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_USE_CMPXCHG_LOCKREF
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 ARCH_32BIT_OFF_T if X86_32
63 select ARCH_CLOCKSOURCE_INIT
64 select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
65 select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64 || (X86_32 && HIGHMEM)
66 select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
67 select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE)
68 select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
69 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
70 select ARCH_HAS_CACHE_LINE_SIZE
71 select ARCH_HAS_DEBUG_VIRTUAL
72 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
73 select ARCH_HAS_DEVMEM_IS_ALLOWED
74 select ARCH_HAS_EARLY_DEBUG if KGDB
75 select ARCH_HAS_ELF_RANDOMIZE
76 select ARCH_HAS_FAST_MULTIPLIER
77 select ARCH_HAS_FILTER_PGPROT
78 select ARCH_HAS_FORTIFY_SOURCE
79 select ARCH_HAS_GCOV_PROFILE_ALL
80 select ARCH_HAS_KCOV if X86_64 && STACK_VALIDATION
81 select ARCH_HAS_MEM_ENCRYPT
82 select ARCH_HAS_MEMBARRIER_SYNC_CORE
83 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
84 select ARCH_HAS_PMEM_API if X86_64
85 select ARCH_HAS_PTE_DEVMAP if X86_64
86 select ARCH_HAS_PTE_SPECIAL
87 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
88 select ARCH_HAS_COPY_MC if X86_64
89 select ARCH_HAS_SET_MEMORY
90 select ARCH_HAS_SET_DIRECT_MAP
91 select ARCH_HAS_STRICT_KERNEL_RWX
92 select ARCH_HAS_STRICT_MODULE_RWX
93 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
94 select ARCH_HAS_SYSCALL_WRAPPER
95 select ARCH_HAS_UBSAN_SANITIZE_ALL
96 select ARCH_HAS_DEBUG_WX
97 select ARCH_HAS_ZONE_DMA_SET if EXPERT
98 select ARCH_HAVE_NMI_SAFE_CMPXCHG
99 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
100 select ARCH_MIGHT_HAVE_PC_PARPORT
101 select ARCH_MIGHT_HAVE_PC_SERIO
102 select ARCH_STACKWALK
103 select ARCH_SUPPORTS_ACPI
104 select ARCH_SUPPORTS_ATOMIC_RMW
105 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
106 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
107 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
108 select ARCH_SUPPORTS_LTO_CLANG
109 select ARCH_SUPPORTS_LTO_CLANG_THIN
110 select ARCH_USE_BUILTIN_BSWAP
111 select ARCH_USE_MEMTEST
112 select ARCH_USE_QUEUED_RWLOCKS
113 select ARCH_USE_QUEUED_SPINLOCKS
114 select ARCH_USE_SYM_ANNOTATIONS
115 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
116 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
117 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
118 select ARCH_WANTS_NO_INSTR
119 select ARCH_WANT_HUGE_PMD_SHARE
120 select ARCH_WANT_LD_ORPHAN_WARN
121 select ARCH_WANTS_THP_SWAP if X86_64
122 select ARCH_HAS_PARANOID_L1D_FLUSH
123 select BUILDTIME_TABLE_SORT
125 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
126 select CLOCKSOURCE_WATCHDOG
127 select DCACHE_WORD_ACCESS
128 select EDAC_ATOMIC_SCRUB
130 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
131 select GENERIC_CLOCKEVENTS_MIN_ADJUST
132 select GENERIC_CMOS_UPDATE
133 select GENERIC_CPU_AUTOPROBE
134 select GENERIC_CPU_VULNERABILITIES
135 select GENERIC_EARLY_IOREMAP
137 select GENERIC_FIND_FIRST_BIT
139 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
140 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
141 select GENERIC_IRQ_MIGRATION if SMP
142 select GENERIC_IRQ_PROBE
143 select GENERIC_IRQ_RESERVATION_MODE
144 select GENERIC_IRQ_SHOW
145 select GENERIC_PENDING_IRQ if SMP
146 select GENERIC_PTDUMP
147 select GENERIC_SMP_IDLE_THREAD
148 select GENERIC_TIME_VSYSCALL
149 select GENERIC_GETTIMEOFDAY
150 select GENERIC_VDSO_TIME_NS
151 select GUP_GET_PTE_LOW_HIGH if X86_PAE
152 select HARDIRQS_SW_RESEND
153 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
154 select HAVE_ACPI_APEI if ACPI
155 select HAVE_ACPI_APEI_NMI if ACPI
156 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
157 select HAVE_ARCH_AUDITSYSCALL
158 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
159 select HAVE_ARCH_JUMP_LABEL
160 select HAVE_ARCH_JUMP_LABEL_RELATIVE
161 select HAVE_ARCH_KASAN if X86_64
162 select HAVE_ARCH_KASAN_VMALLOC if X86_64
163 select HAVE_ARCH_KFENCE
164 select HAVE_ARCH_KGDB
165 select HAVE_ARCH_MMAP_RND_BITS if MMU
166 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
167 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
168 select HAVE_ARCH_PREL32_RELOCATIONS
169 select HAVE_ARCH_SECCOMP_FILTER
170 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
171 select HAVE_ARCH_STACKLEAK
172 select HAVE_ARCH_TRACEHOOK
173 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
174 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
175 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
176 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
177 select HAVE_ARCH_VMAP_STACK if X86_64
178 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
179 select HAVE_ARCH_WITHIN_STACK_FRAMES
180 select HAVE_ASM_MODVERSIONS
181 select HAVE_CMPXCHG_DOUBLE
182 select HAVE_CMPXCHG_LOCAL
183 select HAVE_CONTEXT_TRACKING if X86_64
184 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
185 select HAVE_C_RECORDMCOUNT
186 select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION
187 select HAVE_DEBUG_KMEMLEAK
188 select HAVE_DMA_CONTIGUOUS
189 select HAVE_DYNAMIC_FTRACE
190 select HAVE_DYNAMIC_FTRACE_WITH_REGS
191 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
192 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
194 select HAVE_EFFICIENT_UNALIGNED_ACCESS
196 select HAVE_EXIT_THREAD
198 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
199 select HAVE_FTRACE_MCOUNT_RECORD
200 select HAVE_FUNCTION_GRAPH_TRACER
201 select HAVE_FUNCTION_TRACER
202 select HAVE_GCC_PLUGINS
203 select HAVE_HW_BREAKPOINT
204 select HAVE_IOREMAP_PROT
205 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
206 select HAVE_IRQ_TIME_ACCOUNTING
207 select HAVE_KERNEL_BZIP2
208 select HAVE_KERNEL_GZIP
209 select HAVE_KERNEL_LZ4
210 select HAVE_KERNEL_LZMA
211 select HAVE_KERNEL_LZO
212 select HAVE_KERNEL_XZ
213 select HAVE_KERNEL_ZSTD
215 select HAVE_KPROBES_ON_FTRACE
216 select HAVE_FUNCTION_ERROR_INJECTION
217 select HAVE_KRETPROBES
219 select HAVE_LIVEPATCH if X86_64
220 select HAVE_MIXED_BREAKPOINTS_REGS
221 select HAVE_MOD_ARCH_SPECIFIC
225 select HAVE_OPTPROBES
226 select HAVE_PCSPKR_PLATFORM
227 select HAVE_PERF_EVENTS
228 select HAVE_PERF_EVENTS_NMI
229 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
231 select HAVE_PERF_REGS
232 select HAVE_PERF_USER_STACK_DUMP
233 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
234 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
235 select HAVE_REGS_AND_STACK_ACCESS_API
236 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
237 select HAVE_FUNCTION_ARG_ACCESS_API
238 select HAVE_SOFTIRQ_ON_OWN_STACK
239 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
240 select HAVE_STACK_VALIDATION if X86_64
241 select HAVE_STATIC_CALL
242 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
243 select HAVE_PREEMPT_DYNAMIC
245 select HAVE_SYSCALL_TRACEPOINTS
246 select HAVE_UNSTABLE_SCHED_CLOCK
247 select HAVE_USER_RETURN_NOTIFIER
248 select HAVE_GENERIC_VDSO
249 select HOTPLUG_SMT if SMP
250 select IRQ_FORCED_THREADING
251 select NEED_SG_DMA_LENGTH
252 select PCI_DOMAINS if PCI
253 select PCI_LOCKLESS_CONFIG if PCI
256 select RTC_MC146818_LIB
259 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
260 select SYSCTL_EXCEPTION_TRACE
261 select THREAD_INFO_IN_TASK
262 select TRACE_IRQFLAGS_SUPPORT
263 select TRACE_IRQFLAGS_NMI_SUPPORT
264 select USER_STACKTRACE_SUPPORT
266 select HAVE_ARCH_KCSAN if X86_64
267 select X86_FEATURE_NAMES if PROC_FS
268 select PROC_PID_ARCH_STATUS if PROC_FS
269 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
271 config INSTRUCTION_DECODER
273 depends on KPROBES || PERF_EVENTS || UPROBES
277 default "elf32-i386" if X86_32
278 default "elf64-x86-64" if X86_64
280 config LOCKDEP_SUPPORT
283 config STACKTRACE_SUPPORT
289 config ARCH_MMAP_RND_BITS_MIN
293 config ARCH_MMAP_RND_BITS_MAX
297 config ARCH_MMAP_RND_COMPAT_BITS_MIN
300 config ARCH_MMAP_RND_COMPAT_BITS_MAX
306 config GENERIC_ISA_DMA
308 depends on ISA_DMA_API
313 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
315 config GENERIC_BUG_RELATIVE_POINTERS
318 config ARCH_MAY_HAVE_PC_FDC
320 depends on ISA_DMA_API
322 config GENERIC_CALIBRATE_DELAY
325 config ARCH_HAS_CPU_RELAX
328 config ARCH_HAS_FILTER_PGPROT
331 config HAVE_SETUP_PER_CPU_AREA
334 config NEED_PER_CPU_EMBED_FIRST_CHUNK
337 config NEED_PER_CPU_PAGE_FIRST_CHUNK
340 config ARCH_HIBERNATION_POSSIBLE
345 default 1024 if X86_64
348 config ARCH_SUSPEND_POSSIBLE
351 config ARCH_WANT_GENERAL_HUGETLB
357 config KASAN_SHADOW_OFFSET
360 default 0xdffffc0000000000
362 config HAVE_INTEL_TXT
364 depends on INTEL_IOMMU && ACPI
368 depends on X86_32 && SMP
372 depends on X86_64 && SMP
374 config ARCH_SUPPORTS_UPROBES
377 config FIX_EARLYCON_MEM
380 config DYNAMIC_PHYSICAL_MASK
383 config PGTABLE_LEVELS
385 default 5 if X86_5LEVEL
390 config CC_HAS_SANE_STACKPROTECTOR
392 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
393 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
395 We have to make sure stack protector is unconditionally disabled if
396 the compiler produces broken code or if it does not let us control
397 the segment on 32-bit kernels.
399 menu "Processor type and features"
402 bool "Symmetric multi-processing support"
404 This enables support for systems with more than one CPU. If you have
405 a system with only one CPU, say N. If you have a system with more
408 If you say N here, the kernel will run on uni- and multiprocessor
409 machines, but will use only one CPU of a multiprocessor machine. If
410 you say Y here, the kernel will run on many, but not all,
411 uniprocessor machines. On a uniprocessor machine, the kernel
412 will run faster if you say N here.
414 Note that if you say Y here and choose architecture "586" or
415 "Pentium" under "Processor family", the kernel will not work on 486
416 architectures. Similarly, multiprocessor kernels for the "PPro"
417 architecture may not work on all Pentium based boards.
419 People using multiprocessor machines who say Y here should also say
420 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
421 Management" code will be disabled if you say Y here.
423 See also <file:Documentation/x86/i386/IO-APIC.rst>,
424 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
425 <http://www.tldp.org/docs.html#howto>.
427 If you don't know what to do here, say N.
429 config X86_FEATURE_NAMES
430 bool "Processor feature human-readable names" if EMBEDDED
433 This option compiles in a table of x86 feature bits and corresponding
434 names. This is required to support /proc/cpuinfo and a few kernel
435 messages. You can disable this to save space, at the expense of
436 making those few kernel messages show numeric feature bits instead.
441 bool "Support x2apic"
442 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
444 This enables x2apic support on CPUs that have this feature.
446 This allows 32-bit apic IDs (so it can support very large systems),
447 and accesses the local apic via MSRs not via mmio.
449 If you don't know what to do here, say N.
452 bool "Enable MPS table" if ACPI
454 depends on X86_LOCAL_APIC
456 For old smp systems that do not have proper acpi support. Newer systems
457 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
461 depends on X86_GOLDFISH
463 config X86_CPU_RESCTRL
464 bool "x86 CPU resource control support"
465 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
467 select PROC_CPU_RESCTRL if PROC_FS
469 Enable x86 CPU resource control support.
471 Provide support for the allocation and monitoring of system resources
474 Intel calls this Intel Resource Director Technology
475 (Intel(R) RDT). More information about RDT can be found in the
476 Intel x86 Architecture Software Developer Manual.
478 AMD calls this AMD Platform Quality of Service (AMD QoS).
479 More information about AMD QoS can be found in the AMD64 Technology
480 Platform Quality of Service Extensions manual.
486 bool "Support for big SMP systems with more than 8 CPUs"
489 This option is needed for the systems that have more than 8 CPUs.
491 config X86_EXTENDED_PLATFORM
492 bool "Support for extended (non-PC) x86 platforms"
495 If you disable this option then the kernel will only support
496 standard PC platforms. (which covers the vast majority of
499 If you enable this option then you'll be able to select support
500 for the following (non-PC) 32 bit x86 platforms:
501 Goldfish (Android emulator)
504 SGI 320/540 (Visual Workstation)
505 STA2X11-based (e.g. Northville)
506 Moorestown MID devices
508 If you have one of these systems, or if you want to build a
509 generic distribution kernel, say Y here - otherwise say N.
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) 64 bit x86 platforms:
527 If you have one of these systems, or if you want to build a
528 generic distribution kernel, say Y here - otherwise say N.
530 # This is an alphabetically sorted list of 64 bit extended platforms
531 # Please maintain the alphabetic order if and when there are additions
533 bool "Numascale NumaChip"
535 depends on X86_EXTENDED_PLATFORM
538 depends on X86_X2APIC
539 depends on PCI_MMCONFIG
541 Adds support for Numascale NumaChip large-SMP systems. Needed to
542 enable more than ~168 cores.
543 If you don't have one of these, you should say N here.
547 select HYPERVISOR_GUEST
549 depends on X86_64 && PCI
550 depends on X86_EXTENDED_PLATFORM
553 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
554 supposed to run on these EM64T-based machines. Only choose this option
555 if you have one of these machines.
558 bool "SGI Ultraviolet"
560 depends on X86_EXTENDED_PLATFORM
563 depends on KEXEC_CORE
564 depends on X86_X2APIC
567 This option is needed in order to support SGI Ultraviolet systems.
568 If you don't have one of these, you should say N here.
570 # Following is an alphabetically sorted list of 32 bit extended platforms
571 # Please maintain the alphabetic order if and when there are additions
574 bool "Goldfish (Virtual Platform)"
575 depends on X86_EXTENDED_PLATFORM
577 Enable support for the Goldfish virtual platform used primarily
578 for Android development. Unless you are building for the Android
579 Goldfish emulator say N here.
582 bool "CE4100 TV platform"
584 depends on PCI_GODIRECT
585 depends on X86_IO_APIC
587 depends on X86_EXTENDED_PLATFORM
588 select X86_REBOOTFIXUPS
590 select OF_EARLY_FLATTREE
592 Select for the Intel CE media processor (CE4100) SOC.
593 This option compiles in support for the CE4100 SOC for settop
594 boxes and media devices.
597 bool "Intel MID platform support"
598 depends on X86_EXTENDED_PLATFORM
599 depends on X86_PLATFORM_DEVICES
601 depends on X86_64 || (PCI_GOANY && X86_32)
602 depends on X86_IO_APIC
607 select MFD_INTEL_MSIC
609 Select to build a kernel capable of supporting Intel MID (Mobile
610 Internet Device) platform systems which do not have the PCI legacy
611 interfaces. If you are building for a PC class system say N here.
613 Intel MID platforms are based on an Intel processor and chipset which
614 consume less power than most of the x86 derivatives.
616 config X86_INTEL_QUARK
617 bool "Intel Quark platform support"
619 depends on X86_EXTENDED_PLATFORM
620 depends on X86_PLATFORM_DEVICES
624 depends on X86_IO_APIC
629 Select to include support for Quark X1000 SoC.
630 Say Y here if you have a Quark based system such as the Arduino
631 compatible Intel Galileo.
633 config X86_INTEL_LPSS
634 bool "Intel Low Power Subsystem Support"
635 depends on X86 && ACPI && PCI
640 Select to build support for Intel Low Power Subsystem such as
641 found on Intel Lynxpoint PCH. Selecting this option enables
642 things like clock tree (common clock framework) and pincontrol
643 which are needed by the LPSS peripheral drivers.
645 config X86_AMD_PLATFORM_DEVICE
646 bool "AMD ACPI2Platform devices support"
651 Select to interpret AMD specific ACPI device to platform device
652 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
653 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
654 implemented under PINCTRL subsystem.
657 tristate "Intel SoC IOSF Sideband support for SoC platforms"
660 This option enables sideband register access support for Intel SoC
661 platforms. On these platforms the IOSF sideband is used in lieu of
662 MSR's for some register accesses, mostly but not limited to thermal
663 and power. Drivers may query the availability of this device to
664 determine if they need the sideband in order to work on these
665 platforms. The sideband is available on the following SoC products.
666 This list is not meant to be exclusive.
671 You should say Y if you are running a kernel on one of these SoC's.
673 config IOSF_MBI_DEBUG
674 bool "Enable IOSF sideband access through debugfs"
675 depends on IOSF_MBI && DEBUG_FS
677 Select this option to expose the IOSF sideband access registers (MCR,
678 MDR, MCRX) through debugfs to write and read register information from
679 different units on the SoC. This is most useful for obtaining device
680 state information for debug and analysis. As this is a general access
681 mechanism, users of this option would have specific knowledge of the
682 device they want to access.
684 If you don't require the option or are in doubt, say N.
687 bool "RDC R-321x SoC"
689 depends on X86_EXTENDED_PLATFORM
691 select X86_REBOOTFIXUPS
693 This option is needed for RDC R-321x system-on-chip, also known
695 If you don't have one of these chips, you should say N here.
697 config X86_32_NON_STANDARD
698 bool "Support non-standard 32-bit SMP architectures"
699 depends on X86_32 && SMP
700 depends on X86_EXTENDED_PLATFORM
702 This option compiles in the bigsmp and STA2X11 default
703 subarchitectures. It is intended for a generic binary
704 kernel. If you select them all, kernel will probe it one by
705 one and will fallback to default.
707 # Alphabetically sorted list of Non standard 32 bit platforms
709 config X86_SUPPORTS_MEMORY_FAILURE
711 # MCE code calls memory_failure():
713 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
714 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
715 depends on X86_64 || !SPARSEMEM
716 select ARCH_SUPPORTS_MEMORY_FAILURE
719 bool "STA2X11 Companion Chip Support"
720 depends on X86_32_NON_STANDARD && PCI
725 This adds support for boards based on the STA2X11 IO-Hub,
726 a.k.a. "ConneXt". The chip is used in place of the standard
727 PC chipset, so all "standard" peripherals are missing. If this
728 option is selected the kernel will still be able to boot on
729 standard PC machines.
732 tristate "Eurobraille/Iris poweroff module"
735 The Iris machines from EuroBraille do not have APM or ACPI support
736 to shut themselves down properly. A special I/O sequence is
737 needed to do so, which is what this module does at
740 This is only for Iris machines from EuroBraille.
744 config SCHED_OMIT_FRAME_POINTER
746 prompt "Single-depth WCHAN output"
749 Calculate simpler /proc/<PID>/wchan values. If this option
750 is disabled then wchan values will recurse back to the
751 caller function. This provides more accurate wchan values,
752 at the expense of slightly more scheduling overhead.
754 If in doubt, say "Y".
756 menuconfig HYPERVISOR_GUEST
757 bool "Linux guest support"
759 Say Y here to enable options for running Linux under various hyper-
760 visors. This option enables basic hypervisor detection and platform
763 If you say N, all options in this submenu will be skipped and
764 disabled, and Linux guest support won't be built in.
769 bool "Enable paravirtualization code"
770 depends on HAVE_STATIC_CALL
772 This changes the kernel so it can modify itself when it is run
773 under a hypervisor, potentially improving performance significantly
774 over full virtualization. However, when run without a hypervisor
775 the kernel is theoretically slower and slightly larger.
780 config PARAVIRT_DEBUG
781 bool "paravirt-ops debugging"
782 depends on PARAVIRT && DEBUG_KERNEL
784 Enable to debug paravirt_ops internals. Specifically, BUG if
785 a paravirt_op is missing when it is called.
787 config PARAVIRT_SPINLOCKS
788 bool "Paravirtualization layer for spinlocks"
789 depends on PARAVIRT && SMP
791 Paravirtualized spinlocks allow a pvops backend to replace the
792 spinlock implementation with something virtualization-friendly
793 (for example, block the virtual CPU rather than spinning).
795 It has a minimal impact on native kernels and gives a nice performance
796 benefit on paravirtualized KVM / Xen kernels.
798 If you are unsure how to answer this question, answer Y.
800 config X86_HV_CALLBACK_VECTOR
803 source "arch/x86/xen/Kconfig"
806 bool "KVM Guest support (including kvmclock)"
808 select PARAVIRT_CLOCK
809 select ARCH_CPUIDLE_HALTPOLL
810 select X86_HV_CALLBACK_VECTOR
813 This option enables various optimizations for running under the KVM
814 hypervisor. It includes a paravirtualized clock, so that instead
815 of relying on a PIT (or probably other) emulation by the
816 underlying device model, the host provides the guest with
817 timing infrastructure such as time of day, and system time
819 config ARCH_CPUIDLE_HALTPOLL
821 prompt "Disable host haltpoll when loading haltpoll driver"
823 If virtualized under KVM, disable host haltpoll.
826 bool "Support for running PVH guests"
828 This option enables the PVH entry point for guest virtual machines
829 as specified in the x86/HVM direct boot ABI.
831 config PARAVIRT_TIME_ACCOUNTING
832 bool "Paravirtual steal time accounting"
835 Select this option to enable fine granularity task steal time
836 accounting. Time spent executing other tasks in parallel with
837 the current vCPU is discounted from the vCPU power. To account for
838 that, there can be a small performance impact.
840 If in doubt, say N here.
842 config PARAVIRT_CLOCK
845 config JAILHOUSE_GUEST
846 bool "Jailhouse non-root cell support"
847 depends on X86_64 && PCI
850 This option allows to run Linux as guest in a Jailhouse non-root
851 cell. You can leave this option disabled if you only want to start
852 Jailhouse and run Linux afterwards in the root cell.
855 bool "ACRN Guest support"
857 select X86_HV_CALLBACK_VECTOR
859 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
860 a flexible, lightweight reference open-source hypervisor, built with
861 real-time and safety-criticality in mind. It is built for embedded
862 IOT with small footprint and real-time features. More details can be
863 found in https://projectacrn.org/.
865 endif #HYPERVISOR_GUEST
867 source "arch/x86/Kconfig.cpu"
871 prompt "HPET Timer Support" if X86_32
873 Use the IA-PC HPET (High Precision Event Timer) to manage
874 time in preference to the PIT and RTC, if a HPET is
876 HPET is the next generation timer replacing legacy 8254s.
877 The HPET provides a stable time base on SMP
878 systems, unlike the TSC, but it is more expensive to access,
879 as it is off-chip. The interface used is documented
880 in the HPET spec, revision 1.
882 You can safely choose Y here. However, HPET will only be
883 activated if the platform and the BIOS support this feature.
884 Otherwise the 8254 will be used for timing services.
886 Choose N to continue using the legacy 8254 timer.
888 config HPET_EMULATE_RTC
890 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
892 # Mark as expert because too many people got it wrong.
893 # The code disables itself when not needed.
896 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
897 bool "Enable DMI scanning" if EXPERT
899 Enabled scanning of DMI to identify machine quirks. Say Y
900 here unless you have verified that your setup is not
901 affected by entries in the DMI blacklist. Required by PNP
905 bool "Old AMD GART IOMMU support"
909 depends on X86_64 && PCI && AMD_NB
911 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
912 GART based hardware IOMMUs.
914 The GART supports full DMA access for devices with 32-bit access
915 limitations, on systems with more than 3 GB. This is usually needed
916 for USB, sound, many IDE/SATA chipsets and some other devices.
918 Newer systems typically have a modern AMD IOMMU, supported via
919 the CONFIG_AMD_IOMMU=y config option.
921 In normal configurations this driver is only active when needed:
922 there's more than 3 GB of memory and the system contains a
923 32-bit limited device.
928 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
929 depends on X86_64 && SMP && DEBUG_KERNEL
930 select CPUMASK_OFFSTACK
932 Enable maximum number of CPUS and NUMA Nodes for this architecture.
936 # The maximum number of CPUs supported:
938 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
939 # and which can be configured interactively in the
940 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
942 # The ranges are different on 32-bit and 64-bit kernels, depending on
943 # hardware capabilities and scalability features of the kernel.
945 # ( If MAXSMP is enabled we just use the highest possible value and disable
946 # interactive configuration. )
949 config NR_CPUS_RANGE_BEGIN
951 default NR_CPUS_RANGE_END if MAXSMP
955 config NR_CPUS_RANGE_END
958 default 64 if SMP && X86_BIGSMP
959 default 8 if SMP && !X86_BIGSMP
962 config NR_CPUS_RANGE_END
965 default 8192 if SMP && CPUMASK_OFFSTACK
966 default 512 if SMP && !CPUMASK_OFFSTACK
969 config NR_CPUS_DEFAULT
972 default 32 if X86_BIGSMP
976 config NR_CPUS_DEFAULT
979 default 8192 if MAXSMP
984 int "Maximum number of CPUs" if SMP && !MAXSMP
985 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
986 default NR_CPUS_DEFAULT
988 This allows you to specify the maximum number of CPUs which this
989 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
990 supported value is 8192, otherwise the maximum value is 512. The
991 minimum value which makes sense is 2.
993 This is purely to save memory: each supported CPU adds about 8KB
1001 prompt "Multi-core scheduler support"
1004 Multi-core scheduler support improves the CPU scheduler's decision
1005 making when dealing with multi-core CPU chips at a cost of slightly
1006 increased overhead in some places. If unsure say N here.
1008 config SCHED_MC_PRIO
1009 bool "CPU core priorities scheduler support"
1010 depends on SCHED_MC && CPU_SUP_INTEL
1011 select X86_INTEL_PSTATE
1015 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1016 core ordering determined at manufacturing time, which allows
1017 certain cores to reach higher turbo frequencies (when running
1018 single threaded workloads) than others.
1020 Enabling this kernel feature teaches the scheduler about
1021 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1022 scheduler's CPU selection logic accordingly, so that higher
1023 overall system performance can be achieved.
1025 This feature will have no effect on CPUs without this feature.
1027 If unsure say Y here.
1031 depends on !SMP && X86_LOCAL_APIC
1034 bool "Local APIC support on uniprocessors" if !PCI_MSI
1036 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1038 A local APIC (Advanced Programmable Interrupt Controller) is an
1039 integrated interrupt controller in the CPU. If you have a single-CPU
1040 system which has a processor with a local APIC, you can say Y here to
1041 enable and use it. If you say Y here even though your machine doesn't
1042 have a local APIC, then the kernel will still run with no slowdown at
1043 all. The local APIC supports CPU-generated self-interrupts (timer,
1044 performance counters), and the NMI watchdog which detects hard
1047 config X86_UP_IOAPIC
1048 bool "IO-APIC support on uniprocessors"
1049 depends on X86_UP_APIC
1051 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1052 SMP-capable replacement for PC-style interrupt controllers. Most
1053 SMP systems and many recent uniprocessor systems have one.
1055 If you have a single-CPU system with an IO-APIC, you can say Y here
1056 to use it. If you say Y here even though your machine doesn't have
1057 an IO-APIC, then the kernel will still run with no slowdown at all.
1059 config X86_LOCAL_APIC
1061 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1062 select IRQ_DOMAIN_HIERARCHY
1063 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1067 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1069 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1070 bool "Reroute for broken boot IRQs"
1071 depends on X86_IO_APIC
1073 This option enables a workaround that fixes a source of
1074 spurious interrupts. This is recommended when threaded
1075 interrupt handling is used on systems where the generation of
1076 superfluous "boot interrupts" cannot be disabled.
1078 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1079 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1080 kernel does during interrupt handling). On chipsets where this
1081 boot IRQ generation cannot be disabled, this workaround keeps
1082 the original IRQ line masked so that only the equivalent "boot
1083 IRQ" is delivered to the CPUs. The workaround also tells the
1084 kernel to set up the IRQ handler on the boot IRQ line. In this
1085 way only one interrupt is delivered to the kernel. Otherwise
1086 the spurious second interrupt may cause the kernel to bring
1087 down (vital) interrupt lines.
1089 Only affects "broken" chipsets. Interrupt sharing may be
1090 increased on these systems.
1093 bool "Machine Check / overheating reporting"
1094 select GENERIC_ALLOCATOR
1097 Machine Check support allows the processor to notify the
1098 kernel if it detects a problem (e.g. overheating, data corruption).
1099 The action the kernel takes depends on the severity of the problem,
1100 ranging from warning messages to halting the machine.
1102 config X86_MCELOG_LEGACY
1103 bool "Support for deprecated /dev/mcelog character device"
1106 Enable support for /dev/mcelog which is needed by the old mcelog
1107 userspace logging daemon. Consider switching to the new generation
1110 config X86_MCE_INTEL
1112 prompt "Intel MCE features"
1113 depends on X86_MCE && X86_LOCAL_APIC
1115 Additional support for intel specific MCE features such as
1116 the thermal monitor.
1120 prompt "AMD MCE features"
1121 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1123 Additional support for AMD specific MCE features such as
1124 the DRAM Error Threshold.
1126 config X86_ANCIENT_MCE
1127 bool "Support for old Pentium 5 / WinChip machine checks"
1128 depends on X86_32 && X86_MCE
1130 Include support for machine check handling on old Pentium 5 or WinChip
1131 systems. These typically need to be enabled explicitly on the command
1134 config X86_MCE_THRESHOLD
1135 depends on X86_MCE_AMD || X86_MCE_INTEL
1138 config X86_MCE_INJECT
1139 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1140 tristate "Machine check injector support"
1142 Provide support for injecting machine checks for testing purposes.
1143 If you don't know what a machine check is and you don't do kernel
1144 QA it is safe to say n.
1146 source "arch/x86/events/Kconfig"
1148 config X86_LEGACY_VM86
1149 bool "Legacy VM86 support"
1152 This option allows user programs to put the CPU into V8086
1153 mode, which is an 80286-era approximation of 16-bit real mode.
1155 Some very old versions of X and/or vbetool require this option
1156 for user mode setting. Similarly, DOSEMU will use it if
1157 available to accelerate real mode DOS programs. However, any
1158 recent version of DOSEMU, X, or vbetool should be fully
1159 functional even without kernel VM86 support, as they will all
1160 fall back to software emulation. Nevertheless, if you are using
1161 a 16-bit DOS program where 16-bit performance matters, vm86
1162 mode might be faster than emulation and you might want to
1165 Note that any app that works on a 64-bit kernel is unlikely to
1166 need this option, as 64-bit kernels don't, and can't, support
1167 V8086 mode. This option is also unrelated to 16-bit protected
1168 mode and is not needed to run most 16-bit programs under Wine.
1170 Enabling this option increases the complexity of the kernel
1171 and slows down exception handling a tiny bit.
1173 If unsure, say N here.
1177 default X86_LEGACY_VM86
1180 bool "Enable support for 16-bit segments" if EXPERT
1182 depends on MODIFY_LDT_SYSCALL
1184 This option is required by programs like Wine to run 16-bit
1185 protected mode legacy code on x86 processors. Disabling
1186 this option saves about 300 bytes on i386, or around 6K text
1187 plus 16K runtime memory on x86-64,
1191 depends on X86_16BIT && X86_32
1195 depends on X86_16BIT && X86_64
1197 config X86_VSYSCALL_EMULATION
1198 bool "Enable vsyscall emulation" if EXPERT
1202 This enables emulation of the legacy vsyscall page. Disabling
1203 it is roughly equivalent to booting with vsyscall=none, except
1204 that it will also disable the helpful warning if a program
1205 tries to use a vsyscall. With this option set to N, offending
1206 programs will just segfault, citing addresses of the form
1209 This option is required by many programs built before 2013, and
1210 care should be used even with newer programs if set to N.
1212 Disabling this option saves about 7K of kernel size and
1213 possibly 4K of additional runtime pagetable memory.
1215 config X86_IOPL_IOPERM
1216 bool "IOPERM and IOPL Emulation"
1219 This enables the ioperm() and iopl() syscalls which are necessary
1220 for legacy applications.
1222 Legacy IOPL support is an overbroad mechanism which allows user
1223 space aside of accessing all 65536 I/O ports also to disable
1224 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1225 capabilities and permission from potentially active security
1228 The emulation restricts the functionality of the syscall to
1229 only allowing the full range I/O port access, but prevents the
1230 ability to disable interrupts from user space which would be
1231 granted if the hardware IOPL mechanism would be used.
1234 tristate "Toshiba Laptop support"
1237 This adds a driver to safely access the System Management Mode of
1238 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1239 not work on models with a Phoenix BIOS. The System Management Mode
1240 is used to set the BIOS and power saving options on Toshiba portables.
1242 For information on utilities to make use of this driver see the
1243 Toshiba Linux utilities web site at:
1244 <http://www.buzzard.org.uk/toshiba/>.
1246 Say Y if you intend to run this kernel on a Toshiba portable.
1250 tristate "Dell i8k legacy laptop support"
1253 select SENSORS_DELL_SMM
1255 This option enables legacy /proc/i8k userspace interface in hwmon
1256 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1257 temperature and allows controlling fan speeds of Dell laptops via
1258 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1259 it reports also power and hotkey status. For fan speed control is
1260 needed userspace package i8kutils.
1262 Say Y if you intend to run this kernel on old Dell laptops or want to
1263 use userspace package i8kutils.
1266 config X86_REBOOTFIXUPS
1267 bool "Enable X86 board specific fixups for reboot"
1270 This enables chipset and/or board specific fixups to be done
1271 in order to get reboot to work correctly. This is only needed on
1272 some combinations of hardware and BIOS. The symptom, for which
1273 this config is intended, is when reboot ends with a stalled/hung
1276 Currently, the only fixup is for the Geode machines using
1277 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1279 Say Y if you want to enable the fixup. Currently, it's safe to
1280 enable this option even if you don't need it.
1284 bool "CPU microcode loading support"
1286 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1288 If you say Y here, you will be able to update the microcode on
1289 Intel and AMD processors. The Intel support is for the IA32 family,
1290 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1291 AMD support is for families 0x10 and later. You will obviously need
1292 the actual microcode binary data itself which is not shipped with
1295 The preferred method to load microcode from a detached initrd is described
1296 in Documentation/x86/microcode.rst. For that you need to enable
1297 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1298 initrd for microcode blobs.
1300 In addition, you can build the microcode into the kernel. For that you
1301 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1304 config MICROCODE_INTEL
1305 bool "Intel microcode loading support"
1306 depends on CPU_SUP_INTEL && MICROCODE
1309 This options enables microcode patch loading support for Intel
1312 For the current Intel microcode data package go to
1313 <https://downloadcenter.intel.com> and search for
1314 'Linux Processor Microcode Data File'.
1316 config MICROCODE_AMD
1317 bool "AMD microcode loading support"
1318 depends on CPU_SUP_AMD && MICROCODE
1320 If you select this option, microcode patch loading support for AMD
1321 processors will be enabled.
1323 config MICROCODE_OLD_INTERFACE
1324 bool "Ancient loading interface (DEPRECATED)"
1326 depends on MICROCODE
1328 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1329 which was used by userspace tools like iucode_tool and microcode.ctl.
1330 It is inadequate because it runs too late to be able to properly
1331 load microcode on a machine and it needs special tools. Instead, you
1332 should've switched to the early loading method with the initrd or
1333 builtin microcode by now: Documentation/x86/microcode.rst
1336 tristate "/dev/cpu/*/msr - Model-specific register support"
1338 This device gives privileged processes access to the x86
1339 Model-Specific Registers (MSRs). It is a character device with
1340 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1341 MSR accesses are directed to a specific CPU on multi-processor
1345 tristate "/dev/cpu/*/cpuid - CPU information support"
1347 This device gives processes access to the x86 CPUID instruction to
1348 be executed on a specific processor. It is a character device
1349 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1353 prompt "High Memory Support"
1360 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1361 However, the address space of 32-bit x86 processors is only 4
1362 Gigabytes large. That means that, if you have a large amount of
1363 physical memory, not all of it can be "permanently mapped" by the
1364 kernel. The physical memory that's not permanently mapped is called
1367 If you are compiling a kernel which will never run on a machine with
1368 more than 1 Gigabyte total physical RAM, answer "off" here (default
1369 choice and suitable for most users). This will result in a "3GB/1GB"
1370 split: 3GB are mapped so that each process sees a 3GB virtual memory
1371 space and the remaining part of the 4GB virtual memory space is used
1372 by the kernel to permanently map as much physical memory as
1375 If the machine has between 1 and 4 Gigabytes physical RAM, then
1378 If more than 4 Gigabytes is used then answer "64GB" here. This
1379 selection turns Intel PAE (Physical Address Extension) mode on.
1380 PAE implements 3-level paging on IA32 processors. PAE is fully
1381 supported by Linux, PAE mode is implemented on all recent Intel
1382 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1383 then the kernel will not boot on CPUs that don't support PAE!
1385 The actual amount of total physical memory will either be
1386 auto detected or can be forced by using a kernel command line option
1387 such as "mem=256M". (Try "man bootparam" or see the documentation of
1388 your boot loader (lilo or loadlin) about how to pass options to the
1389 kernel at boot time.)
1391 If unsure, say "off".
1396 Select this if you have a 32-bit processor and between 1 and 4
1397 gigabytes of physical RAM.
1401 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1404 Select this if you have a 32-bit processor and more than 4
1405 gigabytes of physical RAM.
1410 prompt "Memory split" if EXPERT
1414 Select the desired split between kernel and user memory.
1416 If the address range available to the kernel is less than the
1417 physical memory installed, the remaining memory will be available
1418 as "high memory". Accessing high memory is a little more costly
1419 than low memory, as it needs to be mapped into the kernel first.
1420 Note that increasing the kernel address space limits the range
1421 available to user programs, making the address space there
1422 tighter. Selecting anything other than the default 3G/1G split
1423 will also likely make your kernel incompatible with binary-only
1426 If you are not absolutely sure what you are doing, leave this
1430 bool "3G/1G user/kernel split"
1431 config VMSPLIT_3G_OPT
1433 bool "3G/1G user/kernel split (for full 1G low memory)"
1435 bool "2G/2G user/kernel split"
1436 config VMSPLIT_2G_OPT
1438 bool "2G/2G user/kernel split (for full 2G low memory)"
1440 bool "1G/3G user/kernel split"
1445 default 0xB0000000 if VMSPLIT_3G_OPT
1446 default 0x80000000 if VMSPLIT_2G
1447 default 0x78000000 if VMSPLIT_2G_OPT
1448 default 0x40000000 if VMSPLIT_1G
1454 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1457 bool "PAE (Physical Address Extension) Support"
1458 depends on X86_32 && !HIGHMEM4G
1459 select PHYS_ADDR_T_64BIT
1462 PAE is required for NX support, and furthermore enables
1463 larger swapspace support for non-overcommit purposes. It
1464 has the cost of more pagetable lookup overhead, and also
1465 consumes more pagetable space per process.
1468 bool "Enable 5-level page tables support"
1470 select DYNAMIC_MEMORY_LAYOUT
1471 select SPARSEMEM_VMEMMAP
1474 5-level paging enables access to larger address space:
1475 upto 128 PiB of virtual address space and 4 PiB of
1476 physical address space.
1478 It will be supported by future Intel CPUs.
1480 A kernel with the option enabled can be booted on machines that
1481 support 4- or 5-level paging.
1483 See Documentation/x86/x86_64/5level-paging.rst for more
1488 config X86_DIRECT_GBPAGES
1492 Certain kernel features effectively disable kernel
1493 linear 1 GB mappings (even if the CPU otherwise
1494 supports them), so don't confuse the user by printing
1495 that we have them enabled.
1497 config X86_CPA_STATISTICS
1498 bool "Enable statistic for Change Page Attribute"
1501 Expose statistics about the Change Page Attribute mechanism, which
1502 helps to determine the effectiveness of preserving large and huge
1503 page mappings when mapping protections are changed.
1505 config AMD_MEM_ENCRYPT
1506 bool "AMD Secure Memory Encryption (SME) support"
1507 depends on X86_64 && CPU_SUP_AMD
1508 select DMA_COHERENT_POOL
1509 select DYNAMIC_PHYSICAL_MASK
1510 select ARCH_USE_MEMREMAP_PROT
1511 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1512 select INSTRUCTION_DECODER
1513 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1514 select ARCH_HAS_CC_PLATFORM
1516 Say yes to enable support for the encryption of system memory.
1517 This requires an AMD processor that supports Secure Memory
1520 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1521 bool "Activate AMD Secure Memory Encryption (SME) by default"
1522 depends on AMD_MEM_ENCRYPT
1524 Say yes to have system memory encrypted by default if running on
1525 an AMD processor that supports Secure Memory Encryption (SME).
1527 If set to Y, then the encryption of system memory can be
1528 deactivated with the mem_encrypt=off command line option.
1530 If set to N, then the encryption of system memory can be
1531 activated with the mem_encrypt=on command line option.
1533 # Common NUMA Features
1535 bool "NUMA Memory Allocation and Scheduler Support"
1537 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1538 default y if X86_BIGSMP
1540 Enable NUMA (Non-Uniform Memory Access) support.
1542 The kernel will try to allocate memory used by a CPU on the
1543 local memory controller of the CPU and add some more
1544 NUMA awareness to the kernel.
1546 For 64-bit this is recommended if the system is Intel Core i7
1547 (or later), AMD Opteron, or EM64T NUMA.
1549 For 32-bit this is only needed if you boot a 32-bit
1550 kernel on a 64-bit NUMA platform.
1552 Otherwise, you should say N.
1556 prompt "Old style AMD Opteron NUMA detection"
1557 depends on X86_64 && NUMA && PCI
1559 Enable AMD NUMA node topology detection. You should say Y here if
1560 you have a multi processor AMD system. This uses an old method to
1561 read the NUMA configuration directly from the builtin Northbridge
1562 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1563 which also takes priority if both are compiled in.
1565 config X86_64_ACPI_NUMA
1567 prompt "ACPI NUMA detection"
1568 depends on X86_64 && NUMA && ACPI && PCI
1571 Enable ACPI SRAT based node topology detection.
1574 bool "NUMA emulation"
1577 Enable NUMA emulation. A flat machine will be split
1578 into virtual nodes when booted with "numa=fake=N", where N is the
1579 number of nodes. This is only useful for debugging.
1582 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1584 default "10" if MAXSMP
1585 default "6" if X86_64
1589 Specify the maximum number of NUMA Nodes available on the target
1590 system. Increases memory reserved to accommodate various tables.
1592 config ARCH_FLATMEM_ENABLE
1594 depends on X86_32 && !NUMA
1596 config ARCH_SPARSEMEM_ENABLE
1598 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1599 select SPARSEMEM_STATIC if X86_32
1600 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1602 config ARCH_SPARSEMEM_DEFAULT
1603 def_bool X86_64 || (NUMA && X86_32)
1605 config ARCH_SELECT_MEMORY_MODEL
1607 depends on ARCH_SPARSEMEM_ENABLE
1609 config ARCH_MEMORY_PROBE
1610 bool "Enable sysfs memory/probe interface"
1611 depends on X86_64 && MEMORY_HOTPLUG
1613 This option enables a sysfs memory/probe interface for testing.
1614 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1615 If you are unsure how to answer this question, answer N.
1617 config ARCH_PROC_KCORE_TEXT
1619 depends on X86_64 && PROC_KCORE
1621 config ILLEGAL_POINTER_VALUE
1624 default 0xdead000000000000 if X86_64
1626 config X86_PMEM_LEGACY_DEVICE
1629 config X86_PMEM_LEGACY
1630 tristate "Support non-standard NVDIMMs and ADR protected memory"
1631 depends on PHYS_ADDR_T_64BIT
1633 select X86_PMEM_LEGACY_DEVICE
1634 select NUMA_KEEP_MEMINFO if NUMA
1637 Treat memory marked using the non-standard e820 type of 12 as used
1638 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1639 The kernel will offer these regions to the 'pmem' driver so
1640 they can be used for persistent storage.
1645 bool "Allocate 3rd-level pagetables from highmem"
1648 The VM uses one page table entry for each page of physical memory.
1649 For systems with a lot of RAM, this can be wasteful of precious
1650 low memory. Setting this option will put user-space page table
1651 entries in high memory.
1653 config X86_CHECK_BIOS_CORRUPTION
1654 bool "Check for low memory corruption"
1656 Periodically check for memory corruption in low memory, which
1657 is suspected to be caused by BIOS. Even when enabled in the
1658 configuration, it is disabled at runtime. Enable it by
1659 setting "memory_corruption_check=1" on the kernel command
1660 line. By default it scans the low 64k of memory every 60
1661 seconds; see the memory_corruption_check_size and
1662 memory_corruption_check_period parameters in
1663 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1665 When enabled with the default parameters, this option has
1666 almost no overhead, as it reserves a relatively small amount
1667 of memory and scans it infrequently. It both detects corruption
1668 and prevents it from affecting the running system.
1670 It is, however, intended as a diagnostic tool; if repeatable
1671 BIOS-originated corruption always affects the same memory,
1672 you can use memmap= to prevent the kernel from using that
1675 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1676 bool "Set the default setting of memory_corruption_check"
1677 depends on X86_CHECK_BIOS_CORRUPTION
1680 Set whether the default state of memory_corruption_check is
1683 config MATH_EMULATION
1685 depends on MODIFY_LDT_SYSCALL
1686 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1688 Linux can emulate a math coprocessor (used for floating point
1689 operations) if you don't have one. 486DX and Pentium processors have
1690 a math coprocessor built in, 486SX and 386 do not, unless you added
1691 a 487DX or 387, respectively. (The messages during boot time can
1692 give you some hints here ["man dmesg"].) Everyone needs either a
1693 coprocessor or this emulation.
1695 If you don't have a math coprocessor, you need to say Y here; if you
1696 say Y here even though you have a coprocessor, the coprocessor will
1697 be used nevertheless. (This behavior can be changed with the kernel
1698 command line option "no387", which comes handy if your coprocessor
1699 is broken. Try "man bootparam" or see the documentation of your boot
1700 loader (lilo or loadlin) about how to pass options to the kernel at
1701 boot time.) This means that it is a good idea to say Y here if you
1702 intend to use this kernel on different machines.
1704 More information about the internals of the Linux math coprocessor
1705 emulation can be found in <file:arch/x86/math-emu/README>.
1707 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1708 kernel, it won't hurt.
1712 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1714 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1715 the Memory Type Range Registers (MTRRs) may be used to control
1716 processor access to memory ranges. This is most useful if you have
1717 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1718 allows bus write transfers to be combined into a larger transfer
1719 before bursting over the PCI/AGP bus. This can increase performance
1720 of image write operations 2.5 times or more. Saying Y here creates a
1721 /proc/mtrr file which may be used to manipulate your processor's
1722 MTRRs. Typically the X server should use this.
1724 This code has a reasonably generic interface so that similar
1725 control registers on other processors can be easily supported
1728 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1729 Registers (ARRs) which provide a similar functionality to MTRRs. For
1730 these, the ARRs are used to emulate the MTRRs.
1731 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1732 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1733 write-combining. All of these processors are supported by this code
1734 and it makes sense to say Y here if you have one of them.
1736 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1737 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1738 can lead to all sorts of problems, so it's good to say Y here.
1740 You can safely say Y even if your machine doesn't have MTRRs, you'll
1741 just add about 9 KB to your kernel.
1743 See <file:Documentation/x86/mtrr.rst> for more information.
1745 config MTRR_SANITIZER
1747 prompt "MTRR cleanup support"
1750 Convert MTRR layout from continuous to discrete, so X drivers can
1751 add writeback entries.
1753 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1754 The largest mtrr entry size for a continuous block can be set with
1759 config MTRR_SANITIZER_ENABLE_DEFAULT
1760 int "MTRR cleanup enable value (0-1)"
1763 depends on MTRR_SANITIZER
1765 Enable mtrr cleanup default value
1767 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1768 int "MTRR cleanup spare reg num (0-7)"
1771 depends on MTRR_SANITIZER
1773 mtrr cleanup spare entries default, it can be changed via
1774 mtrr_spare_reg_nr=N on the kernel command line.
1778 prompt "x86 PAT support" if EXPERT
1781 Use PAT attributes to setup page level cache control.
1783 PATs are the modern equivalents of MTRRs and are much more
1784 flexible than MTRRs.
1786 Say N here if you see bootup problems (boot crash, boot hang,
1787 spontaneous reboots) or a non-working video driver.
1791 config ARCH_USES_PG_UNCACHED
1797 prompt "x86 architectural random number generator" if EXPERT
1799 Enable the x86 architectural RDRAND instruction
1800 (Intel Bull Mountain technology) to generate random numbers.
1801 If supported, this is a high bandwidth, cryptographically
1802 secure hardware random number generator.
1806 prompt "Supervisor Mode Access Prevention" if EXPERT
1808 Supervisor Mode Access Prevention (SMAP) is a security
1809 feature in newer Intel processors. There is a small
1810 performance cost if this enabled and turned on; there is
1811 also a small increase in the kernel size if this is enabled.
1817 prompt "User Mode Instruction Prevention" if EXPERT
1819 User Mode Instruction Prevention (UMIP) is a security feature in
1820 some x86 processors. If enabled, a general protection fault is
1821 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1822 executed in user mode. These instructions unnecessarily expose
1823 information about the hardware state.
1825 The vast majority of applications do not use these instructions.
1826 For the very few that do, software emulation is provided in
1827 specific cases in protected and virtual-8086 modes. Emulated
1830 config X86_INTEL_MEMORY_PROTECTION_KEYS
1831 prompt "Memory Protection Keys"
1833 # Note: only available in 64-bit mode
1834 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1835 select ARCH_USES_HIGH_VMA_FLAGS
1836 select ARCH_HAS_PKEYS
1838 Memory Protection Keys provides a mechanism for enforcing
1839 page-based protections, but without requiring modification of the
1840 page tables when an application changes protection domains.
1842 For details, see Documentation/core-api/protection-keys.rst
1847 prompt "TSX enable mode"
1848 depends on CPU_SUP_INTEL
1849 default X86_INTEL_TSX_MODE_OFF
1851 Intel's TSX (Transactional Synchronization Extensions) feature
1852 allows to optimize locking protocols through lock elision which
1853 can lead to a noticeable performance boost.
1855 On the other hand it has been shown that TSX can be exploited
1856 to form side channel attacks (e.g. TAA) and chances are there
1857 will be more of those attacks discovered in the future.
1859 Therefore TSX is not enabled by default (aka tsx=off). An admin
1860 might override this decision by tsx=on the command line parameter.
1861 Even with TSX enabled, the kernel will attempt to enable the best
1862 possible TAA mitigation setting depending on the microcode available
1863 for the particular machine.
1865 This option allows to set the default tsx mode between tsx=on, =off
1866 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1869 Say off if not sure, auto if TSX is in use but it should be used on safe
1870 platforms or on if TSX is in use and the security aspect of tsx is not
1873 config X86_INTEL_TSX_MODE_OFF
1876 TSX is disabled if possible - equals to tsx=off command line parameter.
1878 config X86_INTEL_TSX_MODE_ON
1881 TSX is always enabled on TSX capable HW - equals the tsx=on command
1884 config X86_INTEL_TSX_MODE_AUTO
1887 TSX is enabled on TSX capable HW that is believed to be safe against
1888 side channel attacks- equals the tsx=auto command line parameter.
1892 bool "Software Guard eXtensions (SGX)"
1893 depends on X86_64 && CPU_SUP_INTEL
1895 depends on CRYPTO_SHA256=y
1898 select NUMA_KEEP_MEMINFO if NUMA
1900 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1901 that can be used by applications to set aside private regions of code
1902 and data, referred to as enclaves. An enclave's private memory can
1903 only be accessed by code running within the enclave. Accesses from
1904 outside the enclave, including other enclaves, are disallowed by
1910 bool "EFI runtime service support"
1913 select EFI_RUNTIME_WRAPPERS
1914 select ARCH_USE_MEMREMAP_PROT
1916 This enables the kernel to use EFI runtime services that are
1917 available (such as the EFI variable services).
1919 This option is only useful on systems that have EFI firmware.
1920 In addition, you should use the latest ELILO loader available
1921 at <http://elilo.sourceforge.net> in order to take advantage
1922 of EFI runtime services. However, even with this option, the
1923 resultant kernel should continue to boot on existing non-EFI
1927 bool "EFI stub support"
1928 depends on EFI && !X86_USE_3DNOW
1929 depends on $(cc-option,-mabi=ms) || X86_32
1932 This kernel feature allows a bzImage to be loaded directly
1933 by EFI firmware without the use of a bootloader.
1935 See Documentation/admin-guide/efi-stub.rst for more information.
1938 bool "EFI mixed-mode support"
1939 depends on EFI_STUB && X86_64
1941 Enabling this feature allows a 64-bit kernel to be booted
1942 on a 32-bit firmware, provided that your CPU supports 64-bit
1945 Note that it is not possible to boot a mixed-mode enabled
1946 kernel via the EFI boot stub - a bootloader that supports
1947 the EFI handover protocol must be used.
1951 source "kernel/Kconfig.hz"
1954 bool "kexec system call"
1957 kexec is a system call that implements the ability to shutdown your
1958 current kernel, and to start another kernel. It is like a reboot
1959 but it is independent of the system firmware. And like a reboot
1960 you can start any kernel with it, not just Linux.
1962 The name comes from the similarity to the exec system call.
1964 It is an ongoing process to be certain the hardware in a machine
1965 is properly shutdown, so do not be surprised if this code does not
1966 initially work for you. As of this writing the exact hardware
1967 interface is strongly in flux, so no good recommendation can be
1971 bool "kexec file based system call"
1976 depends on CRYPTO_SHA256=y
1978 This is new version of kexec system call. This system call is
1979 file based and takes file descriptors as system call argument
1980 for kernel and initramfs as opposed to list of segments as
1981 accepted by previous system call.
1983 config ARCH_HAS_KEXEC_PURGATORY
1987 bool "Verify kernel signature during kexec_file_load() syscall"
1988 depends on KEXEC_FILE
1991 This option makes the kexec_file_load() syscall check for a valid
1992 signature of the kernel image. The image can still be loaded without
1993 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
1994 there's a signature that we can check, then it must be valid.
1996 In addition to this option, you need to enable signature
1997 verification for the corresponding kernel image type being
1998 loaded in order for this to work.
2000 config KEXEC_SIG_FORCE
2001 bool "Require a valid signature in kexec_file_load() syscall"
2002 depends on KEXEC_SIG
2004 This option makes kernel signature verification mandatory for
2005 the kexec_file_load() syscall.
2007 config KEXEC_BZIMAGE_VERIFY_SIG
2008 bool "Enable bzImage signature verification support"
2009 depends on KEXEC_SIG
2010 depends on SIGNED_PE_FILE_VERIFICATION
2011 select SYSTEM_TRUSTED_KEYRING
2013 Enable bzImage signature verification support.
2016 bool "kernel crash dumps"
2017 depends on X86_64 || (X86_32 && HIGHMEM)
2019 Generate crash dump after being started by kexec.
2020 This should be normally only set in special crash dump kernels
2021 which are loaded in the main kernel with kexec-tools into
2022 a specially reserved region and then later executed after
2023 a crash by kdump/kexec. The crash dump kernel must be compiled
2024 to a memory address not used by the main kernel or BIOS using
2025 PHYSICAL_START, or it must be built as a relocatable image
2026 (CONFIG_RELOCATABLE=y).
2027 For more details see Documentation/admin-guide/kdump/kdump.rst
2031 depends on KEXEC && HIBERNATION
2033 Jump between original kernel and kexeced kernel and invoke
2034 code in physical address mode via KEXEC
2036 config PHYSICAL_START
2037 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2040 This gives the physical address where the kernel is loaded.
2042 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2043 bzImage will decompress itself to above physical address and
2044 run from there. Otherwise, bzImage will run from the address where
2045 it has been loaded by the boot loader and will ignore above physical
2048 In normal kdump cases one does not have to set/change this option
2049 as now bzImage can be compiled as a completely relocatable image
2050 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2051 address. This option is mainly useful for the folks who don't want
2052 to use a bzImage for capturing the crash dump and want to use a
2053 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2054 to be specifically compiled to run from a specific memory area
2055 (normally a reserved region) and this option comes handy.
2057 So if you are using bzImage for capturing the crash dump,
2058 leave the value here unchanged to 0x1000000 and set
2059 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2060 for capturing the crash dump change this value to start of
2061 the reserved region. In other words, it can be set based on
2062 the "X" value as specified in the "crashkernel=YM@XM"
2063 command line boot parameter passed to the panic-ed
2064 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2065 for more details about crash dumps.
2067 Usage of bzImage for capturing the crash dump is recommended as
2068 one does not have to build two kernels. Same kernel can be used
2069 as production kernel and capture kernel. Above option should have
2070 gone away after relocatable bzImage support is introduced. But it
2071 is present because there are users out there who continue to use
2072 vmlinux for dump capture. This option should go away down the
2075 Don't change this unless you know what you are doing.
2078 bool "Build a relocatable kernel"
2081 This builds a kernel image that retains relocation information
2082 so it can be loaded someplace besides the default 1MB.
2083 The relocations tend to make the kernel binary about 10% larger,
2084 but are discarded at runtime.
2086 One use is for the kexec on panic case where the recovery kernel
2087 must live at a different physical address than the primary
2090 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2091 it has been loaded at and the compile time physical address
2092 (CONFIG_PHYSICAL_START) is used as the minimum location.
2094 config RANDOMIZE_BASE
2095 bool "Randomize the address of the kernel image (KASLR)"
2096 depends on RELOCATABLE
2099 In support of Kernel Address Space Layout Randomization (KASLR),
2100 this randomizes the physical address at which the kernel image
2101 is decompressed and the virtual address where the kernel
2102 image is mapped, as a security feature that deters exploit
2103 attempts relying on knowledge of the location of kernel
2106 On 64-bit, the kernel physical and virtual addresses are
2107 randomized separately. The physical address will be anywhere
2108 between 16MB and the top of physical memory (up to 64TB). The
2109 virtual address will be randomized from 16MB up to 1GB (9 bits
2110 of entropy). Note that this also reduces the memory space
2111 available to kernel modules from 1.5GB to 1GB.
2113 On 32-bit, the kernel physical and virtual addresses are
2114 randomized together. They will be randomized from 16MB up to
2115 512MB (8 bits of entropy).
2117 Entropy is generated using the RDRAND instruction if it is
2118 supported. If RDTSC is supported, its value is mixed into
2119 the entropy pool as well. If neither RDRAND nor RDTSC are
2120 supported, then entropy is read from the i8254 timer. The
2121 usable entropy is limited by the kernel being built using
2122 2GB addressing, and that PHYSICAL_ALIGN must be at a
2123 minimum of 2MB. As a result, only 10 bits of entropy are
2124 theoretically possible, but the implementations are further
2125 limited due to memory layouts.
2129 # Relocation on x86 needs some additional build support
2130 config X86_NEED_RELOCS
2132 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2134 config PHYSICAL_ALIGN
2135 hex "Alignment value to which kernel should be aligned"
2137 range 0x2000 0x1000000 if X86_32
2138 range 0x200000 0x1000000 if X86_64
2140 This value puts the alignment restrictions on physical address
2141 where kernel is loaded and run from. Kernel is compiled for an
2142 address which meets above alignment restriction.
2144 If bootloader loads the kernel at a non-aligned address and
2145 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2146 address aligned to above value and run from there.
2148 If bootloader loads the kernel at a non-aligned address and
2149 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2150 load address and decompress itself to the address it has been
2151 compiled for and run from there. The address for which kernel is
2152 compiled already meets above alignment restrictions. Hence the
2153 end result is that kernel runs from a physical address meeting
2154 above alignment restrictions.
2156 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2157 this value must be a multiple of 0x200000.
2159 Don't change this unless you know what you are doing.
2161 config DYNAMIC_MEMORY_LAYOUT
2164 This option makes base addresses of vmalloc and vmemmap as well as
2165 __PAGE_OFFSET movable during boot.
2167 config RANDOMIZE_MEMORY
2168 bool "Randomize the kernel memory sections"
2170 depends on RANDOMIZE_BASE
2171 select DYNAMIC_MEMORY_LAYOUT
2172 default RANDOMIZE_BASE
2174 Randomizes the base virtual address of kernel memory sections
2175 (physical memory mapping, vmalloc & vmemmap). This security feature
2176 makes exploits relying on predictable memory locations less reliable.
2178 The order of allocations remains unchanged. Entropy is generated in
2179 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2180 configuration have in average 30,000 different possible virtual
2181 addresses for each memory section.
2185 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2186 hex "Physical memory mapping padding" if EXPERT
2187 depends on RANDOMIZE_MEMORY
2188 default "0xa" if MEMORY_HOTPLUG
2190 range 0x1 0x40 if MEMORY_HOTPLUG
2193 Define the padding in terabytes added to the existing physical
2194 memory size during kernel memory randomization. It is useful
2195 for memory hotplug support but reduces the entropy available for
2196 address randomization.
2198 If unsure, leave at the default value.
2204 config BOOTPARAM_HOTPLUG_CPU0
2205 bool "Set default setting of cpu0_hotpluggable"
2206 depends on HOTPLUG_CPU
2208 Set whether default state of cpu0_hotpluggable is on or off.
2210 Say Y here to enable CPU0 hotplug by default. If this switch
2211 is turned on, there is no need to give cpu0_hotplug kernel
2212 parameter and the CPU0 hotplug feature is enabled by default.
2214 Please note: there are two known CPU0 dependencies if you want
2215 to enable the CPU0 hotplug feature either by this switch or by
2216 cpu0_hotplug kernel parameter.
2218 First, resume from hibernate or suspend always starts from CPU0.
2219 So hibernate and suspend are prevented if CPU0 is offline.
2221 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2222 offline if any interrupt can not migrate out of CPU0. There may
2223 be other CPU0 dependencies.
2225 Please make sure the dependencies are under your control before
2226 you enable this feature.
2228 Say N if you don't want to enable CPU0 hotplug feature by default.
2229 You still can enable the CPU0 hotplug feature at boot by kernel
2230 parameter cpu0_hotplug.
2232 config DEBUG_HOTPLUG_CPU0
2234 prompt "Debug CPU0 hotplug"
2235 depends on HOTPLUG_CPU
2237 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2238 soon as possible and boots up userspace with CPU0 offlined. User
2239 can online CPU0 back after boot time.
2241 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2242 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2243 compilation or giving cpu0_hotplug kernel parameter at boot.
2249 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2250 depends on COMPAT_32
2252 Certain buggy versions of glibc will crash if they are
2253 presented with a 32-bit vDSO that is not mapped at the address
2254 indicated in its segment table.
2256 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2257 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2258 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2259 the only released version with the bug, but OpenSUSE 9
2260 contains a buggy "glibc 2.3.2".
2262 The symptom of the bug is that everything crashes on startup, saying:
2263 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2265 Saying Y here changes the default value of the vdso32 boot
2266 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2267 This works around the glibc bug but hurts performance.
2269 If unsure, say N: if you are compiling your own kernel, you
2270 are unlikely to be using a buggy version of glibc.
2273 prompt "vsyscall table for legacy applications"
2275 default LEGACY_VSYSCALL_XONLY
2277 Legacy user code that does not know how to find the vDSO expects
2278 to be able to issue three syscalls by calling fixed addresses in
2279 kernel space. Since this location is not randomized with ASLR,
2280 it can be used to assist security vulnerability exploitation.
2282 This setting can be changed at boot time via the kernel command
2283 line parameter vsyscall=[emulate|xonly|none].
2285 On a system with recent enough glibc (2.14 or newer) and no
2286 static binaries, you can say None without a performance penalty
2287 to improve security.
2289 If unsure, select "Emulate execution only".
2291 config LEGACY_VSYSCALL_EMULATE
2292 bool "Full emulation"
2294 The kernel traps and emulates calls into the fixed vsyscall
2295 address mapping. This makes the mapping non-executable, but
2296 it still contains readable known contents, which could be
2297 used in certain rare security vulnerability exploits. This
2298 configuration is recommended when using legacy userspace
2299 that still uses vsyscalls along with legacy binary
2300 instrumentation tools that require code to be readable.
2302 An example of this type of legacy userspace is running
2303 Pin on an old binary that still uses vsyscalls.
2305 config LEGACY_VSYSCALL_XONLY
2306 bool "Emulate execution only"
2308 The kernel traps and emulates calls into the fixed vsyscall
2309 address mapping and does not allow reads. This
2310 configuration is recommended when userspace might use the
2311 legacy vsyscall area but support for legacy binary
2312 instrumentation of legacy code is not needed. It mitigates
2313 certain uses of the vsyscall area as an ASLR-bypassing
2316 config LEGACY_VSYSCALL_NONE
2319 There will be no vsyscall mapping at all. This will
2320 eliminate any risk of ASLR bypass due to the vsyscall
2321 fixed address mapping. Attempts to use the vsyscalls
2322 will be reported to dmesg, so that either old or
2323 malicious userspace programs can be identified.
2328 bool "Built-in kernel command line"
2330 Allow for specifying boot arguments to the kernel at
2331 build time. On some systems (e.g. embedded ones), it is
2332 necessary or convenient to provide some or all of the
2333 kernel boot arguments with the kernel itself (that is,
2334 to not rely on the boot loader to provide them.)
2336 To compile command line arguments into the kernel,
2337 set this option to 'Y', then fill in the
2338 boot arguments in CONFIG_CMDLINE.
2340 Systems with fully functional boot loaders (i.e. non-embedded)
2341 should leave this option set to 'N'.
2344 string "Built-in kernel command string"
2345 depends on CMDLINE_BOOL
2348 Enter arguments here that should be compiled into the kernel
2349 image and used at boot time. If the boot loader provides a
2350 command line at boot time, it is appended to this string to
2351 form the full kernel command line, when the system boots.
2353 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2354 change this behavior.
2356 In most cases, the command line (whether built-in or provided
2357 by the boot loader) should specify the device for the root
2360 config CMDLINE_OVERRIDE
2361 bool "Built-in command line overrides boot loader arguments"
2362 depends on CMDLINE_BOOL && CMDLINE != ""
2364 Set this option to 'Y' to have the kernel ignore the boot loader
2365 command line, and use ONLY the built-in command line.
2367 This is used to work around broken boot loaders. This should
2368 be set to 'N' under normal conditions.
2370 config MODIFY_LDT_SYSCALL
2371 bool "Enable the LDT (local descriptor table)" if EXPERT
2374 Linux can allow user programs to install a per-process x86
2375 Local Descriptor Table (LDT) using the modify_ldt(2) system
2376 call. This is required to run 16-bit or segmented code such as
2377 DOSEMU or some Wine programs. It is also used by some very old
2378 threading libraries.
2380 Enabling this feature adds a small amount of overhead to
2381 context switches and increases the low-level kernel attack
2382 surface. Disabling it removes the modify_ldt(2) system call.
2384 Saying 'N' here may make sense for embedded or server kernels.
2386 source "kernel/livepatch/Kconfig"
2391 def_bool $(cc-option,-mharden-sls=all)
2393 config CC_HAS_RETURN_THUNK
2394 def_bool $(cc-option,-mfunction-return=thunk-extern)
2396 menuconfig SPECULATION_MITIGATIONS
2397 bool "Mitigations for speculative execution vulnerabilities"
2400 Say Y here to enable options which enable mitigations for
2401 speculative execution hardware vulnerabilities.
2403 If you say N, all mitigations will be disabled. You really
2404 should know what you are doing to say so.
2406 if SPECULATION_MITIGATIONS
2408 config PAGE_TABLE_ISOLATION
2409 bool "Remove the kernel mapping in user mode"
2411 depends on (X86_64 || X86_PAE)
2413 This feature reduces the number of hardware side channels by
2414 ensuring that the majority of kernel addresses are not mapped
2417 See Documentation/x86/pti.rst for more details.
2420 bool "Avoid speculative indirect branches in kernel"
2423 Compile kernel with the retpoline compiler options to guard against
2424 kernel-to-user data leaks by avoiding speculative indirect
2425 branches. Requires a compiler with -mindirect-branch=thunk-extern
2426 support for full protection. The kernel may run slower.
2429 bool "Enable return-thunks"
2430 depends on RETPOLINE && CC_HAS_RETURN_THUNK
2433 Compile the kernel with the return-thunks compiler option to guard
2434 against kernel-to-user data leaks by avoiding return speculation.
2435 Requires a compiler with -mfunction-return=thunk-extern
2436 support for full protection. The kernel may run slower.
2438 config CPU_UNRET_ENTRY
2439 bool "Enable UNRET on kernel entry"
2440 depends on CPU_SUP_AMD && RETHUNK && X86_64
2443 Compile the kernel with support for the retbleed=unret mitigation.
2445 config CPU_IBPB_ENTRY
2446 bool "Enable IBPB on kernel entry"
2447 depends on CPU_SUP_AMD && X86_64
2450 Compile the kernel with support for the retbleed=ibpb mitigation.
2452 config CPU_IBRS_ENTRY
2453 bool "Enable IBRS on kernel entry"
2454 depends on CPU_SUP_INTEL && X86_64
2457 Compile the kernel with support for the spectre_v2=ibrs mitigation.
2458 This mitigates both spectre_v2 and retbleed at great cost to
2462 bool "Mitigate Straight-Line-Speculation"
2463 depends on CC_HAS_SLS && X86_64
2466 Compile the kernel with straight-line-speculation options to guard
2467 against straight line speculation. The kernel image might be slightly
2472 config ARCH_HAS_ADD_PAGES
2474 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2476 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2479 config USE_PERCPU_NUMA_NODE_ID
2483 menu "Power management and ACPI options"
2485 config ARCH_HIBERNATION_HEADER
2487 depends on HIBERNATION
2489 source "kernel/power/Kconfig"
2491 source "drivers/acpi/Kconfig"
2498 tristate "APM (Advanced Power Management) BIOS support"
2499 depends on X86_32 && PM_SLEEP
2501 APM is a BIOS specification for saving power using several different
2502 techniques. This is mostly useful for battery powered laptops with
2503 APM compliant BIOSes. If you say Y here, the system time will be
2504 reset after a RESUME operation, the /proc/apm device will provide
2505 battery status information, and user-space programs will receive
2506 notification of APM "events" (e.g. battery status change).
2508 If you select "Y" here, you can disable actual use of the APM
2509 BIOS by passing the "apm=off" option to the kernel at boot time.
2511 Note that the APM support is almost completely disabled for
2512 machines with more than one CPU.
2514 In order to use APM, you will need supporting software. For location
2515 and more information, read <file:Documentation/power/apm-acpi.rst>
2516 and the Battery Powered Linux mini-HOWTO, available from
2517 <http://www.tldp.org/docs.html#howto>.
2519 This driver does not spin down disk drives (see the hdparm(8)
2520 manpage ("man 8 hdparm") for that), and it doesn't turn off
2521 VESA-compliant "green" monitors.
2523 This driver does not support the TI 4000M TravelMate and the ACER
2524 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2525 desktop machines also don't have compliant BIOSes, and this driver
2526 may cause those machines to panic during the boot phase.
2528 Generally, if you don't have a battery in your machine, there isn't
2529 much point in using this driver and you should say N. If you get
2530 random kernel OOPSes or reboots that don't seem to be related to
2531 anything, try disabling/enabling this option (or disabling/enabling
2534 Some other things you should try when experiencing seemingly random,
2537 1) make sure that you have enough swap space and that it is
2539 2) pass the "no-hlt" option to the kernel
2540 3) switch on floating point emulation in the kernel and pass
2541 the "no387" option to the kernel
2542 4) pass the "floppy=nodma" option to the kernel
2543 5) pass the "mem=4M" option to the kernel (thereby disabling
2544 all but the first 4 MB of RAM)
2545 6) make sure that the CPU is not over clocked.
2546 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2547 8) disable the cache from your BIOS settings
2548 9) install a fan for the video card or exchange video RAM
2549 10) install a better fan for the CPU
2550 11) exchange RAM chips
2551 12) exchange the motherboard.
2553 To compile this driver as a module, choose M here: the
2554 module will be called apm.
2558 config APM_IGNORE_USER_SUSPEND
2559 bool "Ignore USER SUSPEND"
2561 This option will ignore USER SUSPEND requests. On machines with a
2562 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2563 series notebooks, it is necessary to say Y because of a BIOS bug.
2565 config APM_DO_ENABLE
2566 bool "Enable PM at boot time"
2568 Enable APM features at boot time. From page 36 of the APM BIOS
2569 specification: "When disabled, the APM BIOS does not automatically
2570 power manage devices, enter the Standby State, enter the Suspend
2571 State, or take power saving steps in response to CPU Idle calls."
2572 This driver will make CPU Idle calls when Linux is idle (unless this
2573 feature is turned off -- see "Do CPU IDLE calls", below). This
2574 should always save battery power, but more complicated APM features
2575 will be dependent on your BIOS implementation. You may need to turn
2576 this option off if your computer hangs at boot time when using APM
2577 support, or if it beeps continuously instead of suspending. Turn
2578 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2579 T400CDT. This is off by default since most machines do fine without
2584 bool "Make CPU Idle calls when idle"
2586 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2587 On some machines, this can activate improved power savings, such as
2588 a slowed CPU clock rate, when the machine is idle. These idle calls
2589 are made after the idle loop has run for some length of time (e.g.,
2590 333 mS). On some machines, this will cause a hang at boot time or
2591 whenever the CPU becomes idle. (On machines with more than one CPU,
2592 this option does nothing.)
2594 config APM_DISPLAY_BLANK
2595 bool "Enable console blanking using APM"
2597 Enable console blanking using the APM. Some laptops can use this to
2598 turn off the LCD backlight when the screen blanker of the Linux
2599 virtual console blanks the screen. Note that this is only used by
2600 the virtual console screen blanker, and won't turn off the backlight
2601 when using the X Window system. This also doesn't have anything to
2602 do with your VESA-compliant power-saving monitor. Further, this
2603 option doesn't work for all laptops -- it might not turn off your
2604 backlight at all, or it might print a lot of errors to the console,
2605 especially if you are using gpm.
2607 config APM_ALLOW_INTS
2608 bool "Allow interrupts during APM BIOS calls"
2610 Normally we disable external interrupts while we are making calls to
2611 the APM BIOS as a measure to lessen the effects of a badly behaving
2612 BIOS implementation. The BIOS should reenable interrupts if it
2613 needs to. Unfortunately, some BIOSes do not -- especially those in
2614 many of the newer IBM Thinkpads. If you experience hangs when you
2615 suspend, try setting this to Y. Otherwise, say N.
2619 source "drivers/cpufreq/Kconfig"
2621 source "drivers/cpuidle/Kconfig"
2623 source "drivers/idle/Kconfig"
2628 menu "Bus options (PCI etc.)"
2631 prompt "PCI access mode"
2632 depends on X86_32 && PCI
2635 On PCI systems, the BIOS can be used to detect the PCI devices and
2636 determine their configuration. However, some old PCI motherboards
2637 have BIOS bugs and may crash if this is done. Also, some embedded
2638 PCI-based systems don't have any BIOS at all. Linux can also try to
2639 detect the PCI hardware directly without using the BIOS.
2641 With this option, you can specify how Linux should detect the
2642 PCI devices. If you choose "BIOS", the BIOS will be used,
2643 if you choose "Direct", the BIOS won't be used, and if you
2644 choose "MMConfig", then PCI Express MMCONFIG will be used.
2645 If you choose "Any", the kernel will try MMCONFIG, then the
2646 direct access method and falls back to the BIOS if that doesn't
2647 work. If unsure, go with the default, which is "Any".
2652 config PCI_GOMMCONFIG
2669 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2671 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2674 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2677 bool "Support mmconfig PCI config space access" if X86_64
2679 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2680 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2684 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2688 depends on PCI && XEN
2690 config MMCONF_FAM10H
2692 depends on X86_64 && PCI_MMCONFIG && ACPI
2694 config PCI_CNB20LE_QUIRK
2695 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2698 Read the PCI windows out of the CNB20LE host bridge. This allows
2699 PCI hotplug to work on systems with the CNB20LE chipset which do
2702 There's no public spec for this chipset, and this functionality
2703 is known to be incomplete.
2705 You should say N unless you know you need this.
2708 bool "ISA bus support on modern systems" if EXPERT
2710 Expose ISA bus device drivers and options available for selection and
2711 configuration. Enable this option if your target machine has an ISA
2712 bus. ISA is an older system, displaced by PCI and newer bus
2713 architectures -- if your target machine is modern, it probably does
2714 not have an ISA bus.
2718 # x86_64 have no ISA slots, but can have ISA-style DMA.
2720 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2723 Enables ISA-style DMA support for devices requiring such controllers.
2731 Find out whether you have ISA slots on your motherboard. ISA is the
2732 name of a bus system, i.e. the way the CPU talks to the other stuff
2733 inside your box. Other bus systems are PCI, EISA, MicroChannel
2734 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2735 newer boards don't support it. If you have ISA, say Y, otherwise N.
2738 tristate "NatSemi SCx200 support"
2740 This provides basic support for National Semiconductor's
2741 (now AMD's) Geode processors. The driver probes for the
2742 PCI-IDs of several on-chip devices, so its a good dependency
2743 for other scx200_* drivers.
2745 If compiled as a module, the driver is named scx200.
2747 config SCx200HR_TIMER
2748 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2752 This driver provides a clocksource built upon the on-chip
2753 27MHz high-resolution timer. Its also a workaround for
2754 NSC Geode SC-1100's buggy TSC, which loses time when the
2755 processor goes idle (as is done by the scheduler). The
2756 other workaround is idle=poll boot option.
2759 bool "One Laptop Per Child support"
2767 Add support for detecting the unique features of the OLPC
2771 bool "OLPC XO-1 Power Management"
2772 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2774 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2777 bool "OLPC XO-1 Real Time Clock"
2778 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2780 Add support for the XO-1 real time clock, which can be used as a
2781 programmable wakeup source.
2784 bool "OLPC XO-1 SCI extras"
2785 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2789 Add support for SCI-based features of the OLPC XO-1 laptop:
2790 - EC-driven system wakeups
2794 - AC adapter status updates
2795 - Battery status updates
2797 config OLPC_XO15_SCI
2798 bool "OLPC XO-1.5 SCI extras"
2799 depends on OLPC && ACPI
2802 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2803 - EC-driven system wakeups
2804 - AC adapter status updates
2805 - Battery status updates
2808 bool "PCEngines ALIX System Support (LED setup)"
2811 This option enables system support for the PCEngines ALIX.
2812 At present this just sets up LEDs for GPIO control on
2813 ALIX2/3/6 boards. However, other system specific setup should
2816 Note: You must still enable the drivers for GPIO and LED support
2817 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2819 Note: You have to set alix.force=1 for boards with Award BIOS.
2822 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2825 This option enables system support for the Soekris Engineering net5501.
2828 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2832 This option enables system support for the Traverse Technologies GEOS.
2835 bool "Technologic Systems TS-5500 platform support"
2837 select CHECK_SIGNATURE
2841 This option enables system support for the Technologic Systems TS-5500.
2847 depends on CPU_SUP_AMD && PCI
2852 menu "Binary Emulations"
2854 config IA32_EMULATION
2855 bool "IA32 Emulation"
2857 select ARCH_WANT_OLD_COMPAT_IPC
2859 select COMPAT_OLD_SIGACTION
2861 Include code to run legacy 32-bit programs under a
2862 64-bit kernel. You should likely turn this on, unless you're
2863 100% sure that you don't have any 32-bit programs left.
2866 tristate "IA32 a.out support"
2867 depends on IA32_EMULATION
2870 Support old a.out binaries in the 32bit emulation.
2873 bool "x32 ABI for 64-bit mode"
2875 # llvm-objcopy does not convert x86_64 .note.gnu.property or
2876 # compressed debug sections to x86_x32 properly:
2877 # https://github.com/ClangBuiltLinux/linux/issues/514
2878 # https://github.com/ClangBuiltLinux/linux/issues/1141
2879 depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
2881 Include code to run binaries for the x32 native 32-bit ABI
2882 for 64-bit processors. An x32 process gets access to the
2883 full 64-bit register file and wide data path while leaving
2884 pointers at 32 bits for smaller memory footprint.
2886 You will need a recent binutils (2.22 or later) with
2887 elf32_x86_64 support enabled to compile a kernel with this
2892 depends on IA32_EMULATION || X86_32
2894 select OLD_SIGSUSPEND3
2898 depends on IA32_EMULATION || X86_X32
2901 config COMPAT_FOR_U64_ALIGNMENT
2904 config SYSVIPC_COMPAT
2912 config HAVE_ATOMIC_IOMAP
2916 source "arch/x86/kvm/Kconfig"
2918 source "arch/x86/Kconfig.assembler"