1 # SPDX-License-Identifier: GPL-2.0
4 bool "64-bit kernel" if ARCH = "x86"
7 Say yes to build a 64-bit kernel - formerly known as x86_64
8 Say no to build a 32-bit kernel - formerly known as i386
13 # Options that are inherently 32-bit kernel only:
14 select ARCH_WANT_IPC_PARSE_VERSION
16 select CLONE_BACKWARDS
18 select HAVE_GENERIC_DMA_COHERENT
19 select MODULES_USE_ELF_REL
25 # Options that are inherently 64-bit kernel only:
26 select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
27 select ARCH_SUPPORTS_INT128
28 select ARCH_USE_CMPXCHG_LOCKREF
29 select HAVE_ARCH_SOFT_DIRTY
30 select MODULES_USE_ELF_RELA
31 select X86_DEV_DMA_OPS
36 # ( Note that options that are marked 'if X86_64' could in principle be
37 # ported to 32-bit as well. )
42 # Note: keep this list sorted alphabetically
44 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
45 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
47 select ARCH_CLOCKSOURCE_DATA
48 select ARCH_DISCARD_MEMBLOCK
49 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
50 select ARCH_HAS_DEBUG_VIRTUAL
51 select ARCH_HAS_DEVMEM_IS_ALLOWED
52 select ARCH_HAS_ELF_RANDOMIZE
53 select ARCH_HAS_FAST_MULTIPLIER
54 select ARCH_HAS_FORTIFY_SOURCE
55 select ARCH_HAS_GCOV_PROFILE_ALL
56 select ARCH_HAS_KCOV if X86_64
57 select ARCH_HAS_PMEM_API if X86_64
58 # Causing hangs/crashes, see the commit that added this change for details.
59 select ARCH_HAS_REFCOUNT
60 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
61 select ARCH_HAS_SET_MEMORY
62 select ARCH_HAS_SG_CHAIN
63 select ARCH_HAS_STRICT_KERNEL_RWX
64 select ARCH_HAS_STRICT_MODULE_RWX
65 select ARCH_HAS_UBSAN_SANITIZE_ALL
66 select ARCH_HAS_ZONE_DEVICE if X86_64
67 select ARCH_HAVE_NMI_SAFE_CMPXCHG
68 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
69 select ARCH_MIGHT_HAVE_PC_PARPORT
70 select ARCH_MIGHT_HAVE_PC_SERIO
71 select ARCH_SUPPORTS_ATOMIC_RMW
72 select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
73 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
74 select ARCH_USE_BUILTIN_BSWAP
75 select ARCH_USE_QUEUED_RWLOCKS
76 select ARCH_USE_QUEUED_SPINLOCKS
77 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
78 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
79 select ARCH_WANTS_THP_SWAP if X86_64
80 select BUILDTIME_EXTABLE_SORT
82 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
83 select CLOCKSOURCE_WATCHDOG
84 select DCACHE_WORD_ACCESS
85 select EDAC_ATOMIC_SCRUB
87 select GENERIC_CLOCKEVENTS
88 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
89 select GENERIC_CLOCKEVENTS_MIN_ADJUST
90 select GENERIC_CMOS_UPDATE
91 select GENERIC_CPU_AUTOPROBE
92 select GENERIC_CPU_VULNERABILITIES
93 select GENERIC_EARLY_IOREMAP
94 select GENERIC_FIND_FIRST_BIT
96 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
97 select GENERIC_IRQ_MIGRATION if SMP
98 select GENERIC_IRQ_PROBE
99 select GENERIC_IRQ_SHOW
100 select GENERIC_PENDING_IRQ if SMP
101 select GENERIC_SMP_IDLE_THREAD
102 select GENERIC_STRNCPY_FROM_USER
103 select GENERIC_STRNLEN_USER
104 select GENERIC_TIME_VSYSCALL
105 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
106 select HAVE_ACPI_APEI if ACPI
107 select HAVE_ACPI_APEI_NMI if ACPI
108 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
109 select HAVE_ARCH_AUDITSYSCALL
110 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
111 select HAVE_ARCH_JUMP_LABEL
112 select HAVE_ARCH_KASAN if X86_64
113 select HAVE_ARCH_KGDB
114 select HAVE_ARCH_MMAP_RND_BITS if MMU
115 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
116 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
117 select HAVE_ARCH_SECCOMP_FILTER
118 select HAVE_ARCH_TRACEHOOK
119 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
120 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
121 select HAVE_ARCH_VMAP_STACK if X86_64
122 select HAVE_ARCH_WITHIN_STACK_FRAMES
123 select HAVE_CC_STACKPROTECTOR
124 select HAVE_CMPXCHG_DOUBLE
125 select HAVE_CMPXCHG_LOCAL
126 select HAVE_CONTEXT_TRACKING if X86_64
127 select HAVE_COPY_THREAD_TLS
128 select HAVE_C_RECORDMCOUNT
129 select HAVE_DEBUG_KMEMLEAK
130 select HAVE_DEBUG_STACKOVERFLOW
131 select HAVE_DMA_API_DEBUG
132 select HAVE_DMA_CONTIGUOUS
133 select HAVE_DYNAMIC_FTRACE
134 select HAVE_DYNAMIC_FTRACE_WITH_REGS
135 select HAVE_EBPF_JIT if X86_64
136 select HAVE_EFFICIENT_UNALIGNED_ACCESS
137 select HAVE_EXIT_THREAD
138 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
139 select HAVE_FTRACE_MCOUNT_RECORD
140 select HAVE_FUNCTION_GRAPH_TRACER
141 select HAVE_FUNCTION_TRACER
142 select HAVE_GCC_PLUGINS
143 select HAVE_HW_BREAKPOINT
145 select HAVE_IOREMAP_PROT
146 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
147 select HAVE_IRQ_TIME_ACCOUNTING
148 select HAVE_KERNEL_BZIP2
149 select HAVE_KERNEL_GZIP
150 select HAVE_KERNEL_LZ4
151 select HAVE_KERNEL_LZMA
152 select HAVE_KERNEL_LZO
153 select HAVE_KERNEL_XZ
155 select HAVE_KPROBES_ON_FTRACE
156 select HAVE_KRETPROBES
158 select HAVE_LIVEPATCH if X86_64
160 select HAVE_MEMBLOCK_NODE_MAP
161 select HAVE_MIXED_BREAKPOINTS_REGS
162 select HAVE_MOD_ARCH_SPECIFIC
165 select HAVE_OPTPROBES
166 select HAVE_PCSPKR_PLATFORM
167 select HAVE_PERF_EVENTS
168 select HAVE_PERF_EVENTS_NMI
169 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
170 select HAVE_PERF_REGS
171 select HAVE_PERF_USER_STACK_DUMP
172 select HAVE_RCU_TABLE_FREE
173 select HAVE_RCU_TABLE_INVALIDATE if HAVE_RCU_TABLE_FREE
174 select HAVE_REGS_AND_STACK_ACCESS_API
175 select HAVE_RELIABLE_STACKTRACE if X86_64 && UNWINDER_FRAME_POINTER && STACK_VALIDATION
176 select HAVE_STACK_VALIDATION if X86_64
177 select HAVE_SYSCALL_TRACEPOINTS
178 select HAVE_UNSTABLE_SCHED_CLOCK
179 select HAVE_USER_RETURN_NOTIFIER
180 select HOTPLUG_SMT if SMP
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"
436 select STACK_VALIDATION if HAVE_STACK_VALIDATION
438 Compile kernel with the retpoline compiler options to guard against
439 kernel-to-user data leaks by avoiding speculative indirect
440 branches. Requires a compiler with -mindirect-branch=thunk-extern
441 support for full protection. The kernel may run slower.
444 bool "Intel Resource Director Technology support"
446 depends on X86 && CPU_SUP_INTEL
449 Select to enable resource allocation and monitoring which are
450 sub-features of Intel Resource Director Technology(RDT). More
451 information about RDT can be found in the Intel x86
452 Architecture Software Developer Manual.
457 config X86_EXTENDED_PLATFORM
458 bool "Support for extended (non-PC) x86 platforms"
461 If you disable this option then the kernel will only support
462 standard PC platforms. (which covers the vast majority of
465 If you enable this option then you'll be able to select support
466 for the following (non-PC) 32 bit x86 platforms:
467 Goldfish (Android emulator)
470 SGI 320/540 (Visual Workstation)
471 STA2X11-based (e.g. Northville)
472 Moorestown MID devices
474 If you have one of these systems, or if you want to build a
475 generic distribution kernel, say Y here - otherwise say N.
479 config X86_EXTENDED_PLATFORM
480 bool "Support for extended (non-PC) x86 platforms"
483 If you disable this option then the kernel will only support
484 standard PC platforms. (which covers the vast majority of
487 If you enable this option then you'll be able to select support
488 for the following (non-PC) 64 bit x86 platforms:
493 If you have one of these systems, or if you want to build a
494 generic distribution kernel, say Y here - otherwise say N.
496 # This is an alphabetically sorted list of 64 bit extended platforms
497 # Please maintain the alphabetic order if and when there are additions
499 bool "Numascale NumaChip"
501 depends on X86_EXTENDED_PLATFORM
504 depends on X86_X2APIC
505 depends on PCI_MMCONFIG
507 Adds support for Numascale NumaChip large-SMP systems. Needed to
508 enable more than ~168 cores.
509 If you don't have one of these, you should say N here.
513 select HYPERVISOR_GUEST
515 depends on X86_64 && PCI
516 depends on X86_EXTENDED_PLATFORM
519 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
520 supposed to run on these EM64T-based machines. Only choose this option
521 if you have one of these machines.
524 bool "SGI Ultraviolet"
526 depends on X86_EXTENDED_PLATFORM
529 depends on X86_X2APIC
532 This option is needed in order to support SGI Ultraviolet systems.
533 If you don't have one of these, you should say N here.
535 # Following is an alphabetically sorted list of 32 bit extended platforms
536 # Please maintain the alphabetic order if and when there are additions
539 bool "Goldfish (Virtual Platform)"
540 depends on X86_EXTENDED_PLATFORM
542 Enable support for the Goldfish virtual platform used primarily
543 for Android development. Unless you are building for the Android
544 Goldfish emulator say N here.
547 bool "CE4100 TV platform"
549 depends on PCI_GODIRECT
550 depends on X86_IO_APIC
552 depends on X86_EXTENDED_PLATFORM
553 select X86_REBOOTFIXUPS
555 select OF_EARLY_FLATTREE
557 Select for the Intel CE media processor (CE4100) SOC.
558 This option compiles in support for the CE4100 SOC for settop
559 boxes and media devices.
562 bool "Intel MID platform support"
563 depends on X86_EXTENDED_PLATFORM
564 depends on X86_PLATFORM_DEVICES
566 depends on X86_64 || (PCI_GOANY && X86_32)
567 depends on X86_IO_APIC
573 select MFD_INTEL_MSIC
575 Select to build a kernel capable of supporting Intel MID (Mobile
576 Internet Device) platform systems which do not have the PCI legacy
577 interfaces. If you are building for a PC class system say N here.
579 Intel MID platforms are based on an Intel processor and chipset which
580 consume less power than most of the x86 derivatives.
582 config X86_INTEL_QUARK
583 bool "Intel Quark platform support"
585 depends on X86_EXTENDED_PLATFORM
586 depends on X86_PLATFORM_DEVICES
590 depends on X86_IO_APIC
595 Select to include support for Quark X1000 SoC.
596 Say Y here if you have a Quark based system such as the Arduino
597 compatible Intel Galileo.
599 config X86_INTEL_LPSS
600 bool "Intel Low Power Subsystem Support"
601 depends on X86 && ACPI
606 Select to build support for Intel Low Power Subsystem such as
607 found on Intel Lynxpoint PCH. Selecting this option enables
608 things like clock tree (common clock framework) and pincontrol
609 which are needed by the LPSS peripheral drivers.
611 config X86_AMD_PLATFORM_DEVICE
612 bool "AMD ACPI2Platform devices support"
617 Select to interpret AMD specific ACPI device to platform device
618 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
619 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
620 implemented under PINCTRL subsystem.
623 tristate "Intel SoC IOSF Sideband support for SoC platforms"
626 This option enables sideband register access support for Intel SoC
627 platforms. On these platforms the IOSF sideband is used in lieu of
628 MSR's for some register accesses, mostly but not limited to thermal
629 and power. Drivers may query the availability of this device to
630 determine if they need the sideband in order to work on these
631 platforms. The sideband is available on the following SoC products.
632 This list is not meant to be exclusive.
637 You should say Y if you are running a kernel on one of these SoC's.
639 config IOSF_MBI_DEBUG
640 bool "Enable IOSF sideband access through debugfs"
641 depends on IOSF_MBI && DEBUG_FS
643 Select this option to expose the IOSF sideband access registers (MCR,
644 MDR, MCRX) through debugfs to write and read register information from
645 different units on the SoC. This is most useful for obtaining device
646 state information for debug and analysis. As this is a general access
647 mechanism, users of this option would have specific knowledge of the
648 device they want to access.
650 If you don't require the option or are in doubt, say N.
653 bool "RDC R-321x SoC"
655 depends on X86_EXTENDED_PLATFORM
657 select X86_REBOOTFIXUPS
659 This option is needed for RDC R-321x system-on-chip, also known
661 If you don't have one of these chips, you should say N here.
663 config X86_32_NON_STANDARD
664 bool "Support non-standard 32-bit SMP architectures"
665 depends on X86_32 && SMP
666 depends on X86_EXTENDED_PLATFORM
668 This option compiles in the bigsmp and STA2X11 default
669 subarchitectures. It is intended for a generic binary
670 kernel. If you select them all, kernel will probe it one by
671 one and will fallback to default.
673 # Alphabetically sorted list of Non standard 32 bit platforms
675 config X86_SUPPORTS_MEMORY_FAILURE
677 # MCE code calls memory_failure():
679 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
680 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
681 depends on X86_64 || !SPARSEMEM
682 select ARCH_SUPPORTS_MEMORY_FAILURE
685 bool "STA2X11 Companion Chip Support"
686 depends on X86_32_NON_STANDARD && PCI
687 select X86_DEV_DMA_OPS
694 This adds support for boards based on the STA2X11 IO-Hub,
695 a.k.a. "ConneXt". The chip is used in place of the standard
696 PC chipset, so all "standard" peripherals are missing. If this
697 option is selected the kernel will still be able to boot on
698 standard PC machines.
701 tristate "Eurobraille/Iris poweroff module"
704 The Iris machines from EuroBraille do not have APM or ACPI support
705 to shut themselves down properly. A special I/O sequence is
706 needed to do so, which is what this module does at
709 This is only for Iris machines from EuroBraille.
713 config SCHED_OMIT_FRAME_POINTER
715 prompt "Single-depth WCHAN output"
718 Calculate simpler /proc/<PID>/wchan values. If this option
719 is disabled then wchan values will recurse back to the
720 caller function. This provides more accurate wchan values,
721 at the expense of slightly more scheduling overhead.
723 If in doubt, say "Y".
725 menuconfig HYPERVISOR_GUEST
726 bool "Linux guest support"
728 Say Y here to enable options for running Linux under various hyper-
729 visors. This option enables basic hypervisor detection and platform
732 If you say N, all options in this submenu will be skipped and
733 disabled, and Linux guest support won't be built in.
738 bool "Enable paravirtualization code"
740 This changes the kernel so it can modify itself when it is run
741 under a hypervisor, potentially improving performance significantly
742 over full virtualization. However, when run without a hypervisor
743 the kernel is theoretically slower and slightly larger.
745 config PARAVIRT_DEBUG
746 bool "paravirt-ops debugging"
747 depends on PARAVIRT && DEBUG_KERNEL
749 Enable to debug paravirt_ops internals. Specifically, BUG if
750 a paravirt_op is missing when it is called.
752 config PARAVIRT_SPINLOCKS
753 bool "Paravirtualization layer for spinlocks"
754 depends on PARAVIRT && SMP
756 Paravirtualized spinlocks allow a pvops backend to replace the
757 spinlock implementation with something virtualization-friendly
758 (for example, block the virtual CPU rather than spinning).
760 It has a minimal impact on native kernels and gives a nice performance
761 benefit on paravirtualized KVM / Xen kernels.
763 If you are unsure how to answer this question, answer Y.
765 config QUEUED_LOCK_STAT
766 bool "Paravirt queued spinlock statistics"
767 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
769 Enable the collection of statistical data on the slowpath
770 behavior of paravirtualized queued spinlocks and report
773 source "arch/x86/xen/Kconfig"
776 bool "KVM Guest support (including kvmclock)"
778 select PARAVIRT_CLOCK
781 This option enables various optimizations for running under the KVM
782 hypervisor. It includes a paravirtualized clock, so that instead
783 of relying on a PIT (or probably other) emulation by the
784 underlying device model, the host provides the guest with
785 timing infrastructure such as time of day, and system time
788 bool "Enable debug information for KVM Guests in debugfs"
789 depends on KVM_GUEST && DEBUG_FS
792 This option enables collection of various statistics for KVM guest.
793 Statistics are displayed in debugfs filesystem. Enabling this option
794 may incur significant overhead.
796 config PARAVIRT_TIME_ACCOUNTING
797 bool "Paravirtual steal time accounting"
801 Select this option to enable fine granularity task steal time
802 accounting. Time spent executing other tasks in parallel with
803 the current vCPU is discounted from the vCPU power. To account for
804 that, there can be a small performance impact.
806 If in doubt, say N here.
808 config PARAVIRT_CLOCK
811 endif #HYPERVISOR_GUEST
816 source "arch/x86/Kconfig.cpu"
820 prompt "HPET Timer Support" if X86_32
822 Use the IA-PC HPET (High Precision Event Timer) to manage
823 time in preference to the PIT and RTC, if a HPET is
825 HPET is the next generation timer replacing legacy 8254s.
826 The HPET provides a stable time base on SMP
827 systems, unlike the TSC, but it is more expensive to access,
828 as it is off-chip. The interface used is documented
829 in the HPET spec, revision 1.
831 You can safely choose Y here. However, HPET will only be
832 activated if the platform and the BIOS support this feature.
833 Otherwise the 8254 will be used for timing services.
835 Choose N to continue using the legacy 8254 timer.
837 config HPET_EMULATE_RTC
839 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
842 def_bool y if X86_INTEL_MID
843 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
845 depends on X86_INTEL_MID && SFI
847 APB timer is the replacement for 8254, HPET on X86 MID platforms.
848 The APBT provides a stable time base on SMP
849 systems, unlike the TSC, but it is more expensive to access,
850 as it is off-chip. APB timers are always running regardless of CPU
851 C states, they are used as per CPU clockevent device when possible.
853 # Mark as expert because too many people got it wrong.
854 # The code disables itself when not needed.
857 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
858 bool "Enable DMI scanning" if EXPERT
860 Enabled scanning of DMI to identify machine quirks. Say Y
861 here unless you have verified that your setup is not
862 affected by entries in the DMI blacklist. Required by PNP
866 bool "Old AMD GART IOMMU support"
868 depends on X86_64 && PCI && AMD_NB
870 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
871 GART based hardware IOMMUs.
873 The GART supports full DMA access for devices with 32-bit access
874 limitations, on systems with more than 3 GB. This is usually needed
875 for USB, sound, many IDE/SATA chipsets and some other devices.
877 Newer systems typically have a modern AMD IOMMU, supported via
878 the CONFIG_AMD_IOMMU=y config option.
880 In normal configurations this driver is only active when needed:
881 there's more than 3 GB of memory and the system contains a
882 32-bit limited device.
887 bool "IBM Calgary IOMMU support"
889 depends on X86_64 && PCI
891 Support for hardware IOMMUs in IBM's xSeries x366 and x460
892 systems. Needed to run systems with more than 3GB of memory
893 properly with 32-bit PCI devices that do not support DAC
894 (Double Address Cycle). Calgary also supports bus level
895 isolation, where all DMAs pass through the IOMMU. This
896 prevents them from going anywhere except their intended
897 destination. This catches hard-to-find kernel bugs and
898 mis-behaving drivers and devices that do not use the DMA-API
899 properly to set up their DMA buffers. The IOMMU can be
900 turned off at boot time with the iommu=off parameter.
901 Normally the kernel will make the right choice by itself.
904 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
906 prompt "Should Calgary be enabled by default?"
907 depends on CALGARY_IOMMU
909 Should Calgary be enabled by default? if you choose 'y', Calgary
910 will be used (if it exists). If you choose 'n', Calgary will not be
911 used even if it exists. If you choose 'n' and would like to use
912 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
915 # need this always selected by IOMMU for the VIA workaround
919 Support for software bounce buffers used on x86-64 systems
920 which don't have a hardware IOMMU. Using this PCI devices
921 which can only access 32-bits of memory can be used on systems
922 with more than 3 GB of memory.
927 depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU
930 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
931 depends on X86_64 && SMP && DEBUG_KERNEL
932 select CPUMASK_OFFSTACK
934 Enable maximum number of CPUS and NUMA Nodes for this architecture.
938 int "Maximum number of CPUs" if SMP && !MAXSMP
939 range 2 8 if SMP && X86_32 && !X86_BIGSMP
940 range 2 64 if SMP && X86_32 && X86_BIGSMP
941 range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK && X86_64
942 range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
944 default "8192" if MAXSMP
945 default "32" if SMP && X86_BIGSMP
946 default "8" if SMP && X86_32
949 This allows you to specify the maximum number of CPUs which this
950 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
951 supported value is 8192, otherwise the maximum value is 512. The
952 minimum value which makes sense is 2.
954 This is purely to save memory - each supported CPU adds
955 approximately eight kilobytes to the kernel image.
962 prompt "Multi-core scheduler support"
965 Multi-core scheduler support improves the CPU scheduler's decision
966 making when dealing with multi-core CPU chips at a cost of slightly
967 increased overhead in some places. If unsure say N here.
970 bool "CPU core priorities scheduler support"
971 depends on SCHED_MC && CPU_SUP_INTEL
972 select X86_INTEL_PSTATE
976 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
977 core ordering determined at manufacturing time, which allows
978 certain cores to reach higher turbo frequencies (when running
979 single threaded workloads) than others.
981 Enabling this kernel feature teaches the scheduler about
982 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
983 scheduler's CPU selection logic accordingly, so that higher
984 overall system performance can be achieved.
986 This feature will have no effect on CPUs without this feature.
988 If unsure say Y here.
990 source "kernel/Kconfig.preempt"
994 depends on !SMP && X86_LOCAL_APIC
997 bool "Local APIC support on uniprocessors" if !PCI_MSI
999 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1001 A local APIC (Advanced Programmable Interrupt Controller) is an
1002 integrated interrupt controller in the CPU. If you have a single-CPU
1003 system which has a processor with a local APIC, you can say Y here to
1004 enable and use it. If you say Y here even though your machine doesn't
1005 have a local APIC, then the kernel will still run with no slowdown at
1006 all. The local APIC supports CPU-generated self-interrupts (timer,
1007 performance counters), and the NMI watchdog which detects hard
1010 config X86_UP_IOAPIC
1011 bool "IO-APIC support on uniprocessors"
1012 depends on X86_UP_APIC
1014 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1015 SMP-capable replacement for PC-style interrupt controllers. Most
1016 SMP systems and many recent uniprocessor systems have one.
1018 If you have a single-CPU system with an IO-APIC, you can say Y here
1019 to use it. If you say Y here even though your machine doesn't have
1020 an IO-APIC, then the kernel will still run with no slowdown at all.
1022 config X86_LOCAL_APIC
1024 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1025 select IRQ_DOMAIN_HIERARCHY
1026 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1030 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1032 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1033 bool "Reroute for broken boot IRQs"
1034 depends on X86_IO_APIC
1036 This option enables a workaround that fixes a source of
1037 spurious interrupts. This is recommended when threaded
1038 interrupt handling is used on systems where the generation of
1039 superfluous "boot interrupts" cannot be disabled.
1041 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1042 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1043 kernel does during interrupt handling). On chipsets where this
1044 boot IRQ generation cannot be disabled, this workaround keeps
1045 the original IRQ line masked so that only the equivalent "boot
1046 IRQ" is delivered to the CPUs. The workaround also tells the
1047 kernel to set up the IRQ handler on the boot IRQ line. In this
1048 way only one interrupt is delivered to the kernel. Otherwise
1049 the spurious second interrupt may cause the kernel to bring
1050 down (vital) interrupt lines.
1052 Only affects "broken" chipsets. Interrupt sharing may be
1053 increased on these systems.
1056 bool "Machine Check / overheating reporting"
1057 select GENERIC_ALLOCATOR
1060 Machine Check support allows the processor to notify the
1061 kernel if it detects a problem (e.g. overheating, data corruption).
1062 The action the kernel takes depends on the severity of the problem,
1063 ranging from warning messages to halting the machine.
1065 config X86_MCELOG_LEGACY
1066 bool "Support for deprecated /dev/mcelog character device"
1069 Enable support for /dev/mcelog which is needed by the old mcelog
1070 userspace logging daemon. Consider switching to the new generation
1073 config X86_MCE_INTEL
1075 prompt "Intel MCE features"
1076 depends on X86_MCE && X86_LOCAL_APIC
1078 Additional support for intel specific MCE features such as
1079 the thermal monitor.
1083 prompt "AMD MCE features"
1084 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1086 Additional support for AMD specific MCE features such as
1087 the DRAM Error Threshold.
1089 config X86_ANCIENT_MCE
1090 bool "Support for old Pentium 5 / WinChip machine checks"
1091 depends on X86_32 && X86_MCE
1093 Include support for machine check handling on old Pentium 5 or WinChip
1094 systems. These typically need to be enabled explicitly on the command
1097 config X86_MCE_THRESHOLD
1098 depends on X86_MCE_AMD || X86_MCE_INTEL
1101 config X86_MCE_INJECT
1102 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1103 tristate "Machine check injector support"
1105 Provide support for injecting machine checks for testing purposes.
1106 If you don't know what a machine check is and you don't do kernel
1107 QA it is safe to say n.
1109 config X86_THERMAL_VECTOR
1111 depends on X86_MCE_INTEL
1113 source "arch/x86/events/Kconfig"
1115 config X86_LEGACY_VM86
1116 bool "Legacy VM86 support"
1120 This option allows user programs to put the CPU into V8086
1121 mode, which is an 80286-era approximation of 16-bit real mode.
1123 Some very old versions of X and/or vbetool require this option
1124 for user mode setting. Similarly, DOSEMU will use it if
1125 available to accelerate real mode DOS programs. However, any
1126 recent version of DOSEMU, X, or vbetool should be fully
1127 functional even without kernel VM86 support, as they will all
1128 fall back to software emulation. Nevertheless, if you are using
1129 a 16-bit DOS program where 16-bit performance matters, vm86
1130 mode might be faster than emulation and you might want to
1133 Note that any app that works on a 64-bit kernel is unlikely to
1134 need this option, as 64-bit kernels don't, and can't, support
1135 V8086 mode. This option is also unrelated to 16-bit protected
1136 mode and is not needed to run most 16-bit programs under Wine.
1138 Enabling this option increases the complexity of the kernel
1139 and slows down exception handling a tiny bit.
1141 If unsure, say N here.
1145 default X86_LEGACY_VM86
1148 bool "Enable support for 16-bit segments" if EXPERT
1150 depends on MODIFY_LDT_SYSCALL
1152 This option is required by programs like Wine to run 16-bit
1153 protected mode legacy code on x86 processors. Disabling
1154 this option saves about 300 bytes on i386, or around 6K text
1155 plus 16K runtime memory on x86-64,
1159 depends on X86_16BIT && X86_32
1163 depends on X86_16BIT && X86_64
1165 config X86_VSYSCALL_EMULATION
1166 bool "Enable vsyscall emulation" if EXPERT
1170 This enables emulation of the legacy vsyscall page. Disabling
1171 it is roughly equivalent to booting with vsyscall=none, except
1172 that it will also disable the helpful warning if a program
1173 tries to use a vsyscall. With this option set to N, offending
1174 programs will just segfault, citing addresses of the form
1177 This option is required by many programs built before 2013, and
1178 care should be used even with newer programs if set to N.
1180 Disabling this option saves about 7K of kernel size and
1181 possibly 4K of additional runtime pagetable memory.
1184 tristate "Toshiba Laptop support"
1187 This adds a driver to safely access the System Management Mode of
1188 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1189 not work on models with a Phoenix BIOS. The System Management Mode
1190 is used to set the BIOS and power saving options on Toshiba portables.
1192 For information on utilities to make use of this driver see the
1193 Toshiba Linux utilities web site at:
1194 <http://www.buzzard.org.uk/toshiba/>.
1196 Say Y if you intend to run this kernel on a Toshiba portable.
1200 tristate "Dell i8k legacy laptop support"
1202 select SENSORS_DELL_SMM
1204 This option enables legacy /proc/i8k userspace interface in hwmon
1205 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1206 temperature and allows controlling fan speeds of Dell laptops via
1207 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1208 it reports also power and hotkey status. For fan speed control is
1209 needed userspace package i8kutils.
1211 Say Y if you intend to run this kernel on old Dell laptops or want to
1212 use userspace package i8kutils.
1215 config X86_REBOOTFIXUPS
1216 bool "Enable X86 board specific fixups for reboot"
1219 This enables chipset and/or board specific fixups to be done
1220 in order to get reboot to work correctly. This is only needed on
1221 some combinations of hardware and BIOS. The symptom, for which
1222 this config is intended, is when reboot ends with a stalled/hung
1225 Currently, the only fixup is for the Geode machines using
1226 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1228 Say Y if you want to enable the fixup. Currently, it's safe to
1229 enable this option even if you don't need it.
1233 bool "CPU microcode loading support"
1235 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1238 If you say Y here, you will be able to update the microcode on
1239 Intel and AMD processors. The Intel support is for the IA32 family,
1240 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1241 AMD support is for families 0x10 and later. You will obviously need
1242 the actual microcode binary data itself which is not shipped with
1245 The preferred method to load microcode from a detached initrd is described
1246 in Documentation/x86/early-microcode.txt. For that you need to enable
1247 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1248 initrd for microcode blobs.
1250 In addition, you can build-in the microcode into the kernel. For that you
1251 need to enable FIRMWARE_IN_KERNEL and add the vendor-supplied microcode
1252 to the CONFIG_EXTRA_FIRMWARE config option.
1254 config MICROCODE_INTEL
1255 bool "Intel microcode loading support"
1256 depends on MICROCODE
1260 This options enables microcode patch loading support for Intel
1263 For the current Intel microcode data package go to
1264 <https://downloadcenter.intel.com> and search for
1265 'Linux Processor Microcode Data File'.
1267 config MICROCODE_AMD
1268 bool "AMD microcode loading support"
1269 depends on MICROCODE
1272 If you select this option, microcode patch loading support for AMD
1273 processors will be enabled.
1275 config MICROCODE_OLD_INTERFACE
1277 depends on MICROCODE
1280 tristate "/dev/cpu/*/msr - Model-specific register support"
1282 This device gives privileged processes access to the x86
1283 Model-Specific Registers (MSRs). It is a character device with
1284 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1285 MSR accesses are directed to a specific CPU on multi-processor
1289 tristate "/dev/cpu/*/cpuid - CPU information support"
1291 This device gives processes access to the x86 CPUID instruction to
1292 be executed on a specific processor. It is a character device
1293 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1297 prompt "High Memory Support"
1304 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1305 However, the address space of 32-bit x86 processors is only 4
1306 Gigabytes large. That means that, if you have a large amount of
1307 physical memory, not all of it can be "permanently mapped" by the
1308 kernel. The physical memory that's not permanently mapped is called
1311 If you are compiling a kernel which will never run on a machine with
1312 more than 1 Gigabyte total physical RAM, answer "off" here (default
1313 choice and suitable for most users). This will result in a "3GB/1GB"
1314 split: 3GB are mapped so that each process sees a 3GB virtual memory
1315 space and the remaining part of the 4GB virtual memory space is used
1316 by the kernel to permanently map as much physical memory as
1319 If the machine has between 1 and 4 Gigabytes physical RAM, then
1322 If more than 4 Gigabytes is used then answer "64GB" here. This
1323 selection turns Intel PAE (Physical Address Extension) mode on.
1324 PAE implements 3-level paging on IA32 processors. PAE is fully
1325 supported by Linux, PAE mode is implemented on all recent Intel
1326 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1327 then the kernel will not boot on CPUs that don't support PAE!
1329 The actual amount of total physical memory will either be
1330 auto detected or can be forced by using a kernel command line option
1331 such as "mem=256M". (Try "man bootparam" or see the documentation of
1332 your boot loader (lilo or loadlin) about how to pass options to the
1333 kernel at boot time.)
1335 If unsure, say "off".
1340 Select this if you have a 32-bit processor and between 1 and 4
1341 gigabytes of physical RAM.
1348 Select this if you have a 32-bit processor and more than 4
1349 gigabytes of physical RAM.
1354 prompt "Memory split" if EXPERT
1358 Select the desired split between kernel and user memory.
1360 If the address range available to the kernel is less than the
1361 physical memory installed, the remaining memory will be available
1362 as "high memory". Accessing high memory is a little more costly
1363 than low memory, as it needs to be mapped into the kernel first.
1364 Note that increasing the kernel address space limits the range
1365 available to user programs, making the address space there
1366 tighter. Selecting anything other than the default 3G/1G split
1367 will also likely make your kernel incompatible with binary-only
1370 If you are not absolutely sure what you are doing, leave this
1374 bool "3G/1G user/kernel split"
1375 config VMSPLIT_3G_OPT
1377 bool "3G/1G user/kernel split (for full 1G low memory)"
1379 bool "2G/2G user/kernel split"
1380 config VMSPLIT_2G_OPT
1382 bool "2G/2G user/kernel split (for full 2G low memory)"
1384 bool "1G/3G user/kernel split"
1389 default 0xB0000000 if VMSPLIT_3G_OPT
1390 default 0x80000000 if VMSPLIT_2G
1391 default 0x78000000 if VMSPLIT_2G_OPT
1392 default 0x40000000 if VMSPLIT_1G
1398 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1401 bool "PAE (Physical Address Extension) Support"
1402 depends on X86_32 && !HIGHMEM4G
1405 PAE is required for NX support, and furthermore enables
1406 larger swapspace support for non-overcommit purposes. It
1407 has the cost of more pagetable lookup overhead, and also
1408 consumes more pagetable space per process.
1411 bool "Enable 5-level page tables support"
1414 5-level paging enables access to larger address space:
1415 upto 128 PiB of virtual address space and 4 PiB of
1416 physical address space.
1418 It will be supported by future Intel CPUs.
1420 Note: a kernel with this option enabled can only be booted
1421 on machines that support the feature.
1423 See Documentation/x86/x86_64/5level-paging.txt for more
1428 config ARCH_PHYS_ADDR_T_64BIT
1430 depends on X86_64 || X86_PAE
1432 config ARCH_DMA_ADDR_T_64BIT
1434 depends on X86_64 || HIGHMEM64G
1436 config X86_DIRECT_GBPAGES
1438 depends on X86_64 && !DEBUG_PAGEALLOC
1440 Certain kernel features effectively disable kernel
1441 linear 1 GB mappings (even if the CPU otherwise
1442 supports them), so don't confuse the user by printing
1443 that we have them enabled.
1445 config ARCH_HAS_MEM_ENCRYPT
1448 config AMD_MEM_ENCRYPT
1449 bool "AMD Secure Memory Encryption (SME) support"
1450 depends on X86_64 && CPU_SUP_AMD
1452 Say yes to enable support for the encryption of system memory.
1453 This requires an AMD processor that supports Secure Memory
1456 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1457 bool "Activate AMD Secure Memory Encryption (SME) by default"
1459 depends on AMD_MEM_ENCRYPT
1461 Say yes to have system memory encrypted by default if running on
1462 an AMD processor that supports Secure Memory Encryption (SME).
1464 If set to Y, then the encryption of system memory can be
1465 deactivated with the mem_encrypt=off command line option.
1467 If set to N, then the encryption of system memory can be
1468 activated with the mem_encrypt=on command line option.
1470 config ARCH_USE_MEMREMAP_PROT
1472 depends on AMD_MEM_ENCRYPT
1474 # Common NUMA Features
1476 bool "Numa Memory Allocation and Scheduler Support"
1478 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1479 default y if X86_BIGSMP
1481 Enable NUMA (Non Uniform Memory Access) support.
1483 The kernel will try to allocate memory used by a CPU on the
1484 local memory controller of the CPU and add some more
1485 NUMA awareness to the kernel.
1487 For 64-bit this is recommended if the system is Intel Core i7
1488 (or later), AMD Opteron, or EM64T NUMA.
1490 For 32-bit this is only needed if you boot a 32-bit
1491 kernel on a 64-bit NUMA platform.
1493 Otherwise, you should say N.
1497 prompt "Old style AMD Opteron NUMA detection"
1498 depends on X86_64 && NUMA && PCI
1500 Enable AMD NUMA node topology detection. You should say Y here if
1501 you have a multi processor AMD system. This uses an old method to
1502 read the NUMA configuration directly from the builtin Northbridge
1503 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1504 which also takes priority if both are compiled in.
1506 config X86_64_ACPI_NUMA
1508 prompt "ACPI NUMA detection"
1509 depends on X86_64 && NUMA && ACPI && PCI
1512 Enable ACPI SRAT based node topology detection.
1514 # Some NUMA nodes have memory ranges that span
1515 # other nodes. Even though a pfn is valid and
1516 # between a node's start and end pfns, it may not
1517 # reside on that node. See memmap_init_zone()
1519 config NODES_SPAN_OTHER_NODES
1521 depends on X86_64_ACPI_NUMA
1524 bool "NUMA emulation"
1527 Enable NUMA emulation. A flat machine will be split
1528 into virtual nodes when booted with "numa=fake=N", where N is the
1529 number of nodes. This is only useful for debugging.
1532 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1534 default "10" if MAXSMP
1535 default "6" if X86_64
1537 depends on NEED_MULTIPLE_NODES
1539 Specify the maximum number of NUMA Nodes available on the target
1540 system. Increases memory reserved to accommodate various tables.
1542 config ARCH_HAVE_MEMORY_PRESENT
1544 depends on X86_32 && DISCONTIGMEM
1546 config NEED_NODE_MEMMAP_SIZE
1548 depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
1550 config ARCH_FLATMEM_ENABLE
1552 depends on X86_32 && !NUMA
1554 config ARCH_DISCONTIGMEM_ENABLE
1556 depends on NUMA && X86_32
1558 config ARCH_DISCONTIGMEM_DEFAULT
1560 depends on NUMA && X86_32
1562 config ARCH_SPARSEMEM_ENABLE
1564 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1565 select SPARSEMEM_STATIC if X86_32
1566 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1568 config ARCH_SPARSEMEM_DEFAULT
1572 config ARCH_SELECT_MEMORY_MODEL
1574 depends on ARCH_SPARSEMEM_ENABLE
1576 config ARCH_MEMORY_PROBE
1577 bool "Enable sysfs memory/probe interface"
1578 depends on X86_64 && MEMORY_HOTPLUG
1580 This option enables a sysfs memory/probe interface for testing.
1581 See Documentation/memory-hotplug.txt for more information.
1582 If you are unsure how to answer this question, answer N.
1584 config ARCH_PROC_KCORE_TEXT
1586 depends on X86_64 && PROC_KCORE
1588 config ILLEGAL_POINTER_VALUE
1591 default 0xdead000000000000 if X86_64
1595 config X86_PMEM_LEGACY_DEVICE
1598 config X86_PMEM_LEGACY
1599 tristate "Support non-standard NVDIMMs and ADR protected memory"
1600 depends on PHYS_ADDR_T_64BIT
1602 select X86_PMEM_LEGACY_DEVICE
1605 Treat memory marked using the non-standard e820 type of 12 as used
1606 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1607 The kernel will offer these regions to the 'pmem' driver so
1608 they can be used for persistent storage.
1613 bool "Allocate 3rd-level pagetables from highmem"
1616 The VM uses one page table entry for each page of physical memory.
1617 For systems with a lot of RAM, this can be wasteful of precious
1618 low memory. Setting this option will put user-space page table
1619 entries in high memory.
1621 config X86_CHECK_BIOS_CORRUPTION
1622 bool "Check for low memory corruption"
1624 Periodically check for memory corruption in low memory, which
1625 is suspected to be caused by BIOS. Even when enabled in the
1626 configuration, it is disabled at runtime. Enable it by
1627 setting "memory_corruption_check=1" on the kernel command
1628 line. By default it scans the low 64k of memory every 60
1629 seconds; see the memory_corruption_check_size and
1630 memory_corruption_check_period parameters in
1631 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1633 When enabled with the default parameters, this option has
1634 almost no overhead, as it reserves a relatively small amount
1635 of memory and scans it infrequently. It both detects corruption
1636 and prevents it from affecting the running system.
1638 It is, however, intended as a diagnostic tool; if repeatable
1639 BIOS-originated corruption always affects the same memory,
1640 you can use memmap= to prevent the kernel from using that
1643 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1644 bool "Set the default setting of memory_corruption_check"
1645 depends on X86_CHECK_BIOS_CORRUPTION
1648 Set whether the default state of memory_corruption_check is
1651 config X86_RESERVE_LOW
1652 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1656 Specify the amount of low memory to reserve for the BIOS.
1658 The first page contains BIOS data structures that the kernel
1659 must not use, so that page must always be reserved.
1661 By default we reserve the first 64K of physical RAM, as a
1662 number of BIOSes are known to corrupt that memory range
1663 during events such as suspend/resume or monitor cable
1664 insertion, so it must not be used by the kernel.
1666 You can set this to 4 if you are absolutely sure that you
1667 trust the BIOS to get all its memory reservations and usages
1668 right. If you know your BIOS have problems beyond the
1669 default 64K area, you can set this to 640 to avoid using the
1670 entire low memory range.
1672 If you have doubts about the BIOS (e.g. suspend/resume does
1673 not work or there's kernel crashes after certain hardware
1674 hotplug events) then you might want to enable
1675 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1676 typical corruption patterns.
1678 Leave this to the default value of 64 if you are unsure.
1680 config MATH_EMULATION
1682 depends on MODIFY_LDT_SYSCALL
1683 prompt "Math emulation" if X86_32
1685 Linux can emulate a math coprocessor (used for floating point
1686 operations) if you don't have one. 486DX and Pentium processors have
1687 a math coprocessor built in, 486SX and 386 do not, unless you added
1688 a 487DX or 387, respectively. (The messages during boot time can
1689 give you some hints here ["man dmesg"].) Everyone needs either a
1690 coprocessor or this emulation.
1692 If you don't have a math coprocessor, you need to say Y here; if you
1693 say Y here even though you have a coprocessor, the coprocessor will
1694 be used nevertheless. (This behavior can be changed with the kernel
1695 command line option "no387", which comes handy if your coprocessor
1696 is broken. Try "man bootparam" or see the documentation of your boot
1697 loader (lilo or loadlin) about how to pass options to the kernel at
1698 boot time.) This means that it is a good idea to say Y here if you
1699 intend to use this kernel on different machines.
1701 More information about the internals of the Linux math coprocessor
1702 emulation can be found in <file:arch/x86/math-emu/README>.
1704 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1705 kernel, it won't hurt.
1709 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1711 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1712 the Memory Type Range Registers (MTRRs) may be used to control
1713 processor access to memory ranges. This is most useful if you have
1714 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1715 allows bus write transfers to be combined into a larger transfer
1716 before bursting over the PCI/AGP bus. This can increase performance
1717 of image write operations 2.5 times or more. Saying Y here creates a
1718 /proc/mtrr file which may be used to manipulate your processor's
1719 MTRRs. Typically the X server should use this.
1721 This code has a reasonably generic interface so that similar
1722 control registers on other processors can be easily supported
1725 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1726 Registers (ARRs) which provide a similar functionality to MTRRs. For
1727 these, the ARRs are used to emulate the MTRRs.
1728 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1729 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1730 write-combining. All of these processors are supported by this code
1731 and it makes sense to say Y here if you have one of them.
1733 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1734 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1735 can lead to all sorts of problems, so it's good to say Y here.
1737 You can safely say Y even if your machine doesn't have MTRRs, you'll
1738 just add about 9 KB to your kernel.
1740 See <file:Documentation/x86/mtrr.txt> for more information.
1742 config MTRR_SANITIZER
1744 prompt "MTRR cleanup support"
1747 Convert MTRR layout from continuous to discrete, so X drivers can
1748 add writeback entries.
1750 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1751 The largest mtrr entry size for a continuous block can be set with
1756 config MTRR_SANITIZER_ENABLE_DEFAULT
1757 int "MTRR cleanup enable value (0-1)"
1760 depends on MTRR_SANITIZER
1762 Enable mtrr cleanup default value
1764 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1765 int "MTRR cleanup spare reg num (0-7)"
1768 depends on MTRR_SANITIZER
1770 mtrr cleanup spare entries default, it can be changed via
1771 mtrr_spare_reg_nr=N on the kernel command line.
1775 prompt "x86 PAT support" if EXPERT
1778 Use PAT attributes to setup page level cache control.
1780 PATs are the modern equivalents of MTRRs and are much more
1781 flexible than MTRRs.
1783 Say N here if you see bootup problems (boot crash, boot hang,
1784 spontaneous reboots) or a non-working video driver.
1788 config ARCH_USES_PG_UNCACHED
1794 prompt "x86 architectural random number generator" if EXPERT
1796 Enable the x86 architectural RDRAND instruction
1797 (Intel Bull Mountain technology) to generate random numbers.
1798 If supported, this is a high bandwidth, cryptographically
1799 secure hardware random number generator.
1803 prompt "Supervisor Mode Access Prevention" if EXPERT
1805 Supervisor Mode Access Prevention (SMAP) is a security
1806 feature in newer Intel processors. There is a small
1807 performance cost if this enabled and turned on; there is
1808 also a small increase in the kernel size if this is enabled.
1812 config X86_INTEL_MPX
1813 prompt "Intel MPX (Memory Protection Extensions)"
1815 # Note: only available in 64-bit mode due to VMA flags shortage
1816 depends on CPU_SUP_INTEL && X86_64
1817 select ARCH_USES_HIGH_VMA_FLAGS
1819 MPX provides hardware features that can be used in
1820 conjunction with compiler-instrumented code to check
1821 memory references. It is designed to detect buffer
1822 overflow or underflow bugs.
1824 This option enables running applications which are
1825 instrumented or otherwise use MPX. It does not use MPX
1826 itself inside the kernel or to protect the kernel
1827 against bad memory references.
1829 Enabling this option will make the kernel larger:
1830 ~8k of kernel text and 36 bytes of data on a 64-bit
1831 defconfig. It adds a long to the 'mm_struct' which
1832 will increase the kernel memory overhead of each
1833 process and adds some branches to paths used during
1834 exec() and munmap().
1836 For details, see Documentation/x86/intel_mpx.txt
1840 config X86_INTEL_MEMORY_PROTECTION_KEYS
1841 prompt "Intel Memory Protection Keys"
1843 # Note: only available in 64-bit mode
1844 depends on CPU_SUP_INTEL && X86_64
1845 select ARCH_USES_HIGH_VMA_FLAGS
1846 select ARCH_HAS_PKEYS
1848 Memory Protection Keys provides a mechanism for enforcing
1849 page-based protections, but without requiring modification of the
1850 page tables when an application changes protection domains.
1852 For details, see Documentation/x86/protection-keys.txt
1857 prompt "TSX enable mode"
1858 depends on CPU_SUP_INTEL
1859 default X86_INTEL_TSX_MODE_OFF
1861 Intel's TSX (Transactional Synchronization Extensions) feature
1862 allows to optimize locking protocols through lock elision which
1863 can lead to a noticeable performance boost.
1865 On the other hand it has been shown that TSX can be exploited
1866 to form side channel attacks (e.g. TAA) and chances are there
1867 will be more of those attacks discovered in the future.
1869 Therefore TSX is not enabled by default (aka tsx=off). An admin
1870 might override this decision by tsx=on the command line parameter.
1871 Even with TSX enabled, the kernel will attempt to enable the best
1872 possible TAA mitigation setting depending on the microcode available
1873 for the particular machine.
1875 This option allows to set the default tsx mode between tsx=on, =off
1876 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1879 Say off if not sure, auto if TSX is in use but it should be used on safe
1880 platforms or on if TSX is in use and the security aspect of tsx is not
1883 config X86_INTEL_TSX_MODE_OFF
1886 TSX is disabled if possible - equals to tsx=off command line parameter.
1888 config X86_INTEL_TSX_MODE_ON
1891 TSX is always enabled on TSX capable HW - equals the tsx=on command
1894 config X86_INTEL_TSX_MODE_AUTO
1897 TSX is enabled on TSX capable HW that is believed to be safe against
1898 side channel attacks- equals the tsx=auto command line parameter.
1902 bool "EFI runtime service support"
1905 select EFI_RUNTIME_WRAPPERS
1907 This enables the kernel to use EFI runtime services that are
1908 available (such as the EFI variable services).
1910 This option is only useful on systems that have EFI firmware.
1911 In addition, you should use the latest ELILO loader available
1912 at <http://elilo.sourceforge.net> in order to take advantage
1913 of EFI runtime services. However, even with this option, the
1914 resultant kernel should continue to boot on existing non-EFI
1918 bool "EFI stub support"
1919 depends on EFI && !X86_USE_3DNOW
1922 This kernel feature allows a bzImage to be loaded directly
1923 by EFI firmware without the use of a bootloader.
1925 See Documentation/efi-stub.txt for more information.
1928 bool "EFI mixed-mode support"
1929 depends on EFI_STUB && X86_64
1931 Enabling this feature allows a 64-bit kernel to be booted
1932 on a 32-bit firmware, provided that your CPU supports 64-bit
1935 Note that it is not possible to boot a mixed-mode enabled
1936 kernel via the EFI boot stub - a bootloader that supports
1937 the EFI handover protocol must be used.
1943 prompt "Enable seccomp to safely compute untrusted bytecode"
1945 This kernel feature is useful for number crunching applications
1946 that may need to compute untrusted bytecode during their
1947 execution. By using pipes or other transports made available to
1948 the process as file descriptors supporting the read/write
1949 syscalls, it's possible to isolate those applications in
1950 their own address space using seccomp. Once seccomp is
1951 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1952 and the task is only allowed to execute a few safe syscalls
1953 defined by each seccomp mode.
1955 If unsure, say Y. Only embedded should say N here.
1957 source kernel/Kconfig.hz
1960 bool "kexec system call"
1963 kexec is a system call that implements the ability to shutdown your
1964 current kernel, and to start another kernel. It is like a reboot
1965 but it is independent of the system firmware. And like a reboot
1966 you can start any kernel with it, not just Linux.
1968 The name comes from the similarity to the exec system call.
1970 It is an ongoing process to be certain the hardware in a machine
1971 is properly shutdown, so do not be surprised if this code does not
1972 initially work for you. As of this writing the exact hardware
1973 interface is strongly in flux, so no good recommendation can be
1977 bool "kexec file based system call"
1982 depends on CRYPTO_SHA256=y
1984 This is new version of kexec system call. This system call is
1985 file based and takes file descriptors as system call argument
1986 for kernel and initramfs as opposed to list of segments as
1987 accepted by previous system call.
1989 config KEXEC_VERIFY_SIG
1990 bool "Verify kernel signature during kexec_file_load() syscall"
1991 depends on KEXEC_FILE
1993 This option makes kernel signature verification mandatory for
1994 the kexec_file_load() syscall.
1996 In addition to that option, you need to enable signature
1997 verification for the corresponding kernel image type being
1998 loaded in order for this to work.
2000 config KEXEC_BZIMAGE_VERIFY_SIG
2001 bool "Enable bzImage signature verification support"
2002 depends on KEXEC_VERIFY_SIG
2003 depends on SIGNED_PE_FILE_VERIFICATION
2004 select SYSTEM_TRUSTED_KEYRING
2006 Enable bzImage signature verification support.
2009 bool "kernel crash dumps"
2010 depends on X86_64 || (X86_32 && HIGHMEM)
2012 Generate crash dump after being started by kexec.
2013 This should be normally only set in special crash dump kernels
2014 which are loaded in the main kernel with kexec-tools into
2015 a specially reserved region and then later executed after
2016 a crash by kdump/kexec. The crash dump kernel must be compiled
2017 to a memory address not used by the main kernel or BIOS using
2018 PHYSICAL_START, or it must be built as a relocatable image
2019 (CONFIG_RELOCATABLE=y).
2020 For more details see Documentation/kdump/kdump.txt
2024 depends on KEXEC && HIBERNATION
2026 Jump between original kernel and kexeced kernel and invoke
2027 code in physical address mode via KEXEC
2029 config PHYSICAL_START
2030 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2033 This gives the physical address where the kernel is loaded.
2035 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2036 bzImage will decompress itself to above physical address and
2037 run from there. Otherwise, bzImage will run from the address where
2038 it has been loaded by the boot loader and will ignore above physical
2041 In normal kdump cases one does not have to set/change this option
2042 as now bzImage can be compiled as a completely relocatable image
2043 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2044 address. This option is mainly useful for the folks who don't want
2045 to use a bzImage for capturing the crash dump and want to use a
2046 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2047 to be specifically compiled to run from a specific memory area
2048 (normally a reserved region) and this option comes handy.
2050 So if you are using bzImage for capturing the crash dump,
2051 leave the value here unchanged to 0x1000000 and set
2052 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2053 for capturing the crash dump change this value to start of
2054 the reserved region. In other words, it can be set based on
2055 the "X" value as specified in the "crashkernel=YM@XM"
2056 command line boot parameter passed to the panic-ed
2057 kernel. Please take a look at Documentation/kdump/kdump.txt
2058 for more details about crash dumps.
2060 Usage of bzImage for capturing the crash dump is recommended as
2061 one does not have to build two kernels. Same kernel can be used
2062 as production kernel and capture kernel. Above option should have
2063 gone away after relocatable bzImage support is introduced. But it
2064 is present because there are users out there who continue to use
2065 vmlinux for dump capture. This option should go away down the
2068 Don't change this unless you know what you are doing.
2071 bool "Build a relocatable kernel"
2074 This builds a kernel image that retains relocation information
2075 so it can be loaded someplace besides the default 1MB.
2076 The relocations tend to make the kernel binary about 10% larger,
2077 but are discarded at runtime.
2079 One use is for the kexec on panic case where the recovery kernel
2080 must live at a different physical address than the primary
2083 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2084 it has been loaded at and the compile time physical address
2085 (CONFIG_PHYSICAL_START) is used as the minimum location.
2087 config RANDOMIZE_BASE
2088 bool "Randomize the address of the kernel image (KASLR)"
2089 depends on RELOCATABLE
2092 In support of Kernel Address Space Layout Randomization (KASLR),
2093 this randomizes the physical address at which the kernel image
2094 is decompressed and the virtual address where the kernel
2095 image is mapped, as a security feature that deters exploit
2096 attempts relying on knowledge of the location of kernel
2099 On 64-bit, the kernel physical and virtual addresses are
2100 randomized separately. The physical address will be anywhere
2101 between 16MB and the top of physical memory (up to 64TB). The
2102 virtual address will be randomized from 16MB up to 1GB (9 bits
2103 of entropy). Note that this also reduces the memory space
2104 available to kernel modules from 1.5GB to 1GB.
2106 On 32-bit, the kernel physical and virtual addresses are
2107 randomized together. They will be randomized from 16MB up to
2108 512MB (8 bits of entropy).
2110 Entropy is generated using the RDRAND instruction if it is
2111 supported. If RDTSC is supported, its value is mixed into
2112 the entropy pool as well. If neither RDRAND nor RDTSC are
2113 supported, then entropy is read from the i8254 timer. The
2114 usable entropy is limited by the kernel being built using
2115 2GB addressing, and that PHYSICAL_ALIGN must be at a
2116 minimum of 2MB. As a result, only 10 bits of entropy are
2117 theoretically possible, but the implementations are further
2118 limited due to memory layouts.
2122 # Relocation on x86 needs some additional build support
2123 config X86_NEED_RELOCS
2125 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2127 config PHYSICAL_ALIGN
2128 hex "Alignment value to which kernel should be aligned"
2130 range 0x2000 0x1000000 if X86_32
2131 range 0x200000 0x1000000 if X86_64
2133 This value puts the alignment restrictions on physical address
2134 where kernel is loaded and run from. Kernel is compiled for an
2135 address which meets above alignment restriction.
2137 If bootloader loads the kernel at a non-aligned address and
2138 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2139 address aligned to above value and run from there.
2141 If bootloader loads the kernel at a non-aligned address and
2142 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2143 load address and decompress itself to the address it has been
2144 compiled for and run from there. The address for which kernel is
2145 compiled already meets above alignment restrictions. Hence the
2146 end result is that kernel runs from a physical address meeting
2147 above alignment restrictions.
2149 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2150 this value must be a multiple of 0x200000.
2152 Don't change this unless you know what you are doing.
2154 config RANDOMIZE_MEMORY
2155 bool "Randomize the kernel memory sections"
2157 depends on RANDOMIZE_BASE
2158 default RANDOMIZE_BASE
2160 Randomizes the base virtual address of kernel memory sections
2161 (physical memory mapping, vmalloc & vmemmap). This security feature
2162 makes exploits relying on predictable memory locations less reliable.
2164 The order of allocations remains unchanged. Entropy is generated in
2165 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2166 configuration have in average 30,000 different possible virtual
2167 addresses for each memory section.
2171 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2172 hex "Physical memory mapping padding" if EXPERT
2173 depends on RANDOMIZE_MEMORY
2174 default "0xa" if MEMORY_HOTPLUG
2176 range 0x1 0x40 if MEMORY_HOTPLUG
2179 Define the padding in terabytes added to the existing physical
2180 memory size during kernel memory randomization. It is useful
2181 for memory hotplug support but reduces the entropy available for
2182 address randomization.
2184 If unsure, leave at the default value.
2190 config BOOTPARAM_HOTPLUG_CPU0
2191 bool "Set default setting of cpu0_hotpluggable"
2193 depends on HOTPLUG_CPU
2195 Set whether default state of cpu0_hotpluggable is on or off.
2197 Say Y here to enable CPU0 hotplug by default. If this switch
2198 is turned on, there is no need to give cpu0_hotplug kernel
2199 parameter and the CPU0 hotplug feature is enabled by default.
2201 Please note: there are two known CPU0 dependencies if you want
2202 to enable the CPU0 hotplug feature either by this switch or by
2203 cpu0_hotplug kernel parameter.
2205 First, resume from hibernate or suspend always starts from CPU0.
2206 So hibernate and suspend are prevented if CPU0 is offline.
2208 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2209 offline if any interrupt can not migrate out of CPU0. There may
2210 be other CPU0 dependencies.
2212 Please make sure the dependencies are under your control before
2213 you enable this feature.
2215 Say N if you don't want to enable CPU0 hotplug feature by default.
2216 You still can enable the CPU0 hotplug feature at boot by kernel
2217 parameter cpu0_hotplug.
2219 config DEBUG_HOTPLUG_CPU0
2221 prompt "Debug CPU0 hotplug"
2222 depends on HOTPLUG_CPU
2224 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2225 soon as possible and boots up userspace with CPU0 offlined. User
2226 can online CPU0 back after boot time.
2228 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2229 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2230 compilation or giving cpu0_hotplug kernel parameter at boot.
2236 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2237 depends on COMPAT_32
2239 Certain buggy versions of glibc will crash if they are
2240 presented with a 32-bit vDSO that is not mapped at the address
2241 indicated in its segment table.
2243 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2244 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2245 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2246 the only released version with the bug, but OpenSUSE 9
2247 contains a buggy "glibc 2.3.2".
2249 The symptom of the bug is that everything crashes on startup, saying:
2250 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2252 Saying Y here changes the default value of the vdso32 boot
2253 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2254 This works around the glibc bug but hurts performance.
2256 If unsure, say N: if you are compiling your own kernel, you
2257 are unlikely to be using a buggy version of glibc.
2260 prompt "vsyscall table for legacy applications"
2262 default LEGACY_VSYSCALL_EMULATE
2264 Legacy user code that does not know how to find the vDSO expects
2265 to be able to issue three syscalls by calling fixed addresses in
2266 kernel space. Since this location is not randomized with ASLR,
2267 it can be used to assist security vulnerability exploitation.
2269 This setting can be changed at boot time via the kernel command
2270 line parameter vsyscall=[native|emulate|none].
2272 On a system with recent enough glibc (2.14 or newer) and no
2273 static binaries, you can say None without a performance penalty
2274 to improve security.
2276 If unsure, select "Emulate".
2278 config LEGACY_VSYSCALL_NATIVE
2281 Actual executable code is located in the fixed vsyscall
2282 address mapping, implementing time() efficiently. Since
2283 this makes the mapping executable, it can be used during
2284 security vulnerability exploitation (traditionally as
2285 ROP gadgets). This configuration is not recommended.
2287 config LEGACY_VSYSCALL_EMULATE
2290 The kernel traps and emulates calls into the fixed
2291 vsyscall address mapping. This makes the mapping
2292 non-executable, but it still contains known contents,
2293 which could be used in certain rare security vulnerability
2294 exploits. This configuration is recommended when userspace
2295 still uses the vsyscall area.
2297 config LEGACY_VSYSCALL_NONE
2300 There will be no vsyscall mapping at all. This will
2301 eliminate any risk of ASLR bypass due to the vsyscall
2302 fixed address mapping. Attempts to use the vsyscalls
2303 will be reported to dmesg, so that either old or
2304 malicious userspace programs can be identified.
2309 bool "Built-in kernel command line"
2311 Allow for specifying boot arguments to the kernel at
2312 build time. On some systems (e.g. embedded ones), it is
2313 necessary or convenient to provide some or all of the
2314 kernel boot arguments with the kernel itself (that is,
2315 to not rely on the boot loader to provide them.)
2317 To compile command line arguments into the kernel,
2318 set this option to 'Y', then fill in the
2319 boot arguments in CONFIG_CMDLINE.
2321 Systems with fully functional boot loaders (i.e. non-embedded)
2322 should leave this option set to 'N'.
2325 string "Built-in kernel command string"
2326 depends on CMDLINE_BOOL
2329 Enter arguments here that should be compiled into the kernel
2330 image and used at boot time. If the boot loader provides a
2331 command line at boot time, it is appended to this string to
2332 form the full kernel command line, when the system boots.
2334 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2335 change this behavior.
2337 In most cases, the command line (whether built-in or provided
2338 by the boot loader) should specify the device for the root
2341 config CMDLINE_OVERRIDE
2342 bool "Built-in command line overrides boot loader arguments"
2343 depends on CMDLINE_BOOL
2345 Set this option to 'Y' to have the kernel ignore the boot loader
2346 command line, and use ONLY the built-in command line.
2348 This is used to work around broken boot loaders. This should
2349 be set to 'N' under normal conditions.
2351 config MODIFY_LDT_SYSCALL
2352 bool "Enable the LDT (local descriptor table)" if EXPERT
2355 Linux can allow user programs to install a per-process x86
2356 Local Descriptor Table (LDT) using the modify_ldt(2) system
2357 call. This is required to run 16-bit or segmented code such as
2358 DOSEMU or some Wine programs. It is also used by some very old
2359 threading libraries.
2361 Enabling this feature adds a small amount of overhead to
2362 context switches and increases the low-level kernel attack
2363 surface. Disabling it removes the modify_ldt(2) system call.
2365 Saying 'N' here may make sense for embedded or server kernels.
2367 source "kernel/livepatch/Kconfig"
2371 config ARCH_HAS_ADD_PAGES
2373 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2375 config ARCH_ENABLE_MEMORY_HOTPLUG
2377 depends on X86_64 || (X86_32 && HIGHMEM)
2379 config ARCH_ENABLE_MEMORY_HOTREMOVE
2381 depends on MEMORY_HOTPLUG
2383 config USE_PERCPU_NUMA_NODE_ID
2387 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2389 depends on X86_64 || X86_PAE
2391 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2393 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2395 config ARCH_ENABLE_THP_MIGRATION
2397 depends on X86_64 && TRANSPARENT_HUGEPAGE
2399 menu "Power management and ACPI options"
2401 config ARCH_HIBERNATION_HEADER
2403 depends on X86_64 && HIBERNATION
2405 source "kernel/power/Kconfig"
2407 source "drivers/acpi/Kconfig"
2409 source "drivers/sfi/Kconfig"
2416 tristate "APM (Advanced Power Management) BIOS support"
2417 depends on X86_32 && PM_SLEEP
2419 APM is a BIOS specification for saving power using several different
2420 techniques. This is mostly useful for battery powered laptops with
2421 APM compliant BIOSes. If you say Y here, the system time will be
2422 reset after a RESUME operation, the /proc/apm device will provide
2423 battery status information, and user-space programs will receive
2424 notification of APM "events" (e.g. battery status change).
2426 If you select "Y" here, you can disable actual use of the APM
2427 BIOS by passing the "apm=off" option to the kernel at boot time.
2429 Note that the APM support is almost completely disabled for
2430 machines with more than one CPU.
2432 In order to use APM, you will need supporting software. For location
2433 and more information, read <file:Documentation/power/apm-acpi.txt>
2434 and the Battery Powered Linux mini-HOWTO, available from
2435 <http://www.tldp.org/docs.html#howto>.
2437 This driver does not spin down disk drives (see the hdparm(8)
2438 manpage ("man 8 hdparm") for that), and it doesn't turn off
2439 VESA-compliant "green" monitors.
2441 This driver does not support the TI 4000M TravelMate and the ACER
2442 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2443 desktop machines also don't have compliant BIOSes, and this driver
2444 may cause those machines to panic during the boot phase.
2446 Generally, if you don't have a battery in your machine, there isn't
2447 much point in using this driver and you should say N. If you get
2448 random kernel OOPSes or reboots that don't seem to be related to
2449 anything, try disabling/enabling this option (or disabling/enabling
2452 Some other things you should try when experiencing seemingly random,
2455 1) make sure that you have enough swap space and that it is
2457 2) pass the "no-hlt" option to the kernel
2458 3) switch on floating point emulation in the kernel and pass
2459 the "no387" option to the kernel
2460 4) pass the "floppy=nodma" option to the kernel
2461 5) pass the "mem=4M" option to the kernel (thereby disabling
2462 all but the first 4 MB of RAM)
2463 6) make sure that the CPU is not over clocked.
2464 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2465 8) disable the cache from your BIOS settings
2466 9) install a fan for the video card or exchange video RAM
2467 10) install a better fan for the CPU
2468 11) exchange RAM chips
2469 12) exchange the motherboard.
2471 To compile this driver as a module, choose M here: the
2472 module will be called apm.
2476 config APM_IGNORE_USER_SUSPEND
2477 bool "Ignore USER SUSPEND"
2479 This option will ignore USER SUSPEND requests. On machines with a
2480 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2481 series notebooks, it is necessary to say Y because of a BIOS bug.
2483 config APM_DO_ENABLE
2484 bool "Enable PM at boot time"
2486 Enable APM features at boot time. From page 36 of the APM BIOS
2487 specification: "When disabled, the APM BIOS does not automatically
2488 power manage devices, enter the Standby State, enter the Suspend
2489 State, or take power saving steps in response to CPU Idle calls."
2490 This driver will make CPU Idle calls when Linux is idle (unless this
2491 feature is turned off -- see "Do CPU IDLE calls", below). This
2492 should always save battery power, but more complicated APM features
2493 will be dependent on your BIOS implementation. You may need to turn
2494 this option off if your computer hangs at boot time when using APM
2495 support, or if it beeps continuously instead of suspending. Turn
2496 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2497 T400CDT. This is off by default since most machines do fine without
2502 bool "Make CPU Idle calls when idle"
2504 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2505 On some machines, this can activate improved power savings, such as
2506 a slowed CPU clock rate, when the machine is idle. These idle calls
2507 are made after the idle loop has run for some length of time (e.g.,
2508 333 mS). On some machines, this will cause a hang at boot time or
2509 whenever the CPU becomes idle. (On machines with more than one CPU,
2510 this option does nothing.)
2512 config APM_DISPLAY_BLANK
2513 bool "Enable console blanking using APM"
2515 Enable console blanking using the APM. Some laptops can use this to
2516 turn off the LCD backlight when the screen blanker of the Linux
2517 virtual console blanks the screen. Note that this is only used by
2518 the virtual console screen blanker, and won't turn off the backlight
2519 when using the X Window system. This also doesn't have anything to
2520 do with your VESA-compliant power-saving monitor. Further, this
2521 option doesn't work for all laptops -- it might not turn off your
2522 backlight at all, or it might print a lot of errors to the console,
2523 especially if you are using gpm.
2525 config APM_ALLOW_INTS
2526 bool "Allow interrupts during APM BIOS calls"
2528 Normally we disable external interrupts while we are making calls to
2529 the APM BIOS as a measure to lessen the effects of a badly behaving
2530 BIOS implementation. The BIOS should reenable interrupts if it
2531 needs to. Unfortunately, some BIOSes do not -- especially those in
2532 many of the newer IBM Thinkpads. If you experience hangs when you
2533 suspend, try setting this to Y. Otherwise, say N.
2537 source "drivers/cpufreq/Kconfig"
2539 source "drivers/cpuidle/Kconfig"
2541 source "drivers/idle/Kconfig"
2546 menu "Bus options (PCI etc.)"
2552 Find out whether you have a PCI motherboard. PCI is the name of a
2553 bus system, i.e. the way the CPU talks to the other stuff inside
2554 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2555 VESA. If you have PCI, say Y, otherwise N.
2558 prompt "PCI access mode"
2559 depends on X86_32 && PCI
2562 On PCI systems, the BIOS can be used to detect the PCI devices and
2563 determine their configuration. However, some old PCI motherboards
2564 have BIOS bugs and may crash if this is done. Also, some embedded
2565 PCI-based systems don't have any BIOS at all. Linux can also try to
2566 detect the PCI hardware directly without using the BIOS.
2568 With this option, you can specify how Linux should detect the
2569 PCI devices. If you choose "BIOS", the BIOS will be used,
2570 if you choose "Direct", the BIOS won't be used, and if you
2571 choose "MMConfig", then PCI Express MMCONFIG will be used.
2572 If you choose "Any", the kernel will try MMCONFIG, then the
2573 direct access method and falls back to the BIOS if that doesn't
2574 work. If unsure, go with the default, which is "Any".
2579 config PCI_GOMMCONFIG
2596 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2598 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2601 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2605 depends on X86_32 && PCI && (ACPI || SFI) && (PCI_GOMMCONFIG || PCI_GOANY)
2609 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2613 depends on PCI && XEN
2621 bool "Support mmconfig PCI config space access"
2622 depends on X86_64 && PCI && ACPI
2624 config PCI_CNB20LE_QUIRK
2625 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2628 Read the PCI windows out of the CNB20LE host bridge. This allows
2629 PCI hotplug to work on systems with the CNB20LE chipset which do
2632 There's no public spec for this chipset, and this functionality
2633 is known to be incomplete.
2635 You should say N unless you know you need this.
2637 source "drivers/pci/Kconfig"
2640 bool "ISA-style bus support on modern systems" if EXPERT
2643 Enables ISA-style drivers on modern systems. This is necessary to
2644 support PC/104 devices on X86_64 platforms.
2648 # x86_64 have no ISA slots, but can have ISA-style DMA.
2650 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2653 Enables ISA-style DMA support for devices requiring such controllers.
2661 Find out whether you have ISA slots on your motherboard. ISA is the
2662 name of a bus system, i.e. the way the CPU talks to the other stuff
2663 inside your box. Other bus systems are PCI, EISA, MicroChannel
2664 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2665 newer boards don't support it. If you have ISA, say Y, otherwise N.
2671 The Extended Industry Standard Architecture (EISA) bus was
2672 developed as an open alternative to the IBM MicroChannel bus.
2674 The EISA bus provided some of the features of the IBM MicroChannel
2675 bus while maintaining backward compatibility with cards made for
2676 the older ISA bus. The EISA bus saw limited use between 1988 and
2677 1995 when it was made obsolete by the PCI bus.
2679 Say Y here if you are building a kernel for an EISA-based machine.
2683 source "drivers/eisa/Kconfig"
2686 tristate "NatSemi SCx200 support"
2688 This provides basic support for National Semiconductor's
2689 (now AMD's) Geode processors. The driver probes for the
2690 PCI-IDs of several on-chip devices, so its a good dependency
2691 for other scx200_* drivers.
2693 If compiled as a module, the driver is named scx200.
2695 config SCx200HR_TIMER
2696 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2700 This driver provides a clocksource built upon the on-chip
2701 27MHz high-resolution timer. Its also a workaround for
2702 NSC Geode SC-1100's buggy TSC, which loses time when the
2703 processor goes idle (as is done by the scheduler). The
2704 other workaround is idle=poll boot option.
2707 bool "One Laptop Per Child support"
2714 Add support for detecting the unique features of the OLPC
2718 bool "OLPC XO-1 Power Management"
2719 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2721 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2724 bool "OLPC XO-1 Real Time Clock"
2725 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2727 Add support for the XO-1 real time clock, which can be used as a
2728 programmable wakeup source.
2731 bool "OLPC XO-1 SCI extras"
2732 depends on OLPC && OLPC_XO1_PM
2738 Add support for SCI-based features of the OLPC XO-1 laptop:
2739 - EC-driven system wakeups
2743 - AC adapter status updates
2744 - Battery status updates
2746 config OLPC_XO15_SCI
2747 bool "OLPC XO-1.5 SCI extras"
2748 depends on OLPC && ACPI
2751 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2752 - EC-driven system wakeups
2753 - AC adapter status updates
2754 - Battery status updates
2757 bool "PCEngines ALIX System Support (LED setup)"
2760 This option enables system support for the PCEngines ALIX.
2761 At present this just sets up LEDs for GPIO control on
2762 ALIX2/3/6 boards. However, other system specific setup should
2765 Note: You must still enable the drivers for GPIO and LED support
2766 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2768 Note: You have to set alix.force=1 for boards with Award BIOS.
2771 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2774 This option enables system support for the Soekris Engineering net5501.
2777 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2781 This option enables system support for the Traverse Technologies GEOS.
2784 bool "Technologic Systems TS-5500 platform support"
2786 select CHECK_SIGNATURE
2790 This option enables system support for the Technologic Systems TS-5500.
2796 depends on CPU_SUP_AMD && PCI
2798 source "drivers/pcmcia/Kconfig"
2801 tristate "RapidIO support"
2805 If enabled this option will include drivers and the core
2806 infrastructure code to support RapidIO interconnect devices.
2808 source "drivers/rapidio/Kconfig"
2811 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2813 Firmwares often provide initial graphics framebuffers so the BIOS,
2814 bootloader or kernel can show basic video-output during boot for
2815 user-guidance and debugging. Historically, x86 used the VESA BIOS
2816 Extensions and EFI-framebuffers for this, which are mostly limited
2818 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2819 framebuffers so the new generic system-framebuffer drivers can be
2820 used on x86. If the framebuffer is not compatible with the generic
2821 modes, it is adverticed as fallback platform framebuffer so legacy
2822 drivers like efifb, vesafb and uvesafb can pick it up.
2823 If this option is not selected, all system framebuffers are always
2824 marked as fallback platform framebuffers as usual.
2826 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2827 not be able to pick up generic system framebuffers if this option
2828 is selected. You are highly encouraged to enable simplefb as
2829 replacement if you select this option. simplefb can correctly deal
2830 with generic system framebuffers. But you should still keep vesafb
2831 and others enabled as fallback if a system framebuffer is
2832 incompatible with simplefb.
2839 menu "Executable file formats / Emulations"
2841 source "fs/Kconfig.binfmt"
2843 config IA32_EMULATION
2844 bool "IA32 Emulation"
2846 select ARCH_WANT_OLD_COMPAT_IPC
2848 select COMPAT_BINFMT_ELF
2849 select COMPAT_OLD_SIGACTION
2851 Include code to run legacy 32-bit programs under a
2852 64-bit kernel. You should likely turn this on, unless you're
2853 100% sure that you don't have any 32-bit programs left.
2856 tristate "IA32 a.out support"
2857 depends on IA32_EMULATION
2859 Support old a.out binaries in the 32bit emulation.
2862 bool "x32 ABI for 64-bit mode"
2865 Include code to run binaries for the x32 native 32-bit ABI
2866 for 64-bit processors. An x32 process gets access to the
2867 full 64-bit register file and wide data path while leaving
2868 pointers at 32 bits for smaller memory footprint.
2870 You will need a recent binutils (2.22 or later) with
2871 elf32_x86_64 support enabled to compile a kernel with this
2876 depends on IA32_EMULATION || X86_32
2878 select OLD_SIGSUSPEND3
2882 depends on IA32_EMULATION || X86_X32
2885 config COMPAT_FOR_U64_ALIGNMENT
2888 config SYSVIPC_COMPAT
2896 config HAVE_ATOMIC_IOMAP
2900 config X86_DEV_DMA_OPS
2902 depends on X86_64 || STA2X11
2904 config X86_DMA_REMAP
2908 config HAVE_GENERIC_GUP
2911 source "net/Kconfig"
2913 source "drivers/Kconfig"
2915 source "drivers/firmware/Kconfig"
2919 source "arch/x86/Kconfig.debug"
2921 source "security/Kconfig"
2923 source "crypto/Kconfig"
2925 source "arch/x86/kvm/Kconfig"
2927 source "lib/Kconfig"