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
38 config FORCE_DYNAMIC_FTRACE
41 depends on FUNCTION_TRACER
44 We keep the static function tracing (!DYNAMIC_FTRACE) around
45 in order to test the non static function tracing in the
46 generic code, as other architectures still use it. But we
47 only need to keep it around for x86_64. No need to keep it
48 for x86_32. For x86_32, force DYNAMIC_FTRACE.
52 # ( Note that options that are marked 'if X86_64' could in principle be
53 # ported to 32-bit as well. )
58 # Note: keep this list sorted alphabetically
60 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
61 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
62 select ACPI_HOTPLUG_CPU if ACPI_PROCESSOR && HOTPLUG_CPU
63 select ARCH_32BIT_OFF_T if X86_32
64 select ARCH_CLOCKSOURCE_INIT
65 select ARCH_CONFIGURES_CPU_MITIGATIONS
66 select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
67 select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
68 select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
69 select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
70 select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE)
71 select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
72 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
73 select ARCH_HAS_CACHE_LINE_SIZE
74 select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
75 select ARCH_HAS_CPU_FINALIZE_INIT
76 select ARCH_HAS_CPU_PASID if IOMMU_SVA
77 select ARCH_HAS_CURRENT_STACK_POINTER
78 select ARCH_HAS_DEBUG_VIRTUAL
79 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
80 select ARCH_HAS_DEVMEM_IS_ALLOWED
81 select ARCH_HAS_EARLY_DEBUG if KGDB
82 select ARCH_HAS_ELF_RANDOMIZE
83 select ARCH_HAS_FAST_MULTIPLIER
84 select ARCH_HAS_FORTIFY_SOURCE
85 select ARCH_HAS_GCOV_PROFILE_ALL
86 select ARCH_HAS_KCOV if X86_64
87 select ARCH_HAS_MEM_ENCRYPT
88 select ARCH_HAS_MEMBARRIER_SYNC_CORE
89 select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
90 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
91 select ARCH_HAS_PMEM_API if X86_64
92 select ARCH_HAS_PTE_DEVMAP if X86_64
93 select ARCH_HAS_PTE_SPECIAL
94 select ARCH_HAS_HW_PTE_YOUNG
95 select ARCH_HAS_NONLEAF_PMD_YOUNG if PGTABLE_LEVELS > 2
96 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
97 select ARCH_HAS_COPY_MC if X86_64
98 select ARCH_HAS_SET_MEMORY
99 select ARCH_HAS_SET_DIRECT_MAP
100 select ARCH_HAS_STRICT_KERNEL_RWX
101 select ARCH_HAS_STRICT_MODULE_RWX
102 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
103 select ARCH_HAS_SYSCALL_WRAPPER
104 select ARCH_HAS_UBSAN
105 select ARCH_HAS_DEBUG_WX
106 select ARCH_HAS_ZONE_DMA_SET if EXPERT
107 select ARCH_HAVE_NMI_SAFE_CMPXCHG
108 select ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
109 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
110 select ARCH_MIGHT_HAVE_PC_PARPORT
111 select ARCH_MIGHT_HAVE_PC_SERIO
112 select ARCH_STACKWALK
113 select ARCH_SUPPORTS_ACPI
114 select ARCH_SUPPORTS_ATOMIC_RMW
115 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
116 select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64
117 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
118 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
119 select ARCH_SUPPORTS_CFI_CLANG if X86_64
120 select ARCH_USES_CFI_TRAPS if X86_64 && CFI_CLANG
121 select ARCH_SUPPORTS_LTO_CLANG
122 select ARCH_SUPPORTS_LTO_CLANG_THIN
123 select ARCH_USE_BUILTIN_BSWAP
124 select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64
125 select ARCH_USE_MEMTEST
126 select ARCH_USE_QUEUED_RWLOCKS
127 select ARCH_USE_QUEUED_SPINLOCKS
128 select ARCH_USE_SYM_ANNOTATIONS
129 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
130 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
131 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
132 select ARCH_WANTS_NO_INSTR
133 select ARCH_WANT_GENERAL_HUGETLB
134 select ARCH_WANT_HUGE_PMD_SHARE
135 select ARCH_WANT_LD_ORPHAN_WARN
136 select ARCH_WANT_OPTIMIZE_DAX_VMEMMAP if X86_64
137 select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP if X86_64
138 select ARCH_WANTS_THP_SWAP if X86_64
139 select ARCH_HAS_PARANOID_L1D_FLUSH
140 select BUILDTIME_TABLE_SORT
142 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
143 select CLOCKSOURCE_WATCHDOG
144 # Word-size accesses may read uninitialized data past the trailing \0
145 # in strings and cause false KMSAN reports.
146 select DCACHE_WORD_ACCESS if !KMSAN
147 select DYNAMIC_SIGFRAME
148 select EDAC_ATOMIC_SCRUB
150 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
151 select GENERIC_CLOCKEVENTS_BROADCAST_IDLE if GENERIC_CLOCKEVENTS_BROADCAST
152 select GENERIC_CLOCKEVENTS_MIN_ADJUST
153 select GENERIC_CMOS_UPDATE
154 select GENERIC_CPU_AUTOPROBE
155 select GENERIC_CPU_DEVICES
156 select GENERIC_CPU_VULNERABILITIES
157 select GENERIC_EARLY_IOREMAP
160 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
161 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
162 select GENERIC_IRQ_MIGRATION if SMP
163 select GENERIC_IRQ_PROBE
164 select GENERIC_IRQ_RESERVATION_MODE
165 select GENERIC_IRQ_SHOW
166 select GENERIC_PENDING_IRQ if SMP
167 select GENERIC_PTDUMP
168 select GENERIC_SMP_IDLE_THREAD
169 select GENERIC_TIME_VSYSCALL
170 select GENERIC_GETTIMEOFDAY
171 select GENERIC_VDSO_TIME_NS
172 select GUP_GET_PXX_LOW_HIGH if X86_PAE
173 select HARDIRQS_SW_RESEND
174 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
176 select HAVE_ACPI_APEI if ACPI
177 select HAVE_ACPI_APEI_NMI if ACPI
178 select HAVE_ALIGNED_STRUCT_PAGE
179 select HAVE_ARCH_AUDITSYSCALL
180 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
181 select HAVE_ARCH_HUGE_VMALLOC if X86_64
182 select HAVE_ARCH_JUMP_LABEL
183 select HAVE_ARCH_JUMP_LABEL_RELATIVE
184 select HAVE_ARCH_KASAN if X86_64
185 select HAVE_ARCH_KASAN_VMALLOC if X86_64
186 select HAVE_ARCH_KFENCE
187 select HAVE_ARCH_KMSAN if X86_64
188 select HAVE_ARCH_KGDB
189 select HAVE_ARCH_MMAP_RND_BITS if MMU
190 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
191 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
192 select HAVE_ARCH_PREL32_RELOCATIONS
193 select HAVE_ARCH_SECCOMP_FILTER
194 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
195 select HAVE_ARCH_STACKLEAK
196 select HAVE_ARCH_TRACEHOOK
197 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
198 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
199 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
200 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
201 select HAVE_ARCH_VMAP_STACK if X86_64
202 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
203 select HAVE_ARCH_WITHIN_STACK_FRAMES
204 select HAVE_ASM_MODVERSIONS
205 select HAVE_CMPXCHG_DOUBLE
206 select HAVE_CMPXCHG_LOCAL
207 select HAVE_CONTEXT_TRACKING_USER if X86_64
208 select HAVE_CONTEXT_TRACKING_USER_OFFSTACK if HAVE_CONTEXT_TRACKING_USER
209 select HAVE_C_RECORDMCOUNT
210 select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
211 select HAVE_OBJTOOL_NOP_MCOUNT if HAVE_OBJTOOL_MCOUNT
212 select HAVE_BUILDTIME_MCOUNT_SORT
213 select HAVE_DEBUG_KMEMLEAK
214 select HAVE_DMA_CONTIGUOUS
215 select HAVE_DYNAMIC_FTRACE
216 select HAVE_DYNAMIC_FTRACE_WITH_REGS
217 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
218 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
219 select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
220 select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
222 select HAVE_EFFICIENT_UNALIGNED_ACCESS
224 select HAVE_EXIT_THREAD
226 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
227 select HAVE_FTRACE_MCOUNT_RECORD
228 select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
229 select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
230 select HAVE_FUNCTION_TRACER
231 select HAVE_GCC_PLUGINS
232 select HAVE_HW_BREAKPOINT
233 select HAVE_IOREMAP_PROT
234 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
235 select HAVE_IRQ_TIME_ACCOUNTING
236 select HAVE_JUMP_LABEL_HACK if HAVE_OBJTOOL
237 select HAVE_KERNEL_BZIP2
238 select HAVE_KERNEL_GZIP
239 select HAVE_KERNEL_LZ4
240 select HAVE_KERNEL_LZMA
241 select HAVE_KERNEL_LZO
242 select HAVE_KERNEL_XZ
243 select HAVE_KERNEL_ZSTD
245 select HAVE_KPROBES_ON_FTRACE
246 select HAVE_FUNCTION_ERROR_INJECTION
247 select HAVE_KRETPROBES
249 select HAVE_LIVEPATCH if X86_64
250 select HAVE_MIXED_BREAKPOINTS_REGS
251 select HAVE_MOD_ARCH_SPECIFIC
254 select HAVE_NOINSTR_HACK if HAVE_OBJTOOL
256 select HAVE_NOINSTR_VALIDATION if HAVE_OBJTOOL
257 select HAVE_OBJTOOL if X86_64
258 select HAVE_OPTPROBES
259 select HAVE_PAGE_SIZE_4KB
260 select HAVE_PCSPKR_PLATFORM
261 select HAVE_PERF_EVENTS
262 select HAVE_PERF_EVENTS_NMI
263 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
265 select HAVE_PERF_REGS
266 select HAVE_PERF_USER_STACK_DUMP
267 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
268 select MMU_GATHER_MERGE_VMAS
269 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
270 select HAVE_REGS_AND_STACK_ACCESS_API
271 select HAVE_RELIABLE_STACKTRACE if UNWINDER_ORC || STACK_VALIDATION
272 select HAVE_FUNCTION_ARG_ACCESS_API
273 select HAVE_SETUP_PER_CPU_AREA
274 select HAVE_SOFTIRQ_ON_OWN_STACK
275 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
276 select HAVE_STACK_VALIDATION if HAVE_OBJTOOL
277 select HAVE_STATIC_CALL
278 select HAVE_STATIC_CALL_INLINE if HAVE_OBJTOOL
279 select HAVE_PREEMPT_DYNAMIC_CALL
281 select HAVE_RUST if X86_64
282 select HAVE_SYSCALL_TRACEPOINTS
283 select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
284 select HAVE_UNSTABLE_SCHED_CLOCK
285 select HAVE_USER_RETURN_NOTIFIER
286 select HAVE_GENERIC_VDSO
287 select HOTPLUG_PARALLEL if SMP && X86_64
288 select HOTPLUG_SMT if SMP
289 select HOTPLUG_SPLIT_STARTUP if SMP && X86_32
290 select IRQ_FORCED_THREADING
291 select LOCK_MM_AND_FIND_VMA
292 select NEED_PER_CPU_EMBED_FIRST_CHUNK
293 select NEED_PER_CPU_PAGE_FIRST_CHUNK
294 select NEED_SG_DMA_LENGTH
295 select PCI_DOMAINS if PCI
296 select PCI_LOCKLESS_CONFIG if PCI
299 select RTC_MC146818_LIB
301 select SYSCTL_EXCEPTION_TRACE
302 select THREAD_INFO_IN_TASK
303 select TRACE_IRQFLAGS_SUPPORT
304 select TRACE_IRQFLAGS_NMI_SUPPORT
305 select USER_STACKTRACE_SUPPORT
306 select HAVE_ARCH_KCSAN if X86_64
307 select PROC_PID_ARCH_STATUS if PROC_FS
308 select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
309 select FUNCTION_ALIGNMENT_16B if X86_64 || X86_ALIGNMENT_16
310 select FUNCTION_ALIGNMENT_4B
311 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
312 select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
314 config INSTRUCTION_DECODER
316 depends on KPROBES || PERF_EVENTS || UPROBES
320 default "elf32-i386" if X86_32
321 default "elf64-x86-64" if X86_64
323 config LOCKDEP_SUPPORT
326 config STACKTRACE_SUPPORT
332 config ARCH_MMAP_RND_BITS_MIN
336 config ARCH_MMAP_RND_BITS_MAX
340 config ARCH_MMAP_RND_COMPAT_BITS_MIN
343 config ARCH_MMAP_RND_COMPAT_BITS_MAX
349 config GENERIC_ISA_DMA
351 depends on ISA_DMA_API
355 default y if KMSAN || KASAN
360 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
362 config GENERIC_BUG_RELATIVE_POINTERS
365 config ARCH_MAY_HAVE_PC_FDC
367 depends on ISA_DMA_API
369 config GENERIC_CALIBRATE_DELAY
372 config ARCH_HAS_CPU_RELAX
375 config ARCH_HIBERNATION_POSSIBLE
378 config ARCH_SUSPEND_POSSIBLE
384 config KASAN_SHADOW_OFFSET
387 default 0xdffffc0000000000
389 config HAVE_INTEL_TXT
391 depends on INTEL_IOMMU && ACPI
395 depends on X86_64 && SMP
397 config ARCH_SUPPORTS_UPROBES
400 config FIX_EARLYCON_MEM
403 config DYNAMIC_PHYSICAL_MASK
406 config PGTABLE_LEVELS
408 default 5 if X86_5LEVEL
413 config CC_HAS_SANE_STACKPROTECTOR
415 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) $(CLANG_FLAGS)) if 64BIT
416 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC) $(CLANG_FLAGS))
418 We have to make sure stack protector is unconditionally disabled if
419 the compiler produces broken code or if it does not let us control
420 the segment on 32-bit kernels.
422 menu "Processor type and features"
425 bool "Symmetric multi-processing support"
427 This enables support for systems with more than one CPU. If you have
428 a system with only one CPU, say N. If you have a system with more
431 If you say N here, the kernel will run on uni- and multiprocessor
432 machines, but will use only one CPU of a multiprocessor machine. If
433 you say Y here, the kernel will run on many, but not all,
434 uniprocessor machines. On a uniprocessor machine, the kernel
435 will run faster if you say N here.
437 Note that if you say Y here and choose architecture "586" or
438 "Pentium" under "Processor family", the kernel will not work on 486
439 architectures. Similarly, multiprocessor kernels for the "PPro"
440 architecture may not work on all Pentium based boards.
442 People using multiprocessor machines who say Y here should also say
443 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
444 Management" code will be disabled if you say Y here.
446 See also <file:Documentation/arch/x86/i386/IO-APIC.rst>,
447 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
448 <http://www.tldp.org/docs.html#howto>.
450 If you don't know what to do here, say N.
453 bool "Support x2apic"
454 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
456 This enables x2apic support on CPUs that have this feature.
458 This allows 32-bit apic IDs (so it can support very large systems),
459 and accesses the local apic via MSRs not via mmio.
461 Some Intel systems circa 2022 and later are locked into x2APIC mode
462 and can not fall back to the legacy APIC modes if SGX or TDX are
463 enabled in the BIOS. They will boot with very reduced functionality
464 without enabling this option.
466 If you don't know what to do here, say N.
469 bool "Enable MPS table" if ACPI
471 depends on X86_LOCAL_APIC
473 For old smp systems that do not have proper acpi support. Newer systems
474 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
476 config X86_CPU_RESCTRL
477 bool "x86 CPU resource control support"
478 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
480 select PROC_CPU_RESCTRL if PROC_FS
482 Enable x86 CPU resource control support.
484 Provide support for the allocation and monitoring of system resources
487 Intel calls this Intel Resource Director Technology
488 (Intel(R) RDT). More information about RDT can be found in the
489 Intel x86 Architecture Software Developer Manual.
491 AMD calls this AMD Platform Quality of Service (AMD QoS).
492 More information about AMD QoS can be found in the AMD64 Technology
493 Platform Quality of Service Extensions manual.
498 bool "Flexible Return and Event Delivery"
501 When enabled, try to use Flexible Return and Event Delivery
502 instead of the legacy SYSCALL/SYSENTER/IDT architecture for
503 ring transitions and exception/interrupt handling if the
508 bool "Support for big SMP systems with more than 8 CPUs"
511 This option is needed for the systems that have more than 8 CPUs.
513 config X86_EXTENDED_PLATFORM
514 bool "Support for extended (non-PC) x86 platforms"
517 If you disable this option then the kernel will only support
518 standard PC platforms. (which covers the vast majority of
521 If you enable this option then you'll be able to select support
522 for the following (non-PC) 32 bit x86 platforms:
523 Goldfish (Android emulator)
526 SGI 320/540 (Visual Workstation)
527 STA2X11-based (e.g. Northville)
528 Moorestown MID devices
530 If you have one of these systems, or if you want to build a
531 generic distribution kernel, say Y here - otherwise say N.
535 config X86_EXTENDED_PLATFORM
536 bool "Support for extended (non-PC) x86 platforms"
539 If you disable this option then the kernel will only support
540 standard PC platforms. (which covers the vast majority of
543 If you enable this option then you'll be able to select support
544 for the following (non-PC) 64 bit x86 platforms:
549 If you have one of these systems, or if you want to build a
550 generic distribution kernel, say Y here - otherwise say N.
552 # This is an alphabetically sorted list of 64 bit extended platforms
553 # Please maintain the alphabetic order if and when there are additions
555 bool "Numascale NumaChip"
557 depends on X86_EXTENDED_PLATFORM
560 depends on X86_X2APIC
561 depends on PCI_MMCONFIG
563 Adds support for Numascale NumaChip large-SMP systems. Needed to
564 enable more than ~168 cores.
565 If you don't have one of these, you should say N here.
569 select HYPERVISOR_GUEST
571 depends on X86_64 && PCI
572 depends on X86_EXTENDED_PLATFORM
575 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
576 supposed to run on these EM64T-based machines. Only choose this option
577 if you have one of these machines.
580 bool "SGI Ultraviolet"
582 depends on X86_EXTENDED_PLATFORM
585 depends on KEXEC_CORE
586 depends on X86_X2APIC
589 This option is needed in order to support SGI Ultraviolet systems.
590 If you don't have one of these, you should say N here.
592 # Following is an alphabetically sorted list of 32 bit extended platforms
593 # Please maintain the alphabetic order if and when there are additions
596 bool "Goldfish (Virtual Platform)"
597 depends on X86_EXTENDED_PLATFORM
599 Enable support for the Goldfish virtual platform used primarily
600 for Android development. Unless you are building for the Android
601 Goldfish emulator say N here.
604 bool "CE4100 TV platform"
606 depends on PCI_GODIRECT
607 depends on X86_IO_APIC
609 depends on X86_EXTENDED_PLATFORM
610 select X86_REBOOTFIXUPS
612 select OF_EARLY_FLATTREE
614 Select for the Intel CE media processor (CE4100) SOC.
615 This option compiles in support for the CE4100 SOC for settop
616 boxes and media devices.
619 bool "Intel MID platform support"
620 depends on X86_EXTENDED_PLATFORM
621 depends on X86_PLATFORM_DEVICES
623 depends on X86_64 || (PCI_GOANY && X86_32)
624 depends on X86_IO_APIC
629 Select to build a kernel capable of supporting Intel MID (Mobile
630 Internet Device) platform systems which do not have the PCI legacy
631 interfaces. If you are building for a PC class system say N here.
633 Intel MID platforms are based on an Intel processor and chipset which
634 consume less power than most of the x86 derivatives.
636 config X86_INTEL_QUARK
637 bool "Intel Quark platform support"
639 depends on X86_EXTENDED_PLATFORM
640 depends on X86_PLATFORM_DEVICES
644 depends on X86_IO_APIC
649 Select to include support for Quark X1000 SoC.
650 Say Y here if you have a Quark based system such as the Arduino
651 compatible Intel Galileo.
653 config X86_INTEL_LPSS
654 bool "Intel Low Power Subsystem Support"
655 depends on X86 && ACPI && PCI
660 Select to build support for Intel Low Power Subsystem such as
661 found on Intel Lynxpoint PCH. Selecting this option enables
662 things like clock tree (common clock framework) and pincontrol
663 which are needed by the LPSS peripheral drivers.
665 config X86_AMD_PLATFORM_DEVICE
666 bool "AMD ACPI2Platform devices support"
671 Select to interpret AMD specific ACPI device to platform device
672 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
673 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
674 implemented under PINCTRL subsystem.
677 tristate "Intel SoC IOSF Sideband support for SoC platforms"
680 This option enables sideband register access support for Intel SoC
681 platforms. On these platforms the IOSF sideband is used in lieu of
682 MSR's for some register accesses, mostly but not limited to thermal
683 and power. Drivers may query the availability of this device to
684 determine if they need the sideband in order to work on these
685 platforms. The sideband is available on the following SoC products.
686 This list is not meant to be exclusive.
691 You should say Y if you are running a kernel on one of these SoC's.
693 config IOSF_MBI_DEBUG
694 bool "Enable IOSF sideband access through debugfs"
695 depends on IOSF_MBI && DEBUG_FS
697 Select this option to expose the IOSF sideband access registers (MCR,
698 MDR, MCRX) through debugfs to write and read register information from
699 different units on the SoC. This is most useful for obtaining device
700 state information for debug and analysis. As this is a general access
701 mechanism, users of this option would have specific knowledge of the
702 device they want to access.
704 If you don't require the option or are in doubt, say N.
707 bool "RDC R-321x SoC"
709 depends on X86_EXTENDED_PLATFORM
711 select X86_REBOOTFIXUPS
713 This option is needed for RDC R-321x system-on-chip, also known
715 If you don't have one of these chips, you should say N here.
717 config X86_32_NON_STANDARD
718 bool "Support non-standard 32-bit SMP architectures"
719 depends on X86_32 && SMP
720 depends on X86_EXTENDED_PLATFORM
722 This option compiles in the bigsmp and STA2X11 default
723 subarchitectures. It is intended for a generic binary
724 kernel. If you select them all, kernel will probe it one by
725 one and will fallback to default.
727 # Alphabetically sorted list of Non standard 32 bit platforms
729 config X86_SUPPORTS_MEMORY_FAILURE
731 # MCE code calls memory_failure():
733 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
734 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
735 depends on X86_64 || !SPARSEMEM
736 select ARCH_SUPPORTS_MEMORY_FAILURE
739 bool "STA2X11 Companion Chip Support"
740 depends on X86_32_NON_STANDARD && PCI
745 This adds support for boards based on the STA2X11 IO-Hub,
746 a.k.a. "ConneXt". The chip is used in place of the standard
747 PC chipset, so all "standard" peripherals are missing. If this
748 option is selected the kernel will still be able to boot on
749 standard PC machines.
752 tristate "Eurobraille/Iris poweroff module"
755 The Iris machines from EuroBraille do not have APM or ACPI support
756 to shut themselves down properly. A special I/O sequence is
757 needed to do so, which is what this module does at
760 This is only for Iris machines from EuroBraille.
764 config SCHED_OMIT_FRAME_POINTER
766 prompt "Single-depth WCHAN output"
769 Calculate simpler /proc/<PID>/wchan values. If this option
770 is disabled then wchan values will recurse back to the
771 caller function. This provides more accurate wchan values,
772 at the expense of slightly more scheduling overhead.
774 If in doubt, say "Y".
776 menuconfig HYPERVISOR_GUEST
777 bool "Linux guest support"
779 Say Y here to enable options for running Linux under various hyper-
780 visors. This option enables basic hypervisor detection and platform
783 If you say N, all options in this submenu will be skipped and
784 disabled, and Linux guest support won't be built in.
789 bool "Enable paravirtualization code"
790 depends on HAVE_STATIC_CALL
792 This changes the kernel so it can modify itself when it is run
793 under a hypervisor, potentially improving performance significantly
794 over full virtualization. However, when run without a hypervisor
795 the kernel is theoretically slower and slightly larger.
800 config PARAVIRT_DEBUG
801 bool "paravirt-ops debugging"
802 depends on PARAVIRT && DEBUG_KERNEL
804 Enable to debug paravirt_ops internals. Specifically, BUG if
805 a paravirt_op is missing when it is called.
807 config PARAVIRT_SPINLOCKS
808 bool "Paravirtualization layer for spinlocks"
809 depends on PARAVIRT && SMP
811 Paravirtualized spinlocks allow a pvops backend to replace the
812 spinlock implementation with something virtualization-friendly
813 (for example, block the virtual CPU rather than spinning).
815 It has a minimal impact on native kernels and gives a nice performance
816 benefit on paravirtualized KVM / Xen kernels.
818 If you are unsure how to answer this question, answer Y.
820 config X86_HV_CALLBACK_VECTOR
823 source "arch/x86/xen/Kconfig"
826 bool "KVM Guest support (including kvmclock)"
828 select PARAVIRT_CLOCK
829 select ARCH_CPUIDLE_HALTPOLL
830 select X86_HV_CALLBACK_VECTOR
833 This option enables various optimizations for running under the KVM
834 hypervisor. It includes a paravirtualized clock, so that instead
835 of relying on a PIT (or probably other) emulation by the
836 underlying device model, the host provides the guest with
837 timing infrastructure such as time of day, and system time
839 config ARCH_CPUIDLE_HALTPOLL
841 prompt "Disable host haltpoll when loading haltpoll driver"
843 If virtualized under KVM, disable host haltpoll.
846 bool "Support for running PVH guests"
848 This option enables the PVH entry point for guest virtual machines
849 as specified in the x86/HVM direct boot ABI.
851 config PARAVIRT_TIME_ACCOUNTING
852 bool "Paravirtual steal time accounting"
855 Select this option to enable fine granularity task steal time
856 accounting. Time spent executing other tasks in parallel with
857 the current vCPU is discounted from the vCPU power. To account for
858 that, there can be a small performance impact.
860 If in doubt, say N here.
862 config PARAVIRT_CLOCK
865 config JAILHOUSE_GUEST
866 bool "Jailhouse non-root cell support"
867 depends on X86_64 && PCI
870 This option allows to run Linux as guest in a Jailhouse non-root
871 cell. You can leave this option disabled if you only want to start
872 Jailhouse and run Linux afterwards in the root cell.
875 bool "ACRN Guest support"
877 select X86_HV_CALLBACK_VECTOR
879 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
880 a flexible, lightweight reference open-source hypervisor, built with
881 real-time and safety-criticality in mind. It is built for embedded
882 IOT with small footprint and real-time features. More details can be
883 found in https://projectacrn.org/.
885 config INTEL_TDX_GUEST
886 bool "Intel TDX (Trust Domain Extensions) - Guest Support"
887 depends on X86_64 && CPU_SUP_INTEL
888 depends on X86_X2APIC
890 select ARCH_HAS_CC_PLATFORM
891 select X86_MEM_ENCRYPT
893 select UNACCEPTED_MEMORY
895 Support running as a guest under Intel TDX. Without this support,
896 the guest kernel can not boot or run under TDX.
897 TDX includes memory encryption and integrity capabilities
898 which protect the confidentiality and integrity of guest
899 memory contents and CPU state. TDX guests are protected from
900 some attacks from the VMM.
902 endif # HYPERVISOR_GUEST
904 source "arch/x86/Kconfig.cpu"
908 prompt "HPET Timer Support" if X86_32
910 Use the IA-PC HPET (High Precision Event Timer) to manage
911 time in preference to the PIT and RTC, if a HPET is
913 HPET is the next generation timer replacing legacy 8254s.
914 The HPET provides a stable time base on SMP
915 systems, unlike the TSC, but it is more expensive to access,
916 as it is off-chip. The interface used is documented
917 in the HPET spec, revision 1.
919 You can safely choose Y here. However, HPET will only be
920 activated if the platform and the BIOS support this feature.
921 Otherwise the 8254 will be used for timing services.
923 Choose N to continue using the legacy 8254 timer.
925 config HPET_EMULATE_RTC
927 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
929 # Mark as expert because too many people got it wrong.
930 # The code disables itself when not needed.
933 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
934 bool "Enable DMI scanning" if EXPERT
936 Enabled scanning of DMI to identify machine quirks. Say Y
937 here unless you have verified that your setup is not
938 affected by entries in the DMI blacklist. Required by PNP
942 bool "Old AMD GART IOMMU support"
946 depends on X86_64 && PCI && AMD_NB
948 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
949 GART based hardware IOMMUs.
951 The GART supports full DMA access for devices with 32-bit access
952 limitations, on systems with more than 3 GB. This is usually needed
953 for USB, sound, many IDE/SATA chipsets and some other devices.
955 Newer systems typically have a modern AMD IOMMU, supported via
956 the CONFIG_AMD_IOMMU=y config option.
958 In normal configurations this driver is only active when needed:
959 there's more than 3 GB of memory and the system contains a
960 32-bit limited device.
964 config BOOT_VESA_SUPPORT
967 If true, at least one selected framebuffer driver can take advantage
968 of VESA video modes set at an early boot stage via the vga= parameter.
971 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
972 depends on X86_64 && SMP && DEBUG_KERNEL
973 select CPUMASK_OFFSTACK
975 Enable maximum number of CPUS and NUMA Nodes for this architecture.
979 # The maximum number of CPUs supported:
981 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
982 # and which can be configured interactively in the
983 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
985 # The ranges are different on 32-bit and 64-bit kernels, depending on
986 # hardware capabilities and scalability features of the kernel.
988 # ( If MAXSMP is enabled we just use the highest possible value and disable
989 # interactive configuration. )
992 config NR_CPUS_RANGE_BEGIN
994 default NR_CPUS_RANGE_END if MAXSMP
998 config NR_CPUS_RANGE_END
1001 default 64 if SMP && X86_BIGSMP
1002 default 8 if SMP && !X86_BIGSMP
1005 config NR_CPUS_RANGE_END
1008 default 8192 if SMP && CPUMASK_OFFSTACK
1009 default 512 if SMP && !CPUMASK_OFFSTACK
1012 config NR_CPUS_DEFAULT
1015 default 32 if X86_BIGSMP
1019 config NR_CPUS_DEFAULT
1022 default 8192 if MAXSMP
1027 int "Maximum number of CPUs" if SMP && !MAXSMP
1028 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1029 default NR_CPUS_DEFAULT
1031 This allows you to specify the maximum number of CPUs which this
1032 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1033 supported value is 8192, otherwise the maximum value is 512. The
1034 minimum value which makes sense is 2.
1036 This is purely to save memory: each supported CPU adds about 8KB
1037 to the kernel image.
1039 config SCHED_CLUSTER
1040 bool "Cluster scheduler support"
1044 Cluster scheduler support improves the CPU scheduler's decision
1045 making when dealing with machines that have clusters of CPUs.
1046 Cluster usually means a couple of CPUs which are placed closely
1047 by sharing mid-level caches, last-level cache tags or internal
1055 prompt "Multi-core scheduler support"
1058 Multi-core scheduler support improves the CPU scheduler's decision
1059 making when dealing with multi-core CPU chips at a cost of slightly
1060 increased overhead in some places. If unsure say N here.
1062 config SCHED_MC_PRIO
1063 bool "CPU core priorities scheduler support"
1065 select X86_INTEL_PSTATE if CPU_SUP_INTEL
1066 select X86_AMD_PSTATE if CPU_SUP_AMD && ACPI
1070 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1071 core ordering determined at manufacturing time, which allows
1072 certain cores to reach higher turbo frequencies (when running
1073 single threaded workloads) than others.
1075 Enabling this kernel feature teaches the scheduler about
1076 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1077 scheduler's CPU selection logic accordingly, so that higher
1078 overall system performance can be achieved.
1080 This feature will have no effect on CPUs without this feature.
1082 If unsure say Y here.
1086 depends on !SMP && X86_LOCAL_APIC
1089 bool "Local APIC support on uniprocessors" if !PCI_MSI
1091 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1093 A local APIC (Advanced Programmable Interrupt Controller) is an
1094 integrated interrupt controller in the CPU. If you have a single-CPU
1095 system which has a processor with a local APIC, you can say Y here to
1096 enable and use it. If you say Y here even though your machine doesn't
1097 have a local APIC, then the kernel will still run with no slowdown at
1098 all. The local APIC supports CPU-generated self-interrupts (timer,
1099 performance counters), and the NMI watchdog which detects hard
1102 config X86_UP_IOAPIC
1103 bool "IO-APIC support on uniprocessors"
1104 depends on X86_UP_APIC
1106 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1107 SMP-capable replacement for PC-style interrupt controllers. Most
1108 SMP systems and many recent uniprocessor systems have one.
1110 If you have a single-CPU system with an IO-APIC, you can say Y here
1111 to use it. If you say Y here even though your machine doesn't have
1112 an IO-APIC, then the kernel will still run with no slowdown at all.
1114 config X86_LOCAL_APIC
1116 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1117 select IRQ_DOMAIN_HIERARCHY
1121 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1123 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1124 bool "Reroute for broken boot IRQs"
1125 depends on X86_IO_APIC
1127 This option enables a workaround that fixes a source of
1128 spurious interrupts. This is recommended when threaded
1129 interrupt handling is used on systems where the generation of
1130 superfluous "boot interrupts" cannot be disabled.
1132 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1133 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1134 kernel does during interrupt handling). On chipsets where this
1135 boot IRQ generation cannot be disabled, this workaround keeps
1136 the original IRQ line masked so that only the equivalent "boot
1137 IRQ" is delivered to the CPUs. The workaround also tells the
1138 kernel to set up the IRQ handler on the boot IRQ line. In this
1139 way only one interrupt is delivered to the kernel. Otherwise
1140 the spurious second interrupt may cause the kernel to bring
1141 down (vital) interrupt lines.
1143 Only affects "broken" chipsets. Interrupt sharing may be
1144 increased on these systems.
1147 bool "Machine Check / overheating reporting"
1148 select GENERIC_ALLOCATOR
1151 Machine Check support allows the processor to notify the
1152 kernel if it detects a problem (e.g. overheating, data corruption).
1153 The action the kernel takes depends on the severity of the problem,
1154 ranging from warning messages to halting the machine.
1156 config X86_MCELOG_LEGACY
1157 bool "Support for deprecated /dev/mcelog character device"
1160 Enable support for /dev/mcelog which is needed by the old mcelog
1161 userspace logging daemon. Consider switching to the new generation
1164 config X86_MCE_INTEL
1166 prompt "Intel MCE features"
1167 depends on X86_MCE && X86_LOCAL_APIC
1169 Additional support for intel specific MCE features such as
1170 the thermal monitor.
1174 prompt "AMD MCE features"
1175 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1177 Additional support for AMD specific MCE features such as
1178 the DRAM Error Threshold.
1180 config X86_ANCIENT_MCE
1181 bool "Support for old Pentium 5 / WinChip machine checks"
1182 depends on X86_32 && X86_MCE
1184 Include support for machine check handling on old Pentium 5 or WinChip
1185 systems. These typically need to be enabled explicitly on the command
1188 config X86_MCE_THRESHOLD
1189 depends on X86_MCE_AMD || X86_MCE_INTEL
1192 config X86_MCE_INJECT
1193 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1194 tristate "Machine check injector support"
1196 Provide support for injecting machine checks for testing purposes.
1197 If you don't know what a machine check is and you don't do kernel
1198 QA it is safe to say n.
1200 source "arch/x86/events/Kconfig"
1202 config X86_LEGACY_VM86
1203 bool "Legacy VM86 support"
1206 This option allows user programs to put the CPU into V8086
1207 mode, which is an 80286-era approximation of 16-bit real mode.
1209 Some very old versions of X and/or vbetool require this option
1210 for user mode setting. Similarly, DOSEMU will use it if
1211 available to accelerate real mode DOS programs. However, any
1212 recent version of DOSEMU, X, or vbetool should be fully
1213 functional even without kernel VM86 support, as they will all
1214 fall back to software emulation. Nevertheless, if you are using
1215 a 16-bit DOS program where 16-bit performance matters, vm86
1216 mode might be faster than emulation and you might want to
1219 Note that any app that works on a 64-bit kernel is unlikely to
1220 need this option, as 64-bit kernels don't, and can't, support
1221 V8086 mode. This option is also unrelated to 16-bit protected
1222 mode and is not needed to run most 16-bit programs under Wine.
1224 Enabling this option increases the complexity of the kernel
1225 and slows down exception handling a tiny bit.
1227 If unsure, say N here.
1231 default X86_LEGACY_VM86
1234 bool "Enable support for 16-bit segments" if EXPERT
1236 depends on MODIFY_LDT_SYSCALL
1238 This option is required by programs like Wine to run 16-bit
1239 protected mode legacy code on x86 processors. Disabling
1240 this option saves about 300 bytes on i386, or around 6K text
1241 plus 16K runtime memory on x86-64,
1245 depends on X86_16BIT && X86_32
1249 depends on X86_16BIT && X86_64
1251 config X86_VSYSCALL_EMULATION
1252 bool "Enable vsyscall emulation" if EXPERT
1256 This enables emulation of the legacy vsyscall page. Disabling
1257 it is roughly equivalent to booting with vsyscall=none, except
1258 that it will also disable the helpful warning if a program
1259 tries to use a vsyscall. With this option set to N, offending
1260 programs will just segfault, citing addresses of the form
1263 This option is required by many programs built before 2013, and
1264 care should be used even with newer programs if set to N.
1266 Disabling this option saves about 7K of kernel size and
1267 possibly 4K of additional runtime pagetable memory.
1269 config X86_IOPL_IOPERM
1270 bool "IOPERM and IOPL Emulation"
1273 This enables the ioperm() and iopl() syscalls which are necessary
1274 for legacy applications.
1276 Legacy IOPL support is an overbroad mechanism which allows user
1277 space aside of accessing all 65536 I/O ports also to disable
1278 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1279 capabilities and permission from potentially active security
1282 The emulation restricts the functionality of the syscall to
1283 only allowing the full range I/O port access, but prevents the
1284 ability to disable interrupts from user space which would be
1285 granted if the hardware IOPL mechanism would be used.
1288 tristate "Toshiba Laptop support"
1291 This adds a driver to safely access the System Management Mode of
1292 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1293 not work on models with a Phoenix BIOS. The System Management Mode
1294 is used to set the BIOS and power saving options on Toshiba portables.
1296 For information on utilities to make use of this driver see the
1297 Toshiba Linux utilities web site at:
1298 <http://www.buzzard.org.uk/toshiba/>.
1300 Say Y if you intend to run this kernel on a Toshiba portable.
1303 config X86_REBOOTFIXUPS
1304 bool "Enable X86 board specific fixups for reboot"
1307 This enables chipset and/or board specific fixups to be done
1308 in order to get reboot to work correctly. This is only needed on
1309 some combinations of hardware and BIOS. The symptom, for which
1310 this config is intended, is when reboot ends with a stalled/hung
1313 Currently, the only fixup is for the Geode machines using
1314 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1316 Say Y if you want to enable the fixup. Currently, it's safe to
1317 enable this option even if you don't need it.
1322 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1324 config MICROCODE_INITRD32
1326 depends on MICROCODE && X86_32 && BLK_DEV_INITRD
1328 config MICROCODE_LATE_LOADING
1329 bool "Late microcode loading (DANGEROUS)"
1331 depends on MICROCODE && SMP
1333 Loading microcode late, when the system is up and executing instructions
1334 is a tricky business and should be avoided if possible. Just the sequence
1335 of synchronizing all cores and SMT threads is one fragile dance which does
1336 not guarantee that cores might not softlock after the loading. Therefore,
1337 use this at your own risk. Late loading taints the kernel unless the
1338 microcode header indicates that it is safe for late loading via the
1339 minimal revision check. This minimal revision check can be enforced on
1340 the kernel command line with "microcode.minrev=Y".
1342 config MICROCODE_LATE_FORCE_MINREV
1343 bool "Enforce late microcode loading minimal revision check"
1345 depends on MICROCODE_LATE_LOADING
1347 To prevent that users load microcode late which modifies already
1348 in use features, newer microcode patches have a minimum revision field
1349 in the microcode header, which tells the kernel which minimum
1350 revision must be active in the CPU to safely load that new microcode
1351 late into the running system. If disabled the check will not
1352 be enforced but the kernel will be tainted when the minimal
1353 revision check fails.
1355 This minimal revision check can also be controlled via the
1356 "microcode.minrev" parameter on the kernel command line.
1361 tristate "/dev/cpu/*/msr - Model-specific register support"
1363 This device gives privileged processes access to the x86
1364 Model-Specific Registers (MSRs). It is a character device with
1365 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1366 MSR accesses are directed to a specific CPU on multi-processor
1370 tristate "/dev/cpu/*/cpuid - CPU information support"
1372 This device gives processes access to the x86 CPUID instruction to
1373 be executed on a specific processor. It is a character device
1374 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1378 prompt "High Memory Support"
1385 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1386 However, the address space of 32-bit x86 processors is only 4
1387 Gigabytes large. That means that, if you have a large amount of
1388 physical memory, not all of it can be "permanently mapped" by the
1389 kernel. The physical memory that's not permanently mapped is called
1392 If you are compiling a kernel which will never run on a machine with
1393 more than 1 Gigabyte total physical RAM, answer "off" here (default
1394 choice and suitable for most users). This will result in a "3GB/1GB"
1395 split: 3GB are mapped so that each process sees a 3GB virtual memory
1396 space and the remaining part of the 4GB virtual memory space is used
1397 by the kernel to permanently map as much physical memory as
1400 If the machine has between 1 and 4 Gigabytes physical RAM, then
1403 If more than 4 Gigabytes is used then answer "64GB" here. This
1404 selection turns Intel PAE (Physical Address Extension) mode on.
1405 PAE implements 3-level paging on IA32 processors. PAE is fully
1406 supported by Linux, PAE mode is implemented on all recent Intel
1407 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1408 then the kernel will not boot on CPUs that don't support PAE!
1410 The actual amount of total physical memory will either be
1411 auto detected or can be forced by using a kernel command line option
1412 such as "mem=256M". (Try "man bootparam" or see the documentation of
1413 your boot loader (lilo or loadlin) about how to pass options to the
1414 kernel at boot time.)
1416 If unsure, say "off".
1421 Select this if you have a 32-bit processor and between 1 and 4
1422 gigabytes of physical RAM.
1426 depends on X86_HAVE_PAE
1429 Select this if you have a 32-bit processor and more than 4
1430 gigabytes of physical RAM.
1435 prompt "Memory split" if EXPERT
1439 Select the desired split between kernel and user memory.
1441 If the address range available to the kernel is less than the
1442 physical memory installed, the remaining memory will be available
1443 as "high memory". Accessing high memory is a little more costly
1444 than low memory, as it needs to be mapped into the kernel first.
1445 Note that increasing the kernel address space limits the range
1446 available to user programs, making the address space there
1447 tighter. Selecting anything other than the default 3G/1G split
1448 will also likely make your kernel incompatible with binary-only
1451 If you are not absolutely sure what you are doing, leave this
1455 bool "3G/1G user/kernel split"
1456 config VMSPLIT_3G_OPT
1458 bool "3G/1G user/kernel split (for full 1G low memory)"
1460 bool "2G/2G user/kernel split"
1461 config VMSPLIT_2G_OPT
1463 bool "2G/2G user/kernel split (for full 2G low memory)"
1465 bool "1G/3G user/kernel split"
1470 default 0xB0000000 if VMSPLIT_3G_OPT
1471 default 0x80000000 if VMSPLIT_2G
1472 default 0x78000000 if VMSPLIT_2G_OPT
1473 default 0x40000000 if VMSPLIT_1G
1479 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1482 bool "PAE (Physical Address Extension) Support"
1483 depends on X86_32 && X86_HAVE_PAE
1484 select PHYS_ADDR_T_64BIT
1487 PAE is required for NX support, and furthermore enables
1488 larger swapspace support for non-overcommit purposes. It
1489 has the cost of more pagetable lookup overhead, and also
1490 consumes more pagetable space per process.
1493 bool "Enable 5-level page tables support"
1495 select DYNAMIC_MEMORY_LAYOUT
1496 select SPARSEMEM_VMEMMAP
1499 5-level paging enables access to larger address space:
1500 up to 128 PiB of virtual address space and 4 PiB of
1501 physical address space.
1503 It will be supported by future Intel CPUs.
1505 A kernel with the option enabled can be booted on machines that
1506 support 4- or 5-level paging.
1508 See Documentation/arch/x86/x86_64/5level-paging.rst for more
1513 config X86_DIRECT_GBPAGES
1517 Certain kernel features effectively disable kernel
1518 linear 1 GB mappings (even if the CPU otherwise
1519 supports them), so don't confuse the user by printing
1520 that we have them enabled.
1522 config X86_CPA_STATISTICS
1523 bool "Enable statistic for Change Page Attribute"
1526 Expose statistics about the Change Page Attribute mechanism, which
1527 helps to determine the effectiveness of preserving large and huge
1528 page mappings when mapping protections are changed.
1530 config X86_MEM_ENCRYPT
1531 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1532 select DYNAMIC_PHYSICAL_MASK
1535 config AMD_MEM_ENCRYPT
1536 bool "AMD Secure Memory Encryption (SME) support"
1537 depends on X86_64 && CPU_SUP_AMD
1539 select DMA_COHERENT_POOL
1540 select ARCH_USE_MEMREMAP_PROT
1541 select INSTRUCTION_DECODER
1542 select ARCH_HAS_CC_PLATFORM
1543 select X86_MEM_ENCRYPT
1544 select UNACCEPTED_MEMORY
1546 Say yes to enable support for the encryption of system memory.
1547 This requires an AMD processor that supports Secure Memory
1550 # Common NUMA Features
1552 bool "NUMA Memory Allocation and Scheduler Support"
1554 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1555 default y if X86_BIGSMP
1556 select USE_PERCPU_NUMA_NODE_ID
1557 select OF_NUMA if OF
1559 Enable NUMA (Non-Uniform Memory Access) support.
1561 The kernel will try to allocate memory used by a CPU on the
1562 local memory controller of the CPU and add some more
1563 NUMA awareness to the kernel.
1565 For 64-bit this is recommended if the system is Intel Core i7
1566 (or later), AMD Opteron, or EM64T NUMA.
1568 For 32-bit this is only needed if you boot a 32-bit
1569 kernel on a 64-bit NUMA platform.
1571 Otherwise, you should say N.
1575 prompt "Old style AMD Opteron NUMA detection"
1576 depends on X86_64 && NUMA && PCI
1578 Enable AMD NUMA node topology detection. You should say Y here if
1579 you have a multi processor AMD system. This uses an old method to
1580 read the NUMA configuration directly from the builtin Northbridge
1581 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1582 which also takes priority if both are compiled in.
1584 config X86_64_ACPI_NUMA
1586 prompt "ACPI NUMA detection"
1587 depends on X86_64 && NUMA && ACPI && PCI
1590 Enable ACPI SRAT based node topology detection.
1593 bool "NUMA emulation"
1596 Enable NUMA emulation. A flat machine will be split
1597 into virtual nodes when booted with "numa=fake=N", where N is the
1598 number of nodes. This is only useful for debugging.
1601 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1603 default "10" if MAXSMP
1604 default "6" if X86_64
1608 Specify the maximum number of NUMA Nodes available on the target
1609 system. Increases memory reserved to accommodate various tables.
1611 config ARCH_FLATMEM_ENABLE
1613 depends on X86_32 && !NUMA
1615 config ARCH_SPARSEMEM_ENABLE
1617 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1618 select SPARSEMEM_STATIC if X86_32
1619 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1621 config ARCH_SPARSEMEM_DEFAULT
1622 def_bool X86_64 || (NUMA && X86_32)
1624 config ARCH_SELECT_MEMORY_MODEL
1626 depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE
1628 config ARCH_MEMORY_PROBE
1629 bool "Enable sysfs memory/probe interface"
1630 depends on MEMORY_HOTPLUG
1632 This option enables a sysfs memory/probe interface for testing.
1633 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1634 If you are unsure how to answer this question, answer N.
1636 config ARCH_PROC_KCORE_TEXT
1638 depends on X86_64 && PROC_KCORE
1640 config ILLEGAL_POINTER_VALUE
1643 default 0xdead000000000000 if X86_64
1645 config X86_PMEM_LEGACY_DEVICE
1648 config X86_PMEM_LEGACY
1649 tristate "Support non-standard NVDIMMs and ADR protected memory"
1650 depends on PHYS_ADDR_T_64BIT
1652 select X86_PMEM_LEGACY_DEVICE
1653 select NUMA_KEEP_MEMINFO if NUMA
1656 Treat memory marked using the non-standard e820 type of 12 as used
1657 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1658 The kernel will offer these regions to the 'pmem' driver so
1659 they can be used for persistent storage.
1664 bool "Allocate 3rd-level pagetables from highmem"
1667 The VM uses one page table entry for each page of physical memory.
1668 For systems with a lot of RAM, this can be wasteful of precious
1669 low memory. Setting this option will put user-space page table
1670 entries in high memory.
1672 config X86_CHECK_BIOS_CORRUPTION
1673 bool "Check for low memory corruption"
1675 Periodically check for memory corruption in low memory, which
1676 is suspected to be caused by BIOS. Even when enabled in the
1677 configuration, it is disabled at runtime. Enable it by
1678 setting "memory_corruption_check=1" on the kernel command
1679 line. By default it scans the low 64k of memory every 60
1680 seconds; see the memory_corruption_check_size and
1681 memory_corruption_check_period parameters in
1682 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1684 When enabled with the default parameters, this option has
1685 almost no overhead, as it reserves a relatively small amount
1686 of memory and scans it infrequently. It both detects corruption
1687 and prevents it from affecting the running system.
1689 It is, however, intended as a diagnostic tool; if repeatable
1690 BIOS-originated corruption always affects the same memory,
1691 you can use memmap= to prevent the kernel from using that
1694 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1695 bool "Set the default setting of memory_corruption_check"
1696 depends on X86_CHECK_BIOS_CORRUPTION
1699 Set whether the default state of memory_corruption_check is
1702 config MATH_EMULATION
1704 depends on MODIFY_LDT_SYSCALL
1705 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1707 Linux can emulate a math coprocessor (used for floating point
1708 operations) if you don't have one. 486DX and Pentium processors have
1709 a math coprocessor built in, 486SX and 386 do not, unless you added
1710 a 487DX or 387, respectively. (The messages during boot time can
1711 give you some hints here ["man dmesg"].) Everyone needs either a
1712 coprocessor or this emulation.
1714 If you don't have a math coprocessor, you need to say Y here; if you
1715 say Y here even though you have a coprocessor, the coprocessor will
1716 be used nevertheless. (This behavior can be changed with the kernel
1717 command line option "no387", which comes handy if your coprocessor
1718 is broken. Try "man bootparam" or see the documentation of your boot
1719 loader (lilo or loadlin) about how to pass options to the kernel at
1720 boot time.) This means that it is a good idea to say Y here if you
1721 intend to use this kernel on different machines.
1723 More information about the internals of the Linux math coprocessor
1724 emulation can be found in <file:arch/x86/math-emu/README>.
1726 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1727 kernel, it won't hurt.
1731 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1733 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1734 the Memory Type Range Registers (MTRRs) may be used to control
1735 processor access to memory ranges. This is most useful if you have
1736 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1737 allows bus write transfers to be combined into a larger transfer
1738 before bursting over the PCI/AGP bus. This can increase performance
1739 of image write operations 2.5 times or more. Saying Y here creates a
1740 /proc/mtrr file which may be used to manipulate your processor's
1741 MTRRs. Typically the X server should use this.
1743 This code has a reasonably generic interface so that similar
1744 control registers on other processors can be easily supported
1747 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1748 Registers (ARRs) which provide a similar functionality to MTRRs. For
1749 these, the ARRs are used to emulate the MTRRs.
1750 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1751 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1752 write-combining. All of these processors are supported by this code
1753 and it makes sense to say Y here if you have one of them.
1755 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1756 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1757 can lead to all sorts of problems, so it's good to say Y here.
1759 You can safely say Y even if your machine doesn't have MTRRs, you'll
1760 just add about 9 KB to your kernel.
1762 See <file:Documentation/arch/x86/mtrr.rst> for more information.
1764 config MTRR_SANITIZER
1766 prompt "MTRR cleanup support"
1769 Convert MTRR layout from continuous to discrete, so X drivers can
1770 add writeback entries.
1772 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1773 The largest mtrr entry size for a continuous block can be set with
1778 config MTRR_SANITIZER_ENABLE_DEFAULT
1779 int "MTRR cleanup enable value (0-1)"
1782 depends on MTRR_SANITIZER
1784 Enable mtrr cleanup default value
1786 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1787 int "MTRR cleanup spare reg num (0-7)"
1790 depends on MTRR_SANITIZER
1792 mtrr cleanup spare entries default, it can be changed via
1793 mtrr_spare_reg_nr=N on the kernel command line.
1797 prompt "x86 PAT support" if EXPERT
1800 Use PAT attributes to setup page level cache control.
1802 PATs are the modern equivalents of MTRRs and are much more
1803 flexible than MTRRs.
1805 Say N here if you see bootup problems (boot crash, boot hang,
1806 spontaneous reboots) or a non-working video driver.
1810 config ARCH_USES_PG_UNCACHED
1816 prompt "User Mode Instruction Prevention" if EXPERT
1818 User Mode Instruction Prevention (UMIP) is a security feature in
1819 some x86 processors. If enabled, a general protection fault is
1820 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1821 executed in user mode. These instructions unnecessarily expose
1822 information about the hardware state.
1824 The vast majority of applications do not use these instructions.
1825 For the very few that do, software emulation is provided in
1826 specific cases in protected and virtual-8086 modes. Emulated
1830 # GCC >= 9 and binutils >= 2.29
1831 # Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
1833 # https://github.com/llvm/llvm-project/commit/e0b89df2e0f0130881bf6c39bf31d7f6aac00e0f
1834 # https://github.com/llvm/llvm-project/commit/dfcf69770bc522b9e411c66454934a37c1f35332
1835 def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \
1836 (CC_IS_CLANG && CLANG_VERSION >= 140000)) && \
1842 CET features configured (Shadow stack or IBT)
1844 config X86_KERNEL_IBT
1845 prompt "Indirect Branch Tracking"
1847 depends on X86_64 && CC_HAS_IBT && HAVE_OBJTOOL
1848 # https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
1849 depends on !LD_IS_LLD || LLD_VERSION >= 140000
1853 Build the kernel with support for Indirect Branch Tracking, a
1854 hardware support course-grain forward-edge Control Flow Integrity
1855 protection. It enforces that all indirect calls must land on
1856 an ENDBR instruction, as such, the compiler will instrument the
1857 code with them to make this happen.
1859 In addition to building the kernel with IBT, seal all functions that
1860 are not indirect call targets, avoiding them ever becoming one.
1862 This requires LTO like objtool runs and will slow down the build. It
1863 does significantly reduce the number of ENDBR instructions in the
1866 config X86_INTEL_MEMORY_PROTECTION_KEYS
1867 prompt "Memory Protection Keys"
1869 # Note: only available in 64-bit mode
1870 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1871 select ARCH_USES_HIGH_VMA_FLAGS
1872 select ARCH_HAS_PKEYS
1874 Memory Protection Keys provides a mechanism for enforcing
1875 page-based protections, but without requiring modification of the
1876 page tables when an application changes protection domains.
1878 For details, see Documentation/core-api/protection-keys.rst
1883 prompt "TSX enable mode"
1884 depends on CPU_SUP_INTEL
1885 default X86_INTEL_TSX_MODE_OFF
1887 Intel's TSX (Transactional Synchronization Extensions) feature
1888 allows to optimize locking protocols through lock elision which
1889 can lead to a noticeable performance boost.
1891 On the other hand it has been shown that TSX can be exploited
1892 to form side channel attacks (e.g. TAA) and chances are there
1893 will be more of those attacks discovered in the future.
1895 Therefore TSX is not enabled by default (aka tsx=off). An admin
1896 might override this decision by tsx=on the command line parameter.
1897 Even with TSX enabled, the kernel will attempt to enable the best
1898 possible TAA mitigation setting depending on the microcode available
1899 for the particular machine.
1901 This option allows to set the default tsx mode between tsx=on, =off
1902 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1905 Say off if not sure, auto if TSX is in use but it should be used on safe
1906 platforms or on if TSX is in use and the security aspect of tsx is not
1909 config X86_INTEL_TSX_MODE_OFF
1912 TSX is disabled if possible - equals to tsx=off command line parameter.
1914 config X86_INTEL_TSX_MODE_ON
1917 TSX is always enabled on TSX capable HW - equals the tsx=on command
1920 config X86_INTEL_TSX_MODE_AUTO
1923 TSX is enabled on TSX capable HW that is believed to be safe against
1924 side channel attacks- equals the tsx=auto command line parameter.
1928 bool "Software Guard eXtensions (SGX)"
1929 depends on X86_64 && CPU_SUP_INTEL && X86_X2APIC
1931 depends on CRYPTO_SHA256=y
1933 select NUMA_KEEP_MEMINFO if NUMA
1936 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1937 that can be used by applications to set aside private regions of code
1938 and data, referred to as enclaves. An enclave's private memory can
1939 only be accessed by code running within the enclave. Accesses from
1940 outside the enclave, including other enclaves, are disallowed by
1945 config X86_USER_SHADOW_STACK
1946 bool "X86 userspace shadow stack"
1949 select ARCH_USES_HIGH_VMA_FLAGS
1952 Shadow stack protection is a hardware feature that detects function
1953 return address corruption. This helps mitigate ROP attacks.
1954 Applications must be enabled to use it, and old userspace does not
1955 get protection "for free".
1957 CPUs supporting shadow stacks were first released in 2020.
1959 See Documentation/arch/x86/shstk.rst for more information.
1963 config INTEL_TDX_HOST
1964 bool "Intel Trust Domain Extensions (TDX) host support"
1965 depends on CPU_SUP_INTEL
1967 depends on KVM_INTEL
1968 depends on X86_X2APIC
1969 select ARCH_KEEP_MEMBLOCK
1970 depends on CONTIG_ALLOC
1971 depends on !KEXEC_CORE
1974 Intel Trust Domain Extensions (TDX) protects guest VMs from malicious
1975 host and certain physical attacks. This option enables necessary TDX
1976 support in the host kernel to run confidential VMs.
1981 bool "EFI runtime service support"
1984 select EFI_RUNTIME_WRAPPERS
1985 select ARCH_USE_MEMREMAP_PROT
1986 select EFI_RUNTIME_MAP if KEXEC_CORE
1988 This enables the kernel to use EFI runtime services that are
1989 available (such as the EFI variable services).
1991 This option is only useful on systems that have EFI firmware.
1992 In addition, you should use the latest ELILO loader available
1993 at <http://elilo.sourceforge.net> in order to take advantage
1994 of EFI runtime services. However, even with this option, the
1995 resultant kernel should continue to boot on existing non-EFI
1999 bool "EFI stub support"
2003 This kernel feature allows a bzImage to be loaded directly
2004 by EFI firmware without the use of a bootloader.
2006 See Documentation/admin-guide/efi-stub.rst for more information.
2008 config EFI_HANDOVER_PROTOCOL
2009 bool "EFI handover protocol (DEPRECATED)"
2013 Select this in order to include support for the deprecated EFI
2014 handover protocol, which defines alternative entry points into the
2015 EFI stub. This is a practice that has no basis in the UEFI
2016 specification, and requires a priori knowledge on the part of the
2017 bootloader about Linux/x86 specific ways of passing the command line
2018 and initrd, and where in memory those assets may be loaded.
2020 If in doubt, say Y. Even though the corresponding support is not
2021 present in upstream GRUB or other bootloaders, most distros build
2022 GRUB with numerous downstream patches applied, and may rely on the
2023 handover protocol as as result.
2026 bool "EFI mixed-mode support"
2027 depends on EFI_STUB && X86_64
2029 Enabling this feature allows a 64-bit kernel to be booted
2030 on a 32-bit firmware, provided that your CPU supports 64-bit
2033 Note that it is not possible to boot a mixed-mode enabled
2034 kernel via the EFI boot stub - a bootloader that supports
2035 the EFI handover protocol must be used.
2039 config EFI_FAKE_MEMMAP
2040 bool "Enable EFI fake memory map"
2043 Saying Y here will enable "efi_fake_mem" boot option. By specifying
2044 this parameter, you can add arbitrary attribute to specific memory
2045 range by updating original (firmware provided) EFI memmap. This is
2046 useful for debugging of EFI memmap related feature, e.g., Address
2047 Range Mirroring feature.
2049 config EFI_MAX_FAKE_MEM
2050 int "maximum allowable number of ranges in efi_fake_mem boot option"
2051 depends on EFI_FAKE_MEMMAP
2055 Maximum allowable number of ranges in efi_fake_mem boot option.
2056 Ranges can be set up to this value using comma-separated list.
2057 The default value is 8.
2059 config EFI_RUNTIME_MAP
2060 bool "Export EFI runtime maps to sysfs" if EXPERT
2063 Export EFI runtime memory regions to /sys/firmware/efi/runtime-map.
2064 That memory map is required by the 2nd kernel to set up EFI virtual
2065 mappings after kexec, but can also be used for debugging purposes.
2067 See also Documentation/ABI/testing/sysfs-firmware-efi-runtime-map.
2069 source "kernel/Kconfig.hz"
2071 config ARCH_SUPPORTS_KEXEC
2074 config ARCH_SUPPORTS_KEXEC_FILE
2077 config ARCH_SELECTS_KEXEC_FILE
2079 depends on KEXEC_FILE
2080 select HAVE_IMA_KEXEC if IMA
2082 config ARCH_SUPPORTS_KEXEC_PURGATORY
2085 config ARCH_SUPPORTS_KEXEC_SIG
2088 config ARCH_SUPPORTS_KEXEC_SIG_FORCE
2091 config ARCH_SUPPORTS_KEXEC_BZIMAGE_VERIFY_SIG
2094 config ARCH_SUPPORTS_KEXEC_JUMP
2097 config ARCH_SUPPORTS_CRASH_DUMP
2098 def_bool X86_64 || (X86_32 && HIGHMEM)
2100 config ARCH_SUPPORTS_CRASH_HOTPLUG
2103 config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
2104 def_bool CRASH_RESERVE
2106 config PHYSICAL_START
2107 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2110 This gives the physical address where the kernel is loaded.
2112 If the kernel is not relocatable (CONFIG_RELOCATABLE=n) then bzImage
2113 will decompress itself to above physical address and run from there.
2114 Otherwise, bzImage will run from the address where it has been loaded
2115 by the boot loader. The only exception is if it is loaded below the
2116 above physical address, in which case it will relocate itself there.
2118 In normal kdump cases one does not have to set/change this option
2119 as now bzImage can be compiled as a completely relocatable image
2120 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2121 address. This option is mainly useful for the folks who don't want
2122 to use a bzImage for capturing the crash dump and want to use a
2123 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2124 to be specifically compiled to run from a specific memory area
2125 (normally a reserved region) and this option comes handy.
2127 So if you are using bzImage for capturing the crash dump,
2128 leave the value here unchanged to 0x1000000 and set
2129 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2130 for capturing the crash dump change this value to start of
2131 the reserved region. In other words, it can be set based on
2132 the "X" value as specified in the "crashkernel=YM@XM"
2133 command line boot parameter passed to the panic-ed
2134 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2135 for more details about crash dumps.
2137 Usage of bzImage for capturing the crash dump is recommended as
2138 one does not have to build two kernels. Same kernel can be used
2139 as production kernel and capture kernel. Above option should have
2140 gone away after relocatable bzImage support is introduced. But it
2141 is present because there are users out there who continue to use
2142 vmlinux for dump capture. This option should go away down the
2145 Don't change this unless you know what you are doing.
2148 bool "Build a relocatable kernel"
2151 This builds a kernel image that retains relocation information
2152 so it can be loaded someplace besides the default 1MB.
2153 The relocations tend to make the kernel binary about 10% larger,
2154 but are discarded at runtime.
2156 One use is for the kexec on panic case where the recovery kernel
2157 must live at a different physical address than the primary
2160 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2161 it has been loaded at and the compile time physical address
2162 (CONFIG_PHYSICAL_START) is used as the minimum location.
2164 config RANDOMIZE_BASE
2165 bool "Randomize the address of the kernel image (KASLR)"
2166 depends on RELOCATABLE
2169 In support of Kernel Address Space Layout Randomization (KASLR),
2170 this randomizes the physical address at which the kernel image
2171 is decompressed and the virtual address where the kernel
2172 image is mapped, as a security feature that deters exploit
2173 attempts relying on knowledge of the location of kernel
2176 On 64-bit, the kernel physical and virtual addresses are
2177 randomized separately. The physical address will be anywhere
2178 between 16MB and the top of physical memory (up to 64TB). The
2179 virtual address will be randomized from 16MB up to 1GB (9 bits
2180 of entropy). Note that this also reduces the memory space
2181 available to kernel modules from 1.5GB to 1GB.
2183 On 32-bit, the kernel physical and virtual addresses are
2184 randomized together. They will be randomized from 16MB up to
2185 512MB (8 bits of entropy).
2187 Entropy is generated using the RDRAND instruction if it is
2188 supported. If RDTSC is supported, its value is mixed into
2189 the entropy pool as well. If neither RDRAND nor RDTSC are
2190 supported, then entropy is read from the i8254 timer. The
2191 usable entropy is limited by the kernel being built using
2192 2GB addressing, and that PHYSICAL_ALIGN must be at a
2193 minimum of 2MB. As a result, only 10 bits of entropy are
2194 theoretically possible, but the implementations are further
2195 limited due to memory layouts.
2199 # Relocation on x86 needs some additional build support
2200 config X86_NEED_RELOCS
2202 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2204 config PHYSICAL_ALIGN
2205 hex "Alignment value to which kernel should be aligned"
2207 range 0x2000 0x1000000 if X86_32
2208 range 0x200000 0x1000000 if X86_64
2210 This value puts the alignment restrictions on physical address
2211 where kernel is loaded and run from. Kernel is compiled for an
2212 address which meets above alignment restriction.
2214 If bootloader loads the kernel at a non-aligned address and
2215 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2216 address aligned to above value and run from there.
2218 If bootloader loads the kernel at a non-aligned address and
2219 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2220 load address and decompress itself to the address it has been
2221 compiled for and run from there. The address for which kernel is
2222 compiled already meets above alignment restrictions. Hence the
2223 end result is that kernel runs from a physical address meeting
2224 above alignment restrictions.
2226 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2227 this value must be a multiple of 0x200000.
2229 Don't change this unless you know what you are doing.
2231 config DYNAMIC_MEMORY_LAYOUT
2234 This option makes base addresses of vmalloc and vmemmap as well as
2235 __PAGE_OFFSET movable during boot.
2237 config RANDOMIZE_MEMORY
2238 bool "Randomize the kernel memory sections"
2240 depends on RANDOMIZE_BASE
2241 select DYNAMIC_MEMORY_LAYOUT
2242 default RANDOMIZE_BASE
2244 Randomizes the base virtual address of kernel memory sections
2245 (physical memory mapping, vmalloc & vmemmap). This security feature
2246 makes exploits relying on predictable memory locations less reliable.
2248 The order of allocations remains unchanged. Entropy is generated in
2249 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2250 configuration have in average 30,000 different possible virtual
2251 addresses for each memory section.
2255 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2256 hex "Physical memory mapping padding" if EXPERT
2257 depends on RANDOMIZE_MEMORY
2258 default "0xa" if MEMORY_HOTPLUG
2260 range 0x1 0x40 if MEMORY_HOTPLUG
2263 Define the padding in terabytes added to the existing physical
2264 memory size during kernel memory randomization. It is useful
2265 for memory hotplug support but reduces the entropy available for
2266 address randomization.
2268 If unsure, leave at the default value.
2270 config ADDRESS_MASKING
2271 bool "Linear Address Masking support"
2274 Linear Address Masking (LAM) modifies the checking that is applied
2275 to 64-bit linear addresses, allowing software to use of the
2276 untranslated address bits for metadata.
2278 The capability can be used for efficient address sanitizers (ASAN)
2279 implementation and for optimizations in JITs.
2287 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2288 depends on COMPAT_32
2290 Certain buggy versions of glibc will crash if they are
2291 presented with a 32-bit vDSO that is not mapped at the address
2292 indicated in its segment table.
2294 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2295 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2296 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2297 the only released version with the bug, but OpenSUSE 9
2298 contains a buggy "glibc 2.3.2".
2300 The symptom of the bug is that everything crashes on startup, saying:
2301 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2303 Saying Y here changes the default value of the vdso32 boot
2304 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2305 This works around the glibc bug but hurts performance.
2307 If unsure, say N: if you are compiling your own kernel, you
2308 are unlikely to be using a buggy version of glibc.
2311 prompt "vsyscall table for legacy applications"
2313 default LEGACY_VSYSCALL_XONLY
2315 Legacy user code that does not know how to find the vDSO expects
2316 to be able to issue three syscalls by calling fixed addresses in
2317 kernel space. Since this location is not randomized with ASLR,
2318 it can be used to assist security vulnerability exploitation.
2320 This setting can be changed at boot time via the kernel command
2321 line parameter vsyscall=[emulate|xonly|none]. Emulate mode
2322 is deprecated and can only be enabled using the kernel command
2325 On a system with recent enough glibc (2.14 or newer) and no
2326 static binaries, you can say None without a performance penalty
2327 to improve security.
2329 If unsure, select "Emulate execution only".
2331 config LEGACY_VSYSCALL_XONLY
2332 bool "Emulate execution only"
2334 The kernel traps and emulates calls into the fixed vsyscall
2335 address mapping and does not allow reads. This
2336 configuration is recommended when userspace might use the
2337 legacy vsyscall area but support for legacy binary
2338 instrumentation of legacy code is not needed. It mitigates
2339 certain uses of the vsyscall area as an ASLR-bypassing
2342 config LEGACY_VSYSCALL_NONE
2345 There will be no vsyscall mapping at all. This will
2346 eliminate any risk of ASLR bypass due to the vsyscall
2347 fixed address mapping. Attempts to use the vsyscalls
2348 will be reported to dmesg, so that either old or
2349 malicious userspace programs can be identified.
2354 bool "Built-in kernel command line"
2356 Allow for specifying boot arguments to the kernel at
2357 build time. On some systems (e.g. embedded ones), it is
2358 necessary or convenient to provide some or all of the
2359 kernel boot arguments with the kernel itself (that is,
2360 to not rely on the boot loader to provide them.)
2362 To compile command line arguments into the kernel,
2363 set this option to 'Y', then fill in the
2364 boot arguments in CONFIG_CMDLINE.
2366 Systems with fully functional boot loaders (i.e. non-embedded)
2367 should leave this option set to 'N'.
2370 string "Built-in kernel command string"
2371 depends on CMDLINE_BOOL
2374 Enter arguments here that should be compiled into the kernel
2375 image and used at boot time. If the boot loader provides a
2376 command line at boot time, it is appended to this string to
2377 form the full kernel command line, when the system boots.
2379 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2380 change this behavior.
2382 In most cases, the command line (whether built-in or provided
2383 by the boot loader) should specify the device for the root
2386 config CMDLINE_OVERRIDE
2387 bool "Built-in command line overrides boot loader arguments"
2388 depends on CMDLINE_BOOL && CMDLINE != ""
2390 Set this option to 'Y' to have the kernel ignore the boot loader
2391 command line, and use ONLY the built-in command line.
2393 This is used to work around broken boot loaders. This should
2394 be set to 'N' under normal conditions.
2396 config MODIFY_LDT_SYSCALL
2397 bool "Enable the LDT (local descriptor table)" if EXPERT
2400 Linux can allow user programs to install a per-process x86
2401 Local Descriptor Table (LDT) using the modify_ldt(2) system
2402 call. This is required to run 16-bit or segmented code such as
2403 DOSEMU or some Wine programs. It is also used by some very old
2404 threading libraries.
2406 Enabling this feature adds a small amount of overhead to
2407 context switches and increases the low-level kernel attack
2408 surface. Disabling it removes the modify_ldt(2) system call.
2410 Saying 'N' here may make sense for embedded or server kernels.
2412 config STRICT_SIGALTSTACK_SIZE
2413 bool "Enforce strict size checking for sigaltstack"
2414 depends on DYNAMIC_SIGFRAME
2416 For historical reasons MINSIGSTKSZ is a constant which became
2417 already too small with AVX512 support. Add a mechanism to
2418 enforce strict checking of the sigaltstack size against the
2419 real size of the FPU frame. This option enables the check
2420 by default. It can also be controlled via the kernel command
2421 line option 'strict_sas_size' independent of this config
2422 switch. Enabling it might break existing applications which
2423 allocate a too small sigaltstack but 'work' because they
2424 never get a signal delivered.
2426 Say 'N' unless you want to really enforce this check.
2428 source "kernel/livepatch/Kconfig"
2432 config CC_HAS_NAMED_AS
2433 def_bool CC_IS_GCC && GCC_VERSION >= 120100
2435 config USE_X86_SEG_SUPPORT
2437 depends on CC_HAS_NAMED_AS
2439 # -fsanitize=kernel-address (KASAN) is at the moment incompatible
2440 # with named address spaces - see GCC PR sanitizer/111736.
2443 # -fsanitize=thread (KCSAN) is also incompatible.
2447 def_bool $(cc-option,-mharden-sls=all)
2449 config CC_HAS_RETURN_THUNK
2450 def_bool $(cc-option,-mfunction-return=thunk-extern)
2452 config CC_HAS_ENTRY_PADDING
2453 def_bool $(cc-option,-fpatchable-function-entry=16,16)
2455 config FUNCTION_PADDING_CFI
2457 default 59 if FUNCTION_ALIGNMENT_64B
2458 default 27 if FUNCTION_ALIGNMENT_32B
2459 default 11 if FUNCTION_ALIGNMENT_16B
2460 default 3 if FUNCTION_ALIGNMENT_8B
2463 # Basically: FUNCTION_ALIGNMENT - 5*CFI_CLANG
2464 # except Kconfig can't do arithmetic :/
2465 config FUNCTION_PADDING_BYTES
2467 default FUNCTION_PADDING_CFI if CFI_CLANG
2468 default FUNCTION_ALIGNMENT
2472 depends on CC_HAS_ENTRY_PADDING && OBJTOOL
2473 select FUNCTION_ALIGNMENT_16B
2477 depends on X86_KERNEL_IBT && CFI_CLANG && MITIGATION_RETPOLINE
2480 config HAVE_CALL_THUNKS
2482 depends on CC_HAS_ENTRY_PADDING && MITIGATION_RETHUNK && OBJTOOL
2488 config PREFIX_SYMBOLS
2490 depends on CALL_PADDING && !CFI_CLANG
2492 menuconfig CPU_MITIGATIONS
2493 bool "Mitigations for CPU vulnerabilities"
2496 Say Y here to enable options which enable mitigations for hardware
2497 vulnerabilities (usually related to speculative execution).
2498 Mitigations can be disabled or restricted to SMT systems at runtime
2499 via the "mitigations" kernel parameter.
2501 If you say N, all mitigations will be disabled. This CANNOT be
2502 overridden at runtime.
2504 Say 'Y', unless you really know what you are doing.
2508 config MITIGATION_PAGE_TABLE_ISOLATION
2509 bool "Remove the kernel mapping in user mode"
2511 depends on (X86_64 || X86_PAE)
2513 This feature reduces the number of hardware side channels by
2514 ensuring that the majority of kernel addresses are not mapped
2517 See Documentation/arch/x86/pti.rst for more details.
2519 config MITIGATION_RETPOLINE
2520 bool "Avoid speculative indirect branches in kernel"
2521 select OBJTOOL if HAVE_OBJTOOL
2524 Compile kernel with the retpoline compiler options to guard against
2525 kernel-to-user data leaks by avoiding speculative indirect
2526 branches. Requires a compiler with -mindirect-branch=thunk-extern
2527 support for full protection. The kernel may run slower.
2529 config MITIGATION_RETHUNK
2530 bool "Enable return-thunks"
2531 depends on MITIGATION_RETPOLINE && CC_HAS_RETURN_THUNK
2532 select OBJTOOL if HAVE_OBJTOOL
2535 Compile the kernel with the return-thunks compiler option to guard
2536 against kernel-to-user data leaks by avoiding return speculation.
2537 Requires a compiler with -mfunction-return=thunk-extern
2538 support for full protection. The kernel may run slower.
2540 config MITIGATION_UNRET_ENTRY
2541 bool "Enable UNRET on kernel entry"
2542 depends on CPU_SUP_AMD && MITIGATION_RETHUNK && X86_64
2545 Compile the kernel with support for the retbleed=unret mitigation.
2547 config MITIGATION_CALL_DEPTH_TRACKING
2548 bool "Mitigate RSB underflow with call depth tracking"
2549 depends on CPU_SUP_INTEL && HAVE_CALL_THUNKS
2550 select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
2554 Compile the kernel with call depth tracking to mitigate the Intel
2555 SKL Return-Speculation-Buffer (RSB) underflow issue. The
2556 mitigation is off by default and needs to be enabled on the
2557 kernel command line via the retbleed=stuff option. For
2558 non-affected systems the overhead of this option is marginal as
2559 the call depth tracking is using run-time generated call thunks
2560 in a compiler generated padding area and call patching. This
2561 increases text size by ~5%. For non affected systems this space
2562 is unused. On affected SKL systems this results in a significant
2563 performance gain over the IBRS mitigation.
2565 config CALL_THUNKS_DEBUG
2566 bool "Enable call thunks and call depth tracking debugging"
2567 depends on MITIGATION_CALL_DEPTH_TRACKING
2568 select FUNCTION_ALIGNMENT_32B
2571 Enable call/ret counters for imbalance detection and build in
2572 a noisy dmesg about callthunks generation and call patching for
2573 trouble shooting. The debug prints need to be enabled on the
2574 kernel command line with 'debug-callthunks'.
2575 Only enable this when you are debugging call thunks as this
2576 creates a noticeable runtime overhead. If unsure say N.
2578 config MITIGATION_IBPB_ENTRY
2579 bool "Enable IBPB on kernel entry"
2580 depends on CPU_SUP_AMD && X86_64
2583 Compile the kernel with support for the retbleed=ibpb mitigation.
2585 config MITIGATION_IBRS_ENTRY
2586 bool "Enable IBRS on kernel entry"
2587 depends on CPU_SUP_INTEL && X86_64
2590 Compile the kernel with support for the spectre_v2=ibrs mitigation.
2591 This mitigates both spectre_v2 and retbleed at great cost to
2594 config MITIGATION_SRSO
2595 bool "Mitigate speculative RAS overflow on AMD"
2596 depends on CPU_SUP_AMD && X86_64 && MITIGATION_RETHUNK
2599 Enable the SRSO mitigation needed on AMD Zen1-4 machines.
2601 config MITIGATION_SLS
2602 bool "Mitigate Straight-Line-Speculation"
2603 depends on CC_HAS_SLS && X86_64
2604 select OBJTOOL if HAVE_OBJTOOL
2607 Compile the kernel with straight-line-speculation options to guard
2608 against straight line speculation. The kernel image might be slightly
2611 config MITIGATION_GDS_FORCE
2612 bool "Force GDS Mitigation"
2613 depends on CPU_SUP_INTEL
2616 Gather Data Sampling (GDS) is a hardware vulnerability which allows
2617 unprivileged speculative access to data which was previously stored in
2620 This option is equivalent to setting gather_data_sampling=force on the
2621 command line. The microcode mitigation is used if present, otherwise
2622 AVX is disabled as a mitigation. On affected systems that are missing
2623 the microcode any userspace code that unconditionally uses AVX will
2624 break with this option set.
2626 Setting this option on systems not vulnerable to GDS has no effect.
2630 config MITIGATION_RFDS
2631 bool "RFDS Mitigation"
2632 depends on CPU_SUP_INTEL
2635 Enable mitigation for Register File Data Sampling (RFDS) by default.
2636 RFDS is a hardware vulnerability which affects Intel Atom CPUs. It
2637 allows unprivileged speculative access to stale data previously
2638 stored in floating point, vector and integer registers.
2639 See also <file:Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst>
2641 config MITIGATION_SPECTRE_BHI
2642 bool "Mitigate Spectre-BHB (Branch History Injection)"
2643 depends on CPU_SUP_INTEL
2646 Enable BHI mitigations. BHI attacks are a form of Spectre V2 attacks
2647 where the branch history buffer is poisoned to speculatively steer
2649 See <file:Documentation/admin-guide/hw-vuln/spectre.rst>
2653 config ARCH_HAS_ADD_PAGES
2655 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2657 menu "Power management and ACPI options"
2659 config ARCH_HIBERNATION_HEADER
2661 depends on HIBERNATION
2663 source "kernel/power/Kconfig"
2665 source "drivers/acpi/Kconfig"
2672 tristate "APM (Advanced Power Management) BIOS support"
2673 depends on X86_32 && PM_SLEEP
2675 APM is a BIOS specification for saving power using several different
2676 techniques. This is mostly useful for battery powered laptops with
2677 APM compliant BIOSes. If you say Y here, the system time will be
2678 reset after a RESUME operation, the /proc/apm device will provide
2679 battery status information, and user-space programs will receive
2680 notification of APM "events" (e.g. battery status change).
2682 If you select "Y" here, you can disable actual use of the APM
2683 BIOS by passing the "apm=off" option to the kernel at boot time.
2685 Note that the APM support is almost completely disabled for
2686 machines with more than one CPU.
2688 In order to use APM, you will need supporting software. For location
2689 and more information, read <file:Documentation/power/apm-acpi.rst>
2690 and the Battery Powered Linux mini-HOWTO, available from
2691 <http://www.tldp.org/docs.html#howto>.
2693 This driver does not spin down disk drives (see the hdparm(8)
2694 manpage ("man 8 hdparm") for that), and it doesn't turn off
2695 VESA-compliant "green" monitors.
2697 This driver does not support the TI 4000M TravelMate and the ACER
2698 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2699 desktop machines also don't have compliant BIOSes, and this driver
2700 may cause those machines to panic during the boot phase.
2702 Generally, if you don't have a battery in your machine, there isn't
2703 much point in using this driver and you should say N. If you get
2704 random kernel OOPSes or reboots that don't seem to be related to
2705 anything, try disabling/enabling this option (or disabling/enabling
2708 Some other things you should try when experiencing seemingly random,
2711 1) make sure that you have enough swap space and that it is
2713 2) pass the "idle=poll" option to the kernel
2714 3) switch on floating point emulation in the kernel and pass
2715 the "no387" option to the kernel
2716 4) pass the "floppy=nodma" option to the kernel
2717 5) pass the "mem=4M" option to the kernel (thereby disabling
2718 all but the first 4 MB of RAM)
2719 6) make sure that the CPU is not over clocked.
2720 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2721 8) disable the cache from your BIOS settings
2722 9) install a fan for the video card or exchange video RAM
2723 10) install a better fan for the CPU
2724 11) exchange RAM chips
2725 12) exchange the motherboard.
2727 To compile this driver as a module, choose M here: the
2728 module will be called apm.
2732 config APM_IGNORE_USER_SUSPEND
2733 bool "Ignore USER SUSPEND"
2735 This option will ignore USER SUSPEND requests. On machines with a
2736 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2737 series notebooks, it is necessary to say Y because of a BIOS bug.
2739 config APM_DO_ENABLE
2740 bool "Enable PM at boot time"
2742 Enable APM features at boot time. From page 36 of the APM BIOS
2743 specification: "When disabled, the APM BIOS does not automatically
2744 power manage devices, enter the Standby State, enter the Suspend
2745 State, or take power saving steps in response to CPU Idle calls."
2746 This driver will make CPU Idle calls when Linux is idle (unless this
2747 feature is turned off -- see "Do CPU IDLE calls", below). This
2748 should always save battery power, but more complicated APM features
2749 will be dependent on your BIOS implementation. You may need to turn
2750 this option off if your computer hangs at boot time when using APM
2751 support, or if it beeps continuously instead of suspending. Turn
2752 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2753 T400CDT. This is off by default since most machines do fine without
2758 bool "Make CPU Idle calls when idle"
2760 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2761 On some machines, this can activate improved power savings, such as
2762 a slowed CPU clock rate, when the machine is idle. These idle calls
2763 are made after the idle loop has run for some length of time (e.g.,
2764 333 mS). On some machines, this will cause a hang at boot time or
2765 whenever the CPU becomes idle. (On machines with more than one CPU,
2766 this option does nothing.)
2768 config APM_DISPLAY_BLANK
2769 bool "Enable console blanking using APM"
2771 Enable console blanking using the APM. Some laptops can use this to
2772 turn off the LCD backlight when the screen blanker of the Linux
2773 virtual console blanks the screen. Note that this is only used by
2774 the virtual console screen blanker, and won't turn off the backlight
2775 when using the X Window system. This also doesn't have anything to
2776 do with your VESA-compliant power-saving monitor. Further, this
2777 option doesn't work for all laptops -- it might not turn off your
2778 backlight at all, or it might print a lot of errors to the console,
2779 especially if you are using gpm.
2781 config APM_ALLOW_INTS
2782 bool "Allow interrupts during APM BIOS calls"
2784 Normally we disable external interrupts while we are making calls to
2785 the APM BIOS as a measure to lessen the effects of a badly behaving
2786 BIOS implementation. The BIOS should reenable interrupts if it
2787 needs to. Unfortunately, some BIOSes do not -- especially those in
2788 many of the newer IBM Thinkpads. If you experience hangs when you
2789 suspend, try setting this to Y. Otherwise, say N.
2793 source "drivers/cpufreq/Kconfig"
2795 source "drivers/cpuidle/Kconfig"
2797 source "drivers/idle/Kconfig"
2801 menu "Bus options (PCI etc.)"
2804 prompt "PCI access mode"
2805 depends on X86_32 && PCI
2808 On PCI systems, the BIOS can be used to detect the PCI devices and
2809 determine their configuration. However, some old PCI motherboards
2810 have BIOS bugs and may crash if this is done. Also, some embedded
2811 PCI-based systems don't have any BIOS at all. Linux can also try to
2812 detect the PCI hardware directly without using the BIOS.
2814 With this option, you can specify how Linux should detect the
2815 PCI devices. If you choose "BIOS", the BIOS will be used,
2816 if you choose "Direct", the BIOS won't be used, and if you
2817 choose "MMConfig", then PCI Express MMCONFIG will be used.
2818 If you choose "Any", the kernel will try MMCONFIG, then the
2819 direct access method and falls back to the BIOS if that doesn't
2820 work. If unsure, go with the default, which is "Any".
2825 config PCI_GOMMCONFIG
2842 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2844 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2847 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2850 bool "Support mmconfig PCI config space access" if X86_64
2852 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2853 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2857 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2861 depends on PCI && XEN
2863 config MMCONF_FAM10H
2865 depends on X86_64 && PCI_MMCONFIG && ACPI
2867 config PCI_CNB20LE_QUIRK
2868 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2871 Read the PCI windows out of the CNB20LE host bridge. This allows
2872 PCI hotplug to work on systems with the CNB20LE chipset which do
2875 There's no public spec for this chipset, and this functionality
2876 is known to be incomplete.
2878 You should say N unless you know you need this.
2881 bool "ISA bus support on modern systems" if EXPERT
2883 Expose ISA bus device drivers and options available for selection and
2884 configuration. Enable this option if your target machine has an ISA
2885 bus. ISA is an older system, displaced by PCI and newer bus
2886 architectures -- if your target machine is modern, it probably does
2887 not have an ISA bus.
2891 # x86_64 have no ISA slots, but can have ISA-style DMA.
2893 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2896 Enables ISA-style DMA support for devices requiring such controllers.
2904 Find out whether you have ISA slots on your motherboard. ISA is the
2905 name of a bus system, i.e. the way the CPU talks to the other stuff
2906 inside your box. Other bus systems are PCI, EISA, MicroChannel
2907 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2908 newer boards don't support it. If you have ISA, say Y, otherwise N.
2911 tristate "NatSemi SCx200 support"
2913 This provides basic support for National Semiconductor's
2914 (now AMD's) Geode processors. The driver probes for the
2915 PCI-IDs of several on-chip devices, so its a good dependency
2916 for other scx200_* drivers.
2918 If compiled as a module, the driver is named scx200.
2920 config SCx200HR_TIMER
2921 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2925 This driver provides a clocksource built upon the on-chip
2926 27MHz high-resolution timer. Its also a workaround for
2927 NSC Geode SC-1100's buggy TSC, which loses time when the
2928 processor goes idle (as is done by the scheduler). The
2929 other workaround is idle=poll boot option.
2932 bool "One Laptop Per Child support"
2940 Add support for detecting the unique features of the OLPC
2944 bool "OLPC XO-1 Power Management"
2945 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2947 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2950 bool "OLPC XO-1 Real Time Clock"
2951 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2953 Add support for the XO-1 real time clock, which can be used as a
2954 programmable wakeup source.
2957 bool "OLPC XO-1 SCI extras"
2958 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2962 Add support for SCI-based features of the OLPC XO-1 laptop:
2963 - EC-driven system wakeups
2967 - AC adapter status updates
2968 - Battery status updates
2970 config OLPC_XO15_SCI
2971 bool "OLPC XO-1.5 SCI extras"
2972 depends on OLPC && ACPI
2975 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2976 - EC-driven system wakeups
2977 - AC adapter status updates
2978 - Battery status updates
2981 bool "PCEngines ALIX System Support (LED setup)"
2984 This option enables system support for the PCEngines ALIX.
2985 At present this just sets up LEDs for GPIO control on
2986 ALIX2/3/6 boards. However, other system specific setup should
2989 Note: You must still enable the drivers for GPIO and LED support
2990 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2992 Note: You have to set alix.force=1 for boards with Award BIOS.
2995 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2998 This option enables system support for the Soekris Engineering net5501.
3001 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
3005 This option enables system support for the Traverse Technologies GEOS.
3008 bool "Technologic Systems TS-5500 platform support"
3010 select CHECK_SIGNATURE
3014 This option enables system support for the Technologic Systems TS-5500.
3020 depends on CPU_SUP_AMD && PCI
3024 menu "Binary Emulations"
3026 config IA32_EMULATION
3027 bool "IA32 Emulation"
3029 select ARCH_WANT_OLD_COMPAT_IPC
3031 select COMPAT_OLD_SIGACTION
3033 Include code to run legacy 32-bit programs under a
3034 64-bit kernel. You should likely turn this on, unless you're
3035 100% sure that you don't have any 32-bit programs left.
3037 config IA32_EMULATION_DEFAULT_DISABLED
3038 bool "IA32 emulation disabled by default"
3040 depends on IA32_EMULATION
3042 Make IA32 emulation disabled by default. This prevents loading 32-bit
3043 processes and access to 32-bit syscalls. If unsure, leave it to its
3047 bool "x32 ABI for 64-bit mode"
3049 # llvm-objcopy does not convert x86_64 .note.gnu.property or
3050 # compressed debug sections to x86_x32 properly:
3051 # https://github.com/ClangBuiltLinux/linux/issues/514
3052 # https://github.com/ClangBuiltLinux/linux/issues/1141
3053 depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
3055 Include code to run binaries for the x32 native 32-bit ABI
3056 for 64-bit processors. An x32 process gets access to the
3057 full 64-bit register file and wide data path while leaving
3058 pointers at 32 bits for smaller memory footprint.
3062 depends on IA32_EMULATION || X86_32
3064 select OLD_SIGSUSPEND3
3068 depends on IA32_EMULATION || X86_X32_ABI
3070 config COMPAT_FOR_U64_ALIGNMENT
3076 config HAVE_ATOMIC_IOMAP
3080 source "arch/x86/kvm/Kconfig"
3082 source "arch/x86/Kconfig.assembler"