1 # SPDX-License-Identifier: GPL-2.0
4 bool "64-bit kernel" if "$(ARCH)" = "x86"
5 default "$(ARCH)" != "i386"
7 Say yes to build a 64-bit kernel - formerly known as x86_64
8 Say no to build a 32-bit kernel - formerly known as i386
13 # Options that are inherently 32-bit kernel only:
14 select ARCH_WANT_IPC_PARSE_VERSION
16 select CLONE_BACKWARDS
17 select GENERIC_VDSO_32
18 select HAVE_DEBUG_STACKOVERFLOW
20 select MODULES_USE_ELF_REL
22 select ARCH_SPLIT_ARG64
27 # Options that are inherently 64-bit kernel only:
28 select ARCH_HAS_GIGANTIC_PAGE
29 select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
30 select ARCH_SUPPORTS_PER_VMA_LOCK
31 select HAVE_ARCH_SOFT_DIRTY
32 select MODULES_USE_ELF_RELA
33 select NEED_DMA_MAP_STATE
35 select ARCH_HAS_ELFCORE_COMPAT
37 select EXECMEM if DYNAMIC_FTRACE
39 config FORCE_DYNAMIC_FTRACE
42 depends on FUNCTION_TRACER
45 We keep the static function tracing (!DYNAMIC_FTRACE) around
46 in order to test the non static function tracing in the
47 generic code, as other architectures still use it. But we
48 only need to keep it around for x86_64. No need to keep it
49 for x86_32. For x86_32, force DYNAMIC_FTRACE.
53 # ( Note that options that are marked 'if X86_64' could in principle be
54 # ported to 32-bit as well. )
59 # Note: keep this list sorted alphabetically
61 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
62 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
63 select ACPI_HOTPLUG_CPU if ACPI_PROCESSOR && HOTPLUG_CPU
64 select ARCH_32BIT_OFF_T if X86_32
65 select ARCH_CLOCKSOURCE_INIT
66 select ARCH_CONFIGURES_CPU_MITIGATIONS
67 select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
68 select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
69 select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
70 select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
71 select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE)
72 select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
73 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
74 select ARCH_HAS_CACHE_LINE_SIZE
75 select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
76 select ARCH_HAS_CPU_FINALIZE_INIT
77 select ARCH_HAS_CPU_PASID if IOMMU_SVA
78 select ARCH_HAS_CURRENT_STACK_POINTER
79 select ARCH_HAS_DEBUG_VIRTUAL
80 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
81 select ARCH_HAS_DEVMEM_IS_ALLOWED
82 select ARCH_HAS_EARLY_DEBUG if KGDB
83 select ARCH_HAS_ELF_RANDOMIZE
84 select ARCH_HAS_FAST_MULTIPLIER
85 select ARCH_HAS_FORTIFY_SOURCE
86 select ARCH_HAS_GCOV_PROFILE_ALL
87 select ARCH_HAS_KCOV if X86_64
88 select ARCH_HAS_MEM_ENCRYPT
89 select ARCH_HAS_MEMBARRIER_SYNC_CORE
90 select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
91 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
92 select ARCH_HAS_PMEM_API if X86_64
93 select ARCH_HAS_PTE_DEVMAP if X86_64
94 select ARCH_HAS_PTE_SPECIAL
95 select ARCH_HAS_HW_PTE_YOUNG
96 select ARCH_HAS_NONLEAF_PMD_YOUNG if PGTABLE_LEVELS > 2
97 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
98 select ARCH_HAS_COPY_MC if X86_64
99 select ARCH_HAS_SET_MEMORY
100 select ARCH_HAS_SET_DIRECT_MAP
101 select ARCH_HAS_STRICT_KERNEL_RWX
102 select ARCH_HAS_STRICT_MODULE_RWX
103 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
104 select ARCH_HAS_SYSCALL_WRAPPER
105 select ARCH_HAS_UBSAN
106 select ARCH_HAS_DEBUG_WX
107 select ARCH_HAS_ZONE_DMA_SET if EXPERT
108 select ARCH_HAVE_NMI_SAFE_CMPXCHG
109 select ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
110 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
111 select ARCH_MIGHT_HAVE_PC_PARPORT
112 select ARCH_MIGHT_HAVE_PC_SERIO
113 select ARCH_STACKWALK
114 select ARCH_SUPPORTS_ACPI
115 select ARCH_SUPPORTS_ATOMIC_RMW
116 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
117 select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64
118 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
119 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
120 select ARCH_SUPPORTS_CFI_CLANG if X86_64
121 select ARCH_USES_CFI_TRAPS if X86_64 && CFI_CLANG
122 select ARCH_SUPPORTS_LTO_CLANG
123 select ARCH_SUPPORTS_LTO_CLANG_THIN
124 select ARCH_USE_BUILTIN_BSWAP
125 select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64
126 select ARCH_USE_MEMTEST
127 select ARCH_USE_QUEUED_RWLOCKS
128 select ARCH_USE_QUEUED_SPINLOCKS
129 select ARCH_USE_SYM_ANNOTATIONS
130 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
131 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
132 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
133 select ARCH_WANTS_NO_INSTR
134 select ARCH_WANT_GENERAL_HUGETLB
135 select ARCH_WANT_HUGE_PMD_SHARE
136 select ARCH_WANT_LD_ORPHAN_WARN
137 select ARCH_WANT_OPTIMIZE_DAX_VMEMMAP if X86_64
138 select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP if X86_64
139 select ARCH_WANTS_THP_SWAP if X86_64
140 select ARCH_HAS_PARANOID_L1D_FLUSH
141 select BUILDTIME_TABLE_SORT
143 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
144 select CLOCKSOURCE_WATCHDOG
145 # Word-size accesses may read uninitialized data past the trailing \0
146 # in strings and cause false KMSAN reports.
147 select DCACHE_WORD_ACCESS if !KMSAN
148 select DYNAMIC_SIGFRAME
149 select EDAC_ATOMIC_SCRUB
151 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
152 select GENERIC_CLOCKEVENTS_BROADCAST_IDLE if GENERIC_CLOCKEVENTS_BROADCAST
153 select GENERIC_CLOCKEVENTS_MIN_ADJUST
154 select GENERIC_CMOS_UPDATE
155 select GENERIC_CPU_AUTOPROBE
156 select GENERIC_CPU_DEVICES
157 select GENERIC_CPU_VULNERABILITIES
158 select GENERIC_EARLY_IOREMAP
161 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
162 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
163 select GENERIC_IRQ_MIGRATION if SMP
164 select GENERIC_IRQ_PROBE
165 select GENERIC_IRQ_RESERVATION_MODE
166 select GENERIC_IRQ_SHOW
167 select GENERIC_PENDING_IRQ if SMP
168 select GENERIC_PTDUMP
169 select GENERIC_SMP_IDLE_THREAD
170 select GENERIC_TIME_VSYSCALL
171 select GENERIC_GETTIMEOFDAY
172 select GENERIC_VDSO_TIME_NS
173 select GENERIC_VDSO_OVERFLOW_PROTECT
174 select GUP_GET_PXX_LOW_HIGH if X86_PAE
175 select HARDIRQS_SW_RESEND
176 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
178 select HAVE_ACPI_APEI if ACPI
179 select HAVE_ACPI_APEI_NMI if ACPI
180 select HAVE_ALIGNED_STRUCT_PAGE
181 select HAVE_ARCH_AUDITSYSCALL
182 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
183 select HAVE_ARCH_HUGE_VMALLOC if X86_64
184 select HAVE_ARCH_JUMP_LABEL
185 select HAVE_ARCH_JUMP_LABEL_RELATIVE
186 select HAVE_ARCH_KASAN if X86_64
187 select HAVE_ARCH_KASAN_VMALLOC if X86_64
188 select HAVE_ARCH_KFENCE
189 select HAVE_ARCH_KMSAN if X86_64
190 select HAVE_ARCH_KGDB
191 select HAVE_ARCH_MMAP_RND_BITS if MMU
192 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
193 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
194 select HAVE_ARCH_PREL32_RELOCATIONS
195 select HAVE_ARCH_SECCOMP_FILTER
196 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
197 select HAVE_ARCH_STACKLEAK
198 select HAVE_ARCH_TRACEHOOK
199 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
200 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
201 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
202 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
203 select HAVE_ARCH_VMAP_STACK if X86_64
204 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
205 select HAVE_ARCH_WITHIN_STACK_FRAMES
206 select HAVE_ASM_MODVERSIONS
207 select HAVE_CMPXCHG_DOUBLE
208 select HAVE_CMPXCHG_LOCAL
209 select HAVE_CONTEXT_TRACKING_USER if X86_64
210 select HAVE_CONTEXT_TRACKING_USER_OFFSTACK if HAVE_CONTEXT_TRACKING_USER
211 select HAVE_C_RECORDMCOUNT
212 select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
213 select HAVE_OBJTOOL_NOP_MCOUNT if HAVE_OBJTOOL_MCOUNT
214 select HAVE_BUILDTIME_MCOUNT_SORT
215 select HAVE_DEBUG_KMEMLEAK
216 select HAVE_DMA_CONTIGUOUS
217 select HAVE_DYNAMIC_FTRACE
218 select HAVE_DYNAMIC_FTRACE_WITH_REGS
219 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
220 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
221 select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
222 select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
224 select HAVE_EFFICIENT_UNALIGNED_ACCESS
226 select HAVE_EXIT_THREAD
228 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
229 select HAVE_FTRACE_MCOUNT_RECORD
230 select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
231 select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
232 select HAVE_FUNCTION_TRACER
233 select HAVE_GCC_PLUGINS
234 select HAVE_HW_BREAKPOINT
235 select HAVE_IOREMAP_PROT
236 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
237 select HAVE_IRQ_TIME_ACCOUNTING
238 select HAVE_JUMP_LABEL_HACK if HAVE_OBJTOOL
239 select HAVE_KERNEL_BZIP2
240 select HAVE_KERNEL_GZIP
241 select HAVE_KERNEL_LZ4
242 select HAVE_KERNEL_LZMA
243 select HAVE_KERNEL_LZO
244 select HAVE_KERNEL_XZ
245 select HAVE_KERNEL_ZSTD
247 select HAVE_KPROBES_ON_FTRACE
248 select HAVE_FUNCTION_ERROR_INJECTION
249 select HAVE_KRETPROBES
251 select HAVE_LIVEPATCH if X86_64
252 select HAVE_MIXED_BREAKPOINTS_REGS
253 select HAVE_MOD_ARCH_SPECIFIC
256 select HAVE_NOINSTR_HACK if HAVE_OBJTOOL
258 select HAVE_NOINSTR_VALIDATION if HAVE_OBJTOOL
259 select HAVE_OBJTOOL if X86_64
260 select HAVE_OPTPROBES
261 select HAVE_PAGE_SIZE_4KB
262 select HAVE_PCSPKR_PLATFORM
263 select HAVE_PERF_EVENTS
264 select HAVE_PERF_EVENTS_NMI
265 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
267 select HAVE_PERF_REGS
268 select HAVE_PERF_USER_STACK_DUMP
269 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
270 select MMU_GATHER_MERGE_VMAS
271 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
272 select HAVE_REGS_AND_STACK_ACCESS_API
273 select HAVE_RELIABLE_STACKTRACE if UNWINDER_ORC || STACK_VALIDATION
274 select HAVE_FUNCTION_ARG_ACCESS_API
275 select HAVE_SETUP_PER_CPU_AREA
276 select HAVE_SOFTIRQ_ON_OWN_STACK
277 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
278 select HAVE_STACK_VALIDATION if HAVE_OBJTOOL
279 select HAVE_STATIC_CALL
280 select HAVE_STATIC_CALL_INLINE if HAVE_OBJTOOL
281 select HAVE_PREEMPT_DYNAMIC_CALL
283 select HAVE_RUST if X86_64
284 select HAVE_SYSCALL_TRACEPOINTS
285 select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
286 select HAVE_UNSTABLE_SCHED_CLOCK
287 select HAVE_USER_RETURN_NOTIFIER
288 select HAVE_GENERIC_VDSO
289 select HOTPLUG_PARALLEL if SMP && X86_64
290 select HOTPLUG_SMT if SMP
291 select HOTPLUG_SPLIT_STARTUP if SMP && X86_32
292 select IRQ_FORCED_THREADING
293 select LOCK_MM_AND_FIND_VMA
294 select NEED_PER_CPU_EMBED_FIRST_CHUNK
295 select NEED_PER_CPU_PAGE_FIRST_CHUNK
296 select NEED_SG_DMA_LENGTH
297 select PCI_DOMAINS if PCI
298 select PCI_LOCKLESS_CONFIG if PCI
301 select RTC_MC146818_LIB
303 select SYSCTL_EXCEPTION_TRACE
304 select THREAD_INFO_IN_TASK
305 select TRACE_IRQFLAGS_SUPPORT
306 select TRACE_IRQFLAGS_NMI_SUPPORT
307 select USER_STACKTRACE_SUPPORT
308 select HAVE_ARCH_KCSAN if X86_64
309 select PROC_PID_ARCH_STATUS if PROC_FS
310 select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
311 select FUNCTION_ALIGNMENT_16B if X86_64 || X86_ALIGNMENT_16
312 select FUNCTION_ALIGNMENT_4B
313 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
314 select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
316 config INSTRUCTION_DECODER
318 depends on KPROBES || PERF_EVENTS || UPROBES
322 default "elf32-i386" if X86_32
323 default "elf64-x86-64" if X86_64
325 config LOCKDEP_SUPPORT
328 config STACKTRACE_SUPPORT
334 config ARCH_MMAP_RND_BITS_MIN
338 config ARCH_MMAP_RND_BITS_MAX
342 config ARCH_MMAP_RND_COMPAT_BITS_MIN
345 config ARCH_MMAP_RND_COMPAT_BITS_MAX
351 config GENERIC_ISA_DMA
353 depends on ISA_DMA_API
357 default y if KMSAN || KASAN
362 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
364 config GENERIC_BUG_RELATIVE_POINTERS
367 config ARCH_MAY_HAVE_PC_FDC
369 depends on ISA_DMA_API
371 config GENERIC_CALIBRATE_DELAY
374 config ARCH_HAS_CPU_RELAX
377 config ARCH_HIBERNATION_POSSIBLE
380 config ARCH_SUSPEND_POSSIBLE
386 config KASAN_SHADOW_OFFSET
389 default 0xdffffc0000000000
391 config HAVE_INTEL_TXT
393 depends on INTEL_IOMMU && ACPI
397 depends on X86_64 && SMP
399 config ARCH_SUPPORTS_UPROBES
402 config FIX_EARLYCON_MEM
405 config DYNAMIC_PHYSICAL_MASK
408 config PGTABLE_LEVELS
410 default 5 if X86_5LEVEL
415 config CC_HAS_SANE_STACKPROTECTOR
417 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) $(CLANG_FLAGS)) if 64BIT
418 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC) $(CLANG_FLAGS))
420 We have to make sure stack protector is unconditionally disabled if
421 the compiler produces broken code or if it does not let us control
422 the segment on 32-bit kernels.
424 menu "Processor type and features"
427 bool "Symmetric multi-processing support"
429 This enables support for systems with more than one CPU. If you have
430 a system with only one CPU, say N. If you have a system with more
433 If you say N here, the kernel will run on uni- and multiprocessor
434 machines, but will use only one CPU of a multiprocessor machine. If
435 you say Y here, the kernel will run on many, but not all,
436 uniprocessor machines. On a uniprocessor machine, the kernel
437 will run faster if you say N here.
439 Note that if you say Y here and choose architecture "586" or
440 "Pentium" under "Processor family", the kernel will not work on 486
441 architectures. Similarly, multiprocessor kernels for the "PPro"
442 architecture may not work on all Pentium based boards.
444 People using multiprocessor machines who say Y here should also say
445 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
446 Management" code will be disabled if you say Y here.
448 See also <file:Documentation/arch/x86/i386/IO-APIC.rst>,
449 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
450 <http://www.tldp.org/docs.html#howto>.
452 If you don't know what to do here, say N.
455 bool "Support x2apic"
456 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
458 This enables x2apic support on CPUs that have this feature.
460 This allows 32-bit apic IDs (so it can support very large systems),
461 and accesses the local apic via MSRs not via mmio.
463 Some Intel systems circa 2022 and later are locked into x2APIC mode
464 and can not fall back to the legacy APIC modes if SGX or TDX are
465 enabled in the BIOS. They will boot with very reduced functionality
466 without enabling this option.
468 If you don't know what to do here, say N.
470 config X86_POSTED_MSI
471 bool "Enable MSI and MSI-x delivery by posted interrupts"
472 depends on X86_64 && IRQ_REMAP
474 This enables MSIs that are under interrupt remapping to be delivered as
475 posted interrupts to the host kernel. Interrupt throughput can
476 potentially be improved by coalescing CPU notifications during high
479 If you don't know what to do here, say N.
482 bool "Enable MPS table" if ACPI
484 depends on X86_LOCAL_APIC
486 For old smp systems that do not have proper acpi support. Newer systems
487 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
489 config X86_CPU_RESCTRL
490 bool "x86 CPU resource control support"
491 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
493 select PROC_CPU_RESCTRL if PROC_FS
495 Enable x86 CPU resource control support.
497 Provide support for the allocation and monitoring of system resources
500 Intel calls this Intel Resource Director Technology
501 (Intel(R) RDT). More information about RDT can be found in the
502 Intel x86 Architecture Software Developer Manual.
504 AMD calls this AMD Platform Quality of Service (AMD QoS).
505 More information about AMD QoS can be found in the AMD64 Technology
506 Platform Quality of Service Extensions manual.
511 bool "Flexible Return and Event Delivery"
514 When enabled, try to use Flexible Return and Event Delivery
515 instead of the legacy SYSCALL/SYSENTER/IDT architecture for
516 ring transitions and exception/interrupt handling if the
520 bool "Support for big SMP systems with more than 8 CPUs"
521 depends on SMP && X86_32
523 This option is needed for the systems that have more than 8 CPUs.
525 config X86_EXTENDED_PLATFORM
526 bool "Support for extended (non-PC) x86 platforms"
529 If you disable this option then the kernel will only support
530 standard PC platforms. (which covers the vast majority of
533 If you enable this option then you'll be able to select support
534 for the following non-PC x86 platforms, depending on the value of
537 32-bit platforms (CONFIG_64BIT=n):
538 Goldfish (Android emulator)
541 SGI 320/540 (Visual Workstation)
542 STA2X11-based (e.g. Northville)
543 Moorestown MID devices
545 64-bit platforms (CONFIG_64BIT=y):
550 If you have one of these systems, or if you want to build a
551 generic distribution kernel, say Y here - otherwise say N.
553 # This is an alphabetically sorted list of 64 bit extended platforms
554 # Please maintain the alphabetic order if and when there are additions
556 bool "Numascale NumaChip"
558 depends on X86_EXTENDED_PLATFORM
561 depends on X86_X2APIC
562 depends on PCI_MMCONFIG
564 Adds support for Numascale NumaChip large-SMP systems. Needed to
565 enable more than ~168 cores.
566 If you don't have one of these, you should say N here.
570 select HYPERVISOR_GUEST
572 depends on X86_64 && PCI
573 depends on X86_EXTENDED_PLATFORM
576 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
577 supposed to run on these EM64T-based machines. Only choose this option
578 if you have one of these machines.
581 bool "SGI Ultraviolet"
583 depends on X86_EXTENDED_PLATFORM
586 depends on KEXEC_CORE
587 depends on X86_X2APIC
590 This option is needed in order to support SGI Ultraviolet systems.
591 If you don't have one of these, you should say N here.
593 # Following is an alphabetically sorted list of 32 bit extended platforms
594 # Please maintain the alphabetic order if and when there are additions
597 bool "Goldfish (Virtual Platform)"
598 depends on X86_EXTENDED_PLATFORM
600 Enable support for the Goldfish virtual platform used primarily
601 for Android development. Unless you are building for the Android
602 Goldfish emulator say N here.
605 bool "CE4100 TV platform"
607 depends on PCI_GODIRECT
608 depends on X86_IO_APIC
610 depends on X86_EXTENDED_PLATFORM
611 select X86_REBOOTFIXUPS
613 select OF_EARLY_FLATTREE
615 Select for the Intel CE media processor (CE4100) SOC.
616 This option compiles in support for the CE4100 SOC for settop
617 boxes and media devices.
620 bool "Intel MID platform support"
621 depends on X86_EXTENDED_PLATFORM
622 depends on X86_PLATFORM_DEVICES
624 depends on X86_64 || (PCI_GOANY && X86_32)
625 depends on X86_IO_APIC
630 Select to build a kernel capable of supporting Intel MID (Mobile
631 Internet Device) platform systems which do not have the PCI legacy
632 interfaces. If you are building for a PC class system say N here.
634 Intel MID platforms are based on an Intel processor and chipset which
635 consume less power than most of the x86 derivatives.
637 config X86_INTEL_QUARK
638 bool "Intel Quark platform support"
640 depends on X86_EXTENDED_PLATFORM
641 depends on X86_PLATFORM_DEVICES
645 depends on X86_IO_APIC
650 Select to include support for Quark X1000 SoC.
651 Say Y here if you have a Quark based system such as the Arduino
652 compatible Intel Galileo.
654 config X86_INTEL_LPSS
655 bool "Intel Low Power Subsystem Support"
656 depends on X86 && ACPI && PCI
661 Select to build support for Intel Low Power Subsystem such as
662 found on Intel Lynxpoint PCH. Selecting this option enables
663 things like clock tree (common clock framework) and pincontrol
664 which are needed by the LPSS peripheral drivers.
666 config X86_AMD_PLATFORM_DEVICE
667 bool "AMD ACPI2Platform devices support"
672 Select to interpret AMD specific ACPI device to platform device
673 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
674 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
675 implemented under PINCTRL subsystem.
678 tristate "Intel SoC IOSF Sideband support for SoC platforms"
681 This option enables sideband register access support for Intel SoC
682 platforms. On these platforms the IOSF sideband is used in lieu of
683 MSR's for some register accesses, mostly but not limited to thermal
684 and power. Drivers may query the availability of this device to
685 determine if they need the sideband in order to work on these
686 platforms. The sideband is available on the following SoC products.
687 This list is not meant to be exclusive.
692 You should say Y if you are running a kernel on one of these SoC's.
694 config IOSF_MBI_DEBUG
695 bool "Enable IOSF sideband access through debugfs"
696 depends on IOSF_MBI && DEBUG_FS
698 Select this option to expose the IOSF sideband access registers (MCR,
699 MDR, MCRX) through debugfs to write and read register information from
700 different units on the SoC. This is most useful for obtaining device
701 state information for debug and analysis. As this is a general access
702 mechanism, users of this option would have specific knowledge of the
703 device they want to access.
705 If you don't require the option or are in doubt, say N.
708 bool "RDC R-321x SoC"
710 depends on X86_EXTENDED_PLATFORM
712 select X86_REBOOTFIXUPS
714 This option is needed for RDC R-321x system-on-chip, also known
716 If you don't have one of these chips, you should say N here.
718 config X86_32_NON_STANDARD
719 bool "Support non-standard 32-bit SMP architectures"
720 depends on X86_32 && SMP
721 depends on X86_EXTENDED_PLATFORM
723 This option compiles in the bigsmp and STA2X11 default
724 subarchitectures. It is intended for a generic binary
725 kernel. If you select them all, kernel will probe it one by
726 one and will fallback to default.
728 # Alphabetically sorted list of Non standard 32 bit platforms
730 config X86_SUPPORTS_MEMORY_FAILURE
732 # MCE code calls memory_failure():
734 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
735 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
736 depends on X86_64 || !SPARSEMEM
737 select ARCH_SUPPORTS_MEMORY_FAILURE
740 bool "STA2X11 Companion Chip Support"
741 depends on X86_32_NON_STANDARD && PCI
746 This adds support for boards based on the STA2X11 IO-Hub,
747 a.k.a. "ConneXt". The chip is used in place of the standard
748 PC chipset, so all "standard" peripherals are missing. If this
749 option is selected the kernel will still be able to boot on
750 standard PC machines.
753 tristate "Eurobraille/Iris poweroff module"
756 The Iris machines from EuroBraille do not have APM or ACPI support
757 to shut themselves down properly. A special I/O sequence is
758 needed to do so, which is what this module does at
761 This is only for Iris machines from EuroBraille.
765 config SCHED_OMIT_FRAME_POINTER
767 prompt "Single-depth WCHAN output"
770 Calculate simpler /proc/<PID>/wchan values. If this option
771 is disabled then wchan values will recurse back to the
772 caller function. This provides more accurate wchan values,
773 at the expense of slightly more scheduling overhead.
775 If in doubt, say "Y".
777 menuconfig HYPERVISOR_GUEST
778 bool "Linux guest support"
780 Say Y here to enable options for running Linux under various hyper-
781 visors. This option enables basic hypervisor detection and platform
784 If you say N, all options in this submenu will be skipped and
785 disabled, and Linux guest support won't be built in.
790 bool "Enable paravirtualization code"
791 depends on HAVE_STATIC_CALL
793 This changes the kernel so it can modify itself when it is run
794 under a hypervisor, potentially improving performance significantly
795 over full virtualization. However, when run without a hypervisor
796 the kernel is theoretically slower and slightly larger.
801 config PARAVIRT_DEBUG
802 bool "paravirt-ops debugging"
803 depends on PARAVIRT && DEBUG_KERNEL
805 Enable to debug paravirt_ops internals. Specifically, BUG if
806 a paravirt_op is missing when it is called.
808 config PARAVIRT_SPINLOCKS
809 bool "Paravirtualization layer for spinlocks"
810 depends on PARAVIRT && SMP
812 Paravirtualized spinlocks allow a pvops backend to replace the
813 spinlock implementation with something virtualization-friendly
814 (for example, block the virtual CPU rather than spinning).
816 It has a minimal impact on native kernels and gives a nice performance
817 benefit on paravirtualized KVM / Xen kernels.
819 If you are unsure how to answer this question, answer Y.
821 config X86_HV_CALLBACK_VECTOR
824 source "arch/x86/xen/Kconfig"
827 bool "KVM Guest support (including kvmclock)"
829 select PARAVIRT_CLOCK
830 select ARCH_CPUIDLE_HALTPOLL
831 select X86_HV_CALLBACK_VECTOR
834 This option enables various optimizations for running under the KVM
835 hypervisor. It includes a paravirtualized clock, so that instead
836 of relying on a PIT (or probably other) emulation by the
837 underlying device model, the host provides the guest with
838 timing infrastructure such as time of day, and system time
840 config ARCH_CPUIDLE_HALTPOLL
842 prompt "Disable host haltpoll when loading haltpoll driver"
844 If virtualized under KVM, disable host haltpoll.
847 bool "Support for running PVH guests"
849 This option enables the PVH entry point for guest virtual machines
850 as specified in the x86/HVM direct boot ABI.
852 config PARAVIRT_TIME_ACCOUNTING
853 bool "Paravirtual steal time accounting"
856 Select this option to enable fine granularity task steal time
857 accounting. Time spent executing other tasks in parallel with
858 the current vCPU is discounted from the vCPU power. To account for
859 that, there can be a small performance impact.
861 If in doubt, say N here.
863 config PARAVIRT_CLOCK
866 config JAILHOUSE_GUEST
867 bool "Jailhouse non-root cell support"
868 depends on X86_64 && PCI
871 This option allows to run Linux as guest in a Jailhouse non-root
872 cell. You can leave this option disabled if you only want to start
873 Jailhouse and run Linux afterwards in the root cell.
876 bool "ACRN Guest support"
878 select X86_HV_CALLBACK_VECTOR
880 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
881 a flexible, lightweight reference open-source hypervisor, built with
882 real-time and safety-criticality in mind. It is built for embedded
883 IOT with small footprint and real-time features. More details can be
884 found in https://projectacrn.org/.
886 config INTEL_TDX_GUEST
887 bool "Intel TDX (Trust Domain Extensions) - Guest Support"
888 depends on X86_64 && CPU_SUP_INTEL
889 depends on X86_X2APIC
891 select ARCH_HAS_CC_PLATFORM
892 select X86_MEM_ENCRYPT
894 select UNACCEPTED_MEMORY
896 Support running as a guest under Intel TDX. Without this support,
897 the guest kernel can not boot or run under TDX.
898 TDX includes memory encryption and integrity capabilities
899 which protect the confidentiality and integrity of guest
900 memory contents and CPU state. TDX guests are protected from
901 some attacks from the VMM.
903 endif # HYPERVISOR_GUEST
905 source "arch/x86/Kconfig.cpu"
909 prompt "HPET Timer Support" if X86_32
911 Use the IA-PC HPET (High Precision Event Timer) to manage
912 time in preference to the PIT and RTC, if a HPET is
914 HPET is the next generation timer replacing legacy 8254s.
915 The HPET provides a stable time base on SMP
916 systems, unlike the TSC, but it is more expensive to access,
917 as it is off-chip. The interface used is documented
918 in the HPET spec, revision 1.
920 You can safely choose Y here. However, HPET will only be
921 activated if the platform and the BIOS support this feature.
922 Otherwise the 8254 will be used for timing services.
924 Choose N to continue using the legacy 8254 timer.
926 config HPET_EMULATE_RTC
928 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
930 # Mark as expert because too many people got it wrong.
931 # The code disables itself when not needed.
934 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
935 bool "Enable DMI scanning" if EXPERT
937 Enabled scanning of DMI to identify machine quirks. Say Y
938 here unless you have verified that your setup is not
939 affected by entries in the DMI blacklist. Required by PNP
943 bool "Old AMD GART IOMMU support"
947 depends on X86_64 && PCI && AMD_NB
949 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
950 GART based hardware IOMMUs.
952 The GART supports full DMA access for devices with 32-bit access
953 limitations, on systems with more than 3 GB. This is usually needed
954 for USB, sound, many IDE/SATA chipsets and some other devices.
956 Newer systems typically have a modern AMD IOMMU, supported via
957 the CONFIG_AMD_IOMMU=y config option.
959 In normal configurations this driver is only active when needed:
960 there's more than 3 GB of memory and the system contains a
961 32-bit limited device.
965 config BOOT_VESA_SUPPORT
968 If true, at least one selected framebuffer driver can take advantage
969 of VESA video modes set at an early boot stage via the vga= parameter.
972 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
973 depends on X86_64 && SMP && DEBUG_KERNEL
974 select CPUMASK_OFFSTACK
976 Enable maximum number of CPUS and NUMA Nodes for this architecture.
980 # The maximum number of CPUs supported:
982 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
983 # and which can be configured interactively in the
984 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
986 # The ranges are different on 32-bit and 64-bit kernels, depending on
987 # hardware capabilities and scalability features of the kernel.
989 # ( If MAXSMP is enabled we just use the highest possible value and disable
990 # interactive configuration. )
993 config NR_CPUS_RANGE_BEGIN
995 default NR_CPUS_RANGE_END if MAXSMP
999 config NR_CPUS_RANGE_END
1002 default 64 if SMP && X86_BIGSMP
1003 default 8 if SMP && !X86_BIGSMP
1006 config NR_CPUS_RANGE_END
1009 default 8192 if SMP && CPUMASK_OFFSTACK
1010 default 512 if SMP && !CPUMASK_OFFSTACK
1013 config NR_CPUS_DEFAULT
1016 default 32 if X86_BIGSMP
1020 config NR_CPUS_DEFAULT
1023 default 8192 if MAXSMP
1028 int "Maximum number of CPUs" if SMP && !MAXSMP
1029 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1030 default NR_CPUS_DEFAULT
1032 This allows you to specify the maximum number of CPUs which this
1033 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1034 supported value is 8192, otherwise the maximum value is 512. The
1035 minimum value which makes sense is 2.
1037 This is purely to save memory: each supported CPU adds about 8KB
1038 to the kernel image.
1040 config SCHED_CLUSTER
1041 bool "Cluster scheduler support"
1045 Cluster scheduler support improves the CPU scheduler's decision
1046 making when dealing with machines that have clusters of CPUs.
1047 Cluster usually means a couple of CPUs which are placed closely
1048 by sharing mid-level caches, last-level cache tags or internal
1056 prompt "Multi-core scheduler support"
1059 Multi-core scheduler support improves the CPU scheduler's decision
1060 making when dealing with multi-core CPU chips at a cost of slightly
1061 increased overhead in some places. If unsure say N here.
1063 config SCHED_MC_PRIO
1064 bool "CPU core priorities scheduler support"
1066 select X86_INTEL_PSTATE if CPU_SUP_INTEL
1067 select X86_AMD_PSTATE if CPU_SUP_AMD && ACPI
1071 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1072 core ordering determined at manufacturing time, which allows
1073 certain cores to reach higher turbo frequencies (when running
1074 single threaded workloads) than others.
1076 Enabling this kernel feature teaches the scheduler about
1077 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1078 scheduler's CPU selection logic accordingly, so that higher
1079 overall system performance can be achieved.
1081 This feature will have no effect on CPUs without this feature.
1083 If unsure say Y here.
1087 depends on !SMP && X86_LOCAL_APIC
1090 bool "Local APIC support on uniprocessors" if !PCI_MSI
1092 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1094 A local APIC (Advanced Programmable Interrupt Controller) is an
1095 integrated interrupt controller in the CPU. If you have a single-CPU
1096 system which has a processor with a local APIC, you can say Y here to
1097 enable and use it. If you say Y here even though your machine doesn't
1098 have a local APIC, then the kernel will still run with no slowdown at
1099 all. The local APIC supports CPU-generated self-interrupts (timer,
1100 performance counters), and the NMI watchdog which detects hard
1103 config X86_UP_IOAPIC
1104 bool "IO-APIC support on uniprocessors"
1105 depends on X86_UP_APIC
1107 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1108 SMP-capable replacement for PC-style interrupt controllers. Most
1109 SMP systems and many recent uniprocessor systems have one.
1111 If you have a single-CPU system with an IO-APIC, you can say Y here
1112 to use it. If you say Y here even though your machine doesn't have
1113 an IO-APIC, then the kernel will still run with no slowdown at all.
1115 config X86_LOCAL_APIC
1117 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1118 select IRQ_DOMAIN_HIERARCHY
1122 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1124 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1125 bool "Reroute for broken boot IRQs"
1126 depends on X86_IO_APIC
1128 This option enables a workaround that fixes a source of
1129 spurious interrupts. This is recommended when threaded
1130 interrupt handling is used on systems where the generation of
1131 superfluous "boot interrupts" cannot be disabled.
1133 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1134 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1135 kernel does during interrupt handling). On chipsets where this
1136 boot IRQ generation cannot be disabled, this workaround keeps
1137 the original IRQ line masked so that only the equivalent "boot
1138 IRQ" is delivered to the CPUs. The workaround also tells the
1139 kernel to set up the IRQ handler on the boot IRQ line. In this
1140 way only one interrupt is delivered to the kernel. Otherwise
1141 the spurious second interrupt may cause the kernel to bring
1142 down (vital) interrupt lines.
1144 Only affects "broken" chipsets. Interrupt sharing may be
1145 increased on these systems.
1148 bool "Machine Check / overheating reporting"
1149 select GENERIC_ALLOCATOR
1152 Machine Check support allows the processor to notify the
1153 kernel if it detects a problem (e.g. overheating, data corruption).
1154 The action the kernel takes depends on the severity of the problem,
1155 ranging from warning messages to halting the machine.
1157 config X86_MCELOG_LEGACY
1158 bool "Support for deprecated /dev/mcelog character device"
1161 Enable support for /dev/mcelog which is needed by the old mcelog
1162 userspace logging daemon. Consider switching to the new generation
1165 config X86_MCE_INTEL
1167 prompt "Intel MCE features"
1168 depends on X86_MCE && X86_LOCAL_APIC
1170 Additional support for intel specific MCE features such as
1171 the thermal monitor.
1175 prompt "AMD MCE features"
1176 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1178 Additional support for AMD specific MCE features such as
1179 the DRAM Error Threshold.
1181 config X86_ANCIENT_MCE
1182 bool "Support for old Pentium 5 / WinChip machine checks"
1183 depends on X86_32 && X86_MCE
1185 Include support for machine check handling on old Pentium 5 or WinChip
1186 systems. These typically need to be enabled explicitly on the command
1189 config X86_MCE_THRESHOLD
1190 depends on X86_MCE_AMD || X86_MCE_INTEL
1193 config X86_MCE_INJECT
1194 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1195 tristate "Machine check injector support"
1197 Provide support for injecting machine checks for testing purposes.
1198 If you don't know what a machine check is and you don't do kernel
1199 QA it is safe to say n.
1201 source "arch/x86/events/Kconfig"
1203 config X86_LEGACY_VM86
1204 bool "Legacy VM86 support"
1207 This option allows user programs to put the CPU into V8086
1208 mode, which is an 80286-era approximation of 16-bit real mode.
1210 Some very old versions of X and/or vbetool require this option
1211 for user mode setting. Similarly, DOSEMU will use it if
1212 available to accelerate real mode DOS programs. However, any
1213 recent version of DOSEMU, X, or vbetool should be fully
1214 functional even without kernel VM86 support, as they will all
1215 fall back to software emulation. Nevertheless, if you are using
1216 a 16-bit DOS program where 16-bit performance matters, vm86
1217 mode might be faster than emulation and you might want to
1220 Note that any app that works on a 64-bit kernel is unlikely to
1221 need this option, as 64-bit kernels don't, and can't, support
1222 V8086 mode. This option is also unrelated to 16-bit protected
1223 mode and is not needed to run most 16-bit programs under Wine.
1225 Enabling this option increases the complexity of the kernel
1226 and slows down exception handling a tiny bit.
1228 If unsure, say N here.
1232 default X86_LEGACY_VM86
1235 bool "Enable support for 16-bit segments" if EXPERT
1237 depends on MODIFY_LDT_SYSCALL
1239 This option is required by programs like Wine to run 16-bit
1240 protected mode legacy code on x86 processors. Disabling
1241 this option saves about 300 bytes on i386, or around 6K text
1242 plus 16K runtime memory on x86-64,
1246 depends on X86_16BIT && X86_32
1250 depends on X86_16BIT && X86_64
1252 config X86_VSYSCALL_EMULATION
1253 bool "Enable vsyscall emulation" if EXPERT
1257 This enables emulation of the legacy vsyscall page. Disabling
1258 it is roughly equivalent to booting with vsyscall=none, except
1259 that it will also disable the helpful warning if a program
1260 tries to use a vsyscall. With this option set to N, offending
1261 programs will just segfault, citing addresses of the form
1264 This option is required by many programs built before 2013, and
1265 care should be used even with newer programs if set to N.
1267 Disabling this option saves about 7K of kernel size and
1268 possibly 4K of additional runtime pagetable memory.
1270 config X86_IOPL_IOPERM
1271 bool "IOPERM and IOPL Emulation"
1274 This enables the ioperm() and iopl() syscalls which are necessary
1275 for legacy applications.
1277 Legacy IOPL support is an overbroad mechanism which allows user
1278 space aside of accessing all 65536 I/O ports also to disable
1279 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1280 capabilities and permission from potentially active security
1283 The emulation restricts the functionality of the syscall to
1284 only allowing the full range I/O port access, but prevents the
1285 ability to disable interrupts from user space which would be
1286 granted if the hardware IOPL mechanism would be used.
1289 tristate "Toshiba Laptop support"
1292 This adds a driver to safely access the System Management Mode of
1293 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1294 not work on models with a Phoenix BIOS. The System Management Mode
1295 is used to set the BIOS and power saving options on Toshiba portables.
1297 For information on utilities to make use of this driver see the
1298 Toshiba Linux utilities web site at:
1299 <http://www.buzzard.org.uk/toshiba/>.
1301 Say Y if you intend to run this kernel on a Toshiba portable.
1304 config X86_REBOOTFIXUPS
1305 bool "Enable X86 board specific fixups for reboot"
1308 This enables chipset and/or board specific fixups to be done
1309 in order to get reboot to work correctly. This is only needed on
1310 some combinations of hardware and BIOS. The symptom, for which
1311 this config is intended, is when reboot ends with a stalled/hung
1314 Currently, the only fixup is for the Geode machines using
1315 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1317 Say Y if you want to enable the fixup. Currently, it's safe to
1318 enable this option even if you don't need it.
1323 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1325 config MICROCODE_INITRD32
1327 depends on MICROCODE && X86_32 && BLK_DEV_INITRD
1329 config MICROCODE_LATE_LOADING
1330 bool "Late microcode loading (DANGEROUS)"
1332 depends on MICROCODE && SMP
1334 Loading microcode late, when the system is up and executing instructions
1335 is a tricky business and should be avoided if possible. Just the sequence
1336 of synchronizing all cores and SMT threads is one fragile dance which does
1337 not guarantee that cores might not softlock after the loading. Therefore,
1338 use this at your own risk. Late loading taints the kernel unless the
1339 microcode header indicates that it is safe for late loading via the
1340 minimal revision check. This minimal revision check can be enforced on
1341 the kernel command line with "microcode.minrev=Y".
1343 config MICROCODE_LATE_FORCE_MINREV
1344 bool "Enforce late microcode loading minimal revision check"
1346 depends on MICROCODE_LATE_LOADING
1348 To prevent that users load microcode late which modifies already
1349 in use features, newer microcode patches have a minimum revision field
1350 in the microcode header, which tells the kernel which minimum
1351 revision must be active in the CPU to safely load that new microcode
1352 late into the running system. If disabled the check will not
1353 be enforced but the kernel will be tainted when the minimal
1354 revision check fails.
1356 This minimal revision check can also be controlled via the
1357 "microcode.minrev" parameter on the kernel command line.
1362 tristate "/dev/cpu/*/msr - Model-specific register support"
1364 This device gives privileged processes access to the x86
1365 Model-Specific Registers (MSRs). It is a character device with
1366 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1367 MSR accesses are directed to a specific CPU on multi-processor
1371 tristate "/dev/cpu/*/cpuid - CPU information support"
1373 This device gives processes access to the x86 CPUID instruction to
1374 be executed on a specific processor. It is a character device
1375 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1379 prompt "High Memory Support"
1386 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1387 However, the address space of 32-bit x86 processors is only 4
1388 Gigabytes large. That means that, if you have a large amount of
1389 physical memory, not all of it can be "permanently mapped" by the
1390 kernel. The physical memory that's not permanently mapped is called
1393 If you are compiling a kernel which will never run on a machine with
1394 more than 1 Gigabyte total physical RAM, answer "off" here (default
1395 choice and suitable for most users). This will result in a "3GB/1GB"
1396 split: 3GB are mapped so that each process sees a 3GB virtual memory
1397 space and the remaining part of the 4GB virtual memory space is used
1398 by the kernel to permanently map as much physical memory as
1401 If the machine has between 1 and 4 Gigabytes physical RAM, then
1404 If more than 4 Gigabytes is used then answer "64GB" here. This
1405 selection turns Intel PAE (Physical Address Extension) mode on.
1406 PAE implements 3-level paging on IA32 processors. PAE is fully
1407 supported by Linux, PAE mode is implemented on all recent Intel
1408 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1409 then the kernel will not boot on CPUs that don't support PAE!
1411 The actual amount of total physical memory will either be
1412 auto detected or can be forced by using a kernel command line option
1413 such as "mem=256M". (Try "man bootparam" or see the documentation of
1414 your boot loader (lilo or loadlin) about how to pass options to the
1415 kernel at boot time.)
1417 If unsure, say "off".
1422 Select this if you have a 32-bit processor and between 1 and 4
1423 gigabytes of physical RAM.
1427 depends on X86_HAVE_PAE
1430 Select this if you have a 32-bit processor and more than 4
1431 gigabytes of physical RAM.
1436 prompt "Memory split" if EXPERT
1440 Select the desired split between kernel and user memory.
1442 If the address range available to the kernel is less than the
1443 physical memory installed, the remaining memory will be available
1444 as "high memory". Accessing high memory is a little more costly
1445 than low memory, as it needs to be mapped into the kernel first.
1446 Note that increasing the kernel address space limits the range
1447 available to user programs, making the address space there
1448 tighter. Selecting anything other than the default 3G/1G split
1449 will also likely make your kernel incompatible with binary-only
1452 If you are not absolutely sure what you are doing, leave this
1456 bool "3G/1G user/kernel split"
1457 config VMSPLIT_3G_OPT
1459 bool "3G/1G user/kernel split (for full 1G low memory)"
1461 bool "2G/2G user/kernel split"
1462 config VMSPLIT_2G_OPT
1464 bool "2G/2G user/kernel split (for full 2G low memory)"
1466 bool "1G/3G user/kernel split"
1471 default 0xB0000000 if VMSPLIT_3G_OPT
1472 default 0x80000000 if VMSPLIT_2G
1473 default 0x78000000 if VMSPLIT_2G_OPT
1474 default 0x40000000 if VMSPLIT_1G
1480 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1483 bool "PAE (Physical Address Extension) Support"
1484 depends on X86_32 && X86_HAVE_PAE
1485 select PHYS_ADDR_T_64BIT
1488 PAE is required for NX support, and furthermore enables
1489 larger swapspace support for non-overcommit purposes. It
1490 has the cost of more pagetable lookup overhead, and also
1491 consumes more pagetable space per process.
1494 bool "Enable 5-level page tables support"
1496 select DYNAMIC_MEMORY_LAYOUT
1497 select SPARSEMEM_VMEMMAP
1500 5-level paging enables access to larger address space:
1501 up to 128 PiB of virtual address space and 4 PiB of
1502 physical address space.
1504 It will be supported by future Intel CPUs.
1506 A kernel with the option enabled can be booted on machines that
1507 support 4- or 5-level paging.
1509 See Documentation/arch/x86/x86_64/5level-paging.rst for more
1514 config X86_DIRECT_GBPAGES
1518 Certain kernel features effectively disable kernel
1519 linear 1 GB mappings (even if the CPU otherwise
1520 supports them), so don't confuse the user by printing
1521 that we have them enabled.
1523 config X86_CPA_STATISTICS
1524 bool "Enable statistic for Change Page Attribute"
1527 Expose statistics about the Change Page Attribute mechanism, which
1528 helps to determine the effectiveness of preserving large and huge
1529 page mappings when mapping protections are changed.
1531 config X86_MEM_ENCRYPT
1532 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1533 select DYNAMIC_PHYSICAL_MASK
1536 config AMD_MEM_ENCRYPT
1537 bool "AMD Secure Memory Encryption (SME) support"
1538 depends on X86_64 && CPU_SUP_AMD
1540 select DMA_COHERENT_POOL
1541 select ARCH_USE_MEMREMAP_PROT
1542 select INSTRUCTION_DECODER
1543 select ARCH_HAS_CC_PLATFORM
1544 select X86_MEM_ENCRYPT
1545 select UNACCEPTED_MEMORY
1547 Say yes to enable support for the encryption of system memory.
1548 This requires an AMD processor that supports Secure Memory
1551 # Common NUMA Features
1553 bool "NUMA Memory Allocation and Scheduler Support"
1555 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1556 default y if X86_BIGSMP
1557 select USE_PERCPU_NUMA_NODE_ID
1558 select OF_NUMA if OF
1560 Enable NUMA (Non-Uniform Memory Access) support.
1562 The kernel will try to allocate memory used by a CPU on the
1563 local memory controller of the CPU and add some more
1564 NUMA awareness to the kernel.
1566 For 64-bit this is recommended if the system is Intel Core i7
1567 (or later), AMD Opteron, or EM64T NUMA.
1569 For 32-bit this is only needed if you boot a 32-bit
1570 kernel on a 64-bit NUMA platform.
1572 Otherwise, you should say N.
1576 prompt "Old style AMD Opteron NUMA detection"
1577 depends on X86_64 && NUMA && PCI
1579 Enable AMD NUMA node topology detection. You should say Y here if
1580 you have a multi processor AMD system. This uses an old method to
1581 read the NUMA configuration directly from the builtin Northbridge
1582 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1583 which also takes priority if both are compiled in.
1585 config X86_64_ACPI_NUMA
1587 prompt "ACPI NUMA detection"
1588 depends on X86_64 && NUMA && ACPI && PCI
1591 Enable ACPI SRAT based node topology detection.
1594 bool "NUMA emulation"
1597 Enable NUMA emulation. A flat machine will be split
1598 into virtual nodes when booted with "numa=fake=N", where N is the
1599 number of nodes. This is only useful for debugging.
1602 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1604 default "10" if MAXSMP
1605 default "6" if X86_64
1609 Specify the maximum number of NUMA Nodes available on the target
1610 system. Increases memory reserved to accommodate various tables.
1612 config ARCH_FLATMEM_ENABLE
1614 depends on X86_32 && !NUMA
1616 config ARCH_SPARSEMEM_ENABLE
1618 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1619 select SPARSEMEM_STATIC if X86_32
1620 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1622 config ARCH_SPARSEMEM_DEFAULT
1623 def_bool X86_64 || (NUMA && X86_32)
1625 config ARCH_SELECT_MEMORY_MODEL
1627 depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE
1629 config ARCH_MEMORY_PROBE
1630 bool "Enable sysfs memory/probe interface"
1631 depends on MEMORY_HOTPLUG
1633 This option enables a sysfs memory/probe interface for testing.
1634 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1635 If you are unsure how to answer this question, answer N.
1637 config ARCH_PROC_KCORE_TEXT
1639 depends on X86_64 && PROC_KCORE
1641 config ILLEGAL_POINTER_VALUE
1644 default 0xdead000000000000 if X86_64
1646 config X86_PMEM_LEGACY_DEVICE
1649 config X86_PMEM_LEGACY
1650 tristate "Support non-standard NVDIMMs and ADR protected memory"
1651 depends on PHYS_ADDR_T_64BIT
1653 select X86_PMEM_LEGACY_DEVICE
1654 select NUMA_KEEP_MEMINFO if NUMA
1657 Treat memory marked using the non-standard e820 type of 12 as used
1658 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1659 The kernel will offer these regions to the 'pmem' driver so
1660 they can be used for persistent storage.
1665 bool "Allocate 3rd-level pagetables from highmem"
1668 The VM uses one page table entry for each page of physical memory.
1669 For systems with a lot of RAM, this can be wasteful of precious
1670 low memory. Setting this option will put user-space page table
1671 entries in high memory.
1673 config X86_CHECK_BIOS_CORRUPTION
1674 bool "Check for low memory corruption"
1676 Periodically check for memory corruption in low memory, which
1677 is suspected to be caused by BIOS. Even when enabled in the
1678 configuration, it is disabled at runtime. Enable it by
1679 setting "memory_corruption_check=1" on the kernel command
1680 line. By default it scans the low 64k of memory every 60
1681 seconds; see the memory_corruption_check_size and
1682 memory_corruption_check_period parameters in
1683 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1685 When enabled with the default parameters, this option has
1686 almost no overhead, as it reserves a relatively small amount
1687 of memory and scans it infrequently. It both detects corruption
1688 and prevents it from affecting the running system.
1690 It is, however, intended as a diagnostic tool; if repeatable
1691 BIOS-originated corruption always affects the same memory,
1692 you can use memmap= to prevent the kernel from using that
1695 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1696 bool "Set the default setting of memory_corruption_check"
1697 depends on X86_CHECK_BIOS_CORRUPTION
1700 Set whether the default state of memory_corruption_check is
1703 config MATH_EMULATION
1705 depends on MODIFY_LDT_SYSCALL
1706 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1708 Linux can emulate a math coprocessor (used for floating point
1709 operations) if you don't have one. 486DX and Pentium processors have
1710 a math coprocessor built in, 486SX and 386 do not, unless you added
1711 a 487DX or 387, respectively. (The messages during boot time can
1712 give you some hints here ["man dmesg"].) Everyone needs either a
1713 coprocessor or this emulation.
1715 If you don't have a math coprocessor, you need to say Y here; if you
1716 say Y here even though you have a coprocessor, the coprocessor will
1717 be used nevertheless. (This behavior can be changed with the kernel
1718 command line option "no387", which comes handy if your coprocessor
1719 is broken. Try "man bootparam" or see the documentation of your boot
1720 loader (lilo or loadlin) about how to pass options to the kernel at
1721 boot time.) This means that it is a good idea to say Y here if you
1722 intend to use this kernel on different machines.
1724 More information about the internals of the Linux math coprocessor
1725 emulation can be found in <file:arch/x86/math-emu/README>.
1727 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1728 kernel, it won't hurt.
1732 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1734 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1735 the Memory Type Range Registers (MTRRs) may be used to control
1736 processor access to memory ranges. This is most useful if you have
1737 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1738 allows bus write transfers to be combined into a larger transfer
1739 before bursting over the PCI/AGP bus. This can increase performance
1740 of image write operations 2.5 times or more. Saying Y here creates a
1741 /proc/mtrr file which may be used to manipulate your processor's
1742 MTRRs. Typically the X server should use this.
1744 This code has a reasonably generic interface so that similar
1745 control registers on other processors can be easily supported
1748 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1749 Registers (ARRs) which provide a similar functionality to MTRRs. For
1750 these, the ARRs are used to emulate the MTRRs.
1751 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1752 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1753 write-combining. All of these processors are supported by this code
1754 and it makes sense to say Y here if you have one of them.
1756 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1757 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1758 can lead to all sorts of problems, so it's good to say Y here.
1760 You can safely say Y even if your machine doesn't have MTRRs, you'll
1761 just add about 9 KB to your kernel.
1763 See <file:Documentation/arch/x86/mtrr.rst> for more information.
1765 config MTRR_SANITIZER
1767 prompt "MTRR cleanup support"
1770 Convert MTRR layout from continuous to discrete, so X drivers can
1771 add writeback entries.
1773 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1774 The largest mtrr entry size for a continuous block can be set with
1779 config MTRR_SANITIZER_ENABLE_DEFAULT
1780 int "MTRR cleanup enable value (0-1)"
1783 depends on MTRR_SANITIZER
1785 Enable mtrr cleanup default value
1787 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1788 int "MTRR cleanup spare reg num (0-7)"
1791 depends on MTRR_SANITIZER
1793 mtrr cleanup spare entries default, it can be changed via
1794 mtrr_spare_reg_nr=N on the kernel command line.
1798 prompt "x86 PAT support" if EXPERT
1801 Use PAT attributes to setup page level cache control.
1803 PATs are the modern equivalents of MTRRs and are much more
1804 flexible than MTRRs.
1806 Say N here if you see bootup problems (boot crash, boot hang,
1807 spontaneous reboots) or a non-working video driver.
1811 config ARCH_USES_PG_UNCACHED
1817 prompt "User Mode Instruction Prevention" if EXPERT
1819 User Mode Instruction Prevention (UMIP) is a security feature in
1820 some x86 processors. If enabled, a general protection fault is
1821 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1822 executed in user mode. These instructions unnecessarily expose
1823 information about the hardware state.
1825 The vast majority of applications do not use these instructions.
1826 For the very few that do, software emulation is provided in
1827 specific cases in protected and virtual-8086 modes. Emulated
1831 # GCC >= 9 and binutils >= 2.29
1832 # Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
1834 # https://github.com/llvm/llvm-project/commit/e0b89df2e0f0130881bf6c39bf31d7f6aac00e0f
1835 # https://github.com/llvm/llvm-project/commit/dfcf69770bc522b9e411c66454934a37c1f35332
1836 def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \
1837 (CC_IS_CLANG && CLANG_VERSION >= 140000)) && \
1843 CET features configured (Shadow stack or IBT)
1845 config X86_KERNEL_IBT
1846 prompt "Indirect Branch Tracking"
1848 depends on X86_64 && CC_HAS_IBT && HAVE_OBJTOOL
1849 # https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
1850 depends on !LD_IS_LLD || LLD_VERSION >= 140000
1854 Build the kernel with support for Indirect Branch Tracking, a
1855 hardware support course-grain forward-edge Control Flow Integrity
1856 protection. It enforces that all indirect calls must land on
1857 an ENDBR instruction, as such, the compiler will instrument the
1858 code with them to make this happen.
1860 In addition to building the kernel with IBT, seal all functions that
1861 are not indirect call targets, avoiding them ever becoming one.
1863 This requires LTO like objtool runs and will slow down the build. It
1864 does significantly reduce the number of ENDBR instructions in the
1867 config X86_INTEL_MEMORY_PROTECTION_KEYS
1868 prompt "Memory Protection Keys"
1870 # Note: only available in 64-bit mode
1871 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1872 select ARCH_USES_HIGH_VMA_FLAGS
1873 select ARCH_HAS_PKEYS
1875 Memory Protection Keys provides a mechanism for enforcing
1876 page-based protections, but without requiring modification of the
1877 page tables when an application changes protection domains.
1879 For details, see Documentation/core-api/protection-keys.rst
1884 prompt "TSX enable mode"
1885 depends on CPU_SUP_INTEL
1886 default X86_INTEL_TSX_MODE_OFF
1888 Intel's TSX (Transactional Synchronization Extensions) feature
1889 allows to optimize locking protocols through lock elision which
1890 can lead to a noticeable performance boost.
1892 On the other hand it has been shown that TSX can be exploited
1893 to form side channel attacks (e.g. TAA) and chances are there
1894 will be more of those attacks discovered in the future.
1896 Therefore TSX is not enabled by default (aka tsx=off). An admin
1897 might override this decision by tsx=on the command line parameter.
1898 Even with TSX enabled, the kernel will attempt to enable the best
1899 possible TAA mitigation setting depending on the microcode available
1900 for the particular machine.
1902 This option allows to set the default tsx mode between tsx=on, =off
1903 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1906 Say off if not sure, auto if TSX is in use but it should be used on safe
1907 platforms or on if TSX is in use and the security aspect of tsx is not
1910 config X86_INTEL_TSX_MODE_OFF
1913 TSX is disabled if possible - equals to tsx=off command line parameter.
1915 config X86_INTEL_TSX_MODE_ON
1918 TSX is always enabled on TSX capable HW - equals the tsx=on command
1921 config X86_INTEL_TSX_MODE_AUTO
1924 TSX is enabled on TSX capable HW that is believed to be safe against
1925 side channel attacks- equals the tsx=auto command line parameter.
1929 bool "Software Guard eXtensions (SGX)"
1930 depends on X86_64 && CPU_SUP_INTEL && X86_X2APIC
1932 depends on CRYPTO_SHA256=y
1934 select NUMA_KEEP_MEMINFO if NUMA
1937 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1938 that can be used by applications to set aside private regions of code
1939 and data, referred to as enclaves. An enclave's private memory can
1940 only be accessed by code running within the enclave. Accesses from
1941 outside the enclave, including other enclaves, are disallowed by
1946 config X86_USER_SHADOW_STACK
1947 bool "X86 userspace shadow stack"
1950 select ARCH_USES_HIGH_VMA_FLAGS
1953 Shadow stack protection is a hardware feature that detects function
1954 return address corruption. This helps mitigate ROP attacks.
1955 Applications must be enabled to use it, and old userspace does not
1956 get protection "for free".
1958 CPUs supporting shadow stacks were first released in 2020.
1960 See Documentation/arch/x86/shstk.rst for more information.
1964 config INTEL_TDX_HOST
1965 bool "Intel Trust Domain Extensions (TDX) host support"
1966 depends on CPU_SUP_INTEL
1968 depends on KVM_INTEL
1969 depends on X86_X2APIC
1970 select ARCH_KEEP_MEMBLOCK
1971 depends on CONTIG_ALLOC
1972 depends on !KEXEC_CORE
1975 Intel Trust Domain Extensions (TDX) protects guest VMs from malicious
1976 host and certain physical attacks. This option enables necessary TDX
1977 support in the host kernel to run confidential VMs.
1982 bool "EFI runtime service support"
1985 select EFI_RUNTIME_WRAPPERS
1986 select ARCH_USE_MEMREMAP_PROT
1987 select EFI_RUNTIME_MAP if KEXEC_CORE
1989 This enables the kernel to use EFI runtime services that are
1990 available (such as the EFI variable services).
1992 This option is only useful on systems that have EFI firmware.
1993 In addition, you should use the latest ELILO loader available
1994 at <http://elilo.sourceforge.net> in order to take advantage
1995 of EFI runtime services. However, even with this option, the
1996 resultant kernel should continue to boot on existing non-EFI
2000 bool "EFI stub support"
2004 This kernel feature allows a bzImage to be loaded directly
2005 by EFI firmware without the use of a bootloader.
2007 See Documentation/admin-guide/efi-stub.rst for more information.
2009 config EFI_HANDOVER_PROTOCOL
2010 bool "EFI handover protocol (DEPRECATED)"
2014 Select this in order to include support for the deprecated EFI
2015 handover protocol, which defines alternative entry points into the
2016 EFI stub. This is a practice that has no basis in the UEFI
2017 specification, and requires a priori knowledge on the part of the
2018 bootloader about Linux/x86 specific ways of passing the command line
2019 and initrd, and where in memory those assets may be loaded.
2021 If in doubt, say Y. Even though the corresponding support is not
2022 present in upstream GRUB or other bootloaders, most distros build
2023 GRUB with numerous downstream patches applied, and may rely on the
2024 handover protocol as as result.
2027 bool "EFI mixed-mode support"
2028 depends on EFI_STUB && X86_64
2030 Enabling this feature allows a 64-bit kernel to be booted
2031 on a 32-bit firmware, provided that your CPU supports 64-bit
2034 Note that it is not possible to boot a mixed-mode enabled
2035 kernel via the EFI boot stub - a bootloader that supports
2036 the EFI handover protocol must be used.
2040 config EFI_FAKE_MEMMAP
2041 bool "Enable EFI fake memory map"
2044 Saying Y here will enable "efi_fake_mem" boot option. By specifying
2045 this parameter, you can add arbitrary attribute to specific memory
2046 range by updating original (firmware provided) EFI memmap. This is
2047 useful for debugging of EFI memmap related feature, e.g., Address
2048 Range Mirroring feature.
2050 config EFI_MAX_FAKE_MEM
2051 int "maximum allowable number of ranges in efi_fake_mem boot option"
2052 depends on EFI_FAKE_MEMMAP
2056 Maximum allowable number of ranges in efi_fake_mem boot option.
2057 Ranges can be set up to this value using comma-separated list.
2058 The default value is 8.
2060 config EFI_RUNTIME_MAP
2061 bool "Export EFI runtime maps to sysfs" if EXPERT
2064 Export EFI runtime memory regions to /sys/firmware/efi/runtime-map.
2065 That memory map is required by the 2nd kernel to set up EFI virtual
2066 mappings after kexec, but can also be used for debugging purposes.
2068 See also Documentation/ABI/testing/sysfs-firmware-efi-runtime-map.
2070 source "kernel/Kconfig.hz"
2072 config ARCH_SUPPORTS_KEXEC
2075 config ARCH_SUPPORTS_KEXEC_FILE
2078 config ARCH_SELECTS_KEXEC_FILE
2080 depends on KEXEC_FILE
2081 select HAVE_IMA_KEXEC if IMA
2083 config ARCH_SUPPORTS_KEXEC_PURGATORY
2086 config ARCH_SUPPORTS_KEXEC_SIG
2089 config ARCH_SUPPORTS_KEXEC_SIG_FORCE
2092 config ARCH_SUPPORTS_KEXEC_BZIMAGE_VERIFY_SIG
2095 config ARCH_SUPPORTS_KEXEC_JUMP
2098 config ARCH_SUPPORTS_CRASH_DUMP
2099 def_bool X86_64 || (X86_32 && HIGHMEM)
2101 config ARCH_SUPPORTS_CRASH_HOTPLUG
2104 config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
2105 def_bool CRASH_RESERVE
2107 config PHYSICAL_START
2108 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2111 This gives the physical address where the kernel is loaded.
2113 If the kernel is not relocatable (CONFIG_RELOCATABLE=n) then bzImage
2114 will decompress itself to above physical address and run from there.
2115 Otherwise, bzImage will run from the address where it has been loaded
2116 by the boot loader. The only exception is if it is loaded below the
2117 above physical address, in which case it will relocate itself there.
2119 In normal kdump cases one does not have to set/change this option
2120 as now bzImage can be compiled as a completely relocatable image
2121 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2122 address. This option is mainly useful for the folks who don't want
2123 to use a bzImage for capturing the crash dump and want to use a
2124 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2125 to be specifically compiled to run from a specific memory area
2126 (normally a reserved region) and this option comes handy.
2128 So if you are using bzImage for capturing the crash dump,
2129 leave the value here unchanged to 0x1000000 and set
2130 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2131 for capturing the crash dump change this value to start of
2132 the reserved region. In other words, it can be set based on
2133 the "X" value as specified in the "crashkernel=YM@XM"
2134 command line boot parameter passed to the panic-ed
2135 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2136 for more details about crash dumps.
2138 Usage of bzImage for capturing the crash dump is recommended as
2139 one does not have to build two kernels. Same kernel can be used
2140 as production kernel and capture kernel. Above option should have
2141 gone away after relocatable bzImage support is introduced. But it
2142 is present because there are users out there who continue to use
2143 vmlinux for dump capture. This option should go away down the
2146 Don't change this unless you know what you are doing.
2149 bool "Build a relocatable kernel"
2152 This builds a kernel image that retains relocation information
2153 so it can be loaded someplace besides the default 1MB.
2154 The relocations tend to make the kernel binary about 10% larger,
2155 but are discarded at runtime.
2157 One use is for the kexec on panic case where the recovery kernel
2158 must live at a different physical address than the primary
2161 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2162 it has been loaded at and the compile time physical address
2163 (CONFIG_PHYSICAL_START) is used as the minimum location.
2165 config RANDOMIZE_BASE
2166 bool "Randomize the address of the kernel image (KASLR)"
2167 depends on RELOCATABLE
2170 In support of Kernel Address Space Layout Randomization (KASLR),
2171 this randomizes the physical address at which the kernel image
2172 is decompressed and the virtual address where the kernel
2173 image is mapped, as a security feature that deters exploit
2174 attempts relying on knowledge of the location of kernel
2177 On 64-bit, the kernel physical and virtual addresses are
2178 randomized separately. The physical address will be anywhere
2179 between 16MB and the top of physical memory (up to 64TB). The
2180 virtual address will be randomized from 16MB up to 1GB (9 bits
2181 of entropy). Note that this also reduces the memory space
2182 available to kernel modules from 1.5GB to 1GB.
2184 On 32-bit, the kernel physical and virtual addresses are
2185 randomized together. They will be randomized from 16MB up to
2186 512MB (8 bits of entropy).
2188 Entropy is generated using the RDRAND instruction if it is
2189 supported. If RDTSC is supported, its value is mixed into
2190 the entropy pool as well. If neither RDRAND nor RDTSC are
2191 supported, then entropy is read from the i8254 timer. The
2192 usable entropy is limited by the kernel being built using
2193 2GB addressing, and that PHYSICAL_ALIGN must be at a
2194 minimum of 2MB. As a result, only 10 bits of entropy are
2195 theoretically possible, but the implementations are further
2196 limited due to memory layouts.
2200 # Relocation on x86 needs some additional build support
2201 config X86_NEED_RELOCS
2203 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2205 config PHYSICAL_ALIGN
2206 hex "Alignment value to which kernel should be aligned"
2208 range 0x2000 0x1000000 if X86_32
2209 range 0x200000 0x1000000 if X86_64
2211 This value puts the alignment restrictions on physical address
2212 where kernel is loaded and run from. Kernel is compiled for an
2213 address which meets above alignment restriction.
2215 If bootloader loads the kernel at a non-aligned address and
2216 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2217 address aligned to above value and run from there.
2219 If bootloader loads the kernel at a non-aligned address and
2220 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2221 load address and decompress itself to the address it has been
2222 compiled for and run from there. The address for which kernel is
2223 compiled already meets above alignment restrictions. Hence the
2224 end result is that kernel runs from a physical address meeting
2225 above alignment restrictions.
2227 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2228 this value must be a multiple of 0x200000.
2230 Don't change this unless you know what you are doing.
2232 config DYNAMIC_MEMORY_LAYOUT
2235 This option makes base addresses of vmalloc and vmemmap as well as
2236 __PAGE_OFFSET movable during boot.
2238 config RANDOMIZE_MEMORY
2239 bool "Randomize the kernel memory sections"
2241 depends on RANDOMIZE_BASE
2242 select DYNAMIC_MEMORY_LAYOUT
2243 default RANDOMIZE_BASE
2245 Randomizes the base virtual address of kernel memory sections
2246 (physical memory mapping, vmalloc & vmemmap). This security feature
2247 makes exploits relying on predictable memory locations less reliable.
2249 The order of allocations remains unchanged. Entropy is generated in
2250 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2251 configuration have in average 30,000 different possible virtual
2252 addresses for each memory section.
2256 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2257 hex "Physical memory mapping padding" if EXPERT
2258 depends on RANDOMIZE_MEMORY
2259 default "0xa" if MEMORY_HOTPLUG
2261 range 0x1 0x40 if MEMORY_HOTPLUG
2264 Define the padding in terabytes added to the existing physical
2265 memory size during kernel memory randomization. It is useful
2266 for memory hotplug support but reduces the entropy available for
2267 address randomization.
2269 If unsure, leave at the default value.
2271 config ADDRESS_MASKING
2272 bool "Linear Address Masking support"
2275 Linear Address Masking (LAM) modifies the checking that is applied
2276 to 64-bit linear addresses, allowing software to use of the
2277 untranslated address bits for metadata.
2279 The capability can be used for efficient address sanitizers (ASAN)
2280 implementation and for optimizations in JITs.
2288 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2289 depends on COMPAT_32
2291 Certain buggy versions of glibc will crash if they are
2292 presented with a 32-bit vDSO that is not mapped at the address
2293 indicated in its segment table.
2295 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2296 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2297 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2298 the only released version with the bug, but OpenSUSE 9
2299 contains a buggy "glibc 2.3.2".
2301 The symptom of the bug is that everything crashes on startup, saying:
2302 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2304 Saying Y here changes the default value of the vdso32 boot
2305 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2306 This works around the glibc bug but hurts performance.
2308 If unsure, say N: if you are compiling your own kernel, you
2309 are unlikely to be using a buggy version of glibc.
2312 prompt "vsyscall table for legacy applications"
2314 default LEGACY_VSYSCALL_XONLY
2316 Legacy user code that does not know how to find the vDSO expects
2317 to be able to issue three syscalls by calling fixed addresses in
2318 kernel space. Since this location is not randomized with ASLR,
2319 it can be used to assist security vulnerability exploitation.
2321 This setting can be changed at boot time via the kernel command
2322 line parameter vsyscall=[emulate|xonly|none]. Emulate mode
2323 is deprecated and can only be enabled using the kernel command
2326 On a system with recent enough glibc (2.14 or newer) and no
2327 static binaries, you can say None without a performance penalty
2328 to improve security.
2330 If unsure, select "Emulate execution only".
2332 config LEGACY_VSYSCALL_XONLY
2333 bool "Emulate execution only"
2335 The kernel traps and emulates calls into the fixed vsyscall
2336 address mapping and does not allow reads. This
2337 configuration is recommended when userspace might use the
2338 legacy vsyscall area but support for legacy binary
2339 instrumentation of legacy code is not needed. It mitigates
2340 certain uses of the vsyscall area as an ASLR-bypassing
2343 config LEGACY_VSYSCALL_NONE
2346 There will be no vsyscall mapping at all. This will
2347 eliminate any risk of ASLR bypass due to the vsyscall
2348 fixed address mapping. Attempts to use the vsyscalls
2349 will be reported to dmesg, so that either old or
2350 malicious userspace programs can be identified.
2355 bool "Built-in kernel command line"
2357 Allow for specifying boot arguments to the kernel at
2358 build time. On some systems (e.g. embedded ones), it is
2359 necessary or convenient to provide some or all of the
2360 kernel boot arguments with the kernel itself (that is,
2361 to not rely on the boot loader to provide them.)
2363 To compile command line arguments into the kernel,
2364 set this option to 'Y', then fill in the
2365 boot arguments in CONFIG_CMDLINE.
2367 Systems with fully functional boot loaders (i.e. non-embedded)
2368 should leave this option set to 'N'.
2371 string "Built-in kernel command string"
2372 depends on CMDLINE_BOOL
2375 Enter arguments here that should be compiled into the kernel
2376 image and used at boot time. If the boot loader provides a
2377 command line at boot time, it is appended to this string to
2378 form the full kernel command line, when the system boots.
2380 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2381 change this behavior.
2383 In most cases, the command line (whether built-in or provided
2384 by the boot loader) should specify the device for the root
2387 config CMDLINE_OVERRIDE
2388 bool "Built-in command line overrides boot loader arguments"
2389 depends on CMDLINE_BOOL && CMDLINE != ""
2391 Set this option to 'Y' to have the kernel ignore the boot loader
2392 command line, and use ONLY the built-in command line.
2394 This is used to work around broken boot loaders. This should
2395 be set to 'N' under normal conditions.
2397 config MODIFY_LDT_SYSCALL
2398 bool "Enable the LDT (local descriptor table)" if EXPERT
2401 Linux can allow user programs to install a per-process x86
2402 Local Descriptor Table (LDT) using the modify_ldt(2) system
2403 call. This is required to run 16-bit or segmented code such as
2404 DOSEMU or some Wine programs. It is also used by some very old
2405 threading libraries.
2407 Enabling this feature adds a small amount of overhead to
2408 context switches and increases the low-level kernel attack
2409 surface. Disabling it removes the modify_ldt(2) system call.
2411 Saying 'N' here may make sense for embedded or server kernels.
2413 config STRICT_SIGALTSTACK_SIZE
2414 bool "Enforce strict size checking for sigaltstack"
2415 depends on DYNAMIC_SIGFRAME
2417 For historical reasons MINSIGSTKSZ is a constant which became
2418 already too small with AVX512 support. Add a mechanism to
2419 enforce strict checking of the sigaltstack size against the
2420 real size of the FPU frame. This option enables the check
2421 by default. It can also be controlled via the kernel command
2422 line option 'strict_sas_size' independent of this config
2423 switch. Enabling it might break existing applications which
2424 allocate a too small sigaltstack but 'work' because they
2425 never get a signal delivered.
2427 Say 'N' unless you want to really enforce this check.
2429 source "kernel/livepatch/Kconfig"
2433 config CC_HAS_NAMED_AS
2434 def_bool CC_IS_GCC && GCC_VERSION >= 90100
2436 config CC_HAS_NAMED_AS_FIXED_SANITIZERS
2437 def_bool CC_IS_GCC && GCC_VERSION >= 130300
2439 config USE_X86_SEG_SUPPORT
2441 depends on CC_HAS_NAMED_AS
2443 # -fsanitize=kernel-address (KASAN) and -fsanitize=thread
2444 # (KCSAN) are incompatible with named address spaces with
2445 # GCC < 13.3 - see GCC PR sanitizer/111736.
2447 depends on !(KASAN || KCSAN) || CC_HAS_NAMED_AS_FIXED_SANITIZERS
2450 def_bool $(cc-option,-mharden-sls=all)
2452 config CC_HAS_RETURN_THUNK
2453 def_bool $(cc-option,-mfunction-return=thunk-extern)
2455 config CC_HAS_ENTRY_PADDING
2456 def_bool $(cc-option,-fpatchable-function-entry=16,16)
2458 config FUNCTION_PADDING_CFI
2460 default 59 if FUNCTION_ALIGNMENT_64B
2461 default 27 if FUNCTION_ALIGNMENT_32B
2462 default 11 if FUNCTION_ALIGNMENT_16B
2463 default 3 if FUNCTION_ALIGNMENT_8B
2466 # Basically: FUNCTION_ALIGNMENT - 5*CFI_CLANG
2467 # except Kconfig can't do arithmetic :/
2468 config FUNCTION_PADDING_BYTES
2470 default FUNCTION_PADDING_CFI if CFI_CLANG
2471 default FUNCTION_ALIGNMENT
2475 depends on CC_HAS_ENTRY_PADDING && OBJTOOL
2476 select FUNCTION_ALIGNMENT_16B
2480 depends on X86_KERNEL_IBT && CFI_CLANG && MITIGATION_RETPOLINE
2483 config HAVE_CALL_THUNKS
2485 depends on CC_HAS_ENTRY_PADDING && MITIGATION_RETHUNK && OBJTOOL
2491 config PREFIX_SYMBOLS
2493 depends on CALL_PADDING && !CFI_CLANG
2495 menuconfig CPU_MITIGATIONS
2496 bool "Mitigations for CPU vulnerabilities"
2499 Say Y here to enable options which enable mitigations for hardware
2500 vulnerabilities (usually related to speculative execution).
2501 Mitigations can be disabled or restricted to SMT systems at runtime
2502 via the "mitigations" kernel parameter.
2504 If you say N, all mitigations will be disabled. This CANNOT be
2505 overridden at runtime.
2507 Say 'Y', unless you really know what you are doing.
2511 config MITIGATION_PAGE_TABLE_ISOLATION
2512 bool "Remove the kernel mapping in user mode"
2514 depends on (X86_64 || X86_PAE)
2516 This feature reduces the number of hardware side channels by
2517 ensuring that the majority of kernel addresses are not mapped
2520 See Documentation/arch/x86/pti.rst for more details.
2522 config MITIGATION_RETPOLINE
2523 bool "Avoid speculative indirect branches in kernel"
2524 select OBJTOOL if HAVE_OBJTOOL
2527 Compile kernel with the retpoline compiler options to guard against
2528 kernel-to-user data leaks by avoiding speculative indirect
2529 branches. Requires a compiler with -mindirect-branch=thunk-extern
2530 support for full protection. The kernel may run slower.
2532 config MITIGATION_RETHUNK
2533 bool "Enable return-thunks"
2534 depends on MITIGATION_RETPOLINE && CC_HAS_RETURN_THUNK
2535 select OBJTOOL if HAVE_OBJTOOL
2538 Compile the kernel with the return-thunks compiler option to guard
2539 against kernel-to-user data leaks by avoiding return speculation.
2540 Requires a compiler with -mfunction-return=thunk-extern
2541 support for full protection. The kernel may run slower.
2543 config MITIGATION_UNRET_ENTRY
2544 bool "Enable UNRET on kernel entry"
2545 depends on CPU_SUP_AMD && MITIGATION_RETHUNK && X86_64
2548 Compile the kernel with support for the retbleed=unret mitigation.
2550 config MITIGATION_CALL_DEPTH_TRACKING
2551 bool "Mitigate RSB underflow with call depth tracking"
2552 depends on CPU_SUP_INTEL && HAVE_CALL_THUNKS
2553 select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
2557 Compile the kernel with call depth tracking to mitigate the Intel
2558 SKL Return-Speculation-Buffer (RSB) underflow issue. The
2559 mitigation is off by default and needs to be enabled on the
2560 kernel command line via the retbleed=stuff option. For
2561 non-affected systems the overhead of this option is marginal as
2562 the call depth tracking is using run-time generated call thunks
2563 in a compiler generated padding area and call patching. This
2564 increases text size by ~5%. For non affected systems this space
2565 is unused. On affected SKL systems this results in a significant
2566 performance gain over the IBRS mitigation.
2568 config CALL_THUNKS_DEBUG
2569 bool "Enable call thunks and call depth tracking debugging"
2570 depends on MITIGATION_CALL_DEPTH_TRACKING
2571 select FUNCTION_ALIGNMENT_32B
2574 Enable call/ret counters for imbalance detection and build in
2575 a noisy dmesg about callthunks generation and call patching for
2576 trouble shooting. The debug prints need to be enabled on the
2577 kernel command line with 'debug-callthunks'.
2578 Only enable this when you are debugging call thunks as this
2579 creates a noticeable runtime overhead. If unsure say N.
2581 config MITIGATION_IBPB_ENTRY
2582 bool "Enable IBPB on kernel entry"
2583 depends on CPU_SUP_AMD && X86_64
2586 Compile the kernel with support for the retbleed=ibpb mitigation.
2588 config MITIGATION_IBRS_ENTRY
2589 bool "Enable IBRS on kernel entry"
2590 depends on CPU_SUP_INTEL && X86_64
2593 Compile the kernel with support for the spectre_v2=ibrs mitigation.
2594 This mitigates both spectre_v2 and retbleed at great cost to
2597 config MITIGATION_SRSO
2598 bool "Mitigate speculative RAS overflow on AMD"
2599 depends on CPU_SUP_AMD && X86_64 && MITIGATION_RETHUNK
2602 Enable the SRSO mitigation needed on AMD Zen1-4 machines.
2604 config MITIGATION_SLS
2605 bool "Mitigate Straight-Line-Speculation"
2606 depends on CC_HAS_SLS && X86_64
2607 select OBJTOOL if HAVE_OBJTOOL
2610 Compile the kernel with straight-line-speculation options to guard
2611 against straight line speculation. The kernel image might be slightly
2614 config MITIGATION_GDS_FORCE
2615 bool "Force GDS Mitigation"
2616 depends on CPU_SUP_INTEL
2619 Gather Data Sampling (GDS) is a hardware vulnerability which allows
2620 unprivileged speculative access to data which was previously stored in
2623 This option is equivalent to setting gather_data_sampling=force on the
2624 command line. The microcode mitigation is used if present, otherwise
2625 AVX is disabled as a mitigation. On affected systems that are missing
2626 the microcode any userspace code that unconditionally uses AVX will
2627 break with this option set.
2629 Setting this option on systems not vulnerable to GDS has no effect.
2633 config MITIGATION_RFDS
2634 bool "RFDS Mitigation"
2635 depends on CPU_SUP_INTEL
2638 Enable mitigation for Register File Data Sampling (RFDS) by default.
2639 RFDS is a hardware vulnerability which affects Intel Atom CPUs. It
2640 allows unprivileged speculative access to stale data previously
2641 stored in floating point, vector and integer registers.
2642 See also <file:Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst>
2644 config MITIGATION_SPECTRE_BHI
2645 bool "Mitigate Spectre-BHB (Branch History Injection)"
2646 depends on CPU_SUP_INTEL
2649 Enable BHI mitigations. BHI attacks are a form of Spectre V2 attacks
2650 where the branch history buffer is poisoned to speculatively steer
2652 See <file:Documentation/admin-guide/hw-vuln/spectre.rst>
2656 config ARCH_HAS_ADD_PAGES
2658 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2660 menu "Power management and ACPI options"
2662 config ARCH_HIBERNATION_HEADER
2664 depends on HIBERNATION
2666 source "kernel/power/Kconfig"
2668 source "drivers/acpi/Kconfig"
2675 tristate "APM (Advanced Power Management) BIOS support"
2676 depends on X86_32 && PM_SLEEP
2678 APM is a BIOS specification for saving power using several different
2679 techniques. This is mostly useful for battery powered laptops with
2680 APM compliant BIOSes. If you say Y here, the system time will be
2681 reset after a RESUME operation, the /proc/apm device will provide
2682 battery status information, and user-space programs will receive
2683 notification of APM "events" (e.g. battery status change).
2685 If you select "Y" here, you can disable actual use of the APM
2686 BIOS by passing the "apm=off" option to the kernel at boot time.
2688 Note that the APM support is almost completely disabled for
2689 machines with more than one CPU.
2691 In order to use APM, you will need supporting software. For location
2692 and more information, read <file:Documentation/power/apm-acpi.rst>
2693 and the Battery Powered Linux mini-HOWTO, available from
2694 <http://www.tldp.org/docs.html#howto>.
2696 This driver does not spin down disk drives (see the hdparm(8)
2697 manpage ("man 8 hdparm") for that), and it doesn't turn off
2698 VESA-compliant "green" monitors.
2700 This driver does not support the TI 4000M TravelMate and the ACER
2701 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2702 desktop machines also don't have compliant BIOSes, and this driver
2703 may cause those machines to panic during the boot phase.
2705 Generally, if you don't have a battery in your machine, there isn't
2706 much point in using this driver and you should say N. If you get
2707 random kernel OOPSes or reboots that don't seem to be related to
2708 anything, try disabling/enabling this option (or disabling/enabling
2711 Some other things you should try when experiencing seemingly random,
2714 1) make sure that you have enough swap space and that it is
2716 2) pass the "idle=poll" option to the kernel
2717 3) switch on floating point emulation in the kernel and pass
2718 the "no387" option to the kernel
2719 4) pass the "floppy=nodma" option to the kernel
2720 5) pass the "mem=4M" option to the kernel (thereby disabling
2721 all but the first 4 MB of RAM)
2722 6) make sure that the CPU is not over clocked.
2723 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2724 8) disable the cache from your BIOS settings
2725 9) install a fan for the video card or exchange video RAM
2726 10) install a better fan for the CPU
2727 11) exchange RAM chips
2728 12) exchange the motherboard.
2730 To compile this driver as a module, choose M here: the
2731 module will be called apm.
2735 config APM_IGNORE_USER_SUSPEND
2736 bool "Ignore USER SUSPEND"
2738 This option will ignore USER SUSPEND requests. On machines with a
2739 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2740 series notebooks, it is necessary to say Y because of a BIOS bug.
2742 config APM_DO_ENABLE
2743 bool "Enable PM at boot time"
2745 Enable APM features at boot time. From page 36 of the APM BIOS
2746 specification: "When disabled, the APM BIOS does not automatically
2747 power manage devices, enter the Standby State, enter the Suspend
2748 State, or take power saving steps in response to CPU Idle calls."
2749 This driver will make CPU Idle calls when Linux is idle (unless this
2750 feature is turned off -- see "Do CPU IDLE calls", below). This
2751 should always save battery power, but more complicated APM features
2752 will be dependent on your BIOS implementation. You may need to turn
2753 this option off if your computer hangs at boot time when using APM
2754 support, or if it beeps continuously instead of suspending. Turn
2755 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2756 T400CDT. This is off by default since most machines do fine without
2761 bool "Make CPU Idle calls when idle"
2763 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2764 On some machines, this can activate improved power savings, such as
2765 a slowed CPU clock rate, when the machine is idle. These idle calls
2766 are made after the idle loop has run for some length of time (e.g.,
2767 333 mS). On some machines, this will cause a hang at boot time or
2768 whenever the CPU becomes idle. (On machines with more than one CPU,
2769 this option does nothing.)
2771 config APM_DISPLAY_BLANK
2772 bool "Enable console blanking using APM"
2774 Enable console blanking using the APM. Some laptops can use this to
2775 turn off the LCD backlight when the screen blanker of the Linux
2776 virtual console blanks the screen. Note that this is only used by
2777 the virtual console screen blanker, and won't turn off the backlight
2778 when using the X Window system. This also doesn't have anything to
2779 do with your VESA-compliant power-saving monitor. Further, this
2780 option doesn't work for all laptops -- it might not turn off your
2781 backlight at all, or it might print a lot of errors to the console,
2782 especially if you are using gpm.
2784 config APM_ALLOW_INTS
2785 bool "Allow interrupts during APM BIOS calls"
2787 Normally we disable external interrupts while we are making calls to
2788 the APM BIOS as a measure to lessen the effects of a badly behaving
2789 BIOS implementation. The BIOS should reenable interrupts if it
2790 needs to. Unfortunately, some BIOSes do not -- especially those in
2791 many of the newer IBM Thinkpads. If you experience hangs when you
2792 suspend, try setting this to Y. Otherwise, say N.
2796 source "drivers/cpufreq/Kconfig"
2798 source "drivers/cpuidle/Kconfig"
2800 source "drivers/idle/Kconfig"
2804 menu "Bus options (PCI etc.)"
2807 prompt "PCI access mode"
2808 depends on X86_32 && PCI
2811 On PCI systems, the BIOS can be used to detect the PCI devices and
2812 determine their configuration. However, some old PCI motherboards
2813 have BIOS bugs and may crash if this is done. Also, some embedded
2814 PCI-based systems don't have any BIOS at all. Linux can also try to
2815 detect the PCI hardware directly without using the BIOS.
2817 With this option, you can specify how Linux should detect the
2818 PCI devices. If you choose "BIOS", the BIOS will be used,
2819 if you choose "Direct", the BIOS won't be used, and if you
2820 choose "MMConfig", then PCI Express MMCONFIG will be used.
2821 If you choose "Any", the kernel will try MMCONFIG, then the
2822 direct access method and falls back to the BIOS if that doesn't
2823 work. If unsure, go with the default, which is "Any".
2828 config PCI_GOMMCONFIG
2845 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2847 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2850 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2853 bool "Support mmconfig PCI config space access" if X86_64
2855 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2856 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2860 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2864 depends on PCI && XEN
2866 config MMCONF_FAM10H
2868 depends on X86_64 && PCI_MMCONFIG && ACPI
2870 config PCI_CNB20LE_QUIRK
2871 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2874 Read the PCI windows out of the CNB20LE host bridge. This allows
2875 PCI hotplug to work on systems with the CNB20LE chipset which do
2878 There's no public spec for this chipset, and this functionality
2879 is known to be incomplete.
2881 You should say N unless you know you need this.
2884 bool "ISA bus support on modern systems" if EXPERT
2886 Expose ISA bus device drivers and options available for selection and
2887 configuration. Enable this option if your target machine has an ISA
2888 bus. ISA is an older system, displaced by PCI and newer bus
2889 architectures -- if your target machine is modern, it probably does
2890 not have an ISA bus.
2894 # x86_64 have no ISA slots, but can have ISA-style DMA.
2896 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2899 Enables ISA-style DMA support for devices requiring such controllers.
2907 Find out whether you have ISA slots on your motherboard. ISA is the
2908 name of a bus system, i.e. the way the CPU talks to the other stuff
2909 inside your box. Other bus systems are PCI, EISA, MicroChannel
2910 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2911 newer boards don't support it. If you have ISA, say Y, otherwise N.
2914 tristate "NatSemi SCx200 support"
2916 This provides basic support for National Semiconductor's
2917 (now AMD's) Geode processors. The driver probes for the
2918 PCI-IDs of several on-chip devices, so its a good dependency
2919 for other scx200_* drivers.
2921 If compiled as a module, the driver is named scx200.
2923 config SCx200HR_TIMER
2924 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2928 This driver provides a clocksource built upon the on-chip
2929 27MHz high-resolution timer. Its also a workaround for
2930 NSC Geode SC-1100's buggy TSC, which loses time when the
2931 processor goes idle (as is done by the scheduler). The
2932 other workaround is idle=poll boot option.
2935 bool "One Laptop Per Child support"
2943 Add support for detecting the unique features of the OLPC
2947 bool "OLPC XO-1 Power Management"
2948 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2950 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2953 bool "OLPC XO-1 Real Time Clock"
2954 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2956 Add support for the XO-1 real time clock, which can be used as a
2957 programmable wakeup source.
2960 bool "OLPC XO-1 SCI extras"
2961 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2965 Add support for SCI-based features of the OLPC XO-1 laptop:
2966 - EC-driven system wakeups
2970 - AC adapter status updates
2971 - Battery status updates
2973 config OLPC_XO15_SCI
2974 bool "OLPC XO-1.5 SCI extras"
2975 depends on OLPC && ACPI
2978 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2979 - EC-driven system wakeups
2980 - AC adapter status updates
2981 - Battery status updates
2984 bool "PCEngines ALIX System Support (LED setup)"
2987 This option enables system support for the PCEngines ALIX.
2988 At present this just sets up LEDs for GPIO control on
2989 ALIX2/3/6 boards. However, other system specific setup should
2992 Note: You must still enable the drivers for GPIO and LED support
2993 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2995 Note: You have to set alix.force=1 for boards with Award BIOS.
2998 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
3001 This option enables system support for the Soekris Engineering net5501.
3004 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
3008 This option enables system support for the Traverse Technologies GEOS.
3011 bool "Technologic Systems TS-5500 platform support"
3013 select CHECK_SIGNATURE
3017 This option enables system support for the Technologic Systems TS-5500.
3023 depends on CPU_SUP_AMD && PCI
3027 menu "Binary Emulations"
3029 config IA32_EMULATION
3030 bool "IA32 Emulation"
3032 select ARCH_WANT_OLD_COMPAT_IPC
3034 select COMPAT_OLD_SIGACTION
3036 Include code to run legacy 32-bit programs under a
3037 64-bit kernel. You should likely turn this on, unless you're
3038 100% sure that you don't have any 32-bit programs left.
3040 config IA32_EMULATION_DEFAULT_DISABLED
3041 bool "IA32 emulation disabled by default"
3043 depends on IA32_EMULATION
3045 Make IA32 emulation disabled by default. This prevents loading 32-bit
3046 processes and access to 32-bit syscalls. If unsure, leave it to its
3050 bool "x32 ABI for 64-bit mode"
3052 # llvm-objcopy does not convert x86_64 .note.gnu.property or
3053 # compressed debug sections to x86_x32 properly:
3054 # https://github.com/ClangBuiltLinux/linux/issues/514
3055 # https://github.com/ClangBuiltLinux/linux/issues/1141
3056 depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
3058 Include code to run binaries for the x32 native 32-bit ABI
3059 for 64-bit processors. An x32 process gets access to the
3060 full 64-bit register file and wide data path while leaving
3061 pointers at 32 bits for smaller memory footprint.
3065 depends on IA32_EMULATION || X86_32
3067 select OLD_SIGSUSPEND3
3071 depends on IA32_EMULATION || X86_X32_ABI
3073 config COMPAT_FOR_U64_ALIGNMENT
3079 config HAVE_ATOMIC_IOMAP
3083 source "arch/x86/kvm/Kconfig"
3085 source "arch/x86/Kconfig.assembler"