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
37 config FORCE_DYNAMIC_FTRACE
40 depends on FUNCTION_TRACER
43 We keep the static function tracing (!DYNAMIC_FTRACE) around
44 in order to test the non static function tracing in the
45 generic code, as other architectures still use it. But we
46 only need to keep it around for x86_64. No need to keep it
47 for x86_32. For x86_32, force DYNAMIC_FTRACE.
51 # ( Note that options that are marked 'if X86_64' could in principle be
52 # ported to 32-bit as well. )
57 # Note: keep this list sorted alphabetically
59 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
60 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
61 select ARCH_32BIT_OFF_T if X86_32
62 select ARCH_CLOCKSOURCE_INIT
63 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
64 select ARCH_HAS_DEBUG_VIRTUAL
65 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
66 select ARCH_HAS_DEVMEM_IS_ALLOWED
67 select ARCH_HAS_EARLY_DEBUG if KGDB
68 select ARCH_HAS_ELF_RANDOMIZE
69 select ARCH_HAS_FAST_MULTIPLIER
70 select ARCH_HAS_FILTER_PGPROT
71 select ARCH_HAS_FORTIFY_SOURCE
72 select ARCH_HAS_GCOV_PROFILE_ALL
73 select ARCH_HAS_KCOV if X86_64 && STACK_VALIDATION
74 select ARCH_HAS_MEM_ENCRYPT
75 select ARCH_HAS_MEMBARRIER_SYNC_CORE
76 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
77 select ARCH_HAS_PMEM_API if X86_64
78 select ARCH_HAS_PTE_DEVMAP if X86_64
79 select ARCH_HAS_PTE_SPECIAL
80 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
81 select ARCH_HAS_COPY_MC if X86_64
82 select ARCH_HAS_SET_MEMORY
83 select ARCH_HAS_SET_DIRECT_MAP
84 select ARCH_HAS_STRICT_KERNEL_RWX
85 select ARCH_HAS_STRICT_MODULE_RWX
86 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
87 select ARCH_HAS_SYSCALL_WRAPPER
88 select ARCH_HAS_UBSAN_SANITIZE_ALL
89 select ARCH_HAS_DEBUG_WX
90 select ARCH_HAVE_NMI_SAFE_CMPXCHG
91 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
92 select ARCH_MIGHT_HAVE_PC_PARPORT
93 select ARCH_MIGHT_HAVE_PC_SERIO
95 select ARCH_SUPPORTS_ACPI
96 select ARCH_SUPPORTS_ATOMIC_RMW
97 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
98 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
99 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
100 select ARCH_SUPPORTS_LTO_CLANG if X86_64
101 select ARCH_SUPPORTS_LTO_CLANG_THIN if X86_64
102 select ARCH_USE_BUILTIN_BSWAP
103 select ARCH_USE_QUEUED_RWLOCKS
104 select ARCH_USE_QUEUED_SPINLOCKS
105 select ARCH_USE_SYM_ANNOTATIONS
106 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
107 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
108 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
109 select ARCH_WANT_HUGE_PMD_SHARE
110 select ARCH_WANT_LD_ORPHAN_WARN
111 select ARCH_WANTS_THP_SWAP if X86_64
112 select BUILDTIME_TABLE_SORT
114 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
115 select CLOCKSOURCE_WATCHDOG
116 select DCACHE_WORD_ACCESS
117 select EDAC_ATOMIC_SCRUB
119 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
120 select GENERIC_CLOCKEVENTS_MIN_ADJUST
121 select GENERIC_CMOS_UPDATE
122 select GENERIC_CPU_AUTOPROBE
123 select GENERIC_CPU_VULNERABILITIES
124 select GENERIC_EARLY_IOREMAP
126 select GENERIC_FIND_FIRST_BIT
128 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
129 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
130 select GENERIC_IRQ_MIGRATION if SMP
131 select GENERIC_IRQ_PROBE
132 select GENERIC_IRQ_RESERVATION_MODE
133 select GENERIC_IRQ_SHOW
134 select GENERIC_PENDING_IRQ if SMP
135 select GENERIC_PTDUMP
136 select GENERIC_SMP_IDLE_THREAD
137 select GENERIC_STRNCPY_FROM_USER
138 select GENERIC_STRNLEN_USER
139 select GENERIC_TIME_VSYSCALL
140 select GENERIC_GETTIMEOFDAY
141 select GENERIC_VDSO_TIME_NS
142 select GUP_GET_PTE_LOW_HIGH if X86_PAE
143 select HARDIRQS_SW_RESEND
144 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
145 select HAVE_ACPI_APEI if ACPI
146 select HAVE_ACPI_APEI_NMI if ACPI
147 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
148 select HAVE_ARCH_AUDITSYSCALL
149 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
150 select HAVE_ARCH_JUMP_LABEL
151 select HAVE_ARCH_JUMP_LABEL_RELATIVE
152 select HAVE_ARCH_KASAN if X86_64
153 select HAVE_ARCH_KASAN_VMALLOC if X86_64
154 select HAVE_ARCH_KFENCE
155 select HAVE_ARCH_KGDB
156 select HAVE_ARCH_MMAP_RND_BITS if MMU
157 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
158 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
159 select HAVE_ARCH_PREL32_RELOCATIONS
160 select HAVE_ARCH_SECCOMP_FILTER
161 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
162 select HAVE_ARCH_STACKLEAK
163 select HAVE_ARCH_TRACEHOOK
164 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
165 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
166 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
167 select HAVE_ARCH_VMAP_STACK if X86_64
168 select HAVE_ARCH_WITHIN_STACK_FRAMES
169 select HAVE_ASM_MODVERSIONS
170 select HAVE_CMPXCHG_DOUBLE
171 select HAVE_CMPXCHG_LOCAL
172 select HAVE_CONTEXT_TRACKING if X86_64
173 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
174 select HAVE_C_RECORDMCOUNT
175 select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION
176 select HAVE_DEBUG_KMEMLEAK
177 select HAVE_DMA_CONTIGUOUS
178 select HAVE_DYNAMIC_FTRACE
179 select HAVE_DYNAMIC_FTRACE_WITH_REGS
180 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
181 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
183 select HAVE_EFFICIENT_UNALIGNED_ACCESS
185 select HAVE_EXIT_THREAD
187 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
188 select HAVE_FTRACE_MCOUNT_RECORD
189 select HAVE_FUNCTION_GRAPH_TRACER
190 select HAVE_FUNCTION_TRACER
191 select HAVE_GCC_PLUGINS
192 select HAVE_HW_BREAKPOINT
194 select HAVE_IOREMAP_PROT
195 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
196 select HAVE_IRQ_TIME_ACCOUNTING
197 select HAVE_KERNEL_BZIP2
198 select HAVE_KERNEL_GZIP
199 select HAVE_KERNEL_LZ4
200 select HAVE_KERNEL_LZMA
201 select HAVE_KERNEL_LZO
202 select HAVE_KERNEL_XZ
203 select HAVE_KERNEL_ZSTD
205 select HAVE_KPROBES_ON_FTRACE
206 select HAVE_FUNCTION_ERROR_INJECTION
207 select HAVE_KRETPROBES
209 select HAVE_LIVEPATCH if X86_64
210 select HAVE_MIXED_BREAKPOINTS_REGS
211 select HAVE_MOD_ARCH_SPECIFIC
215 select HAVE_OPTPROBES
216 select HAVE_PCSPKR_PLATFORM
217 select HAVE_PERF_EVENTS
218 select HAVE_PERF_EVENTS_NMI
219 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
221 select HAVE_PERF_REGS
222 select HAVE_PERF_USER_STACK_DUMP
223 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
224 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
225 select HAVE_REGS_AND_STACK_ACCESS_API
226 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
227 select HAVE_FUNCTION_ARG_ACCESS_API
228 select HAVE_SOFTIRQ_ON_OWN_STACK
229 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
230 select HAVE_STACK_VALIDATION if X86_64
231 select HAVE_STATIC_CALL
232 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
233 select HAVE_PREEMPT_DYNAMIC
235 select HAVE_SYSCALL_TRACEPOINTS
236 select HAVE_UNSTABLE_SCHED_CLOCK
237 select HAVE_USER_RETURN_NOTIFIER
238 select HAVE_GENERIC_VDSO
239 select HOTPLUG_SMT if SMP
240 select IRQ_FORCED_THREADING
241 select NEED_SG_DMA_LENGTH
242 select PCI_DOMAINS if PCI
243 select PCI_LOCKLESS_CONFIG if PCI
246 select RTC_MC146818_LIB
249 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
250 select SYSCTL_EXCEPTION_TRACE
251 select THREAD_INFO_IN_TASK
252 select USER_STACKTRACE_SUPPORT
254 select HAVE_ARCH_KCSAN if X86_64
255 select X86_FEATURE_NAMES if PROC_FS
256 select PROC_PID_ARCH_STATUS if PROC_FS
257 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
259 config INSTRUCTION_DECODER
261 depends on KPROBES || PERF_EVENTS || UPROBES
265 default "elf32-i386" if X86_32
266 default "elf64-x86-64" if X86_64
268 config LOCKDEP_SUPPORT
271 config STACKTRACE_SUPPORT
277 config ARCH_MMAP_RND_BITS_MIN
281 config ARCH_MMAP_RND_BITS_MAX
285 config ARCH_MMAP_RND_COMPAT_BITS_MIN
288 config ARCH_MMAP_RND_COMPAT_BITS_MAX
294 config GENERIC_ISA_DMA
296 depends on ISA_DMA_API
301 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
303 config GENERIC_BUG_RELATIVE_POINTERS
306 config ARCH_MAY_HAVE_PC_FDC
308 depends on ISA_DMA_API
310 config GENERIC_CALIBRATE_DELAY
313 config ARCH_HAS_CPU_RELAX
316 config ARCH_HAS_CACHE_LINE_SIZE
319 config ARCH_HAS_FILTER_PGPROT
322 config HAVE_SETUP_PER_CPU_AREA
325 config NEED_PER_CPU_EMBED_FIRST_CHUNK
328 config NEED_PER_CPU_PAGE_FIRST_CHUNK
331 config ARCH_HIBERNATION_POSSIBLE
334 config ARCH_SUSPEND_POSSIBLE
337 config ARCH_WANT_GENERAL_HUGETLB
346 config KASAN_SHADOW_OFFSET
349 default 0xdffffc0000000000
351 config HAVE_INTEL_TXT
353 depends on INTEL_IOMMU && ACPI
357 depends on X86_32 && SMP
361 depends on X86_64 && SMP
363 config X86_32_LAZY_GS
365 depends on X86_32 && !STACKPROTECTOR
367 config ARCH_SUPPORTS_UPROBES
370 config FIX_EARLYCON_MEM
373 config DYNAMIC_PHYSICAL_MASK
376 config PGTABLE_LEVELS
378 default 5 if X86_5LEVEL
383 config CC_HAS_SANE_STACKPROTECTOR
385 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
386 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
388 We have to make sure stack protector is unconditionally disabled if
389 the compiler produces broken code.
391 menu "Processor type and features"
394 bool "DMA memory allocation support" if EXPERT
397 DMA memory allocation support allows devices with less than 32-bit
398 addressing to allocate within the first 16MB of address space.
399 Disable if no such devices will be used.
404 bool "Symmetric multi-processing support"
406 This enables support for systems with more than one CPU. If you have
407 a system with only one CPU, say N. If you have a system with more
410 If you say N here, the kernel will run on uni- and multiprocessor
411 machines, but will use only one CPU of a multiprocessor machine. If
412 you say Y here, the kernel will run on many, but not all,
413 uniprocessor machines. On a uniprocessor machine, the kernel
414 will run faster if you say N here.
416 Note that if you say Y here and choose architecture "586" or
417 "Pentium" under "Processor family", the kernel will not work on 486
418 architectures. Similarly, multiprocessor kernels for the "PPro"
419 architecture may not work on all Pentium based boards.
421 People using multiprocessor machines who say Y here should also say
422 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
423 Management" code will be disabled if you say Y here.
425 See also <file:Documentation/x86/i386/IO-APIC.rst>,
426 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
427 <http://www.tldp.org/docs.html#howto>.
429 If you don't know what to do here, say N.
431 config X86_FEATURE_NAMES
432 bool "Processor feature human-readable names" if EMBEDDED
435 This option compiles in a table of x86 feature bits and corresponding
436 names. This is required to support /proc/cpuinfo and a few kernel
437 messages. You can disable this to save space, at the expense of
438 making those few kernel messages show numeric feature bits instead.
443 bool "Support x2apic"
444 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
446 This enables x2apic support on CPUs that have this feature.
448 This allows 32-bit apic IDs (so it can support very large systems),
449 and accesses the local apic via MSRs not via mmio.
451 If you don't know what to do here, say N.
454 bool "Enable MPS table" if ACPI
456 depends on X86_LOCAL_APIC
458 For old smp systems that do not have proper acpi support. Newer systems
459 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
463 depends on X86_GOLDFISH
466 bool "Avoid speculative indirect branches in kernel"
469 Compile kernel with the retpoline compiler options to guard against
470 kernel-to-user data leaks by avoiding speculative indirect
471 branches. Requires a compiler with -mindirect-branch=thunk-extern
472 support for full protection. The kernel may run slower.
474 config X86_CPU_RESCTRL
475 bool "x86 CPU resource control support"
476 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
478 select PROC_CPU_RESCTRL if PROC_FS
480 Enable x86 CPU resource control support.
482 Provide support for the allocation and monitoring of system resources
485 Intel calls this Intel Resource Director Technology
486 (Intel(R) RDT). More information about RDT can be found in the
487 Intel x86 Architecture Software Developer Manual.
489 AMD calls this AMD Platform Quality of Service (AMD QoS).
490 More information about AMD QoS can be found in the AMD64 Technology
491 Platform Quality of Service Extensions manual.
497 bool "Support for big SMP systems with more than 8 CPUs"
500 This option is needed for the systems that have more than 8 CPUs.
502 config X86_EXTENDED_PLATFORM
503 bool "Support for extended (non-PC) x86 platforms"
506 If you disable this option then the kernel will only support
507 standard PC platforms. (which covers the vast majority of
510 If you enable this option then you'll be able to select support
511 for the following (non-PC) 32 bit x86 platforms:
512 Goldfish (Android emulator)
515 SGI 320/540 (Visual Workstation)
516 STA2X11-based (e.g. Northville)
517 Moorestown MID devices
519 If you have one of these systems, or if you want to build a
520 generic distribution kernel, say Y here - otherwise say N.
524 config X86_EXTENDED_PLATFORM
525 bool "Support for extended (non-PC) x86 platforms"
528 If you disable this option then the kernel will only support
529 standard PC platforms. (which covers the vast majority of
532 If you enable this option then you'll be able to select support
533 for the following (non-PC) 64 bit x86 platforms:
538 If you have one of these systems, or if you want to build a
539 generic distribution kernel, say Y here - otherwise say N.
541 # This is an alphabetically sorted list of 64 bit extended platforms
542 # Please maintain the alphabetic order if and when there are additions
544 bool "Numascale NumaChip"
546 depends on X86_EXTENDED_PLATFORM
549 depends on X86_X2APIC
550 depends on PCI_MMCONFIG
552 Adds support for Numascale NumaChip large-SMP systems. Needed to
553 enable more than ~168 cores.
554 If you don't have one of these, you should say N here.
558 select HYPERVISOR_GUEST
560 depends on X86_64 && PCI
561 depends on X86_EXTENDED_PLATFORM
564 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
565 supposed to run on these EM64T-based machines. Only choose this option
566 if you have one of these machines.
569 bool "SGI Ultraviolet"
571 depends on X86_EXTENDED_PLATFORM
574 depends on X86_X2APIC
577 This option is needed in order to support SGI Ultraviolet systems.
578 If you don't have one of these, you should say N here.
580 # Following is an alphabetically sorted list of 32 bit extended platforms
581 # Please maintain the alphabetic order if and when there are additions
584 bool "Goldfish (Virtual Platform)"
585 depends on X86_EXTENDED_PLATFORM
587 Enable support for the Goldfish virtual platform used primarily
588 for Android development. Unless you are building for the Android
589 Goldfish emulator say N here.
592 bool "CE4100 TV platform"
594 depends on PCI_GODIRECT
595 depends on X86_IO_APIC
597 depends on X86_EXTENDED_PLATFORM
598 select X86_REBOOTFIXUPS
600 select OF_EARLY_FLATTREE
602 Select for the Intel CE media processor (CE4100) SOC.
603 This option compiles in support for the CE4100 SOC for settop
604 boxes and media devices.
607 bool "Intel MID platform support"
608 depends on X86_EXTENDED_PLATFORM
609 depends on X86_PLATFORM_DEVICES
611 depends on X86_64 || (PCI_GOANY && X86_32)
612 depends on X86_IO_APIC
617 select MFD_INTEL_MSIC
619 Select to build a kernel capable of supporting Intel MID (Mobile
620 Internet Device) platform systems which do not have the PCI legacy
621 interfaces. If you are building for a PC class system say N here.
623 Intel MID platforms are based on an Intel processor and chipset which
624 consume less power than most of the x86 derivatives.
626 config X86_INTEL_QUARK
627 bool "Intel Quark platform support"
629 depends on X86_EXTENDED_PLATFORM
630 depends on X86_PLATFORM_DEVICES
634 depends on X86_IO_APIC
639 Select to include support for Quark X1000 SoC.
640 Say Y here if you have a Quark based system such as the Arduino
641 compatible Intel Galileo.
643 config X86_INTEL_LPSS
644 bool "Intel Low Power Subsystem Support"
645 depends on X86 && ACPI && PCI
650 Select to build support for Intel Low Power Subsystem such as
651 found on Intel Lynxpoint PCH. Selecting this option enables
652 things like clock tree (common clock framework) and pincontrol
653 which are needed by the LPSS peripheral drivers.
655 config X86_AMD_PLATFORM_DEVICE
656 bool "AMD ACPI2Platform devices support"
661 Select to interpret AMD specific ACPI device to platform device
662 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
663 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
664 implemented under PINCTRL subsystem.
667 tristate "Intel SoC IOSF Sideband support for SoC platforms"
670 This option enables sideband register access support for Intel SoC
671 platforms. On these platforms the IOSF sideband is used in lieu of
672 MSR's for some register accesses, mostly but not limited to thermal
673 and power. Drivers may query the availability of this device to
674 determine if they need the sideband in order to work on these
675 platforms. The sideband is available on the following SoC products.
676 This list is not meant to be exclusive.
681 You should say Y if you are running a kernel on one of these SoC's.
683 config IOSF_MBI_DEBUG
684 bool "Enable IOSF sideband access through debugfs"
685 depends on IOSF_MBI && DEBUG_FS
687 Select this option to expose the IOSF sideband access registers (MCR,
688 MDR, MCRX) through debugfs to write and read register information from
689 different units on the SoC. This is most useful for obtaining device
690 state information for debug and analysis. As this is a general access
691 mechanism, users of this option would have specific knowledge of the
692 device they want to access.
694 If you don't require the option or are in doubt, say N.
697 bool "RDC R-321x SoC"
699 depends on X86_EXTENDED_PLATFORM
701 select X86_REBOOTFIXUPS
703 This option is needed for RDC R-321x system-on-chip, also known
705 If you don't have one of these chips, you should say N here.
707 config X86_32_NON_STANDARD
708 bool "Support non-standard 32-bit SMP architectures"
709 depends on X86_32 && SMP
710 depends on X86_EXTENDED_PLATFORM
712 This option compiles in the bigsmp and STA2X11 default
713 subarchitectures. It is intended for a generic binary
714 kernel. If you select them all, kernel will probe it one by
715 one and will fallback to default.
717 # Alphabetically sorted list of Non standard 32 bit platforms
719 config X86_SUPPORTS_MEMORY_FAILURE
721 # MCE code calls memory_failure():
723 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
724 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
725 depends on X86_64 || !SPARSEMEM
726 select ARCH_SUPPORTS_MEMORY_FAILURE
729 bool "STA2X11 Companion Chip Support"
730 depends on X86_32_NON_STANDARD && PCI
735 This adds support for boards based on the STA2X11 IO-Hub,
736 a.k.a. "ConneXt". The chip is used in place of the standard
737 PC chipset, so all "standard" peripherals are missing. If this
738 option is selected the kernel will still be able to boot on
739 standard PC machines.
742 tristate "Eurobraille/Iris poweroff module"
745 The Iris machines from EuroBraille do not have APM or ACPI support
746 to shut themselves down properly. A special I/O sequence is
747 needed to do so, which is what this module does at
750 This is only for Iris machines from EuroBraille.
754 config SCHED_OMIT_FRAME_POINTER
756 prompt "Single-depth WCHAN output"
759 Calculate simpler /proc/<PID>/wchan values. If this option
760 is disabled then wchan values will recurse back to the
761 caller function. This provides more accurate wchan values,
762 at the expense of slightly more scheduling overhead.
764 If in doubt, say "Y".
766 menuconfig HYPERVISOR_GUEST
767 bool "Linux guest support"
769 Say Y here to enable options for running Linux under various hyper-
770 visors. This option enables basic hypervisor detection and platform
773 If you say N, all options in this submenu will be skipped and
774 disabled, and Linux guest support won't be built in.
779 bool "Enable paravirtualization code"
781 This changes the kernel so it can modify itself when it is run
782 under a hypervisor, potentially improving performance significantly
783 over full virtualization. However, when run without a hypervisor
784 the kernel is theoretically slower and slightly larger.
789 config PARAVIRT_DEBUG
790 bool "paravirt-ops debugging"
791 depends on PARAVIRT && DEBUG_KERNEL
793 Enable to debug paravirt_ops internals. Specifically, BUG if
794 a paravirt_op is missing when it is called.
796 config PARAVIRT_SPINLOCKS
797 bool "Paravirtualization layer for spinlocks"
798 depends on PARAVIRT && SMP
800 Paravirtualized spinlocks allow a pvops backend to replace the
801 spinlock implementation with something virtualization-friendly
802 (for example, block the virtual CPU rather than spinning).
804 It has a minimal impact on native kernels and gives a nice performance
805 benefit on paravirtualized KVM / Xen kernels.
807 If you are unsure how to answer this question, answer Y.
809 config X86_HV_CALLBACK_VECTOR
812 source "arch/x86/xen/Kconfig"
815 bool "KVM Guest support (including kvmclock)"
817 select PARAVIRT_CLOCK
818 select ARCH_CPUIDLE_HALTPOLL
819 select X86_HV_CALLBACK_VECTOR
822 This option enables various optimizations for running under the KVM
823 hypervisor. It includes a paravirtualized clock, so that instead
824 of relying on a PIT (or probably other) emulation by the
825 underlying device model, the host provides the guest with
826 timing infrastructure such as time of day, and system time
828 config ARCH_CPUIDLE_HALTPOLL
830 prompt "Disable host haltpoll when loading haltpoll driver"
832 If virtualized under KVM, disable host haltpoll.
835 bool "Support for running PVH guests"
837 This option enables the PVH entry point for guest virtual machines
838 as specified in the x86/HVM direct boot ABI.
840 config PARAVIRT_TIME_ACCOUNTING
841 bool "Paravirtual steal time accounting"
844 Select this option to enable fine granularity task steal time
845 accounting. Time spent executing other tasks in parallel with
846 the current vCPU is discounted from the vCPU power. To account for
847 that, there can be a small performance impact.
849 If in doubt, say N here.
851 config PARAVIRT_CLOCK
854 config JAILHOUSE_GUEST
855 bool "Jailhouse non-root cell support"
856 depends on X86_64 && PCI
859 This option allows to run Linux as guest in a Jailhouse non-root
860 cell. You can leave this option disabled if you only want to start
861 Jailhouse and run Linux afterwards in the root cell.
864 bool "ACRN Guest support"
866 select X86_HV_CALLBACK_VECTOR
868 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
869 a flexible, lightweight reference open-source hypervisor, built with
870 real-time and safety-criticality in mind. It is built for embedded
871 IOT with small footprint and real-time features. More details can be
872 found in https://projectacrn.org/.
874 endif #HYPERVISOR_GUEST
876 source "arch/x86/Kconfig.cpu"
880 prompt "HPET Timer Support" if X86_32
882 Use the IA-PC HPET (High Precision Event Timer) to manage
883 time in preference to the PIT and RTC, if a HPET is
885 HPET is the next generation timer replacing legacy 8254s.
886 The HPET provides a stable time base on SMP
887 systems, unlike the TSC, but it is more expensive to access,
888 as it is off-chip. The interface used is documented
889 in the HPET spec, revision 1.
891 You can safely choose Y here. However, HPET will only be
892 activated if the platform and the BIOS support this feature.
893 Otherwise the 8254 will be used for timing services.
895 Choose N to continue using the legacy 8254 timer.
897 config HPET_EMULATE_RTC
899 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
901 # Mark as expert because too many people got it wrong.
902 # The code disables itself when not needed.
905 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
906 bool "Enable DMI scanning" if EXPERT
908 Enabled scanning of DMI to identify machine quirks. Say Y
909 here unless you have verified that your setup is not
910 affected by entries in the DMI blacklist. Required by PNP
914 bool "Old AMD GART IOMMU support"
918 depends on X86_64 && PCI && AMD_NB
920 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
921 GART based hardware IOMMUs.
923 The GART supports full DMA access for devices with 32-bit access
924 limitations, on systems with more than 3 GB. This is usually needed
925 for USB, sound, many IDE/SATA chipsets and some other devices.
927 Newer systems typically have a modern AMD IOMMU, supported via
928 the CONFIG_AMD_IOMMU=y config option.
930 In normal configurations this driver is only active when needed:
931 there's more than 3 GB of memory and the system contains a
932 32-bit limited device.
937 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
938 depends on X86_64 && SMP && DEBUG_KERNEL
939 select CPUMASK_OFFSTACK
941 Enable maximum number of CPUS and NUMA Nodes for this architecture.
945 # The maximum number of CPUs supported:
947 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
948 # and which can be configured interactively in the
949 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
951 # The ranges are different on 32-bit and 64-bit kernels, depending on
952 # hardware capabilities and scalability features of the kernel.
954 # ( If MAXSMP is enabled we just use the highest possible value and disable
955 # interactive configuration. )
958 config NR_CPUS_RANGE_BEGIN
960 default NR_CPUS_RANGE_END if MAXSMP
964 config NR_CPUS_RANGE_END
967 default 64 if SMP && X86_BIGSMP
968 default 8 if SMP && !X86_BIGSMP
971 config NR_CPUS_RANGE_END
974 default 8192 if SMP && CPUMASK_OFFSTACK
975 default 512 if SMP && !CPUMASK_OFFSTACK
978 config NR_CPUS_DEFAULT
981 default 32 if X86_BIGSMP
985 config NR_CPUS_DEFAULT
988 default 8192 if MAXSMP
993 int "Maximum number of CPUs" if SMP && !MAXSMP
994 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
995 default NR_CPUS_DEFAULT
997 This allows you to specify the maximum number of CPUs which this
998 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
999 supported value is 8192, otherwise the maximum value is 512. The
1000 minimum value which makes sense is 2.
1002 This is purely to save memory: each supported CPU adds about 8KB
1003 to the kernel image.
1010 prompt "Multi-core scheduler support"
1013 Multi-core scheduler support improves the CPU scheduler's decision
1014 making when dealing with multi-core CPU chips at a cost of slightly
1015 increased overhead in some places. If unsure say N here.
1017 config SCHED_MC_PRIO
1018 bool "CPU core priorities scheduler support"
1019 depends on SCHED_MC && CPU_SUP_INTEL
1020 select X86_INTEL_PSTATE
1024 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1025 core ordering determined at manufacturing time, which allows
1026 certain cores to reach higher turbo frequencies (when running
1027 single threaded workloads) than others.
1029 Enabling this kernel feature teaches the scheduler about
1030 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1031 scheduler's CPU selection logic accordingly, so that higher
1032 overall system performance can be achieved.
1034 This feature will have no effect on CPUs without this feature.
1036 If unsure say Y here.
1040 depends on !SMP && X86_LOCAL_APIC
1043 bool "Local APIC support on uniprocessors" if !PCI_MSI
1045 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1047 A local APIC (Advanced Programmable Interrupt Controller) is an
1048 integrated interrupt controller in the CPU. If you have a single-CPU
1049 system which has a processor with a local APIC, you can say Y here to
1050 enable and use it. If you say Y here even though your machine doesn't
1051 have a local APIC, then the kernel will still run with no slowdown at
1052 all. The local APIC supports CPU-generated self-interrupts (timer,
1053 performance counters), and the NMI watchdog which detects hard
1056 config X86_UP_IOAPIC
1057 bool "IO-APIC support on uniprocessors"
1058 depends on X86_UP_APIC
1060 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1061 SMP-capable replacement for PC-style interrupt controllers. Most
1062 SMP systems and many recent uniprocessor systems have one.
1064 If you have a single-CPU system with an IO-APIC, you can say Y here
1065 to use it. If you say Y here even though your machine doesn't have
1066 an IO-APIC, then the kernel will still run with no slowdown at all.
1068 config X86_LOCAL_APIC
1070 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1071 select IRQ_DOMAIN_HIERARCHY
1072 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1076 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1078 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1079 bool "Reroute for broken boot IRQs"
1080 depends on X86_IO_APIC
1082 This option enables a workaround that fixes a source of
1083 spurious interrupts. This is recommended when threaded
1084 interrupt handling is used on systems where the generation of
1085 superfluous "boot interrupts" cannot be disabled.
1087 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1088 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1089 kernel does during interrupt handling). On chipsets where this
1090 boot IRQ generation cannot be disabled, this workaround keeps
1091 the original IRQ line masked so that only the equivalent "boot
1092 IRQ" is delivered to the CPUs. The workaround also tells the
1093 kernel to set up the IRQ handler on the boot IRQ line. In this
1094 way only one interrupt is delivered to the kernel. Otherwise
1095 the spurious second interrupt may cause the kernel to bring
1096 down (vital) interrupt lines.
1098 Only affects "broken" chipsets. Interrupt sharing may be
1099 increased on these systems.
1102 bool "Machine Check / overheating reporting"
1103 select GENERIC_ALLOCATOR
1106 Machine Check support allows the processor to notify the
1107 kernel if it detects a problem (e.g. overheating, data corruption).
1108 The action the kernel takes depends on the severity of the problem,
1109 ranging from warning messages to halting the machine.
1111 config X86_MCELOG_LEGACY
1112 bool "Support for deprecated /dev/mcelog character device"
1115 Enable support for /dev/mcelog which is needed by the old mcelog
1116 userspace logging daemon. Consider switching to the new generation
1119 config X86_MCE_INTEL
1121 prompt "Intel MCE features"
1122 depends on X86_MCE && X86_LOCAL_APIC
1124 Additional support for intel specific MCE features such as
1125 the thermal monitor.
1129 prompt "AMD MCE features"
1130 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1132 Additional support for AMD specific MCE features such as
1133 the DRAM Error Threshold.
1135 config X86_ANCIENT_MCE
1136 bool "Support for old Pentium 5 / WinChip machine checks"
1137 depends on X86_32 && X86_MCE
1139 Include support for machine check handling on old Pentium 5 or WinChip
1140 systems. These typically need to be enabled explicitly on the command
1143 config X86_MCE_THRESHOLD
1144 depends on X86_MCE_AMD || X86_MCE_INTEL
1147 config X86_MCE_INJECT
1148 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1149 tristate "Machine check injector support"
1151 Provide support for injecting machine checks for testing purposes.
1152 If you don't know what a machine check is and you don't do kernel
1153 QA it is safe to say n.
1155 source "arch/x86/events/Kconfig"
1157 config X86_LEGACY_VM86
1158 bool "Legacy VM86 support"
1161 This option allows user programs to put the CPU into V8086
1162 mode, which is an 80286-era approximation of 16-bit real mode.
1164 Some very old versions of X and/or vbetool require this option
1165 for user mode setting. Similarly, DOSEMU will use it if
1166 available to accelerate real mode DOS programs. However, any
1167 recent version of DOSEMU, X, or vbetool should be fully
1168 functional even without kernel VM86 support, as they will all
1169 fall back to software emulation. Nevertheless, if you are using
1170 a 16-bit DOS program where 16-bit performance matters, vm86
1171 mode might be faster than emulation and you might want to
1174 Note that any app that works on a 64-bit kernel is unlikely to
1175 need this option, as 64-bit kernels don't, and can't, support
1176 V8086 mode. This option is also unrelated to 16-bit protected
1177 mode and is not needed to run most 16-bit programs under Wine.
1179 Enabling this option increases the complexity of the kernel
1180 and slows down exception handling a tiny bit.
1182 If unsure, say N here.
1186 default X86_LEGACY_VM86
1189 bool "Enable support for 16-bit segments" if EXPERT
1191 depends on MODIFY_LDT_SYSCALL
1193 This option is required by programs like Wine to run 16-bit
1194 protected mode legacy code on x86 processors. Disabling
1195 this option saves about 300 bytes on i386, or around 6K text
1196 plus 16K runtime memory on x86-64,
1200 depends on X86_16BIT && X86_32
1204 depends on X86_16BIT && X86_64
1206 config X86_VSYSCALL_EMULATION
1207 bool "Enable vsyscall emulation" if EXPERT
1211 This enables emulation of the legacy vsyscall page. Disabling
1212 it is roughly equivalent to booting with vsyscall=none, except
1213 that it will also disable the helpful warning if a program
1214 tries to use a vsyscall. With this option set to N, offending
1215 programs will just segfault, citing addresses of the form
1218 This option is required by many programs built before 2013, and
1219 care should be used even with newer programs if set to N.
1221 Disabling this option saves about 7K of kernel size and
1222 possibly 4K of additional runtime pagetable memory.
1224 config X86_IOPL_IOPERM
1225 bool "IOPERM and IOPL Emulation"
1228 This enables the ioperm() and iopl() syscalls which are necessary
1229 for legacy applications.
1231 Legacy IOPL support is an overbroad mechanism which allows user
1232 space aside of accessing all 65536 I/O ports also to disable
1233 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1234 capabilities and permission from potentially active security
1237 The emulation restricts the functionality of the syscall to
1238 only allowing the full range I/O port access, but prevents the
1239 ability to disable interrupts from user space which would be
1240 granted if the hardware IOPL mechanism would be used.
1243 tristate "Toshiba Laptop support"
1246 This adds a driver to safely access the System Management Mode of
1247 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1248 not work on models with a Phoenix BIOS. The System Management Mode
1249 is used to set the BIOS and power saving options on Toshiba portables.
1251 For information on utilities to make use of this driver see the
1252 Toshiba Linux utilities web site at:
1253 <http://www.buzzard.org.uk/toshiba/>.
1255 Say Y if you intend to run this kernel on a Toshiba portable.
1259 tristate "Dell i8k legacy laptop support"
1261 select SENSORS_DELL_SMM
1263 This option enables legacy /proc/i8k userspace interface in hwmon
1264 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1265 temperature and allows controlling fan speeds of Dell laptops via
1266 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1267 it reports also power and hotkey status. For fan speed control is
1268 needed userspace package i8kutils.
1270 Say Y if you intend to run this kernel on old Dell laptops or want to
1271 use userspace package i8kutils.
1274 config X86_REBOOTFIXUPS
1275 bool "Enable X86 board specific fixups for reboot"
1278 This enables chipset and/or board specific fixups to be done
1279 in order to get reboot to work correctly. This is only needed on
1280 some combinations of hardware and BIOS. The symptom, for which
1281 this config is intended, is when reboot ends with a stalled/hung
1284 Currently, the only fixup is for the Geode machines using
1285 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1287 Say Y if you want to enable the fixup. Currently, it's safe to
1288 enable this option even if you don't need it.
1292 bool "CPU microcode loading support"
1294 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1296 If you say Y here, you will be able to update the microcode on
1297 Intel and AMD processors. The Intel support is for the IA32 family,
1298 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1299 AMD support is for families 0x10 and later. You will obviously need
1300 the actual microcode binary data itself which is not shipped with
1303 The preferred method to load microcode from a detached initrd is described
1304 in Documentation/x86/microcode.rst. For that you need to enable
1305 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1306 initrd for microcode blobs.
1308 In addition, you can build the microcode into the kernel. For that you
1309 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1312 config MICROCODE_INTEL
1313 bool "Intel microcode loading support"
1314 depends on MICROCODE
1317 This options enables microcode patch loading support for Intel
1320 For the current Intel microcode data package go to
1321 <https://downloadcenter.intel.com> and search for
1322 'Linux Processor Microcode Data File'.
1324 config MICROCODE_AMD
1325 bool "AMD microcode loading support"
1326 depends on MICROCODE
1328 If you select this option, microcode patch loading support for AMD
1329 processors will be enabled.
1331 config MICROCODE_OLD_INTERFACE
1332 bool "Ancient loading interface (DEPRECATED)"
1334 depends on MICROCODE
1336 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1337 which was used by userspace tools like iucode_tool and microcode.ctl.
1338 It is inadequate because it runs too late to be able to properly
1339 load microcode on a machine and it needs special tools. Instead, you
1340 should've switched to the early loading method with the initrd or
1341 builtin microcode by now: Documentation/x86/microcode.rst
1344 tristate "/dev/cpu/*/msr - Model-specific register support"
1346 This device gives privileged processes access to the x86
1347 Model-Specific Registers (MSRs). It is a character device with
1348 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1349 MSR accesses are directed to a specific CPU on multi-processor
1353 tristate "/dev/cpu/*/cpuid - CPU information support"
1355 This device gives processes access to the x86 CPUID instruction to
1356 be executed on a specific processor. It is a character device
1357 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1361 prompt "High Memory Support"
1368 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1369 However, the address space of 32-bit x86 processors is only 4
1370 Gigabytes large. That means that, if you have a large amount of
1371 physical memory, not all of it can be "permanently mapped" by the
1372 kernel. The physical memory that's not permanently mapped is called
1375 If you are compiling a kernel which will never run on a machine with
1376 more than 1 Gigabyte total physical RAM, answer "off" here (default
1377 choice and suitable for most users). This will result in a "3GB/1GB"
1378 split: 3GB are mapped so that each process sees a 3GB virtual memory
1379 space and the remaining part of the 4GB virtual memory space is used
1380 by the kernel to permanently map as much physical memory as
1383 If the machine has between 1 and 4 Gigabytes physical RAM, then
1386 If more than 4 Gigabytes is used then answer "64GB" here. This
1387 selection turns Intel PAE (Physical Address Extension) mode on.
1388 PAE implements 3-level paging on IA32 processors. PAE is fully
1389 supported by Linux, PAE mode is implemented on all recent Intel
1390 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1391 then the kernel will not boot on CPUs that don't support PAE!
1393 The actual amount of total physical memory will either be
1394 auto detected or can be forced by using a kernel command line option
1395 such as "mem=256M". (Try "man bootparam" or see the documentation of
1396 your boot loader (lilo or loadlin) about how to pass options to the
1397 kernel at boot time.)
1399 If unsure, say "off".
1404 Select this if you have a 32-bit processor and between 1 and 4
1405 gigabytes of physical RAM.
1409 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1412 Select this if you have a 32-bit processor and more than 4
1413 gigabytes of physical RAM.
1418 prompt "Memory split" if EXPERT
1422 Select the desired split between kernel and user memory.
1424 If the address range available to the kernel is less than the
1425 physical memory installed, the remaining memory will be available
1426 as "high memory". Accessing high memory is a little more costly
1427 than low memory, as it needs to be mapped into the kernel first.
1428 Note that increasing the kernel address space limits the range
1429 available to user programs, making the address space there
1430 tighter. Selecting anything other than the default 3G/1G split
1431 will also likely make your kernel incompatible with binary-only
1434 If you are not absolutely sure what you are doing, leave this
1438 bool "3G/1G user/kernel split"
1439 config VMSPLIT_3G_OPT
1441 bool "3G/1G user/kernel split (for full 1G low memory)"
1443 bool "2G/2G user/kernel split"
1444 config VMSPLIT_2G_OPT
1446 bool "2G/2G user/kernel split (for full 2G low memory)"
1448 bool "1G/3G user/kernel split"
1453 default 0xB0000000 if VMSPLIT_3G_OPT
1454 default 0x80000000 if VMSPLIT_2G
1455 default 0x78000000 if VMSPLIT_2G_OPT
1456 default 0x40000000 if VMSPLIT_1G
1462 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1465 bool "PAE (Physical Address Extension) Support"
1466 depends on X86_32 && !HIGHMEM4G
1467 select PHYS_ADDR_T_64BIT
1470 PAE is required for NX support, and furthermore enables
1471 larger swapspace support for non-overcommit purposes. It
1472 has the cost of more pagetable lookup overhead, and also
1473 consumes more pagetable space per process.
1476 bool "Enable 5-level page tables support"
1478 select DYNAMIC_MEMORY_LAYOUT
1479 select SPARSEMEM_VMEMMAP
1482 5-level paging enables access to larger address space:
1483 upto 128 PiB of virtual address space and 4 PiB of
1484 physical address space.
1486 It will be supported by future Intel CPUs.
1488 A kernel with the option enabled can be booted on machines that
1489 support 4- or 5-level paging.
1491 See Documentation/x86/x86_64/5level-paging.rst for more
1496 config X86_DIRECT_GBPAGES
1500 Certain kernel features effectively disable kernel
1501 linear 1 GB mappings (even if the CPU otherwise
1502 supports them), so don't confuse the user by printing
1503 that we have them enabled.
1505 config X86_CPA_STATISTICS
1506 bool "Enable statistic for Change Page Attribute"
1509 Expose statistics about the Change Page Attribute mechanism, which
1510 helps to determine the effectiveness of preserving large and huge
1511 page mappings when mapping protections are changed.
1513 config AMD_MEM_ENCRYPT
1514 bool "AMD Secure Memory Encryption (SME) support"
1515 depends on X86_64 && CPU_SUP_AMD
1516 select DMA_COHERENT_POOL
1517 select DYNAMIC_PHYSICAL_MASK
1518 select ARCH_USE_MEMREMAP_PROT
1519 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1520 select INSTRUCTION_DECODER
1522 Say yes to enable support for the encryption of system memory.
1523 This requires an AMD processor that supports Secure Memory
1526 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1527 bool "Activate AMD Secure Memory Encryption (SME) by default"
1529 depends on AMD_MEM_ENCRYPT
1531 Say yes to have system memory encrypted by default if running on
1532 an AMD processor that supports Secure Memory Encryption (SME).
1534 If set to Y, then the encryption of system memory can be
1535 deactivated with the mem_encrypt=off command line option.
1537 If set to N, then the encryption of system memory can be
1538 activated with the mem_encrypt=on command line option.
1540 # Common NUMA Features
1542 bool "NUMA Memory Allocation and Scheduler Support"
1544 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1545 default y if X86_BIGSMP
1547 Enable NUMA (Non-Uniform Memory Access) support.
1549 The kernel will try to allocate memory used by a CPU on the
1550 local memory controller of the CPU and add some more
1551 NUMA awareness to the kernel.
1553 For 64-bit this is recommended if the system is Intel Core i7
1554 (or later), AMD Opteron, or EM64T NUMA.
1556 For 32-bit this is only needed if you boot a 32-bit
1557 kernel on a 64-bit NUMA platform.
1559 Otherwise, you should say N.
1563 prompt "Old style AMD Opteron NUMA detection"
1564 depends on X86_64 && NUMA && PCI
1566 Enable AMD NUMA node topology detection. You should say Y here if
1567 you have a multi processor AMD system. This uses an old method to
1568 read the NUMA configuration directly from the builtin Northbridge
1569 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1570 which also takes priority if both are compiled in.
1572 config X86_64_ACPI_NUMA
1574 prompt "ACPI NUMA detection"
1575 depends on X86_64 && NUMA && ACPI && PCI
1578 Enable ACPI SRAT based node topology detection.
1581 bool "NUMA emulation"
1584 Enable NUMA emulation. A flat machine will be split
1585 into virtual nodes when booted with "numa=fake=N", where N is the
1586 number of nodes. This is only useful for debugging.
1589 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1591 default "10" if MAXSMP
1592 default "6" if X86_64
1594 depends on NEED_MULTIPLE_NODES
1596 Specify the maximum number of NUMA Nodes available on the target
1597 system. Increases memory reserved to accommodate various tables.
1599 config ARCH_FLATMEM_ENABLE
1601 depends on X86_32 && !NUMA
1603 config ARCH_SPARSEMEM_ENABLE
1605 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1606 select SPARSEMEM_STATIC if X86_32
1607 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1609 config ARCH_SPARSEMEM_DEFAULT
1610 def_bool X86_64 || (NUMA && X86_32)
1612 config ARCH_SELECT_MEMORY_MODEL
1614 depends on ARCH_SPARSEMEM_ENABLE
1616 config ARCH_MEMORY_PROBE
1617 bool "Enable sysfs memory/probe interface"
1618 depends on X86_64 && MEMORY_HOTPLUG
1620 This option enables a sysfs memory/probe interface for testing.
1621 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1622 If you are unsure how to answer this question, answer N.
1624 config ARCH_PROC_KCORE_TEXT
1626 depends on X86_64 && PROC_KCORE
1628 config ILLEGAL_POINTER_VALUE
1631 default 0xdead000000000000 if X86_64
1633 config X86_PMEM_LEGACY_DEVICE
1636 config X86_PMEM_LEGACY
1637 tristate "Support non-standard NVDIMMs and ADR protected memory"
1638 depends on PHYS_ADDR_T_64BIT
1640 select X86_PMEM_LEGACY_DEVICE
1641 select NUMA_KEEP_MEMINFO if NUMA
1644 Treat memory marked using the non-standard e820 type of 12 as used
1645 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1646 The kernel will offer these regions to the 'pmem' driver so
1647 they can be used for persistent storage.
1652 bool "Allocate 3rd-level pagetables from highmem"
1655 The VM uses one page table entry for each page of physical memory.
1656 For systems with a lot of RAM, this can be wasteful of precious
1657 low memory. Setting this option will put user-space page table
1658 entries in high memory.
1660 config X86_CHECK_BIOS_CORRUPTION
1661 bool "Check for low memory corruption"
1663 Periodically check for memory corruption in low memory, which
1664 is suspected to be caused by BIOS. Even when enabled in the
1665 configuration, it is disabled at runtime. Enable it by
1666 setting "memory_corruption_check=1" on the kernel command
1667 line. By default it scans the low 64k of memory every 60
1668 seconds; see the memory_corruption_check_size and
1669 memory_corruption_check_period parameters in
1670 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1672 When enabled with the default parameters, this option has
1673 almost no overhead, as it reserves a relatively small amount
1674 of memory and scans it infrequently. It both detects corruption
1675 and prevents it from affecting the running system.
1677 It is, however, intended as a diagnostic tool; if repeatable
1678 BIOS-originated corruption always affects the same memory,
1679 you can use memmap= to prevent the kernel from using that
1682 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1683 bool "Set the default setting of memory_corruption_check"
1684 depends on X86_CHECK_BIOS_CORRUPTION
1687 Set whether the default state of memory_corruption_check is
1690 config X86_RESERVE_LOW
1691 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1695 Specify the amount of low memory to reserve for the BIOS.
1697 The first page contains BIOS data structures that the kernel
1698 must not use, so that page must always be reserved.
1700 By default we reserve the first 64K of physical RAM, as a
1701 number of BIOSes are known to corrupt that memory range
1702 during events such as suspend/resume or monitor cable
1703 insertion, so it must not be used by the kernel.
1705 You can set this to 4 if you are absolutely sure that you
1706 trust the BIOS to get all its memory reservations and usages
1707 right. If you know your BIOS have problems beyond the
1708 default 64K area, you can set this to 640 to avoid using the
1709 entire low memory range.
1711 If you have doubts about the BIOS (e.g. suspend/resume does
1712 not work or there's kernel crashes after certain hardware
1713 hotplug events) then you might want to enable
1714 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1715 typical corruption patterns.
1717 Leave this to the default value of 64 if you are unsure.
1719 config MATH_EMULATION
1721 depends on MODIFY_LDT_SYSCALL
1722 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1724 Linux can emulate a math coprocessor (used for floating point
1725 operations) if you don't have one. 486DX and Pentium processors have
1726 a math coprocessor built in, 486SX and 386 do not, unless you added
1727 a 487DX or 387, respectively. (The messages during boot time can
1728 give you some hints here ["man dmesg"].) Everyone needs either a
1729 coprocessor or this emulation.
1731 If you don't have a math coprocessor, you need to say Y here; if you
1732 say Y here even though you have a coprocessor, the coprocessor will
1733 be used nevertheless. (This behavior can be changed with the kernel
1734 command line option "no387", which comes handy if your coprocessor
1735 is broken. Try "man bootparam" or see the documentation of your boot
1736 loader (lilo or loadlin) about how to pass options to the kernel at
1737 boot time.) This means that it is a good idea to say Y here if you
1738 intend to use this kernel on different machines.
1740 More information about the internals of the Linux math coprocessor
1741 emulation can be found in <file:arch/x86/math-emu/README>.
1743 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1744 kernel, it won't hurt.
1748 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1750 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1751 the Memory Type Range Registers (MTRRs) may be used to control
1752 processor access to memory ranges. This is most useful if you have
1753 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1754 allows bus write transfers to be combined into a larger transfer
1755 before bursting over the PCI/AGP bus. This can increase performance
1756 of image write operations 2.5 times or more. Saying Y here creates a
1757 /proc/mtrr file which may be used to manipulate your processor's
1758 MTRRs. Typically the X server should use this.
1760 This code has a reasonably generic interface so that similar
1761 control registers on other processors can be easily supported
1764 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1765 Registers (ARRs) which provide a similar functionality to MTRRs. For
1766 these, the ARRs are used to emulate the MTRRs.
1767 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1768 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1769 write-combining. All of these processors are supported by this code
1770 and it makes sense to say Y here if you have one of them.
1772 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1773 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1774 can lead to all sorts of problems, so it's good to say Y here.
1776 You can safely say Y even if your machine doesn't have MTRRs, you'll
1777 just add about 9 KB to your kernel.
1779 See <file:Documentation/x86/mtrr.rst> for more information.
1781 config MTRR_SANITIZER
1783 prompt "MTRR cleanup support"
1786 Convert MTRR layout from continuous to discrete, so X drivers can
1787 add writeback entries.
1789 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1790 The largest mtrr entry size for a continuous block can be set with
1795 config MTRR_SANITIZER_ENABLE_DEFAULT
1796 int "MTRR cleanup enable value (0-1)"
1799 depends on MTRR_SANITIZER
1801 Enable mtrr cleanup default value
1803 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1804 int "MTRR cleanup spare reg num (0-7)"
1807 depends on MTRR_SANITIZER
1809 mtrr cleanup spare entries default, it can be changed via
1810 mtrr_spare_reg_nr=N on the kernel command line.
1814 prompt "x86 PAT support" if EXPERT
1817 Use PAT attributes to setup page level cache control.
1819 PATs are the modern equivalents of MTRRs and are much more
1820 flexible than MTRRs.
1822 Say N here if you see bootup problems (boot crash, boot hang,
1823 spontaneous reboots) or a non-working video driver.
1827 config ARCH_USES_PG_UNCACHED
1833 prompt "x86 architectural random number generator" if EXPERT
1835 Enable the x86 architectural RDRAND instruction
1836 (Intel Bull Mountain technology) to generate random numbers.
1837 If supported, this is a high bandwidth, cryptographically
1838 secure hardware random number generator.
1842 prompt "Supervisor Mode Access Prevention" if EXPERT
1844 Supervisor Mode Access Prevention (SMAP) is a security
1845 feature in newer Intel processors. There is a small
1846 performance cost if this enabled and turned on; there is
1847 also a small increase in the kernel size if this is enabled.
1853 prompt "User Mode Instruction Prevention" if EXPERT
1855 User Mode Instruction Prevention (UMIP) is a security feature in
1856 some x86 processors. If enabled, a general protection fault is
1857 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1858 executed in user mode. These instructions unnecessarily expose
1859 information about the hardware state.
1861 The vast majority of applications do not use these instructions.
1862 For the very few that do, software emulation is provided in
1863 specific cases in protected and virtual-8086 modes. Emulated
1866 config X86_INTEL_MEMORY_PROTECTION_KEYS
1867 prompt "Memory Protection Keys"
1869 # Note: only available in 64-bit mode
1870 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1871 select ARCH_USES_HIGH_VMA_FLAGS
1872 select ARCH_HAS_PKEYS
1874 Memory Protection Keys provides a mechanism for enforcing
1875 page-based protections, but without requiring modification of the
1876 page tables when an application changes protection domains.
1878 For details, see Documentation/core-api/protection-keys.rst
1883 prompt "TSX enable mode"
1884 depends on CPU_SUP_INTEL
1885 default X86_INTEL_TSX_MODE_OFF
1887 Intel's TSX (Transactional Synchronization Extensions) feature
1888 allows to optimize locking protocols through lock elision which
1889 can lead to a noticeable performance boost.
1891 On the other hand it has been shown that TSX can be exploited
1892 to form side channel attacks (e.g. TAA) and chances are there
1893 will be more of those attacks discovered in the future.
1895 Therefore TSX is not enabled by default (aka tsx=off). An admin
1896 might override this decision by tsx=on the command line parameter.
1897 Even with TSX enabled, the kernel will attempt to enable the best
1898 possible TAA mitigation setting depending on the microcode available
1899 for the particular machine.
1901 This option allows to set the default tsx mode between tsx=on, =off
1902 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1905 Say off if not sure, auto if TSX is in use but it should be used on safe
1906 platforms or on if TSX is in use and the security aspect of tsx is not
1909 config X86_INTEL_TSX_MODE_OFF
1912 TSX is disabled if possible - equals to tsx=off command line parameter.
1914 config X86_INTEL_TSX_MODE_ON
1917 TSX is always enabled on TSX capable HW - equals the tsx=on command
1920 config X86_INTEL_TSX_MODE_AUTO
1923 TSX is enabled on TSX capable HW that is believed to be safe against
1924 side channel attacks- equals the tsx=auto command line parameter.
1928 bool "Software Guard eXtensions (SGX)"
1929 depends on X86_64 && CPU_SUP_INTEL
1931 depends on CRYPTO_SHA256=y
1935 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1936 that can be used by applications to set aside private regions of code
1937 and data, referred to as enclaves. An enclave's private memory can
1938 only be accessed by code running within the enclave. Accesses from
1939 outside the enclave, including other enclaves, are disallowed by
1945 bool "EFI runtime service support"
1948 select EFI_RUNTIME_WRAPPERS
1950 This enables the kernel to use EFI runtime services that are
1951 available (such as the EFI variable services).
1953 This option is only useful on systems that have EFI firmware.
1954 In addition, you should use the latest ELILO loader available
1955 at <http://elilo.sourceforge.net> in order to take advantage
1956 of EFI runtime services. However, even with this option, the
1957 resultant kernel should continue to boot on existing non-EFI
1961 bool "EFI stub support"
1962 depends on EFI && !X86_USE_3DNOW
1963 depends on $(cc-option,-mabi=ms) || X86_32
1966 This kernel feature allows a bzImage to be loaded directly
1967 by EFI firmware without the use of a bootloader.
1969 See Documentation/admin-guide/efi-stub.rst for more information.
1972 bool "EFI mixed-mode support"
1973 depends on EFI_STUB && X86_64
1975 Enabling this feature allows a 64-bit kernel to be booted
1976 on a 32-bit firmware, provided that your CPU supports 64-bit
1979 Note that it is not possible to boot a mixed-mode enabled
1980 kernel via the EFI boot stub - a bootloader that supports
1981 the EFI handover protocol must be used.
1985 source "kernel/Kconfig.hz"
1988 bool "kexec system call"
1991 kexec is a system call that implements the ability to shutdown your
1992 current kernel, and to start another kernel. It is like a reboot
1993 but it is independent of the system firmware. And like a reboot
1994 you can start any kernel with it, not just Linux.
1996 The name comes from the similarity to the exec system call.
1998 It is an ongoing process to be certain the hardware in a machine
1999 is properly shutdown, so do not be surprised if this code does not
2000 initially work for you. As of this writing the exact hardware
2001 interface is strongly in flux, so no good recommendation can be
2005 bool "kexec file based system call"
2010 depends on CRYPTO_SHA256=y
2012 This is new version of kexec system call. This system call is
2013 file based and takes file descriptors as system call argument
2014 for kernel and initramfs as opposed to list of segments as
2015 accepted by previous system call.
2017 config ARCH_HAS_KEXEC_PURGATORY
2021 bool "Verify kernel signature during kexec_file_load() syscall"
2022 depends on KEXEC_FILE
2025 This option makes the kexec_file_load() syscall check for a valid
2026 signature of the kernel image. The image can still be loaded without
2027 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2028 there's a signature that we can check, then it must be valid.
2030 In addition to this option, you need to enable signature
2031 verification for the corresponding kernel image type being
2032 loaded in order for this to work.
2034 config KEXEC_SIG_FORCE
2035 bool "Require a valid signature in kexec_file_load() syscall"
2036 depends on KEXEC_SIG
2038 This option makes kernel signature verification mandatory for
2039 the kexec_file_load() syscall.
2041 config KEXEC_BZIMAGE_VERIFY_SIG
2042 bool "Enable bzImage signature verification support"
2043 depends on KEXEC_SIG
2044 depends on SIGNED_PE_FILE_VERIFICATION
2045 select SYSTEM_TRUSTED_KEYRING
2047 Enable bzImage signature verification support.
2050 bool "kernel crash dumps"
2051 depends on X86_64 || (X86_32 && HIGHMEM)
2053 Generate crash dump after being started by kexec.
2054 This should be normally only set in special crash dump kernels
2055 which are loaded in the main kernel with kexec-tools into
2056 a specially reserved region and then later executed after
2057 a crash by kdump/kexec. The crash dump kernel must be compiled
2058 to a memory address not used by the main kernel or BIOS using
2059 PHYSICAL_START, or it must be built as a relocatable image
2060 (CONFIG_RELOCATABLE=y).
2061 For more details see Documentation/admin-guide/kdump/kdump.rst
2065 depends on KEXEC && HIBERNATION
2067 Jump between original kernel and kexeced kernel and invoke
2068 code in physical address mode via KEXEC
2070 config PHYSICAL_START
2071 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2074 This gives the physical address where the kernel is loaded.
2076 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2077 bzImage will decompress itself to above physical address and
2078 run from there. Otherwise, bzImage will run from the address where
2079 it has been loaded by the boot loader and will ignore above physical
2082 In normal kdump cases one does not have to set/change this option
2083 as now bzImage can be compiled as a completely relocatable image
2084 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2085 address. This option is mainly useful for the folks who don't want
2086 to use a bzImage for capturing the crash dump and want to use a
2087 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2088 to be specifically compiled to run from a specific memory area
2089 (normally a reserved region) and this option comes handy.
2091 So if you are using bzImage for capturing the crash dump,
2092 leave the value here unchanged to 0x1000000 and set
2093 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2094 for capturing the crash dump change this value to start of
2095 the reserved region. In other words, it can be set based on
2096 the "X" value as specified in the "crashkernel=YM@XM"
2097 command line boot parameter passed to the panic-ed
2098 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2099 for more details about crash dumps.
2101 Usage of bzImage for capturing the crash dump is recommended as
2102 one does not have to build two kernels. Same kernel can be used
2103 as production kernel and capture kernel. Above option should have
2104 gone away after relocatable bzImage support is introduced. But it
2105 is present because there are users out there who continue to use
2106 vmlinux for dump capture. This option should go away down the
2109 Don't change this unless you know what you are doing.
2112 bool "Build a relocatable kernel"
2115 This builds a kernel image that retains relocation information
2116 so it can be loaded someplace besides the default 1MB.
2117 The relocations tend to make the kernel binary about 10% larger,
2118 but are discarded at runtime.
2120 One use is for the kexec on panic case where the recovery kernel
2121 must live at a different physical address than the primary
2124 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2125 it has been loaded at and the compile time physical address
2126 (CONFIG_PHYSICAL_START) is used as the minimum location.
2128 config RANDOMIZE_BASE
2129 bool "Randomize the address of the kernel image (KASLR)"
2130 depends on RELOCATABLE
2133 In support of Kernel Address Space Layout Randomization (KASLR),
2134 this randomizes the physical address at which the kernel image
2135 is decompressed and the virtual address where the kernel
2136 image is mapped, as a security feature that deters exploit
2137 attempts relying on knowledge of the location of kernel
2140 On 64-bit, the kernel physical and virtual addresses are
2141 randomized separately. The physical address will be anywhere
2142 between 16MB and the top of physical memory (up to 64TB). The
2143 virtual address will be randomized from 16MB up to 1GB (9 bits
2144 of entropy). Note that this also reduces the memory space
2145 available to kernel modules from 1.5GB to 1GB.
2147 On 32-bit, the kernel physical and virtual addresses are
2148 randomized together. They will be randomized from 16MB up to
2149 512MB (8 bits of entropy).
2151 Entropy is generated using the RDRAND instruction if it is
2152 supported. If RDTSC is supported, its value is mixed into
2153 the entropy pool as well. If neither RDRAND nor RDTSC are
2154 supported, then entropy is read from the i8254 timer. The
2155 usable entropy is limited by the kernel being built using
2156 2GB addressing, and that PHYSICAL_ALIGN must be at a
2157 minimum of 2MB. As a result, only 10 bits of entropy are
2158 theoretically possible, but the implementations are further
2159 limited due to memory layouts.
2163 # Relocation on x86 needs some additional build support
2164 config X86_NEED_RELOCS
2166 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2168 config PHYSICAL_ALIGN
2169 hex "Alignment value to which kernel should be aligned"
2171 range 0x2000 0x1000000 if X86_32
2172 range 0x200000 0x1000000 if X86_64
2174 This value puts the alignment restrictions on physical address
2175 where kernel is loaded and run from. Kernel is compiled for an
2176 address which meets above alignment restriction.
2178 If bootloader loads the kernel at a non-aligned address and
2179 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2180 address aligned to above value and run from there.
2182 If bootloader loads the kernel at a non-aligned address and
2183 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2184 load address and decompress itself to the address it has been
2185 compiled for and run from there. The address for which kernel is
2186 compiled already meets above alignment restrictions. Hence the
2187 end result is that kernel runs from a physical address meeting
2188 above alignment restrictions.
2190 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2191 this value must be a multiple of 0x200000.
2193 Don't change this unless you know what you are doing.
2195 config DYNAMIC_MEMORY_LAYOUT
2198 This option makes base addresses of vmalloc and vmemmap as well as
2199 __PAGE_OFFSET movable during boot.
2201 config RANDOMIZE_MEMORY
2202 bool "Randomize the kernel memory sections"
2204 depends on RANDOMIZE_BASE
2205 select DYNAMIC_MEMORY_LAYOUT
2206 default RANDOMIZE_BASE
2208 Randomizes the base virtual address of kernel memory sections
2209 (physical memory mapping, vmalloc & vmemmap). This security feature
2210 makes exploits relying on predictable memory locations less reliable.
2212 The order of allocations remains unchanged. Entropy is generated in
2213 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2214 configuration have in average 30,000 different possible virtual
2215 addresses for each memory section.
2219 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2220 hex "Physical memory mapping padding" if EXPERT
2221 depends on RANDOMIZE_MEMORY
2222 default "0xa" if MEMORY_HOTPLUG
2224 range 0x1 0x40 if MEMORY_HOTPLUG
2227 Define the padding in terabytes added to the existing physical
2228 memory size during kernel memory randomization. It is useful
2229 for memory hotplug support but reduces the entropy available for
2230 address randomization.
2232 If unsure, leave at the default value.
2238 config BOOTPARAM_HOTPLUG_CPU0
2239 bool "Set default setting of cpu0_hotpluggable"
2240 depends on HOTPLUG_CPU
2242 Set whether default state of cpu0_hotpluggable is on or off.
2244 Say Y here to enable CPU0 hotplug by default. If this switch
2245 is turned on, there is no need to give cpu0_hotplug kernel
2246 parameter and the CPU0 hotplug feature is enabled by default.
2248 Please note: there are two known CPU0 dependencies if you want
2249 to enable the CPU0 hotplug feature either by this switch or by
2250 cpu0_hotplug kernel parameter.
2252 First, resume from hibernate or suspend always starts from CPU0.
2253 So hibernate and suspend are prevented if CPU0 is offline.
2255 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2256 offline if any interrupt can not migrate out of CPU0. There may
2257 be other CPU0 dependencies.
2259 Please make sure the dependencies are under your control before
2260 you enable this feature.
2262 Say N if you don't want to enable CPU0 hotplug feature by default.
2263 You still can enable the CPU0 hotplug feature at boot by kernel
2264 parameter cpu0_hotplug.
2266 config DEBUG_HOTPLUG_CPU0
2268 prompt "Debug CPU0 hotplug"
2269 depends on HOTPLUG_CPU
2271 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2272 soon as possible and boots up userspace with CPU0 offlined. User
2273 can online CPU0 back after boot time.
2275 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2276 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2277 compilation or giving cpu0_hotplug kernel parameter at boot.
2283 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2284 depends on COMPAT_32
2286 Certain buggy versions of glibc will crash if they are
2287 presented with a 32-bit vDSO that is not mapped at the address
2288 indicated in its segment table.
2290 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2291 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2292 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2293 the only released version with the bug, but OpenSUSE 9
2294 contains a buggy "glibc 2.3.2".
2296 The symptom of the bug is that everything crashes on startup, saying:
2297 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2299 Saying Y here changes the default value of the vdso32 boot
2300 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2301 This works around the glibc bug but hurts performance.
2303 If unsure, say N: if you are compiling your own kernel, you
2304 are unlikely to be using a buggy version of glibc.
2307 prompt "vsyscall table for legacy applications"
2309 default LEGACY_VSYSCALL_XONLY
2311 Legacy user code that does not know how to find the vDSO expects
2312 to be able to issue three syscalls by calling fixed addresses in
2313 kernel space. Since this location is not randomized with ASLR,
2314 it can be used to assist security vulnerability exploitation.
2316 This setting can be changed at boot time via the kernel command
2317 line parameter vsyscall=[emulate|xonly|none].
2319 On a system with recent enough glibc (2.14 or newer) and no
2320 static binaries, you can say None without a performance penalty
2321 to improve security.
2323 If unsure, select "Emulate execution only".
2325 config LEGACY_VSYSCALL_EMULATE
2326 bool "Full emulation"
2328 The kernel traps and emulates calls into the fixed vsyscall
2329 address mapping. This makes the mapping non-executable, but
2330 it still contains readable known contents, which could be
2331 used in certain rare security vulnerability exploits. This
2332 configuration is recommended when using legacy userspace
2333 that still uses vsyscalls along with legacy binary
2334 instrumentation tools that require code to be readable.
2336 An example of this type of legacy userspace is running
2337 Pin on an old binary that still uses vsyscalls.
2339 config LEGACY_VSYSCALL_XONLY
2340 bool "Emulate execution only"
2342 The kernel traps and emulates calls into the fixed vsyscall
2343 address mapping and does not allow reads. This
2344 configuration is recommended when userspace might use the
2345 legacy vsyscall area but support for legacy binary
2346 instrumentation of legacy code is not needed. It mitigates
2347 certain uses of the vsyscall area as an ASLR-bypassing
2350 config LEGACY_VSYSCALL_NONE
2353 There will be no vsyscall mapping at all. This will
2354 eliminate any risk of ASLR bypass due to the vsyscall
2355 fixed address mapping. Attempts to use the vsyscalls
2356 will be reported to dmesg, so that either old or
2357 malicious userspace programs can be identified.
2362 bool "Built-in kernel command line"
2364 Allow for specifying boot arguments to the kernel at
2365 build time. On some systems (e.g. embedded ones), it is
2366 necessary or convenient to provide some or all of the
2367 kernel boot arguments with the kernel itself (that is,
2368 to not rely on the boot loader to provide them.)
2370 To compile command line arguments into the kernel,
2371 set this option to 'Y', then fill in the
2372 boot arguments in CONFIG_CMDLINE.
2374 Systems with fully functional boot loaders (i.e. non-embedded)
2375 should leave this option set to 'N'.
2378 string "Built-in kernel command string"
2379 depends on CMDLINE_BOOL
2382 Enter arguments here that should be compiled into the kernel
2383 image and used at boot time. If the boot loader provides a
2384 command line at boot time, it is appended to this string to
2385 form the full kernel command line, when the system boots.
2387 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2388 change this behavior.
2390 In most cases, the command line (whether built-in or provided
2391 by the boot loader) should specify the device for the root
2394 config CMDLINE_OVERRIDE
2395 bool "Built-in command line overrides boot loader arguments"
2396 depends on CMDLINE_BOOL && CMDLINE != ""
2398 Set this option to 'Y' to have the kernel ignore the boot loader
2399 command line, and use ONLY the built-in command line.
2401 This is used to work around broken boot loaders. This should
2402 be set to 'N' under normal conditions.
2404 config MODIFY_LDT_SYSCALL
2405 bool "Enable the LDT (local descriptor table)" if EXPERT
2408 Linux can allow user programs to install a per-process x86
2409 Local Descriptor Table (LDT) using the modify_ldt(2) system
2410 call. This is required to run 16-bit or segmented code such as
2411 DOSEMU or some Wine programs. It is also used by some very old
2412 threading libraries.
2414 Enabling this feature adds a small amount of overhead to
2415 context switches and increases the low-level kernel attack
2416 surface. Disabling it removes the modify_ldt(2) system call.
2418 Saying 'N' here may make sense for embedded or server kernels.
2420 source "kernel/livepatch/Kconfig"
2424 config ARCH_HAS_ADD_PAGES
2426 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2428 config ARCH_ENABLE_MEMORY_HOTPLUG
2430 depends on X86_64 || (X86_32 && HIGHMEM)
2432 config ARCH_ENABLE_MEMORY_HOTREMOVE
2434 depends on MEMORY_HOTPLUG
2436 config USE_PERCPU_NUMA_NODE_ID
2440 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2442 depends on X86_64 || X86_PAE
2444 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2446 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2448 config ARCH_ENABLE_THP_MIGRATION
2450 depends on X86_64 && TRANSPARENT_HUGEPAGE
2452 menu "Power management and ACPI options"
2454 config ARCH_HIBERNATION_HEADER
2456 depends on HIBERNATION
2458 source "kernel/power/Kconfig"
2460 source "drivers/acpi/Kconfig"
2467 tristate "APM (Advanced Power Management) BIOS support"
2468 depends on X86_32 && PM_SLEEP
2470 APM is a BIOS specification for saving power using several different
2471 techniques. This is mostly useful for battery powered laptops with
2472 APM compliant BIOSes. If you say Y here, the system time will be
2473 reset after a RESUME operation, the /proc/apm device will provide
2474 battery status information, and user-space programs will receive
2475 notification of APM "events" (e.g. battery status change).
2477 If you select "Y" here, you can disable actual use of the APM
2478 BIOS by passing the "apm=off" option to the kernel at boot time.
2480 Note that the APM support is almost completely disabled for
2481 machines with more than one CPU.
2483 In order to use APM, you will need supporting software. For location
2484 and more information, read <file:Documentation/power/apm-acpi.rst>
2485 and the Battery Powered Linux mini-HOWTO, available from
2486 <http://www.tldp.org/docs.html#howto>.
2488 This driver does not spin down disk drives (see the hdparm(8)
2489 manpage ("man 8 hdparm") for that), and it doesn't turn off
2490 VESA-compliant "green" monitors.
2492 This driver does not support the TI 4000M TravelMate and the ACER
2493 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2494 desktop machines also don't have compliant BIOSes, and this driver
2495 may cause those machines to panic during the boot phase.
2497 Generally, if you don't have a battery in your machine, there isn't
2498 much point in using this driver and you should say N. If you get
2499 random kernel OOPSes or reboots that don't seem to be related to
2500 anything, try disabling/enabling this option (or disabling/enabling
2503 Some other things you should try when experiencing seemingly random,
2506 1) make sure that you have enough swap space and that it is
2508 2) pass the "no-hlt" option to the kernel
2509 3) switch on floating point emulation in the kernel and pass
2510 the "no387" option to the kernel
2511 4) pass the "floppy=nodma" option to the kernel
2512 5) pass the "mem=4M" option to the kernel (thereby disabling
2513 all but the first 4 MB of RAM)
2514 6) make sure that the CPU is not over clocked.
2515 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2516 8) disable the cache from your BIOS settings
2517 9) install a fan for the video card or exchange video RAM
2518 10) install a better fan for the CPU
2519 11) exchange RAM chips
2520 12) exchange the motherboard.
2522 To compile this driver as a module, choose M here: the
2523 module will be called apm.
2527 config APM_IGNORE_USER_SUSPEND
2528 bool "Ignore USER SUSPEND"
2530 This option will ignore USER SUSPEND requests. On machines with a
2531 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2532 series notebooks, it is necessary to say Y because of a BIOS bug.
2534 config APM_DO_ENABLE
2535 bool "Enable PM at boot time"
2537 Enable APM features at boot time. From page 36 of the APM BIOS
2538 specification: "When disabled, the APM BIOS does not automatically
2539 power manage devices, enter the Standby State, enter the Suspend
2540 State, or take power saving steps in response to CPU Idle calls."
2541 This driver will make CPU Idle calls when Linux is idle (unless this
2542 feature is turned off -- see "Do CPU IDLE calls", below). This
2543 should always save battery power, but more complicated APM features
2544 will be dependent on your BIOS implementation. You may need to turn
2545 this option off if your computer hangs at boot time when using APM
2546 support, or if it beeps continuously instead of suspending. Turn
2547 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2548 T400CDT. This is off by default since most machines do fine without
2553 bool "Make CPU Idle calls when idle"
2555 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2556 On some machines, this can activate improved power savings, such as
2557 a slowed CPU clock rate, when the machine is idle. These idle calls
2558 are made after the idle loop has run for some length of time (e.g.,
2559 333 mS). On some machines, this will cause a hang at boot time or
2560 whenever the CPU becomes idle. (On machines with more than one CPU,
2561 this option does nothing.)
2563 config APM_DISPLAY_BLANK
2564 bool "Enable console blanking using APM"
2566 Enable console blanking using the APM. Some laptops can use this to
2567 turn off the LCD backlight when the screen blanker of the Linux
2568 virtual console blanks the screen. Note that this is only used by
2569 the virtual console screen blanker, and won't turn off the backlight
2570 when using the X Window system. This also doesn't have anything to
2571 do with your VESA-compliant power-saving monitor. Further, this
2572 option doesn't work for all laptops -- it might not turn off your
2573 backlight at all, or it might print a lot of errors to the console,
2574 especially if you are using gpm.
2576 config APM_ALLOW_INTS
2577 bool "Allow interrupts during APM BIOS calls"
2579 Normally we disable external interrupts while we are making calls to
2580 the APM BIOS as a measure to lessen the effects of a badly behaving
2581 BIOS implementation. The BIOS should reenable interrupts if it
2582 needs to. Unfortunately, some BIOSes do not -- especially those in
2583 many of the newer IBM Thinkpads. If you experience hangs when you
2584 suspend, try setting this to Y. Otherwise, say N.
2588 source "drivers/cpufreq/Kconfig"
2590 source "drivers/cpuidle/Kconfig"
2592 source "drivers/idle/Kconfig"
2597 menu "Bus options (PCI etc.)"
2600 prompt "PCI access mode"
2601 depends on X86_32 && PCI
2604 On PCI systems, the BIOS can be used to detect the PCI devices and
2605 determine their configuration. However, some old PCI motherboards
2606 have BIOS bugs and may crash if this is done. Also, some embedded
2607 PCI-based systems don't have any BIOS at all. Linux can also try to
2608 detect the PCI hardware directly without using the BIOS.
2610 With this option, you can specify how Linux should detect the
2611 PCI devices. If you choose "BIOS", the BIOS will be used,
2612 if you choose "Direct", the BIOS won't be used, and if you
2613 choose "MMConfig", then PCI Express MMCONFIG will be used.
2614 If you choose "Any", the kernel will try MMCONFIG, then the
2615 direct access method and falls back to the BIOS if that doesn't
2616 work. If unsure, go with the default, which is "Any".
2621 config PCI_GOMMCONFIG
2638 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2640 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2643 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2646 bool "Support mmconfig PCI config space access" if X86_64
2648 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2649 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2653 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2657 depends on PCI && XEN
2660 config MMCONF_FAM10H
2662 depends on X86_64 && PCI_MMCONFIG && ACPI
2664 config PCI_CNB20LE_QUIRK
2665 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2668 Read the PCI windows out of the CNB20LE host bridge. This allows
2669 PCI hotplug to work on systems with the CNB20LE chipset which do
2672 There's no public spec for this chipset, and this functionality
2673 is known to be incomplete.
2675 You should say N unless you know you need this.
2678 bool "ISA bus support on modern systems" if EXPERT
2680 Expose ISA bus device drivers and options available for selection and
2681 configuration. Enable this option if your target machine has an ISA
2682 bus. ISA is an older system, displaced by PCI and newer bus
2683 architectures -- if your target machine is modern, it probably does
2684 not have an ISA bus.
2688 # x86_64 have no ISA slots, but can have ISA-style DMA.
2690 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2693 Enables ISA-style DMA support for devices requiring such controllers.
2701 Find out whether you have ISA slots on your motherboard. ISA is the
2702 name of a bus system, i.e. the way the CPU talks to the other stuff
2703 inside your box. Other bus systems are PCI, EISA, MicroChannel
2704 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2705 newer boards don't support it. If you have ISA, say Y, otherwise N.
2708 tristate "NatSemi SCx200 support"
2710 This provides basic support for National Semiconductor's
2711 (now AMD's) Geode processors. The driver probes for the
2712 PCI-IDs of several on-chip devices, so its a good dependency
2713 for other scx200_* drivers.
2715 If compiled as a module, the driver is named scx200.
2717 config SCx200HR_TIMER
2718 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2722 This driver provides a clocksource built upon the on-chip
2723 27MHz high-resolution timer. Its also a workaround for
2724 NSC Geode SC-1100's buggy TSC, which loses time when the
2725 processor goes idle (as is done by the scheduler). The
2726 other workaround is idle=poll boot option.
2729 bool "One Laptop Per Child support"
2737 Add support for detecting the unique features of the OLPC
2741 bool "OLPC XO-1 Power Management"
2742 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2744 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2747 bool "OLPC XO-1 Real Time Clock"
2748 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2750 Add support for the XO-1 real time clock, which can be used as a
2751 programmable wakeup source.
2754 bool "OLPC XO-1 SCI extras"
2755 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2759 Add support for SCI-based features of the OLPC XO-1 laptop:
2760 - EC-driven system wakeups
2764 - AC adapter status updates
2765 - Battery status updates
2767 config OLPC_XO15_SCI
2768 bool "OLPC XO-1.5 SCI extras"
2769 depends on OLPC && ACPI
2772 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2773 - EC-driven system wakeups
2774 - AC adapter status updates
2775 - Battery status updates
2778 bool "PCEngines ALIX System Support (LED setup)"
2781 This option enables system support for the PCEngines ALIX.
2782 At present this just sets up LEDs for GPIO control on
2783 ALIX2/3/6 boards. However, other system specific setup should
2786 Note: You must still enable the drivers for GPIO and LED support
2787 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2789 Note: You have to set alix.force=1 for boards with Award BIOS.
2792 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2795 This option enables system support for the Soekris Engineering net5501.
2798 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2802 This option enables system support for the Traverse Technologies GEOS.
2805 bool "Technologic Systems TS-5500 platform support"
2807 select CHECK_SIGNATURE
2811 This option enables system support for the Technologic Systems TS-5500.
2817 depends on CPU_SUP_AMD && PCI
2820 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2822 Firmwares often provide initial graphics framebuffers so the BIOS,
2823 bootloader or kernel can show basic video-output during boot for
2824 user-guidance and debugging. Historically, x86 used the VESA BIOS
2825 Extensions and EFI-framebuffers for this, which are mostly limited
2827 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2828 framebuffers so the new generic system-framebuffer drivers can be
2829 used on x86. If the framebuffer is not compatible with the generic
2830 modes, it is advertised as fallback platform framebuffer so legacy
2831 drivers like efifb, vesafb and uvesafb can pick it up.
2832 If this option is not selected, all system framebuffers are always
2833 marked as fallback platform framebuffers as usual.
2835 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2836 not be able to pick up generic system framebuffers if this option
2837 is selected. You are highly encouraged to enable simplefb as
2838 replacement if you select this option. simplefb can correctly deal
2839 with generic system framebuffers. But you should still keep vesafb
2840 and others enabled as fallback if a system framebuffer is
2841 incompatible with simplefb.
2848 menu "Binary Emulations"
2850 config IA32_EMULATION
2851 bool "IA32 Emulation"
2853 select ARCH_WANT_OLD_COMPAT_IPC
2855 select COMPAT_OLD_SIGACTION
2857 Include code to run legacy 32-bit programs under a
2858 64-bit kernel. You should likely turn this on, unless you're
2859 100% sure that you don't have any 32-bit programs left.
2862 tristate "IA32 a.out support"
2863 depends on IA32_EMULATION
2866 Support old a.out binaries in the 32bit emulation.
2869 bool "x32 ABI for 64-bit mode"
2872 Include code to run binaries for the x32 native 32-bit ABI
2873 for 64-bit processors. An x32 process gets access to the
2874 full 64-bit register file and wide data path while leaving
2875 pointers at 32 bits for smaller memory footprint.
2877 You will need a recent binutils (2.22 or later) with
2878 elf32_x86_64 support enabled to compile a kernel with this
2883 depends on IA32_EMULATION || X86_32
2885 select OLD_SIGSUSPEND3
2889 depends on IA32_EMULATION || X86_X32
2892 config COMPAT_FOR_U64_ALIGNMENT
2895 config SYSVIPC_COMPAT
2903 config HAVE_ATOMIC_IOMAP
2907 source "drivers/firmware/Kconfig"
2909 source "arch/x86/kvm/Kconfig"
2911 source "arch/x86/Kconfig.assembler"