Kconfig 97 KB

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  1. # SPDX-License-Identifier: GPL-2.0
  2. # Select 32 or 64 bit
  3. config 64BIT
  4. bool "64-bit kernel" if "$(ARCH)" = "x86"
  5. default "$(ARCH)" != "i386"
  6. help
  7. Say yes to build a 64-bit kernel - formerly known as x86_64
  8. Say no to build a 32-bit kernel - formerly known as i386
  9. config X86_32
  10. def_bool y
  11. depends on !64BIT
  12. # Options that are inherently 32-bit kernel only:
  13. select ARCH_WANT_IPC_PARSE_VERSION
  14. select CLKSRC_I8253
  15. select CLONE_BACKWARDS
  16. select GENERIC_VDSO_32
  17. select HAVE_DEBUG_STACKOVERFLOW
  18. select KMAP_LOCAL
  19. select MODULES_USE_ELF_REL
  20. select OLD_SIGACTION
  21. select ARCH_SPLIT_ARG64
  22. config X86_64
  23. def_bool y
  24. depends on 64BIT
  25. # Options that are inherently 64-bit kernel only:
  26. select ARCH_HAS_GIGANTIC_PAGE
  27. select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
  28. select ARCH_SUPPORTS_PER_VMA_LOCK
  29. select ARCH_USE_CMPXCHG_LOCKREF
  30. select HAVE_ARCH_SOFT_DIRTY
  31. select MODULES_USE_ELF_RELA
  32. select NEED_DMA_MAP_STATE
  33. select SWIOTLB
  34. select ARCH_HAS_ELFCORE_COMPAT
  35. select ZONE_DMA32
  36. config FORCE_DYNAMIC_FTRACE
  37. def_bool y
  38. depends on X86_32
  39. depends on FUNCTION_TRACER
  40. select DYNAMIC_FTRACE
  41. help
  42. We keep the static function tracing (!DYNAMIC_FTRACE) around
  43. in order to test the non static function tracing in the
  44. generic code, as other architectures still use it. But we
  45. only need to keep it around for x86_64. No need to keep it
  46. for x86_32. For x86_32, force DYNAMIC_FTRACE.
  47. #
  48. # Arch settings
  49. #
  50. # ( Note that options that are marked 'if X86_64' could in principle be
  51. # ported to 32-bit as well. )
  52. #
  53. config X86
  54. def_bool y
  55. #
  56. # Note: keep this list sorted alphabetically
  57. #
  58. select ACPI_LEGACY_TABLES_LOOKUP if ACPI
  59. select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
  60. select ARCH_32BIT_OFF_T if X86_32
  61. select ARCH_CLOCKSOURCE_INIT
  62. select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
  63. select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
  64. select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
  65. select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
  66. select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE)
  67. select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
  68. select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
  69. select ARCH_HAS_CACHE_LINE_SIZE
  70. select ARCH_HAS_CPU_FINALIZE_INIT
  71. select ARCH_HAS_CURRENT_STACK_POINTER
  72. select ARCH_HAS_DEBUG_VIRTUAL
  73. select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
  74. select ARCH_HAS_DEVMEM_IS_ALLOWED
  75. select ARCH_HAS_EARLY_DEBUG if KGDB
  76. select ARCH_HAS_ELF_RANDOMIZE
  77. select ARCH_HAS_FAST_MULTIPLIER
  78. select ARCH_HAS_FORTIFY_SOURCE
  79. select ARCH_HAS_GCOV_PROFILE_ALL
  80. select ARCH_HAS_KCOV if X86_64
  81. select ARCH_HAS_MEM_ENCRYPT
  82. select ARCH_HAS_MEMBARRIER_SYNC_CORE
  83. select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
  84. select ARCH_HAS_PMEM_API if X86_64
  85. select ARCH_HAS_PTE_DEVMAP if X86_64
  86. select ARCH_HAS_PTE_SPECIAL
  87. select ARCH_HAS_NONLEAF_PMD_YOUNG if PGTABLE_LEVELS > 2
  88. select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
  89. select ARCH_HAS_COPY_MC if X86_64
  90. select ARCH_HAS_SET_MEMORY
  91. select ARCH_HAS_SET_DIRECT_MAP
  92. select ARCH_HAS_STRICT_KERNEL_RWX
  93. select ARCH_HAS_STRICT_MODULE_RWX
  94. select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
  95. select ARCH_HAS_SYSCALL_WRAPPER
  96. select ARCH_HAS_UBSAN_SANITIZE_ALL
  97. select ARCH_HAS_DEBUG_WX
  98. select ARCH_HAS_ZONE_DMA_SET if EXPERT
  99. select ARCH_HAVE_NMI_SAFE_CMPXCHG
  100. select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
  101. select ARCH_MIGHT_HAVE_PC_PARPORT
  102. select ARCH_MIGHT_HAVE_PC_SERIO
  103. select ARCH_STACKWALK
  104. select ARCH_SUPPORTS_ACPI
  105. select ARCH_SUPPORTS_ATOMIC_RMW
  106. select ARCH_SUPPORTS_DEBUG_PAGEALLOC
  107. select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64
  108. select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
  109. select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
  110. select ARCH_SUPPORTS_CFI_CLANG if X86_64
  111. select ARCH_USES_CFI_TRAPS if X86_64 && CFI_CLANG
  112. select ARCH_SUPPORTS_LTO_CLANG
  113. select ARCH_SUPPORTS_LTO_CLANG_THIN
  114. select ARCH_USE_BUILTIN_BSWAP
  115. select ARCH_USE_MEMTEST
  116. select ARCH_USE_QUEUED_RWLOCKS
  117. select ARCH_USE_QUEUED_SPINLOCKS
  118. select ARCH_USE_SYM_ANNOTATIONS
  119. select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
  120. select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
  121. select ARCH_WANTS_DYNAMIC_TASK_STRUCT
  122. select ARCH_WANTS_NO_INSTR
  123. select ARCH_WANT_GENERAL_HUGETLB
  124. select ARCH_WANT_HUGE_PMD_SHARE
  125. select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP if X86_64
  126. select ARCH_WANT_LD_ORPHAN_WARN
  127. select ARCH_WANTS_THP_SWAP if X86_64
  128. select ARCH_HAS_PARANOID_L1D_FLUSH
  129. select BUILDTIME_TABLE_SORT
  130. select CLKEVT_I8253
  131. select CLOCKSOURCE_VALIDATE_LAST_CYCLE
  132. select CLOCKSOURCE_WATCHDOG
  133. # Word-size accesses may read uninitialized data past the trailing \0
  134. # in strings and cause false KMSAN reports.
  135. select DCACHE_WORD_ACCESS if !KMSAN
  136. select DYNAMIC_SIGFRAME
  137. select EDAC_ATOMIC_SCRUB
  138. select EDAC_SUPPORT
  139. select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
  140. select GENERIC_CLOCKEVENTS_MIN_ADJUST
  141. select GENERIC_CMOS_UPDATE
  142. select GENERIC_CPU_AUTOPROBE
  143. select GENERIC_CPU_VULNERABILITIES
  144. select GENERIC_EARLY_IOREMAP
  145. select GENERIC_ENTRY
  146. select GENERIC_IOMAP
  147. select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
  148. select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
  149. select GENERIC_IRQ_MIGRATION if SMP
  150. select GENERIC_IRQ_PROBE
  151. select GENERIC_IRQ_RESERVATION_MODE
  152. select GENERIC_IRQ_SHOW
  153. select GENERIC_PENDING_IRQ if SMP
  154. select GENERIC_PTDUMP
  155. select GENERIC_SMP_IDLE_THREAD
  156. select GENERIC_TIME_VSYSCALL
  157. select GENERIC_GETTIMEOFDAY
  158. select GENERIC_VDSO_TIME_NS
  159. select GUP_GET_PTE_LOW_HIGH if X86_PAE
  160. select HARDIRQS_SW_RESEND
  161. select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
  162. select HAVE_ACPI_APEI if ACPI
  163. select HAVE_ACPI_APEI_NMI if ACPI
  164. select HAVE_ALIGNED_STRUCT_PAGE if SLUB
  165. select HAVE_ARCH_AUDITSYSCALL
  166. select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
  167. select HAVE_ARCH_HUGE_VMALLOC if X86_64
  168. select HAVE_ARCH_JUMP_LABEL
  169. select HAVE_ARCH_JUMP_LABEL_RELATIVE
  170. select HAVE_ARCH_KASAN if X86_64
  171. select HAVE_ARCH_KASAN_VMALLOC if X86_64
  172. select HAVE_ARCH_KFENCE
  173. select HAVE_ARCH_KMSAN if X86_64
  174. select HAVE_ARCH_KGDB
  175. select HAVE_ARCH_MMAP_RND_BITS if MMU
  176. select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
  177. select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
  178. select HAVE_ARCH_PREL32_RELOCATIONS
  179. select HAVE_ARCH_SECCOMP_FILTER
  180. select HAVE_ARCH_THREAD_STRUCT_WHITELIST
  181. select HAVE_ARCH_STACKLEAK
  182. select HAVE_ARCH_TRACEHOOK
  183. select HAVE_ARCH_TRANSPARENT_HUGEPAGE
  184. select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
  185. select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
  186. select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
  187. select HAVE_ARCH_VMAP_STACK if X86_64
  188. select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
  189. select HAVE_ARCH_WITHIN_STACK_FRAMES
  190. select HAVE_ASM_MODVERSIONS
  191. select HAVE_CMPXCHG_DOUBLE
  192. select HAVE_CMPXCHG_LOCAL
  193. select HAVE_CONTEXT_TRACKING_USER if X86_64
  194. select HAVE_CONTEXT_TRACKING_USER_OFFSTACK if HAVE_CONTEXT_TRACKING_USER
  195. select HAVE_C_RECORDMCOUNT
  196. select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
  197. select HAVE_BUILDTIME_MCOUNT_SORT
  198. select HAVE_DEBUG_KMEMLEAK
  199. select HAVE_DMA_CONTIGUOUS
  200. select HAVE_DYNAMIC_FTRACE
  201. select HAVE_DYNAMIC_FTRACE_WITH_REGS
  202. select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
  203. select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
  204. select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
  205. select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
  206. select HAVE_EBPF_JIT
  207. select HAVE_EFFICIENT_UNALIGNED_ACCESS
  208. select HAVE_EISA
  209. select HAVE_EXIT_THREAD
  210. select HAVE_FAST_GUP
  211. select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
  212. select HAVE_FTRACE_MCOUNT_RECORD
  213. select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
  214. select HAVE_FUNCTION_TRACER
  215. select HAVE_GCC_PLUGINS
  216. select HAVE_HW_BREAKPOINT
  217. select HAVE_IOREMAP_PROT
  218. select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
  219. select HAVE_IRQ_TIME_ACCOUNTING
  220. select HAVE_JUMP_LABEL_HACK if HAVE_OBJTOOL
  221. select HAVE_KERNEL_BZIP2
  222. select HAVE_KERNEL_GZIP
  223. select HAVE_KERNEL_LZ4
  224. select HAVE_KERNEL_LZMA
  225. select HAVE_KERNEL_LZO
  226. select HAVE_KERNEL_XZ
  227. select HAVE_KERNEL_ZSTD
  228. select HAVE_KPROBES
  229. select HAVE_KPROBES_ON_FTRACE
  230. select HAVE_FUNCTION_ERROR_INJECTION
  231. select HAVE_KRETPROBES
  232. select HAVE_RETHOOK
  233. select HAVE_KVM
  234. select HAVE_LIVEPATCH if X86_64
  235. select HAVE_MIXED_BREAKPOINTS_REGS
  236. select HAVE_MOD_ARCH_SPECIFIC
  237. select HAVE_MOVE_PMD
  238. select HAVE_MOVE_PUD
  239. select HAVE_NOINSTR_HACK if HAVE_OBJTOOL
  240. select HAVE_NMI
  241. select HAVE_NOINSTR_VALIDATION if HAVE_OBJTOOL
  242. select HAVE_OBJTOOL if X86_64
  243. select HAVE_OPTPROBES
  244. select HAVE_PCSPKR_PLATFORM
  245. select HAVE_PERF_EVENTS
  246. select HAVE_PERF_EVENTS_NMI
  247. select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
  248. select HAVE_PCI
  249. select HAVE_PERF_REGS
  250. select HAVE_PERF_USER_STACK_DUMP
  251. select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
  252. select MMU_GATHER_MERGE_VMAS
  253. select HAVE_POSIX_CPU_TIMERS_TASK_WORK
  254. select HAVE_REGS_AND_STACK_ACCESS_API
  255. select HAVE_RELIABLE_STACKTRACE if UNWINDER_ORC || STACK_VALIDATION
  256. select HAVE_FUNCTION_ARG_ACCESS_API
  257. select HAVE_SETUP_PER_CPU_AREA
  258. select HAVE_SOFTIRQ_ON_OWN_STACK
  259. select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
  260. select HAVE_STACK_VALIDATION if HAVE_OBJTOOL
  261. select HAVE_STATIC_CALL
  262. select HAVE_STATIC_CALL_INLINE if HAVE_OBJTOOL
  263. select HAVE_PREEMPT_DYNAMIC_CALL
  264. select HAVE_RSEQ
  265. select HAVE_RUST if X86_64
  266. select HAVE_SYSCALL_TRACEPOINTS
  267. select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
  268. select HAVE_UNSTABLE_SCHED_CLOCK
  269. select HAVE_USER_RETURN_NOTIFIER
  270. select HAVE_GENERIC_VDSO
  271. select HOTPLUG_SMT if SMP
  272. select IRQ_FORCED_THREADING
  273. select LOCK_MM_AND_FIND_VMA
  274. select NEED_PER_CPU_EMBED_FIRST_CHUNK
  275. select NEED_PER_CPU_PAGE_FIRST_CHUNK
  276. select NEED_SG_DMA_LENGTH
  277. select PCI_DOMAINS if PCI
  278. select PCI_LOCKLESS_CONFIG if PCI
  279. select PERF_EVENTS
  280. select RTC_LIB
  281. select RTC_MC146818_LIB
  282. select SPARSE_IRQ
  283. select SRCU
  284. select SYSCTL_EXCEPTION_TRACE
  285. select THREAD_INFO_IN_TASK
  286. select TRACE_IRQFLAGS_SUPPORT
  287. select TRACE_IRQFLAGS_NMI_SUPPORT
  288. select USER_STACKTRACE_SUPPORT
  289. select HAVE_ARCH_KCSAN if X86_64
  290. select X86_FEATURE_NAMES if PROC_FS
  291. select PROC_PID_ARCH_STATUS if PROC_FS
  292. select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
  293. imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
  294. select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
  295. config INSTRUCTION_DECODER
  296. def_bool y
  297. depends on KPROBES || PERF_EVENTS || UPROBES
  298. config OUTPUT_FORMAT
  299. string
  300. default "elf32-i386" if X86_32
  301. default "elf64-x86-64" if X86_64
  302. config LOCKDEP_SUPPORT
  303. def_bool y
  304. config STACKTRACE_SUPPORT
  305. def_bool y
  306. config MMU
  307. def_bool y
  308. config ARCH_MMAP_RND_BITS_MIN
  309. default 28 if 64BIT
  310. default 8
  311. config ARCH_MMAP_RND_BITS_MAX
  312. default 32 if 64BIT
  313. default 16
  314. config ARCH_MMAP_RND_COMPAT_BITS_MIN
  315. default 8
  316. config ARCH_MMAP_RND_COMPAT_BITS_MAX
  317. default 16
  318. config SBUS
  319. bool
  320. config GENERIC_ISA_DMA
  321. def_bool y
  322. depends on ISA_DMA_API
  323. config GENERIC_CSUM
  324. bool
  325. default y if KMSAN || KASAN
  326. config GENERIC_BUG
  327. def_bool y
  328. depends on BUG
  329. select GENERIC_BUG_RELATIVE_POINTERS if X86_64
  330. config GENERIC_BUG_RELATIVE_POINTERS
  331. bool
  332. config ARCH_MAY_HAVE_PC_FDC
  333. def_bool y
  334. depends on ISA_DMA_API
  335. config GENERIC_CALIBRATE_DELAY
  336. def_bool y
  337. config ARCH_HAS_CPU_RELAX
  338. def_bool y
  339. config ARCH_HIBERNATION_POSSIBLE
  340. def_bool y
  341. config ARCH_NR_GPIO
  342. int
  343. default 1024 if X86_64
  344. default 512
  345. config ARCH_SUSPEND_POSSIBLE
  346. def_bool y
  347. config AUDIT_ARCH
  348. def_bool y if X86_64
  349. config KASAN_SHADOW_OFFSET
  350. hex
  351. depends on KASAN
  352. default 0xdffffc0000000000
  353. config HAVE_INTEL_TXT
  354. def_bool y
  355. depends on INTEL_IOMMU && ACPI
  356. config X86_32_SMP
  357. def_bool y
  358. depends on X86_32 && SMP
  359. config X86_64_SMP
  360. def_bool y
  361. depends on X86_64 && SMP
  362. config ARCH_SUPPORTS_UPROBES
  363. def_bool y
  364. config FIX_EARLYCON_MEM
  365. def_bool y
  366. config DYNAMIC_PHYSICAL_MASK
  367. bool
  368. config PGTABLE_LEVELS
  369. int
  370. default 5 if X86_5LEVEL
  371. default 4 if X86_64
  372. default 3 if X86_PAE
  373. default 2
  374. config CC_HAS_SANE_STACKPROTECTOR
  375. bool
  376. default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) $(CLANG_FLAGS)) if 64BIT
  377. default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC) $(CLANG_FLAGS))
  378. help
  379. We have to make sure stack protector is unconditionally disabled if
  380. the compiler produces broken code or if it does not let us control
  381. the segment on 32-bit kernels.
  382. menu "Processor type and features"
  383. config SMP
  384. bool "Symmetric multi-processing support"
  385. help
  386. This enables support for systems with more than one CPU. If you have
  387. a system with only one CPU, say N. If you have a system with more
  388. than one CPU, say Y.
  389. If you say N here, the kernel will run on uni- and multiprocessor
  390. machines, but will use only one CPU of a multiprocessor machine. If
  391. you say Y here, the kernel will run on many, but not all,
  392. uniprocessor machines. On a uniprocessor machine, the kernel
  393. will run faster if you say N here.
  394. Note that if you say Y here and choose architecture "586" or
  395. "Pentium" under "Processor family", the kernel will not work on 486
  396. architectures. Similarly, multiprocessor kernels for the "PPro"
  397. architecture may not work on all Pentium based boards.
  398. People using multiprocessor machines who say Y here should also say
  399. Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
  400. Management" code will be disabled if you say Y here.
  401. See also <file:Documentation/x86/i386/IO-APIC.rst>,
  402. <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
  403. <http://www.tldp.org/docs.html#howto>.
  404. If you don't know what to do here, say N.
  405. config X86_FEATURE_NAMES
  406. bool "Processor feature human-readable names" if EMBEDDED
  407. default y
  408. help
  409. This option compiles in a table of x86 feature bits and corresponding
  410. names. This is required to support /proc/cpuinfo and a few kernel
  411. messages. You can disable this to save space, at the expense of
  412. making those few kernel messages show numeric feature bits instead.
  413. If in doubt, say Y.
  414. config X86_X2APIC
  415. bool "Support x2apic"
  416. depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
  417. help
  418. This enables x2apic support on CPUs that have this feature.
  419. This allows 32-bit apic IDs (so it can support very large systems),
  420. and accesses the local apic via MSRs not via mmio.
  421. Some Intel systems circa 2022 and later are locked into x2APIC mode
  422. and can not fall back to the legacy APIC modes if SGX or TDX are
  423. enabled in the BIOS. They will boot with very reduced functionality
  424. without enabling this option.
  425. If you don't know what to do here, say N.
  426. config X86_MPPARSE
  427. bool "Enable MPS table" if ACPI
  428. default y
  429. depends on X86_LOCAL_APIC
  430. help
  431. For old smp systems that do not have proper acpi support. Newer systems
  432. (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
  433. config GOLDFISH
  434. def_bool y
  435. depends on X86_GOLDFISH
  436. config X86_CPU_RESCTRL
  437. bool "x86 CPU resource control support"
  438. depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
  439. select KERNFS
  440. select PROC_CPU_RESCTRL if PROC_FS
  441. help
  442. Enable x86 CPU resource control support.
  443. Provide support for the allocation and monitoring of system resources
  444. usage by the CPU.
  445. Intel calls this Intel Resource Director Technology
  446. (Intel(R) RDT). More information about RDT can be found in the
  447. Intel x86 Architecture Software Developer Manual.
  448. AMD calls this AMD Platform Quality of Service (AMD QoS).
  449. More information about AMD QoS can be found in the AMD64 Technology
  450. Platform Quality of Service Extensions manual.
  451. Say N if unsure.
  452. if X86_32
  453. config X86_BIGSMP
  454. bool "Support for big SMP systems with more than 8 CPUs"
  455. depends on SMP
  456. help
  457. This option is needed for the systems that have more than 8 CPUs.
  458. config X86_EXTENDED_PLATFORM
  459. bool "Support for extended (non-PC) x86 platforms"
  460. default y
  461. help
  462. If you disable this option then the kernel will only support
  463. standard PC platforms. (which covers the vast majority of
  464. systems out there.)
  465. If you enable this option then you'll be able to select support
  466. for the following (non-PC) 32 bit x86 platforms:
  467. Goldfish (Android emulator)
  468. AMD Elan
  469. RDC R-321x SoC
  470. SGI 320/540 (Visual Workstation)
  471. STA2X11-based (e.g. Northville)
  472. Moorestown MID devices
  473. If you have one of these systems, or if you want to build a
  474. generic distribution kernel, say Y here - otherwise say N.
  475. endif # X86_32
  476. if X86_64
  477. config X86_EXTENDED_PLATFORM
  478. bool "Support for extended (non-PC) x86 platforms"
  479. default y
  480. help
  481. If you disable this option then the kernel will only support
  482. standard PC platforms. (which covers the vast majority of
  483. systems out there.)
  484. If you enable this option then you'll be able to select support
  485. for the following (non-PC) 64 bit x86 platforms:
  486. Numascale NumaChip
  487. ScaleMP vSMP
  488. SGI Ultraviolet
  489. If you have one of these systems, or if you want to build a
  490. generic distribution kernel, say Y here - otherwise say N.
  491. endif # X86_64
  492. # This is an alphabetically sorted list of 64 bit extended platforms
  493. # Please maintain the alphabetic order if and when there are additions
  494. config X86_NUMACHIP
  495. bool "Numascale NumaChip"
  496. depends on X86_64
  497. depends on X86_EXTENDED_PLATFORM
  498. depends on NUMA
  499. depends on SMP
  500. depends on X86_X2APIC
  501. depends on PCI_MMCONFIG
  502. help
  503. Adds support for Numascale NumaChip large-SMP systems. Needed to
  504. enable more than ~168 cores.
  505. If you don't have one of these, you should say N here.
  506. config X86_VSMP
  507. bool "ScaleMP vSMP"
  508. select HYPERVISOR_GUEST
  509. select PARAVIRT
  510. depends on X86_64 && PCI
  511. depends on X86_EXTENDED_PLATFORM
  512. depends on SMP
  513. help
  514. Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
  515. supposed to run on these EM64T-based machines. Only choose this option
  516. if you have one of these machines.
  517. config X86_UV
  518. bool "SGI Ultraviolet"
  519. depends on X86_64
  520. depends on X86_EXTENDED_PLATFORM
  521. depends on NUMA
  522. depends on EFI
  523. depends on KEXEC_CORE
  524. depends on X86_X2APIC
  525. depends on PCI
  526. help
  527. This option is needed in order to support SGI Ultraviolet systems.
  528. If you don't have one of these, you should say N here.
  529. # Following is an alphabetically sorted list of 32 bit extended platforms
  530. # Please maintain the alphabetic order if and when there are additions
  531. config X86_GOLDFISH
  532. bool "Goldfish (Virtual Platform)"
  533. depends on X86_EXTENDED_PLATFORM
  534. help
  535. Enable support for the Goldfish virtual platform used primarily
  536. for Android development. Unless you are building for the Android
  537. Goldfish emulator say N here.
  538. config X86_INTEL_CE
  539. bool "CE4100 TV platform"
  540. depends on PCI
  541. depends on PCI_GODIRECT
  542. depends on X86_IO_APIC
  543. depends on X86_32
  544. depends on X86_EXTENDED_PLATFORM
  545. select X86_REBOOTFIXUPS
  546. select OF
  547. select OF_EARLY_FLATTREE
  548. help
  549. Select for the Intel CE media processor (CE4100) SOC.
  550. This option compiles in support for the CE4100 SOC for settop
  551. boxes and media devices.
  552. config X86_INTEL_MID
  553. bool "Intel MID platform support"
  554. depends on X86_EXTENDED_PLATFORM
  555. depends on X86_PLATFORM_DEVICES
  556. depends on PCI
  557. depends on X86_64 || (PCI_GOANY && X86_32)
  558. depends on X86_IO_APIC
  559. select I2C
  560. select DW_APB_TIMER
  561. select INTEL_SCU_PCI
  562. help
  563. Select to build a kernel capable of supporting Intel MID (Mobile
  564. Internet Device) platform systems which do not have the PCI legacy
  565. interfaces. If you are building for a PC class system say N here.
  566. Intel MID platforms are based on an Intel processor and chipset which
  567. consume less power than most of the x86 derivatives.
  568. config X86_INTEL_QUARK
  569. bool "Intel Quark platform support"
  570. depends on X86_32
  571. depends on X86_EXTENDED_PLATFORM
  572. depends on X86_PLATFORM_DEVICES
  573. depends on X86_TSC
  574. depends on PCI
  575. depends on PCI_GOANY
  576. depends on X86_IO_APIC
  577. select IOSF_MBI
  578. select INTEL_IMR
  579. select COMMON_CLK
  580. help
  581. Select to include support for Quark X1000 SoC.
  582. Say Y here if you have a Quark based system such as the Arduino
  583. compatible Intel Galileo.
  584. config X86_INTEL_LPSS
  585. bool "Intel Low Power Subsystem Support"
  586. depends on X86 && ACPI && PCI
  587. select COMMON_CLK
  588. select PINCTRL
  589. select IOSF_MBI
  590. help
  591. Select to build support for Intel Low Power Subsystem such as
  592. found on Intel Lynxpoint PCH. Selecting this option enables
  593. things like clock tree (common clock framework) and pincontrol
  594. which are needed by the LPSS peripheral drivers.
  595. config X86_AMD_PLATFORM_DEVICE
  596. bool "AMD ACPI2Platform devices support"
  597. depends on ACPI
  598. select COMMON_CLK
  599. select PINCTRL
  600. help
  601. Select to interpret AMD specific ACPI device to platform device
  602. such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
  603. I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
  604. implemented under PINCTRL subsystem.
  605. config IOSF_MBI
  606. tristate "Intel SoC IOSF Sideband support for SoC platforms"
  607. depends on PCI
  608. help
  609. This option enables sideband register access support for Intel SoC
  610. platforms. On these platforms the IOSF sideband is used in lieu of
  611. MSR's for some register accesses, mostly but not limited to thermal
  612. and power. Drivers may query the availability of this device to
  613. determine if they need the sideband in order to work on these
  614. platforms. The sideband is available on the following SoC products.
  615. This list is not meant to be exclusive.
  616. - BayTrail
  617. - Braswell
  618. - Quark
  619. You should say Y if you are running a kernel on one of these SoC's.
  620. config IOSF_MBI_DEBUG
  621. bool "Enable IOSF sideband access through debugfs"
  622. depends on IOSF_MBI && DEBUG_FS
  623. help
  624. Select this option to expose the IOSF sideband access registers (MCR,
  625. MDR, MCRX) through debugfs to write and read register information from
  626. different units on the SoC. This is most useful for obtaining device
  627. state information for debug and analysis. As this is a general access
  628. mechanism, users of this option would have specific knowledge of the
  629. device they want to access.
  630. If you don't require the option or are in doubt, say N.
  631. config X86_RDC321X
  632. bool "RDC R-321x SoC"
  633. depends on X86_32
  634. depends on X86_EXTENDED_PLATFORM
  635. select M486
  636. select X86_REBOOTFIXUPS
  637. help
  638. This option is needed for RDC R-321x system-on-chip, also known
  639. as R-8610-(G).
  640. If you don't have one of these chips, you should say N here.
  641. config X86_32_NON_STANDARD
  642. bool "Support non-standard 32-bit SMP architectures"
  643. depends on X86_32 && SMP
  644. depends on X86_EXTENDED_PLATFORM
  645. help
  646. This option compiles in the bigsmp and STA2X11 default
  647. subarchitectures. It is intended for a generic binary
  648. kernel. If you select them all, kernel will probe it one by
  649. one and will fallback to default.
  650. # Alphabetically sorted list of Non standard 32 bit platforms
  651. config X86_SUPPORTS_MEMORY_FAILURE
  652. def_bool y
  653. # MCE code calls memory_failure():
  654. depends on X86_MCE
  655. # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
  656. # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
  657. depends on X86_64 || !SPARSEMEM
  658. select ARCH_SUPPORTS_MEMORY_FAILURE
  659. config STA2X11
  660. bool "STA2X11 Companion Chip Support"
  661. depends on X86_32_NON_STANDARD && PCI
  662. select SWIOTLB
  663. select MFD_STA2X11
  664. select GPIOLIB
  665. help
  666. This adds support for boards based on the STA2X11 IO-Hub,
  667. a.k.a. "ConneXt". The chip is used in place of the standard
  668. PC chipset, so all "standard" peripherals are missing. If this
  669. option is selected the kernel will still be able to boot on
  670. standard PC machines.
  671. config X86_32_IRIS
  672. tristate "Eurobraille/Iris poweroff module"
  673. depends on X86_32
  674. help
  675. The Iris machines from EuroBraille do not have APM or ACPI support
  676. to shut themselves down properly. A special I/O sequence is
  677. needed to do so, which is what this module does at
  678. kernel shutdown.
  679. This is only for Iris machines from EuroBraille.
  680. If unused, say N.
  681. config SCHED_OMIT_FRAME_POINTER
  682. def_bool y
  683. prompt "Single-depth WCHAN output"
  684. depends on X86
  685. help
  686. Calculate simpler /proc/<PID>/wchan values. If this option
  687. is disabled then wchan values will recurse back to the
  688. caller function. This provides more accurate wchan values,
  689. at the expense of slightly more scheduling overhead.
  690. If in doubt, say "Y".
  691. menuconfig HYPERVISOR_GUEST
  692. bool "Linux guest support"
  693. help
  694. Say Y here to enable options for running Linux under various hyper-
  695. visors. This option enables basic hypervisor detection and platform
  696. setup.
  697. If you say N, all options in this submenu will be skipped and
  698. disabled, and Linux guest support won't be built in.
  699. if HYPERVISOR_GUEST
  700. config PARAVIRT
  701. bool "Enable paravirtualization code"
  702. depends on HAVE_STATIC_CALL
  703. help
  704. This changes the kernel so it can modify itself when it is run
  705. under a hypervisor, potentially improving performance significantly
  706. over full virtualization. However, when run without a hypervisor
  707. the kernel is theoretically slower and slightly larger.
  708. config PARAVIRT_XXL
  709. bool
  710. config PARAVIRT_DEBUG
  711. bool "paravirt-ops debugging"
  712. depends on PARAVIRT && DEBUG_KERNEL
  713. help
  714. Enable to debug paravirt_ops internals. Specifically, BUG if
  715. a paravirt_op is missing when it is called.
  716. config PARAVIRT_SPINLOCKS
  717. bool "Paravirtualization layer for spinlocks"
  718. depends on PARAVIRT && SMP
  719. help
  720. Paravirtualized spinlocks allow a pvops backend to replace the
  721. spinlock implementation with something virtualization-friendly
  722. (for example, block the virtual CPU rather than spinning).
  723. It has a minimal impact on native kernels and gives a nice performance
  724. benefit on paravirtualized KVM / Xen kernels.
  725. If you are unsure how to answer this question, answer Y.
  726. config X86_HV_CALLBACK_VECTOR
  727. def_bool n
  728. source "arch/x86/xen/Kconfig"
  729. config KVM_GUEST
  730. bool "KVM Guest support (including kvmclock)"
  731. depends on PARAVIRT
  732. select PARAVIRT_CLOCK
  733. select ARCH_CPUIDLE_HALTPOLL
  734. select X86_HV_CALLBACK_VECTOR
  735. default y
  736. help
  737. This option enables various optimizations for running under the KVM
  738. hypervisor. It includes a paravirtualized clock, so that instead
  739. of relying on a PIT (or probably other) emulation by the
  740. underlying device model, the host provides the guest with
  741. timing infrastructure such as time of day, and system time
  742. config ARCH_CPUIDLE_HALTPOLL
  743. def_bool n
  744. prompt "Disable host haltpoll when loading haltpoll driver"
  745. help
  746. If virtualized under KVM, disable host haltpoll.
  747. config PVH
  748. bool "Support for running PVH guests"
  749. help
  750. This option enables the PVH entry point for guest virtual machines
  751. as specified in the x86/HVM direct boot ABI.
  752. config PARAVIRT_TIME_ACCOUNTING
  753. bool "Paravirtual steal time accounting"
  754. depends on PARAVIRT
  755. help
  756. Select this option to enable fine granularity task steal time
  757. accounting. Time spent executing other tasks in parallel with
  758. the current vCPU is discounted from the vCPU power. To account for
  759. that, there can be a small performance impact.
  760. If in doubt, say N here.
  761. config PARAVIRT_CLOCK
  762. bool
  763. config JAILHOUSE_GUEST
  764. bool "Jailhouse non-root cell support"
  765. depends on X86_64 && PCI
  766. select X86_PM_TIMER
  767. help
  768. This option allows to run Linux as guest in a Jailhouse non-root
  769. cell. You can leave this option disabled if you only want to start
  770. Jailhouse and run Linux afterwards in the root cell.
  771. config ACRN_GUEST
  772. bool "ACRN Guest support"
  773. depends on X86_64
  774. select X86_HV_CALLBACK_VECTOR
  775. help
  776. This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
  777. a flexible, lightweight reference open-source hypervisor, built with
  778. real-time and safety-criticality in mind. It is built for embedded
  779. IOT with small footprint and real-time features. More details can be
  780. found in https://projectacrn.org/.
  781. config INTEL_TDX_GUEST
  782. bool "Intel TDX (Trust Domain Extensions) - Guest Support"
  783. depends on X86_64 && CPU_SUP_INTEL
  784. depends on X86_X2APIC
  785. select ARCH_HAS_CC_PLATFORM
  786. select X86_MEM_ENCRYPT
  787. select X86_MCE
  788. help
  789. Support running as a guest under Intel TDX. Without this support,
  790. the guest kernel can not boot or run under TDX.
  791. TDX includes memory encryption and integrity capabilities
  792. which protect the confidentiality and integrity of guest
  793. memory contents and CPU state. TDX guests are protected from
  794. some attacks from the VMM.
  795. endif # HYPERVISOR_GUEST
  796. source "arch/x86/Kconfig.cpu"
  797. config HPET_TIMER
  798. def_bool X86_64
  799. prompt "HPET Timer Support" if X86_32
  800. help
  801. Use the IA-PC HPET (High Precision Event Timer) to manage
  802. time in preference to the PIT and RTC, if a HPET is
  803. present.
  804. HPET is the next generation timer replacing legacy 8254s.
  805. The HPET provides a stable time base on SMP
  806. systems, unlike the TSC, but it is more expensive to access,
  807. as it is off-chip. The interface used is documented
  808. in the HPET spec, revision 1.
  809. You can safely choose Y here. However, HPET will only be
  810. activated if the platform and the BIOS support this feature.
  811. Otherwise the 8254 will be used for timing services.
  812. Choose N to continue using the legacy 8254 timer.
  813. config HPET_EMULATE_RTC
  814. def_bool y
  815. depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
  816. # Mark as expert because too many people got it wrong.
  817. # The code disables itself when not needed.
  818. config DMI
  819. default y
  820. select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
  821. bool "Enable DMI scanning" if EXPERT
  822. help
  823. Enabled scanning of DMI to identify machine quirks. Say Y
  824. here unless you have verified that your setup is not
  825. affected by entries in the DMI blacklist. Required by PNP
  826. BIOS code.
  827. config GART_IOMMU
  828. bool "Old AMD GART IOMMU support"
  829. select DMA_OPS
  830. select IOMMU_HELPER
  831. select SWIOTLB
  832. depends on X86_64 && PCI && AMD_NB
  833. help
  834. Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
  835. GART based hardware IOMMUs.
  836. The GART supports full DMA access for devices with 32-bit access
  837. limitations, on systems with more than 3 GB. This is usually needed
  838. for USB, sound, many IDE/SATA chipsets and some other devices.
  839. Newer systems typically have a modern AMD IOMMU, supported via
  840. the CONFIG_AMD_IOMMU=y config option.
  841. In normal configurations this driver is only active when needed:
  842. there's more than 3 GB of memory and the system contains a
  843. 32-bit limited device.
  844. If unsure, say Y.
  845. config BOOT_VESA_SUPPORT
  846. bool
  847. help
  848. If true, at least one selected framebuffer driver can take advantage
  849. of VESA video modes set at an early boot stage via the vga= parameter.
  850. config MAXSMP
  851. bool "Enable Maximum number of SMP Processors and NUMA Nodes"
  852. depends on X86_64 && SMP && DEBUG_KERNEL
  853. select CPUMASK_OFFSTACK
  854. help
  855. Enable maximum number of CPUS and NUMA Nodes for this architecture.
  856. If unsure, say N.
  857. #
  858. # The maximum number of CPUs supported:
  859. #
  860. # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
  861. # and which can be configured interactively in the
  862. # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
  863. #
  864. # The ranges are different on 32-bit and 64-bit kernels, depending on
  865. # hardware capabilities and scalability features of the kernel.
  866. #
  867. # ( If MAXSMP is enabled we just use the highest possible value and disable
  868. # interactive configuration. )
  869. #
  870. config NR_CPUS_RANGE_BEGIN
  871. int
  872. default NR_CPUS_RANGE_END if MAXSMP
  873. default 1 if !SMP
  874. default 2
  875. config NR_CPUS_RANGE_END
  876. int
  877. depends on X86_32
  878. default 64 if SMP && X86_BIGSMP
  879. default 8 if SMP && !X86_BIGSMP
  880. default 1 if !SMP
  881. config NR_CPUS_RANGE_END
  882. int
  883. depends on X86_64
  884. default 8192 if SMP && CPUMASK_OFFSTACK
  885. default 512 if SMP && !CPUMASK_OFFSTACK
  886. default 1 if !SMP
  887. config NR_CPUS_DEFAULT
  888. int
  889. depends on X86_32
  890. default 32 if X86_BIGSMP
  891. default 8 if SMP
  892. default 1 if !SMP
  893. config NR_CPUS_DEFAULT
  894. int
  895. depends on X86_64
  896. default 8192 if MAXSMP
  897. default 64 if SMP
  898. default 1 if !SMP
  899. config NR_CPUS
  900. int "Maximum number of CPUs" if SMP && !MAXSMP
  901. range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
  902. default NR_CPUS_DEFAULT
  903. help
  904. This allows you to specify the maximum number of CPUs which this
  905. kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
  906. supported value is 8192, otherwise the maximum value is 512. The
  907. minimum value which makes sense is 2.
  908. This is purely to save memory: each supported CPU adds about 8KB
  909. to the kernel image.
  910. config SCHED_CLUSTER
  911. bool "Cluster scheduler support"
  912. depends on SMP
  913. default y
  914. help
  915. Cluster scheduler support improves the CPU scheduler's decision
  916. making when dealing with machines that have clusters of CPUs.
  917. Cluster usually means a couple of CPUs which are placed closely
  918. by sharing mid-level caches, last-level cache tags or internal
  919. busses.
  920. config SCHED_SMT
  921. def_bool y if SMP
  922. config SCHED_MC
  923. def_bool y
  924. prompt "Multi-core scheduler support"
  925. depends on SMP
  926. help
  927. Multi-core scheduler support improves the CPU scheduler's decision
  928. making when dealing with multi-core CPU chips at a cost of slightly
  929. increased overhead in some places. If unsure say N here.
  930. config SCHED_MC_PRIO
  931. bool "CPU core priorities scheduler support"
  932. depends on SCHED_MC && CPU_SUP_INTEL
  933. select X86_INTEL_PSTATE
  934. select CPU_FREQ
  935. default y
  936. help
  937. Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
  938. core ordering determined at manufacturing time, which allows
  939. certain cores to reach higher turbo frequencies (when running
  940. single threaded workloads) than others.
  941. Enabling this kernel feature teaches the scheduler about
  942. the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
  943. scheduler's CPU selection logic accordingly, so that higher
  944. overall system performance can be achieved.
  945. This feature will have no effect on CPUs without this feature.
  946. If unsure say Y here.
  947. config UP_LATE_INIT
  948. def_bool y
  949. depends on !SMP && X86_LOCAL_APIC
  950. config X86_UP_APIC
  951. bool "Local APIC support on uniprocessors" if !PCI_MSI
  952. default PCI_MSI
  953. depends on X86_32 && !SMP && !X86_32_NON_STANDARD
  954. help
  955. A local APIC (Advanced Programmable Interrupt Controller) is an
  956. integrated interrupt controller in the CPU. If you have a single-CPU
  957. system which has a processor with a local APIC, you can say Y here to
  958. enable and use it. If you say Y here even though your machine doesn't
  959. have a local APIC, then the kernel will still run with no slowdown at
  960. all. The local APIC supports CPU-generated self-interrupts (timer,
  961. performance counters), and the NMI watchdog which detects hard
  962. lockups.
  963. config X86_UP_IOAPIC
  964. bool "IO-APIC support on uniprocessors"
  965. depends on X86_UP_APIC
  966. help
  967. An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
  968. SMP-capable replacement for PC-style interrupt controllers. Most
  969. SMP systems and many recent uniprocessor systems have one.
  970. If you have a single-CPU system with an IO-APIC, you can say Y here
  971. to use it. If you say Y here even though your machine doesn't have
  972. an IO-APIC, then the kernel will still run with no slowdown at all.
  973. config X86_LOCAL_APIC
  974. def_bool y
  975. depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
  976. select IRQ_DOMAIN_HIERARCHY
  977. select PCI_MSI_IRQ_DOMAIN if PCI_MSI
  978. config X86_IO_APIC
  979. def_bool y
  980. depends on X86_LOCAL_APIC || X86_UP_IOAPIC
  981. config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
  982. bool "Reroute for broken boot IRQs"
  983. depends on X86_IO_APIC
  984. help
  985. This option enables a workaround that fixes a source of
  986. spurious interrupts. This is recommended when threaded
  987. interrupt handling is used on systems where the generation of
  988. superfluous "boot interrupts" cannot be disabled.
  989. Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
  990. entry in the chipset's IO-APIC is masked (as, e.g. the RT
  991. kernel does during interrupt handling). On chipsets where this
  992. boot IRQ generation cannot be disabled, this workaround keeps
  993. the original IRQ line masked so that only the equivalent "boot
  994. IRQ" is delivered to the CPUs. The workaround also tells the
  995. kernel to set up the IRQ handler on the boot IRQ line. In this
  996. way only one interrupt is delivered to the kernel. Otherwise
  997. the spurious second interrupt may cause the kernel to bring
  998. down (vital) interrupt lines.
  999. Only affects "broken" chipsets. Interrupt sharing may be
  1000. increased on these systems.
  1001. config X86_MCE
  1002. bool "Machine Check / overheating reporting"
  1003. select GENERIC_ALLOCATOR
  1004. default y
  1005. help
  1006. Machine Check support allows the processor to notify the
  1007. kernel if it detects a problem (e.g. overheating, data corruption).
  1008. The action the kernel takes depends on the severity of the problem,
  1009. ranging from warning messages to halting the machine.
  1010. config X86_MCELOG_LEGACY
  1011. bool "Support for deprecated /dev/mcelog character device"
  1012. depends on X86_MCE
  1013. help
  1014. Enable support for /dev/mcelog which is needed by the old mcelog
  1015. userspace logging daemon. Consider switching to the new generation
  1016. rasdaemon solution.
  1017. config X86_MCE_INTEL
  1018. def_bool y
  1019. prompt "Intel MCE features"
  1020. depends on X86_MCE && X86_LOCAL_APIC
  1021. help
  1022. Additional support for intel specific MCE features such as
  1023. the thermal monitor.
  1024. config X86_MCE_AMD
  1025. def_bool y
  1026. prompt "AMD MCE features"
  1027. depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
  1028. help
  1029. Additional support for AMD specific MCE features such as
  1030. the DRAM Error Threshold.
  1031. config X86_ANCIENT_MCE
  1032. bool "Support for old Pentium 5 / WinChip machine checks"
  1033. depends on X86_32 && X86_MCE
  1034. help
  1035. Include support for machine check handling on old Pentium 5 or WinChip
  1036. systems. These typically need to be enabled explicitly on the command
  1037. line.
  1038. config X86_MCE_THRESHOLD
  1039. depends on X86_MCE_AMD || X86_MCE_INTEL
  1040. def_bool y
  1041. config X86_MCE_INJECT
  1042. depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
  1043. tristate "Machine check injector support"
  1044. help
  1045. Provide support for injecting machine checks for testing purposes.
  1046. If you don't know what a machine check is and you don't do kernel
  1047. QA it is safe to say n.
  1048. source "arch/x86/events/Kconfig"
  1049. config X86_LEGACY_VM86
  1050. bool "Legacy VM86 support"
  1051. depends on X86_32
  1052. help
  1053. This option allows user programs to put the CPU into V8086
  1054. mode, which is an 80286-era approximation of 16-bit real mode.
  1055. Some very old versions of X and/or vbetool require this option
  1056. for user mode setting. Similarly, DOSEMU will use it if
  1057. available to accelerate real mode DOS programs. However, any
  1058. recent version of DOSEMU, X, or vbetool should be fully
  1059. functional even without kernel VM86 support, as they will all
  1060. fall back to software emulation. Nevertheless, if you are using
  1061. a 16-bit DOS program where 16-bit performance matters, vm86
  1062. mode might be faster than emulation and you might want to
  1063. enable this option.
  1064. Note that any app that works on a 64-bit kernel is unlikely to
  1065. need this option, as 64-bit kernels don't, and can't, support
  1066. V8086 mode. This option is also unrelated to 16-bit protected
  1067. mode and is not needed to run most 16-bit programs under Wine.
  1068. Enabling this option increases the complexity of the kernel
  1069. and slows down exception handling a tiny bit.
  1070. If unsure, say N here.
  1071. config VM86
  1072. bool
  1073. default X86_LEGACY_VM86
  1074. config X86_16BIT
  1075. bool "Enable support for 16-bit segments" if EXPERT
  1076. default y
  1077. depends on MODIFY_LDT_SYSCALL
  1078. help
  1079. This option is required by programs like Wine to run 16-bit
  1080. protected mode legacy code on x86 processors. Disabling
  1081. this option saves about 300 bytes on i386, or around 6K text
  1082. plus 16K runtime memory on x86-64,
  1083. config X86_ESPFIX32
  1084. def_bool y
  1085. depends on X86_16BIT && X86_32
  1086. config X86_ESPFIX64
  1087. def_bool y
  1088. depends on X86_16BIT && X86_64
  1089. config X86_VSYSCALL_EMULATION
  1090. bool "Enable vsyscall emulation" if EXPERT
  1091. default y
  1092. depends on X86_64
  1093. help
  1094. This enables emulation of the legacy vsyscall page. Disabling
  1095. it is roughly equivalent to booting with vsyscall=none, except
  1096. that it will also disable the helpful warning if a program
  1097. tries to use a vsyscall. With this option set to N, offending
  1098. programs will just segfault, citing addresses of the form
  1099. 0xffffffffff600?00.
  1100. This option is required by many programs built before 2013, and
  1101. care should be used even with newer programs if set to N.
  1102. Disabling this option saves about 7K of kernel size and
  1103. possibly 4K of additional runtime pagetable memory.
  1104. config X86_IOPL_IOPERM
  1105. bool "IOPERM and IOPL Emulation"
  1106. default y
  1107. help
  1108. This enables the ioperm() and iopl() syscalls which are necessary
  1109. for legacy applications.
  1110. Legacy IOPL support is an overbroad mechanism which allows user
  1111. space aside of accessing all 65536 I/O ports also to disable
  1112. interrupts. To gain this access the caller needs CAP_SYS_RAWIO
  1113. capabilities and permission from potentially active security
  1114. modules.
  1115. The emulation restricts the functionality of the syscall to
  1116. only allowing the full range I/O port access, but prevents the
  1117. ability to disable interrupts from user space which would be
  1118. granted if the hardware IOPL mechanism would be used.
  1119. config TOSHIBA
  1120. tristate "Toshiba Laptop support"
  1121. depends on X86_32
  1122. help
  1123. This adds a driver to safely access the System Management Mode of
  1124. the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
  1125. not work on models with a Phoenix BIOS. The System Management Mode
  1126. is used to set the BIOS and power saving options on Toshiba portables.
  1127. For information on utilities to make use of this driver see the
  1128. Toshiba Linux utilities web site at:
  1129. <http://www.buzzard.org.uk/toshiba/>.
  1130. Say Y if you intend to run this kernel on a Toshiba portable.
  1131. Say N otherwise.
  1132. config X86_REBOOTFIXUPS
  1133. bool "Enable X86 board specific fixups for reboot"
  1134. depends on X86_32
  1135. help
  1136. This enables chipset and/or board specific fixups to be done
  1137. in order to get reboot to work correctly. This is only needed on
  1138. some combinations of hardware and BIOS. The symptom, for which
  1139. this config is intended, is when reboot ends with a stalled/hung
  1140. system.
  1141. Currently, the only fixup is for the Geode machines using
  1142. CS5530A and CS5536 chipsets and the RDC R-321x SoC.
  1143. Say Y if you want to enable the fixup. Currently, it's safe to
  1144. enable this option even if you don't need it.
  1145. Say N otherwise.
  1146. config MICROCODE
  1147. bool "CPU microcode loading support"
  1148. default y
  1149. depends on CPU_SUP_AMD || CPU_SUP_INTEL
  1150. help
  1151. If you say Y here, you will be able to update the microcode on
  1152. Intel and AMD processors. The Intel support is for the IA32 family,
  1153. e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
  1154. AMD support is for families 0x10 and later. You will obviously need
  1155. the actual microcode binary data itself which is not shipped with
  1156. the Linux kernel.
  1157. The preferred method to load microcode from a detached initrd is described
  1158. in Documentation/x86/microcode.rst. For that you need to enable
  1159. CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
  1160. initrd for microcode blobs.
  1161. In addition, you can build the microcode into the kernel. For that you
  1162. need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
  1163. config option.
  1164. config MICROCODE_INTEL
  1165. bool "Intel microcode loading support"
  1166. depends on CPU_SUP_INTEL && MICROCODE
  1167. default MICROCODE
  1168. help
  1169. This options enables microcode patch loading support for Intel
  1170. processors.
  1171. For the current Intel microcode data package go to
  1172. <https://downloadcenter.intel.com> and search for
  1173. 'Linux Processor Microcode Data File'.
  1174. config MICROCODE_AMD
  1175. bool "AMD microcode loading support"
  1176. depends on CPU_SUP_AMD && MICROCODE
  1177. help
  1178. If you select this option, microcode patch loading support for AMD
  1179. processors will be enabled.
  1180. config MICROCODE_LATE_LOADING
  1181. bool "Late microcode loading (DANGEROUS)"
  1182. default n
  1183. depends on MICROCODE
  1184. help
  1185. Loading microcode late, when the system is up and executing instructions
  1186. is a tricky business and should be avoided if possible. Just the sequence
  1187. of synchronizing all cores and SMT threads is one fragile dance which does
  1188. not guarantee that cores might not softlock after the loading. Therefore,
  1189. use this at your own risk. Late loading taints the kernel too.
  1190. config X86_MSR
  1191. tristate "/dev/cpu/*/msr - Model-specific register support"
  1192. help
  1193. This device gives privileged processes access to the x86
  1194. Model-Specific Registers (MSRs). It is a character device with
  1195. major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
  1196. MSR accesses are directed to a specific CPU on multi-processor
  1197. systems.
  1198. config X86_CPUID
  1199. tristate "/dev/cpu/*/cpuid - CPU information support"
  1200. help
  1201. This device gives processes access to the x86 CPUID instruction to
  1202. be executed on a specific processor. It is a character device
  1203. with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
  1204. /dev/cpu/31/cpuid.
  1205. choice
  1206. prompt "High Memory Support"
  1207. default HIGHMEM4G
  1208. depends on X86_32
  1209. config NOHIGHMEM
  1210. bool "off"
  1211. help
  1212. Linux can use up to 64 Gigabytes of physical memory on x86 systems.
  1213. However, the address space of 32-bit x86 processors is only 4
  1214. Gigabytes large. That means that, if you have a large amount of
  1215. physical memory, not all of it can be "permanently mapped" by the
  1216. kernel. The physical memory that's not permanently mapped is called
  1217. "high memory".
  1218. If you are compiling a kernel which will never run on a machine with
  1219. more than 1 Gigabyte total physical RAM, answer "off" here (default
  1220. choice and suitable for most users). This will result in a "3GB/1GB"
  1221. split: 3GB are mapped so that each process sees a 3GB virtual memory
  1222. space and the remaining part of the 4GB virtual memory space is used
  1223. by the kernel to permanently map as much physical memory as
  1224. possible.
  1225. If the machine has between 1 and 4 Gigabytes physical RAM, then
  1226. answer "4GB" here.
  1227. If more than 4 Gigabytes is used then answer "64GB" here. This
  1228. selection turns Intel PAE (Physical Address Extension) mode on.
  1229. PAE implements 3-level paging on IA32 processors. PAE is fully
  1230. supported by Linux, PAE mode is implemented on all recent Intel
  1231. processors (Pentium Pro and better). NOTE: If you say "64GB" here,
  1232. then the kernel will not boot on CPUs that don't support PAE!
  1233. The actual amount of total physical memory will either be
  1234. auto detected or can be forced by using a kernel command line option
  1235. such as "mem=256M". (Try "man bootparam" or see the documentation of
  1236. your boot loader (lilo or loadlin) about how to pass options to the
  1237. kernel at boot time.)
  1238. If unsure, say "off".
  1239. config HIGHMEM4G
  1240. bool "4GB"
  1241. help
  1242. Select this if you have a 32-bit processor and between 1 and 4
  1243. gigabytes of physical RAM.
  1244. config HIGHMEM64G
  1245. bool "64GB"
  1246. depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
  1247. select X86_PAE
  1248. help
  1249. Select this if you have a 32-bit processor and more than 4
  1250. gigabytes of physical RAM.
  1251. endchoice
  1252. choice
  1253. prompt "Memory split" if EXPERT
  1254. default VMSPLIT_3G
  1255. depends on X86_32
  1256. help
  1257. Select the desired split between kernel and user memory.
  1258. If the address range available to the kernel is less than the
  1259. physical memory installed, the remaining memory will be available
  1260. as "high memory". Accessing high memory is a little more costly
  1261. than low memory, as it needs to be mapped into the kernel first.
  1262. Note that increasing the kernel address space limits the range
  1263. available to user programs, making the address space there
  1264. tighter. Selecting anything other than the default 3G/1G split
  1265. will also likely make your kernel incompatible with binary-only
  1266. kernel modules.
  1267. If you are not absolutely sure what you are doing, leave this
  1268. option alone!
  1269. config VMSPLIT_3G
  1270. bool "3G/1G user/kernel split"
  1271. config VMSPLIT_3G_OPT
  1272. depends on !X86_PAE
  1273. bool "3G/1G user/kernel split (for full 1G low memory)"
  1274. config VMSPLIT_2G
  1275. bool "2G/2G user/kernel split"
  1276. config VMSPLIT_2G_OPT
  1277. depends on !X86_PAE
  1278. bool "2G/2G user/kernel split (for full 2G low memory)"
  1279. config VMSPLIT_1G
  1280. bool "1G/3G user/kernel split"
  1281. endchoice
  1282. config PAGE_OFFSET
  1283. hex
  1284. default 0xB0000000 if VMSPLIT_3G_OPT
  1285. default 0x80000000 if VMSPLIT_2G
  1286. default 0x78000000 if VMSPLIT_2G_OPT
  1287. default 0x40000000 if VMSPLIT_1G
  1288. default 0xC0000000
  1289. depends on X86_32
  1290. config HIGHMEM
  1291. def_bool y
  1292. depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
  1293. config X86_PAE
  1294. bool "PAE (Physical Address Extension) Support"
  1295. depends on X86_32 && !HIGHMEM4G
  1296. select PHYS_ADDR_T_64BIT
  1297. select SWIOTLB
  1298. help
  1299. PAE is required for NX support, and furthermore enables
  1300. larger swapspace support for non-overcommit purposes. It
  1301. has the cost of more pagetable lookup overhead, and also
  1302. consumes more pagetable space per process.
  1303. config X86_5LEVEL
  1304. bool "Enable 5-level page tables support"
  1305. default y
  1306. select DYNAMIC_MEMORY_LAYOUT
  1307. select SPARSEMEM_VMEMMAP
  1308. depends on X86_64
  1309. help
  1310. 5-level paging enables access to larger address space:
  1311. upto 128 PiB of virtual address space and 4 PiB of
  1312. physical address space.
  1313. It will be supported by future Intel CPUs.
  1314. A kernel with the option enabled can be booted on machines that
  1315. support 4- or 5-level paging.
  1316. See Documentation/x86/x86_64/5level-paging.rst for more
  1317. information.
  1318. Say N if unsure.
  1319. config X86_DIRECT_GBPAGES
  1320. def_bool y
  1321. depends on X86_64
  1322. help
  1323. Certain kernel features effectively disable kernel
  1324. linear 1 GB mappings (even if the CPU otherwise
  1325. supports them), so don't confuse the user by printing
  1326. that we have them enabled.
  1327. config X86_CPA_STATISTICS
  1328. bool "Enable statistic for Change Page Attribute"
  1329. depends on DEBUG_FS
  1330. help
  1331. Expose statistics about the Change Page Attribute mechanism, which
  1332. helps to determine the effectiveness of preserving large and huge
  1333. page mappings when mapping protections are changed.
  1334. config X86_MEM_ENCRYPT
  1335. select ARCH_HAS_FORCE_DMA_UNENCRYPTED
  1336. select DYNAMIC_PHYSICAL_MASK
  1337. def_bool n
  1338. config AMD_MEM_ENCRYPT
  1339. bool "AMD Secure Memory Encryption (SME) support"
  1340. depends on X86_64 && CPU_SUP_AMD
  1341. select DMA_COHERENT_POOL
  1342. select ARCH_USE_MEMREMAP_PROT
  1343. select INSTRUCTION_DECODER
  1344. select ARCH_HAS_CC_PLATFORM
  1345. select X86_MEM_ENCRYPT
  1346. help
  1347. Say yes to enable support for the encryption of system memory.
  1348. This requires an AMD processor that supports Secure Memory
  1349. Encryption (SME).
  1350. config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
  1351. bool "Activate AMD Secure Memory Encryption (SME) by default"
  1352. depends on AMD_MEM_ENCRYPT
  1353. help
  1354. Say yes to have system memory encrypted by default if running on
  1355. an AMD processor that supports Secure Memory Encryption (SME).
  1356. If set to Y, then the encryption of system memory can be
  1357. deactivated with the mem_encrypt=off command line option.
  1358. If set to N, then the encryption of system memory can be
  1359. activated with the mem_encrypt=on command line option.
  1360. # Common NUMA Features
  1361. config NUMA
  1362. bool "NUMA Memory Allocation and Scheduler Support"
  1363. depends on SMP
  1364. depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
  1365. default y if X86_BIGSMP
  1366. select USE_PERCPU_NUMA_NODE_ID
  1367. help
  1368. Enable NUMA (Non-Uniform Memory Access) support.
  1369. The kernel will try to allocate memory used by a CPU on the
  1370. local memory controller of the CPU and add some more
  1371. NUMA awareness to the kernel.
  1372. For 64-bit this is recommended if the system is Intel Core i7
  1373. (or later), AMD Opteron, or EM64T NUMA.
  1374. For 32-bit this is only needed if you boot a 32-bit
  1375. kernel on a 64-bit NUMA platform.
  1376. Otherwise, you should say N.
  1377. config AMD_NUMA
  1378. def_bool y
  1379. prompt "Old style AMD Opteron NUMA detection"
  1380. depends on X86_64 && NUMA && PCI
  1381. help
  1382. Enable AMD NUMA node topology detection. You should say Y here if
  1383. you have a multi processor AMD system. This uses an old method to
  1384. read the NUMA configuration directly from the builtin Northbridge
  1385. of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
  1386. which also takes priority if both are compiled in.
  1387. config X86_64_ACPI_NUMA
  1388. def_bool y
  1389. prompt "ACPI NUMA detection"
  1390. depends on X86_64 && NUMA && ACPI && PCI
  1391. select ACPI_NUMA
  1392. help
  1393. Enable ACPI SRAT based node topology detection.
  1394. config NUMA_EMU
  1395. bool "NUMA emulation"
  1396. depends on NUMA
  1397. help
  1398. Enable NUMA emulation. A flat machine will be split
  1399. into virtual nodes when booted with "numa=fake=N", where N is the
  1400. number of nodes. This is only useful for debugging.
  1401. config NODES_SHIFT
  1402. int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
  1403. range 1 10
  1404. default "10" if MAXSMP
  1405. default "6" if X86_64
  1406. default "3"
  1407. depends on NUMA
  1408. help
  1409. Specify the maximum number of NUMA Nodes available on the target
  1410. system. Increases memory reserved to accommodate various tables.
  1411. config ARCH_FLATMEM_ENABLE
  1412. def_bool y
  1413. depends on X86_32 && !NUMA
  1414. config ARCH_SPARSEMEM_ENABLE
  1415. def_bool y
  1416. depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
  1417. select SPARSEMEM_STATIC if X86_32
  1418. select SPARSEMEM_VMEMMAP_ENABLE if X86_64
  1419. config ARCH_SPARSEMEM_DEFAULT
  1420. def_bool X86_64 || (NUMA && X86_32)
  1421. config ARCH_SELECT_MEMORY_MODEL
  1422. def_bool y
  1423. depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE
  1424. config ARCH_MEMORY_PROBE
  1425. bool "Enable sysfs memory/probe interface"
  1426. depends on MEMORY_HOTPLUG
  1427. help
  1428. This option enables a sysfs memory/probe interface for testing.
  1429. See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
  1430. If you are unsure how to answer this question, answer N.
  1431. config ARCH_PROC_KCORE_TEXT
  1432. def_bool y
  1433. depends on X86_64 && PROC_KCORE
  1434. config ILLEGAL_POINTER_VALUE
  1435. hex
  1436. default 0 if X86_32
  1437. default 0xdead000000000000 if X86_64
  1438. config X86_PMEM_LEGACY_DEVICE
  1439. bool
  1440. config X86_PMEM_LEGACY
  1441. tristate "Support non-standard NVDIMMs and ADR protected memory"
  1442. depends on PHYS_ADDR_T_64BIT
  1443. depends on BLK_DEV
  1444. select X86_PMEM_LEGACY_DEVICE
  1445. select NUMA_KEEP_MEMINFO if NUMA
  1446. select LIBNVDIMM
  1447. help
  1448. Treat memory marked using the non-standard e820 type of 12 as used
  1449. by the Intel Sandy Bridge-EP reference BIOS as protected memory.
  1450. The kernel will offer these regions to the 'pmem' driver so
  1451. they can be used for persistent storage.
  1452. Say Y if unsure.
  1453. config HIGHPTE
  1454. bool "Allocate 3rd-level pagetables from highmem"
  1455. depends on HIGHMEM
  1456. help
  1457. The VM uses one page table entry for each page of physical memory.
  1458. For systems with a lot of RAM, this can be wasteful of precious
  1459. low memory. Setting this option will put user-space page table
  1460. entries in high memory.
  1461. config X86_CHECK_BIOS_CORRUPTION
  1462. bool "Check for low memory corruption"
  1463. help
  1464. Periodically check for memory corruption in low memory, which
  1465. is suspected to be caused by BIOS. Even when enabled in the
  1466. configuration, it is disabled at runtime. Enable it by
  1467. setting "memory_corruption_check=1" on the kernel command
  1468. line. By default it scans the low 64k of memory every 60
  1469. seconds; see the memory_corruption_check_size and
  1470. memory_corruption_check_period parameters in
  1471. Documentation/admin-guide/kernel-parameters.rst to adjust this.
  1472. When enabled with the default parameters, this option has
  1473. almost no overhead, as it reserves a relatively small amount
  1474. of memory and scans it infrequently. It both detects corruption
  1475. and prevents it from affecting the running system.
  1476. It is, however, intended as a diagnostic tool; if repeatable
  1477. BIOS-originated corruption always affects the same memory,
  1478. you can use memmap= to prevent the kernel from using that
  1479. memory.
  1480. config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
  1481. bool "Set the default setting of memory_corruption_check"
  1482. depends on X86_CHECK_BIOS_CORRUPTION
  1483. default y
  1484. help
  1485. Set whether the default state of memory_corruption_check is
  1486. on or off.
  1487. config MATH_EMULATION
  1488. bool
  1489. depends on MODIFY_LDT_SYSCALL
  1490. prompt "Math emulation" if X86_32 && (M486SX || MELAN)
  1491. help
  1492. Linux can emulate a math coprocessor (used for floating point
  1493. operations) if you don't have one. 486DX and Pentium processors have
  1494. a math coprocessor built in, 486SX and 386 do not, unless you added
  1495. a 487DX or 387, respectively. (The messages during boot time can
  1496. give you some hints here ["man dmesg"].) Everyone needs either a
  1497. coprocessor or this emulation.
  1498. If you don't have a math coprocessor, you need to say Y here; if you
  1499. say Y here even though you have a coprocessor, the coprocessor will
  1500. be used nevertheless. (This behavior can be changed with the kernel
  1501. command line option "no387", which comes handy if your coprocessor
  1502. is broken. Try "man bootparam" or see the documentation of your boot
  1503. loader (lilo or loadlin) about how to pass options to the kernel at
  1504. boot time.) This means that it is a good idea to say Y here if you
  1505. intend to use this kernel on different machines.
  1506. More information about the internals of the Linux math coprocessor
  1507. emulation can be found in <file:arch/x86/math-emu/README>.
  1508. If you are not sure, say Y; apart from resulting in a 66 KB bigger
  1509. kernel, it won't hurt.
  1510. config MTRR
  1511. def_bool y
  1512. prompt "MTRR (Memory Type Range Register) support" if EXPERT
  1513. help
  1514. On Intel P6 family processors (Pentium Pro, Pentium II and later)
  1515. the Memory Type Range Registers (MTRRs) may be used to control
  1516. processor access to memory ranges. This is most useful if you have
  1517. a video (VGA) card on a PCI or AGP bus. Enabling write-combining
  1518. allows bus write transfers to be combined into a larger transfer
  1519. before bursting over the PCI/AGP bus. This can increase performance
  1520. of image write operations 2.5 times or more. Saying Y here creates a
  1521. /proc/mtrr file which may be used to manipulate your processor's
  1522. MTRRs. Typically the X server should use this.
  1523. This code has a reasonably generic interface so that similar
  1524. control registers on other processors can be easily supported
  1525. as well:
  1526. The Cyrix 6x86, 6x86MX and M II processors have Address Range
  1527. Registers (ARRs) which provide a similar functionality to MTRRs. For
  1528. these, the ARRs are used to emulate the MTRRs.
  1529. The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
  1530. MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
  1531. write-combining. All of these processors are supported by this code
  1532. and it makes sense to say Y here if you have one of them.
  1533. Saying Y here also fixes a problem with buggy SMP BIOSes which only
  1534. set the MTRRs for the boot CPU and not for the secondary CPUs. This
  1535. can lead to all sorts of problems, so it's good to say Y here.
  1536. You can safely say Y even if your machine doesn't have MTRRs, you'll
  1537. just add about 9 KB to your kernel.
  1538. See <file:Documentation/x86/mtrr.rst> for more information.
  1539. config MTRR_SANITIZER
  1540. def_bool y
  1541. prompt "MTRR cleanup support"
  1542. depends on MTRR
  1543. help
  1544. Convert MTRR layout from continuous to discrete, so X drivers can
  1545. add writeback entries.
  1546. Can be disabled with disable_mtrr_cleanup on the kernel command line.
  1547. The largest mtrr entry size for a continuous block can be set with
  1548. mtrr_chunk_size.
  1549. If unsure, say Y.
  1550. config MTRR_SANITIZER_ENABLE_DEFAULT
  1551. int "MTRR cleanup enable value (0-1)"
  1552. range 0 1
  1553. default "0"
  1554. depends on MTRR_SANITIZER
  1555. help
  1556. Enable mtrr cleanup default value
  1557. config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
  1558. int "MTRR cleanup spare reg num (0-7)"
  1559. range 0 7
  1560. default "1"
  1561. depends on MTRR_SANITIZER
  1562. help
  1563. mtrr cleanup spare entries default, it can be changed via
  1564. mtrr_spare_reg_nr=N on the kernel command line.
  1565. config X86_PAT
  1566. def_bool y
  1567. prompt "x86 PAT support" if EXPERT
  1568. depends on MTRR
  1569. help
  1570. Use PAT attributes to setup page level cache control.
  1571. PATs are the modern equivalents of MTRRs and are much more
  1572. flexible than MTRRs.
  1573. Say N here if you see bootup problems (boot crash, boot hang,
  1574. spontaneous reboots) or a non-working video driver.
  1575. If unsure, say Y.
  1576. config ARCH_USES_PG_UNCACHED
  1577. def_bool y
  1578. depends on X86_PAT
  1579. config X86_UMIP
  1580. def_bool y
  1581. prompt "User Mode Instruction Prevention" if EXPERT
  1582. help
  1583. User Mode Instruction Prevention (UMIP) is a security feature in
  1584. some x86 processors. If enabled, a general protection fault is
  1585. issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
  1586. executed in user mode. These instructions unnecessarily expose
  1587. information about the hardware state.
  1588. The vast majority of applications do not use these instructions.
  1589. For the very few that do, software emulation is provided in
  1590. specific cases in protected and virtual-8086 modes. Emulated
  1591. results are dummy.
  1592. config CC_HAS_IBT
  1593. # GCC >= 9 and binutils >= 2.29
  1594. # Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
  1595. # Clang/LLVM >= 14
  1596. # https://github.com/llvm/llvm-project/commit/e0b89df2e0f0130881bf6c39bf31d7f6aac00e0f
  1597. # https://github.com/llvm/llvm-project/commit/dfcf69770bc522b9e411c66454934a37c1f35332
  1598. def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \
  1599. (CC_IS_CLANG && CLANG_VERSION >= 140000)) && \
  1600. $(as-instr,endbr64)
  1601. config X86_KERNEL_IBT
  1602. prompt "Indirect Branch Tracking"
  1603. bool
  1604. depends on X86_64 && CC_HAS_IBT && HAVE_OBJTOOL
  1605. # https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
  1606. depends on !LD_IS_LLD || LLD_VERSION >= 140000
  1607. select OBJTOOL
  1608. help
  1609. Build the kernel with support for Indirect Branch Tracking, a
  1610. hardware support course-grain forward-edge Control Flow Integrity
  1611. protection. It enforces that all indirect calls must land on
  1612. an ENDBR instruction, as such, the compiler will instrument the
  1613. code with them to make this happen.
  1614. In addition to building the kernel with IBT, seal all functions that
  1615. are not indirect call targets, avoiding them ever becoming one.
  1616. This requires LTO like objtool runs and will slow down the build. It
  1617. does significantly reduce the number of ENDBR instructions in the
  1618. kernel image.
  1619. config X86_INTEL_MEMORY_PROTECTION_KEYS
  1620. prompt "Memory Protection Keys"
  1621. def_bool y
  1622. # Note: only available in 64-bit mode
  1623. depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
  1624. select ARCH_USES_HIGH_VMA_FLAGS
  1625. select ARCH_HAS_PKEYS
  1626. help
  1627. Memory Protection Keys provides a mechanism for enforcing
  1628. page-based protections, but without requiring modification of the
  1629. page tables when an application changes protection domains.
  1630. For details, see Documentation/core-api/protection-keys.rst
  1631. If unsure, say y.
  1632. choice
  1633. prompt "TSX enable mode"
  1634. depends on CPU_SUP_INTEL
  1635. default X86_INTEL_TSX_MODE_OFF
  1636. help
  1637. Intel's TSX (Transactional Synchronization Extensions) feature
  1638. allows to optimize locking protocols through lock elision which
  1639. can lead to a noticeable performance boost.
  1640. On the other hand it has been shown that TSX can be exploited
  1641. to form side channel attacks (e.g. TAA) and chances are there
  1642. will be more of those attacks discovered in the future.
  1643. Therefore TSX is not enabled by default (aka tsx=off). An admin
  1644. might override this decision by tsx=on the command line parameter.
  1645. Even with TSX enabled, the kernel will attempt to enable the best
  1646. possible TAA mitigation setting depending on the microcode available
  1647. for the particular machine.
  1648. This option allows to set the default tsx mode between tsx=on, =off
  1649. and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
  1650. details.
  1651. Say off if not sure, auto if TSX is in use but it should be used on safe
  1652. platforms or on if TSX is in use and the security aspect of tsx is not
  1653. relevant.
  1654. config X86_INTEL_TSX_MODE_OFF
  1655. bool "off"
  1656. help
  1657. TSX is disabled if possible - equals to tsx=off command line parameter.
  1658. config X86_INTEL_TSX_MODE_ON
  1659. bool "on"
  1660. help
  1661. TSX is always enabled on TSX capable HW - equals the tsx=on command
  1662. line parameter.
  1663. config X86_INTEL_TSX_MODE_AUTO
  1664. bool "auto"
  1665. help
  1666. TSX is enabled on TSX capable HW that is believed to be safe against
  1667. side channel attacks- equals the tsx=auto command line parameter.
  1668. endchoice
  1669. config X86_SGX
  1670. bool "Software Guard eXtensions (SGX)"
  1671. depends on X86_64 && CPU_SUP_INTEL && X86_X2APIC
  1672. depends on CRYPTO=y
  1673. depends on CRYPTO_SHA256=y
  1674. select SRCU
  1675. select MMU_NOTIFIER
  1676. select NUMA_KEEP_MEMINFO if NUMA
  1677. select XARRAY_MULTI
  1678. help
  1679. Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
  1680. that can be used by applications to set aside private regions of code
  1681. and data, referred to as enclaves. An enclave's private memory can
  1682. only be accessed by code running within the enclave. Accesses from
  1683. outside the enclave, including other enclaves, are disallowed by
  1684. hardware.
  1685. If unsure, say N.
  1686. config EFI
  1687. bool "EFI runtime service support"
  1688. depends on ACPI
  1689. select UCS2_STRING
  1690. select EFI_RUNTIME_WRAPPERS
  1691. select ARCH_USE_MEMREMAP_PROT
  1692. help
  1693. This enables the kernel to use EFI runtime services that are
  1694. available (such as the EFI variable services).
  1695. This option is only useful on systems that have EFI firmware.
  1696. In addition, you should use the latest ELILO loader available
  1697. at <http://elilo.sourceforge.net> in order to take advantage
  1698. of EFI runtime services. However, even with this option, the
  1699. resultant kernel should continue to boot on existing non-EFI
  1700. platforms.
  1701. config EFI_STUB
  1702. bool "EFI stub support"
  1703. depends on EFI
  1704. select RELOCATABLE
  1705. help
  1706. This kernel feature allows a bzImage to be loaded directly
  1707. by EFI firmware without the use of a bootloader.
  1708. See Documentation/admin-guide/efi-stub.rst for more information.
  1709. config EFI_MIXED
  1710. bool "EFI mixed-mode support"
  1711. depends on EFI_STUB && X86_64
  1712. help
  1713. Enabling this feature allows a 64-bit kernel to be booted
  1714. on a 32-bit firmware, provided that your CPU supports 64-bit
  1715. mode.
  1716. Note that it is not possible to boot a mixed-mode enabled
  1717. kernel via the EFI boot stub - a bootloader that supports
  1718. the EFI handover protocol must be used.
  1719. If unsure, say N.
  1720. source "kernel/Kconfig.hz"
  1721. config KEXEC
  1722. bool "kexec system call"
  1723. select KEXEC_CORE
  1724. help
  1725. kexec is a system call that implements the ability to shutdown your
  1726. current kernel, and to start another kernel. It is like a reboot
  1727. but it is independent of the system firmware. And like a reboot
  1728. you can start any kernel with it, not just Linux.
  1729. The name comes from the similarity to the exec system call.
  1730. It is an ongoing process to be certain the hardware in a machine
  1731. is properly shutdown, so do not be surprised if this code does not
  1732. initially work for you. As of this writing the exact hardware
  1733. interface is strongly in flux, so no good recommendation can be
  1734. made.
  1735. config KEXEC_FILE
  1736. bool "kexec file based system call"
  1737. select KEXEC_CORE
  1738. select HAVE_IMA_KEXEC if IMA
  1739. depends on X86_64
  1740. depends on CRYPTO=y
  1741. depends on CRYPTO_SHA256=y
  1742. help
  1743. This is new version of kexec system call. This system call is
  1744. file based and takes file descriptors as system call argument
  1745. for kernel and initramfs as opposed to list of segments as
  1746. accepted by previous system call.
  1747. config ARCH_HAS_KEXEC_PURGATORY
  1748. def_bool KEXEC_FILE
  1749. config KEXEC_SIG
  1750. bool "Verify kernel signature during kexec_file_load() syscall"
  1751. depends on KEXEC_FILE
  1752. help
  1753. This option makes the kexec_file_load() syscall check for a valid
  1754. signature of the kernel image. The image can still be loaded without
  1755. a valid signature unless you also enable KEXEC_SIG_FORCE, though if
  1756. there's a signature that we can check, then it must be valid.
  1757. In addition to this option, you need to enable signature
  1758. verification for the corresponding kernel image type being
  1759. loaded in order for this to work.
  1760. config KEXEC_SIG_FORCE
  1761. bool "Require a valid signature in kexec_file_load() syscall"
  1762. depends on KEXEC_SIG
  1763. help
  1764. This option makes kernel signature verification mandatory for
  1765. the kexec_file_load() syscall.
  1766. config KEXEC_BZIMAGE_VERIFY_SIG
  1767. bool "Enable bzImage signature verification support"
  1768. depends on KEXEC_SIG
  1769. depends on SIGNED_PE_FILE_VERIFICATION
  1770. select SYSTEM_TRUSTED_KEYRING
  1771. help
  1772. Enable bzImage signature verification support.
  1773. config CRASH_DUMP
  1774. bool "kernel crash dumps"
  1775. depends on X86_64 || (X86_32 && HIGHMEM)
  1776. help
  1777. Generate crash dump after being started by kexec.
  1778. This should be normally only set in special crash dump kernels
  1779. which are loaded in the main kernel with kexec-tools into
  1780. a specially reserved region and then later executed after
  1781. a crash by kdump/kexec. The crash dump kernel must be compiled
  1782. to a memory address not used by the main kernel or BIOS using
  1783. PHYSICAL_START, or it must be built as a relocatable image
  1784. (CONFIG_RELOCATABLE=y).
  1785. For more details see Documentation/admin-guide/kdump/kdump.rst
  1786. config KEXEC_JUMP
  1787. bool "kexec jump"
  1788. depends on KEXEC && HIBERNATION
  1789. help
  1790. Jump between original kernel and kexeced kernel and invoke
  1791. code in physical address mode via KEXEC
  1792. config PHYSICAL_START
  1793. hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
  1794. default "0x1000000"
  1795. help
  1796. This gives the physical address where the kernel is loaded.
  1797. If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
  1798. bzImage will decompress itself to above physical address and
  1799. run from there. Otherwise, bzImage will run from the address where
  1800. it has been loaded by the boot loader and will ignore above physical
  1801. address.
  1802. In normal kdump cases one does not have to set/change this option
  1803. as now bzImage can be compiled as a completely relocatable image
  1804. (CONFIG_RELOCATABLE=y) and be used to load and run from a different
  1805. address. This option is mainly useful for the folks who don't want
  1806. to use a bzImage for capturing the crash dump and want to use a
  1807. vmlinux instead. vmlinux is not relocatable hence a kernel needs
  1808. to be specifically compiled to run from a specific memory area
  1809. (normally a reserved region) and this option comes handy.
  1810. So if you are using bzImage for capturing the crash dump,
  1811. leave the value here unchanged to 0x1000000 and set
  1812. CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
  1813. for capturing the crash dump change this value to start of
  1814. the reserved region. In other words, it can be set based on
  1815. the "X" value as specified in the "crashkernel=YM@XM"
  1816. command line boot parameter passed to the panic-ed
  1817. kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
  1818. for more details about crash dumps.
  1819. Usage of bzImage for capturing the crash dump is recommended as
  1820. one does not have to build two kernels. Same kernel can be used
  1821. as production kernel and capture kernel. Above option should have
  1822. gone away after relocatable bzImage support is introduced. But it
  1823. is present because there are users out there who continue to use
  1824. vmlinux for dump capture. This option should go away down the
  1825. line.
  1826. Don't change this unless you know what you are doing.
  1827. config RELOCATABLE
  1828. bool "Build a relocatable kernel"
  1829. default y
  1830. help
  1831. This builds a kernel image that retains relocation information
  1832. so it can be loaded someplace besides the default 1MB.
  1833. The relocations tend to make the kernel binary about 10% larger,
  1834. but are discarded at runtime.
  1835. One use is for the kexec on panic case where the recovery kernel
  1836. must live at a different physical address than the primary
  1837. kernel.
  1838. Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
  1839. it has been loaded at and the compile time physical address
  1840. (CONFIG_PHYSICAL_START) is used as the minimum location.
  1841. config RANDOMIZE_BASE
  1842. bool "Randomize the address of the kernel image (KASLR)"
  1843. depends on RELOCATABLE
  1844. default y
  1845. help
  1846. In support of Kernel Address Space Layout Randomization (KASLR),
  1847. this randomizes the physical address at which the kernel image
  1848. is decompressed and the virtual address where the kernel
  1849. image is mapped, as a security feature that deters exploit
  1850. attempts relying on knowledge of the location of kernel
  1851. code internals.
  1852. On 64-bit, the kernel physical and virtual addresses are
  1853. randomized separately. The physical address will be anywhere
  1854. between 16MB and the top of physical memory (up to 64TB). The
  1855. virtual address will be randomized from 16MB up to 1GB (9 bits
  1856. of entropy). Note that this also reduces the memory space
  1857. available to kernel modules from 1.5GB to 1GB.
  1858. On 32-bit, the kernel physical and virtual addresses are
  1859. randomized together. They will be randomized from 16MB up to
  1860. 512MB (8 bits of entropy).
  1861. Entropy is generated using the RDRAND instruction if it is
  1862. supported. If RDTSC is supported, its value is mixed into
  1863. the entropy pool as well. If neither RDRAND nor RDTSC are
  1864. supported, then entropy is read from the i8254 timer. The
  1865. usable entropy is limited by the kernel being built using
  1866. 2GB addressing, and that PHYSICAL_ALIGN must be at a
  1867. minimum of 2MB. As a result, only 10 bits of entropy are
  1868. theoretically possible, but the implementations are further
  1869. limited due to memory layouts.
  1870. If unsure, say Y.
  1871. # Relocation on x86 needs some additional build support
  1872. config X86_NEED_RELOCS
  1873. def_bool y
  1874. depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
  1875. config PHYSICAL_ALIGN
  1876. hex "Alignment value to which kernel should be aligned"
  1877. default "0x200000"
  1878. range 0x2000 0x1000000 if X86_32
  1879. range 0x200000 0x1000000 if X86_64
  1880. help
  1881. This value puts the alignment restrictions on physical address
  1882. where kernel is loaded and run from. Kernel is compiled for an
  1883. address which meets above alignment restriction.
  1884. If bootloader loads the kernel at a non-aligned address and
  1885. CONFIG_RELOCATABLE is set, kernel will move itself to nearest
  1886. address aligned to above value and run from there.
  1887. If bootloader loads the kernel at a non-aligned address and
  1888. CONFIG_RELOCATABLE is not set, kernel will ignore the run time
  1889. load address and decompress itself to the address it has been
  1890. compiled for and run from there. The address for which kernel is
  1891. compiled already meets above alignment restrictions. Hence the
  1892. end result is that kernel runs from a physical address meeting
  1893. above alignment restrictions.
  1894. On 32-bit this value must be a multiple of 0x2000. On 64-bit
  1895. this value must be a multiple of 0x200000.
  1896. Don't change this unless you know what you are doing.
  1897. config DYNAMIC_MEMORY_LAYOUT
  1898. bool
  1899. help
  1900. This option makes base addresses of vmalloc and vmemmap as well as
  1901. __PAGE_OFFSET movable during boot.
  1902. config RANDOMIZE_MEMORY
  1903. bool "Randomize the kernel memory sections"
  1904. depends on X86_64
  1905. depends on RANDOMIZE_BASE
  1906. select DYNAMIC_MEMORY_LAYOUT
  1907. default RANDOMIZE_BASE
  1908. help
  1909. Randomizes the base virtual address of kernel memory sections
  1910. (physical memory mapping, vmalloc & vmemmap). This security feature
  1911. makes exploits relying on predictable memory locations less reliable.
  1912. The order of allocations remains unchanged. Entropy is generated in
  1913. the same way as RANDOMIZE_BASE. Current implementation in the optimal
  1914. configuration have in average 30,000 different possible virtual
  1915. addresses for each memory section.
  1916. If unsure, say Y.
  1917. config RANDOMIZE_MEMORY_PHYSICAL_PADDING
  1918. hex "Physical memory mapping padding" if EXPERT
  1919. depends on RANDOMIZE_MEMORY
  1920. default "0xa" if MEMORY_HOTPLUG
  1921. default "0x0"
  1922. range 0x1 0x40 if MEMORY_HOTPLUG
  1923. range 0x0 0x40
  1924. help
  1925. Define the padding in terabytes added to the existing physical
  1926. memory size during kernel memory randomization. It is useful
  1927. for memory hotplug support but reduces the entropy available for
  1928. address randomization.
  1929. If unsure, leave at the default value.
  1930. config HOTPLUG_CPU
  1931. def_bool y
  1932. depends on SMP
  1933. config BOOTPARAM_HOTPLUG_CPU0
  1934. bool "Set default setting of cpu0_hotpluggable"
  1935. depends on HOTPLUG_CPU
  1936. help
  1937. Set whether default state of cpu0_hotpluggable is on or off.
  1938. Say Y here to enable CPU0 hotplug by default. If this switch
  1939. is turned on, there is no need to give cpu0_hotplug kernel
  1940. parameter and the CPU0 hotplug feature is enabled by default.
  1941. Please note: there are two known CPU0 dependencies if you want
  1942. to enable the CPU0 hotplug feature either by this switch or by
  1943. cpu0_hotplug kernel parameter.
  1944. First, resume from hibernate or suspend always starts from CPU0.
  1945. So hibernate and suspend are prevented if CPU0 is offline.
  1946. Second dependency is PIC interrupts always go to CPU0. CPU0 can not
  1947. offline if any interrupt can not migrate out of CPU0. There may
  1948. be other CPU0 dependencies.
  1949. Please make sure the dependencies are under your control before
  1950. you enable this feature.
  1951. Say N if you don't want to enable CPU0 hotplug feature by default.
  1952. You still can enable the CPU0 hotplug feature at boot by kernel
  1953. parameter cpu0_hotplug.
  1954. config DEBUG_HOTPLUG_CPU0
  1955. def_bool n
  1956. prompt "Debug CPU0 hotplug"
  1957. depends on HOTPLUG_CPU
  1958. help
  1959. Enabling this option offlines CPU0 (if CPU0 can be offlined) as
  1960. soon as possible and boots up userspace with CPU0 offlined. User
  1961. can online CPU0 back after boot time.
  1962. To debug CPU0 hotplug, you need to enable CPU0 offline/online
  1963. feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
  1964. compilation or giving cpu0_hotplug kernel parameter at boot.
  1965. If unsure, say N.
  1966. config COMPAT_VDSO
  1967. def_bool n
  1968. prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
  1969. depends on COMPAT_32
  1970. help
  1971. Certain buggy versions of glibc will crash if they are
  1972. presented with a 32-bit vDSO that is not mapped at the address
  1973. indicated in its segment table.
  1974. The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
  1975. and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
  1976. 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
  1977. the only released version with the bug, but OpenSUSE 9
  1978. contains a buggy "glibc 2.3.2".
  1979. The symptom of the bug is that everything crashes on startup, saying:
  1980. dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
  1981. Saying Y here changes the default value of the vdso32 boot
  1982. option from 1 to 0, which turns off the 32-bit vDSO entirely.
  1983. This works around the glibc bug but hurts performance.
  1984. If unsure, say N: if you are compiling your own kernel, you
  1985. are unlikely to be using a buggy version of glibc.
  1986. choice
  1987. prompt "vsyscall table for legacy applications"
  1988. depends on X86_64
  1989. default LEGACY_VSYSCALL_XONLY
  1990. help
  1991. Legacy user code that does not know how to find the vDSO expects
  1992. to be able to issue three syscalls by calling fixed addresses in
  1993. kernel space. Since this location is not randomized with ASLR,
  1994. it can be used to assist security vulnerability exploitation.
  1995. This setting can be changed at boot time via the kernel command
  1996. line parameter vsyscall=[emulate|xonly|none]. Emulate mode
  1997. is deprecated and can only be enabled using the kernel command
  1998. line.
  1999. On a system with recent enough glibc (2.14 or newer) and no
  2000. static binaries, you can say None without a performance penalty
  2001. to improve security.
  2002. If unsure, select "Emulate execution only".
  2003. config LEGACY_VSYSCALL_XONLY
  2004. bool "Emulate execution only"
  2005. help
  2006. The kernel traps and emulates calls into the fixed vsyscall
  2007. address mapping and does not allow reads. This
  2008. configuration is recommended when userspace might use the
  2009. legacy vsyscall area but support for legacy binary
  2010. instrumentation of legacy code is not needed. It mitigates
  2011. certain uses of the vsyscall area as an ASLR-bypassing
  2012. buffer.
  2013. config LEGACY_VSYSCALL_NONE
  2014. bool "None"
  2015. help
  2016. There will be no vsyscall mapping at all. This will
  2017. eliminate any risk of ASLR bypass due to the vsyscall
  2018. fixed address mapping. Attempts to use the vsyscalls
  2019. will be reported to dmesg, so that either old or
  2020. malicious userspace programs can be identified.
  2021. endchoice
  2022. config CMDLINE_BOOL
  2023. bool "Built-in kernel command line"
  2024. help
  2025. Allow for specifying boot arguments to the kernel at
  2026. build time. On some systems (e.g. embedded ones), it is
  2027. necessary or convenient to provide some or all of the
  2028. kernel boot arguments with the kernel itself (that is,
  2029. to not rely on the boot loader to provide them.)
  2030. To compile command line arguments into the kernel,
  2031. set this option to 'Y', then fill in the
  2032. boot arguments in CONFIG_CMDLINE.
  2033. Systems with fully functional boot loaders (i.e. non-embedded)
  2034. should leave this option set to 'N'.
  2035. config CMDLINE
  2036. string "Built-in kernel command string"
  2037. depends on CMDLINE_BOOL
  2038. default ""
  2039. help
  2040. Enter arguments here that should be compiled into the kernel
  2041. image and used at boot time. If the boot loader provides a
  2042. command line at boot time, it is appended to this string to
  2043. form the full kernel command line, when the system boots.
  2044. However, you can use the CONFIG_CMDLINE_OVERRIDE option to
  2045. change this behavior.
  2046. In most cases, the command line (whether built-in or provided
  2047. by the boot loader) should specify the device for the root
  2048. file system.
  2049. config CMDLINE_OVERRIDE
  2050. bool "Built-in command line overrides boot loader arguments"
  2051. depends on CMDLINE_BOOL && CMDLINE != ""
  2052. help
  2053. Set this option to 'Y' to have the kernel ignore the boot loader
  2054. command line, and use ONLY the built-in command line.
  2055. This is used to work around broken boot loaders. This should
  2056. be set to 'N' under normal conditions.
  2057. config MODIFY_LDT_SYSCALL
  2058. bool "Enable the LDT (local descriptor table)" if EXPERT
  2059. default y
  2060. help
  2061. Linux can allow user programs to install a per-process x86
  2062. Local Descriptor Table (LDT) using the modify_ldt(2) system
  2063. call. This is required to run 16-bit or segmented code such as
  2064. DOSEMU or some Wine programs. It is also used by some very old
  2065. threading libraries.
  2066. Enabling this feature adds a small amount of overhead to
  2067. context switches and increases the low-level kernel attack
  2068. surface. Disabling it removes the modify_ldt(2) system call.
  2069. Saying 'N' here may make sense for embedded or server kernels.
  2070. config STRICT_SIGALTSTACK_SIZE
  2071. bool "Enforce strict size checking for sigaltstack"
  2072. depends on DYNAMIC_SIGFRAME
  2073. help
  2074. For historical reasons MINSIGSTKSZ is a constant which became
  2075. already too small with AVX512 support. Add a mechanism to
  2076. enforce strict checking of the sigaltstack size against the
  2077. real size of the FPU frame. This option enables the check
  2078. by default. It can also be controlled via the kernel command
  2079. line option 'strict_sas_size' independent of this config
  2080. switch. Enabling it might break existing applications which
  2081. allocate a too small sigaltstack but 'work' because they
  2082. never get a signal delivered.
  2083. Say 'N' unless you want to really enforce this check.
  2084. source "kernel/livepatch/Kconfig"
  2085. endmenu
  2086. config CC_HAS_SLS
  2087. def_bool $(cc-option,-mharden-sls=all)
  2088. config CC_HAS_RETURN_THUNK
  2089. def_bool $(cc-option,-mfunction-return=thunk-extern)
  2090. menuconfig SPECULATION_MITIGATIONS
  2091. bool "Mitigations for speculative execution vulnerabilities"
  2092. default y
  2093. help
  2094. Say Y here to enable options which enable mitigations for
  2095. speculative execution hardware vulnerabilities.
  2096. If you say N, all mitigations will be disabled. You really
  2097. should know what you are doing to say so.
  2098. if SPECULATION_MITIGATIONS
  2099. config PAGE_TABLE_ISOLATION
  2100. bool "Remove the kernel mapping in user mode"
  2101. default y
  2102. depends on (X86_64 || X86_PAE)
  2103. help
  2104. This feature reduces the number of hardware side channels by
  2105. ensuring that the majority of kernel addresses are not mapped
  2106. into userspace.
  2107. See Documentation/x86/pti.rst for more details.
  2108. config RETPOLINE
  2109. bool "Avoid speculative indirect branches in kernel"
  2110. select OBJTOOL if HAVE_OBJTOOL
  2111. default y
  2112. help
  2113. Compile kernel with the retpoline compiler options to guard against
  2114. kernel-to-user data leaks by avoiding speculative indirect
  2115. branches. Requires a compiler with -mindirect-branch=thunk-extern
  2116. support for full protection. The kernel may run slower.
  2117. config RETHUNK
  2118. bool "Enable return-thunks"
  2119. depends on RETPOLINE && CC_HAS_RETURN_THUNK
  2120. select OBJTOOL if HAVE_OBJTOOL
  2121. default y if X86_64
  2122. help
  2123. Compile the kernel with the return-thunks compiler option to guard
  2124. against kernel-to-user data leaks by avoiding return speculation.
  2125. Requires a compiler with -mfunction-return=thunk-extern
  2126. support for full protection. The kernel may run slower.
  2127. config CPU_UNRET_ENTRY
  2128. bool "Enable UNRET on kernel entry"
  2129. depends on CPU_SUP_AMD && RETHUNK && X86_64
  2130. default y
  2131. help
  2132. Compile the kernel with support for the retbleed=unret mitigation.
  2133. config CPU_IBPB_ENTRY
  2134. bool "Enable IBPB on kernel entry"
  2135. depends on CPU_SUP_AMD && X86_64
  2136. default y
  2137. help
  2138. Compile the kernel with support for the retbleed=ibpb mitigation.
  2139. config CPU_IBRS_ENTRY
  2140. bool "Enable IBRS on kernel entry"
  2141. depends on CPU_SUP_INTEL && X86_64
  2142. default y
  2143. help
  2144. Compile the kernel with support for the spectre_v2=ibrs mitigation.
  2145. This mitigates both spectre_v2 and retbleed at great cost to
  2146. performance.
  2147. config CPU_SRSO
  2148. bool "Mitigate speculative RAS overflow on AMD"
  2149. depends on CPU_SUP_AMD && X86_64 && RETHUNK
  2150. default y
  2151. help
  2152. Enable the SRSO mitigation needed on AMD Zen1-4 machines.
  2153. config SLS
  2154. bool "Mitigate Straight-Line-Speculation"
  2155. depends on CC_HAS_SLS && X86_64
  2156. select OBJTOOL if HAVE_OBJTOOL
  2157. default n
  2158. help
  2159. Compile the kernel with straight-line-speculation options to guard
  2160. against straight line speculation. The kernel image might be slightly
  2161. larger.
  2162. config GDS_FORCE_MITIGATION
  2163. bool "Force GDS Mitigation"
  2164. depends on CPU_SUP_INTEL
  2165. default n
  2166. help
  2167. Gather Data Sampling (GDS) is a hardware vulnerability which allows
  2168. unprivileged speculative access to data which was previously stored in
  2169. vector registers.
  2170. This option is equivalent to setting gather_data_sampling=force on the
  2171. command line. The microcode mitigation is used if present, otherwise
  2172. AVX is disabled as a mitigation. On affected systems that are missing
  2173. the microcode any userspace code that unconditionally uses AVX will
  2174. break with this option set.
  2175. Setting this option on systems not vulnerable to GDS has no effect.
  2176. If in doubt, say N.
  2177. endif
  2178. config ARCH_HAS_ADD_PAGES
  2179. def_bool y
  2180. depends on ARCH_ENABLE_MEMORY_HOTPLUG
  2181. config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
  2182. def_bool y
  2183. menu "Power management and ACPI options"
  2184. config ARCH_HIBERNATION_HEADER
  2185. def_bool y
  2186. depends on HIBERNATION
  2187. source "kernel/power/Kconfig"
  2188. source "drivers/acpi/Kconfig"
  2189. config X86_APM_BOOT
  2190. def_bool y
  2191. depends on APM
  2192. menuconfig APM
  2193. tristate "APM (Advanced Power Management) BIOS support"
  2194. depends on X86_32 && PM_SLEEP
  2195. help
  2196. APM is a BIOS specification for saving power using several different
  2197. techniques. This is mostly useful for battery powered laptops with
  2198. APM compliant BIOSes. If you say Y here, the system time will be
  2199. reset after a RESUME operation, the /proc/apm device will provide
  2200. battery status information, and user-space programs will receive
  2201. notification of APM "events" (e.g. battery status change).
  2202. If you select "Y" here, you can disable actual use of the APM
  2203. BIOS by passing the "apm=off" option to the kernel at boot time.
  2204. Note that the APM support is almost completely disabled for
  2205. machines with more than one CPU.
  2206. In order to use APM, you will need supporting software. For location
  2207. and more information, read <file:Documentation/power/apm-acpi.rst>
  2208. and the Battery Powered Linux mini-HOWTO, available from
  2209. <http://www.tldp.org/docs.html#howto>.
  2210. This driver does not spin down disk drives (see the hdparm(8)
  2211. manpage ("man 8 hdparm") for that), and it doesn't turn off
  2212. VESA-compliant "green" monitors.
  2213. This driver does not support the TI 4000M TravelMate and the ACER
  2214. 486/DX4/75 because they don't have compliant BIOSes. Many "green"
  2215. desktop machines also don't have compliant BIOSes, and this driver
  2216. may cause those machines to panic during the boot phase.
  2217. Generally, if you don't have a battery in your machine, there isn't
  2218. much point in using this driver and you should say N. If you get
  2219. random kernel OOPSes or reboots that don't seem to be related to
  2220. anything, try disabling/enabling this option (or disabling/enabling
  2221. APM in your BIOS).
  2222. Some other things you should try when experiencing seemingly random,
  2223. "weird" problems:
  2224. 1) make sure that you have enough swap space and that it is
  2225. enabled.
  2226. 2) pass the "idle=poll" option to the kernel
  2227. 3) switch on floating point emulation in the kernel and pass
  2228. the "no387" option to the kernel
  2229. 4) pass the "floppy=nodma" option to the kernel
  2230. 5) pass the "mem=4M" option to the kernel (thereby disabling
  2231. all but the first 4 MB of RAM)
  2232. 6) make sure that the CPU is not over clocked.
  2233. 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
  2234. 8) disable the cache from your BIOS settings
  2235. 9) install a fan for the video card or exchange video RAM
  2236. 10) install a better fan for the CPU
  2237. 11) exchange RAM chips
  2238. 12) exchange the motherboard.
  2239. To compile this driver as a module, choose M here: the
  2240. module will be called apm.
  2241. if APM
  2242. config APM_IGNORE_USER_SUSPEND
  2243. bool "Ignore USER SUSPEND"
  2244. help
  2245. This option will ignore USER SUSPEND requests. On machines with a
  2246. compliant APM BIOS, you want to say N. However, on the NEC Versa M
  2247. series notebooks, it is necessary to say Y because of a BIOS bug.
  2248. config APM_DO_ENABLE
  2249. bool "Enable PM at boot time"
  2250. help
  2251. Enable APM features at boot time. From page 36 of the APM BIOS
  2252. specification: "When disabled, the APM BIOS does not automatically
  2253. power manage devices, enter the Standby State, enter the Suspend
  2254. State, or take power saving steps in response to CPU Idle calls."
  2255. This driver will make CPU Idle calls when Linux is idle (unless this
  2256. feature is turned off -- see "Do CPU IDLE calls", below). This
  2257. should always save battery power, but more complicated APM features
  2258. will be dependent on your BIOS implementation. You may need to turn
  2259. this option off if your computer hangs at boot time when using APM
  2260. support, or if it beeps continuously instead of suspending. Turn
  2261. this off if you have a NEC UltraLite Versa 33/C or a Toshiba
  2262. T400CDT. This is off by default since most machines do fine without
  2263. this feature.
  2264. config APM_CPU_IDLE
  2265. depends on CPU_IDLE
  2266. bool "Make CPU Idle calls when idle"
  2267. help
  2268. Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
  2269. On some machines, this can activate improved power savings, such as
  2270. a slowed CPU clock rate, when the machine is idle. These idle calls
  2271. are made after the idle loop has run for some length of time (e.g.,
  2272. 333 mS). On some machines, this will cause a hang at boot time or
  2273. whenever the CPU becomes idle. (On machines with more than one CPU,
  2274. this option does nothing.)
  2275. config APM_DISPLAY_BLANK
  2276. bool "Enable console blanking using APM"
  2277. help
  2278. Enable console blanking using the APM. Some laptops can use this to
  2279. turn off the LCD backlight when the screen blanker of the Linux
  2280. virtual console blanks the screen. Note that this is only used by
  2281. the virtual console screen blanker, and won't turn off the backlight
  2282. when using the X Window system. This also doesn't have anything to
  2283. do with your VESA-compliant power-saving monitor. Further, this
  2284. option doesn't work for all laptops -- it might not turn off your
  2285. backlight at all, or it might print a lot of errors to the console,
  2286. especially if you are using gpm.
  2287. config APM_ALLOW_INTS
  2288. bool "Allow interrupts during APM BIOS calls"
  2289. help
  2290. Normally we disable external interrupts while we are making calls to
  2291. the APM BIOS as a measure to lessen the effects of a badly behaving
  2292. BIOS implementation. The BIOS should reenable interrupts if it
  2293. needs to. Unfortunately, some BIOSes do not -- especially those in
  2294. many of the newer IBM Thinkpads. If you experience hangs when you
  2295. suspend, try setting this to Y. Otherwise, say N.
  2296. endif # APM
  2297. source "drivers/cpufreq/Kconfig"
  2298. source "drivers/cpuidle/Kconfig"
  2299. source "drivers/idle/Kconfig"
  2300. endmenu
  2301. menu "Bus options (PCI etc.)"
  2302. choice
  2303. prompt "PCI access mode"
  2304. depends on X86_32 && PCI
  2305. default PCI_GOANY
  2306. help
  2307. On PCI systems, the BIOS can be used to detect the PCI devices and
  2308. determine their configuration. However, some old PCI motherboards
  2309. have BIOS bugs and may crash if this is done. Also, some embedded
  2310. PCI-based systems don't have any BIOS at all. Linux can also try to
  2311. detect the PCI hardware directly without using the BIOS.
  2312. With this option, you can specify how Linux should detect the
  2313. PCI devices. If you choose "BIOS", the BIOS will be used,
  2314. if you choose "Direct", the BIOS won't be used, and if you
  2315. choose "MMConfig", then PCI Express MMCONFIG will be used.
  2316. If you choose "Any", the kernel will try MMCONFIG, then the
  2317. direct access method and falls back to the BIOS if that doesn't
  2318. work. If unsure, go with the default, which is "Any".
  2319. config PCI_GOBIOS
  2320. bool "BIOS"
  2321. config PCI_GOMMCONFIG
  2322. bool "MMConfig"
  2323. config PCI_GODIRECT
  2324. bool "Direct"
  2325. config PCI_GOOLPC
  2326. bool "OLPC XO-1"
  2327. depends on OLPC
  2328. config PCI_GOANY
  2329. bool "Any"
  2330. endchoice
  2331. config PCI_BIOS
  2332. def_bool y
  2333. depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
  2334. # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
  2335. config PCI_DIRECT
  2336. def_bool y
  2337. depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
  2338. config PCI_MMCONFIG
  2339. bool "Support mmconfig PCI config space access" if X86_64
  2340. default y
  2341. depends on PCI && (ACPI || JAILHOUSE_GUEST)
  2342. depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
  2343. config PCI_OLPC
  2344. def_bool y
  2345. depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
  2346. config PCI_XEN
  2347. def_bool y
  2348. depends on PCI && XEN
  2349. config MMCONF_FAM10H
  2350. def_bool y
  2351. depends on X86_64 && PCI_MMCONFIG && ACPI
  2352. config PCI_CNB20LE_QUIRK
  2353. bool "Read CNB20LE Host Bridge Windows" if EXPERT
  2354. depends on PCI
  2355. help
  2356. Read the PCI windows out of the CNB20LE host bridge. This allows
  2357. PCI hotplug to work on systems with the CNB20LE chipset which do
  2358. not have ACPI.
  2359. There's no public spec for this chipset, and this functionality
  2360. is known to be incomplete.
  2361. You should say N unless you know you need this.
  2362. config ISA_BUS
  2363. bool "ISA bus support on modern systems" if EXPERT
  2364. help
  2365. Expose ISA bus device drivers and options available for selection and
  2366. configuration. Enable this option if your target machine has an ISA
  2367. bus. ISA is an older system, displaced by PCI and newer bus
  2368. architectures -- if your target machine is modern, it probably does
  2369. not have an ISA bus.
  2370. If unsure, say N.
  2371. # x86_64 have no ISA slots, but can have ISA-style DMA.
  2372. config ISA_DMA_API
  2373. bool "ISA-style DMA support" if (X86_64 && EXPERT)
  2374. default y
  2375. help
  2376. Enables ISA-style DMA support for devices requiring such controllers.
  2377. If unsure, say Y.
  2378. if X86_32
  2379. config ISA
  2380. bool "ISA support"
  2381. help
  2382. Find out whether you have ISA slots on your motherboard. ISA is the
  2383. name of a bus system, i.e. the way the CPU talks to the other stuff
  2384. inside your box. Other bus systems are PCI, EISA, MicroChannel
  2385. (MCA) or VESA. ISA is an older system, now being displaced by PCI;
  2386. newer boards don't support it. If you have ISA, say Y, otherwise N.
  2387. config SCx200
  2388. tristate "NatSemi SCx200 support"
  2389. help
  2390. This provides basic support for National Semiconductor's
  2391. (now AMD's) Geode processors. The driver probes for the
  2392. PCI-IDs of several on-chip devices, so its a good dependency
  2393. for other scx200_* drivers.
  2394. If compiled as a module, the driver is named scx200.
  2395. config SCx200HR_TIMER
  2396. tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
  2397. depends on SCx200
  2398. default y
  2399. help
  2400. This driver provides a clocksource built upon the on-chip
  2401. 27MHz high-resolution timer. Its also a workaround for
  2402. NSC Geode SC-1100's buggy TSC, which loses time when the
  2403. processor goes idle (as is done by the scheduler). The
  2404. other workaround is idle=poll boot option.
  2405. config OLPC
  2406. bool "One Laptop Per Child support"
  2407. depends on !X86_PAE
  2408. select GPIOLIB
  2409. select OF
  2410. select OF_PROMTREE
  2411. select IRQ_DOMAIN
  2412. select OLPC_EC
  2413. help
  2414. Add support for detecting the unique features of the OLPC
  2415. XO hardware.
  2416. config OLPC_XO1_PM
  2417. bool "OLPC XO-1 Power Management"
  2418. depends on OLPC && MFD_CS5535=y && PM_SLEEP
  2419. help
  2420. Add support for poweroff and suspend of the OLPC XO-1 laptop.
  2421. config OLPC_XO1_RTC
  2422. bool "OLPC XO-1 Real Time Clock"
  2423. depends on OLPC_XO1_PM && RTC_DRV_CMOS
  2424. help
  2425. Add support for the XO-1 real time clock, which can be used as a
  2426. programmable wakeup source.
  2427. config OLPC_XO1_SCI
  2428. bool "OLPC XO-1 SCI extras"
  2429. depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
  2430. depends on INPUT=y
  2431. select POWER_SUPPLY
  2432. help
  2433. Add support for SCI-based features of the OLPC XO-1 laptop:
  2434. - EC-driven system wakeups
  2435. - Power button
  2436. - Ebook switch
  2437. - Lid switch
  2438. - AC adapter status updates
  2439. - Battery status updates
  2440. config OLPC_XO15_SCI
  2441. bool "OLPC XO-1.5 SCI extras"
  2442. depends on OLPC && ACPI
  2443. select POWER_SUPPLY
  2444. help
  2445. Add support for SCI-based features of the OLPC XO-1.5 laptop:
  2446. - EC-driven system wakeups
  2447. - AC adapter status updates
  2448. - Battery status updates
  2449. config ALIX
  2450. bool "PCEngines ALIX System Support (LED setup)"
  2451. select GPIOLIB
  2452. help
  2453. This option enables system support for the PCEngines ALIX.
  2454. At present this just sets up LEDs for GPIO control on
  2455. ALIX2/3/6 boards. However, other system specific setup should
  2456. get added here.
  2457. Note: You must still enable the drivers for GPIO and LED support
  2458. (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
  2459. Note: You have to set alix.force=1 for boards with Award BIOS.
  2460. config NET5501
  2461. bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
  2462. select GPIOLIB
  2463. help
  2464. This option enables system support for the Soekris Engineering net5501.
  2465. config GEOS
  2466. bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
  2467. select GPIOLIB
  2468. depends on DMI
  2469. help
  2470. This option enables system support for the Traverse Technologies GEOS.
  2471. config TS5500
  2472. bool "Technologic Systems TS-5500 platform support"
  2473. depends on MELAN
  2474. select CHECK_SIGNATURE
  2475. select NEW_LEDS
  2476. select LEDS_CLASS
  2477. help
  2478. This option enables system support for the Technologic Systems TS-5500.
  2479. endif # X86_32
  2480. config AMD_NB
  2481. def_bool y
  2482. depends on CPU_SUP_AMD && PCI
  2483. endmenu
  2484. menu "Binary Emulations"
  2485. config IA32_EMULATION
  2486. bool "IA32 Emulation"
  2487. depends on X86_64
  2488. select ARCH_WANT_OLD_COMPAT_IPC
  2489. select BINFMT_ELF
  2490. select COMPAT_OLD_SIGACTION
  2491. help
  2492. Include code to run legacy 32-bit programs under a
  2493. 64-bit kernel. You should likely turn this on, unless you're
  2494. 100% sure that you don't have any 32-bit programs left.
  2495. config X86_X32_ABI
  2496. bool "x32 ABI for 64-bit mode"
  2497. depends on X86_64
  2498. # llvm-objcopy does not convert x86_64 .note.gnu.property or
  2499. # compressed debug sections to x86_x32 properly:
  2500. # https://github.com/ClangBuiltLinux/linux/issues/514
  2501. # https://github.com/ClangBuiltLinux/linux/issues/1141
  2502. depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
  2503. help
  2504. Include code to run binaries for the x32 native 32-bit ABI
  2505. for 64-bit processors. An x32 process gets access to the
  2506. full 64-bit register file and wide data path while leaving
  2507. pointers at 32 bits for smaller memory footprint.
  2508. config COMPAT_32
  2509. def_bool y
  2510. depends on IA32_EMULATION || X86_32
  2511. select HAVE_UID16
  2512. select OLD_SIGSUSPEND3
  2513. config COMPAT
  2514. def_bool y
  2515. depends on IA32_EMULATION || X86_X32_ABI
  2516. config COMPAT_FOR_U64_ALIGNMENT
  2517. def_bool y
  2518. depends on COMPAT
  2519. endmenu
  2520. config HAVE_ATOMIC_IOMAP
  2521. def_bool y
  2522. depends on X86_32
  2523. source "arch/x86/kvm/Kconfig"
  2524. source "arch/x86/Kconfig.assembler"