hardware IOMMU. Using this PCI devices
933 which can only access 32-bits of memory can be used on systems
934 with more than 3 GB of memory.
939 depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU
942 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
943 depends on X86_64 && SMP && DEBUG_KERNEL
944 select CPUMASK_OFFSTACK
946 Enable maximum number of CPUS and NUMA Nodes for this architecture.
950 int "Maximum number of CPUs" if SMP && !MAXSMP
951 range 2 8 if SMP && X86_32 && !X86_BIGSMP
952 range 2 64 if SMP && X86_32 && X86_BIGSMP
953 range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK && X86_64
954 range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
956 default "8192" if MAXSMP
957 default "32" if SMP && X86_BIGSMP
958 default "8" if SMP && X86_32
961 This allows you to specify the maximum number of CPUs which this
962 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
963 supported value is 8192, otherwise the maximum value is 512. The
964 minimum value which makes sense is 2.
966 This is purely to save memory - each supported CPU adds
967 approximately eight kilobytes to the kernel image.
970 bool "SMT (Hyperthreading) scheduler support"
973 SMT scheduler support improves the CPU scheduler's decision making
974 when dealing with Intel Pentium 4 chips with HyperThreading at a
975 cost of slightly increased overhead in some places. If unsure say
980 prompt "Multi-core scheduler support"
983 Multi-core scheduler support improves the CPU scheduler's decision
984 making when dealing with multi-core CPU chips at a cost of slightly
985 increased overhead in some places. If unsure say N here.
988 bool "CPU core priorities scheduler support"
989 depends on SCHED_MC && CPU_SUP_INTEL
990 select X86_INTEL_PSTATE
994 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
995 core ordering determined at manufacturing time, which allows
996 certain cores to reach higher turbo frequencies (when running
997 single threaded workloads) than others.
999 Enabling this kernel feature teaches the scheduler about
1000 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1001 scheduler's CPU selection logic accordingly, so that higher
1002 overall system performance can be achieved.
1004 This feature will have no effect on CPUs without this feature.
1006 If unsure say Y here.
1008 source "kernel/Kconfig.preempt"
1012 depends on !SMP && X86_LOCAL_APIC
1015 bool "Local APIC support on uniprocessors" if !PCI_MSI
1017 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1019 A local APIC (Advanced Programmable Interrupt Controller) is an
1020 integrated interrupt controller in the CPU. If you have a single-CPU
1021 system which has a processor with a local APIC, you can say Y here to
1022 enable and use it. If you say Y here even though your machine doesn't
1023 have a local APIC, then the kernel will still run with no slowdown at
1024 all. The local APIC supports CPU-generated self-interrupts (timer,
1025 performance counters), and the NMI watchdog which detects hard
1028 config X86_UP_IOAPIC
1029 bool "IO-APIC support on uniprocessors"
1030 depends on X86_UP_APIC
1032 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1033 SMP-capable replacement for PC-style interrupt controllers. Most
1034 SMP systems and many recent uniprocessor systems have one.
1036 If you have a single-CPU system with an IO-APIC, you can say Y here
1037 to use it. If you say Y here even though your machine doesn't have
1038 an IO-APIC, then the kernel will still run with no slowdown at all.
1040 config X86_LOCAL_APIC
1042 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1043 select IRQ_DOMAIN_HIERARCHY
1044 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1048 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1050 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1051 bool "Reroute for broken boot IRQs"
1052 depends on X86_IO_APIC
1054 This option enables a workaround that fixes a source of
1055 spurious interrupts. This is recommended when threaded
1056 interrupt handling is used on systems where the generation of
1057 superfluous "boot interrupts" cannot be disabled.
1059 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1060 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1061 kernel does during interrupt handling). On chipsets where this
1062 boot IRQ generation cannot be disabled, this workaround keeps
1063 the original IRQ line masked so that only the equivalent "boot
1064 IRQ" is delivered to the CPUs. The workaround also tells the
1065 kernel to set up the IRQ handler on the boot IRQ line. In this
1066 way only one interrupt is delivered to the kernel. Otherwise
1067 the spurious second interrupt may cause the kernel to bring
1068 down (vital) interrupt lines.
1070 Only affects "broken" chipsets. Interrupt sharing may be
1071 increased on these systems.
1074 bool "Machine Check / overheating reporting"
1075 select GENERIC_ALLOCATOR
1078 Machine Check support allows the processor to notify the
1079 kernel if it detects a problem (e.g. overheating, data corruption).
1080 The action the kernel takes depends on the severity of the problem,
1081 ranging from warning messages to halting the machine.
1083 config X86_MCELOG_LEGACY
1084 bool "Support for deprecated /dev/mcelog character device"
1087 Enable support for /dev/mcelog which is needed by the old mcelog
1088 userspace logging daemon. Consider switching to the new generation
1091 config X86_MCE_INTEL
1093 prompt "Intel MCE features"
1094 depends on X86_MCE && X86_LOCAL_APIC
1096 Additional support for intel specific MCE features such as
1097 the thermal monitor.
1101 prompt "AMD MCE features"
1102 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1104 Additional support for AMD specific MCE features such as
1105 the DRAM Error Threshold.
1107 config X86_ANCIENT_MCE
1108 bool "Support for old Pentium 5 / WinChip machine checks"
1109 depends on X86_32 && X86_MCE
1111 Include support for machine check handling on old Pentium 5 or WinChip
1112 systems. These typically need to be enabled explicitly on the command
1115 config X86_MCE_THRESHOLD
1116 depends on X86_MCE_AMD || X86_MCE_INTEL
1119 config X86_MCE_INJECT
1120 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1121 tristate "Machine check injector support"
1123 Provide support for injecting machine checks for testing purposes.
1124 If you don't know what a machine check is and you don't do kernel
1125 QA it is safe to say n.
1127 config X86_THERMAL_VECTOR
1129 depends on X86_MCE_INTEL
1131 source "arch/x86/events/Kconfig"
1133 config X86_LEGACY_VM86
1134 bool "Legacy VM86 support"
1138 This option allows user programs to put the CPU into V8086
1139 mode, which is an 80286-era approximation of 16-bit real mode.
1141 Some very old versions of X and/or vbetool require this option
1142 for user mode setting. Similarly, DOSEMU will use it if
1143 available to accelerate real mode DOS programs. However, any
1144 recent version of DOSEMU, X, or vbetool should be fully
1145 functional even without kernel VM86 support, as they will all
1146 fall back to software emulation. Nevertheless, if you are using
1147 a 16-bit DOS program where 16-bit performance matters, vm86
1148 mode might be faster than emulation and you might want to
1151 Note that any app that works on a 64-bit kernel is unlikely to
1152 need this option, as 64-bit kernels don't, and can't, support
1153 V8086 mode. This option is also unrelated to 16-bit protected
1154 mode and is not needed to run most 16-bit programs under Wine.
1156 Enabling this option increases the complexity of the kernel
1157 and slows down exception handling a tiny bit.
1159 If unsure, say N here.
1163 default X86_LEGACY_VM86
1166 bool "Enable support for 16-bit segments" if EXPERT
1168 depends on MODIFY_LDT_SYSCALL
1170 This option is required by programs like Wine to run 16-bit
1171 protected mode legacy code on x86 processors. Disabling
1172 this option saves about 300 bytes on i386, or around 6K text
1173 plus 16K runtime memory on x86-64,
1177 depends on X86_16BIT && X86_32
1181 depends on X86_16BIT && X86_64
1183 config X86_VSYSCALL_EMULATION
1184 bool "Enable vsyscall emulation" if EXPERT
1188 This enables emulation of the legacy vsyscall page. Disabling
1189 it is roughly equivalent to booting with vsyscall=none, except
1190 that it will also disable the helpful warning if a program
1191 tries to use a vsyscall. With this option set to N, offending
1192 programs will just segfault, citing addresses of the form
1195 This option is required by many programs built before 2013, and
1196 care should be used even with newer programs if set to N.
1198 Disabling this option saves about 7K of kernel size and
1199 possibly 4K of additional runtime pagetable memory.
1202 tristate "Toshiba Laptop support"
1205 This adds a driver to safely access the System Management Mode of
1206 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1207 not work on models with a Phoenix BIOS. The System Management Mode
1208 is used to set the BIOS and power saving options on Toshiba portables.
1210 For information on utilities to make use of this driver see the
1211 Toshiba Linux utilities web site at:
1212 <http://www.buzzard.org.uk/toshiba/>.
1214 Say Y if you intend to run this kernel on a Toshiba portable.
1218 tristate "Dell i8k legacy laptop support"
1220 select SENSORS_DELL_SMM
1222 This option enables legacy /proc/i8k userspace interface in hwmon
1223 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1224 temperature and allows controlling fan speeds of Dell laptops via
1225 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1226 it reports also power and hotkey status. For fan speed control is
1227 needed userspace package i8kutils.
1229 Say Y if you intend to run this kernel on old Dell laptops or want to
1230 use userspace package i8kutils.
1233 config X86_REBOOTFIXUPS
1234 bool "Enable X86 board specific fixups for reboot"
1237 This enables chipset and/or board specific fixups to be done
1238 in order to get reboot to work correctly. This is only needed on
1239 some combinations of hardware and BIOS. The symptom, for which
1240 this config is intended, is when reboot ends with a stalled/hung
1243 Currently, the only fixup is for the Geode machines using
1244 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1246 Say Y if you want to enable the fixup. Currently, it's safe to
1247 enable this option even if you don't need it.
1251 bool "CPU microcode loading support"
1253 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1256 If you say Y here, you will be able to update the microcode on
1257 Intel and AMD processors. The Intel support is for the IA32 family,
1258 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1259 AMD support is for families 0x10 and later. You will obviously need
1260 the actual microcode binary data itself which is not shipped with
1263 The preferred method to load microcode from a detached initrd is described
1264 in Documentation/x86/early-microcode.txt. For that you need to enable
1265 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1266 initrd for microcode blobs.
1268 In addition, you can build-in the microcode into the kernel. For that you
1269 need to enable FIRMWARE_IN_KERNEL and add the vendor-supplied microcode
1270 to the CONFIG_EXTRA_FIRMWARE config option.
1272 config MICROCODE_INTEL
1273 bool "Intel microcode loading support"
1274 depends on MICROCODE
1278 This options enables microcode patch loading support for Intel
1281 For the current Intel microcode data package go to
1282 <https://downloadcenter.intel.com> and search for
1283 'Linux Processor Microcode Data File'.
1285 config MICROCODE_AMD
1286 bool "AMD microcode loading support"
1287 depends on MICROCODE
1290 If you select this option, microcode patch loading support for AMD
1291 processors will be enabled.
1293 config MICROCODE_OLD_INTERFACE
1295 depends on MICROCODE
1298 tristate "/dev/cpu/*/msr - Model-specific register support"
1300 This device gives privileged processes access to the x86
1301 Model-Specific Registers (MSRs). It is a character device with
1302 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1303 MSR accesses are directed to a specific CPU on multi-processor
1307 tristate "/dev/cpu/*/cpuid - CPU information support"
1309 This device gives processes access to the x86 CPUID instruction to
1310 be executed on a specific processor. It is a character device
1311 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1315 prompt "High Memory Support"
1322 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1323 However, the address space of 32-bit x86 processors is only 4
1324 Gigabytes large. That means that, if you have a large amount of
1325 physical memory, not all of it can be "permanently mapped" by the
1326 kernel. The physical memory that's not permanently mapped is called
1329 If you are compiling a kernel which will never run on a machine with
1330 more than 1 Gigabyte total physical RAM, answer "off" here (default
1331 choice and suitable for most users). This will result in a "3GB/1GB"
1332 split: 3GB are mapped so that each process sees a 3GB virtual memory
1333 space and the remaining part of the 4GB virtual memory space is used
1334 by the kernel to permanently map as much physical memory as
1337 If the machine has between 1 and 4 Gigabytes physical RAM, then
1340 If more than 4 Gigabytes is used then answer "64GB" here. This
1341 selection turns Intel PAE (Physical Address Extension) mode on.
1342 PAE implements 3-level paging on IA32 processors. PAE is fully
1343 supported by Linux, PAE mode is implemented on all recent Intel
1344 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1345 then the kernel will not boot on CPUs that don't support PAE!
1347 The actual amount of total physical memory will either be
1348 auto detected or can be forced by using a kernel command line option
1349 such as "mem=256M". (Try "man bootparam" or see the documentation of
1350 your boot loader (lilo or loadlin) about how to pass options to the
1351 kernel at boot time.)
1353 If unsure, say "off".
1358 Select this if you have a 32-bit processor and between 1 and 4
1359 gigabytes of physical RAM.
1366 Select this if you have a 32-bit processor and more than 4
1367 gigabytes of physical RAM.
1372 prompt "Memory split" if EXPERT
1376 Select the desired split between kernel and user memory.
1378 If the address range available to the kernel is less than the
1379 physical memory installed, the remaining memory will be available
1380 as "high memory". Accessing high memory is a little more costly
1381 than low memory, as it needs to be mapped into the kernel first.
1382 Note that increasing the kernel address space limits the range
1383 available to user programs, making the address space there
1384 tighter. Selecting anything other than the default 3G/1G split
1385 will also likely make your kernel incompatible with binary-only
1388 If you are not absolutely sure what you are doing, leave this
1392 bool "3G/1G user/kernel split"
1393 config VMSPLIT_3G_OPT
1395 bool "3G/1G user/kernel split (for full 1G low memory)"
1397 bool "2G/2G user/kernel split"
1398 config VMSPLIT_2G_OPT
1400 bool "2G/2G user/kernel split (for full 2G low memory)"
1402 bool "1G/3G user/kernel split"
1407 default 0xB0000000 if VMSPLIT_3G_OPT
1408 default 0x80000000 if VMSPLIT_2G
1409 default 0x78000000 if VMSPLIT_2G_OPT
1410 default 0x40000000 if VMSPLIT_1G
1416 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1419 bool "PAE (Physical Address Extension) Support"
1420 depends on X86_32 && !HIGHMEM4G
1423 PAE is required for NX support, and furthermore enables
1424 larger swapspace support for non-overcommit purposes. It
1425 has the cost of more pagetable lookup overhead, and also
1426 consumes more pagetable space per process.
1429 bool "Enable 5-level page tables support"
1432 5-level paging enables access to larger address space:
1433 upto 128 PiB of virtual address space and 4 PiB of
1434 physical address space.
1436 It will be supported by future Intel CPUs.
1438 Note: a kernel with this option enabled can only be booted
1439 on machines that support the feature.
1441 See Documentation/x86/x86_64/5level-paging.txt for more
1446 config ARCH_PHYS_ADDR_T_64BIT
1448 depends on X86_64 || X86_PAE
1450 config ARCH_DMA_ADDR_T_64BIT
1452 depends on X86_64 || HIGHMEM64G
1454 config X86_DIRECT_GBPAGES
1456 depends on X86_64 && !DEBUG_PAGEALLOC
1458 Certain kernel features effectively disable kernel
1459 linear 1 GB mappings (even if the CPU otherwise
1460 supports them), so don't confuse the user by printing
1461 that we have them enabled.
1463 config ARCH_HAS_MEM_ENCRYPT
1466 config AMD_MEM_ENCRYPT
1467 bool "AMD Secure Memory Encryption (SME) support"
1468 depends on X86_64 && CPU_SUP_AMD
1470 Say yes to enable support for the encryption of system memory.
1471 This requires an AMD processor that supports Secure Memory
1474 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1475 bool "Activate AMD Secure Memory Encryption (SME) by default"
1477 depends on AMD_MEM_ENCRYPT
1479 Say yes to have system memory encrypted by default if running on
1480 an AMD processor that supports Secure Memory Encryption (SME).
1482 If set to Y, then the encryption of system memory can be
1483 deactivated with the mem_encrypt=off command line option.
1485 If set to N, then the encryption of system memory can be
1486 activated with the mem_encrypt=on command line option.
1488 config ARCH_USE_MEMREMAP_PROT
1490 depends on AMD_MEM_ENCRYPT
1492 # Common NUMA Features
1494 bool "Numa Memory Allocation and Scheduler Support"
1496 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1497 default y if X86_BIGSMP
1499 Enable NUMA (Non Uniform Memory Access) support.
1501 The kernel will try to allocate memory used by a CPU on the
1502 local memory controller of the CPU and add some more
1503 NUMA awareness to the kernel.
1505 For 64-bit this is recommended if the system is Intel Core i7
1506 (or later), AMD Opteron, or EM64T NUMA.
1508 For 32-bit this is only needed if you boot a 32-bit
1509 kernel on a 64-bit NUMA platform.
1511 Otherwise, you should say N.
1515 prompt "Old style AMD Opteron NUMA detection"
1516 depends on X86_64 && NUMA && PCI
1518 Enable AMD NUMA node topology detection. You should say Y here if
1519 you have a multi processor AMD system. This uses an old method to
1520 read the NUMA configuration directly from the builtin Northbridge
1521 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1522 which also takes priority if both are compiled in.
1524 config X86_64_ACPI_NUMA
1526 prompt "ACPI NUMA detection"
1527 depends on X86_64 && NUMA && ACPI && PCI
1530 Enable ACPI SRAT based node topology detection.
1532 # Some NUMA nodes have memory ranges that span
1533 # other nodes. Even though a pfn is valid and
1534 # between a node's start and end pfns, it may not
1535 # reside on that node. See memmap_init_zone()
1537 config NODES_SPAN_OTHER_NODES
1539 depends on X86_64_ACPI_NUMA
1542 bool "NUMA emulation"
1545 Enable NUMA emulation. A flat machine will be split
1546 into virtual nodes when booted with "numa=fake=N", where N is the
1547 number of nodes. This is only useful for debugging.
1550 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1552 default "10" if MAXSMP
1553 default "6" if X86_64
1555 depends on NEED_MULTIPLE_NODES
1557 Specify the maximum number of NUMA Nodes available on the target
1558 system. Increases memory reserved to accommodate various tables.
1560 config ARCH_HAVE_MEMORY_PRESENT
1562 depends on X86_32 && DISCONTIGMEM
1564 config NEED_NODE_MEMMAP_SIZE
1566 depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
1568 config ARCH_FLATMEM_ENABLE
1570 depends on X86_32 && !NUMA
1572 config ARCH_DISCONTIGMEM_ENABLE
1574 depends on NUMA && X86_32
1576 config ARCH_DISCONTIGMEM_DEFAULT
1578 depends on NUMA && X86_32
1580 config ARCH_SPARSEMEM_ENABLE
1582 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1583 select SPARSEMEM_STATIC if X86_32
1584 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1586 config ARCH_SPARSEMEM_DEFAULT
1590 config ARCH_SELECT_MEMORY_MODEL
1592 depends on ARCH_SPARSEMEM_ENABLE
1594 config ARCH_MEMORY_PROBE
1595 bool "Enable sysfs memory/probe interface"
1596 depends on X86_64 && MEMORY_HOTPLUG
1598 This option enables a sysfs memory/probe interface for testing.
1599 See Documentation/memory-hotplug.txt for more information.
1600 If you are unsure how to answer this question, answer N.
1602 config ARCH_PROC_KCORE_TEXT
1604 depends on X86_64 && PROC_KCORE
1606 config ILLEGAL_POINTER_VALUE
1609 default 0xdead000000000000 if X86_64
1613 config X86_PMEM_LEGACY_DEVICE
1616 config X86_PMEM_LEGACY
1617 tristate "Support non-standard NVDIMMs and ADR protected memory"
1618 depends on PHYS_ADDR_T_64BIT
1620 select X86_PMEM_LEGACY_DEVICE
1623 Treat memory marked using the non-standard e820 type of 12 as used
1624 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1625 The kernel will offer these regions to the 'pmem' driver so
1626 they can be used for persistent storage.
1631 bool "Allocate 3rd-level pagetables from highmem"
1634 The VM uses one page table entry for each page of physical memory.
1635 For systems with a lot of RAM, this can be wasteful of precious
1636 low memory. Setting this option will put user-space page table
1637 entries in high memory.
1639 config X86_CHECK_BIOS_CORRUPTION
1640 bool "Check for low memory corruption"
1642 Periodically check for memory corruption in low memory, which
1643 is suspected to be caused by BIOS. Even when enabled in the
1644 configuration, it is disabled at runtime. Enable it by
1645 setting "memory_corruption_check=1" on the kernel command
1646 line. By default it scans the low 64k of memory every 60
1647 seconds; see the memory_corruption_check_size and
1648 memory_corruption_check_period parameters in
1649 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1651 When enabled with the default parameters, this option has
1652 almost no overhead, as it reserves a relatively small amount
1653 of memory and scans it infrequently. It both detects corruption
1654 and prevents it from affecting the running system.
1656 It is, however, intended as a diagnostic tool; if repeatable
1657 BIOS-originated corruption always affects the same memory,
1658 you can use memmap= to prevent the kernel from using that
1661 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1662 bool "Set the default setting of memory_corruption_check"
1663 depends on X86_CHECK_BIOS_CORRUPTION
1666 Set whether the default state of memory_corruption_check is
1669 config X86_RESERVE_LOW
1670 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1674 Specify the amount of low memory to reserve for the BIOS.
1676 The first page contains BIOS data structures that the kernel
1677 must not use, so that page must always be reserved.
1679 By default we reserve the first 64K of physical RAM, as a
1680 number of BIOSes are known to corrupt that memory range
1681 during events such as suspend/resume or monitor cable
1682 insertion, so it must not be used by the kernel.
1684 You can set this to 4 if you are absolutely sure that you
1685 trust the BIOS to get all its memory reservations and usages
1686 right. If you know your BIOS have problems beyond the
1687 default 64K area, you can set this to 640 to avoid using the
1688 entire low memory range.
1690 If you have doubts about the BIOS (e.g. suspend/resume does
1691 not work or there's kernel crashes after certain hardware
1692 hotplug events) then you might want to enable
1693 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1694 typical corruption patterns.
1696 Leave this to the default value of 64 if you are unsure.
1698 config MATH_EMULATION
1700 depends on MODIFY_LDT_SYSCALL
1701 prompt "Math emulation" if X86_32
1703 Linux can emulate a math coprocessor (used for floating point
1704 operations) if you don't have one. 486DX and Pentium processors have
1705 a math coprocessor built in, 486SX and 386 do not, unless you added
1706 a 487DX or 387, respectively. (The messages during boot time can
1707 give you some hints here ["man dmesg"].) Everyone needs either a
1708 coprocessor or this emulation.
1710 If you don't have a math coprocessor, you need to say Y here; if you
1711 say Y here even though you have a coprocessor, the coprocessor will
1712 be used nevertheless. (This behavior can be changed with the kernel
1713 command line option "no387", which comes handy if your coprocessor
1714 is broken. Try "man bootparam" or see the documentation of your boot
1715 loader (lilo or loadlin) about how to pass options to the kernel at
1716 boot time.) This means that it is a good idea to say Y here if you
1717 intend to use this kernel on different machines.
1719 More information about the internals of the Linux math coprocessor
1720 emulation can be found in <file:arch/x86/math-emu/README>.
1722 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1723 kernel, it won't hurt.
1727 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1729 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1730 the Memory Type Range Registers (MTRRs) may be used to control
1731 processor access to memory ranges. This is most useful if you have
1732 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1733 allows bus write transfers to be combined into a larger transfer
1734 before bursting over the PCI/AGP bus. This can increase performance
1735 of image write operations 2.5 times or more. Saying Y here creates a
1736 /proc/mtrr file which may be used to manipulate your processor's
1737 MTRRs. Typically the X server should use this.
1739 This code has a reasonably generic interface so that similar
1740 control registers on other processors can be easily supported
1743 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1744 Registers (ARRs) which provide a similar functionality to MTRRs. For
1745 these, the ARRs are used to emulate the MTRRs.
1746 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1747 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1748 write-combining. All of these processors are supported by this code
1749 and it makes sense to say Y here if you have one of them.
1751 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1752 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1753 can lead to all sorts of problems, so it's good to say Y here.
1755 You can safely say Y even if your machine doesn't have MTRRs, you'll
1756 just add about 9 KB to your kernel.
1758 See <file:Documentation/x86/mtrr.txt> for more information.
1760 config MTRR_SANITIZER
1762 prompt "MTRR cleanup support"
1765 Convert MTRR layout from continuous to discrete, so X drivers can
1766 add writeback entries.
1768 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1769 The largest mtrr entry size for a continuous block can be set with
1774 config MTRR_SANITIZER_ENABLE_DEFAULT
1775 int "MTRR cleanup enable value (0-1)"
1778 depends on MTRR_SANITIZER
1780 Enable mtrr cleanup default value
1782 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1783 int "MTRR cleanup spare reg num (0-7)"
1786 depends on MTRR_SANITIZER
1788 mtrr cleanup spare entries default, it can be changed via
1789 mtrr_spare_reg_nr=N on the kernel command line.
1793 prompt "x86 PAT support" if EXPERT
1796 Use PAT attributes to setup page level cache control.
1798 PATs are the modern equivalents of MTRRs and are much more
1799 flexible than MTRRs.
1801 Say N here if you see bootup problems (boot crash, boot hang,
1802 spontaneous reboots) or a non-working video driver.
1806 config ARCH_USES_PG_UNCACHED
1812 prompt "x86 architectural random number generator" if EXPERT
1814 Enable the x86 architectural RDRAND instruction
1815 (Intel Bull Mountain technology) to generate random numbers.
1816 If supported, this is a high bandwidth, cryptographically
1817 secure hardware random number generator.
1821 prompt "Supervisor Mode Access Prevention" if EXPERT
1823 Supervisor Mode Access Prevention (SMAP) is a security
1824 feature in newer Intel processors. There is a small
1825 performance cost if this enabled and turned on; there is
1826 also a small increase in the kernel size if this is enabled.
1830 config X86_INTEL_UMIP
1832 depends on CPU_SUP_INTEL
1833 prompt "Intel User Mode Instruction Prevention" if EXPERT
1835 The User Mode Instruction Prevention (UMIP) is a security
1836 feature in newer Intel processors. If enabled, a general
1837 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1838 or STR instructions are executed in user mode. These instructions
1839 unnecessarily expose information about the hardware state.
1841 The vast majority of applications do not use these instructions.
1842 For the very few that do, software emulation is provided in
1843 specific cases in protected and virtual-8086 modes. Emulated
1846 config X86_INTEL_MPX
1847 prompt "Intel MPX (Memory Protection Extensions)"
1849 # Note: only available in 64-bit mode due to VMA flags shortage
1850 depends on CPU_SUP_INTEL && X86_64
1851 select ARCH_USES_HIGH_VMA_FLAGS
1853 MPX provides hardware features that can be used in
1854 conjunction with compiler-instrumented code to check
1855 memory references. It is designed to detect buffer
1856 overflow or underflow bugs.
1858 This option enables running applications which are
1859 instrumented or otherwise use MPX. It does not use MPX
1860 itself inside the kernel or to protect the kernel
1861 against bad memory references.
1863 Enabling this option will make the kernel larger:
1864 ~8k of kernel text and 36 bytes of data on a 64-bit
1865 defconfig. It adds a long to the 'mm_struct' which
1866 will increase the kernel memory overhead of each
1867 process and adds some branches to paths used during
1868 exec() and munmap().
1870 For details, see Documentation/x86/intel_mpx.txt
1874 config X86_INTEL_MEMORY_PROTECTION_KEYS
1875 prompt "Intel Memory Protection Keys"
1877 # Note: only available in 64-bit mode
1878 depends on CPU_SUP_INTEL && X86_64
1879 select ARCH_USES_HIGH_VMA_FLAGS
1880 select ARCH_HAS_PKEYS
1882 Memory Protection Keys provides a mechanism for enforcing
1883 page-based protections, but without requiring modification of the
1884 page tables when an application changes protection domains.
1886 For details, see Documentation/x86/protection-keys.txt
1891 bool "EFI runtime service support"
1894 select EFI_RUNTIME_WRAPPERS
1896 This enables the kernel to use EFI runtime services that are
1897 available (such as the EFI variable services).
1899 This option is only useful on systems that have EFI firmware.
1900 In addition, you should use the latest ELILO loader available
1901 at <http://elilo.sourceforge.net> in order to take advantage
1902 of EFI runtime services. However, even with this option, the
1903 resultant kernel should continue to boot on existing non-EFI
1907 bool "EFI stub support"
1908 depends on EFI && !X86_USE_3DNOW
1911 This kernel feature allows a bzImage to be loaded directly
1912 by EFI firmware without the use of a bootloader.
1914 See Documentation/efi-stub.txt for more information.
1917 bool "EFI mixed-mode support"
1918 depends on EFI_STUB && X86_64
1920 Enabling this feature allows a 64-bit kernel to be booted
1921 on a 32-bit firmware, provided that your CPU supports 64-bit
1924 Note that it is not possible to boot a mixed-mode enabled
1925 kernel via the EFI boot stub - a bootloader that supports
1926 the EFI handover protocol must be used.
1932 prompt "Enable seccomp to safely compute untrusted bytecode"
1934 This kernel feature is useful for number crunching applications
1935 that may need to compute untrusted bytecode during their
1936 execution. By using pipes or other transports made available to
1937 the process as file descriptors supporting the read/write
1938 syscalls, it's possible to isolate those applications in
1939 their own address space using seccomp. Once seccomp is
1940 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1941 and the task is only allowed to execute a few safe syscalls
1942 defined by each seccomp mode.
1944 If unsure, say Y. Only embedded should say N here.
1946 source kernel/Kconfig.hz
1949 bool "kexec system call"
1952 kexec is a system call that implements the ability to shutdown your
1953 current kernel, and to start another kernel. It is like a reboot
1954 but it is independent of the system firmware. And like a reboot
1955 you can start any kernel with it, not just Linux.
1957 The name comes from the similarity to the exec system call.
1959 It is an ongoing process to be certain the hardware in a machine
1960 is properly shutdown, so do not be surprised if this code does not
1961 initially work for you. As of this writing the exact hardware
1962 interface is strongly in flux, so no good recommendation can be
1966 bool "kexec file based system call"
1971 depends on CRYPTO_SHA256=y
1973 This is new version of kexec system call. This system call is
1974 file based and takes file descriptors as system call argument
1975 for kernel and initramfs as opposed to list of segments as
1976 accepted by previous system call.
1978 config KEXEC_VERIFY_SIG
1979 bool "Verify kernel signature during kexec_file_load() syscall"
1980 depends on KEXEC_FILE
1982 This option makes kernel signature verification mandatory for
1983 the kexec_file_load() syscall.
1985 In addition to that option, you need to enable signature
1986 verification for the corresponding kernel image type being
1987 loaded in order for this to work.
1989 config KEXEC_BZIMAGE_VERIFY_SIG
1990 bool "Enable bzImage signature verification support"
1991 depends on KEXEC_VERIFY_SIG
1992 depends on SIGNED_PE_FILE_VERIFICATION
1993 select SYSTEM_TRUSTED_KEYRING
1995 Enable bzImage signature verification support.
1998 bool "kernel crash dumps"
1999 depends on X86_64 || (X86_32 && HIGHMEM)
2001 Generate crash dump after being started by kexec.
2002 This should be normally only set in special crash dump kernels
2003 which are loaded in the main kernel with kexec-tools into
2004 a specially reserved region and then later executed after
2005 a crash by kdump/kexec. The crash dump kernel must be compiled
2006 to a memory address not used by the main kernel or BIOS using
2007 PHYSICAL_START, or it must be built as a relocatable image
2008 (CONFIG_RELOCATABLE=y).
2009 For more details see Documentation/kdump/kdump.txt
2013 depends on KEXEC && HIBERNATION
2015 Jump between original kernel and kexeced kernel and invoke
2016 code in physical address mode via KEXEC
2018 config PHYSICAL_START
2019 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2022 This gives the physical address where the kernel is loaded.
2024 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2025 bzImage will decompress itself to above physical address and
2026 run from there. Otherwise, bzImage will run from the address where
2027 it has been loaded by the boot loader and will ignore above physical
2030 In normal kdump cases one does not have to set/change this option
2031 as now bzImage can be compiled as a completely relocatable image
2032 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2033 address. This option is mainly useful for the folks who don't want
2034 to use a bzImage for capturing the crash dump and want to use a
2035 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2036 to be specifically compiled to run from a specific memory area
2037 (normally a reserved region) and this option comes handy.
2039 So if you are using bzImage for capturing the crash dump,
2040 leave the value here unchanged to 0x1000000 and set
2041 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2042 for capturing the crash dump change this value to start of
2043 the reserved region. In other words, it can be set based on
2044 the "X" value as specified in the "crashkernel=YM@XM"
2045 command line boot parameter passed to the panic-ed
2046 kernel. Please take a look at Documentation/kdump/kdump.txt
2047 for more details about crash dumps.
2049 Usage of bzImage for capturing the crash dump is recommended as
2050 one does not have to build two kernels. Same kernel can be used
2051 as production kernel and capture kernel. Above option should have
2052 gone away after relocatable bzImage support is introduced. But it
2053 is present because there are users out there who continue to use
2054 vmlinux for dump capture. This option should go away down the
2057 Don't change this unless you know what you are doing.
2060 bool "Build a relocatable kernel"
2063 This builds a kernel image that retains relocation information
2064 so it can be loaded someplace besides the default 1MB.
2065 The relocations tend to make the kernel binary about 10% larger,
2066 but are discarded at runtime.
2068 One use is for the kexec on panic case where the recovery kernel
2069 must live at a different physical address than the primary
2072 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2073 it has been loaded at and the compile time physical address
2074 (CONFIG_PHYSICAL_START) is used as the minimum location.
2076 config RANDOMIZE_BASE
2077 bool "Randomize the address of the kernel image (KASLR)"
2078 depends on RELOCATABLE
2081 In support of Kernel Address Space Layout Randomization (KASLR),
2082 this randomizes the physical address at which the kernel image
2083 is decompressed and the virtual address where the kernel
2084 image is mapped, as a security feature that deters exploit
2085 attempts relying on knowledge of the location of kernel
2088 On 64-bit, the kernel physical and virtual addresses are
2089 randomized separately. The physical address will be anywhere
2090 between 16MB and the top of physical memory (up to 64TB). The
2091 virtual address will be randomized from 16MB up to 1GB (9 bits
2092 of entropy). Note that this also reduces the memory space
2093 available to kernel modules from 1.5GB to 1GB.
2095 On 32-bit, the kernel physical and virtual addresses are
2096 randomized together. They will be randomized from 16MB up to
2097 512MB (8 bits of entropy).
2099 Entropy is generated using the RDRAND instruction if it is
2100 supported. If RDTSC is supported, its value is mixed into
2101 the entropy pool as well. If neither RDRAND nor RDTSC are
2102 supported, then entropy is read from the i8254 timer. The
2103 usable entropy is limited by the kernel being built using
2104 2GB addressing, and that PHYSICAL_ALIGN must be at a
2105 minimum of 2MB. As a result, only 10 bits of entropy are
2106 theoretically possible, but the implementations are further
2107 limited due to memory layouts.
2111 # Relocation on x86 needs some additional build support
2112 config X86_NEED_RELOCS
2114 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2116 config PHYSICAL_ALIGN
2117 hex "Alignment value to which kernel should be aligned"
2119 range 0x2000 0x1000000 if X86_32
2120 range 0x200000 0x1000000 if X86_64
2122 This value puts the alignment restrictions on physical address
2123 where kernel is loaded and run from. Kernel is compiled for an
2124 address which meets above alignment restriction.
2126 If bootloader loads the kernel at a non-aligned address and
2127 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2128 address aligned to above value and run from there.
2130 If bootloader loads the kernel at a non-aligned address and
2131 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2132 load address and decompress itself to the address it has been
2133 compiled for and run from there. The address for which kernel is
2134 compiled already meets above alignment restrictions. Hence the
2135 end result is that kernel runs from a physical address meeting
2136 above alignment restrictions.
2138 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2139 this value must be a multiple of 0x200000.
2141 Don't change this unless you know what you are doing.
2143 config RANDOMIZE_MEMORY
2144 bool "Randomize the kernel memory sections"
2146 depends on RANDOMIZE_BASE
2147 default RANDOMIZE_BASE
2149 Randomizes the base virtual address of kernel memory sections
2150 (physical memory mapping, vmalloc & vmemmap). This security feature
2151 makes exploits relying on predictable memory locations less reliable.
2153 The order of allocations remains unchanged. Entropy is generated in
2154 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2155 configuration have in average 30,000 different possible virtual
2156 addresses for each memory section.
2160 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2161 hex "Physical memory mapping padding" if EXPERT
2162 depends on RANDOMIZE_MEMORY
2163 default "0xa" if MEMORY_HOTPLUG
2165 range 0x1 0x40 if MEMORY_HOTPLUG
2168 Define the padding in terabytes added to the existing physical
2169 memory size during kernel memory randomization. It is useful
2170 for memory hotplug support but reduces the entropy available for
2171 address randomization.
2173 If unsure, leave at the default value.
2176 bool "Support for hot-pluggable CPUs"
2179 Say Y here to allow turning CPUs off and on. CPUs can be
2180 controlled through /sys/devices/system/cpu.
2181 ( Note: power management support will enable this option
2182 automatically on SMP systems. )
2183 Say N if you want to disable CPU hotplug.
2185 config BOOTPARAM_HOTPLUG_CPU0
2186 bool "Set default setting of cpu0_hotpluggable"
2188 depends on HOTPLUG_CPU
2190 Set whether default state of cpu0_hotpluggable is on or off.
2192 Say Y here to enable CPU0 hotplug by default. If this switch
2193 is turned on, there is no need to give cpu0_hotplug kernel
2194 parameter and the CPU0 hotplug feature is enabled by default.
2196 Please note: there are two known CPU0 dependencies if you want
2197 to enable the CPU0 hotplug feature either by this switch or by
2198 cpu0_hotplug kernel parameter.
2200 First, resume from hibernate or suspend always starts from CPU0.
2201 So hibernate and suspend are prevented if CPU0 is offline.
2203 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2204 offline if any interrupt can not migrate out of CPU0. There may
2205 be other CPU0 dependencies.
2207 Please make sure the dependencies are under your control before
2208 you enable this feature.
2210 Say N if you don't want to enable CPU0 hotplug feature by default.
2211 You still can enable the CPU0 hotplug feature at boot by kernel
2212 parameter cpu0_hotplug.
2214 config DEBUG_HOTPLUG_CPU0
2216 prompt "Debug CPU0 hotplug"
2217 depends on HOTPLUG_CPU
2219 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2220 soon as possible and boots up userspace with CPU0 offlined. User
2221 can online CPU0 back after boot time.
2223 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2224 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2225 compilation or giving cpu0_hotplug kernel parameter at boot.
2231 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2232 depends on COMPAT_32
2234 Certain buggy versions of glibc will crash if they are
2235 presented with a 32-bit vDSO that is not mapped at the address
2236 indicated in its segment table.
2238 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2239 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2240 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2241 the only released version with the bug, but OpenSUSE 9
2242 contains a buggy "glibc 2.3.2".
2244 The symptom of the bug is that everything crashes on startup, saying:
2245 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2247 Saying Y here changes the default value of the vdso32 boot
2248 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2249 This works around the glibc bug but hurts performance.
2251 If unsure, say N: if you are compiling your own kernel, you
2252 are unlikely to be using a buggy version of glibc.
2255 prompt "vsyscall table for legacy applications"
2257 default LEGACY_VSYSCALL_EMULATE
2259 Legacy user code that does not know how to find the vDSO expects
2260 to be able to issue three syscalls by calling fixed addresses in
2261 kernel space. Since this location is not randomized with ASLR,
2262 it can be used to assist security vulnerability exploitation.
2264 This setting can be changed at boot time via the kernel command
2265 line parameter vsyscall=[native|emulate|none].
2267 On a system with recent enough glibc (2.14 or newer) and no
2268 static binaries, you can say None without a performance penalty
2269 to improve security.
2271 If unsure, select "Emulate".
2273 config LEGACY_VSYSCALL_NATIVE
2276 Actual executable code is located in the fixed vsyscall
2277 address mapping, implementing time() efficiently. Since
2278 this makes the mapping executable, it can be used during
2279 security vulnerability exploitation (traditionally as
2280 ROP gadgets). This configuration is not recommended.
2282 config LEGACY_VSYSCALL_EMULATE
2285 The kernel traps and emulates calls into the fixed
2286 vsyscall address mapping. This makes the mapping
2287 non-executable, but it still contains known contents,
2288 which could be used in certain rare security vulnerability
2289 exploits. This configuration is recommended when userspace
2290 still uses the vsyscall area.
2292 config LEGACY_VSYSCALL_NONE
2295 There will be no vsyscall mapping at all. This will
2296 eliminate any risk of ASLR bypass due to the vsyscall
2297 fixed address mapping. Attempts to use the vsyscalls
2298 will be reported to dmesg, so that either old or
2299 malicious userspace programs can be identified.
2304 bool "Built-in kernel command line"
2306 Allow for specifying boot arguments to the kernel at
2307 build time. On some systems (e.g. embedded ones), it is
2308 necessary or convenient to provide some or all of the
2309 kernel boot arguments with the kernel itself (that is,
2310 to not rely on the boot loader to provide them.)
2312 To compile command line arguments into the kernel,
2313 set this option to 'Y', then fill in the
2314 boot arguments in CONFIG_CMDLINE.
2316 Systems with fully functional boot loaders (i.e. non-embedded)
2317 should leave this option set to 'N'.
2320 string "Built-in kernel command string"
2321 depends on CMDLINE_BOOL
2324 Enter arguments here that should be compiled into the kernel
2325 image and used at boot time. If the boot loader provides a
2326 command line at boot time, it is appended to this string to
2327 form the full kernel command line, when the system boots.
2329 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2330 change this behavior.
2332 In most cases, the command line (whether built-in or provided
2333 by the boot loader) should specify the device for the root
2336 config CMDLINE_OVERRIDE
2337 bool "Built-in command line overrides boot loader arguments"
2338 depends on CMDLINE_BOOL
2340 Set this option to 'Y' to have the kernel ignore the boot loader
2341 command line, and use ONLY the built-in command line.
2343 This is used to work around broken boot loaders. This should
2344 be set to 'N' under normal conditions.
2346 config MODIFY_LDT_SYSCALL
2347 bool "Enable the LDT (local descriptor table)" if EXPERT
2350 Linux can allow user programs to install a per-process x86
2351 Local Descriptor Table (LDT) using the modify_ldt(2) system
2352 call. This is required to run 16-bit or segmented code such as
2353 DOSEMU or some Wine programs. It is also used by some very old
2354 threading libraries.
2356 Enabling this feature adds a small amount of overhead to
2357 context switches and increases the low-level kernel attack
2358 surface. Disabling it removes the modify_ldt(2) system call.
2360 Saying 'N' here may make sense for embedded or server kernels.
2362 source "kernel/livepatch/Kconfig"
2366 config ARCH_HAS_ADD_PAGES
2368 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2370 config ARCH_ENABLE_MEMORY_HOTPLUG
2372 depends on X86_64 || (X86_32 && HIGHMEM)
2374 config ARCH_ENABLE_MEMORY_HOTREMOVE
2376 depends on MEMORY_HOTPLUG
2378 config USE_PERCPU_NUMA_NODE_ID
2382 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2384 depends on X86_64 || X86_PAE
2386 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2388 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2390 config ARCH_ENABLE_THP_MIGRATION
2392 depends on X86_64 && TRANSPARENT_HUGEPAGE
2394 menu "Power management and ACPI options"
2396 config ARCH_HIBERNATION_HEADER
2398 depends on X86_64 && HIBERNATION
2400 source "kernel/power/Kconfig"
2402 source "drivers/acpi/Kconfig"
2404 source "drivers/sfi/Kconfig"
2411 tristate "APM (Advanced Power Management) BIOS support"
2412 depends on X86_32 && PM_SLEEP
2414 APM is a BIOS specification for saving power using several different
2415 techniques. This is mostly useful for battery powered laptops with
2416 APM compliant BIOSes. If you say Y here, the system time will be
2417 reset after a RESUME operation, the /proc/apm device will provide
2418 battery status information, and user-space programs will receive
2419 notification of APM "events" (e.g. battery status change).
2421 If you select "Y" here, you can disable actual use of the APM
2422 BIOS by passing the "apm=off" option to the kernel at boot time.
2424 Note that the APM support is almost completely disabled for
2425 machines with more than one CPU.
2427 In order to use APM, you will need supporting software. For location
2428 and more information, read <file:Documentation/power/apm-acpi.txt>
2429 and the Battery Powered Linux mini-HOWTO, available from
2430 <http://www.tldp.org/docs.html#howto>.
2432 This driver does not spin down disk drives (see the hdparm(8)
2433 manpage ("man 8 hdparm") for that), and it doesn't turn off
2434 VESA-compliant "green" monitors.
2436 This driver does not support the TI 4000M TravelMate and the ACER
2437 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2438 desktop machines also don't have compliant BIOSes, and this driver
2439 may cause those machines to panic during the boot phase.
2441 Generally, if you don't have a battery in your machine, there isn't
2442 much point in using this driver and you should say N. If you get
2443 random kernel OOPSes or reboots that don't seem to be related to
2444 anything, try disabling/enabling this option (or disabling/enabling
2447 Some other things you should try when experiencing seemingly random,
2450 1) make sure that you have enough swap space and that it is
2452 2) pass the "no-hlt" option to the kernel
2453 3) switch on floating point emulation in the kernel and pass
2454 the "no387" option to the kernel
2455 4) pass the "floppy=nodma" option to the kernel
2456 5) pass the "mem=4M" option to the kernel (thereby disabling
2457 all but the first 4 MB of RAM)
2458 6) make sure that the CPU is not over clocked.
2459 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2460 8) disable the cache from your BIOS settings
2461 9) install a fan for the video card or exchange video RAM
2462 10) install a better fan for the CPU
2463 11) exchange RAM chips
2464 12) exchange the motherboard.
2466 To compile this driver as a module, choose M here: the
2467 module will be called apm.
2471 config APM_IGNORE_USER_SUSPEND
2472 bool "Ignore USER SUSPEND"
2474 This option will ignore USER SUSPEND requests. On machines with a
2475 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2476 series notebooks, it is necessary to say Y because of a BIOS bug.
2478 config APM_DO_ENABLE
2479 bool "Enable PM at boot time"
2481 Enable APM features at boot time. From page 36 of the APM BIOS
2482 specification: "When disabled, the APM BIOS does not automatically
2483 power manage devices, enter the Standby State, enter the Suspend
2484 State, or take power saving steps in response to CPU Idle calls."
2485 This driver will make CPU Idle calls when Linux is idle (unless this
2486 feature is turned off -- see "Do CPU IDLE calls", below). This
2487 should always save battery power, but more complicated APM features
2488 will be dependent on your BIOS implementation. You may need to turn
2489 this option off if your computer hangs at boot time when using APM
2490 support, or if it beeps continuously instead of suspending. Turn
2491 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2492 T400CDT. This is off by default since most machines do fine without
2497 bool "Make CPU Idle calls when idle"
2499 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2500 On some machines, this can activate improved power savings, such as
2501 a slowed CPU clock rate, when the machine is idle. These idle calls
2502 are made after the idle loop has run for some length of time (e.g.,
2503 333 mS). On some machines, this will cause a hang at boot time or
2504 whenever the CPU becomes idle. (On machines with more than one CPU,
2505 this option does nothing.)
2507 config APM_DISPLAY_BLANK
2508 bool "Enable console blanking using APM"
2510 Enable console blanking using the APM. Some laptops can use this to
2511 turn off the LCD backlight when the screen blanker of the Linux
2512 virtual console blanks the screen. Note that this is only used by
2513 the virtual console screen blanker, and won't turn off the backlight
2514 when using the X Window system. This also doesn't have anything to
2515 do with your VESA-compliant power-saving monitor. Further, this
2516 option doesn't work for all laptops -- it might not turn off your
2517 backlight at all, or it might print a lot of errors to the console,
2518 especially if you are using gpm.
2520 config APM_ALLOW_INTS
2521 bool "Allow interrupts during APM BIOS calls"
2523 Normally we disable external interrupts while we are making calls to
2524 the APM BIOS as a measure to lessen the effects of a badly behaving
2525 BIOS implementation. The BIOS should reenable interrupts if it
2526 needs to. Unfortunately, some BIOSes do not -- especially those in
2527 many of the newer IBM Thinkpads. If you experience hangs when you
2528 suspend, try setting this to Y. Otherwise, say N.
2532 source "drivers/cpufreq/Kconfig"
2534 source "drivers/cpuidle/Kconfig"
2536 source "drivers/idle/Kconfig"
2541 menu "Bus options (PCI etc.)"
2547 Find out whether you have a PCI motherboard. PCI is the name of a
2548 bus system, i.e. the way the CPU talks to the other stuff inside
2549 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2550 VESA. If you have PCI, say Y, otherwise N.
2553 prompt "PCI access mode"
2554 depends on X86_32 && PCI
2557 On PCI systems, the BIOS can be used to detect the PCI devices and
2558 determine their configuration. However, some old PCI motherboards
2559 have BIOS bugs and may crash if this is done. Also, some embedded
2560 PCI-based systems don't have any BIOS at all. Linux can also try to
2561 detect the PCI hardware directly without using the BIOS.
2563 With this option, you can specify how Linux should detect the
2564 PCI devices. If you choose "BIOS", the BIOS will be used,
2565 if you choose "Direct", the BIOS won't be used, and if you
2566 choose "MMConfig", then PCI Express MMCONFIG will be used.
2567 If you choose "Any", the kernel will try MMCONFIG, then the
2568 direct access method and falls back to the BIOS if that doesn't
2569 work. If unsure, go with the default, which is "Any".
2574 config PCI_GOMMCONFIG
2591 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2593 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2596 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2600 depends on X86_32 && PCI && (ACPI || SFI) && (PCI_GOMMCONFIG || PCI_GOANY)
2604 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2608 depends on PCI && XEN
2616 bool "Support mmconfig PCI config space access"
2617 depends on X86_64 && PCI && ACPI
2619 config PCI_CNB20LE_QUIRK
2620 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2623 Read the PCI windows out of the CNB20LE host bridge. This allows
2624 PCI hotplug to work on systems with the CNB20LE chipset which do
2627 There's no public spec for this chipset, and this functionality
2628 is known to be incomplete.
2630 You should say N unless you know you need this.
2632 source "drivers/pci/Kconfig"
2635 bool "ISA-style bus support on modern systems" if EXPERT
2638 Enables ISA-style drivers on modern systems. This is necessary to
2639 support PC/104 devices on X86_64 platforms.
2643 # x86_64 have no ISA slots, but can have ISA-style DMA.
2645 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2648 Enables ISA-style DMA support for devices requiring such controllers.
2656 Find out whether you have ISA slots on your motherboard. ISA is the
2657 name of a bus system, i.e. the way the CPU talks to the other stuff
2658 inside your box. Other bus systems are PCI, EISA, MicroChannel
2659 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2660 newer boards don't support it. If you have ISA, say Y, otherwise N.
2666 The Extended Industry Standard Architecture (EISA) bus was
2667 developed as an open alternative to the IBM MicroChannel bus.
2669 The EISA bus provided some of the features of the IBM MicroChannel
2670 bus while maintaining backward compatibility with cards made for
2671 the older ISA bus. The EISA bus saw limited use between 1988 and
2672 1995 when it was made obsolete by the PCI bus.
2674 Say Y here if you are building a kernel for an EISA-based machine.
2678 source "drivers/eisa/Kconfig"
2681 tristate "NatSemi SCx200 support"
2683 This provides basic support for National Semiconductor's
2684 (now AMD's) Geode processors. The driver probes for the
2685 PCI-IDs of several on-chip devices, so its a good dependency
2686 for other scx200_* drivers.
2688 If compiled as a module, the driver is named scx200.
2690 config SCx200HR_TIMER
2691 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2695 This driver provides a clocksource built upon the on-chip
2696 27MHz high-resolution timer. Its also a workaround for
2697 NSC Geode SC-1100's buggy TSC, which loses time when the
2698 processor goes idle (as is done by the scheduler). The
2699 other workaround is idle=poll boot option.
2702 bool "One Laptop Per Child support"
2709 Add support for detecting the unique features of the OLPC
2713 bool "OLPC XO-1 Power Management"
2714 depends on OLPC && MFD_CS5535 && PM_SLEEP
2717 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2720 bool "OLPC XO-1 Real Time Clock"
2721 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2723 Add support for the XO-1 real time clock, which can be used as a
2724 programmable wakeup source.
2727 bool "OLPC XO-1 SCI extras"
2728 depends on OLPC && OLPC_XO1_PM
2734 Add support for SCI-based features of the OLPC XO-1 laptop:
2735 - EC-driven system wakeups
2739 - AC adapter status updates
2740 - Battery status updates
2742 config OLPC_XO15_SCI
2743 bool "OLPC XO-1.5 SCI extras"
2744 depends on OLPC && ACPI
2747 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2748 - EC-driven system wakeups
2749 - AC adapter status updates
2750 - Battery status updates
2753 bool "PCEngines ALIX System Support (LED setup)"
2756 This option enables system support for the PCEngines ALIX.
2757 At present this just sets up LEDs for GPIO control on
2758 ALIX2/3/6 boards. However, other system specific setup should
2761 Note: You must still enable the drivers for GPIO and LED support
2762 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2764 Note: You have to set alix.force=1 for boards with Award BIOS.
2767 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2770 This option enables system support for the Soekris Engineering net5501.
2773 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2777 This option enables system support for the Traverse Technologies GEOS.
2780 bool "Technologic Systems TS-5500 platform support"
2782 select CHECK_SIGNATURE
2786 This option enables system support for the Technologic Systems TS-5500.
2792 depends on CPU_SUP_AMD && PCI
2794 source "drivers/pcmcia/Kconfig"
2797 tristate "RapidIO support"
2801 If enabled this option will include drivers and the core
2802 infrastructure code to support RapidIO interconnect devices.
2804 source "drivers/rapidio/Kconfig"
2807 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2809 Firmwares often provide initial graphics framebuffers so the BIOS,
2810 bootloader or kernel can show basic video-output during boot for
2811 user-guidance and debugging. Historically, x86 used the VESA BIOS
2812 Extensions and EFI-framebuffers for this, which are mostly limited
2814 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2815 framebuffers so the new generic system-framebuffer drivers can be
2816 used on x86. If the framebuffer is not compatible with the generic
2817 modes, it is adverticed as fallback platform framebuffer so legacy
2818 drivers like efifb, vesafb and uvesafb can pick it up.
2819 If this option is not selected, all system framebuffers are always
2820 marked as fallback platform framebuffers as usual.
2822 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2823 not be able to pick up generic system framebuffers if this option
2824 is selected. You are highly encouraged to enable simplefb as
2825 replacement if you select this option. simplefb can correctly deal
2826 with generic system framebuffers. But you should still keep vesafb
2827 and others enabled as fallback if a system framebuffer is
2828 incompatible with simplefb.
2835 menu "Executable file formats / Emulations"
2837 source "fs/Kconfig.binfmt"
2839 config IA32_EMULATION
2840 bool "IA32 Emulation"
2842 select ARCH_WANT_OLD_COMPAT_IPC
2844 select COMPAT_BINFMT_ELF
2845 select COMPAT_OLD_SIGACTION
2847 Include code to run legacy 32-bit programs under a
2848 64-bit kernel. You should likely turn this on, unless you're
2849 100% sure that you don't have any 32-bit programs left.
2852 tristate "IA32 a.out support"
2853 depends on IA32_EMULATION
2855 Support old a.out binaries in the 32bit emulation.
2858 bool "x32 ABI for 64-bit mode"
2861 Include code to run binaries for the x32 native 32-bit ABI
2862 for 64-bit processors. An x32 process gets access to the
2863 full 64-bit register file and wide data path while leaving
2864 pointers at 32 bits for smaller memory footprint.
2866 You will need a recent binutils (2.22 or later) with
2867 elf32_x86_64 support enabled to compile a kernel with this
2872 depends on IA32_EMULATION || X86_32
2874 select OLD_SIGSUSPEND3
2878 depends on IA32_EMULATION || X86_X32
2881 config COMPAT_FOR_U64_ALIGNMENT
2884 config SYSVIPC_COMPAT
2892 config HAVE_ATOMIC_IOMAP
2896 config X86_DEV_DMA_OPS
2898 depends on X86_64 || STA2X11
2900 config X86_DMA_REMAP
2904 config HAVE_GENERIC_GUP
2907 source "net/Kconfig"
2909 source "drivers/Kconfig"
2911 source "drivers/firmware/Kconfig"
2915 source "arch/x86/Kconfig.debug"
2917 source "security/Kconfig"
2919 source "crypto/Kconfig"
2921 source "arch/x86/kvm/Kconfig"
2923 source "lib/Kconfig"
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