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 MODULES_USE_ELF_REL
23 # Options that are inherently 64-bit kernel only:
24 select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
25 select ARCH_SUPPORTS_INT128
26 select ARCH_USE_CMPXCHG_LOCKREF
27 select HAVE_ARCH_SOFT_DIRTY
28 select MODULES_USE_ELF_RELA
29 select NEED_DMA_MAP_STATE
31 select X86_DEV_DMA_OPS
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
48 select ARCH_32BIT_OFF_T if X86_32
49 select ARCH_CLOCKSOURCE_DATA
50 select ARCH_CLOCKSOURCE_INIT
51 select ARCH_DISCARD_MEMBLOCK
52 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
53 select ARCH_HAS_DEBUG_VIRTUAL
54 select ARCH_HAS_DEVMEM_IS_ALLOWED
55 select ARCH_HAS_ELF_RANDOMIZE
56 select ARCH_HAS_FAST_MULTIPLIER
57 select ARCH_HAS_FILTER_PGPROT
58 select ARCH_HAS_FORTIFY_SOURCE
59 select ARCH_HAS_GCOV_PROFILE_ALL
60 select ARCH_HAS_KCOV if X86_64
61 select ARCH_HAS_MEMBARRIER_SYNC_CORE
62 select ARCH_HAS_PMEM_API if X86_64
63 select ARCH_HAS_PTE_SPECIAL
64 select ARCH_HAS_REFCOUNT
65 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
66 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
67 select ARCH_HAS_SET_MEMORY
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_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_DEBUG_STACKOVERFLOW
142 select HAVE_DMA_CONTIGUOUS
143 select HAVE_DYNAMIC_FTRACE
144 select HAVE_DYNAMIC_FTRACE_WITH_REGS
146 select HAVE_EFFICIENT_UNALIGNED_ACCESS
148 select HAVE_EXIT_THREAD
149 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
150 select HAVE_FTRACE_MCOUNT_RECORD
151 select HAVE_FUNCTION_GRAPH_TRACER
152 select HAVE_FUNCTION_TRACER
153 select HAVE_GCC_PLUGINS
154 select HAVE_HW_BREAKPOINT
156 select HAVE_IOREMAP_PROT
157 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
158 select HAVE_IRQ_TIME_ACCOUNTING
159 select HAVE_KERNEL_BZIP2
160 select HAVE_KERNEL_GZIP
161 select HAVE_KERNEL_LZ4
162 select HAVE_KERNEL_LZMA
163 select HAVE_KERNEL_LZO
164 select HAVE_KERNEL_XZ
166 select HAVE_KPROBES_ON_FTRACE
167 select HAVE_FUNCTION_ERROR_INJECTION
168 select HAVE_KRETPROBES
170 select HAVE_LIVEPATCH if X86_64
171 select HAVE_MEMBLOCK_NODE_MAP
172 select HAVE_MIXED_BREAKPOINTS_REGS
173 select HAVE_MOD_ARCH_SPECIFIC
177 select HAVE_OPTPROBES
178 select HAVE_PCSPKR_PLATFORM
179 select HAVE_PERF_EVENTS
180 select HAVE_PERF_EVENTS_NMI
181 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
183 select HAVE_PERF_REGS
184 select HAVE_PERF_USER_STACK_DUMP
185 select HAVE_RCU_TABLE_FREE if PARAVIRT
186 select HAVE_RCU_TABLE_INVALIDATE if HAVE_RCU_TABLE_FREE
187 select HAVE_REGS_AND_STACK_ACCESS_API
188 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
189 select HAVE_FUNCTION_ARG_ACCESS_API
190 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
191 select HAVE_STACK_VALIDATION if X86_64
193 select HAVE_SYSCALL_TRACEPOINTS
194 select HAVE_UNSTABLE_SCHED_CLOCK
195 select HAVE_USER_RETURN_NOTIFIER
196 select HOTPLUG_SMT if SMP
197 select IRQ_FORCED_THREADING
198 select NEED_SG_DMA_LENGTH
199 select PCI_DOMAINS if PCI
200 select PCI_LOCKLESS_CONFIG if PCI
203 select RTC_MC146818_LIB
206 select SYSCTL_EXCEPTION_TRACE
207 select THREAD_INFO_IN_TASK
208 select USER_STACKTRACE_SUPPORT
210 select X86_FEATURE_NAMES if PROC_FS
212 config INSTRUCTION_DECODER
214 depends on KPROBES || PERF_EVENTS || UPROBES
218 default "elf32-i386" if X86_32
219 default "elf64-x86-64" if X86_64
221 config ARCH_DEFCONFIG
223 default "arch/x86/configs/i386_defconfig" if X86_32
224 default "arch/x86/configs/x86_64_defconfig" if X86_64
226 config LOCKDEP_SUPPORT
229 config STACKTRACE_SUPPORT
235 config ARCH_MMAP_RND_BITS_MIN
239 config ARCH_MMAP_RND_BITS_MAX
243 config ARCH_MMAP_RND_COMPAT_BITS_MIN
246 config ARCH_MMAP_RND_COMPAT_BITS_MAX
252 config GENERIC_ISA_DMA
254 depends on ISA_DMA_API
259 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
261 config GENERIC_BUG_RELATIVE_POINTERS
264 config GENERIC_HWEIGHT
267 config ARCH_MAY_HAVE_PC_FDC
269 depends on ISA_DMA_API
271 config GENERIC_CALIBRATE_DELAY
274 config ARCH_HAS_CPU_RELAX
277 config ARCH_HAS_CACHE_LINE_SIZE
280 config ARCH_HAS_FILTER_PGPROT
283 config HAVE_SETUP_PER_CPU_AREA
286 config NEED_PER_CPU_EMBED_FIRST_CHUNK
289 config NEED_PER_CPU_PAGE_FIRST_CHUNK
292 config ARCH_HIBERNATION_POSSIBLE
295 config ARCH_SUSPEND_POSSIBLE
298 config ARCH_WANT_HUGE_PMD_SHARE
301 config ARCH_WANT_GENERAL_HUGETLB
310 config ARCH_SUPPORTS_OPTIMIZED_INLINING
313 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
316 config KASAN_SHADOW_OFFSET
319 default 0xdffffc0000000000
321 config HAVE_INTEL_TXT
323 depends on INTEL_IOMMU && ACPI
327 depends on X86_32 && SMP
331 depends on X86_64 && SMP
333 config X86_32_LAZY_GS
335 depends on X86_32 && !STACKPROTECTOR
337 config ARCH_SUPPORTS_UPROBES
340 config FIX_EARLYCON_MEM
343 config DYNAMIC_PHYSICAL_MASK
346 config PGTABLE_LEVELS
348 default 5 if X86_5LEVEL
353 config CC_HAS_SANE_STACKPROTECTOR
355 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
356 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
358 We have to make sure stack protector is unconditionally disabled if
359 the compiler produces broken code.
361 menu "Processor type and features"
364 bool "DMA memory allocation support" if EXPERT
367 DMA memory allocation support allows devices with less than 32-bit
368 addressing to allocate within the first 16MB of address space.
369 Disable if no such devices will be used.
374 bool "Symmetric multi-processing support"
376 This enables support for systems with more than one CPU. If you have
377 a system with only one CPU, say N. If you have a system with more
380 If you say N here, the kernel will run on uni- and multiprocessor
381 machines, but will use only one CPU of a multiprocessor machine. If
382 you say Y here, the kernel will run on many, but not all,
383 uniprocessor machines. On a uniprocessor machine, the kernel
384 will run faster if you say N here.
386 Note that if you say Y here and choose architecture "586" or
387 "Pentium" under "Processor family", the kernel will not work on 486
388 architectures. Similarly, multiprocessor kernels for the "PPro"
389 architecture may not work on all Pentium based boards.
391 People using multiprocessor machines who say Y here should also say
392 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
393 Management" code will be disabled if you say Y here.
395 See also <file:Documentation/x86/i386/IO-APIC.txt>,
396 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
397 <http://www.tldp.org/docs.html#howto>.
399 If you don't know what to do here, say N.
401 config X86_FEATURE_NAMES
402 bool "Processor feature human-readable names" if EMBEDDED
405 This option compiles in a table of x86 feature bits and corresponding
406 names. This is required to support /proc/cpuinfo and a few kernel
407 messages. You can disable this to save space, at the expense of
408 making those few kernel messages show numeric feature bits instead.
413 bool "Support x2apic"
414 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
416 This enables x2apic support on CPUs that have this feature.
418 This allows 32-bit apic IDs (so it can support very large systems),
419 and accesses the local apic via MSRs not via mmio.
421 If you don't know what to do here, say N.
424 bool "Enable MPS table" if ACPI || SFI
426 depends on X86_LOCAL_APIC
428 For old smp systems that do not have proper acpi support. Newer systems
429 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
433 depends on X86_GOLDFISH
436 bool "Avoid speculative indirect branches in kernel"
438 select STACK_VALIDATION if HAVE_STACK_VALIDATION
440 Compile kernel with the retpoline compiler options to guard against
441 kernel-to-user data leaks by avoiding speculative indirect
442 branches. Requires a compiler with -mindirect-branch=thunk-extern
443 support for full protection. The kernel may run slower.
445 config X86_CPU_RESCTRL
446 bool "x86 CPU resource control support"
447 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
450 Enable x86 CPU resource control support.
452 Provide support for the allocation and monitoring of system resources
455 Intel calls this Intel Resource Director Technology
456 (Intel(R) RDT). More information about RDT can be found in the
457 Intel x86 Architecture Software Developer Manual.
459 AMD calls this AMD Platform Quality of Service (AMD QoS).
460 More information about AMD QoS can be found in the AMD64 Technology
461 Platform Quality of Service Extensions manual.
467 bool "Support for big SMP systems with more than 8 CPUs"
470 This option is needed for the systems that have more than 8 CPUs
472 config X86_EXTENDED_PLATFORM
473 bool "Support for extended (non-PC) x86 platforms"
476 If you disable this option then the kernel will only support
477 standard PC platforms. (which covers the vast majority of
480 If you enable this option then you'll be able to select support
481 for the following (non-PC) 32 bit x86 platforms:
482 Goldfish (Android emulator)
485 SGI 320/540 (Visual Workstation)
486 STA2X11-based (e.g. Northville)
487 Moorestown MID devices
489 If you have one of these systems, or if you want to build a
490 generic distribution kernel, say Y here - otherwise say N.
494 config X86_EXTENDED_PLATFORM
495 bool "Support for extended (non-PC) x86 platforms"
498 If you disable this option then the kernel will only support
499 standard PC platforms. (which covers the vast majority of
502 If you enable this option then you'll be able to select support
503 for the following (non-PC) 64 bit x86 platforms:
508 If you have one of these systems, or if you want to build a
509 generic distribution kernel, say Y here - otherwise say N.
511 # This is an alphabetically sorted list of 64 bit extended platforms
512 # Please maintain the alphabetic order if and when there are additions
514 bool "Numascale NumaChip"
516 depends on X86_EXTENDED_PLATFORM
519 depends on X86_X2APIC
520 depends on PCI_MMCONFIG
522 Adds support for Numascale NumaChip large-SMP systems. Needed to
523 enable more than ~168 cores.
524 If you don't have one of these, you should say N here.
528 select HYPERVISOR_GUEST
530 depends on X86_64 && PCI
531 depends on X86_EXTENDED_PLATFORM
534 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
535 supposed to run on these EM64T-based machines. Only choose this option
536 if you have one of these machines.
539 bool "SGI Ultraviolet"
541 depends on X86_EXTENDED_PLATFORM
544 depends on X86_X2APIC
547 This option is needed in order to support SGI Ultraviolet systems.
548 If you don't have one of these, you should say N here.
550 # Following is an alphabetically sorted list of 32 bit extended platforms
551 # Please maintain the alphabetic order if and when there are additions
554 bool "Goldfish (Virtual Platform)"
555 depends on X86_EXTENDED_PLATFORM
557 Enable support for the Goldfish virtual platform used primarily
558 for Android development. Unless you are building for the Android
559 Goldfish emulator say N here.
562 bool "CE4100 TV platform"
564 depends on PCI_GODIRECT
565 depends on X86_IO_APIC
567 depends on X86_EXTENDED_PLATFORM
568 select X86_REBOOTFIXUPS
570 select OF_EARLY_FLATTREE
572 Select for the Intel CE media processor (CE4100) SOC.
573 This option compiles in support for the CE4100 SOC for settop
574 boxes and media devices.
577 bool "Intel MID platform support"
578 depends on X86_EXTENDED_PLATFORM
579 depends on X86_PLATFORM_DEVICES
581 depends on X86_64 || (PCI_GOANY && X86_32)
582 depends on X86_IO_APIC
588 select MFD_INTEL_MSIC
590 Select to build a kernel capable of supporting Intel MID (Mobile
591 Internet Device) platform systems which do not have the PCI legacy
592 interfaces. If you are building for a PC class system say N here.
594 Intel MID platforms are based on an Intel processor and chipset which
595 consume less power than most of the x86 derivatives.
597 config X86_INTEL_QUARK
598 bool "Intel Quark platform support"
600 depends on X86_EXTENDED_PLATFORM
601 depends on X86_PLATFORM_DEVICES
605 depends on X86_IO_APIC
610 Select to include support for Quark X1000 SoC.
611 Say Y here if you have a Quark based system such as the Arduino
612 compatible Intel Galileo.
614 config X86_INTEL_LPSS
615 bool "Intel Low Power Subsystem Support"
616 depends on X86 && ACPI && PCI
621 Select to build support for Intel Low Power Subsystem such as
622 found on Intel Lynxpoint PCH. Selecting this option enables
623 things like clock tree (common clock framework) and pincontrol
624 which are needed by the LPSS peripheral drivers.
626 config X86_AMD_PLATFORM_DEVICE
627 bool "AMD ACPI2Platform devices support"
632 Select to interpret AMD specific ACPI device to platform device
633 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
634 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
635 implemented under PINCTRL subsystem.
638 tristate "Intel SoC IOSF Sideband support for SoC platforms"
641 This option enables sideband register access support for Intel SoC
642 platforms. On these platforms the IOSF sideband is used in lieu of
643 MSR's for some register accesses, mostly but not limited to thermal
644 and power. Drivers may query the availability of this device to
645 determine if they need the sideband in order to work on these
646 platforms. The sideband is available on the following SoC products.
647 This list is not meant to be exclusive.
652 You should say Y if you are running a kernel on one of these SoC's.
654 config IOSF_MBI_DEBUG
655 bool "Enable IOSF sideband access through debugfs"
656 depends on IOSF_MBI && DEBUG_FS
658 Select this option to expose the IOSF sideband access registers (MCR,
659 MDR, MCRX) through debugfs to write and read register information from
660 different units on the SoC. This is most useful for obtaining device
661 state information for debug and analysis. As this is a general access
662 mechanism, users of this option would have specific knowledge of the
663 device they want to access.
665 If you don't require the option or are in doubt, say N.
668 bool "RDC R-321x SoC"
670 depends on X86_EXTENDED_PLATFORM
672 select X86_REBOOTFIXUPS
674 This option is needed for RDC R-321x system-on-chip, also known
676 If you don't have one of these chips, you should say N here.
678 config X86_32_NON_STANDARD
679 bool "Support non-standard 32-bit SMP architectures"
680 depends on X86_32 && SMP
681 depends on X86_EXTENDED_PLATFORM
683 This option compiles in the bigsmp and STA2X11 default
684 subarchitectures. It is intended for a generic binary
685 kernel. If you select them all, kernel will probe it one by
686 one and will fallback to default.
688 # Alphabetically sorted list of Non standard 32 bit platforms
690 config X86_SUPPORTS_MEMORY_FAILURE
692 # MCE code calls memory_failure():
694 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
695 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
696 depends on X86_64 || !SPARSEMEM
697 select ARCH_SUPPORTS_MEMORY_FAILURE
700 bool "STA2X11 Companion Chip Support"
701 depends on X86_32_NON_STANDARD && PCI
702 select ARCH_HAS_PHYS_TO_DMA
703 select X86_DEV_DMA_OPS
709 This adds support for boards based on the STA2X11 IO-Hub,
710 a.k.a. "ConneXt". The chip is used in place of the standard
711 PC chipset, so all "standard" peripherals are missing. If this
712 option is selected the kernel will still be able to boot on
713 standard PC machines.
716 tristate "Eurobraille/Iris poweroff module"
719 The Iris machines from EuroBraille do not have APM or ACPI support
720 to shut themselves down properly. A special I/O sequence is
721 needed to do so, which is what this module does at
724 This is only for Iris machines from EuroBraille.
728 config SCHED_OMIT_FRAME_POINTER
730 prompt "Single-depth WCHAN output"
733 Calculate simpler /proc/<PID>/wchan values. If this option
734 is disabled then wchan values will recurse back to the
735 caller function. This provides more accurate wchan values,
736 at the expense of slightly more scheduling overhead.
738 If in doubt, say "Y".
740 menuconfig HYPERVISOR_GUEST
741 bool "Linux guest support"
743 Say Y here to enable options for running Linux under various hyper-
744 visors. This option enables basic hypervisor detection and platform
747 If you say N, all options in this submenu will be skipped and
748 disabled, and Linux guest support won't be built in.
753 bool "Enable paravirtualization code"
755 This changes the kernel so it can modify itself when it is run
756 under a hypervisor, potentially improving performance significantly
757 over full virtualization. However, when run without a hypervisor
758 the kernel is theoretically slower and slightly larger.
763 config PARAVIRT_DEBUG
764 bool "paravirt-ops debugging"
765 depends on PARAVIRT && DEBUG_KERNEL
767 Enable to debug paravirt_ops internals. Specifically, BUG if
768 a paravirt_op is missing when it is called.
770 config PARAVIRT_SPINLOCKS
771 bool "Paravirtualization layer for spinlocks"
772 depends on PARAVIRT && SMP
774 Paravirtualized spinlocks allow a pvops backend to replace the
775 spinlock implementation with something virtualization-friendly
776 (for example, block the virtual CPU rather than spinning).
778 It has a minimal impact on native kernels and gives a nice performance
779 benefit on paravirtualized KVM / Xen kernels.
781 If you are unsure how to answer this question, answer Y.
783 config QUEUED_LOCK_STAT
784 bool "Paravirt queued spinlock statistics"
785 depends on PARAVIRT_SPINLOCKS && DEBUG_FS
787 Enable the collection of statistical data on the slowpath
788 behavior of paravirtualized queued spinlocks and report
791 source "arch/x86/xen/Kconfig"
794 bool "KVM Guest support (including kvmclock)"
796 select PARAVIRT_CLOCK
799 This option enables various optimizations for running under the KVM
800 hypervisor. It includes a paravirtualized clock, so that instead
801 of relying on a PIT (or probably other) emulation by the
802 underlying device model, the host provides the guest with
803 timing infrastructure such as time of day, and system time
806 bool "Support for running PVH guests"
808 This option enables the PVH entry point for guest virtual machines
809 as specified in the x86/HVM direct boot ABI.
812 bool "Enable debug information for KVM Guests in debugfs"
813 depends on KVM_GUEST && DEBUG_FS
815 This option enables collection of various statistics for KVM guest.
816 Statistics are displayed in debugfs filesystem. Enabling this option
817 may incur significant overhead.
819 config PARAVIRT_TIME_ACCOUNTING
820 bool "Paravirtual steal time accounting"
823 Select this option to enable fine granularity task steal time
824 accounting. Time spent executing other tasks in parallel with
825 the current vCPU is discounted from the vCPU power. To account for
826 that, there can be a small performance impact.
828 If in doubt, say N here.
830 config PARAVIRT_CLOCK
833 config JAILHOUSE_GUEST
834 bool "Jailhouse non-root cell support"
835 depends on X86_64 && PCI
838 This option allows to run Linux as guest in a Jailhouse non-root
839 cell. You can leave this option disabled if you only want to start
840 Jailhouse and run Linux afterwards in the root cell.
842 endif #HYPERVISOR_GUEST
844 source "arch/x86/Kconfig.cpu"
848 prompt "HPET Timer Support" if X86_32
850 Use the IA-PC HPET (High Precision Event Timer) to manage
851 time in preference to the PIT and RTC, if a HPET is
853 HPET is the next generation timer replacing legacy 8254s.
854 The HPET provides a stable time base on SMP
855 systems, unlike the TSC, but it is more expensive to access,
856 as it is off-chip. The interface used is documented
857 in the HPET spec, revision 1.
859 You can safely choose Y here. However, HPET will only be
860 activated if the platform and the BIOS support this feature.
861 Otherwise the 8254 will be used for timing services.
863 Choose N to continue using the legacy 8254 timer.
865 config HPET_EMULATE_RTC
867 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
870 def_bool y if X86_INTEL_MID
871 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
873 depends on X86_INTEL_MID && SFI
875 APB timer is the replacement for 8254, HPET on X86 MID platforms.
876 The APBT provides a stable time base on SMP
877 systems, unlike the TSC, but it is more expensive to access,
878 as it is off-chip. APB timers are always running regardless of CPU
879 C states, they are used as per CPU clockevent device when possible.
881 # Mark as expert because too many people got it wrong.
882 # The code disables itself when not needed.
885 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
886 bool "Enable DMI scanning" if EXPERT
888 Enabled scanning of DMI to identify machine quirks. Say Y
889 here unless you have verified that your setup is not
890 affected by entries in the DMI blacklist. Required by PNP
894 bool "Old AMD GART IOMMU support"
897 depends on X86_64 && PCI && AMD_NB
899 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
900 GART based hardware IOMMUs.
902 The GART supports full DMA access for devices with 32-bit access
903 limitations, on systems with more than 3 GB. This is usually needed
904 for USB, sound, many IDE/SATA chipsets and some other devices.
906 Newer systems typically have a modern AMD IOMMU, supported via
907 the CONFIG_AMD_IOMMU=y config option.
909 In normal configurations this driver is only active when needed:
910 there's more than 3 GB of memory and the system contains a
911 32-bit limited device.
916 bool "IBM Calgary IOMMU support"
919 depends on X86_64 && PCI
921 Support for hardware IOMMUs in IBM's xSeries x366 and x460
922 systems. Needed to run systems with more than 3GB of memory
923 properly with 32-bit PCI devices that do not support DAC
924 (Double Address Cycle). Calgary also supports bus level
925 isolation, where all DMAs pass through the IOMMU. This
926 prevents them from going anywhere except their intended
927 destination. This catches hard-to-find kernel bugs and
928 mis-behaving drivers and devices that do not use the DMA-API
929 properly to set up their DMA buffers. The IOMMU can be
930 turned off at boot time with the iommu=off parameter.
931 Normally the kernel will make the right choice by itself.
934 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
936 prompt "Should Calgary be enabled by default?"
937 depends on CALGARY_IOMMU
939 Should Calgary be enabled by default? if you choose 'y', Calgary
940 will be used (if it exists). If you choose 'n', Calgary will not be
941 used even if it exists. If you choose 'n' and would like to use
942 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
946 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
947 depends on X86_64 && SMP && DEBUG_KERNEL
948 select CPUMASK_OFFSTACK
950 Enable maximum number of CPUS and NUMA Nodes for this architecture.
954 # The maximum number of CPUs supported:
956 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
957 # and which can be configured interactively in the
958 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
960 # The ranges are different on 32-bit and 64-bit kernels, depending on
961 # hardware capabilities and scalability features of the kernel.
963 # ( If MAXSMP is enabled we just use the highest possible value and disable
964 # interactive configuration. )
967 config NR_CPUS_RANGE_BEGIN
969 default NR_CPUS_RANGE_END if MAXSMP
973 config NR_CPUS_RANGE_END
976 default 64 if SMP && X86_BIGSMP
977 default 8 if SMP && !X86_BIGSMP
980 config NR_CPUS_RANGE_END
983 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
984 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
987 config NR_CPUS_DEFAULT
990 default 32 if X86_BIGSMP
994 config NR_CPUS_DEFAULT
997 default 8192 if MAXSMP
1002 int "Maximum number of CPUs" if SMP && !MAXSMP
1003 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1004 default NR_CPUS_DEFAULT
1006 This allows you to specify the maximum number of CPUs which this
1007 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1008 supported value is 8192, otherwise the maximum value is 512. The
1009 minimum value which makes sense is 2.
1011 This is purely to save memory: each supported CPU adds about 8KB
1012 to the kernel image.
1019 prompt "Multi-core scheduler support"
1022 Multi-core scheduler support improves the CPU scheduler's decision
1023 making when dealing with multi-core CPU chips at a cost of slightly
1024 increased overhead in some places. If unsure say N here.
1026 config SCHED_MC_PRIO
1027 bool "CPU core priorities scheduler support"
1028 depends on SCHED_MC && CPU_SUP_INTEL
1029 select X86_INTEL_PSTATE
1033 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1034 core ordering determined at manufacturing time, which allows
1035 certain cores to reach higher turbo frequencies (when running
1036 single threaded workloads) than others.
1038 Enabling this kernel feature teaches the scheduler about
1039 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1040 scheduler's CPU selection logic accordingly, so that higher
1041 overall system performance can be achieved.
1043 This feature will have no effect on CPUs without this feature.
1045 If unsure say Y here.
1049 depends on !SMP && X86_LOCAL_APIC
1052 bool "Local APIC support on uniprocessors" if !PCI_MSI
1054 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1056 A local APIC (Advanced Programmable Interrupt Controller) is an
1057 integrated interrupt controller in the CPU. If you have a single-CPU
1058 system which has a processor with a local APIC, you can say Y here to
1059 enable and use it. If you say Y here even though your machine doesn't
1060 have a local APIC, then the kernel will still run with no slowdown at
1061 all. The local APIC supports CPU-generated self-interrupts (timer,
1062 performance counters), and the NMI watchdog which detects hard
1065 config X86_UP_IOAPIC
1066 bool "IO-APIC support on uniprocessors"
1067 depends on X86_UP_APIC
1069 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1070 SMP-capable replacement for PC-style interrupt controllers. Most
1071 SMP systems and many recent uniprocessor systems have one.
1073 If you have a single-CPU system with an IO-APIC, you can say Y here
1074 to use it. If you say Y here even though your machine doesn't have
1075 an IO-APIC, then the kernel will still run with no slowdown at all.
1077 config X86_LOCAL_APIC
1079 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1080 select IRQ_DOMAIN_HIERARCHY
1081 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1085 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1087 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1088 bool "Reroute for broken boot IRQs"
1089 depends on X86_IO_APIC
1091 This option enables a workaround that fixes a source of
1092 spurious interrupts. This is recommended when threaded
1093 interrupt handling is used on systems where the generation of
1094 superfluous "boot interrupts" cannot be disabled.
1096 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1097 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1098 kernel does during interrupt handling). On chipsets where this
1099 boot IRQ generation cannot be disabled, this workaround keeps
1100 the original IRQ line masked so that only the equivalent "boot
1101 IRQ" is delivered to the CPUs. The workaround also tells the
1102 kernel to set up the IRQ handler on the boot IRQ line. In this
1103 way only one interrupt is delivered to the kernel. Otherwise
1104 the spurious second interrupt may cause the kernel to bring
1105 down (vital) interrupt lines.
1107 Only affects "broken" chipsets. Interrupt sharing may be
1108 increased on these systems.
1111 bool "Machine Check / overheating reporting"
1112 select GENERIC_ALLOCATOR
1115 Machine Check support allows the processor to notify the
1116 kernel if it detects a problem (e.g. overheating, data corruption).
1117 The action the kernel takes depends on the severity of the problem,
1118 ranging from warning messages to halting the machine.
1120 config X86_MCELOG_LEGACY
1121 bool "Support for deprecated /dev/mcelog character device"
1124 Enable support for /dev/mcelog which is needed by the old mcelog
1125 userspace logging daemon. Consider switching to the new generation
1128 config X86_MCE_INTEL
1130 prompt "Intel MCE features"
1131 depends on X86_MCE && X86_LOCAL_APIC
1133 Additional support for intel specific MCE features such as
1134 the thermal monitor.
1138 prompt "AMD MCE features"
1139 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1141 Additional support for AMD specific MCE features such as
1142 the DRAM Error Threshold.
1144 config X86_ANCIENT_MCE
1145 bool "Support for old Pentium 5 / WinChip machine checks"
1146 depends on X86_32 && X86_MCE
1148 Include support for machine check handling on old Pentium 5 or WinChip
1149 systems. These typically need to be enabled explicitly on the command
1152 config X86_MCE_THRESHOLD
1153 depends on X86_MCE_AMD || X86_MCE_INTEL
1156 config X86_MCE_INJECT
1157 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1158 tristate "Machine check injector support"
1160 Provide support for injecting machine checks for testing purposes.
1161 If you don't know what a machine check is and you don't do kernel
1162 QA it is safe to say n.
1164 config X86_THERMAL_VECTOR
1166 depends on X86_MCE_INTEL
1168 source "arch/x86/events/Kconfig"
1170 config X86_LEGACY_VM86
1171 bool "Legacy VM86 support"
1174 This option allows user programs to put the CPU into V8086
1175 mode, which is an 80286-era approximation of 16-bit real mode.
1177 Some very old versions of X and/or vbetool require this option
1178 for user mode setting. Similarly, DOSEMU will use it if
1179 available to accelerate real mode DOS programs. However, any
1180 recent version of DOSEMU, X, or vbetool should be fully
1181 functional even without kernel VM86 support, as they will all
1182 fall back to software emulation. Nevertheless, if you are using
1183 a 16-bit DOS program where 16-bit performance matters, vm86
1184 mode might be faster than emulation and you might want to
1187 Note that any app that works on a 64-bit kernel is unlikely to
1188 need this option, as 64-bit kernels don't, and can't, support
1189 V8086 mode. This option is also unrelated to 16-bit protected
1190 mode and is not needed to run most 16-bit programs under Wine.
1192 Enabling this option increases the complexity of the kernel
1193 and slows down exception handling a tiny bit.
1195 If unsure, say N here.
1199 default X86_LEGACY_VM86
1202 bool "Enable support for 16-bit segments" if EXPERT
1204 depends on MODIFY_LDT_SYSCALL
1206 This option is required by programs like Wine to run 16-bit
1207 protected mode legacy code on x86 processors. Disabling
1208 this option saves about 300 bytes on i386, or around 6K text
1209 plus 16K runtime memory on x86-64,
1213 depends on X86_16BIT && X86_32
1217 depends on X86_16BIT && X86_64
1219 config X86_VSYSCALL_EMULATION
1220 bool "Enable vsyscall emulation" if EXPERT
1224 This enables emulation of the legacy vsyscall page. Disabling
1225 it is roughly equivalent to booting with vsyscall=none, except
1226 that it will also disable the helpful warning if a program
1227 tries to use a vsyscall. With this option set to N, offending
1228 programs will just segfault, citing addresses of the form
1231 This option is required by many programs built before 2013, and
1232 care should be used even with newer programs if set to N.
1234 Disabling this option saves about 7K of kernel size and
1235 possibly 4K of additional runtime pagetable memory.
1238 tristate "Toshiba Laptop support"
1241 This adds a driver to safely access the System Management Mode of
1242 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1243 not work on models with a Phoenix BIOS. The System Management Mode
1244 is used to set the BIOS and power saving options on Toshiba portables.
1246 For information on utilities to make use of this driver see the
1247 Toshiba Linux utilities web site at:
1248 <http://www.buzzard.org.uk/toshiba/>.
1250 Say Y if you intend to run this kernel on a Toshiba portable.
1254 tristate "Dell i8k legacy laptop support"
1256 select SENSORS_DELL_SMM
1258 This option enables legacy /proc/i8k userspace interface in hwmon
1259 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1260 temperature and allows controlling fan speeds of Dell laptops via
1261 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1262 it reports also power and hotkey status. For fan speed control is
1263 needed userspace package i8kutils.
1265 Say Y if you intend to run this kernel on old Dell laptops or want to
1266 use userspace package i8kutils.
1269 config X86_REBOOTFIXUPS
1270 bool "Enable X86 board specific fixups for reboot"
1273 This enables chipset and/or board specific fixups to be done
1274 in order to get reboot to work correctly. This is only needed on
1275 some combinations of hardware and BIOS. The symptom, for which
1276 this config is intended, is when reboot ends with a stalled/hung
1279 Currently, the only fixup is for the Geode machines using
1280 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1282 Say Y if you want to enable the fixup. Currently, it's safe to
1283 enable this option even if you don't need it.
1287 bool "CPU microcode loading support"
1289 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1292 If you say Y here, you will be able to update the microcode on
1293 Intel and AMD processors. The Intel support is for the IA32 family,
1294 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1295 AMD support is for families 0x10 and later. You will obviously need
1296 the actual microcode binary data itself which is not shipped with
1299 The preferred method to load microcode from a detached initrd is described
1300 in Documentation/x86/microcode.txt. For that you need to enable
1301 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1302 initrd for microcode blobs.
1304 In addition, you can build the microcode into the kernel. For that you
1305 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1308 config MICROCODE_INTEL
1309 bool "Intel microcode loading support"
1310 depends on MICROCODE
1314 This options enables microcode patch loading support for Intel
1317 For the current Intel microcode data package go to
1318 <https://downloadcenter.intel.com> and search for
1319 'Linux Processor Microcode Data File'.
1321 config MICROCODE_AMD
1322 bool "AMD microcode loading support"
1323 depends on MICROCODE
1326 If you select this option, microcode patch loading support for AMD
1327 processors will be enabled.
1329 config MICROCODE_OLD_INTERFACE
1331 depends on MICROCODE
1334 tristate "/dev/cpu/*/msr - Model-specific register support"
1336 This device gives privileged processes access to the x86
1337 Model-Specific Registers (MSRs). It is a character device with
1338 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1339 MSR accesses are directed to a specific CPU on multi-processor
1343 tristate "/dev/cpu/*/cpuid - CPU information support"
1345 This device gives processes access to the x86 CPUID instruction to
1346 be executed on a specific processor. It is a character device
1347 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1351 prompt "High Memory Support"
1358 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1359 However, the address space of 32-bit x86 processors is only 4
1360 Gigabytes large. That means that, if you have a large amount of
1361 physical memory, not all of it can be "permanently mapped" by the
1362 kernel. The physical memory that's not permanently mapped is called
1365 If you are compiling a kernel which will never run on a machine with
1366 more than 1 Gigabyte total physical RAM, answer "off" here (default
1367 choice and suitable for most users). This will result in a "3GB/1GB"
1368 split: 3GB are mapped so that each process sees a 3GB virtual memory
1369 space and the remaining part of the 4GB virtual memory space is used
1370 by the kernel to permanently map as much physical memory as
1373 If the machine has between 1 and 4 Gigabytes physical RAM, then
1376 If more than 4 Gigabytes is used then answer "64GB" here. This
1377 selection turns Intel PAE (Physical Address Extension) mode on.
1378 PAE implements 3-level paging on IA32 processors. PAE is fully
1379 supported by Linux, PAE mode is implemented on all recent Intel
1380 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1381 then the kernel will not boot on CPUs that don't support PAE!
1383 The actual amount of total physical memory will either be
1384 auto detected or can be forced by using a kernel command line option
1385 such as "mem=256M". (Try "man bootparam" or see the documentation of
1386 your boot loader (lilo or loadlin) about how to pass options to the
1387 kernel at boot time.)
1389 If unsure, say "off".
1394 Select this if you have a 32-bit processor and between 1 and 4
1395 gigabytes of physical RAM.
1399 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1402 Select this if you have a 32-bit processor and more than 4
1403 gigabytes of physical RAM.
1408 prompt "Memory split" if EXPERT
1412 Select the desired split between kernel and user memory.
1414 If the address range available to the kernel is less than the
1415 physical memory installed, the remaining memory will be available
1416 as "high memory". Accessing high memory is a little more costly
1417 than low memory, as it needs to be mapped into the kernel first.
1418 Note that increasing the kernel address space limits the range
1419 available to user programs, making the address space there
1420 tighter. Selecting anything other than the default 3G/1G split
1421 will also likely make your kernel incompatible with binary-only
1424 If you are not absolutely sure what you are doing, leave this
1428 bool "3G/1G user/kernel split"
1429 config VMSPLIT_3G_OPT
1431 bool "3G/1G user/kernel split (for full 1G low memory)"
1433 bool "2G/2G user/kernel split"
1434 config VMSPLIT_2G_OPT
1436 bool "2G/2G user/kernel split (for full 2G low memory)"
1438 bool "1G/3G user/kernel split"
1443 default 0xB0000000 if VMSPLIT_3G_OPT
1444 default 0x80000000 if VMSPLIT_2G
1445 default 0x78000000 if VMSPLIT_2G_OPT
1446 default 0x40000000 if VMSPLIT_1G
1452 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1455 bool "PAE (Physical Address Extension) Support"
1456 depends on X86_32 && !HIGHMEM4G
1457 select PHYS_ADDR_T_64BIT
1460 PAE is required for NX support, and furthermore enables
1461 larger swapspace support for non-overcommit purposes. It
1462 has the cost of more pagetable lookup overhead, and also
1463 consumes more pagetable space per process.
1466 bool "Enable 5-level page tables support"
1467 select DYNAMIC_MEMORY_LAYOUT
1468 select SPARSEMEM_VMEMMAP
1471 5-level paging enables access to larger address space:
1472 upto 128 PiB of virtual address space and 4 PiB of
1473 physical address space.
1475 It will be supported by future Intel CPUs.
1477 A kernel with the option enabled can be booted on machines that
1478 support 4- or 5-level paging.
1480 See Documentation/x86/x86_64/5level-paging.txt for more
1485 config X86_DIRECT_GBPAGES
1487 depends on X86_64 && !DEBUG_PAGEALLOC
1489 Certain kernel features effectively disable kernel
1490 linear 1 GB mappings (even if the CPU otherwise
1491 supports them), so don't confuse the user by printing
1492 that we have them enabled.
1494 config X86_CPA_STATISTICS
1495 bool "Enable statistic for Change Page Attribute"
1498 Expose statistics about the Change Page Attribute mechanims, which
1499 helps to determine the effectivness of preserving large and huge
1500 page mappings when mapping protections are changed.
1502 config ARCH_HAS_MEM_ENCRYPT
1505 config AMD_MEM_ENCRYPT
1506 bool "AMD Secure Memory Encryption (SME) support"
1507 depends on X86_64 && CPU_SUP_AMD
1508 select DYNAMIC_PHYSICAL_MASK
1509 select ARCH_USE_MEMREMAP_PROT
1511 Say yes to enable support for the encryption of system memory.
1512 This requires an AMD processor that supports Secure Memory
1515 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1516 bool "Activate AMD Secure Memory Encryption (SME) by default"
1518 depends on AMD_MEM_ENCRYPT
1520 Say yes to have system memory encrypted by default if running on
1521 an AMD processor that supports Secure Memory Encryption (SME).
1523 If set to Y, then the encryption of system memory can be
1524 deactivated with the mem_encrypt=off command line option.
1526 If set to N, then the encryption of system memory can be
1527 activated with the mem_encrypt=on command line option.
1529 # Common NUMA Features
1531 bool "Numa Memory Allocation and Scheduler Support"
1533 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1534 default y if X86_BIGSMP
1536 Enable NUMA (Non Uniform Memory Access) support.
1538 The kernel will try to allocate memory used by a CPU on the
1539 local memory controller of the CPU and add some more
1540 NUMA awareness to the kernel.
1542 For 64-bit this is recommended if the system is Intel Core i7
1543 (or later), AMD Opteron, or EM64T NUMA.
1545 For 32-bit this is only needed if you boot a 32-bit
1546 kernel on a 64-bit NUMA platform.
1548 Otherwise, you should say N.
1552 prompt "Old style AMD Opteron NUMA detection"
1553 depends on X86_64 && NUMA && PCI
1555 Enable AMD NUMA node topology detection. You should say Y here if
1556 you have a multi processor AMD system. This uses an old method to
1557 read the NUMA configuration directly from the builtin Northbridge
1558 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1559 which also takes priority if both are compiled in.
1561 config X86_64_ACPI_NUMA
1563 prompt "ACPI NUMA detection"
1564 depends on X86_64 && NUMA && ACPI && PCI
1567 Enable ACPI SRAT based node topology detection.
1569 # Some NUMA nodes have memory ranges that span
1570 # other nodes. Even though a pfn is valid and
1571 # between a node's start and end pfns, it may not
1572 # reside on that node. See memmap_init_zone()
1574 config NODES_SPAN_OTHER_NODES
1576 depends on X86_64_ACPI_NUMA
1579 bool "NUMA emulation"
1582 Enable NUMA emulation. A flat machine will be split
1583 into virtual nodes when booted with "numa=fake=N", where N is the
1584 number of nodes. This is only useful for debugging.
1587 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1589 default "10" if MAXSMP
1590 default "6" if X86_64
1592 depends on NEED_MULTIPLE_NODES
1594 Specify the maximum number of NUMA Nodes available on the target
1595 system. Increases memory reserved to accommodate various tables.
1597 config ARCH_HAVE_MEMORY_PRESENT
1599 depends on X86_32 && DISCONTIGMEM
1601 config ARCH_FLATMEM_ENABLE
1603 depends on X86_32 && !NUMA
1605 config ARCH_DISCONTIGMEM_ENABLE
1607 depends on NUMA && X86_32
1609 config ARCH_DISCONTIGMEM_DEFAULT
1611 depends on NUMA && X86_32
1613 config ARCH_SPARSEMEM_ENABLE
1615 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1616 select SPARSEMEM_STATIC if X86_32
1617 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1619 config ARCH_SPARSEMEM_DEFAULT
1623 config ARCH_SELECT_MEMORY_MODEL
1625 depends on ARCH_SPARSEMEM_ENABLE
1627 config ARCH_MEMORY_PROBE
1628 bool "Enable sysfs memory/probe interface"
1629 depends on X86_64 && MEMORY_HOTPLUG
1631 This option enables a sysfs memory/probe interface for testing.
1632 See Documentation/memory-hotplug.txt for more information.
1633 If you are unsure how to answer this question, answer N.
1635 config ARCH_PROC_KCORE_TEXT
1637 depends on X86_64 && PROC_KCORE
1639 config ILLEGAL_POINTER_VALUE
1642 default 0xdead000000000000 if X86_64
1644 config X86_PMEM_LEGACY_DEVICE
1647 config X86_PMEM_LEGACY
1648 tristate "Support non-standard NVDIMMs and ADR protected memory"
1649 depends on PHYS_ADDR_T_64BIT
1651 select X86_PMEM_LEGACY_DEVICE
1654 Treat memory marked using the non-standard e820 type of 12 as used
1655 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1656 The kernel will offer these regions to the 'pmem' driver so
1657 they can be used for persistent storage.
1662 bool "Allocate 3rd-level pagetables from highmem"
1665 The VM uses one page table entry for each page of physical memory.
1666 For systems with a lot of RAM, this can be wasteful of precious
1667 low memory. Setting this option will put user-space page table
1668 entries in high memory.
1670 config X86_CHECK_BIOS_CORRUPTION
1671 bool "Check for low memory corruption"
1673 Periodically check for memory corruption in low memory, which
1674 is suspected to be caused by BIOS. Even when enabled in the
1675 configuration, it is disabled at runtime. Enable it by
1676 setting "memory_corruption_check=1" on the kernel command
1677 line. By default it scans the low 64k of memory every 60
1678 seconds; see the memory_corruption_check_size and
1679 memory_corruption_check_period parameters in
1680 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1682 When enabled with the default parameters, this option has
1683 almost no overhead, as it reserves a relatively small amount
1684 of memory and scans it infrequently. It both detects corruption
1685 and prevents it from affecting the running system.
1687 It is, however, intended as a diagnostic tool; if repeatable
1688 BIOS-originated corruption always affects the same memory,
1689 you can use memmap= to prevent the kernel from using that
1692 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1693 bool "Set the default setting of memory_corruption_check"
1694 depends on X86_CHECK_BIOS_CORRUPTION
1697 Set whether the default state of memory_corruption_check is
1700 config X86_RESERVE_LOW
1701 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1705 Specify the amount of low memory to reserve for the BIOS.
1707 The first page contains BIOS data structures that the kernel
1708 must not use, so that page must always be reserved.
1710 By default we reserve the first 64K of physical RAM, as a
1711 number of BIOSes are known to corrupt that memory range
1712 during events such as suspend/resume or monitor cable
1713 insertion, so it must not be used by the kernel.
1715 You can set this to 4 if you are absolutely sure that you
1716 trust the BIOS to get all its memory reservations and usages
1717 right. If you know your BIOS have problems beyond the
1718 default 64K area, you can set this to 640 to avoid using the
1719 entire low memory range.
1721 If you have doubts about the BIOS (e.g. suspend/resume does
1722 not work or there's kernel crashes after certain hardware
1723 hotplug events) then you might want to enable
1724 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1725 typical corruption patterns.
1727 Leave this to the default value of 64 if you are unsure.
1729 config MATH_EMULATION
1731 depends on MODIFY_LDT_SYSCALL
1732 prompt "Math emulation" if X86_32
1734 Linux can emulate a math coprocessor (used for floating point
1735 operations) if you don't have one. 486DX and Pentium processors have
1736 a math coprocessor built in, 486SX and 386 do not, unless you added
1737 a 487DX or 387, respectively. (The messages during boot time can
1738 give you some hints here ["man dmesg"].) Everyone needs either a
1739 coprocessor or this emulation.
1741 If you don't have a math coprocessor, you need to say Y here; if you
1742 say Y here even though you have a coprocessor, the coprocessor will
1743 be used nevertheless. (This behavior can be changed with the kernel
1744 command line option "no387", which comes handy if your coprocessor
1745 is broken. Try "man bootparam" or see the documentation of your boot
1746 loader (lilo or loadlin) about how to pass options to the kernel at
1747 boot time.) This means that it is a good idea to say Y here if you
1748 intend to use this kernel on different machines.
1750 More information about the internals of the Linux math coprocessor
1751 emulation can be found in <file:arch/x86/math-emu/README>.
1753 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1754 kernel, it won't hurt.
1758 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1760 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1761 the Memory Type Range Registers (MTRRs) may be used to control
1762 processor access to memory ranges. This is most useful if you have
1763 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1764 allows bus write transfers to be combined into a larger transfer
1765 before bursting over the PCI/AGP bus. This can increase performance
1766 of image write operations 2.5 times or more. Saying Y here creates a
1767 /proc/mtrr file which may be used to manipulate your processor's
1768 MTRRs. Typically the X server should use this.
1770 This code has a reasonably generic interface so that similar
1771 control registers on other processors can be easily supported
1774 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1775 Registers (ARRs) which provide a similar functionality to MTRRs. For
1776 these, the ARRs are used to emulate the MTRRs.
1777 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1778 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1779 write-combining. All of these processors are supported by this code
1780 and it makes sense to say Y here if you have one of them.
1782 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1783 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1784 can lead to all sorts of problems, so it's good to say Y here.
1786 You can safely say Y even if your machine doesn't have MTRRs, you'll
1787 just add about 9 KB to your kernel.
1789 See <file:Documentation/x86/mtrr.txt> for more information.
1791 config MTRR_SANITIZER
1793 prompt "MTRR cleanup support"
1796 Convert MTRR layout from continuous to discrete, so X drivers can
1797 add writeback entries.
1799 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1800 The largest mtrr entry size for a continuous block can be set with
1805 config MTRR_SANITIZER_ENABLE_DEFAULT
1806 int "MTRR cleanup enable value (0-1)"
1809 depends on MTRR_SANITIZER
1811 Enable mtrr cleanup default value
1813 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1814 int "MTRR cleanup spare reg num (0-7)"
1817 depends on MTRR_SANITIZER
1819 mtrr cleanup spare entries default, it can be changed via
1820 mtrr_spare_reg_nr=N on the kernel command line.
1824 prompt "x86 PAT support" if EXPERT
1827 Use PAT attributes to setup page level cache control.
1829 PATs are the modern equivalents of MTRRs and are much more
1830 flexible than MTRRs.
1832 Say N here if you see bootup problems (boot crash, boot hang,
1833 spontaneous reboots) or a non-working video driver.
1837 config ARCH_USES_PG_UNCACHED
1843 prompt "x86 architectural random number generator" if EXPERT
1845 Enable the x86 architectural RDRAND instruction
1846 (Intel Bull Mountain technology) to generate random numbers.
1847 If supported, this is a high bandwidth, cryptographically
1848 secure hardware random number generator.
1852 prompt "Supervisor Mode Access Prevention" if EXPERT
1854 Supervisor Mode Access Prevention (SMAP) is a security
1855 feature in newer Intel processors. There is a small
1856 performance cost if this enabled and turned on; there is
1857 also a small increase in the kernel size if this is enabled.
1861 config X86_INTEL_UMIP
1863 depends on CPU_SUP_INTEL
1864 prompt "Intel User Mode Instruction Prevention" if EXPERT
1866 The User Mode Instruction Prevention (UMIP) is a security
1867 feature in newer Intel processors. If enabled, a general
1868 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1869 or STR instructions are executed in user mode. These instructions
1870 unnecessarily expose information about the hardware state.
1872 The vast majority of applications do not use these instructions.
1873 For the very few that do, software emulation is provided in
1874 specific cases in protected and virtual-8086 modes. Emulated
1877 config X86_INTEL_MPX
1878 prompt "Intel MPX (Memory Protection Extensions)"
1880 # Note: only available in 64-bit mode due to VMA flags shortage
1881 depends on CPU_SUP_INTEL && X86_64
1882 select ARCH_USES_HIGH_VMA_FLAGS
1884 MPX provides hardware features that can be used in
1885 conjunction with compiler-instrumented code to check
1886 memory references. It is designed to detect buffer
1887 overflow or underflow bugs.
1889 This option enables running applications which are
1890 instrumented or otherwise use MPX. It does not use MPX
1891 itself inside the kernel or to protect the kernel
1892 against bad memory references.
1894 Enabling this option will make the kernel larger:
1895 ~8k of kernel text and 36 bytes of data on a 64-bit
1896 defconfig. It adds a long to the 'mm_struct' which
1897 will increase the kernel memory overhead of each
1898 process and adds some branches to paths used during
1899 exec() and munmap().
1901 For details, see Documentation/x86/intel_mpx.txt
1905 config X86_INTEL_MEMORY_PROTECTION_KEYS
1906 prompt "Intel Memory Protection Keys"
1908 # Note: only available in 64-bit mode
1909 depends on CPU_SUP_INTEL && X86_64
1910 select ARCH_USES_HIGH_VMA_FLAGS
1911 select ARCH_HAS_PKEYS
1913 Memory Protection Keys provides a mechanism for enforcing
1914 page-based protections, but without requiring modification of the
1915 page tables when an application changes protection domains.
1917 For details, see Documentation/x86/protection-keys.txt
1922 bool "EFI runtime service support"
1925 select EFI_RUNTIME_WRAPPERS
1927 This enables the kernel to use EFI runtime services that are
1928 available (such as the EFI variable services).
1930 This option is only useful on systems that have EFI firmware.
1931 In addition, you should use the latest ELILO loader available
1932 at <http://elilo.sourceforge.net> in order to take advantage
1933 of EFI runtime services. However, even with this option, the
1934 resultant kernel should continue to boot on existing non-EFI
1938 bool "EFI stub support"
1939 depends on EFI && !X86_USE_3DNOW
1942 This kernel feature allows a bzImage to be loaded directly
1943 by EFI firmware without the use of a bootloader.
1945 See Documentation/efi-stub.txt for more information.
1948 bool "EFI mixed-mode support"
1949 depends on EFI_STUB && X86_64
1951 Enabling this feature allows a 64-bit kernel to be booted
1952 on a 32-bit firmware, provided that your CPU supports 64-bit
1955 Note that it is not possible to boot a mixed-mode enabled
1956 kernel via the EFI boot stub - a bootloader that supports
1957 the EFI handover protocol must be used.
1963 prompt "Enable seccomp to safely compute untrusted bytecode"
1965 This kernel feature is useful for number crunching applications
1966 that may need to compute untrusted bytecode during their
1967 execution. By using pipes or other transports made available to
1968 the process as file descriptors supporting the read/write
1969 syscalls, it's possible to isolate those applications in
1970 their own address space using seccomp. Once seccomp is
1971 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1972 and the task is only allowed to execute a few safe syscalls
1973 defined by each seccomp mode.
1975 If unsure, say Y. Only embedded should say N here.
1977 source "kernel/Kconfig.hz"
1980 bool "kexec system call"
1983 kexec is a system call that implements the ability to shutdown your
1984 current kernel, and to start another kernel. It is like a reboot
1985 but it is independent of the system firmware. And like a reboot
1986 you can start any kernel with it, not just Linux.
1988 The name comes from the similarity to the exec system call.
1990 It is an ongoing process to be certain the hardware in a machine
1991 is properly shutdown, so do not be surprised if this code does not
1992 initially work for you. As of this writing the exact hardware
1993 interface is strongly in flux, so no good recommendation can be
1997 bool "kexec file based system call"
2002 depends on CRYPTO_SHA256=y
2004 This is new version of kexec system call. This system call is
2005 file based and takes file descriptors as system call argument
2006 for kernel and initramfs as opposed to list of segments as
2007 accepted by previous system call.
2009 config ARCH_HAS_KEXEC_PURGATORY
2012 config KEXEC_VERIFY_SIG
2013 bool "Verify kernel signature during kexec_file_load() syscall"
2014 depends on KEXEC_FILE
2016 This option makes kernel signature verification mandatory for
2017 the kexec_file_load() syscall.
2019 In addition to that option, you need to enable signature
2020 verification for the corresponding kernel image type being
2021 loaded in order for this to work.
2023 config KEXEC_BZIMAGE_VERIFY_SIG
2024 bool "Enable bzImage signature verification support"
2025 depends on KEXEC_VERIFY_SIG
2026 depends on SIGNED_PE_FILE_VERIFICATION
2027 select SYSTEM_TRUSTED_KEYRING
2029 Enable bzImage signature verification support.
2032 bool "kernel crash dumps"
2033 depends on X86_64 || (X86_32 && HIGHMEM)
2035 Generate crash dump after being started by kexec.
2036 This should be normally only set in special crash dump kernels
2037 which are loaded in the main kernel with kexec-tools into
2038 a specially reserved region and then later executed after
2039 a crash by kdump/kexec. The crash dump kernel must be compiled
2040 to a memory address not used by the main kernel or BIOS using
2041 PHYSICAL_START, or it must be built as a relocatable image
2042 (CONFIG_RELOCATABLE=y).
2043 For more details see Documentation/kdump/kdump.txt
2047 depends on KEXEC && HIBERNATION
2049 Jump between original kernel and kexeced kernel and invoke
2050 code in physical address mode via KEXEC
2052 config PHYSICAL_START
2053 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2056 This gives the physical address where the kernel is loaded.
2058 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2059 bzImage will decompress itself to above physical address and
2060 run from there. Otherwise, bzImage will run from the address where
2061 it has been loaded by the boot loader and will ignore above physical
2064 In normal kdump cases one does not have to set/change this option
2065 as now bzImage can be compiled as a completely relocatable image
2066 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2067 address. This option is mainly useful for the folks who don't want
2068 to use a bzImage for capturing the crash dump and want to use a
2069 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2070 to be specifically compiled to run from a specific memory area
2071 (normally a reserved region) and this option comes handy.
2073 So if you are using bzImage for capturing the crash dump,
2074 leave the value here unchanged to 0x1000000 and set
2075 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2076 for capturing the crash dump change this value to start of
2077 the reserved region. In other words, it can be set based on
2078 the "X" value as specified in the "crashkernel=YM@XM"
2079 command line boot parameter passed to the panic-ed
2080 kernel. Please take a look at Documentation/kdump/kdump.txt
2081 for more details about crash dumps.
2083 Usage of bzImage for capturing the crash dump is recommended as
2084 one does not have to build two kernels. Same kernel can be used
2085 as production kernel and capture kernel. Above option should have
2086 gone away after relocatable bzImage support is introduced. But it
2087 is present because there are users out there who continue to use
2088 vmlinux for dump capture. This option should go away down the
2091 Don't change this unless you know what you are doing.
2094 bool "Build a relocatable kernel"
2097 This builds a kernel image that retains relocation information
2098 so it can be loaded someplace besides the default 1MB.
2099 The relocations tend to make the kernel binary about 10% larger,
2100 but are discarded at runtime.
2102 One use is for the kexec on panic case where the recovery kernel
2103 must live at a different physical address than the primary
2106 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2107 it has been loaded at and the compile time physical address
2108 (CONFIG_PHYSICAL_START) is used as the minimum location.
2110 config RANDOMIZE_BASE
2111 bool "Randomize the address of the kernel image (KASLR)"
2112 depends on RELOCATABLE
2115 In support of Kernel Address Space Layout Randomization (KASLR),
2116 this randomizes the physical address at which the kernel image
2117 is decompressed and the virtual address where the kernel
2118 image is mapped, as a security feature that deters exploit
2119 attempts relying on knowledge of the location of kernel
2122 On 64-bit, the kernel physical and virtual addresses are
2123 randomized separately. The physical address will be anywhere
2124 between 16MB and the top of physical memory (up to 64TB). The
2125 virtual address will be randomized from 16MB up to 1GB (9 bits
2126 of entropy). Note that this also reduces the memory space
2127 available to kernel modules from 1.5GB to 1GB.
2129 On 32-bit, the kernel physical and virtual addresses are
2130 randomized together. They will be randomized from 16MB up to
2131 512MB (8 bits of entropy).
2133 Entropy is generated using the RDRAND instruction if it is
2134 supported. If RDTSC is supported, its value is mixed into
2135 the entropy pool as well. If neither RDRAND nor RDTSC are
2136 supported, then entropy is read from the i8254 timer. The
2137 usable entropy is limited by the kernel being built using
2138 2GB addressing, and that PHYSICAL_ALIGN must be at a
2139 minimum of 2MB. As a result, only 10 bits of entropy are
2140 theoretically possible, but the implementations are further
2141 limited due to memory layouts.
2145 # Relocation on x86 needs some additional build support
2146 config X86_NEED_RELOCS
2148 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2150 config PHYSICAL_ALIGN
2151 hex "Alignment value to which kernel should be aligned"
2153 range 0x2000 0x1000000 if X86_32
2154 range 0x200000 0x1000000 if X86_64
2156 This value puts the alignment restrictions on physical address
2157 where kernel is loaded and run from. Kernel is compiled for an
2158 address which meets above alignment restriction.
2160 If bootloader loads the kernel at a non-aligned address and
2161 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2162 address aligned to above value and run from there.
2164 If bootloader loads the kernel at a non-aligned address and
2165 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2166 load address and decompress itself to the address it has been
2167 compiled for and run from there. The address for which kernel is
2168 compiled already meets above alignment restrictions. Hence the
2169 end result is that kernel runs from a physical address meeting
2170 above alignment restrictions.
2172 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2173 this value must be a multiple of 0x200000.
2175 Don't change this unless you know what you are doing.
2177 config DYNAMIC_MEMORY_LAYOUT
2180 This option makes base addresses of vmalloc and vmemmap as well as
2181 __PAGE_OFFSET movable during boot.
2183 config RANDOMIZE_MEMORY
2184 bool "Randomize the kernel memory sections"
2186 depends on RANDOMIZE_BASE
2187 select DYNAMIC_MEMORY_LAYOUT
2188 default RANDOMIZE_BASE
2190 Randomizes the base virtual address of kernel memory sections
2191 (physical memory mapping, vmalloc & vmemmap). This security feature
2192 makes exploits relying on predictable memory locations less reliable.
2194 The order of allocations remains unchanged. Entropy is generated in
2195 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2196 configuration have in average 30,000 different possible virtual
2197 addresses for each memory section.
2201 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2202 hex "Physical memory mapping padding" if EXPERT
2203 depends on RANDOMIZE_MEMORY
2204 default "0xa" if MEMORY_HOTPLUG
2206 range 0x1 0x40 if MEMORY_HOTPLUG
2209 Define the padding in terabytes added to the existing physical
2210 memory size during kernel memory randomization. It is useful
2211 for memory hotplug support but reduces the entropy available for
2212 address randomization.
2214 If unsure, leave at the default value.
2220 config BOOTPARAM_HOTPLUG_CPU0
2221 bool "Set default setting of cpu0_hotpluggable"
2222 depends on HOTPLUG_CPU
2224 Set whether default state of cpu0_hotpluggable is on or off.
2226 Say Y here to enable CPU0 hotplug by default. If this switch
2227 is turned on, there is no need to give cpu0_hotplug kernel
2228 parameter and the CPU0 hotplug feature is enabled by default.
2230 Please note: there are two known CPU0 dependencies if you want
2231 to enable the CPU0 hotplug feature either by this switch or by
2232 cpu0_hotplug kernel parameter.
2234 First, resume from hibernate or suspend always starts from CPU0.
2235 So hibernate and suspend are prevented if CPU0 is offline.
2237 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2238 offline if any interrupt can not migrate out of CPU0. There may
2239 be other CPU0 dependencies.
2241 Please make sure the dependencies are under your control before
2242 you enable this feature.
2244 Say N if you don't want to enable CPU0 hotplug feature by default.
2245 You still can enable the CPU0 hotplug feature at boot by kernel
2246 parameter cpu0_hotplug.
2248 config DEBUG_HOTPLUG_CPU0
2250 prompt "Debug CPU0 hotplug"
2251 depends on HOTPLUG_CPU
2253 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2254 soon as possible and boots up userspace with CPU0 offlined. User
2255 can online CPU0 back after boot time.
2257 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2258 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2259 compilation or giving cpu0_hotplug kernel parameter at boot.
2265 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2266 depends on COMPAT_32
2268 Certain buggy versions of glibc will crash if they are
2269 presented with a 32-bit vDSO that is not mapped at the address
2270 indicated in its segment table.
2272 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2273 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2274 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2275 the only released version with the bug, but OpenSUSE 9
2276 contains a buggy "glibc 2.3.2".
2278 The symptom of the bug is that everything crashes on startup, saying:
2279 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2281 Saying Y here changes the default value of the vdso32 boot
2282 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2283 This works around the glibc bug but hurts performance.
2285 If unsure, say N: if you are compiling your own kernel, you
2286 are unlikely to be using a buggy version of glibc.
2289 prompt "vsyscall table for legacy applications"
2291 default LEGACY_VSYSCALL_EMULATE
2293 Legacy user code that does not know how to find the vDSO expects
2294 to be able to issue three syscalls by calling fixed addresses in
2295 kernel space. Since this location is not randomized with ASLR,
2296 it can be used to assist security vulnerability exploitation.
2298 This setting can be changed at boot time via the kernel command
2299 line parameter vsyscall=[emulate|none].
2301 On a system with recent enough glibc (2.14 or newer) and no
2302 static binaries, you can say None without a performance penalty
2303 to improve security.
2305 If unsure, select "Emulate".
2307 config LEGACY_VSYSCALL_EMULATE
2310 The kernel traps and emulates calls into the fixed
2311 vsyscall address mapping. This makes the mapping
2312 non-executable, but it still contains known contents,
2313 which could be used in certain rare security vulnerability
2314 exploits. This configuration is recommended when userspace
2315 still uses the vsyscall area.
2317 config LEGACY_VSYSCALL_NONE
2320 There will be no vsyscall mapping at all. This will
2321 eliminate any risk of ASLR bypass due to the vsyscall
2322 fixed address mapping. Attempts to use the vsyscalls
2323 will be reported to dmesg, so that either old or
2324 malicious userspace programs can be identified.
2329 bool "Built-in kernel command line"
2331 Allow for specifying boot arguments to the kernel at
2332 build time. On some systems (e.g. embedded ones), it is
2333 necessary or convenient to provide some or all of the
2334 kernel boot arguments with the kernel itself (that is,
2335 to not rely on the boot loader to provide them.)
2337 To compile command line arguments into the kernel,
2338 set this option to 'Y', then fill in the
2339 boot arguments in CONFIG_CMDLINE.
2341 Systems with fully functional boot loaders (i.e. non-embedded)
2342 should leave this option set to 'N'.
2345 string "Built-in kernel command string"
2346 depends on CMDLINE_BOOL
2349 Enter arguments here that should be compiled into the kernel
2350 image and used at boot time. If the boot loader provides a
2351 command line at boot time, it is appended to this string to
2352 form the full kernel command line, when the system boots.
2354 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2355 change this behavior.
2357 In most cases, the command line (whether built-in or provided
2358 by the boot loader) should specify the device for the root
2361 config CMDLINE_OVERRIDE
2362 bool "Built-in command line overrides boot loader arguments"
2363 depends on CMDLINE_BOOL
2365 Set this option to 'Y' to have the kernel ignore the boot loader
2366 command line, and use ONLY the built-in command line.
2368 This is used to work around broken boot loaders. This should
2369 be set to 'N' under normal conditions.
2371 config MODIFY_LDT_SYSCALL
2372 bool "Enable the LDT (local descriptor table)" if EXPERT
2375 Linux can allow user programs to install a per-process x86
2376 Local Descriptor Table (LDT) using the modify_ldt(2) system
2377 call. This is required to run 16-bit or segmented code such as
2378 DOSEMU or some Wine programs. It is also used by some very old
2379 threading libraries.
2381 Enabling this feature adds a small amount of overhead to
2382 context switches and increases the low-level kernel attack
2383 surface. Disabling it removes the modify_ldt(2) system call.
2385 Saying 'N' here may make sense for embedded or server kernels.
2387 source "kernel/livepatch/Kconfig"
2391 config ARCH_HAS_ADD_PAGES
2393 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2395 config ARCH_ENABLE_MEMORY_HOTPLUG
2397 depends on X86_64 || (X86_32 && HIGHMEM)
2399 config ARCH_ENABLE_MEMORY_HOTREMOVE
2401 depends on MEMORY_HOTPLUG
2403 config USE_PERCPU_NUMA_NODE_ID
2407 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2409 depends on X86_64 || X86_PAE
2411 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2413 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2415 config ARCH_ENABLE_THP_MIGRATION
2417 depends on X86_64 && TRANSPARENT_HUGEPAGE
2419 menu "Power management and ACPI options"
2421 config ARCH_HIBERNATION_HEADER
2423 depends on HIBERNATION
2425 source "kernel/power/Kconfig"
2427 source "drivers/acpi/Kconfig"
2429 source "drivers/sfi/Kconfig"
2436 tristate "APM (Advanced Power Management) BIOS support"
2437 depends on X86_32 && PM_SLEEP
2439 APM is a BIOS specification for saving power using several different
2440 techniques. This is mostly useful for battery powered laptops with
2441 APM compliant BIOSes. If you say Y here, the system time will be
2442 reset after a RESUME operation, the /proc/apm device will provide
2443 battery status information, and user-space programs will receive
2444 notification of APM "events" (e.g. battery status change).
2446 If you select "Y" here, you can disable actual use of the APM
2447 BIOS by passing the "apm=off" option to the kernel at boot time.
2449 Note that the APM support is almost completely disabled for
2450 machines with more than one CPU.
2452 In order to use APM, you will need supporting software. For location
2453 and more information, read <file:Documentation/power/apm-acpi.txt>
2454 and the Battery Powered Linux mini-HOWTO, available from
2455 <http://www.tldp.org/docs.html#howto>.
2457 This driver does not spin down disk drives (see the hdparm(8)
2458 manpage ("man 8 hdparm") for that), and it doesn't turn off
2459 VESA-compliant "green" monitors.
2461 This driver does not support the TI 4000M TravelMate and the ACER
2462 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2463 desktop machines also don't have compliant BIOSes, and this driver
2464 may cause those machines to panic during the boot phase.
2466 Generally, if you don't have a battery in your machine, there isn't
2467 much point in using this driver and you should say N. If you get
2468 random kernel OOPSes or reboots that don't seem to be related to
2469 anything, try disabling/enabling this option (or disabling/enabling
2472 Some other things you should try when experiencing seemingly random,
2475 1) make sure that you have enough swap space and that it is
2477 2) pass the "no-hlt" option to the kernel
2478 3) switch on floating point emulation in the kernel and pass
2479 the "no387" option to the kernel
2480 4) pass the "floppy=nodma" option to the kernel
2481 5) pass the "mem=4M" option to the kernel (thereby disabling
2482 all but the first 4 MB of RAM)
2483 6) make sure that the CPU is not over clocked.
2484 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2485 8) disable the cache from your BIOS settings
2486 9) install a fan for the video card or exchange video RAM
2487 10) install a better fan for the CPU
2488 11) exchange RAM chips
2489 12) exchange the motherboard.
2491 To compile this driver as a module, choose M here: the
2492 module will be called apm.
2496 config APM_IGNORE_USER_SUSPEND
2497 bool "Ignore USER SUSPEND"
2499 This option will ignore USER SUSPEND requests. On machines with a
2500 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2501 series notebooks, it is necessary to say Y because of a BIOS bug.
2503 config APM_DO_ENABLE
2504 bool "Enable PM at boot time"
2506 Enable APM features at boot time. From page 36 of the APM BIOS
2507 specification: "When disabled, the APM BIOS does not automatically
2508 power manage devices, enter the Standby State, enter the Suspend
2509 State, or take power saving steps in response to CPU Idle calls."
2510 This driver will make CPU Idle calls when Linux is idle (unless this
2511 feature is turned off -- see "Do CPU IDLE calls", below). This
2512 should always save battery power, but more complicated APM features
2513 will be dependent on your BIOS implementation. You may need to turn
2514 this option off if your computer hangs at boot time when using APM
2515 support, or if it beeps continuously instead of suspending. Turn
2516 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2517 T400CDT. This is off by default since most machines do fine without
2522 bool "Make CPU Idle calls when idle"
2524 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2525 On some machines, this can activate improved power savings, such as
2526 a slowed CPU clock rate, when the machine is idle. These idle calls
2527 are made after the idle loop has run for some length of time (e.g.,
2528 333 mS). On some machines, this will cause a hang at boot time or
2529 whenever the CPU becomes idle. (On machines with more than one CPU,
2530 this option does nothing.)
2532 config APM_DISPLAY_BLANK
2533 bool "Enable console blanking using APM"
2535 Enable console blanking using the APM. Some laptops can use this to
2536 turn off the LCD backlight when the screen blanker of the Linux
2537 virtual console blanks the screen. Note that this is only used by
2538 the virtual console screen blanker, and won't turn off the backlight
2539 when using the X Window system. This also doesn't have anything to
2540 do with your VESA-compliant power-saving monitor. Further, this
2541 option doesn't work for all laptops -- it might not turn off your
2542 backlight at all, or it might print a lot of errors to the console,
2543 especially if you are using gpm.
2545 config APM_ALLOW_INTS
2546 bool "Allow interrupts during APM BIOS calls"
2548 Normally we disable external interrupts while we are making calls to
2549 the APM BIOS as a measure to lessen the effects of a badly behaving
2550 BIOS implementation. The BIOS should reenable interrupts if it
2551 needs to. Unfortunately, some BIOSes do not -- especially those in
2552 many of the newer IBM Thinkpads. If you experience hangs when you
2553 suspend, try setting this to Y. Otherwise, say N.
2557 source "drivers/cpufreq/Kconfig"
2559 source "drivers/cpuidle/Kconfig"
2561 source "drivers/idle/Kconfig"
2566 menu "Bus options (PCI etc.)"
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
2629 config MMCONF_FAM10H
2631 depends on X86_64 && PCI_MMCONFIG && ACPI
2633 config PCI_CNB20LE_QUIRK
2634 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2637 Read the PCI windows out of the CNB20LE host bridge. This allows
2638 PCI hotplug to work on systems with the CNB20LE chipset which do
2641 There's no public spec for this chipset, and this functionality
2642 is known to be incomplete.
2644 You should say N unless you know you need this.
2647 bool "ISA bus support on modern systems" if EXPERT
2649 Expose ISA bus device drivers and options available for selection and
2650 configuration. Enable this option if your target machine has an ISA
2651 bus. ISA is an older system, displaced by PCI and newer bus
2652 architectures -- if your target machine is modern, it probably does
2653 not have an ISA bus.
2657 # x86_64 have no ISA slots, but can have ISA-style DMA.
2659 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2662 Enables ISA-style DMA support for devices requiring such controllers.
2670 Find out whether you have ISA slots on your motherboard. ISA is the
2671 name of a bus system, i.e. the way the CPU talks to the other stuff
2672 inside your box. Other bus systems are PCI, EISA, MicroChannel
2673 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2674 newer boards don't support it. If you have ISA, say Y, otherwise N.
2677 tristate "NatSemi SCx200 support"
2679 This provides basic support for National Semiconductor's
2680 (now AMD's) Geode processors. The driver probes for the
2681 PCI-IDs of several on-chip devices, so its a good dependency
2682 for other scx200_* drivers.
2684 If compiled as a module, the driver is named scx200.
2686 config SCx200HR_TIMER
2687 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2691 This driver provides a clocksource built upon the on-chip
2692 27MHz high-resolution timer. Its also a workaround for
2693 NSC Geode SC-1100's buggy TSC, which loses time when the
2694 processor goes idle (as is done by the scheduler). The
2695 other workaround is idle=poll boot option.
2698 bool "One Laptop Per Child support"
2705 Add support for detecting the unique features of the OLPC
2709 bool "OLPC XO-1 Power Management"
2710 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2712 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2715 bool "OLPC XO-1 Real Time Clock"
2716 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2718 Add support for the XO-1 real time clock, which can be used as a
2719 programmable wakeup source.
2722 bool "OLPC XO-1 SCI extras"
2723 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2727 Add support for SCI-based features of the OLPC XO-1 laptop:
2728 - EC-driven system wakeups
2732 - AC adapter status updates
2733 - Battery status updates
2735 config OLPC_XO15_SCI
2736 bool "OLPC XO-1.5 SCI extras"
2737 depends on OLPC && ACPI
2740 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2741 - EC-driven system wakeups
2742 - AC adapter status updates
2743 - Battery status updates
2746 bool "PCEngines ALIX System Support (LED setup)"
2749 This option enables system support for the PCEngines ALIX.
2750 At present this just sets up LEDs for GPIO control on
2751 ALIX2/3/6 boards. However, other system specific setup should
2754 Note: You must still enable the drivers for GPIO and LED support
2755 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2757 Note: You have to set alix.force=1 for boards with Award BIOS.
2760 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2763 This option enables system support for the Soekris Engineering net5501.
2766 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2770 This option enables system support for the Traverse Technologies GEOS.
2773 bool "Technologic Systems TS-5500 platform support"
2775 select CHECK_SIGNATURE
2779 This option enables system support for the Technologic Systems TS-5500.
2785 depends on CPU_SUP_AMD && PCI
2788 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2790 Firmwares often provide initial graphics framebuffers so the BIOS,
2791 bootloader or kernel can show basic video-output during boot for
2792 user-guidance and debugging. Historically, x86 used the VESA BIOS
2793 Extensions and EFI-framebuffers for this, which are mostly limited
2795 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2796 framebuffers so the new generic system-framebuffer drivers can be
2797 used on x86. If the framebuffer is not compatible with the generic
2798 modes, it is advertised as fallback platform framebuffer so legacy
2799 drivers like efifb, vesafb and uvesafb can pick it up.
2800 If this option is not selected, all system framebuffers are always
2801 marked as fallback platform framebuffers as usual.
2803 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2804 not be able to pick up generic system framebuffers if this option
2805 is selected. You are highly encouraged to enable simplefb as
2806 replacement if you select this option. simplefb can correctly deal
2807 with generic system framebuffers. But you should still keep vesafb
2808 and others enabled as fallback if a system framebuffer is
2809 incompatible with simplefb.
2816 menu "Binary Emulations"
2818 config IA32_EMULATION
2819 bool "IA32 Emulation"
2821 select ARCH_WANT_OLD_COMPAT_IPC
2823 select COMPAT_BINFMT_ELF
2824 select COMPAT_OLD_SIGACTION
2826 Include code to run legacy 32-bit programs under a
2827 64-bit kernel. You should likely turn this on, unless you're
2828 100% sure that you don't have any 32-bit programs left.
2831 tristate "IA32 a.out support"
2832 depends on IA32_EMULATION
2835 Support old a.out binaries in the 32bit emulation.
2838 bool "x32 ABI for 64-bit mode"
2841 Include code to run binaries for the x32 native 32-bit ABI
2842 for 64-bit processors. An x32 process gets access to the
2843 full 64-bit register file and wide data path while leaving
2844 pointers at 32 bits for smaller memory footprint.
2846 You will need a recent binutils (2.22 or later) with
2847 elf32_x86_64 support enabled to compile a kernel with this
2852 depends on IA32_EMULATION || X86_32
2854 select OLD_SIGSUSPEND3
2858 depends on IA32_EMULATION || X86_X32
2861 config COMPAT_FOR_U64_ALIGNMENT
2864 config SYSVIPC_COMPAT
2872 config HAVE_ATOMIC_IOMAP
2876 config X86_DEV_DMA_OPS
2878 depends on X86_64 || STA2X11
2880 config X86_DMA_REMAP
2884 config HAVE_GENERIC_GUP
2887 source "drivers/firmware/Kconfig"
2889 source "arch/x86/kvm/Kconfig"