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
34 config FORCE_DYNAMIC_FTRACE
37 depends on FUNCTION_TRACER
40 We keep the static function tracing (!DYNAMIC_FTRACE) around
41 in order to test the non static function tracing in the
42 generic code, as other architectures still use it. But we
43 only need to keep it around for x86_64. No need to keep it
44 for x86_32. For x86_32, force DYNAMIC_FTRACE.
48 # ( Note that options that are marked 'if X86_64' could in principle be
49 # ported to 32-bit as well. )
54 # Note: keep this list sorted alphabetically
56 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
57 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
58 select ARCH_32BIT_OFF_T if X86_32
59 select ARCH_CLOCKSOURCE_DATA
60 select ARCH_CLOCKSOURCE_INIT
61 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
62 select ARCH_HAS_DEBUG_VIRTUAL
63 select ARCH_HAS_DEVMEM_IS_ALLOWED
64 select ARCH_HAS_ELF_RANDOMIZE
65 select ARCH_HAS_FAST_MULTIPLIER
66 select ARCH_HAS_FILTER_PGPROT
67 select ARCH_HAS_FORTIFY_SOURCE
68 select ARCH_HAS_GCOV_PROFILE_ALL
69 select ARCH_HAS_KCOV if X86_64
70 select ARCH_HAS_MEMBARRIER_SYNC_CORE
71 select ARCH_HAS_PMEM_API if X86_64
72 select ARCH_HAS_PTE_SPECIAL
73 select ARCH_HAS_REFCOUNT
74 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
75 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
76 select ARCH_HAS_SET_MEMORY
77 select ARCH_HAS_SET_DIRECT_MAP
78 select ARCH_HAS_STRICT_KERNEL_RWX
79 select ARCH_HAS_STRICT_MODULE_RWX
80 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
81 select ARCH_HAS_UBSAN_SANITIZE_ALL
82 select ARCH_HAS_ZONE_DEVICE if X86_64
83 select ARCH_HAVE_NMI_SAFE_CMPXCHG
84 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
85 select ARCH_MIGHT_HAVE_PC_PARPORT
86 select ARCH_MIGHT_HAVE_PC_SERIO
88 select ARCH_SUPPORTS_ACPI
89 select ARCH_SUPPORTS_ATOMIC_RMW
90 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
91 select ARCH_USE_BUILTIN_BSWAP
92 select ARCH_USE_QUEUED_RWLOCKS
93 select ARCH_USE_QUEUED_SPINLOCKS
94 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
95 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
96 select ARCH_WANTS_THP_SWAP if X86_64
97 select BUILDTIME_EXTABLE_SORT
99 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
100 select CLOCKSOURCE_WATCHDOG
101 select DCACHE_WORD_ACCESS
102 select EDAC_ATOMIC_SCRUB
104 select GENERIC_CLOCKEVENTS
105 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
106 select GENERIC_CLOCKEVENTS_MIN_ADJUST
107 select GENERIC_CMOS_UPDATE
108 select GENERIC_CPU_AUTOPROBE
109 select GENERIC_CPU_VULNERABILITIES
110 select GENERIC_EARLY_IOREMAP
111 select GENERIC_FIND_FIRST_BIT
113 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
114 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
115 select GENERIC_IRQ_MIGRATION if SMP
116 select GENERIC_IRQ_PROBE
117 select GENERIC_IRQ_RESERVATION_MODE
118 select GENERIC_IRQ_SHOW
119 select GENERIC_PENDING_IRQ if SMP
120 select GENERIC_SMP_IDLE_THREAD
121 select GENERIC_STRNCPY_FROM_USER
122 select GENERIC_STRNLEN_USER
123 select GENERIC_TIME_VSYSCALL
124 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
125 select HAVE_ACPI_APEI if ACPI
126 select HAVE_ACPI_APEI_NMI if ACPI
127 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
128 select HAVE_ARCH_AUDITSYSCALL
129 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
130 select HAVE_ARCH_JUMP_LABEL
131 select HAVE_ARCH_JUMP_LABEL_RELATIVE
132 select HAVE_ARCH_KASAN if X86_64
133 select HAVE_ARCH_KGDB
134 select HAVE_ARCH_MMAP_RND_BITS if MMU
135 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
136 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
137 select HAVE_ARCH_PREL32_RELOCATIONS
138 select HAVE_ARCH_SECCOMP_FILTER
139 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
140 select HAVE_ARCH_STACKLEAK
141 select HAVE_ARCH_TRACEHOOK
142 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
143 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
144 select HAVE_ARCH_VMAP_STACK if X86_64
145 select HAVE_ARCH_WITHIN_STACK_FRAMES
146 select HAVE_CMPXCHG_DOUBLE
147 select HAVE_CMPXCHG_LOCAL
148 select HAVE_CONTEXT_TRACKING if X86_64
149 select HAVE_COPY_THREAD_TLS
150 select HAVE_C_RECORDMCOUNT
151 select HAVE_DEBUG_KMEMLEAK
152 select HAVE_DMA_CONTIGUOUS
153 select HAVE_DYNAMIC_FTRACE
154 select HAVE_DYNAMIC_FTRACE_WITH_REGS
156 select HAVE_EFFICIENT_UNALIGNED_ACCESS
158 select HAVE_EXIT_THREAD
159 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
160 select HAVE_FTRACE_MCOUNT_RECORD
161 select HAVE_FUNCTION_GRAPH_TRACER
162 select HAVE_FUNCTION_TRACER
163 select HAVE_GCC_PLUGINS
164 select HAVE_HW_BREAKPOINT
166 select HAVE_IOREMAP_PROT
167 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
168 select HAVE_IRQ_TIME_ACCOUNTING
169 select HAVE_KERNEL_BZIP2
170 select HAVE_KERNEL_GZIP
171 select HAVE_KERNEL_LZ4
172 select HAVE_KERNEL_LZMA
173 select HAVE_KERNEL_LZO
174 select HAVE_KERNEL_XZ
176 select HAVE_KPROBES_ON_FTRACE
177 select HAVE_FUNCTION_ERROR_INJECTION
178 select HAVE_KRETPROBES
180 select HAVE_LIVEPATCH if X86_64
181 select HAVE_MEMBLOCK_NODE_MAP
182 select HAVE_MIXED_BREAKPOINTS_REGS
183 select HAVE_MOD_ARCH_SPECIFIC
187 select HAVE_OPTPROBES
188 select HAVE_PCSPKR_PLATFORM
189 select HAVE_PERF_EVENTS
190 select HAVE_PERF_EVENTS_NMI
191 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
193 select HAVE_PERF_REGS
194 select HAVE_PERF_USER_STACK_DUMP
195 select HAVE_RCU_TABLE_FREE if PARAVIRT
196 select HAVE_REGS_AND_STACK_ACCESS_API
197 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
198 select HAVE_FUNCTION_ARG_ACCESS_API
199 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
200 select HAVE_STACK_VALIDATION if X86_64
202 select HAVE_SYSCALL_TRACEPOINTS
203 select HAVE_UNSTABLE_SCHED_CLOCK
204 select HAVE_USER_RETURN_NOTIFIER
205 select HOTPLUG_SMT if SMP
206 select IRQ_FORCED_THREADING
207 select NEED_SG_DMA_LENGTH
208 select PCI_DOMAINS if PCI
209 select PCI_LOCKLESS_CONFIG if PCI
212 select RTC_MC146818_LIB
215 select SYSCTL_EXCEPTION_TRACE
216 select THREAD_INFO_IN_TASK
217 select USER_STACKTRACE_SUPPORT
219 select X86_FEATURE_NAMES if PROC_FS
221 config INSTRUCTION_DECODER
223 depends on KPROBES || PERF_EVENTS || UPROBES
227 default "elf32-i386" if X86_32
228 default "elf64-x86-64" if X86_64
230 config ARCH_DEFCONFIG
232 default "arch/x86/configs/i386_defconfig" if X86_32
233 default "arch/x86/configs/x86_64_defconfig" if X86_64
235 config LOCKDEP_SUPPORT
238 config STACKTRACE_SUPPORT
244 config ARCH_MMAP_RND_BITS_MIN
248 config ARCH_MMAP_RND_BITS_MAX
252 config ARCH_MMAP_RND_COMPAT_BITS_MIN
255 config ARCH_MMAP_RND_COMPAT_BITS_MAX
261 config GENERIC_ISA_DMA
263 depends on ISA_DMA_API
268 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
270 config GENERIC_BUG_RELATIVE_POINTERS
273 config ARCH_MAY_HAVE_PC_FDC
275 depends on ISA_DMA_API
277 config GENERIC_CALIBRATE_DELAY
280 config ARCH_HAS_CPU_RELAX
283 config ARCH_HAS_CACHE_LINE_SIZE
286 config ARCH_HAS_FILTER_PGPROT
289 config HAVE_SETUP_PER_CPU_AREA
292 config NEED_PER_CPU_EMBED_FIRST_CHUNK
295 config NEED_PER_CPU_PAGE_FIRST_CHUNK
298 config ARCH_HIBERNATION_POSSIBLE
301 config ARCH_SUSPEND_POSSIBLE
304 config ARCH_WANT_HUGE_PMD_SHARE
307 config ARCH_WANT_GENERAL_HUGETLB
316 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
319 config KASAN_SHADOW_OFFSET
322 default 0xdffffc0000000000
324 config HAVE_INTEL_TXT
326 depends on INTEL_IOMMU && ACPI
330 depends on X86_32 && SMP
334 depends on X86_64 && SMP
336 config X86_32_LAZY_GS
338 depends on X86_32 && !STACKPROTECTOR
340 config ARCH_SUPPORTS_UPROBES
343 config FIX_EARLYCON_MEM
346 config DYNAMIC_PHYSICAL_MASK
349 config PGTABLE_LEVELS
351 default 5 if X86_5LEVEL
356 config CC_HAS_SANE_STACKPROTECTOR
358 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
359 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
361 We have to make sure stack protector is unconditionally disabled if
362 the compiler produces broken code.
364 menu "Processor type and features"
367 bool "DMA memory allocation support" if EXPERT
370 DMA memory allocation support allows devices with less than 32-bit
371 addressing to allocate within the first 16MB of address space.
372 Disable if no such devices will be used.
377 bool "Symmetric multi-processing support"
379 This enables support for systems with more than one CPU. If you have
380 a system with only one CPU, say N. If you have a system with more
383 If you say N here, the kernel will run on uni- and multiprocessor
384 machines, but will use only one CPU of a multiprocessor machine. If
385 you say Y here, the kernel will run on many, but not all,
386 uniprocessor machines. On a uniprocessor machine, the kernel
387 will run faster if you say N here.
389 Note that if you say Y here and choose architecture "586" or
390 "Pentium" under "Processor family", the kernel will not work on 486
391 architectures. Similarly, multiprocessor kernels for the "PPro"
392 architecture may not work on all Pentium based boards.
394 People using multiprocessor machines who say Y here should also say
395 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
396 Management" code will be disabled if you say Y here.
398 See also <file:Documentation/x86/i386/IO-APIC.txt>,
399 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
400 <http://www.tldp.org/docs.html#howto>.
402 If you don't know what to do here, say N.
404 config X86_FEATURE_NAMES
405 bool "Processor feature human-readable names" if EMBEDDED
408 This option compiles in a table of x86 feature bits and corresponding
409 names. This is required to support /proc/cpuinfo and a few kernel
410 messages. You can disable this to save space, at the expense of
411 making those few kernel messages show numeric feature bits instead.
416 bool "Support x2apic"
417 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
419 This enables x2apic support on CPUs that have this feature.
421 This allows 32-bit apic IDs (so it can support very large systems),
422 and accesses the local apic via MSRs not via mmio.
424 If you don't know what to do here, say N.
427 bool "Enable MPS table" if ACPI || SFI
429 depends on X86_LOCAL_APIC
431 For old smp systems that do not have proper acpi support. Newer systems
432 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
436 depends on X86_GOLDFISH
439 bool "Avoid speculative indirect branches in kernel"
441 select STACK_VALIDATION if HAVE_STACK_VALIDATION
443 Compile kernel with the retpoline compiler options to guard against
444 kernel-to-user data leaks by avoiding speculative indirect
445 branches. Requires a compiler with -mindirect-branch=thunk-extern
446 support for full protection. The kernel may run slower.
448 config X86_CPU_RESCTRL
449 bool "x86 CPU resource control support"
450 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
453 Enable x86 CPU resource control support.
455 Provide support for the allocation and monitoring of system resources
458 Intel calls this Intel Resource Director Technology
459 (Intel(R) RDT). More information about RDT can be found in the
460 Intel x86 Architecture Software Developer Manual.
462 AMD calls this AMD Platform Quality of Service (AMD QoS).
463 More information about AMD QoS can be found in the AMD64 Technology
464 Platform Quality of Service Extensions manual.
470 bool "Support for big SMP systems with more than 8 CPUs"
473 This option is needed for the systems that have more than 8 CPUs
475 config X86_EXTENDED_PLATFORM
476 bool "Support for extended (non-PC) x86 platforms"
479 If you disable this option then the kernel will only support
480 standard PC platforms. (which covers the vast majority of
483 If you enable this option then you'll be able to select support
484 for the following (non-PC) 32 bit x86 platforms:
485 Goldfish (Android emulator)
488 SGI 320/540 (Visual Workstation)
489 STA2X11-based (e.g. Northville)
490 Moorestown MID devices
492 If you have one of these systems, or if you want to build a
493 generic distribution kernel, say Y here - otherwise say N.
497 config X86_EXTENDED_PLATFORM
498 bool "Support for extended (non-PC) x86 platforms"
501 If you disable this option then the kernel will only support
502 standard PC platforms. (which covers the vast majority of
505 If you enable this option then you'll be able to select support
506 for the following (non-PC) 64 bit x86 platforms:
511 If you have one of these systems, or if you want to build a
512 generic distribution kernel, say Y here - otherwise say N.
514 # This is an alphabetically sorted list of 64 bit extended platforms
515 # Please maintain the alphabetic order if and when there are additions
517 bool "Numascale NumaChip"
519 depends on X86_EXTENDED_PLATFORM
522 depends on X86_X2APIC
523 depends on PCI_MMCONFIG
525 Adds support for Numascale NumaChip large-SMP systems. Needed to
526 enable more than ~168 cores.
527 If you don't have one of these, you should say N here.
531 select HYPERVISOR_GUEST
533 depends on X86_64 && PCI
534 depends on X86_EXTENDED_PLATFORM
537 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
538 supposed to run on these EM64T-based machines. Only choose this option
539 if you have one of these machines.
542 bool "SGI Ultraviolet"
544 depends on X86_EXTENDED_PLATFORM
547 depends on X86_X2APIC
550 This option is needed in order to support SGI Ultraviolet systems.
551 If you don't have one of these, you should say N here.
553 # Following is an alphabetically sorted list of 32 bit extended platforms
554 # Please maintain the alphabetic order if and when there are additions
557 bool "Goldfish (Virtual Platform)"
558 depends on X86_EXTENDED_PLATFORM
560 Enable support for the Goldfish virtual platform used primarily
561 for Android development. Unless you are building for the Android
562 Goldfish emulator say N here.
565 bool "CE4100 TV platform"
567 depends on PCI_GODIRECT
568 depends on X86_IO_APIC
570 depends on X86_EXTENDED_PLATFORM
571 select X86_REBOOTFIXUPS
573 select OF_EARLY_FLATTREE
575 Select for the Intel CE media processor (CE4100) SOC.
576 This option compiles in support for the CE4100 SOC for settop
577 boxes and media devices.
580 bool "Intel MID platform support"
581 depends on X86_EXTENDED_PLATFORM
582 depends on X86_PLATFORM_DEVICES
584 depends on X86_64 || (PCI_GOANY && X86_32)
585 depends on X86_IO_APIC
591 select MFD_INTEL_MSIC
593 Select to build a kernel capable of supporting Intel MID (Mobile
594 Internet Device) platform systems which do not have the PCI legacy
595 interfaces. If you are building for a PC class system say N here.
597 Intel MID platforms are based on an Intel processor and chipset which
598 consume less power than most of the x86 derivatives.
600 config X86_INTEL_QUARK
601 bool "Intel Quark platform support"
603 depends on X86_EXTENDED_PLATFORM
604 depends on X86_PLATFORM_DEVICES
608 depends on X86_IO_APIC
613 Select to include support for Quark X1000 SoC.
614 Say Y here if you have a Quark based system such as the Arduino
615 compatible Intel Galileo.
617 config X86_INTEL_LPSS
618 bool "Intel Low Power Subsystem Support"
619 depends on X86 && ACPI && PCI
624 Select to build support for Intel Low Power Subsystem such as
625 found on Intel Lynxpoint PCH. Selecting this option enables
626 things like clock tree (common clock framework) and pincontrol
627 which are needed by the LPSS peripheral drivers.
629 config X86_AMD_PLATFORM_DEVICE
630 bool "AMD ACPI2Platform devices support"
635 Select to interpret AMD specific ACPI device to platform device
636 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
637 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
638 implemented under PINCTRL subsystem.
641 tristate "Intel SoC IOSF Sideband support for SoC platforms"
644 This option enables sideband register access support for Intel SoC
645 platforms. On these platforms the IOSF sideband is used in lieu of
646 MSR's for some register accesses, mostly but not limited to thermal
647 and power. Drivers may query the availability of this device to
648 determine if they need the sideband in order to work on these
649 platforms. The sideband is available on the following SoC products.
650 This list is not meant to be exclusive.
655 You should say Y if you are running a kernel on one of these SoC's.
657 config IOSF_MBI_DEBUG
658 bool "Enable IOSF sideband access through debugfs"
659 depends on IOSF_MBI && DEBUG_FS
661 Select this option to expose the IOSF sideband access registers (MCR,
662 MDR, MCRX) through debugfs to write and read register information from
663 different units on the SoC. This is most useful for obtaining device
664 state information for debug and analysis. As this is a general access
665 mechanism, users of this option would have specific knowledge of the
666 device they want to access.
668 If you don't require the option or are in doubt, say N.
671 bool "RDC R-321x SoC"
673 depends on X86_EXTENDED_PLATFORM
675 select X86_REBOOTFIXUPS
677 This option is needed for RDC R-321x system-on-chip, also known
679 If you don't have one of these chips, you should say N here.
681 config X86_32_NON_STANDARD
682 bool "Support non-standard 32-bit SMP architectures"
683 depends on X86_32 && SMP
684 depends on X86_EXTENDED_PLATFORM
686 This option compiles in the bigsmp and STA2X11 default
687 subarchitectures. It is intended for a generic binary
688 kernel. If you select them all, kernel will probe it one by
689 one and will fallback to default.
691 # Alphabetically sorted list of Non standard 32 bit platforms
693 config X86_SUPPORTS_MEMORY_FAILURE
695 # MCE code calls memory_failure():
697 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
698 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
699 depends on X86_64 || !SPARSEMEM
700 select ARCH_SUPPORTS_MEMORY_FAILURE
703 bool "STA2X11 Companion Chip Support"
704 depends on X86_32_NON_STANDARD && PCI
705 select ARCH_HAS_PHYS_TO_DMA
710 This adds support for boards based on the STA2X11 IO-Hub,
711 a.k.a. "ConneXt". The chip is used in place of the standard
712 PC chipset, so all "standard" peripherals are missing. If this
713 option is selected the kernel will still be able to boot on
714 standard PC machines.
717 tristate "Eurobraille/Iris poweroff module"
720 The Iris machines from EuroBraille do not have APM or ACPI support
721 to shut themselves down properly. A special I/O sequence is
722 needed to do so, which is what this module does at
725 This is only for Iris machines from EuroBraille.
729 config SCHED_OMIT_FRAME_POINTER
731 prompt "Single-depth WCHAN output"
734 Calculate simpler /proc/<PID>/wchan values. If this option
735 is disabled then wchan values will recurse back to the
736 caller function. This provides more accurate wchan values,
737 at the expense of slightly more scheduling overhead.
739 If in doubt, say "Y".
741 menuconfig HYPERVISOR_GUEST
742 bool "Linux guest support"
744 Say Y here to enable options for running Linux under various hyper-
745 visors. This option enables basic hypervisor detection and platform
748 If you say N, all options in this submenu will be skipped and
749 disabled, and Linux guest support won't be built in.
754 bool "Enable paravirtualization code"
756 This changes the kernel so it can modify itself when it is run
757 under a hypervisor, potentially improving performance significantly
758 over full virtualization. However, when run without a hypervisor
759 the kernel is theoretically slower and slightly larger.
764 config PARAVIRT_DEBUG
765 bool "paravirt-ops debugging"
766 depends on PARAVIRT && DEBUG_KERNEL
768 Enable to debug paravirt_ops internals. Specifically, BUG if
769 a paravirt_op is missing when it is called.
771 config PARAVIRT_SPINLOCKS
772 bool "Paravirtualization layer for spinlocks"
773 depends on PARAVIRT && SMP
775 Paravirtualized spinlocks allow a pvops backend to replace the
776 spinlock implementation with something virtualization-friendly
777 (for example, block the virtual CPU rather than spinning).
779 It has a minimal impact on native kernels and gives a nice performance
780 benefit on paravirtualized KVM / Xen kernels.
782 If you are unsure how to answer this question, answer Y.
784 source "arch/x86/xen/Kconfig"
787 bool "KVM Guest support (including kvmclock)"
789 select PARAVIRT_CLOCK
792 This option enables various optimizations for running under the KVM
793 hypervisor. It includes a paravirtualized clock, so that instead
794 of relying on a PIT (or probably other) emulation by the
795 underlying device model, the host provides the guest with
796 timing infrastructure such as time of day, and system time
799 bool "Support for running PVH guests"
801 This option enables the PVH entry point for guest virtual machines
802 as specified in the x86/HVM direct boot ABI.
805 bool "Enable debug information for KVM Guests in debugfs"
806 depends on KVM_GUEST && DEBUG_FS
808 This option enables collection of various statistics for KVM guest.
809 Statistics are displayed in debugfs filesystem. Enabling this option
810 may incur significant overhead.
812 config PARAVIRT_TIME_ACCOUNTING
813 bool "Paravirtual steal time accounting"
816 Select this option to enable fine granularity task steal time
817 accounting. Time spent executing other tasks in parallel with
818 the current vCPU is discounted from the vCPU power. To account for
819 that, there can be a small performance impact.
821 If in doubt, say N here.
823 config PARAVIRT_CLOCK
826 config JAILHOUSE_GUEST
827 bool "Jailhouse non-root cell support"
828 depends on X86_64 && PCI
831 This option allows to run Linux as guest in a Jailhouse non-root
832 cell. You can leave this option disabled if you only want to start
833 Jailhouse and run Linux afterwards in the root cell.
835 endif #HYPERVISOR_GUEST
837 source "arch/x86/Kconfig.cpu"
841 prompt "HPET Timer Support" if X86_32
843 Use the IA-PC HPET (High Precision Event Timer) to manage
844 time in preference to the PIT and RTC, if a HPET is
846 HPET is the next generation timer replacing legacy 8254s.
847 The HPET provides a stable time base on SMP
848 systems, unlike the TSC, but it is more expensive to access,
849 as it is off-chip. The interface used is documented
850 in the HPET spec, revision 1.
852 You can safely choose Y here. However, HPET will only be
853 activated if the platform and the BIOS support this feature.
854 Otherwise the 8254 will be used for timing services.
856 Choose N to continue using the legacy 8254 timer.
858 config HPET_EMULATE_RTC
860 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
863 def_bool y if X86_INTEL_MID
864 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
866 depends on X86_INTEL_MID && SFI
868 APB timer is the replacement for 8254, HPET on X86 MID platforms.
869 The APBT provides a stable time base on SMP
870 systems, unlike the TSC, but it is more expensive to access,
871 as it is off-chip. APB timers are always running regardless of CPU
872 C states, they are used as per CPU clockevent device when possible.
874 # Mark as expert because too many people got it wrong.
875 # The code disables itself when not needed.
878 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
879 bool "Enable DMI scanning" if EXPERT
881 Enabled scanning of DMI to identify machine quirks. Say Y
882 here unless you have verified that your setup is not
883 affected by entries in the DMI blacklist. Required by PNP
887 bool "Old AMD GART IOMMU support"
890 depends on X86_64 && PCI && AMD_NB
892 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
893 GART based hardware IOMMUs.
895 The GART supports full DMA access for devices with 32-bit access
896 limitations, on systems with more than 3 GB. This is usually needed
897 for USB, sound, many IDE/SATA chipsets and some other devices.
899 Newer systems typically have a modern AMD IOMMU, supported via
900 the CONFIG_AMD_IOMMU=y config option.
902 In normal configurations this driver is only active when needed:
903 there's more than 3 GB of memory and the system contains a
904 32-bit limited device.
909 bool "IBM Calgary IOMMU support"
912 depends on X86_64 && PCI
914 Support for hardware IOMMUs in IBM's xSeries x366 and x460
915 systems. Needed to run systems with more than 3GB of memory
916 properly with 32-bit PCI devices that do not support DAC
917 (Double Address Cycle). Calgary also supports bus level
918 isolation, where all DMAs pass through the IOMMU. This
919 prevents them from going anywhere except their intended
920 destination. This catches hard-to-find kernel bugs and
921 mis-behaving drivers and devices that do not use the DMA-API
922 properly to set up their DMA buffers. The IOMMU can be
923 turned off at boot time with the iommu=off parameter.
924 Normally the kernel will make the right choice by itself.
927 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
929 prompt "Should Calgary be enabled by default?"
930 depends on CALGARY_IOMMU
932 Should Calgary be enabled by default? if you choose 'y', Calgary
933 will be used (if it exists). If you choose 'n', Calgary will not be
934 used even if it exists. If you choose 'n' and would like to use
935 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
939 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
940 depends on X86_64 && SMP && DEBUG_KERNEL
941 select CPUMASK_OFFSTACK
943 Enable maximum number of CPUS and NUMA Nodes for this architecture.
947 # The maximum number of CPUs supported:
949 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
950 # and which can be configured interactively in the
951 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
953 # The ranges are different on 32-bit and 64-bit kernels, depending on
954 # hardware capabilities and scalability features of the kernel.
956 # ( If MAXSMP is enabled we just use the highest possible value and disable
957 # interactive configuration. )
960 config NR_CPUS_RANGE_BEGIN
962 default NR_CPUS_RANGE_END if MAXSMP
966 config NR_CPUS_RANGE_END
969 default 64 if SMP && X86_BIGSMP
970 default 8 if SMP && !X86_BIGSMP
973 config NR_CPUS_RANGE_END
976 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
977 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
980 config NR_CPUS_DEFAULT
983 default 32 if X86_BIGSMP
987 config NR_CPUS_DEFAULT
990 default 8192 if MAXSMP
995 int "Maximum number of CPUs" if SMP && !MAXSMP
996 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
997 default NR_CPUS_DEFAULT
999 This allows you to specify the maximum number of CPUs which this
1000 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1001 supported value is 8192, otherwise the maximum value is 512. The
1002 minimum value which makes sense is 2.
1004 This is purely to save memory: each supported CPU adds about 8KB
1005 to the kernel image.
1012 prompt "Multi-core scheduler support"
1015 Multi-core scheduler support improves the CPU scheduler's decision
1016 making when dealing with multi-core CPU chips at a cost of slightly
1017 increased overhead in some places. If unsure say N here.
1019 config SCHED_MC_PRIO
1020 bool "CPU core priorities scheduler support"
1021 depends on SCHED_MC && CPU_SUP_INTEL
1022 select X86_INTEL_PSTATE
1026 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1027 core ordering determined at manufacturing time, which allows
1028 certain cores to reach higher turbo frequencies (when running
1029 single threaded workloads) than others.
1031 Enabling this kernel feature teaches the scheduler about
1032 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1033 scheduler's CPU selection logic accordingly, so that higher
1034 overall system performance can be achieved.
1036 This feature will have no effect on CPUs without this feature.
1038 If unsure say Y here.
1042 depends on !SMP && X86_LOCAL_APIC
1045 bool "Local APIC support on uniprocessors" if !PCI_MSI
1047 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1049 A local APIC (Advanced Programmable Interrupt Controller) is an
1050 integrated interrupt controller in the CPU. If you have a single-CPU
1051 system which has a processor with a local APIC, you can say Y here to
1052 enable and use it. If you say Y here even though your machine doesn't
1053 have a local APIC, then the kernel will still run with no slowdown at
1054 all. The local APIC supports CPU-generated self-interrupts (timer,
1055 performance counters), and the NMI watchdog which detects hard
1058 config X86_UP_IOAPIC
1059 bool "IO-APIC support on uniprocessors"
1060 depends on X86_UP_APIC
1062 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1063 SMP-capable replacement for PC-style interrupt controllers. Most
1064 SMP systems and many recent uniprocessor systems have one.
1066 If you have a single-CPU system with an IO-APIC, you can say Y here
1067 to use it. If you say Y here even though your machine doesn't have
1068 an IO-APIC, then the kernel will still run with no slowdown at all.
1070 config X86_LOCAL_APIC
1072 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1073 select IRQ_DOMAIN_HIERARCHY
1074 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1078 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1080 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1081 bool "Reroute for broken boot IRQs"
1082 depends on X86_IO_APIC
1084 This option enables a workaround that fixes a source of
1085 spurious interrupts. This is recommended when threaded
1086 interrupt handling is used on systems where the generation of
1087 superfluous "boot interrupts" cannot be disabled.
1089 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1090 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1091 kernel does during interrupt handling). On chipsets where this
1092 boot IRQ generation cannot be disabled, this workaround keeps
1093 the original IRQ line masked so that only the equivalent "boot
1094 IRQ" is delivered to the CPUs. The workaround also tells the
1095 kernel to set up the IRQ handler on the boot IRQ line. In this
1096 way only one interrupt is delivered to the kernel. Otherwise
1097 the spurious second interrupt may cause the kernel to bring
1098 down (vital) interrupt lines.
1100 Only affects "broken" chipsets. Interrupt sharing may be
1101 increased on these systems.
1104 bool "Machine Check / overheating reporting"
1105 select GENERIC_ALLOCATOR
1108 Machine Check support allows the processor to notify the
1109 kernel if it detects a problem (e.g. overheating, data corruption).
1110 The action the kernel takes depends on the severity of the problem,
1111 ranging from warning messages to halting the machine.
1113 config X86_MCELOG_LEGACY
1114 bool "Support for deprecated /dev/mcelog character device"
1117 Enable support for /dev/mcelog which is needed by the old mcelog
1118 userspace logging daemon. Consider switching to the new generation
1121 config X86_MCE_INTEL
1123 prompt "Intel MCE features"
1124 depends on X86_MCE && X86_LOCAL_APIC
1126 Additional support for intel specific MCE features such as
1127 the thermal monitor.
1131 prompt "AMD MCE features"
1132 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1134 Additional support for AMD specific MCE features such as
1135 the DRAM Error Threshold.
1137 config X86_ANCIENT_MCE
1138 bool "Support for old Pentium 5 / WinChip machine checks"
1139 depends on X86_32 && X86_MCE
1141 Include support for machine check handling on old Pentium 5 or WinChip
1142 systems. These typically need to be enabled explicitly on the command
1145 config X86_MCE_THRESHOLD
1146 depends on X86_MCE_AMD || X86_MCE_INTEL
1149 config X86_MCE_INJECT
1150 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1151 tristate "Machine check injector support"
1153 Provide support for injecting machine checks for testing purposes.
1154 If you don't know what a machine check is and you don't do kernel
1155 QA it is safe to say n.
1157 config X86_THERMAL_VECTOR
1159 depends on X86_MCE_INTEL
1161 source "arch/x86/events/Kconfig"
1163 config X86_LEGACY_VM86
1164 bool "Legacy VM86 support"
1167 This option allows user programs to put the CPU into V8086
1168 mode, which is an 80286-era approximation of 16-bit real mode.
1170 Some very old versions of X and/or vbetool require this option
1171 for user mode setting. Similarly, DOSEMU will use it if
1172 available to accelerate real mode DOS programs. However, any
1173 recent version of DOSEMU, X, or vbetool should be fully
1174 functional even without kernel VM86 support, as they will all
1175 fall back to software emulation. Nevertheless, if you are using
1176 a 16-bit DOS program where 16-bit performance matters, vm86
1177 mode might be faster than emulation and you might want to
1180 Note that any app that works on a 64-bit kernel is unlikely to
1181 need this option, as 64-bit kernels don't, and can't, support
1182 V8086 mode. This option is also unrelated to 16-bit protected
1183 mode and is not needed to run most 16-bit programs under Wine.
1185 Enabling this option increases the complexity of the kernel
1186 and slows down exception handling a tiny bit.
1188 If unsure, say N here.
1192 default X86_LEGACY_VM86
1195 bool "Enable support for 16-bit segments" if EXPERT
1197 depends on MODIFY_LDT_SYSCALL
1199 This option is required by programs like Wine to run 16-bit
1200 protected mode legacy code on x86 processors. Disabling
1201 this option saves about 300 bytes on i386, or around 6K text
1202 plus 16K runtime memory on x86-64,
1206 depends on X86_16BIT && X86_32
1210 depends on X86_16BIT && X86_64
1212 config X86_VSYSCALL_EMULATION
1213 bool "Enable vsyscall emulation" if EXPERT
1217 This enables emulation of the legacy vsyscall page. Disabling
1218 it is roughly equivalent to booting with vsyscall=none, except
1219 that it will also disable the helpful warning if a program
1220 tries to use a vsyscall. With this option set to N, offending
1221 programs will just segfault, citing addresses of the form
1224 This option is required by many programs built before 2013, and
1225 care should be used even with newer programs if set to N.
1227 Disabling this option saves about 7K of kernel size and
1228 possibly 4K of additional runtime pagetable memory.
1231 tristate "Toshiba Laptop support"
1234 This adds a driver to safely access the System Management Mode of
1235 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1236 not work on models with a Phoenix BIOS. The System Management Mode
1237 is used to set the BIOS and power saving options on Toshiba portables.
1239 For information on utilities to make use of this driver see the
1240 Toshiba Linux utilities web site at:
1241 <http://www.buzzard.org.uk/toshiba/>.
1243 Say Y if you intend to run this kernel on a Toshiba portable.
1247 tristate "Dell i8k legacy laptop support"
1249 select SENSORS_DELL_SMM
1251 This option enables legacy /proc/i8k userspace interface in hwmon
1252 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1253 temperature and allows controlling fan speeds of Dell laptops via
1254 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1255 it reports also power and hotkey status. For fan speed control is
1256 needed userspace package i8kutils.
1258 Say Y if you intend to run this kernel on old Dell laptops or want to
1259 use userspace package i8kutils.
1262 config X86_REBOOTFIXUPS
1263 bool "Enable X86 board specific fixups for reboot"
1266 This enables chipset and/or board specific fixups to be done
1267 in order to get reboot to work correctly. This is only needed on
1268 some combinations of hardware and BIOS. The symptom, for which
1269 this config is intended, is when reboot ends with a stalled/hung
1272 Currently, the only fixup is for the Geode machines using
1273 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1275 Say Y if you want to enable the fixup. Currently, it's safe to
1276 enable this option even if you don't need it.
1280 bool "CPU microcode loading support"
1282 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1285 If you say Y here, you will be able to update the microcode on
1286 Intel and AMD processors. The Intel support is for the IA32 family,
1287 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1288 AMD support is for families 0x10 and later. You will obviously need
1289 the actual microcode binary data itself which is not shipped with
1292 The preferred method to load microcode from a detached initrd is described
1293 in Documentation/x86/microcode.txt. For that you need to enable
1294 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1295 initrd for microcode blobs.
1297 In addition, you can build the microcode into the kernel. For that you
1298 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1301 config MICROCODE_INTEL
1302 bool "Intel microcode loading support"
1303 depends on MICROCODE
1307 This options enables microcode patch loading support for Intel
1310 For the current Intel microcode data package go to
1311 <https://downloadcenter.intel.com> and search for
1312 'Linux Processor Microcode Data File'.
1314 config MICROCODE_AMD
1315 bool "AMD microcode loading support"
1316 depends on MICROCODE
1319 If you select this option, microcode patch loading support for AMD
1320 processors will be enabled.
1322 config MICROCODE_OLD_INTERFACE
1323 bool "Ancient loading interface (DEPRECATED)"
1325 depends on MICROCODE
1327 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1328 which was used by userspace tools like iucode_tool and microcode.ctl.
1329 It is inadequate because it runs too late to be able to properly
1330 load microcode on a machine and it needs special tools. Instead, you
1331 should've switched to the early loading method with the initrd or
1332 builtin microcode by now: Documentation/x86/microcode.txt
1335 tristate "/dev/cpu/*/msr - Model-specific register support"
1337 This device gives privileged processes access to the x86
1338 Model-Specific Registers (MSRs). It is a character device with
1339 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1340 MSR accesses are directed to a specific CPU on multi-processor
1344 tristate "/dev/cpu/*/cpuid - CPU information support"
1346 This device gives processes access to the x86 CPUID instruction to
1347 be executed on a specific processor. It is a character device
1348 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1352 prompt "High Memory Support"
1359 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1360 However, the address space of 32-bit x86 processors is only 4
1361 Gigabytes large. That means that, if you have a large amount of
1362 physical memory, not all of it can be "permanently mapped" by the
1363 kernel. The physical memory that's not permanently mapped is called
1366 If you are compiling a kernel which will never run on a machine with
1367 more than 1 Gigabyte total physical RAM, answer "off" here (default
1368 choice and suitable for most users). This will result in a "3GB/1GB"
1369 split: 3GB are mapped so that each process sees a 3GB virtual memory
1370 space and the remaining part of the 4GB virtual memory space is used
1371 by the kernel to permanently map as much physical memory as
1374 If the machine has between 1 and 4 Gigabytes physical RAM, then
1377 If more than 4 Gigabytes is used then answer "64GB" here. This
1378 selection turns Intel PAE (Physical Address Extension) mode on.
1379 PAE implements 3-level paging on IA32 processors. PAE is fully
1380 supported by Linux, PAE mode is implemented on all recent Intel
1381 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1382 then the kernel will not boot on CPUs that don't support PAE!
1384 The actual amount of total physical memory will either be
1385 auto detected or can be forced by using a kernel command line option
1386 such as "mem=256M". (Try "man bootparam" or see the documentation of
1387 your boot loader (lilo or loadlin) about how to pass options to the
1388 kernel at boot time.)
1390 If unsure, say "off".
1395 Select this if you have a 32-bit processor and between 1 and 4
1396 gigabytes of physical RAM.
1400 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1403 Select this if you have a 32-bit processor and more than 4
1404 gigabytes of physical RAM.
1409 prompt "Memory split" if EXPERT
1413 Select the desired split between kernel and user memory.
1415 If the address range available to the kernel is less than the
1416 physical memory installed, the remaining memory will be available
1417 as "high memory". Accessing high memory is a little more costly
1418 than low memory, as it needs to be mapped into the kernel first.
1419 Note that increasing the kernel address space limits the range
1420 available to user programs, making the address space there
1421 tighter. Selecting anything other than the default 3G/1G split
1422 will also likely make your kernel incompatible with binary-only
1425 If you are not absolutely sure what you are doing, leave this
1429 bool "3G/1G user/kernel split"
1430 config VMSPLIT_3G_OPT
1432 bool "3G/1G user/kernel split (for full 1G low memory)"
1434 bool "2G/2G user/kernel split"
1435 config VMSPLIT_2G_OPT
1437 bool "2G/2G user/kernel split (for full 2G low memory)"
1439 bool "1G/3G user/kernel split"
1444 default 0xB0000000 if VMSPLIT_3G_OPT
1445 default 0x80000000 if VMSPLIT_2G
1446 default 0x78000000 if VMSPLIT_2G_OPT
1447 default 0x40000000 if VMSPLIT_1G
1453 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1456 bool "PAE (Physical Address Extension) Support"
1457 depends on X86_32 && !HIGHMEM4G
1458 select PHYS_ADDR_T_64BIT
1461 PAE is required for NX support, and furthermore enables
1462 larger swapspace support for non-overcommit purposes. It
1463 has the cost of more pagetable lookup overhead, and also
1464 consumes more pagetable space per process.
1467 bool "Enable 5-level page tables support"
1468 select DYNAMIC_MEMORY_LAYOUT
1469 select SPARSEMEM_VMEMMAP
1472 5-level paging enables access to larger address space:
1473 upto 128 PiB of virtual address space and 4 PiB of
1474 physical address space.
1476 It will be supported by future Intel CPUs.
1478 A kernel with the option enabled can be booted on machines that
1479 support 4- or 5-level paging.
1481 See Documentation/x86/x86_64/5level-paging.txt for more
1486 config X86_DIRECT_GBPAGES
1488 depends on X86_64 && !DEBUG_PAGEALLOC
1490 Certain kernel features effectively disable kernel
1491 linear 1 GB mappings (even if the CPU otherwise
1492 supports them), so don't confuse the user by printing
1493 that we have them enabled.
1495 config X86_CPA_STATISTICS
1496 bool "Enable statistic for Change Page Attribute"
1499 Expose statistics about the Change Page Attribute mechanims, which
1500 helps to determine the effectiveness of preserving large and huge
1501 page mappings when mapping protections are changed.
1503 config ARCH_HAS_MEM_ENCRYPT
1506 config AMD_MEM_ENCRYPT
1507 bool "AMD Secure Memory Encryption (SME) support"
1508 depends on X86_64 && CPU_SUP_AMD
1509 select DYNAMIC_PHYSICAL_MASK
1510 select ARCH_USE_MEMREMAP_PROT
1512 Say yes to enable support for the encryption of system memory.
1513 This requires an AMD processor that supports Secure Memory
1516 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1517 bool "Activate AMD Secure Memory Encryption (SME) by default"
1519 depends on AMD_MEM_ENCRYPT
1521 Say yes to have system memory encrypted by default if running on
1522 an AMD processor that supports Secure Memory Encryption (SME).
1524 If set to Y, then the encryption of system memory can be
1525 deactivated with the mem_encrypt=off command line option.
1527 If set to N, then the encryption of system memory can be
1528 activated with the mem_encrypt=on command line option.
1530 # Common NUMA Features
1532 bool "Numa Memory Allocation and Scheduler Support"
1534 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1535 default y if X86_BIGSMP
1537 Enable NUMA (Non Uniform Memory Access) support.
1539 The kernel will try to allocate memory used by a CPU on the
1540 local memory controller of the CPU and add some more
1541 NUMA awareness to the kernel.
1543 For 64-bit this is recommended if the system is Intel Core i7
1544 (or later), AMD Opteron, or EM64T NUMA.
1546 For 32-bit this is only needed if you boot a 32-bit
1547 kernel on a 64-bit NUMA platform.
1549 Otherwise, you should say N.
1553 prompt "Old style AMD Opteron NUMA detection"
1554 depends on X86_64 && NUMA && PCI
1556 Enable AMD NUMA node topology detection. You should say Y here if
1557 you have a multi processor AMD system. This uses an old method to
1558 read the NUMA configuration directly from the builtin Northbridge
1559 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1560 which also takes priority if both are compiled in.
1562 config X86_64_ACPI_NUMA
1564 prompt "ACPI NUMA detection"
1565 depends on X86_64 && NUMA && ACPI && PCI
1568 Enable ACPI SRAT based node topology detection.
1570 # Some NUMA nodes have memory ranges that span
1571 # other nodes. Even though a pfn is valid and
1572 # between a node's start and end pfns, it may not
1573 # reside on that node. See memmap_init_zone()
1575 config NODES_SPAN_OTHER_NODES
1577 depends on X86_64_ACPI_NUMA
1580 bool "NUMA emulation"
1583 Enable NUMA emulation. A flat machine will be split
1584 into virtual nodes when booted with "numa=fake=N", where N is the
1585 number of nodes. This is only useful for debugging.
1588 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1590 default "10" if MAXSMP
1591 default "6" if X86_64
1593 depends on NEED_MULTIPLE_NODES
1595 Specify the maximum number of NUMA Nodes available on the target
1596 system. Increases memory reserved to accommodate various tables.
1598 config ARCH_HAVE_MEMORY_PRESENT
1600 depends on X86_32 && DISCONTIGMEM
1602 config ARCH_FLATMEM_ENABLE
1604 depends on X86_32 && !NUMA
1606 config ARCH_DISCONTIGMEM_ENABLE
1608 depends on NUMA && X86_32
1611 config ARCH_SPARSEMEM_ENABLE
1613 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1614 select SPARSEMEM_STATIC if X86_32
1615 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1617 config ARCH_SPARSEMEM_DEFAULT
1618 def_bool X86_64 || (NUMA && X86_32)
1620 config ARCH_SELECT_MEMORY_MODEL
1622 depends on ARCH_SPARSEMEM_ENABLE
1624 config ARCH_MEMORY_PROBE
1625 bool "Enable sysfs memory/probe interface"
1626 depends on X86_64 && MEMORY_HOTPLUG
1628 This option enables a sysfs memory/probe interface for testing.
1629 See Documentation/memory-hotplug.txt for more information.
1630 If you are unsure how to answer this question, answer N.
1632 config ARCH_PROC_KCORE_TEXT
1634 depends on X86_64 && PROC_KCORE
1636 config ILLEGAL_POINTER_VALUE
1639 default 0xdead000000000000 if X86_64
1641 config X86_PMEM_LEGACY_DEVICE
1644 config X86_PMEM_LEGACY
1645 tristate "Support non-standard NVDIMMs and ADR protected memory"
1646 depends on PHYS_ADDR_T_64BIT
1648 select X86_PMEM_LEGACY_DEVICE
1651 Treat memory marked using the non-standard e820 type of 12 as used
1652 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1653 The kernel will offer these regions to the 'pmem' driver so
1654 they can be used for persistent storage.
1659 bool "Allocate 3rd-level pagetables from highmem"
1662 The VM uses one page table entry for each page of physical memory.
1663 For systems with a lot of RAM, this can be wasteful of precious
1664 low memory. Setting this option will put user-space page table
1665 entries in high memory.
1667 config X86_CHECK_BIOS_CORRUPTION
1668 bool "Check for low memory corruption"
1670 Periodically check for memory corruption in low memory, which
1671 is suspected to be caused by BIOS. Even when enabled in the
1672 configuration, it is disabled at runtime. Enable it by
1673 setting "memory_corruption_check=1" on the kernel command
1674 line. By default it scans the low 64k of memory every 60
1675 seconds; see the memory_corruption_check_size and
1676 memory_corruption_check_period parameters in
1677 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1679 When enabled with the default parameters, this option has
1680 almost no overhead, as it reserves a relatively small amount
1681 of memory and scans it infrequently. It both detects corruption
1682 and prevents it from affecting the running system.
1684 It is, however, intended as a diagnostic tool; if repeatable
1685 BIOS-originated corruption always affects the same memory,
1686 you can use memmap= to prevent the kernel from using that
1689 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1690 bool "Set the default setting of memory_corruption_check"
1691 depends on X86_CHECK_BIOS_CORRUPTION
1694 Set whether the default state of memory_corruption_check is
1697 config X86_RESERVE_LOW
1698 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1702 Specify the amount of low memory to reserve for the BIOS.
1704 The first page contains BIOS data structures that the kernel
1705 must not use, so that page must always be reserved.
1707 By default we reserve the first 64K of physical RAM, as a
1708 number of BIOSes are known to corrupt that memory range
1709 during events such as suspend/resume or monitor cable
1710 insertion, so it must not be used by the kernel.
1712 You can set this to 4 if you are absolutely sure that you
1713 trust the BIOS to get all its memory reservations and usages
1714 right. If you know your BIOS have problems beyond the
1715 default 64K area, you can set this to 640 to avoid using the
1716 entire low memory range.
1718 If you have doubts about the BIOS (e.g. suspend/resume does
1719 not work or there's kernel crashes after certain hardware
1720 hotplug events) then you might want to enable
1721 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1722 typical corruption patterns.
1724 Leave this to the default value of 64 if you are unsure.
1726 config MATH_EMULATION
1728 depends on MODIFY_LDT_SYSCALL
1729 prompt "Math emulation" if X86_32
1731 Linux can emulate a math coprocessor (used for floating point
1732 operations) if you don't have one. 486DX and Pentium processors have
1733 a math coprocessor built in, 486SX and 386 do not, unless you added
1734 a 487DX or 387, respectively. (The messages during boot time can
1735 give you some hints here ["man dmesg"].) Everyone needs either a
1736 coprocessor or this emulation.
1738 If you don't have a math coprocessor, you need to say Y here; if you
1739 say Y here even though you have a coprocessor, the coprocessor will
1740 be used nevertheless. (This behavior can be changed with the kernel
1741 command line option "no387", which comes handy if your coprocessor
1742 is broken. Try "man bootparam" or see the documentation of your boot
1743 loader (lilo or loadlin) about how to pass options to the kernel at
1744 boot time.) This means that it is a good idea to say Y here if you
1745 intend to use this kernel on different machines.
1747 More information about the internals of the Linux math coprocessor
1748 emulation can be found in <file:arch/x86/math-emu/README>.
1750 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1751 kernel, it won't hurt.
1755 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1757 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1758 the Memory Type Range Registers (MTRRs) may be used to control
1759 processor access to memory ranges. This is most useful if you have
1760 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1761 allows bus write transfers to be combined into a larger transfer
1762 before bursting over the PCI/AGP bus. This can increase performance
1763 of image write operations 2.5 times or more. Saying Y here creates a
1764 /proc/mtrr file which may be used to manipulate your processor's
1765 MTRRs. Typically the X server should use this.
1767 This code has a reasonably generic interface so that similar
1768 control registers on other processors can be easily supported
1771 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1772 Registers (ARRs) which provide a similar functionality to MTRRs. For
1773 these, the ARRs are used to emulate the MTRRs.
1774 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1775 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1776 write-combining. All of these processors are supported by this code
1777 and it makes sense to say Y here if you have one of them.
1779 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1780 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1781 can lead to all sorts of problems, so it's good to say Y here.
1783 You can safely say Y even if your machine doesn't have MTRRs, you'll
1784 just add about 9 KB to your kernel.
1786 See <file:Documentation/x86/mtrr.txt> for more information.
1788 config MTRR_SANITIZER
1790 prompt "MTRR cleanup support"
1793 Convert MTRR layout from continuous to discrete, so X drivers can
1794 add writeback entries.
1796 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1797 The largest mtrr entry size for a continuous block can be set with
1802 config MTRR_SANITIZER_ENABLE_DEFAULT
1803 int "MTRR cleanup enable value (0-1)"
1806 depends on MTRR_SANITIZER
1808 Enable mtrr cleanup default value
1810 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1811 int "MTRR cleanup spare reg num (0-7)"
1814 depends on MTRR_SANITIZER
1816 mtrr cleanup spare entries default, it can be changed via
1817 mtrr_spare_reg_nr=N on the kernel command line.
1821 prompt "x86 PAT support" if EXPERT
1824 Use PAT attributes to setup page level cache control.
1826 PATs are the modern equivalents of MTRRs and are much more
1827 flexible than MTRRs.
1829 Say N here if you see bootup problems (boot crash, boot hang,
1830 spontaneous reboots) or a non-working video driver.
1834 config ARCH_USES_PG_UNCACHED
1840 prompt "x86 architectural random number generator" if EXPERT
1842 Enable the x86 architectural RDRAND instruction
1843 (Intel Bull Mountain technology) to generate random numbers.
1844 If supported, this is a high bandwidth, cryptographically
1845 secure hardware random number generator.
1849 prompt "Supervisor Mode Access Prevention" if EXPERT
1851 Supervisor Mode Access Prevention (SMAP) is a security
1852 feature in newer Intel processors. There is a small
1853 performance cost if this enabled and turned on; there is
1854 also a small increase in the kernel size if this is enabled.
1858 config X86_INTEL_UMIP
1860 depends on CPU_SUP_INTEL
1861 prompt "Intel User Mode Instruction Prevention" if EXPERT
1863 The User Mode Instruction Prevention (UMIP) is a security
1864 feature in newer Intel processors. If enabled, a general
1865 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1866 or STR instructions are executed in user mode. These instructions
1867 unnecessarily expose information about the hardware state.
1869 The vast majority of applications do not use these instructions.
1870 For the very few that do, software emulation is provided in
1871 specific cases in protected and virtual-8086 modes. Emulated
1874 config X86_INTEL_MPX
1875 prompt "Intel MPX (Memory Protection Extensions)"
1877 # Note: only available in 64-bit mode due to VMA flags shortage
1878 depends on CPU_SUP_INTEL && X86_64
1879 select ARCH_USES_HIGH_VMA_FLAGS
1881 MPX provides hardware features that can be used in
1882 conjunction with compiler-instrumented code to check
1883 memory references. It is designed to detect buffer
1884 overflow or underflow bugs.
1886 This option enables running applications which are
1887 instrumented or otherwise use MPX. It does not use MPX
1888 itself inside the kernel or to protect the kernel
1889 against bad memory references.
1891 Enabling this option will make the kernel larger:
1892 ~8k of kernel text and 36 bytes of data on a 64-bit
1893 defconfig. It adds a long to the 'mm_struct' which
1894 will increase the kernel memory overhead of each
1895 process and adds some branches to paths used during
1896 exec() and munmap().
1898 For details, see Documentation/x86/intel_mpx.txt
1902 config X86_INTEL_MEMORY_PROTECTION_KEYS
1903 prompt "Intel Memory Protection Keys"
1905 # Note: only available in 64-bit mode
1906 depends on CPU_SUP_INTEL && X86_64
1907 select ARCH_USES_HIGH_VMA_FLAGS
1908 select ARCH_HAS_PKEYS
1910 Memory Protection Keys provides a mechanism for enforcing
1911 page-based protections, but without requiring modification of the
1912 page tables when an application changes protection domains.
1914 For details, see Documentation/x86/protection-keys.txt
1919 bool "EFI runtime service support"
1922 select EFI_RUNTIME_WRAPPERS
1924 This enables the kernel to use EFI runtime services that are
1925 available (such as the EFI variable services).
1927 This option is only useful on systems that have EFI firmware.
1928 In addition, you should use the latest ELILO loader available
1929 at <http://elilo.sourceforge.net> in order to take advantage
1930 of EFI runtime services. However, even with this option, the
1931 resultant kernel should continue to boot on existing non-EFI
1935 bool "EFI stub support"
1936 depends on EFI && !X86_USE_3DNOW
1939 This kernel feature allows a bzImage to be loaded directly
1940 by EFI firmware without the use of a bootloader.
1942 See Documentation/efi-stub.txt for more information.
1945 bool "EFI mixed-mode support"
1946 depends on EFI_STUB && X86_64
1948 Enabling this feature allows a 64-bit kernel to be booted
1949 on a 32-bit firmware, provided that your CPU supports 64-bit
1952 Note that it is not possible to boot a mixed-mode enabled
1953 kernel via the EFI boot stub - a bootloader that supports
1954 the EFI handover protocol must be used.
1960 prompt "Enable seccomp to safely compute untrusted bytecode"
1962 This kernel feature is useful for number crunching applications
1963 that may need to compute untrusted bytecode during their
1964 execution. By using pipes or other transports made available to
1965 the process as file descriptors supporting the read/write
1966 syscalls, it's possible to isolate those applications in
1967 their own address space using seccomp. Once seccomp is
1968 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1969 and the task is only allowed to execute a few safe syscalls
1970 defined by each seccomp mode.
1972 If unsure, say Y. Only embedded should say N here.
1974 source "kernel/Kconfig.hz"
1977 bool "kexec system call"
1980 kexec is a system call that implements the ability to shutdown your
1981 current kernel, and to start another kernel. It is like a reboot
1982 but it is independent of the system firmware. And like a reboot
1983 you can start any kernel with it, not just Linux.
1985 The name comes from the similarity to the exec system call.
1987 It is an ongoing process to be certain the hardware in a machine
1988 is properly shutdown, so do not be surprised if this code does not
1989 initially work for you. As of this writing the exact hardware
1990 interface is strongly in flux, so no good recommendation can be
1994 bool "kexec file based system call"
1999 depends on CRYPTO_SHA256=y
2001 This is new version of kexec system call. This system call is
2002 file based and takes file descriptors as system call argument
2003 for kernel and initramfs as opposed to list of segments as
2004 accepted by previous system call.
2006 config ARCH_HAS_KEXEC_PURGATORY
2010 bool "Verify kernel signature during kexec_file_load() syscall"
2011 depends on KEXEC_FILE
2014 This option makes the kexec_file_load() syscall check for a valid
2015 signature of the kernel image. The image can still be loaded without
2016 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2017 there's a signature that we can check, then it must be valid.
2019 In addition to this 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_SIG_FORCE
2024 bool "Require a valid signature in kexec_file_load() syscall"
2025 depends on KEXEC_SIG
2027 This option makes kernel signature verification mandatory for
2028 the kexec_file_load() syscall.
2030 config KEXEC_BZIMAGE_VERIFY_SIG
2031 bool "Enable bzImage signature verification support"
2032 depends on KEXEC_SIG
2033 depends on SIGNED_PE_FILE_VERIFICATION
2034 select SYSTEM_TRUSTED_KEYRING
2036 Enable bzImage signature verification support.
2039 bool "kernel crash dumps"
2040 depends on X86_64 || (X86_32 && HIGHMEM)
2042 Generate crash dump after being started by kexec.
2043 This should be normally only set in special crash dump kernels
2044 which are loaded in the main kernel with kexec-tools into
2045 a specially reserved region and then later executed after
2046 a crash by kdump/kexec. The crash dump kernel must be compiled
2047 to a memory address not used by the main kernel or BIOS using
2048 PHYSICAL_START, or it must be built as a relocatable image
2049 (CONFIG_RELOCATABLE=y).
2050 For more details see Documentation/kdump/kdump.txt
2054 depends on KEXEC && HIBERNATION
2056 Jump between original kernel and kexeced kernel and invoke
2057 code in physical address mode via KEXEC
2059 config PHYSICAL_START
2060 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2063 This gives the physical address where the kernel is loaded.
2065 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2066 bzImage will decompress itself to above physical address and
2067 run from there. Otherwise, bzImage will run from the address where
2068 it has been loaded by the boot loader and will ignore above physical
2071 In normal kdump cases one does not have to set/change this option
2072 as now bzImage can be compiled as a completely relocatable image
2073 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2074 address. This option is mainly useful for the folks who don't want
2075 to use a bzImage for capturing the crash dump and want to use a
2076 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2077 to be specifically compiled to run from a specific memory area
2078 (normally a reserved region) and this option comes handy.
2080 So if you are using bzImage for capturing the crash dump,
2081 leave the value here unchanged to 0x1000000 and set
2082 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2083 for capturing the crash dump change this value to start of
2084 the reserved region. In other words, it can be set based on
2085 the "X" value as specified in the "crashkernel=YM@XM"
2086 command line boot parameter passed to the panic-ed
2087 kernel. Please take a look at Documentation/kdump/kdump.txt
2088 for more details about crash dumps.
2090 Usage of bzImage for capturing the crash dump is recommended as
2091 one does not have to build two kernels. Same kernel can be used
2092 as production kernel and capture kernel. Above option should have
2093 gone away after relocatable bzImage support is introduced. But it
2094 is present because there are users out there who continue to use
2095 vmlinux for dump capture. This option should go away down the
2098 Don't change this unless you know what you are doing.
2101 bool "Build a relocatable kernel"
2104 This builds a kernel image that retains relocation information
2105 so it can be loaded someplace besides the default 1MB.
2106 The relocations tend to make the kernel binary about 10% larger,
2107 but are discarded at runtime.
2109 One use is for the kexec on panic case where the recovery kernel
2110 must live at a different physical address than the primary
2113 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2114 it has been loaded at and the compile time physical address
2115 (CONFIG_PHYSICAL_START) is used as the minimum location.
2117 config RANDOMIZE_BASE
2118 bool "Randomize the address of the kernel image (KASLR)"
2119 depends on RELOCATABLE
2122 In support of Kernel Address Space Layout Randomization (KASLR),
2123 this randomizes the physical address at which the kernel image
2124 is decompressed and the virtual address where the kernel
2125 image is mapped, as a security feature that deters exploit
2126 attempts relying on knowledge of the location of kernel
2129 On 64-bit, the kernel physical and virtual addresses are
2130 randomized separately. The physical address will be anywhere
2131 between 16MB and the top of physical memory (up to 64TB). The
2132 virtual address will be randomized from 16MB up to 1GB (9 bits
2133 of entropy). Note that this also reduces the memory space
2134 available to kernel modules from 1.5GB to 1GB.
2136 On 32-bit, the kernel physical and virtual addresses are
2137 randomized together. They will be randomized from 16MB up to
2138 512MB (8 bits of entropy).
2140 Entropy is generated using the RDRAND instruction if it is
2141 supported. If RDTSC is supported, its value is mixed into
2142 the entropy pool as well. If neither RDRAND nor RDTSC are
2143 supported, then entropy is read from the i8254 timer. The
2144 usable entropy is limited by the kernel being built using
2145 2GB addressing, and that PHYSICAL_ALIGN must be at a
2146 minimum of 2MB. As a result, only 10 bits of entropy are
2147 theoretically possible, but the implementations are further
2148 limited due to memory layouts.
2152 # Relocation on x86 needs some additional build support
2153 config X86_NEED_RELOCS
2155 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2157 config PHYSICAL_ALIGN
2158 hex "Alignment value to which kernel should be aligned"
2160 range 0x2000 0x1000000 if X86_32
2161 range 0x200000 0x1000000 if X86_64
2163 This value puts the alignment restrictions on physical address
2164 where kernel is loaded and run from. Kernel is compiled for an
2165 address which meets above alignment restriction.
2167 If bootloader loads the kernel at a non-aligned address and
2168 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2169 address aligned to above value and run from there.
2171 If bootloader loads the kernel at a non-aligned address and
2172 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2173 load address and decompress itself to the address it has been
2174 compiled for and run from there. The address for which kernel is
2175 compiled already meets above alignment restrictions. Hence the
2176 end result is that kernel runs from a physical address meeting
2177 above alignment restrictions.
2179 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2180 this value must be a multiple of 0x200000.
2182 Don't change this unless you know what you are doing.
2184 config DYNAMIC_MEMORY_LAYOUT
2187 This option makes base addresses of vmalloc and vmemmap as well as
2188 __PAGE_OFFSET movable during boot.
2190 config RANDOMIZE_MEMORY
2191 bool "Randomize the kernel memory sections"
2193 depends on RANDOMIZE_BASE
2194 select DYNAMIC_MEMORY_LAYOUT
2195 default RANDOMIZE_BASE
2197 Randomizes the base virtual address of kernel memory sections
2198 (physical memory mapping, vmalloc & vmemmap). This security feature
2199 makes exploits relying on predictable memory locations less reliable.
2201 The order of allocations remains unchanged. Entropy is generated in
2202 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2203 configuration have in average 30,000 different possible virtual
2204 addresses for each memory section.
2208 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2209 hex "Physical memory mapping padding" if EXPERT
2210 depends on RANDOMIZE_MEMORY
2211 default "0xa" if MEMORY_HOTPLUG
2213 range 0x1 0x40 if MEMORY_HOTPLUG
2216 Define the padding in terabytes added to the existing physical
2217 memory size during kernel memory randomization. It is useful
2218 for memory hotplug support but reduces the entropy available for
2219 address randomization.
2221 If unsure, leave at the default value.
2227 config BOOTPARAM_HOTPLUG_CPU0
2228 bool "Set default setting of cpu0_hotpluggable"
2229 depends on HOTPLUG_CPU
2231 Set whether default state of cpu0_hotpluggable is on or off.
2233 Say Y here to enable CPU0 hotplug by default. If this switch
2234 is turned on, there is no need to give cpu0_hotplug kernel
2235 parameter and the CPU0 hotplug feature is enabled by default.
2237 Please note: there are two known CPU0 dependencies if you want
2238 to enable the CPU0 hotplug feature either by this switch or by
2239 cpu0_hotplug kernel parameter.
2241 First, resume from hibernate or suspend always starts from CPU0.
2242 So hibernate and suspend are prevented if CPU0 is offline.
2244 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2245 offline if any interrupt can not migrate out of CPU0. There may
2246 be other CPU0 dependencies.
2248 Please make sure the dependencies are under your control before
2249 you enable this feature.
2251 Say N if you don't want to enable CPU0 hotplug feature by default.
2252 You still can enable the CPU0 hotplug feature at boot by kernel
2253 parameter cpu0_hotplug.
2255 config DEBUG_HOTPLUG_CPU0
2257 prompt "Debug CPU0 hotplug"
2258 depends on HOTPLUG_CPU
2260 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2261 soon as possible and boots up userspace with CPU0 offlined. User
2262 can online CPU0 back after boot time.
2264 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2265 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2266 compilation or giving cpu0_hotplug kernel parameter at boot.
2272 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2273 depends on COMPAT_32
2275 Certain buggy versions of glibc will crash if they are
2276 presented with a 32-bit vDSO that is not mapped at the address
2277 indicated in its segment table.
2279 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2280 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2281 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2282 the only released version with the bug, but OpenSUSE 9
2283 contains a buggy "glibc 2.3.2".
2285 The symptom of the bug is that everything crashes on startup, saying:
2286 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2288 Saying Y here changes the default value of the vdso32 boot
2289 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2290 This works around the glibc bug but hurts performance.
2292 If unsure, say N: if you are compiling your own kernel, you
2293 are unlikely to be using a buggy version of glibc.
2296 prompt "vsyscall table for legacy applications"
2298 default LEGACY_VSYSCALL_EMULATE
2300 Legacy user code that does not know how to find the vDSO expects
2301 to be able to issue three syscalls by calling fixed addresses in
2302 kernel space. Since this location is not randomized with ASLR,
2303 it can be used to assist security vulnerability exploitation.
2305 This setting can be changed at boot time via the kernel command
2306 line parameter vsyscall=[emulate|none].
2308 On a system with recent enough glibc (2.14 or newer) and no
2309 static binaries, you can say None without a performance penalty
2310 to improve security.
2312 If unsure, select "Emulate".
2314 config LEGACY_VSYSCALL_EMULATE
2317 The kernel traps and emulates calls into the fixed
2318 vsyscall address mapping. This makes the mapping
2319 non-executable, but it still contains known contents,
2320 which could be used in certain rare security vulnerability
2321 exploits. This configuration is recommended when userspace
2322 still uses the vsyscall area.
2324 config LEGACY_VSYSCALL_NONE
2327 There will be no vsyscall mapping at all. This will
2328 eliminate any risk of ASLR bypass due to the vsyscall
2329 fixed address mapping. Attempts to use the vsyscalls
2330 will be reported to dmesg, so that either old or
2331 malicious userspace programs can be identified.
2336 bool "Built-in kernel command line"
2338 Allow for specifying boot arguments to the kernel at
2339 build time. On some systems (e.g. embedded ones), it is
2340 necessary or convenient to provide some or all of the
2341 kernel boot arguments with the kernel itself (that is,
2342 to not rely on the boot loader to provide them.)
2344 To compile command line arguments into the kernel,
2345 set this option to 'Y', then fill in the
2346 boot arguments in CONFIG_CMDLINE.
2348 Systems with fully functional boot loaders (i.e. non-embedded)
2349 should leave this option set to 'N'.
2352 string "Built-in kernel command string"
2353 depends on CMDLINE_BOOL
2356 Enter arguments here that should be compiled into the kernel
2357 image and used at boot time. If the boot loader provides a
2358 command line at boot time, it is appended to this string to
2359 form the full kernel command line, when the system boots.
2361 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2362 change this behavior.
2364 In most cases, the command line (whether built-in or provided
2365 by the boot loader) should specify the device for the root
2368 config CMDLINE_OVERRIDE
2369 bool "Built-in command line overrides boot loader arguments"
2370 depends on CMDLINE_BOOL
2372 Set this option to 'Y' to have the kernel ignore the boot loader
2373 command line, and use ONLY the built-in command line.
2375 This is used to work around broken boot loaders. This should
2376 be set to 'N' under normal conditions.
2378 config MODIFY_LDT_SYSCALL
2379 bool "Enable the LDT (local descriptor table)" if EXPERT
2382 Linux can allow user programs to install a per-process x86
2383 Local Descriptor Table (LDT) using the modify_ldt(2) system
2384 call. This is required to run 16-bit or segmented code such as
2385 DOSEMU or some Wine programs. It is also used by some very old
2386 threading libraries.
2388 Enabling this feature adds a small amount of overhead to
2389 context switches and increases the low-level kernel attack
2390 surface. Disabling it removes the modify_ldt(2) system call.
2392 Saying 'N' here may make sense for embedded or server kernels.
2394 source "kernel/livepatch/Kconfig"
2398 config ARCH_HAS_ADD_PAGES
2400 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2402 config ARCH_ENABLE_MEMORY_HOTPLUG
2404 depends on X86_64 || (X86_32 && HIGHMEM)
2406 config ARCH_ENABLE_MEMORY_HOTREMOVE
2408 depends on MEMORY_HOTPLUG
2410 config USE_PERCPU_NUMA_NODE_ID
2414 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2416 depends on X86_64 || X86_PAE
2418 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2420 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2422 config ARCH_ENABLE_THP_MIGRATION
2424 depends on X86_64 && TRANSPARENT_HUGEPAGE
2426 menu "Power management and ACPI options"
2428 config ARCH_HIBERNATION_HEADER
2430 depends on HIBERNATION
2432 source "kernel/power/Kconfig"
2434 source "drivers/acpi/Kconfig"
2436 source "drivers/sfi/Kconfig"
2443 tristate "APM (Advanced Power Management) BIOS support"
2444 depends on X86_32 && PM_SLEEP
2446 APM is a BIOS specification for saving power using several different
2447 techniques. This is mostly useful for battery powered laptops with
2448 APM compliant BIOSes. If you say Y here, the system time will be
2449 reset after a RESUME operation, the /proc/apm device will provide
2450 battery status information, and user-space programs will receive
2451 notification of APM "events" (e.g. battery status change).
2453 If you select "Y" here, you can disable actual use of the APM
2454 BIOS by passing the "apm=off" option to the kernel at boot time.
2456 Note that the APM support is almost completely disabled for
2457 machines with more than one CPU.
2459 In order to use APM, you will need supporting software. For location
2460 and more information, read <file:Documentation/power/apm-acpi.txt>
2461 and the Battery Powered Linux mini-HOWTO, available from
2462 <http://www.tldp.org/docs.html#howto>.
2464 This driver does not spin down disk drives (see the hdparm(8)
2465 manpage ("man 8 hdparm") for that), and it doesn't turn off
2466 VESA-compliant "green" monitors.
2468 This driver does not support the TI 4000M TravelMate and the ACER
2469 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2470 desktop machines also don't have compliant BIOSes, and this driver
2471 may cause those machines to panic during the boot phase.
2473 Generally, if you don't have a battery in your machine, there isn't
2474 much point in using this driver and you should say N. If you get
2475 random kernel OOPSes or reboots that don't seem to be related to
2476 anything, try disabling/enabling this option (or disabling/enabling
2479 Some other things you should try when experiencing seemingly random,
2482 1) make sure that you have enough swap space and that it is
2484 2) pass the "no-hlt" option to the kernel
2485 3) switch on floating point emulation in the kernel and pass
2486 the "no387" option to the kernel
2487 4) pass the "floppy=nodma" option to the kernel
2488 5) pass the "mem=4M" option to the kernel (thereby disabling
2489 all but the first 4 MB of RAM)
2490 6) make sure that the CPU is not over clocked.
2491 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2492 8) disable the cache from your BIOS settings
2493 9) install a fan for the video card or exchange video RAM
2494 10) install a better fan for the CPU
2495 11) exchange RAM chips
2496 12) exchange the motherboard.
2498 To compile this driver as a module, choose M here: the
2499 module will be called apm.
2503 config APM_IGNORE_USER_SUSPEND
2504 bool "Ignore USER SUSPEND"
2506 This option will ignore USER SUSPEND requests. On machines with a
2507 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2508 series notebooks, it is necessary to say Y because of a BIOS bug.
2510 config APM_DO_ENABLE
2511 bool "Enable PM at boot time"
2513 Enable APM features at boot time. From page 36 of the APM BIOS
2514 specification: "When disabled, the APM BIOS does not automatically
2515 power manage devices, enter the Standby State, enter the Suspend
2516 State, or take power saving steps in response to CPU Idle calls."
2517 This driver will make CPU Idle calls when Linux is idle (unless this
2518 feature is turned off -- see "Do CPU IDLE calls", below). This
2519 should always save battery power, but more complicated APM features
2520 will be dependent on your BIOS implementation. You may need to turn
2521 this option off if your computer hangs at boot time when using APM
2522 support, or if it beeps continuously instead of suspending. Turn
2523 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2524 T400CDT. This is off by default since most machines do fine without
2529 bool "Make CPU Idle calls when idle"
2531 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2532 On some machines, this can activate improved power savings, such as
2533 a slowed CPU clock rate, when the machine is idle. These idle calls
2534 are made after the idle loop has run for some length of time (e.g.,
2535 333 mS). On some machines, this will cause a hang at boot time or
2536 whenever the CPU becomes idle. (On machines with more than one CPU,
2537 this option does nothing.)
2539 config APM_DISPLAY_BLANK
2540 bool "Enable console blanking using APM"
2542 Enable console blanking using the APM. Some laptops can use this to
2543 turn off the LCD backlight when the screen blanker of the Linux
2544 virtual console blanks the screen. Note that this is only used by
2545 the virtual console screen blanker, and won't turn off the backlight
2546 when using the X Window system. This also doesn't have anything to
2547 do with your VESA-compliant power-saving monitor. Further, this
2548 option doesn't work for all laptops -- it might not turn off your
2549 backlight at all, or it might print a lot of errors to the console,
2550 especially if you are using gpm.
2552 config APM_ALLOW_INTS
2553 bool "Allow interrupts during APM BIOS calls"
2555 Normally we disable external interrupts while we are making calls to
2556 the APM BIOS as a measure to lessen the effects of a badly behaving
2557 BIOS implementation. The BIOS should reenable interrupts if it
2558 needs to. Unfortunately, some BIOSes do not -- especially those in
2559 many of the newer IBM Thinkpads. If you experience hangs when you
2560 suspend, try setting this to Y. Otherwise, say N.
2564 source "drivers/cpufreq/Kconfig"
2566 source "drivers/cpuidle/Kconfig"
2568 source "drivers/idle/Kconfig"
2573 menu "Bus options (PCI etc.)"
2576 prompt "PCI access mode"
2577 depends on X86_32 && PCI
2580 On PCI systems, the BIOS can be used to detect the PCI devices and
2581 determine their configuration. However, some old PCI motherboards
2582 have BIOS bugs and may crash if this is done. Also, some embedded
2583 PCI-based systems don't have any BIOS at all. Linux can also try to
2584 detect the PCI hardware directly without using the BIOS.
2586 With this option, you can specify how Linux should detect the
2587 PCI devices. If you choose "BIOS", the BIOS will be used,
2588 if you choose "Direct", the BIOS won't be used, and if you
2589 choose "MMConfig", then PCI Express MMCONFIG will be used.
2590 If you choose "Any", the kernel will try MMCONFIG, then the
2591 direct access method and falls back to the BIOS if that doesn't
2592 work. If unsure, go with the default, which is "Any".
2597 config PCI_GOMMCONFIG
2614 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2616 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2619 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2622 bool "Support mmconfig PCI config space access" if X86_64
2624 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2625 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2629 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2633 depends on PCI && XEN
2636 config MMCONF_FAM10H
2638 depends on X86_64 && PCI_MMCONFIG && ACPI
2640 config PCI_CNB20LE_QUIRK
2641 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2644 Read the PCI windows out of the CNB20LE host bridge. This allows
2645 PCI hotplug to work on systems with the CNB20LE chipset which do
2648 There's no public spec for this chipset, and this functionality
2649 is known to be incomplete.
2651 You should say N unless you know you need this.
2654 bool "ISA bus support on modern systems" if EXPERT
2656 Expose ISA bus device drivers and options available for selection and
2657 configuration. Enable this option if your target machine has an ISA
2658 bus. ISA is an older system, displaced by PCI and newer bus
2659 architectures -- if your target machine is modern, it probably does
2660 not have an ISA bus.
2664 # x86_64 have no ISA slots, but can have ISA-style DMA.
2666 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2669 Enables ISA-style DMA support for devices requiring such controllers.
2677 Find out whether you have ISA slots on your motherboard. ISA is the
2678 name of a bus system, i.e. the way the CPU talks to the other stuff
2679 inside your box. Other bus systems are PCI, EISA, MicroChannel
2680 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2681 newer boards don't support it. If you have ISA, say Y, otherwise N.
2684 tristate "NatSemi SCx200 support"
2686 This provides basic support for National Semiconductor's
2687 (now AMD's) Geode processors. The driver probes for the
2688 PCI-IDs of several on-chip devices, so its a good dependency
2689 for other scx200_* drivers.
2691 If compiled as a module, the driver is named scx200.
2693 config SCx200HR_TIMER
2694 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2698 This driver provides a clocksource built upon the on-chip
2699 27MHz high-resolution timer. Its also a workaround for
2700 NSC Geode SC-1100's buggy TSC, which loses time when the
2701 processor goes idle (as is done by the scheduler). The
2702 other workaround is idle=poll boot option.
2705 bool "One Laptop Per Child support"
2712 Add support for detecting the unique features of the OLPC
2716 bool "OLPC XO-1 Power Management"
2717 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2719 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2722 bool "OLPC XO-1 Real Time Clock"
2723 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2725 Add support for the XO-1 real time clock, which can be used as a
2726 programmable wakeup source.
2729 bool "OLPC XO-1 SCI extras"
2730 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2734 Add support for SCI-based features of the OLPC XO-1 laptop:
2735 - EC-driven system wakeups
2739 - AC adapter status updates
2740 - Battery status updates
2742 config OLPC_XO15_SCI
2743 bool "OLPC XO-1.5 SCI extras"
2744 depends on OLPC && ACPI
2747 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2748 - EC-driven system wakeups
2749 - AC adapter status updates
2750 - Battery status updates
2753 bool "PCEngines ALIX System Support (LED setup)"
2756 This option enables system support for the PCEngines ALIX.
2757 At present this just sets up LEDs for GPIO control on
2758 ALIX2/3/6 boards. However, other system specific setup should
2761 Note: You must still enable the drivers for GPIO and LED support
2762 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2764 Note: You have to set alix.force=1 for boards with Award BIOS.
2767 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2770 This option enables system support for the Soekris Engineering net5501.
2773 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2777 This option enables system support for the Traverse Technologies GEOS.
2780 bool "Technologic Systems TS-5500 platform support"
2782 select CHECK_SIGNATURE
2786 This option enables system support for the Technologic Systems TS-5500.
2792 depends on CPU_SUP_AMD && PCI
2795 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2797 Firmwares often provide initial graphics framebuffers so the BIOS,
2798 bootloader or kernel can show basic video-output during boot for
2799 user-guidance and debugging. Historically, x86 used the VESA BIOS
2800 Extensions and EFI-framebuffers for this, which are mostly limited
2802 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2803 framebuffers so the new generic system-framebuffer drivers can be
2804 used on x86. If the framebuffer is not compatible with the generic
2805 modes, it is advertised as fallback platform framebuffer so legacy
2806 drivers like efifb, vesafb and uvesafb can pick it up.
2807 If this option is not selected, all system framebuffers are always
2808 marked as fallback platform framebuffers as usual.
2810 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2811 not be able to pick up generic system framebuffers if this option
2812 is selected. You are highly encouraged to enable simplefb as
2813 replacement if you select this option. simplefb can correctly deal
2814 with generic system framebuffers. But you should still keep vesafb
2815 and others enabled as fallback if a system framebuffer is
2816 incompatible with simplefb.
2823 menu "Binary Emulations"
2825 config IA32_EMULATION
2826 bool "IA32 Emulation"
2828 select ARCH_WANT_OLD_COMPAT_IPC
2830 select COMPAT_BINFMT_ELF
2831 select COMPAT_OLD_SIGACTION
2833 Include code to run legacy 32-bit programs under a
2834 64-bit kernel. You should likely turn this on, unless you're
2835 100% sure that you don't have any 32-bit programs left.
2838 tristate "IA32 a.out support"
2839 depends on IA32_EMULATION
2842 Support old a.out binaries in the 32bit emulation.
2845 bool "x32 ABI for 64-bit mode"
2848 Include code to run binaries for the x32 native 32-bit ABI
2849 for 64-bit processors. An x32 process gets access to the
2850 full 64-bit register file and wide data path while leaving
2851 pointers at 32 bits for smaller memory footprint.
2853 You will need a recent binutils (2.22 or later) with
2854 elf32_x86_64 support enabled to compile a kernel with this
2859 depends on IA32_EMULATION || X86_32
2861 select OLD_SIGSUSPEND3
2865 depends on IA32_EMULATION || X86_X32
2868 config COMPAT_FOR_U64_ALIGNMENT
2871 config SYSVIPC_COMPAT
2879 config HAVE_ATOMIC_IOMAP
2883 config X86_DEV_DMA_OPS
2886 config HAVE_GENERIC_GUP
2889 source "drivers/firmware/Kconfig"
2891 source "arch/x86/kvm/Kconfig"