1 # SPDX-License-Identifier: GPL-2.0
4 bool "64-bit kernel" if ARCH = "x86"
7 Say yes to build a 64-bit kernel - formerly known as x86_64
8 Say no to build a 32-bit kernel - formerly known as i386
13 # Options that are inherently 32-bit kernel only:
14 select ARCH_WANT_IPC_PARSE_VERSION
16 select CLONE_BACKWARDS
18 select HAVE_GENERIC_DMA_COHERENT
19 select MODULES_USE_ELF_REL
25 # Options that are inherently 64-bit kernel only:
26 select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
27 select ARCH_SUPPORTS_INT128
28 select ARCH_USE_CMPXCHG_LOCKREF
29 select HAVE_ARCH_SOFT_DIRTY
30 select MODULES_USE_ELF_RELA
31 select X86_DEV_DMA_OPS
36 # ( Note that options that are marked 'if X86_64' could in principle be
37 # ported to 32-bit as well. )
42 # Note: keep this list sorted alphabetically
44 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
45 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
47 select ARCH_CLOCKSOURCE_DATA
48 select ARCH_DISCARD_MEMBLOCK
49 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
50 select ARCH_HAS_DEBUG_VIRTUAL
51 select ARCH_HAS_DEVMEM_IS_ALLOWED
52 select ARCH_HAS_ELF_RANDOMIZE
53 select ARCH_HAS_FAST_MULTIPLIER
54 select ARCH_HAS_FORTIFY_SOURCE
55 select ARCH_HAS_GCOV_PROFILE_ALL
56 select ARCH_HAS_KCOV if X86_64
57 select ARCH_HAS_PHYS_TO_DMA
58 select ARCH_HAS_PMEM_API if X86_64
59 select ARCH_HAS_REFCOUNT
60 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
61 select ARCH_HAS_SET_MEMORY
62 select ARCH_HAS_SG_CHAIN
63 select ARCH_HAS_STRICT_KERNEL_RWX
64 select ARCH_HAS_STRICT_MODULE_RWX
65 select ARCH_HAS_UBSAN_SANITIZE_ALL
66 select ARCH_HAS_ZONE_DEVICE if X86_64
67 select ARCH_HAVE_NMI_SAFE_CMPXCHG
68 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
69 select ARCH_MIGHT_HAVE_PC_PARPORT
70 select ARCH_MIGHT_HAVE_PC_SERIO
71 select ARCH_SUPPORTS_ATOMIC_RMW
72 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
73 select ARCH_USE_BUILTIN_BSWAP
74 select ARCH_USE_QUEUED_RWLOCKS
75 select ARCH_USE_QUEUED_SPINLOCKS
76 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
77 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
78 select ARCH_WANTS_THP_SWAP if X86_64
79 select BUILDTIME_EXTABLE_SORT
81 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
82 select CLOCKSOURCE_WATCHDOG
83 select DCACHE_WORD_ACCESS
84 select EDAC_ATOMIC_SCRUB
86 select GENERIC_CLOCKEVENTS
87 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
88 select GENERIC_CLOCKEVENTS_MIN_ADJUST
89 select GENERIC_CMOS_UPDATE
90 select GENERIC_CPU_AUTOPROBE
91 select GENERIC_CPU_VULNERABILITIES
92 select GENERIC_EARLY_IOREMAP
93 select GENERIC_FIND_FIRST_BIT
95 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
96 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
97 select GENERIC_IRQ_MIGRATION if SMP
98 select GENERIC_IRQ_PROBE
99 select GENERIC_IRQ_RESERVATION_MODE
100 select GENERIC_IRQ_SHOW
101 select GENERIC_PENDING_IRQ if SMP
102 select GENERIC_SMP_IDLE_THREAD
103 select GENERIC_STRNCPY_FROM_USER
104 select GENERIC_STRNLEN_USER
105 select GENERIC_TIME_VSYSCALL
106 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
107 select HAVE_ACPI_APEI if ACPI
108 select HAVE_ACPI_APEI_NMI if ACPI
109 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
110 select HAVE_ARCH_AUDITSYSCALL
111 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
112 select HAVE_ARCH_JUMP_LABEL
113 select HAVE_ARCH_KASAN if X86_64
114 select HAVE_ARCH_KGDB
115 select HAVE_ARCH_MMAP_RND_BITS if MMU
116 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
117 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
118 select HAVE_ARCH_SECCOMP_FILTER
119 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
120 select HAVE_ARCH_TRACEHOOK
121 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
122 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
123 select HAVE_ARCH_VMAP_STACK if X86_64
124 select HAVE_ARCH_WITHIN_STACK_FRAMES
125 select HAVE_CC_STACKPROTECTOR
126 select HAVE_CMPXCHG_DOUBLE
127 select HAVE_CMPXCHG_LOCAL
128 select HAVE_CONTEXT_TRACKING if X86_64
129 select HAVE_COPY_THREAD_TLS
130 select HAVE_C_RECORDMCOUNT
131 select HAVE_DEBUG_KMEMLEAK
132 select HAVE_DEBUG_STACKOVERFLOW
133 select HAVE_DMA_API_DEBUG
134 select HAVE_DMA_CONTIGUOUS
135 select HAVE_DYNAMIC_FTRACE
136 select HAVE_DYNAMIC_FTRACE_WITH_REGS
137 select HAVE_EBPF_JIT if X86_64
138 select HAVE_EFFICIENT_UNALIGNED_ACCESS
139 select HAVE_EXIT_THREAD
140 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
141 select HAVE_FTRACE_MCOUNT_RECORD
142 select HAVE_FUNCTION_GRAPH_TRACER
143 select HAVE_FUNCTION_TRACER
144 select HAVE_GCC_PLUGINS
145 select HAVE_HW_BREAKPOINT
147 select HAVE_IOREMAP_PROT
148 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
149 select HAVE_IRQ_TIME_ACCOUNTING
150 select HAVE_KERNEL_BZIP2
151 select HAVE_KERNEL_GZIP
152 select HAVE_KERNEL_LZ4
153 select HAVE_KERNEL_LZMA
154 select HAVE_KERNEL_LZO
155 select HAVE_KERNEL_XZ
157 select HAVE_KPROBES_ON_FTRACE
158 select HAVE_FUNCTION_ERROR_INJECTION
159 select HAVE_KRETPROBES
161 select HAVE_LIVEPATCH if X86_64
163 select HAVE_MEMBLOCK_NODE_MAP
164 select HAVE_MIXED_BREAKPOINTS_REGS
165 select HAVE_MOD_ARCH_SPECIFIC
168 select HAVE_OPTPROBES
169 select HAVE_PCSPKR_PLATFORM
170 select HAVE_PERF_EVENTS
171 select HAVE_PERF_EVENTS_NMI
172 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
173 select HAVE_PERF_REGS
174 select HAVE_PERF_USER_STACK_DUMP
175 select HAVE_RCU_TABLE_FREE
176 select HAVE_REGS_AND_STACK_ACCESS_API
177 select HAVE_RELIABLE_STACKTRACE if X86_64 && UNWINDER_FRAME_POINTER && STACK_VALIDATION
178 select HAVE_STACK_VALIDATION if X86_64
179 select HAVE_SYSCALL_TRACEPOINTS
180 select HAVE_UNSTABLE_SCHED_CLOCK
181 select HAVE_USER_RETURN_NOTIFIER
182 select IRQ_FORCED_THREADING
183 select PCI_LOCKLESS_CONFIG
186 select RTC_MC146818_LIB
189 select SYSCTL_EXCEPTION_TRACE
190 select THREAD_INFO_IN_TASK
191 select USER_STACKTRACE_SUPPORT
193 select X86_FEATURE_NAMES if PROC_FS
195 config INSTRUCTION_DECODER
197 depends on KPROBES || PERF_EVENTS || UPROBES
201 default "elf32-i386" if X86_32
202 default "elf64-x86-64" if X86_64
204 config ARCH_DEFCONFIG
206 default "arch/x86/configs/i386_defconfig" if X86_32
207 default "arch/x86/configs/x86_64_defconfig" if X86_64
209 config LOCKDEP_SUPPORT
212 config STACKTRACE_SUPPORT
218 config ARCH_MMAP_RND_BITS_MIN
222 config ARCH_MMAP_RND_BITS_MAX
226 config ARCH_MMAP_RND_COMPAT_BITS_MIN
229 config ARCH_MMAP_RND_COMPAT_BITS_MAX
235 config NEED_DMA_MAP_STATE
237 depends on X86_64 || INTEL_IOMMU || DMA_API_DEBUG || SWIOTLB
239 config NEED_SG_DMA_LENGTH
242 config GENERIC_ISA_DMA
244 depends on ISA_DMA_API
249 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
251 config GENERIC_BUG_RELATIVE_POINTERS
254 config GENERIC_HWEIGHT
257 config ARCH_MAY_HAVE_PC_FDC
259 depends on ISA_DMA_API
261 config RWSEM_XCHGADD_ALGORITHM
264 config GENERIC_CALIBRATE_DELAY
267 config ARCH_HAS_CPU_RELAX
270 config ARCH_HAS_CACHE_LINE_SIZE
273 config HAVE_SETUP_PER_CPU_AREA
276 config NEED_PER_CPU_EMBED_FIRST_CHUNK
279 config NEED_PER_CPU_PAGE_FIRST_CHUNK
282 config ARCH_HIBERNATION_POSSIBLE
285 config ARCH_SUSPEND_POSSIBLE
288 config ARCH_WANT_HUGE_PMD_SHARE
291 config ARCH_WANT_GENERAL_HUGETLB
300 config ARCH_SUPPORTS_OPTIMIZED_INLINING
303 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
306 config KASAN_SHADOW_OFFSET
309 default 0xdffffc0000000000
311 config HAVE_INTEL_TXT
313 depends on INTEL_IOMMU && ACPI
317 depends on X86_32 && SMP
321 depends on X86_64 && SMP
323 config X86_32_LAZY_GS
325 depends on X86_32 && !CC_STACKPROTECTOR
327 config ARCH_SUPPORTS_UPROBES
330 config FIX_EARLYCON_MEM
333 config PGTABLE_LEVELS
335 default 5 if X86_5LEVEL
340 source "init/Kconfig"
341 source "kernel/Kconfig.freezer"
343 menu "Processor type and features"
346 bool "DMA memory allocation support" if EXPERT
349 DMA memory allocation support allows devices with less than 32-bit
350 addressing to allocate within the first 16MB of address space.
351 Disable if no such devices will be used.
356 bool "Symmetric multi-processing support"
358 This enables support for systems with more than one CPU. If you have
359 a system with only one CPU, say N. If you have a system with more
362 If you say N here, the kernel will run on uni- and multiprocessor
363 machines, but will use only one CPU of a multiprocessor machine. If
364 you say Y here, the kernel will run on many, but not all,
365 uniprocessor machines. On a uniprocessor machine, the kernel
366 will run faster if you say N here.
368 Note that if you say Y here and choose architecture "586" or
369 "Pentium" under "Processor family", the kernel will not work on 486
370 architectures. Similarly, multiprocessor kernels for the "PPro"
371 architecture may not work on all Pentium based boards.
373 People using multiprocessor machines who say Y here should also say
374 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
375 Management" code will be disabled if you say Y here.
377 See also <file:Documentation/x86/i386/IO-APIC.txt>,
378 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
379 <http://www.tldp.org/docs.html#howto>.
381 If you don't know what to do here, say N.
383 config X86_FEATURE_NAMES
384 bool "Processor feature human-readable names" if EMBEDDED
387 This option compiles in a table of x86 feature bits and corresponding
388 names. This is required to support /proc/cpuinfo and a few kernel
389 messages. You can disable this to save space, at the expense of
390 making those few kernel messages show numeric feature bits instead.
394 config X86_FAST_FEATURE_TESTS
395 bool "Fast CPU feature tests" if EMBEDDED
398 Some fast-paths in the kernel depend on the capabilities of the CPU.
399 Say Y here for the kernel to patch in the appropriate code at runtime
400 based on the capabilities of the CPU. The infrastructure for patching
401 code at runtime takes up some additional space; space-constrained
402 embedded systems may wish to say N here to produce smaller, slightly
406 bool "Support x2apic"
407 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
409 This enables x2apic support on CPUs that have this feature.
411 This allows 32-bit apic IDs (so it can support very large systems),
412 and accesses the local apic via MSRs not via mmio.
414 If you don't know what to do here, say N.
417 bool "Enable MPS table" if ACPI || SFI
419 depends on X86_LOCAL_APIC
421 For old smp systems that do not have proper acpi support. Newer systems
422 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
425 bool "Support for big SMP systems with more than 8 CPUs"
426 depends on X86_32 && SMP
428 This option is needed for the systems that have more than 8 CPUs
432 depends on X86_GOLDFISH
435 bool "Avoid speculative indirect branches in kernel"
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.
443 Without compiler support, at least indirect branches in assembler
444 code are eliminated. Since this includes the syscall entry path,
445 it is not entirely pointless.
448 bool "Intel Resource Director Technology support"
450 depends on X86 && CPU_SUP_INTEL
453 Select to enable resource allocation and monitoring which are
454 sub-features of Intel Resource Director Technology(RDT). More
455 information about RDT can be found in the Intel x86
456 Architecture Software Developer Manual.
461 config X86_EXTENDED_PLATFORM
462 bool "Support for extended (non-PC) x86 platforms"
465 If you disable this option then the kernel will only support
466 standard PC platforms. (which covers the vast majority of
469 If you enable this option then you'll be able to select support
470 for the following (non-PC) 32 bit x86 platforms:
471 Goldfish (Android emulator)
474 SGI 320/540 (Visual Workstation)
475 STA2X11-based (e.g. Northville)
476 Moorestown MID devices
478 If you have one of these systems, or if you want to build a
479 generic distribution kernel, say Y here - otherwise say N.
483 config X86_EXTENDED_PLATFORM
484 bool "Support for extended (non-PC) x86 platforms"
487 If you disable this option then the kernel will only support
488 standard PC platforms. (which covers the vast majority of
491 If you enable this option then you'll be able to select support
492 for the following (non-PC) 64 bit x86 platforms:
497 If you have one of these systems, or if you want to build a
498 generic distribution kernel, say Y here - otherwise say N.
500 # This is an alphabetically sorted list of 64 bit extended platforms
501 # Please maintain the alphabetic order if and when there are additions
503 bool "Numascale NumaChip"
505 depends on X86_EXTENDED_PLATFORM
508 depends on X86_X2APIC
509 depends on PCI_MMCONFIG
511 Adds support for Numascale NumaChip large-SMP systems. Needed to
512 enable more than ~168 cores.
513 If you don't have one of these, you should say N here.
517 select HYPERVISOR_GUEST
519 depends on X86_64 && PCI
520 depends on X86_EXTENDED_PLATFORM
523 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
524 supposed to run on these EM64T-based machines. Only choose this option
525 if you have one of these machines.
528 bool "SGI Ultraviolet"
530 depends on X86_EXTENDED_PLATFORM
533 depends on X86_X2APIC
536 This option is needed in order to support SGI Ultraviolet systems.
537 If you don't have one of these, you should say N here.
539 # Following is an alphabetically sorted list of 32 bit extended platforms
540 # Please maintain the alphabetic order if and when there are additions
543 bool "Goldfish (Virtual Platform)"
544 depends on X86_EXTENDED_PLATFORM
546 Enable support for the Goldfish virtual platform used primarily
547 for Android development. Unless you are building for the Android
548 Goldfish emulator say N here.
551 bool "CE4100 TV platform"
553 depends on PCI_GODIRECT
554 depends on X86_IO_APIC
556 depends on X86_EXTENDED_PLATFORM
557 select X86_REBOOTFIXUPS
559 select OF_EARLY_FLATTREE
561 Select for the Intel CE media processor (CE4100) SOC.
562 This option compiles in support for the CE4100 SOC for settop
563 boxes and media devices.
566 bool "Intel MID platform support"
567 depends on X86_EXTENDED_PLATFORM
568 depends on X86_PLATFORM_DEVICES
570 depends on X86_64 || (PCI_GOANY && X86_32)
571 depends on X86_IO_APIC
577 select MFD_INTEL_MSIC
579 Select to build a kernel capable of supporting Intel MID (Mobile
580 Internet Device) platform systems which do not have the PCI legacy
581 interfaces. If you are building for a PC class system say N here.
583 Intel MID platforms are based on an Intel processor and chipset which
584 consume less power than most of the x86 derivatives.
586 config X86_INTEL_QUARK
587 bool "Intel Quark platform support"
589 depends on X86_EXTENDED_PLATFORM
590 depends on X86_PLATFORM_DEVICES
594 depends on X86_IO_APIC
599 Select to include support for Quark X1000 SoC.
600 Say Y here if you have a Quark based system such as the Arduino
601 compatible Intel Galileo.
603 config X86_INTEL_LPSS
604 bool "Intel Low Power Subsystem Support"
605 depends on X86 && ACPI
610 Select to build support for Intel Low Power Subsystem such as
611 found on Intel Lynxpoint PCH. Selecting this option enables
612 things like clock tree (common clock framework) and pincontrol
613 which are needed by the LPSS peripheral drivers.
615 config X86_AMD_PLATFORM_DEVICE
616 bool "AMD ACPI2Platform devices support"
621 Select to interpret AMD specific ACPI device to platform device
622 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
623 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
624 implemented under PINCTRL subsystem.
627 tristate "Intel SoC IOSF Sideband support for SoC platforms"
630 This option enables sideband register access support for Intel SoC
631 platforms. On these platforms the IOSF sideband is used in lieu of
632 MSR's for some register accesses, mostly but not limited to thermal
633 and power. Drivers may query the availability of this device to
634 determine if they need the sideband in order to work on these
635 platforms. The sideband is available on the following SoC products.
636 This list is not meant to be exclusive.
641 You should say Y if you are running a kernel on one of these SoC's.
643 config IOSF_MBI_DEBUG
644 bool "Enable IOSF sideband access through debugfs"
645 depends on IOSF_MBI && DEBUG_FS
647 Select this option to expose the IOSF sideband access registers (MCR,
648 MDR, MCRX) through debugfs to write and read register information from
649 different units on the SoC. This is most useful for obtaining device
650 state information for debug and analysis. As this is a general access
651 mechanism, users of this option would have specific knowledge of the
652 device they want to access.
654 If you don't require the option or are in doubt, say N.
657 bool "RDC R-321x SoC"
659 depends on X86_EXTENDED_PLATFORM
661 select X86_REBOOTFIXUPS
663 This option is needed for RDC R-321x system-on-chip, also known
665 If you don't have one of these chips, you should say N here.
667 config X86_32_NON_STANDARD
668 bool "Support non-standard 32-bit SMP architectures"
669 depends on X86_32 && SMP
670 depends on X86_EXTENDED_PLATFORM
672 This option compiles in the bigsmp and STA2X11 default
673 subarchitectures. It is intended for a generic binary
674 kernel. If you select them all, kernel will probe it one by
675 one and will fallback to default.
677 # Alphabetically sorted list of Non standard 32 bit platforms
679 config X86_SUPPORTS_MEMORY_FAILURE
681 # MCE code calls memory_failure():
683 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
684 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
685 depends on X86_64 || !SPARSEMEM
686 select ARCH_SUPPORTS_MEMORY_FAILURE
689 bool "STA2X11 Companion Chip Support"
690 depends on X86_32_NON_STANDARD && PCI
691 select X86_DEV_DMA_OPS
698 This adds support for boards based on the STA2X11 IO-Hub,
699 a.k.a. "ConneXt". The chip is used in place of the standard
700 PC chipset, so all "standard" peripherals are missing. If this
701 option is selected the kernel will still be able to boot on
702 standard PC machines.
705 tristate "Eurobraille/Iris poweroff module"
708 The Iris machines from EuroBraille do not have APM or ACPI support
709 to shut themselves down properly. A special I/O sequence is
710 needed to do so, which is what this module does at
713 This is only for Iris machines from EuroBraille.
717 config SCHED_OMIT_FRAME_POINTER
719 prompt "Single-depth WCHAN output"
722 Calculate simpler /proc/<PID>/wchan values. If this option
723 is disabled then wchan values will recurse back to the
724 caller function. This provides more accurate wchan values,
725 at the expense of slightly more scheduling overhead.
727 If in doubt, say "Y".
729 menuconfig HYPERVISOR_GUEST
730 bool "Linux guest support"
732 Say Y here to enable options for running Linux under various hyper-
733 visors. This option enables basic hypervisor detection and platform
736 If you say N, all options in this submenu will be skipped and
737 disabled, and Linux guest support won't be built in.
742 bool "Enable paravirtualization code"
744 This changes the kernel so it can modify itself when it is run
745 under a hypervisor, potentially improving performance significantly
746 over full virtualization. However, when run without a hypervisor
747 the kernel is theoretically slower and slightly larger.
749 config PARAVIRT_DEBUG
750 bool "paravirt-ops debugging"
751 depends on PARAVIRT && DEBUG_KERNEL
753 Enable to debug paravirt_ops internals. Specifically, BUG if
754 a paravirt_op is missing when it is called.
756 config PARAVIRT_SPINLOCKS
757 bool "Paravirtualization layer for spinlocks"
758 depends on PARAVIRT && SMP
760 Paravirtualized spinlocks allow a pvops backend to replace the
761 spinlock implementation with something virtualization-friendly
762 (for example, block the virtual CPU rather than spinning).
764 It has a minimal impact on native kernels and gives a nice performance
765 benefit on paravirtualized KVM / Xen kernels.
767 If you are unsure how to answer this question, answer Y.
769 config QUEUED_LOCK_STAT
770 bool "Paravirt queued spinlock statistics"
771 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
773 Enable the collection of statistical data on the slowpath
774 behavior of paravirtualized queued spinlocks and report
777 source "arch/x86/xen/Kconfig"
780 bool "KVM Guest support (including kvmclock)"
782 select PARAVIRT_CLOCK
785 This option enables various optimizations for running under the KVM
786 hypervisor. It includes a paravirtualized clock, so that instead
787 of relying on a PIT (or probably other) emulation by the
788 underlying device model, the host provides the guest with
789 timing infrastructure such as time of day, and system time
792 bool "Enable debug information for KVM Guests in debugfs"
793 depends on KVM_GUEST && DEBUG_FS
796 This option enables collection of various statistics for KVM guest.
797 Statistics are displayed in debugfs filesystem. Enabling this option
798 may incur significant overhead.
800 config PARAVIRT_TIME_ACCOUNTING
801 bool "Paravirtual steal time accounting"
805 Select this option to enable fine granularity task steal time
806 accounting. Time spent executing other tasks in parallel with
807 the current vCPU is discounted from the vCPU power. To account for
808 that, there can be a small performance impact.
810 If in doubt, say N here.
812 config PARAVIRT_CLOCK
815 config JAILHOUSE_GUEST
816 bool "Jailhouse non-root cell support"
817 depends on X86_64 && PCI
820 This option allows to run Linux as guest in a Jailhouse non-root
821 cell. You can leave this option disabled if you only want to start
822 Jailhouse and run Linux afterwards in the root cell.
824 endif #HYPERVISOR_GUEST
829 source "arch/x86/Kconfig.cpu"
833 prompt "HPET Timer Support" if X86_32
835 Use the IA-PC HPET (High Precision Event Timer) to manage
836 time in preference to the PIT and RTC, if a HPET is
838 HPET is the next generation timer replacing legacy 8254s.
839 The HPET provides a stable time base on SMP
840 systems, unlike the TSC, but it is more expensive to access,
841 as it is off-chip. The interface used is documented
842 in the HPET spec, revision 1.
844 You can safely choose Y here. However, HPET will only be
845 activated if the platform and the BIOS support this feature.
846 Otherwise the 8254 will be used for timing services.
848 Choose N to continue using the legacy 8254 timer.
850 config HPET_EMULATE_RTC
852 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
855 def_bool y if X86_INTEL_MID
856 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
858 depends on X86_INTEL_MID && SFI
860 APB timer is the replacement for 8254, HPET on X86 MID platforms.
861 The APBT provides a stable time base on SMP
862 systems, unlike the TSC, but it is more expensive to access,
863 as it is off-chip. APB timers are always running regardless of CPU
864 C states, they are used as per CPU clockevent device when possible.
866 # Mark as expert because too many people got it wrong.
867 # The code disables itself when not needed.
870 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
871 bool "Enable DMI scanning" if EXPERT
873 Enabled scanning of DMI to identify machine quirks. Say Y
874 here unless you have verified that your setup is not
875 affected by entries in the DMI blacklist. Required by PNP
879 bool "Old AMD GART IOMMU support"
881 depends on X86_64 && PCI && AMD_NB
883 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
884 GART based hardware IOMMUs.
886 The GART supports full DMA access for devices with 32-bit access
887 limitations, on systems with more than 3 GB. This is usually needed
888 for USB, sound, many IDE/SATA chipsets and some other devices.
890 Newer systems typically have a modern AMD IOMMU, supported via
891 the CONFIG_AMD_IOMMU=y config option.
893 In normal configurations this driver is only active when needed:
894 there's more than 3 GB of memory and the system contains a
895 32-bit limited device.
900 bool "IBM Calgary IOMMU support"
902 depends on X86_64 && PCI
904 Support for hardware IOMMUs in IBM's xSeries x366 and x460
905 systems. Needed to run systems with more than 3GB of memory
906 properly with 32-bit PCI devices that do not support DAC
907 (Double Address Cycle). Calgary also supports bus level
908 isolation, where all DMAs pass through the IOMMU. This
909 prevents them from going anywhere except their intended
910 destination. This catches hard-to-find kernel bugs and
911 mis-behaving drivers and devices that do not use the DMA-API
912 properly to set up their DMA buffers. The IOMMU can be
913 turned off at boot time with the iommu=off parameter.
914 Normally the kernel will make the right choice by itself.
917 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
919 prompt "Should Calgary be enabled by default?"
920 depends on CALGARY_IOMMU
922 Should Calgary be enabled by default? if you choose 'y', Calgary
923 will be used (if it exists). If you choose 'n', Calgary will not be
924 used even if it exists. If you choose 'n' and would like to use
925 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
928 # need this always selected by IOMMU for the VIA workaround
932 Support for software bounce buffers used on x86-64 systems
933 which don't have a hardware IOMMU. Using this PCI devices
934 which can only access 32-bits of memory can be used on systems
935 with more than 3 GB of memory.
940 depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU
943 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
944 depends on X86_64 && SMP && DEBUG_KERNEL
945 select CPUMASK_OFFSTACK
947 Enable maximum number of CPUS and NUMA Nodes for this architecture.
951 int "Maximum number of CPUs" if SMP && !MAXSMP
952 range 2 8 if SMP && X86_32 && !X86_BIGSMP
953 range 2 64 if SMP && X86_32 && X86_BIGSMP
954 range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK && X86_64
955 range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
957 default "8192" if MAXSMP
958 default "32" if SMP && X86_BIGSMP
959 default "8" if SMP && X86_32
962 This allows you to specify the maximum number of CPUs which this
963 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
964 supported value is 8192, otherwise the maximum value is 512. The
965 minimum value which makes sense is 2.
967 This is purely to save memory - each supported CPU adds
968 approximately eight kilobytes to the kernel image.
971 bool "SMT (Hyperthreading) scheduler support"
974 SMT scheduler support improves the CPU scheduler's decision making
975 when dealing with Intel Pentium 4 chips with HyperThreading at a
976 cost of slightly increased overhead in some places. If unsure say
981 prompt "Multi-core scheduler support"
984 Multi-core scheduler support improves the CPU scheduler's decision
985 making when dealing with multi-core CPU chips at a cost of slightly
986 increased overhead in some places. If unsure say N here.
989 bool "CPU core priorities scheduler support"
990 depends on SCHED_MC && CPU_SUP_INTEL
991 select X86_INTEL_PSTATE
995 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
996 core ordering determined at manufacturing time, which allows
997 certain cores to reach higher turbo frequencies (when running
998 single threaded workloads) than others.
1000 Enabling this kernel feature teaches the scheduler about
1001 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1002 scheduler's CPU selection logic accordingly, so that higher
1003 overall system performance can be achieved.
1005 This feature will have no effect on CPUs without this feature.
1007 If unsure say Y here.
1009 source "kernel/Kconfig.preempt"
1013 depends on !SMP && X86_LOCAL_APIC
1016 bool "Local APIC support on uniprocessors" if !PCI_MSI
1018 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1020 A local APIC (Advanced Programmable Interrupt Controller) is an
1021 integrated interrupt controller in the CPU. If you have a single-CPU
1022 system which has a processor with a local APIC, you can say Y here to
1023 enable and use it. If you say Y here even though your machine doesn't
1024 have a local APIC, then the kernel will still run with no slowdown at
1025 all. The local APIC supports CPU-generated self-interrupts (timer,
1026 performance counters), and the NMI watchdog which detects hard
1029 config X86_UP_IOAPIC
1030 bool "IO-APIC support on uniprocessors"
1031 depends on X86_UP_APIC
1033 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1034 SMP-capable replacement for PC-style interrupt controllers. Most
1035 SMP systems and many recent uniprocessor systems have one.
1037 If you have a single-CPU system with an IO-APIC, you can say Y here
1038 to use it. If you say Y here even though your machine doesn't have
1039 an IO-APIC, then the kernel will still run with no slowdown at all.
1041 config X86_LOCAL_APIC
1043 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1044 select IRQ_DOMAIN_HIERARCHY
1045 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1049 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1051 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1052 bool "Reroute for broken boot IRQs"
1053 depends on X86_IO_APIC
1055 This option enables a workaround that fixes a source of
1056 spurious interrupts. This is recommended when threaded
1057 interrupt handling is used on systems where the generation of
1058 superfluous "boot interrupts" cannot be disabled.
1060 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1061 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1062 kernel does during interrupt handling). On chipsets where this
1063 boot IRQ generation cannot be disabled, this workaround keeps
1064 the original IRQ line masked so that only the equivalent "boot
1065 IRQ" is delivered to the CPUs. The workaround also tells the
1066 kernel to set up the IRQ handler on the boot IRQ line. In this
1067 way only one interrupt is delivered to the kernel. Otherwise
1068 the spurious second interrupt may cause the kernel to bring
1069 down (vital) interrupt lines.
1071 Only affects "broken" chipsets. Interrupt sharing may be
1072 increased on these systems.
1075 bool "Machine Check / overheating reporting"
1076 select GENERIC_ALLOCATOR
1079 Machine Check support allows the processor to notify the
1080 kernel if it detects a problem (e.g. overheating, data corruption).
1081 The action the kernel takes depends on the severity of the problem,
1082 ranging from warning messages to halting the machine.
1084 config X86_MCELOG_LEGACY
1085 bool "Support for deprecated /dev/mcelog character device"
1088 Enable support for /dev/mcelog which is needed by the old mcelog
1089 userspace logging daemon. Consider switching to the new generation
1092 config X86_MCE_INTEL
1094 prompt "Intel MCE features"
1095 depends on X86_MCE && X86_LOCAL_APIC
1097 Additional support for intel specific MCE features such as
1098 the thermal monitor.
1102 prompt "AMD MCE features"
1103 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1105 Additional support for AMD specific MCE features such as
1106 the DRAM Error Threshold.
1108 config X86_ANCIENT_MCE
1109 bool "Support for old Pentium 5 / WinChip machine checks"
1110 depends on X86_32 && X86_MCE
1112 Include support for machine check handling on old Pentium 5 or WinChip
1113 systems. These typically need to be enabled explicitly on the command
1116 config X86_MCE_THRESHOLD
1117 depends on X86_MCE_AMD || X86_MCE_INTEL
1120 config X86_MCE_INJECT
1121 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1122 tristate "Machine check injector support"
1124 Provide support for injecting machine checks for testing purposes.
1125 If you don't know what a machine check is and you don't do kernel
1126 QA it is safe to say n.
1128 config X86_THERMAL_VECTOR
1130 depends on X86_MCE_INTEL
1132 source "arch/x86/events/Kconfig"
1134 config X86_LEGACY_VM86
1135 bool "Legacy VM86 support"
1139 This option allows user programs to put the CPU into V8086
1140 mode, which is an 80286-era approximation of 16-bit real mode.
1142 Some very old versions of X and/or vbetool require this option
1143 for user mode setting. Similarly, DOSEMU will use it if
1144 available to accelerate real mode DOS programs. However, any
1145 recent version of DOSEMU, X, or vbetool should be fully
1146 functional even without kernel VM86 support, as they will all
1147 fall back to software emulation. Nevertheless, if you are using
1148 a 16-bit DOS program where 16-bit performance matters, vm86
1149 mode might be faster than emulation and you might want to
1152 Note that any app that works on a 64-bit kernel is unlikely to
1153 need this option, as 64-bit kernels don't, and can't, support
1154 V8086 mode. This option is also unrelated to 16-bit protected
1155 mode and is not needed to run most 16-bit programs under Wine.
1157 Enabling this option increases the complexity of the kernel
1158 and slows down exception handling a tiny bit.
1160 If unsure, say N here.
1164 default X86_LEGACY_VM86
1167 bool "Enable support for 16-bit segments" if EXPERT
1169 depends on MODIFY_LDT_SYSCALL
1171 This option is required by programs like Wine to run 16-bit
1172 protected mode legacy code on x86 processors. Disabling
1173 this option saves about 300 bytes on i386, or around 6K text
1174 plus 16K runtime memory on x86-64,
1178 depends on X86_16BIT && X86_32
1182 depends on X86_16BIT && X86_64
1184 config X86_VSYSCALL_EMULATION
1185 bool "Enable vsyscall emulation" if EXPERT
1189 This enables emulation of the legacy vsyscall page. Disabling
1190 it is roughly equivalent to booting with vsyscall=none, except
1191 that it will also disable the helpful warning if a program
1192 tries to use a vsyscall. With this option set to N, offending
1193 programs will just segfault, citing addresses of the form
1196 This option is required by many programs built before 2013, and
1197 care should be used even with newer programs if set to N.
1199 Disabling this option saves about 7K of kernel size and
1200 possibly 4K of additional runtime pagetable memory.
1203 tristate "Toshiba Laptop support"
1206 This adds a driver to safely access the System Management Mode of
1207 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1208 not work on models with a Phoenix BIOS. The System Management Mode
1209 is used to set the BIOS and power saving options on Toshiba portables.
1211 For information on utilities to make use of this driver see the
1212 Toshiba Linux utilities web site at:
1213 <http://www.buzzard.org.uk/toshiba/>.
1215 Say Y if you intend to run this kernel on a Toshiba portable.
1219 tristate "Dell i8k legacy laptop support"
1221 select SENSORS_DELL_SMM
1223 This option enables legacy /proc/i8k userspace interface in hwmon
1224 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1225 temperature and allows controlling fan speeds of Dell laptops via
1226 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1227 it reports also power and hotkey status. For fan speed control is
1228 needed userspace package i8kutils.
1230 Say Y if you intend to run this kernel on old Dell laptops or want to
1231 use userspace package i8kutils.
1234 config X86_REBOOTFIXUPS
1235 bool "Enable X86 board specific fixups for reboot"
1238 This enables chipset and/or board specific fixups to be done
1239 in order to get reboot to work correctly. This is only needed on
1240 some combinations of hardware and BIOS. The symptom, for which
1241 this config is intended, is when reboot ends with a stalled/hung
1244 Currently, the only fixup is for the Geode machines using
1245 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1247 Say Y if you want to enable the fixup. Currently, it's safe to
1248 enable this option even if you don't need it.
1252 bool "CPU microcode loading support"
1254 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1257 If you say Y here, you will be able to update the microcode on
1258 Intel and AMD processors. The Intel support is for the IA32 family,
1259 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1260 AMD support is for families 0x10 and later. You will obviously need
1261 the actual microcode binary data itself which is not shipped with
1264 The preferred method to load microcode from a detached initrd is described
1265 in Documentation/x86/early-microcode.txt. For that you need to enable
1266 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1267 initrd for microcode blobs.
1269 In addition, you can build the microcode into the kernel. For that you
1270 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1273 config MICROCODE_INTEL
1274 bool "Intel microcode loading support"
1275 depends on MICROCODE
1279 This options enables microcode patch loading support for Intel
1282 For the current Intel microcode data package go to
1283 <https://downloadcenter.intel.com> and search for
1284 'Linux Processor Microcode Data File'.
1286 config MICROCODE_AMD
1287 bool "AMD microcode loading support"
1288 depends on MICROCODE
1291 If you select this option, microcode patch loading support for AMD
1292 processors will be enabled.
1294 config MICROCODE_OLD_INTERFACE
1296 depends on MICROCODE
1299 tristate "/dev/cpu/*/msr - Model-specific register support"
1301 This device gives privileged processes access to the x86
1302 Model-Specific Registers (MSRs). It is a character device with
1303 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1304 MSR accesses are directed to a specific CPU on multi-processor
1308 tristate "/dev/cpu/*/cpuid - CPU information support"
1310 This device gives processes access to the x86 CPUID instruction to
1311 be executed on a specific processor. It is a character device
1312 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1316 prompt "High Memory Support"
1323 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1324 However, the address space of 32-bit x86 processors is only 4
1325 Gigabytes large. That means that, if you have a large amount of
1326 physical memory, not all of it can be "permanently mapped" by the
1327 kernel. The physical memory that's not permanently mapped is called
1330 If you are compiling a kernel which will never run on a machine with
1331 more than 1 Gigabyte total physical RAM, answer "off" here (default
1332 choice and suitable for most users). This will result in a "3GB/1GB"
1333 split: 3GB are mapped so that each process sees a 3GB virtual memory
1334 space and the remaining part of the 4GB virtual memory space is used
1335 by the kernel to permanently map as much physical memory as
1338 If the machine has between 1 and 4 Gigabytes physical RAM, then
1341 If more than 4 Gigabytes is used then answer "64GB" here. This
1342 selection turns Intel PAE (Physical Address Extension) mode on.
1343 PAE implements 3-level paging on IA32 processors. PAE is fully
1344 supported by Linux, PAE mode is implemented on all recent Intel
1345 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1346 then the kernel will not boot on CPUs that don't support PAE!
1348 The actual amount of total physical memory will either be
1349 auto detected or can be forced by using a kernel command line option
1350 such as "mem=256M". (Try "man bootparam" or see the documentation of
1351 your boot loader (lilo or loadlin) about how to pass options to the
1352 kernel at boot time.)
1354 If unsure, say "off".
1359 Select this if you have a 32-bit processor and between 1 and 4
1360 gigabytes of physical RAM.
1367 Select this if you have a 32-bit processor and more than 4
1368 gigabytes of physical RAM.
1373 prompt "Memory split" if EXPERT
1377 Select the desired split between kernel and user memory.
1379 If the address range available to the kernel is less than the
1380 physical memory installed, the remaining memory will be available
1381 as "high memory". Accessing high memory is a little more costly
1382 than low memory, as it needs to be mapped into the kernel first.
1383 Note that increasing the kernel address space limits the range
1384 available to user programs, making the address space there
1385 tighter. Selecting anything other than the default 3G/1G split
1386 will also likely make your kernel incompatible with binary-only
1389 If you are not absolutely sure what you are doing, leave this
1393 bool "3G/1G user/kernel split"
1394 config VMSPLIT_3G_OPT
1396 bool "3G/1G user/kernel split (for full 1G low memory)"
1398 bool "2G/2G user/kernel split"
1399 config VMSPLIT_2G_OPT
1401 bool "2G/2G user/kernel split (for full 2G low memory)"
1403 bool "1G/3G user/kernel split"
1408 default 0xB0000000 if VMSPLIT_3G_OPT
1409 default 0x80000000 if VMSPLIT_2G
1410 default 0x78000000 if VMSPLIT_2G_OPT
1411 default 0x40000000 if VMSPLIT_1G
1417 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1420 bool "PAE (Physical Address Extension) Support"
1421 depends on X86_32 && !HIGHMEM4G
1424 PAE is required for NX support, and furthermore enables
1425 larger swapspace support for non-overcommit purposes. It
1426 has the cost of more pagetable lookup overhead, and also
1427 consumes more pagetable space per process.
1430 bool "Enable 5-level page tables support"
1433 5-level paging enables access to larger address space:
1434 upto 128 PiB of virtual address space and 4 PiB of
1435 physical address space.
1437 It will be supported by future Intel CPUs.
1439 Note: a kernel with this option enabled can only be booted
1440 on machines that support the feature.
1442 See Documentation/x86/x86_64/5level-paging.txt for more
1447 config ARCH_PHYS_ADDR_T_64BIT
1449 depends on X86_64 || X86_PAE
1451 config ARCH_DMA_ADDR_T_64BIT
1453 depends on X86_64 || HIGHMEM64G
1455 config X86_DIRECT_GBPAGES
1457 depends on X86_64 && !DEBUG_PAGEALLOC
1459 Certain kernel features effectively disable kernel
1460 linear 1 GB mappings (even if the CPU otherwise
1461 supports them), so don't confuse the user by printing
1462 that we have them enabled.
1464 config ARCH_HAS_MEM_ENCRYPT
1467 config AMD_MEM_ENCRYPT
1468 bool "AMD Secure Memory Encryption (SME) support"
1469 depends on X86_64 && CPU_SUP_AMD
1471 Say yes to enable support for the encryption of system memory.
1472 This requires an AMD processor that supports Secure Memory
1475 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1476 bool "Activate AMD Secure Memory Encryption (SME) by default"
1478 depends on AMD_MEM_ENCRYPT
1480 Say yes to have system memory encrypted by default if running on
1481 an AMD processor that supports Secure Memory Encryption (SME).
1483 If set to Y, then the encryption of system memory can be
1484 deactivated with the mem_encrypt=off command line option.
1486 If set to N, then the encryption of system memory can be
1487 activated with the mem_encrypt=on command line option.
1489 config ARCH_USE_MEMREMAP_PROT
1491 depends on AMD_MEM_ENCRYPT
1493 # Common NUMA Features
1495 bool "Numa Memory Allocation and Scheduler Support"
1497 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1498 default y if X86_BIGSMP
1500 Enable NUMA (Non Uniform Memory Access) support.
1502 The kernel will try to allocate memory used by a CPU on the
1503 local memory controller of the CPU and add some more
1504 NUMA awareness to the kernel.
1506 For 64-bit this is recommended if the system is Intel Core i7
1507 (or later), AMD Opteron, or EM64T NUMA.
1509 For 32-bit this is only needed if you boot a 32-bit
1510 kernel on a 64-bit NUMA platform.
1512 Otherwise, you should say N.
1516 prompt "Old style AMD Opteron NUMA detection"
1517 depends on X86_64 && NUMA && PCI
1519 Enable AMD NUMA node topology detection. You should say Y here if
1520 you have a multi processor AMD system. This uses an old method to
1521 read the NUMA configuration directly from the builtin Northbridge
1522 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1523 which also takes priority if both are compiled in.
1525 config X86_64_ACPI_NUMA
1527 prompt "ACPI NUMA detection"
1528 depends on X86_64 && NUMA && ACPI && PCI
1531 Enable ACPI SRAT based node topology detection.
1533 # Some NUMA nodes have memory ranges that span
1534 # other nodes. Even though a pfn is valid and
1535 # between a node's start and end pfns, it may not
1536 # reside on that node. See memmap_init_zone()
1538 config NODES_SPAN_OTHER_NODES
1540 depends on X86_64_ACPI_NUMA
1543 bool "NUMA emulation"
1546 Enable NUMA emulation. A flat machine will be split
1547 into virtual nodes when booted with "numa=fake=N", where N is the
1548 number of nodes. This is only useful for debugging.
1551 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1553 default "10" if MAXSMP
1554 default "6" if X86_64
1556 depends on NEED_MULTIPLE_NODES
1558 Specify the maximum number of NUMA Nodes available on the target
1559 system. Increases memory reserved to accommodate various tables.
1561 config ARCH_HAVE_MEMORY_PRESENT
1563 depends on X86_32 && DISCONTIGMEM
1565 config NEED_NODE_MEMMAP_SIZE
1567 depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
1569 config ARCH_FLATMEM_ENABLE
1571 depends on X86_32 && !NUMA
1573 config ARCH_DISCONTIGMEM_ENABLE
1575 depends on NUMA && X86_32
1577 config ARCH_DISCONTIGMEM_DEFAULT
1579 depends on NUMA && X86_32
1581 config ARCH_SPARSEMEM_ENABLE
1583 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1584 select SPARSEMEM_STATIC if X86_32
1585 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1587 config ARCH_SPARSEMEM_DEFAULT
1591 config ARCH_SELECT_MEMORY_MODEL
1593 depends on ARCH_SPARSEMEM_ENABLE
1595 config ARCH_MEMORY_PROBE
1596 bool "Enable sysfs memory/probe interface"
1597 depends on X86_64 && MEMORY_HOTPLUG
1599 This option enables a sysfs memory/probe interface for testing.
1600 See Documentation/memory-hotplug.txt for more information.
1601 If you are unsure how to answer this question, answer N.
1603 config ARCH_PROC_KCORE_TEXT
1605 depends on X86_64 && PROC_KCORE
1607 config ILLEGAL_POINTER_VALUE
1610 default 0xdead000000000000 if X86_64
1614 config X86_PMEM_LEGACY_DEVICE
1617 config X86_PMEM_LEGACY
1618 tristate "Support non-standard NVDIMMs and ADR protected memory"
1619 depends on PHYS_ADDR_T_64BIT
1621 select X86_PMEM_LEGACY_DEVICE
1624 Treat memory marked using the non-standard e820 type of 12 as used
1625 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1626 The kernel will offer these regions to the 'pmem' driver so
1627 they can be used for persistent storage.
1632 bool "Allocate 3rd-level pagetables from highmem"
1635 The VM uses one page table entry for each page of physical memory.
1636 For systems with a lot of RAM, this can be wasteful of precious
1637 low memory. Setting this option will put user-space page table
1638 entries in high memory.
1640 config X86_CHECK_BIOS_CORRUPTION
1641 bool "Check for low memory corruption"
1643 Periodically check for memory corruption in low memory, which
1644 is suspected to be caused by BIOS. Even when enabled in the
1645 configuration, it is disabled at runtime. Enable it by
1646 setting "memory_corruption_check=1" on the kernel command
1647 line. By default it scans the low 64k of memory every 60
1648 seconds; see the memory_corruption_check_size and
1649 memory_corruption_check_period parameters in
1650 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1652 When enabled with the default parameters, this option has
1653 almost no overhead, as it reserves a relatively small amount
1654 of memory and scans it infrequently. It both detects corruption
1655 and prevents it from affecting the running system.
1657 It is, however, intended as a diagnostic tool; if repeatable
1658 BIOS-originated corruption always affects the same memory,
1659 you can use memmap= to prevent the kernel from using that
1662 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1663 bool "Set the default setting of memory_corruption_check"
1664 depends on X86_CHECK_BIOS_CORRUPTION
1667 Set whether the default state of memory_corruption_check is
1670 config X86_RESERVE_LOW
1671 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1675 Specify the amount of low memory to reserve for the BIOS.
1677 The first page contains BIOS data structures that the kernel
1678 must not use, so that page must always be reserved.
1680 By default we reserve the first 64K of physical RAM, as a
1681 number of BIOSes are known to corrupt that memory range
1682 during events such as suspend/resume or monitor cable
1683 insertion, so it must not be used by the kernel.
1685 You can set this to 4 if you are absolutely sure that you
1686 trust the BIOS to get all its memory reservations and usages
1687 right. If you know your BIOS have problems beyond the
1688 default 64K area, you can set this to 640 to avoid using the
1689 entire low memory range.
1691 If you have doubts about the BIOS (e.g. suspend/resume does
1692 not work or there's kernel crashes after certain hardware
1693 hotplug events) then you might want to enable
1694 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1695 typical corruption patterns.
1697 Leave this to the default value of 64 if you are unsure.
1699 config MATH_EMULATION
1701 depends on MODIFY_LDT_SYSCALL
1702 prompt "Math emulation" if X86_32
1704 Linux can emulate a math coprocessor (used for floating point
1705 operations) if you don't have one. 486DX and Pentium processors have
1706 a math coprocessor built in, 486SX and 386 do not, unless you added
1707 a 487DX or 387, respectively. (The messages during boot time can
1708 give you some hints here ["man dmesg"].) Everyone needs either a
1709 coprocessor or this emulation.
1711 If you don't have a math coprocessor, you need to say Y here; if you
1712 say Y here even though you have a coprocessor, the coprocessor will
1713 be used nevertheless. (This behavior can be changed with the kernel
1714 command line option "no387", which comes handy if your coprocessor
1715 is broken. Try "man bootparam" or see the documentation of your boot
1716 loader (lilo or loadlin) about how to pass options to the kernel at
1717 boot time.) This means that it is a good idea to say Y here if you
1718 intend to use this kernel on different machines.
1720 More information about the internals of the Linux math coprocessor
1721 emulation can be found in <file:arch/x86/math-emu/README>.
1723 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1724 kernel, it won't hurt.
1728 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1730 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1731 the Memory Type Range Registers (MTRRs) may be used to control
1732 processor access to memory ranges. This is most useful if you have
1733 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1734 allows bus write transfers to be combined into a larger transfer
1735 before bursting over the PCI/AGP bus. This can increase performance
1736 of image write operations 2.5 times or more. Saying Y here creates a
1737 /proc/mtrr file which may be used to manipulate your processor's
1738 MTRRs. Typically the X server should use this.
1740 This code has a reasonably generic interface so that similar
1741 control registers on other processors can be easily supported
1744 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1745 Registers (ARRs) which provide a similar functionality to MTRRs. For
1746 these, the ARRs are used to emulate the MTRRs.
1747 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1748 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1749 write-combining. All of these processors are supported by this code
1750 and it makes sense to say Y here if you have one of them.
1752 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1753 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1754 can lead to all sorts of problems, so it's good to say Y here.
1756 You can safely say Y even if your machine doesn't have MTRRs, you'll
1757 just add about 9 KB to your kernel.
1759 See <file:Documentation/x86/mtrr.txt> for more information.
1761 config MTRR_SANITIZER
1763 prompt "MTRR cleanup support"
1766 Convert MTRR layout from continuous to discrete, so X drivers can
1767 add writeback entries.
1769 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1770 The largest mtrr entry size for a continuous block can be set with
1775 config MTRR_SANITIZER_ENABLE_DEFAULT
1776 int "MTRR cleanup enable value (0-1)"
1779 depends on MTRR_SANITIZER
1781 Enable mtrr cleanup default value
1783 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1784 int "MTRR cleanup spare reg num (0-7)"
1787 depends on MTRR_SANITIZER
1789 mtrr cleanup spare entries default, it can be changed via
1790 mtrr_spare_reg_nr=N on the kernel command line.
1794 prompt "x86 PAT support" if EXPERT
1797 Use PAT attributes to setup page level cache control.
1799 PATs are the modern equivalents of MTRRs and are much more
1800 flexible than MTRRs.
1802 Say N here if you see bootup problems (boot crash, boot hang,
1803 spontaneous reboots) or a non-working video driver.
1807 config ARCH_USES_PG_UNCACHED
1813 prompt "x86 architectural random number generator" if EXPERT
1815 Enable the x86 architectural RDRAND instruction
1816 (Intel Bull Mountain technology) to generate random numbers.
1817 If supported, this is a high bandwidth, cryptographically
1818 secure hardware random number generator.
1822 prompt "Supervisor Mode Access Prevention" if EXPERT
1824 Supervisor Mode Access Prevention (SMAP) is a security
1825 feature in newer Intel processors. There is a small
1826 performance cost if this enabled and turned on; there is
1827 also a small increase in the kernel size if this is enabled.
1831 config X86_INTEL_UMIP
1833 depends on CPU_SUP_INTEL
1834 prompt "Intel User Mode Instruction Prevention" if EXPERT
1836 The User Mode Instruction Prevention (UMIP) is a security
1837 feature in newer Intel processors. If enabled, a general
1838 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1839 or STR instructions are executed in user mode. These instructions
1840 unnecessarily expose information about the hardware state.
1842 The vast majority of applications do not use these instructions.
1843 For the very few that do, software emulation is provided in
1844 specific cases in protected and virtual-8086 modes. Emulated
1847 config X86_INTEL_MPX
1848 prompt "Intel MPX (Memory Protection Extensions)"
1850 # Note: only available in 64-bit mode due to VMA flags shortage
1851 depends on CPU_SUP_INTEL && X86_64
1852 select ARCH_USES_HIGH_VMA_FLAGS
1854 MPX provides hardware features that can be used in
1855 conjunction with compiler-instrumented code to check
1856 memory references. It is designed to detect buffer
1857 overflow or underflow bugs.
1859 This option enables running applications which are
1860 instrumented or otherwise use MPX. It does not use MPX
1861 itself inside the kernel or to protect the kernel
1862 against bad memory references.
1864 Enabling this option will make the kernel larger:
1865 ~8k of kernel text and 36 bytes of data on a 64-bit
1866 defconfig. It adds a long to the 'mm_struct' which
1867 will increase the kernel memory overhead of each
1868 process and adds some branches to paths used during
1869 exec() and munmap().
1871 For details, see Documentation/x86/intel_mpx.txt
1875 config X86_INTEL_MEMORY_PROTECTION_KEYS
1876 prompt "Intel Memory Protection Keys"
1878 # Note: only available in 64-bit mode
1879 depends on CPU_SUP_INTEL && X86_64
1880 select ARCH_USES_HIGH_VMA_FLAGS
1881 select ARCH_HAS_PKEYS
1883 Memory Protection Keys provides a mechanism for enforcing
1884 page-based protections, but without requiring modification of the
1885 page tables when an application changes protection domains.
1887 For details, see Documentation/x86/protection-keys.txt
1892 bool "EFI runtime service support"
1895 select EFI_RUNTIME_WRAPPERS
1897 This enables the kernel to use EFI runtime services that are
1898 available (such as the EFI variable services).
1900 This option is only useful on systems that have EFI firmware.
1901 In addition, you should use the latest ELILO loader available
1902 at <http://elilo.sourceforge.net> in order to take advantage
1903 of EFI runtime services. However, even with this option, the
1904 resultant kernel should continue to boot on existing non-EFI
1908 bool "EFI stub support"
1909 depends on EFI && !X86_USE_3DNOW
1912 This kernel feature allows a bzImage to be loaded directly
1913 by EFI firmware without the use of a bootloader.
1915 See Documentation/efi-stub.txt for more information.
1918 bool "EFI mixed-mode support"
1919 depends on EFI_STUB && X86_64
1921 Enabling this feature allows a 64-bit kernel to be booted
1922 on a 32-bit firmware, provided that your CPU supports 64-bit
1925 Note that it is not possible to boot a mixed-mode enabled
1926 kernel via the EFI boot stub - a bootloader that supports
1927 the EFI handover protocol must be used.
1933 prompt "Enable seccomp to safely compute untrusted bytecode"
1935 This kernel feature is useful for number crunching applications
1936 that may need to compute untrusted bytecode during their
1937 execution. By using pipes or other transports made available to
1938 the process as file descriptors supporting the read/write
1939 syscalls, it's possible to isolate those applications in
1940 their own address space using seccomp. Once seccomp is
1941 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1942 and the task is only allowed to execute a few safe syscalls
1943 defined by each seccomp mode.
1945 If unsure, say Y. Only embedded should say N here.
1947 source kernel/Kconfig.hz
1950 bool "kexec system call"
1953 kexec is a system call that implements the ability to shutdown your
1954 current kernel, and to start another kernel. It is like a reboot
1955 but it is independent of the system firmware. And like a reboot
1956 you can start any kernel with it, not just Linux.
1958 The name comes from the similarity to the exec system call.
1960 It is an ongoing process to be certain the hardware in a machine
1961 is properly shutdown, so do not be surprised if this code does not
1962 initially work for you. As of this writing the exact hardware
1963 interface is strongly in flux, so no good recommendation can be
1967 bool "kexec file based system call"
1972 depends on CRYPTO_SHA256=y
1974 This is new version of kexec system call. This system call is
1975 file based and takes file descriptors as system call argument
1976 for kernel and initramfs as opposed to list of segments as
1977 accepted by previous system call.
1979 config KEXEC_VERIFY_SIG
1980 bool "Verify kernel signature during kexec_file_load() syscall"
1981 depends on KEXEC_FILE
1983 This option makes kernel signature verification mandatory for
1984 the kexec_file_load() syscall.
1986 In addition to that option, you need to enable signature
1987 verification for the corresponding kernel image type being
1988 loaded in order for this to work.
1990 config KEXEC_BZIMAGE_VERIFY_SIG
1991 bool "Enable bzImage signature verification support"
1992 depends on KEXEC_VERIFY_SIG
1993 depends on SIGNED_PE_FILE_VERIFICATION
1994 select SYSTEM_TRUSTED_KEYRING
1996 Enable bzImage signature verification support.
1999 bool "kernel crash dumps"
2000 depends on X86_64 || (X86_32 && HIGHMEM)
2002 Generate crash dump after being started by kexec.
2003 This should be normally only set in special crash dump kernels
2004 which are loaded in the main kernel with kexec-tools into
2005 a specially reserved region and then later executed after
2006 a crash by kdump/kexec. The crash dump kernel must be compiled
2007 to a memory address not used by the main kernel or BIOS using
2008 PHYSICAL_START, or it must be built as a relocatable image
2009 (CONFIG_RELOCATABLE=y).
2010 For more details see Documentation/kdump/kdump.txt
2014 depends on KEXEC && HIBERNATION
2016 Jump between original kernel and kexeced kernel and invoke
2017 code in physical address mode via KEXEC
2019 config PHYSICAL_START
2020 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2023 This gives the physical address where the kernel is loaded.
2025 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2026 bzImage will decompress itself to above physical address and
2027 run from there. Otherwise, bzImage will run from the address where
2028 it has been loaded by the boot loader and will ignore above physical
2031 In normal kdump cases one does not have to set/change this option
2032 as now bzImage can be compiled as a completely relocatable image
2033 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2034 address. This option is mainly useful for the folks who don't want
2035 to use a bzImage for capturing the crash dump and want to use a
2036 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2037 to be specifically compiled to run from a specific memory area
2038 (normally a reserved region) and this option comes handy.
2040 So if you are using bzImage for capturing the crash dump,
2041 leave the value here unchanged to 0x1000000 and set
2042 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2043 for capturing the crash dump change this value to start of
2044 the reserved region. In other words, it can be set based on
2045 the "X" value as specified in the "crashkernel=YM@XM"
2046 command line boot parameter passed to the panic-ed
2047 kernel. Please take a look at Documentation/kdump/kdump.txt
2048 for more details about crash dumps.
2050 Usage of bzImage for capturing the crash dump is recommended as
2051 one does not have to build two kernels. Same kernel can be used
2052 as production kernel and capture kernel. Above option should have
2053 gone away after relocatable bzImage support is introduced. But it
2054 is present because there are users out there who continue to use
2055 vmlinux for dump capture. This option should go away down the
2058 Don't change this unless you know what you are doing.
2061 bool "Build a relocatable kernel"
2064 This builds a kernel image that retains relocation information
2065 so it can be loaded someplace besides the default 1MB.
2066 The relocations tend to make the kernel binary about 10% larger,
2067 but are discarded at runtime.
2069 One use is for the kexec on panic case where the recovery kernel
2070 must live at a different physical address than the primary
2073 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2074 it has been loaded at and the compile time physical address
2075 (CONFIG_PHYSICAL_START) is used as the minimum location.
2077 config RANDOMIZE_BASE
2078 bool "Randomize the address of the kernel image (KASLR)"
2079 depends on RELOCATABLE
2082 In support of Kernel Address Space Layout Randomization (KASLR),
2083 this randomizes the physical address at which the kernel image
2084 is decompressed and the virtual address where the kernel
2085 image is mapped, as a security feature that deters exploit
2086 attempts relying on knowledge of the location of kernel
2089 On 64-bit, the kernel physical and virtual addresses are
2090 randomized separately. The physical address will be anywhere
2091 between 16MB and the top of physical memory (up to 64TB). The
2092 virtual address will be randomized from 16MB up to 1GB (9 bits
2093 of entropy). Note that this also reduces the memory space
2094 available to kernel modules from 1.5GB to 1GB.
2096 On 32-bit, the kernel physical and virtual addresses are
2097 randomized together. They will be randomized from 16MB up to
2098 512MB (8 bits of entropy).
2100 Entropy is generated using the RDRAND instruction if it is
2101 supported. If RDTSC is supported, its value is mixed into
2102 the entropy pool as well. If neither RDRAND nor RDTSC are
2103 supported, then entropy is read from the i8254 timer. The
2104 usable entropy is limited by the kernel being built using
2105 2GB addressing, and that PHYSICAL_ALIGN must be at a
2106 minimum of 2MB. As a result, only 10 bits of entropy are
2107 theoretically possible, but the implementations are further
2108 limited due to memory layouts.
2112 # Relocation on x86 needs some additional build support
2113 config X86_NEED_RELOCS
2115 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2117 config PHYSICAL_ALIGN
2118 hex "Alignment value to which kernel should be aligned"
2120 range 0x2000 0x1000000 if X86_32
2121 range 0x200000 0x1000000 if X86_64
2123 This value puts the alignment restrictions on physical address
2124 where kernel is loaded and run from. Kernel is compiled for an
2125 address which meets above alignment restriction.
2127 If bootloader loads the kernel at a non-aligned address and
2128 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2129 address aligned to above value and run from there.
2131 If bootloader loads the kernel at a non-aligned address and
2132 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2133 load address and decompress itself to the address it has been
2134 compiled for and run from there. The address for which kernel is
2135 compiled already meets above alignment restrictions. Hence the
2136 end result is that kernel runs from a physical address meeting
2137 above alignment restrictions.
2139 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2140 this value must be a multiple of 0x200000.
2142 Don't change this unless you know what you are doing.
2144 config RANDOMIZE_MEMORY
2145 bool "Randomize the kernel memory sections"
2147 depends on RANDOMIZE_BASE
2148 default RANDOMIZE_BASE
2150 Randomizes the base virtual address of kernel memory sections
2151 (physical memory mapping, vmalloc & vmemmap). This security feature
2152 makes exploits relying on predictable memory locations less reliable.
2154 The order of allocations remains unchanged. Entropy is generated in
2155 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2156 configuration have in average 30,000 different possible virtual
2157 addresses for each memory section.
2161 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2162 hex "Physical memory mapping padding" if EXPERT
2163 depends on RANDOMIZE_MEMORY
2164 default "0xa" if MEMORY_HOTPLUG
2166 range 0x1 0x40 if MEMORY_HOTPLUG
2169 Define the padding in terabytes added to the existing physical
2170 memory size during kernel memory randomization. It is useful
2171 for memory hotplug support but reduces the entropy available for
2172 address randomization.
2174 If unsure, leave at the default value.
2177 bool "Support for hot-pluggable CPUs"
2180 Say Y here to allow turning CPUs off and on. CPUs can be
2181 controlled through /sys/devices/system/cpu.
2182 ( Note: power management support will enable this option
2183 automatically on SMP systems. )
2184 Say N if you want to disable CPU hotplug.
2186 config BOOTPARAM_HOTPLUG_CPU0
2187 bool "Set default setting of cpu0_hotpluggable"
2189 depends on HOTPLUG_CPU
2191 Set whether default state of cpu0_hotpluggable is on or off.
2193 Say Y here to enable CPU0 hotplug by default. If this switch
2194 is turned on, there is no need to give cpu0_hotplug kernel
2195 parameter and the CPU0 hotplug feature is enabled by default.
2197 Please note: there are two known CPU0 dependencies if you want
2198 to enable the CPU0 hotplug feature either by this switch or by
2199 cpu0_hotplug kernel parameter.
2201 First, resume from hibernate or suspend always starts from CPU0.
2202 So hibernate and suspend are prevented if CPU0 is offline.
2204 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2205 offline if any interrupt can not migrate out of CPU0. There may
2206 be other CPU0 dependencies.
2208 Please make sure the dependencies are under your control before
2209 you enable this feature.
2211 Say N if you don't want to enable CPU0 hotplug feature by default.
2212 You still can enable the CPU0 hotplug feature at boot by kernel
2213 parameter cpu0_hotplug.
2215 config DEBUG_HOTPLUG_CPU0
2217 prompt "Debug CPU0 hotplug"
2218 depends on HOTPLUG_CPU
2220 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2221 soon as possible and boots up userspace with CPU0 offlined. User
2222 can online CPU0 back after boot time.
2224 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2225 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2226 compilation or giving cpu0_hotplug kernel parameter at boot.
2232 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2233 depends on COMPAT_32
2235 Certain buggy versions of glibc will crash if they are
2236 presented with a 32-bit vDSO that is not mapped at the address
2237 indicated in its segment table.
2239 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2240 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2241 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2242 the only released version with the bug, but OpenSUSE 9
2243 contains a buggy "glibc 2.3.2".
2245 The symptom of the bug is that everything crashes on startup, saying:
2246 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2248 Saying Y here changes the default value of the vdso32 boot
2249 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2250 This works around the glibc bug but hurts performance.
2252 If unsure, say N: if you are compiling your own kernel, you
2253 are unlikely to be using a buggy version of glibc.
2256 prompt "vsyscall table for legacy applications"
2258 default LEGACY_VSYSCALL_EMULATE
2260 Legacy user code that does not know how to find the vDSO expects
2261 to be able to issue three syscalls by calling fixed addresses in
2262 kernel space. Since this location is not randomized with ASLR,
2263 it can be used to assist security vulnerability exploitation.
2265 This setting can be changed at boot time via the kernel command
2266 line parameter vsyscall=[native|emulate|none].
2268 On a system with recent enough glibc (2.14 or newer) and no
2269 static binaries, you can say None without a performance penalty
2270 to improve security.
2272 If unsure, select "Emulate".
2274 config LEGACY_VSYSCALL_NATIVE
2277 Actual executable code is located in the fixed vsyscall
2278 address mapping, implementing time() efficiently. Since
2279 this makes the mapping executable, it can be used during
2280 security vulnerability exploitation (traditionally as
2281 ROP gadgets). This configuration is not recommended.
2283 config LEGACY_VSYSCALL_EMULATE
2286 The kernel traps and emulates calls into the fixed
2287 vsyscall address mapping. This makes the mapping
2288 non-executable, but it still contains known contents,
2289 which could be used in certain rare security vulnerability
2290 exploits. This configuration is recommended when userspace
2291 still uses the vsyscall area.
2293 config LEGACY_VSYSCALL_NONE
2296 There will be no vsyscall mapping at all. This will
2297 eliminate any risk of ASLR bypass due to the vsyscall
2298 fixed address mapping. Attempts to use the vsyscalls
2299 will be reported to dmesg, so that either old or
2300 malicious userspace programs can be identified.
2305 bool "Built-in kernel command line"
2307 Allow for specifying boot arguments to the kernel at
2308 build time. On some systems (e.g. embedded ones), it is
2309 necessary or convenient to provide some or all of the
2310 kernel boot arguments with the kernel itself (that is,
2311 to not rely on the boot loader to provide them.)
2313 To compile command line arguments into the kernel,
2314 set this option to 'Y', then fill in the
2315 boot arguments in CONFIG_CMDLINE.
2317 Systems with fully functional boot loaders (i.e. non-embedded)
2318 should leave this option set to 'N'.
2321 string "Built-in kernel command string"
2322 depends on CMDLINE_BOOL
2325 Enter arguments here that should be compiled into the kernel
2326 image and used at boot time. If the boot loader provides a
2327 command line at boot time, it is appended to this string to
2328 form the full kernel command line, when the system boots.
2330 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2331 change this behavior.
2333 In most cases, the command line (whether built-in or provided
2334 by the boot loader) should specify the device for the root
2337 config CMDLINE_OVERRIDE
2338 bool "Built-in command line overrides boot loader arguments"
2339 depends on CMDLINE_BOOL
2341 Set this option to 'Y' to have the kernel ignore the boot loader
2342 command line, and use ONLY the built-in command line.
2344 This is used to work around broken boot loaders. This should
2345 be set to 'N' under normal conditions.
2347 config MODIFY_LDT_SYSCALL
2348 bool "Enable the LDT (local descriptor table)" if EXPERT
2351 Linux can allow user programs to install a per-process x86
2352 Local Descriptor Table (LDT) using the modify_ldt(2) system
2353 call. This is required to run 16-bit or segmented code such as
2354 DOSEMU or some Wine programs. It is also used by some very old
2355 threading libraries.
2357 Enabling this feature adds a small amount of overhead to
2358 context switches and increases the low-level kernel attack
2359 surface. Disabling it removes the modify_ldt(2) system call.
2361 Saying 'N' here may make sense for embedded or server kernels.
2363 source "kernel/livepatch/Kconfig"
2367 config ARCH_HAS_ADD_PAGES
2369 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2371 config ARCH_ENABLE_MEMORY_HOTPLUG
2373 depends on X86_64 || (X86_32 && HIGHMEM)
2375 config ARCH_ENABLE_MEMORY_HOTREMOVE
2377 depends on MEMORY_HOTPLUG
2379 config USE_PERCPU_NUMA_NODE_ID
2383 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2385 depends on X86_64 || X86_PAE
2387 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2389 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2391 config ARCH_ENABLE_THP_MIGRATION
2393 depends on X86_64 && TRANSPARENT_HUGEPAGE
2395 menu "Power management and ACPI options"
2397 config ARCH_HIBERNATION_HEADER
2399 depends on X86_64 && HIBERNATION
2401 source "kernel/power/Kconfig"
2403 source "drivers/acpi/Kconfig"
2405 source "drivers/sfi/Kconfig"
2412 tristate "APM (Advanced Power Management) BIOS support"
2413 depends on X86_32 && PM_SLEEP
2415 APM is a BIOS specification for saving power using several different
2416 techniques. This is mostly useful for battery powered laptops with
2417 APM compliant BIOSes. If you say Y here, the system time will be
2418 reset after a RESUME operation, the /proc/apm device will provide
2419 battery status information, and user-space programs will receive
2420 notification of APM "events" (e.g. battery status change).
2422 If you select "Y" here, you can disable actual use of the APM
2423 BIOS by passing the "apm=off" option to the kernel at boot time.
2425 Note that the APM support is almost completely disabled for
2426 machines with more than one CPU.
2428 In order to use APM, you will need supporting software. For location
2429 and more information, read <file:Documentation/power/apm-acpi.txt>
2430 and the Battery Powered Linux mini-HOWTO, available from
2431 <http://www.tldp.org/docs.html#howto>.
2433 This driver does not spin down disk drives (see the hdparm(8)
2434 manpage ("man 8 hdparm") for that), and it doesn't turn off
2435 VESA-compliant "green" monitors.
2437 This driver does not support the TI 4000M TravelMate and the ACER
2438 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2439 desktop machines also don't have compliant BIOSes, and this driver
2440 may cause those machines to panic during the boot phase.
2442 Generally, if you don't have a battery in your machine, there isn't
2443 much point in using this driver and you should say N. If you get
2444 random kernel OOPSes or reboots that don't seem to be related to
2445 anything, try disabling/enabling this option (or disabling/enabling
2448 Some other things you should try when experiencing seemingly random,
2451 1) make sure that you have enough swap space and that it is
2453 2) pass the "no-hlt" option to the kernel
2454 3) switch on floating point emulation in the kernel and pass
2455 the "no387" option to the kernel
2456 4) pass the "floppy=nodma" option to the kernel
2457 5) pass the "mem=4M" option to the kernel (thereby disabling
2458 all but the first 4 MB of RAM)
2459 6) make sure that the CPU is not over clocked.
2460 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2461 8) disable the cache from your BIOS settings
2462 9) install a fan for the video card or exchange video RAM
2463 10) install a better fan for the CPU
2464 11) exchange RAM chips
2465 12) exchange the motherboard.
2467 To compile this driver as a module, choose M here: the
2468 module will be called apm.
2472 config APM_IGNORE_USER_SUSPEND
2473 bool "Ignore USER SUSPEND"
2475 This option will ignore USER SUSPEND requests. On machines with a
2476 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2477 series notebooks, it is necessary to say Y because of a BIOS bug.
2479 config APM_DO_ENABLE
2480 bool "Enable PM at boot time"
2482 Enable APM features at boot time. From page 36 of the APM BIOS
2483 specification: "When disabled, the APM BIOS does not automatically
2484 power manage devices, enter the Standby State, enter the Suspend
2485 State, or take power saving steps in response to CPU Idle calls."
2486 This driver will make CPU Idle calls when Linux is idle (unless this
2487 feature is turned off -- see "Do CPU IDLE calls", below). This
2488 should always save battery power, but more complicated APM features
2489 will be dependent on your BIOS implementation. You may need to turn
2490 this option off if your computer hangs at boot time when using APM
2491 support, or if it beeps continuously instead of suspending. Turn
2492 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2493 T400CDT. This is off by default since most machines do fine without
2498 bool "Make CPU Idle calls when idle"
2500 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2501 On some machines, this can activate improved power savings, such as
2502 a slowed CPU clock rate, when the machine is idle. These idle calls
2503 are made after the idle loop has run for some length of time (e.g.,
2504 333 mS). On some machines, this will cause a hang at boot time or
2505 whenever the CPU becomes idle. (On machines with more than one CPU,
2506 this option does nothing.)
2508 config APM_DISPLAY_BLANK
2509 bool "Enable console blanking using APM"
2511 Enable console blanking using the APM. Some laptops can use this to
2512 turn off the LCD backlight when the screen blanker of the Linux
2513 virtual console blanks the screen. Note that this is only used by
2514 the virtual console screen blanker, and won't turn off the backlight
2515 when using the X Window system. This also doesn't have anything to
2516 do with your VESA-compliant power-saving monitor. Further, this
2517 option doesn't work for all laptops -- it might not turn off your
2518 backlight at all, or it might print a lot of errors to the console,
2519 especially if you are using gpm.
2521 config APM_ALLOW_INTS
2522 bool "Allow interrupts during APM BIOS calls"
2524 Normally we disable external interrupts while we are making calls to
2525 the APM BIOS as a measure to lessen the effects of a badly behaving
2526 BIOS implementation. The BIOS should reenable interrupts if it
2527 needs to. Unfortunately, some BIOSes do not -- especially those in
2528 many of the newer IBM Thinkpads. If you experience hangs when you
2529 suspend, try setting this to Y. Otherwise, say N.
2533 source "drivers/cpufreq/Kconfig"
2535 source "drivers/cpuidle/Kconfig"
2537 source "drivers/idle/Kconfig"
2542 menu "Bus options (PCI etc.)"
2548 Find out whether you have a PCI motherboard. PCI is the name of a
2549 bus system, i.e. the way the CPU talks to the other stuff inside
2550 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2551 VESA. If you have PCI, say Y, otherwise N.
2554 prompt "PCI access mode"
2555 depends on X86_32 && PCI
2558 On PCI systems, the BIOS can be used to detect the PCI devices and
2559 determine their configuration. However, some old PCI motherboards
2560 have BIOS bugs and may crash if this is done. Also, some embedded
2561 PCI-based systems don't have any BIOS at all. Linux can also try to
2562 detect the PCI hardware directly without using the BIOS.
2564 With this option, you can specify how Linux should detect the
2565 PCI devices. If you choose "BIOS", the BIOS will be used,
2566 if you choose "Direct", the BIOS won't be used, and if you
2567 choose "MMConfig", then PCI Express MMCONFIG will be used.
2568 If you choose "Any", the kernel will try MMCONFIG, then the
2569 direct access method and falls back to the BIOS if that doesn't
2570 work. If unsure, go with the default, which is "Any".
2575 config PCI_GOMMCONFIG
2592 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2594 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2597 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2601 depends on X86_32 && PCI && (ACPI || SFI) && (PCI_GOMMCONFIG || PCI_GOANY)
2605 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2609 depends on PCI && XEN
2617 bool "Support mmconfig PCI config space access"
2618 depends on X86_64 && PCI && ACPI
2620 config PCI_CNB20LE_QUIRK
2621 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2624 Read the PCI windows out of the CNB20LE host bridge. This allows
2625 PCI hotplug to work on systems with the CNB20LE chipset which do
2628 There's no public spec for this chipset, and this functionality
2629 is known to be incomplete.
2631 You should say N unless you know you need this.
2633 source "drivers/pci/Kconfig"
2636 bool "ISA-style bus support on modern systems" if EXPERT
2639 Enables ISA-style drivers on modern systems. This is necessary to
2640 support PC/104 devices on X86_64 platforms.
2644 # x86_64 have no ISA slots, but can have ISA-style DMA.
2646 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2649 Enables ISA-style DMA support for devices requiring such controllers.
2657 Find out whether you have ISA slots on your motherboard. ISA is the
2658 name of a bus system, i.e. the way the CPU talks to the other stuff
2659 inside your box. Other bus systems are PCI, EISA, MicroChannel
2660 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2661 newer boards don't support it. If you have ISA, say Y, otherwise N.
2667 The Extended Industry Standard Architecture (EISA) bus was
2668 developed as an open alternative to the IBM MicroChannel bus.
2670 The EISA bus provided some of the features of the IBM MicroChannel
2671 bus while maintaining backward compatibility with cards made for
2672 the older ISA bus. The EISA bus saw limited use between 1988 and
2673 1995 when it was made obsolete by the PCI bus.
2675 Say Y here if you are building a kernel for an EISA-based machine.
2679 source "drivers/eisa/Kconfig"
2682 tristate "NatSemi SCx200 support"
2684 This provides basic support for National Semiconductor's
2685 (now AMD's) Geode processors. The driver probes for the
2686 PCI-IDs of several on-chip devices, so its a good dependency
2687 for other scx200_* drivers.
2689 If compiled as a module, the driver is named scx200.
2691 config SCx200HR_TIMER
2692 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2696 This driver provides a clocksource built upon the on-chip
2697 27MHz high-resolution timer. Its also a workaround for
2698 NSC Geode SC-1100's buggy TSC, which loses time when the
2699 processor goes idle (as is done by the scheduler). The
2700 other workaround is idle=poll boot option.
2703 bool "One Laptop Per Child support"
2710 Add support for detecting the unique features of the OLPC
2714 bool "OLPC XO-1 Power Management"
2715 depends on OLPC && MFD_CS5535 && PM_SLEEP
2718 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2721 bool "OLPC XO-1 Real Time Clock"
2722 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2724 Add support for the XO-1 real time clock, which can be used as a
2725 programmable wakeup source.
2728 bool "OLPC XO-1 SCI extras"
2729 depends on OLPC && OLPC_XO1_PM
2735 Add support for SCI-based features of the OLPC XO-1 laptop:
2736 - EC-driven system wakeups
2740 - AC adapter status updates
2741 - Battery status updates
2743 config OLPC_XO15_SCI
2744 bool "OLPC XO-1.5 SCI extras"
2745 depends on OLPC && ACPI
2748 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2749 - EC-driven system wakeups
2750 - AC adapter status updates
2751 - Battery status updates
2754 bool "PCEngines ALIX System Support (LED setup)"
2757 This option enables system support for the PCEngines ALIX.
2758 At present this just sets up LEDs for GPIO control on
2759 ALIX2/3/6 boards. However, other system specific setup should
2762 Note: You must still enable the drivers for GPIO and LED support
2763 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2765 Note: You have to set alix.force=1 for boards with Award BIOS.
2768 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2771 This option enables system support for the Soekris Engineering net5501.
2774 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2778 This option enables system support for the Traverse Technologies GEOS.
2781 bool "Technologic Systems TS-5500 platform support"
2783 select CHECK_SIGNATURE
2787 This option enables system support for the Technologic Systems TS-5500.
2793 depends on CPU_SUP_AMD && PCI
2795 source "drivers/pcmcia/Kconfig"
2798 tristate "RapidIO support"
2802 If enabled this option will include drivers and the core
2803 infrastructure code to support RapidIO interconnect devices.
2805 source "drivers/rapidio/Kconfig"
2808 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2810 Firmwares often provide initial graphics framebuffers so the BIOS,
2811 bootloader or kernel can show basic video-output during boot for
2812 user-guidance and debugging. Historically, x86 used the VESA BIOS
2813 Extensions and EFI-framebuffers for this, which are mostly limited
2815 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2816 framebuffers so the new generic system-framebuffer drivers can be
2817 used on x86. If the framebuffer is not compatible with the generic
2818 modes, it is adverticed as fallback platform framebuffer so legacy
2819 drivers like efifb, vesafb and uvesafb can pick it up.
2820 If this option is not selected, all system framebuffers are always
2821 marked as fallback platform framebuffers as usual.
2823 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2824 not be able to pick up generic system framebuffers if this option
2825 is selected. You are highly encouraged to enable simplefb as
2826 replacement if you select this option. simplefb can correctly deal
2827 with generic system framebuffers. But you should still keep vesafb
2828 and others enabled as fallback if a system framebuffer is
2829 incompatible with simplefb.
2836 menu "Executable file formats / Emulations"
2838 source "fs/Kconfig.binfmt"
2840 config IA32_EMULATION
2841 bool "IA32 Emulation"
2843 select ARCH_WANT_OLD_COMPAT_IPC
2845 select COMPAT_BINFMT_ELF
2846 select COMPAT_OLD_SIGACTION
2848 Include code to run legacy 32-bit programs under a
2849 64-bit kernel. You should likely turn this on, unless you're
2850 100% sure that you don't have any 32-bit programs left.
2853 tristate "IA32 a.out support"
2854 depends on IA32_EMULATION
2856 Support old a.out binaries in the 32bit emulation.
2859 bool "x32 ABI for 64-bit mode"
2862 Include code to run binaries for the x32 native 32-bit ABI
2863 for 64-bit processors. An x32 process gets access to the
2864 full 64-bit register file and wide data path while leaving
2865 pointers at 32 bits for smaller memory footprint.
2867 You will need a recent binutils (2.22 or later) with
2868 elf32_x86_64 support enabled to compile a kernel with this
2873 depends on IA32_EMULATION || X86_32
2875 select OLD_SIGSUSPEND3
2879 depends on IA32_EMULATION || X86_X32
2882 config COMPAT_FOR_U64_ALIGNMENT
2885 config SYSVIPC_COMPAT
2893 config HAVE_ATOMIC_IOMAP
2897 config X86_DEV_DMA_OPS
2899 depends on X86_64 || STA2X11
2901 config X86_DMA_REMAP
2905 config HAVE_GENERIC_GUP
2908 source "net/Kconfig"
2910 source "drivers/Kconfig"
2912 source "drivers/firmware/Kconfig"
2916 source "arch/x86/Kconfig.debug"
2918 source "security/Kconfig"
2920 source "crypto/Kconfig"
2922 source "arch/x86/kvm/Kconfig"
2924 source "lib/Kconfig"