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
17 select HAVE_DEBUG_STACKOVERFLOW
18 select MODULES_USE_ELF_REL
24 # Options that are inherently 64-bit kernel only:
25 select ARCH_HAS_GIGANTIC_PAGE
26 select ARCH_SUPPORTS_INT128
27 select ARCH_USE_CMPXCHG_LOCKREF
28 select HAVE_ARCH_SOFT_DIRTY
29 select MODULES_USE_ELF_RELA
30 select NEED_DMA_MAP_STATE
32 select ARCH_HAS_SYSCALL_WRAPPER
37 # ( Note that options that are marked 'if X86_64' could in principle be
38 # ported to 32-bit as well. )
43 # Note: keep this list sorted alphabetically
45 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
46 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
47 select ARCH_32BIT_OFF_T if X86_32
48 select ARCH_CLOCKSOURCE_DATA
49 select ARCH_CLOCKSOURCE_INIT
50 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
51 select ARCH_HAS_DEBUG_VIRTUAL
52 select ARCH_HAS_DEVMEM_IS_ALLOWED
53 select ARCH_HAS_ELF_RANDOMIZE
54 select ARCH_HAS_FAST_MULTIPLIER
55 select ARCH_HAS_FILTER_PGPROT
56 select ARCH_HAS_FORTIFY_SOURCE
57 select ARCH_HAS_GCOV_PROFILE_ALL
58 select ARCH_HAS_KCOV if X86_64
59 select ARCH_HAS_MEMBARRIER_SYNC_CORE
60 select ARCH_HAS_PMEM_API if X86_64
61 select ARCH_HAS_PTE_SPECIAL
62 select ARCH_HAS_REFCOUNT
63 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
64 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
65 select ARCH_HAS_SET_MEMORY
66 select ARCH_HAS_SET_DIRECT_MAP
67 select ARCH_HAS_STRICT_KERNEL_RWX
68 select ARCH_HAS_STRICT_MODULE_RWX
69 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
70 select ARCH_HAS_UBSAN_SANITIZE_ALL
71 select ARCH_HAS_ZONE_DEVICE if X86_64
72 select ARCH_HAVE_NMI_SAFE_CMPXCHG
73 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
74 select ARCH_MIGHT_HAVE_PC_PARPORT
75 select ARCH_MIGHT_HAVE_PC_SERIO
77 select ARCH_SUPPORTS_ACPI
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
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_JUMP_LABEL_RELATIVE
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_PREL32_RELOCATIONS
127 select HAVE_ARCH_SECCOMP_FILTER
128 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
129 select HAVE_ARCH_STACKLEAK
130 select HAVE_ARCH_TRACEHOOK
131 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
132 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
133 select HAVE_ARCH_VMAP_STACK if X86_64
134 select HAVE_ARCH_WITHIN_STACK_FRAMES
135 select HAVE_CMPXCHG_DOUBLE
136 select HAVE_CMPXCHG_LOCAL
137 select HAVE_CONTEXT_TRACKING if X86_64
138 select HAVE_COPY_THREAD_TLS
139 select HAVE_C_RECORDMCOUNT
140 select HAVE_DEBUG_KMEMLEAK
141 select HAVE_DMA_CONTIGUOUS
142 select HAVE_DYNAMIC_FTRACE
143 select HAVE_DYNAMIC_FTRACE_WITH_REGS
145 select HAVE_EFFICIENT_UNALIGNED_ACCESS
147 select HAVE_EXIT_THREAD
148 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
149 select HAVE_FTRACE_MCOUNT_RECORD
150 select HAVE_FUNCTION_GRAPH_TRACER
151 select HAVE_FUNCTION_TRACER
152 select HAVE_GCC_PLUGINS
153 select HAVE_HW_BREAKPOINT
155 select HAVE_IOREMAP_PROT
156 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
157 select HAVE_IRQ_TIME_ACCOUNTING
158 select HAVE_KERNEL_BZIP2
159 select HAVE_KERNEL_GZIP
160 select HAVE_KERNEL_LZ4
161 select HAVE_KERNEL_LZMA
162 select HAVE_KERNEL_LZO
163 select HAVE_KERNEL_XZ
165 select HAVE_KPROBES_ON_FTRACE
166 select HAVE_FUNCTION_ERROR_INJECTION
167 select HAVE_KRETPROBES
169 select HAVE_LIVEPATCH if X86_64
170 select HAVE_MEMBLOCK_NODE_MAP
171 select HAVE_MIXED_BREAKPOINTS_REGS
172 select HAVE_MOD_ARCH_SPECIFIC
176 select HAVE_OPTPROBES
177 select HAVE_PCSPKR_PLATFORM
178 select HAVE_PERF_EVENTS
179 select HAVE_PERF_EVENTS_NMI
180 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
182 select HAVE_PERF_REGS
183 select HAVE_PERF_USER_STACK_DUMP
184 select HAVE_RCU_TABLE_FREE if PARAVIRT
185 select HAVE_REGS_AND_STACK_ACCESS_API
186 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
187 select HAVE_FUNCTION_ARG_ACCESS_API
188 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
189 select HAVE_STACK_VALIDATION if X86_64
191 select HAVE_SYSCALL_TRACEPOINTS
192 select HAVE_UNSTABLE_SCHED_CLOCK
193 select HAVE_USER_RETURN_NOTIFIER
194 select HOTPLUG_SMT if SMP
195 select IRQ_FORCED_THREADING
196 select NEED_SG_DMA_LENGTH
197 select PCI_DOMAINS if PCI
198 select PCI_LOCKLESS_CONFIG if PCI
201 select RTC_MC146818_LIB
204 select SYSCTL_EXCEPTION_TRACE
205 select THREAD_INFO_IN_TASK
206 select USER_STACKTRACE_SUPPORT
208 select X86_FEATURE_NAMES if PROC_FS
210 config INSTRUCTION_DECODER
212 depends on KPROBES || PERF_EVENTS || UPROBES
216 default "elf32-i386" if X86_32
217 default "elf64-x86-64" if X86_64
219 config ARCH_DEFCONFIG
221 default "arch/x86/configs/i386_defconfig" if X86_32
222 default "arch/x86/configs/x86_64_defconfig" if X86_64
224 config LOCKDEP_SUPPORT
227 config STACKTRACE_SUPPORT
233 config ARCH_MMAP_RND_BITS_MIN
237 config ARCH_MMAP_RND_BITS_MAX
241 config ARCH_MMAP_RND_COMPAT_BITS_MIN
244 config ARCH_MMAP_RND_COMPAT_BITS_MAX
250 config GENERIC_ISA_DMA
252 depends on ISA_DMA_API
257 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
259 config GENERIC_BUG_RELATIVE_POINTERS
262 config GENERIC_HWEIGHT
265 config ARCH_MAY_HAVE_PC_FDC
267 depends on ISA_DMA_API
269 config GENERIC_CALIBRATE_DELAY
272 config ARCH_HAS_CPU_RELAX
275 config ARCH_HAS_CACHE_LINE_SIZE
278 config ARCH_HAS_FILTER_PGPROT
281 config HAVE_SETUP_PER_CPU_AREA
284 config NEED_PER_CPU_EMBED_FIRST_CHUNK
287 config NEED_PER_CPU_PAGE_FIRST_CHUNK
290 config ARCH_HIBERNATION_POSSIBLE
293 config ARCH_SUSPEND_POSSIBLE
296 config ARCH_WANT_HUGE_PMD_SHARE
299 config ARCH_WANT_GENERAL_HUGETLB
308 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
311 config KASAN_SHADOW_OFFSET
314 default 0xdffffc0000000000
316 config HAVE_INTEL_TXT
318 depends on INTEL_IOMMU && ACPI
322 depends on X86_32 && SMP
326 depends on X86_64 && SMP
328 config X86_32_LAZY_GS
330 depends on X86_32 && !STACKPROTECTOR
332 config ARCH_SUPPORTS_UPROBES
335 config FIX_EARLYCON_MEM
338 config DYNAMIC_PHYSICAL_MASK
341 config PGTABLE_LEVELS
343 default 5 if X86_5LEVEL
348 config CC_HAS_SANE_STACKPROTECTOR
350 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
351 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
353 We have to make sure stack protector is unconditionally disabled if
354 the compiler produces broken code.
356 menu "Processor type and features"
359 bool "DMA memory allocation support" if EXPERT
362 DMA memory allocation support allows devices with less than 32-bit
363 addressing to allocate within the first 16MB of address space.
364 Disable if no such devices will be used.
369 bool "Symmetric multi-processing support"
371 This enables support for systems with more than one CPU. If you have
372 a system with only one CPU, say N. If you have a system with more
375 If you say N here, the kernel will run on uni- and multiprocessor
376 machines, but will use only one CPU of a multiprocessor machine. If
377 you say Y here, the kernel will run on many, but not all,
378 uniprocessor machines. On a uniprocessor machine, the kernel
379 will run faster if you say N here.
381 Note that if you say Y here and choose architecture "586" or
382 "Pentium" under "Processor family", the kernel will not work on 486
383 architectures. Similarly, multiprocessor kernels for the "PPro"
384 architecture may not work on all Pentium based boards.
386 People using multiprocessor machines who say Y here should also say
387 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
388 Management" code will be disabled if you say Y here.
390 See also <file:Documentation/x86/i386/IO-APIC.txt>,
391 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
392 <http://www.tldp.org/docs.html#howto>.
394 If you don't know what to do here, say N.
396 config X86_FEATURE_NAMES
397 bool "Processor feature human-readable names" if EMBEDDED
400 This option compiles in a table of x86 feature bits and corresponding
401 names. This is required to support /proc/cpuinfo and a few kernel
402 messages. You can disable this to save space, at the expense of
403 making those few kernel messages show numeric feature bits instead.
408 bool "Support x2apic"
409 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
411 This enables x2apic support on CPUs that have this feature.
413 This allows 32-bit apic IDs (so it can support very large systems),
414 and accesses the local apic via MSRs not via mmio.
416 If you don't know what to do here, say N.
419 bool "Enable MPS table" if ACPI || SFI
421 depends on X86_LOCAL_APIC
423 For old smp systems that do not have proper acpi support. Newer systems
424 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
428 depends on X86_GOLDFISH
431 bool "Avoid speculative indirect branches in kernel"
433 select STACK_VALIDATION if HAVE_STACK_VALIDATION
435 Compile kernel with the retpoline compiler options to guard against
436 kernel-to-user data leaks by avoiding speculative indirect
437 branches. Requires a compiler with -mindirect-branch=thunk-extern
438 support for full protection. The kernel may run slower.
440 config X86_CPU_RESCTRL
441 bool "x86 CPU resource control support"
442 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
445 Enable x86 CPU resource control support.
447 Provide support for the allocation and monitoring of system resources
450 Intel calls this Intel Resource Director Technology
451 (Intel(R) RDT). More information about RDT can be found in the
452 Intel x86 Architecture Software Developer Manual.
454 AMD calls this AMD Platform Quality of Service (AMD QoS).
455 More information about AMD QoS can be found in the AMD64 Technology
456 Platform Quality of Service Extensions manual.
462 bool "Support for big SMP systems with more than 8 CPUs"
465 This option is needed for the systems that have more than 8 CPUs
467 config X86_EXTENDED_PLATFORM
468 bool "Support for extended (non-PC) x86 platforms"
471 If you disable this option then the kernel will only support
472 standard PC platforms. (which covers the vast majority of
475 If you enable this option then you'll be able to select support
476 for the following (non-PC) 32 bit x86 platforms:
477 Goldfish (Android emulator)
480 SGI 320/540 (Visual Workstation)
481 STA2X11-based (e.g. Northville)
482 Moorestown MID devices
484 If you have one of these systems, or if you want to build a
485 generic distribution kernel, say Y here - otherwise say N.
489 config X86_EXTENDED_PLATFORM
490 bool "Support for extended (non-PC) x86 platforms"
493 If you disable this option then the kernel will only support
494 standard PC platforms. (which covers the vast majority of
497 If you enable this option then you'll be able to select support
498 for the following (non-PC) 64 bit x86 platforms:
503 If you have one of these systems, or if you want to build a
504 generic distribution kernel, say Y here - otherwise say N.
506 # This is an alphabetically sorted list of 64 bit extended platforms
507 # Please maintain the alphabetic order if and when there are additions
509 bool "Numascale NumaChip"
511 depends on X86_EXTENDED_PLATFORM
514 depends on X86_X2APIC
515 depends on PCI_MMCONFIG
517 Adds support for Numascale NumaChip large-SMP systems. Needed to
518 enable more than ~168 cores.
519 If you don't have one of these, you should say N here.
523 select HYPERVISOR_GUEST
525 depends on X86_64 && PCI
526 depends on X86_EXTENDED_PLATFORM
529 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
530 supposed to run on these EM64T-based machines. Only choose this option
531 if you have one of these machines.
534 bool "SGI Ultraviolet"
536 depends on X86_EXTENDED_PLATFORM
539 depends on X86_X2APIC
542 This option is needed in order to support SGI Ultraviolet systems.
543 If you don't have one of these, you should say N here.
545 # Following is an alphabetically sorted list of 32 bit extended platforms
546 # Please maintain the alphabetic order if and when there are additions
549 bool "Goldfish (Virtual Platform)"
550 depends on X86_EXTENDED_PLATFORM
552 Enable support for the Goldfish virtual platform used primarily
553 for Android development. Unless you are building for the Android
554 Goldfish emulator say N here.
557 bool "CE4100 TV platform"
559 depends on PCI_GODIRECT
560 depends on X86_IO_APIC
562 depends on X86_EXTENDED_PLATFORM
563 select X86_REBOOTFIXUPS
565 select OF_EARLY_FLATTREE
567 Select for the Intel CE media processor (CE4100) SOC.
568 This option compiles in support for the CE4100 SOC for settop
569 boxes and media devices.
572 bool "Intel MID platform support"
573 depends on X86_EXTENDED_PLATFORM
574 depends on X86_PLATFORM_DEVICES
576 depends on X86_64 || (PCI_GOANY && X86_32)
577 depends on X86_IO_APIC
583 select MFD_INTEL_MSIC
585 Select to build a kernel capable of supporting Intel MID (Mobile
586 Internet Device) platform systems which do not have the PCI legacy
587 interfaces. If you are building for a PC class system say N here.
589 Intel MID platforms are based on an Intel processor and chipset which
590 consume less power than most of the x86 derivatives.
592 config X86_INTEL_QUARK
593 bool "Intel Quark platform support"
595 depends on X86_EXTENDED_PLATFORM
596 depends on X86_PLATFORM_DEVICES
600 depends on X86_IO_APIC
605 Select to include support for Quark X1000 SoC.
606 Say Y here if you have a Quark based system such as the Arduino
607 compatible Intel Galileo.
609 config X86_INTEL_LPSS
610 bool "Intel Low Power Subsystem Support"
611 depends on X86 && ACPI && PCI
616 Select to build support for Intel Low Power Subsystem such as
617 found on Intel Lynxpoint PCH. Selecting this option enables
618 things like clock tree (common clock framework) and pincontrol
619 which are needed by the LPSS peripheral drivers.
621 config X86_AMD_PLATFORM_DEVICE
622 bool "AMD ACPI2Platform devices support"
627 Select to interpret AMD specific ACPI device to platform device
628 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
629 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
630 implemented under PINCTRL subsystem.
633 tristate "Intel SoC IOSF Sideband support for SoC platforms"
636 This option enables sideband register access support for Intel SoC
637 platforms. On these platforms the IOSF sideband is used in lieu of
638 MSR's for some register accesses, mostly but not limited to thermal
639 and power. Drivers may query the availability of this device to
640 determine if they need the sideband in order to work on these
641 platforms. The sideband is available on the following SoC products.
642 This list is not meant to be exclusive.
647 You should say Y if you are running a kernel on one of these SoC's.
649 config IOSF_MBI_DEBUG
650 bool "Enable IOSF sideband access through debugfs"
651 depends on IOSF_MBI && DEBUG_FS
653 Select this option to expose the IOSF sideband access registers (MCR,
654 MDR, MCRX) through debugfs to write and read register information from
655 different units on the SoC. This is most useful for obtaining device
656 state information for debug and analysis. As this is a general access
657 mechanism, users of this option would have specific knowledge of the
658 device they want to access.
660 If you don't require the option or are in doubt, say N.
663 bool "RDC R-321x SoC"
665 depends on X86_EXTENDED_PLATFORM
667 select X86_REBOOTFIXUPS
669 This option is needed for RDC R-321x system-on-chip, also known
671 If you don't have one of these chips, you should say N here.
673 config X86_32_NON_STANDARD
674 bool "Support non-standard 32-bit SMP architectures"
675 depends on X86_32 && SMP
676 depends on X86_EXTENDED_PLATFORM
678 This option compiles in the bigsmp and STA2X11 default
679 subarchitectures. It is intended for a generic binary
680 kernel. If you select them all, kernel will probe it one by
681 one and will fallback to default.
683 # Alphabetically sorted list of Non standard 32 bit platforms
685 config X86_SUPPORTS_MEMORY_FAILURE
687 # MCE code calls memory_failure():
689 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
690 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
691 depends on X86_64 || !SPARSEMEM
692 select ARCH_SUPPORTS_MEMORY_FAILURE
695 bool "STA2X11 Companion Chip Support"
696 depends on X86_32_NON_STANDARD && PCI
697 select ARCH_HAS_PHYS_TO_DMA
702 This adds support for boards based on the STA2X11 IO-Hub,
703 a.k.a. "ConneXt". The chip is used in place of the standard
704 PC chipset, so all "standard" peripherals are missing. If this
705 option is selected the kernel will still be able to boot on
706 standard PC machines.
709 tristate "Eurobraille/Iris poweroff module"
712 The Iris machines from EuroBraille do not have APM or ACPI support
713 to shut themselves down properly. A special I/O sequence is
714 needed to do so, which is what this module does at
717 This is only for Iris machines from EuroBraille.
721 config SCHED_OMIT_FRAME_POINTER
723 prompt "Single-depth WCHAN output"
726 Calculate simpler /proc/<PID>/wchan values. If this option
727 is disabled then wchan values will recurse back to the
728 caller function. This provides more accurate wchan values,
729 at the expense of slightly more scheduling overhead.
731 If in doubt, say "Y".
733 menuconfig HYPERVISOR_GUEST
734 bool "Linux guest support"
736 Say Y here to enable options for running Linux under various hyper-
737 visors. This option enables basic hypervisor detection and platform
740 If you say N, all options in this submenu will be skipped and
741 disabled, and Linux guest support won't be built in.
746 bool "Enable paravirtualization code"
748 This changes the kernel so it can modify itself when it is run
749 under a hypervisor, potentially improving performance significantly
750 over full virtualization. However, when run without a hypervisor
751 the kernel is theoretically slower and slightly larger.
756 config PARAVIRT_DEBUG
757 bool "paravirt-ops debugging"
758 depends on PARAVIRT && DEBUG_KERNEL
760 Enable to debug paravirt_ops internals. Specifically, BUG if
761 a paravirt_op is missing when it is called.
763 config PARAVIRT_SPINLOCKS
764 bool "Paravirtualization layer for spinlocks"
765 depends on PARAVIRT && SMP
767 Paravirtualized spinlocks allow a pvops backend to replace the
768 spinlock implementation with something virtualization-friendly
769 (for example, block the virtual CPU rather than spinning).
771 It has a minimal impact on native kernels and gives a nice performance
772 benefit on paravirtualized KVM / Xen kernels.
774 If you are unsure how to answer this question, answer Y.
776 source "arch/x86/xen/Kconfig"
779 bool "KVM Guest support (including kvmclock)"
781 select PARAVIRT_CLOCK
784 This option enables various optimizations for running under the KVM
785 hypervisor. It includes a paravirtualized clock, so that instead
786 of relying on a PIT (or probably other) emulation by the
787 underlying device model, the host provides the guest with
788 timing infrastructure such as time of day, and system time
791 bool "Support for running PVH guests"
793 This option enables the PVH entry point for guest virtual machines
794 as specified in the x86/HVM direct boot ABI.
797 bool "Enable debug information for KVM Guests in debugfs"
798 depends on KVM_GUEST && DEBUG_FS
800 This option enables collection of various statistics for KVM guest.
801 Statistics are displayed in debugfs filesystem. Enabling this option
802 may incur significant overhead.
804 config PARAVIRT_TIME_ACCOUNTING
805 bool "Paravirtual steal time accounting"
808 Select this option to enable fine granularity task steal time
809 accounting. Time spent executing other tasks in parallel with
810 the current vCPU is discounted from the vCPU power. To account for
811 that, there can be a small performance impact.
813 If in doubt, say N here.
815 config PARAVIRT_CLOCK
818 config JAILHOUSE_GUEST
819 bool "Jailhouse non-root cell support"
820 depends on X86_64 && PCI
823 This option allows to run Linux as guest in a Jailhouse non-root
824 cell. You can leave this option disabled if you only want to start
825 Jailhouse and run Linux afterwards in the root cell.
827 endif #HYPERVISOR_GUEST
829 source "arch/x86/Kconfig.cpu"
833 prompt "HPET Timer Support" if X86_32
835 Use the IA-PC HPET (High Precision Event Timer) to manage
836 time in preference to the PIT and RTC, if a HPET is
838 HPET is the next generation timer replacing legacy 8254s.
839 The HPET provides a stable time base on SMP
840 systems, unlike the TSC, but it is more expensive to access,
841 as it is off-chip. The interface used is documented
842 in the HPET spec, revision 1.
844 You can safely choose Y here. However, HPET will only be
845 activated if the platform and the BIOS support this feature.
846 Otherwise the 8254 will be used for timing services.
848 Choose N to continue using the legacy 8254 timer.
850 config HPET_EMULATE_RTC
852 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
855 def_bool y if X86_INTEL_MID
856 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
858 depends on X86_INTEL_MID && SFI
860 APB timer is the replacement for 8254, HPET on X86 MID platforms.
861 The APBT provides a stable time base on SMP
862 systems, unlike the TSC, but it is more expensive to access,
863 as it is off-chip. APB timers are always running regardless of CPU
864 C states, they are used as per CPU clockevent device when possible.
866 # Mark as expert because too many people got it wrong.
867 # The code disables itself when not needed.
870 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
871 bool "Enable DMI scanning" if EXPERT
873 Enabled scanning of DMI to identify machine quirks. Say Y
874 here unless you have verified that your setup is not
875 affected by entries in the DMI blacklist. Required by PNP
879 bool "Old AMD GART IOMMU support"
882 depends on X86_64 && PCI && AMD_NB
884 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
885 GART based hardware IOMMUs.
887 The GART supports full DMA access for devices with 32-bit access
888 limitations, on systems with more than 3 GB. This is usually needed
889 for USB, sound, many IDE/SATA chipsets and some other devices.
891 Newer systems typically have a modern AMD IOMMU, supported via
892 the CONFIG_AMD_IOMMU=y config option.
894 In normal configurations this driver is only active when needed:
895 there's more than 3 GB of memory and the system contains a
896 32-bit limited device.
901 bool "IBM Calgary IOMMU support"
904 depends on X86_64 && PCI
906 Support for hardware IOMMUs in IBM's xSeries x366 and x460
907 systems. Needed to run systems with more than 3GB of memory
908 properly with 32-bit PCI devices that do not support DAC
909 (Double Address Cycle). Calgary also supports bus level
910 isolation, where all DMAs pass through the IOMMU. This
911 prevents them from going anywhere except their intended
912 destination. This catches hard-to-find kernel bugs and
913 mis-behaving drivers and devices that do not use the DMA-API
914 properly to set up their DMA buffers. The IOMMU can be
915 turned off at boot time with the iommu=off parameter.
916 Normally the kernel will make the right choice by itself.
919 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
921 prompt "Should Calgary be enabled by default?"
922 depends on CALGARY_IOMMU
924 Should Calgary be enabled by default? if you choose 'y', Calgary
925 will be used (if it exists). If you choose 'n', Calgary will not be
926 used even if it exists. If you choose 'n' and would like to use
927 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
931 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
932 depends on X86_64 && SMP && DEBUG_KERNEL
933 select CPUMASK_OFFSTACK
935 Enable maximum number of CPUS and NUMA Nodes for this architecture.
939 # The maximum number of CPUs supported:
941 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
942 # and which can be configured interactively in the
943 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
945 # The ranges are different on 32-bit and 64-bit kernels, depending on
946 # hardware capabilities and scalability features of the kernel.
948 # ( If MAXSMP is enabled we just use the highest possible value and disable
949 # interactive configuration. )
952 config NR_CPUS_RANGE_BEGIN
954 default NR_CPUS_RANGE_END if MAXSMP
958 config NR_CPUS_RANGE_END
961 default 64 if SMP && X86_BIGSMP
962 default 8 if SMP && !X86_BIGSMP
965 config NR_CPUS_RANGE_END
968 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
969 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
972 config NR_CPUS_DEFAULT
975 default 32 if X86_BIGSMP
979 config NR_CPUS_DEFAULT
982 default 8192 if MAXSMP
987 int "Maximum number of CPUs" if SMP && !MAXSMP
988 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
989 default NR_CPUS_DEFAULT
991 This allows you to specify the maximum number of CPUs which this
992 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
993 supported value is 8192, otherwise the maximum value is 512. The
994 minimum value which makes sense is 2.
996 This is purely to save memory: each supported CPU adds about 8KB
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.
1034 depends on !SMP && X86_LOCAL_APIC
1037 bool "Local APIC support on uniprocessors" if !PCI_MSI
1039 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1041 A local APIC (Advanced Programmable Interrupt Controller) is an
1042 integrated interrupt controller in the CPU. If you have a single-CPU
1043 system which has a processor with a local APIC, you can say Y here to
1044 enable and use it. If you say Y here even though your machine doesn't
1045 have a local APIC, then the kernel will still run with no slowdown at
1046 all. The local APIC supports CPU-generated self-interrupts (timer,
1047 performance counters), and the NMI watchdog which detects hard
1050 config X86_UP_IOAPIC
1051 bool "IO-APIC support on uniprocessors"
1052 depends on X86_UP_APIC
1054 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1055 SMP-capable replacement for PC-style interrupt controllers. Most
1056 SMP systems and many recent uniprocessor systems have one.
1058 If you have a single-CPU system with an IO-APIC, you can say Y here
1059 to use it. If you say Y here even though your machine doesn't have
1060 an IO-APIC, then the kernel will still run with no slowdown at all.
1062 config X86_LOCAL_APIC
1064 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1065 select IRQ_DOMAIN_HIERARCHY
1066 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1070 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1072 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1073 bool "Reroute for broken boot IRQs"
1074 depends on X86_IO_APIC
1076 This option enables a workaround that fixes a source of
1077 spurious interrupts. This is recommended when threaded
1078 interrupt handling is used on systems where the generation of
1079 superfluous "boot interrupts" cannot be disabled.
1081 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1082 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1083 kernel does during interrupt handling). On chipsets where this
1084 boot IRQ generation cannot be disabled, this workaround keeps
1085 the original IRQ line masked so that only the equivalent "boot
1086 IRQ" is delivered to the CPUs. The workaround also tells the
1087 kernel to set up the IRQ handler on the boot IRQ line. In this
1088 way only one interrupt is delivered to the kernel. Otherwise
1089 the spurious second interrupt may cause the kernel to bring
1090 down (vital) interrupt lines.
1092 Only affects "broken" chipsets. Interrupt sharing may be
1093 increased on these systems.
1096 bool "Machine Check / overheating reporting"
1097 select GENERIC_ALLOCATOR
1100 Machine Check support allows the processor to notify the
1101 kernel if it detects a problem (e.g. overheating, data corruption).
1102 The action the kernel takes depends on the severity of the problem,
1103 ranging from warning messages to halting the machine.
1105 config X86_MCELOG_LEGACY
1106 bool "Support for deprecated /dev/mcelog character device"
1109 Enable support for /dev/mcelog which is needed by the old mcelog
1110 userspace logging daemon. Consider switching to the new generation
1113 config X86_MCE_INTEL
1115 prompt "Intel MCE features"
1116 depends on X86_MCE && X86_LOCAL_APIC
1118 Additional support for intel specific MCE features such as
1119 the thermal monitor.
1123 prompt "AMD MCE features"
1124 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1126 Additional support for AMD specific MCE features such as
1127 the DRAM Error Threshold.
1129 config X86_ANCIENT_MCE
1130 bool "Support for old Pentium 5 / WinChip machine checks"
1131 depends on X86_32 && X86_MCE
1133 Include support for machine check handling on old Pentium 5 or WinChip
1134 systems. These typically need to be enabled explicitly on the command
1137 config X86_MCE_THRESHOLD
1138 depends on X86_MCE_AMD || X86_MCE_INTEL
1141 config X86_MCE_INJECT
1142 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1143 tristate "Machine check injector support"
1145 Provide support for injecting machine checks for testing purposes.
1146 If you don't know what a machine check is and you don't do kernel
1147 QA it is safe to say n.
1149 config X86_THERMAL_VECTOR
1151 depends on X86_MCE_INTEL
1153 source "arch/x86/events/Kconfig"
1155 config X86_LEGACY_VM86
1156 bool "Legacy VM86 support"
1159 This option allows user programs to put the CPU into V8086
1160 mode, which is an 80286-era approximation of 16-bit real mode.
1162 Some very old versions of X and/or vbetool require this option
1163 for user mode setting. Similarly, DOSEMU will use it if
1164 available to accelerate real mode DOS programs. However, any
1165 recent version of DOSEMU, X, or vbetool should be fully
1166 functional even without kernel VM86 support, as they will all
1167 fall back to software emulation. Nevertheless, if you are using
1168 a 16-bit DOS program where 16-bit performance matters, vm86
1169 mode might be faster than emulation and you might want to
1172 Note that any app that works on a 64-bit kernel is unlikely to
1173 need this option, as 64-bit kernels don't, and can't, support
1174 V8086 mode. This option is also unrelated to 16-bit protected
1175 mode and is not needed to run most 16-bit programs under Wine.
1177 Enabling this option increases the complexity of the kernel
1178 and slows down exception handling a tiny bit.
1180 If unsure, say N here.
1184 default X86_LEGACY_VM86
1187 bool "Enable support for 16-bit segments" if EXPERT
1189 depends on MODIFY_LDT_SYSCALL
1191 This option is required by programs like Wine to run 16-bit
1192 protected mode legacy code on x86 processors. Disabling
1193 this option saves about 300 bytes on i386, or around 6K text
1194 plus 16K runtime memory on x86-64,
1198 depends on X86_16BIT && X86_32
1202 depends on X86_16BIT && X86_64
1204 config X86_VSYSCALL_EMULATION
1205 bool "Enable vsyscall emulation" if EXPERT
1209 This enables emulation of the legacy vsyscall page. Disabling
1210 it is roughly equivalent to booting with vsyscall=none, except
1211 that it will also disable the helpful warning if a program
1212 tries to use a vsyscall. With this option set to N, offending
1213 programs will just segfault, citing addresses of the form
1216 This option is required by many programs built before 2013, and
1217 care should be used even with newer programs if set to N.
1219 Disabling this option saves about 7K of kernel size and
1220 possibly 4K of additional runtime pagetable memory.
1223 tristate "Toshiba Laptop support"
1226 This adds a driver to safely access the System Management Mode of
1227 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1228 not work on models with a Phoenix BIOS. The System Management Mode
1229 is used to set the BIOS and power saving options on Toshiba portables.
1231 For information on utilities to make use of this driver see the
1232 Toshiba Linux utilities web site at:
1233 <http://www.buzzard.org.uk/toshiba/>.
1235 Say Y if you intend to run this kernel on a Toshiba portable.
1239 tristate "Dell i8k legacy laptop support"
1241 select SENSORS_DELL_SMM
1243 This option enables legacy /proc/i8k userspace interface in hwmon
1244 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1245 temperature and allows controlling fan speeds of Dell laptops via
1246 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1247 it reports also power and hotkey status. For fan speed control is
1248 needed userspace package i8kutils.
1250 Say Y if you intend to run this kernel on old Dell laptops or want to
1251 use userspace package i8kutils.
1254 config X86_REBOOTFIXUPS
1255 bool "Enable X86 board specific fixups for reboot"
1258 This enables chipset and/or board specific fixups to be done
1259 in order to get reboot to work correctly. This is only needed on
1260 some combinations of hardware and BIOS. The symptom, for which
1261 this config is intended, is when reboot ends with a stalled/hung
1264 Currently, the only fixup is for the Geode machines using
1265 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1267 Say Y if you want to enable the fixup. Currently, it's safe to
1268 enable this option even if you don't need it.
1272 bool "CPU microcode loading support"
1274 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1277 If you say Y here, you will be able to update the microcode on
1278 Intel and AMD processors. The Intel support is for the IA32 family,
1279 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1280 AMD support is for families 0x10 and later. You will obviously need
1281 the actual microcode binary data itself which is not shipped with
1284 The preferred method to load microcode from a detached initrd is described
1285 in Documentation/x86/microcode.txt. For that you need to enable
1286 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1287 initrd for microcode blobs.
1289 In addition, you can build the microcode into the kernel. For that you
1290 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1293 config MICROCODE_INTEL
1294 bool "Intel microcode loading support"
1295 depends on MICROCODE
1299 This options enables microcode patch loading support for Intel
1302 For the current Intel microcode data package go to
1303 <https://downloadcenter.intel.com> and search for
1304 'Linux Processor Microcode Data File'.
1306 config MICROCODE_AMD
1307 bool "AMD microcode loading support"
1308 depends on MICROCODE
1311 If you select this option, microcode patch loading support for AMD
1312 processors will be enabled.
1314 config MICROCODE_OLD_INTERFACE
1315 bool "Ancient loading interface (DEPRECATED)"
1317 depends on MICROCODE
1319 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1320 which was used by userspace tools like iucode_tool and microcode.ctl.
1321 It is inadequate because it runs too late to be able to properly
1322 load microcode on a machine and it needs special tools. Instead, you
1323 should've switched to the early loading method with the initrd or
1324 builtin microcode by now: Documentation/x86/microcode.txt
1327 tristate "/dev/cpu/*/msr - Model-specific register support"
1329 This device gives privileged processes access to the x86
1330 Model-Specific Registers (MSRs). It is a character device with
1331 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1332 MSR accesses are directed to a specific CPU on multi-processor
1336 tristate "/dev/cpu/*/cpuid - CPU information support"
1338 This device gives processes access to the x86 CPUID instruction to
1339 be executed on a specific processor. It is a character device
1340 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1344 prompt "High Memory Support"
1351 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1352 However, the address space of 32-bit x86 processors is only 4
1353 Gigabytes large. That means that, if you have a large amount of
1354 physical memory, not all of it can be "permanently mapped" by the
1355 kernel. The physical memory that's not permanently mapped is called
1358 If you are compiling a kernel which will never run on a machine with
1359 more than 1 Gigabyte total physical RAM, answer "off" here (default
1360 choice and suitable for most users). This will result in a "3GB/1GB"
1361 split: 3GB are mapped so that each process sees a 3GB virtual memory
1362 space and the remaining part of the 4GB virtual memory space is used
1363 by the kernel to permanently map as much physical memory as
1366 If the machine has between 1 and 4 Gigabytes physical RAM, then
1369 If more than 4 Gigabytes is used then answer "64GB" here. This
1370 selection turns Intel PAE (Physical Address Extension) mode on.
1371 PAE implements 3-level paging on IA32 processors. PAE is fully
1372 supported by Linux, PAE mode is implemented on all recent Intel
1373 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1374 then the kernel will not boot on CPUs that don't support PAE!
1376 The actual amount of total physical memory will either be
1377 auto detected or can be forced by using a kernel command line option
1378 such as "mem=256M". (Try "man bootparam" or see the documentation of
1379 your boot loader (lilo or loadlin) about how to pass options to the
1380 kernel at boot time.)
1382 If unsure, say "off".
1387 Select this if you have a 32-bit processor and between 1 and 4
1388 gigabytes of physical RAM.
1392 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1395 Select this if you have a 32-bit processor and more than 4
1396 gigabytes of physical RAM.
1401 prompt "Memory split" if EXPERT
1405 Select the desired split between kernel and user memory.
1407 If the address range available to the kernel is less than the
1408 physical memory installed, the remaining memory will be available
1409 as "high memory". Accessing high memory is a little more costly
1410 than low memory, as it needs to be mapped into the kernel first.
1411 Note that increasing the kernel address space limits the range
1412 available to user programs, making the address space there
1413 tighter. Selecting anything other than the default 3G/1G split
1414 will also likely make your kernel incompatible with binary-only
1417 If you are not absolutely sure what you are doing, leave this
1421 bool "3G/1G user/kernel split"
1422 config VMSPLIT_3G_OPT
1424 bool "3G/1G user/kernel split (for full 1G low memory)"
1426 bool "2G/2G user/kernel split"
1427 config VMSPLIT_2G_OPT
1429 bool "2G/2G user/kernel split (for full 2G low memory)"
1431 bool "1G/3G user/kernel split"
1436 default 0xB0000000 if VMSPLIT_3G_OPT
1437 default 0x80000000 if VMSPLIT_2G
1438 default 0x78000000 if VMSPLIT_2G_OPT
1439 default 0x40000000 if VMSPLIT_1G
1445 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1448 bool "PAE (Physical Address Extension) Support"
1449 depends on X86_32 && !HIGHMEM4G
1450 select PHYS_ADDR_T_64BIT
1453 PAE is required for NX support, and furthermore enables
1454 larger swapspace support for non-overcommit purposes. It
1455 has the cost of more pagetable lookup overhead, and also
1456 consumes more pagetable space per process.
1459 bool "Enable 5-level page tables support"
1460 select DYNAMIC_MEMORY_LAYOUT
1461 select SPARSEMEM_VMEMMAP
1464 5-level paging enables access to larger address space:
1465 upto 128 PiB of virtual address space and 4 PiB of
1466 physical address space.
1468 It will be supported by future Intel CPUs.
1470 A kernel with the option enabled can be booted on machines that
1471 support 4- or 5-level paging.
1473 See Documentation/x86/x86_64/5level-paging.txt for more
1478 config X86_DIRECT_GBPAGES
1480 depends on X86_64 && !DEBUG_PAGEALLOC
1482 Certain kernel features effectively disable kernel
1483 linear 1 GB mappings (even if the CPU otherwise
1484 supports them), so don't confuse the user by printing
1485 that we have them enabled.
1487 config X86_CPA_STATISTICS
1488 bool "Enable statistic for Change Page Attribute"
1491 Expose statistics about the Change Page Attribute mechanims, which
1492 helps to determine the effectiveness of preserving large and huge
1493 page mappings when mapping protections are changed.
1495 config ARCH_HAS_MEM_ENCRYPT
1498 config AMD_MEM_ENCRYPT
1499 bool "AMD Secure Memory Encryption (SME) support"
1500 depends on X86_64 && CPU_SUP_AMD
1501 select DYNAMIC_PHYSICAL_MASK
1502 select ARCH_USE_MEMREMAP_PROT
1504 Say yes to enable support for the encryption of system memory.
1505 This requires an AMD processor that supports Secure Memory
1508 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1509 bool "Activate AMD Secure Memory Encryption (SME) by default"
1511 depends on AMD_MEM_ENCRYPT
1513 Say yes to have system memory encrypted by default if running on
1514 an AMD processor that supports Secure Memory Encryption (SME).
1516 If set to Y, then the encryption of system memory can be
1517 deactivated with the mem_encrypt=off command line option.
1519 If set to N, then the encryption of system memory can be
1520 activated with the mem_encrypt=on command line option.
1522 # Common NUMA Features
1524 bool "Numa Memory Allocation and Scheduler Support"
1526 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1527 default y if X86_BIGSMP
1529 Enable NUMA (Non Uniform Memory Access) support.
1531 The kernel will try to allocate memory used by a CPU on the
1532 local memory controller of the CPU and add some more
1533 NUMA awareness to the kernel.
1535 For 64-bit this is recommended if the system is Intel Core i7
1536 (or later), AMD Opteron, or EM64T NUMA.
1538 For 32-bit this is only needed if you boot a 32-bit
1539 kernel on a 64-bit NUMA platform.
1541 Otherwise, you should say N.
1545 prompt "Old style AMD Opteron NUMA detection"
1546 depends on X86_64 && NUMA && PCI
1548 Enable AMD NUMA node topology detection. You should say Y here if
1549 you have a multi processor AMD system. This uses an old method to
1550 read the NUMA configuration directly from the builtin Northbridge
1551 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1552 which also takes priority if both are compiled in.
1554 config X86_64_ACPI_NUMA
1556 prompt "ACPI NUMA detection"
1557 depends on X86_64 && NUMA && ACPI && PCI
1560 Enable ACPI SRAT based node topology detection.
1562 # Some NUMA nodes have memory ranges that span
1563 # other nodes. Even though a pfn is valid and
1564 # between a node's start and end pfns, it may not
1565 # reside on that node. See memmap_init_zone()
1567 config NODES_SPAN_OTHER_NODES
1569 depends on X86_64_ACPI_NUMA
1572 bool "NUMA emulation"
1575 Enable NUMA emulation. A flat machine will be split
1576 into virtual nodes when booted with "numa=fake=N", where N is the
1577 number of nodes. This is only useful for debugging.
1580 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1582 default "10" if MAXSMP
1583 default "6" if X86_64
1585 depends on NEED_MULTIPLE_NODES
1587 Specify the maximum number of NUMA Nodes available on the target
1588 system. Increases memory reserved to accommodate various tables.
1590 config ARCH_HAVE_MEMORY_PRESENT
1592 depends on X86_32 && DISCONTIGMEM
1594 config ARCH_FLATMEM_ENABLE
1596 depends on X86_32 && !NUMA
1598 config ARCH_DISCONTIGMEM_ENABLE
1600 depends on NUMA && X86_32
1603 config ARCH_SPARSEMEM_ENABLE
1605 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1606 select SPARSEMEM_STATIC if X86_32
1607 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1609 config ARCH_SPARSEMEM_DEFAULT
1610 def_bool X86_64 || (NUMA && X86_32)
1612 config ARCH_SELECT_MEMORY_MODEL
1614 depends on ARCH_SPARSEMEM_ENABLE
1616 config ARCH_MEMORY_PROBE
1617 bool "Enable sysfs memory/probe interface"
1618 depends on X86_64 && MEMORY_HOTPLUG
1620 This option enables a sysfs memory/probe interface for testing.
1621 See Documentation/memory-hotplug.txt for more information.
1622 If you are unsure how to answer this question, answer N.
1624 config ARCH_PROC_KCORE_TEXT
1626 depends on X86_64 && PROC_KCORE
1628 config ILLEGAL_POINTER_VALUE
1631 default 0xdead000000000000 if X86_64
1633 config X86_PMEM_LEGACY_DEVICE
1636 config X86_PMEM_LEGACY
1637 tristate "Support non-standard NVDIMMs and ADR protected memory"
1638 depends on PHYS_ADDR_T_64BIT
1640 select X86_PMEM_LEGACY_DEVICE
1643 Treat memory marked using the non-standard e820 type of 12 as used
1644 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1645 The kernel will offer these regions to the 'pmem' driver so
1646 they can be used for persistent storage.
1651 bool "Allocate 3rd-level pagetables from highmem"
1654 The VM uses one page table entry for each page of physical memory.
1655 For systems with a lot of RAM, this can be wasteful of precious
1656 low memory. Setting this option will put user-space page table
1657 entries in high memory.
1659 config X86_CHECK_BIOS_CORRUPTION
1660 bool "Check for low memory corruption"
1662 Periodically check for memory corruption in low memory, which
1663 is suspected to be caused by BIOS. Even when enabled in the
1664 configuration, it is disabled at runtime. Enable it by
1665 setting "memory_corruption_check=1" on the kernel command
1666 line. By default it scans the low 64k of memory every 60
1667 seconds; see the memory_corruption_check_size and
1668 memory_corruption_check_period parameters in
1669 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1671 When enabled with the default parameters, this option has
1672 almost no overhead, as it reserves a relatively small amount
1673 of memory and scans it infrequently. It both detects corruption
1674 and prevents it from affecting the running system.
1676 It is, however, intended as a diagnostic tool; if repeatable
1677 BIOS-originated corruption always affects the same memory,
1678 you can use memmap= to prevent the kernel from using that
1681 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1682 bool "Set the default setting of memory_corruption_check"
1683 depends on X86_CHECK_BIOS_CORRUPTION
1686 Set whether the default state of memory_corruption_check is
1689 config X86_RESERVE_LOW
1690 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1694 Specify the amount of low memory to reserve for the BIOS.
1696 The first page contains BIOS data structures that the kernel
1697 must not use, so that page must always be reserved.
1699 By default we reserve the first 64K of physical RAM, as a
1700 number of BIOSes are known to corrupt that memory range
1701 during events such as suspend/resume or monitor cable
1702 insertion, so it must not be used by the kernel.
1704 You can set this to 4 if you are absolutely sure that you
1705 trust the BIOS to get all its memory reservations and usages
1706 right. If you know your BIOS have problems beyond the
1707 default 64K area, you can set this to 640 to avoid using the
1708 entire low memory range.
1710 If you have doubts about the BIOS (e.g. suspend/resume does
1711 not work or there's kernel crashes after certain hardware
1712 hotplug events) then you might want to enable
1713 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1714 typical corruption patterns.
1716 Leave this to the default value of 64 if you are unsure.
1718 config MATH_EMULATION
1720 depends on MODIFY_LDT_SYSCALL
1721 prompt "Math emulation" if X86_32
1723 Linux can emulate a math coprocessor (used for floating point
1724 operations) if you don't have one. 486DX and Pentium processors have
1725 a math coprocessor built in, 486SX and 386 do not, unless you added
1726 a 487DX or 387, respectively. (The messages during boot time can
1727 give you some hints here ["man dmesg"].) Everyone needs either a
1728 coprocessor or this emulation.
1730 If you don't have a math coprocessor, you need to say Y here; if you
1731 say Y here even though you have a coprocessor, the coprocessor will
1732 be used nevertheless. (This behavior can be changed with the kernel
1733 command line option "no387", which comes handy if your coprocessor
1734 is broken. Try "man bootparam" or see the documentation of your boot
1735 loader (lilo or loadlin) about how to pass options to the kernel at
1736 boot time.) This means that it is a good idea to say Y here if you
1737 intend to use this kernel on different machines.
1739 More information about the internals of the Linux math coprocessor
1740 emulation can be found in <file:arch/x86/math-emu/README>.
1742 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1743 kernel, it won't hurt.
1747 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1749 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1750 the Memory Type Range Registers (MTRRs) may be used to control
1751 processor access to memory ranges. This is most useful if you have
1752 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1753 allows bus write transfers to be combined into a larger transfer
1754 before bursting over the PCI/AGP bus. This can increase performance
1755 of image write operations 2.5 times or more. Saying Y here creates a
1756 /proc/mtrr file which may be used to manipulate your processor's
1757 MTRRs. Typically the X server should use this.
1759 This code has a reasonably generic interface so that similar
1760 control registers on other processors can be easily supported
1763 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1764 Registers (ARRs) which provide a similar functionality to MTRRs. For
1765 these, the ARRs are used to emulate the MTRRs.
1766 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1767 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1768 write-combining. All of these processors are supported by this code
1769 and it makes sense to say Y here if you have one of them.
1771 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1772 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1773 can lead to all sorts of problems, so it's good to say Y here.
1775 You can safely say Y even if your machine doesn't have MTRRs, you'll
1776 just add about 9 KB to your kernel.
1778 See <file:Documentation/x86/mtrr.txt> for more information.
1780 config MTRR_SANITIZER
1782 prompt "MTRR cleanup support"
1785 Convert MTRR layout from continuous to discrete, so X drivers can
1786 add writeback entries.
1788 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1789 The largest mtrr entry size for a continuous block can be set with
1794 config MTRR_SANITIZER_ENABLE_DEFAULT
1795 int "MTRR cleanup enable value (0-1)"
1798 depends on MTRR_SANITIZER
1800 Enable mtrr cleanup default value
1802 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1803 int "MTRR cleanup spare reg num (0-7)"
1806 depends on MTRR_SANITIZER
1808 mtrr cleanup spare entries default, it can be changed via
1809 mtrr_spare_reg_nr=N on the kernel command line.
1813 prompt "x86 PAT support" if EXPERT
1816 Use PAT attributes to setup page level cache control.
1818 PATs are the modern equivalents of MTRRs and are much more
1819 flexible than MTRRs.
1821 Say N here if you see bootup problems (boot crash, boot hang,
1822 spontaneous reboots) or a non-working video driver.
1826 config ARCH_USES_PG_UNCACHED
1832 prompt "x86 architectural random number generator" if EXPERT
1834 Enable the x86 architectural RDRAND instruction
1835 (Intel Bull Mountain technology) to generate random numbers.
1836 If supported, this is a high bandwidth, cryptographically
1837 secure hardware random number generator.
1841 prompt "Supervisor Mode Access Prevention" if EXPERT
1843 Supervisor Mode Access Prevention (SMAP) is a security
1844 feature in newer Intel processors. There is a small
1845 performance cost if this enabled and turned on; there is
1846 also a small increase in the kernel size if this is enabled.
1850 config X86_INTEL_UMIP
1852 depends on CPU_SUP_INTEL
1853 prompt "Intel User Mode Instruction Prevention" if EXPERT
1855 The User Mode Instruction Prevention (UMIP) is a security
1856 feature in newer Intel processors. If enabled, a general
1857 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1858 or STR instructions are executed in user mode. These instructions
1859 unnecessarily expose information about the hardware state.
1861 The vast majority of applications do not use these instructions.
1862 For the very few that do, software emulation is provided in
1863 specific cases in protected and virtual-8086 modes. Emulated
1866 config X86_INTEL_MPX
1867 prompt "Intel MPX (Memory Protection Extensions)"
1869 # Note: only available in 64-bit mode due to VMA flags shortage
1870 depends on CPU_SUP_INTEL && X86_64
1871 select ARCH_USES_HIGH_VMA_FLAGS
1873 MPX provides hardware features that can be used in
1874 conjunction with compiler-instrumented code to check
1875 memory references. It is designed to detect buffer
1876 overflow or underflow bugs.
1878 This option enables running applications which are
1879 instrumented or otherwise use MPX. It does not use MPX
1880 itself inside the kernel or to protect the kernel
1881 against bad memory references.
1883 Enabling this option will make the kernel larger:
1884 ~8k of kernel text and 36 bytes of data on a 64-bit
1885 defconfig. It adds a long to the 'mm_struct' which
1886 will increase the kernel memory overhead of each
1887 process and adds some branches to paths used during
1888 exec() and munmap().
1890 For details, see Documentation/x86/intel_mpx.txt
1894 config X86_INTEL_MEMORY_PROTECTION_KEYS
1895 prompt "Intel Memory Protection Keys"
1897 # Note: only available in 64-bit mode
1898 depends on CPU_SUP_INTEL && X86_64
1899 select ARCH_USES_HIGH_VMA_FLAGS
1900 select ARCH_HAS_PKEYS
1902 Memory Protection Keys provides a mechanism for enforcing
1903 page-based protections, but without requiring modification of the
1904 page tables when an application changes protection domains.
1906 For details, see Documentation/x86/protection-keys.txt
1911 bool "EFI runtime service support"
1914 select EFI_RUNTIME_WRAPPERS
1916 This enables the kernel to use EFI runtime services that are
1917 available (such as the EFI variable services).
1919 This option is only useful on systems that have EFI firmware.
1920 In addition, you should use the latest ELILO loader available
1921 at <http://elilo.sourceforge.net> in order to take advantage
1922 of EFI runtime services. However, even with this option, the
1923 resultant kernel should continue to boot on existing non-EFI
1927 bool "EFI stub support"
1928 depends on EFI && !X86_USE_3DNOW
1931 This kernel feature allows a bzImage to be loaded directly
1932 by EFI firmware without the use of a bootloader.
1934 See Documentation/efi-stub.txt for more information.
1937 bool "EFI mixed-mode support"
1938 depends on EFI_STUB && X86_64
1940 Enabling this feature allows a 64-bit kernel to be booted
1941 on a 32-bit firmware, provided that your CPU supports 64-bit
1944 Note that it is not possible to boot a mixed-mode enabled
1945 kernel via the EFI boot stub - a bootloader that supports
1946 the EFI handover protocol must be used.
1952 prompt "Enable seccomp to safely compute untrusted bytecode"
1954 This kernel feature is useful for number crunching applications
1955 that may need to compute untrusted bytecode during their
1956 execution. By using pipes or other transports made available to
1957 the process as file descriptors supporting the read/write
1958 syscalls, it's possible to isolate those applications in
1959 their own address space using seccomp. Once seccomp is
1960 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1961 and the task is only allowed to execute a few safe syscalls
1962 defined by each seccomp mode.
1964 If unsure, say Y. Only embedded should say N here.
1966 source "kernel/Kconfig.hz"
1969 bool "kexec system call"
1972 kexec is a system call that implements the ability to shutdown your
1973 current kernel, and to start another kernel. It is like a reboot
1974 but it is independent of the system firmware. And like a reboot
1975 you can start any kernel with it, not just Linux.
1977 The name comes from the similarity to the exec system call.
1979 It is an ongoing process to be certain the hardware in a machine
1980 is properly shutdown, so do not be surprised if this code does not
1981 initially work for you. As of this writing the exact hardware
1982 interface is strongly in flux, so no good recommendation can be
1986 bool "kexec file based system call"
1991 depends on CRYPTO_SHA256=y
1993 This is new version of kexec system call. This system call is
1994 file based and takes file descriptors as system call argument
1995 for kernel and initramfs as opposed to list of segments as
1996 accepted by previous system call.
1998 config ARCH_HAS_KEXEC_PURGATORY
2001 config KEXEC_VERIFY_SIG
2002 bool "Verify kernel signature during kexec_file_load() syscall"
2003 depends on KEXEC_FILE
2005 This option makes kernel signature verification mandatory for
2006 the kexec_file_load() syscall.
2008 In addition to that option, you need to enable signature
2009 verification for the corresponding kernel image type being
2010 loaded in order for this to work.
2012 config KEXEC_BZIMAGE_VERIFY_SIG
2013 bool "Enable bzImage signature verification support"
2014 depends on KEXEC_VERIFY_SIG
2015 depends on SIGNED_PE_FILE_VERIFICATION
2016 select SYSTEM_TRUSTED_KEYRING
2018 Enable bzImage signature verification support.
2021 bool "kernel crash dumps"
2022 depends on X86_64 || (X86_32 && HIGHMEM)
2024 Generate crash dump after being started by kexec.
2025 This should be normally only set in special crash dump kernels
2026 which are loaded in the main kernel with kexec-tools into
2027 a specially reserved region and then later executed after
2028 a crash by kdump/kexec. The crash dump kernel must be compiled
2029 to a memory address not used by the main kernel or BIOS using
2030 PHYSICAL_START, or it must be built as a relocatable image
2031 (CONFIG_RELOCATABLE=y).
2032 For more details see Documentation/kdump/kdump.txt
2036 depends on KEXEC && HIBERNATION
2038 Jump between original kernel and kexeced kernel and invoke
2039 code in physical address mode via KEXEC
2041 config PHYSICAL_START
2042 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2045 This gives the physical address where the kernel is loaded.
2047 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2048 bzImage will decompress itself to above physical address and
2049 run from there. Otherwise, bzImage will run from the address where
2050 it has been loaded by the boot loader and will ignore above physical
2053 In normal kdump cases one does not have to set/change this option
2054 as now bzImage can be compiled as a completely relocatable image
2055 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2056 address. This option is mainly useful for the folks who don't want
2057 to use a bzImage for capturing the crash dump and want to use a
2058 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2059 to be specifically compiled to run from a specific memory area
2060 (normally a reserved region) and this option comes handy.
2062 So if you are using bzImage for capturing the crash dump,
2063 leave the value here unchanged to 0x1000000 and set
2064 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2065 for capturing the crash dump change this value to start of
2066 the reserved region. In other words, it can be set based on
2067 the "X" value as specified in the "crashkernel=YM@XM"
2068 command line boot parameter passed to the panic-ed
2069 kernel. Please take a look at Documentation/kdump/kdump.txt
2070 for more details about crash dumps.
2072 Usage of bzImage for capturing the crash dump is recommended as
2073 one does not have to build two kernels. Same kernel can be used
2074 as production kernel and capture kernel. Above option should have
2075 gone away after relocatable bzImage support is introduced. But it
2076 is present because there are users out there who continue to use
2077 vmlinux for dump capture. This option should go away down the
2080 Don't change this unless you know what you are doing.
2083 bool "Build a relocatable kernel"
2086 This builds a kernel image that retains relocation information
2087 so it can be loaded someplace besides the default 1MB.
2088 The relocations tend to make the kernel binary about 10% larger,
2089 but are discarded at runtime.
2091 One use is for the kexec on panic case where the recovery kernel
2092 must live at a different physical address than the primary
2095 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2096 it has been loaded at and the compile time physical address
2097 (CONFIG_PHYSICAL_START) is used as the minimum location.
2099 config RANDOMIZE_BASE
2100 bool "Randomize the address of the kernel image (KASLR)"
2101 depends on RELOCATABLE
2104 In support of Kernel Address Space Layout Randomization (KASLR),
2105 this randomizes the physical address at which the kernel image
2106 is decompressed and the virtual address where the kernel
2107 image is mapped, as a security feature that deters exploit
2108 attempts relying on knowledge of the location of kernel
2111 On 64-bit, the kernel physical and virtual addresses are
2112 randomized separately. The physical address will be anywhere
2113 between 16MB and the top of physical memory (up to 64TB). The
2114 virtual address will be randomized from 16MB up to 1GB (9 bits
2115 of entropy). Note that this also reduces the memory space
2116 available to kernel modules from 1.5GB to 1GB.
2118 On 32-bit, the kernel physical and virtual addresses are
2119 randomized together. They will be randomized from 16MB up to
2120 512MB (8 bits of entropy).
2122 Entropy is generated using the RDRAND instruction if it is
2123 supported. If RDTSC is supported, its value is mixed into
2124 the entropy pool as well. If neither RDRAND nor RDTSC are
2125 supported, then entropy is read from the i8254 timer. The
2126 usable entropy is limited by the kernel being built using
2127 2GB addressing, and that PHYSICAL_ALIGN must be at a
2128 minimum of 2MB. As a result, only 10 bits of entropy are
2129 theoretically possible, but the implementations are further
2130 limited due to memory layouts.
2134 # Relocation on x86 needs some additional build support
2135 config X86_NEED_RELOCS
2137 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2139 config PHYSICAL_ALIGN
2140 hex "Alignment value to which kernel should be aligned"
2142 range 0x2000 0x1000000 if X86_32
2143 range 0x200000 0x1000000 if X86_64
2145 This value puts the alignment restrictions on physical address
2146 where kernel is loaded and run from. Kernel is compiled for an
2147 address which meets above alignment restriction.
2149 If bootloader loads the kernel at a non-aligned address and
2150 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2151 address aligned to above value and run from there.
2153 If bootloader loads the kernel at a non-aligned address and
2154 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2155 load address and decompress itself to the address it has been
2156 compiled for and run from there. The address for which kernel is
2157 compiled already meets above alignment restrictions. Hence the
2158 end result is that kernel runs from a physical address meeting
2159 above alignment restrictions.
2161 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2162 this value must be a multiple of 0x200000.
2164 Don't change this unless you know what you are doing.
2166 config DYNAMIC_MEMORY_LAYOUT
2169 This option makes base addresses of vmalloc and vmemmap as well as
2170 __PAGE_OFFSET movable during boot.
2172 config RANDOMIZE_MEMORY
2173 bool "Randomize the kernel memory sections"
2175 depends on RANDOMIZE_BASE
2176 select DYNAMIC_MEMORY_LAYOUT
2177 default RANDOMIZE_BASE
2179 Randomizes the base virtual address of kernel memory sections
2180 (physical memory mapping, vmalloc & vmemmap). This security feature
2181 makes exploits relying on predictable memory locations less reliable.
2183 The order of allocations remains unchanged. Entropy is generated in
2184 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2185 configuration have in average 30,000 different possible virtual
2186 addresses for each memory section.
2190 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2191 hex "Physical memory mapping padding" if EXPERT
2192 depends on RANDOMIZE_MEMORY
2193 default "0xa" if MEMORY_HOTPLUG
2195 range 0x1 0x40 if MEMORY_HOTPLUG
2198 Define the padding in terabytes added to the existing physical
2199 memory size during kernel memory randomization. It is useful
2200 for memory hotplug support but reduces the entropy available for
2201 address randomization.
2203 If unsure, leave at the default value.
2209 config BOOTPARAM_HOTPLUG_CPU0
2210 bool "Set default setting of cpu0_hotpluggable"
2211 depends on HOTPLUG_CPU
2213 Set whether default state of cpu0_hotpluggable is on or off.
2215 Say Y here to enable CPU0 hotplug by default. If this switch
2216 is turned on, there is no need to give cpu0_hotplug kernel
2217 parameter and the CPU0 hotplug feature is enabled by default.
2219 Please note: there are two known CPU0 dependencies if you want
2220 to enable the CPU0 hotplug feature either by this switch or by
2221 cpu0_hotplug kernel parameter.
2223 First, resume from hibernate or suspend always starts from CPU0.
2224 So hibernate and suspend are prevented if CPU0 is offline.
2226 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2227 offline if any interrupt can not migrate out of CPU0. There may
2228 be other CPU0 dependencies.
2230 Please make sure the dependencies are under your control before
2231 you enable this feature.
2233 Say N if you don't want to enable CPU0 hotplug feature by default.
2234 You still can enable the CPU0 hotplug feature at boot by kernel
2235 parameter cpu0_hotplug.
2237 config DEBUG_HOTPLUG_CPU0
2239 prompt "Debug CPU0 hotplug"
2240 depends on HOTPLUG_CPU
2242 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2243 soon as possible and boots up userspace with CPU0 offlined. User
2244 can online CPU0 back after boot time.
2246 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2247 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2248 compilation or giving cpu0_hotplug kernel parameter at boot.
2254 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2255 depends on COMPAT_32
2257 Certain buggy versions of glibc will crash if they are
2258 presented with a 32-bit vDSO that is not mapped at the address
2259 indicated in its segment table.
2261 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2262 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2263 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2264 the only released version with the bug, but OpenSUSE 9
2265 contains a buggy "glibc 2.3.2".
2267 The symptom of the bug is that everything crashes on startup, saying:
2268 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2270 Saying Y here changes the default value of the vdso32 boot
2271 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2272 This works around the glibc bug but hurts performance.
2274 If unsure, say N: if you are compiling your own kernel, you
2275 are unlikely to be using a buggy version of glibc.
2278 prompt "vsyscall table for legacy applications"
2280 default LEGACY_VSYSCALL_EMULATE
2282 Legacy user code that does not know how to find the vDSO expects
2283 to be able to issue three syscalls by calling fixed addresses in
2284 kernel space. Since this location is not randomized with ASLR,
2285 it can be used to assist security vulnerability exploitation.
2287 This setting can be changed at boot time via the kernel command
2288 line parameter vsyscall=[emulate|none].
2290 On a system with recent enough glibc (2.14 or newer) and no
2291 static binaries, you can say None without a performance penalty
2292 to improve security.
2294 If unsure, select "Emulate".
2296 config LEGACY_VSYSCALL_EMULATE
2299 The kernel traps and emulates calls into the fixed
2300 vsyscall address mapping. This makes the mapping
2301 non-executable, but it still contains known contents,
2302 which could be used in certain rare security vulnerability
2303 exploits. This configuration is recommended when userspace
2304 still uses the vsyscall area.
2306 config LEGACY_VSYSCALL_NONE
2309 There will be no vsyscall mapping at all. This will
2310 eliminate any risk of ASLR bypass due to the vsyscall
2311 fixed address mapping. Attempts to use the vsyscalls
2312 will be reported to dmesg, so that either old or
2313 malicious userspace programs can be identified.
2318 bool "Built-in kernel command line"
2320 Allow for specifying boot arguments to the kernel at
2321 build time. On some systems (e.g. embedded ones), it is
2322 necessary or convenient to provide some or all of the
2323 kernel boot arguments with the kernel itself (that is,
2324 to not rely on the boot loader to provide them.)
2326 To compile command line arguments into the kernel,
2327 set this option to 'Y', then fill in the
2328 boot arguments in CONFIG_CMDLINE.
2330 Systems with fully functional boot loaders (i.e. non-embedded)
2331 should leave this option set to 'N'.
2334 string "Built-in kernel command string"
2335 depends on CMDLINE_BOOL
2338 Enter arguments here that should be compiled into the kernel
2339 image and used at boot time. If the boot loader provides a
2340 command line at boot time, it is appended to this string to
2341 form the full kernel command line, when the system boots.
2343 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2344 change this behavior.
2346 In most cases, the command line (whether built-in or provided
2347 by the boot loader) should specify the device for the root
2350 config CMDLINE_OVERRIDE
2351 bool "Built-in command line overrides boot loader arguments"
2352 depends on CMDLINE_BOOL
2354 Set this option to 'Y' to have the kernel ignore the boot loader
2355 command line, and use ONLY the built-in command line.
2357 This is used to work around broken boot loaders. This should
2358 be set to 'N' under normal conditions.
2360 config MODIFY_LDT_SYSCALL
2361 bool "Enable the LDT (local descriptor table)" if EXPERT
2364 Linux can allow user programs to install a per-process x86
2365 Local Descriptor Table (LDT) using the modify_ldt(2) system
2366 call. This is required to run 16-bit or segmented code such as
2367 DOSEMU or some Wine programs. It is also used by some very old
2368 threading libraries.
2370 Enabling this feature adds a small amount of overhead to
2371 context switches and increases the low-level kernel attack
2372 surface. Disabling it removes the modify_ldt(2) system call.
2374 Saying 'N' here may make sense for embedded or server kernels.
2376 source "kernel/livepatch/Kconfig"
2380 config ARCH_HAS_ADD_PAGES
2382 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2384 config ARCH_ENABLE_MEMORY_HOTPLUG
2386 depends on X86_64 || (X86_32 && HIGHMEM)
2388 config ARCH_ENABLE_MEMORY_HOTREMOVE
2390 depends on MEMORY_HOTPLUG
2392 config USE_PERCPU_NUMA_NODE_ID
2396 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2398 depends on X86_64 || X86_PAE
2400 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2402 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2404 config ARCH_ENABLE_THP_MIGRATION
2406 depends on X86_64 && TRANSPARENT_HUGEPAGE
2408 menu "Power management and ACPI options"
2410 config ARCH_HIBERNATION_HEADER
2412 depends on HIBERNATION
2414 source "kernel/power/Kconfig"
2416 source "drivers/acpi/Kconfig"
2418 source "drivers/sfi/Kconfig"
2425 tristate "APM (Advanced Power Management) BIOS support"
2426 depends on X86_32 && PM_SLEEP
2428 APM is a BIOS specification for saving power using several different
2429 techniques. This is mostly useful for battery powered laptops with
2430 APM compliant BIOSes. If you say Y here, the system time will be
2431 reset after a RESUME operation, the /proc/apm device will provide
2432 battery status information, and user-space programs will receive
2433 notification of APM "events" (e.g. battery status change).
2435 If you select "Y" here, you can disable actual use of the APM
2436 BIOS by passing the "apm=off" option to the kernel at boot time.
2438 Note that the APM support is almost completely disabled for
2439 machines with more than one CPU.
2441 In order to use APM, you will need supporting software. For location
2442 and more information, read <file:Documentation/power/apm-acpi.txt>
2443 and the Battery Powered Linux mini-HOWTO, available from
2444 <http://www.tldp.org/docs.html#howto>.
2446 This driver does not spin down disk drives (see the hdparm(8)
2447 manpage ("man 8 hdparm") for that), and it doesn't turn off
2448 VESA-compliant "green" monitors.
2450 This driver does not support the TI 4000M TravelMate and the ACER
2451 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2452 desktop machines also don't have compliant BIOSes, and this driver
2453 may cause those machines to panic during the boot phase.
2455 Generally, if you don't have a battery in your machine, there isn't
2456 much point in using this driver and you should say N. If you get
2457 random kernel OOPSes or reboots that don't seem to be related to
2458 anything, try disabling/enabling this option (or disabling/enabling
2461 Some other things you should try when experiencing seemingly random,
2464 1) make sure that you have enough swap space and that it is
2466 2) pass the "no-hlt" option to the kernel
2467 3) switch on floating point emulation in the kernel and pass
2468 the "no387" option to the kernel
2469 4) pass the "floppy=nodma" option to the kernel
2470 5) pass the "mem=4M" option to the kernel (thereby disabling
2471 all but the first 4 MB of RAM)
2472 6) make sure that the CPU is not over clocked.
2473 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2474 8) disable the cache from your BIOS settings
2475 9) install a fan for the video card or exchange video RAM
2476 10) install a better fan for the CPU
2477 11) exchange RAM chips
2478 12) exchange the motherboard.
2480 To compile this driver as a module, choose M here: the
2481 module will be called apm.
2485 config APM_IGNORE_USER_SUSPEND
2486 bool "Ignore USER SUSPEND"
2488 This option will ignore USER SUSPEND requests. On machines with a
2489 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2490 series notebooks, it is necessary to say Y because of a BIOS bug.
2492 config APM_DO_ENABLE
2493 bool "Enable PM at boot time"
2495 Enable APM features at boot time. From page 36 of the APM BIOS
2496 specification: "When disabled, the APM BIOS does not automatically
2497 power manage devices, enter the Standby State, enter the Suspend
2498 State, or take power saving steps in response to CPU Idle calls."
2499 This driver will make CPU Idle calls when Linux is idle (unless this
2500 feature is turned off -- see "Do CPU IDLE calls", below). This
2501 should always save battery power, but more complicated APM features
2502 will be dependent on your BIOS implementation. You may need to turn
2503 this option off if your computer hangs at boot time when using APM
2504 support, or if it beeps continuously instead of suspending. Turn
2505 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2506 T400CDT. This is off by default since most machines do fine without
2511 bool "Make CPU Idle calls when idle"
2513 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2514 On some machines, this can activate improved power savings, such as
2515 a slowed CPU clock rate, when the machine is idle. These idle calls
2516 are made after the idle loop has run for some length of time (e.g.,
2517 333 mS). On some machines, this will cause a hang at boot time or
2518 whenever the CPU becomes idle. (On machines with more than one CPU,
2519 this option does nothing.)
2521 config APM_DISPLAY_BLANK
2522 bool "Enable console blanking using APM"
2524 Enable console blanking using the APM. Some laptops can use this to
2525 turn off the LCD backlight when the screen blanker of the Linux
2526 virtual console blanks the screen. Note that this is only used by
2527 the virtual console screen blanker, and won't turn off the backlight
2528 when using the X Window system. This also doesn't have anything to
2529 do with your VESA-compliant power-saving monitor. Further, this
2530 option doesn't work for all laptops -- it might not turn off your
2531 backlight at all, or it might print a lot of errors to the console,
2532 especially if you are using gpm.
2534 config APM_ALLOW_INTS
2535 bool "Allow interrupts during APM BIOS calls"
2537 Normally we disable external interrupts while we are making calls to
2538 the APM BIOS as a measure to lessen the effects of a badly behaving
2539 BIOS implementation. The BIOS should reenable interrupts if it
2540 needs to. Unfortunately, some BIOSes do not -- especially those in
2541 many of the newer IBM Thinkpads. If you experience hangs when you
2542 suspend, try setting this to Y. Otherwise, say N.
2546 source "drivers/cpufreq/Kconfig"
2548 source "drivers/cpuidle/Kconfig"
2550 source "drivers/idle/Kconfig"
2555 menu "Bus options (PCI etc.)"
2558 prompt "PCI access mode"
2559 depends on X86_32 && PCI
2562 On PCI systems, the BIOS can be used to detect the PCI devices and
2563 determine their configuration. However, some old PCI motherboards
2564 have BIOS bugs and may crash if this is done. Also, some embedded
2565 PCI-based systems don't have any BIOS at all. Linux can also try to
2566 detect the PCI hardware directly without using the BIOS.
2568 With this option, you can specify how Linux should detect the
2569 PCI devices. If you choose "BIOS", the BIOS will be used,
2570 if you choose "Direct", the BIOS won't be used, and if you
2571 choose "MMConfig", then PCI Express MMCONFIG will be used.
2572 If you choose "Any", the kernel will try MMCONFIG, then the
2573 direct access method and falls back to the BIOS if that doesn't
2574 work. If unsure, go with the default, which is "Any".
2579 config PCI_GOMMCONFIG
2596 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2598 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2601 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2604 bool "Support mmconfig PCI config space access" if X86_64
2606 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2607 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2611 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2615 depends on PCI && XEN
2618 config MMCONF_FAM10H
2620 depends on X86_64 && PCI_MMCONFIG && ACPI
2622 config PCI_CNB20LE_QUIRK
2623 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2626 Read the PCI windows out of the CNB20LE host bridge. This allows
2627 PCI hotplug to work on systems with the CNB20LE chipset which do
2630 There's no public spec for this chipset, and this functionality
2631 is known to be incomplete.
2633 You should say N unless you know you need this.
2636 bool "ISA bus support on modern systems" if EXPERT
2638 Expose ISA bus device drivers and options available for selection and
2639 configuration. Enable this option if your target machine has an ISA
2640 bus. ISA is an older system, displaced by PCI and newer bus
2641 architectures -- if your target machine is modern, it probably does
2642 not have an ISA bus.
2646 # x86_64 have no ISA slots, but can have ISA-style DMA.
2648 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2651 Enables ISA-style DMA support for devices requiring such controllers.
2659 Find out whether you have ISA slots on your motherboard. ISA is the
2660 name of a bus system, i.e. the way the CPU talks to the other stuff
2661 inside your box. Other bus systems are PCI, EISA, MicroChannel
2662 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2663 newer boards don't support it. If you have ISA, say Y, otherwise N.
2666 tristate "NatSemi SCx200 support"
2668 This provides basic support for National Semiconductor's
2669 (now AMD's) Geode processors. The driver probes for the
2670 PCI-IDs of several on-chip devices, so its a good dependency
2671 for other scx200_* drivers.
2673 If compiled as a module, the driver is named scx200.
2675 config SCx200HR_TIMER
2676 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2680 This driver provides a clocksource built upon the on-chip
2681 27MHz high-resolution timer. Its also a workaround for
2682 NSC Geode SC-1100's buggy TSC, which loses time when the
2683 processor goes idle (as is done by the scheduler). The
2684 other workaround is idle=poll boot option.
2687 bool "One Laptop Per Child support"
2694 Add support for detecting the unique features of the OLPC
2698 bool "OLPC XO-1 Power Management"
2699 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2701 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2704 bool "OLPC XO-1 Real Time Clock"
2705 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2707 Add support for the XO-1 real time clock, which can be used as a
2708 programmable wakeup source.
2711 bool "OLPC XO-1 SCI extras"
2712 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2716 Add support for SCI-based features of the OLPC XO-1 laptop:
2717 - EC-driven system wakeups
2721 - AC adapter status updates
2722 - Battery status updates
2724 config OLPC_XO15_SCI
2725 bool "OLPC XO-1.5 SCI extras"
2726 depends on OLPC && ACPI
2729 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2730 - EC-driven system wakeups
2731 - AC adapter status updates
2732 - Battery status updates
2735 bool "PCEngines ALIX System Support (LED setup)"
2738 This option enables system support for the PCEngines ALIX.
2739 At present this just sets up LEDs for GPIO control on
2740 ALIX2/3/6 boards. However, other system specific setup should
2743 Note: You must still enable the drivers for GPIO and LED support
2744 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2746 Note: You have to set alix.force=1 for boards with Award BIOS.
2749 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2752 This option enables system support for the Soekris Engineering net5501.
2755 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2759 This option enables system support for the Traverse Technologies GEOS.
2762 bool "Technologic Systems TS-5500 platform support"
2764 select CHECK_SIGNATURE
2768 This option enables system support for the Technologic Systems TS-5500.
2774 depends on CPU_SUP_AMD && PCI
2777 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2779 Firmwares often provide initial graphics framebuffers so the BIOS,
2780 bootloader or kernel can show basic video-output during boot for
2781 user-guidance and debugging. Historically, x86 used the VESA BIOS
2782 Extensions and EFI-framebuffers for this, which are mostly limited
2784 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2785 framebuffers so the new generic system-framebuffer drivers can be
2786 used on x86. If the framebuffer is not compatible with the generic
2787 modes, it is advertised as fallback platform framebuffer so legacy
2788 drivers like efifb, vesafb and uvesafb can pick it up.
2789 If this option is not selected, all system framebuffers are always
2790 marked as fallback platform framebuffers as usual.
2792 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2793 not be able to pick up generic system framebuffers if this option
2794 is selected. You are highly encouraged to enable simplefb as
2795 replacement if you select this option. simplefb can correctly deal
2796 with generic system framebuffers. But you should still keep vesafb
2797 and others enabled as fallback if a system framebuffer is
2798 incompatible with simplefb.
2805 menu "Binary Emulations"
2807 config IA32_EMULATION
2808 bool "IA32 Emulation"
2810 select ARCH_WANT_OLD_COMPAT_IPC
2812 select COMPAT_BINFMT_ELF
2813 select COMPAT_OLD_SIGACTION
2815 Include code to run legacy 32-bit programs under a
2816 64-bit kernel. You should likely turn this on, unless you're
2817 100% sure that you don't have any 32-bit programs left.
2820 tristate "IA32 a.out support"
2821 depends on IA32_EMULATION
2824 Support old a.out binaries in the 32bit emulation.
2827 bool "x32 ABI for 64-bit mode"
2830 Include code to run binaries for the x32 native 32-bit ABI
2831 for 64-bit processors. An x32 process gets access to the
2832 full 64-bit register file and wide data path while leaving
2833 pointers at 32 bits for smaller memory footprint.
2835 You will need a recent binutils (2.22 or later) with
2836 elf32_x86_64 support enabled to compile a kernel with this
2841 depends on IA32_EMULATION || X86_32
2843 select OLD_SIGSUSPEND3
2847 depends on IA32_EMULATION || X86_X32
2850 config COMPAT_FOR_U64_ALIGNMENT
2853 config SYSVIPC_COMPAT
2861 config HAVE_ATOMIC_IOMAP
2865 config X86_DEV_DMA_OPS
2868 config HAVE_GENERIC_GUP
2871 source "drivers/firmware/Kconfig"
2873 source "arch/x86/kvm/Kconfig"