1 # SPDX-License-Identifier: GPL-2.0
4 bool "64-bit kernel" if "$(ARCH)" = "x86"
5 default "$(ARCH)" != "i386"
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 NEED_DMA_MAP_STATE
33 select X86_DEV_DMA_OPS
34 select ARCH_HAS_SYSCALL_WRAPPER
39 # ( Note that options that are marked 'if X86_64' could in principle be
40 # ported to 32-bit as well. )
45 # Note: keep this list sorted alphabetically
47 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
48 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
50 select ARCH_CLOCKSOURCE_DATA
51 select ARCH_DISCARD_MEMBLOCK
52 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
53 select ARCH_HAS_DEBUG_VIRTUAL
54 select ARCH_HAS_DEVMEM_IS_ALLOWED
55 select ARCH_HAS_ELF_RANDOMIZE
56 select ARCH_HAS_FAST_MULTIPLIER
57 select ARCH_HAS_FILTER_PGPROT
58 select ARCH_HAS_FORTIFY_SOURCE
59 select ARCH_HAS_GCOV_PROFILE_ALL
60 select ARCH_HAS_KCOV if X86_64
61 select ARCH_HAS_MEMBARRIER_SYNC_CORE
62 select ARCH_HAS_PMEM_API if X86_64
63 select ARCH_HAS_PTE_SPECIAL
64 select ARCH_HAS_REFCOUNT
65 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
66 select ARCH_HAS_UACCESS_MCSAFE if X86_64
67 select ARCH_HAS_SET_MEMORY
68 select ARCH_HAS_SG_CHAIN
69 select ARCH_HAS_STRICT_KERNEL_RWX
70 select ARCH_HAS_STRICT_MODULE_RWX
71 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
72 select ARCH_HAS_UBSAN_SANITIZE_ALL
73 select ARCH_HAS_ZONE_DEVICE if X86_64
74 select ARCH_HAVE_NMI_SAFE_CMPXCHG
75 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
76 select ARCH_MIGHT_HAVE_PC_PARPORT
77 select ARCH_MIGHT_HAVE_PC_SERIO
78 select ARCH_SUPPORTS_ATOMIC_RMW
79 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
80 select ARCH_USE_BUILTIN_BSWAP
81 select ARCH_USE_QUEUED_RWLOCKS
82 select ARCH_USE_QUEUED_SPINLOCKS
83 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
84 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
85 select ARCH_WANTS_THP_SWAP if X86_64
86 select BUILDTIME_EXTABLE_SORT
88 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
89 select CLOCKSOURCE_WATCHDOG
90 select DCACHE_WORD_ACCESS
92 select EDAC_ATOMIC_SCRUB
94 select GENERIC_CLOCKEVENTS
95 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
96 select GENERIC_CLOCKEVENTS_MIN_ADJUST
97 select GENERIC_CMOS_UPDATE
98 select GENERIC_CPU_AUTOPROBE
99 select GENERIC_CPU_VULNERABILITIES
100 select GENERIC_EARLY_IOREMAP
101 select GENERIC_FIND_FIRST_BIT
103 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
104 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
105 select GENERIC_IRQ_MIGRATION if SMP
106 select GENERIC_IRQ_PROBE
107 select GENERIC_IRQ_RESERVATION_MODE
108 select GENERIC_IRQ_SHOW
109 select GENERIC_PENDING_IRQ if SMP
110 select GENERIC_SMP_IDLE_THREAD
111 select GENERIC_STRNCPY_FROM_USER
112 select GENERIC_STRNLEN_USER
113 select GENERIC_TIME_VSYSCALL
114 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
115 select HAVE_ACPI_APEI if ACPI
116 select HAVE_ACPI_APEI_NMI if ACPI
117 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
118 select HAVE_ARCH_AUDITSYSCALL
119 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
120 select HAVE_ARCH_JUMP_LABEL
121 select HAVE_ARCH_KASAN if X86_64
122 select HAVE_ARCH_KGDB
123 select HAVE_ARCH_MMAP_RND_BITS if MMU
124 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
125 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
126 select HAVE_ARCH_SECCOMP_FILTER
127 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
128 select HAVE_ARCH_TRACEHOOK
129 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
130 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
131 select HAVE_ARCH_VMAP_STACK if X86_64
132 select HAVE_ARCH_WITHIN_STACK_FRAMES
133 select HAVE_CC_STACKPROTECTOR
134 select HAVE_CMPXCHG_DOUBLE
135 select HAVE_CMPXCHG_LOCAL
136 select HAVE_CONTEXT_TRACKING if X86_64
137 select HAVE_COPY_THREAD_TLS
138 select HAVE_C_RECORDMCOUNT
139 select HAVE_DEBUG_KMEMLEAK
140 select HAVE_DEBUG_STACKOVERFLOW
141 select HAVE_DMA_CONTIGUOUS
142 select HAVE_DYNAMIC_FTRACE
143 select HAVE_DYNAMIC_FTRACE_WITH_REGS
145 select HAVE_EFFICIENT_UNALIGNED_ACCESS
146 select HAVE_EXIT_THREAD
147 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
148 select HAVE_FTRACE_MCOUNT_RECORD
149 select HAVE_FUNCTION_GRAPH_TRACER
150 select HAVE_FUNCTION_TRACER
151 select HAVE_GCC_PLUGINS
152 select HAVE_HW_BREAKPOINT
154 select HAVE_IOREMAP_PROT
155 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
156 select HAVE_IRQ_TIME_ACCOUNTING
157 select HAVE_KERNEL_BZIP2
158 select HAVE_KERNEL_GZIP
159 select HAVE_KERNEL_LZ4
160 select HAVE_KERNEL_LZMA
161 select HAVE_KERNEL_LZO
162 select HAVE_KERNEL_XZ
164 select HAVE_KPROBES_ON_FTRACE
165 select HAVE_FUNCTION_ERROR_INJECTION
166 select HAVE_KRETPROBES
168 select HAVE_LIVEPATCH if X86_64
170 select HAVE_MEMBLOCK_NODE_MAP
171 select HAVE_MIXED_BREAKPOINTS_REGS
172 select HAVE_MOD_ARCH_SPECIFIC
175 select HAVE_OPTPROBES
176 select HAVE_PCSPKR_PLATFORM
177 select HAVE_PERF_EVENTS
178 select HAVE_PERF_EVENTS_NMI
179 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
180 select HAVE_PERF_REGS
181 select HAVE_PERF_USER_STACK_DUMP
182 select HAVE_RCU_TABLE_FREE
183 select HAVE_REGS_AND_STACK_ACCESS_API
184 select HAVE_RELIABLE_STACKTRACE if X86_64 && UNWINDER_FRAME_POINTER && STACK_VALIDATION
185 select HAVE_STACK_VALIDATION if X86_64
186 select HAVE_SYSCALL_TRACEPOINTS
187 select HAVE_UNSTABLE_SCHED_CLOCK
188 select HAVE_USER_RETURN_NOTIFIER
189 select IRQ_FORCED_THREADING
190 select NEED_SG_DMA_LENGTH
191 select PCI_LOCKLESS_CONFIG
194 select RTC_MC146818_LIB
197 select SYSCTL_EXCEPTION_TRACE
198 select THREAD_INFO_IN_TASK
199 select USER_STACKTRACE_SUPPORT
201 select X86_FEATURE_NAMES if PROC_FS
203 config INSTRUCTION_DECODER
205 depends on KPROBES || PERF_EVENTS || UPROBES
209 default "elf32-i386" if X86_32
210 default "elf64-x86-64" if X86_64
212 config ARCH_DEFCONFIG
214 default "arch/x86/configs/i386_defconfig" if X86_32
215 default "arch/x86/configs/x86_64_defconfig" if X86_64
217 config LOCKDEP_SUPPORT
220 config STACKTRACE_SUPPORT
226 config ARCH_MMAP_RND_BITS_MIN
230 config ARCH_MMAP_RND_BITS_MAX
234 config ARCH_MMAP_RND_COMPAT_BITS_MIN
237 config ARCH_MMAP_RND_COMPAT_BITS_MAX
243 config GENERIC_ISA_DMA
245 depends on ISA_DMA_API
250 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
252 config GENERIC_BUG_RELATIVE_POINTERS
255 config GENERIC_HWEIGHT
258 config ARCH_MAY_HAVE_PC_FDC
260 depends on ISA_DMA_API
262 config RWSEM_XCHGADD_ALGORITHM
265 config GENERIC_CALIBRATE_DELAY
268 config ARCH_HAS_CPU_RELAX
271 config ARCH_HAS_CACHE_LINE_SIZE
274 config ARCH_HAS_FILTER_PGPROT
277 config HAVE_SETUP_PER_CPU_AREA
280 config NEED_PER_CPU_EMBED_FIRST_CHUNK
283 config NEED_PER_CPU_PAGE_FIRST_CHUNK
286 config ARCH_HIBERNATION_POSSIBLE
289 config ARCH_SUSPEND_POSSIBLE
292 config ARCH_WANT_HUGE_PMD_SHARE
295 config ARCH_WANT_GENERAL_HUGETLB
304 config ARCH_SUPPORTS_OPTIMIZED_INLINING
307 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
310 config KASAN_SHADOW_OFFSET
313 default 0xdffffc0000000000
315 config HAVE_INTEL_TXT
317 depends on INTEL_IOMMU && ACPI
321 depends on X86_32 && SMP
325 depends on X86_64 && SMP
327 config X86_32_LAZY_GS
329 depends on X86_32 && CC_STACKPROTECTOR_NONE
331 config ARCH_SUPPORTS_UPROBES
334 config FIX_EARLYCON_MEM
337 config PGTABLE_LEVELS
339 default 5 if X86_5LEVEL
344 source "init/Kconfig"
345 source "kernel/Kconfig.freezer"
347 menu "Processor type and features"
350 bool "DMA memory allocation support" if EXPERT
353 DMA memory allocation support allows devices with less than 32-bit
354 addressing to allocate within the first 16MB of address space.
355 Disable if no such devices will be used.
360 bool "Symmetric multi-processing support"
362 This enables support for systems with more than one CPU. If you have
363 a system with only one CPU, say N. If you have a system with more
366 If you say N here, the kernel will run on uni- and multiprocessor
367 machines, but will use only one CPU of a multiprocessor machine. If
368 you say Y here, the kernel will run on many, but not all,
369 uniprocessor machines. On a uniprocessor machine, the kernel
370 will run faster if you say N here.
372 Note that if you say Y here and choose architecture "586" or
373 "Pentium" under "Processor family", the kernel will not work on 486
374 architectures. Similarly, multiprocessor kernels for the "PPro"
375 architecture may not work on all Pentium based boards.
377 People using multiprocessor machines who say Y here should also say
378 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
379 Management" code will be disabled if you say Y here.
381 See also <file:Documentation/x86/i386/IO-APIC.txt>,
382 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
383 <http://www.tldp.org/docs.html#howto>.
385 If you don't know what to do here, say N.
387 config X86_FEATURE_NAMES
388 bool "Processor feature human-readable names" if EMBEDDED
391 This option compiles in a table of x86 feature bits and corresponding
392 names. This is required to support /proc/cpuinfo and a few kernel
393 messages. You can disable this to save space, at the expense of
394 making those few kernel messages show numeric feature bits instead.
399 bool "Support x2apic"
400 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
402 This enables x2apic support on CPUs that have this feature.
404 This allows 32-bit apic IDs (so it can support very large systems),
405 and accesses the local apic via MSRs not via mmio.
407 If you don't know what to do here, say N.
410 bool "Enable MPS table" if ACPI || SFI
412 depends on X86_LOCAL_APIC
414 For old smp systems that do not have proper acpi support. Newer systems
415 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
419 depends on X86_GOLDFISH
422 bool "Avoid speculative indirect branches in kernel"
424 select STACK_VALIDATION if HAVE_STACK_VALIDATION
426 Compile kernel with the retpoline compiler options to guard against
427 kernel-to-user data leaks by avoiding speculative indirect
428 branches. Requires a compiler with -mindirect-branch=thunk-extern
429 support for full protection. The kernel may run slower.
431 Without compiler support, at least indirect branches in assembler
432 code are eliminated. Since this includes the syscall entry path,
433 it is not entirely pointless.
436 bool "Intel Resource Director Technology support"
438 depends on X86 && CPU_SUP_INTEL
441 Select to enable resource allocation and monitoring which are
442 sub-features of Intel Resource Director Technology(RDT). More
443 information about RDT can be found in the Intel x86
444 Architecture Software Developer Manual.
450 bool "Support for big SMP systems with more than 8 CPUs"
453 This option is needed for the systems that have more than 8 CPUs
455 config X86_EXTENDED_PLATFORM
456 bool "Support for extended (non-PC) x86 platforms"
459 If you disable this option then the kernel will only support
460 standard PC platforms. (which covers the vast majority of
463 If you enable this option then you'll be able to select support
464 for the following (non-PC) 32 bit x86 platforms:
465 Goldfish (Android emulator)
468 SGI 320/540 (Visual Workstation)
469 STA2X11-based (e.g. Northville)
470 Moorestown MID devices
472 If you have one of these systems, or if you want to build a
473 generic distribution kernel, say Y here - otherwise say N.
477 config X86_EXTENDED_PLATFORM
478 bool "Support for extended (non-PC) x86 platforms"
481 If you disable this option then the kernel will only support
482 standard PC platforms. (which covers the vast majority of
485 If you enable this option then you'll be able to select support
486 for the following (non-PC) 64 bit x86 platforms:
491 If you have one of these systems, or if you want to build a
492 generic distribution kernel, say Y here - otherwise say N.
494 # This is an alphabetically sorted list of 64 bit extended platforms
495 # Please maintain the alphabetic order if and when there are additions
497 bool "Numascale NumaChip"
499 depends on X86_EXTENDED_PLATFORM
502 depends on X86_X2APIC
503 depends on PCI_MMCONFIG
505 Adds support for Numascale NumaChip large-SMP systems. Needed to
506 enable more than ~168 cores.
507 If you don't have one of these, you should say N here.
511 select HYPERVISOR_GUEST
513 depends on X86_64 && PCI
514 depends on X86_EXTENDED_PLATFORM
517 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
518 supposed to run on these EM64T-based machines. Only choose this option
519 if you have one of these machines.
522 bool "SGI Ultraviolet"
524 depends on X86_EXTENDED_PLATFORM
527 depends on X86_X2APIC
530 This option is needed in order to support SGI Ultraviolet systems.
531 If you don't have one of these, you should say N here.
533 # Following is an alphabetically sorted list of 32 bit extended platforms
534 # Please maintain the alphabetic order if and when there are additions
537 bool "Goldfish (Virtual Platform)"
538 depends on X86_EXTENDED_PLATFORM
540 Enable support for the Goldfish virtual platform used primarily
541 for Android development. Unless you are building for the Android
542 Goldfish emulator say N here.
545 bool "CE4100 TV platform"
547 depends on PCI_GODIRECT
548 depends on X86_IO_APIC
550 depends on X86_EXTENDED_PLATFORM
551 select X86_REBOOTFIXUPS
553 select OF_EARLY_FLATTREE
555 Select for the Intel CE media processor (CE4100) SOC.
556 This option compiles in support for the CE4100 SOC for settop
557 boxes and media devices.
560 bool "Intel MID platform support"
561 depends on X86_EXTENDED_PLATFORM
562 depends on X86_PLATFORM_DEVICES
564 depends on X86_64 || (PCI_GOANY && X86_32)
565 depends on X86_IO_APIC
571 select MFD_INTEL_MSIC
573 Select to build a kernel capable of supporting Intel MID (Mobile
574 Internet Device) platform systems which do not have the PCI legacy
575 interfaces. If you are building for a PC class system say N here.
577 Intel MID platforms are based on an Intel processor and chipset which
578 consume less power than most of the x86 derivatives.
580 config X86_INTEL_QUARK
581 bool "Intel Quark platform support"
583 depends on X86_EXTENDED_PLATFORM
584 depends on X86_PLATFORM_DEVICES
588 depends on X86_IO_APIC
593 Select to include support for Quark X1000 SoC.
594 Say Y here if you have a Quark based system such as the Arduino
595 compatible Intel Galileo.
597 config X86_INTEL_LPSS
598 bool "Intel Low Power Subsystem Support"
599 depends on X86 && ACPI
604 Select to build support for Intel Low Power Subsystem such as
605 found on Intel Lynxpoint PCH. Selecting this option enables
606 things like clock tree (common clock framework) and pincontrol
607 which are needed by the LPSS peripheral drivers.
609 config X86_AMD_PLATFORM_DEVICE
610 bool "AMD ACPI2Platform devices support"
615 Select to interpret AMD specific ACPI device to platform device
616 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
617 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
618 implemented under PINCTRL subsystem.
621 tristate "Intel SoC IOSF Sideband support for SoC platforms"
624 This option enables sideband register access support for Intel SoC
625 platforms. On these platforms the IOSF sideband is used in lieu of
626 MSR's for some register accesses, mostly but not limited to thermal
627 and power. Drivers may query the availability of this device to
628 determine if they need the sideband in order to work on these
629 platforms. The sideband is available on the following SoC products.
630 This list is not meant to be exclusive.
635 You should say Y if you are running a kernel on one of these SoC's.
637 config IOSF_MBI_DEBUG
638 bool "Enable IOSF sideband access through debugfs"
639 depends on IOSF_MBI && DEBUG_FS
641 Select this option to expose the IOSF sideband access registers (MCR,
642 MDR, MCRX) through debugfs to write and read register information from
643 different units on the SoC. This is most useful for obtaining device
644 state information for debug and analysis. As this is a general access
645 mechanism, users of this option would have specific knowledge of the
646 device they want to access.
648 If you don't require the option or are in doubt, say N.
651 bool "RDC R-321x SoC"
653 depends on X86_EXTENDED_PLATFORM
655 select X86_REBOOTFIXUPS
657 This option is needed for RDC R-321x system-on-chip, also known
659 If you don't have one of these chips, you should say N here.
661 config X86_32_NON_STANDARD
662 bool "Support non-standard 32-bit SMP architectures"
663 depends on X86_32 && SMP
664 depends on X86_EXTENDED_PLATFORM
666 This option compiles in the bigsmp and STA2X11 default
667 subarchitectures. It is intended for a generic binary
668 kernel. If you select them all, kernel will probe it one by
669 one and will fallback to default.
671 # Alphabetically sorted list of Non standard 32 bit platforms
673 config X86_SUPPORTS_MEMORY_FAILURE
675 # MCE code calls memory_failure():
677 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
678 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
679 depends on X86_64 || !SPARSEMEM
680 select ARCH_SUPPORTS_MEMORY_FAILURE
683 bool "STA2X11 Companion Chip Support"
684 depends on X86_32_NON_STANDARD && PCI
685 select ARCH_HAS_PHYS_TO_DMA
686 select X86_DEV_DMA_OPS
693 This adds support for boards based on the STA2X11 IO-Hub,
694 a.k.a. "ConneXt". The chip is used in place of the standard
695 PC chipset, so all "standard" peripherals are missing. If this
696 option is selected the kernel will still be able to boot on
697 standard PC machines.
700 tristate "Eurobraille/Iris poweroff module"
703 The Iris machines from EuroBraille do not have APM or ACPI support
704 to shut themselves down properly. A special I/O sequence is
705 needed to do so, which is what this module does at
708 This is only for Iris machines from EuroBraille.
712 config SCHED_OMIT_FRAME_POINTER
714 prompt "Single-depth WCHAN output"
717 Calculate simpler /proc/<PID>/wchan values. If this option
718 is disabled then wchan values will recurse back to the
719 caller function. This provides more accurate wchan values,
720 at the expense of slightly more scheduling overhead.
722 If in doubt, say "Y".
724 menuconfig HYPERVISOR_GUEST
725 bool "Linux guest support"
727 Say Y here to enable options for running Linux under various hyper-
728 visors. This option enables basic hypervisor detection and platform
731 If you say N, all options in this submenu will be skipped and
732 disabled, and Linux guest support won't be built in.
737 bool "Enable paravirtualization code"
739 This changes the kernel so it can modify itself when it is run
740 under a hypervisor, potentially improving performance significantly
741 over full virtualization. However, when run without a hypervisor
742 the kernel is theoretically slower and slightly larger.
744 config PARAVIRT_DEBUG
745 bool "paravirt-ops debugging"
746 depends on PARAVIRT && DEBUG_KERNEL
748 Enable to debug paravirt_ops internals. Specifically, BUG if
749 a paravirt_op is missing when it is called.
751 config PARAVIRT_SPINLOCKS
752 bool "Paravirtualization layer for spinlocks"
753 depends on PARAVIRT && SMP
755 Paravirtualized spinlocks allow a pvops backend to replace the
756 spinlock implementation with something virtualization-friendly
757 (for example, block the virtual CPU rather than spinning).
759 It has a minimal impact on native kernels and gives a nice performance
760 benefit on paravirtualized KVM / Xen kernels.
762 If you are unsure how to answer this question, answer Y.
764 config QUEUED_LOCK_STAT
765 bool "Paravirt queued spinlock statistics"
766 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
768 Enable the collection of statistical data on the slowpath
769 behavior of paravirtualized queued spinlocks and report
772 source "arch/x86/xen/Kconfig"
775 bool "KVM Guest support (including kvmclock)"
777 select PARAVIRT_CLOCK
780 This option enables various optimizations for running under the KVM
781 hypervisor. It includes a paravirtualized clock, so that instead
782 of relying on a PIT (or probably other) emulation by the
783 underlying device model, the host provides the guest with
784 timing infrastructure such as time of day, and system time
787 bool "Enable debug information for KVM Guests in debugfs"
788 depends on KVM_GUEST && DEBUG_FS
791 This option enables collection of various statistics for KVM guest.
792 Statistics are displayed in debugfs filesystem. Enabling this option
793 may incur significant overhead.
795 config PARAVIRT_TIME_ACCOUNTING
796 bool "Paravirtual steal time accounting"
800 Select this option to enable fine granularity task steal time
801 accounting. Time spent executing other tasks in parallel with
802 the current vCPU is discounted from the vCPU power. To account for
803 that, there can be a small performance impact.
805 If in doubt, say N here.
807 config PARAVIRT_CLOCK
810 config JAILHOUSE_GUEST
811 bool "Jailhouse non-root cell support"
812 depends on X86_64 && PCI
815 This option allows to run Linux as guest in a Jailhouse non-root
816 cell. You can leave this option disabled if you only want to start
817 Jailhouse and run Linux afterwards in the root cell.
819 endif #HYPERVISOR_GUEST
824 source "arch/x86/Kconfig.cpu"
828 prompt "HPET Timer Support" if X86_32
830 Use the IA-PC HPET (High Precision Event Timer) to manage
831 time in preference to the PIT and RTC, if a HPET is
833 HPET is the next generation timer replacing legacy 8254s.
834 The HPET provides a stable time base on SMP
835 systems, unlike the TSC, but it is more expensive to access,
836 as it is off-chip. The interface used is documented
837 in the HPET spec, revision 1.
839 You can safely choose Y here. However, HPET will only be
840 activated if the platform and the BIOS support this feature.
841 Otherwise the 8254 will be used for timing services.
843 Choose N to continue using the legacy 8254 timer.
845 config HPET_EMULATE_RTC
847 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
850 def_bool y if X86_INTEL_MID
851 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
853 depends on X86_INTEL_MID && SFI
855 APB timer is the replacement for 8254, HPET on X86 MID platforms.
856 The APBT provides a stable time base on SMP
857 systems, unlike the TSC, but it is more expensive to access,
858 as it is off-chip. APB timers are always running regardless of CPU
859 C states, they are used as per CPU clockevent device when possible.
861 # Mark as expert because too many people got it wrong.
862 # The code disables itself when not needed.
865 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
866 bool "Enable DMI scanning" if EXPERT
868 Enabled scanning of DMI to identify machine quirks. Say Y
869 here unless you have verified that your setup is not
870 affected by entries in the DMI blacklist. Required by PNP
874 bool "Old AMD GART IOMMU support"
877 depends on X86_64 && PCI && AMD_NB
879 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
880 GART based hardware IOMMUs.
882 The GART supports full DMA access for devices with 32-bit access
883 limitations, on systems with more than 3 GB. This is usually needed
884 for USB, sound, many IDE/SATA chipsets and some other devices.
886 Newer systems typically have a modern AMD IOMMU, supported via
887 the CONFIG_AMD_IOMMU=y config option.
889 In normal configurations this driver is only active when needed:
890 there's more than 3 GB of memory and the system contains a
891 32-bit limited device.
896 bool "IBM Calgary IOMMU support"
899 depends on X86_64 && PCI
901 Support for hardware IOMMUs in IBM's xSeries x366 and x460
902 systems. Needed to run systems with more than 3GB of memory
903 properly with 32-bit PCI devices that do not support DAC
904 (Double Address Cycle). Calgary also supports bus level
905 isolation, where all DMAs pass through the IOMMU. This
906 prevents them from going anywhere except their intended
907 destination. This catches hard-to-find kernel bugs and
908 mis-behaving drivers and devices that do not use the DMA-API
909 properly to set up their DMA buffers. The IOMMU can be
910 turned off at boot time with the iommu=off parameter.
911 Normally the kernel will make the right choice by itself.
914 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
916 prompt "Should Calgary be enabled by default?"
917 depends on CALGARY_IOMMU
919 Should Calgary be enabled by default? if you choose 'y', Calgary
920 will be used (if it exists). If you choose 'n', Calgary will not be
921 used even if it exists. If you choose 'n' and would like to use
922 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
926 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
927 depends on X86_64 && SMP && DEBUG_KERNEL
928 select CPUMASK_OFFSTACK
930 Enable maximum number of CPUS and NUMA Nodes for this architecture.
934 # The maximum number of CPUs supported:
936 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
937 # and which can be configured interactively in the
938 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
940 # The ranges are different on 32-bit and 64-bit kernels, depending on
941 # hardware capabilities and scalability features of the kernel.
943 # ( If MAXSMP is enabled we just use the highest possible value and disable
944 # interactive configuration. )
947 config NR_CPUS_RANGE_BEGIN
949 default NR_CPUS_RANGE_END if MAXSMP
953 config NR_CPUS_RANGE_END
956 default 64 if SMP && X86_BIGSMP
957 default 8 if SMP && !X86_BIGSMP
960 config NR_CPUS_RANGE_END
963 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
964 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
967 config NR_CPUS_DEFAULT
970 default 32 if X86_BIGSMP
974 config NR_CPUS_DEFAULT
977 default 8192 if MAXSMP
982 int "Maximum number of CPUs" if SMP && !MAXSMP
983 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
984 default NR_CPUS_DEFAULT
986 This allows you to specify the maximum number of CPUs which this
987 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
988 supported value is 8192, otherwise the maximum value is 512. The
989 minimum value which makes sense is 2.
991 This is purely to save memory: each supported CPU adds about 8KB
995 bool "SMT (Hyperthreading) scheduler support"
998 SMT scheduler support improves the CPU scheduler's decision making
999 when dealing with Intel Pentium 4 chips with HyperThreading at a
1000 cost of slightly increased overhead in some places. If unsure say
1005 prompt "Multi-core scheduler support"
1008 Multi-core scheduler support improves the CPU scheduler's decision
1009 making when dealing with multi-core CPU chips at a cost of slightly
1010 increased overhead in some places. If unsure say N here.
1012 config SCHED_MC_PRIO
1013 bool "CPU core priorities scheduler support"
1014 depends on SCHED_MC && CPU_SUP_INTEL
1015 select X86_INTEL_PSTATE
1019 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1020 core ordering determined at manufacturing time, which allows
1021 certain cores to reach higher turbo frequencies (when running
1022 single threaded workloads) than others.
1024 Enabling this kernel feature teaches the scheduler about
1025 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1026 scheduler's CPU selection logic accordingly, so that higher
1027 overall system performance can be achieved.
1029 This feature will have no effect on CPUs without this feature.
1031 If unsure say Y here.
1033 source "kernel/Kconfig.preempt"
1037 depends on !SMP && X86_LOCAL_APIC
1040 bool "Local APIC support on uniprocessors" if !PCI_MSI
1042 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1044 A local APIC (Advanced Programmable Interrupt Controller) is an
1045 integrated interrupt controller in the CPU. If you have a single-CPU
1046 system which has a processor with a local APIC, you can say Y here to
1047 enable and use it. If you say Y here even though your machine doesn't
1048 have a local APIC, then the kernel will still run with no slowdown at
1049 all. The local APIC supports CPU-generated self-interrupts (timer,
1050 performance counters), and the NMI watchdog which detects hard
1053 config X86_UP_IOAPIC
1054 bool "IO-APIC support on uniprocessors"
1055 depends on X86_UP_APIC
1057 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1058 SMP-capable replacement for PC-style interrupt controllers. Most
1059 SMP systems and many recent uniprocessor systems have one.
1061 If you have a single-CPU system with an IO-APIC, you can say Y here
1062 to use it. If you say Y here even though your machine doesn't have
1063 an IO-APIC, then the kernel will still run with no slowdown at all.
1065 config X86_LOCAL_APIC
1067 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1068 select IRQ_DOMAIN_HIERARCHY
1069 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1073 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1075 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1076 bool "Reroute for broken boot IRQs"
1077 depends on X86_IO_APIC
1079 This option enables a workaround that fixes a source of
1080 spurious interrupts. This is recommended when threaded
1081 interrupt handling is used on systems where the generation of
1082 superfluous "boot interrupts" cannot be disabled.
1084 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1085 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1086 kernel does during interrupt handling). On chipsets where this
1087 boot IRQ generation cannot be disabled, this workaround keeps
1088 the original IRQ line masked so that only the equivalent "boot
1089 IRQ" is delivered to the CPUs. The workaround also tells the
1090 kernel to set up the IRQ handler on the boot IRQ line. In this
1091 way only one interrupt is delivered to the kernel. Otherwise
1092 the spurious second interrupt may cause the kernel to bring
1093 down (vital) interrupt lines.
1095 Only affects "broken" chipsets. Interrupt sharing may be
1096 increased on these systems.
1099 bool "Machine Check / overheating reporting"
1100 select GENERIC_ALLOCATOR
1103 Machine Check support allows the processor to notify the
1104 kernel if it detects a problem (e.g. overheating, data corruption).
1105 The action the kernel takes depends on the severity of the problem,
1106 ranging from warning messages to halting the machine.
1108 config X86_MCELOG_LEGACY
1109 bool "Support for deprecated /dev/mcelog character device"
1112 Enable support for /dev/mcelog which is needed by the old mcelog
1113 userspace logging daemon. Consider switching to the new generation
1116 config X86_MCE_INTEL
1118 prompt "Intel MCE features"
1119 depends on X86_MCE && X86_LOCAL_APIC
1121 Additional support for intel specific MCE features such as
1122 the thermal monitor.
1126 prompt "AMD MCE features"
1127 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1129 Additional support for AMD specific MCE features such as
1130 the DRAM Error Threshold.
1132 config X86_ANCIENT_MCE
1133 bool "Support for old Pentium 5 / WinChip machine checks"
1134 depends on X86_32 && X86_MCE
1136 Include support for machine check handling on old Pentium 5 or WinChip
1137 systems. These typically need to be enabled explicitly on the command
1140 config X86_MCE_THRESHOLD
1141 depends on X86_MCE_AMD || X86_MCE_INTEL
1144 config X86_MCE_INJECT
1145 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1146 tristate "Machine check injector support"
1148 Provide support for injecting machine checks for testing purposes.
1149 If you don't know what a machine check is and you don't do kernel
1150 QA it is safe to say n.
1152 config X86_THERMAL_VECTOR
1154 depends on X86_MCE_INTEL
1156 source "arch/x86/events/Kconfig"
1158 config X86_LEGACY_VM86
1159 bool "Legacy VM86 support"
1163 This option allows user programs to put the CPU into V8086
1164 mode, which is an 80286-era approximation of 16-bit real mode.
1166 Some very old versions of X and/or vbetool require this option
1167 for user mode setting. Similarly, DOSEMU will use it if
1168 available to accelerate real mode DOS programs. However, any
1169 recent version of DOSEMU, X, or vbetool should be fully
1170 functional even without kernel VM86 support, as they will all
1171 fall back to software emulation. Nevertheless, if you are using
1172 a 16-bit DOS program where 16-bit performance matters, vm86
1173 mode might be faster than emulation and you might want to
1176 Note that any app that works on a 64-bit kernel is unlikely to
1177 need this option, as 64-bit kernels don't, and can't, support
1178 V8086 mode. This option is also unrelated to 16-bit protected
1179 mode and is not needed to run most 16-bit programs under Wine.
1181 Enabling this option increases the complexity of the kernel
1182 and slows down exception handling a tiny bit.
1184 If unsure, say N here.
1188 default X86_LEGACY_VM86
1191 bool "Enable support for 16-bit segments" if EXPERT
1193 depends on MODIFY_LDT_SYSCALL
1195 This option is required by programs like Wine to run 16-bit
1196 protected mode legacy code on x86 processors. Disabling
1197 this option saves about 300 bytes on i386, or around 6K text
1198 plus 16K runtime memory on x86-64,
1202 depends on X86_16BIT && X86_32
1206 depends on X86_16BIT && X86_64
1208 config X86_VSYSCALL_EMULATION
1209 bool "Enable vsyscall emulation" if EXPERT
1213 This enables emulation of the legacy vsyscall page. Disabling
1214 it is roughly equivalent to booting with vsyscall=none, except
1215 that it will also disable the helpful warning if a program
1216 tries to use a vsyscall. With this option set to N, offending
1217 programs will just segfault, citing addresses of the form
1220 This option is required by many programs built before 2013, and
1221 care should be used even with newer programs if set to N.
1223 Disabling this option saves about 7K of kernel size and
1224 possibly 4K of additional runtime pagetable memory.
1227 tristate "Toshiba Laptop support"
1230 This adds a driver to safely access the System Management Mode of
1231 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1232 not work on models with a Phoenix BIOS. The System Management Mode
1233 is used to set the BIOS and power saving options on Toshiba portables.
1235 For information on utilities to make use of this driver see the
1236 Toshiba Linux utilities web site at:
1237 <http://www.buzzard.org.uk/toshiba/>.
1239 Say Y if you intend to run this kernel on a Toshiba portable.
1243 tristate "Dell i8k legacy laptop support"
1245 select SENSORS_DELL_SMM
1247 This option enables legacy /proc/i8k userspace interface in hwmon
1248 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1249 temperature and allows controlling fan speeds of Dell laptops via
1250 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1251 it reports also power and hotkey status. For fan speed control is
1252 needed userspace package i8kutils.
1254 Say Y if you intend to run this kernel on old Dell laptops or want to
1255 use userspace package i8kutils.
1258 config X86_REBOOTFIXUPS
1259 bool "Enable X86 board specific fixups for reboot"
1262 This enables chipset and/or board specific fixups to be done
1263 in order to get reboot to work correctly. This is only needed on
1264 some combinations of hardware and BIOS. The symptom, for which
1265 this config is intended, is when reboot ends with a stalled/hung
1268 Currently, the only fixup is for the Geode machines using
1269 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1271 Say Y if you want to enable the fixup. Currently, it's safe to
1272 enable this option even if you don't need it.
1276 bool "CPU microcode loading support"
1278 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1281 If you say Y here, you will be able to update the microcode on
1282 Intel and AMD processors. The Intel support is for the IA32 family,
1283 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1284 AMD support is for families 0x10 and later. You will obviously need
1285 the actual microcode binary data itself which is not shipped with
1288 The preferred method to load microcode from a detached initrd is described
1289 in Documentation/x86/microcode.txt. For that you need to enable
1290 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1291 initrd for microcode blobs.
1293 In addition, you can build the microcode into the kernel. For that you
1294 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1297 config MICROCODE_INTEL
1298 bool "Intel microcode loading support"
1299 depends on MICROCODE
1303 This options enables microcode patch loading support for Intel
1306 For the current Intel microcode data package go to
1307 <https://downloadcenter.intel.com> and search for
1308 'Linux Processor Microcode Data File'.
1310 config MICROCODE_AMD
1311 bool "AMD microcode loading support"
1312 depends on MICROCODE
1315 If you select this option, microcode patch loading support for AMD
1316 processors will be enabled.
1318 config MICROCODE_OLD_INTERFACE
1320 depends on MICROCODE
1323 tristate "/dev/cpu/*/msr - Model-specific register support"
1325 This device gives privileged processes access to the x86
1326 Model-Specific Registers (MSRs). It is a character device with
1327 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1328 MSR accesses are directed to a specific CPU on multi-processor
1332 tristate "/dev/cpu/*/cpuid - CPU information support"
1334 This device gives processes access to the x86 CPUID instruction to
1335 be executed on a specific processor. It is a character device
1336 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1340 prompt "High Memory Support"
1347 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1348 However, the address space of 32-bit x86 processors is only 4
1349 Gigabytes large. That means that, if you have a large amount of
1350 physical memory, not all of it can be "permanently mapped" by the
1351 kernel. The physical memory that's not permanently mapped is called
1354 If you are compiling a kernel which will never run on a machine with
1355 more than 1 Gigabyte total physical RAM, answer "off" here (default
1356 choice and suitable for most users). This will result in a "3GB/1GB"
1357 split: 3GB are mapped so that each process sees a 3GB virtual memory
1358 space and the remaining part of the 4GB virtual memory space is used
1359 by the kernel to permanently map as much physical memory as
1362 If the machine has between 1 and 4 Gigabytes physical RAM, then
1365 If more than 4 Gigabytes is used then answer "64GB" here. This
1366 selection turns Intel PAE (Physical Address Extension) mode on.
1367 PAE implements 3-level paging on IA32 processors. PAE is fully
1368 supported by Linux, PAE mode is implemented on all recent Intel
1369 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1370 then the kernel will not boot on CPUs that don't support PAE!
1372 The actual amount of total physical memory will either be
1373 auto detected or can be forced by using a kernel command line option
1374 such as "mem=256M". (Try "man bootparam" or see the documentation of
1375 your boot loader (lilo or loadlin) about how to pass options to the
1376 kernel at boot time.)
1378 If unsure, say "off".
1383 Select this if you have a 32-bit processor and between 1 and 4
1384 gigabytes of physical RAM.
1388 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1391 Select this if you have a 32-bit processor and more than 4
1392 gigabytes of physical RAM.
1397 prompt "Memory split" if EXPERT
1401 Select the desired split between kernel and user memory.
1403 If the address range available to the kernel is less than the
1404 physical memory installed, the remaining memory will be available
1405 as "high memory". Accessing high memory is a little more costly
1406 than low memory, as it needs to be mapped into the kernel first.
1407 Note that increasing the kernel address space limits the range
1408 available to user programs, making the address space there
1409 tighter. Selecting anything other than the default 3G/1G split
1410 will also likely make your kernel incompatible with binary-only
1413 If you are not absolutely sure what you are doing, leave this
1417 bool "3G/1G user/kernel split"
1418 config VMSPLIT_3G_OPT
1420 bool "3G/1G user/kernel split (for full 1G low memory)"
1422 bool "2G/2G user/kernel split"
1423 config VMSPLIT_2G_OPT
1425 bool "2G/2G user/kernel split (for full 2G low memory)"
1427 bool "1G/3G user/kernel split"
1432 default 0xB0000000 if VMSPLIT_3G_OPT
1433 default 0x80000000 if VMSPLIT_2G
1434 default 0x78000000 if VMSPLIT_2G_OPT
1435 default 0x40000000 if VMSPLIT_1G
1441 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1444 bool "PAE (Physical Address Extension) Support"
1445 depends on X86_32 && !HIGHMEM4G
1446 select PHYS_ADDR_T_64BIT
1449 PAE is required for NX support, and furthermore enables
1450 larger swapspace support for non-overcommit purposes. It
1451 has the cost of more pagetable lookup overhead, and also
1452 consumes more pagetable space per process.
1455 bool "Enable 5-level page tables support"
1456 select DYNAMIC_MEMORY_LAYOUT
1457 select SPARSEMEM_VMEMMAP
1460 5-level paging enables access to larger address space:
1461 upto 128 PiB of virtual address space and 4 PiB of
1462 physical address space.
1464 It will be supported by future Intel CPUs.
1466 A kernel with the option enabled can be booted on machines that
1467 support 4- or 5-level paging.
1469 See Documentation/x86/x86_64/5level-paging.txt for more
1474 config X86_DIRECT_GBPAGES
1476 depends on X86_64 && !DEBUG_PAGEALLOC
1478 Certain kernel features effectively disable kernel
1479 linear 1 GB mappings (even if the CPU otherwise
1480 supports them), so don't confuse the user by printing
1481 that we have them enabled.
1483 config ARCH_HAS_MEM_ENCRYPT
1486 config AMD_MEM_ENCRYPT
1487 bool "AMD Secure Memory Encryption (SME) support"
1488 depends on X86_64 && CPU_SUP_AMD
1490 Say yes to enable support for the encryption of system memory.
1491 This requires an AMD processor that supports Secure Memory
1494 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1495 bool "Activate AMD Secure Memory Encryption (SME) by default"
1497 depends on AMD_MEM_ENCRYPT
1499 Say yes to have system memory encrypted by default if running on
1500 an AMD processor that supports Secure Memory Encryption (SME).
1502 If set to Y, then the encryption of system memory can be
1503 deactivated with the mem_encrypt=off command line option.
1505 If set to N, then the encryption of system memory can be
1506 activated with the mem_encrypt=on command line option.
1508 config ARCH_USE_MEMREMAP_PROT
1510 depends on AMD_MEM_ENCRYPT
1512 # Common NUMA Features
1514 bool "Numa Memory Allocation and Scheduler Support"
1516 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1517 default y if X86_BIGSMP
1519 Enable NUMA (Non Uniform Memory Access) support.
1521 The kernel will try to allocate memory used by a CPU on the
1522 local memory controller of the CPU and add some more
1523 NUMA awareness to the kernel.
1525 For 64-bit this is recommended if the system is Intel Core i7
1526 (or later), AMD Opteron, or EM64T NUMA.
1528 For 32-bit this is only needed if you boot a 32-bit
1529 kernel on a 64-bit NUMA platform.
1531 Otherwise, you should say N.
1535 prompt "Old style AMD Opteron NUMA detection"
1536 depends on X86_64 && NUMA && PCI
1538 Enable AMD NUMA node topology detection. You should say Y here if
1539 you have a multi processor AMD system. This uses an old method to
1540 read the NUMA configuration directly from the builtin Northbridge
1541 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1542 which also takes priority if both are compiled in.
1544 config X86_64_ACPI_NUMA
1546 prompt "ACPI NUMA detection"
1547 depends on X86_64 && NUMA && ACPI && PCI
1550 Enable ACPI SRAT based node topology detection.
1552 # Some NUMA nodes have memory ranges that span
1553 # other nodes. Even though a pfn is valid and
1554 # between a node's start and end pfns, it may not
1555 # reside on that node. See memmap_init_zone()
1557 config NODES_SPAN_OTHER_NODES
1559 depends on X86_64_ACPI_NUMA
1562 bool "NUMA emulation"
1565 Enable NUMA emulation. A flat machine will be split
1566 into virtual nodes when booted with "numa=fake=N", where N is the
1567 number of nodes. This is only useful for debugging.
1570 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1572 default "10" if MAXSMP
1573 default "6" if X86_64
1575 depends on NEED_MULTIPLE_NODES
1577 Specify the maximum number of NUMA Nodes available on the target
1578 system. Increases memory reserved to accommodate various tables.
1580 config ARCH_HAVE_MEMORY_PRESENT
1582 depends on X86_32 && DISCONTIGMEM
1584 config ARCH_FLATMEM_ENABLE
1586 depends on X86_32 && !NUMA
1588 config ARCH_DISCONTIGMEM_ENABLE
1590 depends on NUMA && X86_32
1592 config ARCH_DISCONTIGMEM_DEFAULT
1594 depends on NUMA && X86_32
1596 config ARCH_SPARSEMEM_ENABLE
1598 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1599 select SPARSEMEM_STATIC if X86_32
1600 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1602 config ARCH_SPARSEMEM_DEFAULT
1606 config ARCH_SELECT_MEMORY_MODEL
1608 depends on ARCH_SPARSEMEM_ENABLE
1610 config ARCH_MEMORY_PROBE
1611 bool "Enable sysfs memory/probe interface"
1612 depends on X86_64 && MEMORY_HOTPLUG
1614 This option enables a sysfs memory/probe interface for testing.
1615 See Documentation/memory-hotplug.txt for more information.
1616 If you are unsure how to answer this question, answer N.
1618 config ARCH_PROC_KCORE_TEXT
1620 depends on X86_64 && PROC_KCORE
1622 config ILLEGAL_POINTER_VALUE
1625 default 0xdead000000000000 if X86_64
1629 config X86_PMEM_LEGACY_DEVICE
1632 config X86_PMEM_LEGACY
1633 tristate "Support non-standard NVDIMMs and ADR protected memory"
1634 depends on PHYS_ADDR_T_64BIT
1636 select X86_PMEM_LEGACY_DEVICE
1639 Treat memory marked using the non-standard e820 type of 12 as used
1640 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1641 The kernel will offer these regions to the 'pmem' driver so
1642 they can be used for persistent storage.
1647 bool "Allocate 3rd-level pagetables from highmem"
1650 The VM uses one page table entry for each page of physical memory.
1651 For systems with a lot of RAM, this can be wasteful of precious
1652 low memory. Setting this option will put user-space page table
1653 entries in high memory.
1655 config X86_CHECK_BIOS_CORRUPTION
1656 bool "Check for low memory corruption"
1658 Periodically check for memory corruption in low memory, which
1659 is suspected to be caused by BIOS. Even when enabled in the
1660 configuration, it is disabled at runtime. Enable it by
1661 setting "memory_corruption_check=1" on the kernel command
1662 line. By default it scans the low 64k of memory every 60
1663 seconds; see the memory_corruption_check_size and
1664 memory_corruption_check_period parameters in
1665 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1667 When enabled with the default parameters, this option has
1668 almost no overhead, as it reserves a relatively small amount
1669 of memory and scans it infrequently. It both detects corruption
1670 and prevents it from affecting the running system.
1672 It is, however, intended as a diagnostic tool; if repeatable
1673 BIOS-originated corruption always affects the same memory,
1674 you can use memmap= to prevent the kernel from using that
1677 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1678 bool "Set the default setting of memory_corruption_check"
1679 depends on X86_CHECK_BIOS_CORRUPTION
1682 Set whether the default state of memory_corruption_check is
1685 config X86_RESERVE_LOW
1686 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1690 Specify the amount of low memory to reserve for the BIOS.
1692 The first page contains BIOS data structures that the kernel
1693 must not use, so that page must always be reserved.
1695 By default we reserve the first 64K of physical RAM, as a
1696 number of BIOSes are known to corrupt that memory range
1697 during events such as suspend/resume or monitor cable
1698 insertion, so it must not be used by the kernel.
1700 You can set this to 4 if you are absolutely sure that you
1701 trust the BIOS to get all its memory reservations and usages
1702 right. If you know your BIOS have problems beyond the
1703 default 64K area, you can set this to 640 to avoid using the
1704 entire low memory range.
1706 If you have doubts about the BIOS (e.g. suspend/resume does
1707 not work or there's kernel crashes after certain hardware
1708 hotplug events) then you might want to enable
1709 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1710 typical corruption patterns.
1712 Leave this to the default value of 64 if you are unsure.
1714 config MATH_EMULATION
1716 depends on MODIFY_LDT_SYSCALL
1717 prompt "Math emulation" if X86_32
1719 Linux can emulate a math coprocessor (used for floating point
1720 operations) if you don't have one. 486DX and Pentium processors have
1721 a math coprocessor built in, 486SX and 386 do not, unless you added
1722 a 487DX or 387, respectively. (The messages during boot time can
1723 give you some hints here ["man dmesg"].) Everyone needs either a
1724 coprocessor or this emulation.
1726 If you don't have a math coprocessor, you need to say Y here; if you
1727 say Y here even though you have a coprocessor, the coprocessor will
1728 be used nevertheless. (This behavior can be changed with the kernel
1729 command line option "no387", which comes handy if your coprocessor
1730 is broken. Try "man bootparam" or see the documentation of your boot
1731 loader (lilo or loadlin) about how to pass options to the kernel at
1732 boot time.) This means that it is a good idea to say Y here if you
1733 intend to use this kernel on different machines.
1735 More information about the internals of the Linux math coprocessor
1736 emulation can be found in <file:arch/x86/math-emu/README>.
1738 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1739 kernel, it won't hurt.
1743 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1745 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1746 the Memory Type Range Registers (MTRRs) may be used to control
1747 processor access to memory ranges. This is most useful if you have
1748 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1749 allows bus write transfers to be combined into a larger transfer
1750 before bursting over the PCI/AGP bus. This can increase performance
1751 of image write operations 2.5 times or more. Saying Y here creates a
1752 /proc/mtrr file which may be used to manipulate your processor's
1753 MTRRs. Typically the X server should use this.
1755 This code has a reasonably generic interface so that similar
1756 control registers on other processors can be easily supported
1759 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1760 Registers (ARRs) which provide a similar functionality to MTRRs. For
1761 these, the ARRs are used to emulate the MTRRs.
1762 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1763 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1764 write-combining. All of these processors are supported by this code
1765 and it makes sense to say Y here if you have one of them.
1767 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1768 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1769 can lead to all sorts of problems, so it's good to say Y here.
1771 You can safely say Y even if your machine doesn't have MTRRs, you'll
1772 just add about 9 KB to your kernel.
1774 See <file:Documentation/x86/mtrr.txt> for more information.
1776 config MTRR_SANITIZER
1778 prompt "MTRR cleanup support"
1781 Convert MTRR layout from continuous to discrete, so X drivers can
1782 add writeback entries.
1784 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1785 The largest mtrr entry size for a continuous block can be set with
1790 config MTRR_SANITIZER_ENABLE_DEFAULT
1791 int "MTRR cleanup enable value (0-1)"
1794 depends on MTRR_SANITIZER
1796 Enable mtrr cleanup default value
1798 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1799 int "MTRR cleanup spare reg num (0-7)"
1802 depends on MTRR_SANITIZER
1804 mtrr cleanup spare entries default, it can be changed via
1805 mtrr_spare_reg_nr=N on the kernel command line.
1809 prompt "x86 PAT support" if EXPERT
1812 Use PAT attributes to setup page level cache control.
1814 PATs are the modern equivalents of MTRRs and are much more
1815 flexible than MTRRs.
1817 Say N here if you see bootup problems (boot crash, boot hang,
1818 spontaneous reboots) or a non-working video driver.
1822 config ARCH_USES_PG_UNCACHED
1828 prompt "x86 architectural random number generator" if EXPERT
1830 Enable the x86 architectural RDRAND instruction
1831 (Intel Bull Mountain technology) to generate random numbers.
1832 If supported, this is a high bandwidth, cryptographically
1833 secure hardware random number generator.
1837 prompt "Supervisor Mode Access Prevention" if EXPERT
1839 Supervisor Mode Access Prevention (SMAP) is a security
1840 feature in newer Intel processors. There is a small
1841 performance cost if this enabled and turned on; there is
1842 also a small increase in the kernel size if this is enabled.
1846 config X86_INTEL_UMIP
1848 depends on CPU_SUP_INTEL
1849 prompt "Intel User Mode Instruction Prevention" if EXPERT
1851 The User Mode Instruction Prevention (UMIP) is a security
1852 feature in newer Intel processors. If enabled, a general
1853 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1854 or STR instructions are executed in user mode. These instructions
1855 unnecessarily expose information about the hardware state.
1857 The vast majority of applications do not use these instructions.
1858 For the very few that do, software emulation is provided in
1859 specific cases in protected and virtual-8086 modes. Emulated
1862 config X86_INTEL_MPX
1863 prompt "Intel MPX (Memory Protection Extensions)"
1865 # Note: only available in 64-bit mode due to VMA flags shortage
1866 depends on CPU_SUP_INTEL && X86_64
1867 select ARCH_USES_HIGH_VMA_FLAGS
1869 MPX provides hardware features that can be used in
1870 conjunction with compiler-instrumented code to check
1871 memory references. It is designed to detect buffer
1872 overflow or underflow bugs.
1874 This option enables running applications which are
1875 instrumented or otherwise use MPX. It does not use MPX
1876 itself inside the kernel or to protect the kernel
1877 against bad memory references.
1879 Enabling this option will make the kernel larger:
1880 ~8k of kernel text and 36 bytes of data on a 64-bit
1881 defconfig. It adds a long to the 'mm_struct' which
1882 will increase the kernel memory overhead of each
1883 process and adds some branches to paths used during
1884 exec() and munmap().
1886 For details, see Documentation/x86/intel_mpx.txt
1890 config X86_INTEL_MEMORY_PROTECTION_KEYS
1891 prompt "Intel Memory Protection Keys"
1893 # Note: only available in 64-bit mode
1894 depends on CPU_SUP_INTEL && X86_64
1895 select ARCH_USES_HIGH_VMA_FLAGS
1896 select ARCH_HAS_PKEYS
1898 Memory Protection Keys provides a mechanism for enforcing
1899 page-based protections, but without requiring modification of the
1900 page tables when an application changes protection domains.
1902 For details, see Documentation/x86/protection-keys.txt
1907 bool "EFI runtime service support"
1910 select EFI_RUNTIME_WRAPPERS
1912 This enables the kernel to use EFI runtime services that are
1913 available (such as the EFI variable services).
1915 This option is only useful on systems that have EFI firmware.
1916 In addition, you should use the latest ELILO loader available
1917 at <http://elilo.sourceforge.net> in order to take advantage
1918 of EFI runtime services. However, even with this option, the
1919 resultant kernel should continue to boot on existing non-EFI
1923 bool "EFI stub support"
1924 depends on EFI && !X86_USE_3DNOW
1927 This kernel feature allows a bzImage to be loaded directly
1928 by EFI firmware without the use of a bootloader.
1930 See Documentation/efi-stub.txt for more information.
1933 bool "EFI mixed-mode support"
1934 depends on EFI_STUB && X86_64
1936 Enabling this feature allows a 64-bit kernel to be booted
1937 on a 32-bit firmware, provided that your CPU supports 64-bit
1940 Note that it is not possible to boot a mixed-mode enabled
1941 kernel via the EFI boot stub - a bootloader that supports
1942 the EFI handover protocol must be used.
1948 prompt "Enable seccomp to safely compute untrusted bytecode"
1950 This kernel feature is useful for number crunching applications
1951 that may need to compute untrusted bytecode during their
1952 execution. By using pipes or other transports made available to
1953 the process as file descriptors supporting the read/write
1954 syscalls, it's possible to isolate those applications in
1955 their own address space using seccomp. Once seccomp is
1956 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1957 and the task is only allowed to execute a few safe syscalls
1958 defined by each seccomp mode.
1960 If unsure, say Y. Only embedded should say N here.
1962 source kernel/Kconfig.hz
1965 bool "kexec system call"
1968 kexec is a system call that implements the ability to shutdown your
1969 current kernel, and to start another kernel. It is like a reboot
1970 but it is independent of the system firmware. And like a reboot
1971 you can start any kernel with it, not just Linux.
1973 The name comes from the similarity to the exec system call.
1975 It is an ongoing process to be certain the hardware in a machine
1976 is properly shutdown, so do not be surprised if this code does not
1977 initially work for you. As of this writing the exact hardware
1978 interface is strongly in flux, so no good recommendation can be
1982 bool "kexec file based system call"
1987 depends on CRYPTO_SHA256=y
1989 This is new version of kexec system call. This system call is
1990 file based and takes file descriptors as system call argument
1991 for kernel and initramfs as opposed to list of segments as
1992 accepted by previous system call.
1994 config ARCH_HAS_KEXEC_PURGATORY
1997 config KEXEC_VERIFY_SIG
1998 bool "Verify kernel signature during kexec_file_load() syscall"
1999 depends on KEXEC_FILE
2001 This option makes kernel signature verification mandatory for
2002 the kexec_file_load() syscall.
2004 In addition to that option, you need to enable signature
2005 verification for the corresponding kernel image type being
2006 loaded in order for this to work.
2008 config KEXEC_BZIMAGE_VERIFY_SIG
2009 bool "Enable bzImage signature verification support"
2010 depends on KEXEC_VERIFY_SIG
2011 depends on SIGNED_PE_FILE_VERIFICATION
2012 select SYSTEM_TRUSTED_KEYRING
2014 Enable bzImage signature verification support.
2017 bool "kernel crash dumps"
2018 depends on X86_64 || (X86_32 && HIGHMEM)
2020 Generate crash dump after being started by kexec.
2021 This should be normally only set in special crash dump kernels
2022 which are loaded in the main kernel with kexec-tools into
2023 a specially reserved region and then later executed after
2024 a crash by kdump/kexec. The crash dump kernel must be compiled
2025 to a memory address not used by the main kernel or BIOS using
2026 PHYSICAL_START, or it must be built as a relocatable image
2027 (CONFIG_RELOCATABLE=y).
2028 For more details see Documentation/kdump/kdump.txt
2032 depends on KEXEC && HIBERNATION
2034 Jump between original kernel and kexeced kernel and invoke
2035 code in physical address mode via KEXEC
2037 config PHYSICAL_START
2038 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2041 This gives the physical address where the kernel is loaded.
2043 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2044 bzImage will decompress itself to above physical address and
2045 run from there. Otherwise, bzImage will run from the address where
2046 it has been loaded by the boot loader and will ignore above physical
2049 In normal kdump cases one does not have to set/change this option
2050 as now bzImage can be compiled as a completely relocatable image
2051 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2052 address. This option is mainly useful for the folks who don't want
2053 to use a bzImage for capturing the crash dump and want to use a
2054 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2055 to be specifically compiled to run from a specific memory area
2056 (normally a reserved region) and this option comes handy.
2058 So if you are using bzImage for capturing the crash dump,
2059 leave the value here unchanged to 0x1000000 and set
2060 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2061 for capturing the crash dump change this value to start of
2062 the reserved region. In other words, it can be set based on
2063 the "X" value as specified in the "crashkernel=YM@XM"
2064 command line boot parameter passed to the panic-ed
2065 kernel. Please take a look at Documentation/kdump/kdump.txt
2066 for more details about crash dumps.
2068 Usage of bzImage for capturing the crash dump is recommended as
2069 one does not have to build two kernels. Same kernel can be used
2070 as production kernel and capture kernel. Above option should have
2071 gone away after relocatable bzImage support is introduced. But it
2072 is present because there are users out there who continue to use
2073 vmlinux for dump capture. This option should go away down the
2076 Don't change this unless you know what you are doing.
2079 bool "Build a relocatable kernel"
2082 This builds a kernel image that retains relocation information
2083 so it can be loaded someplace besides the default 1MB.
2084 The relocations tend to make the kernel binary about 10% larger,
2085 but are discarded at runtime.
2087 One use is for the kexec on panic case where the recovery kernel
2088 must live at a different physical address than the primary
2091 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2092 it has been loaded at and the compile time physical address
2093 (CONFIG_PHYSICAL_START) is used as the minimum location.
2095 config RANDOMIZE_BASE
2096 bool "Randomize the address of the kernel image (KASLR)"
2097 depends on RELOCATABLE
2100 In support of Kernel Address Space Layout Randomization (KASLR),
2101 this randomizes the physical address at which the kernel image
2102 is decompressed and the virtual address where the kernel
2103 image is mapped, as a security feature that deters exploit
2104 attempts relying on knowledge of the location of kernel
2107 On 64-bit, the kernel physical and virtual addresses are
2108 randomized separately. The physical address will be anywhere
2109 between 16MB and the top of physical memory (up to 64TB). The
2110 virtual address will be randomized from 16MB up to 1GB (9 bits
2111 of entropy). Note that this also reduces the memory space
2112 available to kernel modules from 1.5GB to 1GB.
2114 On 32-bit, the kernel physical and virtual addresses are
2115 randomized together. They will be randomized from 16MB up to
2116 512MB (8 bits of entropy).
2118 Entropy is generated using the RDRAND instruction if it is
2119 supported. If RDTSC is supported, its value is mixed into
2120 the entropy pool as well. If neither RDRAND nor RDTSC are
2121 supported, then entropy is read from the i8254 timer. The
2122 usable entropy is limited by the kernel being built using
2123 2GB addressing, and that PHYSICAL_ALIGN must be at a
2124 minimum of 2MB. As a result, only 10 bits of entropy are
2125 theoretically possible, but the implementations are further
2126 limited due to memory layouts.
2130 # Relocation on x86 needs some additional build support
2131 config X86_NEED_RELOCS
2133 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2135 config PHYSICAL_ALIGN
2136 hex "Alignment value to which kernel should be aligned"
2138 range 0x2000 0x1000000 if X86_32
2139 range 0x200000 0x1000000 if X86_64
2141 This value puts the alignment restrictions on physical address
2142 where kernel is loaded and run from. Kernel is compiled for an
2143 address which meets above alignment restriction.
2145 If bootloader loads the kernel at a non-aligned address and
2146 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2147 address aligned to above value and run from there.
2149 If bootloader loads the kernel at a non-aligned address and
2150 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2151 load address and decompress itself to the address it has been
2152 compiled for and run from there. The address for which kernel is
2153 compiled already meets above alignment restrictions. Hence the
2154 end result is that kernel runs from a physical address meeting
2155 above alignment restrictions.
2157 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2158 this value must be a multiple of 0x200000.
2160 Don't change this unless you know what you are doing.
2162 config DYNAMIC_MEMORY_LAYOUT
2165 This option makes base addresses of vmalloc and vmemmap as well as
2166 __PAGE_OFFSET movable during boot.
2168 config RANDOMIZE_MEMORY
2169 bool "Randomize the kernel memory sections"
2171 depends on RANDOMIZE_BASE
2172 select DYNAMIC_MEMORY_LAYOUT
2173 default RANDOMIZE_BASE
2175 Randomizes the base virtual address of kernel memory sections
2176 (physical memory mapping, vmalloc & vmemmap). This security feature
2177 makes exploits relying on predictable memory locations less reliable.
2179 The order of allocations remains unchanged. Entropy is generated in
2180 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2181 configuration have in average 30,000 different possible virtual
2182 addresses for each memory section.
2186 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2187 hex "Physical memory mapping padding" if EXPERT
2188 depends on RANDOMIZE_MEMORY
2189 default "0xa" if MEMORY_HOTPLUG
2191 range 0x1 0x40 if MEMORY_HOTPLUG
2194 Define the padding in terabytes added to the existing physical
2195 memory size during kernel memory randomization. It is useful
2196 for memory hotplug support but reduces the entropy available for
2197 address randomization.
2199 If unsure, leave at the default value.
2202 bool "Support for hot-pluggable CPUs"
2205 Say Y here to allow turning CPUs off and on. CPUs can be
2206 controlled through /sys/devices/system/cpu.
2207 ( Note: power management support will enable this option
2208 automatically on SMP systems. )
2209 Say N if you want to disable CPU hotplug.
2211 config BOOTPARAM_HOTPLUG_CPU0
2212 bool "Set default setting of cpu0_hotpluggable"
2214 depends on HOTPLUG_CPU
2216 Set whether default state of cpu0_hotpluggable is on or off.
2218 Say Y here to enable CPU0 hotplug by default. If this switch
2219 is turned on, there is no need to give cpu0_hotplug kernel
2220 parameter and the CPU0 hotplug feature is enabled by default.
2222 Please note: there are two known CPU0 dependencies if you want
2223 to enable the CPU0 hotplug feature either by this switch or by
2224 cpu0_hotplug kernel parameter.
2226 First, resume from hibernate or suspend always starts from CPU0.
2227 So hibernate and suspend are prevented if CPU0 is offline.
2229 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2230 offline if any interrupt can not migrate out of CPU0. There may
2231 be other CPU0 dependencies.
2233 Please make sure the dependencies are under your control before
2234 you enable this feature.
2236 Say N if you don't want to enable CPU0 hotplug feature by default.
2237 You still can enable the CPU0 hotplug feature at boot by kernel
2238 parameter cpu0_hotplug.
2240 config DEBUG_HOTPLUG_CPU0
2242 prompt "Debug CPU0 hotplug"
2243 depends on HOTPLUG_CPU
2245 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2246 soon as possible and boots up userspace with CPU0 offlined. User
2247 can online CPU0 back after boot time.
2249 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2250 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2251 compilation or giving cpu0_hotplug kernel parameter at boot.
2257 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2258 depends on COMPAT_32
2260 Certain buggy versions of glibc will crash if they are
2261 presented with a 32-bit vDSO that is not mapped at the address
2262 indicated in its segment table.
2264 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2265 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2266 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2267 the only released version with the bug, but OpenSUSE 9
2268 contains a buggy "glibc 2.3.2".
2270 The symptom of the bug is that everything crashes on startup, saying:
2271 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2273 Saying Y here changes the default value of the vdso32 boot
2274 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2275 This works around the glibc bug but hurts performance.
2277 If unsure, say N: if you are compiling your own kernel, you
2278 are unlikely to be using a buggy version of glibc.
2281 prompt "vsyscall table for legacy applications"
2283 default LEGACY_VSYSCALL_EMULATE
2285 Legacy user code that does not know how to find the vDSO expects
2286 to be able to issue three syscalls by calling fixed addresses in
2287 kernel space. Since this location is not randomized with ASLR,
2288 it can be used to assist security vulnerability exploitation.
2290 This setting can be changed at boot time via the kernel command
2291 line parameter vsyscall=[emulate|none].
2293 On a system with recent enough glibc (2.14 or newer) and no
2294 static binaries, you can say None without a performance penalty
2295 to improve security.
2297 If unsure, select "Emulate".
2299 config LEGACY_VSYSCALL_EMULATE
2302 The kernel traps and emulates calls into the fixed
2303 vsyscall address mapping. This makes the mapping
2304 non-executable, but it still contains known contents,
2305 which could be used in certain rare security vulnerability
2306 exploits. This configuration is recommended when userspace
2307 still uses the vsyscall area.
2309 config LEGACY_VSYSCALL_NONE
2312 There will be no vsyscall mapping at all. This will
2313 eliminate any risk of ASLR bypass due to the vsyscall
2314 fixed address mapping. Attempts to use the vsyscalls
2315 will be reported to dmesg, so that either old or
2316 malicious userspace programs can be identified.
2321 bool "Built-in kernel command line"
2323 Allow for specifying boot arguments to the kernel at
2324 build time. On some systems (e.g. embedded ones), it is
2325 necessary or convenient to provide some or all of the
2326 kernel boot arguments with the kernel itself (that is,
2327 to not rely on the boot loader to provide them.)
2329 To compile command line arguments into the kernel,
2330 set this option to 'Y', then fill in the
2331 boot arguments in CONFIG_CMDLINE.
2333 Systems with fully functional boot loaders (i.e. non-embedded)
2334 should leave this option set to 'N'.
2337 string "Built-in kernel command string"
2338 depends on CMDLINE_BOOL
2341 Enter arguments here that should be compiled into the kernel
2342 image and used at boot time. If the boot loader provides a
2343 command line at boot time, it is appended to this string to
2344 form the full kernel command line, when the system boots.
2346 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2347 change this behavior.
2349 In most cases, the command line (whether built-in or provided
2350 by the boot loader) should specify the device for the root
2353 config CMDLINE_OVERRIDE
2354 bool "Built-in command line overrides boot loader arguments"
2355 depends on CMDLINE_BOOL
2357 Set this option to 'Y' to have the kernel ignore the boot loader
2358 command line, and use ONLY the built-in command line.
2360 This is used to work around broken boot loaders. This should
2361 be set to 'N' under normal conditions.
2363 config MODIFY_LDT_SYSCALL
2364 bool "Enable the LDT (local descriptor table)" if EXPERT
2367 Linux can allow user programs to install a per-process x86
2368 Local Descriptor Table (LDT) using the modify_ldt(2) system
2369 call. This is required to run 16-bit or segmented code such as
2370 DOSEMU or some Wine programs. It is also used by some very old
2371 threading libraries.
2373 Enabling this feature adds a small amount of overhead to
2374 context switches and increases the low-level kernel attack
2375 surface. Disabling it removes the modify_ldt(2) system call.
2377 Saying 'N' here may make sense for embedded or server kernels.
2379 source "kernel/livepatch/Kconfig"
2383 config ARCH_HAS_ADD_PAGES
2385 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2387 config ARCH_ENABLE_MEMORY_HOTPLUG
2389 depends on X86_64 || (X86_32 && HIGHMEM)
2391 config ARCH_ENABLE_MEMORY_HOTREMOVE
2393 depends on MEMORY_HOTPLUG
2395 config USE_PERCPU_NUMA_NODE_ID
2399 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2401 depends on X86_64 || X86_PAE
2403 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2405 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2407 config ARCH_ENABLE_THP_MIGRATION
2409 depends on X86_64 && TRANSPARENT_HUGEPAGE
2411 menu "Power management and ACPI options"
2413 config ARCH_HIBERNATION_HEADER
2415 depends on X86_64 && HIBERNATION
2417 source "kernel/power/Kconfig"
2419 source "drivers/acpi/Kconfig"
2421 source "drivers/sfi/Kconfig"
2428 tristate "APM (Advanced Power Management) BIOS support"
2429 depends on X86_32 && PM_SLEEP
2431 APM is a BIOS specification for saving power using several different
2432 techniques. This is mostly useful for battery powered laptops with
2433 APM compliant BIOSes. If you say Y here, the system time will be
2434 reset after a RESUME operation, the /proc/apm device will provide
2435 battery status information, and user-space programs will receive
2436 notification of APM "events" (e.g. battery status change).
2438 If you select "Y" here, you can disable actual use of the APM
2439 BIOS by passing the "apm=off" option to the kernel at boot time.
2441 Note that the APM support is almost completely disabled for
2442 machines with more than one CPU.
2444 In order to use APM, you will need supporting software. For location
2445 and more information, read <file:Documentation/power/apm-acpi.txt>
2446 and the Battery Powered Linux mini-HOWTO, available from
2447 <http://www.tldp.org/docs.html#howto>.
2449 This driver does not spin down disk drives (see the hdparm(8)
2450 manpage ("man 8 hdparm") for that), and it doesn't turn off
2451 VESA-compliant "green" monitors.
2453 This driver does not support the TI 4000M TravelMate and the ACER
2454 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2455 desktop machines also don't have compliant BIOSes, and this driver
2456 may cause those machines to panic during the boot phase.
2458 Generally, if you don't have a battery in your machine, there isn't
2459 much point in using this driver and you should say N. If you get
2460 random kernel OOPSes or reboots that don't seem to be related to
2461 anything, try disabling/enabling this option (or disabling/enabling
2464 Some other things you should try when experiencing seemingly random,
2467 1) make sure that you have enough swap space and that it is
2469 2) pass the "no-hlt" option to the kernel
2470 3) switch on floating point emulation in the kernel and pass
2471 the "no387" option to the kernel
2472 4) pass the "floppy=nodma" option to the kernel
2473 5) pass the "mem=4M" option to the kernel (thereby disabling
2474 all but the first 4 MB of RAM)
2475 6) make sure that the CPU is not over clocked.
2476 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2477 8) disable the cache from your BIOS settings
2478 9) install a fan for the video card or exchange video RAM
2479 10) install a better fan for the CPU
2480 11) exchange RAM chips
2481 12) exchange the motherboard.
2483 To compile this driver as a module, choose M here: the
2484 module will be called apm.
2488 config APM_IGNORE_USER_SUSPEND
2489 bool "Ignore USER SUSPEND"
2491 This option will ignore USER SUSPEND requests. On machines with a
2492 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2493 series notebooks, it is necessary to say Y because of a BIOS bug.
2495 config APM_DO_ENABLE
2496 bool "Enable PM at boot time"
2498 Enable APM features at boot time. From page 36 of the APM BIOS
2499 specification: "When disabled, the APM BIOS does not automatically
2500 power manage devices, enter the Standby State, enter the Suspend
2501 State, or take power saving steps in response to CPU Idle calls."
2502 This driver will make CPU Idle calls when Linux is idle (unless this
2503 feature is turned off -- see "Do CPU IDLE calls", below). This
2504 should always save battery power, but more complicated APM features
2505 will be dependent on your BIOS implementation. You may need to turn
2506 this option off if your computer hangs at boot time when using APM
2507 support, or if it beeps continuously instead of suspending. Turn
2508 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2509 T400CDT. This is off by default since most machines do fine without
2514 bool "Make CPU Idle calls when idle"
2516 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2517 On some machines, this can activate improved power savings, such as
2518 a slowed CPU clock rate, when the machine is idle. These idle calls
2519 are made after the idle loop has run for some length of time (e.g.,
2520 333 mS). On some machines, this will cause a hang at boot time or
2521 whenever the CPU becomes idle. (On machines with more than one CPU,
2522 this option does nothing.)
2524 config APM_DISPLAY_BLANK
2525 bool "Enable console blanking using APM"
2527 Enable console blanking using the APM. Some laptops can use this to
2528 turn off the LCD backlight when the screen blanker of the Linux
2529 virtual console blanks the screen. Note that this is only used by
2530 the virtual console screen blanker, and won't turn off the backlight
2531 when using the X Window system. This also doesn't have anything to
2532 do with your VESA-compliant power-saving monitor. Further, this
2533 option doesn't work for all laptops -- it might not turn off your
2534 backlight at all, or it might print a lot of errors to the console,
2535 especially if you are using gpm.
2537 config APM_ALLOW_INTS
2538 bool "Allow interrupts during APM BIOS calls"
2540 Normally we disable external interrupts while we are making calls to
2541 the APM BIOS as a measure to lessen the effects of a badly behaving
2542 BIOS implementation. The BIOS should reenable interrupts if it
2543 needs to. Unfortunately, some BIOSes do not -- especially those in
2544 many of the newer IBM Thinkpads. If you experience hangs when you
2545 suspend, try setting this to Y. Otherwise, say N.
2549 source "drivers/cpufreq/Kconfig"
2551 source "drivers/cpuidle/Kconfig"
2553 source "drivers/idle/Kconfig"
2558 menu "Bus options (PCI etc.)"
2564 Find out whether you have a PCI motherboard. PCI is the name of a
2565 bus system, i.e. the way the CPU talks to the other stuff inside
2566 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2567 VESA. If you have PCI, say Y, otherwise N.
2570 prompt "PCI access mode"
2571 depends on X86_32 && PCI
2574 On PCI systems, the BIOS can be used to detect the PCI devices and
2575 determine their configuration. However, some old PCI motherboards
2576 have BIOS bugs and may crash if this is done. Also, some embedded
2577 PCI-based systems don't have any BIOS at all. Linux can also try to
2578 detect the PCI hardware directly without using the BIOS.
2580 With this option, you can specify how Linux should detect the
2581 PCI devices. If you choose "BIOS", the BIOS will be used,
2582 if you choose "Direct", the BIOS won't be used, and if you
2583 choose "MMConfig", then PCI Express MMCONFIG will be used.
2584 If you choose "Any", the kernel will try MMCONFIG, then the
2585 direct access method and falls back to the BIOS if that doesn't
2586 work. If unsure, go with the default, which is "Any".
2591 config PCI_GOMMCONFIG
2608 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2610 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2613 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2616 bool "Support mmconfig PCI config space access" if X86_64
2618 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2619 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2623 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2627 depends on PCI && XEN
2634 config MMCONF_FAM10H
2636 depends on X86_64 && PCI_MMCONFIG && ACPI
2638 config PCI_CNB20LE_QUIRK
2639 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2642 Read the PCI windows out of the CNB20LE host bridge. This allows
2643 PCI hotplug to work on systems with the CNB20LE chipset which do
2646 There's no public spec for this chipset, and this functionality
2647 is known to be incomplete.
2649 You should say N unless you know you need this.
2651 source "drivers/pci/Kconfig"
2654 bool "ISA bus support on modern systems" if EXPERT
2656 Expose ISA bus device drivers and options available for selection and
2657 configuration. Enable this option if your target machine has an ISA
2658 bus. ISA is an older system, displaced by PCI and newer bus
2659 architectures -- if your target machine is modern, it probably does
2660 not have an ISA bus.
2664 # x86_64 have no ISA slots, but can have ISA-style DMA.
2666 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2669 Enables ISA-style DMA support for devices requiring such controllers.
2677 Find out whether you have ISA slots on your motherboard. ISA is the
2678 name of a bus system, i.e. the way the CPU talks to the other stuff
2679 inside your box. Other bus systems are PCI, EISA, MicroChannel
2680 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2681 newer boards don't support it. If you have ISA, say Y, otherwise N.
2687 The Extended Industry Standard Architecture (EISA) bus was
2688 developed as an open alternative to the IBM MicroChannel bus.
2690 The EISA bus provided some of the features of the IBM MicroChannel
2691 bus while maintaining backward compatibility with cards made for
2692 the older ISA bus. The EISA bus saw limited use between 1988 and
2693 1995 when it was made obsolete by the PCI bus.
2695 Say Y here if you are building a kernel for an EISA-based machine.
2699 source "drivers/eisa/Kconfig"
2702 tristate "NatSemi SCx200 support"
2704 This provides basic support for National Semiconductor's
2705 (now AMD's) Geode processors. The driver probes for the
2706 PCI-IDs of several on-chip devices, so its a good dependency
2707 for other scx200_* drivers.
2709 If compiled as a module, the driver is named scx200.
2711 config SCx200HR_TIMER
2712 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2716 This driver provides a clocksource built upon the on-chip
2717 27MHz high-resolution timer. Its also a workaround for
2718 NSC Geode SC-1100's buggy TSC, which loses time when the
2719 processor goes idle (as is done by the scheduler). The
2720 other workaround is idle=poll boot option.
2723 bool "One Laptop Per Child support"
2730 Add support for detecting the unique features of the OLPC
2734 bool "OLPC XO-1 Power Management"
2735 depends on OLPC && MFD_CS5535 && PM_SLEEP
2738 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2741 bool "OLPC XO-1 Real Time Clock"
2742 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2744 Add support for the XO-1 real time clock, which can be used as a
2745 programmable wakeup source.
2748 bool "OLPC XO-1 SCI extras"
2749 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2753 Add support for SCI-based features of the OLPC XO-1 laptop:
2754 - EC-driven system wakeups
2758 - AC adapter status updates
2759 - Battery status updates
2761 config OLPC_XO15_SCI
2762 bool "OLPC XO-1.5 SCI extras"
2763 depends on OLPC && ACPI
2766 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2767 - EC-driven system wakeups
2768 - AC adapter status updates
2769 - Battery status updates
2772 bool "PCEngines ALIX System Support (LED setup)"
2775 This option enables system support for the PCEngines ALIX.
2776 At present this just sets up LEDs for GPIO control on
2777 ALIX2/3/6 boards. However, other system specific setup should
2780 Note: You must still enable the drivers for GPIO and LED support
2781 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2783 Note: You have to set alix.force=1 for boards with Award BIOS.
2786 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2789 This option enables system support for the Soekris Engineering net5501.
2792 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2796 This option enables system support for the Traverse Technologies GEOS.
2799 bool "Technologic Systems TS-5500 platform support"
2801 select CHECK_SIGNATURE
2805 This option enables system support for the Technologic Systems TS-5500.
2811 depends on CPU_SUP_AMD && PCI
2813 source "drivers/pcmcia/Kconfig"
2816 tristate "RapidIO support"
2820 If enabled this option will include drivers and the core
2821 infrastructure code to support RapidIO interconnect devices.
2823 source "drivers/rapidio/Kconfig"
2826 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2828 Firmwares often provide initial graphics framebuffers so the BIOS,
2829 bootloader or kernel can show basic video-output during boot for
2830 user-guidance and debugging. Historically, x86 used the VESA BIOS
2831 Extensions and EFI-framebuffers for this, which are mostly limited
2833 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2834 framebuffers so the new generic system-framebuffer drivers can be
2835 used on x86. If the framebuffer is not compatible with the generic
2836 modes, it is adverticed as fallback platform framebuffer so legacy
2837 drivers like efifb, vesafb and uvesafb can pick it up.
2838 If this option is not selected, all system framebuffers are always
2839 marked as fallback platform framebuffers as usual.
2841 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2842 not be able to pick up generic system framebuffers if this option
2843 is selected. You are highly encouraged to enable simplefb as
2844 replacement if you select this option. simplefb can correctly deal
2845 with generic system framebuffers. But you should still keep vesafb
2846 and others enabled as fallback if a system framebuffer is
2847 incompatible with simplefb.
2854 menu "Executable file formats / Emulations"
2856 source "fs/Kconfig.binfmt"
2858 config IA32_EMULATION
2859 bool "IA32 Emulation"
2861 select ARCH_WANT_OLD_COMPAT_IPC
2863 select COMPAT_BINFMT_ELF
2864 select COMPAT_OLD_SIGACTION
2866 Include code to run legacy 32-bit programs under a
2867 64-bit kernel. You should likely turn this on, unless you're
2868 100% sure that you don't have any 32-bit programs left.
2871 tristate "IA32 a.out support"
2872 depends on IA32_EMULATION
2874 Support old a.out binaries in the 32bit emulation.
2877 bool "x32 ABI for 64-bit mode"
2880 Include code to run binaries for the x32 native 32-bit ABI
2881 for 64-bit processors. An x32 process gets access to the
2882 full 64-bit register file and wide data path while leaving
2883 pointers at 32 bits for smaller memory footprint.
2885 You will need a recent binutils (2.22 or later) with
2886 elf32_x86_64 support enabled to compile a kernel with this
2891 depends on IA32_EMULATION || X86_32
2893 select OLD_SIGSUSPEND3
2897 depends on IA32_EMULATION || X86_X32
2900 config COMPAT_FOR_U64_ALIGNMENT
2903 config SYSVIPC_COMPAT
2911 config HAVE_ATOMIC_IOMAP
2915 config X86_DEV_DMA_OPS
2917 depends on X86_64 || STA2X11
2919 config X86_DMA_REMAP
2923 config HAVE_GENERIC_GUP
2926 source "net/Kconfig"
2928 source "drivers/Kconfig"
2930 source "drivers/firmware/Kconfig"
2934 source "arch/x86/Kconfig.debug"
2936 source "security/Kconfig"
2938 source "crypto/Kconfig"
2940 source "arch/x86/kvm/Kconfig"
2942 source "lib/Kconfig"