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_MEMBARRIER_SYNC_CORE
59 select ARCH_HAS_PMEM_API if X86_64
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_SYNC_CORE_BEFORE_USERMODE
67 select ARCH_HAS_UBSAN_SANITIZE_ALL
68 select ARCH_HAS_ZONE_DEVICE if X86_64
69 select ARCH_HAVE_NMI_SAFE_CMPXCHG
70 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
71 select ARCH_MIGHT_HAVE_PC_PARPORT
72 select ARCH_MIGHT_HAVE_PC_SERIO
73 select ARCH_SUPPORTS_ATOMIC_RMW
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_MATRIX_ALLOCATOR if X86_LOCAL_APIC
99 select GENERIC_IRQ_MIGRATION if SMP
100 select GENERIC_IRQ_PROBE
101 select GENERIC_IRQ_RESERVATION_MODE
102 select GENERIC_IRQ_SHOW
103 select GENERIC_PENDING_IRQ if SMP
104 select GENERIC_SMP_IDLE_THREAD
105 select GENERIC_STRNCPY_FROM_USER
106 select GENERIC_STRNLEN_USER
107 select GENERIC_TIME_VSYSCALL
108 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
109 select HAVE_ACPI_APEI if ACPI
110 select HAVE_ACPI_APEI_NMI if ACPI
111 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
112 select HAVE_ARCH_AUDITSYSCALL
113 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
114 select HAVE_ARCH_JUMP_LABEL
115 select HAVE_ARCH_KASAN if X86_64
116 select HAVE_ARCH_KGDB
117 select HAVE_ARCH_MMAP_RND_BITS if MMU
118 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
119 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
120 select HAVE_ARCH_SECCOMP_FILTER
121 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
122 select HAVE_ARCH_TRACEHOOK
123 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
124 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
125 select HAVE_ARCH_VMAP_STACK if X86_64
126 select HAVE_ARCH_WITHIN_STACK_FRAMES
127 select HAVE_CC_STACKPROTECTOR
128 select HAVE_CMPXCHG_DOUBLE
129 select HAVE_CMPXCHG_LOCAL
130 select HAVE_CONTEXT_TRACKING if X86_64
131 select HAVE_COPY_THREAD_TLS
132 select HAVE_C_RECORDMCOUNT
133 select HAVE_DEBUG_KMEMLEAK
134 select HAVE_DEBUG_STACKOVERFLOW
135 select HAVE_DMA_API_DEBUG
136 select HAVE_DMA_CONTIGUOUS
137 select HAVE_DYNAMIC_FTRACE
138 select HAVE_DYNAMIC_FTRACE_WITH_REGS
139 select HAVE_EBPF_JIT if X86_64
140 select HAVE_EFFICIENT_UNALIGNED_ACCESS
141 select HAVE_EXIT_THREAD
142 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
143 select HAVE_FTRACE_MCOUNT_RECORD
144 select HAVE_FUNCTION_GRAPH_TRACER
145 select HAVE_FUNCTION_TRACER
146 select HAVE_GCC_PLUGINS
147 select HAVE_HW_BREAKPOINT
149 select HAVE_IOREMAP_PROT
150 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
151 select HAVE_IRQ_TIME_ACCOUNTING
152 select HAVE_KERNEL_BZIP2
153 select HAVE_KERNEL_GZIP
154 select HAVE_KERNEL_LZ4
155 select HAVE_KERNEL_LZMA
156 select HAVE_KERNEL_LZO
157 select HAVE_KERNEL_XZ
159 select HAVE_KPROBES_ON_FTRACE
160 select HAVE_FUNCTION_ERROR_INJECTION
161 select HAVE_KRETPROBES
163 select HAVE_LIVEPATCH if X86_64
165 select HAVE_MEMBLOCK_NODE_MAP
166 select HAVE_MIXED_BREAKPOINTS_REGS
167 select HAVE_MOD_ARCH_SPECIFIC
170 select HAVE_OPTPROBES
171 select HAVE_PCSPKR_PLATFORM
172 select HAVE_PERF_EVENTS
173 select HAVE_PERF_EVENTS_NMI
174 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
175 select HAVE_PERF_REGS
176 select HAVE_PERF_USER_STACK_DUMP
177 select HAVE_RCU_TABLE_FREE
178 select HAVE_REGS_AND_STACK_ACCESS_API
179 select HAVE_RELIABLE_STACKTRACE if X86_64 && UNWINDER_FRAME_POINTER && STACK_VALIDATION
180 select HAVE_STACK_VALIDATION if X86_64
181 select HAVE_SYSCALL_TRACEPOINTS
182 select HAVE_UNSTABLE_SCHED_CLOCK
183 select HAVE_USER_RETURN_NOTIFIER
184 select IRQ_FORCED_THREADING
185 select PCI_LOCKLESS_CONFIG
188 select RTC_MC146818_LIB
191 select SYSCTL_EXCEPTION_TRACE
192 select THREAD_INFO_IN_TASK
193 select USER_STACKTRACE_SUPPORT
195 select X86_FEATURE_NAMES if PROC_FS
197 config INSTRUCTION_DECODER
199 depends on KPROBES || PERF_EVENTS || UPROBES
203 default "elf32-i386" if X86_32
204 default "elf64-x86-64" if X86_64
206 config ARCH_DEFCONFIG
208 default "arch/x86/configs/i386_defconfig" if X86_32
209 default "arch/x86/configs/x86_64_defconfig" if X86_64
211 config LOCKDEP_SUPPORT
214 config STACKTRACE_SUPPORT
220 config ARCH_MMAP_RND_BITS_MIN
224 config ARCH_MMAP_RND_BITS_MAX
228 config ARCH_MMAP_RND_COMPAT_BITS_MIN
231 config ARCH_MMAP_RND_COMPAT_BITS_MAX
237 config NEED_DMA_MAP_STATE
239 depends on X86_64 || INTEL_IOMMU || DMA_API_DEBUG || SWIOTLB
241 config NEED_SG_DMA_LENGTH
244 config GENERIC_ISA_DMA
246 depends on ISA_DMA_API
251 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
253 config GENERIC_BUG_RELATIVE_POINTERS
256 config GENERIC_HWEIGHT
259 config ARCH_MAY_HAVE_PC_FDC
261 depends on ISA_DMA_API
263 config RWSEM_XCHGADD_ALGORITHM
266 config GENERIC_CALIBRATE_DELAY
269 config ARCH_HAS_CPU_RELAX
272 config ARCH_HAS_CACHE_LINE_SIZE
275 config HAVE_SETUP_PER_CPU_AREA
278 config NEED_PER_CPU_EMBED_FIRST_CHUNK
281 config NEED_PER_CPU_PAGE_FIRST_CHUNK
284 config ARCH_HIBERNATION_POSSIBLE
287 config ARCH_SUSPEND_POSSIBLE
290 config ARCH_WANT_HUGE_PMD_SHARE
293 config ARCH_WANT_GENERAL_HUGETLB
302 config ARCH_SUPPORTS_OPTIMIZED_INLINING
305 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
308 config KASAN_SHADOW_OFFSET
311 default 0xdffffc0000000000
313 config HAVE_INTEL_TXT
315 depends on INTEL_IOMMU && ACPI
319 depends on X86_32 && SMP
323 depends on X86_64 && SMP
325 config X86_32_LAZY_GS
327 depends on X86_32 && CC_STACKPROTECTOR_NONE
329 config ARCH_SUPPORTS_UPROBES
332 config FIX_EARLYCON_MEM
335 config PGTABLE_LEVELS
337 default 5 if X86_5LEVEL
342 source "init/Kconfig"
343 source "kernel/Kconfig.freezer"
345 menu "Processor type and features"
348 bool "DMA memory allocation support" if EXPERT
351 DMA memory allocation support allows devices with less than 32-bit
352 addressing to allocate within the first 16MB of address space.
353 Disable if no such devices will be used.
358 bool "Symmetric multi-processing support"
360 This enables support for systems with more than one CPU. If you have
361 a system with only one CPU, say N. If you have a system with more
364 If you say N here, the kernel will run on uni- and multiprocessor
365 machines, but will use only one CPU of a multiprocessor machine. If
366 you say Y here, the kernel will run on many, but not all,
367 uniprocessor machines. On a uniprocessor machine, the kernel
368 will run faster if you say N here.
370 Note that if you say Y here and choose architecture "586" or
371 "Pentium" under "Processor family", the kernel will not work on 486
372 architectures. Similarly, multiprocessor kernels for the "PPro"
373 architecture may not work on all Pentium based boards.
375 People using multiprocessor machines who say Y here should also say
376 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
377 Management" code will be disabled if you say Y here.
379 See also <file:Documentation/x86/i386/IO-APIC.txt>,
380 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
381 <http://www.tldp.org/docs.html#howto>.
383 If you don't know what to do here, say N.
385 config X86_FEATURE_NAMES
386 bool "Processor feature human-readable names" if EMBEDDED
389 This option compiles in a table of x86 feature bits and corresponding
390 names. This is required to support /proc/cpuinfo and a few kernel
391 messages. You can disable this to save space, at the expense of
392 making those few kernel messages show numeric feature bits instead.
396 config X86_FAST_FEATURE_TESTS
397 bool "Fast CPU feature tests" if EMBEDDED
400 Some fast-paths in the kernel depend on the capabilities of the CPU.
401 Say Y here for the kernel to patch in the appropriate code at runtime
402 based on the capabilities of the CPU. The infrastructure for patching
403 code at runtime takes up some additional space; space-constrained
404 embedded systems may wish to say N here to produce smaller, slightly
408 bool "Support x2apic"
409 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
411 This enables x2apic support on CPUs that have this feature.
413 This allows 32-bit apic IDs (so it can support very large systems),
414 and accesses the local apic via MSRs not via mmio.
416 If you don't know what to do here, say N.
419 bool "Enable MPS table" if ACPI || SFI
421 depends on X86_LOCAL_APIC
423 For old smp systems that do not have proper acpi support. Newer systems
424 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
427 bool "Support for big SMP systems with more than 8 CPUs"
428 depends on X86_32 && SMP
430 This option is needed for the systems that have more than 8 CPUs
434 depends on X86_GOLDFISH
437 bool "Avoid speculative indirect branches in kernel"
439 select STACK_VALIDATION if HAVE_STACK_VALIDATION
441 Compile kernel with the retpoline compiler options to guard against
442 kernel-to-user data leaks by avoiding speculative indirect
443 branches. Requires a compiler with -mindirect-branch=thunk-extern
444 support for full protection. The kernel may run slower.
446 Without compiler support, at least indirect branches in assembler
447 code are eliminated. Since this includes the syscall entry path,
448 it is not entirely pointless.
451 bool "Intel Resource Director Technology support"
453 depends on X86 && CPU_SUP_INTEL
456 Select to enable resource allocation and monitoring which are
457 sub-features of Intel Resource Director Technology(RDT). More
458 information about RDT can be found in the Intel x86
459 Architecture Software Developer Manual.
464 config X86_EXTENDED_PLATFORM
465 bool "Support for extended (non-PC) x86 platforms"
468 If you disable this option then the kernel will only support
469 standard PC platforms. (which covers the vast majority of
472 If you enable this option then you'll be able to select support
473 for the following (non-PC) 32 bit x86 platforms:
474 Goldfish (Android emulator)
477 SGI 320/540 (Visual Workstation)
478 STA2X11-based (e.g. Northville)
479 Moorestown MID devices
481 If you have one of these systems, or if you want to build a
482 generic distribution kernel, say Y here - otherwise say N.
486 config X86_EXTENDED_PLATFORM
487 bool "Support for extended (non-PC) x86 platforms"
490 If you disable this option then the kernel will only support
491 standard PC platforms. (which covers the vast majority of
494 If you enable this option then you'll be able to select support
495 for the following (non-PC) 64 bit x86 platforms:
500 If you have one of these systems, or if you want to build a
501 generic distribution kernel, say Y here - otherwise say N.
503 # This is an alphabetically sorted list of 64 bit extended platforms
504 # Please maintain the alphabetic order if and when there are additions
506 bool "Numascale NumaChip"
508 depends on X86_EXTENDED_PLATFORM
511 depends on X86_X2APIC
512 depends on PCI_MMCONFIG
514 Adds support for Numascale NumaChip large-SMP systems. Needed to
515 enable more than ~168 cores.
516 If you don't have one of these, you should say N here.
520 select HYPERVISOR_GUEST
522 depends on X86_64 && PCI
523 depends on X86_EXTENDED_PLATFORM
526 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
527 supposed to run on these EM64T-based machines. Only choose this option
528 if you have one of these machines.
531 bool "SGI Ultraviolet"
533 depends on X86_EXTENDED_PLATFORM
536 depends on X86_X2APIC
539 This option is needed in order to support SGI Ultraviolet systems.
540 If you don't have one of these, you should say N here.
542 # Following is an alphabetically sorted list of 32 bit extended platforms
543 # Please maintain the alphabetic order if and when there are additions
546 bool "Goldfish (Virtual Platform)"
547 depends on X86_EXTENDED_PLATFORM
549 Enable support for the Goldfish virtual platform used primarily
550 for Android development. Unless you are building for the Android
551 Goldfish emulator say N here.
554 bool "CE4100 TV platform"
556 depends on PCI_GODIRECT
557 depends on X86_IO_APIC
559 depends on X86_EXTENDED_PLATFORM
560 select X86_REBOOTFIXUPS
562 select OF_EARLY_FLATTREE
564 Select for the Intel CE media processor (CE4100) SOC.
565 This option compiles in support for the CE4100 SOC for settop
566 boxes and media devices.
569 bool "Intel MID platform support"
570 depends on X86_EXTENDED_PLATFORM
571 depends on X86_PLATFORM_DEVICES
573 depends on X86_64 || (PCI_GOANY && X86_32)
574 depends on X86_IO_APIC
580 select MFD_INTEL_MSIC
582 Select to build a kernel capable of supporting Intel MID (Mobile
583 Internet Device) platform systems which do not have the PCI legacy
584 interfaces. If you are building for a PC class system say N here.
586 Intel MID platforms are based on an Intel processor and chipset which
587 consume less power than most of the x86 derivatives.
589 config X86_INTEL_QUARK
590 bool "Intel Quark platform support"
592 depends on X86_EXTENDED_PLATFORM
593 depends on X86_PLATFORM_DEVICES
597 depends on X86_IO_APIC
602 Select to include support for Quark X1000 SoC.
603 Say Y here if you have a Quark based system such as the Arduino
604 compatible Intel Galileo.
606 config X86_INTEL_LPSS
607 bool "Intel Low Power Subsystem Support"
608 depends on X86 && ACPI
613 Select to build support for Intel Low Power Subsystem such as
614 found on Intel Lynxpoint PCH. Selecting this option enables
615 things like clock tree (common clock framework) and pincontrol
616 which are needed by the LPSS peripheral drivers.
618 config X86_AMD_PLATFORM_DEVICE
619 bool "AMD ACPI2Platform devices support"
624 Select to interpret AMD specific ACPI device to platform device
625 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
626 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
627 implemented under PINCTRL subsystem.
630 tristate "Intel SoC IOSF Sideband support for SoC platforms"
633 This option enables sideband register access support for Intel SoC
634 platforms. On these platforms the IOSF sideband is used in lieu of
635 MSR's for some register accesses, mostly but not limited to thermal
636 and power. Drivers may query the availability of this device to
637 determine if they need the sideband in order to work on these
638 platforms. The sideband is available on the following SoC products.
639 This list is not meant to be exclusive.
644 You should say Y if you are running a kernel on one of these SoC's.
646 config IOSF_MBI_DEBUG
647 bool "Enable IOSF sideband access through debugfs"
648 depends on IOSF_MBI && DEBUG_FS
650 Select this option to expose the IOSF sideband access registers (MCR,
651 MDR, MCRX) through debugfs to write and read register information from
652 different units on the SoC. This is most useful for obtaining device
653 state information for debug and analysis. As this is a general access
654 mechanism, users of this option would have specific knowledge of the
655 device they want to access.
657 If you don't require the option or are in doubt, say N.
660 bool "RDC R-321x SoC"
662 depends on X86_EXTENDED_PLATFORM
664 select X86_REBOOTFIXUPS
666 This option is needed for RDC R-321x system-on-chip, also known
668 If you don't have one of these chips, you should say N here.
670 config X86_32_NON_STANDARD
671 bool "Support non-standard 32-bit SMP architectures"
672 depends on X86_32 && SMP
673 depends on X86_EXTENDED_PLATFORM
675 This option compiles in the bigsmp and STA2X11 default
676 subarchitectures. It is intended for a generic binary
677 kernel. If you select them all, kernel will probe it one by
678 one and will fallback to default.
680 # Alphabetically sorted list of Non standard 32 bit platforms
682 config X86_SUPPORTS_MEMORY_FAILURE
684 # MCE code calls memory_failure():
686 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
687 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
688 depends on X86_64 || !SPARSEMEM
689 select ARCH_SUPPORTS_MEMORY_FAILURE
692 bool "STA2X11 Companion Chip Support"
693 depends on X86_32_NON_STANDARD && PCI
694 select X86_DEV_DMA_OPS
701 This adds support for boards based on the STA2X11 IO-Hub,
702 a.k.a. "ConneXt". The chip is used in place of the standard
703 PC chipset, so all "standard" peripherals are missing. If this
704 option is selected the kernel will still be able to boot on
705 standard PC machines.
708 tristate "Eurobraille/Iris poweroff module"
711 The Iris machines from EuroBraille do not have APM or ACPI support
712 to shut themselves down properly. A special I/O sequence is
713 needed to do so, which is what this module does at
716 This is only for Iris machines from EuroBraille.
720 config SCHED_OMIT_FRAME_POINTER
722 prompt "Single-depth WCHAN output"
725 Calculate simpler /proc/<PID>/wchan values. If this option
726 is disabled then wchan values will recurse back to the
727 caller function. This provides more accurate wchan values,
728 at the expense of slightly more scheduling overhead.
730 If in doubt, say "Y".
732 menuconfig HYPERVISOR_GUEST
733 bool "Linux guest support"
735 Say Y here to enable options for running Linux under various hyper-
736 visors. This option enables basic hypervisor detection and platform
739 If you say N, all options in this submenu will be skipped and
740 disabled, and Linux guest support won't be built in.
745 bool "Enable paravirtualization code"
747 This changes the kernel so it can modify itself when it is run
748 under a hypervisor, potentially improving performance significantly
749 over full virtualization. However, when run without a hypervisor
750 the kernel is theoretically slower and slightly larger.
752 config PARAVIRT_DEBUG
753 bool "paravirt-ops debugging"
754 depends on PARAVIRT && DEBUG_KERNEL
756 Enable to debug paravirt_ops internals. Specifically, BUG if
757 a paravirt_op is missing when it is called.
759 config PARAVIRT_SPINLOCKS
760 bool "Paravirtualization layer for spinlocks"
761 depends on PARAVIRT && SMP
763 Paravirtualized spinlocks allow a pvops backend to replace the
764 spinlock implementation with something virtualization-friendly
765 (for example, block the virtual CPU rather than spinning).
767 It has a minimal impact on native kernels and gives a nice performance
768 benefit on paravirtualized KVM / Xen kernels.
770 If you are unsure how to answer this question, answer Y.
772 config QUEUED_LOCK_STAT
773 bool "Paravirt queued spinlock statistics"
774 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
776 Enable the collection of statistical data on the slowpath
777 behavior of paravirtualized queued spinlocks and report
780 source "arch/x86/xen/Kconfig"
783 bool "KVM Guest support (including kvmclock)"
785 select PARAVIRT_CLOCK
788 This option enables various optimizations for running under the KVM
789 hypervisor. It includes a paravirtualized clock, so that instead
790 of relying on a PIT (or probably other) emulation by the
791 underlying device model, the host provides the guest with
792 timing infrastructure such as time of day, and system time
795 bool "Enable debug information for KVM Guests in debugfs"
796 depends on KVM_GUEST && DEBUG_FS
799 This option enables collection of various statistics for KVM guest.
800 Statistics are displayed in debugfs filesystem. Enabling this option
801 may incur significant overhead.
803 config PARAVIRT_TIME_ACCOUNTING
804 bool "Paravirtual steal time accounting"
808 Select this option to enable fine granularity task steal time
809 accounting. Time spent executing other tasks in parallel with
810 the current vCPU is discounted from the vCPU power. To account for
811 that, there can be a small performance impact.
813 If in doubt, say N here.
815 config PARAVIRT_CLOCK
818 config JAILHOUSE_GUEST
819 bool "Jailhouse non-root cell support"
820 depends on X86_64 && PCI
823 This option allows to run Linux as guest in a Jailhouse non-root
824 cell. You can leave this option disabled if you only want to start
825 Jailhouse and run Linux afterwards in the root cell.
827 endif #HYPERVISOR_GUEST
832 source "arch/x86/Kconfig.cpu"
836 prompt "HPET Timer Support" if X86_32
838 Use the IA-PC HPET (High Precision Event Timer) to manage
839 time in preference to the PIT and RTC, if a HPET is
841 HPET is the next generation timer replacing legacy 8254s.
842 The HPET provides a stable time base on SMP
843 systems, unlike the TSC, but it is more expensive to access,
844 as it is off-chip. The interface used is documented
845 in the HPET spec, revision 1.
847 You can safely choose Y here. However, HPET will only be
848 activated if the platform and the BIOS support this feature.
849 Otherwise the 8254 will be used for timing services.
851 Choose N to continue using the legacy 8254 timer.
853 config HPET_EMULATE_RTC
855 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
858 def_bool y if X86_INTEL_MID
859 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
861 depends on X86_INTEL_MID && SFI
863 APB timer is the replacement for 8254, HPET on X86 MID platforms.
864 The APBT provides a stable time base on SMP
865 systems, unlike the TSC, but it is more expensive to access,
866 as it is off-chip. APB timers are always running regardless of CPU
867 C states, they are used as per CPU clockevent device when possible.
869 # Mark as expert because too many people got it wrong.
870 # The code disables itself when not needed.
873 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
874 bool "Enable DMI scanning" if EXPERT
876 Enabled scanning of DMI to identify machine quirks. Say Y
877 here unless you have verified that your setup is not
878 affected by entries in the DMI blacklist. Required by PNP
882 bool "Old AMD GART IOMMU support"
884 depends on X86_64 && PCI && AMD_NB
886 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
887 GART based hardware IOMMUs.
889 The GART supports full DMA access for devices with 32-bit access
890 limitations, on systems with more than 3 GB. This is usually needed
891 for USB, sound, many IDE/SATA chipsets and some other devices.
893 Newer systems typically have a modern AMD IOMMU, supported via
894 the CONFIG_AMD_IOMMU=y config option.
896 In normal configurations this driver is only active when needed:
897 there's more than 3 GB of memory and the system contains a
898 32-bit limited device.
903 bool "IBM Calgary IOMMU support"
905 depends on X86_64 && PCI
907 Support for hardware IOMMUs in IBM's xSeries x366 and x460
908 systems. Needed to run systems with more than 3GB of memory
909 properly with 32-bit PCI devices that do not support DAC
910 (Double Address Cycle). Calgary also supports bus level
911 isolation, where all DMAs pass through the IOMMU. This
912 prevents them from going anywhere except their intended
913 destination. This catches hard-to-find kernel bugs and
914 mis-behaving drivers and devices that do not use the DMA-API
915 properly to set up their DMA buffers. The IOMMU can be
916 turned off at boot time with the iommu=off parameter.
917 Normally the kernel will make the right choice by itself.
920 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
922 prompt "Should Calgary be enabled by default?"
923 depends on CALGARY_IOMMU
925 Should Calgary be enabled by default? if you choose 'y', Calgary
926 will be used (if it exists). If you choose 'n', Calgary will not be
927 used even if it exists. If you choose 'n' and would like to use
928 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
931 # need this always selected by IOMMU for the VIA workaround
935 Support for software bounce buffers used on x86-64 systems
936 which don't have a hardware IOMMU. Using this PCI devices
937 which can only access 32-bits of memory can be used on systems
938 with more than 3 GB of memory.
943 depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU
946 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
947 depends on X86_64 && SMP && DEBUG_KERNEL
948 select CPUMASK_OFFSTACK
950 Enable maximum number of CPUS and NUMA Nodes for this architecture.
954 int "Maximum number of CPUs" if SMP && !MAXSMP
955 range 2 8 if SMP && X86_32 && !X86_BIGSMP
956 range 2 64 if SMP && X86_32 && X86_BIGSMP
957 range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK && X86_64
958 range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
960 default "8192" if MAXSMP
961 default "32" if SMP && X86_BIGSMP
962 default "8" if SMP && X86_32
965 This allows you to specify the maximum number of CPUs which this
966 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
967 supported value is 8192, otherwise the maximum value is 512. The
968 minimum value which makes sense is 2.
970 This is purely to save memory - each supported CPU adds
971 approximately eight kilobytes to the kernel image.
974 bool "SMT (Hyperthreading) scheduler support"
977 SMT scheduler support improves the CPU scheduler's decision making
978 when dealing with Intel Pentium 4 chips with HyperThreading at a
979 cost of slightly increased overhead in some places. If unsure say
984 prompt "Multi-core scheduler support"
987 Multi-core scheduler support improves the CPU scheduler's decision
988 making when dealing with multi-core CPU chips at a cost of slightly
989 increased overhead in some places. If unsure say N here.
992 bool "CPU core priorities scheduler support"
993 depends on SCHED_MC && CPU_SUP_INTEL
994 select X86_INTEL_PSTATE
998 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
999 core ordering determined at manufacturing time, which allows
1000 certain cores to reach higher turbo frequencies (when running
1001 single threaded workloads) than others.
1003 Enabling this kernel feature teaches the scheduler about
1004 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1005 scheduler's CPU selection logic accordingly, so that higher
1006 overall system performance can be achieved.
1008 This feature will have no effect on CPUs without this feature.
1010 If unsure say Y here.
1012 source "kernel/Kconfig.preempt"
1016 depends on !SMP && X86_LOCAL_APIC
1019 bool "Local APIC support on uniprocessors" if !PCI_MSI
1021 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1023 A local APIC (Advanced Programmable Interrupt Controller) is an
1024 integrated interrupt controller in the CPU. If you have a single-CPU
1025 system which has a processor with a local APIC, you can say Y here to
1026 enable and use it. If you say Y here even though your machine doesn't
1027 have a local APIC, then the kernel will still run with no slowdown at
1028 all. The local APIC supports CPU-generated self-interrupts (timer,
1029 performance counters), and the NMI watchdog which detects hard
1032 config X86_UP_IOAPIC
1033 bool "IO-APIC support on uniprocessors"
1034 depends on X86_UP_APIC
1036 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1037 SMP-capable replacement for PC-style interrupt controllers. Most
1038 SMP systems and many recent uniprocessor systems have one.
1040 If you have a single-CPU system with an IO-APIC, you can say Y here
1041 to use it. If you say Y here even though your machine doesn't have
1042 an IO-APIC, then the kernel will still run with no slowdown at all.
1044 config X86_LOCAL_APIC
1046 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1047 select IRQ_DOMAIN_HIERARCHY
1048 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1052 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1054 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1055 bool "Reroute for broken boot IRQs"
1056 depends on X86_IO_APIC
1058 This option enables a workaround that fixes a source of
1059 spurious interrupts. This is recommended when threaded
1060 interrupt handling is used on systems where the generation of
1061 superfluous "boot interrupts" cannot be disabled.
1063 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1064 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1065 kernel does during interrupt handling). On chipsets where this
1066 boot IRQ generation cannot be disabled, this workaround keeps
1067 the original IRQ line masked so that only the equivalent "boot
1068 IRQ" is delivered to the CPUs. The workaround also tells the
1069 kernel to set up the IRQ handler on the boot IRQ line. In this
1070 way only one interrupt is delivered to the kernel. Otherwise
1071 the spurious second interrupt may cause the kernel to bring
1072 down (vital) interrupt lines.
1074 Only affects "broken" chipsets. Interrupt sharing may be
1075 increased on these systems.
1078 bool "Machine Check / overheating reporting"
1079 select GENERIC_ALLOCATOR
1082 Machine Check support allows the processor to notify the
1083 kernel if it detects a problem (e.g. overheating, data corruption).
1084 The action the kernel takes depends on the severity of the problem,
1085 ranging from warning messages to halting the machine.
1087 config X86_MCELOG_LEGACY
1088 bool "Support for deprecated /dev/mcelog character device"
1091 Enable support for /dev/mcelog which is needed by the old mcelog
1092 userspace logging daemon. Consider switching to the new generation
1095 config X86_MCE_INTEL
1097 prompt "Intel MCE features"
1098 depends on X86_MCE && X86_LOCAL_APIC
1100 Additional support for intel specific MCE features such as
1101 the thermal monitor.
1105 prompt "AMD MCE features"
1106 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1108 Additional support for AMD specific MCE features such as
1109 the DRAM Error Threshold.
1111 config X86_ANCIENT_MCE
1112 bool "Support for old Pentium 5 / WinChip machine checks"
1113 depends on X86_32 && X86_MCE
1115 Include support for machine check handling on old Pentium 5 or WinChip
1116 systems. These typically need to be enabled explicitly on the command
1119 config X86_MCE_THRESHOLD
1120 depends on X86_MCE_AMD || X86_MCE_INTEL
1123 config X86_MCE_INJECT
1124 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1125 tristate "Machine check injector support"
1127 Provide support for injecting machine checks for testing purposes.
1128 If you don't know what a machine check is and you don't do kernel
1129 QA it is safe to say n.
1131 config X86_THERMAL_VECTOR
1133 depends on X86_MCE_INTEL
1135 source "arch/x86/events/Kconfig"
1137 config X86_LEGACY_VM86
1138 bool "Legacy VM86 support"
1142 This option allows user programs to put the CPU into V8086
1143 mode, which is an 80286-era approximation of 16-bit real mode.
1145 Some very old versions of X and/or vbetool require this option
1146 for user mode setting. Similarly, DOSEMU will use it if
1147 available to accelerate real mode DOS programs. However, any
1148 recent version of DOSEMU, X, or vbetool should be fully
1149 functional even without kernel VM86 support, as they will all
1150 fall back to software emulation. Nevertheless, if you are using
1151 a 16-bit DOS program where 16-bit performance matters, vm86
1152 mode might be faster than emulation and you might want to
1155 Note that any app that works on a 64-bit kernel is unlikely to
1156 need this option, as 64-bit kernels don't, and can't, support
1157 V8086 mode. This option is also unrelated to 16-bit protected
1158 mode and is not needed to run most 16-bit programs under Wine.
1160 Enabling this option increases the complexity of the kernel
1161 and slows down exception handling a tiny bit.
1163 If unsure, say N here.
1167 default X86_LEGACY_VM86
1170 bool "Enable support for 16-bit segments" if EXPERT
1172 depends on MODIFY_LDT_SYSCALL
1174 This option is required by programs like Wine to run 16-bit
1175 protected mode legacy code on x86 processors. Disabling
1176 this option saves about 300 bytes on i386, or around 6K text
1177 plus 16K runtime memory on x86-64,
1181 depends on X86_16BIT && X86_32
1185 depends on X86_16BIT && X86_64
1187 config X86_VSYSCALL_EMULATION
1188 bool "Enable vsyscall emulation" if EXPERT
1192 This enables emulation of the legacy vsyscall page. Disabling
1193 it is roughly equivalent to booting with vsyscall=none, except
1194 that it will also disable the helpful warning if a program
1195 tries to use a vsyscall. With this option set to N, offending
1196 programs will just segfault, citing addresses of the form
1199 This option is required by many programs built before 2013, and
1200 care should be used even with newer programs if set to N.
1202 Disabling this option saves about 7K of kernel size and
1203 possibly 4K of additional runtime pagetable memory.
1206 tristate "Toshiba Laptop support"
1209 This adds a driver to safely access the System Management Mode of
1210 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1211 not work on models with a Phoenix BIOS. The System Management Mode
1212 is used to set the BIOS and power saving options on Toshiba portables.
1214 For information on utilities to make use of this driver see the
1215 Toshiba Linux utilities web site at:
1216 <http://www.buzzard.org.uk/toshiba/>.
1218 Say Y if you intend to run this kernel on a Toshiba portable.
1222 tristate "Dell i8k legacy laptop support"
1224 select SENSORS_DELL_SMM
1226 This option enables legacy /proc/i8k userspace interface in hwmon
1227 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1228 temperature and allows controlling fan speeds of Dell laptops via
1229 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1230 it reports also power and hotkey status. For fan speed control is
1231 needed userspace package i8kutils.
1233 Say Y if you intend to run this kernel on old Dell laptops or want to
1234 use userspace package i8kutils.
1237 config X86_REBOOTFIXUPS
1238 bool "Enable X86 board specific fixups for reboot"
1241 This enables chipset and/or board specific fixups to be done
1242 in order to get reboot to work correctly. This is only needed on
1243 some combinations of hardware and BIOS. The symptom, for which
1244 this config is intended, is when reboot ends with a stalled/hung
1247 Currently, the only fixup is for the Geode machines using
1248 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1250 Say Y if you want to enable the fixup. Currently, it's safe to
1251 enable this option even if you don't need it.
1255 bool "CPU microcode loading support"
1257 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1260 If you say Y here, you will be able to update the microcode on
1261 Intel and AMD processors. The Intel support is for the IA32 family,
1262 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1263 AMD support is for families 0x10 and later. You will obviously need
1264 the actual microcode binary data itself which is not shipped with
1267 The preferred method to load microcode from a detached initrd is described
1268 in Documentation/x86/early-microcode.txt. For that you need to enable
1269 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1270 initrd for microcode blobs.
1272 In addition, you can build the microcode into the kernel. For that you
1273 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1276 config MICROCODE_INTEL
1277 bool "Intel microcode loading support"
1278 depends on MICROCODE
1282 This options enables microcode patch loading support for Intel
1285 For the current Intel microcode data package go to
1286 <https://downloadcenter.intel.com> and search for
1287 'Linux Processor Microcode Data File'.
1289 config MICROCODE_AMD
1290 bool "AMD microcode loading support"
1291 depends on MICROCODE
1294 If you select this option, microcode patch loading support for AMD
1295 processors will be enabled.
1297 config MICROCODE_OLD_INTERFACE
1299 depends on MICROCODE
1302 tristate "/dev/cpu/*/msr - Model-specific register support"
1304 This device gives privileged processes access to the x86
1305 Model-Specific Registers (MSRs). It is a character device with
1306 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1307 MSR accesses are directed to a specific CPU on multi-processor
1311 tristate "/dev/cpu/*/cpuid - CPU information support"
1313 This device gives processes access to the x86 CPUID instruction to
1314 be executed on a specific processor. It is a character device
1315 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1319 prompt "High Memory Support"
1326 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1327 However, the address space of 32-bit x86 processors is only 4
1328 Gigabytes large. That means that, if you have a large amount of
1329 physical memory, not all of it can be "permanently mapped" by the
1330 kernel. The physical memory that's not permanently mapped is called
1333 If you are compiling a kernel which will never run on a machine with
1334 more than 1 Gigabyte total physical RAM, answer "off" here (default
1335 choice and suitable for most users). This will result in a "3GB/1GB"
1336 split: 3GB are mapped so that each process sees a 3GB virtual memory
1337 space and the remaining part of the 4GB virtual memory space is used
1338 by the kernel to permanently map as much physical memory as
1341 If the machine has between 1 and 4 Gigabytes physical RAM, then
1344 If more than 4 Gigabytes is used then answer "64GB" here. This
1345 selection turns Intel PAE (Physical Address Extension) mode on.
1346 PAE implements 3-level paging on IA32 processors. PAE is fully
1347 supported by Linux, PAE mode is implemented on all recent Intel
1348 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1349 then the kernel will not boot on CPUs that don't support PAE!
1351 The actual amount of total physical memory will either be
1352 auto detected or can be forced by using a kernel command line option
1353 such as "mem=256M". (Try "man bootparam" or see the documentation of
1354 your boot loader (lilo or loadlin) about how to pass options to the
1355 kernel at boot time.)
1357 If unsure, say "off".
1362 Select this if you have a 32-bit processor and between 1 and 4
1363 gigabytes of physical RAM.
1370 Select this if you have a 32-bit processor and more than 4
1371 gigabytes of physical RAM.
1376 prompt "Memory split" if EXPERT
1380 Select the desired split between kernel and user memory.
1382 If the address range available to the kernel is less than the
1383 physical memory installed, the remaining memory will be available
1384 as "high memory". Accessing high memory is a little more costly
1385 than low memory, as it needs to be mapped into the kernel first.
1386 Note that increasing the kernel address space limits the range
1387 available to user programs, making the address space there
1388 tighter. Selecting anything other than the default 3G/1G split
1389 will also likely make your kernel incompatible with binary-only
1392 If you are not absolutely sure what you are doing, leave this
1396 bool "3G/1G user/kernel split"
1397 config VMSPLIT_3G_OPT
1399 bool "3G/1G user/kernel split (for full 1G low memory)"
1401 bool "2G/2G user/kernel split"
1402 config VMSPLIT_2G_OPT
1404 bool "2G/2G user/kernel split (for full 2G low memory)"
1406 bool "1G/3G user/kernel split"
1411 default 0xB0000000 if VMSPLIT_3G_OPT
1412 default 0x80000000 if VMSPLIT_2G
1413 default 0x78000000 if VMSPLIT_2G_OPT
1414 default 0x40000000 if VMSPLIT_1G
1420 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1423 bool "PAE (Physical Address Extension) Support"
1424 depends on X86_32 && !HIGHMEM4G
1427 PAE is required for NX support, and furthermore enables
1428 larger swapspace support for non-overcommit purposes. It
1429 has the cost of more pagetable lookup overhead, and also
1430 consumes more pagetable space per process.
1433 bool "Enable 5-level page tables support"
1436 5-level paging enables access to larger address space:
1437 upto 128 PiB of virtual address space and 4 PiB of
1438 physical address space.
1440 It will be supported by future Intel CPUs.
1442 Note: a kernel with this option enabled can only be booted
1443 on machines that support the feature.
1445 See Documentation/x86/x86_64/5level-paging.txt for more
1450 config ARCH_PHYS_ADDR_T_64BIT
1452 depends on X86_64 || X86_PAE
1454 config ARCH_DMA_ADDR_T_64BIT
1456 depends on X86_64 || HIGHMEM64G
1458 config X86_DIRECT_GBPAGES
1460 depends on X86_64 && !DEBUG_PAGEALLOC
1462 Certain kernel features effectively disable kernel
1463 linear 1 GB mappings (even if the CPU otherwise
1464 supports them), so don't confuse the user by printing
1465 that we have them enabled.
1467 config ARCH_HAS_MEM_ENCRYPT
1470 config AMD_MEM_ENCRYPT
1471 bool "AMD Secure Memory Encryption (SME) support"
1472 depends on X86_64 && CPU_SUP_AMD
1474 Say yes to enable support for the encryption of system memory.
1475 This requires an AMD processor that supports Secure Memory
1478 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1479 bool "Activate AMD Secure Memory Encryption (SME) by default"
1481 depends on AMD_MEM_ENCRYPT
1483 Say yes to have system memory encrypted by default if running on
1484 an AMD processor that supports Secure Memory Encryption (SME).
1486 If set to Y, then the encryption of system memory can be
1487 deactivated with the mem_encrypt=off command line option.
1489 If set to N, then the encryption of system memory can be
1490 activated with the mem_encrypt=on command line option.
1492 config ARCH_USE_MEMREMAP_PROT
1494 depends on AMD_MEM_ENCRYPT
1496 # Common NUMA Features
1498 bool "Numa Memory Allocation and Scheduler Support"
1500 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1501 default y if X86_BIGSMP
1503 Enable NUMA (Non Uniform Memory Access) support.
1505 The kernel will try to allocate memory used by a CPU on the
1506 local memory controller of the CPU and add some more
1507 NUMA awareness to the kernel.
1509 For 64-bit this is recommended if the system is Intel Core i7
1510 (or later), AMD Opteron, or EM64T NUMA.
1512 For 32-bit this is only needed if you boot a 32-bit
1513 kernel on a 64-bit NUMA platform.
1515 Otherwise, you should say N.
1519 prompt "Old style AMD Opteron NUMA detection"
1520 depends on X86_64 && NUMA && PCI
1522 Enable AMD NUMA node topology detection. You should say Y here if
1523 you have a multi processor AMD system. This uses an old method to
1524 read the NUMA configuration directly from the builtin Northbridge
1525 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1526 which also takes priority if both are compiled in.
1528 config X86_64_ACPI_NUMA
1530 prompt "ACPI NUMA detection"
1531 depends on X86_64 && NUMA && ACPI && PCI
1534 Enable ACPI SRAT based node topology detection.
1536 # Some NUMA nodes have memory ranges that span
1537 # other nodes. Even though a pfn is valid and
1538 # between a node's start and end pfns, it may not
1539 # reside on that node. See memmap_init_zone()
1541 config NODES_SPAN_OTHER_NODES
1543 depends on X86_64_ACPI_NUMA
1546 bool "NUMA emulation"
1549 Enable NUMA emulation. A flat machine will be split
1550 into virtual nodes when booted with "numa=fake=N", where N is the
1551 number of nodes. This is only useful for debugging.
1554 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1556 default "10" if MAXSMP
1557 default "6" if X86_64
1559 depends on NEED_MULTIPLE_NODES
1561 Specify the maximum number of NUMA Nodes available on the target
1562 system. Increases memory reserved to accommodate various tables.
1564 config ARCH_HAVE_MEMORY_PRESENT
1566 depends on X86_32 && DISCONTIGMEM
1568 config NEED_NODE_MEMMAP_SIZE
1570 depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
1572 config ARCH_FLATMEM_ENABLE
1574 depends on X86_32 && !NUMA
1576 config ARCH_DISCONTIGMEM_ENABLE
1578 depends on NUMA && X86_32
1580 config ARCH_DISCONTIGMEM_DEFAULT
1582 depends on NUMA && X86_32
1584 config ARCH_SPARSEMEM_ENABLE
1586 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1587 select SPARSEMEM_STATIC if X86_32
1588 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1590 config ARCH_SPARSEMEM_DEFAULT
1594 config ARCH_SELECT_MEMORY_MODEL
1596 depends on ARCH_SPARSEMEM_ENABLE
1598 config ARCH_MEMORY_PROBE
1599 bool "Enable sysfs memory/probe interface"
1600 depends on X86_64 && MEMORY_HOTPLUG
1602 This option enables a sysfs memory/probe interface for testing.
1603 See Documentation/memory-hotplug.txt for more information.
1604 If you are unsure how to answer this question, answer N.
1606 config ARCH_PROC_KCORE_TEXT
1608 depends on X86_64 && PROC_KCORE
1610 config ILLEGAL_POINTER_VALUE
1613 default 0xdead000000000000 if X86_64
1617 config X86_PMEM_LEGACY_DEVICE
1620 config X86_PMEM_LEGACY
1621 tristate "Support non-standard NVDIMMs and ADR protected memory"
1622 depends on PHYS_ADDR_T_64BIT
1624 select X86_PMEM_LEGACY_DEVICE
1627 Treat memory marked using the non-standard e820 type of 12 as used
1628 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1629 The kernel will offer these regions to the 'pmem' driver so
1630 they can be used for persistent storage.
1635 bool "Allocate 3rd-level pagetables from highmem"
1638 The VM uses one page table entry for each page of physical memory.
1639 For systems with a lot of RAM, this can be wasteful of precious
1640 low memory. Setting this option will put user-space page table
1641 entries in high memory.
1643 config X86_CHECK_BIOS_CORRUPTION
1644 bool "Check for low memory corruption"
1646 Periodically check for memory corruption in low memory, which
1647 is suspected to be caused by BIOS. Even when enabled in the
1648 configuration, it is disabled at runtime. Enable it by
1649 setting "memory_corruption_check=1" on the kernel command
1650 line. By default it scans the low 64k of memory every 60
1651 seconds; see the memory_corruption_check_size and
1652 memory_corruption_check_period parameters in
1653 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1655 When enabled with the default parameters, this option has
1656 almost no overhead, as it reserves a relatively small amount
1657 of memory and scans it infrequently. It both detects corruption
1658 and prevents it from affecting the running system.
1660 It is, however, intended as a diagnostic tool; if repeatable
1661 BIOS-originated corruption always affects the same memory,
1662 you can use memmap= to prevent the kernel from using that
1665 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1666 bool "Set the default setting of memory_corruption_check"
1667 depends on X86_CHECK_BIOS_CORRUPTION
1670 Set whether the default state of memory_corruption_check is
1673 config X86_RESERVE_LOW
1674 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1678 Specify the amount of low memory to reserve for the BIOS.
1680 The first page contains BIOS data structures that the kernel
1681 must not use, so that page must always be reserved.
1683 By default we reserve the first 64K of physical RAM, as a
1684 number of BIOSes are known to corrupt that memory range
1685 during events such as suspend/resume or monitor cable
1686 insertion, so it must not be used by the kernel.
1688 You can set this to 4 if you are absolutely sure that you
1689 trust the BIOS to get all its memory reservations and usages
1690 right. If you know your BIOS have problems beyond the
1691 default 64K area, you can set this to 640 to avoid using the
1692 entire low memory range.
1694 If you have doubts about the BIOS (e.g. suspend/resume does
1695 not work or there's kernel crashes after certain hardware
1696 hotplug events) then you might want to enable
1697 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1698 typical corruption patterns.
1700 Leave this to the default value of 64 if you are unsure.
1702 config MATH_EMULATION
1704 depends on MODIFY_LDT_SYSCALL
1705 prompt "Math emulation" if X86_32
1707 Linux can emulate a math coprocessor (used for floating point
1708 operations) if you don't have one. 486DX and Pentium processors have
1709 a math coprocessor built in, 486SX and 386 do not, unless you added
1710 a 487DX or 387, respectively. (The messages during boot time can
1711 give you some hints here ["man dmesg"].) Everyone needs either a
1712 coprocessor or this emulation.
1714 If you don't have a math coprocessor, you need to say Y here; if you
1715 say Y here even though you have a coprocessor, the coprocessor will
1716 be used nevertheless. (This behavior can be changed with the kernel
1717 command line option "no387", which comes handy if your coprocessor
1718 is broken. Try "man bootparam" or see the documentation of your boot
1719 loader (lilo or loadlin) about how to pass options to the kernel at
1720 boot time.) This means that it is a good idea to say Y here if you
1721 intend to use this kernel on different machines.
1723 More information about the internals of the Linux math coprocessor
1724 emulation can be found in <file:arch/x86/math-emu/README>.
1726 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1727 kernel, it won't hurt.
1731 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1733 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1734 the Memory Type Range Registers (MTRRs) may be used to control
1735 processor access to memory ranges. This is most useful if you have
1736 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1737 allows bus write transfers to be combined into a larger transfer
1738 before bursting over the PCI/AGP bus. This can increase performance
1739 of image write operations 2.5 times or more. Saying Y here creates a
1740 /proc/mtrr file which may be used to manipulate your processor's
1741 MTRRs. Typically the X server should use this.
1743 This code has a reasonably generic interface so that similar
1744 control registers on other processors can be easily supported
1747 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1748 Registers (ARRs) which provide a similar functionality to MTRRs. For
1749 these, the ARRs are used to emulate the MTRRs.
1750 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1751 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1752 write-combining. All of these processors are supported by this code
1753 and it makes sense to say Y here if you have one of them.
1755 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1756 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1757 can lead to all sorts of problems, so it's good to say Y here.
1759 You can safely say Y even if your machine doesn't have MTRRs, you'll
1760 just add about 9 KB to your kernel.
1762 See <file:Documentation/x86/mtrr.txt> for more information.
1764 config MTRR_SANITIZER
1766 prompt "MTRR cleanup support"
1769 Convert MTRR layout from continuous to discrete, so X drivers can
1770 add writeback entries.
1772 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1773 The largest mtrr entry size for a continuous block can be set with
1778 config MTRR_SANITIZER_ENABLE_DEFAULT
1779 int "MTRR cleanup enable value (0-1)"
1782 depends on MTRR_SANITIZER
1784 Enable mtrr cleanup default value
1786 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1787 int "MTRR cleanup spare reg num (0-7)"
1790 depends on MTRR_SANITIZER
1792 mtrr cleanup spare entries default, it can be changed via
1793 mtrr_spare_reg_nr=N on the kernel command line.
1797 prompt "x86 PAT support" if EXPERT
1800 Use PAT attributes to setup page level cache control.
1802 PATs are the modern equivalents of MTRRs and are much more
1803 flexible than MTRRs.
1805 Say N here if you see bootup problems (boot crash, boot hang,
1806 spontaneous reboots) or a non-working video driver.
1810 config ARCH_USES_PG_UNCACHED
1816 prompt "x86 architectural random number generator" if EXPERT
1818 Enable the x86 architectural RDRAND instruction
1819 (Intel Bull Mountain technology) to generate random numbers.
1820 If supported, this is a high bandwidth, cryptographically
1821 secure hardware random number generator.
1825 prompt "Supervisor Mode Access Prevention" if EXPERT
1827 Supervisor Mode Access Prevention (SMAP) is a security
1828 feature in newer Intel processors. There is a small
1829 performance cost if this enabled and turned on; there is
1830 also a small increase in the kernel size if this is enabled.
1834 config X86_INTEL_UMIP
1836 depends on CPU_SUP_INTEL
1837 prompt "Intel User Mode Instruction Prevention" if EXPERT
1839 The User Mode Instruction Prevention (UMIP) is a security
1840 feature in newer Intel processors. If enabled, a general
1841 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1842 or STR instructions are executed in user mode. These instructions
1843 unnecessarily expose information about the hardware state.
1845 The vast majority of applications do not use these instructions.
1846 For the very few that do, software emulation is provided in
1847 specific cases in protected and virtual-8086 modes. Emulated
1850 config X86_INTEL_MPX
1851 prompt "Intel MPX (Memory Protection Extensions)"
1853 # Note: only available in 64-bit mode due to VMA flags shortage
1854 depends on CPU_SUP_INTEL && X86_64
1855 select ARCH_USES_HIGH_VMA_FLAGS
1857 MPX provides hardware features that can be used in
1858 conjunction with compiler-instrumented code to check
1859 memory references. It is designed to detect buffer
1860 overflow or underflow bugs.
1862 This option enables running applications which are
1863 instrumented or otherwise use MPX. It does not use MPX
1864 itself inside the kernel or to protect the kernel
1865 against bad memory references.
1867 Enabling this option will make the kernel larger:
1868 ~8k of kernel text and 36 bytes of data on a 64-bit
1869 defconfig. It adds a long to the 'mm_struct' which
1870 will increase the kernel memory overhead of each
1871 process and adds some branches to paths used during
1872 exec() and munmap().
1874 For details, see Documentation/x86/intel_mpx.txt
1878 config X86_INTEL_MEMORY_PROTECTION_KEYS
1879 prompt "Intel Memory Protection Keys"
1881 # Note: only available in 64-bit mode
1882 depends on CPU_SUP_INTEL && X86_64
1883 select ARCH_USES_HIGH_VMA_FLAGS
1884 select ARCH_HAS_PKEYS
1886 Memory Protection Keys provides a mechanism for enforcing
1887 page-based protections, but without requiring modification of the
1888 page tables when an application changes protection domains.
1890 For details, see Documentation/x86/protection-keys.txt
1895 bool "EFI runtime service support"
1898 select EFI_RUNTIME_WRAPPERS
1900 This enables the kernel to use EFI runtime services that are
1901 available (such as the EFI variable services).
1903 This option is only useful on systems that have EFI firmware.
1904 In addition, you should use the latest ELILO loader available
1905 at <http://elilo.sourceforge.net> in order to take advantage
1906 of EFI runtime services. However, even with this option, the
1907 resultant kernel should continue to boot on existing non-EFI
1911 bool "EFI stub support"
1912 depends on EFI && !X86_USE_3DNOW
1915 This kernel feature allows a bzImage to be loaded directly
1916 by EFI firmware without the use of a bootloader.
1918 See Documentation/efi-stub.txt for more information.
1921 bool "EFI mixed-mode support"
1922 depends on EFI_STUB && X86_64
1924 Enabling this feature allows a 64-bit kernel to be booted
1925 on a 32-bit firmware, provided that your CPU supports 64-bit
1928 Note that it is not possible to boot a mixed-mode enabled
1929 kernel via the EFI boot stub - a bootloader that supports
1930 the EFI handover protocol must be used.
1936 prompt "Enable seccomp to safely compute untrusted bytecode"
1938 This kernel feature is useful for number crunching applications
1939 that may need to compute untrusted bytecode during their
1940 execution. By using pipes or other transports made available to
1941 the process as file descriptors supporting the read/write
1942 syscalls, it's possible to isolate those applications in
1943 their own address space using seccomp. Once seccomp is
1944 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1945 and the task is only allowed to execute a few safe syscalls
1946 defined by each seccomp mode.
1948 If unsure, say Y. Only embedded should say N here.
1950 source kernel/Kconfig.hz
1953 bool "kexec system call"
1956 kexec is a system call that implements the ability to shutdown your
1957 current kernel, and to start another kernel. It is like a reboot
1958 but it is independent of the system firmware. And like a reboot
1959 you can start any kernel with it, not just Linux.
1961 The name comes from the similarity to the exec system call.
1963 It is an ongoing process to be certain the hardware in a machine
1964 is properly shutdown, so do not be surprised if this code does not
1965 initially work for you. As of this writing the exact hardware
1966 interface is strongly in flux, so no good recommendation can be
1970 bool "kexec file based system call"
1975 depends on CRYPTO_SHA256=y
1977 This is new version of kexec system call. This system call is
1978 file based and takes file descriptors as system call argument
1979 for kernel and initramfs as opposed to list of segments as
1980 accepted by previous system call.
1982 config KEXEC_VERIFY_SIG
1983 bool "Verify kernel signature during kexec_file_load() syscall"
1984 depends on KEXEC_FILE
1986 This option makes kernel signature verification mandatory for
1987 the kexec_file_load() syscall.
1989 In addition to that option, you need to enable signature
1990 verification for the corresponding kernel image type being
1991 loaded in order for this to work.
1993 config KEXEC_BZIMAGE_VERIFY_SIG
1994 bool "Enable bzImage signature verification support"
1995 depends on KEXEC_VERIFY_SIG
1996 depends on SIGNED_PE_FILE_VERIFICATION
1997 select SYSTEM_TRUSTED_KEYRING
1999 Enable bzImage signature verification support.
2002 bool "kernel crash dumps"
2003 depends on X86_64 || (X86_32 && HIGHMEM)
2005 Generate crash dump after being started by kexec.
2006 This should be normally only set in special crash dump kernels
2007 which are loaded in the main kernel with kexec-tools into
2008 a specially reserved region and then later executed after
2009 a crash by kdump/kexec. The crash dump kernel must be compiled
2010 to a memory address not used by the main kernel or BIOS using
2011 PHYSICAL_START, or it must be built as a relocatable image
2012 (CONFIG_RELOCATABLE=y).
2013 For more details see Documentation/kdump/kdump.txt
2017 depends on KEXEC && HIBERNATION
2019 Jump between original kernel and kexeced kernel and invoke
2020 code in physical address mode via KEXEC
2022 config PHYSICAL_START
2023 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2026 This gives the physical address where the kernel is loaded.
2028 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2029 bzImage will decompress itself to above physical address and
2030 run from there. Otherwise, bzImage will run from the address where
2031 it has been loaded by the boot loader and will ignore above physical
2034 In normal kdump cases one does not have to set/change this option
2035 as now bzImage can be compiled as a completely relocatable image
2036 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2037 address. This option is mainly useful for the folks who don't want
2038 to use a bzImage for capturing the crash dump and want to use a
2039 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2040 to be specifically compiled to run from a specific memory area
2041 (normally a reserved region) and this option comes handy.
2043 So if you are using bzImage for capturing the crash dump,
2044 leave the value here unchanged to 0x1000000 and set
2045 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2046 for capturing the crash dump change this value to start of
2047 the reserved region. In other words, it can be set based on
2048 the "X" value as specified in the "crashkernel=YM@XM"
2049 command line boot parameter passed to the panic-ed
2050 kernel. Please take a look at Documentation/kdump/kdump.txt
2051 for more details about crash dumps.
2053 Usage of bzImage for capturing the crash dump is recommended as
2054 one does not have to build two kernels. Same kernel can be used
2055 as production kernel and capture kernel. Above option should have
2056 gone away after relocatable bzImage support is introduced. But it
2057 is present because there are users out there who continue to use
2058 vmlinux for dump capture. This option should go away down the
2061 Don't change this unless you know what you are doing.
2064 bool "Build a relocatable kernel"
2067 This builds a kernel image that retains relocation information
2068 so it can be loaded someplace besides the default 1MB.
2069 The relocations tend to make the kernel binary about 10% larger,
2070 but are discarded at runtime.
2072 One use is for the kexec on panic case where the recovery kernel
2073 must live at a different physical address than the primary
2076 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2077 it has been loaded at and the compile time physical address
2078 (CONFIG_PHYSICAL_START) is used as the minimum location.
2080 config RANDOMIZE_BASE
2081 bool "Randomize the address of the kernel image (KASLR)"
2082 depends on RELOCATABLE
2085 In support of Kernel Address Space Layout Randomization (KASLR),
2086 this randomizes the physical address at which the kernel image
2087 is decompressed and the virtual address where the kernel
2088 image is mapped, as a security feature that deters exploit
2089 attempts relying on knowledge of the location of kernel
2092 On 64-bit, the kernel physical and virtual addresses are
2093 randomized separately. The physical address will be anywhere
2094 between 16MB and the top of physical memory (up to 64TB). The
2095 virtual address will be randomized from 16MB up to 1GB (9 bits
2096 of entropy). Note that this also reduces the memory space
2097 available to kernel modules from 1.5GB to 1GB.
2099 On 32-bit, the kernel physical and virtual addresses are
2100 randomized together. They will be randomized from 16MB up to
2101 512MB (8 bits of entropy).
2103 Entropy is generated using the RDRAND instruction if it is
2104 supported. If RDTSC is supported, its value is mixed into
2105 the entropy pool as well. If neither RDRAND nor RDTSC are
2106 supported, then entropy is read from the i8254 timer. The
2107 usable entropy is limited by the kernel being built using
2108 2GB addressing, and that PHYSICAL_ALIGN must be at a
2109 minimum of 2MB. As a result, only 10 bits of entropy are
2110 theoretically possible, but the implementations are further
2111 limited due to memory layouts.
2115 # Relocation on x86 needs some additional build support
2116 config X86_NEED_RELOCS
2118 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2120 config PHYSICAL_ALIGN
2121 hex "Alignment value to which kernel should be aligned"
2123 range 0x2000 0x1000000 if X86_32
2124 range 0x200000 0x1000000 if X86_64
2126 This value puts the alignment restrictions on physical address
2127 where kernel is loaded and run from. Kernel is compiled for an
2128 address which meets above alignment restriction.
2130 If bootloader loads the kernel at a non-aligned address and
2131 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2132 address aligned to above value and run from there.
2134 If bootloader loads the kernel at a non-aligned address and
2135 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2136 load address and decompress itself to the address it has been
2137 compiled for and run from there. The address for which kernel is
2138 compiled already meets above alignment restrictions. Hence the
2139 end result is that kernel runs from a physical address meeting
2140 above alignment restrictions.
2142 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2143 this value must be a multiple of 0x200000.
2145 Don't change this unless you know what you are doing.
2147 config RANDOMIZE_MEMORY
2148 bool "Randomize the kernel memory sections"
2150 depends on RANDOMIZE_BASE
2151 default RANDOMIZE_BASE
2153 Randomizes the base virtual address of kernel memory sections
2154 (physical memory mapping, vmalloc & vmemmap). This security feature
2155 makes exploits relying on predictable memory locations less reliable.
2157 The order of allocations remains unchanged. Entropy is generated in
2158 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2159 configuration have in average 30,000 different possible virtual
2160 addresses for each memory section.
2164 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2165 hex "Physical memory mapping padding" if EXPERT
2166 depends on RANDOMIZE_MEMORY
2167 default "0xa" if MEMORY_HOTPLUG
2169 range 0x1 0x40 if MEMORY_HOTPLUG
2172 Define the padding in terabytes added to the existing physical
2173 memory size during kernel memory randomization. It is useful
2174 for memory hotplug support but reduces the entropy available for
2175 address randomization.
2177 If unsure, leave at the default value.
2180 bool "Support for hot-pluggable CPUs"
2183 Say Y here to allow turning CPUs off and on. CPUs can be
2184 controlled through /sys/devices/system/cpu.
2185 ( Note: power management support will enable this option
2186 automatically on SMP systems. )
2187 Say N if you want to disable CPU hotplug.
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 ARCH_ENABLE_HUGEPAGE_MIGRATION
2392 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2394 config ARCH_ENABLE_THP_MIGRATION
2396 depends on X86_64 && TRANSPARENT_HUGEPAGE
2398 menu "Power management and ACPI options"
2400 config ARCH_HIBERNATION_HEADER
2402 depends on X86_64 && HIBERNATION
2404 source "kernel/power/Kconfig"
2406 source "drivers/acpi/Kconfig"
2408 source "drivers/sfi/Kconfig"
2415 tristate "APM (Advanced Power Management) BIOS support"
2416 depends on X86_32 && PM_SLEEP
2418 APM is a BIOS specification for saving power using several different
2419 techniques. This is mostly useful for battery powered laptops with
2420 APM compliant BIOSes. If you say Y here, the system time will be
2421 reset after a RESUME operation, the /proc/apm device will provide
2422 battery status information, and user-space programs will receive
2423 notification of APM "events" (e.g. battery status change).
2425 If you select "Y" here, you can disable actual use of the APM
2426 BIOS by passing the "apm=off" option to the kernel at boot time.
2428 Note that the APM support is almost completely disabled for
2429 machines with more than one CPU.
2431 In order to use APM, you will need supporting software. For location
2432 and more information, read <file:Documentation/power/apm-acpi.txt>
2433 and the Battery Powered Linux mini-HOWTO, available from
2434 <http://www.tldp.org/docs.html#howto>.
2436 This driver does not spin down disk drives (see the hdparm(8)
2437 manpage ("man 8 hdparm") for that), and it doesn't turn off
2438 VESA-compliant "green" monitors.
2440 This driver does not support the TI 4000M TravelMate and the ACER
2441 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2442 desktop machines also don't have compliant BIOSes, and this driver
2443 may cause those machines to panic during the boot phase.
2445 Generally, if you don't have a battery in your machine, there isn't
2446 much point in using this driver and you should say N. If you get
2447 random kernel OOPSes or reboots that don't seem to be related to
2448 anything, try disabling/enabling this option (or disabling/enabling
2451 Some other things you should try when experiencing seemingly random,
2454 1) make sure that you have enough swap space and that it is
2456 2) pass the "no-hlt" option to the kernel
2457 3) switch on floating point emulation in the kernel and pass
2458 the "no387" option to the kernel
2459 4) pass the "floppy=nodma" option to the kernel
2460 5) pass the "mem=4M" option to the kernel (thereby disabling
2461 all but the first 4 MB of RAM)
2462 6) make sure that the CPU is not over clocked.
2463 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2464 8) disable the cache from your BIOS settings
2465 9) install a fan for the video card or exchange video RAM
2466 10) install a better fan for the CPU
2467 11) exchange RAM chips
2468 12) exchange the motherboard.
2470 To compile this driver as a module, choose M here: the
2471 module will be called apm.
2475 config APM_IGNORE_USER_SUSPEND
2476 bool "Ignore USER SUSPEND"
2478 This option will ignore USER SUSPEND requests. On machines with a
2479 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2480 series notebooks, it is necessary to say Y because of a BIOS bug.
2482 config APM_DO_ENABLE
2483 bool "Enable PM at boot time"
2485 Enable APM features at boot time. From page 36 of the APM BIOS
2486 specification: "When disabled, the APM BIOS does not automatically
2487 power manage devices, enter the Standby State, enter the Suspend
2488 State, or take power saving steps in response to CPU Idle calls."
2489 This driver will make CPU Idle calls when Linux is idle (unless this
2490 feature is turned off -- see "Do CPU IDLE calls", below). This
2491 should always save battery power, but more complicated APM features
2492 will be dependent on your BIOS implementation. You may need to turn
2493 this option off if your computer hangs at boot time when using APM
2494 support, or if it beeps continuously instead of suspending. Turn
2495 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2496 T400CDT. This is off by default since most machines do fine without
2501 bool "Make CPU Idle calls when idle"
2503 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2504 On some machines, this can activate improved power savings, such as
2505 a slowed CPU clock rate, when the machine is idle. These idle calls
2506 are made after the idle loop has run for some length of time (e.g.,
2507 333 mS). On some machines, this will cause a hang at boot time or
2508 whenever the CPU becomes idle. (On machines with more than one CPU,
2509 this option does nothing.)
2511 config APM_DISPLAY_BLANK
2512 bool "Enable console blanking using APM"
2514 Enable console blanking using the APM. Some laptops can use this to
2515 turn off the LCD backlight when the screen blanker of the Linux
2516 virtual console blanks the screen. Note that this is only used by
2517 the virtual console screen blanker, and won't turn off the backlight
2518 when using the X Window system. This also doesn't have anything to
2519 do with your VESA-compliant power-saving monitor. Further, this
2520 option doesn't work for all laptops -- it might not turn off your
2521 backlight at all, or it might print a lot of errors to the console,
2522 especially if you are using gpm.
2524 config APM_ALLOW_INTS
2525 bool "Allow interrupts during APM BIOS calls"
2527 Normally we disable external interrupts while we are making calls to
2528 the APM BIOS as a measure to lessen the effects of a badly behaving
2529 BIOS implementation. The BIOS should reenable interrupts if it
2530 needs to. Unfortunately, some BIOSes do not -- especially those in
2531 many of the newer IBM Thinkpads. If you experience hangs when you
2532 suspend, try setting this to Y. Otherwise, say N.
2536 source "drivers/cpufreq/Kconfig"
2538 source "drivers/cpuidle/Kconfig"
2540 source "drivers/idle/Kconfig"
2545 menu "Bus options (PCI etc.)"
2551 Find out whether you have a PCI motherboard. PCI is the name of a
2552 bus system, i.e. the way the CPU talks to the other stuff inside
2553 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2554 VESA. If you have PCI, say Y, otherwise N.
2557 prompt "PCI access mode"
2558 depends on X86_32 && PCI
2561 On PCI systems, the BIOS can be used to detect the PCI devices and
2562 determine their configuration. However, some old PCI motherboards
2563 have BIOS bugs and may crash if this is done. Also, some embedded
2564 PCI-based systems don't have any BIOS at all. Linux can also try to
2565 detect the PCI hardware directly without using the BIOS.
2567 With this option, you can specify how Linux should detect the
2568 PCI devices. If you choose "BIOS", the BIOS will be used,
2569 if you choose "Direct", the BIOS won't be used, and if you
2570 choose "MMConfig", then PCI Express MMCONFIG will be used.
2571 If you choose "Any", the kernel will try MMCONFIG, then the
2572 direct access method and falls back to the BIOS if that doesn't
2573 work. If unsure, go with the default, which is "Any".
2578 config PCI_GOMMCONFIG
2595 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2597 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2600 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2604 depends on X86_32 && PCI && (ACPI || SFI) && (PCI_GOMMCONFIG || PCI_GOANY)
2608 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2612 depends on PCI && XEN
2620 bool "Support mmconfig PCI config space access"
2621 depends on X86_64 && PCI && ACPI
2623 config PCI_CNB20LE_QUIRK
2624 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2627 Read the PCI windows out of the CNB20LE host bridge. This allows
2628 PCI hotplug to work on systems with the CNB20LE chipset which do
2631 There's no public spec for this chipset, and this functionality
2632 is known to be incomplete.
2634 You should say N unless you know you need this.
2636 source "drivers/pci/Kconfig"
2639 bool "ISA-style bus support on modern systems" if EXPERT
2642 Enables ISA-style drivers on modern systems. This is necessary to
2643 support PC/104 devices on X86_64 platforms.
2647 # x86_64 have no ISA slots, but can have ISA-style DMA.
2649 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2652 Enables ISA-style DMA support for devices requiring such controllers.
2660 Find out whether you have ISA slots on your motherboard. ISA is the
2661 name of a bus system, i.e. the way the CPU talks to the other stuff
2662 inside your box. Other bus systems are PCI, EISA, MicroChannel
2663 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2664 newer boards don't support it. If you have ISA, say Y, otherwise N.
2670 The Extended Industry Standard Architecture (EISA) bus was
2671 developed as an open alternative to the IBM MicroChannel bus.
2673 The EISA bus provided some of the features of the IBM MicroChannel
2674 bus while maintaining backward compatibility with cards made for
2675 the older ISA bus. The EISA bus saw limited use between 1988 and
2676 1995 when it was made obsolete by the PCI bus.
2678 Say Y here if you are building a kernel for an EISA-based machine.
2682 source "drivers/eisa/Kconfig"
2685 tristate "NatSemi SCx200 support"
2687 This provides basic support for National Semiconductor's
2688 (now AMD's) Geode processors. The driver probes for the
2689 PCI-IDs of several on-chip devices, so its a good dependency
2690 for other scx200_* drivers.
2692 If compiled as a module, the driver is named scx200.
2694 config SCx200HR_TIMER
2695 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2699 This driver provides a clocksource built upon the on-chip
2700 27MHz high-resolution timer. Its also a workaround for
2701 NSC Geode SC-1100's buggy TSC, which loses time when the
2702 processor goes idle (as is done by the scheduler). The
2703 other workaround is idle=poll boot option.
2706 bool "One Laptop Per Child support"
2713 Add support for detecting the unique features of the OLPC
2717 bool "OLPC XO-1 Power Management"
2718 depends on OLPC && MFD_CS5535 && PM_SLEEP
2721 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2724 bool "OLPC XO-1 Real Time Clock"
2725 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2727 Add support for the XO-1 real time clock, which can be used as a
2728 programmable wakeup source.
2731 bool "OLPC XO-1 SCI extras"
2732 depends on OLPC && OLPC_XO1_PM
2738 Add support for SCI-based features of the OLPC XO-1 laptop:
2739 - EC-driven system wakeups
2743 - AC adapter status updates
2744 - Battery status updates
2746 config OLPC_XO15_SCI
2747 bool "OLPC XO-1.5 SCI extras"
2748 depends on OLPC && ACPI
2751 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2752 - EC-driven system wakeups
2753 - AC adapter status updates
2754 - Battery status updates
2757 bool "PCEngines ALIX System Support (LED setup)"
2760 This option enables system support for the PCEngines ALIX.
2761 At present this just sets up LEDs for GPIO control on
2762 ALIX2/3/6 boards. However, other system specific setup should
2765 Note: You must still enable the drivers for GPIO and LED support
2766 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2768 Note: You have to set alix.force=1 for boards with Award BIOS.
2771 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2774 This option enables system support for the Soekris Engineering net5501.
2777 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2781 This option enables system support for the Traverse Technologies GEOS.
2784 bool "Technologic Systems TS-5500 platform support"
2786 select CHECK_SIGNATURE
2790 This option enables system support for the Technologic Systems TS-5500.
2796 depends on CPU_SUP_AMD && PCI
2798 source "drivers/pcmcia/Kconfig"
2801 tristate "RapidIO support"
2805 If enabled this option will include drivers and the core
2806 infrastructure code to support RapidIO interconnect devices.
2808 source "drivers/rapidio/Kconfig"
2811 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2813 Firmwares often provide initial graphics framebuffers so the BIOS,
2814 bootloader or kernel can show basic video-output during boot for
2815 user-guidance and debugging. Historically, x86 used the VESA BIOS
2816 Extensions and EFI-framebuffers for this, which are mostly limited
2818 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2819 framebuffers so the new generic system-framebuffer drivers can be
2820 used on x86. If the framebuffer is not compatible with the generic
2821 modes, it is adverticed as fallback platform framebuffer so legacy
2822 drivers like efifb, vesafb and uvesafb can pick it up.
2823 If this option is not selected, all system framebuffers are always
2824 marked as fallback platform framebuffers as usual.
2826 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2827 not be able to pick up generic system framebuffers if this option
2828 is selected. You are highly encouraged to enable simplefb as
2829 replacement if you select this option. simplefb can correctly deal
2830 with generic system framebuffers. But you should still keep vesafb
2831 and others enabled as fallback if a system framebuffer is
2832 incompatible with simplefb.
2839 menu "Executable file formats / Emulations"
2841 source "fs/Kconfig.binfmt"
2843 config IA32_EMULATION
2844 bool "IA32 Emulation"
2846 select ARCH_WANT_OLD_COMPAT_IPC
2848 select COMPAT_BINFMT_ELF
2849 select COMPAT_OLD_SIGACTION
2851 Include code to run legacy 32-bit programs under a
2852 64-bit kernel. You should likely turn this on, unless you're
2853 100% sure that you don't have any 32-bit programs left.
2856 tristate "IA32 a.out support"
2857 depends on IA32_EMULATION
2859 Support old a.out binaries in the 32bit emulation.
2862 bool "x32 ABI for 64-bit mode"
2865 Include code to run binaries for the x32 native 32-bit ABI
2866 for 64-bit processors. An x32 process gets access to the
2867 full 64-bit register file and wide data path while leaving
2868 pointers at 32 bits for smaller memory footprint.
2870 You will need a recent binutils (2.22 or later) with
2871 elf32_x86_64 support enabled to compile a kernel with this
2876 depends on IA32_EMULATION || X86_32
2878 select OLD_SIGSUSPEND3
2882 depends on IA32_EMULATION || X86_X32
2885 config COMPAT_FOR_U64_ALIGNMENT
2888 config SYSVIPC_COMPAT
2896 config HAVE_ATOMIC_IOMAP
2900 config X86_DEV_DMA_OPS
2902 depends on X86_64 || STA2X11
2904 config X86_DMA_REMAP
2908 config HAVE_GENERIC_GUP
2911 source "net/Kconfig"
2913 source "drivers/Kconfig"
2915 source "drivers/firmware/Kconfig"
2919 source "arch/x86/Kconfig.debug"
2921 source "security/Kconfig"
2923 source "crypto/Kconfig"
2925 source "arch/x86/kvm/Kconfig"
2927 source "lib/Kconfig"
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