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
20 select GENERIC_VDSO_32
25 # Options that are inherently 64-bit kernel only:
26 select ARCH_HAS_GIGANTIC_PAGE
27 select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
28 select ARCH_USE_CMPXCHG_LOCKREF
29 select HAVE_ARCH_SOFT_DIRTY
30 select MODULES_USE_ELF_RELA
31 select NEED_DMA_MAP_STATE
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_INIT
60 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
61 select ARCH_HAS_DEBUG_VIRTUAL
62 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
63 select ARCH_HAS_DEVMEM_IS_ALLOWED
64 select ARCH_HAS_EARLY_DEBUG if KGDB
65 select ARCH_HAS_ELF_RANDOMIZE
66 select ARCH_HAS_FAST_MULTIPLIER
67 select ARCH_HAS_FILTER_PGPROT
68 select ARCH_HAS_FORTIFY_SOURCE
69 select ARCH_HAS_GCOV_PROFILE_ALL
70 select ARCH_HAS_KCOV if X86_64 && STACK_VALIDATION
71 select ARCH_HAS_MEM_ENCRYPT
72 select ARCH_HAS_MEMBARRIER_SYNC_CORE
73 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
74 select ARCH_HAS_PMEM_API if X86_64
75 select ARCH_HAS_PTE_DEVMAP if X86_64
76 select ARCH_HAS_PTE_SPECIAL
77 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
78 select ARCH_HAS_COPY_MC if X86_64
79 select ARCH_HAS_SET_MEMORY
80 select ARCH_HAS_SET_DIRECT_MAP
81 select ARCH_HAS_STRICT_KERNEL_RWX
82 select ARCH_HAS_STRICT_MODULE_RWX
83 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
84 select ARCH_HAS_SYSCALL_WRAPPER
85 select ARCH_HAS_UBSAN_SANITIZE_ALL
86 select ARCH_HAS_DEBUG_WX
87 select ARCH_HAVE_NMI_SAFE_CMPXCHG
88 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
89 select ARCH_MIGHT_HAVE_PC_PARPORT
90 select ARCH_MIGHT_HAVE_PC_SERIO
92 select ARCH_SUPPORTS_ACPI
93 select ARCH_SUPPORTS_ATOMIC_RMW
94 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
95 select ARCH_USE_BUILTIN_BSWAP
96 select ARCH_USE_QUEUED_RWLOCKS
97 select ARCH_USE_QUEUED_SPINLOCKS
98 select ARCH_USE_SYM_ANNOTATIONS
99 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
100 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
101 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
102 select ARCH_WANT_HUGE_PMD_SHARE
103 select ARCH_WANT_LD_ORPHAN_WARN
104 select ARCH_WANTS_THP_SWAP if X86_64
105 select BUILDTIME_TABLE_SORT
107 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
108 select CLOCKSOURCE_WATCHDOG
109 select DCACHE_WORD_ACCESS
110 select EDAC_ATOMIC_SCRUB
112 select GENERIC_CLOCKEVENTS
113 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
114 select GENERIC_CLOCKEVENTS_MIN_ADJUST
115 select GENERIC_CMOS_UPDATE
116 select GENERIC_CPU_AUTOPROBE
117 select GENERIC_CPU_VULNERABILITIES
118 select GENERIC_EARLY_IOREMAP
120 select GENERIC_FIND_FIRST_BIT
122 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
123 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
124 select GENERIC_IRQ_MIGRATION if SMP
125 select GENERIC_IRQ_PROBE
126 select GENERIC_IRQ_RESERVATION_MODE
127 select GENERIC_IRQ_SHOW
128 select GENERIC_PENDING_IRQ if SMP
129 select GENERIC_PTDUMP
130 select GENERIC_SMP_IDLE_THREAD
131 select GENERIC_STRNCPY_FROM_USER
132 select GENERIC_STRNLEN_USER
133 select GENERIC_TIME_VSYSCALL
134 select GENERIC_GETTIMEOFDAY
135 select GENERIC_VDSO_TIME_NS
136 select GUP_GET_PTE_LOW_HIGH if X86_PAE
137 select HARDIRQS_SW_RESEND
138 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
139 select HAVE_ACPI_APEI if ACPI
140 select HAVE_ACPI_APEI_NMI if ACPI
141 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
142 select HAVE_ARCH_AUDITSYSCALL
143 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
144 select HAVE_ARCH_JUMP_LABEL
145 select HAVE_ARCH_JUMP_LABEL_RELATIVE
146 select HAVE_ARCH_KASAN if X86_64
147 select HAVE_ARCH_KASAN_VMALLOC if X86_64
148 select HAVE_ARCH_KGDB
149 select HAVE_ARCH_MMAP_RND_BITS if MMU
150 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
151 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
152 select HAVE_ARCH_PREL32_RELOCATIONS
153 select HAVE_ARCH_SECCOMP_FILTER
154 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
155 select HAVE_ARCH_STACKLEAK
156 select HAVE_ARCH_TRACEHOOK
157 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
158 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
159 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
160 select HAVE_ARCH_VMAP_STACK if X86_64
161 select HAVE_ARCH_WITHIN_STACK_FRAMES
162 select HAVE_ASM_MODVERSIONS
163 select HAVE_CMPXCHG_DOUBLE
164 select HAVE_CMPXCHG_LOCAL
165 select HAVE_CONTEXT_TRACKING if X86_64
166 select HAVE_C_RECORDMCOUNT
167 select HAVE_DEBUG_KMEMLEAK
168 select HAVE_DMA_CONTIGUOUS
169 select HAVE_DYNAMIC_FTRACE
170 select HAVE_DYNAMIC_FTRACE_WITH_REGS
171 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
173 select HAVE_EFFICIENT_UNALIGNED_ACCESS
175 select HAVE_EXIT_THREAD
177 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
178 select HAVE_FTRACE_MCOUNT_RECORD
179 select HAVE_FUNCTION_GRAPH_TRACER
180 select HAVE_FUNCTION_TRACER
181 select HAVE_GCC_PLUGINS
182 select HAVE_HW_BREAKPOINT
184 select HAVE_IOREMAP_PROT
185 select HAVE_IRQ_TIME_ACCOUNTING
186 select HAVE_KERNEL_BZIP2
187 select HAVE_KERNEL_GZIP
188 select HAVE_KERNEL_LZ4
189 select HAVE_KERNEL_LZMA
190 select HAVE_KERNEL_LZO
191 select HAVE_KERNEL_XZ
192 select HAVE_KERNEL_ZSTD
194 select HAVE_KPROBES_ON_FTRACE
195 select HAVE_FUNCTION_ERROR_INJECTION
196 select HAVE_KRETPROBES
198 select HAVE_LIVEPATCH if X86_64
199 select HAVE_MIXED_BREAKPOINTS_REGS
200 select HAVE_MOD_ARCH_SPECIFIC
204 select HAVE_OPTPROBES
205 select HAVE_PCSPKR_PLATFORM
206 select HAVE_PERF_EVENTS
207 select HAVE_PERF_EVENTS_NMI
208 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
210 select HAVE_PERF_REGS
211 select HAVE_PERF_USER_STACK_DUMP
212 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
213 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
214 select HAVE_REGS_AND_STACK_ACCESS_API
215 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
216 select HAVE_FUNCTION_ARG_ACCESS_API
217 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
218 select HAVE_STACK_VALIDATION if X86_64
219 select HAVE_STATIC_CALL
220 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
222 select HAVE_SYSCALL_TRACEPOINTS
223 select HAVE_UNSTABLE_SCHED_CLOCK
224 select HAVE_USER_RETURN_NOTIFIER
225 select HAVE_GENERIC_VDSO
226 select HOTPLUG_SMT if SMP
227 select IRQ_FORCED_THREADING
228 select NEED_SG_DMA_LENGTH
229 select PCI_DOMAINS if PCI
230 select PCI_LOCKLESS_CONFIG if PCI
233 select RTC_MC146818_LIB
236 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
237 select SYSCTL_EXCEPTION_TRACE
238 select THREAD_INFO_IN_TASK
239 select USER_STACKTRACE_SUPPORT
241 select HAVE_ARCH_KCSAN if X86_64
242 select X86_FEATURE_NAMES if PROC_FS
243 select PROC_PID_ARCH_STATUS if PROC_FS
244 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
246 config INSTRUCTION_DECODER
248 depends on KPROBES || PERF_EVENTS || UPROBES
252 default "elf32-i386" if X86_32
253 default "elf64-x86-64" if X86_64
255 config LOCKDEP_SUPPORT
258 config STACKTRACE_SUPPORT
264 config ARCH_MMAP_RND_BITS_MIN
268 config ARCH_MMAP_RND_BITS_MAX
272 config ARCH_MMAP_RND_COMPAT_BITS_MIN
275 config ARCH_MMAP_RND_COMPAT_BITS_MAX
281 config GENERIC_ISA_DMA
283 depends on ISA_DMA_API
288 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
290 config GENERIC_BUG_RELATIVE_POINTERS
293 config ARCH_MAY_HAVE_PC_FDC
295 depends on ISA_DMA_API
297 config GENERIC_CALIBRATE_DELAY
300 config ARCH_HAS_CPU_RELAX
303 config ARCH_HAS_CACHE_LINE_SIZE
306 config ARCH_HAS_FILTER_PGPROT
309 config HAVE_SETUP_PER_CPU_AREA
312 config NEED_PER_CPU_EMBED_FIRST_CHUNK
315 config NEED_PER_CPU_PAGE_FIRST_CHUNK
318 config ARCH_HIBERNATION_POSSIBLE
321 config ARCH_SUSPEND_POSSIBLE
324 config ARCH_WANT_GENERAL_HUGETLB
333 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
336 config KASAN_SHADOW_OFFSET
339 default 0xdffffc0000000000
341 config HAVE_INTEL_TXT
343 depends on INTEL_IOMMU && ACPI
347 depends on X86_32 && SMP
351 depends on X86_64 && SMP
353 config X86_32_LAZY_GS
355 depends on X86_32 && !STACKPROTECTOR
357 config ARCH_SUPPORTS_UPROBES
360 config FIX_EARLYCON_MEM
363 config DYNAMIC_PHYSICAL_MASK
366 config PGTABLE_LEVELS
368 default 5 if X86_5LEVEL
373 config CC_HAS_SANE_STACKPROTECTOR
375 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
376 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
378 We have to make sure stack protector is unconditionally disabled if
379 the compiler produces broken code.
381 menu "Processor type and features"
384 bool "DMA memory allocation support" if EXPERT
387 DMA memory allocation support allows devices with less than 32-bit
388 addressing to allocate within the first 16MB of address space.
389 Disable if no such devices will be used.
394 bool "Symmetric multi-processing support"
396 This enables support for systems with more than one CPU. If you have
397 a system with only one CPU, say N. If you have a system with more
400 If you say N here, the kernel will run on uni- and multiprocessor
401 machines, but will use only one CPU of a multiprocessor machine. If
402 you say Y here, the kernel will run on many, but not all,
403 uniprocessor machines. On a uniprocessor machine, the kernel
404 will run faster if you say N here.
406 Note that if you say Y here and choose architecture "586" or
407 "Pentium" under "Processor family", the kernel will not work on 486
408 architectures. Similarly, multiprocessor kernels for the "PPro"
409 architecture may not work on all Pentium based boards.
411 People using multiprocessor machines who say Y here should also say
412 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
413 Management" code will be disabled if you say Y here.
415 See also <file:Documentation/x86/i386/IO-APIC.rst>,
416 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
417 <http://www.tldp.org/docs.html#howto>.
419 If you don't know what to do here, say N.
421 config X86_FEATURE_NAMES
422 bool "Processor feature human-readable names" if EMBEDDED
425 This option compiles in a table of x86 feature bits and corresponding
426 names. This is required to support /proc/cpuinfo and a few kernel
427 messages. You can disable this to save space, at the expense of
428 making those few kernel messages show numeric feature bits instead.
433 bool "Support x2apic"
434 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
436 This enables x2apic support on CPUs that have this feature.
438 This allows 32-bit apic IDs (so it can support very large systems),
439 and accesses the local apic via MSRs not via mmio.
441 If you don't know what to do here, say N.
444 bool "Enable MPS table" if ACPI || SFI
446 depends on X86_LOCAL_APIC
448 For old smp systems that do not have proper acpi support. Newer systems
449 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
453 depends on X86_GOLDFISH
456 bool "Avoid speculative indirect branches in kernel"
459 Compile kernel with the retpoline compiler options to guard against
460 kernel-to-user data leaks by avoiding speculative indirect
461 branches. Requires a compiler with -mindirect-branch=thunk-extern
462 support for full protection. The kernel may run slower.
464 config X86_CPU_RESCTRL
465 bool "x86 CPU resource control support"
466 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
468 select PROC_CPU_RESCTRL if PROC_FS
470 Enable x86 CPU resource control support.
472 Provide support for the allocation and monitoring of system resources
475 Intel calls this Intel Resource Director Technology
476 (Intel(R) RDT). More information about RDT can be found in the
477 Intel x86 Architecture Software Developer Manual.
479 AMD calls this AMD Platform Quality of Service (AMD QoS).
480 More information about AMD QoS can be found in the AMD64 Technology
481 Platform Quality of Service Extensions manual.
487 bool "Support for big SMP systems with more than 8 CPUs"
490 This option is needed for the systems that have more than 8 CPUs.
492 config X86_EXTENDED_PLATFORM
493 bool "Support for extended (non-PC) x86 platforms"
496 If you disable this option then the kernel will only support
497 standard PC platforms. (which covers the vast majority of
500 If you enable this option then you'll be able to select support
501 for the following (non-PC) 32 bit x86 platforms:
502 Goldfish (Android emulator)
505 SGI 320/540 (Visual Workstation)
506 STA2X11-based (e.g. Northville)
507 Moorestown MID devices
509 If you have one of these systems, or if you want to build a
510 generic distribution kernel, say Y here - otherwise say N.
514 config X86_EXTENDED_PLATFORM
515 bool "Support for extended (non-PC) x86 platforms"
518 If you disable this option then the kernel will only support
519 standard PC platforms. (which covers the vast majority of
522 If you enable this option then you'll be able to select support
523 for the following (non-PC) 64 bit x86 platforms:
528 If you have one of these systems, or if you want to build a
529 generic distribution kernel, say Y here - otherwise say N.
531 # This is an alphabetically sorted list of 64 bit extended platforms
532 # Please maintain the alphabetic order if and when there are additions
534 bool "Numascale NumaChip"
536 depends on X86_EXTENDED_PLATFORM
539 depends on X86_X2APIC
540 depends on PCI_MMCONFIG
542 Adds support for Numascale NumaChip large-SMP systems. Needed to
543 enable more than ~168 cores.
544 If you don't have one of these, you should say N here.
548 select HYPERVISOR_GUEST
550 depends on X86_64 && PCI
551 depends on X86_EXTENDED_PLATFORM
554 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
555 supposed to run on these EM64T-based machines. Only choose this option
556 if you have one of these machines.
559 bool "SGI Ultraviolet"
561 depends on X86_EXTENDED_PLATFORM
564 depends on X86_X2APIC
567 This option is needed in order to support SGI Ultraviolet systems.
568 If you don't have one of these, you should say N here.
570 # Following is an alphabetically sorted list of 32 bit extended platforms
571 # Please maintain the alphabetic order if and when there are additions
574 bool "Goldfish (Virtual Platform)"
575 depends on X86_EXTENDED_PLATFORM
577 Enable support for the Goldfish virtual platform used primarily
578 for Android development. Unless you are building for the Android
579 Goldfish emulator say N here.
582 bool "CE4100 TV platform"
584 depends on PCI_GODIRECT
585 depends on X86_IO_APIC
587 depends on X86_EXTENDED_PLATFORM
588 select X86_REBOOTFIXUPS
590 select OF_EARLY_FLATTREE
592 Select for the Intel CE media processor (CE4100) SOC.
593 This option compiles in support for the CE4100 SOC for settop
594 boxes and media devices.
597 bool "Intel MID platform support"
598 depends on X86_EXTENDED_PLATFORM
599 depends on X86_PLATFORM_DEVICES
601 depends on X86_64 || (PCI_GOANY && X86_32)
602 depends on X86_IO_APIC
608 select MFD_INTEL_MSIC
610 Select to build a kernel capable of supporting Intel MID (Mobile
611 Internet Device) platform systems which do not have the PCI legacy
612 interfaces. If you are building for a PC class system say N here.
614 Intel MID platforms are based on an Intel processor and chipset which
615 consume less power than most of the x86 derivatives.
617 config X86_INTEL_QUARK
618 bool "Intel Quark platform support"
620 depends on X86_EXTENDED_PLATFORM
621 depends on X86_PLATFORM_DEVICES
625 depends on X86_IO_APIC
630 Select to include support for Quark X1000 SoC.
631 Say Y here if you have a Quark based system such as the Arduino
632 compatible Intel Galileo.
634 config X86_INTEL_LPSS
635 bool "Intel Low Power Subsystem Support"
636 depends on X86 && ACPI && PCI
641 Select to build support for Intel Low Power Subsystem such as
642 found on Intel Lynxpoint PCH. Selecting this option enables
643 things like clock tree (common clock framework) and pincontrol
644 which are needed by the LPSS peripheral drivers.
646 config X86_AMD_PLATFORM_DEVICE
647 bool "AMD ACPI2Platform devices support"
652 Select to interpret AMD specific ACPI device to platform device
653 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
654 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
655 implemented under PINCTRL subsystem.
658 tristate "Intel SoC IOSF Sideband support for SoC platforms"
661 This option enables sideband register access support for Intel SoC
662 platforms. On these platforms the IOSF sideband is used in lieu of
663 MSR's for some register accesses, mostly but not limited to thermal
664 and power. Drivers may query the availability of this device to
665 determine if they need the sideband in order to work on these
666 platforms. The sideband is available on the following SoC products.
667 This list is not meant to be exclusive.
672 You should say Y if you are running a kernel on one of these SoC's.
674 config IOSF_MBI_DEBUG
675 bool "Enable IOSF sideband access through debugfs"
676 depends on IOSF_MBI && DEBUG_FS
678 Select this option to expose the IOSF sideband access registers (MCR,
679 MDR, MCRX) through debugfs to write and read register information from
680 different units on the SoC. This is most useful for obtaining device
681 state information for debug and analysis. As this is a general access
682 mechanism, users of this option would have specific knowledge of the
683 device they want to access.
685 If you don't require the option or are in doubt, say N.
688 bool "RDC R-321x SoC"
690 depends on X86_EXTENDED_PLATFORM
692 select X86_REBOOTFIXUPS
694 This option is needed for RDC R-321x system-on-chip, also known
696 If you don't have one of these chips, you should say N here.
698 config X86_32_NON_STANDARD
699 bool "Support non-standard 32-bit SMP architectures"
700 depends on X86_32 && SMP
701 depends on X86_EXTENDED_PLATFORM
703 This option compiles in the bigsmp and STA2X11 default
704 subarchitectures. It is intended for a generic binary
705 kernel. If you select them all, kernel will probe it one by
706 one and will fallback to default.
708 # Alphabetically sorted list of Non standard 32 bit platforms
710 config X86_SUPPORTS_MEMORY_FAILURE
712 # MCE code calls memory_failure():
714 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
715 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
716 depends on X86_64 || !SPARSEMEM
717 select ARCH_SUPPORTS_MEMORY_FAILURE
720 bool "STA2X11 Companion Chip Support"
721 depends on X86_32_NON_STANDARD && PCI
726 This adds support for boards based on the STA2X11 IO-Hub,
727 a.k.a. "ConneXt". The chip is used in place of the standard
728 PC chipset, so all "standard" peripherals are missing. If this
729 option is selected the kernel will still be able to boot on
730 standard PC machines.
733 tristate "Eurobraille/Iris poweroff module"
736 The Iris machines from EuroBraille do not have APM or ACPI support
737 to shut themselves down properly. A special I/O sequence is
738 needed to do so, which is what this module does at
741 This is only for Iris machines from EuroBraille.
745 config SCHED_OMIT_FRAME_POINTER
747 prompt "Single-depth WCHAN output"
750 Calculate simpler /proc/<PID>/wchan values. If this option
751 is disabled then wchan values will recurse back to the
752 caller function. This provides more accurate wchan values,
753 at the expense of slightly more scheduling overhead.
755 If in doubt, say "Y".
757 menuconfig HYPERVISOR_GUEST
758 bool "Linux guest support"
760 Say Y here to enable options for running Linux under various hyper-
761 visors. This option enables basic hypervisor detection and platform
764 If you say N, all options in this submenu will be skipped and
765 disabled, and Linux guest support won't be built in.
770 bool "Enable paravirtualization code"
772 This changes the kernel so it can modify itself when it is run
773 under a hypervisor, potentially improving performance significantly
774 over full virtualization. However, when run without a hypervisor
775 the kernel is theoretically slower and slightly larger.
780 config PARAVIRT_DEBUG
781 bool "paravirt-ops debugging"
782 depends on PARAVIRT && DEBUG_KERNEL
784 Enable to debug paravirt_ops internals. Specifically, BUG if
785 a paravirt_op is missing when it is called.
787 config PARAVIRT_SPINLOCKS
788 bool "Paravirtualization layer for spinlocks"
789 depends on PARAVIRT && SMP
791 Paravirtualized spinlocks allow a pvops backend to replace the
792 spinlock implementation with something virtualization-friendly
793 (for example, block the virtual CPU rather than spinning).
795 It has a minimal impact on native kernels and gives a nice performance
796 benefit on paravirtualized KVM / Xen kernels.
798 If you are unsure how to answer this question, answer Y.
800 config X86_HV_CALLBACK_VECTOR
803 source "arch/x86/xen/Kconfig"
806 bool "KVM Guest support (including kvmclock)"
808 select PARAVIRT_CLOCK
809 select ARCH_CPUIDLE_HALTPOLL
810 select X86_HV_CALLBACK_VECTOR
813 This option enables various optimizations for running under the KVM
814 hypervisor. It includes a paravirtualized clock, so that instead
815 of relying on a PIT (or probably other) emulation by the
816 underlying device model, the host provides the guest with
817 timing infrastructure such as time of day, and system time
819 config ARCH_CPUIDLE_HALTPOLL
821 prompt "Disable host haltpoll when loading haltpoll driver"
823 If virtualized under KVM, disable host haltpoll.
826 bool "Support for running PVH guests"
828 This option enables the PVH entry point for guest virtual machines
829 as specified in the x86/HVM direct boot ABI.
831 config PARAVIRT_TIME_ACCOUNTING
832 bool "Paravirtual steal time accounting"
835 Select this option to enable fine granularity task steal time
836 accounting. Time spent executing other tasks in parallel with
837 the current vCPU is discounted from the vCPU power. To account for
838 that, there can be a small performance impact.
840 If in doubt, say N here.
842 config PARAVIRT_CLOCK
845 config JAILHOUSE_GUEST
846 bool "Jailhouse non-root cell support"
847 depends on X86_64 && PCI
850 This option allows to run Linux as guest in a Jailhouse non-root
851 cell. You can leave this option disabled if you only want to start
852 Jailhouse and run Linux afterwards in the root cell.
855 bool "ACRN Guest support"
857 select X86_HV_CALLBACK_VECTOR
859 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
860 a flexible, lightweight reference open-source hypervisor, built with
861 real-time and safety-criticality in mind. It is built for embedded
862 IOT with small footprint and real-time features. More details can be
863 found in https://projectacrn.org/.
865 endif #HYPERVISOR_GUEST
867 source "arch/x86/Kconfig.cpu"
871 prompt "HPET Timer Support" if X86_32
873 Use the IA-PC HPET (High Precision Event Timer) to manage
874 time in preference to the PIT and RTC, if a HPET is
876 HPET is the next generation timer replacing legacy 8254s.
877 The HPET provides a stable time base on SMP
878 systems, unlike the TSC, but it is more expensive to access,
879 as it is off-chip. The interface used is documented
880 in the HPET spec, revision 1.
882 You can safely choose Y here. However, HPET will only be
883 activated if the platform and the BIOS support this feature.
884 Otherwise the 8254 will be used for timing services.
886 Choose N to continue using the legacy 8254 timer.
888 config HPET_EMULATE_RTC
890 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
893 def_bool y if X86_INTEL_MID
894 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
896 depends on X86_INTEL_MID && SFI
898 APB timer is the replacement for 8254, HPET on X86 MID platforms.
899 The APBT provides a stable time base on SMP
900 systems, unlike the TSC, but it is more expensive to access,
901 as it is off-chip. APB timers are always running regardless of CPU
902 C states, they are used as per CPU clockevent device when possible.
904 # Mark as expert because too many people got it wrong.
905 # The code disables itself when not needed.
908 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
909 bool "Enable DMI scanning" if EXPERT
911 Enabled scanning of DMI to identify machine quirks. Say Y
912 here unless you have verified that your setup is not
913 affected by entries in the DMI blacklist. Required by PNP
917 bool "Old AMD GART IOMMU support"
921 depends on X86_64 && PCI && AMD_NB
923 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
924 GART based hardware IOMMUs.
926 The GART supports full DMA access for devices with 32-bit access
927 limitations, on systems with more than 3 GB. This is usually needed
928 for USB, sound, many IDE/SATA chipsets and some other devices.
930 Newer systems typically have a modern AMD IOMMU, supported via
931 the CONFIG_AMD_IOMMU=y config option.
933 In normal configurations this driver is only active when needed:
934 there's more than 3 GB of memory and the system contains a
935 32-bit limited device.
940 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
941 depends on X86_64 && SMP && DEBUG_KERNEL
942 select CPUMASK_OFFSTACK
944 Enable maximum number of CPUS and NUMA Nodes for this architecture.
948 # The maximum number of CPUs supported:
950 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
951 # and which can be configured interactively in the
952 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
954 # The ranges are different on 32-bit and 64-bit kernels, depending on
955 # hardware capabilities and scalability features of the kernel.
957 # ( If MAXSMP is enabled we just use the highest possible value and disable
958 # interactive configuration. )
961 config NR_CPUS_RANGE_BEGIN
963 default NR_CPUS_RANGE_END if MAXSMP
967 config NR_CPUS_RANGE_END
970 default 64 if SMP && X86_BIGSMP
971 default 8 if SMP && !X86_BIGSMP
974 config NR_CPUS_RANGE_END
977 default 8192 if SMP && CPUMASK_OFFSTACK
978 default 512 if SMP && !CPUMASK_OFFSTACK
981 config NR_CPUS_DEFAULT
984 default 32 if X86_BIGSMP
988 config NR_CPUS_DEFAULT
991 default 8192 if MAXSMP
996 int "Maximum number of CPUs" if SMP && !MAXSMP
997 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
998 default NR_CPUS_DEFAULT
1000 This allows you to specify the maximum number of CPUs which this
1001 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1002 supported value is 8192, otherwise the maximum value is 512. The
1003 minimum value which makes sense is 2.
1005 This is purely to save memory: each supported CPU adds about 8KB
1006 to the kernel image.
1013 prompt "Multi-core scheduler support"
1016 Multi-core scheduler support improves the CPU scheduler's decision
1017 making when dealing with multi-core CPU chips at a cost of slightly
1018 increased overhead in some places. If unsure say N here.
1020 config SCHED_MC_PRIO
1021 bool "CPU core priorities scheduler support"
1022 depends on SCHED_MC && CPU_SUP_INTEL
1023 select X86_INTEL_PSTATE
1027 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1028 core ordering determined at manufacturing time, which allows
1029 certain cores to reach higher turbo frequencies (when running
1030 single threaded workloads) than others.
1032 Enabling this kernel feature teaches the scheduler about
1033 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1034 scheduler's CPU selection logic accordingly, so that higher
1035 overall system performance can be achieved.
1037 This feature will have no effect on CPUs without this feature.
1039 If unsure say Y here.
1043 depends on !SMP && X86_LOCAL_APIC
1046 bool "Local APIC support on uniprocessors" if !PCI_MSI
1048 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1050 A local APIC (Advanced Programmable Interrupt Controller) is an
1051 integrated interrupt controller in the CPU. If you have a single-CPU
1052 system which has a processor with a local APIC, you can say Y here to
1053 enable and use it. If you say Y here even though your machine doesn't
1054 have a local APIC, then the kernel will still run with no slowdown at
1055 all. The local APIC supports CPU-generated self-interrupts (timer,
1056 performance counters), and the NMI watchdog which detects hard
1059 config X86_UP_IOAPIC
1060 bool "IO-APIC support on uniprocessors"
1061 depends on X86_UP_APIC
1063 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1064 SMP-capable replacement for PC-style interrupt controllers. Most
1065 SMP systems and many recent uniprocessor systems have one.
1067 If you have a single-CPU system with an IO-APIC, you can say Y here
1068 to use it. If you say Y here even though your machine doesn't have
1069 an IO-APIC, then the kernel will still run with no slowdown at all.
1071 config X86_LOCAL_APIC
1073 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1074 select IRQ_DOMAIN_HIERARCHY
1075 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1079 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1081 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1082 bool "Reroute for broken boot IRQs"
1083 depends on X86_IO_APIC
1085 This option enables a workaround that fixes a source of
1086 spurious interrupts. This is recommended when threaded
1087 interrupt handling is used on systems where the generation of
1088 superfluous "boot interrupts" cannot be disabled.
1090 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1091 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1092 kernel does during interrupt handling). On chipsets where this
1093 boot IRQ generation cannot be disabled, this workaround keeps
1094 the original IRQ line masked so that only the equivalent "boot
1095 IRQ" is delivered to the CPUs. The workaround also tells the
1096 kernel to set up the IRQ handler on the boot IRQ line. In this
1097 way only one interrupt is delivered to the kernel. Otherwise
1098 the spurious second interrupt may cause the kernel to bring
1099 down (vital) interrupt lines.
1101 Only affects "broken" chipsets. Interrupt sharing may be
1102 increased on these systems.
1105 bool "Machine Check / overheating reporting"
1106 select GENERIC_ALLOCATOR
1109 Machine Check support allows the processor to notify the
1110 kernel if it detects a problem (e.g. overheating, data corruption).
1111 The action the kernel takes depends on the severity of the problem,
1112 ranging from warning messages to halting the machine.
1114 config X86_MCELOG_LEGACY
1115 bool "Support for deprecated /dev/mcelog character device"
1118 Enable support for /dev/mcelog which is needed by the old mcelog
1119 userspace logging daemon. Consider switching to the new generation
1122 config X86_MCE_INTEL
1124 prompt "Intel MCE features"
1125 depends on X86_MCE && X86_LOCAL_APIC
1127 Additional support for intel specific MCE features such as
1128 the thermal monitor.
1132 prompt "AMD MCE features"
1133 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1135 Additional support for AMD specific MCE features such as
1136 the DRAM Error Threshold.
1138 config X86_ANCIENT_MCE
1139 bool "Support for old Pentium 5 / WinChip machine checks"
1140 depends on X86_32 && X86_MCE
1142 Include support for machine check handling on old Pentium 5 or WinChip
1143 systems. These typically need to be enabled explicitly on the command
1146 config X86_MCE_THRESHOLD
1147 depends on X86_MCE_AMD || X86_MCE_INTEL
1150 config X86_MCE_INJECT
1151 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1152 tristate "Machine check injector support"
1154 Provide support for injecting machine checks for testing purposes.
1155 If you don't know what a machine check is and you don't do kernel
1156 QA it is safe to say n.
1158 config X86_THERMAL_VECTOR
1160 depends on X86_MCE_INTEL
1162 source "arch/x86/events/Kconfig"
1164 config X86_LEGACY_VM86
1165 bool "Legacy VM86 support"
1168 This option allows user programs to put the CPU into V8086
1169 mode, which is an 80286-era approximation of 16-bit real mode.
1171 Some very old versions of X and/or vbetool require this option
1172 for user mode setting. Similarly, DOSEMU will use it if
1173 available to accelerate real mode DOS programs. However, any
1174 recent version of DOSEMU, X, or vbetool should be fully
1175 functional even without kernel VM86 support, as they will all
1176 fall back to software emulation. Nevertheless, if you are using
1177 a 16-bit DOS program where 16-bit performance matters, vm86
1178 mode might be faster than emulation and you might want to
1181 Note that any app that works on a 64-bit kernel is unlikely to
1182 need this option, as 64-bit kernels don't, and can't, support
1183 V8086 mode. This option is also unrelated to 16-bit protected
1184 mode and is not needed to run most 16-bit programs under Wine.
1186 Enabling this option increases the complexity of the kernel
1187 and slows down exception handling a tiny bit.
1189 If unsure, say N here.
1193 default X86_LEGACY_VM86
1196 bool "Enable support for 16-bit segments" if EXPERT
1198 depends on MODIFY_LDT_SYSCALL
1200 This option is required by programs like Wine to run 16-bit
1201 protected mode legacy code on x86 processors. Disabling
1202 this option saves about 300 bytes on i386, or around 6K text
1203 plus 16K runtime memory on x86-64,
1207 depends on X86_16BIT && X86_32
1211 depends on X86_16BIT && X86_64
1213 config X86_VSYSCALL_EMULATION
1214 bool "Enable vsyscall emulation" if EXPERT
1218 This enables emulation of the legacy vsyscall page. Disabling
1219 it is roughly equivalent to booting with vsyscall=none, except
1220 that it will also disable the helpful warning if a program
1221 tries to use a vsyscall. With this option set to N, offending
1222 programs will just segfault, citing addresses of the form
1225 This option is required by many programs built before 2013, and
1226 care should be used even with newer programs if set to N.
1228 Disabling this option saves about 7K of kernel size and
1229 possibly 4K of additional runtime pagetable memory.
1231 config X86_IOPL_IOPERM
1232 bool "IOPERM and IOPL Emulation"
1235 This enables the ioperm() and iopl() syscalls which are necessary
1236 for legacy applications.
1238 Legacy IOPL support is an overbroad mechanism which allows user
1239 space aside of accessing all 65536 I/O ports also to disable
1240 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1241 capabilities and permission from potentially active security
1244 The emulation restricts the functionality of the syscall to
1245 only allowing the full range I/O port access, but prevents the
1246 ability to disable interrupts from user space which would be
1247 granted if the hardware IOPL mechanism would be used.
1250 tristate "Toshiba Laptop support"
1253 This adds a driver to safely access the System Management Mode of
1254 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1255 not work on models with a Phoenix BIOS. The System Management Mode
1256 is used to set the BIOS and power saving options on Toshiba portables.
1258 For information on utilities to make use of this driver see the
1259 Toshiba Linux utilities web site at:
1260 <http://www.buzzard.org.uk/toshiba/>.
1262 Say Y if you intend to run this kernel on a Toshiba portable.
1266 tristate "Dell i8k legacy laptop support"
1268 select SENSORS_DELL_SMM
1270 This option enables legacy /proc/i8k userspace interface in hwmon
1271 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1272 temperature and allows controlling fan speeds of Dell laptops via
1273 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1274 it reports also power and hotkey status. For fan speed control is
1275 needed userspace package i8kutils.
1277 Say Y if you intend to run this kernel on old Dell laptops or want to
1278 use userspace package i8kutils.
1281 config X86_REBOOTFIXUPS
1282 bool "Enable X86 board specific fixups for reboot"
1285 This enables chipset and/or board specific fixups to be done
1286 in order to get reboot to work correctly. This is only needed on
1287 some combinations of hardware and BIOS. The symptom, for which
1288 this config is intended, is when reboot ends with a stalled/hung
1291 Currently, the only fixup is for the Geode machines using
1292 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1294 Say Y if you want to enable the fixup. Currently, it's safe to
1295 enable this option even if you don't need it.
1299 bool "CPU microcode loading support"
1301 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1303 If you say Y here, you will be able to update the microcode on
1304 Intel and AMD processors. The Intel support is for the IA32 family,
1305 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1306 AMD support is for families 0x10 and later. You will obviously need
1307 the actual microcode binary data itself which is not shipped with
1310 The preferred method to load microcode from a detached initrd is described
1311 in Documentation/x86/microcode.rst. For that you need to enable
1312 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1313 initrd for microcode blobs.
1315 In addition, you can build the microcode into the kernel. For that you
1316 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1319 config MICROCODE_INTEL
1320 bool "Intel microcode loading support"
1321 depends on MICROCODE
1324 This options enables microcode patch loading support for Intel
1327 For the current Intel microcode data package go to
1328 <https://downloadcenter.intel.com> and search for
1329 'Linux Processor Microcode Data File'.
1331 config MICROCODE_AMD
1332 bool "AMD microcode loading support"
1333 depends on MICROCODE
1335 If you select this option, microcode patch loading support for AMD
1336 processors will be enabled.
1338 config MICROCODE_OLD_INTERFACE
1339 bool "Ancient loading interface (DEPRECATED)"
1341 depends on MICROCODE
1343 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1344 which was used by userspace tools like iucode_tool and microcode.ctl.
1345 It is inadequate because it runs too late to be able to properly
1346 load microcode on a machine and it needs special tools. Instead, you
1347 should've switched to the early loading method with the initrd or
1348 builtin microcode by now: Documentation/x86/microcode.rst
1351 tristate "/dev/cpu/*/msr - Model-specific register support"
1353 This device gives privileged processes access to the x86
1354 Model-Specific Registers (MSRs). It is a character device with
1355 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1356 MSR accesses are directed to a specific CPU on multi-processor
1360 tristate "/dev/cpu/*/cpuid - CPU information support"
1362 This device gives processes access to the x86 CPUID instruction to
1363 be executed on a specific processor. It is a character device
1364 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1368 prompt "High Memory Support"
1375 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1376 However, the address space of 32-bit x86 processors is only 4
1377 Gigabytes large. That means that, if you have a large amount of
1378 physical memory, not all of it can be "permanently mapped" by the
1379 kernel. The physical memory that's not permanently mapped is called
1382 If you are compiling a kernel which will never run on a machine with
1383 more than 1 Gigabyte total physical RAM, answer "off" here (default
1384 choice and suitable for most users). This will result in a "3GB/1GB"
1385 split: 3GB are mapped so that each process sees a 3GB virtual memory
1386 space and the remaining part of the 4GB virtual memory space is used
1387 by the kernel to permanently map as much physical memory as
1390 If the machine has between 1 and 4 Gigabytes physical RAM, then
1393 If more than 4 Gigabytes is used then answer "64GB" here. This
1394 selection turns Intel PAE (Physical Address Extension) mode on.
1395 PAE implements 3-level paging on IA32 processors. PAE is fully
1396 supported by Linux, PAE mode is implemented on all recent Intel
1397 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1398 then the kernel will not boot on CPUs that don't support PAE!
1400 The actual amount of total physical memory will either be
1401 auto detected or can be forced by using a kernel command line option
1402 such as "mem=256M". (Try "man bootparam" or see the documentation of
1403 your boot loader (lilo or loadlin) about how to pass options to the
1404 kernel at boot time.)
1406 If unsure, say "off".
1411 Select this if you have a 32-bit processor and between 1 and 4
1412 gigabytes of physical RAM.
1416 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1419 Select this if you have a 32-bit processor and more than 4
1420 gigabytes of physical RAM.
1425 prompt "Memory split" if EXPERT
1429 Select the desired split between kernel and user memory.
1431 If the address range available to the kernel is less than the
1432 physical memory installed, the remaining memory will be available
1433 as "high memory". Accessing high memory is a little more costly
1434 than low memory, as it needs to be mapped into the kernel first.
1435 Note that increasing the kernel address space limits the range
1436 available to user programs, making the address space there
1437 tighter. Selecting anything other than the default 3G/1G split
1438 will also likely make your kernel incompatible with binary-only
1441 If you are not absolutely sure what you are doing, leave this
1445 bool "3G/1G user/kernel split"
1446 config VMSPLIT_3G_OPT
1448 bool "3G/1G user/kernel split (for full 1G low memory)"
1450 bool "2G/2G user/kernel split"
1451 config VMSPLIT_2G_OPT
1453 bool "2G/2G user/kernel split (for full 2G low memory)"
1455 bool "1G/3G user/kernel split"
1460 default 0xB0000000 if VMSPLIT_3G_OPT
1461 default 0x80000000 if VMSPLIT_2G
1462 default 0x78000000 if VMSPLIT_2G_OPT
1463 default 0x40000000 if VMSPLIT_1G
1469 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1472 bool "PAE (Physical Address Extension) Support"
1473 depends on X86_32 && !HIGHMEM4G
1474 select PHYS_ADDR_T_64BIT
1477 PAE is required for NX support, and furthermore enables
1478 larger swapspace support for non-overcommit purposes. It
1479 has the cost of more pagetable lookup overhead, and also
1480 consumes more pagetable space per process.
1483 bool "Enable 5-level page tables support"
1485 select DYNAMIC_MEMORY_LAYOUT
1486 select SPARSEMEM_VMEMMAP
1489 5-level paging enables access to larger address space:
1490 upto 128 PiB of virtual address space and 4 PiB of
1491 physical address space.
1493 It will be supported by future Intel CPUs.
1495 A kernel with the option enabled can be booted on machines that
1496 support 4- or 5-level paging.
1498 See Documentation/x86/x86_64/5level-paging.rst for more
1503 config X86_DIRECT_GBPAGES
1507 Certain kernel features effectively disable kernel
1508 linear 1 GB mappings (even if the CPU otherwise
1509 supports them), so don't confuse the user by printing
1510 that we have them enabled.
1512 config X86_CPA_STATISTICS
1513 bool "Enable statistic for Change Page Attribute"
1516 Expose statistics about the Change Page Attribute mechanism, which
1517 helps to determine the effectiveness of preserving large and huge
1518 page mappings when mapping protections are changed.
1520 config AMD_MEM_ENCRYPT
1521 bool "AMD Secure Memory Encryption (SME) support"
1522 depends on X86_64 && CPU_SUP_AMD
1523 select DMA_COHERENT_POOL
1524 select DYNAMIC_PHYSICAL_MASK
1525 select ARCH_USE_MEMREMAP_PROT
1526 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1527 select INSTRUCTION_DECODER
1529 Say yes to enable support for the encryption of system memory.
1530 This requires an AMD processor that supports Secure Memory
1533 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1534 bool "Activate AMD Secure Memory Encryption (SME) by default"
1536 depends on AMD_MEM_ENCRYPT
1538 Say yes to have system memory encrypted by default if running on
1539 an AMD processor that supports Secure Memory Encryption (SME).
1541 If set to Y, then the encryption of system memory can be
1542 deactivated with the mem_encrypt=off command line option.
1544 If set to N, then the encryption of system memory can be
1545 activated with the mem_encrypt=on command line option.
1547 # Common NUMA Features
1549 bool "NUMA Memory Allocation and Scheduler Support"
1551 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1552 default y if X86_BIGSMP
1554 Enable NUMA (Non-Uniform Memory Access) support.
1556 The kernel will try to allocate memory used by a CPU on the
1557 local memory controller of the CPU and add some more
1558 NUMA awareness to the kernel.
1560 For 64-bit this is recommended if the system is Intel Core i7
1561 (or later), AMD Opteron, or EM64T NUMA.
1563 For 32-bit this is only needed if you boot a 32-bit
1564 kernel on a 64-bit NUMA platform.
1566 Otherwise, you should say N.
1570 prompt "Old style AMD Opteron NUMA detection"
1571 depends on X86_64 && NUMA && PCI
1573 Enable AMD NUMA node topology detection. You should say Y here if
1574 you have a multi processor AMD system. This uses an old method to
1575 read the NUMA configuration directly from the builtin Northbridge
1576 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1577 which also takes priority if both are compiled in.
1579 config X86_64_ACPI_NUMA
1581 prompt "ACPI NUMA detection"
1582 depends on X86_64 && NUMA && ACPI && PCI
1585 Enable ACPI SRAT based node topology detection.
1588 bool "NUMA emulation"
1591 Enable NUMA emulation. A flat machine will be split
1592 into virtual nodes when booted with "numa=fake=N", where N is the
1593 number of nodes. This is only useful for debugging.
1596 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1598 default "10" if MAXSMP
1599 default "6" if X86_64
1601 depends on NEED_MULTIPLE_NODES
1603 Specify the maximum number of NUMA Nodes available on the target
1604 system. Increases memory reserved to accommodate various tables.
1606 config ARCH_FLATMEM_ENABLE
1608 depends on X86_32 && !NUMA
1610 config ARCH_SPARSEMEM_ENABLE
1612 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1613 select SPARSEMEM_STATIC if X86_32
1614 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1616 config ARCH_SPARSEMEM_DEFAULT
1617 def_bool X86_64 || (NUMA && X86_32)
1619 config ARCH_SELECT_MEMORY_MODEL
1621 depends on ARCH_SPARSEMEM_ENABLE
1623 config ARCH_MEMORY_PROBE
1624 bool "Enable sysfs memory/probe interface"
1625 depends on X86_64 && MEMORY_HOTPLUG
1627 This option enables a sysfs memory/probe interface for testing.
1628 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1629 If you are unsure how to answer this question, answer N.
1631 config ARCH_PROC_KCORE_TEXT
1633 depends on X86_64 && PROC_KCORE
1635 config ILLEGAL_POINTER_VALUE
1638 default 0xdead000000000000 if X86_64
1640 config X86_PMEM_LEGACY_DEVICE
1643 config X86_PMEM_LEGACY
1644 tristate "Support non-standard NVDIMMs and ADR protected memory"
1645 depends on PHYS_ADDR_T_64BIT
1647 select X86_PMEM_LEGACY_DEVICE
1648 select NUMA_KEEP_MEMINFO if NUMA
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 && (M486SX || MELAN)
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.rst> 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.
1860 prompt "User Mode Instruction Prevention" if EXPERT
1862 User Mode Instruction Prevention (UMIP) is a security feature in
1863 some x86 processors. If enabled, a general protection fault is
1864 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1865 executed in user mode. These instructions unnecessarily expose
1866 information about the hardware state.
1868 The vast majority of applications do not use these instructions.
1869 For the very few that do, software emulation is provided in
1870 specific cases in protected and virtual-8086 modes. Emulated
1873 config X86_INTEL_MEMORY_PROTECTION_KEYS
1874 prompt "Memory Protection Keys"
1876 # Note: only available in 64-bit mode
1877 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1878 select ARCH_USES_HIGH_VMA_FLAGS
1879 select ARCH_HAS_PKEYS
1881 Memory Protection Keys provides a mechanism for enforcing
1882 page-based protections, but without requiring modification of the
1883 page tables when an application changes protection domains.
1885 For details, see Documentation/core-api/protection-keys.rst
1890 prompt "TSX enable mode"
1891 depends on CPU_SUP_INTEL
1892 default X86_INTEL_TSX_MODE_OFF
1894 Intel's TSX (Transactional Synchronization Extensions) feature
1895 allows to optimize locking protocols through lock elision which
1896 can lead to a noticeable performance boost.
1898 On the other hand it has been shown that TSX can be exploited
1899 to form side channel attacks (e.g. TAA) and chances are there
1900 will be more of those attacks discovered in the future.
1902 Therefore TSX is not enabled by default (aka tsx=off). An admin
1903 might override this decision by tsx=on the command line parameter.
1904 Even with TSX enabled, the kernel will attempt to enable the best
1905 possible TAA mitigation setting depending on the microcode available
1906 for the particular machine.
1908 This option allows to set the default tsx mode between tsx=on, =off
1909 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1912 Say off if not sure, auto if TSX is in use but it should be used on safe
1913 platforms or on if TSX is in use and the security aspect of tsx is not
1916 config X86_INTEL_TSX_MODE_OFF
1919 TSX is disabled if possible - equals to tsx=off command line parameter.
1921 config X86_INTEL_TSX_MODE_ON
1924 TSX is always enabled on TSX capable HW - equals the tsx=on command
1927 config X86_INTEL_TSX_MODE_AUTO
1930 TSX is enabled on TSX capable HW that is believed to be safe against
1931 side channel attacks- equals the tsx=auto command line parameter.
1935 bool "EFI runtime service support"
1938 select EFI_RUNTIME_WRAPPERS
1940 This enables the kernel to use EFI runtime services that are
1941 available (such as the EFI variable services).
1943 This option is only useful on systems that have EFI firmware.
1944 In addition, you should use the latest ELILO loader available
1945 at <http://elilo.sourceforge.net> in order to take advantage
1946 of EFI runtime services. However, even with this option, the
1947 resultant kernel should continue to boot on existing non-EFI
1951 bool "EFI stub support"
1952 depends on EFI && !X86_USE_3DNOW
1953 depends on $(cc-option,-mabi=ms) || X86_32
1956 This kernel feature allows a bzImage to be loaded directly
1957 by EFI firmware without the use of a bootloader.
1959 See Documentation/admin-guide/efi-stub.rst for more information.
1962 bool "EFI mixed-mode support"
1963 depends on EFI_STUB && X86_64
1965 Enabling this feature allows a 64-bit kernel to be booted
1966 on a 32-bit firmware, provided that your CPU supports 64-bit
1969 Note that it is not possible to boot a mixed-mode enabled
1970 kernel via the EFI boot stub - a bootloader that supports
1971 the EFI handover protocol must be used.
1975 source "kernel/Kconfig.hz"
1978 bool "kexec system call"
1981 kexec is a system call that implements the ability to shutdown your
1982 current kernel, and to start another kernel. It is like a reboot
1983 but it is independent of the system firmware. And like a reboot
1984 you can start any kernel with it, not just Linux.
1986 The name comes from the similarity to the exec system call.
1988 It is an ongoing process to be certain the hardware in a machine
1989 is properly shutdown, so do not be surprised if this code does not
1990 initially work for you. As of this writing the exact hardware
1991 interface is strongly in flux, so no good recommendation can be
1995 bool "kexec file based system call"
2000 depends on CRYPTO_SHA256=y
2002 This is new version of kexec system call. This system call is
2003 file based and takes file descriptors as system call argument
2004 for kernel and initramfs as opposed to list of segments as
2005 accepted by previous system call.
2007 config ARCH_HAS_KEXEC_PURGATORY
2011 bool "Verify kernel signature during kexec_file_load() syscall"
2012 depends on KEXEC_FILE
2015 This option makes the kexec_file_load() syscall check for a valid
2016 signature of the kernel image. The image can still be loaded without
2017 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2018 there's a signature that we can check, then it must be valid.
2020 In addition to this option, you need to enable signature
2021 verification for the corresponding kernel image type being
2022 loaded in order for this to work.
2024 config KEXEC_SIG_FORCE
2025 bool "Require a valid signature in kexec_file_load() syscall"
2026 depends on KEXEC_SIG
2028 This option makes kernel signature verification mandatory for
2029 the kexec_file_load() syscall.
2031 config KEXEC_BZIMAGE_VERIFY_SIG
2032 bool "Enable bzImage signature verification support"
2033 depends on KEXEC_SIG
2034 depends on SIGNED_PE_FILE_VERIFICATION
2035 select SYSTEM_TRUSTED_KEYRING
2037 Enable bzImage signature verification support.
2040 bool "kernel crash dumps"
2041 depends on X86_64 || (X86_32 && HIGHMEM)
2043 Generate crash dump after being started by kexec.
2044 This should be normally only set in special crash dump kernels
2045 which are loaded in the main kernel with kexec-tools into
2046 a specially reserved region and then later executed after
2047 a crash by kdump/kexec. The crash dump kernel must be compiled
2048 to a memory address not used by the main kernel or BIOS using
2049 PHYSICAL_START, or it must be built as a relocatable image
2050 (CONFIG_RELOCATABLE=y).
2051 For more details see Documentation/admin-guide/kdump/kdump.rst
2055 depends on KEXEC && HIBERNATION
2057 Jump between original kernel and kexeced kernel and invoke
2058 code in physical address mode via KEXEC
2060 config PHYSICAL_START
2061 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2064 This gives the physical address where the kernel is loaded.
2066 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2067 bzImage will decompress itself to above physical address and
2068 run from there. Otherwise, bzImage will run from the address where
2069 it has been loaded by the boot loader and will ignore above physical
2072 In normal kdump cases one does not have to set/change this option
2073 as now bzImage can be compiled as a completely relocatable image
2074 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2075 address. This option is mainly useful for the folks who don't want
2076 to use a bzImage for capturing the crash dump and want to use a
2077 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2078 to be specifically compiled to run from a specific memory area
2079 (normally a reserved region) and this option comes handy.
2081 So if you are using bzImage for capturing the crash dump,
2082 leave the value here unchanged to 0x1000000 and set
2083 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2084 for capturing the crash dump change this value to start of
2085 the reserved region. In other words, it can be set based on
2086 the "X" value as specified in the "crashkernel=YM@XM"
2087 command line boot parameter passed to the panic-ed
2088 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2089 for more details about crash dumps.
2091 Usage of bzImage for capturing the crash dump is recommended as
2092 one does not have to build two kernels. Same kernel can be used
2093 as production kernel and capture kernel. Above option should have
2094 gone away after relocatable bzImage support is introduced. But it
2095 is present because there are users out there who continue to use
2096 vmlinux for dump capture. This option should go away down the
2099 Don't change this unless you know what you are doing.
2102 bool "Build a relocatable kernel"
2105 This builds a kernel image that retains relocation information
2106 so it can be loaded someplace besides the default 1MB.
2107 The relocations tend to make the kernel binary about 10% larger,
2108 but are discarded at runtime.
2110 One use is for the kexec on panic case where the recovery kernel
2111 must live at a different physical address than the primary
2114 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2115 it has been loaded at and the compile time physical address
2116 (CONFIG_PHYSICAL_START) is used as the minimum location.
2118 config RANDOMIZE_BASE
2119 bool "Randomize the address of the kernel image (KASLR)"
2120 depends on RELOCATABLE
2123 In support of Kernel Address Space Layout Randomization (KASLR),
2124 this randomizes the physical address at which the kernel image
2125 is decompressed and the virtual address where the kernel
2126 image is mapped, as a security feature that deters exploit
2127 attempts relying on knowledge of the location of kernel
2130 On 64-bit, the kernel physical and virtual addresses are
2131 randomized separately. The physical address will be anywhere
2132 between 16MB and the top of physical memory (up to 64TB). The
2133 virtual address will be randomized from 16MB up to 1GB (9 bits
2134 of entropy). Note that this also reduces the memory space
2135 available to kernel modules from 1.5GB to 1GB.
2137 On 32-bit, the kernel physical and virtual addresses are
2138 randomized together. They will be randomized from 16MB up to
2139 512MB (8 bits of entropy).
2141 Entropy is generated using the RDRAND instruction if it is
2142 supported. If RDTSC is supported, its value is mixed into
2143 the entropy pool as well. If neither RDRAND nor RDTSC are
2144 supported, then entropy is read from the i8254 timer. The
2145 usable entropy is limited by the kernel being built using
2146 2GB addressing, and that PHYSICAL_ALIGN must be at a
2147 minimum of 2MB. As a result, only 10 bits of entropy are
2148 theoretically possible, but the implementations are further
2149 limited due to memory layouts.
2153 # Relocation on x86 needs some additional build support
2154 config X86_NEED_RELOCS
2156 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2158 config PHYSICAL_ALIGN
2159 hex "Alignment value to which kernel should be aligned"
2161 range 0x2000 0x1000000 if X86_32
2162 range 0x200000 0x1000000 if X86_64
2164 This value puts the alignment restrictions on physical address
2165 where kernel is loaded and run from. Kernel is compiled for an
2166 address which meets above alignment restriction.
2168 If bootloader loads the kernel at a non-aligned address and
2169 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2170 address aligned to above value and run from there.
2172 If bootloader loads the kernel at a non-aligned address and
2173 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2174 load address and decompress itself to the address it has been
2175 compiled for and run from there. The address for which kernel is
2176 compiled already meets above alignment restrictions. Hence the
2177 end result is that kernel runs from a physical address meeting
2178 above alignment restrictions.
2180 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2181 this value must be a multiple of 0x200000.
2183 Don't change this unless you know what you are doing.
2185 config DYNAMIC_MEMORY_LAYOUT
2188 This option makes base addresses of vmalloc and vmemmap as well as
2189 __PAGE_OFFSET movable during boot.
2191 config RANDOMIZE_MEMORY
2192 bool "Randomize the kernel memory sections"
2194 depends on RANDOMIZE_BASE
2195 select DYNAMIC_MEMORY_LAYOUT
2196 default RANDOMIZE_BASE
2198 Randomizes the base virtual address of kernel memory sections
2199 (physical memory mapping, vmalloc & vmemmap). This security feature
2200 makes exploits relying on predictable memory locations less reliable.
2202 The order of allocations remains unchanged. Entropy is generated in
2203 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2204 configuration have in average 30,000 different possible virtual
2205 addresses for each memory section.
2209 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2210 hex "Physical memory mapping padding" if EXPERT
2211 depends on RANDOMIZE_MEMORY
2212 default "0xa" if MEMORY_HOTPLUG
2214 range 0x1 0x40 if MEMORY_HOTPLUG
2217 Define the padding in terabytes added to the existing physical
2218 memory size during kernel memory randomization. It is useful
2219 for memory hotplug support but reduces the entropy available for
2220 address randomization.
2222 If unsure, leave at the default value.
2228 config BOOTPARAM_HOTPLUG_CPU0
2229 bool "Set default setting of cpu0_hotpluggable"
2230 depends on HOTPLUG_CPU
2232 Set whether default state of cpu0_hotpluggable is on or off.
2234 Say Y here to enable CPU0 hotplug by default. If this switch
2235 is turned on, there is no need to give cpu0_hotplug kernel
2236 parameter and the CPU0 hotplug feature is enabled by default.
2238 Please note: there are two known CPU0 dependencies if you want
2239 to enable the CPU0 hotplug feature either by this switch or by
2240 cpu0_hotplug kernel parameter.
2242 First, resume from hibernate or suspend always starts from CPU0.
2243 So hibernate and suspend are prevented if CPU0 is offline.
2245 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2246 offline if any interrupt can not migrate out of CPU0. There may
2247 be other CPU0 dependencies.
2249 Please make sure the dependencies are under your control before
2250 you enable this feature.
2252 Say N if you don't want to enable CPU0 hotplug feature by default.
2253 You still can enable the CPU0 hotplug feature at boot by kernel
2254 parameter cpu0_hotplug.
2256 config DEBUG_HOTPLUG_CPU0
2258 prompt "Debug CPU0 hotplug"
2259 depends on HOTPLUG_CPU
2261 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2262 soon as possible and boots up userspace with CPU0 offlined. User
2263 can online CPU0 back after boot time.
2265 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2266 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2267 compilation or giving cpu0_hotplug kernel parameter at boot.
2273 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2274 depends on COMPAT_32
2276 Certain buggy versions of glibc will crash if they are
2277 presented with a 32-bit vDSO that is not mapped at the address
2278 indicated in its segment table.
2280 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2281 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2282 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2283 the only released version with the bug, but OpenSUSE 9
2284 contains a buggy "glibc 2.3.2".
2286 The symptom of the bug is that everything crashes on startup, saying:
2287 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2289 Saying Y here changes the default value of the vdso32 boot
2290 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2291 This works around the glibc bug but hurts performance.
2293 If unsure, say N: if you are compiling your own kernel, you
2294 are unlikely to be using a buggy version of glibc.
2297 prompt "vsyscall table for legacy applications"
2299 default LEGACY_VSYSCALL_XONLY
2301 Legacy user code that does not know how to find the vDSO expects
2302 to be able to issue three syscalls by calling fixed addresses in
2303 kernel space. Since this location is not randomized with ASLR,
2304 it can be used to assist security vulnerability exploitation.
2306 This setting can be changed at boot time via the kernel command
2307 line parameter vsyscall=[emulate|xonly|none].
2309 On a system with recent enough glibc (2.14 or newer) and no
2310 static binaries, you can say None without a performance penalty
2311 to improve security.
2313 If unsure, select "Emulate execution only".
2315 config LEGACY_VSYSCALL_EMULATE
2316 bool "Full emulation"
2318 The kernel traps and emulates calls into the fixed vsyscall
2319 address mapping. This makes the mapping non-executable, but
2320 it still contains readable known contents, which could be
2321 used in certain rare security vulnerability exploits. This
2322 configuration is recommended when using legacy userspace
2323 that still uses vsyscalls along with legacy binary
2324 instrumentation tools that require code to be readable.
2326 An example of this type of legacy userspace is running
2327 Pin on an old binary that still uses vsyscalls.
2329 config LEGACY_VSYSCALL_XONLY
2330 bool "Emulate execution only"
2332 The kernel traps and emulates calls into the fixed vsyscall
2333 address mapping and does not allow reads. This
2334 configuration is recommended when userspace might use the
2335 legacy vsyscall area but support for legacy binary
2336 instrumentation of legacy code is not needed. It mitigates
2337 certain uses of the vsyscall area as an ASLR-bypassing
2340 config LEGACY_VSYSCALL_NONE
2343 There will be no vsyscall mapping at all. This will
2344 eliminate any risk of ASLR bypass due to the vsyscall
2345 fixed address mapping. Attempts to use the vsyscalls
2346 will be reported to dmesg, so that either old or
2347 malicious userspace programs can be identified.
2352 bool "Built-in kernel command line"
2354 Allow for specifying boot arguments to the kernel at
2355 build time. On some systems (e.g. embedded ones), it is
2356 necessary or convenient to provide some or all of the
2357 kernel boot arguments with the kernel itself (that is,
2358 to not rely on the boot loader to provide them.)
2360 To compile command line arguments into the kernel,
2361 set this option to 'Y', then fill in the
2362 boot arguments in CONFIG_CMDLINE.
2364 Systems with fully functional boot loaders (i.e. non-embedded)
2365 should leave this option set to 'N'.
2368 string "Built-in kernel command string"
2369 depends on CMDLINE_BOOL
2372 Enter arguments here that should be compiled into the kernel
2373 image and used at boot time. If the boot loader provides a
2374 command line at boot time, it is appended to this string to
2375 form the full kernel command line, when the system boots.
2377 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2378 change this behavior.
2380 In most cases, the command line (whether built-in or provided
2381 by the boot loader) should specify the device for the root
2384 config CMDLINE_OVERRIDE
2385 bool "Built-in command line overrides boot loader arguments"
2386 depends on CMDLINE_BOOL && CMDLINE != ""
2388 Set this option to 'Y' to have the kernel ignore the boot loader
2389 command line, and use ONLY the built-in command line.
2391 This is used to work around broken boot loaders. This should
2392 be set to 'N' under normal conditions.
2394 config MODIFY_LDT_SYSCALL
2395 bool "Enable the LDT (local descriptor table)" if EXPERT
2398 Linux can allow user programs to install a per-process x86
2399 Local Descriptor Table (LDT) using the modify_ldt(2) system
2400 call. This is required to run 16-bit or segmented code such as
2401 DOSEMU or some Wine programs. It is also used by some very old
2402 threading libraries.
2404 Enabling this feature adds a small amount of overhead to
2405 context switches and increases the low-level kernel attack
2406 surface. Disabling it removes the modify_ldt(2) system call.
2408 Saying 'N' here may make sense for embedded or server kernels.
2410 source "kernel/livepatch/Kconfig"
2414 config ARCH_HAS_ADD_PAGES
2416 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2418 config ARCH_ENABLE_MEMORY_HOTPLUG
2420 depends on X86_64 || (X86_32 && HIGHMEM)
2422 config ARCH_ENABLE_MEMORY_HOTREMOVE
2424 depends on MEMORY_HOTPLUG
2426 config USE_PERCPU_NUMA_NODE_ID
2430 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2432 depends on X86_64 || X86_PAE
2434 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2436 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2438 config ARCH_ENABLE_THP_MIGRATION
2440 depends on X86_64 && TRANSPARENT_HUGEPAGE
2442 menu "Power management and ACPI options"
2444 config ARCH_HIBERNATION_HEADER
2446 depends on HIBERNATION
2448 source "kernel/power/Kconfig"
2450 source "drivers/acpi/Kconfig"
2452 source "drivers/sfi/Kconfig"
2459 tristate "APM (Advanced Power Management) BIOS support"
2460 depends on X86_32 && PM_SLEEP
2462 APM is a BIOS specification for saving power using several different
2463 techniques. This is mostly useful for battery powered laptops with
2464 APM compliant BIOSes. If you say Y here, the system time will be
2465 reset after a RESUME operation, the /proc/apm device will provide
2466 battery status information, and user-space programs will receive
2467 notification of APM "events" (e.g. battery status change).
2469 If you select "Y" here, you can disable actual use of the APM
2470 BIOS by passing the "apm=off" option to the kernel at boot time.
2472 Note that the APM support is almost completely disabled for
2473 machines with more than one CPU.
2475 In order to use APM, you will need supporting software. For location
2476 and more information, read <file:Documentation/power/apm-acpi.rst>
2477 and the Battery Powered Linux mini-HOWTO, available from
2478 <http://www.tldp.org/docs.html#howto>.
2480 This driver does not spin down disk drives (see the hdparm(8)
2481 manpage ("man 8 hdparm") for that), and it doesn't turn off
2482 VESA-compliant "green" monitors.
2484 This driver does not support the TI 4000M TravelMate and the ACER
2485 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2486 desktop machines also don't have compliant BIOSes, and this driver
2487 may cause those machines to panic during the boot phase.
2489 Generally, if you don't have a battery in your machine, there isn't
2490 much point in using this driver and you should say N. If you get
2491 random kernel OOPSes or reboots that don't seem to be related to
2492 anything, try disabling/enabling this option (or disabling/enabling
2495 Some other things you should try when experiencing seemingly random,
2498 1) make sure that you have enough swap space and that it is
2500 2) pass the "no-hlt" option to the kernel
2501 3) switch on floating point emulation in the kernel and pass
2502 the "no387" option to the kernel
2503 4) pass the "floppy=nodma" option to the kernel
2504 5) pass the "mem=4M" option to the kernel (thereby disabling
2505 all but the first 4 MB of RAM)
2506 6) make sure that the CPU is not over clocked.
2507 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2508 8) disable the cache from your BIOS settings
2509 9) install a fan for the video card or exchange video RAM
2510 10) install a better fan for the CPU
2511 11) exchange RAM chips
2512 12) exchange the motherboard.
2514 To compile this driver as a module, choose M here: the
2515 module will be called apm.
2519 config APM_IGNORE_USER_SUSPEND
2520 bool "Ignore USER SUSPEND"
2522 This option will ignore USER SUSPEND requests. On machines with a
2523 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2524 series notebooks, it is necessary to say Y because of a BIOS bug.
2526 config APM_DO_ENABLE
2527 bool "Enable PM at boot time"
2529 Enable APM features at boot time. From page 36 of the APM BIOS
2530 specification: "When disabled, the APM BIOS does not automatically
2531 power manage devices, enter the Standby State, enter the Suspend
2532 State, or take power saving steps in response to CPU Idle calls."
2533 This driver will make CPU Idle calls when Linux is idle (unless this
2534 feature is turned off -- see "Do CPU IDLE calls", below). This
2535 should always save battery power, but more complicated APM features
2536 will be dependent on your BIOS implementation. You may need to turn
2537 this option off if your computer hangs at boot time when using APM
2538 support, or if it beeps continuously instead of suspending. Turn
2539 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2540 T400CDT. This is off by default since most machines do fine without
2545 bool "Make CPU Idle calls when idle"
2547 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2548 On some machines, this can activate improved power savings, such as
2549 a slowed CPU clock rate, when the machine is idle. These idle calls
2550 are made after the idle loop has run for some length of time (e.g.,
2551 333 mS). On some machines, this will cause a hang at boot time or
2552 whenever the CPU becomes idle. (On machines with more than one CPU,
2553 this option does nothing.)
2555 config APM_DISPLAY_BLANK
2556 bool "Enable console blanking using APM"
2558 Enable console blanking using the APM. Some laptops can use this to
2559 turn off the LCD backlight when the screen blanker of the Linux
2560 virtual console blanks the screen. Note that this is only used by
2561 the virtual console screen blanker, and won't turn off the backlight
2562 when using the X Window system. This also doesn't have anything to
2563 do with your VESA-compliant power-saving monitor. Further, this
2564 option doesn't work for all laptops -- it might not turn off your
2565 backlight at all, or it might print a lot of errors to the console,
2566 especially if you are using gpm.
2568 config APM_ALLOW_INTS
2569 bool "Allow interrupts during APM BIOS calls"
2571 Normally we disable external interrupts while we are making calls to
2572 the APM BIOS as a measure to lessen the effects of a badly behaving
2573 BIOS implementation. The BIOS should reenable interrupts if it
2574 needs to. Unfortunately, some BIOSes do not -- especially those in
2575 many of the newer IBM Thinkpads. If you experience hangs when you
2576 suspend, try setting this to Y. Otherwise, say N.
2580 source "drivers/cpufreq/Kconfig"
2582 source "drivers/cpuidle/Kconfig"
2584 source "drivers/idle/Kconfig"
2589 menu "Bus options (PCI etc.)"
2592 prompt "PCI access mode"
2593 depends on X86_32 && PCI
2596 On PCI systems, the BIOS can be used to detect the PCI devices and
2597 determine their configuration. However, some old PCI motherboards
2598 have BIOS bugs and may crash if this is done. Also, some embedded
2599 PCI-based systems don't have any BIOS at all. Linux can also try to
2600 detect the PCI hardware directly without using the BIOS.
2602 With this option, you can specify how Linux should detect the
2603 PCI devices. If you choose "BIOS", the BIOS will be used,
2604 if you choose "Direct", the BIOS won't be used, and if you
2605 choose "MMConfig", then PCI Express MMCONFIG will be used.
2606 If you choose "Any", the kernel will try MMCONFIG, then the
2607 direct access method and falls back to the BIOS if that doesn't
2608 work. If unsure, go with the default, which is "Any".
2613 config PCI_GOMMCONFIG
2630 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2632 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2635 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2638 bool "Support mmconfig PCI config space access" if X86_64
2640 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2641 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2645 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2649 depends on PCI && XEN
2652 config MMCONF_FAM10H
2654 depends on X86_64 && PCI_MMCONFIG && ACPI
2656 config PCI_CNB20LE_QUIRK
2657 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2660 Read the PCI windows out of the CNB20LE host bridge. This allows
2661 PCI hotplug to work on systems with the CNB20LE chipset which do
2664 There's no public spec for this chipset, and this functionality
2665 is known to be incomplete.
2667 You should say N unless you know you need this.
2670 bool "ISA bus support on modern systems" if EXPERT
2672 Expose ISA bus device drivers and options available for selection and
2673 configuration. Enable this option if your target machine has an ISA
2674 bus. ISA is an older system, displaced by PCI and newer bus
2675 architectures -- if your target machine is modern, it probably does
2676 not have an ISA bus.
2680 # x86_64 have no ISA slots, but can have ISA-style DMA.
2682 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2685 Enables ISA-style DMA support for devices requiring such controllers.
2693 Find out whether you have ISA slots on your motherboard. ISA is the
2694 name of a bus system, i.e. the way the CPU talks to the other stuff
2695 inside your box. Other bus systems are PCI, EISA, MicroChannel
2696 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2697 newer boards don't support it. If you have ISA, say Y, otherwise N.
2700 tristate "NatSemi SCx200 support"
2702 This provides basic support for National Semiconductor's
2703 (now AMD's) Geode processors. The driver probes for the
2704 PCI-IDs of several on-chip devices, so its a good dependency
2705 for other scx200_* drivers.
2707 If compiled as a module, the driver is named scx200.
2709 config SCx200HR_TIMER
2710 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2714 This driver provides a clocksource built upon the on-chip
2715 27MHz high-resolution timer. Its also a workaround for
2716 NSC Geode SC-1100's buggy TSC, which loses time when the
2717 processor goes idle (as is done by the scheduler). The
2718 other workaround is idle=poll boot option.
2721 bool "One Laptop Per Child support"
2729 Add support for detecting the unique features of the OLPC
2733 bool "OLPC XO-1 Power Management"
2734 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2736 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2739 bool "OLPC XO-1 Real Time Clock"
2740 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2742 Add support for the XO-1 real time clock, which can be used as a
2743 programmable wakeup source.
2746 bool "OLPC XO-1 SCI extras"
2747 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2751 Add support for SCI-based features of the OLPC XO-1 laptop:
2752 - EC-driven system wakeups
2756 - AC adapter status updates
2757 - Battery status updates
2759 config OLPC_XO15_SCI
2760 bool "OLPC XO-1.5 SCI extras"
2761 depends on OLPC && ACPI
2764 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2765 - EC-driven system wakeups
2766 - AC adapter status updates
2767 - Battery status updates
2770 bool "PCEngines ALIX System Support (LED setup)"
2773 This option enables system support for the PCEngines ALIX.
2774 At present this just sets up LEDs for GPIO control on
2775 ALIX2/3/6 boards. However, other system specific setup should
2778 Note: You must still enable the drivers for GPIO and LED support
2779 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2781 Note: You have to set alix.force=1 for boards with Award BIOS.
2784 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2787 This option enables system support for the Soekris Engineering net5501.
2790 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2794 This option enables system support for the Traverse Technologies GEOS.
2797 bool "Technologic Systems TS-5500 platform support"
2799 select CHECK_SIGNATURE
2803 This option enables system support for the Technologic Systems TS-5500.
2809 depends on CPU_SUP_AMD && PCI
2812 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2814 Firmwares often provide initial graphics framebuffers so the BIOS,
2815 bootloader or kernel can show basic video-output during boot for
2816 user-guidance and debugging. Historically, x86 used the VESA BIOS
2817 Extensions and EFI-framebuffers for this, which are mostly limited
2819 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2820 framebuffers so the new generic system-framebuffer drivers can be
2821 used on x86. If the framebuffer is not compatible with the generic
2822 modes, it is advertised as fallback platform framebuffer so legacy
2823 drivers like efifb, vesafb and uvesafb can pick it up.
2824 If this option is not selected, all system framebuffers are always
2825 marked as fallback platform framebuffers as usual.
2827 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2828 not be able to pick up generic system framebuffers if this option
2829 is selected. You are highly encouraged to enable simplefb as
2830 replacement if you select this option. simplefb can correctly deal
2831 with generic system framebuffers. But you should still keep vesafb
2832 and others enabled as fallback if a system framebuffer is
2833 incompatible with simplefb.
2840 menu "Binary Emulations"
2842 config IA32_EMULATION
2843 bool "IA32 Emulation"
2845 select ARCH_WANT_OLD_COMPAT_IPC
2847 select COMPAT_BINFMT_ELF
2848 select COMPAT_OLD_SIGACTION
2850 Include code to run legacy 32-bit programs under a
2851 64-bit kernel. You should likely turn this on, unless you're
2852 100% sure that you don't have any 32-bit programs left.
2855 tristate "IA32 a.out support"
2856 depends on IA32_EMULATION
2859 Support old a.out binaries in the 32bit emulation.
2862 bool "x32 ABI for 64-bit mode"
2865 Include code to run binaries for the x32 native 32-bit ABI
2866 for 64-bit processors. An x32 process gets access to the
2867 full 64-bit register file and wide data path while leaving
2868 pointers at 32 bits for smaller memory footprint.
2870 You will need a recent binutils (2.22 or later) with
2871 elf32_x86_64 support enabled to compile a kernel with this
2876 depends on IA32_EMULATION || X86_32
2878 select OLD_SIGSUSPEND3
2882 depends on IA32_EMULATION || X86_X32
2885 config COMPAT_FOR_U64_ALIGNMENT
2888 config SYSVIPC_COMPAT
2896 config HAVE_ATOMIC_IOMAP
2900 source "drivers/firmware/Kconfig"
2902 source "arch/x86/kvm/Kconfig"
2904 source "arch/x86/Kconfig.assembler"