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_CPU_FINALIZE_INIT
72 select ARCH_HAS_DEBUG_VIRTUAL
73 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
74 select ARCH_HAS_DEVMEM_IS_ALLOWED
75 select ARCH_HAS_EARLY_DEBUG if KGDB
76 select ARCH_HAS_ELF_RANDOMIZE
77 select ARCH_HAS_FAST_MULTIPLIER
78 select ARCH_HAS_FILTER_PGPROT
79 select ARCH_HAS_FORTIFY_SOURCE
80 select ARCH_HAS_GCOV_PROFILE_ALL
81 select ARCH_HAS_KCOV if X86_64 && STACK_VALIDATION
82 select ARCH_HAS_MEM_ENCRYPT
83 select ARCH_HAS_MEMBARRIER_SYNC_CORE
84 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
85 select ARCH_HAS_PMEM_API if X86_64
86 select ARCH_HAS_PTE_DEVMAP if X86_64
87 select ARCH_HAS_PTE_SPECIAL
88 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
89 select ARCH_HAS_COPY_MC if X86_64
90 select ARCH_HAS_SET_MEMORY
91 select ARCH_HAS_SET_DIRECT_MAP
92 select ARCH_HAS_STRICT_KERNEL_RWX
93 select ARCH_HAS_STRICT_MODULE_RWX
94 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
95 select ARCH_HAS_SYSCALL_WRAPPER
96 select ARCH_HAS_UBSAN_SANITIZE_ALL
97 select ARCH_HAS_DEBUG_WX
98 select ARCH_HAS_ZONE_DMA_SET if EXPERT
99 select ARCH_HAVE_NMI_SAFE_CMPXCHG
100 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
101 select ARCH_MIGHT_HAVE_PC_PARPORT
102 select ARCH_MIGHT_HAVE_PC_SERIO
103 select ARCH_STACKWALK
104 select ARCH_SUPPORTS_ACPI
105 select ARCH_SUPPORTS_ATOMIC_RMW
106 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
107 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
108 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
109 select ARCH_SUPPORTS_LTO_CLANG
110 select ARCH_SUPPORTS_LTO_CLANG_THIN
111 select ARCH_USE_BUILTIN_BSWAP
112 select ARCH_USE_MEMTEST
113 select ARCH_USE_QUEUED_RWLOCKS
114 select ARCH_USE_QUEUED_SPINLOCKS
115 select ARCH_USE_SYM_ANNOTATIONS
116 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
117 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
118 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
119 select ARCH_WANTS_NO_INSTR
120 select ARCH_WANT_HUGE_PMD_SHARE
121 select ARCH_WANT_LD_ORPHAN_WARN
122 select ARCH_WANTS_THP_SWAP if X86_64
123 select ARCH_HAS_PARANOID_L1D_FLUSH
124 select BUILDTIME_TABLE_SORT
126 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
127 select CLOCKSOURCE_WATCHDOG
128 select DCACHE_WORD_ACCESS
129 select EDAC_ATOMIC_SCRUB
131 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
132 select GENERIC_CLOCKEVENTS_MIN_ADJUST
133 select GENERIC_CMOS_UPDATE
134 select GENERIC_CPU_AUTOPROBE
135 select GENERIC_CPU_VULNERABILITIES
136 select GENERIC_EARLY_IOREMAP
138 select GENERIC_FIND_FIRST_BIT
140 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
141 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
142 select GENERIC_IRQ_MIGRATION if SMP
143 select GENERIC_IRQ_PROBE
144 select GENERIC_IRQ_RESERVATION_MODE
145 select GENERIC_IRQ_SHOW
146 select GENERIC_PENDING_IRQ if SMP
147 select GENERIC_PTDUMP
148 select GENERIC_SMP_IDLE_THREAD
149 select GENERIC_TIME_VSYSCALL
150 select GENERIC_GETTIMEOFDAY
151 select GENERIC_VDSO_TIME_NS
152 select GUP_GET_PTE_LOW_HIGH if X86_PAE
153 select HARDIRQS_SW_RESEND
154 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
155 select HAVE_ACPI_APEI if ACPI
156 select HAVE_ACPI_APEI_NMI if ACPI
157 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
158 select HAVE_ARCH_AUDITSYSCALL
159 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
160 select HAVE_ARCH_JUMP_LABEL
161 select HAVE_ARCH_JUMP_LABEL_RELATIVE
162 select HAVE_ARCH_KASAN if X86_64
163 select HAVE_ARCH_KASAN_VMALLOC if X86_64
164 select HAVE_ARCH_KFENCE
165 select HAVE_ARCH_KGDB
166 select HAVE_ARCH_MMAP_RND_BITS if MMU
167 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
168 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
169 select HAVE_ARCH_PREL32_RELOCATIONS
170 select HAVE_ARCH_SECCOMP_FILTER
171 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
172 select HAVE_ARCH_STACKLEAK
173 select HAVE_ARCH_TRACEHOOK
174 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
175 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
176 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
177 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
178 select HAVE_ARCH_VMAP_STACK if X86_64
179 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
180 select HAVE_ARCH_WITHIN_STACK_FRAMES
181 select HAVE_ASM_MODVERSIONS
182 select HAVE_CMPXCHG_DOUBLE
183 select HAVE_CMPXCHG_LOCAL
184 select HAVE_CONTEXT_TRACKING if X86_64
185 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
186 select HAVE_C_RECORDMCOUNT
187 select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION
188 select HAVE_DEBUG_KMEMLEAK
189 select HAVE_DMA_CONTIGUOUS
190 select HAVE_DYNAMIC_FTRACE
191 select HAVE_DYNAMIC_FTRACE_WITH_REGS
192 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
193 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
195 select HAVE_EFFICIENT_UNALIGNED_ACCESS
197 select HAVE_EXIT_THREAD
199 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
200 select HAVE_FTRACE_MCOUNT_RECORD
201 select HAVE_FUNCTION_GRAPH_TRACER
202 select HAVE_FUNCTION_TRACER
203 select HAVE_GCC_PLUGINS
204 select HAVE_HW_BREAKPOINT
205 select HAVE_IOREMAP_PROT
206 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
207 select HAVE_IRQ_TIME_ACCOUNTING
208 select HAVE_KERNEL_BZIP2
209 select HAVE_KERNEL_GZIP
210 select HAVE_KERNEL_LZ4
211 select HAVE_KERNEL_LZMA
212 select HAVE_KERNEL_LZO
213 select HAVE_KERNEL_XZ
214 select HAVE_KERNEL_ZSTD
216 select HAVE_KPROBES_ON_FTRACE
217 select HAVE_FUNCTION_ERROR_INJECTION
218 select HAVE_KRETPROBES
220 select HAVE_LIVEPATCH if X86_64
221 select HAVE_MIXED_BREAKPOINTS_REGS
222 select HAVE_MOD_ARCH_SPECIFIC
226 select HAVE_OPTPROBES
227 select HAVE_PCSPKR_PLATFORM
228 select HAVE_PERF_EVENTS
229 select HAVE_PERF_EVENTS_NMI
230 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
232 select HAVE_PERF_REGS
233 select HAVE_PERF_USER_STACK_DUMP
234 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
235 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
236 select HAVE_REGS_AND_STACK_ACCESS_API
237 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
238 select HAVE_FUNCTION_ARG_ACCESS_API
239 select HAVE_SOFTIRQ_ON_OWN_STACK
240 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
241 select HAVE_STACK_VALIDATION if X86_64
242 select HAVE_STATIC_CALL
243 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
244 select HAVE_PREEMPT_DYNAMIC
246 select HAVE_SYSCALL_TRACEPOINTS
247 select HAVE_UNSTABLE_SCHED_CLOCK
248 select HAVE_USER_RETURN_NOTIFIER
249 select HAVE_GENERIC_VDSO
250 select HOTPLUG_SMT if SMP
251 select IRQ_FORCED_THREADING
252 select NEED_SG_DMA_LENGTH
253 select PCI_DOMAINS if PCI
254 select PCI_LOCKLESS_CONFIG if PCI
257 select RTC_MC146818_LIB
260 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
261 select SYSCTL_EXCEPTION_TRACE
262 select THREAD_INFO_IN_TASK
263 select TRACE_IRQFLAGS_SUPPORT
264 select TRACE_IRQFLAGS_NMI_SUPPORT
265 select USER_STACKTRACE_SUPPORT
267 select HAVE_ARCH_KCSAN if X86_64
268 select X86_FEATURE_NAMES if PROC_FS
269 select PROC_PID_ARCH_STATUS if PROC_FS
270 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
272 config INSTRUCTION_DECODER
274 depends on KPROBES || PERF_EVENTS || UPROBES
278 default "elf32-i386" if X86_32
279 default "elf64-x86-64" if X86_64
281 config LOCKDEP_SUPPORT
284 config STACKTRACE_SUPPORT
290 config ARCH_MMAP_RND_BITS_MIN
294 config ARCH_MMAP_RND_BITS_MAX
298 config ARCH_MMAP_RND_COMPAT_BITS_MIN
301 config ARCH_MMAP_RND_COMPAT_BITS_MAX
307 config GENERIC_ISA_DMA
309 depends on ISA_DMA_API
314 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
316 config GENERIC_BUG_RELATIVE_POINTERS
319 config ARCH_MAY_HAVE_PC_FDC
321 depends on ISA_DMA_API
323 config GENERIC_CALIBRATE_DELAY
326 config ARCH_HAS_CPU_RELAX
329 config ARCH_HAS_FILTER_PGPROT
332 config HAVE_SETUP_PER_CPU_AREA
335 config NEED_PER_CPU_EMBED_FIRST_CHUNK
338 config NEED_PER_CPU_PAGE_FIRST_CHUNK
341 config ARCH_HIBERNATION_POSSIBLE
346 default 1024 if X86_64
349 config ARCH_SUSPEND_POSSIBLE
352 config ARCH_WANT_GENERAL_HUGETLB
358 config KASAN_SHADOW_OFFSET
361 default 0xdffffc0000000000
363 config HAVE_INTEL_TXT
365 depends on INTEL_IOMMU && ACPI
369 depends on X86_32 && SMP
373 depends on X86_64 && SMP
375 config ARCH_SUPPORTS_UPROBES
378 config FIX_EARLYCON_MEM
381 config DYNAMIC_PHYSICAL_MASK
384 config PGTABLE_LEVELS
386 default 5 if X86_5LEVEL
391 config CC_HAS_SANE_STACKPROTECTOR
393 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
394 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
396 We have to make sure stack protector is unconditionally disabled if
397 the compiler produces broken code or if it does not let us control
398 the segment on 32-bit kernels.
400 menu "Processor type and features"
403 bool "Symmetric multi-processing support"
405 This enables support for systems with more than one CPU. If you have
406 a system with only one CPU, say N. If you have a system with more
409 If you say N here, the kernel will run on uni- and multiprocessor
410 machines, but will use only one CPU of a multiprocessor machine. If
411 you say Y here, the kernel will run on many, but not all,
412 uniprocessor machines. On a uniprocessor machine, the kernel
413 will run faster if you say N here.
415 Note that if you say Y here and choose architecture "586" or
416 "Pentium" under "Processor family", the kernel will not work on 486
417 architectures. Similarly, multiprocessor kernels for the "PPro"
418 architecture may not work on all Pentium based boards.
420 People using multiprocessor machines who say Y here should also say
421 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
422 Management" code will be disabled if you say Y here.
424 See also <file:Documentation/x86/i386/IO-APIC.rst>,
425 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
426 <http://www.tldp.org/docs.html#howto>.
428 If you don't know what to do here, say N.
430 config X86_FEATURE_NAMES
431 bool "Processor feature human-readable names" if EMBEDDED
434 This option compiles in a table of x86 feature bits and corresponding
435 names. This is required to support /proc/cpuinfo and a few kernel
436 messages. You can disable this to save space, at the expense of
437 making those few kernel messages show numeric feature bits instead.
442 bool "Support x2apic"
443 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
445 This enables x2apic support on CPUs that have this feature.
447 This allows 32-bit apic IDs (so it can support very large systems),
448 and accesses the local apic via MSRs not via mmio.
450 If you don't know what to do here, say N.
453 bool "Enable MPS table" if ACPI
455 depends on X86_LOCAL_APIC
457 For old smp systems that do not have proper acpi support. Newer systems
458 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
462 depends on X86_GOLDFISH
464 config X86_CPU_RESCTRL
465 bool "x86 CPU resource control support"
466 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
468 select PROC_CPU_RESCTRL if PROC_FS
470 Enable x86 CPU resource control support.
472 Provide support for the allocation and monitoring of system resources
475 Intel calls this Intel Resource Director Technology
476 (Intel(R) RDT). More information about RDT can be found in the
477 Intel x86 Architecture Software Developer Manual.
479 AMD calls this AMD Platform Quality of Service (AMD QoS).
480 More information about AMD QoS can be found in the AMD64 Technology
481 Platform Quality of Service Extensions manual.
487 bool "Support for big SMP systems with more than 8 CPUs"
490 This option is needed for the systems that have more than 8 CPUs.
492 config X86_EXTENDED_PLATFORM
493 bool "Support for extended (non-PC) x86 platforms"
496 If you disable this option then the kernel will only support
497 standard PC platforms. (which covers the vast majority of
500 If you enable this option then you'll be able to select support
501 for the following (non-PC) 32 bit x86 platforms:
502 Goldfish (Android emulator)
505 SGI 320/540 (Visual Workstation)
506 STA2X11-based (e.g. Northville)
507 Moorestown MID devices
509 If you have one of these systems, or if you want to build a
510 generic distribution kernel, say Y here - otherwise say N.
514 config X86_EXTENDED_PLATFORM
515 bool "Support for extended (non-PC) x86 platforms"
518 If you disable this option then the kernel will only support
519 standard PC platforms. (which covers the vast majority of
522 If you enable this option then you'll be able to select support
523 for the following (non-PC) 64 bit x86 platforms:
528 If you have one of these systems, or if you want to build a
529 generic distribution kernel, say Y here - otherwise say N.
531 # This is an alphabetically sorted list of 64 bit extended platforms
532 # Please maintain the alphabetic order if and when there are additions
534 bool "Numascale NumaChip"
536 depends on X86_EXTENDED_PLATFORM
539 depends on X86_X2APIC
540 depends on PCI_MMCONFIG
542 Adds support for Numascale NumaChip large-SMP systems. Needed to
543 enable more than ~168 cores.
544 If you don't have one of these, you should say N here.
548 select HYPERVISOR_GUEST
550 depends on X86_64 && PCI
551 depends on X86_EXTENDED_PLATFORM
554 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
555 supposed to run on these EM64T-based machines. Only choose this option
556 if you have one of these machines.
559 bool "SGI Ultraviolet"
561 depends on X86_EXTENDED_PLATFORM
564 depends on KEXEC_CORE
565 depends on X86_X2APIC
568 This option is needed in order to support SGI Ultraviolet systems.
569 If you don't have one of these, you should say N here.
571 # Following is an alphabetically sorted list of 32 bit extended platforms
572 # Please maintain the alphabetic order if and when there are additions
575 bool "Goldfish (Virtual Platform)"
576 depends on X86_EXTENDED_PLATFORM
578 Enable support for the Goldfish virtual platform used primarily
579 for Android development. Unless you are building for the Android
580 Goldfish emulator say N here.
583 bool "CE4100 TV platform"
585 depends on PCI_GODIRECT
586 depends on X86_IO_APIC
588 depends on X86_EXTENDED_PLATFORM
589 select X86_REBOOTFIXUPS
591 select OF_EARLY_FLATTREE
593 Select for the Intel CE media processor (CE4100) SOC.
594 This option compiles in support for the CE4100 SOC for settop
595 boxes and media devices.
598 bool "Intel MID platform support"
599 depends on X86_EXTENDED_PLATFORM
600 depends on X86_PLATFORM_DEVICES
602 depends on X86_64 || (PCI_GOANY && X86_32)
603 depends on X86_IO_APIC
608 select MFD_INTEL_MSIC
610 Select to build a kernel capable of supporting Intel MID (Mobile
611 Internet Device) platform systems which do not have the PCI legacy
612 interfaces. If you are building for a PC class system say N here.
614 Intel MID platforms are based on an Intel processor and chipset which
615 consume less power than most of the x86 derivatives.
617 config X86_INTEL_QUARK
618 bool "Intel Quark platform support"
620 depends on X86_EXTENDED_PLATFORM
621 depends on X86_PLATFORM_DEVICES
625 depends on X86_IO_APIC
630 Select to include support for Quark X1000 SoC.
631 Say Y here if you have a Quark based system such as the Arduino
632 compatible Intel Galileo.
634 config X86_INTEL_LPSS
635 bool "Intel Low Power Subsystem Support"
636 depends on X86 && ACPI && PCI
641 Select to build support for Intel Low Power Subsystem such as
642 found on Intel Lynxpoint PCH. Selecting this option enables
643 things like clock tree (common clock framework) and pincontrol
644 which are needed by the LPSS peripheral drivers.
646 config X86_AMD_PLATFORM_DEVICE
647 bool "AMD ACPI2Platform devices support"
652 Select to interpret AMD specific ACPI device to platform device
653 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
654 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
655 implemented under PINCTRL subsystem.
658 tristate "Intel SoC IOSF Sideband support for SoC platforms"
661 This option enables sideband register access support for Intel SoC
662 platforms. On these platforms the IOSF sideband is used in lieu of
663 MSR's for some register accesses, mostly but not limited to thermal
664 and power. Drivers may query the availability of this device to
665 determine if they need the sideband in order to work on these
666 platforms. The sideband is available on the following SoC products.
667 This list is not meant to be exclusive.
672 You should say Y if you are running a kernel on one of these SoC's.
674 config IOSF_MBI_DEBUG
675 bool "Enable IOSF sideband access through debugfs"
676 depends on IOSF_MBI && DEBUG_FS
678 Select this option to expose the IOSF sideband access registers (MCR,
679 MDR, MCRX) through debugfs to write and read register information from
680 different units on the SoC. This is most useful for obtaining device
681 state information for debug and analysis. As this is a general access
682 mechanism, users of this option would have specific knowledge of the
683 device they want to access.
685 If you don't require the option or are in doubt, say N.
688 bool "RDC R-321x SoC"
690 depends on X86_EXTENDED_PLATFORM
692 select X86_REBOOTFIXUPS
694 This option is needed for RDC R-321x system-on-chip, also known
696 If you don't have one of these chips, you should say N here.
698 config X86_32_NON_STANDARD
699 bool "Support non-standard 32-bit SMP architectures"
700 depends on X86_32 && SMP
701 depends on X86_EXTENDED_PLATFORM
703 This option compiles in the bigsmp and STA2X11 default
704 subarchitectures. It is intended for a generic binary
705 kernel. If you select them all, kernel will probe it one by
706 one and will fallback to default.
708 # Alphabetically sorted list of Non standard 32 bit platforms
710 config X86_SUPPORTS_MEMORY_FAILURE
712 # MCE code calls memory_failure():
714 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
715 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
716 depends on X86_64 || !SPARSEMEM
717 select ARCH_SUPPORTS_MEMORY_FAILURE
720 bool "STA2X11 Companion Chip Support"
721 depends on X86_32_NON_STANDARD && PCI
726 This adds support for boards based on the STA2X11 IO-Hub,
727 a.k.a. "ConneXt". The chip is used in place of the standard
728 PC chipset, so all "standard" peripherals are missing. If this
729 option is selected the kernel will still be able to boot on
730 standard PC machines.
733 tristate "Eurobraille/Iris poweroff module"
736 The Iris machines from EuroBraille do not have APM or ACPI support
737 to shut themselves down properly. A special I/O sequence is
738 needed to do so, which is what this module does at
741 This is only for Iris machines from EuroBraille.
745 config SCHED_OMIT_FRAME_POINTER
747 prompt "Single-depth WCHAN output"
750 Calculate simpler /proc/<PID>/wchan values. If this option
751 is disabled then wchan values will recurse back to the
752 caller function. This provides more accurate wchan values,
753 at the expense of slightly more scheduling overhead.
755 If in doubt, say "Y".
757 menuconfig HYPERVISOR_GUEST
758 bool "Linux guest support"
760 Say Y here to enable options for running Linux under various hyper-
761 visors. This option enables basic hypervisor detection and platform
764 If you say N, all options in this submenu will be skipped and
765 disabled, and Linux guest support won't be built in.
770 bool "Enable paravirtualization code"
771 depends on HAVE_STATIC_CALL
773 This changes the kernel so it can modify itself when it is run
774 under a hypervisor, potentially improving performance significantly
775 over full virtualization. However, when run without a hypervisor
776 the kernel is theoretically slower and slightly larger.
781 config PARAVIRT_DEBUG
782 bool "paravirt-ops debugging"
783 depends on PARAVIRT && DEBUG_KERNEL
785 Enable to debug paravirt_ops internals. Specifically, BUG if
786 a paravirt_op is missing when it is called.
788 config PARAVIRT_SPINLOCKS
789 bool "Paravirtualization layer for spinlocks"
790 depends on PARAVIRT && SMP
792 Paravirtualized spinlocks allow a pvops backend to replace the
793 spinlock implementation with something virtualization-friendly
794 (for example, block the virtual CPU rather than spinning).
796 It has a minimal impact on native kernels and gives a nice performance
797 benefit on paravirtualized KVM / Xen kernels.
799 If you are unsure how to answer this question, answer Y.
801 config X86_HV_CALLBACK_VECTOR
804 source "arch/x86/xen/Kconfig"
807 bool "KVM Guest support (including kvmclock)"
809 select PARAVIRT_CLOCK
810 select ARCH_CPUIDLE_HALTPOLL
811 select X86_HV_CALLBACK_VECTOR
814 This option enables various optimizations for running under the KVM
815 hypervisor. It includes a paravirtualized clock, so that instead
816 of relying on a PIT (or probably other) emulation by the
817 underlying device model, the host provides the guest with
818 timing infrastructure such as time of day, and system time
820 config ARCH_CPUIDLE_HALTPOLL
822 prompt "Disable host haltpoll when loading haltpoll driver"
824 If virtualized under KVM, disable host haltpoll.
827 bool "Support for running PVH guests"
829 This option enables the PVH entry point for guest virtual machines
830 as specified in the x86/HVM direct boot ABI.
832 config PARAVIRT_TIME_ACCOUNTING
833 bool "Paravirtual steal time accounting"
836 Select this option to enable fine granularity task steal time
837 accounting. Time spent executing other tasks in parallel with
838 the current vCPU is discounted from the vCPU power. To account for
839 that, there can be a small performance impact.
841 If in doubt, say N here.
843 config PARAVIRT_CLOCK
846 config JAILHOUSE_GUEST
847 bool "Jailhouse non-root cell support"
848 depends on X86_64 && PCI
851 This option allows to run Linux as guest in a Jailhouse non-root
852 cell. You can leave this option disabled if you only want to start
853 Jailhouse and run Linux afterwards in the root cell.
856 bool "ACRN Guest support"
858 select X86_HV_CALLBACK_VECTOR
860 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
861 a flexible, lightweight reference open-source hypervisor, built with
862 real-time and safety-criticality in mind. It is built for embedded
863 IOT with small footprint and real-time features. More details can be
864 found in https://projectacrn.org/.
866 endif #HYPERVISOR_GUEST
868 source "arch/x86/Kconfig.cpu"
872 prompt "HPET Timer Support" if X86_32
874 Use the IA-PC HPET (High Precision Event Timer) to manage
875 time in preference to the PIT and RTC, if a HPET is
877 HPET is the next generation timer replacing legacy 8254s.
878 The HPET provides a stable time base on SMP
879 systems, unlike the TSC, but it is more expensive to access,
880 as it is off-chip. The interface used is documented
881 in the HPET spec, revision 1.
883 You can safely choose Y here. However, HPET will only be
884 activated if the platform and the BIOS support this feature.
885 Otherwise the 8254 will be used for timing services.
887 Choose N to continue using the legacy 8254 timer.
889 config HPET_EMULATE_RTC
891 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
893 # Mark as expert because too many people got it wrong.
894 # The code disables itself when not needed.
897 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
898 bool "Enable DMI scanning" if EXPERT
900 Enabled scanning of DMI to identify machine quirks. Say Y
901 here unless you have verified that your setup is not
902 affected by entries in the DMI blacklist. Required by PNP
906 bool "Old AMD GART IOMMU support"
910 depends on X86_64 && PCI && AMD_NB
912 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
913 GART based hardware IOMMUs.
915 The GART supports full DMA access for devices with 32-bit access
916 limitations, on systems with more than 3 GB. This is usually needed
917 for USB, sound, many IDE/SATA chipsets and some other devices.
919 Newer systems typically have a modern AMD IOMMU, supported via
920 the CONFIG_AMD_IOMMU=y config option.
922 In normal configurations this driver is only active when needed:
923 there's more than 3 GB of memory and the system contains a
924 32-bit limited device.
929 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
930 depends on X86_64 && SMP && DEBUG_KERNEL
931 select CPUMASK_OFFSTACK
933 Enable maximum number of CPUS and NUMA Nodes for this architecture.
937 # The maximum number of CPUs supported:
939 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
940 # and which can be configured interactively in the
941 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
943 # The ranges are different on 32-bit and 64-bit kernels, depending on
944 # hardware capabilities and scalability features of the kernel.
946 # ( If MAXSMP is enabled we just use the highest possible value and disable
947 # interactive configuration. )
950 config NR_CPUS_RANGE_BEGIN
952 default NR_CPUS_RANGE_END if MAXSMP
956 config NR_CPUS_RANGE_END
959 default 64 if SMP && X86_BIGSMP
960 default 8 if SMP && !X86_BIGSMP
963 config NR_CPUS_RANGE_END
966 default 8192 if SMP && CPUMASK_OFFSTACK
967 default 512 if SMP && !CPUMASK_OFFSTACK
970 config NR_CPUS_DEFAULT
973 default 32 if X86_BIGSMP
977 config NR_CPUS_DEFAULT
980 default 8192 if MAXSMP
985 int "Maximum number of CPUs" if SMP && !MAXSMP
986 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
987 default NR_CPUS_DEFAULT
989 This allows you to specify the maximum number of CPUs which this
990 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
991 supported value is 8192, otherwise the maximum value is 512. The
992 minimum value which makes sense is 2.
994 This is purely to save memory: each supported CPU adds about 8KB
1002 prompt "Multi-core scheduler support"
1005 Multi-core scheduler support improves the CPU scheduler's decision
1006 making when dealing with multi-core CPU chips at a cost of slightly
1007 increased overhead in some places. If unsure say N here.
1009 config SCHED_MC_PRIO
1010 bool "CPU core priorities scheduler support"
1011 depends on SCHED_MC && CPU_SUP_INTEL
1012 select X86_INTEL_PSTATE
1016 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1017 core ordering determined at manufacturing time, which allows
1018 certain cores to reach higher turbo frequencies (when running
1019 single threaded workloads) than others.
1021 Enabling this kernel feature teaches the scheduler about
1022 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1023 scheduler's CPU selection logic accordingly, so that higher
1024 overall system performance can be achieved.
1026 This feature will have no effect on CPUs without this feature.
1028 If unsure say Y here.
1032 depends on !SMP && X86_LOCAL_APIC
1035 bool "Local APIC support on uniprocessors" if !PCI_MSI
1037 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1039 A local APIC (Advanced Programmable Interrupt Controller) is an
1040 integrated interrupt controller in the CPU. If you have a single-CPU
1041 system which has a processor with a local APIC, you can say Y here to
1042 enable and use it. If you say Y here even though your machine doesn't
1043 have a local APIC, then the kernel will still run with no slowdown at
1044 all. The local APIC supports CPU-generated self-interrupts (timer,
1045 performance counters), and the NMI watchdog which detects hard
1048 config X86_UP_IOAPIC
1049 bool "IO-APIC support on uniprocessors"
1050 depends on X86_UP_APIC
1052 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1053 SMP-capable replacement for PC-style interrupt controllers. Most
1054 SMP systems and many recent uniprocessor systems have one.
1056 If you have a single-CPU system with an IO-APIC, you can say Y here
1057 to use it. If you say Y here even though your machine doesn't have
1058 an IO-APIC, then the kernel will still run with no slowdown at all.
1060 config X86_LOCAL_APIC
1062 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1063 select IRQ_DOMAIN_HIERARCHY
1064 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1068 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1070 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1071 bool "Reroute for broken boot IRQs"
1072 depends on X86_IO_APIC
1074 This option enables a workaround that fixes a source of
1075 spurious interrupts. This is recommended when threaded
1076 interrupt handling is used on systems where the generation of
1077 superfluous "boot interrupts" cannot be disabled.
1079 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1080 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1081 kernel does during interrupt handling). On chipsets where this
1082 boot IRQ generation cannot be disabled, this workaround keeps
1083 the original IRQ line masked so that only the equivalent "boot
1084 IRQ" is delivered to the CPUs. The workaround also tells the
1085 kernel to set up the IRQ handler on the boot IRQ line. In this
1086 way only one interrupt is delivered to the kernel. Otherwise
1087 the spurious second interrupt may cause the kernel to bring
1088 down (vital) interrupt lines.
1090 Only affects "broken" chipsets. Interrupt sharing may be
1091 increased on these systems.
1094 bool "Machine Check / overheating reporting"
1095 select GENERIC_ALLOCATOR
1098 Machine Check support allows the processor to notify the
1099 kernel if it detects a problem (e.g. overheating, data corruption).
1100 The action the kernel takes depends on the severity of the problem,
1101 ranging from warning messages to halting the machine.
1103 config X86_MCELOG_LEGACY
1104 bool "Support for deprecated /dev/mcelog character device"
1107 Enable support for /dev/mcelog which is needed by the old mcelog
1108 userspace logging daemon. Consider switching to the new generation
1111 config X86_MCE_INTEL
1113 prompt "Intel MCE features"
1114 depends on X86_MCE && X86_LOCAL_APIC
1116 Additional support for intel specific MCE features such as
1117 the thermal monitor.
1121 prompt "AMD MCE features"
1122 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1124 Additional support for AMD specific MCE features such as
1125 the DRAM Error Threshold.
1127 config X86_ANCIENT_MCE
1128 bool "Support for old Pentium 5 / WinChip machine checks"
1129 depends on X86_32 && X86_MCE
1131 Include support for machine check handling on old Pentium 5 or WinChip
1132 systems. These typically need to be enabled explicitly on the command
1135 config X86_MCE_THRESHOLD
1136 depends on X86_MCE_AMD || X86_MCE_INTEL
1139 config X86_MCE_INJECT
1140 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1141 tristate "Machine check injector support"
1143 Provide support for injecting machine checks for testing purposes.
1144 If you don't know what a machine check is and you don't do kernel
1145 QA it is safe to say n.
1147 source "arch/x86/events/Kconfig"
1149 config X86_LEGACY_VM86
1150 bool "Legacy VM86 support"
1153 This option allows user programs to put the CPU into V8086
1154 mode, which is an 80286-era approximation of 16-bit real mode.
1156 Some very old versions of X and/or vbetool require this option
1157 for user mode setting. Similarly, DOSEMU will use it if
1158 available to accelerate real mode DOS programs. However, any
1159 recent version of DOSEMU, X, or vbetool should be fully
1160 functional even without kernel VM86 support, as they will all
1161 fall back to software emulation. Nevertheless, if you are using
1162 a 16-bit DOS program where 16-bit performance matters, vm86
1163 mode might be faster than emulation and you might want to
1166 Note that any app that works on a 64-bit kernel is unlikely to
1167 need this option, as 64-bit kernels don't, and can't, support
1168 V8086 mode. This option is also unrelated to 16-bit protected
1169 mode and is not needed to run most 16-bit programs under Wine.
1171 Enabling this option increases the complexity of the kernel
1172 and slows down exception handling a tiny bit.
1174 If unsure, say N here.
1178 default X86_LEGACY_VM86
1181 bool "Enable support for 16-bit segments" if EXPERT
1183 depends on MODIFY_LDT_SYSCALL
1185 This option is required by programs like Wine to run 16-bit
1186 protected mode legacy code on x86 processors. Disabling
1187 this option saves about 300 bytes on i386, or around 6K text
1188 plus 16K runtime memory on x86-64,
1192 depends on X86_16BIT && X86_32
1196 depends on X86_16BIT && X86_64
1198 config X86_VSYSCALL_EMULATION
1199 bool "Enable vsyscall emulation" if EXPERT
1203 This enables emulation of the legacy vsyscall page. Disabling
1204 it is roughly equivalent to booting with vsyscall=none, except
1205 that it will also disable the helpful warning if a program
1206 tries to use a vsyscall. With this option set to N, offending
1207 programs will just segfault, citing addresses of the form
1210 This option is required by many programs built before 2013, and
1211 care should be used even with newer programs if set to N.
1213 Disabling this option saves about 7K of kernel size and
1214 possibly 4K of additional runtime pagetable memory.
1216 config X86_IOPL_IOPERM
1217 bool "IOPERM and IOPL Emulation"
1220 This enables the ioperm() and iopl() syscalls which are necessary
1221 for legacy applications.
1223 Legacy IOPL support is an overbroad mechanism which allows user
1224 space aside of accessing all 65536 I/O ports also to disable
1225 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1226 capabilities and permission from potentially active security
1229 The emulation restricts the functionality of the syscall to
1230 only allowing the full range I/O port access, but prevents the
1231 ability to disable interrupts from user space which would be
1232 granted if the hardware IOPL mechanism would be used.
1235 tristate "Toshiba Laptop support"
1238 This adds a driver to safely access the System Management Mode of
1239 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1240 not work on models with a Phoenix BIOS. The System Management Mode
1241 is used to set the BIOS and power saving options on Toshiba portables.
1243 For information on utilities to make use of this driver see the
1244 Toshiba Linux utilities web site at:
1245 <http://www.buzzard.org.uk/toshiba/>.
1247 Say Y if you intend to run this kernel on a Toshiba portable.
1251 tristate "Dell i8k legacy laptop support"
1254 select SENSORS_DELL_SMM
1256 This option enables legacy /proc/i8k userspace interface in hwmon
1257 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1258 temperature and allows controlling fan speeds of Dell laptops via
1259 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1260 it reports also power and hotkey status. For fan speed control is
1261 needed userspace package i8kutils.
1263 Say Y if you intend to run this kernel on old Dell laptops or want to
1264 use userspace package i8kutils.
1267 config X86_REBOOTFIXUPS
1268 bool "Enable X86 board specific fixups for reboot"
1271 This enables chipset and/or board specific fixups to be done
1272 in order to get reboot to work correctly. This is only needed on
1273 some combinations of hardware and BIOS. The symptom, for which
1274 this config is intended, is when reboot ends with a stalled/hung
1277 Currently, the only fixup is for the Geode machines using
1278 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1280 Say Y if you want to enable the fixup. Currently, it's safe to
1281 enable this option even if you don't need it.
1285 bool "CPU microcode loading support"
1287 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1289 If you say Y here, you will be able to update the microcode on
1290 Intel and AMD processors. The Intel support is for the IA32 family,
1291 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1292 AMD support is for families 0x10 and later. You will obviously need
1293 the actual microcode binary data itself which is not shipped with
1296 The preferred method to load microcode from a detached initrd is described
1297 in Documentation/x86/microcode.rst. For that you need to enable
1298 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1299 initrd for microcode blobs.
1301 In addition, you can build the microcode into the kernel. For that you
1302 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1305 config MICROCODE_INTEL
1306 bool "Intel microcode loading support"
1307 depends on CPU_SUP_INTEL && MICROCODE
1310 This options enables microcode patch loading support for Intel
1313 For the current Intel microcode data package go to
1314 <https://downloadcenter.intel.com> and search for
1315 'Linux Processor Microcode Data File'.
1317 config MICROCODE_AMD
1318 bool "AMD microcode loading support"
1319 depends on CPU_SUP_AMD && MICROCODE
1321 If you select this option, microcode patch loading support for AMD
1322 processors will be enabled.
1324 config MICROCODE_LATE_LOADING
1325 bool "Late microcode loading (DANGEROUS)"
1327 depends on MICROCODE
1329 Loading microcode late, when the system is up and executing instructions
1330 is a tricky business and should be avoided if possible. Just the sequence
1331 of synchronizing all cores and SMT threads is one fragile dance which does
1332 not guarantee that cores might not softlock after the loading. Therefore,
1333 use this at your own risk. Late loading taints the kernel too.
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
1931 This kernel feature allows a bzImage to be loaded directly
1932 by EFI firmware without the use of a bootloader.
1934 See Documentation/admin-guide/efi-stub.rst for more information.
1937 bool "EFI mixed-mode support"
1938 depends on EFI_STUB && X86_64
1940 Enabling this feature allows a 64-bit kernel to be booted
1941 on a 32-bit firmware, provided that your CPU supports 64-bit
1944 Note that it is not possible to boot a mixed-mode enabled
1945 kernel via the EFI boot stub - a bootloader that supports
1946 the EFI handover protocol must be used.
1950 source "kernel/Kconfig.hz"
1953 bool "kexec system call"
1956 kexec is a system call that implements the ability to shutdown your
1957 current kernel, and to start another kernel. It is like a reboot
1958 but it is independent of the system firmware. And like a reboot
1959 you can start any kernel with it, not just Linux.
1961 The name comes from the similarity to the exec system call.
1963 It is an ongoing process to be certain the hardware in a machine
1964 is properly shutdown, so do not be surprised if this code does not
1965 initially work for you. As of this writing the exact hardware
1966 interface is strongly in flux, so no good recommendation can be
1970 bool "kexec file based system call"
1975 depends on CRYPTO_SHA256=y
1977 This is new version of kexec system call. This system call is
1978 file based and takes file descriptors as system call argument
1979 for kernel and initramfs as opposed to list of segments as
1980 accepted by previous system call.
1982 config ARCH_HAS_KEXEC_PURGATORY
1986 bool "Verify kernel signature during kexec_file_load() syscall"
1987 depends on KEXEC_FILE
1990 This option makes the kexec_file_load() syscall check for a valid
1991 signature of the kernel image. The image can still be loaded without
1992 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
1993 there's a signature that we can check, then it must be valid.
1995 In addition to this option, you need to enable signature
1996 verification for the corresponding kernel image type being
1997 loaded in order for this to work.
1999 config KEXEC_SIG_FORCE
2000 bool "Require a valid signature in kexec_file_load() syscall"
2001 depends on KEXEC_SIG
2003 This option makes kernel signature verification mandatory for
2004 the kexec_file_load() syscall.
2006 config KEXEC_BZIMAGE_VERIFY_SIG
2007 bool "Enable bzImage signature verification support"
2008 depends on KEXEC_SIG
2009 depends on SIGNED_PE_FILE_VERIFICATION
2010 select SYSTEM_TRUSTED_KEYRING
2012 Enable bzImage signature verification support.
2015 bool "kernel crash dumps"
2016 depends on X86_64 || (X86_32 && HIGHMEM)
2018 Generate crash dump after being started by kexec.
2019 This should be normally only set in special crash dump kernels
2020 which are loaded in the main kernel with kexec-tools into
2021 a specially reserved region and then later executed after
2022 a crash by kdump/kexec. The crash dump kernel must be compiled
2023 to a memory address not used by the main kernel or BIOS using
2024 PHYSICAL_START, or it must be built as a relocatable image
2025 (CONFIG_RELOCATABLE=y).
2026 For more details see Documentation/admin-guide/kdump/kdump.rst
2030 depends on KEXEC && HIBERNATION
2032 Jump between original kernel and kexeced kernel and invoke
2033 code in physical address mode via KEXEC
2035 config PHYSICAL_START
2036 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2039 This gives the physical address where the kernel is loaded.
2041 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2042 bzImage will decompress itself to above physical address and
2043 run from there. Otherwise, bzImage will run from the address where
2044 it has been loaded by the boot loader and will ignore above physical
2047 In normal kdump cases one does not have to set/change this option
2048 as now bzImage can be compiled as a completely relocatable image
2049 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2050 address. This option is mainly useful for the folks who don't want
2051 to use a bzImage for capturing the crash dump and want to use a
2052 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2053 to be specifically compiled to run from a specific memory area
2054 (normally a reserved region) and this option comes handy.
2056 So if you are using bzImage for capturing the crash dump,
2057 leave the value here unchanged to 0x1000000 and set
2058 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2059 for capturing the crash dump change this value to start of
2060 the reserved region. In other words, it can be set based on
2061 the "X" value as specified in the "crashkernel=YM@XM"
2062 command line boot parameter passed to the panic-ed
2063 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2064 for more details about crash dumps.
2066 Usage of bzImage for capturing the crash dump is recommended as
2067 one does not have to build two kernels. Same kernel can be used
2068 as production kernel and capture kernel. Above option should have
2069 gone away after relocatable bzImage support is introduced. But it
2070 is present because there are users out there who continue to use
2071 vmlinux for dump capture. This option should go away down the
2074 Don't change this unless you know what you are doing.
2077 bool "Build a relocatable kernel"
2080 This builds a kernel image that retains relocation information
2081 so it can be loaded someplace besides the default 1MB.
2082 The relocations tend to make the kernel binary about 10% larger,
2083 but are discarded at runtime.
2085 One use is for the kexec on panic case where the recovery kernel
2086 must live at a different physical address than the primary
2089 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2090 it has been loaded at and the compile time physical address
2091 (CONFIG_PHYSICAL_START) is used as the minimum location.
2093 config RANDOMIZE_BASE
2094 bool "Randomize the address of the kernel image (KASLR)"
2095 depends on RELOCATABLE
2098 In support of Kernel Address Space Layout Randomization (KASLR),
2099 this randomizes the physical address at which the kernel image
2100 is decompressed and the virtual address where the kernel
2101 image is mapped, as a security feature that deters exploit
2102 attempts relying on knowledge of the location of kernel
2105 On 64-bit, the kernel physical and virtual addresses are
2106 randomized separately. The physical address will be anywhere
2107 between 16MB and the top of physical memory (up to 64TB). The
2108 virtual address will be randomized from 16MB up to 1GB (9 bits
2109 of entropy). Note that this also reduces the memory space
2110 available to kernel modules from 1.5GB to 1GB.
2112 On 32-bit, the kernel physical and virtual addresses are
2113 randomized together. They will be randomized from 16MB up to
2114 512MB (8 bits of entropy).
2116 Entropy is generated using the RDRAND instruction if it is
2117 supported. If RDTSC is supported, its value is mixed into
2118 the entropy pool as well. If neither RDRAND nor RDTSC are
2119 supported, then entropy is read from the i8254 timer. The
2120 usable entropy is limited by the kernel being built using
2121 2GB addressing, and that PHYSICAL_ALIGN must be at a
2122 minimum of 2MB. As a result, only 10 bits of entropy are
2123 theoretically possible, but the implementations are further
2124 limited due to memory layouts.
2128 # Relocation on x86 needs some additional build support
2129 config X86_NEED_RELOCS
2131 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2133 config PHYSICAL_ALIGN
2134 hex "Alignment value to which kernel should be aligned"
2136 range 0x2000 0x1000000 if X86_32
2137 range 0x200000 0x1000000 if X86_64
2139 This value puts the alignment restrictions on physical address
2140 where kernel is loaded and run from. Kernel is compiled for an
2141 address which meets above alignment restriction.
2143 If bootloader loads the kernel at a non-aligned address and
2144 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2145 address aligned to above value and run from there.
2147 If bootloader loads the kernel at a non-aligned address and
2148 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2149 load address and decompress itself to the address it has been
2150 compiled for and run from there. The address for which kernel is
2151 compiled already meets above alignment restrictions. Hence the
2152 end result is that kernel runs from a physical address meeting
2153 above alignment restrictions.
2155 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2156 this value must be a multiple of 0x200000.
2158 Don't change this unless you know what you are doing.
2160 config DYNAMIC_MEMORY_LAYOUT
2163 This option makes base addresses of vmalloc and vmemmap as well as
2164 __PAGE_OFFSET movable during boot.
2166 config RANDOMIZE_MEMORY
2167 bool "Randomize the kernel memory sections"
2169 depends on RANDOMIZE_BASE
2170 select DYNAMIC_MEMORY_LAYOUT
2171 default RANDOMIZE_BASE
2173 Randomizes the base virtual address of kernel memory sections
2174 (physical memory mapping, vmalloc & vmemmap). This security feature
2175 makes exploits relying on predictable memory locations less reliable.
2177 The order of allocations remains unchanged. Entropy is generated in
2178 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2179 configuration have in average 30,000 different possible virtual
2180 addresses for each memory section.
2184 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2185 hex "Physical memory mapping padding" if EXPERT
2186 depends on RANDOMIZE_MEMORY
2187 default "0xa" if MEMORY_HOTPLUG
2189 range 0x1 0x40 if MEMORY_HOTPLUG
2192 Define the padding in terabytes added to the existing physical
2193 memory size during kernel memory randomization. It is useful
2194 for memory hotplug support but reduces the entropy available for
2195 address randomization.
2197 If unsure, leave at the default value.
2203 config BOOTPARAM_HOTPLUG_CPU0
2204 bool "Set default setting of cpu0_hotpluggable"
2205 depends on HOTPLUG_CPU
2207 Set whether default state of cpu0_hotpluggable is on or off.
2209 Say Y here to enable CPU0 hotplug by default. If this switch
2210 is turned on, there is no need to give cpu0_hotplug kernel
2211 parameter and the CPU0 hotplug feature is enabled by default.
2213 Please note: there are two known CPU0 dependencies if you want
2214 to enable the CPU0 hotplug feature either by this switch or by
2215 cpu0_hotplug kernel parameter.
2217 First, resume from hibernate or suspend always starts from CPU0.
2218 So hibernate and suspend are prevented if CPU0 is offline.
2220 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2221 offline if any interrupt can not migrate out of CPU0. There may
2222 be other CPU0 dependencies.
2224 Please make sure the dependencies are under your control before
2225 you enable this feature.
2227 Say N if you don't want to enable CPU0 hotplug feature by default.
2228 You still can enable the CPU0 hotplug feature at boot by kernel
2229 parameter cpu0_hotplug.
2231 config DEBUG_HOTPLUG_CPU0
2233 prompt "Debug CPU0 hotplug"
2234 depends on HOTPLUG_CPU
2236 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2237 soon as possible and boots up userspace with CPU0 offlined. User
2238 can online CPU0 back after boot time.
2240 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2241 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2242 compilation or giving cpu0_hotplug kernel parameter at boot.
2248 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2249 depends on COMPAT_32
2251 Certain buggy versions of glibc will crash if they are
2252 presented with a 32-bit vDSO that is not mapped at the address
2253 indicated in its segment table.
2255 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2256 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2257 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2258 the only released version with the bug, but OpenSUSE 9
2259 contains a buggy "glibc 2.3.2".
2261 The symptom of the bug is that everything crashes on startup, saying:
2262 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2264 Saying Y here changes the default value of the vdso32 boot
2265 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2266 This works around the glibc bug but hurts performance.
2268 If unsure, say N: if you are compiling your own kernel, you
2269 are unlikely to be using a buggy version of glibc.
2272 prompt "vsyscall table for legacy applications"
2274 default LEGACY_VSYSCALL_XONLY
2276 Legacy user code that does not know how to find the vDSO expects
2277 to be able to issue three syscalls by calling fixed addresses in
2278 kernel space. Since this location is not randomized with ASLR,
2279 it can be used to assist security vulnerability exploitation.
2281 This setting can be changed at boot time via the kernel command
2282 line parameter vsyscall=[emulate|xonly|none].
2284 On a system with recent enough glibc (2.14 or newer) and no
2285 static binaries, you can say None without a performance penalty
2286 to improve security.
2288 If unsure, select "Emulate execution only".
2290 config LEGACY_VSYSCALL_EMULATE
2291 bool "Full emulation"
2293 The kernel traps and emulates calls into the fixed vsyscall
2294 address mapping. This makes the mapping non-executable, but
2295 it still contains readable known contents, which could be
2296 used in certain rare security vulnerability exploits. This
2297 configuration is recommended when using legacy userspace
2298 that still uses vsyscalls along with legacy binary
2299 instrumentation tools that require code to be readable.
2301 An example of this type of legacy userspace is running
2302 Pin on an old binary that still uses vsyscalls.
2304 config LEGACY_VSYSCALL_XONLY
2305 bool "Emulate execution only"
2307 The kernel traps and emulates calls into the fixed vsyscall
2308 address mapping and does not allow reads. This
2309 configuration is recommended when userspace might use the
2310 legacy vsyscall area but support for legacy binary
2311 instrumentation of legacy code is not needed. It mitigates
2312 certain uses of the vsyscall area as an ASLR-bypassing
2315 config LEGACY_VSYSCALL_NONE
2318 There will be no vsyscall mapping at all. This will
2319 eliminate any risk of ASLR bypass due to the vsyscall
2320 fixed address mapping. Attempts to use the vsyscalls
2321 will be reported to dmesg, so that either old or
2322 malicious userspace programs can be identified.
2327 bool "Built-in kernel command line"
2329 Allow for specifying boot arguments to the kernel at
2330 build time. On some systems (e.g. embedded ones), it is
2331 necessary or convenient to provide some or all of the
2332 kernel boot arguments with the kernel itself (that is,
2333 to not rely on the boot loader to provide them.)
2335 To compile command line arguments into the kernel,
2336 set this option to 'Y', then fill in the
2337 boot arguments in CONFIG_CMDLINE.
2339 Systems with fully functional boot loaders (i.e. non-embedded)
2340 should leave this option set to 'N'.
2343 string "Built-in kernel command string"
2344 depends on CMDLINE_BOOL
2347 Enter arguments here that should be compiled into the kernel
2348 image and used at boot time. If the boot loader provides a
2349 command line at boot time, it is appended to this string to
2350 form the full kernel command line, when the system boots.
2352 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2353 change this behavior.
2355 In most cases, the command line (whether built-in or provided
2356 by the boot loader) should specify the device for the root
2359 config CMDLINE_OVERRIDE
2360 bool "Built-in command line overrides boot loader arguments"
2361 depends on CMDLINE_BOOL && CMDLINE != ""
2363 Set this option to 'Y' to have the kernel ignore the boot loader
2364 command line, and use ONLY the built-in command line.
2366 This is used to work around broken boot loaders. This should
2367 be set to 'N' under normal conditions.
2369 config MODIFY_LDT_SYSCALL
2370 bool "Enable the LDT (local descriptor table)" if EXPERT
2373 Linux can allow user programs to install a per-process x86
2374 Local Descriptor Table (LDT) using the modify_ldt(2) system
2375 call. This is required to run 16-bit or segmented code such as
2376 DOSEMU or some Wine programs. It is also used by some very old
2377 threading libraries.
2379 Enabling this feature adds a small amount of overhead to
2380 context switches and increases the low-level kernel attack
2381 surface. Disabling it removes the modify_ldt(2) system call.
2383 Saying 'N' here may make sense for embedded or server kernels.
2385 source "kernel/livepatch/Kconfig"
2390 def_bool $(cc-option,-mharden-sls=all)
2392 config CC_HAS_RETURN_THUNK
2393 def_bool $(cc-option,-mfunction-return=thunk-extern)
2395 menuconfig SPECULATION_MITIGATIONS
2396 bool "Mitigations for speculative execution vulnerabilities"
2399 Say Y here to enable options which enable mitigations for
2400 speculative execution hardware vulnerabilities.
2402 If you say N, all mitigations will be disabled. You really
2403 should know what you are doing to say so.
2405 if SPECULATION_MITIGATIONS
2407 config PAGE_TABLE_ISOLATION
2408 bool "Remove the kernel mapping in user mode"
2410 depends on (X86_64 || X86_PAE)
2412 This feature reduces the number of hardware side channels by
2413 ensuring that the majority of kernel addresses are not mapped
2416 See Documentation/x86/pti.rst for more details.
2419 bool "Avoid speculative indirect branches in kernel"
2422 Compile kernel with the retpoline compiler options to guard against
2423 kernel-to-user data leaks by avoiding speculative indirect
2424 branches. Requires a compiler with -mindirect-branch=thunk-extern
2425 support for full protection. The kernel may run slower.
2428 bool "Enable return-thunks"
2429 depends on RETPOLINE && CC_HAS_RETURN_THUNK
2432 Compile the kernel with the return-thunks compiler option to guard
2433 against kernel-to-user data leaks by avoiding return speculation.
2434 Requires a compiler with -mfunction-return=thunk-extern
2435 support for full protection. The kernel may run slower.
2437 config CPU_UNRET_ENTRY
2438 bool "Enable UNRET on kernel entry"
2439 depends on CPU_SUP_AMD && RETHUNK && X86_64
2442 Compile the kernel with support for the retbleed=unret mitigation.
2444 config CPU_IBPB_ENTRY
2445 bool "Enable IBPB on kernel entry"
2446 depends on CPU_SUP_AMD && X86_64
2449 Compile the kernel with support for the retbleed=ibpb mitigation.
2451 config CPU_IBRS_ENTRY
2452 bool "Enable IBRS on kernel entry"
2453 depends on CPU_SUP_INTEL && X86_64
2456 Compile the kernel with support for the spectre_v2=ibrs mitigation.
2457 This mitigates both spectre_v2 and retbleed at great cost to
2461 bool "Mitigate speculative RAS overflow on AMD"
2462 depends on CPU_SUP_AMD && X86_64 && RETHUNK
2465 Enable the SRSO mitigation needed on AMD Zen1-4 machines.
2468 bool "Mitigate Straight-Line-Speculation"
2469 depends on CC_HAS_SLS && X86_64
2472 Compile the kernel with straight-line-speculation options to guard
2473 against straight line speculation. The kernel image might be slightly
2476 config GDS_FORCE_MITIGATION
2477 bool "Force GDS Mitigation"
2478 depends on CPU_SUP_INTEL
2481 Gather Data Sampling (GDS) is a hardware vulnerability which allows
2482 unprivileged speculative access to data which was previously stored in
2485 This option is equivalent to setting gather_data_sampling=force on the
2486 command line. The microcode mitigation is used if present, otherwise
2487 AVX is disabled as a mitigation. On affected systems that are missing
2488 the microcode any userspace code that unconditionally uses AVX will
2489 break with this option set.
2491 Setting this option on systems not vulnerable to GDS has no effect.
2497 config ARCH_HAS_ADD_PAGES
2499 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2501 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2504 config USE_PERCPU_NUMA_NODE_ID
2508 menu "Power management and ACPI options"
2510 config ARCH_HIBERNATION_HEADER
2512 depends on HIBERNATION
2514 source "kernel/power/Kconfig"
2516 source "drivers/acpi/Kconfig"
2523 tristate "APM (Advanced Power Management) BIOS support"
2524 depends on X86_32 && PM_SLEEP
2526 APM is a BIOS specification for saving power using several different
2527 techniques. This is mostly useful for battery powered laptops with
2528 APM compliant BIOSes. If you say Y here, the system time will be
2529 reset after a RESUME operation, the /proc/apm device will provide
2530 battery status information, and user-space programs will receive
2531 notification of APM "events" (e.g. battery status change).
2533 If you select "Y" here, you can disable actual use of the APM
2534 BIOS by passing the "apm=off" option to the kernel at boot time.
2536 Note that the APM support is almost completely disabled for
2537 machines with more than one CPU.
2539 In order to use APM, you will need supporting software. For location
2540 and more information, read <file:Documentation/power/apm-acpi.rst>
2541 and the Battery Powered Linux mini-HOWTO, available from
2542 <http://www.tldp.org/docs.html#howto>.
2544 This driver does not spin down disk drives (see the hdparm(8)
2545 manpage ("man 8 hdparm") for that), and it doesn't turn off
2546 VESA-compliant "green" monitors.
2548 This driver does not support the TI 4000M TravelMate and the ACER
2549 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2550 desktop machines also don't have compliant BIOSes, and this driver
2551 may cause those machines to panic during the boot phase.
2553 Generally, if you don't have a battery in your machine, there isn't
2554 much point in using this driver and you should say N. If you get
2555 random kernel OOPSes or reboots that don't seem to be related to
2556 anything, try disabling/enabling this option (or disabling/enabling
2559 Some other things you should try when experiencing seemingly random,
2562 1) make sure that you have enough swap space and that it is
2564 2) pass the "no-hlt" option to the kernel
2565 3) switch on floating point emulation in the kernel and pass
2566 the "no387" option to the kernel
2567 4) pass the "floppy=nodma" option to the kernel
2568 5) pass the "mem=4M" option to the kernel (thereby disabling
2569 all but the first 4 MB of RAM)
2570 6) make sure that the CPU is not over clocked.
2571 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2572 8) disable the cache from your BIOS settings
2573 9) install a fan for the video card or exchange video RAM
2574 10) install a better fan for the CPU
2575 11) exchange RAM chips
2576 12) exchange the motherboard.
2578 To compile this driver as a module, choose M here: the
2579 module will be called apm.
2583 config APM_IGNORE_USER_SUSPEND
2584 bool "Ignore USER SUSPEND"
2586 This option will ignore USER SUSPEND requests. On machines with a
2587 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2588 series notebooks, it is necessary to say Y because of a BIOS bug.
2590 config APM_DO_ENABLE
2591 bool "Enable PM at boot time"
2593 Enable APM features at boot time. From page 36 of the APM BIOS
2594 specification: "When disabled, the APM BIOS does not automatically
2595 power manage devices, enter the Standby State, enter the Suspend
2596 State, or take power saving steps in response to CPU Idle calls."
2597 This driver will make CPU Idle calls when Linux is idle (unless this
2598 feature is turned off -- see "Do CPU IDLE calls", below). This
2599 should always save battery power, but more complicated APM features
2600 will be dependent on your BIOS implementation. You may need to turn
2601 this option off if your computer hangs at boot time when using APM
2602 support, or if it beeps continuously instead of suspending. Turn
2603 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2604 T400CDT. This is off by default since most machines do fine without
2609 bool "Make CPU Idle calls when idle"
2611 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2612 On some machines, this can activate improved power savings, such as
2613 a slowed CPU clock rate, when the machine is idle. These idle calls
2614 are made after the idle loop has run for some length of time (e.g.,
2615 333 mS). On some machines, this will cause a hang at boot time or
2616 whenever the CPU becomes idle. (On machines with more than one CPU,
2617 this option does nothing.)
2619 config APM_DISPLAY_BLANK
2620 bool "Enable console blanking using APM"
2622 Enable console blanking using the APM. Some laptops can use this to
2623 turn off the LCD backlight when the screen blanker of the Linux
2624 virtual console blanks the screen. Note that this is only used by
2625 the virtual console screen blanker, and won't turn off the backlight
2626 when using the X Window system. This also doesn't have anything to
2627 do with your VESA-compliant power-saving monitor. Further, this
2628 option doesn't work for all laptops -- it might not turn off your
2629 backlight at all, or it might print a lot of errors to the console,
2630 especially if you are using gpm.
2632 config APM_ALLOW_INTS
2633 bool "Allow interrupts during APM BIOS calls"
2635 Normally we disable external interrupts while we are making calls to
2636 the APM BIOS as a measure to lessen the effects of a badly behaving
2637 BIOS implementation. The BIOS should reenable interrupts if it
2638 needs to. Unfortunately, some BIOSes do not -- especially those in
2639 many of the newer IBM Thinkpads. If you experience hangs when you
2640 suspend, try setting this to Y. Otherwise, say N.
2644 source "drivers/cpufreq/Kconfig"
2646 source "drivers/cpuidle/Kconfig"
2648 source "drivers/idle/Kconfig"
2653 menu "Bus options (PCI etc.)"
2656 prompt "PCI access mode"
2657 depends on X86_32 && PCI
2660 On PCI systems, the BIOS can be used to detect the PCI devices and
2661 determine their configuration. However, some old PCI motherboards
2662 have BIOS bugs and may crash if this is done. Also, some embedded
2663 PCI-based systems don't have any BIOS at all. Linux can also try to
2664 detect the PCI hardware directly without using the BIOS.
2666 With this option, you can specify how Linux should detect the
2667 PCI devices. If you choose "BIOS", the BIOS will be used,
2668 if you choose "Direct", the BIOS won't be used, and if you
2669 choose "MMConfig", then PCI Express MMCONFIG will be used.
2670 If you choose "Any", the kernel will try MMCONFIG, then the
2671 direct access method and falls back to the BIOS if that doesn't
2672 work. If unsure, go with the default, which is "Any".
2677 config PCI_GOMMCONFIG
2694 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2696 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2699 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2702 bool "Support mmconfig PCI config space access" if X86_64
2704 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2705 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2709 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2713 depends on PCI && XEN
2715 config MMCONF_FAM10H
2717 depends on X86_64 && PCI_MMCONFIG && ACPI
2719 config PCI_CNB20LE_QUIRK
2720 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2723 Read the PCI windows out of the CNB20LE host bridge. This allows
2724 PCI hotplug to work on systems with the CNB20LE chipset which do
2727 There's no public spec for this chipset, and this functionality
2728 is known to be incomplete.
2730 You should say N unless you know you need this.
2733 bool "ISA bus support on modern systems" if EXPERT
2735 Expose ISA bus device drivers and options available for selection and
2736 configuration. Enable this option if your target machine has an ISA
2737 bus. ISA is an older system, displaced by PCI and newer bus
2738 architectures -- if your target machine is modern, it probably does
2739 not have an ISA bus.
2743 # x86_64 have no ISA slots, but can have ISA-style DMA.
2745 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2748 Enables ISA-style DMA support for devices requiring such controllers.
2756 Find out whether you have ISA slots on your motherboard. ISA is the
2757 name of a bus system, i.e. the way the CPU talks to the other stuff
2758 inside your box. Other bus systems are PCI, EISA, MicroChannel
2759 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2760 newer boards don't support it. If you have ISA, say Y, otherwise N.
2763 tristate "NatSemi SCx200 support"
2765 This provides basic support for National Semiconductor's
2766 (now AMD's) Geode processors. The driver probes for the
2767 PCI-IDs of several on-chip devices, so its a good dependency
2768 for other scx200_* drivers.
2770 If compiled as a module, the driver is named scx200.
2772 config SCx200HR_TIMER
2773 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2777 This driver provides a clocksource built upon the on-chip
2778 27MHz high-resolution timer. Its also a workaround for
2779 NSC Geode SC-1100's buggy TSC, which loses time when the
2780 processor goes idle (as is done by the scheduler). The
2781 other workaround is idle=poll boot option.
2784 bool "One Laptop Per Child support"
2792 Add support for detecting the unique features of the OLPC
2796 bool "OLPC XO-1 Power Management"
2797 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2799 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2802 bool "OLPC XO-1 Real Time Clock"
2803 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2805 Add support for the XO-1 real time clock, which can be used as a
2806 programmable wakeup source.
2809 bool "OLPC XO-1 SCI extras"
2810 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2814 Add support for SCI-based features of the OLPC XO-1 laptop:
2815 - EC-driven system wakeups
2819 - AC adapter status updates
2820 - Battery status updates
2822 config OLPC_XO15_SCI
2823 bool "OLPC XO-1.5 SCI extras"
2824 depends on OLPC && ACPI
2827 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2828 - EC-driven system wakeups
2829 - AC adapter status updates
2830 - Battery status updates
2833 bool "PCEngines ALIX System Support (LED setup)"
2836 This option enables system support for the PCEngines ALIX.
2837 At present this just sets up LEDs for GPIO control on
2838 ALIX2/3/6 boards. However, other system specific setup should
2841 Note: You must still enable the drivers for GPIO and LED support
2842 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2844 Note: You have to set alix.force=1 for boards with Award BIOS.
2847 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2850 This option enables system support for the Soekris Engineering net5501.
2853 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2857 This option enables system support for the Traverse Technologies GEOS.
2860 bool "Technologic Systems TS-5500 platform support"
2862 select CHECK_SIGNATURE
2866 This option enables system support for the Technologic Systems TS-5500.
2872 depends on CPU_SUP_AMD && PCI
2877 menu "Binary Emulations"
2879 config IA32_EMULATION
2880 bool "IA32 Emulation"
2882 select ARCH_WANT_OLD_COMPAT_IPC
2884 select COMPAT_OLD_SIGACTION
2886 Include code to run legacy 32-bit programs under a
2887 64-bit kernel. You should likely turn this on, unless you're
2888 100% sure that you don't have any 32-bit programs left.
2891 tristate "IA32 a.out support"
2892 depends on IA32_EMULATION
2895 Support old a.out binaries in the 32bit emulation.
2898 bool "x32 ABI for 64-bit mode"
2900 # llvm-objcopy does not convert x86_64 .note.gnu.property or
2901 # compressed debug sections to x86_x32 properly:
2902 # https://github.com/ClangBuiltLinux/linux/issues/514
2903 # https://github.com/ClangBuiltLinux/linux/issues/1141
2904 depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
2906 Include code to run binaries for the x32 native 32-bit ABI
2907 for 64-bit processors. An x32 process gets access to the
2908 full 64-bit register file and wide data path while leaving
2909 pointers at 32 bits for smaller memory footprint.
2911 You will need a recent binutils (2.22 or later) with
2912 elf32_x86_64 support enabled to compile a kernel with this
2917 depends on IA32_EMULATION || X86_32
2919 select OLD_SIGSUSPEND3
2923 depends on IA32_EMULATION || X86_X32
2926 config COMPAT_FOR_U64_ALIGNMENT
2929 config SYSVIPC_COMPAT
2937 config HAVE_ATOMIC_IOMAP
2941 source "arch/x86/kvm/Kconfig"
2943 source "arch/x86/Kconfig.assembler"