0001 # SPDX-License-Identifier: GPL-2.0
0002 # Select 32 or 64 bit
0003 config 64BIT
0004 bool "64-bit kernel" if "$(ARCH)" = "x86"
0005 default "$(ARCH)" != "i386"
0006 help
0007 Say yes to build a 64-bit kernel - formerly known as x86_64
0008 Say no to build a 32-bit kernel - formerly known as i386
0009
0010 config X86_32
0011 def_bool y
0012 depends on !64BIT
0013 # Options that are inherently 32-bit kernel only:
0014 select ARCH_WANT_IPC_PARSE_VERSION
0015 select CLKSRC_I8253
0016 select CLONE_BACKWARDS
0017 select GENERIC_VDSO_32
0018 select HAVE_DEBUG_STACKOVERFLOW
0019 select KMAP_LOCAL
0020 select MODULES_USE_ELF_REL
0021 select OLD_SIGACTION
0022 select ARCH_SPLIT_ARG64
0023
0024 config X86_64
0025 def_bool y
0026 depends on 64BIT
0027 # Options that are inherently 64-bit kernel only:
0028 select ARCH_HAS_GIGANTIC_PAGE
0029 select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
0030 select ARCH_USE_CMPXCHG_LOCKREF
0031 select HAVE_ARCH_SOFT_DIRTY
0032 select MODULES_USE_ELF_RELA
0033 select NEED_DMA_MAP_STATE
0034 select SWIOTLB
0035 select ARCH_HAS_ELFCORE_COMPAT
0036 select ZONE_DMA32
0037
0038 config FORCE_DYNAMIC_FTRACE
0039 def_bool y
0040 depends on X86_32
0041 depends on FUNCTION_TRACER
0042 select DYNAMIC_FTRACE
0043 help
0044 We keep the static function tracing (!DYNAMIC_FTRACE) around
0045 in order to test the non static function tracing in the
0046 generic code, as other architectures still use it. But we
0047 only need to keep it around for x86_64. No need to keep it
0048 for x86_32. For x86_32, force DYNAMIC_FTRACE.
0049 #
0050 # Arch settings
0051 #
0052 # ( Note that options that are marked 'if X86_64' could in principle be
0053 # ported to 32-bit as well. )
0054 #
0055 config X86
0056 def_bool y
0057 #
0058 # Note: keep this list sorted alphabetically
0059 #
0060 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
0061 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
0062 select ARCH_32BIT_OFF_T if X86_32
0063 select ARCH_CLOCKSOURCE_INIT
0064 select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
0065 select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
0066 select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
0067 select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
0068 select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE)
0069 select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
0070 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
0071 select ARCH_HAS_CACHE_LINE_SIZE
0072 select ARCH_HAS_CURRENT_STACK_POINTER
0073 select ARCH_HAS_DEBUG_VIRTUAL
0074 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
0075 select ARCH_HAS_DEVMEM_IS_ALLOWED
0076 select ARCH_HAS_EARLY_DEBUG if KGDB
0077 select ARCH_HAS_ELF_RANDOMIZE
0078 select ARCH_HAS_FAST_MULTIPLIER
0079 select ARCH_HAS_FORTIFY_SOURCE
0080 select ARCH_HAS_GCOV_PROFILE_ALL
0081 select ARCH_HAS_KCOV if X86_64
0082 select ARCH_HAS_MEM_ENCRYPT
0083 select ARCH_HAS_MEMBARRIER_SYNC_CORE
0084 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
0085 select ARCH_HAS_PMEM_API if X86_64
0086 select ARCH_HAS_PTE_DEVMAP if X86_64
0087 select ARCH_HAS_PTE_SPECIAL
0088 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
0089 select ARCH_HAS_COPY_MC if X86_64
0090 select ARCH_HAS_SET_MEMORY
0091 select ARCH_HAS_SET_DIRECT_MAP
0092 select ARCH_HAS_STRICT_KERNEL_RWX
0093 select ARCH_HAS_STRICT_MODULE_RWX
0094 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
0095 select ARCH_HAS_SYSCALL_WRAPPER
0096 select ARCH_HAS_UBSAN_SANITIZE_ALL
0097 select ARCH_HAS_DEBUG_WX
0098 select ARCH_HAS_ZONE_DMA_SET if EXPERT
0099 select ARCH_HAVE_NMI_SAFE_CMPXCHG
0100 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
0101 select ARCH_MIGHT_HAVE_PC_PARPORT
0102 select ARCH_MIGHT_HAVE_PC_SERIO
0103 select ARCH_STACKWALK
0104 select ARCH_SUPPORTS_ACPI
0105 select ARCH_SUPPORTS_ATOMIC_RMW
0106 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
0107 select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64
0108 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
0109 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
0110 select ARCH_SUPPORTS_LTO_CLANG
0111 select ARCH_SUPPORTS_LTO_CLANG_THIN
0112 select ARCH_USE_BUILTIN_BSWAP
0113 select ARCH_USE_MEMTEST
0114 select ARCH_USE_QUEUED_RWLOCKS
0115 select ARCH_USE_QUEUED_SPINLOCKS
0116 select ARCH_USE_SYM_ANNOTATIONS
0117 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
0118 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
0119 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
0120 select ARCH_WANTS_NO_INSTR
0121 select ARCH_WANT_GENERAL_HUGETLB
0122 select ARCH_WANT_HUGE_PMD_SHARE
0123 select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP if X86_64
0124 select ARCH_WANT_LD_ORPHAN_WARN
0125 select ARCH_WANTS_THP_SWAP if X86_64
0126 select ARCH_HAS_PARANOID_L1D_FLUSH
0127 select BUILDTIME_TABLE_SORT
0128 select CLKEVT_I8253
0129 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
0130 select CLOCKSOURCE_WATCHDOG
0131 select DCACHE_WORD_ACCESS
0132 select DYNAMIC_SIGFRAME
0133 select EDAC_ATOMIC_SCRUB
0134 select EDAC_SUPPORT
0135 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
0136 select GENERIC_CLOCKEVENTS_MIN_ADJUST
0137 select GENERIC_CMOS_UPDATE
0138 select GENERIC_CPU_AUTOPROBE
0139 select GENERIC_CPU_VULNERABILITIES
0140 select GENERIC_EARLY_IOREMAP
0141 select GENERIC_ENTRY
0142 select GENERIC_IOMAP
0143 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
0144 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
0145 select GENERIC_IRQ_MIGRATION if SMP
0146 select GENERIC_IRQ_PROBE
0147 select GENERIC_IRQ_RESERVATION_MODE
0148 select GENERIC_IRQ_SHOW
0149 select GENERIC_PENDING_IRQ if SMP
0150 select GENERIC_PTDUMP
0151 select GENERIC_SMP_IDLE_THREAD
0152 select GENERIC_TIME_VSYSCALL
0153 select GENERIC_GETTIMEOFDAY
0154 select GENERIC_VDSO_TIME_NS
0155 select GUP_GET_PTE_LOW_HIGH if X86_PAE
0156 select HARDIRQS_SW_RESEND
0157 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
0158 select HAVE_ACPI_APEI if ACPI
0159 select HAVE_ACPI_APEI_NMI if ACPI
0160 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
0161 select HAVE_ARCH_AUDITSYSCALL
0162 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
0163 select HAVE_ARCH_HUGE_VMALLOC if X86_64
0164 select HAVE_ARCH_JUMP_LABEL
0165 select HAVE_ARCH_JUMP_LABEL_RELATIVE
0166 select HAVE_ARCH_KASAN if X86_64
0167 select HAVE_ARCH_KASAN_VMALLOC if X86_64
0168 select HAVE_ARCH_KFENCE
0169 select HAVE_ARCH_KGDB
0170 select HAVE_ARCH_MMAP_RND_BITS if MMU
0171 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
0172 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
0173 select HAVE_ARCH_PREL32_RELOCATIONS
0174 select HAVE_ARCH_SECCOMP_FILTER
0175 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
0176 select HAVE_ARCH_STACKLEAK
0177 select HAVE_ARCH_TRACEHOOK
0178 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
0179 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
0180 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
0181 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
0182 select HAVE_ARCH_VMAP_STACK if X86_64
0183 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
0184 select HAVE_ARCH_WITHIN_STACK_FRAMES
0185 select HAVE_ASM_MODVERSIONS
0186 select HAVE_CMPXCHG_DOUBLE
0187 select HAVE_CMPXCHG_LOCAL
0188 select HAVE_CONTEXT_TRACKING_USER if X86_64
0189 select HAVE_CONTEXT_TRACKING_USER_OFFSTACK if HAVE_CONTEXT_TRACKING_USER
0190 select HAVE_C_RECORDMCOUNT
0191 select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
0192 select HAVE_BUILDTIME_MCOUNT_SORT
0193 select HAVE_DEBUG_KMEMLEAK
0194 select HAVE_DMA_CONTIGUOUS
0195 select HAVE_DYNAMIC_FTRACE
0196 select HAVE_DYNAMIC_FTRACE_WITH_REGS
0197 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
0198 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
0199 select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
0200 select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
0201 select HAVE_EBPF_JIT
0202 select HAVE_EFFICIENT_UNALIGNED_ACCESS
0203 select HAVE_EISA
0204 select HAVE_EXIT_THREAD
0205 select HAVE_FAST_GUP
0206 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
0207 select HAVE_FTRACE_MCOUNT_RECORD
0208 select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
0209 select HAVE_FUNCTION_TRACER
0210 select HAVE_GCC_PLUGINS
0211 select HAVE_HW_BREAKPOINT
0212 select HAVE_IOREMAP_PROT
0213 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
0214 select HAVE_IRQ_TIME_ACCOUNTING
0215 select HAVE_JUMP_LABEL_HACK if HAVE_OBJTOOL
0216 select HAVE_KERNEL_BZIP2
0217 select HAVE_KERNEL_GZIP
0218 select HAVE_KERNEL_LZ4
0219 select HAVE_KERNEL_LZMA
0220 select HAVE_KERNEL_LZO
0221 select HAVE_KERNEL_XZ
0222 select HAVE_KERNEL_ZSTD
0223 select HAVE_KPROBES
0224 select HAVE_KPROBES_ON_FTRACE
0225 select HAVE_FUNCTION_ERROR_INJECTION
0226 select HAVE_KRETPROBES
0227 select HAVE_RETHOOK
0228 select HAVE_KVM
0229 select HAVE_LIVEPATCH if X86_64
0230 select HAVE_MIXED_BREAKPOINTS_REGS
0231 select HAVE_MOD_ARCH_SPECIFIC
0232 select HAVE_MOVE_PMD
0233 select HAVE_MOVE_PUD
0234 select HAVE_NOINSTR_HACK if HAVE_OBJTOOL
0235 select HAVE_NMI
0236 select HAVE_NOINSTR_VALIDATION if HAVE_OBJTOOL
0237 select HAVE_OBJTOOL if X86_64
0238 select HAVE_OPTPROBES
0239 select HAVE_PCSPKR_PLATFORM
0240 select HAVE_PERF_EVENTS
0241 select HAVE_PERF_EVENTS_NMI
0242 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
0243 select HAVE_PCI
0244 select HAVE_PERF_REGS
0245 select HAVE_PERF_USER_STACK_DUMP
0246 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
0247 select MMU_GATHER_MERGE_VMAS
0248 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
0249 select HAVE_REGS_AND_STACK_ACCESS_API
0250 select HAVE_RELIABLE_STACKTRACE if UNWINDER_ORC || STACK_VALIDATION
0251 select HAVE_FUNCTION_ARG_ACCESS_API
0252 select HAVE_SETUP_PER_CPU_AREA
0253 select HAVE_SOFTIRQ_ON_OWN_STACK
0254 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
0255 select HAVE_STACK_VALIDATION if HAVE_OBJTOOL
0256 select HAVE_STATIC_CALL
0257 select HAVE_STATIC_CALL_INLINE if HAVE_OBJTOOL
0258 select HAVE_PREEMPT_DYNAMIC_CALL
0259 select HAVE_RSEQ
0260 select HAVE_SYSCALL_TRACEPOINTS
0261 select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
0262 select HAVE_UNSTABLE_SCHED_CLOCK
0263 select HAVE_USER_RETURN_NOTIFIER
0264 select HAVE_GENERIC_VDSO
0265 select HOTPLUG_SMT if SMP
0266 select IRQ_FORCED_THREADING
0267 select NEED_PER_CPU_EMBED_FIRST_CHUNK
0268 select NEED_PER_CPU_PAGE_FIRST_CHUNK
0269 select NEED_SG_DMA_LENGTH
0270 select PCI_DOMAINS if PCI
0271 select PCI_LOCKLESS_CONFIG if PCI
0272 select PERF_EVENTS
0273 select RTC_LIB
0274 select RTC_MC146818_LIB
0275 select SPARSE_IRQ
0276 select SRCU
0277 select SYSCTL_EXCEPTION_TRACE
0278 select THREAD_INFO_IN_TASK
0279 select TRACE_IRQFLAGS_SUPPORT
0280 select TRACE_IRQFLAGS_NMI_SUPPORT
0281 select USER_STACKTRACE_SUPPORT
0282 select HAVE_ARCH_KCSAN if X86_64
0283 select X86_FEATURE_NAMES if PROC_FS
0284 select PROC_PID_ARCH_STATUS if PROC_FS
0285 select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
0286 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
0287
0288 config INSTRUCTION_DECODER
0289 def_bool y
0290 depends on KPROBES || PERF_EVENTS || UPROBES
0291
0292 config OUTPUT_FORMAT
0293 string
0294 default "elf32-i386" if X86_32
0295 default "elf64-x86-64" if X86_64
0296
0297 config LOCKDEP_SUPPORT
0298 def_bool y
0299
0300 config STACKTRACE_SUPPORT
0301 def_bool y
0302
0303 config MMU
0304 def_bool y
0305
0306 config ARCH_MMAP_RND_BITS_MIN
0307 default 28 if 64BIT
0308 default 8
0309
0310 config ARCH_MMAP_RND_BITS_MAX
0311 default 32 if 64BIT
0312 default 16
0313
0314 config ARCH_MMAP_RND_COMPAT_BITS_MIN
0315 default 8
0316
0317 config ARCH_MMAP_RND_COMPAT_BITS_MAX
0318 default 16
0319
0320 config SBUS
0321 bool
0322
0323 config GENERIC_ISA_DMA
0324 def_bool y
0325 depends on ISA_DMA_API
0326
0327 config GENERIC_BUG
0328 def_bool y
0329 depends on BUG
0330 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
0331
0332 config GENERIC_BUG_RELATIVE_POINTERS
0333 bool
0334
0335 config ARCH_MAY_HAVE_PC_FDC
0336 def_bool y
0337 depends on ISA_DMA_API
0338
0339 config GENERIC_CALIBRATE_DELAY
0340 def_bool y
0341
0342 config ARCH_HAS_CPU_RELAX
0343 def_bool y
0344
0345 config ARCH_HIBERNATION_POSSIBLE
0346 def_bool y
0347
0348 config ARCH_NR_GPIO
0349 int
0350 default 1024 if X86_64
0351 default 512
0352
0353 config ARCH_SUSPEND_POSSIBLE
0354 def_bool y
0355
0356 config AUDIT_ARCH
0357 def_bool y if X86_64
0358
0359 config KASAN_SHADOW_OFFSET
0360 hex
0361 depends on KASAN
0362 default 0xdffffc0000000000
0363
0364 config HAVE_INTEL_TXT
0365 def_bool y
0366 depends on INTEL_IOMMU && ACPI
0367
0368 config X86_32_SMP
0369 def_bool y
0370 depends on X86_32 && SMP
0371
0372 config X86_64_SMP
0373 def_bool y
0374 depends on X86_64 && SMP
0375
0376 config ARCH_SUPPORTS_UPROBES
0377 def_bool y
0378
0379 config FIX_EARLYCON_MEM
0380 def_bool y
0381
0382 config DYNAMIC_PHYSICAL_MASK
0383 bool
0384
0385 config PGTABLE_LEVELS
0386 int
0387 default 5 if X86_5LEVEL
0388 default 4 if X86_64
0389 default 3 if X86_PAE
0390 default 2
0391
0392 config CC_HAS_SANE_STACKPROTECTOR
0393 bool
0394 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) $(CLANG_FLAGS)) if 64BIT
0395 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC) $(CLANG_FLAGS))
0396 help
0397 We have to make sure stack protector is unconditionally disabled if
0398 the compiler produces broken code or if it does not let us control
0399 the segment on 32-bit kernels.
0400
0401 menu "Processor type and features"
0402
0403 config SMP
0404 bool "Symmetric multi-processing support"
0405 help
0406 This enables support for systems with more than one CPU. If you have
0407 a system with only one CPU, say N. If you have a system with more
0408 than one CPU, say Y.
0409
0410 If you say N here, the kernel will run on uni- and multiprocessor
0411 machines, but will use only one CPU of a multiprocessor machine. If
0412 you say Y here, the kernel will run on many, but not all,
0413 uniprocessor machines. On a uniprocessor machine, the kernel
0414 will run faster if you say N here.
0415
0416 Note that if you say Y here and choose architecture "586" or
0417 "Pentium" under "Processor family", the kernel will not work on 486
0418 architectures. Similarly, multiprocessor kernels for the "PPro"
0419 architecture may not work on all Pentium based boards.
0420
0421 People using multiprocessor machines who say Y here should also say
0422 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
0423 Management" code will be disabled if you say Y here.
0424
0425 See also <file:Documentation/x86/i386/IO-APIC.rst>,
0426 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
0427 <http://www.tldp.org/docs.html#howto>.
0428
0429 If you don't know what to do here, say N.
0430
0431 config X86_FEATURE_NAMES
0432 bool "Processor feature human-readable names" if EMBEDDED
0433 default y
0434 help
0435 This option compiles in a table of x86 feature bits and corresponding
0436 names. This is required to support /proc/cpuinfo and a few kernel
0437 messages. You can disable this to save space, at the expense of
0438 making those few kernel messages show numeric feature bits instead.
0439
0440 If in doubt, say Y.
0441
0442 config X86_X2APIC
0443 bool "Support x2apic"
0444 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
0445 help
0446 This enables x2apic support on CPUs that have this feature.
0447
0448 This allows 32-bit apic IDs (so it can support very large systems),
0449 and accesses the local apic via MSRs not via mmio.
0450
0451 If you don't know what to do here, say N.
0452
0453 config X86_MPPARSE
0454 bool "Enable MPS table" if ACPI
0455 default y
0456 depends on X86_LOCAL_APIC
0457 help
0458 For old smp systems that do not have proper acpi support. Newer systems
0459 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
0460
0461 config GOLDFISH
0462 def_bool y
0463 depends on X86_GOLDFISH
0464
0465 config X86_CPU_RESCTRL
0466 bool "x86 CPU resource control support"
0467 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
0468 select KERNFS
0469 select PROC_CPU_RESCTRL if PROC_FS
0470 help
0471 Enable x86 CPU resource control support.
0472
0473 Provide support for the allocation and monitoring of system resources
0474 usage by the CPU.
0475
0476 Intel calls this Intel Resource Director Technology
0477 (Intel(R) RDT). More information about RDT can be found in the
0478 Intel x86 Architecture Software Developer Manual.
0479
0480 AMD calls this AMD Platform Quality of Service (AMD QoS).
0481 More information about AMD QoS can be found in the AMD64 Technology
0482 Platform Quality of Service Extensions manual.
0483
0484 Say N if unsure.
0485
0486 if X86_32
0487 config X86_BIGSMP
0488 bool "Support for big SMP systems with more than 8 CPUs"
0489 depends on SMP
0490 help
0491 This option is needed for the systems that have more than 8 CPUs.
0492
0493 config X86_EXTENDED_PLATFORM
0494 bool "Support for extended (non-PC) x86 platforms"
0495 default y
0496 help
0497 If you disable this option then the kernel will only support
0498 standard PC platforms. (which covers the vast majority of
0499 systems out there.)
0500
0501 If you enable this option then you'll be able to select support
0502 for the following (non-PC) 32 bit x86 platforms:
0503 Goldfish (Android emulator)
0504 AMD Elan
0505 RDC R-321x SoC
0506 SGI 320/540 (Visual Workstation)
0507 STA2X11-based (e.g. Northville)
0508 Moorestown MID devices
0509
0510 If you have one of these systems, or if you want to build a
0511 generic distribution kernel, say Y here - otherwise say N.
0512 endif # X86_32
0513
0514 if X86_64
0515 config X86_EXTENDED_PLATFORM
0516 bool "Support for extended (non-PC) x86 platforms"
0517 default y
0518 help
0519 If you disable this option then the kernel will only support
0520 standard PC platforms. (which covers the vast majority of
0521 systems out there.)
0522
0523 If you enable this option then you'll be able to select support
0524 for the following (non-PC) 64 bit x86 platforms:
0525 Numascale NumaChip
0526 ScaleMP vSMP
0527 SGI Ultraviolet
0528
0529 If you have one of these systems, or if you want to build a
0530 generic distribution kernel, say Y here - otherwise say N.
0531 endif # X86_64
0532 # This is an alphabetically sorted list of 64 bit extended platforms
0533 # Please maintain the alphabetic order if and when there are additions
0534 config X86_NUMACHIP
0535 bool "Numascale NumaChip"
0536 depends on X86_64
0537 depends on X86_EXTENDED_PLATFORM
0538 depends on NUMA
0539 depends on SMP
0540 depends on X86_X2APIC
0541 depends on PCI_MMCONFIG
0542 help
0543 Adds support for Numascale NumaChip large-SMP systems. Needed to
0544 enable more than ~168 cores.
0545 If you don't have one of these, you should say N here.
0546
0547 config X86_VSMP
0548 bool "ScaleMP vSMP"
0549 select HYPERVISOR_GUEST
0550 select PARAVIRT
0551 depends on X86_64 && PCI
0552 depends on X86_EXTENDED_PLATFORM
0553 depends on SMP
0554 help
0555 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
0556 supposed to run on these EM64T-based machines. Only choose this option
0557 if you have one of these machines.
0558
0559 config X86_UV
0560 bool "SGI Ultraviolet"
0561 depends on X86_64
0562 depends on X86_EXTENDED_PLATFORM
0563 depends on NUMA
0564 depends on EFI
0565 depends on KEXEC_CORE
0566 depends on X86_X2APIC
0567 depends on PCI
0568 help
0569 This option is needed in order to support SGI Ultraviolet systems.
0570 If you don't have one of these, you should say N here.
0571
0572 # Following is an alphabetically sorted list of 32 bit extended platforms
0573 # Please maintain the alphabetic order if and when there are additions
0574
0575 config X86_GOLDFISH
0576 bool "Goldfish (Virtual Platform)"
0577 depends on X86_EXTENDED_PLATFORM
0578 help
0579 Enable support for the Goldfish virtual platform used primarily
0580 for Android development. Unless you are building for the Android
0581 Goldfish emulator say N here.
0582
0583 config X86_INTEL_CE
0584 bool "CE4100 TV platform"
0585 depends on PCI
0586 depends on PCI_GODIRECT
0587 depends on X86_IO_APIC
0588 depends on X86_32
0589 depends on X86_EXTENDED_PLATFORM
0590 select X86_REBOOTFIXUPS
0591 select OF
0592 select OF_EARLY_FLATTREE
0593 help
0594 Select for the Intel CE media processor (CE4100) SOC.
0595 This option compiles in support for the CE4100 SOC for settop
0596 boxes and media devices.
0597
0598 config X86_INTEL_MID
0599 bool "Intel MID platform support"
0600 depends on X86_EXTENDED_PLATFORM
0601 depends on X86_PLATFORM_DEVICES
0602 depends on PCI
0603 depends on X86_64 || (PCI_GOANY && X86_32)
0604 depends on X86_IO_APIC
0605 select I2C
0606 select DW_APB_TIMER
0607 select INTEL_SCU_PCI
0608 help
0609 Select to build a kernel capable of supporting Intel MID (Mobile
0610 Internet Device) platform systems which do not have the PCI legacy
0611 interfaces. If you are building for a PC class system say N here.
0612
0613 Intel MID platforms are based on an Intel processor and chipset which
0614 consume less power than most of the x86 derivatives.
0615
0616 config X86_INTEL_QUARK
0617 bool "Intel Quark platform support"
0618 depends on X86_32
0619 depends on X86_EXTENDED_PLATFORM
0620 depends on X86_PLATFORM_DEVICES
0621 depends on X86_TSC
0622 depends on PCI
0623 depends on PCI_GOANY
0624 depends on X86_IO_APIC
0625 select IOSF_MBI
0626 select INTEL_IMR
0627 select COMMON_CLK
0628 help
0629 Select to include support for Quark X1000 SoC.
0630 Say Y here if you have a Quark based system such as the Arduino
0631 compatible Intel Galileo.
0632
0633 config X86_INTEL_LPSS
0634 bool "Intel Low Power Subsystem Support"
0635 depends on X86 && ACPI && PCI
0636 select COMMON_CLK
0637 select PINCTRL
0638 select IOSF_MBI
0639 help
0640 Select to build support for Intel Low Power Subsystem such as
0641 found on Intel Lynxpoint PCH. Selecting this option enables
0642 things like clock tree (common clock framework) and pincontrol
0643 which are needed by the LPSS peripheral drivers.
0644
0645 config X86_AMD_PLATFORM_DEVICE
0646 bool "AMD ACPI2Platform devices support"
0647 depends on ACPI
0648 select COMMON_CLK
0649 select PINCTRL
0650 help
0651 Select to interpret AMD specific ACPI device to platform device
0652 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
0653 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
0654 implemented under PINCTRL subsystem.
0655
0656 config IOSF_MBI
0657 tristate "Intel SoC IOSF Sideband support for SoC platforms"
0658 depends on PCI
0659 help
0660 This option enables sideband register access support for Intel SoC
0661 platforms. On these platforms the IOSF sideband is used in lieu of
0662 MSR's for some register accesses, mostly but not limited to thermal
0663 and power. Drivers may query the availability of this device to
0664 determine if they need the sideband in order to work on these
0665 platforms. The sideband is available on the following SoC products.
0666 This list is not meant to be exclusive.
0667 - BayTrail
0668 - Braswell
0669 - Quark
0670
0671 You should say Y if you are running a kernel on one of these SoC's.
0672
0673 config IOSF_MBI_DEBUG
0674 bool "Enable IOSF sideband access through debugfs"
0675 depends on IOSF_MBI && DEBUG_FS
0676 help
0677 Select this option to expose the IOSF sideband access registers (MCR,
0678 MDR, MCRX) through debugfs to write and read register information from
0679 different units on the SoC. This is most useful for obtaining device
0680 state information for debug and analysis. As this is a general access
0681 mechanism, users of this option would have specific knowledge of the
0682 device they want to access.
0683
0684 If you don't require the option or are in doubt, say N.
0685
0686 config X86_RDC321X
0687 bool "RDC R-321x SoC"
0688 depends on X86_32
0689 depends on X86_EXTENDED_PLATFORM
0690 select M486
0691 select X86_REBOOTFIXUPS
0692 help
0693 This option is needed for RDC R-321x system-on-chip, also known
0694 as R-8610-(G).
0695 If you don't have one of these chips, you should say N here.
0696
0697 config X86_32_NON_STANDARD
0698 bool "Support non-standard 32-bit SMP architectures"
0699 depends on X86_32 && SMP
0700 depends on X86_EXTENDED_PLATFORM
0701 help
0702 This option compiles in the bigsmp and STA2X11 default
0703 subarchitectures. It is intended for a generic binary
0704 kernel. If you select them all, kernel will probe it one by
0705 one and will fallback to default.
0706
0707 # Alphabetically sorted list of Non standard 32 bit platforms
0708
0709 config X86_SUPPORTS_MEMORY_FAILURE
0710 def_bool y
0711 # MCE code calls memory_failure():
0712 depends on X86_MCE
0713 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
0714 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
0715 depends on X86_64 || !SPARSEMEM
0716 select ARCH_SUPPORTS_MEMORY_FAILURE
0717
0718 config STA2X11
0719 bool "STA2X11 Companion Chip Support"
0720 depends on X86_32_NON_STANDARD && PCI
0721 select SWIOTLB
0722 select MFD_STA2X11
0723 select GPIOLIB
0724 help
0725 This adds support for boards based on the STA2X11 IO-Hub,
0726 a.k.a. "ConneXt". The chip is used in place of the standard
0727 PC chipset, so all "standard" peripherals are missing. If this
0728 option is selected the kernel will still be able to boot on
0729 standard PC machines.
0730
0731 config X86_32_IRIS
0732 tristate "Eurobraille/Iris poweroff module"
0733 depends on X86_32
0734 help
0735 The Iris machines from EuroBraille do not have APM or ACPI support
0736 to shut themselves down properly. A special I/O sequence is
0737 needed to do so, which is what this module does at
0738 kernel shutdown.
0739
0740 This is only for Iris machines from EuroBraille.
0741
0742 If unused, say N.
0743
0744 config SCHED_OMIT_FRAME_POINTER
0745 def_bool y
0746 prompt "Single-depth WCHAN output"
0747 depends on X86
0748 help
0749 Calculate simpler /proc/<PID>/wchan values. If this option
0750 is disabled then wchan values will recurse back to the
0751 caller function. This provides more accurate wchan values,
0752 at the expense of slightly more scheduling overhead.
0753
0754 If in doubt, say "Y".
0755
0756 menuconfig HYPERVISOR_GUEST
0757 bool "Linux guest support"
0758 help
0759 Say Y here to enable options for running Linux under various hyper-
0760 visors. This option enables basic hypervisor detection and platform
0761 setup.
0762
0763 If you say N, all options in this submenu will be skipped and
0764 disabled, and Linux guest support won't be built in.
0765
0766 if HYPERVISOR_GUEST
0767
0768 config PARAVIRT
0769 bool "Enable paravirtualization code"
0770 depends on HAVE_STATIC_CALL
0771 help
0772 This changes the kernel so it can modify itself when it is run
0773 under a hypervisor, potentially improving performance significantly
0774 over full virtualization. However, when run without a hypervisor
0775 the kernel is theoretically slower and slightly larger.
0776
0777 config PARAVIRT_XXL
0778 bool
0779
0780 config PARAVIRT_DEBUG
0781 bool "paravirt-ops debugging"
0782 depends on PARAVIRT && DEBUG_KERNEL
0783 help
0784 Enable to debug paravirt_ops internals. Specifically, BUG if
0785 a paravirt_op is missing when it is called.
0786
0787 config PARAVIRT_SPINLOCKS
0788 bool "Paravirtualization layer for spinlocks"
0789 depends on PARAVIRT && SMP
0790 help
0791 Paravirtualized spinlocks allow a pvops backend to replace the
0792 spinlock implementation with something virtualization-friendly
0793 (for example, block the virtual CPU rather than spinning).
0794
0795 It has a minimal impact on native kernels and gives a nice performance
0796 benefit on paravirtualized KVM / Xen kernels.
0797
0798 If you are unsure how to answer this question, answer Y.
0799
0800 config X86_HV_CALLBACK_VECTOR
0801 def_bool n
0802
0803 source "arch/x86/xen/Kconfig"
0804
0805 config KVM_GUEST
0806 bool "KVM Guest support (including kvmclock)"
0807 depends on PARAVIRT
0808 select PARAVIRT_CLOCK
0809 select ARCH_CPUIDLE_HALTPOLL
0810 select X86_HV_CALLBACK_VECTOR
0811 default y
0812 help
0813 This option enables various optimizations for running under the KVM
0814 hypervisor. It includes a paravirtualized clock, so that instead
0815 of relying on a PIT (or probably other) emulation by the
0816 underlying device model, the host provides the guest with
0817 timing infrastructure such as time of day, and system time
0818
0819 config ARCH_CPUIDLE_HALTPOLL
0820 def_bool n
0821 prompt "Disable host haltpoll when loading haltpoll driver"
0822 help
0823 If virtualized under KVM, disable host haltpoll.
0824
0825 config PVH
0826 bool "Support for running PVH guests"
0827 help
0828 This option enables the PVH entry point for guest virtual machines
0829 as specified in the x86/HVM direct boot ABI.
0830
0831 config PARAVIRT_TIME_ACCOUNTING
0832 bool "Paravirtual steal time accounting"
0833 depends on PARAVIRT
0834 help
0835 Select this option to enable fine granularity task steal time
0836 accounting. Time spent executing other tasks in parallel with
0837 the current vCPU is discounted from the vCPU power. To account for
0838 that, there can be a small performance impact.
0839
0840 If in doubt, say N here.
0841
0842 config PARAVIRT_CLOCK
0843 bool
0844
0845 config JAILHOUSE_GUEST
0846 bool "Jailhouse non-root cell support"
0847 depends on X86_64 && PCI
0848 select X86_PM_TIMER
0849 help
0850 This option allows to run Linux as guest in a Jailhouse non-root
0851 cell. You can leave this option disabled if you only want to start
0852 Jailhouse and run Linux afterwards in the root cell.
0853
0854 config ACRN_GUEST
0855 bool "ACRN Guest support"
0856 depends on X86_64
0857 select X86_HV_CALLBACK_VECTOR
0858 help
0859 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
0860 a flexible, lightweight reference open-source hypervisor, built with
0861 real-time and safety-criticality in mind. It is built for embedded
0862 IOT with small footprint and real-time features. More details can be
0863 found in https://projectacrn.org/.
0864
0865 config INTEL_TDX_GUEST
0866 bool "Intel TDX (Trust Domain Extensions) - Guest Support"
0867 depends on X86_64 && CPU_SUP_INTEL
0868 depends on X86_X2APIC
0869 select ARCH_HAS_CC_PLATFORM
0870 select X86_MEM_ENCRYPT
0871 select X86_MCE
0872 help
0873 Support running as a guest under Intel TDX. Without this support,
0874 the guest kernel can not boot or run under TDX.
0875 TDX includes memory encryption and integrity capabilities
0876 which protect the confidentiality and integrity of guest
0877 memory contents and CPU state. TDX guests are protected from
0878 some attacks from the VMM.
0879
0880 endif # HYPERVISOR_GUEST
0881
0882 source "arch/x86/Kconfig.cpu"
0883
0884 config HPET_TIMER
0885 def_bool X86_64
0886 prompt "HPET Timer Support" if X86_32
0887 help
0888 Use the IA-PC HPET (High Precision Event Timer) to manage
0889 time in preference to the PIT and RTC, if a HPET is
0890 present.
0891 HPET is the next generation timer replacing legacy 8254s.
0892 The HPET provides a stable time base on SMP
0893 systems, unlike the TSC, but it is more expensive to access,
0894 as it is off-chip. The interface used is documented
0895 in the HPET spec, revision 1.
0896
0897 You can safely choose Y here. However, HPET will only be
0898 activated if the platform and the BIOS support this feature.
0899 Otherwise the 8254 will be used for timing services.
0900
0901 Choose N to continue using the legacy 8254 timer.
0902
0903 config HPET_EMULATE_RTC
0904 def_bool y
0905 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
0906
0907 # Mark as expert because too many people got it wrong.
0908 # The code disables itself when not needed.
0909 config DMI
0910 default y
0911 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
0912 bool "Enable DMI scanning" if EXPERT
0913 help
0914 Enabled scanning of DMI to identify machine quirks. Say Y
0915 here unless you have verified that your setup is not
0916 affected by entries in the DMI blacklist. Required by PNP
0917 BIOS code.
0918
0919 config GART_IOMMU
0920 bool "Old AMD GART IOMMU support"
0921 select DMA_OPS
0922 select IOMMU_HELPER
0923 select SWIOTLB
0924 depends on X86_64 && PCI && AMD_NB
0925 help
0926 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
0927 GART based hardware IOMMUs.
0928
0929 The GART supports full DMA access for devices with 32-bit access
0930 limitations, on systems with more than 3 GB. This is usually needed
0931 for USB, sound, many IDE/SATA chipsets and some other devices.
0932
0933 Newer systems typically have a modern AMD IOMMU, supported via
0934 the CONFIG_AMD_IOMMU=y config option.
0935
0936 In normal configurations this driver is only active when needed:
0937 there's more than 3 GB of memory and the system contains a
0938 32-bit limited device.
0939
0940 If unsure, say Y.
0941
0942 config BOOT_VESA_SUPPORT
0943 bool
0944 help
0945 If true, at least one selected framebuffer driver can take advantage
0946 of VESA video modes set at an early boot stage via the vga= parameter.
0947
0948 config MAXSMP
0949 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
0950 depends on X86_64 && SMP && DEBUG_KERNEL
0951 select CPUMASK_OFFSTACK
0952 help
0953 Enable maximum number of CPUS and NUMA Nodes for this architecture.
0954 If unsure, say N.
0955
0956 #
0957 # The maximum number of CPUs supported:
0958 #
0959 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
0960 # and which can be configured interactively in the
0961 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
0962 #
0963 # The ranges are different on 32-bit and 64-bit kernels, depending on
0964 # hardware capabilities and scalability features of the kernel.
0965 #
0966 # ( If MAXSMP is enabled we just use the highest possible value and disable
0967 # interactive configuration. )
0968 #
0969
0970 config NR_CPUS_RANGE_BEGIN
0971 int
0972 default NR_CPUS_RANGE_END if MAXSMP
0973 default 1 if !SMP
0974 default 2
0975
0976 config NR_CPUS_RANGE_END
0977 int
0978 depends on X86_32
0979 default 64 if SMP && X86_BIGSMP
0980 default 8 if SMP && !X86_BIGSMP
0981 default 1 if !SMP
0982
0983 config NR_CPUS_RANGE_END
0984 int
0985 depends on X86_64
0986 default 8192 if SMP && CPUMASK_OFFSTACK
0987 default 512 if SMP && !CPUMASK_OFFSTACK
0988 default 1 if !SMP
0989
0990 config NR_CPUS_DEFAULT
0991 int
0992 depends on X86_32
0993 default 32 if X86_BIGSMP
0994 default 8 if SMP
0995 default 1 if !SMP
0996
0997 config NR_CPUS_DEFAULT
0998 int
0999 depends on X86_64
1000 default 8192 if MAXSMP
1001 default 64 if SMP
1002 default 1 if !SMP
1003
1004 config NR_CPUS
1005 int "Maximum number of CPUs" if SMP && !MAXSMP
1006 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1007 default NR_CPUS_DEFAULT
1008 help
1009 This allows you to specify the maximum number of CPUs which this
1010 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1011 supported value is 8192, otherwise the maximum value is 512. The
1012 minimum value which makes sense is 2.
1013
1014 This is purely to save memory: each supported CPU adds about 8KB
1015 to the kernel image.
1016
1017 config SCHED_CLUSTER
1018 bool "Cluster scheduler support"
1019 depends on SMP
1020 default y
1021 help
1022 Cluster scheduler support improves the CPU scheduler's decision
1023 making when dealing with machines that have clusters of CPUs.
1024 Cluster usually means a couple of CPUs which are placed closely
1025 by sharing mid-level caches, last-level cache tags or internal
1026 busses.
1027
1028 config SCHED_SMT
1029 def_bool y if SMP
1030
1031 config SCHED_MC
1032 def_bool y
1033 prompt "Multi-core scheduler support"
1034 depends on SMP
1035 help
1036 Multi-core scheduler support improves the CPU scheduler's decision
1037 making when dealing with multi-core CPU chips at a cost of slightly
1038 increased overhead in some places. If unsure say N here.
1039
1040 config SCHED_MC_PRIO
1041 bool "CPU core priorities scheduler support"
1042 depends on SCHED_MC && CPU_SUP_INTEL
1043 select X86_INTEL_PSTATE
1044 select CPU_FREQ
1045 default y
1046 help
1047 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1048 core ordering determined at manufacturing time, which allows
1049 certain cores to reach higher turbo frequencies (when running
1050 single threaded workloads) than others.
1051
1052 Enabling this kernel feature teaches the scheduler about
1053 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1054 scheduler's CPU selection logic accordingly, so that higher
1055 overall system performance can be achieved.
1056
1057 This feature will have no effect on CPUs without this feature.
1058
1059 If unsure say Y here.
1060
1061 config UP_LATE_INIT
1062 def_bool y
1063 depends on !SMP && X86_LOCAL_APIC
1064
1065 config X86_UP_APIC
1066 bool "Local APIC support on uniprocessors" if !PCI_MSI
1067 default PCI_MSI
1068 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1069 help
1070 A local APIC (Advanced Programmable Interrupt Controller) is an
1071 integrated interrupt controller in the CPU. If you have a single-CPU
1072 system which has a processor with a local APIC, you can say Y here to
1073 enable and use it. If you say Y here even though your machine doesn't
1074 have a local APIC, then the kernel will still run with no slowdown at
1075 all. The local APIC supports CPU-generated self-interrupts (timer,
1076 performance counters), and the NMI watchdog which detects hard
1077 lockups.
1078
1079 config X86_UP_IOAPIC
1080 bool "IO-APIC support on uniprocessors"
1081 depends on X86_UP_APIC
1082 help
1083 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1084 SMP-capable replacement for PC-style interrupt controllers. Most
1085 SMP systems and many recent uniprocessor systems have one.
1086
1087 If you have a single-CPU system with an IO-APIC, you can say Y here
1088 to use it. If you say Y here even though your machine doesn't have
1089 an IO-APIC, then the kernel will still run with no slowdown at all.
1090
1091 config X86_LOCAL_APIC
1092 def_bool y
1093 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1094 select IRQ_DOMAIN_HIERARCHY
1095 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1096
1097 config X86_IO_APIC
1098 def_bool y
1099 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1100
1101 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1102 bool "Reroute for broken boot IRQs"
1103 depends on X86_IO_APIC
1104 help
1105 This option enables a workaround that fixes a source of
1106 spurious interrupts. This is recommended when threaded
1107 interrupt handling is used on systems where the generation of
1108 superfluous "boot interrupts" cannot be disabled.
1109
1110 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1111 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1112 kernel does during interrupt handling). On chipsets where this
1113 boot IRQ generation cannot be disabled, this workaround keeps
1114 the original IRQ line masked so that only the equivalent "boot
1115 IRQ" is delivered to the CPUs. The workaround also tells the
1116 kernel to set up the IRQ handler on the boot IRQ line. In this
1117 way only one interrupt is delivered to the kernel. Otherwise
1118 the spurious second interrupt may cause the kernel to bring
1119 down (vital) interrupt lines.
1120
1121 Only affects "broken" chipsets. Interrupt sharing may be
1122 increased on these systems.
1123
1124 config X86_MCE
1125 bool "Machine Check / overheating reporting"
1126 select GENERIC_ALLOCATOR
1127 default y
1128 help
1129 Machine Check support allows the processor to notify the
1130 kernel if it detects a problem (e.g. overheating, data corruption).
1131 The action the kernel takes depends on the severity of the problem,
1132 ranging from warning messages to halting the machine.
1133
1134 config X86_MCELOG_LEGACY
1135 bool "Support for deprecated /dev/mcelog character device"
1136 depends on X86_MCE
1137 help
1138 Enable support for /dev/mcelog which is needed by the old mcelog
1139 userspace logging daemon. Consider switching to the new generation
1140 rasdaemon solution.
1141
1142 config X86_MCE_INTEL
1143 def_bool y
1144 prompt "Intel MCE features"
1145 depends on X86_MCE && X86_LOCAL_APIC
1146 help
1147 Additional support for intel specific MCE features such as
1148 the thermal monitor.
1149
1150 config X86_MCE_AMD
1151 def_bool y
1152 prompt "AMD MCE features"
1153 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1154 help
1155 Additional support for AMD specific MCE features such as
1156 the DRAM Error Threshold.
1157
1158 config X86_ANCIENT_MCE
1159 bool "Support for old Pentium 5 / WinChip machine checks"
1160 depends on X86_32 && X86_MCE
1161 help
1162 Include support for machine check handling on old Pentium 5 or WinChip
1163 systems. These typically need to be enabled explicitly on the command
1164 line.
1165
1166 config X86_MCE_THRESHOLD
1167 depends on X86_MCE_AMD || X86_MCE_INTEL
1168 def_bool y
1169
1170 config X86_MCE_INJECT
1171 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1172 tristate "Machine check injector support"
1173 help
1174 Provide support for injecting machine checks for testing purposes.
1175 If you don't know what a machine check is and you don't do kernel
1176 QA it is safe to say n.
1177
1178 source "arch/x86/events/Kconfig"
1179
1180 config X86_LEGACY_VM86
1181 bool "Legacy VM86 support"
1182 depends on X86_32
1183 help
1184 This option allows user programs to put the CPU into V8086
1185 mode, which is an 80286-era approximation of 16-bit real mode.
1186
1187 Some very old versions of X and/or vbetool require this option
1188 for user mode setting. Similarly, DOSEMU will use it if
1189 available to accelerate real mode DOS programs. However, any
1190 recent version of DOSEMU, X, or vbetool should be fully
1191 functional even without kernel VM86 support, as they will all
1192 fall back to software emulation. Nevertheless, if you are using
1193 a 16-bit DOS program where 16-bit performance matters, vm86
1194 mode might be faster than emulation and you might want to
1195 enable this option.
1196
1197 Note that any app that works on a 64-bit kernel is unlikely to
1198 need this option, as 64-bit kernels don't, and can't, support
1199 V8086 mode. This option is also unrelated to 16-bit protected
1200 mode and is not needed to run most 16-bit programs under Wine.
1201
1202 Enabling this option increases the complexity of the kernel
1203 and slows down exception handling a tiny bit.
1204
1205 If unsure, say N here.
1206
1207 config VM86
1208 bool
1209 default X86_LEGACY_VM86
1210
1211 config X86_16BIT
1212 bool "Enable support for 16-bit segments" if EXPERT
1213 default y
1214 depends on MODIFY_LDT_SYSCALL
1215 help
1216 This option is required by programs like Wine to run 16-bit
1217 protected mode legacy code on x86 processors. Disabling
1218 this option saves about 300 bytes on i386, or around 6K text
1219 plus 16K runtime memory on x86-64,
1220
1221 config X86_ESPFIX32
1222 def_bool y
1223 depends on X86_16BIT && X86_32
1224
1225 config X86_ESPFIX64
1226 def_bool y
1227 depends on X86_16BIT && X86_64
1228
1229 config X86_VSYSCALL_EMULATION
1230 bool "Enable vsyscall emulation" if EXPERT
1231 default y
1232 depends on X86_64
1233 help
1234 This enables emulation of the legacy vsyscall page. Disabling
1235 it is roughly equivalent to booting with vsyscall=none, except
1236 that it will also disable the helpful warning if a program
1237 tries to use a vsyscall. With this option set to N, offending
1238 programs will just segfault, citing addresses of the form
1239 0xffffffffff600?00.
1240
1241 This option is required by many programs built before 2013, and
1242 care should be used even with newer programs if set to N.
1243
1244 Disabling this option saves about 7K of kernel size and
1245 possibly 4K of additional runtime pagetable memory.
1246
1247 config X86_IOPL_IOPERM
1248 bool "IOPERM and IOPL Emulation"
1249 default y
1250 help
1251 This enables the ioperm() and iopl() syscalls which are necessary
1252 for legacy applications.
1253
1254 Legacy IOPL support is an overbroad mechanism which allows user
1255 space aside of accessing all 65536 I/O ports also to disable
1256 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1257 capabilities and permission from potentially active security
1258 modules.
1259
1260 The emulation restricts the functionality of the syscall to
1261 only allowing the full range I/O port access, but prevents the
1262 ability to disable interrupts from user space which would be
1263 granted if the hardware IOPL mechanism would be used.
1264
1265 config TOSHIBA
1266 tristate "Toshiba Laptop support"
1267 depends on X86_32
1268 help
1269 This adds a driver to safely access the System Management Mode of
1270 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1271 not work on models with a Phoenix BIOS. The System Management Mode
1272 is used to set the BIOS and power saving options on Toshiba portables.
1273
1274 For information on utilities to make use of this driver see the
1275 Toshiba Linux utilities web site at:
1276 <http://www.buzzard.org.uk/toshiba/>.
1277
1278 Say Y if you intend to run this kernel on a Toshiba portable.
1279 Say N otherwise.
1280
1281 config X86_REBOOTFIXUPS
1282 bool "Enable X86 board specific fixups for reboot"
1283 depends on X86_32
1284 help
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
1289 system.
1290
1291 Currently, the only fixup is for the Geode machines using
1292 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1293
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.
1296 Say N otherwise.
1297
1298 config MICROCODE
1299 bool "CPU microcode loading support"
1300 default y
1301 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1302 help
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
1308 the Linux kernel.
1309
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.
1314
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
1317 config option.
1318
1319 config MICROCODE_INTEL
1320 bool "Intel microcode loading support"
1321 depends on CPU_SUP_INTEL && MICROCODE
1322 default MICROCODE
1323 help
1324 This options enables microcode patch loading support for Intel
1325 processors.
1326
1327 For the current Intel microcode data package go to
1328 <https://downloadcenter.intel.com> and search for
1329 'Linux Processor Microcode Data File'.
1330
1331 config MICROCODE_AMD
1332 bool "AMD microcode loading support"
1333 depends on CPU_SUP_AMD && MICROCODE
1334 help
1335 If you select this option, microcode patch loading support for AMD
1336 processors will be enabled.
1337
1338 config MICROCODE_LATE_LOADING
1339 bool "Late microcode loading (DANGEROUS)"
1340 default n
1341 depends on MICROCODE
1342 help
1343 Loading microcode late, when the system is up and executing instructions
1344 is a tricky business and should be avoided if possible. Just the sequence
1345 of synchronizing all cores and SMT threads is one fragile dance which does
1346 not guarantee that cores might not softlock after the loading. Therefore,
1347 use this at your own risk. Late loading taints the kernel too.
1348
1349 config X86_MSR
1350 tristate "/dev/cpu/*/msr - Model-specific register support"
1351 help
1352 This device gives privileged processes access to the x86
1353 Model-Specific Registers (MSRs). It is a character device with
1354 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1355 MSR accesses are directed to a specific CPU on multi-processor
1356 systems.
1357
1358 config X86_CPUID
1359 tristate "/dev/cpu/*/cpuid - CPU information support"
1360 help
1361 This device gives processes access to the x86 CPUID instruction to
1362 be executed on a specific processor. It is a character device
1363 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1364 /dev/cpu/31/cpuid.
1365
1366 choice
1367 prompt "High Memory Support"
1368 default HIGHMEM4G
1369 depends on X86_32
1370
1371 config NOHIGHMEM
1372 bool "off"
1373 help
1374 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1375 However, the address space of 32-bit x86 processors is only 4
1376 Gigabytes large. That means that, if you have a large amount of
1377 physical memory, not all of it can be "permanently mapped" by the
1378 kernel. The physical memory that's not permanently mapped is called
1379 "high memory".
1380
1381 If you are compiling a kernel which will never run on a machine with
1382 more than 1 Gigabyte total physical RAM, answer "off" here (default
1383 choice and suitable for most users). This will result in a "3GB/1GB"
1384 split: 3GB are mapped so that each process sees a 3GB virtual memory
1385 space and the remaining part of the 4GB virtual memory space is used
1386 by the kernel to permanently map as much physical memory as
1387 possible.
1388
1389 If the machine has between 1 and 4 Gigabytes physical RAM, then
1390 answer "4GB" here.
1391
1392 If more than 4 Gigabytes is used then answer "64GB" here. This
1393 selection turns Intel PAE (Physical Address Extension) mode on.
1394 PAE implements 3-level paging on IA32 processors. PAE is fully
1395 supported by Linux, PAE mode is implemented on all recent Intel
1396 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1397 then the kernel will not boot on CPUs that don't support PAE!
1398
1399 The actual amount of total physical memory will either be
1400 auto detected or can be forced by using a kernel command line option
1401 such as "mem=256M". (Try "man bootparam" or see the documentation of
1402 your boot loader (lilo or loadlin) about how to pass options to the
1403 kernel at boot time.)
1404
1405 If unsure, say "off".
1406
1407 config HIGHMEM4G
1408 bool "4GB"
1409 help
1410 Select this if you have a 32-bit processor and between 1 and 4
1411 gigabytes of physical RAM.
1412
1413 config HIGHMEM64G
1414 bool "64GB"
1415 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1416 select X86_PAE
1417 help
1418 Select this if you have a 32-bit processor and more than 4
1419 gigabytes of physical RAM.
1420
1421 endchoice
1422
1423 choice
1424 prompt "Memory split" if EXPERT
1425 default VMSPLIT_3G
1426 depends on X86_32
1427 help
1428 Select the desired split between kernel and user memory.
1429
1430 If the address range available to the kernel is less than the
1431 physical memory installed, the remaining memory will be available
1432 as "high memory". Accessing high memory is a little more costly
1433 than low memory, as it needs to be mapped into the kernel first.
1434 Note that increasing the kernel address space limits the range
1435 available to user programs, making the address space there
1436 tighter. Selecting anything other than the default 3G/1G split
1437 will also likely make your kernel incompatible with binary-only
1438 kernel modules.
1439
1440 If you are not absolutely sure what you are doing, leave this
1441 option alone!
1442
1443 config VMSPLIT_3G
1444 bool "3G/1G user/kernel split"
1445 config VMSPLIT_3G_OPT
1446 depends on !X86_PAE
1447 bool "3G/1G user/kernel split (for full 1G low memory)"
1448 config VMSPLIT_2G
1449 bool "2G/2G user/kernel split"
1450 config VMSPLIT_2G_OPT
1451 depends on !X86_PAE
1452 bool "2G/2G user/kernel split (for full 2G low memory)"
1453 config VMSPLIT_1G
1454 bool "1G/3G user/kernel split"
1455 endchoice
1456
1457 config PAGE_OFFSET
1458 hex
1459 default 0xB0000000 if VMSPLIT_3G_OPT
1460 default 0x80000000 if VMSPLIT_2G
1461 default 0x78000000 if VMSPLIT_2G_OPT
1462 default 0x40000000 if VMSPLIT_1G
1463 default 0xC0000000
1464 depends on X86_32
1465
1466 config HIGHMEM
1467 def_bool y
1468 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1469
1470 config X86_PAE
1471 bool "PAE (Physical Address Extension) Support"
1472 depends on X86_32 && !HIGHMEM4G
1473 select PHYS_ADDR_T_64BIT
1474 select SWIOTLB
1475 help
1476 PAE is required for NX support, and furthermore enables
1477 larger swapspace support for non-overcommit purposes. It
1478 has the cost of more pagetable lookup overhead, and also
1479 consumes more pagetable space per process.
1480
1481 config X86_5LEVEL
1482 bool "Enable 5-level page tables support"
1483 default y
1484 select DYNAMIC_MEMORY_LAYOUT
1485 select SPARSEMEM_VMEMMAP
1486 depends on X86_64
1487 help
1488 5-level paging enables access to larger address space:
1489 upto 128 PiB of virtual address space and 4 PiB of
1490 physical address space.
1491
1492 It will be supported by future Intel CPUs.
1493
1494 A kernel with the option enabled can be booted on machines that
1495 support 4- or 5-level paging.
1496
1497 See Documentation/x86/x86_64/5level-paging.rst for more
1498 information.
1499
1500 Say N if unsure.
1501
1502 config X86_DIRECT_GBPAGES
1503 def_bool y
1504 depends on X86_64
1505 help
1506 Certain kernel features effectively disable kernel
1507 linear 1 GB mappings (even if the CPU otherwise
1508 supports them), so don't confuse the user by printing
1509 that we have them enabled.
1510
1511 config X86_CPA_STATISTICS
1512 bool "Enable statistic for Change Page Attribute"
1513 depends on DEBUG_FS
1514 help
1515 Expose statistics about the Change Page Attribute mechanism, which
1516 helps to determine the effectiveness of preserving large and huge
1517 page mappings when mapping protections are changed.
1518
1519 config X86_MEM_ENCRYPT
1520 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1521 select DYNAMIC_PHYSICAL_MASK
1522 def_bool n
1523
1524 config AMD_MEM_ENCRYPT
1525 bool "AMD Secure Memory Encryption (SME) support"
1526 depends on X86_64 && CPU_SUP_AMD
1527 select DMA_COHERENT_POOL
1528 select ARCH_USE_MEMREMAP_PROT
1529 select INSTRUCTION_DECODER
1530 select ARCH_HAS_CC_PLATFORM
1531 select X86_MEM_ENCRYPT
1532 help
1533 Say yes to enable support for the encryption of system memory.
1534 This requires an AMD processor that supports Secure Memory
1535 Encryption (SME).
1536
1537 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1538 bool "Activate AMD Secure Memory Encryption (SME) by default"
1539 depends on AMD_MEM_ENCRYPT
1540 help
1541 Say yes to have system memory encrypted by default if running on
1542 an AMD processor that supports Secure Memory Encryption (SME).
1543
1544 If set to Y, then the encryption of system memory can be
1545 deactivated with the mem_encrypt=off command line option.
1546
1547 If set to N, then the encryption of system memory can be
1548 activated with the mem_encrypt=on command line option.
1549
1550 # Common NUMA Features
1551 config NUMA
1552 bool "NUMA Memory Allocation and Scheduler Support"
1553 depends on SMP
1554 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1555 default y if X86_BIGSMP
1556 select USE_PERCPU_NUMA_NODE_ID
1557 help
1558 Enable NUMA (Non-Uniform Memory Access) support.
1559
1560 The kernel will try to allocate memory used by a CPU on the
1561 local memory controller of the CPU and add some more
1562 NUMA awareness to the kernel.
1563
1564 For 64-bit this is recommended if the system is Intel Core i7
1565 (or later), AMD Opteron, or EM64T NUMA.
1566
1567 For 32-bit this is only needed if you boot a 32-bit
1568 kernel on a 64-bit NUMA platform.
1569
1570 Otherwise, you should say N.
1571
1572 config AMD_NUMA
1573 def_bool y
1574 prompt "Old style AMD Opteron NUMA detection"
1575 depends on X86_64 && NUMA && PCI
1576 help
1577 Enable AMD NUMA node topology detection. You should say Y here if
1578 you have a multi processor AMD system. This uses an old method to
1579 read the NUMA configuration directly from the builtin Northbridge
1580 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1581 which also takes priority if both are compiled in.
1582
1583 config X86_64_ACPI_NUMA
1584 def_bool y
1585 prompt "ACPI NUMA detection"
1586 depends on X86_64 && NUMA && ACPI && PCI
1587 select ACPI_NUMA
1588 help
1589 Enable ACPI SRAT based node topology detection.
1590
1591 config NUMA_EMU
1592 bool "NUMA emulation"
1593 depends on NUMA
1594 help
1595 Enable NUMA emulation. A flat machine will be split
1596 into virtual nodes when booted with "numa=fake=N", where N is the
1597 number of nodes. This is only useful for debugging.
1598
1599 config NODES_SHIFT
1600 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1601 range 1 10
1602 default "10" if MAXSMP
1603 default "6" if X86_64
1604 default "3"
1605 depends on NUMA
1606 help
1607 Specify the maximum number of NUMA Nodes available on the target
1608 system. Increases memory reserved to accommodate various tables.
1609
1610 config ARCH_FLATMEM_ENABLE
1611 def_bool y
1612 depends on X86_32 && !NUMA
1613
1614 config ARCH_SPARSEMEM_ENABLE
1615 def_bool y
1616 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1617 select SPARSEMEM_STATIC if X86_32
1618 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1619
1620 config ARCH_SPARSEMEM_DEFAULT
1621 def_bool X86_64 || (NUMA && X86_32)
1622
1623 config ARCH_SELECT_MEMORY_MODEL
1624 def_bool y
1625 depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE
1626
1627 config ARCH_MEMORY_PROBE
1628 bool "Enable sysfs memory/probe interface"
1629 depends on MEMORY_HOTPLUG
1630 help
1631 This option enables a sysfs memory/probe interface for testing.
1632 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1633 If you are unsure how to answer this question, answer N.
1634
1635 config ARCH_PROC_KCORE_TEXT
1636 def_bool y
1637 depends on X86_64 && PROC_KCORE
1638
1639 config ILLEGAL_POINTER_VALUE
1640 hex
1641 default 0 if X86_32
1642 default 0xdead000000000000 if X86_64
1643
1644 config X86_PMEM_LEGACY_DEVICE
1645 bool
1646
1647 config X86_PMEM_LEGACY
1648 tristate "Support non-standard NVDIMMs and ADR protected memory"
1649 depends on PHYS_ADDR_T_64BIT
1650 depends on BLK_DEV
1651 select X86_PMEM_LEGACY_DEVICE
1652 select NUMA_KEEP_MEMINFO if NUMA
1653 select LIBNVDIMM
1654 help
1655 Treat memory marked using the non-standard e820 type of 12 as used
1656 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1657 The kernel will offer these regions to the 'pmem' driver so
1658 they can be used for persistent storage.
1659
1660 Say Y if unsure.
1661
1662 config HIGHPTE
1663 bool "Allocate 3rd-level pagetables from highmem"
1664 depends on HIGHMEM
1665 help
1666 The VM uses one page table entry for each page of physical memory.
1667 For systems with a lot of RAM, this can be wasteful of precious
1668 low memory. Setting this option will put user-space page table
1669 entries in high memory.
1670
1671 config X86_CHECK_BIOS_CORRUPTION
1672 bool "Check for low memory corruption"
1673 help
1674 Periodically check for memory corruption in low memory, which
1675 is suspected to be caused by BIOS. Even when enabled in the
1676 configuration, it is disabled at runtime. Enable it by
1677 setting "memory_corruption_check=1" on the kernel command
1678 line. By default it scans the low 64k of memory every 60
1679 seconds; see the memory_corruption_check_size and
1680 memory_corruption_check_period parameters in
1681 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1682
1683 When enabled with the default parameters, this option has
1684 almost no overhead, as it reserves a relatively small amount
1685 of memory and scans it infrequently. It both detects corruption
1686 and prevents it from affecting the running system.
1687
1688 It is, however, intended as a diagnostic tool; if repeatable
1689 BIOS-originated corruption always affects the same memory,
1690 you can use memmap= to prevent the kernel from using that
1691 memory.
1692
1693 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1694 bool "Set the default setting of memory_corruption_check"
1695 depends on X86_CHECK_BIOS_CORRUPTION
1696 default y
1697 help
1698 Set whether the default state of memory_corruption_check is
1699 on or off.
1700
1701 config MATH_EMULATION
1702 bool
1703 depends on MODIFY_LDT_SYSCALL
1704 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1705 help
1706 Linux can emulate a math coprocessor (used for floating point
1707 operations) if you don't have one. 486DX and Pentium processors have
1708 a math coprocessor built in, 486SX and 386 do not, unless you added
1709 a 487DX or 387, respectively. (The messages during boot time can
1710 give you some hints here ["man dmesg"].) Everyone needs either a
1711 coprocessor or this emulation.
1712
1713 If you don't have a math coprocessor, you need to say Y here; if you
1714 say Y here even though you have a coprocessor, the coprocessor will
1715 be used nevertheless. (This behavior can be changed with the kernel
1716 command line option "no387", which comes handy if your coprocessor
1717 is broken. Try "man bootparam" or see the documentation of your boot
1718 loader (lilo or loadlin) about how to pass options to the kernel at
1719 boot time.) This means that it is a good idea to say Y here if you
1720 intend to use this kernel on different machines.
1721
1722 More information about the internals of the Linux math coprocessor
1723 emulation can be found in <file:arch/x86/math-emu/README>.
1724
1725 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1726 kernel, it won't hurt.
1727
1728 config MTRR
1729 def_bool y
1730 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1731 help
1732 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1733 the Memory Type Range Registers (MTRRs) may be used to control
1734 processor access to memory ranges. This is most useful if you have
1735 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1736 allows bus write transfers to be combined into a larger transfer
1737 before bursting over the PCI/AGP bus. This can increase performance
1738 of image write operations 2.5 times or more. Saying Y here creates a
1739 /proc/mtrr file which may be used to manipulate your processor's
1740 MTRRs. Typically the X server should use this.
1741
1742 This code has a reasonably generic interface so that similar
1743 control registers on other processors can be easily supported
1744 as well:
1745
1746 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1747 Registers (ARRs) which provide a similar functionality to MTRRs. For
1748 these, the ARRs are used to emulate the MTRRs.
1749 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1750 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1751 write-combining. All of these processors are supported by this code
1752 and it makes sense to say Y here if you have one of them.
1753
1754 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1755 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1756 can lead to all sorts of problems, so it's good to say Y here.
1757
1758 You can safely say Y even if your machine doesn't have MTRRs, you'll
1759 just add about 9 KB to your kernel.
1760
1761 See <file:Documentation/x86/mtrr.rst> for more information.
1762
1763 config MTRR_SANITIZER
1764 def_bool y
1765 prompt "MTRR cleanup support"
1766 depends on MTRR
1767 help
1768 Convert MTRR layout from continuous to discrete, so X drivers can
1769 add writeback entries.
1770
1771 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1772 The largest mtrr entry size for a continuous block can be set with
1773 mtrr_chunk_size.
1774
1775 If unsure, say Y.
1776
1777 config MTRR_SANITIZER_ENABLE_DEFAULT
1778 int "MTRR cleanup enable value (0-1)"
1779 range 0 1
1780 default "0"
1781 depends on MTRR_SANITIZER
1782 help
1783 Enable mtrr cleanup default value
1784
1785 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1786 int "MTRR cleanup spare reg num (0-7)"
1787 range 0 7
1788 default "1"
1789 depends on MTRR_SANITIZER
1790 help
1791 mtrr cleanup spare entries default, it can be changed via
1792 mtrr_spare_reg_nr=N on the kernel command line.
1793
1794 config X86_PAT
1795 def_bool y
1796 prompt "x86 PAT support" if EXPERT
1797 depends on MTRR
1798 help
1799 Use PAT attributes to setup page level cache control.
1800
1801 PATs are the modern equivalents of MTRRs and are much more
1802 flexible than MTRRs.
1803
1804 Say N here if you see bootup problems (boot crash, boot hang,
1805 spontaneous reboots) or a non-working video driver.
1806
1807 If unsure, say Y.
1808
1809 config ARCH_USES_PG_UNCACHED
1810 def_bool y
1811 depends on X86_PAT
1812
1813 config X86_UMIP
1814 def_bool y
1815 prompt "User Mode Instruction Prevention" if EXPERT
1816 help
1817 User Mode Instruction Prevention (UMIP) is a security feature in
1818 some x86 processors. If enabled, a general protection fault is
1819 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1820 executed in user mode. These instructions unnecessarily expose
1821 information about the hardware state.
1822
1823 The vast majority of applications do not use these instructions.
1824 For the very few that do, software emulation is provided in
1825 specific cases in protected and virtual-8086 modes. Emulated
1826 results are dummy.
1827
1828 config CC_HAS_IBT
1829 # GCC >= 9 and binutils >= 2.29
1830 # Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
1831 # Clang/LLVM >= 14
1832 # https://github.com/llvm/llvm-project/commit/e0b89df2e0f0130881bf6c39bf31d7f6aac00e0f
1833 # https://github.com/llvm/llvm-project/commit/dfcf69770bc522b9e411c66454934a37c1f35332
1834 def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \
1835 (CC_IS_CLANG && CLANG_VERSION >= 140000)) && \
1836 $(as-instr,endbr64)
1837
1838 config X86_KERNEL_IBT
1839 prompt "Indirect Branch Tracking"
1840 bool
1841 depends on X86_64 && CC_HAS_IBT && HAVE_OBJTOOL
1842 # https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
1843 depends on !LD_IS_LLD || LLD_VERSION >= 140000
1844 select OBJTOOL
1845 help
1846 Build the kernel with support for Indirect Branch Tracking, a
1847 hardware support course-grain forward-edge Control Flow Integrity
1848 protection. It enforces that all indirect calls must land on
1849 an ENDBR instruction, as such, the compiler will instrument the
1850 code with them to make this happen.
1851
1852 In addition to building the kernel with IBT, seal all functions that
1853 are not indirect call targets, avoiding them ever becoming one.
1854
1855 This requires LTO like objtool runs and will slow down the build. It
1856 does significantly reduce the number of ENDBR instructions in the
1857 kernel image.
1858
1859 config X86_INTEL_MEMORY_PROTECTION_KEYS
1860 prompt "Memory Protection Keys"
1861 def_bool y
1862 # Note: only available in 64-bit mode
1863 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1864 select ARCH_USES_HIGH_VMA_FLAGS
1865 select ARCH_HAS_PKEYS
1866 help
1867 Memory Protection Keys provides a mechanism for enforcing
1868 page-based protections, but without requiring modification of the
1869 page tables when an application changes protection domains.
1870
1871 For details, see Documentation/core-api/protection-keys.rst
1872
1873 If unsure, say y.
1874
1875 choice
1876 prompt "TSX enable mode"
1877 depends on CPU_SUP_INTEL
1878 default X86_INTEL_TSX_MODE_OFF
1879 help
1880 Intel's TSX (Transactional Synchronization Extensions) feature
1881 allows to optimize locking protocols through lock elision which
1882 can lead to a noticeable performance boost.
1883
1884 On the other hand it has been shown that TSX can be exploited
1885 to form side channel attacks (e.g. TAA) and chances are there
1886 will be more of those attacks discovered in the future.
1887
1888 Therefore TSX is not enabled by default (aka tsx=off). An admin
1889 might override this decision by tsx=on the command line parameter.
1890 Even with TSX enabled, the kernel will attempt to enable the best
1891 possible TAA mitigation setting depending on the microcode available
1892 for the particular machine.
1893
1894 This option allows to set the default tsx mode between tsx=on, =off
1895 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1896 details.
1897
1898 Say off if not sure, auto if TSX is in use but it should be used on safe
1899 platforms or on if TSX is in use and the security aspect of tsx is not
1900 relevant.
1901
1902 config X86_INTEL_TSX_MODE_OFF
1903 bool "off"
1904 help
1905 TSX is disabled if possible - equals to tsx=off command line parameter.
1906
1907 config X86_INTEL_TSX_MODE_ON
1908 bool "on"
1909 help
1910 TSX is always enabled on TSX capable HW - equals the tsx=on command
1911 line parameter.
1912
1913 config X86_INTEL_TSX_MODE_AUTO
1914 bool "auto"
1915 help
1916 TSX is enabled on TSX capable HW that is believed to be safe against
1917 side channel attacks- equals the tsx=auto command line parameter.
1918 endchoice
1919
1920 config X86_SGX
1921 bool "Software Guard eXtensions (SGX)"
1922 depends on X86_64 && CPU_SUP_INTEL
1923 depends on CRYPTO=y
1924 depends on CRYPTO_SHA256=y
1925 select SRCU
1926 select MMU_NOTIFIER
1927 select NUMA_KEEP_MEMINFO if NUMA
1928 select XARRAY_MULTI
1929 help
1930 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1931 that can be used by applications to set aside private regions of code
1932 and data, referred to as enclaves. An enclave's private memory can
1933 only be accessed by code running within the enclave. Accesses from
1934 outside the enclave, including other enclaves, are disallowed by
1935 hardware.
1936
1937 If unsure, say N.
1938
1939 config EFI
1940 bool "EFI runtime service support"
1941 depends on ACPI
1942 select UCS2_STRING
1943 select EFI_RUNTIME_WRAPPERS
1944 select ARCH_USE_MEMREMAP_PROT
1945 help
1946 This enables the kernel to use EFI runtime services that are
1947 available (such as the EFI variable services).
1948
1949 This option is only useful on systems that have EFI firmware.
1950 In addition, you should use the latest ELILO loader available
1951 at <http://elilo.sourceforge.net> in order to take advantage
1952 of EFI runtime services. However, even with this option, the
1953 resultant kernel should continue to boot on existing non-EFI
1954 platforms.
1955
1956 config EFI_STUB
1957 bool "EFI stub support"
1958 depends on EFI
1959 depends on $(cc-option,-mabi=ms) || X86_32
1960 select RELOCATABLE
1961 help
1962 This kernel feature allows a bzImage to be loaded directly
1963 by EFI firmware without the use of a bootloader.
1964
1965 See Documentation/admin-guide/efi-stub.rst for more information.
1966
1967 config EFI_MIXED
1968 bool "EFI mixed-mode support"
1969 depends on EFI_STUB && X86_64
1970 help
1971 Enabling this feature allows a 64-bit kernel to be booted
1972 on a 32-bit firmware, provided that your CPU supports 64-bit
1973 mode.
1974
1975 Note that it is not possible to boot a mixed-mode enabled
1976 kernel via the EFI boot stub - a bootloader that supports
1977 the EFI handover protocol must be used.
1978
1979 If unsure, say N.
1980
1981 source "kernel/Kconfig.hz"
1982
1983 config KEXEC
1984 bool "kexec system call"
1985 select KEXEC_CORE
1986 help
1987 kexec is a system call that implements the ability to shutdown your
1988 current kernel, and to start another kernel. It is like a reboot
1989 but it is independent of the system firmware. And like a reboot
1990 you can start any kernel with it, not just Linux.
1991
1992 The name comes from the similarity to the exec system call.
1993
1994 It is an ongoing process to be certain the hardware in a machine
1995 is properly shutdown, so do not be surprised if this code does not
1996 initially work for you. As of this writing the exact hardware
1997 interface is strongly in flux, so no good recommendation can be
1998 made.
1999
2000 config KEXEC_FILE
2001 bool "kexec file based system call"
2002 select KEXEC_CORE
2003 select HAVE_IMA_KEXEC if IMA
2004 depends on X86_64
2005 depends on CRYPTO=y
2006 depends on CRYPTO_SHA256=y
2007 help
2008 This is new version of kexec system call. This system call is
2009 file based and takes file descriptors as system call argument
2010 for kernel and initramfs as opposed to list of segments as
2011 accepted by previous system call.
2012
2013 config ARCH_HAS_KEXEC_PURGATORY
2014 def_bool KEXEC_FILE
2015
2016 config KEXEC_SIG
2017 bool "Verify kernel signature during kexec_file_load() syscall"
2018 depends on KEXEC_FILE
2019 help
2020
2021 This option makes the kexec_file_load() syscall check for a valid
2022 signature of the kernel image. The image can still be loaded without
2023 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2024 there's a signature that we can check, then it must be valid.
2025
2026 In addition to this option, you need to enable signature
2027 verification for the corresponding kernel image type being
2028 loaded in order for this to work.
2029
2030 config KEXEC_SIG_FORCE
2031 bool "Require a valid signature in kexec_file_load() syscall"
2032 depends on KEXEC_SIG
2033 help
2034 This option makes kernel signature verification mandatory for
2035 the kexec_file_load() syscall.
2036
2037 config KEXEC_BZIMAGE_VERIFY_SIG
2038 bool "Enable bzImage signature verification support"
2039 depends on KEXEC_SIG
2040 depends on SIGNED_PE_FILE_VERIFICATION
2041 select SYSTEM_TRUSTED_KEYRING
2042 help
2043 Enable bzImage signature verification support.
2044
2045 config CRASH_DUMP
2046 bool "kernel crash dumps"
2047 depends on X86_64 || (X86_32 && HIGHMEM)
2048 help
2049 Generate crash dump after being started by kexec.
2050 This should be normally only set in special crash dump kernels
2051 which are loaded in the main kernel with kexec-tools into
2052 a specially reserved region and then later executed after
2053 a crash by kdump/kexec. The crash dump kernel must be compiled
2054 to a memory address not used by the main kernel or BIOS using
2055 PHYSICAL_START, or it must be built as a relocatable image
2056 (CONFIG_RELOCATABLE=y).
2057 For more details see Documentation/admin-guide/kdump/kdump.rst
2058
2059 config KEXEC_JUMP
2060 bool "kexec jump"
2061 depends on KEXEC && HIBERNATION
2062 help
2063 Jump between original kernel and kexeced kernel and invoke
2064 code in physical address mode via KEXEC
2065
2066 config PHYSICAL_START
2067 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2068 default "0x1000000"
2069 help
2070 This gives the physical address where the kernel is loaded.
2071
2072 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2073 bzImage will decompress itself to above physical address and
2074 run from there. Otherwise, bzImage will run from the address where
2075 it has been loaded by the boot loader and will ignore above physical
2076 address.
2077
2078 In normal kdump cases one does not have to set/change this option
2079 as now bzImage can be compiled as a completely relocatable image
2080 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2081 address. This option is mainly useful for the folks who don't want
2082 to use a bzImage for capturing the crash dump and want to use a
2083 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2084 to be specifically compiled to run from a specific memory area
2085 (normally a reserved region) and this option comes handy.
2086
2087 So if you are using bzImage for capturing the crash dump,
2088 leave the value here unchanged to 0x1000000 and set
2089 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2090 for capturing the crash dump change this value to start of
2091 the reserved region. In other words, it can be set based on
2092 the "X" value as specified in the "crashkernel=YM@XM"
2093 command line boot parameter passed to the panic-ed
2094 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2095 for more details about crash dumps.
2096
2097 Usage of bzImage for capturing the crash dump is recommended as
2098 one does not have to build two kernels. Same kernel can be used
2099 as production kernel and capture kernel. Above option should have
2100 gone away after relocatable bzImage support is introduced. But it
2101 is present because there are users out there who continue to use
2102 vmlinux for dump capture. This option should go away down the
2103 line.
2104
2105 Don't change this unless you know what you are doing.
2106
2107 config RELOCATABLE
2108 bool "Build a relocatable kernel"
2109 default y
2110 help
2111 This builds a kernel image that retains relocation information
2112 so it can be loaded someplace besides the default 1MB.
2113 The relocations tend to make the kernel binary about 10% larger,
2114 but are discarded at runtime.
2115
2116 One use is for the kexec on panic case where the recovery kernel
2117 must live at a different physical address than the primary
2118 kernel.
2119
2120 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2121 it has been loaded at and the compile time physical address
2122 (CONFIG_PHYSICAL_START) is used as the minimum location.
2123
2124 config RANDOMIZE_BASE
2125 bool "Randomize the address of the kernel image (KASLR)"
2126 depends on RELOCATABLE
2127 default y
2128 help
2129 In support of Kernel Address Space Layout Randomization (KASLR),
2130 this randomizes the physical address at which the kernel image
2131 is decompressed and the virtual address where the kernel
2132 image is mapped, as a security feature that deters exploit
2133 attempts relying on knowledge of the location of kernel
2134 code internals.
2135
2136 On 64-bit, the kernel physical and virtual addresses are
2137 randomized separately. The physical address will be anywhere
2138 between 16MB and the top of physical memory (up to 64TB). The
2139 virtual address will be randomized from 16MB up to 1GB (9 bits
2140 of entropy). Note that this also reduces the memory space
2141 available to kernel modules from 1.5GB to 1GB.
2142
2143 On 32-bit, the kernel physical and virtual addresses are
2144 randomized together. They will be randomized from 16MB up to
2145 512MB (8 bits of entropy).
2146
2147 Entropy is generated using the RDRAND instruction if it is
2148 supported. If RDTSC is supported, its value is mixed into
2149 the entropy pool as well. If neither RDRAND nor RDTSC are
2150 supported, then entropy is read from the i8254 timer. The
2151 usable entropy is limited by the kernel being built using
2152 2GB addressing, and that PHYSICAL_ALIGN must be at a
2153 minimum of 2MB. As a result, only 10 bits of entropy are
2154 theoretically possible, but the implementations are further
2155 limited due to memory layouts.
2156
2157 If unsure, say Y.
2158
2159 # Relocation on x86 needs some additional build support
2160 config X86_NEED_RELOCS
2161 def_bool y
2162 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2163
2164 config PHYSICAL_ALIGN
2165 hex "Alignment value to which kernel should be aligned"
2166 default "0x200000"
2167 range 0x2000 0x1000000 if X86_32
2168 range 0x200000 0x1000000 if X86_64
2169 help
2170 This value puts the alignment restrictions on physical address
2171 where kernel is loaded and run from. Kernel is compiled for an
2172 address which meets above alignment restriction.
2173
2174 If bootloader loads the kernel at a non-aligned address and
2175 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2176 address aligned to above value and run from there.
2177
2178 If bootloader loads the kernel at a non-aligned address and
2179 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2180 load address and decompress itself to the address it has been
2181 compiled for and run from there. The address for which kernel is
2182 compiled already meets above alignment restrictions. Hence the
2183 end result is that kernel runs from a physical address meeting
2184 above alignment restrictions.
2185
2186 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2187 this value must be a multiple of 0x200000.
2188
2189 Don't change this unless you know what you are doing.
2190
2191 config DYNAMIC_MEMORY_LAYOUT
2192 bool
2193 help
2194 This option makes base addresses of vmalloc and vmemmap as well as
2195 __PAGE_OFFSET movable during boot.
2196
2197 config RANDOMIZE_MEMORY
2198 bool "Randomize the kernel memory sections"
2199 depends on X86_64
2200 depends on RANDOMIZE_BASE
2201 select DYNAMIC_MEMORY_LAYOUT
2202 default RANDOMIZE_BASE
2203 help
2204 Randomizes the base virtual address of kernel memory sections
2205 (physical memory mapping, vmalloc & vmemmap). This security feature
2206 makes exploits relying on predictable memory locations less reliable.
2207
2208 The order of allocations remains unchanged. Entropy is generated in
2209 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2210 configuration have in average 30,000 different possible virtual
2211 addresses for each memory section.
2212
2213 If unsure, say Y.
2214
2215 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2216 hex "Physical memory mapping padding" if EXPERT
2217 depends on RANDOMIZE_MEMORY
2218 default "0xa" if MEMORY_HOTPLUG
2219 default "0x0"
2220 range 0x1 0x40 if MEMORY_HOTPLUG
2221 range 0x0 0x40
2222 help
2223 Define the padding in terabytes added to the existing physical
2224 memory size during kernel memory randomization. It is useful
2225 for memory hotplug support but reduces the entropy available for
2226 address randomization.
2227
2228 If unsure, leave at the default value.
2229
2230 config HOTPLUG_CPU
2231 def_bool y
2232 depends on SMP
2233
2234 config BOOTPARAM_HOTPLUG_CPU0
2235 bool "Set default setting of cpu0_hotpluggable"
2236 depends on HOTPLUG_CPU
2237 help
2238 Set whether default state of cpu0_hotpluggable is on or off.
2239
2240 Say Y here to enable CPU0 hotplug by default. If this switch
2241 is turned on, there is no need to give cpu0_hotplug kernel
2242 parameter and the CPU0 hotplug feature is enabled by default.
2243
2244 Please note: there are two known CPU0 dependencies if you want
2245 to enable the CPU0 hotplug feature either by this switch or by
2246 cpu0_hotplug kernel parameter.
2247
2248 First, resume from hibernate or suspend always starts from CPU0.
2249 So hibernate and suspend are prevented if CPU0 is offline.
2250
2251 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2252 offline if any interrupt can not migrate out of CPU0. There may
2253 be other CPU0 dependencies.
2254
2255 Please make sure the dependencies are under your control before
2256 you enable this feature.
2257
2258 Say N if you don't want to enable CPU0 hotplug feature by default.
2259 You still can enable the CPU0 hotplug feature at boot by kernel
2260 parameter cpu0_hotplug.
2261
2262 config DEBUG_HOTPLUG_CPU0
2263 def_bool n
2264 prompt "Debug CPU0 hotplug"
2265 depends on HOTPLUG_CPU
2266 help
2267 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2268 soon as possible and boots up userspace with CPU0 offlined. User
2269 can online CPU0 back after boot time.
2270
2271 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2272 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2273 compilation or giving cpu0_hotplug kernel parameter at boot.
2274
2275 If unsure, say N.
2276
2277 config COMPAT_VDSO
2278 def_bool n
2279 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2280 depends on COMPAT_32
2281 help
2282 Certain buggy versions of glibc will crash if they are
2283 presented with a 32-bit vDSO that is not mapped at the address
2284 indicated in its segment table.
2285
2286 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2287 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2288 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2289 the only released version with the bug, but OpenSUSE 9
2290 contains a buggy "glibc 2.3.2".
2291
2292 The symptom of the bug is that everything crashes on startup, saying:
2293 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2294
2295 Saying Y here changes the default value of the vdso32 boot
2296 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2297 This works around the glibc bug but hurts performance.
2298
2299 If unsure, say N: if you are compiling your own kernel, you
2300 are unlikely to be using a buggy version of glibc.
2301
2302 choice
2303 prompt "vsyscall table for legacy applications"
2304 depends on X86_64
2305 default LEGACY_VSYSCALL_XONLY
2306 help
2307 Legacy user code that does not know how to find the vDSO expects
2308 to be able to issue three syscalls by calling fixed addresses in
2309 kernel space. Since this location is not randomized with ASLR,
2310 it can be used to assist security vulnerability exploitation.
2311
2312 This setting can be changed at boot time via the kernel command
2313 line parameter vsyscall=[emulate|xonly|none]. Emulate mode
2314 is deprecated and can only be enabled using the kernel command
2315 line.
2316
2317 On a system with recent enough glibc (2.14 or newer) and no
2318 static binaries, you can say None without a performance penalty
2319 to improve security.
2320
2321 If unsure, select "Emulate execution only".
2322
2323 config LEGACY_VSYSCALL_XONLY
2324 bool "Emulate execution only"
2325 help
2326 The kernel traps and emulates calls into the fixed vsyscall
2327 address mapping and does not allow reads. This
2328 configuration is recommended when userspace might use the
2329 legacy vsyscall area but support for legacy binary
2330 instrumentation of legacy code is not needed. It mitigates
2331 certain uses of the vsyscall area as an ASLR-bypassing
2332 buffer.
2333
2334 config LEGACY_VSYSCALL_NONE
2335 bool "None"
2336 help
2337 There will be no vsyscall mapping at all. This will
2338 eliminate any risk of ASLR bypass due to the vsyscall
2339 fixed address mapping. Attempts to use the vsyscalls
2340 will be reported to dmesg, so that either old or
2341 malicious userspace programs can be identified.
2342
2343 endchoice
2344
2345 config CMDLINE_BOOL
2346 bool "Built-in kernel command line"
2347 help
2348 Allow for specifying boot arguments to the kernel at
2349 build time. On some systems (e.g. embedded ones), it is
2350 necessary or convenient to provide some or all of the
2351 kernel boot arguments with the kernel itself (that is,
2352 to not rely on the boot loader to provide them.)
2353
2354 To compile command line arguments into the kernel,
2355 set this option to 'Y', then fill in the
2356 boot arguments in CONFIG_CMDLINE.
2357
2358 Systems with fully functional boot loaders (i.e. non-embedded)
2359 should leave this option set to 'N'.
2360
2361 config CMDLINE
2362 string "Built-in kernel command string"
2363 depends on CMDLINE_BOOL
2364 default ""
2365 help
2366 Enter arguments here that should be compiled into the kernel
2367 image and used at boot time. If the boot loader provides a
2368 command line at boot time, it is appended to this string to
2369 form the full kernel command line, when the system boots.
2370
2371 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2372 change this behavior.
2373
2374 In most cases, the command line (whether built-in or provided
2375 by the boot loader) should specify the device for the root
2376 file system.
2377
2378 config CMDLINE_OVERRIDE
2379 bool "Built-in command line overrides boot loader arguments"
2380 depends on CMDLINE_BOOL && CMDLINE != ""
2381 help
2382 Set this option to 'Y' to have the kernel ignore the boot loader
2383 command line, and use ONLY the built-in command line.
2384
2385 This is used to work around broken boot loaders. This should
2386 be set to 'N' under normal conditions.
2387
2388 config MODIFY_LDT_SYSCALL
2389 bool "Enable the LDT (local descriptor table)" if EXPERT
2390 default y
2391 help
2392 Linux can allow user programs to install a per-process x86
2393 Local Descriptor Table (LDT) using the modify_ldt(2) system
2394 call. This is required to run 16-bit or segmented code such as
2395 DOSEMU or some Wine programs. It is also used by some very old
2396 threading libraries.
2397
2398 Enabling this feature adds a small amount of overhead to
2399 context switches and increases the low-level kernel attack
2400 surface. Disabling it removes the modify_ldt(2) system call.
2401
2402 Saying 'N' here may make sense for embedded or server kernels.
2403
2404 config STRICT_SIGALTSTACK_SIZE
2405 bool "Enforce strict size checking for sigaltstack"
2406 depends on DYNAMIC_SIGFRAME
2407 help
2408 For historical reasons MINSIGSTKSZ is a constant which became
2409 already too small with AVX512 support. Add a mechanism to
2410 enforce strict checking of the sigaltstack size against the
2411 real size of the FPU frame. This option enables the check
2412 by default. It can also be controlled via the kernel command
2413 line option 'strict_sas_size' independent of this config
2414 switch. Enabling it might break existing applications which
2415 allocate a too small sigaltstack but 'work' because they
2416 never get a signal delivered.
2417
2418 Say 'N' unless you want to really enforce this check.
2419
2420 source "kernel/livepatch/Kconfig"
2421
2422 endmenu
2423
2424 config CC_HAS_SLS
2425 def_bool $(cc-option,-mharden-sls=all)
2426
2427 config CC_HAS_RETURN_THUNK
2428 def_bool $(cc-option,-mfunction-return=thunk-extern)
2429
2430 menuconfig SPECULATION_MITIGATIONS
2431 bool "Mitigations for speculative execution vulnerabilities"
2432 default y
2433 help
2434 Say Y here to enable options which enable mitigations for
2435 speculative execution hardware vulnerabilities.
2436
2437 If you say N, all mitigations will be disabled. You really
2438 should know what you are doing to say so.
2439
2440 if SPECULATION_MITIGATIONS
2441
2442 config PAGE_TABLE_ISOLATION
2443 bool "Remove the kernel mapping in user mode"
2444 default y
2445 depends on (X86_64 || X86_PAE)
2446 help
2447 This feature reduces the number of hardware side channels by
2448 ensuring that the majority of kernel addresses are not mapped
2449 into userspace.
2450
2451 See Documentation/x86/pti.rst for more details.
2452
2453 config RETPOLINE
2454 bool "Avoid speculative indirect branches in kernel"
2455 select OBJTOOL if HAVE_OBJTOOL
2456 default y
2457 help
2458 Compile kernel with the retpoline compiler options to guard against
2459 kernel-to-user data leaks by avoiding speculative indirect
2460 branches. Requires a compiler with -mindirect-branch=thunk-extern
2461 support for full protection. The kernel may run slower.
2462
2463 config RETHUNK
2464 bool "Enable return-thunks"
2465 depends on RETPOLINE && CC_HAS_RETURN_THUNK
2466 select OBJTOOL if HAVE_OBJTOOL
2467 default y if X86_64
2468 help
2469 Compile the kernel with the return-thunks compiler option to guard
2470 against kernel-to-user data leaks by avoiding return speculation.
2471 Requires a compiler with -mfunction-return=thunk-extern
2472 support for full protection. The kernel may run slower.
2473
2474 config CPU_UNRET_ENTRY
2475 bool "Enable UNRET on kernel entry"
2476 depends on CPU_SUP_AMD && RETHUNK && X86_64
2477 default y
2478 help
2479 Compile the kernel with support for the retbleed=unret mitigation.
2480
2481 config CPU_IBPB_ENTRY
2482 bool "Enable IBPB on kernel entry"
2483 depends on CPU_SUP_AMD && X86_64
2484 default y
2485 help
2486 Compile the kernel with support for the retbleed=ibpb mitigation.
2487
2488 config CPU_IBRS_ENTRY
2489 bool "Enable IBRS on kernel entry"
2490 depends on CPU_SUP_INTEL && X86_64
2491 default y
2492 help
2493 Compile the kernel with support for the spectre_v2=ibrs mitigation.
2494 This mitigates both spectre_v2 and retbleed at great cost to
2495 performance.
2496
2497 config SLS
2498 bool "Mitigate Straight-Line-Speculation"
2499 depends on CC_HAS_SLS && X86_64
2500 select OBJTOOL if HAVE_OBJTOOL
2501 default n
2502 help
2503 Compile the kernel with straight-line-speculation options to guard
2504 against straight line speculation. The kernel image might be slightly
2505 larger.
2506
2507 endif
2508
2509 config ARCH_HAS_ADD_PAGES
2510 def_bool y
2511 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2512
2513 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2514 def_bool y
2515
2516 menu "Power management and ACPI options"
2517
2518 config ARCH_HIBERNATION_HEADER
2519 def_bool y
2520 depends on HIBERNATION
2521
2522 source "kernel/power/Kconfig"
2523
2524 source "drivers/acpi/Kconfig"
2525
2526 config X86_APM_BOOT
2527 def_bool y
2528 depends on APM
2529
2530 menuconfig APM
2531 tristate "APM (Advanced Power Management) BIOS support"
2532 depends on X86_32 && PM_SLEEP
2533 help
2534 APM is a BIOS specification for saving power using several different
2535 techniques. This is mostly useful for battery powered laptops with
2536 APM compliant BIOSes. If you say Y here, the system time will be
2537 reset after a RESUME operation, the /proc/apm device will provide
2538 battery status information, and user-space programs will receive
2539 notification of APM "events" (e.g. battery status change).
2540
2541 If you select "Y" here, you can disable actual use of the APM
2542 BIOS by passing the "apm=off" option to the kernel at boot time.
2543
2544 Note that the APM support is almost completely disabled for
2545 machines with more than one CPU.
2546
2547 In order to use APM, you will need supporting software. For location
2548 and more information, read <file:Documentation/power/apm-acpi.rst>
2549 and the Battery Powered Linux mini-HOWTO, available from
2550 <http://www.tldp.org/docs.html#howto>.
2551
2552 This driver does not spin down disk drives (see the hdparm(8)
2553 manpage ("man 8 hdparm") for that), and it doesn't turn off
2554 VESA-compliant "green" monitors.
2555
2556 This driver does not support the TI 4000M TravelMate and the ACER
2557 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2558 desktop machines also don't have compliant BIOSes, and this driver
2559 may cause those machines to panic during the boot phase.
2560
2561 Generally, if you don't have a battery in your machine, there isn't
2562 much point in using this driver and you should say N. If you get
2563 random kernel OOPSes or reboots that don't seem to be related to
2564 anything, try disabling/enabling this option (or disabling/enabling
2565 APM in your BIOS).
2566
2567 Some other things you should try when experiencing seemingly random,
2568 "weird" problems:
2569
2570 1) make sure that you have enough swap space and that it is
2571 enabled.
2572 2) pass the "no-hlt" option to the kernel
2573 3) switch on floating point emulation in the kernel and pass
2574 the "no387" option to the kernel
2575 4) pass the "floppy=nodma" option to the kernel
2576 5) pass the "mem=4M" option to the kernel (thereby disabling
2577 all but the first 4 MB of RAM)
2578 6) make sure that the CPU is not over clocked.
2579 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2580 8) disable the cache from your BIOS settings
2581 9) install a fan for the video card or exchange video RAM
2582 10) install a better fan for the CPU
2583 11) exchange RAM chips
2584 12) exchange the motherboard.
2585
2586 To compile this driver as a module, choose M here: the
2587 module will be called apm.
2588
2589 if APM
2590
2591 config APM_IGNORE_USER_SUSPEND
2592 bool "Ignore USER SUSPEND"
2593 help
2594 This option will ignore USER SUSPEND requests. On machines with a
2595 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2596 series notebooks, it is necessary to say Y because of a BIOS bug.
2597
2598 config APM_DO_ENABLE
2599 bool "Enable PM at boot time"
2600 help
2601 Enable APM features at boot time. From page 36 of the APM BIOS
2602 specification: "When disabled, the APM BIOS does not automatically
2603 power manage devices, enter the Standby State, enter the Suspend
2604 State, or take power saving steps in response to CPU Idle calls."
2605 This driver will make CPU Idle calls when Linux is idle (unless this
2606 feature is turned off -- see "Do CPU IDLE calls", below). This
2607 should always save battery power, but more complicated APM features
2608 will be dependent on your BIOS implementation. You may need to turn
2609 this option off if your computer hangs at boot time when using APM
2610 support, or if it beeps continuously instead of suspending. Turn
2611 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2612 T400CDT. This is off by default since most machines do fine without
2613 this feature.
2614
2615 config APM_CPU_IDLE
2616 depends on CPU_IDLE
2617 bool "Make CPU Idle calls when idle"
2618 help
2619 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2620 On some machines, this can activate improved power savings, such as
2621 a slowed CPU clock rate, when the machine is idle. These idle calls
2622 are made after the idle loop has run for some length of time (e.g.,
2623 333 mS). On some machines, this will cause a hang at boot time or
2624 whenever the CPU becomes idle. (On machines with more than one CPU,
2625 this option does nothing.)
2626
2627 config APM_DISPLAY_BLANK
2628 bool "Enable console blanking using APM"
2629 help
2630 Enable console blanking using the APM. Some laptops can use this to
2631 turn off the LCD backlight when the screen blanker of the Linux
2632 virtual console blanks the screen. Note that this is only used by
2633 the virtual console screen blanker, and won't turn off the backlight
2634 when using the X Window system. This also doesn't have anything to
2635 do with your VESA-compliant power-saving monitor. Further, this
2636 option doesn't work for all laptops -- it might not turn off your
2637 backlight at all, or it might print a lot of errors to the console,
2638 especially if you are using gpm.
2639
2640 config APM_ALLOW_INTS
2641 bool "Allow interrupts during APM BIOS calls"
2642 help
2643 Normally we disable external interrupts while we are making calls to
2644 the APM BIOS as a measure to lessen the effects of a badly behaving
2645 BIOS implementation. The BIOS should reenable interrupts if it
2646 needs to. Unfortunately, some BIOSes do not -- especially those in
2647 many of the newer IBM Thinkpads. If you experience hangs when you
2648 suspend, try setting this to Y. Otherwise, say N.
2649
2650 endif # APM
2651
2652 source "drivers/cpufreq/Kconfig"
2653
2654 source "drivers/cpuidle/Kconfig"
2655
2656 source "drivers/idle/Kconfig"
2657
2658 endmenu
2659
2660 menu "Bus options (PCI etc.)"
2661
2662 choice
2663 prompt "PCI access mode"
2664 depends on X86_32 && PCI
2665 default PCI_GOANY
2666 help
2667 On PCI systems, the BIOS can be used to detect the PCI devices and
2668 determine their configuration. However, some old PCI motherboards
2669 have BIOS bugs and may crash if this is done. Also, some embedded
2670 PCI-based systems don't have any BIOS at all. Linux can also try to
2671 detect the PCI hardware directly without using the BIOS.
2672
2673 With this option, you can specify how Linux should detect the
2674 PCI devices. If you choose "BIOS", the BIOS will be used,
2675 if you choose "Direct", the BIOS won't be used, and if you
2676 choose "MMConfig", then PCI Express MMCONFIG will be used.
2677 If you choose "Any", the kernel will try MMCONFIG, then the
2678 direct access method and falls back to the BIOS if that doesn't
2679 work. If unsure, go with the default, which is "Any".
2680
2681 config PCI_GOBIOS
2682 bool "BIOS"
2683
2684 config PCI_GOMMCONFIG
2685 bool "MMConfig"
2686
2687 config PCI_GODIRECT
2688 bool "Direct"
2689
2690 config PCI_GOOLPC
2691 bool "OLPC XO-1"
2692 depends on OLPC
2693
2694 config PCI_GOANY
2695 bool "Any"
2696
2697 endchoice
2698
2699 config PCI_BIOS
2700 def_bool y
2701 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2702
2703 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2704 config PCI_DIRECT
2705 def_bool y
2706 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2707
2708 config PCI_MMCONFIG
2709 bool "Support mmconfig PCI config space access" if X86_64
2710 default y
2711 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2712 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2713
2714 config PCI_OLPC
2715 def_bool y
2716 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2717
2718 config PCI_XEN
2719 def_bool y
2720 depends on PCI && XEN
2721
2722 config MMCONF_FAM10H
2723 def_bool y
2724 depends on X86_64 && PCI_MMCONFIG && ACPI
2725
2726 config PCI_CNB20LE_QUIRK
2727 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2728 depends on PCI
2729 help
2730 Read the PCI windows out of the CNB20LE host bridge. This allows
2731 PCI hotplug to work on systems with the CNB20LE chipset which do
2732 not have ACPI.
2733
2734 There's no public spec for this chipset, and this functionality
2735 is known to be incomplete.
2736
2737 You should say N unless you know you need this.
2738
2739 config ISA_BUS
2740 bool "ISA bus support on modern systems" if EXPERT
2741 help
2742 Expose ISA bus device drivers and options available for selection and
2743 configuration. Enable this option if your target machine has an ISA
2744 bus. ISA is an older system, displaced by PCI and newer bus
2745 architectures -- if your target machine is modern, it probably does
2746 not have an ISA bus.
2747
2748 If unsure, say N.
2749
2750 # x86_64 have no ISA slots, but can have ISA-style DMA.
2751 config ISA_DMA_API
2752 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2753 default y
2754 help
2755 Enables ISA-style DMA support for devices requiring such controllers.
2756 If unsure, say Y.
2757
2758 if X86_32
2759
2760 config ISA
2761 bool "ISA support"
2762 help
2763 Find out whether you have ISA slots on your motherboard. ISA is the
2764 name of a bus system, i.e. the way the CPU talks to the other stuff
2765 inside your box. Other bus systems are PCI, EISA, MicroChannel
2766 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2767 newer boards don't support it. If you have ISA, say Y, otherwise N.
2768
2769 config SCx200
2770 tristate "NatSemi SCx200 support"
2771 help
2772 This provides basic support for National Semiconductor's
2773 (now AMD's) Geode processors. The driver probes for the
2774 PCI-IDs of several on-chip devices, so its a good dependency
2775 for other scx200_* drivers.
2776
2777 If compiled as a module, the driver is named scx200.
2778
2779 config SCx200HR_TIMER
2780 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2781 depends on SCx200
2782 default y
2783 help
2784 This driver provides a clocksource built upon the on-chip
2785 27MHz high-resolution timer. Its also a workaround for
2786 NSC Geode SC-1100's buggy TSC, which loses time when the
2787 processor goes idle (as is done by the scheduler). The
2788 other workaround is idle=poll boot option.
2789
2790 config OLPC
2791 bool "One Laptop Per Child support"
2792 depends on !X86_PAE
2793 select GPIOLIB
2794 select OF
2795 select OF_PROMTREE
2796 select IRQ_DOMAIN
2797 select OLPC_EC
2798 help
2799 Add support for detecting the unique features of the OLPC
2800 XO hardware.
2801
2802 config OLPC_XO1_PM
2803 bool "OLPC XO-1 Power Management"
2804 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2805 help
2806 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2807
2808 config OLPC_XO1_RTC
2809 bool "OLPC XO-1 Real Time Clock"
2810 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2811 help
2812 Add support for the XO-1 real time clock, which can be used as a
2813 programmable wakeup source.
2814
2815 config OLPC_XO1_SCI
2816 bool "OLPC XO-1 SCI extras"
2817 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2818 depends on INPUT=y
2819 select POWER_SUPPLY
2820 help
2821 Add support for SCI-based features of the OLPC XO-1 laptop:
2822 - EC-driven system wakeups
2823 - Power button
2824 - Ebook switch
2825 - Lid switch
2826 - AC adapter status updates
2827 - Battery status updates
2828
2829 config OLPC_XO15_SCI
2830 bool "OLPC XO-1.5 SCI extras"
2831 depends on OLPC && ACPI
2832 select POWER_SUPPLY
2833 help
2834 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2835 - EC-driven system wakeups
2836 - AC adapter status updates
2837 - Battery status updates
2838
2839 config ALIX
2840 bool "PCEngines ALIX System Support (LED setup)"
2841 select GPIOLIB
2842 help
2843 This option enables system support for the PCEngines ALIX.
2844 At present this just sets up LEDs for GPIO control on
2845 ALIX2/3/6 boards. However, other system specific setup should
2846 get added here.
2847
2848 Note: You must still enable the drivers for GPIO and LED support
2849 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2850
2851 Note: You have to set alix.force=1 for boards with Award BIOS.
2852
2853 config NET5501
2854 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2855 select GPIOLIB
2856 help
2857 This option enables system support for the Soekris Engineering net5501.
2858
2859 config GEOS
2860 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2861 select GPIOLIB
2862 depends on DMI
2863 help
2864 This option enables system support for the Traverse Technologies GEOS.
2865
2866 config TS5500
2867 bool "Technologic Systems TS-5500 platform support"
2868 depends on MELAN
2869 select CHECK_SIGNATURE
2870 select NEW_LEDS
2871 select LEDS_CLASS
2872 help
2873 This option enables system support for the Technologic Systems TS-5500.
2874
2875 endif # X86_32
2876
2877 config AMD_NB
2878 def_bool y
2879 depends on CPU_SUP_AMD && PCI
2880
2881 endmenu
2882
2883 menu "Binary Emulations"
2884
2885 config IA32_EMULATION
2886 bool "IA32 Emulation"
2887 depends on X86_64
2888 select ARCH_WANT_OLD_COMPAT_IPC
2889 select BINFMT_ELF
2890 select COMPAT_OLD_SIGACTION
2891 help
2892 Include code to run legacy 32-bit programs under a
2893 64-bit kernel. You should likely turn this on, unless you're
2894 100% sure that you don't have any 32-bit programs left.
2895
2896 config X86_X32_ABI
2897 bool "x32 ABI for 64-bit mode"
2898 depends on X86_64
2899 # llvm-objcopy does not convert x86_64 .note.gnu.property or
2900 # compressed debug sections to x86_x32 properly:
2901 # https://github.com/ClangBuiltLinux/linux/issues/514
2902 # https://github.com/ClangBuiltLinux/linux/issues/1141
2903 depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
2904 help
2905 Include code to run binaries for the x32 native 32-bit ABI
2906 for 64-bit processors. An x32 process gets access to the
2907 full 64-bit register file and wide data path while leaving
2908 pointers at 32 bits for smaller memory footprint.
2909
2910 config COMPAT_32
2911 def_bool y
2912 depends on IA32_EMULATION || X86_32
2913 select HAVE_UID16
2914 select OLD_SIGSUSPEND3
2915
2916 config COMPAT
2917 def_bool y
2918 depends on IA32_EMULATION || X86_X32_ABI
2919
2920 config COMPAT_FOR_U64_ALIGNMENT
2921 def_bool y
2922 depends on COMPAT
2923
2924 endmenu
2925
2926 config HAVE_ATOMIC_IOMAP
2927 def_bool y
2928 depends on X86_32
2929
2930 source "arch/x86/kvm/Kconfig"
2931
2932 source "arch/x86/Kconfig.assembler"