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
428 depends on X86_GOLDFISH
431 bool "Avoid speculative indirect branches in kernel"
434 Compile kernel with the retpoline compiler options to guard against
435 kernel-to-user data leaks by avoiding speculative indirect
436 branches. Requires a compiler with -mindirect-branch=thunk-extern
437 support for full protection. The kernel may run slower.
439 Without compiler support, at least indirect branches in assembler
440 code are eliminated. Since this includes the syscall entry path,
441 it is not entirely pointless.
444 bool "Intel Resource Director Technology support"
446 depends on X86 && CPU_SUP_INTEL
449 Select to enable resource allocation and monitoring which are
450 sub-features of Intel Resource Director Technology(RDT). More
451 information about RDT can be found in the Intel x86
452 Architecture Software Developer Manual.
458 bool "Support for big SMP systems with more than 8 CPUs"
461 This option is needed for the systems that have more than 8 CPUs
463 config X86_EXTENDED_PLATFORM
464 bool "Support for extended (non-PC) x86 platforms"
467 If you disable this option then the kernel will only support
468 standard PC platforms. (which covers the vast majority of
471 If you enable this option then you'll be able to select support
472 for the following (non-PC) 32 bit x86 platforms:
473 Goldfish (Android emulator)
476 SGI 320/540 (Visual Workstation)
477 STA2X11-based (e.g. Northville)
478 Moorestown MID devices
480 If you have one of these systems, or if you want to build a
481 generic distribution kernel, say Y here - otherwise say N.
485 config X86_EXTENDED_PLATFORM
486 bool "Support for extended (non-PC) x86 platforms"
489 If you disable this option then the kernel will only support
490 standard PC platforms. (which covers the vast majority of
493 If you enable this option then you'll be able to select support
494 for the following (non-PC) 64 bit x86 platforms:
499 If you have one of these systems, or if you want to build a
500 generic distribution kernel, say Y here - otherwise say N.
502 # This is an alphabetically sorted list of 64 bit extended platforms
503 # Please maintain the alphabetic order if and when there are additions
505 bool "Numascale NumaChip"
507 depends on X86_EXTENDED_PLATFORM
510 depends on X86_X2APIC
511 depends on PCI_MMCONFIG
513 Adds support for Numascale NumaChip large-SMP systems. Needed to
514 enable more than ~168 cores.
515 If you don't have one of these, you should say N here.
519 select HYPERVISOR_GUEST
521 depends on X86_64 && PCI
522 depends on X86_EXTENDED_PLATFORM
525 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
526 supposed to run on these EM64T-based machines. Only choose this option
527 if you have one of these machines.
530 bool "SGI Ultraviolet"
532 depends on X86_EXTENDED_PLATFORM
535 depends on X86_X2APIC
538 This option is needed in order to support SGI Ultraviolet systems.
539 If you don't have one of these, you should say N here.
541 # Following is an alphabetically sorted list of 32 bit extended platforms
542 # Please maintain the alphabetic order if and when there are additions
545 bool "Goldfish (Virtual Platform)"
546 depends on X86_EXTENDED_PLATFORM
548 Enable support for the Goldfish virtual platform used primarily
549 for Android development. Unless you are building for the Android
550 Goldfish emulator say N here.
553 bool "CE4100 TV platform"
555 depends on PCI_GODIRECT
556 depends on X86_IO_APIC
558 depends on X86_EXTENDED_PLATFORM
559 select X86_REBOOTFIXUPS
561 select OF_EARLY_FLATTREE
563 Select for the Intel CE media processor (CE4100) SOC.
564 This option compiles in support for the CE4100 SOC for settop
565 boxes and media devices.
568 bool "Intel MID platform support"
569 depends on X86_EXTENDED_PLATFORM
570 depends on X86_PLATFORM_DEVICES
572 depends on X86_64 || (PCI_GOANY && X86_32)
573 depends on X86_IO_APIC
579 select MFD_INTEL_MSIC
581 Select to build a kernel capable of supporting Intel MID (Mobile
582 Internet Device) platform systems which do not have the PCI legacy
583 interfaces. If you are building for a PC class system say N here.
585 Intel MID platforms are based on an Intel processor and chipset which
586 consume less power than most of the x86 derivatives.
588 config X86_INTEL_QUARK
589 bool "Intel Quark platform support"
591 depends on X86_EXTENDED_PLATFORM
592 depends on X86_PLATFORM_DEVICES
596 depends on X86_IO_APIC
601 Select to include support for Quark X1000 SoC.
602 Say Y here if you have a Quark based system such as the Arduino
603 compatible Intel Galileo.
605 config X86_INTEL_LPSS
606 bool "Intel Low Power Subsystem Support"
607 depends on X86 && ACPI
612 Select to build support for Intel Low Power Subsystem such as
613 found on Intel Lynxpoint PCH. Selecting this option enables
614 things like clock tree (common clock framework) and pincontrol
615 which are needed by the LPSS peripheral drivers.
617 config X86_AMD_PLATFORM_DEVICE
618 bool "AMD ACPI2Platform devices support"
623 Select to interpret AMD specific ACPI device to platform device
624 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
625 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
626 implemented under PINCTRL subsystem.
629 tristate "Intel SoC IOSF Sideband support for SoC platforms"
632 This option enables sideband register access support for Intel SoC
633 platforms. On these platforms the IOSF sideband is used in lieu of
634 MSR's for some register accesses, mostly but not limited to thermal
635 and power. Drivers may query the availability of this device to
636 determine if they need the sideband in order to work on these
637 platforms. The sideband is available on the following SoC products.
638 This list is not meant to be exclusive.
643 You should say Y if you are running a kernel on one of these SoC's.
645 config IOSF_MBI_DEBUG
646 bool "Enable IOSF sideband access through debugfs"
647 depends on IOSF_MBI && DEBUG_FS
649 Select this option to expose the IOSF sideband access registers (MCR,
650 MDR, MCRX) through debugfs to write and read register information from
651 different units on the SoC. This is most useful for obtaining device
652 state information for debug and analysis. As this is a general access
653 mechanism, users of this option would have specific knowledge of the
654 device they want to access.
656 If you don't require the option or are in doubt, say N.
659 bool "RDC R-321x SoC"
661 depends on X86_EXTENDED_PLATFORM
663 select X86_REBOOTFIXUPS
665 This option is needed for RDC R-321x system-on-chip, also known
667 If you don't have one of these chips, you should say N here.
669 config X86_32_NON_STANDARD
670 bool "Support non-standard 32-bit SMP architectures"
671 depends on X86_32 && SMP
672 depends on X86_EXTENDED_PLATFORM
674 This option compiles in the bigsmp and STA2X11 default
675 subarchitectures. It is intended for a generic binary
676 kernel. If you select them all, kernel will probe it one by
677 one and will fallback to default.
679 # Alphabetically sorted list of Non standard 32 bit platforms
681 config X86_SUPPORTS_MEMORY_FAILURE
683 # MCE code calls memory_failure():
685 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
686 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
687 depends on X86_64 || !SPARSEMEM
688 select ARCH_SUPPORTS_MEMORY_FAILURE
691 bool "STA2X11 Companion Chip Support"
692 depends on X86_32_NON_STANDARD && PCI
693 select X86_DEV_DMA_OPS
700 This adds support for boards based on the STA2X11 IO-Hub,
701 a.k.a. "ConneXt". The chip is used in place of the standard
702 PC chipset, so all "standard" peripherals are missing. If this
703 option is selected the kernel will still be able to boot on
704 standard PC machines.
707 tristate "Eurobraille/Iris poweroff module"
710 The Iris machines from EuroBraille do not have APM or ACPI support
711 to shut themselves down properly. A special I/O sequence is
712 needed to do so, which is what this module does at
715 This is only for Iris machines from EuroBraille.
719 config SCHED_OMIT_FRAME_POINTER
721 prompt "Single-depth WCHAN output"
724 Calculate simpler /proc/<PID>/wchan values. If this option
725 is disabled then wchan values will recurse back to the
726 caller function. This provides more accurate wchan values,
727 at the expense of slightly more scheduling overhead.
729 If in doubt, say "Y".
731 menuconfig HYPERVISOR_GUEST
732 bool "Linux guest support"
734 Say Y here to enable options for running Linux under various hyper-
735 visors. This option enables basic hypervisor detection and platform
738 If you say N, all options in this submenu will be skipped and
739 disabled, and Linux guest support won't be built in.
744 bool "Enable paravirtualization code"
746 This changes the kernel so it can modify itself when it is run
747 under a hypervisor, potentially improving performance significantly
748 over full virtualization. However, when run without a hypervisor
749 the kernel is theoretically slower and slightly larger.
751 config PARAVIRT_DEBUG
752 bool "paravirt-ops debugging"
753 depends on PARAVIRT && DEBUG_KERNEL
755 Enable to debug paravirt_ops internals. Specifically, BUG if
756 a paravirt_op is missing when it is called.
758 config PARAVIRT_SPINLOCKS
759 bool "Paravirtualization layer for spinlocks"
760 depends on PARAVIRT && SMP
762 Paravirtualized spinlocks allow a pvops backend to replace the
763 spinlock implementation with something virtualization-friendly
764 (for example, block the virtual CPU rather than spinning).
766 It has a minimal impact on native kernels and gives a nice performance
767 benefit on paravirtualized KVM / Xen kernels.
769 If you are unsure how to answer this question, answer Y.
771 config QUEUED_LOCK_STAT
772 bool "Paravirt queued spinlock statistics"
773 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
775 Enable the collection of statistical data on the slowpath
776 behavior of paravirtualized queued spinlocks and report
779 source "arch/x86/xen/Kconfig"
782 bool "KVM Guest support (including kvmclock)"
784 select PARAVIRT_CLOCK
787 This option enables various optimizations for running under the KVM
788 hypervisor. It includes a paravirtualized clock, so that instead
789 of relying on a PIT (or probably other) emulation by the
790 underlying device model, the host provides the guest with
791 timing infrastructure such as time of day, and system time
794 bool "Enable debug information for KVM Guests in debugfs"
795 depends on KVM_GUEST && DEBUG_FS
798 This option enables collection of various statistics for KVM guest.
799 Statistics are displayed in debugfs filesystem. Enabling this option
800 may incur significant overhead.
802 config PARAVIRT_TIME_ACCOUNTING
803 bool "Paravirtual steal time accounting"
807 Select this option to enable fine granularity task steal time
808 accounting. Time spent executing other tasks in parallel with
809 the current vCPU is discounted from the vCPU power. To account for
810 that, there can be a small performance impact.
812 If in doubt, say N here.
814 config PARAVIRT_CLOCK
817 config JAILHOUSE_GUEST
818 bool "Jailhouse non-root cell support"
819 depends on X86_64 && PCI
822 This option allows to run Linux as guest in a Jailhouse non-root
823 cell. You can leave this option disabled if you only want to start
824 Jailhouse and run Linux afterwards in the root cell.
826 endif #HYPERVISOR_GUEST
831 source "arch/x86/Kconfig.cpu"
835 prompt "HPET Timer Support" if X86_32
837 Use the IA-PC HPET (High Precision Event Timer) to manage
838 time in preference to the PIT and RTC, if a HPET is
840 HPET is the next generation timer replacing legacy 8254s.
841 The HPET provides a stable time base on SMP
842 systems, unlike the TSC, but it is more expensive to access,
843 as it is off-chip. The interface used is documented
844 in the HPET spec, revision 1.
846 You can safely choose Y here. However, HPET will only be
847 activated if the platform and the BIOS support this feature.
848 Otherwise the 8254 will be used for timing services.
850 Choose N to continue using the legacy 8254 timer.
852 config HPET_EMULATE_RTC
854 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
857 def_bool y if X86_INTEL_MID
858 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
860 depends on X86_INTEL_MID && SFI
862 APB timer is the replacement for 8254, HPET on X86 MID platforms.
863 The APBT provides a stable time base on SMP
864 systems, unlike the TSC, but it is more expensive to access,
865 as it is off-chip. APB timers are always running regardless of CPU
866 C states, they are used as per CPU clockevent device when possible.
868 # Mark as expert because too many people got it wrong.
869 # The code disables itself when not needed.
872 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
873 bool "Enable DMI scanning" if EXPERT
875 Enabled scanning of DMI to identify machine quirks. Say Y
876 here unless you have verified that your setup is not
877 affected by entries in the DMI blacklist. Required by PNP
881 bool "Old AMD GART IOMMU support"
883 depends on X86_64 && PCI && AMD_NB
885 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
886 GART based hardware IOMMUs.
888 The GART supports full DMA access for devices with 32-bit access
889 limitations, on systems with more than 3 GB. This is usually needed
890 for USB, sound, many IDE/SATA chipsets and some other devices.
892 Newer systems typically have a modern AMD IOMMU, supported via
893 the CONFIG_AMD_IOMMU=y config option.
895 In normal configurations this driver is only active when needed:
896 there's more than 3 GB of memory and the system contains a
897 32-bit limited device.
902 bool "IBM Calgary IOMMU support"
904 depends on X86_64 && PCI
906 Support for hardware IOMMUs in IBM's xSeries x366 and x460
907 systems. Needed to run systems with more than 3GB of memory
908 properly with 32-bit PCI devices that do not support DAC
909 (Double Address Cycle). Calgary also supports bus level
910 isolation, where all DMAs pass through the IOMMU. This
911 prevents them from going anywhere except their intended
912 destination. This catches hard-to-find kernel bugs and
913 mis-behaving drivers and devices that do not use the DMA-API
914 properly to set up their DMA buffers. The IOMMU can be
915 turned off at boot time with the iommu=off parameter.
916 Normally the kernel will make the right choice by itself.
919 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
921 prompt "Should Calgary be enabled by default?"
922 depends on CALGARY_IOMMU
924 Should Calgary be enabled by default? if you choose 'y', Calgary
925 will be used (if it exists). If you choose 'n', Calgary will not be
926 used even if it exists. If you choose 'n' and would like to use
927 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
930 # need this always selected by IOMMU for the VIA workaround
934 Support for software bounce buffers used on x86-64 systems
935 which don't have a hardware IOMMU. Using this PCI devices
936 which can only access 32-bits of memory can be used on systems
937 with more than 3 GB of memory.
942 depends on CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU
945 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
946 depends on X86_64 && SMP && DEBUG_KERNEL
947 select CPUMASK_OFFSTACK
949 Enable maximum number of CPUS and NUMA Nodes for this architecture.
953 # The maximum number of CPUs supported:
955 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
956 # and which can be configured interactively in the
957 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
959 # The ranges are different on 32-bit and 64-bit kernels, depending on
960 # hardware capabilities and scalability features of the kernel.
962 # ( If MAXSMP is enabled we just use the highest possible value and disable
963 # interactive configuration. )
966 config NR_CPUS_RANGE_BEGIN
968 default NR_CPUS_RANGE_END if MAXSMP
972 config NR_CPUS_RANGE_END
975 default 64 if SMP && X86_BIGSMP
976 default 8 if SMP && !X86_BIGSMP
979 config NR_CPUS_RANGE_END
982 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
983 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
986 config NR_CPUS_DEFAULT
989 default 32 if X86_BIGSMP
993 config NR_CPUS_DEFAULT
996 default 8192 if MAXSMP
1001 int "Maximum number of CPUs" if SMP && !MAXSMP
1002 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1003 default NR_CPUS_DEFAULT
1005 This allows you to specify the maximum number of CPUs which this
1006 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1007 supported value is 8192, otherwise the maximum value is 512. The
1008 minimum value which makes sense is 2.
1010 This is purely to save memory: each supported CPU adds about 8KB
1011 to the kernel image.
1014 bool "SMT (Hyperthreading) scheduler support"
1017 SMT scheduler support improves the CPU scheduler's decision making
1018 when dealing with Intel Pentium 4 chips with HyperThreading at a
1019 cost of slightly increased overhead in some places. If unsure say
1024 prompt "Multi-core scheduler support"
1027 Multi-core scheduler support improves the CPU scheduler's decision
1028 making when dealing with multi-core CPU chips at a cost of slightly
1029 increased overhead in some places. If unsure say N here.
1031 config SCHED_MC_PRIO
1032 bool "CPU core priorities scheduler support"
1033 depends on SCHED_MC && CPU_SUP_INTEL
1034 select X86_INTEL_PSTATE
1038 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1039 core ordering determined at manufacturing time, which allows
1040 certain cores to reach higher turbo frequencies (when running
1041 single threaded workloads) than others.
1043 Enabling this kernel feature teaches the scheduler about
1044 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1045 scheduler's CPU selection logic accordingly, so that higher
1046 overall system performance can be achieved.
1048 This feature will have no effect on CPUs without this feature.
1050 If unsure say Y here.
1052 source "kernel/Kconfig.preempt"
1056 depends on !SMP && X86_LOCAL_APIC
1059 bool "Local APIC support on uniprocessors" if !PCI_MSI
1061 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1063 A local APIC (Advanced Programmable Interrupt Controller) is an
1064 integrated interrupt controller in the CPU. If you have a single-CPU
1065 system which has a processor with a local APIC, you can say Y here to
1066 enable and use it. If you say Y here even though your machine doesn't
1067 have a local APIC, then the kernel will still run with no slowdown at
1068 all. The local APIC supports CPU-generated self-interrupts (timer,
1069 performance counters), and the NMI watchdog which detects hard
1072 config X86_UP_IOAPIC
1073 bool "IO-APIC support on uniprocessors"
1074 depends on X86_UP_APIC
1076 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1077 SMP-capable replacement for PC-style interrupt controllers. Most
1078 SMP systems and many recent uniprocessor systems have one.
1080 If you have a single-CPU system with an IO-APIC, you can say Y here
1081 to use it. If you say Y here even though your machine doesn't have
1082 an IO-APIC, then the kernel will still run with no slowdown at all.
1084 config X86_LOCAL_APIC
1086 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1087 select IRQ_DOMAIN_HIERARCHY
1088 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1092 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1094 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1095 bool "Reroute for broken boot IRQs"
1096 depends on X86_IO_APIC
1098 This option enables a workaround that fixes a source of
1099 spurious interrupts. This is recommended when threaded
1100 interrupt handling is used on systems where the generation of
1101 superfluous "boot interrupts" cannot be disabled.
1103 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1104 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1105 kernel does during interrupt handling). On chipsets where this
1106 boot IRQ generation cannot be disabled, this workaround keeps
1107 the original IRQ line masked so that only the equivalent "boot
1108 IRQ" is delivered to the CPUs. The workaround also tells the
1109 kernel to set up the IRQ handler on the boot IRQ line. In this
1110 way only one interrupt is delivered to the kernel. Otherwise
1111 the spurious second interrupt may cause the kernel to bring
1112 down (vital) interrupt lines.
1114 Only affects "broken" chipsets. Interrupt sharing may be
1115 increased on these systems.
1118 bool "Machine Check / overheating reporting"
1119 select GENERIC_ALLOCATOR
1122 Machine Check support allows the processor to notify the
1123 kernel if it detects a problem (e.g. overheating, data corruption).
1124 The action the kernel takes depends on the severity of the problem,
1125 ranging from warning messages to halting the machine.
1127 config X86_MCELOG_LEGACY
1128 bool "Support for deprecated /dev/mcelog character device"
1131 Enable support for /dev/mcelog which is needed by the old mcelog
1132 userspace logging daemon. Consider switching to the new generation
1135 config X86_MCE_INTEL
1137 prompt "Intel MCE features"
1138 depends on X86_MCE && X86_LOCAL_APIC
1140 Additional support for intel specific MCE features such as
1141 the thermal monitor.
1145 prompt "AMD MCE features"
1146 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1148 Additional support for AMD specific MCE features such as
1149 the DRAM Error Threshold.
1151 config X86_ANCIENT_MCE
1152 bool "Support for old Pentium 5 / WinChip machine checks"
1153 depends on X86_32 && X86_MCE
1155 Include support for machine check handling on old Pentium 5 or WinChip
1156 systems. These typically need to be enabled explicitly on the command
1159 config X86_MCE_THRESHOLD
1160 depends on X86_MCE_AMD || X86_MCE_INTEL
1163 config X86_MCE_INJECT
1164 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1165 tristate "Machine check injector support"
1167 Provide support for injecting machine checks for testing purposes.
1168 If you don't know what a machine check is and you don't do kernel
1169 QA it is safe to say n.
1171 config X86_THERMAL_VECTOR
1173 depends on X86_MCE_INTEL
1175 source "arch/x86/events/Kconfig"
1177 config X86_LEGACY_VM86
1178 bool "Legacy VM86 support"
1182 This option allows user programs to put the CPU into V8086
1183 mode, which is an 80286-era approximation of 16-bit real mode.
1185 Some very old versions of X and/or vbetool require this option
1186 for user mode setting. Similarly, DOSEMU will use it if
1187 available to accelerate real mode DOS programs. However, any
1188 recent version of DOSEMU, X, or vbetool should be fully
1189 functional even without kernel VM86 support, as they will all
1190 fall back to software emulation. Nevertheless, if you are using
1191 a 16-bit DOS program where 16-bit performance matters, vm86
1192 mode might be faster than emulation and you might want to
1195 Note that any app that works on a 64-bit kernel is unlikely to
1196 need this option, as 64-bit kernels don't, and can't, support
1197 V8086 mode. This option is also unrelated to 16-bit protected
1198 mode and is not needed to run most 16-bit programs under Wine.
1200 Enabling this option increases the complexity of the kernel
1201 and slows down exception handling a tiny bit.
1203 If unsure, say N here.
1207 default X86_LEGACY_VM86
1210 bool "Enable support for 16-bit segments" if EXPERT
1212 depends on MODIFY_LDT_SYSCALL
1214 This option is required by programs like Wine to run 16-bit
1215 protected mode legacy code on x86 processors. Disabling
1216 this option saves about 300 bytes on i386, or around 6K text
1217 plus 16K runtime memory on x86-64,
1221 depends on X86_16BIT && X86_32
1225 depends on X86_16BIT && X86_64
1227 config X86_VSYSCALL_EMULATION
1228 bool "Enable vsyscall emulation" if EXPERT
1232 This enables emulation of the legacy vsyscall page. Disabling
1233 it is roughly equivalent to booting with vsyscall=none, except
1234 that it will also disable the helpful warning if a program
1235 tries to use a vsyscall. With this option set to N, offending
1236 programs will just segfault, citing addresses of the form
1239 This option is required by many programs built before 2013, and
1240 care should be used even with newer programs if set to N.
1242 Disabling this option saves about 7K of kernel size and
1243 possibly 4K of additional runtime pagetable memory.
1246 tristate "Toshiba Laptop support"
1249 This adds a driver to safely access the System Management Mode of
1250 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1251 not work on models with a Phoenix BIOS. The System Management Mode
1252 is used to set the BIOS and power saving options on Toshiba portables.
1254 For information on utilities to make use of this driver see the
1255 Toshiba Linux utilities web site at:
1256 <http://www.buzzard.org.uk/toshiba/>.
1258 Say Y if you intend to run this kernel on a Toshiba portable.
1262 tristate "Dell i8k legacy laptop support"
1264 select SENSORS_DELL_SMM
1266 This option enables legacy /proc/i8k userspace interface in hwmon
1267 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1268 temperature and allows controlling fan speeds of Dell laptops via
1269 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1270 it reports also power and hotkey status. For fan speed control is
1271 needed userspace package i8kutils.
1273 Say Y if you intend to run this kernel on old Dell laptops or want to
1274 use userspace package i8kutils.
1277 config X86_REBOOTFIXUPS
1278 bool "Enable X86 board specific fixups for reboot"
1281 This enables chipset and/or board specific fixups to be done
1282 in order to get reboot to work correctly. This is only needed on
1283 some combinations of hardware and BIOS. The symptom, for which
1284 this config is intended, is when reboot ends with a stalled/hung
1287 Currently, the only fixup is for the Geode machines using
1288 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1290 Say Y if you want to enable the fixup. Currently, it's safe to
1291 enable this option even if you don't need it.
1295 bool "CPU microcode loading support"
1297 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1300 If you say Y here, you will be able to update the microcode on
1301 Intel and AMD processors. The Intel support is for the IA32 family,
1302 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1303 AMD support is for families 0x10 and later. You will obviously need
1304 the actual microcode binary data itself which is not shipped with
1307 The preferred method to load microcode from a detached initrd is described
1308 in Documentation/x86/early-microcode.txt. For that you need to enable
1309 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1310 initrd for microcode blobs.
1312 In addition, you can build the microcode into the kernel. For that you
1313 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1316 config MICROCODE_INTEL
1317 bool "Intel microcode loading support"
1318 depends on MICROCODE
1322 This options enables microcode patch loading support for Intel
1325 For the current Intel microcode data package go to
1326 <https://downloadcenter.intel.com> and search for
1327 'Linux Processor Microcode Data File'.
1329 config MICROCODE_AMD
1330 bool "AMD microcode loading support"
1331 depends on MICROCODE
1334 If you select this option, microcode patch loading support for AMD
1335 processors will be enabled.
1337 config MICROCODE_OLD_INTERFACE
1339 depends on MICROCODE
1342 tristate "/dev/cpu/*/msr - Model-specific register support"
1344 This device gives privileged processes access to the x86
1345 Model-Specific Registers (MSRs). It is a character device with
1346 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1347 MSR accesses are directed to a specific CPU on multi-processor
1351 tristate "/dev/cpu/*/cpuid - CPU information support"
1353 This device gives processes access to the x86 CPUID instruction to
1354 be executed on a specific processor. It is a character device
1355 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1359 prompt "High Memory Support"
1366 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1367 However, the address space of 32-bit x86 processors is only 4
1368 Gigabytes large. That means that, if you have a large amount of
1369 physical memory, not all of it can be "permanently mapped" by the
1370 kernel. The physical memory that's not permanently mapped is called
1373 If you are compiling a kernel which will never run on a machine with
1374 more than 1 Gigabyte total physical RAM, answer "off" here (default
1375 choice and suitable for most users). This will result in a "3GB/1GB"
1376 split: 3GB are mapped so that each process sees a 3GB virtual memory
1377 space and the remaining part of the 4GB virtual memory space is used
1378 by the kernel to permanently map as much physical memory as
1381 If the machine has between 1 and 4 Gigabytes physical RAM, then
1384 If more than 4 Gigabytes is used then answer "64GB" here. This
1385 selection turns Intel PAE (Physical Address Extension) mode on.
1386 PAE implements 3-level paging on IA32 processors. PAE is fully
1387 supported by Linux, PAE mode is implemented on all recent Intel
1388 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1389 then the kernel will not boot on CPUs that don't support PAE!
1391 The actual amount of total physical memory will either be
1392 auto detected or can be forced by using a kernel command line option
1393 such as "mem=256M". (Try "man bootparam" or see the documentation of
1394 your boot loader (lilo or loadlin) about how to pass options to the
1395 kernel at boot time.)
1397 If unsure, say "off".
1402 Select this if you have a 32-bit processor and between 1 and 4
1403 gigabytes of physical RAM.
1410 Select this if you have a 32-bit processor and more than 4
1411 gigabytes of physical RAM.
1416 prompt "Memory split" if EXPERT
1420 Select the desired split between kernel and user memory.
1422 If the address range available to the kernel is less than the
1423 physical memory installed, the remaining memory will be available
1424 as "high memory". Accessing high memory is a little more costly
1425 than low memory, as it needs to be mapped into the kernel first.
1426 Note that increasing the kernel address space limits the range
1427 available to user programs, making the address space there
1428 tighter. Selecting anything other than the default 3G/1G split
1429 will also likely make your kernel incompatible with binary-only
1432 If you are not absolutely sure what you are doing, leave this
1436 bool "3G/1G user/kernel split"
1437 config VMSPLIT_3G_OPT
1439 bool "3G/1G user/kernel split (for full 1G low memory)"
1441 bool "2G/2G user/kernel split"
1442 config VMSPLIT_2G_OPT
1444 bool "2G/2G user/kernel split (for full 2G low memory)"
1446 bool "1G/3G user/kernel split"
1451 default 0xB0000000 if VMSPLIT_3G_OPT
1452 default 0x80000000 if VMSPLIT_2G
1453 default 0x78000000 if VMSPLIT_2G_OPT
1454 default 0x40000000 if VMSPLIT_1G
1460 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1463 bool "PAE (Physical Address Extension) Support"
1464 depends on X86_32 && !HIGHMEM4G
1467 PAE is required for NX support, and furthermore enables
1468 larger swapspace support for non-overcommit purposes. It
1469 has the cost of more pagetable lookup overhead, and also
1470 consumes more pagetable space per process.
1473 bool "Enable 5-level page tables support"
1476 5-level paging enables access to larger address space:
1477 upto 128 PiB of virtual address space and 4 PiB of
1478 physical address space.
1480 It will be supported by future Intel CPUs.
1482 Note: a kernel with this option enabled can only be booted
1483 on machines that support the feature.
1485 See Documentation/x86/x86_64/5level-paging.txt for more
1490 config ARCH_PHYS_ADDR_T_64BIT
1492 depends on X86_64 || X86_PAE
1494 config ARCH_DMA_ADDR_T_64BIT
1496 depends on X86_64 || HIGHMEM64G
1498 config X86_DIRECT_GBPAGES
1500 depends on X86_64 && !DEBUG_PAGEALLOC
1502 Certain kernel features effectively disable kernel
1503 linear 1 GB mappings (even if the CPU otherwise
1504 supports them), so don't confuse the user by printing
1505 that we have them enabled.
1507 config ARCH_HAS_MEM_ENCRYPT
1510 config AMD_MEM_ENCRYPT
1511 bool "AMD Secure Memory Encryption (SME) support"
1512 depends on X86_64 && CPU_SUP_AMD
1514 Say yes to enable support for the encryption of system memory.
1515 This requires an AMD processor that supports Secure Memory
1518 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1519 bool "Activate AMD Secure Memory Encryption (SME) by default"
1521 depends on AMD_MEM_ENCRYPT
1523 Say yes to have system memory encrypted by default if running on
1524 an AMD processor that supports Secure Memory Encryption (SME).
1526 If set to Y, then the encryption of system memory can be
1527 deactivated with the mem_encrypt=off command line option.
1529 If set to N, then the encryption of system memory can be
1530 activated with the mem_encrypt=on command line option.
1532 config ARCH_USE_MEMREMAP_PROT
1534 depends on AMD_MEM_ENCRYPT
1536 # Common NUMA Features
1538 bool "Numa Memory Allocation and Scheduler Support"
1540 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1541 default y if X86_BIGSMP
1543 Enable NUMA (Non Uniform Memory Access) support.
1545 The kernel will try to allocate memory used by a CPU on the
1546 local memory controller of the CPU and add some more
1547 NUMA awareness to the kernel.
1549 For 64-bit this is recommended if the system is Intel Core i7
1550 (or later), AMD Opteron, or EM64T NUMA.
1552 For 32-bit this is only needed if you boot a 32-bit
1553 kernel on a 64-bit NUMA platform.
1555 Otherwise, you should say N.
1559 prompt "Old style AMD Opteron NUMA detection"
1560 depends on X86_64 && NUMA && PCI
1562 Enable AMD NUMA node topology detection. You should say Y here if
1563 you have a multi processor AMD system. This uses an old method to
1564 read the NUMA configuration directly from the builtin Northbridge
1565 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1566 which also takes priority if both are compiled in.
1568 config X86_64_ACPI_NUMA
1570 prompt "ACPI NUMA detection"
1571 depends on X86_64 && NUMA && ACPI && PCI
1574 Enable ACPI SRAT based node topology detection.
1576 # Some NUMA nodes have memory ranges that span
1577 # other nodes. Even though a pfn is valid and
1578 # between a node's start and end pfns, it may not
1579 # reside on that node. See memmap_init_zone()
1581 config NODES_SPAN_OTHER_NODES
1583 depends on X86_64_ACPI_NUMA
1586 bool "NUMA emulation"
1589 Enable NUMA emulation. A flat machine will be split
1590 into virtual nodes when booted with "numa=fake=N", where N is the
1591 number of nodes. This is only useful for debugging.
1594 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1596 default "10" if MAXSMP
1597 default "6" if X86_64
1599 depends on NEED_MULTIPLE_NODES
1601 Specify the maximum number of NUMA Nodes available on the target
1602 system. Increases memory reserved to accommodate various tables.
1604 config ARCH_HAVE_MEMORY_PRESENT
1606 depends on X86_32 && DISCONTIGMEM
1608 config NEED_NODE_MEMMAP_SIZE
1610 depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
1612 config ARCH_FLATMEM_ENABLE
1614 depends on X86_32 && !NUMA
1616 config ARCH_DISCONTIGMEM_ENABLE
1618 depends on NUMA && X86_32
1620 config ARCH_DISCONTIGMEM_DEFAULT
1622 depends on NUMA && X86_32
1624 config ARCH_SPARSEMEM_ENABLE
1626 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1627 select SPARSEMEM_STATIC if X86_32
1628 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1630 config ARCH_SPARSEMEM_DEFAULT
1634 config ARCH_SELECT_MEMORY_MODEL
1636 depends on ARCH_SPARSEMEM_ENABLE
1638 config ARCH_MEMORY_PROBE
1639 bool "Enable sysfs memory/probe interface"
1640 depends on X86_64 && MEMORY_HOTPLUG
1642 This option enables a sysfs memory/probe interface for testing.
1643 See Documentation/memory-hotplug.txt for more information.
1644 If you are unsure how to answer this question, answer N.
1646 config ARCH_PROC_KCORE_TEXT
1648 depends on X86_64 && PROC_KCORE
1650 config ILLEGAL_POINTER_VALUE
1653 default 0xdead000000000000 if X86_64
1657 config X86_PMEM_LEGACY_DEVICE
1660 config X86_PMEM_LEGACY
1661 tristate "Support non-standard NVDIMMs and ADR protected memory"
1662 depends on PHYS_ADDR_T_64BIT
1664 select X86_PMEM_LEGACY_DEVICE
1667 Treat memory marked using the non-standard e820 type of 12 as used
1668 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1669 The kernel will offer these regions to the 'pmem' driver so
1670 they can be used for persistent storage.
1675 bool "Allocate 3rd-level pagetables from highmem"
1678 The VM uses one page table entry for each page of physical memory.
1679 For systems with a lot of RAM, this can be wasteful of precious
1680 low memory. Setting this option will put user-space page table
1681 entries in high memory.
1683 config X86_CHECK_BIOS_CORRUPTION
1684 bool "Check for low memory corruption"
1686 Periodically check for memory corruption in low memory, which
1687 is suspected to be caused by BIOS. Even when enabled in the
1688 configuration, it is disabled at runtime. Enable it by
1689 setting "memory_corruption_check=1" on the kernel command
1690 line. By default it scans the low 64k of memory every 60
1691 seconds; see the memory_corruption_check_size and
1692 memory_corruption_check_period parameters in
1693 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1695 When enabled with the default parameters, this option has
1696 almost no overhead, as it reserves a relatively small amount
1697 of memory and scans it infrequently. It both detects corruption
1698 and prevents it from affecting the running system.
1700 It is, however, intended as a diagnostic tool; if repeatable
1701 BIOS-originated corruption always affects the same memory,
1702 you can use memmap= to prevent the kernel from using that
1705 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1706 bool "Set the default setting of memory_corruption_check"
1707 depends on X86_CHECK_BIOS_CORRUPTION
1710 Set whether the default state of memory_corruption_check is
1713 config X86_RESERVE_LOW
1714 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1718 Specify the amount of low memory to reserve for the BIOS.
1720 The first page contains BIOS data structures that the kernel
1721 must not use, so that page must always be reserved.
1723 By default we reserve the first 64K of physical RAM, as a
1724 number of BIOSes are known to corrupt that memory range
1725 during events such as suspend/resume or monitor cable
1726 insertion, so it must not be used by the kernel.
1728 You can set this to 4 if you are absolutely sure that you
1729 trust the BIOS to get all its memory reservations and usages
1730 right. If you know your BIOS have problems beyond the
1731 default 64K area, you can set this to 640 to avoid using the
1732 entire low memory range.
1734 If you have doubts about the BIOS (e.g. suspend/resume does
1735 not work or there's kernel crashes after certain hardware
1736 hotplug events) then you might want to enable
1737 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1738 typical corruption patterns.
1740 Leave this to the default value of 64 if you are unsure.
1742 config MATH_EMULATION
1744 depends on MODIFY_LDT_SYSCALL
1745 prompt "Math emulation" if X86_32
1747 Linux can emulate a math coprocessor (used for floating point
1748 operations) if you don't have one. 486DX and Pentium processors have
1749 a math coprocessor built in, 486SX and 386 do not, unless you added
1750 a 487DX or 387, respectively. (The messages during boot time can
1751 give you some hints here ["man dmesg"].) Everyone needs either a
1752 coprocessor or this emulation.
1754 If you don't have a math coprocessor, you need to say Y here; if you
1755 say Y here even though you have a coprocessor, the coprocessor will
1756 be used nevertheless. (This behavior can be changed with the kernel
1757 command line option "no387", which comes handy if your coprocessor
1758 is broken. Try "man bootparam" or see the documentation of your boot
1759 loader (lilo or loadlin) about how to pass options to the kernel at
1760 boot time.) This means that it is a good idea to say Y here if you
1761 intend to use this kernel on different machines.
1763 More information about the internals of the Linux math coprocessor
1764 emulation can be found in <file:arch/x86/math-emu/README>.
1766 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1767 kernel, it won't hurt.
1771 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1773 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1774 the Memory Type Range Registers (MTRRs) may be used to control
1775 processor access to memory ranges. This is most useful if you have
1776 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1777 allows bus write transfers to be combined into a larger transfer
1778 before bursting over the PCI/AGP bus. This can increase performance
1779 of image write operations 2.5 times or more. Saying Y here creates a
1780 /proc/mtrr file which may be used to manipulate your processor's
1781 MTRRs. Typically the X server should use this.
1783 This code has a reasonably generic interface so that similar
1784 control registers on other processors can be easily supported
1787 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1788 Registers (ARRs) which provide a similar functionality to MTRRs. For
1789 these, the ARRs are used to emulate the MTRRs.
1790 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1791 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1792 write-combining. All of these processors are supported by this code
1793 and it makes sense to say Y here if you have one of them.
1795 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1796 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1797 can lead to all sorts of problems, so it's good to say Y here.
1799 You can safely say Y even if your machine doesn't have MTRRs, you'll
1800 just add about 9 KB to your kernel.
1802 See <file:Documentation/x86/mtrr.txt> for more information.
1804 config MTRR_SANITIZER
1806 prompt "MTRR cleanup support"
1809 Convert MTRR layout from continuous to discrete, so X drivers can
1810 add writeback entries.
1812 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1813 The largest mtrr entry size for a continuous block can be set with
1818 config MTRR_SANITIZER_ENABLE_DEFAULT
1819 int "MTRR cleanup enable value (0-1)"
1822 depends on MTRR_SANITIZER
1824 Enable mtrr cleanup default value
1826 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1827 int "MTRR cleanup spare reg num (0-7)"
1830 depends on MTRR_SANITIZER
1832 mtrr cleanup spare entries default, it can be changed via
1833 mtrr_spare_reg_nr=N on the kernel command line.
1837 prompt "x86 PAT support" if EXPERT
1840 Use PAT attributes to setup page level cache control.
1842 PATs are the modern equivalents of MTRRs and are much more
1843 flexible than MTRRs.
1845 Say N here if you see bootup problems (boot crash, boot hang,
1846 spontaneous reboots) or a non-working video driver.
1850 config ARCH_USES_PG_UNCACHED
1856 prompt "x86 architectural random number generator" if EXPERT
1858 Enable the x86 architectural RDRAND instruction
1859 (Intel Bull Mountain technology) to generate random numbers.
1860 If supported, this is a high bandwidth, cryptographically
1861 secure hardware random number generator.
1865 prompt "Supervisor Mode Access Prevention" if EXPERT
1867 Supervisor Mode Access Prevention (SMAP) is a security
1868 feature in newer Intel processors. There is a small
1869 performance cost if this enabled and turned on; there is
1870 also a small increase in the kernel size if this is enabled.
1874 config X86_INTEL_UMIP
1876 depends on CPU_SUP_INTEL
1877 prompt "Intel User Mode Instruction Prevention" if EXPERT
1879 The User Mode Instruction Prevention (UMIP) is a security
1880 feature in newer Intel processors. If enabled, a general
1881 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1882 or STR instructions are executed in user mode. These instructions
1883 unnecessarily expose information about the hardware state.
1885 The vast majority of applications do not use these instructions.
1886 For the very few that do, software emulation is provided in
1887 specific cases in protected and virtual-8086 modes. Emulated
1890 config X86_INTEL_MPX
1891 prompt "Intel MPX (Memory Protection Extensions)"
1893 # Note: only available in 64-bit mode due to VMA flags shortage
1894 depends on CPU_SUP_INTEL && X86_64
1895 select ARCH_USES_HIGH_VMA_FLAGS
1897 MPX provides hardware features that can be used in
1898 conjunction with compiler-instrumented code to check
1899 memory references. It is designed to detect buffer
1900 overflow or underflow bugs.
1902 This option enables running applications which are
1903 instrumented or otherwise use MPX. It does not use MPX
1904 itself inside the kernel or to protect the kernel
1905 against bad memory references.
1907 Enabling this option will make the kernel larger:
1908 ~8k of kernel text and 36 bytes of data on a 64-bit
1909 defconfig. It adds a long to the 'mm_struct' which
1910 will increase the kernel memory overhead of each
1911 process and adds some branches to paths used during
1912 exec() and munmap().
1914 For details, see Documentation/x86/intel_mpx.txt
1918 config X86_INTEL_MEMORY_PROTECTION_KEYS
1919 prompt "Intel Memory Protection Keys"
1921 # Note: only available in 64-bit mode
1922 depends on CPU_SUP_INTEL && X86_64
1923 select ARCH_USES_HIGH_VMA_FLAGS
1924 select ARCH_HAS_PKEYS
1926 Memory Protection Keys provides a mechanism for enforcing
1927 page-based protections, but without requiring modification of the
1928 page tables when an application changes protection domains.
1930 For details, see Documentation/x86/protection-keys.txt
1935 bool "EFI runtime service support"
1938 select EFI_RUNTIME_WRAPPERS
1940 This enables the kernel to use EFI runtime services that are
1941 available (such as the EFI variable services).
1943 This option is only useful on systems that have EFI firmware.
1944 In addition, you should use the latest ELILO loader available
1945 at <http://elilo.sourceforge.net> in order to take advantage
1946 of EFI runtime services. However, even with this option, the
1947 resultant kernel should continue to boot on existing non-EFI
1951 bool "EFI stub support"
1952 depends on EFI && !X86_USE_3DNOW
1955 This kernel feature allows a bzImage to be loaded directly
1956 by EFI firmware without the use of a bootloader.
1958 See Documentation/efi-stub.txt for more information.
1961 bool "EFI mixed-mode support"
1962 depends on EFI_STUB && X86_64
1964 Enabling this feature allows a 64-bit kernel to be booted
1965 on a 32-bit firmware, provided that your CPU supports 64-bit
1968 Note that it is not possible to boot a mixed-mode enabled
1969 kernel via the EFI boot stub - a bootloader that supports
1970 the EFI handover protocol must be used.
1976 prompt "Enable seccomp to safely compute untrusted bytecode"
1978 This kernel feature is useful for number crunching applications
1979 that may need to compute untrusted bytecode during their
1980 execution. By using pipes or other transports made available to
1981 the process as file descriptors supporting the read/write
1982 syscalls, it's possible to isolate those applications in
1983 their own address space using seccomp. Once seccomp is
1984 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1985 and the task is only allowed to execute a few safe syscalls
1986 defined by each seccomp mode.
1988 If unsure, say Y. Only embedded should say N here.
1990 source kernel/Kconfig.hz
1993 bool "kexec system call"
1996 kexec is a system call that implements the ability to shutdown your
1997 current kernel, and to start another kernel. It is like a reboot
1998 but it is independent of the system firmware. And like a reboot
1999 you can start any kernel with it, not just Linux.
2001 The name comes from the similarity to the exec system call.
2003 It is an ongoing process to be certain the hardware in a machine
2004 is properly shutdown, so do not be surprised if this code does not
2005 initially work for you. As of this writing the exact hardware
2006 interface is strongly in flux, so no good recommendation can be
2010 bool "kexec file based system call"
2015 depends on CRYPTO_SHA256=y
2017 This is new version of kexec system call. This system call is
2018 file based and takes file descriptors as system call argument
2019 for kernel and initramfs as opposed to list of segments as
2020 accepted by previous system call.
2022 config KEXEC_VERIFY_SIG
2023 bool "Verify kernel signature during kexec_file_load() syscall"
2024 depends on KEXEC_FILE
2026 This option makes kernel signature verification mandatory for
2027 the kexec_file_load() syscall.
2029 In addition to that option, you need to enable signature
2030 verification for the corresponding kernel image type being
2031 loaded in order for this to work.
2033 config KEXEC_BZIMAGE_VERIFY_SIG
2034 bool "Enable bzImage signature verification support"
2035 depends on KEXEC_VERIFY_SIG
2036 depends on SIGNED_PE_FILE_VERIFICATION
2037 select SYSTEM_TRUSTED_KEYRING
2039 Enable bzImage signature verification support.
2042 bool "kernel crash dumps"
2043 depends on X86_64 || (X86_32 && HIGHMEM)
2045 Generate crash dump after being started by kexec.
2046 This should be normally only set in special crash dump kernels
2047 which are loaded in the main kernel with kexec-tools into
2048 a specially reserved region and then later executed after
2049 a crash by kdump/kexec. The crash dump kernel must be compiled
2050 to a memory address not used by the main kernel or BIOS using
2051 PHYSICAL_START, or it must be built as a relocatable image
2052 (CONFIG_RELOCATABLE=y).
2053 For more details see Documentation/kdump/kdump.txt
2057 depends on KEXEC && HIBERNATION
2059 Jump between original kernel and kexeced kernel and invoke
2060 code in physical address mode via KEXEC
2062 config PHYSICAL_START
2063 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2066 This gives the physical address where the kernel is loaded.
2068 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2069 bzImage will decompress itself to above physical address and
2070 run from there. Otherwise, bzImage will run from the address where
2071 it has been loaded by the boot loader and will ignore above physical
2074 In normal kdump cases one does not have to set/change this option
2075 as now bzImage can be compiled as a completely relocatable image
2076 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2077 address. This option is mainly useful for the folks who don't want
2078 to use a bzImage for capturing the crash dump and want to use a
2079 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2080 to be specifically compiled to run from a specific memory area
2081 (normally a reserved region) and this option comes handy.
2083 So if you are using bzImage for capturing the crash dump,
2084 leave the value here unchanged to 0x1000000 and set
2085 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2086 for capturing the crash dump change this value to start of
2087 the reserved region. In other words, it can be set based on
2088 the "X" value as specified in the "crashkernel=YM@XM"
2089 command line boot parameter passed to the panic-ed
2090 kernel. Please take a look at Documentation/kdump/kdump.txt
2091 for more details about crash dumps.
2093 Usage of bzImage for capturing the crash dump is recommended as
2094 one does not have to build two kernels. Same kernel can be used
2095 as production kernel and capture kernel. Above option should have
2096 gone away after relocatable bzImage support is introduced. But it
2097 is present because there are users out there who continue to use
2098 vmlinux for dump capture. This option should go away down the
2101 Don't change this unless you know what you are doing.
2104 bool "Build a relocatable kernel"
2107 This builds a kernel image that retains relocation information
2108 so it can be loaded someplace besides the default 1MB.
2109 The relocations tend to make the kernel binary about 10% larger,
2110 but are discarded at runtime.
2112 One use is for the kexec on panic case where the recovery kernel
2113 must live at a different physical address than the primary
2116 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2117 it has been loaded at and the compile time physical address
2118 (CONFIG_PHYSICAL_START) is used as the minimum location.
2120 config RANDOMIZE_BASE
2121 bool "Randomize the address of the kernel image (KASLR)"
2122 depends on RELOCATABLE
2125 In support of Kernel Address Space Layout Randomization (KASLR),
2126 this randomizes the physical address at which the kernel image
2127 is decompressed and the virtual address where the kernel
2128 image is mapped, as a security feature that deters exploit
2129 attempts relying on knowledge of the location of kernel
2132 On 64-bit, the kernel physical and virtual addresses are
2133 randomized separately. The physical address will be anywhere
2134 between 16MB and the top of physical memory (up to 64TB). The
2135 virtual address will be randomized from 16MB up to 1GB (9 bits
2136 of entropy). Note that this also reduces the memory space
2137 available to kernel modules from 1.5GB to 1GB.
2139 On 32-bit, the kernel physical and virtual addresses are
2140 randomized together. They will be randomized from 16MB up to
2141 512MB (8 bits of entropy).
2143 Entropy is generated using the RDRAND instruction if it is
2144 supported. If RDTSC is supported, its value is mixed into
2145 the entropy pool as well. If neither RDRAND nor RDTSC are
2146 supported, then entropy is read from the i8254 timer. The
2147 usable entropy is limited by the kernel being built using
2148 2GB addressing, and that PHYSICAL_ALIGN must be at a
2149 minimum of 2MB. As a result, only 10 bits of entropy are
2150 theoretically possible, but the implementations are further
2151 limited due to memory layouts.
2155 # Relocation on x86 needs some additional build support
2156 config X86_NEED_RELOCS
2158 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2160 config PHYSICAL_ALIGN
2161 hex "Alignment value to which kernel should be aligned"
2163 range 0x2000 0x1000000 if X86_32
2164 range 0x200000 0x1000000 if X86_64
2166 This value puts the alignment restrictions on physical address
2167 where kernel is loaded and run from. Kernel is compiled for an
2168 address which meets above alignment restriction.
2170 If bootloader loads the kernel at a non-aligned address and
2171 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2172 address aligned to above value and run from there.
2174 If bootloader loads the kernel at a non-aligned address and
2175 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2176 load address and decompress itself to the address it has been
2177 compiled for and run from there. The address for which kernel is
2178 compiled already meets above alignment restrictions. Hence the
2179 end result is that kernel runs from a physical address meeting
2180 above alignment restrictions.
2182 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2183 this value must be a multiple of 0x200000.
2185 Don't change this unless you know what you are doing.
2187 config RANDOMIZE_MEMORY
2188 bool "Randomize the kernel memory sections"
2190 depends on RANDOMIZE_BASE
2191 default RANDOMIZE_BASE
2193 Randomizes the base virtual address of kernel memory sections
2194 (physical memory mapping, vmalloc & vmemmap). This security feature
2195 makes exploits relying on predictable memory locations less reliable.
2197 The order of allocations remains unchanged. Entropy is generated in
2198 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2199 configuration have in average 30,000 different possible virtual
2200 addresses for each memory section.
2204 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2205 hex "Physical memory mapping padding" if EXPERT
2206 depends on RANDOMIZE_MEMORY
2207 default "0xa" if MEMORY_HOTPLUG
2209 range 0x1 0x40 if MEMORY_HOTPLUG
2212 Define the padding in terabytes added to the existing physical
2213 memory size during kernel memory randomization. It is useful
2214 for memory hotplug support but reduces the entropy available for
2215 address randomization.
2217 If unsure, leave at the default value.
2220 bool "Support for hot-pluggable CPUs"
2223 Say Y here to allow turning CPUs off and on. CPUs can be
2224 controlled through /sys/devices/system/cpu.
2225 ( Note: power management support will enable this option
2226 automatically on SMP systems. )
2227 Say N if you want to disable CPU hotplug.
2229 config BOOTPARAM_HOTPLUG_CPU0
2230 bool "Set default setting of cpu0_hotpluggable"
2232 depends on HOTPLUG_CPU
2234 Set whether default state of cpu0_hotpluggable is on or off.
2236 Say Y here to enable CPU0 hotplug by default. If this switch
2237 is turned on, there is no need to give cpu0_hotplug kernel
2238 parameter and the CPU0 hotplug feature is enabled by default.
2240 Please note: there are two known CPU0 dependencies if you want
2241 to enable the CPU0 hotplug feature either by this switch or by
2242 cpu0_hotplug kernel parameter.
2244 First, resume from hibernate or suspend always starts from CPU0.
2245 So hibernate and suspend are prevented if CPU0 is offline.
2247 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2248 offline if any interrupt can not migrate out of CPU0. There may
2249 be other CPU0 dependencies.
2251 Please make sure the dependencies are under your control before
2252 you enable this feature.
2254 Say N if you don't want to enable CPU0 hotplug feature by default.
2255 You still can enable the CPU0 hotplug feature at boot by kernel
2256 parameter cpu0_hotplug.
2258 config DEBUG_HOTPLUG_CPU0
2260 prompt "Debug CPU0 hotplug"
2261 depends on HOTPLUG_CPU
2263 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2264 soon as possible and boots up userspace with CPU0 offlined. User
2265 can online CPU0 back after boot time.
2267 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2268 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2269 compilation or giving cpu0_hotplug kernel parameter at boot.
2275 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2276 depends on COMPAT_32
2278 Certain buggy versions of glibc will crash if they are
2279 presented with a 32-bit vDSO that is not mapped at the address
2280 indicated in its segment table.
2282 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2283 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2284 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2285 the only released version with the bug, but OpenSUSE 9
2286 contains a buggy "glibc 2.3.2".
2288 The symptom of the bug is that everything crashes on startup, saying:
2289 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2291 Saying Y here changes the default value of the vdso32 boot
2292 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2293 This works around the glibc bug but hurts performance.
2295 If unsure, say N: if you are compiling your own kernel, you
2296 are unlikely to be using a buggy version of glibc.
2299 prompt "vsyscall table for legacy applications"
2301 default LEGACY_VSYSCALL_EMULATE
2303 Legacy user code that does not know how to find the vDSO expects
2304 to be able to issue three syscalls by calling fixed addresses in
2305 kernel space. Since this location is not randomized with ASLR,
2306 it can be used to assist security vulnerability exploitation.
2308 This setting can be changed at boot time via the kernel command
2309 line parameter vsyscall=[native|emulate|none].
2311 On a system with recent enough glibc (2.14 or newer) and no
2312 static binaries, you can say None without a performance penalty
2313 to improve security.
2315 If unsure, select "Emulate".
2317 config LEGACY_VSYSCALL_NATIVE
2320 Actual executable code is located in the fixed vsyscall
2321 address mapping, implementing time() efficiently. Since
2322 this makes the mapping executable, it can be used during
2323 security vulnerability exploitation (traditionally as
2324 ROP gadgets). This configuration is not recommended.
2326 config LEGACY_VSYSCALL_EMULATE
2329 The kernel traps and emulates calls into the fixed
2330 vsyscall address mapping. This makes the mapping
2331 non-executable, but it still contains known contents,
2332 which could be used in certain rare security vulnerability
2333 exploits. This configuration is recommended when userspace
2334 still uses the vsyscall area.
2336 config LEGACY_VSYSCALL_NONE
2339 There will be no vsyscall mapping at all. This will
2340 eliminate any risk of ASLR bypass due to the vsyscall
2341 fixed address mapping. Attempts to use the vsyscalls
2342 will be reported to dmesg, so that either old or
2343 malicious userspace programs can be identified.
2348 bool "Built-in kernel command line"
2350 Allow for specifying boot arguments to the kernel at
2351 build time. On some systems (e.g. embedded ones), it is
2352 necessary or convenient to provide some or all of the
2353 kernel boot arguments with the kernel itself (that is,
2354 to not rely on the boot loader to provide them.)
2356 To compile command line arguments into the kernel,
2357 set this option to 'Y', then fill in the
2358 boot arguments in CONFIG_CMDLINE.
2360 Systems with fully functional boot loaders (i.e. non-embedded)
2361 should leave this option set to 'N'.
2364 string "Built-in kernel command string"
2365 depends on CMDLINE_BOOL
2368 Enter arguments here that should be compiled into the kernel
2369 image and used at boot time. If the boot loader provides a
2370 command line at boot time, it is appended to this string to
2371 form the full kernel command line, when the system boots.
2373 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2374 change this behavior.
2376 In most cases, the command line (whether built-in or provided
2377 by the boot loader) should specify the device for the root
2380 config CMDLINE_OVERRIDE
2381 bool "Built-in command line overrides boot loader arguments"
2382 depends on CMDLINE_BOOL
2384 Set this option to 'Y' to have the kernel ignore the boot loader
2385 command line, and use ONLY the built-in command line.
2387 This is used to work around broken boot loaders. This should
2388 be set to 'N' under normal conditions.
2390 config MODIFY_LDT_SYSCALL
2391 bool "Enable the LDT (local descriptor table)" if EXPERT
2394 Linux can allow user programs to install a per-process x86
2395 Local Descriptor Table (LDT) using the modify_ldt(2) system
2396 call. This is required to run 16-bit or segmented code such as
2397 DOSEMU or some Wine programs. It is also used by some very old
2398 threading libraries.
2400 Enabling this feature adds a small amount of overhead to
2401 context switches and increases the low-level kernel attack
2402 surface. Disabling it removes the modify_ldt(2) system call.
2404 Saying 'N' here may make sense for embedded or server kernels.
2406 source "kernel/livepatch/Kconfig"
2410 config ARCH_HAS_ADD_PAGES
2412 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2414 config ARCH_ENABLE_MEMORY_HOTPLUG
2416 depends on X86_64 || (X86_32 && HIGHMEM)
2418 config ARCH_ENABLE_MEMORY_HOTREMOVE
2420 depends on MEMORY_HOTPLUG
2422 config USE_PERCPU_NUMA_NODE_ID
2426 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2428 depends on X86_64 || X86_PAE
2430 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2432 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2434 config ARCH_ENABLE_THP_MIGRATION
2436 depends on X86_64 && TRANSPARENT_HUGEPAGE
2438 menu "Power management and ACPI options"
2440 config ARCH_HIBERNATION_HEADER
2442 depends on X86_64 && HIBERNATION
2444 source "kernel/power/Kconfig"
2446 source "drivers/acpi/Kconfig"
2448 source "drivers/sfi/Kconfig"
2455 tristate "APM (Advanced Power Management) BIOS support"
2456 depends on X86_32 && PM_SLEEP
2458 APM is a BIOS specification for saving power using several different
2459 techniques. This is mostly useful for battery powered laptops with
2460 APM compliant BIOSes. If you say Y here, the system time will be
2461 reset after a RESUME operation, the /proc/apm device will provide
2462 battery status information, and user-space programs will receive
2463 notification of APM "events" (e.g. battery status change).
2465 If you select "Y" here, you can disable actual use of the APM
2466 BIOS by passing the "apm=off" option to the kernel at boot time.
2468 Note that the APM support is almost completely disabled for
2469 machines with more than one CPU.
2471 In order to use APM, you will need supporting software. For location
2472 and more information, read <file:Documentation/power/apm-acpi.txt>
2473 and the Battery Powered Linux mini-HOWTO, available from
2474 <http://www.tldp.org/docs.html#howto>.
2476 This driver does not spin down disk drives (see the hdparm(8)
2477 manpage ("man 8 hdparm") for that), and it doesn't turn off
2478 VESA-compliant "green" monitors.
2480 This driver does not support the TI 4000M TravelMate and the ACER
2481 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2482 desktop machines also don't have compliant BIOSes, and this driver
2483 may cause those machines to panic during the boot phase.
2485 Generally, if you don't have a battery in your machine, there isn't
2486 much point in using this driver and you should say N. If you get
2487 random kernel OOPSes or reboots that don't seem to be related to
2488 anything, try disabling/enabling this option (or disabling/enabling
2491 Some other things you should try when experiencing seemingly random,
2494 1) make sure that you have enough swap space and that it is
2496 2) pass the "no-hlt" option to the kernel
2497 3) switch on floating point emulation in the kernel and pass
2498 the "no387" option to the kernel
2499 4) pass the "floppy=nodma" option to the kernel
2500 5) pass the "mem=4M" option to the kernel (thereby disabling
2501 all but the first 4 MB of RAM)
2502 6) make sure that the CPU is not over clocked.
2503 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2504 8) disable the cache from your BIOS settings
2505 9) install a fan for the video card or exchange video RAM
2506 10) install a better fan for the CPU
2507 11) exchange RAM chips
2508 12) exchange the motherboard.
2510 To compile this driver as a module, choose M here: the
2511 module will be called apm.
2515 config APM_IGNORE_USER_SUSPEND
2516 bool "Ignore USER SUSPEND"
2518 This option will ignore USER SUSPEND requests. On machines with a
2519 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2520 series notebooks, it is necessary to say Y because of a BIOS bug.
2522 config APM_DO_ENABLE
2523 bool "Enable PM at boot time"
2525 Enable APM features at boot time. From page 36 of the APM BIOS
2526 specification: "When disabled, the APM BIOS does not automatically
2527 power manage devices, enter the Standby State, enter the Suspend
2528 State, or take power saving steps in response to CPU Idle calls."
2529 This driver will make CPU Idle calls when Linux is idle (unless this
2530 feature is turned off -- see "Do CPU IDLE calls", below). This
2531 should always save battery power, but more complicated APM features
2532 will be dependent on your BIOS implementation. You may need to turn
2533 this option off if your computer hangs at boot time when using APM
2534 support, or if it beeps continuously instead of suspending. Turn
2535 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2536 T400CDT. This is off by default since most machines do fine without
2541 bool "Make CPU Idle calls when idle"
2543 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2544 On some machines, this can activate improved power savings, such as
2545 a slowed CPU clock rate, when the machine is idle. These idle calls
2546 are made after the idle loop has run for some length of time (e.g.,
2547 333 mS). On some machines, this will cause a hang at boot time or
2548 whenever the CPU becomes idle. (On machines with more than one CPU,
2549 this option does nothing.)
2551 config APM_DISPLAY_BLANK
2552 bool "Enable console blanking using APM"
2554 Enable console blanking using the APM. Some laptops can use this to
2555 turn off the LCD backlight when the screen blanker of the Linux
2556 virtual console blanks the screen. Note that this is only used by
2557 the virtual console screen blanker, and won't turn off the backlight
2558 when using the X Window system. This also doesn't have anything to
2559 do with your VESA-compliant power-saving monitor. Further, this
2560 option doesn't work for all laptops -- it might not turn off your
2561 backlight at all, or it might print a lot of errors to the console,
2562 especially if you are using gpm.
2564 config APM_ALLOW_INTS
2565 bool "Allow interrupts during APM BIOS calls"
2567 Normally we disable external interrupts while we are making calls to
2568 the APM BIOS as a measure to lessen the effects of a badly behaving
2569 BIOS implementation. The BIOS should reenable interrupts if it
2570 needs to. Unfortunately, some BIOSes do not -- especially those in
2571 many of the newer IBM Thinkpads. If you experience hangs when you
2572 suspend, try setting this to Y. Otherwise, say N.
2576 source "drivers/cpufreq/Kconfig"
2578 source "drivers/cpuidle/Kconfig"
2580 source "drivers/idle/Kconfig"
2585 menu "Bus options (PCI etc.)"
2591 Find out whether you have a PCI motherboard. PCI is the name of a
2592 bus system, i.e. the way the CPU talks to the other stuff inside
2593 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2594 VESA. If you have PCI, say Y, otherwise N.
2597 prompt "PCI access mode"
2598 depends on X86_32 && PCI
2601 On PCI systems, the BIOS can be used to detect the PCI devices and
2602 determine their configuration. However, some old PCI motherboards
2603 have BIOS bugs and may crash if this is done. Also, some embedded
2604 PCI-based systems don't have any BIOS at all. Linux can also try to
2605 detect the PCI hardware directly without using the BIOS.
2607 With this option, you can specify how Linux should detect the
2608 PCI devices. If you choose "BIOS", the BIOS will be used,
2609 if you choose "Direct", the BIOS won't be used, and if you
2610 choose "MMConfig", then PCI Express MMCONFIG will be used.
2611 If you choose "Any", the kernel will try MMCONFIG, then the
2612 direct access method and falls back to the BIOS if that doesn't
2613 work. If unsure, go with the default, which is "Any".
2618 config PCI_GOMMCONFIG
2635 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2637 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2640 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2644 depends on X86_32 && PCI && (ACPI || SFI) && (PCI_GOMMCONFIG || PCI_GOANY)
2648 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2652 depends on PCI && XEN
2660 bool "Support mmconfig PCI config space access"
2661 depends on X86_64 && PCI && ACPI
2663 config PCI_CNB20LE_QUIRK
2664 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2667 Read the PCI windows out of the CNB20LE host bridge. This allows
2668 PCI hotplug to work on systems with the CNB20LE chipset which do
2671 There's no public spec for this chipset, and this functionality
2672 is known to be incomplete.
2674 You should say N unless you know you need this.
2676 source "drivers/pci/Kconfig"
2679 bool "ISA-style bus support on modern systems" if EXPERT
2682 Enables ISA-style drivers on modern systems. This is necessary to
2683 support PC/104 devices on X86_64 platforms.
2687 # x86_64 have no ISA slots, but can have ISA-style DMA.
2689 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2692 Enables ISA-style DMA support for devices requiring such controllers.
2700 Find out whether you have ISA slots on your motherboard. ISA is the
2701 name of a bus system, i.e. the way the CPU talks to the other stuff
2702 inside your box. Other bus systems are PCI, EISA, MicroChannel
2703 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2704 newer boards don't support it. If you have ISA, say Y, otherwise N.
2710 The Extended Industry Standard Architecture (EISA) bus was
2711 developed as an open alternative to the IBM MicroChannel bus.
2713 The EISA bus provided some of the features of the IBM MicroChannel
2714 bus while maintaining backward compatibility with cards made for
2715 the older ISA bus. The EISA bus saw limited use between 1988 and
2716 1995 when it was made obsolete by the PCI bus.
2718 Say Y here if you are building a kernel for an EISA-based machine.
2722 source "drivers/eisa/Kconfig"
2725 tristate "NatSemi SCx200 support"
2727 This provides basic support for National Semiconductor's
2728 (now AMD's) Geode processors. The driver probes for the
2729 PCI-IDs of several on-chip devices, so its a good dependency
2730 for other scx200_* drivers.
2732 If compiled as a module, the driver is named scx200.
2734 config SCx200HR_TIMER
2735 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2739 This driver provides a clocksource built upon the on-chip
2740 27MHz high-resolution timer. Its also a workaround for
2741 NSC Geode SC-1100's buggy TSC, which loses time when the
2742 processor goes idle (as is done by the scheduler). The
2743 other workaround is idle=poll boot option.
2746 bool "One Laptop Per Child support"
2753 Add support for detecting the unique features of the OLPC
2757 bool "OLPC XO-1 Power Management"
2758 depends on OLPC && MFD_CS5535 && PM_SLEEP
2761 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2764 bool "OLPC XO-1 Real Time Clock"
2765 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2767 Add support for the XO-1 real time clock, which can be used as a
2768 programmable wakeup source.
2771 bool "OLPC XO-1 SCI extras"
2772 depends on OLPC && OLPC_XO1_PM
2778 Add support for SCI-based features of the OLPC XO-1 laptop:
2779 - EC-driven system wakeups
2783 - AC adapter status updates
2784 - Battery status updates
2786 config OLPC_XO15_SCI
2787 bool "OLPC XO-1.5 SCI extras"
2788 depends on OLPC && ACPI
2791 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2792 - EC-driven system wakeups
2793 - AC adapter status updates
2794 - Battery status updates
2797 bool "PCEngines ALIX System Support (LED setup)"
2800 This option enables system support for the PCEngines ALIX.
2801 At present this just sets up LEDs for GPIO control on
2802 ALIX2/3/6 boards. However, other system specific setup should
2805 Note: You must still enable the drivers for GPIO and LED support
2806 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2808 Note: You have to set alix.force=1 for boards with Award BIOS.
2811 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2814 This option enables system support for the Soekris Engineering net5501.
2817 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2821 This option enables system support for the Traverse Technologies GEOS.
2824 bool "Technologic Systems TS-5500 platform support"
2826 select CHECK_SIGNATURE
2830 This option enables system support for the Technologic Systems TS-5500.
2836 depends on CPU_SUP_AMD && PCI
2838 source "drivers/pcmcia/Kconfig"
2841 tristate "RapidIO support"
2845 If enabled this option will include drivers and the core
2846 infrastructure code to support RapidIO interconnect devices.
2848 source "drivers/rapidio/Kconfig"
2851 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2853 Firmwares often provide initial graphics framebuffers so the BIOS,
2854 bootloader or kernel can show basic video-output during boot for
2855 user-guidance and debugging. Historically, x86 used the VESA BIOS
2856 Extensions and EFI-framebuffers for this, which are mostly limited
2858 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2859 framebuffers so the new generic system-framebuffer drivers can be
2860 used on x86. If the framebuffer is not compatible with the generic
2861 modes, it is adverticed as fallback platform framebuffer so legacy
2862 drivers like efifb, vesafb and uvesafb can pick it up.
2863 If this option is not selected, all system framebuffers are always
2864 marked as fallback platform framebuffers as usual.
2866 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2867 not be able to pick up generic system framebuffers if this option
2868 is selected. You are highly encouraged to enable simplefb as
2869 replacement if you select this option. simplefb can correctly deal
2870 with generic system framebuffers. But you should still keep vesafb
2871 and others enabled as fallback if a system framebuffer is
2872 incompatible with simplefb.
2879 menu "Executable file formats / Emulations"
2881 source "fs/Kconfig.binfmt"
2883 config IA32_EMULATION
2884 bool "IA32 Emulation"
2886 select ARCH_WANT_OLD_COMPAT_IPC
2888 select COMPAT_BINFMT_ELF
2889 select COMPAT_OLD_SIGACTION
2891 Include code to run legacy 32-bit programs under a
2892 64-bit kernel. You should likely turn this on, unless you're
2893 100% sure that you don't have any 32-bit programs left.
2896 tristate "IA32 a.out support"
2897 depends on IA32_EMULATION
2899 Support old a.out binaries in the 32bit emulation.
2902 bool "x32 ABI for 64-bit mode"
2905 Include code to run binaries for the x32 native 32-bit ABI
2906 for 64-bit processors. An x32 process gets access to the
2907 full 64-bit register file and wide data path while leaving
2908 pointers at 32 bits for smaller memory footprint.
2910 You will need a recent binutils (2.22 or later) with
2911 elf32_x86_64 support enabled to compile a kernel with this
2916 depends on IA32_EMULATION || X86_32
2918 select OLD_SIGSUSPEND3
2922 depends on IA32_EMULATION || X86_X32
2925 config COMPAT_FOR_U64_ALIGNMENT
2928 config SYSVIPC_COMPAT
2936 config HAVE_ATOMIC_IOMAP
2940 config X86_DEV_DMA_OPS
2942 depends on X86_64 || STA2X11
2944 config X86_DMA_REMAP
2948 config HAVE_GENERIC_GUP
2951 source "net/Kconfig"
2953 source "drivers/Kconfig"
2955 source "drivers/firmware/Kconfig"
2959 source "arch/x86/Kconfig.debug"
2961 source "security/Kconfig"
2963 source "crypto/Kconfig"
2965 source "arch/x86/kvm/Kconfig"
2967 source "lib/Kconfig"
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