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_CPU_FINALIZE_INIT
51 select ARCH_HAS_DEBUG_VIRTUAL
52 select ARCH_HAS_DEVMEM_IS_ALLOWED
53 select ARCH_HAS_ELF_RANDOMIZE
54 select ARCH_HAS_FAST_MULTIPLIER
55 select ARCH_HAS_FORTIFY_SOURCE
56 select ARCH_HAS_GCOV_PROFILE_ALL
57 select ARCH_HAS_KCOV if X86_64
58 select ARCH_HAS_PMEM_API if X86_64
59 # Causing hangs/crashes, see the commit that added this change for details.
60 select ARCH_HAS_REFCOUNT
61 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
62 select ARCH_HAS_SET_MEMORY
63 select ARCH_HAS_SG_CHAIN
64 select ARCH_HAS_STRICT_KERNEL_RWX
65 select ARCH_HAS_STRICT_MODULE_RWX
66 select ARCH_HAS_UBSAN_SANITIZE_ALL
67 select ARCH_HAS_ZONE_DEVICE if X86_64
68 select ARCH_HAVE_NMI_SAFE_CMPXCHG
69 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
70 select ARCH_MIGHT_HAVE_PC_PARPORT
71 select ARCH_MIGHT_HAVE_PC_SERIO
72 select ARCH_SUPPORTS_ATOMIC_RMW
73 select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
74 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
75 select ARCH_USE_BUILTIN_BSWAP
76 select ARCH_USE_QUEUED_RWLOCKS
77 select ARCH_USE_QUEUED_SPINLOCKS
78 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
79 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
80 select ARCH_WANTS_THP_SWAP if X86_64
81 select BUILDTIME_EXTABLE_SORT
83 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
84 select CLOCKSOURCE_WATCHDOG
85 select DCACHE_WORD_ACCESS
86 select EDAC_ATOMIC_SCRUB
88 select GENERIC_CLOCKEVENTS
89 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
90 select GENERIC_CLOCKEVENTS_MIN_ADJUST
91 select GENERIC_CMOS_UPDATE
92 select GENERIC_CPU_AUTOPROBE
93 select GENERIC_CPU_VULNERABILITIES
94 select GENERIC_EARLY_IOREMAP
95 select GENERIC_FIND_FIRST_BIT
97 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
98 select GENERIC_IRQ_MIGRATION if SMP
99 select GENERIC_IRQ_PROBE
100 select GENERIC_IRQ_SHOW
101 select GENERIC_PENDING_IRQ if SMP
102 select GENERIC_SMP_IDLE_THREAD
103 select GENERIC_STRNCPY_FROM_USER
104 select GENERIC_STRNLEN_USER
105 select GENERIC_TIME_VSYSCALL
106 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
107 select HAVE_ACPI_APEI if ACPI
108 select HAVE_ACPI_APEI_NMI if ACPI
109 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
110 select HAVE_ARCH_AUDITSYSCALL
111 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
112 select HAVE_ARCH_JUMP_LABEL
113 select HAVE_ARCH_KASAN if X86_64
114 select HAVE_ARCH_KGDB
115 select HAVE_ARCH_MMAP_RND_BITS if MMU
116 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
117 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
118 select HAVE_ARCH_SECCOMP_FILTER
119 select HAVE_ARCH_TRACEHOOK
120 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
121 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
122 select HAVE_ARCH_VMAP_STACK if X86_64
123 select HAVE_ARCH_WITHIN_STACK_FRAMES
124 select HAVE_CC_STACKPROTECTOR
125 select HAVE_CMPXCHG_DOUBLE
126 select HAVE_CMPXCHG_LOCAL
127 select HAVE_CONTEXT_TRACKING if X86_64
128 select HAVE_COPY_THREAD_TLS
129 select HAVE_C_RECORDMCOUNT
130 select HAVE_DEBUG_KMEMLEAK
131 select HAVE_DEBUG_STACKOVERFLOW
132 select HAVE_DMA_API_DEBUG
133 select HAVE_DMA_CONTIGUOUS
134 select HAVE_DYNAMIC_FTRACE
135 select HAVE_DYNAMIC_FTRACE_WITH_REGS
136 select HAVE_EBPF_JIT if X86_64
137 select HAVE_EFFICIENT_UNALIGNED_ACCESS
138 select HAVE_EXIT_THREAD
139 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
140 select HAVE_FTRACE_MCOUNT_RECORD
141 select HAVE_FUNCTION_GRAPH_TRACER
142 select HAVE_FUNCTION_TRACER
143 select HAVE_GCC_PLUGINS
144 select HAVE_HW_BREAKPOINT
146 select HAVE_IOREMAP_PROT
147 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
148 select HAVE_IRQ_TIME_ACCOUNTING
149 select HAVE_KERNEL_BZIP2
150 select HAVE_KERNEL_GZIP
151 select HAVE_KERNEL_LZ4
152 select HAVE_KERNEL_LZMA
153 select HAVE_KERNEL_LZO
154 select HAVE_KERNEL_XZ
156 select HAVE_KPROBES_ON_FTRACE
157 select HAVE_KRETPROBES
159 select HAVE_LIVEPATCH if X86_64
161 select HAVE_MEMBLOCK_NODE_MAP
162 select HAVE_MIXED_BREAKPOINTS_REGS
163 select HAVE_MOD_ARCH_SPECIFIC
166 select HAVE_OPTPROBES
167 select HAVE_PCSPKR_PLATFORM
168 select HAVE_PERF_EVENTS
169 select HAVE_PERF_EVENTS_NMI
170 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
171 select HAVE_PERF_REGS
172 select HAVE_PERF_USER_STACK_DUMP
173 select HAVE_RCU_TABLE_FREE
174 select HAVE_RCU_TABLE_INVALIDATE if HAVE_RCU_TABLE_FREE
175 select HAVE_REGS_AND_STACK_ACCESS_API
176 select HAVE_RELIABLE_STACKTRACE if X86_64 && UNWINDER_FRAME_POINTER && STACK_VALIDATION
177 select HAVE_STACK_VALIDATION if X86_64
178 select HAVE_SYSCALL_TRACEPOINTS
179 select HAVE_UNSTABLE_SCHED_CLOCK
180 select HAVE_USER_RETURN_NOTIFIER
181 select HOTPLUG_SMT if SMP
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"
437 select STACK_VALIDATION if HAVE_STACK_VALIDATION
439 Compile kernel with the retpoline compiler options to guard against
440 kernel-to-user data leaks by avoiding speculative indirect
441 branches. Requires a compiler with -mindirect-branch=thunk-extern
442 support for full protection. The kernel may run slower.
445 bool "Intel Resource Director Technology support"
447 depends on X86 && CPU_SUP_INTEL
450 Select to enable resource allocation and monitoring which are
451 sub-features of Intel Resource Director Technology(RDT). More
452 information about RDT can be found in the Intel x86
453 Architecture Software Developer Manual.
458 config X86_EXTENDED_PLATFORM
459 bool "Support for extended (non-PC) x86 platforms"
462 If you disable this option then the kernel will only support
463 standard PC platforms. (which covers the vast majority of
466 If you enable this option then you'll be able to select support
467 for the following (non-PC) 32 bit x86 platforms:
468 Goldfish (Android emulator)
471 SGI 320/540 (Visual Workstation)
472 STA2X11-based (e.g. Northville)
473 Moorestown MID devices
475 If you have one of these systems, or if you want to build a
476 generic distribution kernel, say Y here - otherwise say N.
480 config X86_EXTENDED_PLATFORM
481 bool "Support for extended (non-PC) x86 platforms"
484 If you disable this option then the kernel will only support
485 standard PC platforms. (which covers the vast majority of
488 If you enable this option then you'll be able to select support
489 for the following (non-PC) 64 bit x86 platforms:
494 If you have one of these systems, or if you want to build a
495 generic distribution kernel, say Y here - otherwise say N.
497 # This is an alphabetically sorted list of 64 bit extended platforms
498 # Please maintain the alphabetic order if and when there are additions
500 bool "Numascale NumaChip"
502 depends on X86_EXTENDED_PLATFORM
505 depends on X86_X2APIC
506 depends on PCI_MMCONFIG
508 Adds support for Numascale NumaChip large-SMP systems. Needed to
509 enable more than ~168 cores.
510 If you don't have one of these, you should say N here.
514 select HYPERVISOR_GUEST
516 depends on X86_64 && PCI
517 depends on X86_EXTENDED_PLATFORM
520 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
521 supposed to run on these EM64T-based machines. Only choose this option
522 if you have one of these machines.
525 bool "SGI Ultraviolet"
527 depends on X86_EXTENDED_PLATFORM
530 depends on KEXEC_CORE
531 depends on X86_X2APIC
534 This option is needed in order to support SGI Ultraviolet systems.
535 If you don't have one of these, you should say N here.
537 # Following is an alphabetically sorted list of 32 bit extended platforms
538 # Please maintain the alphabetic order if and when there are additions
541 bool "Goldfish (Virtual Platform)"
542 depends on X86_EXTENDED_PLATFORM
544 Enable support for the Goldfish virtual platform used primarily
545 for Android development. Unless you are building for the Android
546 Goldfish emulator say N here.
549 bool "CE4100 TV platform"
551 depends on PCI_GODIRECT
552 depends on X86_IO_APIC
554 depends on X86_EXTENDED_PLATFORM
555 select X86_REBOOTFIXUPS
557 select OF_EARLY_FLATTREE
559 Select for the Intel CE media processor (CE4100) SOC.
560 This option compiles in support for the CE4100 SOC for settop
561 boxes and media devices.
564 bool "Intel MID platform support"
565 depends on X86_EXTENDED_PLATFORM
566 depends on X86_PLATFORM_DEVICES
568 depends on X86_64 || (PCI_GOANY && X86_32)
569 depends on X86_IO_APIC
575 select MFD_INTEL_MSIC
577 Select to build a kernel capable of supporting Intel MID (Mobile
578 Internet Device) platform systems which do not have the PCI legacy
579 interfaces. If you are building for a PC class system say N here.
581 Intel MID platforms are based on an Intel processor and chipset which
582 consume less power than most of the x86 derivatives.
584 config X86_INTEL_QUARK
585 bool "Intel Quark platform support"
587 depends on X86_EXTENDED_PLATFORM
588 depends on X86_PLATFORM_DEVICES
592 depends on X86_IO_APIC
597 Select to include support for Quark X1000 SoC.
598 Say Y here if you have a Quark based system such as the Arduino
599 compatible Intel Galileo.
601 config X86_INTEL_LPSS
602 bool "Intel Low Power Subsystem Support"
603 depends on X86 && ACPI
608 Select to build support for Intel Low Power Subsystem such as
609 found on Intel Lynxpoint PCH. Selecting this option enables
610 things like clock tree (common clock framework) and pincontrol
611 which are needed by the LPSS peripheral drivers.
613 config X86_AMD_PLATFORM_DEVICE
614 bool "AMD ACPI2Platform devices support"
619 Select to interpret AMD specific ACPI device to platform device
620 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
621 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
622 implemented under PINCTRL subsystem.
625 tristate "Intel SoC IOSF Sideband support for SoC platforms"
628 This option enables sideband register access support for Intel SoC
629 platforms. On these platforms the IOSF sideband is used in lieu of
630 MSR's for some register accesses, mostly but not limited to thermal
631 and power. Drivers may query the availability of this device to
632 determine if they need the sideband in order to work on these
633 platforms. The sideband is available on the following SoC products.
634 This list is not meant to be exclusive.
639 You should say Y if you are running a kernel on one of these SoC's.
641 config IOSF_MBI_DEBUG
642 bool "Enable IOSF sideband access through debugfs"
643 depends on IOSF_MBI && DEBUG_FS
645 Select this option to expose the IOSF sideband access registers (MCR,
646 MDR, MCRX) through debugfs to write and read register information from
647 different units on the SoC. This is most useful for obtaining device
648 state information for debug and analysis. As this is a general access
649 mechanism, users of this option would have specific knowledge of the
650 device they want to access.
652 If you don't require the option or are in doubt, say N.
655 bool "RDC R-321x SoC"
657 depends on X86_EXTENDED_PLATFORM
659 select X86_REBOOTFIXUPS
661 This option is needed for RDC R-321x system-on-chip, also known
663 If you don't have one of these chips, you should say N here.
665 config X86_32_NON_STANDARD
666 bool "Support non-standard 32-bit SMP architectures"
667 depends on X86_32 && SMP
668 depends on X86_EXTENDED_PLATFORM
670 This option compiles in the bigsmp and STA2X11 default
671 subarchitectures. It is intended for a generic binary
672 kernel. If you select them all, kernel will probe it one by
673 one and will fallback to default.
675 # Alphabetically sorted list of Non standard 32 bit platforms
677 config X86_SUPPORTS_MEMORY_FAILURE
679 # MCE code calls memory_failure():
681 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
682 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
683 depends on X86_64 || !SPARSEMEM
684 select ARCH_SUPPORTS_MEMORY_FAILURE
687 bool "STA2X11 Companion Chip Support"
688 depends on X86_32_NON_STANDARD && PCI
689 select X86_DEV_DMA_OPS
696 This adds support for boards based on the STA2X11 IO-Hub,
697 a.k.a. "ConneXt". The chip is used in place of the standard
698 PC chipset, so all "standard" peripherals are missing. If this
699 option is selected the kernel will still be able to boot on
700 standard PC machines.
703 tristate "Eurobraille/Iris poweroff module"
706 The Iris machines from EuroBraille do not have APM or ACPI support
707 to shut themselves down properly. A special I/O sequence is
708 needed to do so, which is what this module does at
711 This is only for Iris machines from EuroBraille.
715 config SCHED_OMIT_FRAME_POINTER
717 prompt "Single-depth WCHAN output"
720 Calculate simpler /proc/<PID>/wchan values. If this option
721 is disabled then wchan values will recurse back to the
722 caller function. This provides more accurate wchan values,
723 at the expense of slightly more scheduling overhead.
725 If in doubt, say "Y".
727 menuconfig HYPERVISOR_GUEST
728 bool "Linux guest support"
730 Say Y here to enable options for running Linux under various hyper-
731 visors. This option enables basic hypervisor detection and platform
734 If you say N, all options in this submenu will be skipped and
735 disabled, and Linux guest support won't be built in.
740 bool "Enable paravirtualization code"
742 This changes the kernel so it can modify itself when it is run
743 under a hypervisor, potentially improving performance significantly
744 over full virtualization. However, when run without a hypervisor
745 the kernel is theoretically slower and slightly larger.
747 config PARAVIRT_DEBUG
748 bool "paravirt-ops debugging"
749 depends on PARAVIRT && DEBUG_KERNEL
751 Enable to debug paravirt_ops internals. Specifically, BUG if
752 a paravirt_op is missing when it is called.
754 config PARAVIRT_SPINLOCKS
755 bool "Paravirtualization layer for spinlocks"
756 depends on PARAVIRT && SMP
758 Paravirtualized spinlocks allow a pvops backend to replace the
759 spinlock implementation with something virtualization-friendly
760 (for example, block the virtual CPU rather than spinning).
762 It has a minimal impact on native kernels and gives a nice performance
763 benefit on paravirtualized KVM / Xen kernels.
765 If you are unsure how to answer this question, answer Y.
767 config QUEUED_LOCK_STAT
768 bool "Paravirt queued spinlock statistics"
769 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
771 Enable the collection of statistical data on the slowpath
772 behavior of paravirtualized queued spinlocks and report
775 source "arch/x86/xen/Kconfig"
778 bool "KVM Guest support (including kvmclock)"
780 select PARAVIRT_CLOCK
783 This option enables various optimizations for running under the KVM
784 hypervisor. It includes a paravirtualized clock, so that instead
785 of relying on a PIT (or probably other) emulation by the
786 underlying device model, the host provides the guest with
787 timing infrastructure such as time of day, and system time
790 bool "Enable debug information for KVM Guests in debugfs"
791 depends on KVM_GUEST && DEBUG_FS
794 This option enables collection of various statistics for KVM guest.
795 Statistics are displayed in debugfs filesystem. Enabling this option
796 may incur significant overhead.
798 config PARAVIRT_TIME_ACCOUNTING
799 bool "Paravirtual steal time accounting"
803 Select this option to enable fine granularity task steal time
804 accounting. Time spent executing other tasks in parallel with
805 the current vCPU is discounted from the vCPU power. To account for
806 that, there can be a small performance impact.
808 If in doubt, say N here.
810 config PARAVIRT_CLOCK
813 endif #HYPERVISOR_GUEST
818 source "arch/x86/Kconfig.cpu"
822 prompt "HPET Timer Support" if X86_32
824 Use the IA-PC HPET (High Precision Event Timer) to manage
825 time in preference to the PIT and RTC, if a HPET is
827 HPET is the next generation timer replacing legacy 8254s.
828 The HPET provides a stable time base on SMP
829 systems, unlike the TSC, but it is more expensive to access,
830 as it is off-chip. The interface used is documented
831 in the HPET spec, revision 1.
833 You can safely choose Y here. However, HPET will only be
834 activated if the platform and the BIOS support this feature.
835 Otherwise the 8254 will be used for timing services.
837 Choose N to continue using the legacy 8254 timer.
839 config HPET_EMULATE_RTC
841 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
844 def_bool y if X86_INTEL_MID
845 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
847 depends on X86_INTEL_MID && SFI
849 APB timer is the replacement for 8254, HPET on X86 MID platforms.
850 The APBT provides a stable time base on SMP
851 systems, unlike the TSC, but it is more expensive to access,
852 as it is off-chip. APB timers are always running regardless of CPU
853 C states, they are used as per CPU clockevent device when possible.
855 # Mark as expert because too many people got it wrong.
856 # The code disables itself when not needed.
859 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
860 bool "Enable DMI scanning" if EXPERT
862 Enabled scanning of DMI to identify machine quirks. Say Y
863 here unless you have verified that your setup is not
864 affected by entries in the DMI blacklist. Required by PNP
868 bool "Old AMD GART IOMMU support"
870 depends on X86_64 && PCI && AMD_NB
872 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
873 GART based hardware IOMMUs.
875 The GART supports full DMA access for devices with 32-bit access
876 limitations, on systems with more than 3 GB. This is usually needed
877 for USB, sound, many IDE/SATA chipsets and some other devices.
879 Newer systems typically have a modern AMD IOMMU, supported via
880 the CONFIG_AMD_IOMMU=y config option.
882 In normal configurations this driver is only active when needed:
883 there's more than 3 GB of memory and the system contains a
884 32-bit limited device.
889 bool "IBM Calgary IOMMU support"
891 depends on X86_64 && PCI
893 Support for hardware IOMMUs in IBM's xSeries x366 and x460
894 systems. Needed to run systems with more than 3GB of memory
895 properly with 32-bit PCI devices that do not support DAC
896 (Double Address Cycle). Calgary also supports bus level
897 isolation, where all DMAs pass through the IOMMU. This
898 prevents them from going anywhere except their intended
899 destination. This catches hard-to-find kernel bugs and
900 mis-behaving drivers and devices that do not use the DMA-API
901 properly to set up their DMA buffers. The IOMMU can be
902 turned off at boot time with the iommu=off parameter.
903 Normally the kernel will make the right choice by itself.
906 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
908 prompt "Should Calgary be enabled by default?"
909 depends on CALGARY_IOMMU
911 Should Calgary be enabled by default? if you choose 'y', Calgary
912 will be used (if it exists). If you choose 'n', Calgary will not be
913 used even if it exists. If you choose 'n' and would like to use
914 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
917 # need this always selected by IOMMU for the VIA workaround
921 Support for software bounce buffers used on x86-64 systems
922 which don't have a hardware IOMMU. Using this PCI devices
923 which can only access 32-bits of memory can be used on systems
924 with more than 3 GB of memory.
929 depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU
932 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
933 depends on X86_64 && SMP && DEBUG_KERNEL
934 select CPUMASK_OFFSTACK
936 Enable maximum number of CPUS and NUMA Nodes for this architecture.
940 int "Maximum number of CPUs" if SMP && !MAXSMP
941 range 2 8 if SMP && X86_32 && !X86_BIGSMP
942 range 2 64 if SMP && X86_32 && X86_BIGSMP
943 range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK && X86_64
944 range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
946 default "8192" if MAXSMP
947 default "32" if SMP && X86_BIGSMP
948 default "8" if SMP && X86_32
951 This allows you to specify the maximum number of CPUs which this
952 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
953 supported value is 8192, otherwise the maximum value is 512. The
954 minimum value which makes sense is 2.
956 This is purely to save memory - each supported CPU adds
957 approximately eight kilobytes to the kernel image.
964 prompt "Multi-core scheduler support"
967 Multi-core scheduler support improves the CPU scheduler's decision
968 making when dealing with multi-core CPU chips at a cost of slightly
969 increased overhead in some places. If unsure say N here.
972 bool "CPU core priorities scheduler support"
973 depends on SCHED_MC && CPU_SUP_INTEL
974 select X86_INTEL_PSTATE
978 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
979 core ordering determined at manufacturing time, which allows
980 certain cores to reach higher turbo frequencies (when running
981 single threaded workloads) than others.
983 Enabling this kernel feature teaches the scheduler about
984 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
985 scheduler's CPU selection logic accordingly, so that higher
986 overall system performance can be achieved.
988 This feature will have no effect on CPUs without this feature.
990 If unsure say Y here.
992 source "kernel/Kconfig.preempt"
996 depends on !SMP && X86_LOCAL_APIC
999 bool "Local APIC support on uniprocessors" if !PCI_MSI
1001 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1003 A local APIC (Advanced Programmable Interrupt Controller) is an
1004 integrated interrupt controller in the CPU. If you have a single-CPU
1005 system which has a processor with a local APIC, you can say Y here to
1006 enable and use it. If you say Y here even though your machine doesn't
1007 have a local APIC, then the kernel will still run with no slowdown at
1008 all. The local APIC supports CPU-generated self-interrupts (timer,
1009 performance counters), and the NMI watchdog which detects hard
1012 config X86_UP_IOAPIC
1013 bool "IO-APIC support on uniprocessors"
1014 depends on X86_UP_APIC
1016 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1017 SMP-capable replacement for PC-style interrupt controllers. Most
1018 SMP systems and many recent uniprocessor systems have one.
1020 If you have a single-CPU system with an IO-APIC, you can say Y here
1021 to use it. If you say Y here even though your machine doesn't have
1022 an IO-APIC, then the kernel will still run with no slowdown at all.
1024 config X86_LOCAL_APIC
1026 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1027 select IRQ_DOMAIN_HIERARCHY
1028 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1032 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1034 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1035 bool "Reroute for broken boot IRQs"
1036 depends on X86_IO_APIC
1038 This option enables a workaround that fixes a source of
1039 spurious interrupts. This is recommended when threaded
1040 interrupt handling is used on systems where the generation of
1041 superfluous "boot interrupts" cannot be disabled.
1043 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1044 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1045 kernel does during interrupt handling). On chipsets where this
1046 boot IRQ generation cannot be disabled, this workaround keeps
1047 the original IRQ line masked so that only the equivalent "boot
1048 IRQ" is delivered to the CPUs. The workaround also tells the
1049 kernel to set up the IRQ handler on the boot IRQ line. In this
1050 way only one interrupt is delivered to the kernel. Otherwise
1051 the spurious second interrupt may cause the kernel to bring
1052 down (vital) interrupt lines.
1054 Only affects "broken" chipsets. Interrupt sharing may be
1055 increased on these systems.
1058 bool "Machine Check / overheating reporting"
1059 select GENERIC_ALLOCATOR
1062 Machine Check support allows the processor to notify the
1063 kernel if it detects a problem (e.g. overheating, data corruption).
1064 The action the kernel takes depends on the severity of the problem,
1065 ranging from warning messages to halting the machine.
1067 config X86_MCELOG_LEGACY
1068 bool "Support for deprecated /dev/mcelog character device"
1071 Enable support for /dev/mcelog which is needed by the old mcelog
1072 userspace logging daemon. Consider switching to the new generation
1075 config X86_MCE_INTEL
1077 prompt "Intel MCE features"
1078 depends on X86_MCE && X86_LOCAL_APIC
1080 Additional support for intel specific MCE features such as
1081 the thermal monitor.
1085 prompt "AMD MCE features"
1086 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1088 Additional support for AMD specific MCE features such as
1089 the DRAM Error Threshold.
1091 config X86_ANCIENT_MCE
1092 bool "Support for old Pentium 5 / WinChip machine checks"
1093 depends on X86_32 && X86_MCE
1095 Include support for machine check handling on old Pentium 5 or WinChip
1096 systems. These typically need to be enabled explicitly on the command
1099 config X86_MCE_THRESHOLD
1100 depends on X86_MCE_AMD || X86_MCE_INTEL
1103 config X86_MCE_INJECT
1104 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1105 tristate "Machine check injector support"
1107 Provide support for injecting machine checks for testing purposes.
1108 If you don't know what a machine check is and you don't do kernel
1109 QA it is safe to say n.
1111 config X86_THERMAL_VECTOR
1113 depends on X86_MCE_INTEL
1115 source "arch/x86/events/Kconfig"
1117 config X86_LEGACY_VM86
1118 bool "Legacy VM86 support"
1122 This option allows user programs to put the CPU into V8086
1123 mode, which is an 80286-era approximation of 16-bit real mode.
1125 Some very old versions of X and/or vbetool require this option
1126 for user mode setting. Similarly, DOSEMU will use it if
1127 available to accelerate real mode DOS programs. However, any
1128 recent version of DOSEMU, X, or vbetool should be fully
1129 functional even without kernel VM86 support, as they will all
1130 fall back to software emulation. Nevertheless, if you are using
1131 a 16-bit DOS program where 16-bit performance matters, vm86
1132 mode might be faster than emulation and you might want to
1135 Note that any app that works on a 64-bit kernel is unlikely to
1136 need this option, as 64-bit kernels don't, and can't, support
1137 V8086 mode. This option is also unrelated to 16-bit protected
1138 mode and is not needed to run most 16-bit programs under Wine.
1140 Enabling this option increases the complexity of the kernel
1141 and slows down exception handling a tiny bit.
1143 If unsure, say N here.
1147 default X86_LEGACY_VM86
1150 bool "Enable support for 16-bit segments" if EXPERT
1152 depends on MODIFY_LDT_SYSCALL
1154 This option is required by programs like Wine to run 16-bit
1155 protected mode legacy code on x86 processors. Disabling
1156 this option saves about 300 bytes on i386, or around 6K text
1157 plus 16K runtime memory on x86-64,
1161 depends on X86_16BIT && X86_32
1165 depends on X86_16BIT && X86_64
1167 config X86_VSYSCALL_EMULATION
1168 bool "Enable vsyscall emulation" if EXPERT
1172 This enables emulation of the legacy vsyscall page. Disabling
1173 it is roughly equivalent to booting with vsyscall=none, except
1174 that it will also disable the helpful warning if a program
1175 tries to use a vsyscall. With this option set to N, offending
1176 programs will just segfault, citing addresses of the form
1179 This option is required by many programs built before 2013, and
1180 care should be used even with newer programs if set to N.
1182 Disabling this option saves about 7K of kernel size and
1183 possibly 4K of additional runtime pagetable memory.
1186 tristate "Toshiba Laptop support"
1189 This adds a driver to safely access the System Management Mode of
1190 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1191 not work on models with a Phoenix BIOS. The System Management Mode
1192 is used to set the BIOS and power saving options on Toshiba portables.
1194 For information on utilities to make use of this driver see the
1195 Toshiba Linux utilities web site at:
1196 <http://www.buzzard.org.uk/toshiba/>.
1198 Say Y if you intend to run this kernel on a Toshiba portable.
1202 tristate "Dell i8k legacy laptop support"
1204 select SENSORS_DELL_SMM
1206 This option enables legacy /proc/i8k userspace interface in hwmon
1207 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1208 temperature and allows controlling fan speeds of Dell laptops via
1209 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1210 it reports also power and hotkey status. For fan speed control is
1211 needed userspace package i8kutils.
1213 Say Y if you intend to run this kernel on old Dell laptops or want to
1214 use userspace package i8kutils.
1217 config X86_REBOOTFIXUPS
1218 bool "Enable X86 board specific fixups for reboot"
1221 This enables chipset and/or board specific fixups to be done
1222 in order to get reboot to work correctly. This is only needed on
1223 some combinations of hardware and BIOS. The symptom, for which
1224 this config is intended, is when reboot ends with a stalled/hung
1227 Currently, the only fixup is for the Geode machines using
1228 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1230 Say Y if you want to enable the fixup. Currently, it's safe to
1231 enable this option even if you don't need it.
1235 bool "CPU microcode loading support"
1237 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1240 If you say Y here, you will be able to update the microcode on
1241 Intel and AMD processors. The Intel support is for the IA32 family,
1242 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1243 AMD support is for families 0x10 and later. You will obviously need
1244 the actual microcode binary data itself which is not shipped with
1247 The preferred method to load microcode from a detached initrd is described
1248 in Documentation/x86/early-microcode.txt. For that you need to enable
1249 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1250 initrd for microcode blobs.
1252 In addition, you can build-in the microcode into the kernel. For that you
1253 need to enable FIRMWARE_IN_KERNEL and add the vendor-supplied microcode
1254 to the CONFIG_EXTRA_FIRMWARE config option.
1256 config MICROCODE_INTEL
1257 bool "Intel microcode loading support"
1258 depends on MICROCODE
1262 This options enables microcode patch loading support for Intel
1265 For the current Intel microcode data package go to
1266 <https://downloadcenter.intel.com> and search for
1267 'Linux Processor Microcode Data File'.
1269 config MICROCODE_AMD
1270 bool "AMD microcode loading support"
1271 depends on MICROCODE
1274 If you select this option, microcode patch loading support for AMD
1275 processors will be enabled.
1277 config MICROCODE_OLD_INTERFACE
1279 depends on MICROCODE
1282 tristate "/dev/cpu/*/msr - Model-specific register support"
1284 This device gives privileged processes access to the x86
1285 Model-Specific Registers (MSRs). It is a character device with
1286 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1287 MSR accesses are directed to a specific CPU on multi-processor
1291 tristate "/dev/cpu/*/cpuid - CPU information support"
1293 This device gives processes access to the x86 CPUID instruction to
1294 be executed on a specific processor. It is a character device
1295 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1299 prompt "High Memory Support"
1306 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1307 However, the address space of 32-bit x86 processors is only 4
1308 Gigabytes large. That means that, if you have a large amount of
1309 physical memory, not all of it can be "permanently mapped" by the
1310 kernel. The physical memory that's not permanently mapped is called
1313 If you are compiling a kernel which will never run on a machine with
1314 more than 1 Gigabyte total physical RAM, answer "off" here (default
1315 choice and suitable for most users). This will result in a "3GB/1GB"
1316 split: 3GB are mapped so that each process sees a 3GB virtual memory
1317 space and the remaining part of the 4GB virtual memory space is used
1318 by the kernel to permanently map as much physical memory as
1321 If the machine has between 1 and 4 Gigabytes physical RAM, then
1324 If more than 4 Gigabytes is used then answer "64GB" here. This
1325 selection turns Intel PAE (Physical Address Extension) mode on.
1326 PAE implements 3-level paging on IA32 processors. PAE is fully
1327 supported by Linux, PAE mode is implemented on all recent Intel
1328 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1329 then the kernel will not boot on CPUs that don't support PAE!
1331 The actual amount of total physical memory will either be
1332 auto detected or can be forced by using a kernel command line option
1333 such as "mem=256M". (Try "man bootparam" or see the documentation of
1334 your boot loader (lilo or loadlin) about how to pass options to the
1335 kernel at boot time.)
1337 If unsure, say "off".
1342 Select this if you have a 32-bit processor and between 1 and 4
1343 gigabytes of physical RAM.
1350 Select this if you have a 32-bit processor and more than 4
1351 gigabytes of physical RAM.
1356 prompt "Memory split" if EXPERT
1360 Select the desired split between kernel and user memory.
1362 If the address range available to the kernel is less than the
1363 physical memory installed, the remaining memory will be available
1364 as "high memory". Accessing high memory is a little more costly
1365 than low memory, as it needs to be mapped into the kernel first.
1366 Note that increasing the kernel address space limits the range
1367 available to user programs, making the address space there
1368 tighter. Selecting anything other than the default 3G/1G split
1369 will also likely make your kernel incompatible with binary-only
1372 If you are not absolutely sure what you are doing, leave this
1376 bool "3G/1G user/kernel split"
1377 config VMSPLIT_3G_OPT
1379 bool "3G/1G user/kernel split (for full 1G low memory)"
1381 bool "2G/2G user/kernel split"
1382 config VMSPLIT_2G_OPT
1384 bool "2G/2G user/kernel split (for full 2G low memory)"
1386 bool "1G/3G user/kernel split"
1391 default 0xB0000000 if VMSPLIT_3G_OPT
1392 default 0x80000000 if VMSPLIT_2G
1393 default 0x78000000 if VMSPLIT_2G_OPT
1394 default 0x40000000 if VMSPLIT_1G
1400 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1403 bool "PAE (Physical Address Extension) Support"
1404 depends on X86_32 && !HIGHMEM4G
1407 PAE is required for NX support, and furthermore enables
1408 larger swapspace support for non-overcommit purposes. It
1409 has the cost of more pagetable lookup overhead, and also
1410 consumes more pagetable space per process.
1413 bool "Enable 5-level page tables support"
1416 5-level paging enables access to larger address space:
1417 upto 128 PiB of virtual address space and 4 PiB of
1418 physical address space.
1420 It will be supported by future Intel CPUs.
1422 Note: a kernel with this option enabled can only be booted
1423 on machines that support the feature.
1425 See Documentation/x86/x86_64/5level-paging.txt for more
1430 config ARCH_PHYS_ADDR_T_64BIT
1432 depends on X86_64 || X86_PAE
1434 config ARCH_DMA_ADDR_T_64BIT
1436 depends on X86_64 || HIGHMEM64G
1438 config X86_DIRECT_GBPAGES
1440 depends on X86_64 && !DEBUG_PAGEALLOC
1442 Certain kernel features effectively disable kernel
1443 linear 1 GB mappings (even if the CPU otherwise
1444 supports them), so don't confuse the user by printing
1445 that we have them enabled.
1447 config ARCH_HAS_MEM_ENCRYPT
1450 config AMD_MEM_ENCRYPT
1451 bool "AMD Secure Memory Encryption (SME) support"
1452 depends on X86_64 && CPU_SUP_AMD
1453 select ARCH_USE_MEMREMAP_PROT
1455 Say yes to enable support for the encryption of system memory.
1456 This requires an AMD processor that supports Secure Memory
1459 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1460 bool "Activate AMD Secure Memory Encryption (SME) by default"
1461 depends on AMD_MEM_ENCRYPT
1463 Say yes to have system memory encrypted by default if running on
1464 an AMD processor that supports Secure Memory Encryption (SME).
1466 If set to Y, then the encryption of system memory can be
1467 deactivated with the mem_encrypt=off command line option.
1469 If set to N, then the encryption of system memory can be
1470 activated with the mem_encrypt=on command line option.
1472 # Common NUMA Features
1474 bool "Numa Memory Allocation and Scheduler Support"
1476 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1477 default y if X86_BIGSMP
1479 Enable NUMA (Non Uniform Memory Access) support.
1481 The kernel will try to allocate memory used by a CPU on the
1482 local memory controller of the CPU and add some more
1483 NUMA awareness to the kernel.
1485 For 64-bit this is recommended if the system is Intel Core i7
1486 (or later), AMD Opteron, or EM64T NUMA.
1488 For 32-bit this is only needed if you boot a 32-bit
1489 kernel on a 64-bit NUMA platform.
1491 Otherwise, you should say N.
1495 prompt "Old style AMD Opteron NUMA detection"
1496 depends on X86_64 && NUMA && PCI
1498 Enable AMD NUMA node topology detection. You should say Y here if
1499 you have a multi processor AMD system. This uses an old method to
1500 read the NUMA configuration directly from the builtin Northbridge
1501 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1502 which also takes priority if both are compiled in.
1504 config X86_64_ACPI_NUMA
1506 prompt "ACPI NUMA detection"
1507 depends on X86_64 && NUMA && ACPI && PCI
1510 Enable ACPI SRAT based node topology detection.
1512 # Some NUMA nodes have memory ranges that span
1513 # other nodes. Even though a pfn is valid and
1514 # between a node's start and end pfns, it may not
1515 # reside on that node. See memmap_init_zone()
1517 config NODES_SPAN_OTHER_NODES
1519 depends on X86_64_ACPI_NUMA
1522 bool "NUMA emulation"
1525 Enable NUMA emulation. A flat machine will be split
1526 into virtual nodes when booted with "numa=fake=N", where N is the
1527 number of nodes. This is only useful for debugging.
1530 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1532 default "10" if MAXSMP
1533 default "6" if X86_64
1535 depends on NEED_MULTIPLE_NODES
1537 Specify the maximum number of NUMA Nodes available on the target
1538 system. Increases memory reserved to accommodate various tables.
1540 config ARCH_HAVE_MEMORY_PRESENT
1542 depends on X86_32 && DISCONTIGMEM
1544 config NEED_NODE_MEMMAP_SIZE
1546 depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
1548 config ARCH_FLATMEM_ENABLE
1550 depends on X86_32 && !NUMA
1552 config ARCH_DISCONTIGMEM_ENABLE
1554 depends on NUMA && X86_32
1556 config ARCH_DISCONTIGMEM_DEFAULT
1558 depends on NUMA && X86_32
1560 config ARCH_SPARSEMEM_ENABLE
1562 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1563 select SPARSEMEM_STATIC if X86_32
1564 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1566 config ARCH_SPARSEMEM_DEFAULT
1570 config ARCH_SELECT_MEMORY_MODEL
1572 depends on ARCH_SPARSEMEM_ENABLE
1574 config ARCH_MEMORY_PROBE
1575 bool "Enable sysfs memory/probe interface"
1576 depends on X86_64 && MEMORY_HOTPLUG
1578 This option enables a sysfs memory/probe interface for testing.
1579 See Documentation/memory-hotplug.txt for more information.
1580 If you are unsure how to answer this question, answer N.
1582 config ARCH_PROC_KCORE_TEXT
1584 depends on X86_64 && PROC_KCORE
1586 config ILLEGAL_POINTER_VALUE
1589 default 0xdead000000000000 if X86_64
1593 config X86_PMEM_LEGACY_DEVICE
1596 config X86_PMEM_LEGACY
1597 tristate "Support non-standard NVDIMMs and ADR protected memory"
1598 depends on PHYS_ADDR_T_64BIT
1600 select X86_PMEM_LEGACY_DEVICE
1603 Treat memory marked using the non-standard e820 type of 12 as used
1604 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1605 The kernel will offer these regions to the 'pmem' driver so
1606 they can be used for persistent storage.
1611 bool "Allocate 3rd-level pagetables from highmem"
1614 The VM uses one page table entry for each page of physical memory.
1615 For systems with a lot of RAM, this can be wasteful of precious
1616 low memory. Setting this option will put user-space page table
1617 entries in high memory.
1619 config X86_CHECK_BIOS_CORRUPTION
1620 bool "Check for low memory corruption"
1622 Periodically check for memory corruption in low memory, which
1623 is suspected to be caused by BIOS. Even when enabled in the
1624 configuration, it is disabled at runtime. Enable it by
1625 setting "memory_corruption_check=1" on the kernel command
1626 line. By default it scans the low 64k of memory every 60
1627 seconds; see the memory_corruption_check_size and
1628 memory_corruption_check_period parameters in
1629 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1631 When enabled with the default parameters, this option has
1632 almost no overhead, as it reserves a relatively small amount
1633 of memory and scans it infrequently. It both detects corruption
1634 and prevents it from affecting the running system.
1636 It is, however, intended as a diagnostic tool; if repeatable
1637 BIOS-originated corruption always affects the same memory,
1638 you can use memmap= to prevent the kernel from using that
1641 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1642 bool "Set the default setting of memory_corruption_check"
1643 depends on X86_CHECK_BIOS_CORRUPTION
1646 Set whether the default state of memory_corruption_check is
1649 config X86_RESERVE_LOW
1650 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1654 Specify the amount of low memory to reserve for the BIOS.
1656 The first page contains BIOS data structures that the kernel
1657 must not use, so that page must always be reserved.
1659 By default we reserve the first 64K of physical RAM, as a
1660 number of BIOSes are known to corrupt that memory range
1661 during events such as suspend/resume or monitor cable
1662 insertion, so it must not be used by the kernel.
1664 You can set this to 4 if you are absolutely sure that you
1665 trust the BIOS to get all its memory reservations and usages
1666 right. If you know your BIOS have problems beyond the
1667 default 64K area, you can set this to 640 to avoid using the
1668 entire low memory range.
1670 If you have doubts about the BIOS (e.g. suspend/resume does
1671 not work or there's kernel crashes after certain hardware
1672 hotplug events) then you might want to enable
1673 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1674 typical corruption patterns.
1676 Leave this to the default value of 64 if you are unsure.
1678 config MATH_EMULATION
1680 depends on MODIFY_LDT_SYSCALL
1681 prompt "Math emulation" if X86_32
1683 Linux can emulate a math coprocessor (used for floating point
1684 operations) if you don't have one. 486DX and Pentium processors have
1685 a math coprocessor built in, 486SX and 386 do not, unless you added
1686 a 487DX or 387, respectively. (The messages during boot time can
1687 give you some hints here ["man dmesg"].) Everyone needs either a
1688 coprocessor or this emulation.
1690 If you don't have a math coprocessor, you need to say Y here; if you
1691 say Y here even though you have a coprocessor, the coprocessor will
1692 be used nevertheless. (This behavior can be changed with the kernel
1693 command line option "no387", which comes handy if your coprocessor
1694 is broken. Try "man bootparam" or see the documentation of your boot
1695 loader (lilo or loadlin) about how to pass options to the kernel at
1696 boot time.) This means that it is a good idea to say Y here if you
1697 intend to use this kernel on different machines.
1699 More information about the internals of the Linux math coprocessor
1700 emulation can be found in <file:arch/x86/math-emu/README>.
1702 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1703 kernel, it won't hurt.
1707 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1709 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1710 the Memory Type Range Registers (MTRRs) may be used to control
1711 processor access to memory ranges. This is most useful if you have
1712 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1713 allows bus write transfers to be combined into a larger transfer
1714 before bursting over the PCI/AGP bus. This can increase performance
1715 of image write operations 2.5 times or more. Saying Y here creates a
1716 /proc/mtrr file which may be used to manipulate your processor's
1717 MTRRs. Typically the X server should use this.
1719 This code has a reasonably generic interface so that similar
1720 control registers on other processors can be easily supported
1723 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1724 Registers (ARRs) which provide a similar functionality to MTRRs. For
1725 these, the ARRs are used to emulate the MTRRs.
1726 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1727 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1728 write-combining. All of these processors are supported by this code
1729 and it makes sense to say Y here if you have one of them.
1731 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1732 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1733 can lead to all sorts of problems, so it's good to say Y here.
1735 You can safely say Y even if your machine doesn't have MTRRs, you'll
1736 just add about 9 KB to your kernel.
1738 See <file:Documentation/x86/mtrr.txt> for more information.
1740 config MTRR_SANITIZER
1742 prompt "MTRR cleanup support"
1745 Convert MTRR layout from continuous to discrete, so X drivers can
1746 add writeback entries.
1748 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1749 The largest mtrr entry size for a continuous block can be set with
1754 config MTRR_SANITIZER_ENABLE_DEFAULT
1755 int "MTRR cleanup enable value (0-1)"
1758 depends on MTRR_SANITIZER
1760 Enable mtrr cleanup default value
1762 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1763 int "MTRR cleanup spare reg num (0-7)"
1766 depends on MTRR_SANITIZER
1768 mtrr cleanup spare entries default, it can be changed via
1769 mtrr_spare_reg_nr=N on the kernel command line.
1773 prompt "x86 PAT support" if EXPERT
1776 Use PAT attributes to setup page level cache control.
1778 PATs are the modern equivalents of MTRRs and are much more
1779 flexible than MTRRs.
1781 Say N here if you see bootup problems (boot crash, boot hang,
1782 spontaneous reboots) or a non-working video driver.
1786 config ARCH_USES_PG_UNCACHED
1792 prompt "x86 architectural random number generator" if EXPERT
1794 Enable the x86 architectural RDRAND instruction
1795 (Intel Bull Mountain technology) to generate random numbers.
1796 If supported, this is a high bandwidth, cryptographically
1797 secure hardware random number generator.
1801 prompt "Supervisor Mode Access Prevention" if EXPERT
1803 Supervisor Mode Access Prevention (SMAP) is a security
1804 feature in newer Intel processors. There is a small
1805 performance cost if this enabled and turned on; there is
1806 also a small increase in the kernel size if this is enabled.
1810 config X86_INTEL_MPX
1811 prompt "Intel MPX (Memory Protection Extensions)"
1813 # Note: only available in 64-bit mode due to VMA flags shortage
1814 depends on CPU_SUP_INTEL && X86_64
1815 select ARCH_USES_HIGH_VMA_FLAGS
1817 MPX provides hardware features that can be used in
1818 conjunction with compiler-instrumented code to check
1819 memory references. It is designed to detect buffer
1820 overflow or underflow bugs.
1822 This option enables running applications which are
1823 instrumented or otherwise use MPX. It does not use MPX
1824 itself inside the kernel or to protect the kernel
1825 against bad memory references.
1827 Enabling this option will make the kernel larger:
1828 ~8k of kernel text and 36 bytes of data on a 64-bit
1829 defconfig. It adds a long to the 'mm_struct' which
1830 will increase the kernel memory overhead of each
1831 process and adds some branches to paths used during
1832 exec() and munmap().
1834 For details, see Documentation/x86/intel_mpx.txt
1838 config X86_INTEL_MEMORY_PROTECTION_KEYS
1839 prompt "Intel Memory Protection Keys"
1841 # Note: only available in 64-bit mode
1842 depends on CPU_SUP_INTEL && X86_64
1843 select ARCH_USES_HIGH_VMA_FLAGS
1844 select ARCH_HAS_PKEYS
1846 Memory Protection Keys provides a mechanism for enforcing
1847 page-based protections, but without requiring modification of the
1848 page tables when an application changes protection domains.
1850 For details, see Documentation/x86/protection-keys.txt
1855 prompt "TSX enable mode"
1856 depends on CPU_SUP_INTEL
1857 default X86_INTEL_TSX_MODE_OFF
1859 Intel's TSX (Transactional Synchronization Extensions) feature
1860 allows to optimize locking protocols through lock elision which
1861 can lead to a noticeable performance boost.
1863 On the other hand it has been shown that TSX can be exploited
1864 to form side channel attacks (e.g. TAA) and chances are there
1865 will be more of those attacks discovered in the future.
1867 Therefore TSX is not enabled by default (aka tsx=off). An admin
1868 might override this decision by tsx=on the command line parameter.
1869 Even with TSX enabled, the kernel will attempt to enable the best
1870 possible TAA mitigation setting depending on the microcode available
1871 for the particular machine.
1873 This option allows to set the default tsx mode between tsx=on, =off
1874 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1877 Say off if not sure, auto if TSX is in use but it should be used on safe
1878 platforms or on if TSX is in use and the security aspect of tsx is not
1881 config X86_INTEL_TSX_MODE_OFF
1884 TSX is disabled if possible - equals to tsx=off command line parameter.
1886 config X86_INTEL_TSX_MODE_ON
1889 TSX is always enabled on TSX capable HW - equals the tsx=on command
1892 config X86_INTEL_TSX_MODE_AUTO
1895 TSX is enabled on TSX capable HW that is believed to be safe against
1896 side channel attacks- equals the tsx=auto command line parameter.
1900 bool "EFI runtime service support"
1903 select EFI_RUNTIME_WRAPPERS
1904 select ARCH_USE_MEMREMAP_PROT
1906 This enables the kernel to use EFI runtime services that are
1907 available (such as the EFI variable services).
1909 This option is only useful on systems that have EFI firmware.
1910 In addition, you should use the latest ELILO loader available
1911 at <http://elilo.sourceforge.net> in order to take advantage
1912 of EFI runtime services. However, even with this option, the
1913 resultant kernel should continue to boot on existing non-EFI
1917 bool "EFI stub support"
1918 depends on EFI && !X86_USE_3DNOW
1921 This kernel feature allows a bzImage to be loaded directly
1922 by EFI firmware without the use of a bootloader.
1924 See Documentation/efi-stub.txt for more information.
1927 bool "EFI mixed-mode support"
1928 depends on EFI_STUB && X86_64
1930 Enabling this feature allows a 64-bit kernel to be booted
1931 on a 32-bit firmware, provided that your CPU supports 64-bit
1934 Note that it is not possible to boot a mixed-mode enabled
1935 kernel via the EFI boot stub - a bootloader that supports
1936 the EFI handover protocol must be used.
1942 prompt "Enable seccomp to safely compute untrusted bytecode"
1944 This kernel feature is useful for number crunching applications
1945 that may need to compute untrusted bytecode during their
1946 execution. By using pipes or other transports made available to
1947 the process as file descriptors supporting the read/write
1948 syscalls, it's possible to isolate those applications in
1949 their own address space using seccomp. Once seccomp is
1950 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1951 and the task is only allowed to execute a few safe syscalls
1952 defined by each seccomp mode.
1954 If unsure, say Y. Only embedded should say N here.
1956 source kernel/Kconfig.hz
1959 bool "kexec system call"
1962 kexec is a system call that implements the ability to shutdown your
1963 current kernel, and to start another kernel. It is like a reboot
1964 but it is independent of the system firmware. And like a reboot
1965 you can start any kernel with it, not just Linux.
1967 The name comes from the similarity to the exec system call.
1969 It is an ongoing process to be certain the hardware in a machine
1970 is properly shutdown, so do not be surprised if this code does not
1971 initially work for you. As of this writing the exact hardware
1972 interface is strongly in flux, so no good recommendation can be
1976 bool "kexec file based system call"
1981 depends on CRYPTO_SHA256=y
1983 This is new version of kexec system call. This system call is
1984 file based and takes file descriptors as system call argument
1985 for kernel and initramfs as opposed to list of segments as
1986 accepted by previous system call.
1988 config KEXEC_VERIFY_SIG
1989 bool "Verify kernel signature during kexec_file_load() syscall"
1990 depends on KEXEC_FILE
1992 This option makes kernel signature verification mandatory for
1993 the kexec_file_load() syscall.
1995 In addition to that option, you need to enable signature
1996 verification for the corresponding kernel image type being
1997 loaded in order for this to work.
1999 config KEXEC_BZIMAGE_VERIFY_SIG
2000 bool "Enable bzImage signature verification support"
2001 depends on KEXEC_VERIFY_SIG
2002 depends on SIGNED_PE_FILE_VERIFICATION
2003 select SYSTEM_TRUSTED_KEYRING
2005 Enable bzImage signature verification support.
2008 bool "kernel crash dumps"
2009 depends on X86_64 || (X86_32 && HIGHMEM)
2011 Generate crash dump after being started by kexec.
2012 This should be normally only set in special crash dump kernels
2013 which are loaded in the main kernel with kexec-tools into
2014 a specially reserved region and then later executed after
2015 a crash by kdump/kexec. The crash dump kernel must be compiled
2016 to a memory address not used by the main kernel or BIOS using
2017 PHYSICAL_START, or it must be built as a relocatable image
2018 (CONFIG_RELOCATABLE=y).
2019 For more details see Documentation/kdump/kdump.txt
2023 depends on KEXEC && HIBERNATION
2025 Jump between original kernel and kexeced kernel and invoke
2026 code in physical address mode via KEXEC
2028 config PHYSICAL_START
2029 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2032 This gives the physical address where the kernel is loaded.
2034 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2035 bzImage will decompress itself to above physical address and
2036 run from there. Otherwise, bzImage will run from the address where
2037 it has been loaded by the boot loader and will ignore above physical
2040 In normal kdump cases one does not have to set/change this option
2041 as now bzImage can be compiled as a completely relocatable image
2042 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2043 address. This option is mainly useful for the folks who don't want
2044 to use a bzImage for capturing the crash dump and want to use a
2045 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2046 to be specifically compiled to run from a specific memory area
2047 (normally a reserved region) and this option comes handy.
2049 So if you are using bzImage for capturing the crash dump,
2050 leave the value here unchanged to 0x1000000 and set
2051 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2052 for capturing the crash dump change this value to start of
2053 the reserved region. In other words, it can be set based on
2054 the "X" value as specified in the "crashkernel=YM@XM"
2055 command line boot parameter passed to the panic-ed
2056 kernel. Please take a look at Documentation/kdump/kdump.txt
2057 for more details about crash dumps.
2059 Usage of bzImage for capturing the crash dump is recommended as
2060 one does not have to build two kernels. Same kernel can be used
2061 as production kernel and capture kernel. Above option should have
2062 gone away after relocatable bzImage support is introduced. But it
2063 is present because there are users out there who continue to use
2064 vmlinux for dump capture. This option should go away down the
2067 Don't change this unless you know what you are doing.
2070 bool "Build a relocatable kernel"
2073 This builds a kernel image that retains relocation information
2074 so it can be loaded someplace besides the default 1MB.
2075 The relocations tend to make the kernel binary about 10% larger,
2076 but are discarded at runtime.
2078 One use is for the kexec on panic case where the recovery kernel
2079 must live at a different physical address than the primary
2082 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2083 it has been loaded at and the compile time physical address
2084 (CONFIG_PHYSICAL_START) is used as the minimum location.
2086 config RANDOMIZE_BASE
2087 bool "Randomize the address of the kernel image (KASLR)"
2088 depends on RELOCATABLE
2091 In support of Kernel Address Space Layout Randomization (KASLR),
2092 this randomizes the physical address at which the kernel image
2093 is decompressed and the virtual address where the kernel
2094 image is mapped, as a security feature that deters exploit
2095 attempts relying on knowledge of the location of kernel
2098 On 64-bit, the kernel physical and virtual addresses are
2099 randomized separately. The physical address will be anywhere
2100 between 16MB and the top of physical memory (up to 64TB). The
2101 virtual address will be randomized from 16MB up to 1GB (9 bits
2102 of entropy). Note that this also reduces the memory space
2103 available to kernel modules from 1.5GB to 1GB.
2105 On 32-bit, the kernel physical and virtual addresses are
2106 randomized together. They will be randomized from 16MB up to
2107 512MB (8 bits of entropy).
2109 Entropy is generated using the RDRAND instruction if it is
2110 supported. If RDTSC is supported, its value is mixed into
2111 the entropy pool as well. If neither RDRAND nor RDTSC are
2112 supported, then entropy is read from the i8254 timer. The
2113 usable entropy is limited by the kernel being built using
2114 2GB addressing, and that PHYSICAL_ALIGN must be at a
2115 minimum of 2MB. As a result, only 10 bits of entropy are
2116 theoretically possible, but the implementations are further
2117 limited due to memory layouts.
2121 # Relocation on x86 needs some additional build support
2122 config X86_NEED_RELOCS
2124 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2126 config PHYSICAL_ALIGN
2127 hex "Alignment value to which kernel should be aligned"
2129 range 0x2000 0x1000000 if X86_32
2130 range 0x200000 0x1000000 if X86_64
2132 This value puts the alignment restrictions on physical address
2133 where kernel is loaded and run from. Kernel is compiled for an
2134 address which meets above alignment restriction.
2136 If bootloader loads the kernel at a non-aligned address and
2137 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2138 address aligned to above value and run from there.
2140 If bootloader loads the kernel at a non-aligned address and
2141 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2142 load address and decompress itself to the address it has been
2143 compiled for and run from there. The address for which kernel is
2144 compiled already meets above alignment restrictions. Hence the
2145 end result is that kernel runs from a physical address meeting
2146 above alignment restrictions.
2148 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2149 this value must be a multiple of 0x200000.
2151 Don't change this unless you know what you are doing.
2153 config RANDOMIZE_MEMORY
2154 bool "Randomize the kernel memory sections"
2156 depends on RANDOMIZE_BASE
2157 default RANDOMIZE_BASE
2159 Randomizes the base virtual address of kernel memory sections
2160 (physical memory mapping, vmalloc & vmemmap). This security feature
2161 makes exploits relying on predictable memory locations less reliable.
2163 The order of allocations remains unchanged. Entropy is generated in
2164 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2165 configuration have in average 30,000 different possible virtual
2166 addresses for each memory section.
2170 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2171 hex "Physical memory mapping padding" if EXPERT
2172 depends on RANDOMIZE_MEMORY
2173 default "0xa" if MEMORY_HOTPLUG
2175 range 0x1 0x40 if MEMORY_HOTPLUG
2178 Define the padding in terabytes added to the existing physical
2179 memory size during kernel memory randomization. It is useful
2180 for memory hotplug support but reduces the entropy available for
2181 address randomization.
2183 If unsure, leave at the default value.
2189 config BOOTPARAM_HOTPLUG_CPU0
2190 bool "Set default setting of cpu0_hotpluggable"
2192 depends on HOTPLUG_CPU
2194 Set whether default state of cpu0_hotpluggable is on or off.
2196 Say Y here to enable CPU0 hotplug by default. If this switch
2197 is turned on, there is no need to give cpu0_hotplug kernel
2198 parameter and the CPU0 hotplug feature is enabled by default.
2200 Please note: there are two known CPU0 dependencies if you want
2201 to enable the CPU0 hotplug feature either by this switch or by
2202 cpu0_hotplug kernel parameter.
2204 First, resume from hibernate or suspend always starts from CPU0.
2205 So hibernate and suspend are prevented if CPU0 is offline.
2207 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2208 offline if any interrupt can not migrate out of CPU0. There may
2209 be other CPU0 dependencies.
2211 Please make sure the dependencies are under your control before
2212 you enable this feature.
2214 Say N if you don't want to enable CPU0 hotplug feature by default.
2215 You still can enable the CPU0 hotplug feature at boot by kernel
2216 parameter cpu0_hotplug.
2218 config DEBUG_HOTPLUG_CPU0
2220 prompt "Debug CPU0 hotplug"
2221 depends on HOTPLUG_CPU
2223 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2224 soon as possible and boots up userspace with CPU0 offlined. User
2225 can online CPU0 back after boot time.
2227 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2228 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2229 compilation or giving cpu0_hotplug kernel parameter at boot.
2235 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2236 depends on COMPAT_32
2238 Certain buggy versions of glibc will crash if they are
2239 presented with a 32-bit vDSO that is not mapped at the address
2240 indicated in its segment table.
2242 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2243 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2244 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2245 the only released version with the bug, but OpenSUSE 9
2246 contains a buggy "glibc 2.3.2".
2248 The symptom of the bug is that everything crashes on startup, saying:
2249 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2251 Saying Y here changes the default value of the vdso32 boot
2252 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2253 This works around the glibc bug but hurts performance.
2255 If unsure, say N: if you are compiling your own kernel, you
2256 are unlikely to be using a buggy version of glibc.
2259 prompt "vsyscall table for legacy applications"
2261 default LEGACY_VSYSCALL_EMULATE
2263 Legacy user code that does not know how to find the vDSO expects
2264 to be able to issue three syscalls by calling fixed addresses in
2265 kernel space. Since this location is not randomized with ASLR,
2266 it can be used to assist security vulnerability exploitation.
2268 This setting can be changed at boot time via the kernel command
2269 line parameter vsyscall=[native|emulate|none].
2271 On a system with recent enough glibc (2.14 or newer) and no
2272 static binaries, you can say None without a performance penalty
2273 to improve security.
2275 If unsure, select "Emulate".
2277 config LEGACY_VSYSCALL_NATIVE
2280 Actual executable code is located in the fixed vsyscall
2281 address mapping, implementing time() efficiently. Since
2282 this makes the mapping executable, it can be used during
2283 security vulnerability exploitation (traditionally as
2284 ROP gadgets). This configuration is not recommended.
2286 config LEGACY_VSYSCALL_EMULATE
2289 The kernel traps and emulates calls into the fixed
2290 vsyscall address mapping. This makes the mapping
2291 non-executable, but it still contains known contents,
2292 which could be used in certain rare security vulnerability
2293 exploits. This configuration is recommended when userspace
2294 still uses the vsyscall area.
2296 config LEGACY_VSYSCALL_NONE
2299 There will be no vsyscall mapping at all. This will
2300 eliminate any risk of ASLR bypass due to the vsyscall
2301 fixed address mapping. Attempts to use the vsyscalls
2302 will be reported to dmesg, so that either old or
2303 malicious userspace programs can be identified.
2308 bool "Built-in kernel command line"
2310 Allow for specifying boot arguments to the kernel at
2311 build time. On some systems (e.g. embedded ones), it is
2312 necessary or convenient to provide some or all of the
2313 kernel boot arguments with the kernel itself (that is,
2314 to not rely on the boot loader to provide them.)
2316 To compile command line arguments into the kernel,
2317 set this option to 'Y', then fill in the
2318 boot arguments in CONFIG_CMDLINE.
2320 Systems with fully functional boot loaders (i.e. non-embedded)
2321 should leave this option set to 'N'.
2324 string "Built-in kernel command string"
2325 depends on CMDLINE_BOOL
2328 Enter arguments here that should be compiled into the kernel
2329 image and used at boot time. If the boot loader provides a
2330 command line at boot time, it is appended to this string to
2331 form the full kernel command line, when the system boots.
2333 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2334 change this behavior.
2336 In most cases, the command line (whether built-in or provided
2337 by the boot loader) should specify the device for the root
2340 config CMDLINE_OVERRIDE
2341 bool "Built-in command line overrides boot loader arguments"
2342 depends on CMDLINE_BOOL
2344 Set this option to 'Y' to have the kernel ignore the boot loader
2345 command line, and use ONLY the built-in command line.
2347 This is used to work around broken boot loaders. This should
2348 be set to 'N' under normal conditions.
2350 config MODIFY_LDT_SYSCALL
2351 bool "Enable the LDT (local descriptor table)" if EXPERT
2354 Linux can allow user programs to install a per-process x86
2355 Local Descriptor Table (LDT) using the modify_ldt(2) system
2356 call. This is required to run 16-bit or segmented code such as
2357 DOSEMU or some Wine programs. It is also used by some very old
2358 threading libraries.
2360 Enabling this feature adds a small amount of overhead to
2361 context switches and increases the low-level kernel attack
2362 surface. Disabling it removes the modify_ldt(2) system call.
2364 Saying 'N' here may make sense for embedded or server kernels.
2366 source "kernel/livepatch/Kconfig"
2370 config ARCH_HAS_ADD_PAGES
2372 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2374 config ARCH_ENABLE_MEMORY_HOTPLUG
2376 depends on X86_64 || (X86_32 && HIGHMEM)
2378 config ARCH_ENABLE_MEMORY_HOTREMOVE
2380 depends on MEMORY_HOTPLUG
2382 config USE_PERCPU_NUMA_NODE_ID
2386 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2388 depends on X86_64 || X86_PAE
2390 config GDS_FORCE_MITIGATION
2391 bool "Force GDS Mitigation"
2392 depends on CPU_SUP_INTEL
2395 Gather Data Sampling (GDS) is a hardware vulnerability which allows
2396 unprivileged speculative access to data which was previously stored in
2399 This option is equivalent to setting gather_data_sampling=force on the
2400 command line. The microcode mitigation is used if present, otherwise
2401 AVX is disabled as a mitigation. On affected systems that are missing
2402 the microcode any userspace code that unconditionally uses AVX will
2403 break with this option set.
2405 Setting this option on systems not vulnerable to GDS has no effect.
2409 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2411 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2413 config ARCH_ENABLE_THP_MIGRATION
2415 depends on X86_64 && TRANSPARENT_HUGEPAGE
2417 menu "Power management and ACPI options"
2419 config ARCH_HIBERNATION_HEADER
2421 depends on X86_64 && HIBERNATION
2423 source "kernel/power/Kconfig"
2425 source "drivers/acpi/Kconfig"
2427 source "drivers/sfi/Kconfig"
2434 tristate "APM (Advanced Power Management) BIOS support"
2435 depends on X86_32 && PM_SLEEP
2437 APM is a BIOS specification for saving power using several different
2438 techniques. This is mostly useful for battery powered laptops with
2439 APM compliant BIOSes. If you say Y here, the system time will be
2440 reset after a RESUME operation, the /proc/apm device will provide
2441 battery status information, and user-space programs will receive
2442 notification of APM "events" (e.g. battery status change).
2444 If you select "Y" here, you can disable actual use of the APM
2445 BIOS by passing the "apm=off" option to the kernel at boot time.
2447 Note that the APM support is almost completely disabled for
2448 machines with more than one CPU.
2450 In order to use APM, you will need supporting software. For location
2451 and more information, read <file:Documentation/power/apm-acpi.txt>
2452 and the Battery Powered Linux mini-HOWTO, available from
2453 <http://www.tldp.org/docs.html#howto>.
2455 This driver does not spin down disk drives (see the hdparm(8)
2456 manpage ("man 8 hdparm") for that), and it doesn't turn off
2457 VESA-compliant "green" monitors.
2459 This driver does not support the TI 4000M TravelMate and the ACER
2460 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2461 desktop machines also don't have compliant BIOSes, and this driver
2462 may cause those machines to panic during the boot phase.
2464 Generally, if you don't have a battery in your machine, there isn't
2465 much point in using this driver and you should say N. If you get
2466 random kernel OOPSes or reboots that don't seem to be related to
2467 anything, try disabling/enabling this option (or disabling/enabling
2470 Some other things you should try when experiencing seemingly random,
2473 1) make sure that you have enough swap space and that it is
2475 2) pass the "no-hlt" option to the kernel
2476 3) switch on floating point emulation in the kernel and pass
2477 the "no387" option to the kernel
2478 4) pass the "floppy=nodma" option to the kernel
2479 5) pass the "mem=4M" option to the kernel (thereby disabling
2480 all but the first 4 MB of RAM)
2481 6) make sure that the CPU is not over clocked.
2482 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2483 8) disable the cache from your BIOS settings
2484 9) install a fan for the video card or exchange video RAM
2485 10) install a better fan for the CPU
2486 11) exchange RAM chips
2487 12) exchange the motherboard.
2489 To compile this driver as a module, choose M here: the
2490 module will be called apm.
2494 config APM_IGNORE_USER_SUSPEND
2495 bool "Ignore USER SUSPEND"
2497 This option will ignore USER SUSPEND requests. On machines with a
2498 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2499 series notebooks, it is necessary to say Y because of a BIOS bug.
2501 config APM_DO_ENABLE
2502 bool "Enable PM at boot time"
2504 Enable APM features at boot time. From page 36 of the APM BIOS
2505 specification: "When disabled, the APM BIOS does not automatically
2506 power manage devices, enter the Standby State, enter the Suspend
2507 State, or take power saving steps in response to CPU Idle calls."
2508 This driver will make CPU Idle calls when Linux is idle (unless this
2509 feature is turned off -- see "Do CPU IDLE calls", below). This
2510 should always save battery power, but more complicated APM features
2511 will be dependent on your BIOS implementation. You may need to turn
2512 this option off if your computer hangs at boot time when using APM
2513 support, or if it beeps continuously instead of suspending. Turn
2514 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2515 T400CDT. This is off by default since most machines do fine without
2520 bool "Make CPU Idle calls when idle"
2522 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2523 On some machines, this can activate improved power savings, such as
2524 a slowed CPU clock rate, when the machine is idle. These idle calls
2525 are made after the idle loop has run for some length of time (e.g.,
2526 333 mS). On some machines, this will cause a hang at boot time or
2527 whenever the CPU becomes idle. (On machines with more than one CPU,
2528 this option does nothing.)
2530 config APM_DISPLAY_BLANK
2531 bool "Enable console blanking using APM"
2533 Enable console blanking using the APM. Some laptops can use this to
2534 turn off the LCD backlight when the screen blanker of the Linux
2535 virtual console blanks the screen. Note that this is only used by
2536 the virtual console screen blanker, and won't turn off the backlight
2537 when using the X Window system. This also doesn't have anything to
2538 do with your VESA-compliant power-saving monitor. Further, this
2539 option doesn't work for all laptops -- it might not turn off your
2540 backlight at all, or it might print a lot of errors to the console,
2541 especially if you are using gpm.
2543 config APM_ALLOW_INTS
2544 bool "Allow interrupts during APM BIOS calls"
2546 Normally we disable external interrupts while we are making calls to
2547 the APM BIOS as a measure to lessen the effects of a badly behaving
2548 BIOS implementation. The BIOS should reenable interrupts if it
2549 needs to. Unfortunately, some BIOSes do not -- especially those in
2550 many of the newer IBM Thinkpads. If you experience hangs when you
2551 suspend, try setting this to Y. Otherwise, say N.
2555 source "drivers/cpufreq/Kconfig"
2557 source "drivers/cpuidle/Kconfig"
2559 source "drivers/idle/Kconfig"
2564 menu "Bus options (PCI etc.)"
2570 Find out whether you have a PCI motherboard. PCI is the name of a
2571 bus system, i.e. the way the CPU talks to the other stuff inside
2572 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2573 VESA. If you have PCI, say Y, otherwise N.
2576 prompt "PCI access mode"
2577 depends on X86_32 && PCI
2580 On PCI systems, the BIOS can be used to detect the PCI devices and
2581 determine their configuration. However, some old PCI motherboards
2582 have BIOS bugs and may crash if this is done. Also, some embedded
2583 PCI-based systems don't have any BIOS at all. Linux can also try to
2584 detect the PCI hardware directly without using the BIOS.
2586 With this option, you can specify how Linux should detect the
2587 PCI devices. If you choose "BIOS", the BIOS will be used,
2588 if you choose "Direct", the BIOS won't be used, and if you
2589 choose "MMConfig", then PCI Express MMCONFIG will be used.
2590 If you choose "Any", the kernel will try MMCONFIG, then the
2591 direct access method and falls back to the BIOS if that doesn't
2592 work. If unsure, go with the default, which is "Any".
2597 config PCI_GOMMCONFIG
2614 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2616 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2619 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2623 depends on X86_32 && PCI && (ACPI || SFI) && (PCI_GOMMCONFIG || PCI_GOANY)
2627 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2631 depends on PCI && XEN
2639 bool "Support mmconfig PCI config space access"
2640 depends on X86_64 && PCI && ACPI
2642 config PCI_CNB20LE_QUIRK
2643 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2646 Read the PCI windows out of the CNB20LE host bridge. This allows
2647 PCI hotplug to work on systems with the CNB20LE chipset which do
2650 There's no public spec for this chipset, and this functionality
2651 is known to be incomplete.
2653 You should say N unless you know you need this.
2655 source "drivers/pci/Kconfig"
2658 bool "ISA-style bus support on modern systems" if EXPERT
2661 Enables ISA-style drivers on modern systems. This is necessary to
2662 support PC/104 devices on X86_64 platforms.
2666 # x86_64 have no ISA slots, but can have ISA-style DMA.
2668 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2671 Enables ISA-style DMA support for devices requiring such controllers.
2679 Find out whether you have ISA slots on your motherboard. ISA is the
2680 name of a bus system, i.e. the way the CPU talks to the other stuff
2681 inside your box. Other bus systems are PCI, EISA, MicroChannel
2682 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2683 newer boards don't support it. If you have ISA, say Y, otherwise N.
2689 The Extended Industry Standard Architecture (EISA) bus was
2690 developed as an open alternative to the IBM MicroChannel bus.
2692 The EISA bus provided some of the features of the IBM MicroChannel
2693 bus while maintaining backward compatibility with cards made for
2694 the older ISA bus. The EISA bus saw limited use between 1988 and
2695 1995 when it was made obsolete by the PCI bus.
2697 Say Y here if you are building a kernel for an EISA-based machine.
2701 source "drivers/eisa/Kconfig"
2704 tristate "NatSemi SCx200 support"
2706 This provides basic support for National Semiconductor's
2707 (now AMD's) Geode processors. The driver probes for the
2708 PCI-IDs of several on-chip devices, so its a good dependency
2709 for other scx200_* drivers.
2711 If compiled as a module, the driver is named scx200.
2713 config SCx200HR_TIMER
2714 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2718 This driver provides a clocksource built upon the on-chip
2719 27MHz high-resolution timer. Its also a workaround for
2720 NSC Geode SC-1100's buggy TSC, which loses time when the
2721 processor goes idle (as is done by the scheduler). The
2722 other workaround is idle=poll boot option.
2725 bool "One Laptop Per Child support"
2732 Add support for detecting the unique features of the OLPC
2736 bool "OLPC XO-1 Power Management"
2737 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2739 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2742 bool "OLPC XO-1 Real Time Clock"
2743 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2745 Add support for the XO-1 real time clock, which can be used as a
2746 programmable wakeup source.
2749 bool "OLPC XO-1 SCI extras"
2750 depends on OLPC && OLPC_XO1_PM
2756 Add support for SCI-based features of the OLPC XO-1 laptop:
2757 - EC-driven system wakeups
2761 - AC adapter status updates
2762 - Battery status updates
2764 config OLPC_XO15_SCI
2765 bool "OLPC XO-1.5 SCI extras"
2766 depends on OLPC && ACPI
2769 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2770 - EC-driven system wakeups
2771 - AC adapter status updates
2772 - Battery status updates
2775 bool "PCEngines ALIX System Support (LED setup)"
2778 This option enables system support for the PCEngines ALIX.
2779 At present this just sets up LEDs for GPIO control on
2780 ALIX2/3/6 boards. However, other system specific setup should
2783 Note: You must still enable the drivers for GPIO and LED support
2784 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2786 Note: You have to set alix.force=1 for boards with Award BIOS.
2789 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2792 This option enables system support for the Soekris Engineering net5501.
2795 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2799 This option enables system support for the Traverse Technologies GEOS.
2802 bool "Technologic Systems TS-5500 platform support"
2804 select CHECK_SIGNATURE
2808 This option enables system support for the Technologic Systems TS-5500.
2814 depends on CPU_SUP_AMD && PCI
2816 source "drivers/pcmcia/Kconfig"
2819 tristate "RapidIO support"
2823 If enabled this option will include drivers and the core
2824 infrastructure code to support RapidIO interconnect devices.
2826 source "drivers/rapidio/Kconfig"
2829 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2831 Firmwares often provide initial graphics framebuffers so the BIOS,
2832 bootloader or kernel can show basic video-output during boot for
2833 user-guidance and debugging. Historically, x86 used the VESA BIOS
2834 Extensions and EFI-framebuffers for this, which are mostly limited
2836 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2837 framebuffers so the new generic system-framebuffer drivers can be
2838 used on x86. If the framebuffer is not compatible with the generic
2839 modes, it is adverticed as fallback platform framebuffer so legacy
2840 drivers like efifb, vesafb and uvesafb can pick it up.
2841 If this option is not selected, all system framebuffers are always
2842 marked as fallback platform framebuffers as usual.
2844 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2845 not be able to pick up generic system framebuffers if this option
2846 is selected. You are highly encouraged to enable simplefb as
2847 replacement if you select this option. simplefb can correctly deal
2848 with generic system framebuffers. But you should still keep vesafb
2849 and others enabled as fallback if a system framebuffer is
2850 incompatible with simplefb.
2857 menu "Executable file formats / Emulations"
2859 source "fs/Kconfig.binfmt"
2861 config IA32_EMULATION
2862 bool "IA32 Emulation"
2864 select ARCH_WANT_OLD_COMPAT_IPC
2866 select COMPAT_BINFMT_ELF
2867 select COMPAT_OLD_SIGACTION
2869 Include code to run legacy 32-bit programs under a
2870 64-bit kernel. You should likely turn this on, unless you're
2871 100% sure that you don't have any 32-bit programs left.
2874 tristate "IA32 a.out support"
2875 depends on IA32_EMULATION
2877 Support old a.out binaries in the 32bit emulation.
2880 bool "x32 ABI for 64-bit mode"
2883 Include code to run binaries for the x32 native 32-bit ABI
2884 for 64-bit processors. An x32 process gets access to the
2885 full 64-bit register file and wide data path while leaving
2886 pointers at 32 bits for smaller memory footprint.
2888 You will need a recent binutils (2.22 or later) with
2889 elf32_x86_64 support enabled to compile a kernel with this
2894 depends on IA32_EMULATION || X86_32
2896 select OLD_SIGSUSPEND3
2900 depends on IA32_EMULATION || X86_X32
2903 config COMPAT_FOR_U64_ALIGNMENT
2906 config SYSVIPC_COMPAT
2914 config HAVE_ATOMIC_IOMAP
2918 config X86_DEV_DMA_OPS
2920 depends on X86_64 || STA2X11
2922 config X86_DMA_REMAP
2926 config HAVE_GENERIC_GUP
2929 source "net/Kconfig"
2931 source "drivers/Kconfig"
2933 source "drivers/firmware/Kconfig"
2937 source "arch/x86/Kconfig.debug"
2939 source "security/Kconfig"
2941 source "crypto/Kconfig"
2943 source "arch/x86/kvm/Kconfig"
2945 source "lib/Kconfig"
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