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_REFCOUNT
64 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
65 select ARCH_HAS_UACCESS_MCSAFE if X86_64
66 select ARCH_HAS_SET_MEMORY
67 select ARCH_HAS_SG_CHAIN
68 select ARCH_HAS_STRICT_KERNEL_RWX
69 select ARCH_HAS_STRICT_MODULE_RWX
70 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
71 select ARCH_HAS_UBSAN_SANITIZE_ALL
72 select ARCH_HAS_ZONE_DEVICE if X86_64
73 select ARCH_HAVE_NMI_SAFE_CMPXCHG
74 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
75 select ARCH_MIGHT_HAVE_PC_PARPORT
76 select ARCH_MIGHT_HAVE_PC_SERIO
77 select ARCH_SUPPORTS_ATOMIC_RMW
78 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
79 select ARCH_USE_BUILTIN_BSWAP
80 select ARCH_USE_QUEUED_RWLOCKS
81 select ARCH_USE_QUEUED_SPINLOCKS
82 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
83 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
84 select ARCH_WANTS_THP_SWAP if X86_64
85 select BUILDTIME_EXTABLE_SORT
87 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
88 select CLOCKSOURCE_WATCHDOG
89 select DCACHE_WORD_ACCESS
91 select EDAC_ATOMIC_SCRUB
93 select GENERIC_CLOCKEVENTS
94 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
95 select GENERIC_CLOCKEVENTS_MIN_ADJUST
96 select GENERIC_CMOS_UPDATE
97 select GENERIC_CPU_AUTOPROBE
98 select GENERIC_CPU_VULNERABILITIES
99 select GENERIC_EARLY_IOREMAP
100 select GENERIC_FIND_FIRST_BIT
102 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
103 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
104 select GENERIC_IRQ_MIGRATION if SMP
105 select GENERIC_IRQ_PROBE
106 select GENERIC_IRQ_RESERVATION_MODE
107 select GENERIC_IRQ_SHOW
108 select GENERIC_PENDING_IRQ if SMP
109 select GENERIC_SMP_IDLE_THREAD
110 select GENERIC_STRNCPY_FROM_USER
111 select GENERIC_STRNLEN_USER
112 select GENERIC_TIME_VSYSCALL
113 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
114 select HAVE_ACPI_APEI if ACPI
115 select HAVE_ACPI_APEI_NMI if ACPI
116 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
117 select HAVE_ARCH_AUDITSYSCALL
118 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
119 select HAVE_ARCH_JUMP_LABEL
120 select HAVE_ARCH_KASAN if X86_64
121 select HAVE_ARCH_KGDB
122 select HAVE_ARCH_MMAP_RND_BITS if MMU
123 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
124 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
125 select HAVE_ARCH_SECCOMP_FILTER
126 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
127 select HAVE_ARCH_TRACEHOOK
128 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
129 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
130 select HAVE_ARCH_VMAP_STACK if X86_64
131 select HAVE_ARCH_WITHIN_STACK_FRAMES
132 select HAVE_CC_STACKPROTECTOR
133 select HAVE_CMPXCHG_DOUBLE
134 select HAVE_CMPXCHG_LOCAL
135 select HAVE_CONTEXT_TRACKING if X86_64
136 select HAVE_COPY_THREAD_TLS
137 select HAVE_C_RECORDMCOUNT
138 select HAVE_DEBUG_KMEMLEAK
139 select HAVE_DEBUG_STACKOVERFLOW
140 select HAVE_DMA_CONTIGUOUS
141 select HAVE_DYNAMIC_FTRACE
142 select HAVE_DYNAMIC_FTRACE_WITH_REGS
143 select HAVE_EBPF_JIT if X86_64
144 select HAVE_EFFICIENT_UNALIGNED_ACCESS
145 select HAVE_EXIT_THREAD
146 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
147 select HAVE_FTRACE_MCOUNT_RECORD
148 select HAVE_FUNCTION_GRAPH_TRACER
149 select HAVE_FUNCTION_TRACER
150 select HAVE_GCC_PLUGINS
151 select HAVE_HW_BREAKPOINT
153 select HAVE_IOREMAP_PROT
154 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
155 select HAVE_IRQ_TIME_ACCOUNTING
156 select HAVE_KERNEL_BZIP2
157 select HAVE_KERNEL_GZIP
158 select HAVE_KERNEL_LZ4
159 select HAVE_KERNEL_LZMA
160 select HAVE_KERNEL_LZO
161 select HAVE_KERNEL_XZ
163 select HAVE_KPROBES_ON_FTRACE
164 select HAVE_FUNCTION_ERROR_INJECTION
165 select HAVE_KRETPROBES
167 select HAVE_LIVEPATCH if X86_64
169 select HAVE_MEMBLOCK_NODE_MAP
170 select HAVE_MIXED_BREAKPOINTS_REGS
171 select HAVE_MOD_ARCH_SPECIFIC
174 select HAVE_OPTPROBES
175 select HAVE_PCSPKR_PLATFORM
176 select HAVE_PERF_EVENTS
177 select HAVE_PERF_EVENTS_NMI
178 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
179 select HAVE_PERF_REGS
180 select HAVE_PERF_USER_STACK_DUMP
181 select HAVE_RCU_TABLE_FREE
182 select HAVE_REGS_AND_STACK_ACCESS_API
183 select HAVE_RELIABLE_STACKTRACE if X86_64 && UNWINDER_FRAME_POINTER && STACK_VALIDATION
184 select HAVE_STACK_VALIDATION if X86_64
185 select HAVE_SYSCALL_TRACEPOINTS
186 select HAVE_UNSTABLE_SCHED_CLOCK
187 select HAVE_USER_RETURN_NOTIFIER
188 select IRQ_FORCED_THREADING
189 select NEED_SG_DMA_LENGTH
190 select PCI_LOCKLESS_CONFIG
193 select RTC_MC146818_LIB
196 select SYSCTL_EXCEPTION_TRACE
197 select THREAD_INFO_IN_TASK
198 select USER_STACKTRACE_SUPPORT
200 select X86_FEATURE_NAMES if PROC_FS
202 config INSTRUCTION_DECODER
204 depends on KPROBES || PERF_EVENTS || UPROBES
208 default "elf32-i386" if X86_32
209 default "elf64-x86-64" if X86_64
211 config ARCH_DEFCONFIG
213 default "arch/x86/configs/i386_defconfig" if X86_32
214 default "arch/x86/configs/x86_64_defconfig" if X86_64
216 config LOCKDEP_SUPPORT
219 config STACKTRACE_SUPPORT
225 config ARCH_MMAP_RND_BITS_MIN
229 config ARCH_MMAP_RND_BITS_MAX
233 config ARCH_MMAP_RND_COMPAT_BITS_MIN
236 config ARCH_MMAP_RND_COMPAT_BITS_MAX
242 config GENERIC_ISA_DMA
244 depends on ISA_DMA_API
249 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
251 config GENERIC_BUG_RELATIVE_POINTERS
254 config GENERIC_HWEIGHT
257 config ARCH_MAY_HAVE_PC_FDC
259 depends on ISA_DMA_API
261 config RWSEM_XCHGADD_ALGORITHM
264 config GENERIC_CALIBRATE_DELAY
267 config ARCH_HAS_CPU_RELAX
270 config ARCH_HAS_CACHE_LINE_SIZE
273 config ARCH_HAS_FILTER_PGPROT
276 config HAVE_SETUP_PER_CPU_AREA
279 config NEED_PER_CPU_EMBED_FIRST_CHUNK
282 config NEED_PER_CPU_PAGE_FIRST_CHUNK
285 config ARCH_HIBERNATION_POSSIBLE
288 config ARCH_SUSPEND_POSSIBLE
291 config ARCH_WANT_HUGE_PMD_SHARE
294 config ARCH_WANT_GENERAL_HUGETLB
303 config ARCH_SUPPORTS_OPTIMIZED_INLINING
306 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
309 config KASAN_SHADOW_OFFSET
312 default 0xdffffc0000000000
314 config HAVE_INTEL_TXT
316 depends on INTEL_IOMMU && ACPI
320 depends on X86_32 && SMP
324 depends on X86_64 && SMP
326 config X86_32_LAZY_GS
328 depends on X86_32 && CC_STACKPROTECTOR_NONE
330 config ARCH_SUPPORTS_UPROBES
333 config FIX_EARLYCON_MEM
336 config PGTABLE_LEVELS
338 default 5 if X86_5LEVEL
343 source "init/Kconfig"
344 source "kernel/Kconfig.freezer"
346 menu "Processor type and features"
349 bool "DMA memory allocation support" if EXPERT
352 DMA memory allocation support allows devices with less than 32-bit
353 addressing to allocate within the first 16MB of address space.
354 Disable if no such devices will be used.
359 bool "Symmetric multi-processing support"
361 This enables support for systems with more than one CPU. If you have
362 a system with only one CPU, say N. If you have a system with more
365 If you say N here, the kernel will run on uni- and multiprocessor
366 machines, but will use only one CPU of a multiprocessor machine. If
367 you say Y here, the kernel will run on many, but not all,
368 uniprocessor machines. On a uniprocessor machine, the kernel
369 will run faster if you say N here.
371 Note that if you say Y here and choose architecture "586" or
372 "Pentium" under "Processor family", the kernel will not work on 486
373 architectures. Similarly, multiprocessor kernels for the "PPro"
374 architecture may not work on all Pentium based boards.
376 People using multiprocessor machines who say Y here should also say
377 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
378 Management" code will be disabled if you say Y here.
380 See also <file:Documentation/x86/i386/IO-APIC.txt>,
381 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
382 <http://www.tldp.org/docs.html#howto>.
384 If you don't know what to do here, say N.
386 config X86_FEATURE_NAMES
387 bool "Processor feature human-readable names" if EMBEDDED
390 This option compiles in a table of x86 feature bits and corresponding
391 names. This is required to support /proc/cpuinfo and a few kernel
392 messages. You can disable this to save space, at the expense of
393 making those few kernel messages show numeric feature bits instead.
398 bool "Support x2apic"
399 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
401 This enables x2apic support on CPUs that have this feature.
403 This allows 32-bit apic IDs (so it can support very large systems),
404 and accesses the local apic via MSRs not via mmio.
406 If you don't know what to do here, say N.
409 bool "Enable MPS table" if ACPI || SFI
411 depends on X86_LOCAL_APIC
413 For old smp systems that do not have proper acpi support. Newer systems
414 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
418 depends on X86_GOLDFISH
421 bool "Avoid speculative indirect branches in kernel"
423 select STACK_VALIDATION if HAVE_STACK_VALIDATION
425 Compile kernel with the retpoline compiler options to guard against
426 kernel-to-user data leaks by avoiding speculative indirect
427 branches. Requires a compiler with -mindirect-branch=thunk-extern
428 support for full protection. The kernel may run slower.
430 Without compiler support, at least indirect branches in assembler
431 code are eliminated. Since this includes the syscall entry path,
432 it is not entirely pointless.
435 bool "Intel Resource Director Technology support"
437 depends on X86 && CPU_SUP_INTEL
440 Select to enable resource allocation and monitoring which are
441 sub-features of Intel Resource Director Technology(RDT). More
442 information about RDT can be found in the Intel x86
443 Architecture Software Developer Manual.
449 bool "Support for big SMP systems with more than 8 CPUs"
452 This option is needed for the systems that have more than 8 CPUs
454 config X86_EXTENDED_PLATFORM
455 bool "Support for extended (non-PC) x86 platforms"
458 If you disable this option then the kernel will only support
459 standard PC platforms. (which covers the vast majority of
462 If you enable this option then you'll be able to select support
463 for the following (non-PC) 32 bit x86 platforms:
464 Goldfish (Android emulator)
467 SGI 320/540 (Visual Workstation)
468 STA2X11-based (e.g. Northville)
469 Moorestown MID devices
471 If you have one of these systems, or if you want to build a
472 generic distribution kernel, say Y here - otherwise say N.
476 config X86_EXTENDED_PLATFORM
477 bool "Support for extended (non-PC) x86 platforms"
480 If you disable this option then the kernel will only support
481 standard PC platforms. (which covers the vast majority of
484 If you enable this option then you'll be able to select support
485 for the following (non-PC) 64 bit x86 platforms:
490 If you have one of these systems, or if you want to build a
491 generic distribution kernel, say Y here - otherwise say N.
493 # This is an alphabetically sorted list of 64 bit extended platforms
494 # Please maintain the alphabetic order if and when there are additions
496 bool "Numascale NumaChip"
498 depends on X86_EXTENDED_PLATFORM
501 depends on X86_X2APIC
502 depends on PCI_MMCONFIG
504 Adds support for Numascale NumaChip large-SMP systems. Needed to
505 enable more than ~168 cores.
506 If you don't have one of these, you should say N here.
510 select HYPERVISOR_GUEST
512 depends on X86_64 && PCI
513 depends on X86_EXTENDED_PLATFORM
516 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
517 supposed to run on these EM64T-based machines. Only choose this option
518 if you have one of these machines.
521 bool "SGI Ultraviolet"
523 depends on X86_EXTENDED_PLATFORM
526 depends on X86_X2APIC
529 This option is needed in order to support SGI Ultraviolet systems.
530 If you don't have one of these, you should say N here.
532 # Following is an alphabetically sorted list of 32 bit extended platforms
533 # Please maintain the alphabetic order if and when there are additions
536 bool "Goldfish (Virtual Platform)"
537 depends on X86_EXTENDED_PLATFORM
539 Enable support for the Goldfish virtual platform used primarily
540 for Android development. Unless you are building for the Android
541 Goldfish emulator say N here.
544 bool "CE4100 TV platform"
546 depends on PCI_GODIRECT
547 depends on X86_IO_APIC
549 depends on X86_EXTENDED_PLATFORM
550 select X86_REBOOTFIXUPS
552 select OF_EARLY_FLATTREE
554 Select for the Intel CE media processor (CE4100) SOC.
555 This option compiles in support for the CE4100 SOC for settop
556 boxes and media devices.
559 bool "Intel MID platform support"
560 depends on X86_EXTENDED_PLATFORM
561 depends on X86_PLATFORM_DEVICES
563 depends on X86_64 || (PCI_GOANY && X86_32)
564 depends on X86_IO_APIC
570 select MFD_INTEL_MSIC
572 Select to build a kernel capable of supporting Intel MID (Mobile
573 Internet Device) platform systems which do not have the PCI legacy
574 interfaces. If you are building for a PC class system say N here.
576 Intel MID platforms are based on an Intel processor and chipset which
577 consume less power than most of the x86 derivatives.
579 config X86_INTEL_QUARK
580 bool "Intel Quark platform support"
582 depends on X86_EXTENDED_PLATFORM
583 depends on X86_PLATFORM_DEVICES
587 depends on X86_IO_APIC
592 Select to include support for Quark X1000 SoC.
593 Say Y here if you have a Quark based system such as the Arduino
594 compatible Intel Galileo.
596 config X86_INTEL_LPSS
597 bool "Intel Low Power Subsystem Support"
598 depends on X86 && ACPI
603 Select to build support for Intel Low Power Subsystem such as
604 found on Intel Lynxpoint PCH. Selecting this option enables
605 things like clock tree (common clock framework) and pincontrol
606 which are needed by the LPSS peripheral drivers.
608 config X86_AMD_PLATFORM_DEVICE
609 bool "AMD ACPI2Platform devices support"
614 Select to interpret AMD specific ACPI device to platform device
615 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
616 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
617 implemented under PINCTRL subsystem.
620 tristate "Intel SoC IOSF Sideband support for SoC platforms"
623 This option enables sideband register access support for Intel SoC
624 platforms. On these platforms the IOSF sideband is used in lieu of
625 MSR's for some register accesses, mostly but not limited to thermal
626 and power. Drivers may query the availability of this device to
627 determine if they need the sideband in order to work on these
628 platforms. The sideband is available on the following SoC products.
629 This list is not meant to be exclusive.
634 You should say Y if you are running a kernel on one of these SoC's.
636 config IOSF_MBI_DEBUG
637 bool "Enable IOSF sideband access through debugfs"
638 depends on IOSF_MBI && DEBUG_FS
640 Select this option to expose the IOSF sideband access registers (MCR,
641 MDR, MCRX) through debugfs to write and read register information from
642 different units on the SoC. This is most useful for obtaining device
643 state information for debug and analysis. As this is a general access
644 mechanism, users of this option would have specific knowledge of the
645 device they want to access.
647 If you don't require the option or are in doubt, say N.
650 bool "RDC R-321x SoC"
652 depends on X86_EXTENDED_PLATFORM
654 select X86_REBOOTFIXUPS
656 This option is needed for RDC R-321x system-on-chip, also known
658 If you don't have one of these chips, you should say N here.
660 config X86_32_NON_STANDARD
661 bool "Support non-standard 32-bit SMP architectures"
662 depends on X86_32 && SMP
663 depends on X86_EXTENDED_PLATFORM
665 This option compiles in the bigsmp and STA2X11 default
666 subarchitectures. It is intended for a generic binary
667 kernel. If you select them all, kernel will probe it one by
668 one and will fallback to default.
670 # Alphabetically sorted list of Non standard 32 bit platforms
672 config X86_SUPPORTS_MEMORY_FAILURE
674 # MCE code calls memory_failure():
676 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
677 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
678 depends on X86_64 || !SPARSEMEM
679 select ARCH_SUPPORTS_MEMORY_FAILURE
682 bool "STA2X11 Companion Chip Support"
683 depends on X86_32_NON_STANDARD && PCI
684 select ARCH_HAS_PHYS_TO_DMA
685 select X86_DEV_DMA_OPS
692 This adds support for boards based on the STA2X11 IO-Hub,
693 a.k.a. "ConneXt". The chip is used in place of the standard
694 PC chipset, so all "standard" peripherals are missing. If this
695 option is selected the kernel will still be able to boot on
696 standard PC machines.
699 tristate "Eurobraille/Iris poweroff module"
702 The Iris machines from EuroBraille do not have APM or ACPI support
703 to shut themselves down properly. A special I/O sequence is
704 needed to do so, which is what this module does at
707 This is only for Iris machines from EuroBraille.
711 config SCHED_OMIT_FRAME_POINTER
713 prompt "Single-depth WCHAN output"
716 Calculate simpler /proc/<PID>/wchan values. If this option
717 is disabled then wchan values will recurse back to the
718 caller function. This provides more accurate wchan values,
719 at the expense of slightly more scheduling overhead.
721 If in doubt, say "Y".
723 menuconfig HYPERVISOR_GUEST
724 bool "Linux guest support"
726 Say Y here to enable options for running Linux under various hyper-
727 visors. This option enables basic hypervisor detection and platform
730 If you say N, all options in this submenu will be skipped and
731 disabled, and Linux guest support won't be built in.
736 bool "Enable paravirtualization code"
738 This changes the kernel so it can modify itself when it is run
739 under a hypervisor, potentially improving performance significantly
740 over full virtualization. However, when run without a hypervisor
741 the kernel is theoretically slower and slightly larger.
743 config PARAVIRT_DEBUG
744 bool "paravirt-ops debugging"
745 depends on PARAVIRT && DEBUG_KERNEL
747 Enable to debug paravirt_ops internals. Specifically, BUG if
748 a paravirt_op is missing when it is called.
750 config PARAVIRT_SPINLOCKS
751 bool "Paravirtualization layer for spinlocks"
752 depends on PARAVIRT && SMP
754 Paravirtualized spinlocks allow a pvops backend to replace the
755 spinlock implementation with something virtualization-friendly
756 (for example, block the virtual CPU rather than spinning).
758 It has a minimal impact on native kernels and gives a nice performance
759 benefit on paravirtualized KVM / Xen kernels.
761 If you are unsure how to answer this question, answer Y.
763 config QUEUED_LOCK_STAT
764 bool "Paravirt queued spinlock statistics"
765 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
767 Enable the collection of statistical data on the slowpath
768 behavior of paravirtualized queued spinlocks and report
771 source "arch/x86/xen/Kconfig"
774 bool "KVM Guest support (including kvmclock)"
776 select PARAVIRT_CLOCK
779 This option enables various optimizations for running under the KVM
780 hypervisor. It includes a paravirtualized clock, so that instead
781 of relying on a PIT (or probably other) emulation by the
782 underlying device model, the host provides the guest with
783 timing infrastructure such as time of day, and system time
786 bool "Enable debug information for KVM Guests in debugfs"
787 depends on KVM_GUEST && DEBUG_FS
790 This option enables collection of various statistics for KVM guest.
791 Statistics are displayed in debugfs filesystem. Enabling this option
792 may incur significant overhead.
794 config PARAVIRT_TIME_ACCOUNTING
795 bool "Paravirtual steal time accounting"
799 Select this option to enable fine granularity task steal time
800 accounting. Time spent executing other tasks in parallel with
801 the current vCPU is discounted from the vCPU power. To account for
802 that, there can be a small performance impact.
804 If in doubt, say N here.
806 config PARAVIRT_CLOCK
809 config JAILHOUSE_GUEST
810 bool "Jailhouse non-root cell support"
811 depends on X86_64 && PCI
814 This option allows to run Linux as guest in a Jailhouse non-root
815 cell. You can leave this option disabled if you only want to start
816 Jailhouse and run Linux afterwards in the root cell.
818 endif #HYPERVISOR_GUEST
823 source "arch/x86/Kconfig.cpu"
827 prompt "HPET Timer Support" if X86_32
829 Use the IA-PC HPET (High Precision Event Timer) to manage
830 time in preference to the PIT and RTC, if a HPET is
832 HPET is the next generation timer replacing legacy 8254s.
833 The HPET provides a stable time base on SMP
834 systems, unlike the TSC, but it is more expensive to access,
835 as it is off-chip. The interface used is documented
836 in the HPET spec, revision 1.
838 You can safely choose Y here. However, HPET will only be
839 activated if the platform and the BIOS support this feature.
840 Otherwise the 8254 will be used for timing services.
842 Choose N to continue using the legacy 8254 timer.
844 config HPET_EMULATE_RTC
846 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
849 def_bool y if X86_INTEL_MID
850 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
852 depends on X86_INTEL_MID && SFI
854 APB timer is the replacement for 8254, HPET on X86 MID platforms.
855 The APBT provides a stable time base on SMP
856 systems, unlike the TSC, but it is more expensive to access,
857 as it is off-chip. APB timers are always running regardless of CPU
858 C states, they are used as per CPU clockevent device when possible.
860 # Mark as expert because too many people got it wrong.
861 # The code disables itself when not needed.
864 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
865 bool "Enable DMI scanning" if EXPERT
867 Enabled scanning of DMI to identify machine quirks. Say Y
868 here unless you have verified that your setup is not
869 affected by entries in the DMI blacklist. Required by PNP
873 bool "Old AMD GART IOMMU support"
876 depends on X86_64 && PCI && AMD_NB
878 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
879 GART based hardware IOMMUs.
881 The GART supports full DMA access for devices with 32-bit access
882 limitations, on systems with more than 3 GB. This is usually needed
883 for USB, sound, many IDE/SATA chipsets and some other devices.
885 Newer systems typically have a modern AMD IOMMU, supported via
886 the CONFIG_AMD_IOMMU=y config option.
888 In normal configurations this driver is only active when needed:
889 there's more than 3 GB of memory and the system contains a
890 32-bit limited device.
895 bool "IBM Calgary IOMMU support"
898 depends on X86_64 && PCI
900 Support for hardware IOMMUs in IBM's xSeries x366 and x460
901 systems. Needed to run systems with more than 3GB of memory
902 properly with 32-bit PCI devices that do not support DAC
903 (Double Address Cycle). Calgary also supports bus level
904 isolation, where all DMAs pass through the IOMMU. This
905 prevents them from going anywhere except their intended
906 destination. This catches hard-to-find kernel bugs and
907 mis-behaving drivers and devices that do not use the DMA-API
908 properly to set up their DMA buffers. The IOMMU can be
909 turned off at boot time with the iommu=off parameter.
910 Normally the kernel will make the right choice by itself.
913 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
915 prompt "Should Calgary be enabled by default?"
916 depends on CALGARY_IOMMU
918 Should Calgary be enabled by default? if you choose 'y', Calgary
919 will be used (if it exists). If you choose 'n', Calgary will not be
920 used even if it exists. If you choose 'n' and would like to use
921 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
925 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
926 depends on X86_64 && SMP && DEBUG_KERNEL
927 select CPUMASK_OFFSTACK
929 Enable maximum number of CPUS and NUMA Nodes for this architecture.
933 # The maximum number of CPUs supported:
935 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
936 # and which can be configured interactively in the
937 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
939 # The ranges are different on 32-bit and 64-bit kernels, depending on
940 # hardware capabilities and scalability features of the kernel.
942 # ( If MAXSMP is enabled we just use the highest possible value and disable
943 # interactive configuration. )
946 config NR_CPUS_RANGE_BEGIN
948 default NR_CPUS_RANGE_END if MAXSMP
952 config NR_CPUS_RANGE_END
955 default 64 if SMP && X86_BIGSMP
956 default 8 if SMP && !X86_BIGSMP
959 config NR_CPUS_RANGE_END
962 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
963 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
966 config NR_CPUS_DEFAULT
969 default 32 if X86_BIGSMP
973 config NR_CPUS_DEFAULT
976 default 8192 if MAXSMP
981 int "Maximum number of CPUs" if SMP && !MAXSMP
982 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
983 default NR_CPUS_DEFAULT
985 This allows you to specify the maximum number of CPUs which this
986 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
987 supported value is 8192, otherwise the maximum value is 512. The
988 minimum value which makes sense is 2.
990 This is purely to save memory: each supported CPU adds about 8KB
994 bool "SMT (Hyperthreading) scheduler support"
997 SMT scheduler support improves the CPU scheduler's decision making
998 when dealing with Intel Pentium 4 chips with HyperThreading at a
999 cost of slightly increased overhead in some places. If unsure say
1004 prompt "Multi-core scheduler support"
1007 Multi-core scheduler support improves the CPU scheduler's decision
1008 making when dealing with multi-core CPU chips at a cost of slightly
1009 increased overhead in some places. If unsure say N here.
1011 config SCHED_MC_PRIO
1012 bool "CPU core priorities scheduler support"
1013 depends on SCHED_MC && CPU_SUP_INTEL
1014 select X86_INTEL_PSTATE
1018 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1019 core ordering determined at manufacturing time, which allows
1020 certain cores to reach higher turbo frequencies (when running
1021 single threaded workloads) than others.
1023 Enabling this kernel feature teaches the scheduler about
1024 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1025 scheduler's CPU selection logic accordingly, so that higher
1026 overall system performance can be achieved.
1028 This feature will have no effect on CPUs without this feature.
1030 If unsure say Y here.
1032 source "kernel/Kconfig.preempt"
1036 depends on !SMP && X86_LOCAL_APIC
1039 bool "Local APIC support on uniprocessors" if !PCI_MSI
1041 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1043 A local APIC (Advanced Programmable Interrupt Controller) is an
1044 integrated interrupt controller in the CPU. If you have a single-CPU
1045 system which has a processor with a local APIC, you can say Y here to
1046 enable and use it. If you say Y here even though your machine doesn't
1047 have a local APIC, then the kernel will still run with no slowdown at
1048 all. The local APIC supports CPU-generated self-interrupts (timer,
1049 performance counters), and the NMI watchdog which detects hard
1052 config X86_UP_IOAPIC
1053 bool "IO-APIC support on uniprocessors"
1054 depends on X86_UP_APIC
1056 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1057 SMP-capable replacement for PC-style interrupt controllers. Most
1058 SMP systems and many recent uniprocessor systems have one.
1060 If you have a single-CPU system with an IO-APIC, you can say Y here
1061 to use it. If you say Y here even though your machine doesn't have
1062 an IO-APIC, then the kernel will still run with no slowdown at all.
1064 config X86_LOCAL_APIC
1066 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1067 select IRQ_DOMAIN_HIERARCHY
1068 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1072 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1074 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1075 bool "Reroute for broken boot IRQs"
1076 depends on X86_IO_APIC
1078 This option enables a workaround that fixes a source of
1079 spurious interrupts. This is recommended when threaded
1080 interrupt handling is used on systems where the generation of
1081 superfluous "boot interrupts" cannot be disabled.
1083 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1084 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1085 kernel does during interrupt handling). On chipsets where this
1086 boot IRQ generation cannot be disabled, this workaround keeps
1087 the original IRQ line masked so that only the equivalent "boot
1088 IRQ" is delivered to the CPUs. The workaround also tells the
1089 kernel to set up the IRQ handler on the boot IRQ line. In this
1090 way only one interrupt is delivered to the kernel. Otherwise
1091 the spurious second interrupt may cause the kernel to bring
1092 down (vital) interrupt lines.
1094 Only affects "broken" chipsets. Interrupt sharing may be
1095 increased on these systems.
1098 bool "Machine Check / overheating reporting"
1099 select GENERIC_ALLOCATOR
1102 Machine Check support allows the processor to notify the
1103 kernel if it detects a problem (e.g. overheating, data corruption).
1104 The action the kernel takes depends on the severity of the problem,
1105 ranging from warning messages to halting the machine.
1107 config X86_MCELOG_LEGACY
1108 bool "Support for deprecated /dev/mcelog character device"
1111 Enable support for /dev/mcelog which is needed by the old mcelog
1112 userspace logging daemon. Consider switching to the new generation
1115 config X86_MCE_INTEL
1117 prompt "Intel MCE features"
1118 depends on X86_MCE && X86_LOCAL_APIC
1120 Additional support for intel specific MCE features such as
1121 the thermal monitor.
1125 prompt "AMD MCE features"
1126 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1128 Additional support for AMD specific MCE features such as
1129 the DRAM Error Threshold.
1131 config X86_ANCIENT_MCE
1132 bool "Support for old Pentium 5 / WinChip machine checks"
1133 depends on X86_32 && X86_MCE
1135 Include support for machine check handling on old Pentium 5 or WinChip
1136 systems. These typically need to be enabled explicitly on the command
1139 config X86_MCE_THRESHOLD
1140 depends on X86_MCE_AMD || X86_MCE_INTEL
1143 config X86_MCE_INJECT
1144 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1145 tristate "Machine check injector support"
1147 Provide support for injecting machine checks for testing purposes.
1148 If you don't know what a machine check is and you don't do kernel
1149 QA it is safe to say n.
1151 config X86_THERMAL_VECTOR
1153 depends on X86_MCE_INTEL
1155 source "arch/x86/events/Kconfig"
1157 config X86_LEGACY_VM86
1158 bool "Legacy VM86 support"
1162 This option allows user programs to put the CPU into V8086
1163 mode, which is an 80286-era approximation of 16-bit real mode.
1165 Some very old versions of X and/or vbetool require this option
1166 for user mode setting. Similarly, DOSEMU will use it if
1167 available to accelerate real mode DOS programs. However, any
1168 recent version of DOSEMU, X, or vbetool should be fully
1169 functional even without kernel VM86 support, as they will all
1170 fall back to software emulation. Nevertheless, if you are using
1171 a 16-bit DOS program where 16-bit performance matters, vm86
1172 mode might be faster than emulation and you might want to
1175 Note that any app that works on a 64-bit kernel is unlikely to
1176 need this option, as 64-bit kernels don't, and can't, support
1177 V8086 mode. This option is also unrelated to 16-bit protected
1178 mode and is not needed to run most 16-bit programs under Wine.
1180 Enabling this option increases the complexity of the kernel
1181 and slows down exception handling a tiny bit.
1183 If unsure, say N here.
1187 default X86_LEGACY_VM86
1190 bool "Enable support for 16-bit segments" if EXPERT
1192 depends on MODIFY_LDT_SYSCALL
1194 This option is required by programs like Wine to run 16-bit
1195 protected mode legacy code on x86 processors. Disabling
1196 this option saves about 300 bytes on i386, or around 6K text
1197 plus 16K runtime memory on x86-64,
1201 depends on X86_16BIT && X86_32
1205 depends on X86_16BIT && X86_64
1207 config X86_VSYSCALL_EMULATION
1208 bool "Enable vsyscall emulation" if EXPERT
1212 This enables emulation of the legacy vsyscall page. Disabling
1213 it is roughly equivalent to booting with vsyscall=none, except
1214 that it will also disable the helpful warning if a program
1215 tries to use a vsyscall. With this option set to N, offending
1216 programs will just segfault, citing addresses of the form
1219 This option is required by many programs built before 2013, and
1220 care should be used even with newer programs if set to N.
1222 Disabling this option saves about 7K of kernel size and
1223 possibly 4K of additional runtime pagetable memory.
1226 tristate "Toshiba Laptop support"
1229 This adds a driver to safely access the System Management Mode of
1230 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1231 not work on models with a Phoenix BIOS. The System Management Mode
1232 is used to set the BIOS and power saving options on Toshiba portables.
1234 For information on utilities to make use of this driver see the
1235 Toshiba Linux utilities web site at:
1236 <http://www.buzzard.org.uk/toshiba/>.
1238 Say Y if you intend to run this kernel on a Toshiba portable.
1242 tristate "Dell i8k legacy laptop support"
1244 select SENSORS_DELL_SMM
1246 This option enables legacy /proc/i8k userspace interface in hwmon
1247 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1248 temperature and allows controlling fan speeds of Dell laptops via
1249 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1250 it reports also power and hotkey status. For fan speed control is
1251 needed userspace package i8kutils.
1253 Say Y if you intend to run this kernel on old Dell laptops or want to
1254 use userspace package i8kutils.
1257 config X86_REBOOTFIXUPS
1258 bool "Enable X86 board specific fixups for reboot"
1261 This enables chipset and/or board specific fixups to be done
1262 in order to get reboot to work correctly. This is only needed on
1263 some combinations of hardware and BIOS. The symptom, for which
1264 this config is intended, is when reboot ends with a stalled/hung
1267 Currently, the only fixup is for the Geode machines using
1268 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1270 Say Y if you want to enable the fixup. Currently, it's safe to
1271 enable this option even if you don't need it.
1275 bool "CPU microcode loading support"
1277 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1280 If you say Y here, you will be able to update the microcode on
1281 Intel and AMD processors. The Intel support is for the IA32 family,
1282 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1283 AMD support is for families 0x10 and later. You will obviously need
1284 the actual microcode binary data itself which is not shipped with
1287 The preferred method to load microcode from a detached initrd is described
1288 in Documentation/x86/microcode.txt. For that you need to enable
1289 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1290 initrd for microcode blobs.
1292 In addition, you can build the microcode into the kernel. For that you
1293 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1296 config MICROCODE_INTEL
1297 bool "Intel microcode loading support"
1298 depends on MICROCODE
1302 This options enables microcode patch loading support for Intel
1305 For the current Intel microcode data package go to
1306 <https://downloadcenter.intel.com> and search for
1307 'Linux Processor Microcode Data File'.
1309 config MICROCODE_AMD
1310 bool "AMD microcode loading support"
1311 depends on MICROCODE
1314 If you select this option, microcode patch loading support for AMD
1315 processors will be enabled.
1317 config MICROCODE_OLD_INTERFACE
1319 depends on MICROCODE
1322 tristate "/dev/cpu/*/msr - Model-specific register support"
1324 This device gives privileged processes access to the x86
1325 Model-Specific Registers (MSRs). It is a character device with
1326 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1327 MSR accesses are directed to a specific CPU on multi-processor
1331 tristate "/dev/cpu/*/cpuid - CPU information support"
1333 This device gives processes access to the x86 CPUID instruction to
1334 be executed on a specific processor. It is a character device
1335 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1339 prompt "High Memory Support"
1346 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1347 However, the address space of 32-bit x86 processors is only 4
1348 Gigabytes large. That means that, if you have a large amount of
1349 physical memory, not all of it can be "permanently mapped" by the
1350 kernel. The physical memory that's not permanently mapped is called
1353 If you are compiling a kernel which will never run on a machine with
1354 more than 1 Gigabyte total physical RAM, answer "off" here (default
1355 choice and suitable for most users). This will result in a "3GB/1GB"
1356 split: 3GB are mapped so that each process sees a 3GB virtual memory
1357 space and the remaining part of the 4GB virtual memory space is used
1358 by the kernel to permanently map as much physical memory as
1361 If the machine has between 1 and 4 Gigabytes physical RAM, then
1364 If more than 4 Gigabytes is used then answer "64GB" here. This
1365 selection turns Intel PAE (Physical Address Extension) mode on.
1366 PAE implements 3-level paging on IA32 processors. PAE is fully
1367 supported by Linux, PAE mode is implemented on all recent Intel
1368 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1369 then the kernel will not boot on CPUs that don't support PAE!
1371 The actual amount of total physical memory will either be
1372 auto detected or can be forced by using a kernel command line option
1373 such as "mem=256M". (Try "man bootparam" or see the documentation of
1374 your boot loader (lilo or loadlin) about how to pass options to the
1375 kernel at boot time.)
1377 If unsure, say "off".
1382 Select this if you have a 32-bit processor and between 1 and 4
1383 gigabytes of physical RAM.
1387 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1390 Select this if you have a 32-bit processor and more than 4
1391 gigabytes of physical RAM.
1396 prompt "Memory split" if EXPERT
1400 Select the desired split between kernel and user memory.
1402 If the address range available to the kernel is less than the
1403 physical memory installed, the remaining memory will be available
1404 as "high memory". Accessing high memory is a little more costly
1405 than low memory, as it needs to be mapped into the kernel first.
1406 Note that increasing the kernel address space limits the range
1407 available to user programs, making the address space there
1408 tighter. Selecting anything other than the default 3G/1G split
1409 will also likely make your kernel incompatible with binary-only
1412 If you are not absolutely sure what you are doing, leave this
1416 bool "3G/1G user/kernel split"
1417 config VMSPLIT_3G_OPT
1419 bool "3G/1G user/kernel split (for full 1G low memory)"
1421 bool "2G/2G user/kernel split"
1422 config VMSPLIT_2G_OPT
1424 bool "2G/2G user/kernel split (for full 2G low memory)"
1426 bool "1G/3G user/kernel split"
1431 default 0xB0000000 if VMSPLIT_3G_OPT
1432 default 0x80000000 if VMSPLIT_2G
1433 default 0x78000000 if VMSPLIT_2G_OPT
1434 default 0x40000000 if VMSPLIT_1G
1440 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1443 bool "PAE (Physical Address Extension) Support"
1444 depends on X86_32 && !HIGHMEM4G
1445 select PHYS_ADDR_T_64BIT
1448 PAE is required for NX support, and furthermore enables
1449 larger swapspace support for non-overcommit purposes. It
1450 has the cost of more pagetable lookup overhead, and also
1451 consumes more pagetable space per process.
1454 bool "Enable 5-level page tables support"
1455 select DYNAMIC_MEMORY_LAYOUT
1456 select SPARSEMEM_VMEMMAP
1459 5-level paging enables access to larger address space:
1460 upto 128 PiB of virtual address space and 4 PiB of
1461 physical address space.
1463 It will be supported by future Intel CPUs.
1465 A kernel with the option enabled can be booted on machines that
1466 support 4- or 5-level paging.
1468 See Documentation/x86/x86_64/5level-paging.txt for more
1473 config X86_DIRECT_GBPAGES
1475 depends on X86_64 && !DEBUG_PAGEALLOC
1477 Certain kernel features effectively disable kernel
1478 linear 1 GB mappings (even if the CPU otherwise
1479 supports them), so don't confuse the user by printing
1480 that we have them enabled.
1482 config ARCH_HAS_MEM_ENCRYPT
1485 config AMD_MEM_ENCRYPT
1486 bool "AMD Secure Memory Encryption (SME) support"
1487 depends on X86_64 && CPU_SUP_AMD
1489 Say yes to enable support for the encryption of system memory.
1490 This requires an AMD processor that supports Secure Memory
1493 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1494 bool "Activate AMD Secure Memory Encryption (SME) by default"
1496 depends on AMD_MEM_ENCRYPT
1498 Say yes to have system memory encrypted by default if running on
1499 an AMD processor that supports Secure Memory Encryption (SME).
1501 If set to Y, then the encryption of system memory can be
1502 deactivated with the mem_encrypt=off command line option.
1504 If set to N, then the encryption of system memory can be
1505 activated with the mem_encrypt=on command line option.
1507 config ARCH_USE_MEMREMAP_PROT
1509 depends on AMD_MEM_ENCRYPT
1511 # Common NUMA Features
1513 bool "Numa Memory Allocation and Scheduler Support"
1515 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1516 default y if X86_BIGSMP
1518 Enable NUMA (Non Uniform Memory Access) support.
1520 The kernel will try to allocate memory used by a CPU on the
1521 local memory controller of the CPU and add some more
1522 NUMA awareness to the kernel.
1524 For 64-bit this is recommended if the system is Intel Core i7
1525 (or later), AMD Opteron, or EM64T NUMA.
1527 For 32-bit this is only needed if you boot a 32-bit
1528 kernel on a 64-bit NUMA platform.
1530 Otherwise, you should say N.
1534 prompt "Old style AMD Opteron NUMA detection"
1535 depends on X86_64 && NUMA && PCI
1537 Enable AMD NUMA node topology detection. You should say Y here if
1538 you have a multi processor AMD system. This uses an old method to
1539 read the NUMA configuration directly from the builtin Northbridge
1540 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1541 which also takes priority if both are compiled in.
1543 config X86_64_ACPI_NUMA
1545 prompt "ACPI NUMA detection"
1546 depends on X86_64 && NUMA && ACPI && PCI
1549 Enable ACPI SRAT based node topology detection.
1551 # Some NUMA nodes have memory ranges that span
1552 # other nodes. Even though a pfn is valid and
1553 # between a node's start and end pfns, it may not
1554 # reside on that node. See memmap_init_zone()
1556 config NODES_SPAN_OTHER_NODES
1558 depends on X86_64_ACPI_NUMA
1561 bool "NUMA emulation"
1564 Enable NUMA emulation. A flat machine will be split
1565 into virtual nodes when booted with "numa=fake=N", where N is the
1566 number of nodes. This is only useful for debugging.
1569 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1571 default "10" if MAXSMP
1572 default "6" if X86_64
1574 depends on NEED_MULTIPLE_NODES
1576 Specify the maximum number of NUMA Nodes available on the target
1577 system. Increases memory reserved to accommodate various tables.
1579 config ARCH_HAVE_MEMORY_PRESENT
1581 depends on X86_32 && DISCONTIGMEM
1583 config ARCH_FLATMEM_ENABLE
1585 depends on X86_32 && !NUMA
1587 config ARCH_DISCONTIGMEM_ENABLE
1589 depends on NUMA && X86_32
1591 config ARCH_DISCONTIGMEM_DEFAULT
1593 depends on NUMA && X86_32
1595 config ARCH_SPARSEMEM_ENABLE
1597 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1598 select SPARSEMEM_STATIC if X86_32
1599 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1601 config ARCH_SPARSEMEM_DEFAULT
1605 config ARCH_SELECT_MEMORY_MODEL
1607 depends on ARCH_SPARSEMEM_ENABLE
1609 config ARCH_MEMORY_PROBE
1610 bool "Enable sysfs memory/probe interface"
1611 depends on X86_64 && MEMORY_HOTPLUG
1613 This option enables a sysfs memory/probe interface for testing.
1614 See Documentation/memory-hotplug.txt for more information.
1615 If you are unsure how to answer this question, answer N.
1617 config ARCH_PROC_KCORE_TEXT
1619 depends on X86_64 && PROC_KCORE
1621 config ILLEGAL_POINTER_VALUE
1624 default 0xdead000000000000 if X86_64
1628 config X86_PMEM_LEGACY_DEVICE
1631 config X86_PMEM_LEGACY
1632 tristate "Support non-standard NVDIMMs and ADR protected memory"
1633 depends on PHYS_ADDR_T_64BIT
1635 select X86_PMEM_LEGACY_DEVICE
1638 Treat memory marked using the non-standard e820 type of 12 as used
1639 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1640 The kernel will offer these regions to the 'pmem' driver so
1641 they can be used for persistent storage.
1646 bool "Allocate 3rd-level pagetables from highmem"
1649 The VM uses one page table entry for each page of physical memory.
1650 For systems with a lot of RAM, this can be wasteful of precious
1651 low memory. Setting this option will put user-space page table
1652 entries in high memory.
1654 config X86_CHECK_BIOS_CORRUPTION
1655 bool "Check for low memory corruption"
1657 Periodically check for memory corruption in low memory, which
1658 is suspected to be caused by BIOS. Even when enabled in the
1659 configuration, it is disabled at runtime. Enable it by
1660 setting "memory_corruption_check=1" on the kernel command
1661 line. By default it scans the low 64k of memory every 60
1662 seconds; see the memory_corruption_check_size and
1663 memory_corruption_check_period parameters in
1664 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1666 When enabled with the default parameters, this option has
1667 almost no overhead, as it reserves a relatively small amount
1668 of memory and scans it infrequently. It both detects corruption
1669 and prevents it from affecting the running system.
1671 It is, however, intended as a diagnostic tool; if repeatable
1672 BIOS-originated corruption always affects the same memory,
1673 you can use memmap= to prevent the kernel from using that
1676 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1677 bool "Set the default setting of memory_corruption_check"
1678 depends on X86_CHECK_BIOS_CORRUPTION
1681 Set whether the default state of memory_corruption_check is
1684 config X86_RESERVE_LOW
1685 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1689 Specify the amount of low memory to reserve for the BIOS.
1691 The first page contains BIOS data structures that the kernel
1692 must not use, so that page must always be reserved.
1694 By default we reserve the first 64K of physical RAM, as a
1695 number of BIOSes are known to corrupt that memory range
1696 during events such as suspend/resume or monitor cable
1697 insertion, so it must not be used by the kernel.
1699 You can set this to 4 if you are absolutely sure that you
1700 trust the BIOS to get all its memory reservations and usages
1701 right. If you know your BIOS have problems beyond the
1702 default 64K area, you can set this to 640 to avoid using the
1703 entire low memory range.
1705 If you have doubts about the BIOS (e.g. suspend/resume does
1706 not work or there's kernel crashes after certain hardware
1707 hotplug events) then you might want to enable
1708 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1709 typical corruption patterns.
1711 Leave this to the default value of 64 if you are unsure.
1713 config MATH_EMULATION
1715 depends on MODIFY_LDT_SYSCALL
1716 prompt "Math emulation" if X86_32
1718 Linux can emulate a math coprocessor (used for floating point
1719 operations) if you don't have one. 486DX and Pentium processors have
1720 a math coprocessor built in, 486SX and 386 do not, unless you added
1721 a 487DX or 387, respectively. (The messages during boot time can
1722 give you some hints here ["man dmesg"].) Everyone needs either a
1723 coprocessor or this emulation.
1725 If you don't have a math coprocessor, you need to say Y here; if you
1726 say Y here even though you have a coprocessor, the coprocessor will
1727 be used nevertheless. (This behavior can be changed with the kernel
1728 command line option "no387", which comes handy if your coprocessor
1729 is broken. Try "man bootparam" or see the documentation of your boot
1730 loader (lilo or loadlin) about how to pass options to the kernel at
1731 boot time.) This means that it is a good idea to say Y here if you
1732 intend to use this kernel on different machines.
1734 More information about the internals of the Linux math coprocessor
1735 emulation can be found in <file:arch/x86/math-emu/README>.
1737 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1738 kernel, it won't hurt.
1742 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1744 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1745 the Memory Type Range Registers (MTRRs) may be used to control
1746 processor access to memory ranges. This is most useful if you have
1747 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1748 allows bus write transfers to be combined into a larger transfer
1749 before bursting over the PCI/AGP bus. This can increase performance
1750 of image write operations 2.5 times or more. Saying Y here creates a
1751 /proc/mtrr file which may be used to manipulate your processor's
1752 MTRRs. Typically the X server should use this.
1754 This code has a reasonably generic interface so that similar
1755 control registers on other processors can be easily supported
1758 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1759 Registers (ARRs) which provide a similar functionality to MTRRs. For
1760 these, the ARRs are used to emulate the MTRRs.
1761 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1762 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1763 write-combining. All of these processors are supported by this code
1764 and it makes sense to say Y here if you have one of them.
1766 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1767 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1768 can lead to all sorts of problems, so it's good to say Y here.
1770 You can safely say Y even if your machine doesn't have MTRRs, you'll
1771 just add about 9 KB to your kernel.
1773 See <file:Documentation/x86/mtrr.txt> for more information.
1775 config MTRR_SANITIZER
1777 prompt "MTRR cleanup support"
1780 Convert MTRR layout from continuous to discrete, so X drivers can
1781 add writeback entries.
1783 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1784 The largest mtrr entry size for a continuous block can be set with
1789 config MTRR_SANITIZER_ENABLE_DEFAULT
1790 int "MTRR cleanup enable value (0-1)"
1793 depends on MTRR_SANITIZER
1795 Enable mtrr cleanup default value
1797 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1798 int "MTRR cleanup spare reg num (0-7)"
1801 depends on MTRR_SANITIZER
1803 mtrr cleanup spare entries default, it can be changed via
1804 mtrr_spare_reg_nr=N on the kernel command line.
1808 prompt "x86 PAT support" if EXPERT
1811 Use PAT attributes to setup page level cache control.
1813 PATs are the modern equivalents of MTRRs and are much more
1814 flexible than MTRRs.
1816 Say N here if you see bootup problems (boot crash, boot hang,
1817 spontaneous reboots) or a non-working video driver.
1821 config ARCH_USES_PG_UNCACHED
1827 prompt "x86 architectural random number generator" if EXPERT
1829 Enable the x86 architectural RDRAND instruction
1830 (Intel Bull Mountain technology) to generate random numbers.
1831 If supported, this is a high bandwidth, cryptographically
1832 secure hardware random number generator.
1836 prompt "Supervisor Mode Access Prevention" if EXPERT
1838 Supervisor Mode Access Prevention (SMAP) is a security
1839 feature in newer Intel processors. There is a small
1840 performance cost if this enabled and turned on; there is
1841 also a small increase in the kernel size if this is enabled.
1845 config X86_INTEL_UMIP
1847 depends on CPU_SUP_INTEL
1848 prompt "Intel User Mode Instruction Prevention" if EXPERT
1850 The User Mode Instruction Prevention (UMIP) is a security
1851 feature in newer Intel processors. If enabled, a general
1852 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1853 or STR instructions are executed in user mode. These instructions
1854 unnecessarily expose information about the hardware state.
1856 The vast majority of applications do not use these instructions.
1857 For the very few that do, software emulation is provided in
1858 specific cases in protected and virtual-8086 modes. Emulated
1861 config X86_INTEL_MPX
1862 prompt "Intel MPX (Memory Protection Extensions)"
1864 # Note: only available in 64-bit mode due to VMA flags shortage
1865 depends on CPU_SUP_INTEL && X86_64
1866 select ARCH_USES_HIGH_VMA_FLAGS
1868 MPX provides hardware features that can be used in
1869 conjunction with compiler-instrumented code to check
1870 memory references. It is designed to detect buffer
1871 overflow or underflow bugs.
1873 This option enables running applications which are
1874 instrumented or otherwise use MPX. It does not use MPX
1875 itself inside the kernel or to protect the kernel
1876 against bad memory references.
1878 Enabling this option will make the kernel larger:
1879 ~8k of kernel text and 36 bytes of data on a 64-bit
1880 defconfig. It adds a long to the 'mm_struct' which
1881 will increase the kernel memory overhead of each
1882 process and adds some branches to paths used during
1883 exec() and munmap().
1885 For details, see Documentation/x86/intel_mpx.txt
1889 config X86_INTEL_MEMORY_PROTECTION_KEYS
1890 prompt "Intel Memory Protection Keys"
1892 # Note: only available in 64-bit mode
1893 depends on CPU_SUP_INTEL && X86_64
1894 select ARCH_USES_HIGH_VMA_FLAGS
1895 select ARCH_HAS_PKEYS
1897 Memory Protection Keys provides a mechanism for enforcing
1898 page-based protections, but without requiring modification of the
1899 page tables when an application changes protection domains.
1901 For details, see Documentation/x86/protection-keys.txt
1906 bool "EFI runtime service support"
1909 select EFI_RUNTIME_WRAPPERS
1911 This enables the kernel to use EFI runtime services that are
1912 available (such as the EFI variable services).
1914 This option is only useful on systems that have EFI firmware.
1915 In addition, you should use the latest ELILO loader available
1916 at <http://elilo.sourceforge.net> in order to take advantage
1917 of EFI runtime services. However, even with this option, the
1918 resultant kernel should continue to boot on existing non-EFI
1922 bool "EFI stub support"
1923 depends on EFI && !X86_USE_3DNOW
1926 This kernel feature allows a bzImage to be loaded directly
1927 by EFI firmware without the use of a bootloader.
1929 See Documentation/efi-stub.txt for more information.
1932 bool "EFI mixed-mode support"
1933 depends on EFI_STUB && X86_64
1935 Enabling this feature allows a 64-bit kernel to be booted
1936 on a 32-bit firmware, provided that your CPU supports 64-bit
1939 Note that it is not possible to boot a mixed-mode enabled
1940 kernel via the EFI boot stub - a bootloader that supports
1941 the EFI handover protocol must be used.
1947 prompt "Enable seccomp to safely compute untrusted bytecode"
1949 This kernel feature is useful for number crunching applications
1950 that may need to compute untrusted bytecode during their
1951 execution. By using pipes or other transports made available to
1952 the process as file descriptors supporting the read/write
1953 syscalls, it's possible to isolate those applications in
1954 their own address space using seccomp. Once seccomp is
1955 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1956 and the task is only allowed to execute a few safe syscalls
1957 defined by each seccomp mode.
1959 If unsure, say Y. Only embedded should say N here.
1961 source kernel/Kconfig.hz
1964 bool "kexec system call"
1967 kexec is a system call that implements the ability to shutdown your
1968 current kernel, and to start another kernel. It is like a reboot
1969 but it is independent of the system firmware. And like a reboot
1970 you can start any kernel with it, not just Linux.
1972 The name comes from the similarity to the exec system call.
1974 It is an ongoing process to be certain the hardware in a machine
1975 is properly shutdown, so do not be surprised if this code does not
1976 initially work for you. As of this writing the exact hardware
1977 interface is strongly in flux, so no good recommendation can be
1981 bool "kexec file based system call"
1986 depends on CRYPTO_SHA256=y
1988 This is new version of kexec system call. This system call is
1989 file based and takes file descriptors as system call argument
1990 for kernel and initramfs as opposed to list of segments as
1991 accepted by previous system call.
1993 config ARCH_HAS_KEXEC_PURGATORY
1996 config KEXEC_VERIFY_SIG
1997 bool "Verify kernel signature during kexec_file_load() syscall"
1998 depends on KEXEC_FILE
2000 This option makes kernel signature verification mandatory for
2001 the kexec_file_load() syscall.
2003 In addition to that option, you need to enable signature
2004 verification for the corresponding kernel image type being
2005 loaded in order for this to work.
2007 config KEXEC_BZIMAGE_VERIFY_SIG
2008 bool "Enable bzImage signature verification support"
2009 depends on KEXEC_VERIFY_SIG
2010 depends on SIGNED_PE_FILE_VERIFICATION
2011 select SYSTEM_TRUSTED_KEYRING
2013 Enable bzImage signature verification support.
2016 bool "kernel crash dumps"
2017 depends on X86_64 || (X86_32 && HIGHMEM)
2019 Generate crash dump after being started by kexec.
2020 This should be normally only set in special crash dump kernels
2021 which are loaded in the main kernel with kexec-tools into
2022 a specially reserved region and then later executed after
2023 a crash by kdump/kexec. The crash dump kernel must be compiled
2024 to a memory address not used by the main kernel or BIOS using
2025 PHYSICAL_START, or it must be built as a relocatable image
2026 (CONFIG_RELOCATABLE=y).
2027 For more details see Documentation/kdump/kdump.txt
2031 depends on KEXEC && HIBERNATION
2033 Jump between original kernel and kexeced kernel and invoke
2034 code in physical address mode via KEXEC
2036 config PHYSICAL_START
2037 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2040 This gives the physical address where the kernel is loaded.
2042 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2043 bzImage will decompress itself to above physical address and
2044 run from there. Otherwise, bzImage will run from the address where
2045 it has been loaded by the boot loader and will ignore above physical
2048 In normal kdump cases one does not have to set/change this option
2049 as now bzImage can be compiled as a completely relocatable image
2050 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2051 address. This option is mainly useful for the folks who don't want
2052 to use a bzImage for capturing the crash dump and want to use a
2053 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2054 to be specifically compiled to run from a specific memory area
2055 (normally a reserved region) and this option comes handy.
2057 So if you are using bzImage for capturing the crash dump,
2058 leave the value here unchanged to 0x1000000 and set
2059 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2060 for capturing the crash dump change this value to start of
2061 the reserved region. In other words, it can be set based on
2062 the "X" value as specified in the "crashkernel=YM@XM"
2063 command line boot parameter passed to the panic-ed
2064 kernel. Please take a look at Documentation/kdump/kdump.txt
2065 for more details about crash dumps.
2067 Usage of bzImage for capturing the crash dump is recommended as
2068 one does not have to build two kernels. Same kernel can be used
2069 as production kernel and capture kernel. Above option should have
2070 gone away after relocatable bzImage support is introduced. But it
2071 is present because there are users out there who continue to use
2072 vmlinux for dump capture. This option should go away down the
2075 Don't change this unless you know what you are doing.
2078 bool "Build a relocatable kernel"
2081 This builds a kernel image that retains relocation information
2082 so it can be loaded someplace besides the default 1MB.
2083 The relocations tend to make the kernel binary about 10% larger,
2084 but are discarded at runtime.
2086 One use is for the kexec on panic case where the recovery kernel
2087 must live at a different physical address than the primary
2090 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2091 it has been loaded at and the compile time physical address
2092 (CONFIG_PHYSICAL_START) is used as the minimum location.
2094 config RANDOMIZE_BASE
2095 bool "Randomize the address of the kernel image (KASLR)"
2096 depends on RELOCATABLE
2099 In support of Kernel Address Space Layout Randomization (KASLR),
2100 this randomizes the physical address at which the kernel image
2101 is decompressed and the virtual address where the kernel
2102 image is mapped, as a security feature that deters exploit
2103 attempts relying on knowledge of the location of kernel
2106 On 64-bit, the kernel physical and virtual addresses are
2107 randomized separately. The physical address will be anywhere
2108 between 16MB and the top of physical memory (up to 64TB). The
2109 virtual address will be randomized from 16MB up to 1GB (9 bits
2110 of entropy). Note that this also reduces the memory space
2111 available to kernel modules from 1.5GB to 1GB.
2113 On 32-bit, the kernel physical and virtual addresses are
2114 randomized together. They will be randomized from 16MB up to
2115 512MB (8 bits of entropy).
2117 Entropy is generated using the RDRAND instruction if it is
2118 supported. If RDTSC is supported, its value is mixed into
2119 the entropy pool as well. If neither RDRAND nor RDTSC are
2120 supported, then entropy is read from the i8254 timer. The
2121 usable entropy is limited by the kernel being built using
2122 2GB addressing, and that PHYSICAL_ALIGN must be at a
2123 minimum of 2MB. As a result, only 10 bits of entropy are
2124 theoretically possible, but the implementations are further
2125 limited due to memory layouts.
2129 # Relocation on x86 needs some additional build support
2130 config X86_NEED_RELOCS
2132 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2134 config PHYSICAL_ALIGN
2135 hex "Alignment value to which kernel should be aligned"
2137 range 0x2000 0x1000000 if X86_32
2138 range 0x200000 0x1000000 if X86_64
2140 This value puts the alignment restrictions on physical address
2141 where kernel is loaded and run from. Kernel is compiled for an
2142 address which meets above alignment restriction.
2144 If bootloader loads the kernel at a non-aligned address and
2145 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2146 address aligned to above value and run from there.
2148 If bootloader loads the kernel at a non-aligned address and
2149 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2150 load address and decompress itself to the address it has been
2151 compiled for and run from there. The address for which kernel is
2152 compiled already meets above alignment restrictions. Hence the
2153 end result is that kernel runs from a physical address meeting
2154 above alignment restrictions.
2156 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2157 this value must be a multiple of 0x200000.
2159 Don't change this unless you know what you are doing.
2161 config DYNAMIC_MEMORY_LAYOUT
2164 This option makes base addresses of vmalloc and vmemmap as well as
2165 __PAGE_OFFSET movable during boot.
2167 config RANDOMIZE_MEMORY
2168 bool "Randomize the kernel memory sections"
2170 depends on RANDOMIZE_BASE
2171 select DYNAMIC_MEMORY_LAYOUT
2172 default RANDOMIZE_BASE
2174 Randomizes the base virtual address of kernel memory sections
2175 (physical memory mapping, vmalloc & vmemmap). This security feature
2176 makes exploits relying on predictable memory locations less reliable.
2178 The order of allocations remains unchanged. Entropy is generated in
2179 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2180 configuration have in average 30,000 different possible virtual
2181 addresses for each memory section.
2185 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2186 hex "Physical memory mapping padding" if EXPERT
2187 depends on RANDOMIZE_MEMORY
2188 default "0xa" if MEMORY_HOTPLUG
2190 range 0x1 0x40 if MEMORY_HOTPLUG
2193 Define the padding in terabytes added to the existing physical
2194 memory size during kernel memory randomization. It is useful
2195 for memory hotplug support but reduces the entropy available for
2196 address randomization.
2198 If unsure, leave at the default value.
2201 bool "Support for hot-pluggable CPUs"
2204 Say Y here to allow turning CPUs off and on. CPUs can be
2205 controlled through /sys/devices/system/cpu.
2206 ( Note: power management support will enable this option
2207 automatically on SMP systems. )
2208 Say N if you want to disable CPU hotplug.
2210 config BOOTPARAM_HOTPLUG_CPU0
2211 bool "Set default setting of cpu0_hotpluggable"
2213 depends on HOTPLUG_CPU
2215 Set whether default state of cpu0_hotpluggable is on or off.
2217 Say Y here to enable CPU0 hotplug by default. If this switch
2218 is turned on, there is no need to give cpu0_hotplug kernel
2219 parameter and the CPU0 hotplug feature is enabled by default.
2221 Please note: there are two known CPU0 dependencies if you want
2222 to enable the CPU0 hotplug feature either by this switch or by
2223 cpu0_hotplug kernel parameter.
2225 First, resume from hibernate or suspend always starts from CPU0.
2226 So hibernate and suspend are prevented if CPU0 is offline.
2228 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2229 offline if any interrupt can not migrate out of CPU0. There may
2230 be other CPU0 dependencies.
2232 Please make sure the dependencies are under your control before
2233 you enable this feature.
2235 Say N if you don't want to enable CPU0 hotplug feature by default.
2236 You still can enable the CPU0 hotplug feature at boot by kernel
2237 parameter cpu0_hotplug.
2239 config DEBUG_HOTPLUG_CPU0
2241 prompt "Debug CPU0 hotplug"
2242 depends on HOTPLUG_CPU
2244 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2245 soon as possible and boots up userspace with CPU0 offlined. User
2246 can online CPU0 back after boot time.
2248 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2249 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2250 compilation or giving cpu0_hotplug kernel parameter at boot.
2256 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2257 depends on COMPAT_32
2259 Certain buggy versions of glibc will crash if they are
2260 presented with a 32-bit vDSO that is not mapped at the address
2261 indicated in its segment table.
2263 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2264 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2265 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2266 the only released version with the bug, but OpenSUSE 9
2267 contains a buggy "glibc 2.3.2".
2269 The symptom of the bug is that everything crashes on startup, saying:
2270 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2272 Saying Y here changes the default value of the vdso32 boot
2273 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2274 This works around the glibc bug but hurts performance.
2276 If unsure, say N: if you are compiling your own kernel, you
2277 are unlikely to be using a buggy version of glibc.
2280 prompt "vsyscall table for legacy applications"
2282 default LEGACY_VSYSCALL_EMULATE
2284 Legacy user code that does not know how to find the vDSO expects
2285 to be able to issue three syscalls by calling fixed addresses in
2286 kernel space. Since this location is not randomized with ASLR,
2287 it can be used to assist security vulnerability exploitation.
2289 This setting can be changed at boot time via the kernel command
2290 line parameter vsyscall=[emulate|none].
2292 On a system with recent enough glibc (2.14 or newer) and no
2293 static binaries, you can say None without a performance penalty
2294 to improve security.
2296 If unsure, select "Emulate".
2298 config LEGACY_VSYSCALL_EMULATE
2301 The kernel traps and emulates calls into the fixed
2302 vsyscall address mapping. This makes the mapping
2303 non-executable, but it still contains known contents,
2304 which could be used in certain rare security vulnerability
2305 exploits. This configuration is recommended when userspace
2306 still uses the vsyscall area.
2308 config LEGACY_VSYSCALL_NONE
2311 There will be no vsyscall mapping at all. This will
2312 eliminate any risk of ASLR bypass due to the vsyscall
2313 fixed address mapping. Attempts to use the vsyscalls
2314 will be reported to dmesg, so that either old or
2315 malicious userspace programs can be identified.
2320 bool "Built-in kernel command line"
2322 Allow for specifying boot arguments to the kernel at
2323 build time. On some systems (e.g. embedded ones), it is
2324 necessary or convenient to provide some or all of the
2325 kernel boot arguments with the kernel itself (that is,
2326 to not rely on the boot loader to provide them.)
2328 To compile command line arguments into the kernel,
2329 set this option to 'Y', then fill in the
2330 boot arguments in CONFIG_CMDLINE.
2332 Systems with fully functional boot loaders (i.e. non-embedded)
2333 should leave this option set to 'N'.
2336 string "Built-in kernel command string"
2337 depends on CMDLINE_BOOL
2340 Enter arguments here that should be compiled into the kernel
2341 image and used at boot time. If the boot loader provides a
2342 command line at boot time, it is appended to this string to
2343 form the full kernel command line, when the system boots.
2345 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2346 change this behavior.
2348 In most cases, the command line (whether built-in or provided
2349 by the boot loader) should specify the device for the root
2352 config CMDLINE_OVERRIDE
2353 bool "Built-in command line overrides boot loader arguments"
2354 depends on CMDLINE_BOOL
2356 Set this option to 'Y' to have the kernel ignore the boot loader
2357 command line, and use ONLY the built-in command line.
2359 This is used to work around broken boot loaders. This should
2360 be set to 'N' under normal conditions.
2362 config MODIFY_LDT_SYSCALL
2363 bool "Enable the LDT (local descriptor table)" if EXPERT
2366 Linux can allow user programs to install a per-process x86
2367 Local Descriptor Table (LDT) using the modify_ldt(2) system
2368 call. This is required to run 16-bit or segmented code such as
2369 DOSEMU or some Wine programs. It is also used by some very old
2370 threading libraries.
2372 Enabling this feature adds a small amount of overhead to
2373 context switches and increases the low-level kernel attack
2374 surface. Disabling it removes the modify_ldt(2) system call.
2376 Saying 'N' here may make sense for embedded or server kernels.
2378 source "kernel/livepatch/Kconfig"
2382 config ARCH_HAS_ADD_PAGES
2384 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2386 config ARCH_ENABLE_MEMORY_HOTPLUG
2388 depends on X86_64 || (X86_32 && HIGHMEM)
2390 config ARCH_ENABLE_MEMORY_HOTREMOVE
2392 depends on MEMORY_HOTPLUG
2394 config USE_PERCPU_NUMA_NODE_ID
2398 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2400 depends on X86_64 || X86_PAE
2402 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2404 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2406 config ARCH_ENABLE_THP_MIGRATION
2408 depends on X86_64 && TRANSPARENT_HUGEPAGE
2410 menu "Power management and ACPI options"
2412 config ARCH_HIBERNATION_HEADER
2414 depends on X86_64 && HIBERNATION
2416 source "kernel/power/Kconfig"
2418 source "drivers/acpi/Kconfig"
2420 source "drivers/sfi/Kconfig"
2427 tristate "APM (Advanced Power Management) BIOS support"
2428 depends on X86_32 && PM_SLEEP
2430 APM is a BIOS specification for saving power using several different
2431 techniques. This is mostly useful for battery powered laptops with
2432 APM compliant BIOSes. If you say Y here, the system time will be
2433 reset after a RESUME operation, the /proc/apm device will provide
2434 battery status information, and user-space programs will receive
2435 notification of APM "events" (e.g. battery status change).
2437 If you select "Y" here, you can disable actual use of the APM
2438 BIOS by passing the "apm=off" option to the kernel at boot time.
2440 Note that the APM support is almost completely disabled for
2441 machines with more than one CPU.
2443 In order to use APM, you will need supporting software. For location
2444 and more information, read <file:Documentation/power/apm-acpi.txt>
2445 and the Battery Powered Linux mini-HOWTO, available from
2446 <http://www.tldp.org/docs.html#howto>.
2448 This driver does not spin down disk drives (see the hdparm(8)
2449 manpage ("man 8 hdparm") for that), and it doesn't turn off
2450 VESA-compliant "green" monitors.
2452 This driver does not support the TI 4000M TravelMate and the ACER
2453 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2454 desktop machines also don't have compliant BIOSes, and this driver
2455 may cause those machines to panic during the boot phase.
2457 Generally, if you don't have a battery in your machine, there isn't
2458 much point in using this driver and you should say N. If you get
2459 random kernel OOPSes or reboots that don't seem to be related to
2460 anything, try disabling/enabling this option (or disabling/enabling
2463 Some other things you should try when experiencing seemingly random,
2466 1) make sure that you have enough swap space and that it is
2468 2) pass the "no-hlt" option to the kernel
2469 3) switch on floating point emulation in the kernel and pass
2470 the "no387" option to the kernel
2471 4) pass the "floppy=nodma" option to the kernel
2472 5) pass the "mem=4M" option to the kernel (thereby disabling
2473 all but the first 4 MB of RAM)
2474 6) make sure that the CPU is not over clocked.
2475 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2476 8) disable the cache from your BIOS settings
2477 9) install a fan for the video card or exchange video RAM
2478 10) install a better fan for the CPU
2479 11) exchange RAM chips
2480 12) exchange the motherboard.
2482 To compile this driver as a module, choose M here: the
2483 module will be called apm.
2487 config APM_IGNORE_USER_SUSPEND
2488 bool "Ignore USER SUSPEND"
2490 This option will ignore USER SUSPEND requests. On machines with a
2491 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2492 series notebooks, it is necessary to say Y because of a BIOS bug.
2494 config APM_DO_ENABLE
2495 bool "Enable PM at boot time"
2497 Enable APM features at boot time. From page 36 of the APM BIOS
2498 specification: "When disabled, the APM BIOS does not automatically
2499 power manage devices, enter the Standby State, enter the Suspend
2500 State, or take power saving steps in response to CPU Idle calls."
2501 This driver will make CPU Idle calls when Linux is idle (unless this
2502 feature is turned off -- see "Do CPU IDLE calls", below). This
2503 should always save battery power, but more complicated APM features
2504 will be dependent on your BIOS implementation. You may need to turn
2505 this option off if your computer hangs at boot time when using APM
2506 support, or if it beeps continuously instead of suspending. Turn
2507 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2508 T400CDT. This is off by default since most machines do fine without
2513 bool "Make CPU Idle calls when idle"
2515 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2516 On some machines, this can activate improved power savings, such as
2517 a slowed CPU clock rate, when the machine is idle. These idle calls
2518 are made after the idle loop has run for some length of time (e.g.,
2519 333 mS). On some machines, this will cause a hang at boot time or
2520 whenever the CPU becomes idle. (On machines with more than one CPU,
2521 this option does nothing.)
2523 config APM_DISPLAY_BLANK
2524 bool "Enable console blanking using APM"
2526 Enable console blanking using the APM. Some laptops can use this to
2527 turn off the LCD backlight when the screen blanker of the Linux
2528 virtual console blanks the screen. Note that this is only used by
2529 the virtual console screen blanker, and won't turn off the backlight
2530 when using the X Window system. This also doesn't have anything to
2531 do with your VESA-compliant power-saving monitor. Further, this
2532 option doesn't work for all laptops -- it might not turn off your
2533 backlight at all, or it might print a lot of errors to the console,
2534 especially if you are using gpm.
2536 config APM_ALLOW_INTS
2537 bool "Allow interrupts during APM BIOS calls"
2539 Normally we disable external interrupts while we are making calls to
2540 the APM BIOS as a measure to lessen the effects of a badly behaving
2541 BIOS implementation. The BIOS should reenable interrupts if it
2542 needs to. Unfortunately, some BIOSes do not -- especially those in
2543 many of the newer IBM Thinkpads. If you experience hangs when you
2544 suspend, try setting this to Y. Otherwise, say N.
2548 source "drivers/cpufreq/Kconfig"
2550 source "drivers/cpuidle/Kconfig"
2552 source "drivers/idle/Kconfig"
2557 menu "Bus options (PCI etc.)"
2563 Find out whether you have a PCI motherboard. PCI is the name of a
2564 bus system, i.e. the way the CPU talks to the other stuff inside
2565 your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
2566 VESA. If you have PCI, say Y, otherwise N.
2569 prompt "PCI access mode"
2570 depends on X86_32 && PCI
2573 On PCI systems, the BIOS can be used to detect the PCI devices and
2574 determine their configuration. However, some old PCI motherboards
2575 have BIOS bugs and may crash if this is done. Also, some embedded
2576 PCI-based systems don't have any BIOS at all. Linux can also try to
2577 detect the PCI hardware directly without using the BIOS.
2579 With this option, you can specify how Linux should detect the
2580 PCI devices. If you choose "BIOS", the BIOS will be used,
2581 if you choose "Direct", the BIOS won't be used, and if you
2582 choose "MMConfig", then PCI Express MMCONFIG will be used.
2583 If you choose "Any", the kernel will try MMCONFIG, then the
2584 direct access method and falls back to the BIOS if that doesn't
2585 work. If unsure, go with the default, which is "Any".
2590 config PCI_GOMMCONFIG
2607 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2609 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2612 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2615 bool "Support mmconfig PCI config space access" if X86_64
2617 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2618 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2622 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2626 depends on PCI && XEN
2633 config MMCONF_FAM10H
2635 depends on X86_64 && PCI_MMCONFIG && ACPI
2637 config PCI_CNB20LE_QUIRK
2638 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2641 Read the PCI windows out of the CNB20LE host bridge. This allows
2642 PCI hotplug to work on systems with the CNB20LE chipset which do
2645 There's no public spec for this chipset, and this functionality
2646 is known to be incomplete.
2648 You should say N unless you know you need this.
2650 source "drivers/pci/Kconfig"
2653 bool "ISA bus support on modern systems" if EXPERT
2655 Expose ISA bus device drivers and options available for selection and
2656 configuration. Enable this option if your target machine has an ISA
2657 bus. ISA is an older system, displaced by PCI and newer bus
2658 architectures -- if your target machine is modern, it probably does
2659 not have an ISA bus.
2663 # x86_64 have no ISA slots, but can have ISA-style DMA.
2665 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2668 Enables ISA-style DMA support for devices requiring such controllers.
2676 Find out whether you have ISA slots on your motherboard. ISA is the
2677 name of a bus system, i.e. the way the CPU talks to the other stuff
2678 inside your box. Other bus systems are PCI, EISA, MicroChannel
2679 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2680 newer boards don't support it. If you have ISA, say Y, otherwise N.
2686 The Extended Industry Standard Architecture (EISA) bus was
2687 developed as an open alternative to the IBM MicroChannel bus.
2689 The EISA bus provided some of the features of the IBM MicroChannel
2690 bus while maintaining backward compatibility with cards made for
2691 the older ISA bus. The EISA bus saw limited use between 1988 and
2692 1995 when it was made obsolete by the PCI bus.
2694 Say Y here if you are building a kernel for an EISA-based machine.
2698 source "drivers/eisa/Kconfig"
2701 tristate "NatSemi SCx200 support"
2703 This provides basic support for National Semiconductor's
2704 (now AMD's) Geode processors. The driver probes for the
2705 PCI-IDs of several on-chip devices, so its a good dependency
2706 for other scx200_* drivers.
2708 If compiled as a module, the driver is named scx200.
2710 config SCx200HR_TIMER
2711 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2715 This driver provides a clocksource built upon the on-chip
2716 27MHz high-resolution timer. Its also a workaround for
2717 NSC Geode SC-1100's buggy TSC, which loses time when the
2718 processor goes idle (as is done by the scheduler). The
2719 other workaround is idle=poll boot option.
2722 bool "One Laptop Per Child support"
2729 Add support for detecting the unique features of the OLPC
2733 bool "OLPC XO-1 Power Management"
2734 depends on OLPC && MFD_CS5535 && PM_SLEEP
2737 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2740 bool "OLPC XO-1 Real Time Clock"
2741 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2743 Add support for the XO-1 real time clock, which can be used as a
2744 programmable wakeup source.
2747 bool "OLPC XO-1 SCI extras"
2748 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2752 Add support for SCI-based features of the OLPC XO-1 laptop:
2753 - EC-driven system wakeups
2757 - AC adapter status updates
2758 - Battery status updates
2760 config OLPC_XO15_SCI
2761 bool "OLPC XO-1.5 SCI extras"
2762 depends on OLPC && ACPI
2765 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2766 - EC-driven system wakeups
2767 - AC adapter status updates
2768 - Battery status updates
2771 bool "PCEngines ALIX System Support (LED setup)"
2774 This option enables system support for the PCEngines ALIX.
2775 At present this just sets up LEDs for GPIO control on
2776 ALIX2/3/6 boards. However, other system specific setup should
2779 Note: You must still enable the drivers for GPIO and LED support
2780 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2782 Note: You have to set alix.force=1 for boards with Award BIOS.
2785 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2788 This option enables system support for the Soekris Engineering net5501.
2791 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2795 This option enables system support for the Traverse Technologies GEOS.
2798 bool "Technologic Systems TS-5500 platform support"
2800 select CHECK_SIGNATURE
2804 This option enables system support for the Technologic Systems TS-5500.
2810 depends on CPU_SUP_AMD && PCI
2812 source "drivers/pcmcia/Kconfig"
2815 tristate "RapidIO support"
2819 If enabled this option will include drivers and the core
2820 infrastructure code to support RapidIO interconnect devices.
2822 source "drivers/rapidio/Kconfig"
2825 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2827 Firmwares often provide initial graphics framebuffers so the BIOS,
2828 bootloader or kernel can show basic video-output during boot for
2829 user-guidance and debugging. Historically, x86 used the VESA BIOS
2830 Extensions and EFI-framebuffers for this, which are mostly limited
2832 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2833 framebuffers so the new generic system-framebuffer drivers can be
2834 used on x86. If the framebuffer is not compatible with the generic
2835 modes, it is adverticed as fallback platform framebuffer so legacy
2836 drivers like efifb, vesafb and uvesafb can pick it up.
2837 If this option is not selected, all system framebuffers are always
2838 marked as fallback platform framebuffers as usual.
2840 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2841 not be able to pick up generic system framebuffers if this option
2842 is selected. You are highly encouraged to enable simplefb as
2843 replacement if you select this option. simplefb can correctly deal
2844 with generic system framebuffers. But you should still keep vesafb
2845 and others enabled as fallback if a system framebuffer is
2846 incompatible with simplefb.
2853 menu "Executable file formats / Emulations"
2855 source "fs/Kconfig.binfmt"
2857 config IA32_EMULATION
2858 bool "IA32 Emulation"
2860 select ARCH_WANT_OLD_COMPAT_IPC
2862 select COMPAT_BINFMT_ELF
2863 select COMPAT_OLD_SIGACTION
2865 Include code to run legacy 32-bit programs under a
2866 64-bit kernel. You should likely turn this on, unless you're
2867 100% sure that you don't have any 32-bit programs left.
2870 tristate "IA32 a.out support"
2871 depends on IA32_EMULATION
2873 Support old a.out binaries in the 32bit emulation.
2876 bool "x32 ABI for 64-bit mode"
2879 Include code to run binaries for the x32 native 32-bit ABI
2880 for 64-bit processors. An x32 process gets access to the
2881 full 64-bit register file and wide data path while leaving
2882 pointers at 32 bits for smaller memory footprint.
2884 You will need a recent binutils (2.22 or later) with
2885 elf32_x86_64 support enabled to compile a kernel with this
2890 depends on IA32_EMULATION || X86_32
2892 select OLD_SIGSUSPEND3
2896 depends on IA32_EMULATION || X86_X32
2899 config COMPAT_FOR_U64_ALIGNMENT
2902 config SYSVIPC_COMPAT
2910 config HAVE_ATOMIC_IOMAP
2914 config X86_DEV_DMA_OPS
2916 depends on X86_64 || STA2X11
2918 config X86_DMA_REMAP
2922 config HAVE_GENERIC_GUP
2925 source "net/Kconfig"
2927 source "drivers/Kconfig"
2929 source "drivers/firmware/Kconfig"
2933 source "arch/x86/Kconfig.debug"
2935 source "security/Kconfig"
2937 source "crypto/Kconfig"
2939 source "arch/x86/kvm/Kconfig"
2941 source "lib/Kconfig"