3 bool "64-bit kernel" if ARCH = "x86"
6 Say yes to build a 64-bit kernel - formerly known as x86_64
7 Say no to build a 32-bit kernel - formerly known as i386
12 # Options that are inherently 32-bit kernel only:
13 select ARCH_WANT_IPC_PARSE_VERSION
15 select CLONE_BACKWARDS
17 select HAVE_GENERIC_DMA_COHERENT
18 select MODULES_USE_ELF_REL
24 # Options that are inherently 64-bit kernel only:
25 select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
26 select ARCH_SUPPORTS_INT128
27 select ARCH_USE_CMPXCHG_LOCKREF
28 select HAVE_ARCH_SOFT_DIRTY
29 select MODULES_USE_ELF_RELA
30 select X86_DEV_DMA_OPS
35 # ( Note that options that are marked 'if X86_64' could in principle be
36 # ported to 32-bit as well. )
41 # Note: keep this list sorted alphabetically
43 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
44 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
46 select ARCH_CLOCKSOURCE_DATA
47 select ARCH_DISCARD_MEMBLOCK
48 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
49 select ARCH_HAS_DEBUG_VIRTUAL
50 select ARCH_HAS_DEVMEM_IS_ALLOWED
51 select ARCH_HAS_ELF_RANDOMIZE
52 select ARCH_HAS_FAST_MULTIPLIER
53 select ARCH_HAS_FORTIFY_SOURCE
54 select ARCH_HAS_GCOV_PROFILE_ALL
55 select ARCH_HAS_KCOV if X86_64
56 select ARCH_HAS_MMIO_FLUSH
57 select ARCH_HAS_PMEM_API if X86_64
58 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
59 select ARCH_HAS_SET_MEMORY
60 select ARCH_HAS_SG_CHAIN
61 select ARCH_HAS_STRICT_KERNEL_RWX
62 select ARCH_HAS_STRICT_MODULE_RWX
63 select ARCH_HAS_UBSAN_SANITIZE_ALL
64 select ARCH_HAS_ZONE_DEVICE if X86_64
65 select ARCH_HAVE_NMI_SAFE_CMPXCHG
66 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
67 select ARCH_MIGHT_HAVE_PC_PARPORT
68 select ARCH_MIGHT_HAVE_PC_SERIO
69 select ARCH_SUPPORTS_ATOMIC_RMW
70 select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
71 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
72 select ARCH_USE_BUILTIN_BSWAP
73 select ARCH_USE_QUEUED_RWLOCKS
74 select ARCH_USE_QUEUED_SPINLOCKS
75 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
76 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
77 select ARCH_WANTS_THP_SWAP if X86_64
78 select BUILDTIME_EXTABLE_SORT
80 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
81 select CLOCKSOURCE_WATCHDOG
82 select DCACHE_WORD_ACCESS
83 select EDAC_ATOMIC_SCRUB
85 select GENERIC_CLOCKEVENTS
86 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
87 select GENERIC_CLOCKEVENTS_MIN_ADJUST
88 select GENERIC_CMOS_UPDATE
89 select GENERIC_CPU_AUTOPROBE
90 select GENERIC_CPU_VULNERABILITIES
91 select GENERIC_EARLY_IOREMAP
92 select GENERIC_FIND_FIRST_BIT
94 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
95 select GENERIC_IRQ_MIGRATION if SMP
96 select GENERIC_IRQ_PROBE
97 select GENERIC_IRQ_SHOW
98 select GENERIC_PENDING_IRQ if SMP
99 select GENERIC_SMP_IDLE_THREAD
100 select GENERIC_STRNCPY_FROM_USER
101 select GENERIC_STRNLEN_USER
102 select GENERIC_TIME_VSYSCALL
103 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
104 select HAVE_ACPI_APEI if ACPI
105 select HAVE_ACPI_APEI_NMI if ACPI
106 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
107 select HAVE_ARCH_AUDITSYSCALL
108 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
109 select HAVE_ARCH_JUMP_LABEL
110 select HAVE_ARCH_KASAN if X86_64
111 select HAVE_ARCH_KGDB
112 select HAVE_ARCH_KMEMCHECK
113 select HAVE_ARCH_MMAP_RND_BITS if MMU
114 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
115 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
116 select HAVE_ARCH_SECCOMP_FILTER
117 select HAVE_ARCH_TRACEHOOK
118 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
119 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
120 select HAVE_ARCH_VMAP_STACK if X86_64
121 select HAVE_ARCH_WITHIN_STACK_FRAMES
122 select HAVE_CC_STACKPROTECTOR
123 select HAVE_CMPXCHG_DOUBLE
124 select HAVE_CMPXCHG_LOCAL
125 select HAVE_CONTEXT_TRACKING if X86_64
126 select HAVE_COPY_THREAD_TLS
127 select HAVE_C_RECORDMCOUNT
128 select HAVE_DEBUG_KMEMLEAK
129 select HAVE_DEBUG_STACKOVERFLOW
130 select HAVE_DMA_API_DEBUG
131 select HAVE_DMA_CONTIGUOUS
132 select HAVE_DYNAMIC_FTRACE
133 select HAVE_DYNAMIC_FTRACE_WITH_REGS
134 select HAVE_EBPF_JIT if X86_64
135 select HAVE_EFFICIENT_UNALIGNED_ACCESS
136 select HAVE_EXIT_THREAD
137 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
138 select HAVE_FTRACE_MCOUNT_RECORD
139 select HAVE_FUNCTION_GRAPH_TRACER
140 select HAVE_FUNCTION_TRACER
141 select HAVE_GCC_PLUGINS
142 select HAVE_HW_BREAKPOINT
144 select HAVE_IOREMAP_PROT
145 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
146 select HAVE_IRQ_TIME_ACCOUNTING
147 select HAVE_KERNEL_BZIP2
148 select HAVE_KERNEL_GZIP
149 select HAVE_KERNEL_LZ4
150 select HAVE_KERNEL_LZMA
151 select HAVE_KERNEL_LZO
152 select HAVE_KERNEL_XZ
154 select HAVE_KPROBES_ON_FTRACE
155 select HAVE_KRETPROBES
157 select HAVE_LIVEPATCH if X86_64
159 select HAVE_MEMBLOCK_NODE_MAP
160 select HAVE_MIXED_BREAKPOINTS_REGS
161 select HAVE_MOD_ARCH_SPECIFIC
164 select HAVE_OPTPROBES
165 select HAVE_PCSPKR_PLATFORM
166 select HAVE_PERF_EVENTS
167 select HAVE_PERF_EVENTS_NMI
168 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
169 select HAVE_PERF_REGS
170 select HAVE_PERF_USER_STACK_DUMP
171 select HAVE_REGS_AND_STACK_ACCESS_API
172 select HAVE_RELIABLE_STACKTRACE if X86_64 && UNWINDER_FRAME_POINTER && STACK_VALIDATION
173 select HAVE_STACK_VALIDATION if X86_64
174 select HAVE_SYSCALL_TRACEPOINTS
175 select HAVE_UNSTABLE_SCHED_CLOCK
176 select HAVE_USER_RETURN_NOTIFIER
177 select IRQ_FORCED_THREADING
178 select PCI_LOCKLESS_CONFIG
181 select RTC_MC146818_LIB
184 select SYSCTL_EXCEPTION_TRACE
185 select THREAD_INFO_IN_TASK
186 select USER_STACKTRACE_SUPPORT
188 select X86_FEATURE_NAMES if PROC_FS
190 config INSTRUCTION_DECODER
192 depends on KPROBES || PERF_EVENTS || UPROBES
196 default "elf32-i386" if X86_32
197 default "elf64-x86-64" if X86_64
199 config ARCH_DEFCONFIG
201 default "arch/x86/configs/i386_defconfig" if X86_32
202 default "arch/x86/configs/x86_64_defconfig" if X86_64
204 config LOCKDEP_SUPPORT
207 config STACKTRACE_SUPPORT
213 config ARCH_MMAP_RND_BITS_MIN
217 config ARCH_MMAP_RND_BITS_MAX
221 config ARCH_MMAP_RND_COMPAT_BITS_MIN
224 config ARCH_MMAP_RND_COMPAT_BITS_MAX
230 config NEED_DMA_MAP_STATE
232 depends on X86_64 || INTEL_IOMMU || DMA_API_DEBUG || SWIOTLB
234 config NEED_SG_DMA_LENGTH
237 config GENERIC_ISA_DMA
239 depends on ISA_DMA_API
244 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
246 config GENERIC_BUG_RELATIVE_POINTERS
249 config GENERIC_HWEIGHT
252 config ARCH_MAY_HAVE_PC_FDC
254 depends on ISA_DMA_API
256 config RWSEM_XCHGADD_ALGORITHM
259 config GENERIC_CALIBRATE_DELAY
262 config ARCH_HAS_CPU_RELAX
265 config ARCH_HAS_CACHE_LINE_SIZE
268 config HAVE_SETUP_PER_CPU_AREA
271 config NEED_PER_CPU_EMBED_FIRST_CHUNK
274 config NEED_PER_CPU_PAGE_FIRST_CHUNK
277 config ARCH_HIBERNATION_POSSIBLE
280 config ARCH_SUSPEND_POSSIBLE
283 config ARCH_WANT_HUGE_PMD_SHARE
286 config ARCH_WANT_GENERAL_HUGETLB
295 config ARCH_SUPPORTS_OPTIMIZED_INLINING
298 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
301 config KASAN_SHADOW_OFFSET
304 default 0xdffffc0000000000
306 config HAVE_INTEL_TXT
308 depends on INTEL_IOMMU && ACPI
312 depends on X86_32 && SMP
316 depends on X86_64 && SMP
318 config X86_32_LAZY_GS
320 depends on X86_32 && !CC_STACKPROTECTOR
322 config ARCH_SUPPORTS_UPROBES
325 config FIX_EARLYCON_MEM
328 config PGTABLE_LEVELS
334 source "init/Kconfig"
335 source "kernel/Kconfig.freezer"
337 menu "Processor type and features"
340 bool "DMA memory allocation support" if EXPERT
343 DMA memory allocation support allows devices with less than 32-bit
344 addressing to allocate within the first 16MB of address space.
345 Disable if no such devices will be used.
350 bool "Symmetric multi-processing support"
352 This enables support for systems with more than one CPU. If you have
353 a system with only one CPU, say N. If you have a system with more
356 If you say N here, the kernel will run on uni- and multiprocessor
357 machines, but will use only one CPU of a multiprocessor machine. If
358 you say Y here, the kernel will run on many, but not all,
359 uniprocessor machines. On a uniprocessor machine, the kernel
360 will run faster if you say N here.
362 Note that if you say Y here and choose architecture "586" or
363 "Pentium" under "Processor family", the kernel will not work on 486
364 architectures. Similarly, multiprocessor kernels for the "PPro"
365 architecture may not work on all Pentium based boards.
367 People using multiprocessor machines who say Y here should also say
368 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
369 Management" code will be disabled if you say Y here.
371 See also <file:Documentation/x86/i386/IO-APIC.txt>,
372 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
373 <http://www.tldp.org/docs.html#howto>.
375 If you don't know what to do here, say N.
377 config X86_FEATURE_NAMES
378 bool "Processor feature human-readable names" if EMBEDDED
381 This option compiles in a table of x86 feature bits and corresponding
382 names. This is required to support /proc/cpuinfo and a few kernel
383 messages. You can disable this to save space, at the expense of
384 making those few kernel messages show numeric feature bits instead.
388 config X86_FAST_FEATURE_TESTS
389 bool "Fast CPU feature tests" if EMBEDDED
392 Some fast-paths in the kernel depend on the capabilities of the CPU.
393 Say Y here for the kernel to patch in the appropriate code at runtime
394 based on the capabilities of the CPU. The infrastructure for patching
395 code at runtime takes up some additional space; space-constrained
396 embedded systems may wish to say N here to produce smaller, slightly
400 bool "Support x2apic"
401 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
403 This enables x2apic support on CPUs that have this feature.
405 This allows 32-bit apic IDs (so it can support very large systems),
406 and accesses the local apic via MSRs not via mmio.
408 If you don't know what to do here, say N.
411 bool "Enable MPS table" if ACPI || SFI
413 depends on X86_LOCAL_APIC
415 For old smp systems that do not have proper acpi support. Newer systems
416 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
419 bool "Support for big SMP systems with more than 8 CPUs"
420 depends on X86_32 && SMP
422 This option is needed for the systems that have more than 8 CPUs
426 depends on X86_GOLDFISH
429 bool "Avoid speculative indirect branches in kernel"
432 Compile kernel with the retpoline compiler options to guard against
433 kernel-to-user data leaks by avoiding speculative indirect
434 branches. Requires a compiler with -mindirect-branch=thunk-extern
435 support for full protection. The kernel may run slower.
437 Without compiler support, at least indirect branches in assembler
438 code are eliminated. Since this includes the syscall entry path,
439 it is not entirely pointless.
442 bool "Intel Resource Director Technology support"
444 depends on X86 && CPU_SUP_INTEL
447 Select to enable resource allocation and monitoring which are
448 sub-features of Intel Resource Director Technology(RDT). More
449 information about RDT can be found in the Intel x86
450 Architecture Software Developer Manual.
455 config X86_EXTENDED_PLATFORM
456 bool "Support for extended (non-PC) x86 platforms"
459 If you disable this option then the kernel will only support
460 standard PC platforms. (which covers the vast majority of
463 If you enable this option then you'll be able to select support
464 for the following (non-PC) 32 bit x86 platforms:
465 Goldfish (Android emulator)
468 SGI 320/540 (Visual Workstation)
469 STA2X11-based (e.g. Northville)
470 Moorestown MID devices
472 If you have one of these systems, or if you want to build a
473 generic distribution kernel, say Y here - otherwise say N.
477 config X86_EXTENDED_PLATFORM
478 bool "Support for extended (non-PC) x86 platforms"
481 If you disable this option then the kernel will only support
482 standard PC platforms. (which covers the vast majority of
485 If you enable this option then you'll be able to select support
486 for the following (non-PC) 64 bit x86 platforms:
491 If you have one of these systems, or if you want to build a
492 generic distribution kernel, say Y here - otherwise say N.
494 # This is an alphabetically sorted list of 64 bit extended platforms
495 # Please maintain the alphabetic order if and when there are additions
497 bool "Numascale NumaChip"
499 depends on X86_EXTENDED_PLATFORM
502 depends on X86_X2APIC
503 depends on PCI_MMCONFIG
505 Adds support for Numascale NumaChip large-SMP systems. Needed to
506 enable more than ~168 cores.
507 If you don't have one of these, you should say N here.
511 select HYPERVISOR_GUEST
513 depends on X86_64 && PCI
514 depends on X86_EXTENDED_PLATFORM
517 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
518 supposed to run on these EM64T-based machines. Only choose this option
519 if you have one of these machines.
522 bool "SGI Ultraviolet"
524 depends on X86_EXTENDED_PLATFORM
527 depends on X86_X2APIC
530 This option is needed in order to support SGI Ultraviolet systems.
531 If you don't have one of these, you should say N here.
533 # Following is an alphabetically sorted list of 32 bit extended platforms
534 # Please maintain the alphabetic order if and when there are additions
537 bool "Goldfish (Virtual Platform)"
538 depends on X86_EXTENDED_PLATFORM
540 Enable support for the Goldfish virtual platform used primarily
541 for Android development. Unless you are building for the Android
542 Goldfish emulator say N here.
545 bool "CE4100 TV platform"
547 depends on PCI_GODIRECT
548 depends on X86_IO_APIC
550 depends on X86_EXTENDED_PLATFORM
551 select X86_REBOOTFIXUPS
553 select OF_EARLY_FLATTREE
555 Select for the Intel CE media processor (CE4100) SOC.
556 This option compiles in support for the CE4100 SOC for settop
557 boxes and media devices.
560 bool "Intel MID platform support"
561 depends on X86_EXTENDED_PLATFORM
562 depends on X86_PLATFORM_DEVICES
564 depends on X86_64 || (PCI_GOANY && X86_32)
565 depends on X86_IO_APIC
571 select MFD_INTEL_MSIC
573 Select to build a kernel capable of supporting Intel MID (Mobile
574 Internet Device) platform systems which do not have the PCI legacy
575 interfaces. If you are building for a PC class system say N here.
577 Intel MID platforms are based on an Intel processor and chipset which
578 consume less power than most of the x86 derivatives.
580 config X86_INTEL_QUARK
581 bool "Intel Quark platform support"
583 depends on X86_EXTENDED_PLATFORM
584 depends on X86_PLATFORM_DEVICES
588 depends on X86_IO_APIC
593 Select to include support for Quark X1000 SoC.
594 Say Y here if you have a Quark based system such as the Arduino
595 compatible Intel Galileo.
597 config X86_INTEL_LPSS
598 bool "Intel Low Power Subsystem Support"
599 depends on X86 && ACPI
604 Select to build support for Intel Low Power Subsystem such as
605 found on Intel Lynxpoint PCH. Selecting this option enables
606 things like clock tree (common clock framework) and pincontrol
607 which are needed by the LPSS peripheral drivers.
609 config X86_AMD_PLATFORM_DEVICE
610 bool "AMD ACPI2Platform devices support"
615 Select to interpret AMD specific ACPI device to platform device
616 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
617 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
618 implemented under PINCTRL subsystem.
621 tristate "Intel SoC IOSF Sideband support for SoC platforms"
624 This option enables sideband register access support for Intel SoC
625 platforms. On these platforms the IOSF sideband is used in lieu of
626 MSR's for some register accesses, mostly but not limited to thermal
627 and power. Drivers may query the availability of this device to
628 determine if they need the sideband in order to work on these
629 platforms. The sideband is available on the following SoC products.
630 This list is not meant to be exclusive.
635 You should say Y if you are running a kernel on one of these SoC's.
637 config IOSF_MBI_DEBUG
638 bool "Enable IOSF sideband access through debugfs"
639 depends on IOSF_MBI && DEBUG_FS
641 Select this option to expose the IOSF sideband access registers (MCR,
642 MDR, MCRX) through debugfs to write and read register information from
643 different units on the SoC. This is most useful for obtaining device
644 state information for debug and analysis. As this is a general access
645 mechanism, users of this option would have specific knowledge of the
646 device they want to access.
648 If you don't require the option or are in doubt, say N.
651 bool "RDC R-321x SoC"
653 depends on X86_EXTENDED_PLATFORM
655 select X86_REBOOTFIXUPS
657 This option is needed for RDC R-321x system-on-chip, also known
659 If you don't have one of these chips, you should say N here.
661 config X86_32_NON_STANDARD
662 bool "Support non-standard 32-bit SMP architectures"
663 depends on X86_32 && SMP
664 depends on X86_EXTENDED_PLATFORM
666 This option compiles in the bigsmp and STA2X11 default
667 subarchitectures. It is intended for a generic binary
668 kernel. If you select them all, kernel will probe it one by
669 one and will fallback to default.
671 # Alphabetically sorted list of Non standard 32 bit platforms
673 config X86_SUPPORTS_MEMORY_FAILURE
675 # MCE code calls memory_failure():
677 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
678 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
679 depends on X86_64 || !SPARSEMEM
680 select ARCH_SUPPORTS_MEMORY_FAILURE
683 bool "STA2X11 Companion Chip Support"
684 depends on X86_32_NON_STANDARD && PCI
685 select X86_DEV_DMA_OPS
692 This adds support for boards based on the STA2X11 IO-Hub,
693 a.k.a. "ConneXt". The chip is used in place of the standard
694 PC chipset, so all "standard" peripherals are missing. If this
695 option is selected the kernel will still be able to boot on
696 standard PC machines.
699 tristate "Eurobraille/Iris poweroff module"
702 The Iris machines from EuroBraille do not have APM or ACPI support
703 to shut themselves down properly. A special I/O sequence is
704 needed to do so, which is what this module does at
707 This is only for Iris machines from EuroBraille.
711 config SCHED_OMIT_FRAME_POINTER
713 prompt "Single-depth WCHAN output"
716 Calculate simpler /proc/<PID>/wchan values. If this option
717 is disabled then wchan values will recurse back to the
718 caller function. This provides more accurate wchan values,
719 at the expense of slightly more scheduling overhead.
721 If in doubt, say "Y".
723 menuconfig HYPERVISOR_GUEST
724 bool "Linux guest support"
726 Say Y here to enable options for running Linux under various hyper-
727 visors. This option enables basic hypervisor detection and platform
730 If you say N, all options in this submenu will be skipped and
731 disabled, and Linux guest support won't be built in.
736 bool "Enable paravirtualization code"
738 This changes the kernel so it can modify itself when it is run
739 under a hypervisor, potentially improving performance significantly
740 over full virtualization. However, when run without a hypervisor
741 the kernel is theoretically slower and slightly larger.
743 config PARAVIRT_DEBUG
744 bool "paravirt-ops debugging"
745 depends on PARAVIRT && DEBUG_KERNEL
747 Enable to debug paravirt_ops internals. Specifically, BUG if
748 a paravirt_op is missing when it is called.
750 config PARAVIRT_SPINLOCKS
751 bool "Paravirtualization layer for spinlocks"
752 depends on PARAVIRT && SMP
754 Paravirtualized spinlocks allow a pvops backend to replace the
755 spinlock implementation with something virtualization-friendly
756 (for example, block the virtual CPU rather than spinning).
758 It has a minimal impact on native kernels and gives a nice performance
759 benefit on paravirtualized KVM / Xen kernels.
761 If you are unsure how to answer this question, answer Y.
763 config QUEUED_LOCK_STAT
764 bool "Paravirt queued spinlock statistics"
765 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
767 Enable the collection of statistical data on the slowpath
768 behavior of paravirtualized queued spinlocks and report
771 source "arch/x86/xen/Kconfig"
774 bool "KVM Guest support (including kvmclock)"
776 select PARAVIRT_CLOCK
779 This option enables various optimizations for running under the KVM
780 hypervisor. It includes a paravirtualized clock, so that instead
781 of relying on a PIT (or probably other) emulation by the
782 underlying device model, the host provides the guest with
783 timing infrastructure such as time of day, and system time
786 bool "Enable debug information for KVM Guests in debugfs"
787 depends on KVM_GUEST && DEBUG_FS
790 This option enables collection of various statistics for KVM guest.
791 Statistics are displayed in debugfs filesystem. Enabling this option
792 may incur significant overhead.
794 source "arch/x86/lguest/Kconfig"
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.
958 bool "SMT (Hyperthreading) scheduler support"
961 SMT scheduler support improves the CPU scheduler's decision making
962 when dealing with Intel Pentium 4 chips with HyperThreading at a
963 cost of slightly increased overhead in some places. If unsure say
968 prompt "Multi-core scheduler support"
971 Multi-core scheduler support improves the CPU scheduler's decision
972 making when dealing with multi-core CPU chips at a cost of slightly
973 increased overhead in some places. If unsure say N here.
976 bool "CPU core priorities scheduler support"
977 depends on SCHED_MC && CPU_SUP_INTEL
978 select X86_INTEL_PSTATE
982 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
983 core ordering determined at manufacturing time, which allows
984 certain cores to reach higher turbo frequencies (when running
985 single threaded workloads) than others.
987 Enabling this kernel feature teaches the scheduler about
988 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
989 scheduler's CPU selection logic accordingly, so that higher
990 overall system performance can be achieved.
992 This feature will have no effect on CPUs without this feature.
994 If unsure say Y here.
996 source "kernel/Kconfig.preempt"
1000 depends on !SMP && X86_LOCAL_APIC
1003 bool "Local APIC support on uniprocessors" if !PCI_MSI
1005 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1007 A local APIC (Advanced Programmable Interrupt Controller) is an
1008 integrated interrupt controller in the CPU. If you have a single-CPU
1009 system which has a processor with a local APIC, you can say Y here to
1010 enable and use it. If you say Y here even though your machine doesn't
1011 have a local APIC, then the kernel will still run with no slowdown at
1012 all. The local APIC supports CPU-generated self-interrupts (timer,
1013 performance counters), and the NMI watchdog which detects hard
1016 config X86_UP_IOAPIC
1017 bool "IO-APIC support on uniprocessors"
1018 depends on X86_UP_APIC
1020 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1021 SMP-capable replacement for PC-style interrupt controllers. Most
1022 SMP systems and many recent uniprocessor systems have one.
1024 If you have a single-CPU system with an IO-APIC, you can say Y here
1025 to use it. If you say Y here even though your machine doesn't have
1026 an IO-APIC, then the kernel will still run with no slowdown at all.
1028 config X86_LOCAL_APIC
1030 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1031 select IRQ_DOMAIN_HIERARCHY
1032 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1036 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1038 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1039 bool "Reroute for broken boot IRQs"
1040 depends on X86_IO_APIC
1042 This option enables a workaround that fixes a source of
1043 spurious interrupts. This is recommended when threaded
1044 interrupt handling is used on systems where the generation of
1045 superfluous "boot interrupts" cannot be disabled.
1047 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1048 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1049 kernel does during interrupt handling). On chipsets where this
1050 boot IRQ generation cannot be disabled, this workaround keeps
1051 the original IRQ line masked so that only the equivalent "boot
1052 IRQ" is delivered to the CPUs. The workaround also tells the
1053 kernel to set up the IRQ handler on the boot IRQ line. In this
1054 way only one interrupt is delivered to the kernel. Otherwise
1055 the spurious second interrupt may cause the kernel to bring
1056 down (vital) interrupt lines.
1058 Only affects "broken" chipsets. Interrupt sharing may be
1059 increased on these systems.
1062 bool "Machine Check / overheating reporting"
1063 select GENERIC_ALLOCATOR
1066 Machine Check support allows the processor to notify the
1067 kernel if it detects a problem (e.g. overheating, data corruption).
1068 The action the kernel takes depends on the severity of the problem,
1069 ranging from warning messages to halting the machine.
1071 config X86_MCELOG_LEGACY
1072 bool "Support for deprecated /dev/mcelog character device"
1075 Enable support for /dev/mcelog which is needed by the old mcelog
1076 userspace logging daemon. Consider switching to the new generation
1079 config X86_MCE_INTEL
1081 prompt "Intel MCE features"
1082 depends on X86_MCE && X86_LOCAL_APIC
1084 Additional support for intel specific MCE features such as
1085 the thermal monitor.
1089 prompt "AMD MCE features"
1090 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1092 Additional support for AMD specific MCE features such as
1093 the DRAM Error Threshold.
1095 config X86_ANCIENT_MCE
1096 bool "Support for old Pentium 5 / WinChip machine checks"
1097 depends on X86_32 && X86_MCE
1099 Include support for machine check handling on old Pentium 5 or WinChip
1100 systems. These typically need to be enabled explicitly on the command
1103 config X86_MCE_THRESHOLD
1104 depends on X86_MCE_AMD || X86_MCE_INTEL
1107 config X86_MCE_INJECT
1108 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1109 tristate "Machine check injector support"
1111 Provide support for injecting machine checks for testing purposes.
1112 If you don't know what a machine check is and you don't do kernel
1113 QA it is safe to say n.
1115 config X86_THERMAL_VECTOR
1117 depends on X86_MCE_INTEL
1119 source "arch/x86/events/Kconfig"
1121 config X86_LEGACY_VM86
1122 bool "Legacy VM86 support"
1126 This option allows user programs to put the CPU into V8086
1127 mode, which is an 80286-era approximation of 16-bit real mode.
1129 Some very old versions of X and/or vbetool require this option
1130 for user mode setting. Similarly, DOSEMU will use it if
1131 available to accelerate real mode DOS programs. However, any
1132 recent version of DOSEMU, X, or vbetool should be fully
1133 functional even without kernel VM86 support, as they will all
1134 fall back to software emulation. Nevertheless, if you are using
1135 a 16-bit DOS program where 16-bit performance matters, vm86
1136 mode might be faster than emulation and you might want to
1139 Note that any app that works on a 64-bit kernel is unlikely to
1140 need this option, as 64-bit kernels don't, and can't, support
1141 V8086 mode. This option is also unrelated to 16-bit protected
1142 mode and is not needed to run most 16-bit programs under Wine.
1144 Enabling this option increases the complexity of the kernel
1145 and slows down exception handling a tiny bit.
1147 If unsure, say N here.
1151 default X86_LEGACY_VM86
1154 bool "Enable support for 16-bit segments" if EXPERT
1156 depends on MODIFY_LDT_SYSCALL
1158 This option is required by programs like Wine to run 16-bit
1159 protected mode legacy code on x86 processors. Disabling
1160 this option saves about 300 bytes on i386, or around 6K text
1161 plus 16K runtime memory on x86-64,
1165 depends on X86_16BIT && X86_32
1169 depends on X86_16BIT && X86_64
1171 config X86_VSYSCALL_EMULATION
1172 bool "Enable vsyscall emulation" if EXPERT
1176 This enables emulation of the legacy vsyscall page. Disabling
1177 it is roughly equivalent to booting with vsyscall=none, except
1178 that it will also disable the helpful warning if a program
1179 tries to use a vsyscall. With this option set to N, offending
1180 programs will just segfault, citing addresses of the form
1183 This option is required by many programs built before 2013, and
1184 care should be used even with newer programs if set to N.
1186 Disabling this option saves about 7K of kernel size and
1187 possibly 4K of additional runtime pagetable memory.
1190 tristate "Toshiba Laptop support"
1193 This adds a driver to safely access the System Management Mode of
1194 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1195 not work on models with a Phoenix BIOS. The System Management Mode
1196 is used to set the BIOS and power saving options on Toshiba portables.
1198 For information on utilities to make use of this driver see the
1199 Toshiba Linux utilities web site at:
1200 <http://www.buzzard.org.uk/toshiba/>.
1202 Say Y if you intend to run this kernel on a Toshiba portable.
1206 tristate "Dell i8k legacy laptop support"
1208 select SENSORS_DELL_SMM
1210 This option enables legacy /proc/i8k userspace interface in hwmon
1211 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1212 temperature and allows controlling fan speeds of Dell laptops via
1213 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1214 it reports also power and hotkey status. For fan speed control is
1215 needed userspace package i8kutils.
1217 Say Y if you intend to run this kernel on old Dell laptops or want to
1218 use userspace package i8kutils.
1221 config X86_REBOOTFIXUPS
1222 bool "Enable X86 board specific fixups for reboot"
1225 This enables chipset and/or board specific fixups to be done
1226 in order to get reboot to work correctly. This is only needed on
1227 some combinations of hardware and BIOS. The symptom, for which
1228 this config is intended, is when reboot ends with a stalled/hung
1231 Currently, the only fixup is for the Geode machines using
1232 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1234 Say Y if you want to enable the fixup. Currently, it's safe to
1235 enable this option even if you don't need it.
1239 bool "CPU microcode loading support"
1241 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1244 If you say Y here, you will be able to update the microcode on
1245 Intel and AMD processors. The Intel support is for the IA32 family,
1246 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1247 AMD support is for families 0x10 and later. You will obviously need
1248 the actual microcode binary data itself which is not shipped with
1251 The preferred method to load microcode from a detached initrd is described
1252 in Documentation/x86/early-microcode.txt. For that you need to enable
1253 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1254 initrd for microcode blobs.
1256 In addition, you can build-in the microcode into the kernel. For that you
1257 need to enable FIRMWARE_IN_KERNEL and add the vendor-supplied microcode
1258 to the CONFIG_EXTRA_FIRMWARE config option.
1260 config MICROCODE_INTEL
1261 bool "Intel microcode loading support"
1262 depends on MICROCODE
1266 This options enables microcode patch loading support for Intel
1269 For the current Intel microcode data package go to
1270 <https://downloadcenter.intel.com> and search for
1271 'Linux Processor Microcode Data File'.
1273 config MICROCODE_AMD
1274 bool "AMD microcode loading support"
1275 depends on MICROCODE
1278 If you select this option, microcode patch loading support for AMD
1279 processors will be enabled.
1281 config MICROCODE_OLD_INTERFACE
1283 depends on MICROCODE
1286 tristate "/dev/cpu/*/msr - Model-specific register support"
1288 This device gives privileged processes access to the x86
1289 Model-Specific Registers (MSRs). It is a character device with
1290 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1291 MSR accesses are directed to a specific CPU on multi-processor
1295 tristate "/dev/cpu/*/cpuid - CPU information support"
1297 This device gives processes access to the x86 CPUID instruction to
1298 be executed on a specific processor. It is a character device
1299 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1303 prompt "High Memory Support"
1310 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1311 However, the address space of 32-bit x86 processors is only 4
1312 Gigabytes large. That means that, if you have a large amount of
1313 physical memory, not all of it can be "permanently mapped" by the
1314 kernel. The physical memory that's not permanently mapped is called
1317 If you are compiling a kernel which will never run on a machine with
1318 more than 1 Gigabyte total physical RAM, answer "off" here (default
1319 choice and suitable for most users). This will result in a "3GB/1GB"
1320 split: 3GB are mapped so that each process sees a 3GB virtual memory
1321 space and the remaining part of the 4GB virtual memory space is used
1322 by the kernel to permanently map as much physical memory as
1325 If the machine has between 1 and 4 Gigabytes physical RAM, then
1328 If more than 4 Gigabytes is used then answer "64GB" here. This
1329 selection turns Intel PAE (Physical Address Extension) mode on.
1330 PAE implements 3-level paging on IA32 processors. PAE is fully
1331 supported by Linux, PAE mode is implemented on all recent Intel
1332 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1333 then the kernel will not boot on CPUs that don't support PAE!
1335 The actual amount of total physical memory will either be
1336 auto detected or can be forced by using a kernel command line option
1337 such as "mem=256M". (Try "man bootparam" or see the documentation of
1338 your boot loader (lilo or loadlin) about how to pass options to the
1339 kernel at boot time.)
1341 If unsure, say "off".
1346 Select this if you have a 32-bit processor and between 1 and 4
1347 gigabytes of physical RAM.
1354 Select this if you have a 32-bit processor and more than 4
1355 gigabytes of physical RAM.
1360 prompt "Memory split" if EXPERT
1364 Select the desired split between kernel and user memory.
1366 If the address range available to the kernel is less than the
1367 physical memory installed, the remaining memory will be available
1368 as "high memory". Accessing high memory is a little more costly
1369 than low memory, as it needs to be mapped into the kernel first.
1370 Note that increasing the kernel address space limits the range
1371 available to user programs, making the address space there
1372 tighter. Selecting anything other than the default 3G/1G split
1373 will also likely make your kernel incompatible with binary-only
1376 If you are not absolutely sure what you are doing, leave this
1380 bool "3G/1G user/kernel split"
1381 config VMSPLIT_3G_OPT
1383 bool "3G/1G user/kernel split (for full 1G low memory)"
1385 bool "2G/2G user/kernel split"
1386 config VMSPLIT_2G_OPT
1388 bool "2G/2G user/kernel split (for full 2G low memory)"
1390 bool "1G/3G user/kernel split"
1395 default 0xB0000000 if VMSPLIT_3G_OPT
1396 default 0x80000000 if VMSPLIT_2G
1397 default 0x78000000 if VMSPLIT_2G_OPT
1398 default 0x40000000 if VMSPLIT_1G
1404 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1407 bool "PAE (Physical Address Extension) Support"
1408 depends on X86_32 && !HIGHMEM4G
1411 PAE is required for NX support, and furthermore enables
1412 larger swapspace support for non-overcommit purposes. It
1413 has the cost of more pagetable lookup overhead, and also
1414 consumes more pagetable space per process.
1416 config ARCH_PHYS_ADDR_T_64BIT
1418 depends on X86_64 || X86_PAE
1420 config ARCH_DMA_ADDR_T_64BIT
1422 depends on X86_64 || HIGHMEM64G
1424 config X86_DIRECT_GBPAGES
1426 depends on X86_64 && !DEBUG_PAGEALLOC && !KMEMCHECK
1428 Certain kernel features effectively disable kernel
1429 linear 1 GB mappings (even if the CPU otherwise
1430 supports them), so don't confuse the user by printing
1431 that we have them enabled.
1433 # Common NUMA Features
1435 bool "Numa Memory Allocation and Scheduler Support"
1437 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1438 default y if X86_BIGSMP
1440 Enable NUMA (Non Uniform Memory Access) support.
1442 The kernel will try to allocate memory used by a CPU on the
1443 local memory controller of the CPU and add some more
1444 NUMA awareness to the kernel.
1446 For 64-bit this is recommended if the system is Intel Core i7
1447 (or later), AMD Opteron, or EM64T NUMA.
1449 For 32-bit this is only needed if you boot a 32-bit
1450 kernel on a 64-bit NUMA platform.
1452 Otherwise, you should say N.
1456 prompt "Old style AMD Opteron NUMA detection"
1457 depends on X86_64 && NUMA && PCI
1459 Enable AMD NUMA node topology detection. You should say Y here if
1460 you have a multi processor AMD system. This uses an old method to
1461 read the NUMA configuration directly from the builtin Northbridge
1462 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1463 which also takes priority if both are compiled in.
1465 config X86_64_ACPI_NUMA
1467 prompt "ACPI NUMA detection"
1468 depends on X86_64 && NUMA && ACPI && PCI
1471 Enable ACPI SRAT based node topology detection.
1473 # Some NUMA nodes have memory ranges that span
1474 # other nodes. Even though a pfn is valid and
1475 # between a node's start and end pfns, it may not
1476 # reside on that node. See memmap_init_zone()
1478 config NODES_SPAN_OTHER_NODES
1480 depends on X86_64_ACPI_NUMA
1483 bool "NUMA emulation"
1486 Enable NUMA emulation. A flat machine will be split
1487 into virtual nodes when booted with "numa=fake=N", where N is the
1488 number of nodes. This is only useful for debugging.
1491 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1493 default "10" if MAXSMP
1494 default "6" if X86_64
1496 depends on NEED_MULTIPLE_NODES
1498 Specify the maximum number of NUMA Nodes available on the target
1499 system. Increases memory reserved to accommodate various tables.
1501 config ARCH_HAVE_MEMORY_PRESENT
1503 depends on X86_32 && DISCONTIGMEM
1505 config NEED_NODE_MEMMAP_SIZE
1507 depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
1509 config ARCH_FLATMEM_ENABLE
1511 depends on X86_32 && !NUMA
1513 config ARCH_DISCONTIGMEM_ENABLE
1515 depends on NUMA && X86_32
1517 config ARCH_DISCONTIGMEM_DEFAULT
1519 depends on NUMA && X86_32
1521 config ARCH_SPARSEMEM_ENABLE
1523 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1524 select SPARSEMEM_STATIC if X86_32
1525 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1527 config ARCH_SPARSEMEM_DEFAULT
1531 config ARCH_SELECT_MEMORY_MODEL
1533 depends on ARCH_SPARSEMEM_ENABLE
1535 config ARCH_MEMORY_PROBE
1536 bool "Enable sysfs memory/probe interface"
1537 depends on X86_64 && MEMORY_HOTPLUG
1539 This option enables a sysfs memory/probe interface for testing.
1540 See Documentation/memory-hotplug.txt for more information.
1541 If you are unsure how to answer this question, answer N.
1543 config ARCH_PROC_KCORE_TEXT
1545 depends on X86_64 && PROC_KCORE
1547 config ILLEGAL_POINTER_VALUE
1550 default 0xdead000000000000 if X86_64
1554 config X86_PMEM_LEGACY_DEVICE
1557 config X86_PMEM_LEGACY
1558 tristate "Support non-standard NVDIMMs and ADR protected memory"
1559 depends on PHYS_ADDR_T_64BIT
1561 select X86_PMEM_LEGACY_DEVICE
1564 Treat memory marked using the non-standard e820 type of 12 as used
1565 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1566 The kernel will offer these regions to the 'pmem' driver so
1567 they can be used for persistent storage.
1572 bool "Allocate 3rd-level pagetables from highmem"
1575 The VM uses one page table entry for each page of physical memory.
1576 For systems with a lot of RAM, this can be wasteful of precious
1577 low memory. Setting this option will put user-space page table
1578 entries in high memory.
1580 config X86_CHECK_BIOS_CORRUPTION
1581 bool "Check for low memory corruption"
1583 Periodically check for memory corruption in low memory, which
1584 is suspected to be caused by BIOS. Even when enabled in the
1585 configuration, it is disabled at runtime. Enable it by
1586 setting "memory_corruption_check=1" on the kernel command
1587 line. By default it scans the low 64k of memory every 60
1588 seconds; see the memory_corruption_check_size and
1589 memory_corruption_check_period parameters in
1590 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1592 When enabled with the default parameters, this option has
1593 almost no overhead, as it reserves a relatively small amount
1594 of memory and scans it infrequently. It both detects corruption
1595 and prevents it from affecting the running system.
1597 It is, however, intended as a diagnostic tool; if repeatable
1598 BIOS-originated corruption always affects the same memory,
1599 you can use memmap= to prevent the kernel from using that
1602 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1603 bool "Set the default setting of memory_corruption_check"
1604 depends on X86_CHECK_BIOS_CORRUPTION
1607 Set whether the default state of memory_corruption_check is
1610 config X86_RESERVE_LOW
1611 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1615 Specify the amount of low memory to reserve for the BIOS.
1617 The first page contains BIOS data structures that the kernel
1618 must not use, so that page must always be reserved.
1620 By default we reserve the first 64K of physical RAM, as a
1621 number of BIOSes are known to corrupt that memory range
1622 during events such as suspend/resume or monitor cable
1623 insertion, so it must not be used by the kernel.
1625 You can set this to 4 if you are absolutely sure that you
1626 trust the BIOS to get all its memory reservations and usages
1627 right. If you know your BIOS have problems beyond the
1628 default 64K area, you can set this to 640 to avoid using the
1629 entire low memory range.
1631 If you have doubts about the BIOS (e.g. suspend/resume does
1632 not work or there's kernel crashes after certain hardware
1633 hotplug events) then you might want to enable
1634 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1635 typical corruption patterns.
1637 Leave this to the default value of 64 if you are unsure.
1639 config MATH_EMULATION
1641 depends on MODIFY_LDT_SYSCALL
1642 prompt "Math emulation" if X86_32
1644 Linux can emulate a math coprocessor (used for floating point
1645 operations) if you don't have one. 486DX and Pentium processors have
1646 a math coprocessor built in, 486SX and 386 do not, unless you added
1647 a 487DX or 387, respectively. (The messages during boot time can
1648 give you some hints here ["man dmesg"].) Everyone needs either a
1649 coprocessor or this emulation.
1651 If you don't have a math coprocessor, you need to say Y here; if you
1652 say Y here even though you have a coprocessor, the coprocessor will
1653 be used nevertheless. (This behavior can be changed with the kernel
1654 command line option "no387", which comes handy if your coprocessor
1655 is broken. Try "man bootparam" or see the documentation of your boot
1656 loader (lilo or loadlin) about how to pass options to the kernel at
1657 boot time.) This means that it is a good idea to say Y here if you
1658 intend to use this kernel on different machines.
1660 More information about the internals of the Linux math coprocessor
1661 emulation can be found in <file:arch/x86/math-emu/README>.
1663 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1664 kernel, it won't hurt.
1668 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1670 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1671 the Memory Type Range Registers (MTRRs) may be used to control
1672 processor access to memory ranges. This is most useful if you have
1673 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1674 allows bus write transfers to be combined into a larger transfer
1675 before bursting over the PCI/AGP bus. This can increase performance
1676 of image write operations 2.5 times or more. Saying Y here creates a
1677 /proc/mtrr file which may be used to manipulate your processor's
1678 MTRRs. Typically the X server should use this.
1680 This code has a reasonably generic interface so that similar
1681 control registers on other processors can be easily supported
1684 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1685 Registers (ARRs) which provide a similar functionality to MTRRs. For
1686 these, the ARRs are used to emulate the MTRRs.
1687 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1688 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1689 write-combining. All of these processors are supported by this code
1690 and it makes sense to say Y here if you have one of them.
1692 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1693 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1694 can lead to all sorts of problems, so it's good to say Y here.
1696 You can safely say Y even if your machine doesn't have MTRRs, you'll
1697 just add about 9 KB to your kernel.
1699 See <file:Documentation/x86/mtrr.txt> for more information.
1701 config MTRR_SANITIZER
1703 prompt "MTRR cleanup support"
1706 Convert MTRR layout from continuous to discrete, so X drivers can
1707 add writeback entries.
1709 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1710 The largest mtrr entry size for a continuous block can be set with
1715 config MTRR_SANITIZER_ENABLE_DEFAULT
1716 int "MTRR cleanup enable value (0-1)"
1719 depends on MTRR_SANITIZER
1721 Enable mtrr cleanup default value
1723 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1724 int "MTRR cleanup spare reg num (0-7)"
1727 depends on MTRR_SANITIZER
1729 mtrr cleanup spare entries default, it can be changed via
1730 mtrr_spare_reg_nr=N on the kernel command line.
1734 prompt "x86 PAT support" if EXPERT
1737 Use PAT attributes to setup page level cache control.
1739 PATs are the modern equivalents of MTRRs and are much more
1740 flexible than MTRRs.
1742 Say N here if you see bootup problems (boot crash, boot hang,
1743 spontaneous reboots) or a non-working video driver.
1747 config ARCH_USES_PG_UNCACHED
1753 prompt "x86 architectural random number generator" if EXPERT
1755 Enable the x86 architectural RDRAND instruction
1756 (Intel Bull Mountain technology) to generate random numbers.
1757 If supported, this is a high bandwidth, cryptographically
1758 secure hardware random number generator.
1762 prompt "Supervisor Mode Access Prevention" if EXPERT
1764 Supervisor Mode Access Prevention (SMAP) is a security
1765 feature in newer Intel processors. There is a small
1766 performance cost if this enabled and turned on; there is
1767 also a small increase in the kernel size if this is enabled.
1771 config X86_INTEL_MPX
1772 prompt "Intel MPX (Memory Protection Extensions)"
1774 depends on CPU_SUP_INTEL
1776 MPX provides hardware features that can be used in
1777 conjunction with compiler-instrumented code to check
1778 memory references. It is designed to detect buffer
1779 overflow or underflow bugs.
1781 This option enables running applications which are
1782 instrumented or otherwise use MPX. It does not use MPX
1783 itself inside the kernel or to protect the kernel
1784 against bad memory references.
1786 Enabling this option will make the kernel larger:
1787 ~8k of kernel text and 36 bytes of data on a 64-bit
1788 defconfig. It adds a long to the 'mm_struct' which
1789 will increase the kernel memory overhead of each
1790 process and adds some branches to paths used during
1791 exec() and munmap().
1793 For details, see Documentation/x86/intel_mpx.txt
1797 config X86_INTEL_MEMORY_PROTECTION_KEYS
1798 prompt "Intel Memory Protection Keys"
1800 # Note: only available in 64-bit mode
1801 depends on CPU_SUP_INTEL && X86_64
1802 select ARCH_USES_HIGH_VMA_FLAGS
1803 select ARCH_HAS_PKEYS
1805 Memory Protection Keys provides a mechanism for enforcing
1806 page-based protections, but without requiring modification of the
1807 page tables when an application changes protection domains.
1809 For details, see Documentation/x86/protection-keys.txt
1814 bool "EFI runtime service support"
1817 select EFI_RUNTIME_WRAPPERS
1819 This enables the kernel to use EFI runtime services that are
1820 available (such as the EFI variable services).
1822 This option is only useful on systems that have EFI firmware.
1823 In addition, you should use the latest ELILO loader available
1824 at <http://elilo.sourceforge.net> in order to take advantage
1825 of EFI runtime services. However, even with this option, the
1826 resultant kernel should continue to boot on existing non-EFI
1830 bool "EFI stub support"
1831 depends on EFI && !X86_USE_3DNOW
1834 This kernel feature allows a bzImage to be loaded directly
1835 by EFI firmware without the use of a bootloader.
1837 See Documentation/efi-stub.txt for more information.
1840 bool "EFI mixed-mode support"
1841 depends on EFI_STUB && X86_64
1843 Enabling this feature allows a 64-bit kernel to be booted
1844 on a 32-bit firmware, provided that your CPU supports 64-bit
1847 Note that it is not possible to boot a mixed-mode enabled
1848 kernel via the EFI boot stub - a bootloader that supports
1849 the EFI handover protocol must be used.
1853 config EFI_SECURE_BOOT_LOCK_DOWN
1856 prompt "Lock down the kernel when UEFI Secure Boot is enabled"
1858 UEFI Secure Boot provides a mechanism for ensuring that the firmware
1859 will only load signed bootloaders and kernels. Certain use cases may
1860 also require that all kernel modules also be signed and that
1861 userspace is prevented from directly changing the running kernel
1862 image. Say Y here to automatically lock down the kernel when a
1863 system boots with UEFI Secure Boot enabled.
1865 config EFI_ALLOW_SECURE_BOOT_EXIT
1867 depends on EFI_SECURE_BOOT_LOCK_DOWN && MAGIC_SYSRQ
1868 select ALLOW_LOCKDOWN_LIFT
1869 prompt "Allow secure boot mode to be exited with SysRq+x on a keyboard"
1871 Allow secure boot mode to be exited and the kernel lockdown lifted by
1872 typing SysRq+x on a keyboard attached to the system (not permitted
1877 prompt "Enable seccomp to safely compute untrusted bytecode"
1879 This kernel feature is useful for number crunching applications
1880 that may need to compute untrusted bytecode during their
1881 execution. By using pipes or other transports made available to
1882 the process as file descriptors supporting the read/write
1883 syscalls, it's possible to isolate those applications in
1884 their own address space using seccomp. Once seccomp is
1885 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1886 and the task is only allowed to execute a few safe syscalls
1887 defined by each seccomp mode.
1889 If unsure, say Y. Only embedded should say N here.
1891 source kernel/Kconfig.hz
1894 bool "kexec system call"
1897 kexec is a system call that implements the ability to shutdown your
1898 current kernel, and to start another kernel. It is like a reboot
1899 but it is independent of the system firmware. And like a reboot
1900 you can start any kernel with it, not just Linux.
1902 The name comes from the similarity to the exec system call.
1904 It is an ongoing process to be certain the hardware in a machine
1905 is properly shutdown, so do not be surprised if this code does not
1906 initially work for you. As of this writing the exact hardware
1907 interface is strongly in flux, so no good recommendation can be
1911 bool "kexec file based system call"
1916 depends on CRYPTO_SHA256=y
1918 This is new version of kexec system call. This system call is
1919 file based and takes file descriptors as system call argument
1920 for kernel and initramfs as opposed to list of segments as
1921 accepted by previous system call.
1923 config KEXEC_VERIFY_SIG
1924 bool "Verify kernel signature during kexec_file_load() syscall"
1925 depends on KEXEC_FILE
1927 This option makes kernel signature verification mandatory for
1928 the kexec_file_load() syscall.
1930 In addition to that option, you need to enable signature
1931 verification for the corresponding kernel image type being
1932 loaded in order for this to work.
1934 config KEXEC_BZIMAGE_VERIFY_SIG
1935 bool "Enable bzImage signature verification support"
1936 depends on KEXEC_VERIFY_SIG
1937 depends on SIGNED_PE_FILE_VERIFICATION
1938 select SYSTEM_TRUSTED_KEYRING
1940 Enable bzImage signature verification support.
1943 bool "kernel crash dumps"
1944 depends on X86_64 || (X86_32 && HIGHMEM)
1946 Generate crash dump after being started by kexec.
1947 This should be normally only set in special crash dump kernels
1948 which are loaded in the main kernel with kexec-tools into
1949 a specially reserved region and then later executed after
1950 a crash by kdump/kexec. The crash dump kernel must be compiled
1951 to a memory address not used by the main kernel or BIOS using
1952 PHYSICAL_START, or it must be built as a relocatable image
1953 (CONFIG_RELOCATABLE=y).
1954 For more details see Documentation/kdump/kdump.txt
1958 depends on KEXEC && HIBERNATION
1960 Jump between original kernel and kexeced kernel and invoke
1961 code in physical address mode via KEXEC
1963 config PHYSICAL_START
1964 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
1967 This gives the physical address where the kernel is loaded.
1969 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
1970 bzImage will decompress itself to above physical address and
1971 run from there. Otherwise, bzImage will run from the address where
1972 it has been loaded by the boot loader and will ignore above physical
1975 In normal kdump cases one does not have to set/change this option
1976 as now bzImage can be compiled as a completely relocatable image
1977 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
1978 address. This option is mainly useful for the folks who don't want
1979 to use a bzImage for capturing the crash dump and want to use a
1980 vmlinux instead. vmlinux is not relocatable hence a kernel needs
1981 to be specifically compiled to run from a specific memory area
1982 (normally a reserved region) and this option comes handy.
1984 So if you are using bzImage for capturing the crash dump,
1985 leave the value here unchanged to 0x1000000 and set
1986 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
1987 for capturing the crash dump change this value to start of
1988 the reserved region. In other words, it can be set based on
1989 the "X" value as specified in the "crashkernel=YM@XM"
1990 command line boot parameter passed to the panic-ed
1991 kernel. Please take a look at Documentation/kdump/kdump.txt
1992 for more details about crash dumps.
1994 Usage of bzImage for capturing the crash dump is recommended as
1995 one does not have to build two kernels. Same kernel can be used
1996 as production kernel and capture kernel. Above option should have
1997 gone away after relocatable bzImage support is introduced. But it
1998 is present because there are users out there who continue to use
1999 vmlinux for dump capture. This option should go away down the
2002 Don't change this unless you know what you are doing.
2005 bool "Build a relocatable kernel"
2008 This builds a kernel image that retains relocation information
2009 so it can be loaded someplace besides the default 1MB.
2010 The relocations tend to make the kernel binary about 10% larger,
2011 but are discarded at runtime.
2013 One use is for the kexec on panic case where the recovery kernel
2014 must live at a different physical address than the primary
2017 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2018 it has been loaded at and the compile time physical address
2019 (CONFIG_PHYSICAL_START) is used as the minimum location.
2021 config RANDOMIZE_BASE
2022 bool "Randomize the address of the kernel image (KASLR)"
2023 depends on RELOCATABLE
2026 In support of Kernel Address Space Layout Randomization (KASLR),
2027 this randomizes the physical address at which the kernel image
2028 is decompressed and the virtual address where the kernel
2029 image is mapped, as a security feature that deters exploit
2030 attempts relying on knowledge of the location of kernel
2033 On 64-bit, the kernel physical and virtual addresses are
2034 randomized separately. The physical address will be anywhere
2035 between 16MB and the top of physical memory (up to 64TB). The
2036 virtual address will be randomized from 16MB up to 1GB (9 bits
2037 of entropy). Note that this also reduces the memory space
2038 available to kernel modules from 1.5GB to 1GB.
2040 On 32-bit, the kernel physical and virtual addresses are
2041 randomized together. They will be randomized from 16MB up to
2042 512MB (8 bits of entropy).
2044 Entropy is generated using the RDRAND instruction if it is
2045 supported. If RDTSC is supported, its value is mixed into
2046 the entropy pool as well. If neither RDRAND nor RDTSC are
2047 supported, then entropy is read from the i8254 timer. The
2048 usable entropy is limited by the kernel being built using
2049 2GB addressing, and that PHYSICAL_ALIGN must be at a
2050 minimum of 2MB. As a result, only 10 bits of entropy are
2051 theoretically possible, but the implementations are further
2052 limited due to memory layouts.
2056 # Relocation on x86 needs some additional build support
2057 config X86_NEED_RELOCS
2059 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2061 config PHYSICAL_ALIGN
2062 hex "Alignment value to which kernel should be aligned"
2064 range 0x2000 0x1000000 if X86_32
2065 range 0x200000 0x1000000 if X86_64
2067 This value puts the alignment restrictions on physical address
2068 where kernel is loaded and run from. Kernel is compiled for an
2069 address which meets above alignment restriction.
2071 If bootloader loads the kernel at a non-aligned address and
2072 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2073 address aligned to above value and run from there.
2075 If bootloader loads the kernel at a non-aligned address and
2076 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2077 load address and decompress itself to the address it has been
2078 compiled for and run from there. The address for which kernel is
2079 compiled already meets above alignment restrictions. Hence the
2080 end result is that kernel runs from a physical address meeting
2081 above alignment restrictions.
2083 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2084 this value must be a multiple of 0x200000.
2086 Don't change this unless you know what you are doing.
2088 config RANDOMIZE_MEMORY
2089 bool "Randomize the kernel memory sections"
2091 depends on RANDOMIZE_BASE
2092 default RANDOMIZE_BASE
2094 Randomizes the base virtual address of kernel memory sections
2095 (physical memory mapping, vmalloc & vmemmap). This security feature
2096 makes exploits relying on predictable memory locations less reliable.
2098 The order of allocations remains unchanged. Entropy is generated in
2099 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2100 configuration have in average 30,000 different possible virtual
2101 addresses for each memory section.
2105 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2106 hex "Physical memory mapping padding" if EXPERT
2107 depends on RANDOMIZE_MEMORY
2108 default "0xa" if MEMORY_HOTPLUG
2110 range 0x1 0x40 if MEMORY_HOTPLUG
2113 Define the padding in terabytes added to the existing physical
2114 memory size during kernel memory randomization. It is useful
2115 for memory hotplug support but reduces the entropy available for
2116 address randomization.
2118 If unsure, leave at the default value.
2121 bool "Support for hot-pluggable CPUs"
2124 Say Y here to allow turning CPUs off and on. CPUs can be
2125 controlled through /sys/devices/system/cpu.
2126 ( Note: power management support will enable this option
2127 automatically on SMP systems. )
2128 Say N if you want to disable CPU hotplug.
2130 config BOOTPARAM_HOTPLUG_CPU0
2131 bool "Set default setting of cpu0_hotpluggable"
2133 depends on HOTPLUG_CPU
2135 Set whether default state of cpu0_hotpluggable is on or off.
2137 Say Y here to enable CPU0 hotplug by default. If this switch
2138 is turned on, there is no need to give cpu0_hotplug kernel
2139 parameter and the CPU0 hotplug feature is enabled by default.
2141 Please note: there are two known CPU0 dependencies if you want
2142 to enable the CPU0 hotplug feature either by this switch or by
2143 cpu0_hotplug kernel parameter.
2145 First, resume from hibernate or suspend always starts from CPU0.
2146 So hibernate and suspend are prevented if CPU0 is offline.
2148 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2149 offline if any interrupt can not migrate out of CPU0. There may
2150 be other CPU0 dependencies.
2152 Please make sure the dependencies are under your control before
2153 you enable this feature.
2155 Say N if you don't want to enable CPU0 hotplug feature by default.
2156 You still can enable the CPU0 hotplug feature at boot by kernel
2157 parameter cpu0_hotplug.
2159 config DEBUG_HOTPLUG_CPU0
2161 prompt "Debug CPU0 hotplug"
2162 depends on HOTPLUG_CPU
2164 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2165 soon as possible and boots up userspace with CPU0 offlined. User
2166 can online CPU0 back after boot time.
2168 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2169 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2170 compilation or giving cpu0_hotplug kernel parameter at boot.
2176 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2177 depends on COMPAT_32
2179 Certain buggy versions of glibc will crash if they are
2180 presented with a 32-bit vDSO that is not mapped at the address
2181 indicated in its segment table.
2183 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2184 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2185 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2186 the only released version with the bug, but OpenSUSE 9
2187 contains a buggy "glibc 2.3.2".
2189 The symptom of the bug is that everything crashes on startup, saying:
2190 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2192 Saying Y here changes the default value of the vdso32 boot
2193 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2194 This works around the glibc bug but hurts performance.
2196 If unsure, say N: if you are compiling your own kernel, you
2197 are unlikely to be using a buggy version of glibc.
2200 prompt "vsyscall table for legacy applications"
2202 default LEGACY_VSYSCALL_EMULATE
2204 Legacy user code that does not know how to find the vDSO expects
2205 to be able to issue three syscalls by calling fixed addresses in
2206 kernel space. Since this location is not randomized with ASLR,
2207 it can be used to assist security vulnerability exploitation.
2209 This setting can be changed at boot time via the kernel command
2210 line parameter vsyscall=[native|emulate|none].
2212 On a system with recent enough glibc (2.14 or newer) and no
2213 static binaries, you can say None without a performance penalty
2214 to improve security.
2216 If unsure, select "Emulate".
2218 config LEGACY_VSYSCALL_NATIVE
2221 Actual executable code is located in the fixed vsyscall
2222 address mapping, implementing time() efficiently. Since
2223 this makes the mapping executable, it can be used during
2224 security vulnerability exploitation (traditionally as
2225 ROP gadgets). This configuration is not recommended.
2227 config LEGACY_VSYSCALL_EMULATE
2230 The kernel traps and emulates calls into the fixed
2231 vsyscall address mapping. This makes the mapping
2232 non-executable, but it still contains known contents,
2233 which could be used in certain rare security vulnerability
2234 exploits. This configuration is recommended when userspace
2235 still uses the vsyscall area.
2237 config LEGACY_VSYSCALL_NONE
2240 There will be no vsyscall mapping at all. This will
2241 eliminate any risk of ASLR bypass due to the vsyscall
2242 fixed address mapping. Attempts to use the vsyscalls
2243 will be reported to dmesg, so that either old or
2244 malicious userspace programs can be identified.
2249 bool "Built-in kernel command line"
2251 Allow for specifying boot arguments to the kernel at
2252 build time. On some systems (e.g. embedded ones), it is
2253 necessary or convenient to provide some or all of the
2254 kernel boot arguments with the kernel itself (that is,
2255 to not rely on the boot loader to provide them.)
2257 To compile command line arguments into the kernel,
2258 set this option to 'Y', then fill in the
2259 boot arguments in CONFIG_CMDLINE.
2261 Systems with fully functional boot loaders (i.e. non-embedded)
2262 should leave this option set to 'N'.
2265 string "Built-in kernel command string"
2266 depends on CMDLINE_BOOL
2269 Enter arguments here that should be compiled into the kernel
2270 image and used at boot time. If the boot loader provides a
2271 command line at boot time, it is appended to this string to
2272 form the full kernel command line, when the system boots.
2274 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2275 change this behavior.
2277 In most cases, the command line (whether built-in or provided
2278 by the boot loader) should specify the device for the root
2281 config CMDLINE_OVERRIDE
2282 bool "Built-in command line overrides boot loader arguments"
2283 depends on CMDLINE_BOOL
2285 Set this option to 'Y' to have the kernel ignore the boot loader
2286 command line, and use ONLY the built-in command line.
2288 This is used to work around broken boot loaders. This should
2289 be set to 'N' under normal conditions.
2291 config MODIFY_LDT_SYSCALL
2292 bool "Enable the LDT (local descriptor table)" if EXPERT
2295 Linux can allow user programs to install a per-process x86
2296 Local Descriptor Table (LDT) using the modify_ldt(2) system
2297 call. This is required to run 16-bit or segmented code such as
2298 DOSEMU or some Wine programs. It is also used by some very old
2299 threading libraries.
2301 Enabling this feature adds a small amount of overhead to
2302 context switches and increases the low-level kernel attack
2303 surface. Disabling it removes the modify_ldt(2) system call.
2305 Saying 'N' here may make sense for embedded or server kernels.
2307 source "kernel/livepatch/Kconfig"
2311 config ARCH_ENABLE_MEMORY_HOTPLUG
2313 depends on X86_64 || (X86_32 && HIGHMEM)
2315 config ARCH_ENABLE_MEMORY_HOTREMOVE
2317 depends on MEMORY_HOTPLUG
2319 config USE_PERCPU_NUMA_NODE_ID
2323 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2325 depends on X86_64 || X86_PAE
2327 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2329 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2331 menu "Power management and ACPI options"
2333 config ARCH_HIBERNATION_HEADER
2335 depends on X86_64 && HIBERNATION
2337 source "kernel/power/Kconfig"
2339 source "drivers/acpi/Kconfig"
2341 source "drivers/sfi/Kconfig"
2348 tristate "APM (Advanced Power Management) BIOS support"
2349 depends on X86_32 && PM_SLEEP
2351 APM is a BIOS specification for saving power using several different
2352 techniques. This is mostly useful for battery powered laptops with
2353 APM compliant BIOSes. If you say Y here, the system time will be
2354 reset after a RESUME operation, the /proc/apm device will provide
2355 battery status information, and user-space programs will receive
2356 notification of APM "events" (e.g. battery status change).
2358 If you select "Y" here, you can disable actual use of the APM
2359 BIOS by passing the "apm=off" option to the kernel at boot time.
2361 Note that the APM support is almost completely disabled for
2362 machines with more than one CPU.
2364 In order to use APM, you will need supporting software. For location
2365 and more information, read <file:Documentation/power/apm-acpi.txt>
2366 and the Battery Powered Linux mini-HOWTO, available from
2367 <http://www.tldp.org/docs.html#howto>.
2369 This driver does not spin down disk drives (see the hdparm(8)
2370 manpage ("man 8 hdparm") for that), and it doesn't turn off
2371 VESA-compliant "green" monitors.
2373 This driver does not support the TI 4000M TravelMate and the ACER
2374 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2375 desktop machines also don't have compliant BIOSes, and this driver
2376 may cause those machines to panic during the boot phase.
2378 Generally, if you don't have a battery in your machine, there isn't
2379 much point in using this driver and you should say N. If you get
2380 random kernel OOPSes or reboots that don't seem to be related to
2381 anything, try disabling/enabling this option (or disabling/enabling
2384 Some other things you should try when experiencing seemingly random,
2387 1) make sure that you have enough swap space and that it is
2389 2) pass the "no-hlt" option to the kernel
2390 3) switch on floating point emulation in the kernel and pass
2391 the "no387" option to the kernel
2392 4) pass the "floppy=nodma" option to the kernel
2393 5) pass the "mem=4M" option to the kernel (thereby disabling
2394 all but the first 4 MB of RAM)
2395 6) make sure that the CPU is not over clocked.
2396 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2397 8) disable the cache from your BIOS settings
2398 9) install a fan for the video card or exchange video RAM
2399 10) install a better fan for the CPU
2400 11) exchange RAM chips
2401 12) exchange the motherboard.
2403 To compile this driver as a module, choose M here: the
2404 module will be called apm.
2408 config APM_IGNORE_USER_SUSPEND
2409 bool "Ignore USER SUSPEND"
2411 This option will ignore USER SUSPEND requests. On machines with a
2412 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2413 series notebooks, it is necessary to say Y because of a BIOS bug.
2415 config APM_DO_ENABLE
2416 bool "Enable PM at boot time"
2418 Enable APM features at boot time. From page 36 of the APM BIOS
2419 specification: "When disabled, the APM BIOS does not automatically
2420 power manage devices, enter the Standby State, enter the Suspend
2421 State, or take power saving steps in response to CPU Idle calls."
2422 This driver will make CPU Idle calls when Linux is idle (unless this
2423 feature is turned off -- see "Do CPU IDLE calls", below). This
2424 should always save battery power, but more complicated APM features
2425 will be dependent on your BIOS implementation. You may need to turn
2426 this option off if your computer hangs at boot time when using APM
2427 support, or if it beeps continuously instead of suspending. Turn
2428 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2429 T400CDT. This is off by default since most machines do fine without
2434 bool "Make CPU Idle calls when idle"
2436 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2437 On some machines, this can activate improved power savings, such as
2438 a slowed CPU clock rate, when the machine is idle. These idle calls
2439 are made after the idle loop has run for some length of time (e.g.,
2440 333 mS). On some machines, this will cause a hang at boot time or
2441 whenever the CPU becomes idle. (On machines with more than one CPU,
2442 this option does nothing.)
2444 config APM_DISPLAY_BLANK
2445 bool "Enable console blanking using APM"
2447 Enable console blanking using the APM. Some laptops can use this to
2448 turn off the LCD backlight when the screen blanker of the Linux
2449 virtual console blanks the screen. Note that this is only used by
2450 the virtual console screen blanker, and won't turn off the backlight
2451 when using the X Window system. This also doesn't have anything to
2452 do with your VESA-compliant power-saving monitor. Further, this
2453 option doesn't work for all laptops -- it might not turn off your
2454 backlight at all, or it might print a lot of errors to the console,
2455 especially if you are using gpm.
2457 config APM_ALLOW_INTS
2458 bool "Allow interrupts during APM BIOS calls"
2460 Normally we disable external interrupts while we are making calls to
2461 the APM BIOS as a measure to lessen the effects of a badly behaving
2462 BIOS implementation. The BIOS should reenable interrupts if it
2463 needs to. Unfortunately, some BIOSes do not -- especially those in
2464 many of the newer IBM Thinkpads. If you experience hangs when you
2465 suspend, try setting this to Y. Otherwise, say N.
2469 source "drivers/cpufreq/Kconfig"
2471 source "drivers/cpuidle/Kconfig"
2473 source "drivers/idle/Kconfig"
2478 menu "Bus options (PCI etc.)"
2484 Find out whether you have a PCI motherboard. PCI is the name of a
2485 bus system, i.e. the way the CPU talks to the other stuff inside
2486 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2487 VESA. If you have PCI, say Y, otherwise N.
2490 prompt "PCI access mode"
2491 depends on X86_32 && PCI
2494 On PCI systems, the BIOS can be used to detect the PCI devices and
2495 determine their configuration. However, some old PCI motherboards
2496 have BIOS bugs and may crash if this is done. Also, some embedded
2497 PCI-based systems don't have any BIOS at all. Linux can also try to
2498 detect the PCI hardware directly without using the BIOS.
2500 With this option, you can specify how Linux should detect the
2501 PCI devices. If you choose "BIOS", the BIOS will be used,
2502 if you choose "Direct", the BIOS won't be used, and if you
2503 choose "MMConfig", then PCI Express MMCONFIG will be used.
2504 If you choose "Any", the kernel will try MMCONFIG, then the
2505 direct access method and falls back to the BIOS if that doesn't
2506 work. If unsure, go with the default, which is "Any".
2511 config PCI_GOMMCONFIG
2528 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2530 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2533 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2537 depends on X86_32 && PCI && (ACPI || SFI) && (PCI_GOMMCONFIG || PCI_GOANY)
2541 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2545 depends on PCI && XEN
2553 bool "Support mmconfig PCI config space access"
2554 depends on X86_64 && PCI && ACPI
2556 config PCI_CNB20LE_QUIRK
2557 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2560 Read the PCI windows out of the CNB20LE host bridge. This allows
2561 PCI hotplug to work on systems with the CNB20LE chipset which do
2564 There's no public spec for this chipset, and this functionality
2565 is known to be incomplete.
2567 You should say N unless you know you need this.
2569 source "drivers/pci/Kconfig"
2572 bool "ISA-style bus support on modern systems" if EXPERT
2575 Enables ISA-style drivers on modern systems. This is necessary to
2576 support PC/104 devices on X86_64 platforms.
2580 # x86_64 have no ISA slots, but can have ISA-style DMA.
2582 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2585 Enables ISA-style DMA support for devices requiring such controllers.
2593 Find out whether you have ISA slots on your motherboard. ISA is the
2594 name of a bus system, i.e. the way the CPU talks to the other stuff
2595 inside your box. Other bus systems are PCI, EISA, MicroChannel
2596 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2597 newer boards don't support it. If you have ISA, say Y, otherwise N.
2603 The Extended Industry Standard Architecture (EISA) bus was
2604 developed as an open alternative to the IBM MicroChannel bus.
2606 The EISA bus provided some of the features of the IBM MicroChannel
2607 bus while maintaining backward compatibility with cards made for
2608 the older ISA bus. The EISA bus saw limited use between 1988 and
2609 1995 when it was made obsolete by the PCI bus.
2611 Say Y here if you are building a kernel for an EISA-based machine.
2615 source "drivers/eisa/Kconfig"
2618 tristate "NatSemi SCx200 support"
2620 This provides basic support for National Semiconductor's
2621 (now AMD's) Geode processors. The driver probes for the
2622 PCI-IDs of several on-chip devices, so its a good dependency
2623 for other scx200_* drivers.
2625 If compiled as a module, the driver is named scx200.
2627 config SCx200HR_TIMER
2628 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2632 This driver provides a clocksource built upon the on-chip
2633 27MHz high-resolution timer. Its also a workaround for
2634 NSC Geode SC-1100's buggy TSC, which loses time when the
2635 processor goes idle (as is done by the scheduler). The
2636 other workaround is idle=poll boot option.
2639 bool "One Laptop Per Child support"
2646 Add support for detecting the unique features of the OLPC
2650 bool "OLPC XO-1 Power Management"
2651 depends on OLPC && MFD_CS5535 && PM_SLEEP
2654 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2657 bool "OLPC XO-1 Real Time Clock"
2658 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2660 Add support for the XO-1 real time clock, which can be used as a
2661 programmable wakeup source.
2664 bool "OLPC XO-1 SCI extras"
2665 depends on OLPC && OLPC_XO1_PM
2671 Add support for SCI-based features of the OLPC XO-1 laptop:
2672 - EC-driven system wakeups
2676 - AC adapter status updates
2677 - Battery status updates
2679 config OLPC_XO15_SCI
2680 bool "OLPC XO-1.5 SCI extras"
2681 depends on OLPC && ACPI
2684 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2685 - EC-driven system wakeups
2686 - AC adapter status updates
2687 - Battery status updates
2690 bool "PCEngines ALIX System Support (LED setup)"
2693 This option enables system support for the PCEngines ALIX.
2694 At present this just sets up LEDs for GPIO control on
2695 ALIX2/3/6 boards. However, other system specific setup should
2698 Note: You must still enable the drivers for GPIO and LED support
2699 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2701 Note: You have to set alix.force=1 for boards with Award BIOS.
2704 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2707 This option enables system support for the Soekris Engineering net5501.
2710 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2714 This option enables system support for the Traverse Technologies GEOS.
2717 bool "Technologic Systems TS-5500 platform support"
2719 select CHECK_SIGNATURE
2723 This option enables system support for the Technologic Systems TS-5500.
2729 depends on CPU_SUP_AMD && PCI
2731 source "drivers/pcmcia/Kconfig"
2734 tristate "RapidIO support"
2738 If enabled this option will include drivers and the core
2739 infrastructure code to support RapidIO interconnect devices.
2741 source "drivers/rapidio/Kconfig"
2744 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2746 Firmwares often provide initial graphics framebuffers so the BIOS,
2747 bootloader or kernel can show basic video-output during boot for
2748 user-guidance and debugging. Historically, x86 used the VESA BIOS
2749 Extensions and EFI-framebuffers for this, which are mostly limited
2751 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2752 framebuffers so the new generic system-framebuffer drivers can be
2753 used on x86. If the framebuffer is not compatible with the generic
2754 modes, it is adverticed as fallback platform framebuffer so legacy
2755 drivers like efifb, vesafb and uvesafb can pick it up.
2756 If this option is not selected, all system framebuffers are always
2757 marked as fallback platform framebuffers as usual.
2759 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2760 not be able to pick up generic system framebuffers if this option
2761 is selected. You are highly encouraged to enable simplefb as
2762 replacement if you select this option. simplefb can correctly deal
2763 with generic system framebuffers. But you should still keep vesafb
2764 and others enabled as fallback if a system framebuffer is
2765 incompatible with simplefb.
2772 menu "Executable file formats / Emulations"
2774 source "fs/Kconfig.binfmt"
2776 config IA32_EMULATION
2777 bool "IA32 Emulation"
2779 select ARCH_WANT_OLD_COMPAT_IPC
2781 select COMPAT_BINFMT_ELF
2782 select COMPAT_OLD_SIGACTION
2784 Include code to run legacy 32-bit programs under a
2785 64-bit kernel. You should likely turn this on, unless you're
2786 100% sure that you don't have any 32-bit programs left.
2789 tristate "IA32 a.out support"
2790 depends on IA32_EMULATION
2792 Support old a.out binaries in the 32bit emulation.
2795 bool "x32 ABI for 64-bit mode"
2798 Include code to run binaries for the x32 native 32-bit ABI
2799 for 64-bit processors. An x32 process gets access to the
2800 full 64-bit register file and wide data path while leaving
2801 pointers at 32 bits for smaller memory footprint.
2803 You will need a recent binutils (2.22 or later) with
2804 elf32_x86_64 support enabled to compile a kernel with this
2809 depends on IA32_EMULATION || X86_32
2811 select OLD_SIGSUSPEND3
2815 depends on IA32_EMULATION || X86_X32
2818 config COMPAT_FOR_U64_ALIGNMENT
2821 config SYSVIPC_COMPAT
2829 config HAVE_ATOMIC_IOMAP
2833 config X86_DEV_DMA_OPS
2835 depends on X86_64 || STA2X11
2837 config X86_DMA_REMAP
2841 config HAVE_GENERIC_GUP
2844 source "net/Kconfig"
2846 source "drivers/Kconfig"
2848 source "ubuntu/Kconfig"
2850 source "drivers/firmware/Kconfig"
2854 source "arch/x86/Kconfig.debug"
2856 source "security/Kconfig"
2858 source "crypto/Kconfig"
2860 source "arch/x86/kvm/Kconfig"
2862 source "lib/Kconfig"