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"
780 depends on HAVE_STATIC_CALL
782 This changes the kernel so it can modify itself when it is run
783 under a hypervisor, potentially improving performance significantly
784 over full virtualization. However, when run without a hypervisor
785 the kernel is theoretically slower and slightly larger.
790 config PARAVIRT_DEBUG
791 bool "paravirt-ops debugging"
792 depends on PARAVIRT && DEBUG_KERNEL
794 Enable to debug paravirt_ops internals. Specifically, BUG if
795 a paravirt_op is missing when it is called.
797 config PARAVIRT_SPINLOCKS
798 bool "Paravirtualization layer for spinlocks"
799 depends on PARAVIRT && SMP
801 Paravirtualized spinlocks allow a pvops backend to replace the
802 spinlock implementation with something virtualization-friendly
803 (for example, block the virtual CPU rather than spinning).
805 It has a minimal impact on native kernels and gives a nice performance
806 benefit on paravirtualized KVM / Xen kernels.
808 If you are unsure how to answer this question, answer Y.
810 config X86_HV_CALLBACK_VECTOR
813 source "arch/x86/xen/Kconfig"
816 bool "KVM Guest support (including kvmclock)"
818 select PARAVIRT_CLOCK
819 select ARCH_CPUIDLE_HALTPOLL
820 select X86_HV_CALLBACK_VECTOR
823 This option enables various optimizations for running under the KVM
824 hypervisor. It includes a paravirtualized clock, so that instead
825 of relying on a PIT (or probably other) emulation by the
826 underlying device model, the host provides the guest with
827 timing infrastructure such as time of day, and system time
829 config ARCH_CPUIDLE_HALTPOLL
831 prompt "Disable host haltpoll when loading haltpoll driver"
833 If virtualized under KVM, disable host haltpoll.
836 bool "Support for running PVH guests"
838 This option enables the PVH entry point for guest virtual machines
839 as specified in the x86/HVM direct boot ABI.
841 config PARAVIRT_TIME_ACCOUNTING
842 bool "Paravirtual steal time accounting"
845 Select this option to enable fine granularity task steal time
846 accounting. Time spent executing other tasks in parallel with
847 the current vCPU is discounted from the vCPU power. To account for
848 that, there can be a small performance impact.
850 If in doubt, say N here.
852 config PARAVIRT_CLOCK
855 config JAILHOUSE_GUEST
856 bool "Jailhouse non-root cell support"
857 depends on X86_64 && PCI
860 This option allows to run Linux as guest in a Jailhouse non-root
861 cell. You can leave this option disabled if you only want to start
862 Jailhouse and run Linux afterwards in the root cell.
865 bool "ACRN Guest support"
867 select X86_HV_CALLBACK_VECTOR
869 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
870 a flexible, lightweight reference open-source hypervisor, built with
871 real-time and safety-criticality in mind. It is built for embedded
872 IOT with small footprint and real-time features. More details can be
873 found in https://projectacrn.org/.
875 endif #HYPERVISOR_GUEST
877 source "arch/x86/Kconfig.cpu"
881 prompt "HPET Timer Support" if X86_32
883 Use the IA-PC HPET (High Precision Event Timer) to manage
884 time in preference to the PIT and RTC, if a HPET is
886 HPET is the next generation timer replacing legacy 8254s.
887 The HPET provides a stable time base on SMP
888 systems, unlike the TSC, but it is more expensive to access,
889 as it is off-chip. The interface used is documented
890 in the HPET spec, revision 1.
892 You can safely choose Y here. However, HPET will only be
893 activated if the platform and the BIOS support this feature.
894 Otherwise the 8254 will be used for timing services.
896 Choose N to continue using the legacy 8254 timer.
898 config HPET_EMULATE_RTC
900 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
902 # Mark as expert because too many people got it wrong.
903 # The code disables itself when not needed.
906 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
907 bool "Enable DMI scanning" if EXPERT
909 Enabled scanning of DMI to identify machine quirks. Say Y
910 here unless you have verified that your setup is not
911 affected by entries in the DMI blacklist. Required by PNP
915 bool "Old AMD GART IOMMU support"
919 depends on X86_64 && PCI && AMD_NB
921 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
922 GART based hardware IOMMUs.
924 The GART supports full DMA access for devices with 32-bit access
925 limitations, on systems with more than 3 GB. This is usually needed
926 for USB, sound, many IDE/SATA chipsets and some other devices.
928 Newer systems typically have a modern AMD IOMMU, supported via
929 the CONFIG_AMD_IOMMU=y config option.
931 In normal configurations this driver is only active when needed:
932 there's more than 3 GB of memory and the system contains a
933 32-bit limited device.
938 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
939 depends on X86_64 && SMP && DEBUG_KERNEL
940 select CPUMASK_OFFSTACK
942 Enable maximum number of CPUS and NUMA Nodes for this architecture.
946 # The maximum number of CPUs supported:
948 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
949 # and which can be configured interactively in the
950 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
952 # The ranges are different on 32-bit and 64-bit kernels, depending on
953 # hardware capabilities and scalability features of the kernel.
955 # ( If MAXSMP is enabled we just use the highest possible value and disable
956 # interactive configuration. )
959 config NR_CPUS_RANGE_BEGIN
961 default NR_CPUS_RANGE_END if MAXSMP
965 config NR_CPUS_RANGE_END
968 default 64 if SMP && X86_BIGSMP
969 default 8 if SMP && !X86_BIGSMP
972 config NR_CPUS_RANGE_END
975 default 8192 if SMP && CPUMASK_OFFSTACK
976 default 512 if SMP && !CPUMASK_OFFSTACK
979 config NR_CPUS_DEFAULT
982 default 32 if X86_BIGSMP
986 config NR_CPUS_DEFAULT
989 default 8192 if MAXSMP
994 int "Maximum number of CPUs" if SMP && !MAXSMP
995 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
996 default NR_CPUS_DEFAULT
998 This allows you to specify the maximum number of CPUs which this
999 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1000 supported value is 8192, otherwise the maximum value is 512. The
1001 minimum value which makes sense is 2.
1003 This is purely to save memory: each supported CPU adds about 8KB
1004 to the kernel image.
1011 prompt "Multi-core scheduler support"
1014 Multi-core scheduler support improves the CPU scheduler's decision
1015 making when dealing with multi-core CPU chips at a cost of slightly
1016 increased overhead in some places. If unsure say N here.
1018 config SCHED_MC_PRIO
1019 bool "CPU core priorities scheduler support"
1020 depends on SCHED_MC && CPU_SUP_INTEL
1021 select X86_INTEL_PSTATE
1025 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1026 core ordering determined at manufacturing time, which allows
1027 certain cores to reach higher turbo frequencies (when running
1028 single threaded workloads) than others.
1030 Enabling this kernel feature teaches the scheduler about
1031 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1032 scheduler's CPU selection logic accordingly, so that higher
1033 overall system performance can be achieved.
1035 This feature will have no effect on CPUs without this feature.
1037 If unsure say Y here.
1041 depends on !SMP && X86_LOCAL_APIC
1044 bool "Local APIC support on uniprocessors" if !PCI_MSI
1046 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1048 A local APIC (Advanced Programmable Interrupt Controller) is an
1049 integrated interrupt controller in the CPU. If you have a single-CPU
1050 system which has a processor with a local APIC, you can say Y here to
1051 enable and use it. If you say Y here even though your machine doesn't
1052 have a local APIC, then the kernel will still run with no slowdown at
1053 all. The local APIC supports CPU-generated self-interrupts (timer,
1054 performance counters), and the NMI watchdog which detects hard
1057 config X86_UP_IOAPIC
1058 bool "IO-APIC support on uniprocessors"
1059 depends on X86_UP_APIC
1061 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1062 SMP-capable replacement for PC-style interrupt controllers. Most
1063 SMP systems and many recent uniprocessor systems have one.
1065 If you have a single-CPU system with an IO-APIC, you can say Y here
1066 to use it. If you say Y here even though your machine doesn't have
1067 an IO-APIC, then the kernel will still run with no slowdown at all.
1069 config X86_LOCAL_APIC
1071 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1072 select IRQ_DOMAIN_HIERARCHY
1073 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1077 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1079 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1080 bool "Reroute for broken boot IRQs"
1081 depends on X86_IO_APIC
1083 This option enables a workaround that fixes a source of
1084 spurious interrupts. This is recommended when threaded
1085 interrupt handling is used on systems where the generation of
1086 superfluous "boot interrupts" cannot be disabled.
1088 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1089 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1090 kernel does during interrupt handling). On chipsets where this
1091 boot IRQ generation cannot be disabled, this workaround keeps
1092 the original IRQ line masked so that only the equivalent "boot
1093 IRQ" is delivered to the CPUs. The workaround also tells the
1094 kernel to set up the IRQ handler on the boot IRQ line. In this
1095 way only one interrupt is delivered to the kernel. Otherwise
1096 the spurious second interrupt may cause the kernel to bring
1097 down (vital) interrupt lines.
1099 Only affects "broken" chipsets. Interrupt sharing may be
1100 increased on these systems.
1103 bool "Machine Check / overheating reporting"
1104 select GENERIC_ALLOCATOR
1107 Machine Check support allows the processor to notify the
1108 kernel if it detects a problem (e.g. overheating, data corruption).
1109 The action the kernel takes depends on the severity of the problem,
1110 ranging from warning messages to halting the machine.
1112 config X86_MCELOG_LEGACY
1113 bool "Support for deprecated /dev/mcelog character device"
1116 Enable support for /dev/mcelog which is needed by the old mcelog
1117 userspace logging daemon. Consider switching to the new generation
1120 config X86_MCE_INTEL
1122 prompt "Intel MCE features"
1123 depends on X86_MCE && X86_LOCAL_APIC
1125 Additional support for intel specific MCE features such as
1126 the thermal monitor.
1130 prompt "AMD MCE features"
1131 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1133 Additional support for AMD specific MCE features such as
1134 the DRAM Error Threshold.
1136 config X86_ANCIENT_MCE
1137 bool "Support for old Pentium 5 / WinChip machine checks"
1138 depends on X86_32 && X86_MCE
1140 Include support for machine check handling on old Pentium 5 or WinChip
1141 systems. These typically need to be enabled explicitly on the command
1144 config X86_MCE_THRESHOLD
1145 depends on X86_MCE_AMD || X86_MCE_INTEL
1148 config X86_MCE_INJECT
1149 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1150 tristate "Machine check injector support"
1152 Provide support for injecting machine checks for testing purposes.
1153 If you don't know what a machine check is and you don't do kernel
1154 QA it is safe to say n.
1156 source "arch/x86/events/Kconfig"
1158 config X86_LEGACY_VM86
1159 bool "Legacy VM86 support"
1162 This option allows user programs to put the CPU into V8086
1163 mode, which is an 80286-era approximation of 16-bit real mode.
1165 Some very old versions of X and/or vbetool require this option
1166 for user mode setting. Similarly, DOSEMU will use it if
1167 available to accelerate real mode DOS programs. However, any
1168 recent version of DOSEMU, X, or vbetool should be fully
1169 functional even without kernel VM86 support, as they will all
1170 fall back to software emulation. Nevertheless, if you are using
1171 a 16-bit DOS program where 16-bit performance matters, vm86
1172 mode might be faster than emulation and you might want to
1175 Note that any app that works on a 64-bit kernel is unlikely to
1176 need this option, as 64-bit kernels don't, and can't, support
1177 V8086 mode. This option is also unrelated to 16-bit protected
1178 mode and is not needed to run most 16-bit programs under Wine.
1180 Enabling this option increases the complexity of the kernel
1181 and slows down exception handling a tiny bit.
1183 If unsure, say N here.
1187 default X86_LEGACY_VM86
1190 bool "Enable support for 16-bit segments" if EXPERT
1192 depends on MODIFY_LDT_SYSCALL
1194 This option is required by programs like Wine to run 16-bit
1195 protected mode legacy code on x86 processors. Disabling
1196 this option saves about 300 bytes on i386, or around 6K text
1197 plus 16K runtime memory on x86-64,
1201 depends on X86_16BIT && X86_32
1205 depends on X86_16BIT && X86_64
1207 config X86_VSYSCALL_EMULATION
1208 bool "Enable vsyscall emulation" if EXPERT
1212 This enables emulation of the legacy vsyscall page. Disabling
1213 it is roughly equivalent to booting with vsyscall=none, except
1214 that it will also disable the helpful warning if a program
1215 tries to use a vsyscall. With this option set to N, offending
1216 programs will just segfault, citing addresses of the form
1219 This option is required by many programs built before 2013, and
1220 care should be used even with newer programs if set to N.
1222 Disabling this option saves about 7K of kernel size and
1223 possibly 4K of additional runtime pagetable memory.
1225 config X86_IOPL_IOPERM
1226 bool "IOPERM and IOPL Emulation"
1229 This enables the ioperm() and iopl() syscalls which are necessary
1230 for legacy applications.
1232 Legacy IOPL support is an overbroad mechanism which allows user
1233 space aside of accessing all 65536 I/O ports also to disable
1234 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1235 capabilities and permission from potentially active security
1238 The emulation restricts the functionality of the syscall to
1239 only allowing the full range I/O port access, but prevents the
1240 ability to disable interrupts from user space which would be
1241 granted if the hardware IOPL mechanism would be used.
1244 tristate "Toshiba Laptop support"
1247 This adds a driver to safely access the System Management Mode of
1248 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1249 not work on models with a Phoenix BIOS. The System Management Mode
1250 is used to set the BIOS and power saving options on Toshiba portables.
1252 For information on utilities to make use of this driver see the
1253 Toshiba Linux utilities web site at:
1254 <http://www.buzzard.org.uk/toshiba/>.
1256 Say Y if you intend to run this kernel on a Toshiba portable.
1260 tristate "Dell i8k legacy laptop support"
1262 select SENSORS_DELL_SMM
1264 This option enables legacy /proc/i8k userspace interface in hwmon
1265 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1266 temperature and allows controlling fan speeds of Dell laptops via
1267 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1268 it reports also power and hotkey status. For fan speed control is
1269 needed userspace package i8kutils.
1271 Say Y if you intend to run this kernel on old Dell laptops or want to
1272 use userspace package i8kutils.
1275 config X86_REBOOTFIXUPS
1276 bool "Enable X86 board specific fixups for reboot"
1279 This enables chipset and/or board specific fixups to be done
1280 in order to get reboot to work correctly. This is only needed on
1281 some combinations of hardware and BIOS. The symptom, for which
1282 this config is intended, is when reboot ends with a stalled/hung
1285 Currently, the only fixup is for the Geode machines using
1286 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1288 Say Y if you want to enable the fixup. Currently, it's safe to
1289 enable this option even if you don't need it.
1293 bool "CPU microcode loading support"
1295 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1297 If you say Y here, you will be able to update the microcode on
1298 Intel and AMD processors. The Intel support is for the IA32 family,
1299 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1300 AMD support is for families 0x10 and later. You will obviously need
1301 the actual microcode binary data itself which is not shipped with
1304 The preferred method to load microcode from a detached initrd is described
1305 in Documentation/x86/microcode.rst. For that you need to enable
1306 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1307 initrd for microcode blobs.
1309 In addition, you can build the microcode into the kernel. For that you
1310 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1313 config MICROCODE_INTEL
1314 bool "Intel microcode loading support"
1315 depends on MICROCODE
1318 This options enables microcode patch loading support for Intel
1321 For the current Intel microcode data package go to
1322 <https://downloadcenter.intel.com> and search for
1323 'Linux Processor Microcode Data File'.
1325 config MICROCODE_AMD
1326 bool "AMD microcode loading support"
1327 depends on MICROCODE
1329 If you select this option, microcode patch loading support for AMD
1330 processors will be enabled.
1332 config MICROCODE_OLD_INTERFACE
1333 bool "Ancient loading interface (DEPRECATED)"
1335 depends on MICROCODE
1337 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1338 which was used by userspace tools like iucode_tool and microcode.ctl.
1339 It is inadequate because it runs too late to be able to properly
1340 load microcode on a machine and it needs special tools. Instead, you
1341 should've switched to the early loading method with the initrd or
1342 builtin microcode by now: Documentation/x86/microcode.rst
1345 tristate "/dev/cpu/*/msr - Model-specific register support"
1347 This device gives privileged processes access to the x86
1348 Model-Specific Registers (MSRs). It is a character device with
1349 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1350 MSR accesses are directed to a specific CPU on multi-processor
1354 tristate "/dev/cpu/*/cpuid - CPU information support"
1356 This device gives processes access to the x86 CPUID instruction to
1357 be executed on a specific processor. It is a character device
1358 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1362 prompt "High Memory Support"
1369 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1370 However, the address space of 32-bit x86 processors is only 4
1371 Gigabytes large. That means that, if you have a large amount of
1372 physical memory, not all of it can be "permanently mapped" by the
1373 kernel. The physical memory that's not permanently mapped is called
1376 If you are compiling a kernel which will never run on a machine with
1377 more than 1 Gigabyte total physical RAM, answer "off" here (default
1378 choice and suitable for most users). This will result in a "3GB/1GB"
1379 split: 3GB are mapped so that each process sees a 3GB virtual memory
1380 space and the remaining part of the 4GB virtual memory space is used
1381 by the kernel to permanently map as much physical memory as
1384 If the machine has between 1 and 4 Gigabytes physical RAM, then
1387 If more than 4 Gigabytes is used then answer "64GB" here. This
1388 selection turns Intel PAE (Physical Address Extension) mode on.
1389 PAE implements 3-level paging on IA32 processors. PAE is fully
1390 supported by Linux, PAE mode is implemented on all recent Intel
1391 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1392 then the kernel will not boot on CPUs that don't support PAE!
1394 The actual amount of total physical memory will either be
1395 auto detected or can be forced by using a kernel command line option
1396 such as "mem=256M". (Try "man bootparam" or see the documentation of
1397 your boot loader (lilo or loadlin) about how to pass options to the
1398 kernel at boot time.)
1400 If unsure, say "off".
1405 Select this if you have a 32-bit processor and between 1 and 4
1406 gigabytes of physical RAM.
1410 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1413 Select this if you have a 32-bit processor and more than 4
1414 gigabytes of physical RAM.
1419 prompt "Memory split" if EXPERT
1423 Select the desired split between kernel and user memory.
1425 If the address range available to the kernel is less than the
1426 physical memory installed, the remaining memory will be available
1427 as "high memory". Accessing high memory is a little more costly
1428 than low memory, as it needs to be mapped into the kernel first.
1429 Note that increasing the kernel address space limits the range
1430 available to user programs, making the address space there
1431 tighter. Selecting anything other than the default 3G/1G split
1432 will also likely make your kernel incompatible with binary-only
1435 If you are not absolutely sure what you are doing, leave this
1439 bool "3G/1G user/kernel split"
1440 config VMSPLIT_3G_OPT
1442 bool "3G/1G user/kernel split (for full 1G low memory)"
1444 bool "2G/2G user/kernel split"
1445 config VMSPLIT_2G_OPT
1447 bool "2G/2G user/kernel split (for full 2G low memory)"
1449 bool "1G/3G user/kernel split"
1454 default 0xB0000000 if VMSPLIT_3G_OPT
1455 default 0x80000000 if VMSPLIT_2G
1456 default 0x78000000 if VMSPLIT_2G_OPT
1457 default 0x40000000 if VMSPLIT_1G
1463 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1466 bool "PAE (Physical Address Extension) Support"
1467 depends on X86_32 && !HIGHMEM4G
1468 select PHYS_ADDR_T_64BIT
1471 PAE is required for NX support, and furthermore enables
1472 larger swapspace support for non-overcommit purposes. It
1473 has the cost of more pagetable lookup overhead, and also
1474 consumes more pagetable space per process.
1477 bool "Enable 5-level page tables support"
1479 select DYNAMIC_MEMORY_LAYOUT
1480 select SPARSEMEM_VMEMMAP
1483 5-level paging enables access to larger address space:
1484 upto 128 PiB of virtual address space and 4 PiB of
1485 physical address space.
1487 It will be supported by future Intel CPUs.
1489 A kernel with the option enabled can be booted on machines that
1490 support 4- or 5-level paging.
1492 See Documentation/x86/x86_64/5level-paging.rst for more
1497 config X86_DIRECT_GBPAGES
1501 Certain kernel features effectively disable kernel
1502 linear 1 GB mappings (even if the CPU otherwise
1503 supports them), so don't confuse the user by printing
1504 that we have them enabled.
1506 config X86_CPA_STATISTICS
1507 bool "Enable statistic for Change Page Attribute"
1510 Expose statistics about the Change Page Attribute mechanism, which
1511 helps to determine the effectiveness of preserving large and huge
1512 page mappings when mapping protections are changed.
1514 config AMD_MEM_ENCRYPT
1515 bool "AMD Secure Memory Encryption (SME) support"
1516 depends on X86_64 && CPU_SUP_AMD
1517 select DMA_COHERENT_POOL
1518 select DYNAMIC_PHYSICAL_MASK
1519 select ARCH_USE_MEMREMAP_PROT
1520 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1521 select INSTRUCTION_DECODER
1522 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1524 Say yes to enable support for the encryption of system memory.
1525 This requires an AMD processor that supports Secure Memory
1528 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1529 bool "Activate AMD Secure Memory Encryption (SME) by default"
1531 depends on AMD_MEM_ENCRYPT
1533 Say yes to have system memory encrypted by default if running on
1534 an AMD processor that supports Secure Memory Encryption (SME).
1536 If set to Y, then the encryption of system memory can be
1537 deactivated with the mem_encrypt=off command line option.
1539 If set to N, then the encryption of system memory can be
1540 activated with the mem_encrypt=on command line option.
1542 # Common NUMA Features
1544 bool "NUMA Memory Allocation and Scheduler Support"
1546 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1547 default y if X86_BIGSMP
1549 Enable NUMA (Non-Uniform Memory Access) support.
1551 The kernel will try to allocate memory used by a CPU on the
1552 local memory controller of the CPU and add some more
1553 NUMA awareness to the kernel.
1555 For 64-bit this is recommended if the system is Intel Core i7
1556 (or later), AMD Opteron, or EM64T NUMA.
1558 For 32-bit this is only needed if you boot a 32-bit
1559 kernel on a 64-bit NUMA platform.
1561 Otherwise, you should say N.
1565 prompt "Old style AMD Opteron NUMA detection"
1566 depends on X86_64 && NUMA && PCI
1568 Enable AMD NUMA node topology detection. You should say Y here if
1569 you have a multi processor AMD system. This uses an old method to
1570 read the NUMA configuration directly from the builtin Northbridge
1571 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1572 which also takes priority if both are compiled in.
1574 config X86_64_ACPI_NUMA
1576 prompt "ACPI NUMA detection"
1577 depends on X86_64 && NUMA && ACPI && PCI
1580 Enable ACPI SRAT based node topology detection.
1583 bool "NUMA emulation"
1586 Enable NUMA emulation. A flat machine will be split
1587 into virtual nodes when booted with "numa=fake=N", where N is the
1588 number of nodes. This is only useful for debugging.
1591 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1593 default "10" if MAXSMP
1594 default "6" if X86_64
1596 depends on NEED_MULTIPLE_NODES
1598 Specify the maximum number of NUMA Nodes available on the target
1599 system. Increases memory reserved to accommodate various tables.
1601 config ARCH_FLATMEM_ENABLE
1603 depends on X86_32 && !NUMA
1605 config ARCH_SPARSEMEM_ENABLE
1607 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1608 select SPARSEMEM_STATIC if X86_32
1609 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1611 config ARCH_SPARSEMEM_DEFAULT
1612 def_bool X86_64 || (NUMA && X86_32)
1614 config ARCH_SELECT_MEMORY_MODEL
1616 depends on ARCH_SPARSEMEM_ENABLE
1618 config ARCH_MEMORY_PROBE
1619 bool "Enable sysfs memory/probe interface"
1620 depends on X86_64 && MEMORY_HOTPLUG
1622 This option enables a sysfs memory/probe interface for testing.
1623 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1624 If you are unsure how to answer this question, answer N.
1626 config ARCH_PROC_KCORE_TEXT
1628 depends on X86_64 && PROC_KCORE
1630 config ILLEGAL_POINTER_VALUE
1633 default 0xdead000000000000 if X86_64
1635 config X86_PMEM_LEGACY_DEVICE
1638 config X86_PMEM_LEGACY
1639 tristate "Support non-standard NVDIMMs and ADR protected memory"
1640 depends on PHYS_ADDR_T_64BIT
1642 select X86_PMEM_LEGACY_DEVICE
1643 select NUMA_KEEP_MEMINFO if NUMA
1646 Treat memory marked using the non-standard e820 type of 12 as used
1647 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1648 The kernel will offer these regions to the 'pmem' driver so
1649 they can be used for persistent storage.
1654 bool "Allocate 3rd-level pagetables from highmem"
1657 The VM uses one page table entry for each page of physical memory.
1658 For systems with a lot of RAM, this can be wasteful of precious
1659 low memory. Setting this option will put user-space page table
1660 entries in high memory.
1662 config X86_CHECK_BIOS_CORRUPTION
1663 bool "Check for low memory corruption"
1665 Periodically check for memory corruption in low memory, which
1666 is suspected to be caused by BIOS. Even when enabled in the
1667 configuration, it is disabled at runtime. Enable it by
1668 setting "memory_corruption_check=1" on the kernel command
1669 line. By default it scans the low 64k of memory every 60
1670 seconds; see the memory_corruption_check_size and
1671 memory_corruption_check_period parameters in
1672 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1674 When enabled with the default parameters, this option has
1675 almost no overhead, as it reserves a relatively small amount
1676 of memory and scans it infrequently. It both detects corruption
1677 and prevents it from affecting the running system.
1679 It is, however, intended as a diagnostic tool; if repeatable
1680 BIOS-originated corruption always affects the same memory,
1681 you can use memmap= to prevent the kernel from using that
1684 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1685 bool "Set the default setting of memory_corruption_check"
1686 depends on X86_CHECK_BIOS_CORRUPTION
1689 Set whether the default state of memory_corruption_check is
1692 config X86_RESERVE_LOW
1693 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1697 Specify the amount of low memory to reserve for the BIOS.
1699 The first page contains BIOS data structures that the kernel
1700 must not use, so that page must always be reserved.
1702 By default we reserve the first 64K of physical RAM, as a
1703 number of BIOSes are known to corrupt that memory range
1704 during events such as suspend/resume or monitor cable
1705 insertion, so it must not be used by the kernel.
1707 You can set this to 4 if you are absolutely sure that you
1708 trust the BIOS to get all its memory reservations and usages
1709 right. If you know your BIOS have problems beyond the
1710 default 64K area, you can set this to 640 to avoid using the
1711 entire low memory range.
1713 If you have doubts about the BIOS (e.g. suspend/resume does
1714 not work or there's kernel crashes after certain hardware
1715 hotplug events) then you might want to enable
1716 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1717 typical corruption patterns.
1719 Leave this to the default value of 64 if you are unsure.
1721 config MATH_EMULATION
1723 depends on MODIFY_LDT_SYSCALL
1724 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1726 Linux can emulate a math coprocessor (used for floating point
1727 operations) if you don't have one. 486DX and Pentium processors have
1728 a math coprocessor built in, 486SX and 386 do not, unless you added
1729 a 487DX or 387, respectively. (The messages during boot time can
1730 give you some hints here ["man dmesg"].) Everyone needs either a
1731 coprocessor or this emulation.
1733 If you don't have a math coprocessor, you need to say Y here; if you
1734 say Y here even though you have a coprocessor, the coprocessor will
1735 be used nevertheless. (This behavior can be changed with the kernel
1736 command line option "no387", which comes handy if your coprocessor
1737 is broken. Try "man bootparam" or see the documentation of your boot
1738 loader (lilo or loadlin) about how to pass options to the kernel at
1739 boot time.) This means that it is a good idea to say Y here if you
1740 intend to use this kernel on different machines.
1742 More information about the internals of the Linux math coprocessor
1743 emulation can be found in <file:arch/x86/math-emu/README>.
1745 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1746 kernel, it won't hurt.
1750 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1752 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1753 the Memory Type Range Registers (MTRRs) may be used to control
1754 processor access to memory ranges. This is most useful if you have
1755 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1756 allows bus write transfers to be combined into a larger transfer
1757 before bursting over the PCI/AGP bus. This can increase performance
1758 of image write operations 2.5 times or more. Saying Y here creates a
1759 /proc/mtrr file which may be used to manipulate your processor's
1760 MTRRs. Typically the X server should use this.
1762 This code has a reasonably generic interface so that similar
1763 control registers on other processors can be easily supported
1766 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1767 Registers (ARRs) which provide a similar functionality to MTRRs. For
1768 these, the ARRs are used to emulate the MTRRs.
1769 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1770 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1771 write-combining. All of these processors are supported by this code
1772 and it makes sense to say Y here if you have one of them.
1774 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1775 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1776 can lead to all sorts of problems, so it's good to say Y here.
1778 You can safely say Y even if your machine doesn't have MTRRs, you'll
1779 just add about 9 KB to your kernel.
1781 See <file:Documentation/x86/mtrr.rst> for more information.
1783 config MTRR_SANITIZER
1785 prompt "MTRR cleanup support"
1788 Convert MTRR layout from continuous to discrete, so X drivers can
1789 add writeback entries.
1791 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1792 The largest mtrr entry size for a continuous block can be set with
1797 config MTRR_SANITIZER_ENABLE_DEFAULT
1798 int "MTRR cleanup enable value (0-1)"
1801 depends on MTRR_SANITIZER
1803 Enable mtrr cleanup default value
1805 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1806 int "MTRR cleanup spare reg num (0-7)"
1809 depends on MTRR_SANITIZER
1811 mtrr cleanup spare entries default, it can be changed via
1812 mtrr_spare_reg_nr=N on the kernel command line.
1816 prompt "x86 PAT support" if EXPERT
1819 Use PAT attributes to setup page level cache control.
1821 PATs are the modern equivalents of MTRRs and are much more
1822 flexible than MTRRs.
1824 Say N here if you see bootup problems (boot crash, boot hang,
1825 spontaneous reboots) or a non-working video driver.
1829 config ARCH_USES_PG_UNCACHED
1835 prompt "x86 architectural random number generator" if EXPERT
1837 Enable the x86 architectural RDRAND instruction
1838 (Intel Bull Mountain technology) to generate random numbers.
1839 If supported, this is a high bandwidth, cryptographically
1840 secure hardware random number generator.
1844 prompt "Supervisor Mode Access Prevention" if EXPERT
1846 Supervisor Mode Access Prevention (SMAP) is a security
1847 feature in newer Intel processors. There is a small
1848 performance cost if this enabled and turned on; there is
1849 also a small increase in the kernel size if this is enabled.
1855 prompt "User Mode Instruction Prevention" if EXPERT
1857 User Mode Instruction Prevention (UMIP) is a security feature in
1858 some x86 processors. If enabled, a general protection fault is
1859 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1860 executed in user mode. These instructions unnecessarily expose
1861 information about the hardware state.
1863 The vast majority of applications do not use these instructions.
1864 For the very few that do, software emulation is provided in
1865 specific cases in protected and virtual-8086 modes. Emulated
1868 config X86_INTEL_MEMORY_PROTECTION_KEYS
1869 prompt "Memory Protection Keys"
1871 # Note: only available in 64-bit mode
1872 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1873 select ARCH_USES_HIGH_VMA_FLAGS
1874 select ARCH_HAS_PKEYS
1876 Memory Protection Keys provides a mechanism for enforcing
1877 page-based protections, but without requiring modification of the
1878 page tables when an application changes protection domains.
1880 For details, see Documentation/core-api/protection-keys.rst
1885 prompt "TSX enable mode"
1886 depends on CPU_SUP_INTEL
1887 default X86_INTEL_TSX_MODE_OFF
1889 Intel's TSX (Transactional Synchronization Extensions) feature
1890 allows to optimize locking protocols through lock elision which
1891 can lead to a noticeable performance boost.
1893 On the other hand it has been shown that TSX can be exploited
1894 to form side channel attacks (e.g. TAA) and chances are there
1895 will be more of those attacks discovered in the future.
1897 Therefore TSX is not enabled by default (aka tsx=off). An admin
1898 might override this decision by tsx=on the command line parameter.
1899 Even with TSX enabled, the kernel will attempt to enable the best
1900 possible TAA mitigation setting depending on the microcode available
1901 for the particular machine.
1903 This option allows to set the default tsx mode between tsx=on, =off
1904 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1907 Say off if not sure, auto if TSX is in use but it should be used on safe
1908 platforms or on if TSX is in use and the security aspect of tsx is not
1911 config X86_INTEL_TSX_MODE_OFF
1914 TSX is disabled if possible - equals to tsx=off command line parameter.
1916 config X86_INTEL_TSX_MODE_ON
1919 TSX is always enabled on TSX capable HW - equals the tsx=on command
1922 config X86_INTEL_TSX_MODE_AUTO
1925 TSX is enabled on TSX capable HW that is believed to be safe against
1926 side channel attacks- equals the tsx=auto command line parameter.
1930 bool "Software Guard eXtensions (SGX)"
1931 depends on X86_64 && CPU_SUP_INTEL
1933 depends on CRYPTO_SHA256=y
1937 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1938 that can be used by applications to set aside private regions of code
1939 and data, referred to as enclaves. An enclave's private memory can
1940 only be accessed by code running within the enclave. Accesses from
1941 outside the enclave, including other enclaves, are disallowed by
1947 bool "EFI runtime service support"
1950 select EFI_RUNTIME_WRAPPERS
1952 This enables the kernel to use EFI runtime services that are
1953 available (such as the EFI variable services).
1955 This option is only useful on systems that have EFI firmware.
1956 In addition, you should use the latest ELILO loader available
1957 at <http://elilo.sourceforge.net> in order to take advantage
1958 of EFI runtime services. However, even with this option, the
1959 resultant kernel should continue to boot on existing non-EFI
1963 bool "EFI stub support"
1964 depends on EFI && !X86_USE_3DNOW
1965 depends on $(cc-option,-mabi=ms) || X86_32
1968 This kernel feature allows a bzImage to be loaded directly
1969 by EFI firmware without the use of a bootloader.
1971 See Documentation/admin-guide/efi-stub.rst for more information.
1974 bool "EFI mixed-mode support"
1975 depends on EFI_STUB && X86_64
1977 Enabling this feature allows a 64-bit kernel to be booted
1978 on a 32-bit firmware, provided that your CPU supports 64-bit
1981 Note that it is not possible to boot a mixed-mode enabled
1982 kernel via the EFI boot stub - a bootloader that supports
1983 the EFI handover protocol must be used.
1987 source "kernel/Kconfig.hz"
1990 bool "kexec system call"
1993 kexec is a system call that implements the ability to shutdown your
1994 current kernel, and to start another kernel. It is like a reboot
1995 but it is independent of the system firmware. And like a reboot
1996 you can start any kernel with it, not just Linux.
1998 The name comes from the similarity to the exec system call.
2000 It is an ongoing process to be certain the hardware in a machine
2001 is properly shutdown, so do not be surprised if this code does not
2002 initially work for you. As of this writing the exact hardware
2003 interface is strongly in flux, so no good recommendation can be
2007 bool "kexec file based system call"
2012 depends on CRYPTO_SHA256=y
2014 This is new version of kexec system call. This system call is
2015 file based and takes file descriptors as system call argument
2016 for kernel and initramfs as opposed to list of segments as
2017 accepted by previous system call.
2019 config ARCH_HAS_KEXEC_PURGATORY
2023 bool "Verify kernel signature during kexec_file_load() syscall"
2024 depends on KEXEC_FILE
2027 This option makes the kexec_file_load() syscall check for a valid
2028 signature of the kernel image. The image can still be loaded without
2029 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2030 there's a signature that we can check, then it must be valid.
2032 In addition to this option, you need to enable signature
2033 verification for the corresponding kernel image type being
2034 loaded in order for this to work.
2036 config KEXEC_SIG_FORCE
2037 bool "Require a valid signature in kexec_file_load() syscall"
2038 depends on KEXEC_SIG
2040 This option makes kernel signature verification mandatory for
2041 the kexec_file_load() syscall.
2043 config KEXEC_BZIMAGE_VERIFY_SIG
2044 bool "Enable bzImage signature verification support"
2045 depends on KEXEC_SIG
2046 depends on SIGNED_PE_FILE_VERIFICATION
2047 select SYSTEM_TRUSTED_KEYRING
2049 Enable bzImage signature verification support.
2052 bool "kernel crash dumps"
2053 depends on X86_64 || (X86_32 && HIGHMEM)
2055 Generate crash dump after being started by kexec.
2056 This should be normally only set in special crash dump kernels
2057 which are loaded in the main kernel with kexec-tools into
2058 a specially reserved region and then later executed after
2059 a crash by kdump/kexec. The crash dump kernel must be compiled
2060 to a memory address not used by the main kernel or BIOS using
2061 PHYSICAL_START, or it must be built as a relocatable image
2062 (CONFIG_RELOCATABLE=y).
2063 For more details see Documentation/admin-guide/kdump/kdump.rst
2067 depends on KEXEC && HIBERNATION
2069 Jump between original kernel and kexeced kernel and invoke
2070 code in physical address mode via KEXEC
2072 config PHYSICAL_START
2073 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2076 This gives the physical address where the kernel is loaded.
2078 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2079 bzImage will decompress itself to above physical address and
2080 run from there. Otherwise, bzImage will run from the address where
2081 it has been loaded by the boot loader and will ignore above physical
2084 In normal kdump cases one does not have to set/change this option
2085 as now bzImage can be compiled as a completely relocatable image
2086 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2087 address. This option is mainly useful for the folks who don't want
2088 to use a bzImage for capturing the crash dump and want to use a
2089 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2090 to be specifically compiled to run from a specific memory area
2091 (normally a reserved region) and this option comes handy.
2093 So if you are using bzImage for capturing the crash dump,
2094 leave the value here unchanged to 0x1000000 and set
2095 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2096 for capturing the crash dump change this value to start of
2097 the reserved region. In other words, it can be set based on
2098 the "X" value as specified in the "crashkernel=YM@XM"
2099 command line boot parameter passed to the panic-ed
2100 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2101 for more details about crash dumps.
2103 Usage of bzImage for capturing the crash dump is recommended as
2104 one does not have to build two kernels. Same kernel can be used
2105 as production kernel and capture kernel. Above option should have
2106 gone away after relocatable bzImage support is introduced. But it
2107 is present because there are users out there who continue to use
2108 vmlinux for dump capture. This option should go away down the
2111 Don't change this unless you know what you are doing.
2114 bool "Build a relocatable kernel"
2117 This builds a kernel image that retains relocation information
2118 so it can be loaded someplace besides the default 1MB.
2119 The relocations tend to make the kernel binary about 10% larger,
2120 but are discarded at runtime.
2122 One use is for the kexec on panic case where the recovery kernel
2123 must live at a different physical address than the primary
2126 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2127 it has been loaded at and the compile time physical address
2128 (CONFIG_PHYSICAL_START) is used as the minimum location.
2130 config RANDOMIZE_BASE
2131 bool "Randomize the address of the kernel image (KASLR)"
2132 depends on RELOCATABLE
2135 In support of Kernel Address Space Layout Randomization (KASLR),
2136 this randomizes the physical address at which the kernel image
2137 is decompressed and the virtual address where the kernel
2138 image is mapped, as a security feature that deters exploit
2139 attempts relying on knowledge of the location of kernel
2142 On 64-bit, the kernel physical and virtual addresses are
2143 randomized separately. The physical address will be anywhere
2144 between 16MB and the top of physical memory (up to 64TB). The
2145 virtual address will be randomized from 16MB up to 1GB (9 bits
2146 of entropy). Note that this also reduces the memory space
2147 available to kernel modules from 1.5GB to 1GB.
2149 On 32-bit, the kernel physical and virtual addresses are
2150 randomized together. They will be randomized from 16MB up to
2151 512MB (8 bits of entropy).
2153 Entropy is generated using the RDRAND instruction if it is
2154 supported. If RDTSC is supported, its value is mixed into
2155 the entropy pool as well. If neither RDRAND nor RDTSC are
2156 supported, then entropy is read from the i8254 timer. The
2157 usable entropy is limited by the kernel being built using
2158 2GB addressing, and that PHYSICAL_ALIGN must be at a
2159 minimum of 2MB. As a result, only 10 bits of entropy are
2160 theoretically possible, but the implementations are further
2161 limited due to memory layouts.
2165 # Relocation on x86 needs some additional build support
2166 config X86_NEED_RELOCS
2168 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2170 config PHYSICAL_ALIGN
2171 hex "Alignment value to which kernel should be aligned"
2173 range 0x2000 0x1000000 if X86_32
2174 range 0x200000 0x1000000 if X86_64
2176 This value puts the alignment restrictions on physical address
2177 where kernel is loaded and run from. Kernel is compiled for an
2178 address which meets above alignment restriction.
2180 If bootloader loads the kernel at a non-aligned address and
2181 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2182 address aligned to above value and run from there.
2184 If bootloader loads the kernel at a non-aligned address and
2185 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2186 load address and decompress itself to the address it has been
2187 compiled for and run from there. The address for which kernel is
2188 compiled already meets above alignment restrictions. Hence the
2189 end result is that kernel runs from a physical address meeting
2190 above alignment restrictions.
2192 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2193 this value must be a multiple of 0x200000.
2195 Don't change this unless you know what you are doing.
2197 config DYNAMIC_MEMORY_LAYOUT
2200 This option makes base addresses of vmalloc and vmemmap as well as
2201 __PAGE_OFFSET movable during boot.
2203 config RANDOMIZE_MEMORY
2204 bool "Randomize the kernel memory sections"
2206 depends on RANDOMIZE_BASE
2207 select DYNAMIC_MEMORY_LAYOUT
2208 default RANDOMIZE_BASE
2210 Randomizes the base virtual address of kernel memory sections
2211 (physical memory mapping, vmalloc & vmemmap). This security feature
2212 makes exploits relying on predictable memory locations less reliable.
2214 The order of allocations remains unchanged. Entropy is generated in
2215 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2216 configuration have in average 30,000 different possible virtual
2217 addresses for each memory section.
2221 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2222 hex "Physical memory mapping padding" if EXPERT
2223 depends on RANDOMIZE_MEMORY
2224 default "0xa" if MEMORY_HOTPLUG
2226 range 0x1 0x40 if MEMORY_HOTPLUG
2229 Define the padding in terabytes added to the existing physical
2230 memory size during kernel memory randomization. It is useful
2231 for memory hotplug support but reduces the entropy available for
2232 address randomization.
2234 If unsure, leave at the default value.
2240 config BOOTPARAM_HOTPLUG_CPU0
2241 bool "Set default setting of cpu0_hotpluggable"
2242 depends on HOTPLUG_CPU
2244 Set whether default state of cpu0_hotpluggable is on or off.
2246 Say Y here to enable CPU0 hotplug by default. If this switch
2247 is turned on, there is no need to give cpu0_hotplug kernel
2248 parameter and the CPU0 hotplug feature is enabled by default.
2250 Please note: there are two known CPU0 dependencies if you want
2251 to enable the CPU0 hotplug feature either by this switch or by
2252 cpu0_hotplug kernel parameter.
2254 First, resume from hibernate or suspend always starts from CPU0.
2255 So hibernate and suspend are prevented if CPU0 is offline.
2257 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2258 offline if any interrupt can not migrate out of CPU0. There may
2259 be other CPU0 dependencies.
2261 Please make sure the dependencies are under your control before
2262 you enable this feature.
2264 Say N if you don't want to enable CPU0 hotplug feature by default.
2265 You still can enable the CPU0 hotplug feature at boot by kernel
2266 parameter cpu0_hotplug.
2268 config DEBUG_HOTPLUG_CPU0
2270 prompt "Debug CPU0 hotplug"
2271 depends on HOTPLUG_CPU
2273 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2274 soon as possible and boots up userspace with CPU0 offlined. User
2275 can online CPU0 back after boot time.
2277 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2278 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2279 compilation or giving cpu0_hotplug kernel parameter at boot.
2285 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2286 depends on COMPAT_32
2288 Certain buggy versions of glibc will crash if they are
2289 presented with a 32-bit vDSO that is not mapped at the address
2290 indicated in its segment table.
2292 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2293 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2294 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2295 the only released version with the bug, but OpenSUSE 9
2296 contains a buggy "glibc 2.3.2".
2298 The symptom of the bug is that everything crashes on startup, saying:
2299 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2301 Saying Y here changes the default value of the vdso32 boot
2302 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2303 This works around the glibc bug but hurts performance.
2305 If unsure, say N: if you are compiling your own kernel, you
2306 are unlikely to be using a buggy version of glibc.
2309 prompt "vsyscall table for legacy applications"
2311 default LEGACY_VSYSCALL_XONLY
2313 Legacy user code that does not know how to find the vDSO expects
2314 to be able to issue three syscalls by calling fixed addresses in
2315 kernel space. Since this location is not randomized with ASLR,
2316 it can be used to assist security vulnerability exploitation.
2318 This setting can be changed at boot time via the kernel command
2319 line parameter vsyscall=[emulate|xonly|none].
2321 On a system with recent enough glibc (2.14 or newer) and no
2322 static binaries, you can say None without a performance penalty
2323 to improve security.
2325 If unsure, select "Emulate execution only".
2327 config LEGACY_VSYSCALL_EMULATE
2328 bool "Full emulation"
2330 The kernel traps and emulates calls into the fixed vsyscall
2331 address mapping. This makes the mapping non-executable, but
2332 it still contains readable known contents, which could be
2333 used in certain rare security vulnerability exploits. This
2334 configuration is recommended when using legacy userspace
2335 that still uses vsyscalls along with legacy binary
2336 instrumentation tools that require code to be readable.
2338 An example of this type of legacy userspace is running
2339 Pin on an old binary that still uses vsyscalls.
2341 config LEGACY_VSYSCALL_XONLY
2342 bool "Emulate execution only"
2344 The kernel traps and emulates calls into the fixed vsyscall
2345 address mapping and does not allow reads. This
2346 configuration is recommended when userspace might use the
2347 legacy vsyscall area but support for legacy binary
2348 instrumentation of legacy code is not needed. It mitigates
2349 certain uses of the vsyscall area as an ASLR-bypassing
2352 config LEGACY_VSYSCALL_NONE
2355 There will be no vsyscall mapping at all. This will
2356 eliminate any risk of ASLR bypass due to the vsyscall
2357 fixed address mapping. Attempts to use the vsyscalls
2358 will be reported to dmesg, so that either old or
2359 malicious userspace programs can be identified.
2364 bool "Built-in kernel command line"
2366 Allow for specifying boot arguments to the kernel at
2367 build time. On some systems (e.g. embedded ones), it is
2368 necessary or convenient to provide some or all of the
2369 kernel boot arguments with the kernel itself (that is,
2370 to not rely on the boot loader to provide them.)
2372 To compile command line arguments into the kernel,
2373 set this option to 'Y', then fill in the
2374 boot arguments in CONFIG_CMDLINE.
2376 Systems with fully functional boot loaders (i.e. non-embedded)
2377 should leave this option set to 'N'.
2380 string "Built-in kernel command string"
2381 depends on CMDLINE_BOOL
2384 Enter arguments here that should be compiled into the kernel
2385 image and used at boot time. If the boot loader provides a
2386 command line at boot time, it is appended to this string to
2387 form the full kernel command line, when the system boots.
2389 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2390 change this behavior.
2392 In most cases, the command line (whether built-in or provided
2393 by the boot loader) should specify the device for the root
2396 config CMDLINE_OVERRIDE
2397 bool "Built-in command line overrides boot loader arguments"
2398 depends on CMDLINE_BOOL && CMDLINE != ""
2400 Set this option to 'Y' to have the kernel ignore the boot loader
2401 command line, and use ONLY the built-in command line.
2403 This is used to work around broken boot loaders. This should
2404 be set to 'N' under normal conditions.
2406 config MODIFY_LDT_SYSCALL
2407 bool "Enable the LDT (local descriptor table)" if EXPERT
2410 Linux can allow user programs to install a per-process x86
2411 Local Descriptor Table (LDT) using the modify_ldt(2) system
2412 call. This is required to run 16-bit or segmented code such as
2413 DOSEMU or some Wine programs. It is also used by some very old
2414 threading libraries.
2416 Enabling this feature adds a small amount of overhead to
2417 context switches and increases the low-level kernel attack
2418 surface. Disabling it removes the modify_ldt(2) system call.
2420 Saying 'N' here may make sense for embedded or server kernels.
2422 source "kernel/livepatch/Kconfig"
2426 config ARCH_HAS_ADD_PAGES
2428 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2430 config ARCH_ENABLE_MEMORY_HOTPLUG
2432 depends on X86_64 || (X86_32 && HIGHMEM)
2434 config ARCH_ENABLE_MEMORY_HOTREMOVE
2436 depends on MEMORY_HOTPLUG
2438 config USE_PERCPU_NUMA_NODE_ID
2442 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2444 depends on X86_64 || X86_PAE
2446 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2448 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2450 config ARCH_ENABLE_THP_MIGRATION
2452 depends on X86_64 && TRANSPARENT_HUGEPAGE
2454 menu "Power management and ACPI options"
2456 config ARCH_HIBERNATION_HEADER
2458 depends on HIBERNATION
2460 source "kernel/power/Kconfig"
2462 source "drivers/acpi/Kconfig"
2469 tristate "APM (Advanced Power Management) BIOS support"
2470 depends on X86_32 && PM_SLEEP
2472 APM is a BIOS specification for saving power using several different
2473 techniques. This is mostly useful for battery powered laptops with
2474 APM compliant BIOSes. If you say Y here, the system time will be
2475 reset after a RESUME operation, the /proc/apm device will provide
2476 battery status information, and user-space programs will receive
2477 notification of APM "events" (e.g. battery status change).
2479 If you select "Y" here, you can disable actual use of the APM
2480 BIOS by passing the "apm=off" option to the kernel at boot time.
2482 Note that the APM support is almost completely disabled for
2483 machines with more than one CPU.
2485 In order to use APM, you will need supporting software. For location
2486 and more information, read <file:Documentation/power/apm-acpi.rst>
2487 and the Battery Powered Linux mini-HOWTO, available from
2488 <http://www.tldp.org/docs.html#howto>.
2490 This driver does not spin down disk drives (see the hdparm(8)
2491 manpage ("man 8 hdparm") for that), and it doesn't turn off
2492 VESA-compliant "green" monitors.
2494 This driver does not support the TI 4000M TravelMate and the ACER
2495 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2496 desktop machines also don't have compliant BIOSes, and this driver
2497 may cause those machines to panic during the boot phase.
2499 Generally, if you don't have a battery in your machine, there isn't
2500 much point in using this driver and you should say N. If you get
2501 random kernel OOPSes or reboots that don't seem to be related to
2502 anything, try disabling/enabling this option (or disabling/enabling
2505 Some other things you should try when experiencing seemingly random,
2508 1) make sure that you have enough swap space and that it is
2510 2) pass the "no-hlt" option to the kernel
2511 3) switch on floating point emulation in the kernel and pass
2512 the "no387" option to the kernel
2513 4) pass the "floppy=nodma" option to the kernel
2514 5) pass the "mem=4M" option to the kernel (thereby disabling
2515 all but the first 4 MB of RAM)
2516 6) make sure that the CPU is not over clocked.
2517 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2518 8) disable the cache from your BIOS settings
2519 9) install a fan for the video card or exchange video RAM
2520 10) install a better fan for the CPU
2521 11) exchange RAM chips
2522 12) exchange the motherboard.
2524 To compile this driver as a module, choose M here: the
2525 module will be called apm.
2529 config APM_IGNORE_USER_SUSPEND
2530 bool "Ignore USER SUSPEND"
2532 This option will ignore USER SUSPEND requests. On machines with a
2533 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2534 series notebooks, it is necessary to say Y because of a BIOS bug.
2536 config APM_DO_ENABLE
2537 bool "Enable PM at boot time"
2539 Enable APM features at boot time. From page 36 of the APM BIOS
2540 specification: "When disabled, the APM BIOS does not automatically
2541 power manage devices, enter the Standby State, enter the Suspend
2542 State, or take power saving steps in response to CPU Idle calls."
2543 This driver will make CPU Idle calls when Linux is idle (unless this
2544 feature is turned off -- see "Do CPU IDLE calls", below). This
2545 should always save battery power, but more complicated APM features
2546 will be dependent on your BIOS implementation. You may need to turn
2547 this option off if your computer hangs at boot time when using APM
2548 support, or if it beeps continuously instead of suspending. Turn
2549 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2550 T400CDT. This is off by default since most machines do fine without
2555 bool "Make CPU Idle calls when idle"
2557 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2558 On some machines, this can activate improved power savings, such as
2559 a slowed CPU clock rate, when the machine is idle. These idle calls
2560 are made after the idle loop has run for some length of time (e.g.,
2561 333 mS). On some machines, this will cause a hang at boot time or
2562 whenever the CPU becomes idle. (On machines with more than one CPU,
2563 this option does nothing.)
2565 config APM_DISPLAY_BLANK
2566 bool "Enable console blanking using APM"
2568 Enable console blanking using the APM. Some laptops can use this to
2569 turn off the LCD backlight when the screen blanker of the Linux
2570 virtual console blanks the screen. Note that this is only used by
2571 the virtual console screen blanker, and won't turn off the backlight
2572 when using the X Window system. This also doesn't have anything to
2573 do with your VESA-compliant power-saving monitor. Further, this
2574 option doesn't work for all laptops -- it might not turn off your
2575 backlight at all, or it might print a lot of errors to the console,
2576 especially if you are using gpm.
2578 config APM_ALLOW_INTS
2579 bool "Allow interrupts during APM BIOS calls"
2581 Normally we disable external interrupts while we are making calls to
2582 the APM BIOS as a measure to lessen the effects of a badly behaving
2583 BIOS implementation. The BIOS should reenable interrupts if it
2584 needs to. Unfortunately, some BIOSes do not -- especially those in
2585 many of the newer IBM Thinkpads. If you experience hangs when you
2586 suspend, try setting this to Y. Otherwise, say N.
2590 source "drivers/cpufreq/Kconfig"
2592 source "drivers/cpuidle/Kconfig"
2594 source "drivers/idle/Kconfig"
2599 menu "Bus options (PCI etc.)"
2602 prompt "PCI access mode"
2603 depends on X86_32 && PCI
2606 On PCI systems, the BIOS can be used to detect the PCI devices and
2607 determine their configuration. However, some old PCI motherboards
2608 have BIOS bugs and may crash if this is done. Also, some embedded
2609 PCI-based systems don't have any BIOS at all. Linux can also try to
2610 detect the PCI hardware directly without using the BIOS.
2612 With this option, you can specify how Linux should detect the
2613 PCI devices. If you choose "BIOS", the BIOS will be used,
2614 if you choose "Direct", the BIOS won't be used, and if you
2615 choose "MMConfig", then PCI Express MMCONFIG will be used.
2616 If you choose "Any", the kernel will try MMCONFIG, then the
2617 direct access method and falls back to the BIOS if that doesn't
2618 work. If unsure, go with the default, which is "Any".
2623 config PCI_GOMMCONFIG
2640 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2642 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2645 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2648 bool "Support mmconfig PCI config space access" if X86_64
2650 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2651 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2655 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2659 depends on PCI && XEN
2662 config MMCONF_FAM10H
2664 depends on X86_64 && PCI_MMCONFIG && ACPI
2666 config PCI_CNB20LE_QUIRK
2667 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2670 Read the PCI windows out of the CNB20LE host bridge. This allows
2671 PCI hotplug to work on systems with the CNB20LE chipset which do
2674 There's no public spec for this chipset, and this functionality
2675 is known to be incomplete.
2677 You should say N unless you know you need this.
2680 bool "ISA bus support on modern systems" if EXPERT
2682 Expose ISA bus device drivers and options available for selection and
2683 configuration. Enable this option if your target machine has an ISA
2684 bus. ISA is an older system, displaced by PCI and newer bus
2685 architectures -- if your target machine is modern, it probably does
2686 not have an ISA bus.
2690 # x86_64 have no ISA slots, but can have ISA-style DMA.
2692 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2695 Enables ISA-style DMA support for devices requiring such controllers.
2703 Find out whether you have ISA slots on your motherboard. ISA is the
2704 name of a bus system, i.e. the way the CPU talks to the other stuff
2705 inside your box. Other bus systems are PCI, EISA, MicroChannel
2706 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2707 newer boards don't support it. If you have ISA, say Y, otherwise N.
2710 tristate "NatSemi SCx200 support"
2712 This provides basic support for National Semiconductor's
2713 (now AMD's) Geode processors. The driver probes for the
2714 PCI-IDs of several on-chip devices, so its a good dependency
2715 for other scx200_* drivers.
2717 If compiled as a module, the driver is named scx200.
2719 config SCx200HR_TIMER
2720 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2724 This driver provides a clocksource built upon the on-chip
2725 27MHz high-resolution timer. Its also a workaround for
2726 NSC Geode SC-1100's buggy TSC, which loses time when the
2727 processor goes idle (as is done by the scheduler). The
2728 other workaround is idle=poll boot option.
2731 bool "One Laptop Per Child support"
2739 Add support for detecting the unique features of the OLPC
2743 bool "OLPC XO-1 Power Management"
2744 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2746 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2749 bool "OLPC XO-1 Real Time Clock"
2750 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2752 Add support for the XO-1 real time clock, which can be used as a
2753 programmable wakeup source.
2756 bool "OLPC XO-1 SCI extras"
2757 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2761 Add support for SCI-based features of the OLPC XO-1 laptop:
2762 - EC-driven system wakeups
2766 - AC adapter status updates
2767 - Battery status updates
2769 config OLPC_XO15_SCI
2770 bool "OLPC XO-1.5 SCI extras"
2771 depends on OLPC && ACPI
2774 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2775 - EC-driven system wakeups
2776 - AC adapter status updates
2777 - Battery status updates
2780 bool "PCEngines ALIX System Support (LED setup)"
2783 This option enables system support for the PCEngines ALIX.
2784 At present this just sets up LEDs for GPIO control on
2785 ALIX2/3/6 boards. However, other system specific setup should
2788 Note: You must still enable the drivers for GPIO and LED support
2789 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2791 Note: You have to set alix.force=1 for boards with Award BIOS.
2794 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2797 This option enables system support for the Soekris Engineering net5501.
2800 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2804 This option enables system support for the Traverse Technologies GEOS.
2807 bool "Technologic Systems TS-5500 platform support"
2809 select CHECK_SIGNATURE
2813 This option enables system support for the Technologic Systems TS-5500.
2819 depends on CPU_SUP_AMD && PCI
2822 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2824 Firmwares often provide initial graphics framebuffers so the BIOS,
2825 bootloader or kernel can show basic video-output during boot for
2826 user-guidance and debugging. Historically, x86 used the VESA BIOS
2827 Extensions and EFI-framebuffers for this, which are mostly limited
2829 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2830 framebuffers so the new generic system-framebuffer drivers can be
2831 used on x86. If the framebuffer is not compatible with the generic
2832 modes, it is advertised as fallback platform framebuffer so legacy
2833 drivers like efifb, vesafb and uvesafb can pick it up.
2834 If this option is not selected, all system framebuffers are always
2835 marked as fallback platform framebuffers as usual.
2837 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2838 not be able to pick up generic system framebuffers if this option
2839 is selected. You are highly encouraged to enable simplefb as
2840 replacement if you select this option. simplefb can correctly deal
2841 with generic system framebuffers. But you should still keep vesafb
2842 and others enabled as fallback if a system framebuffer is
2843 incompatible with simplefb.
2850 menu "Binary Emulations"
2852 config IA32_EMULATION
2853 bool "IA32 Emulation"
2855 select ARCH_WANT_OLD_COMPAT_IPC
2857 select COMPAT_OLD_SIGACTION
2859 Include code to run legacy 32-bit programs under a
2860 64-bit kernel. You should likely turn this on, unless you're
2861 100% sure that you don't have any 32-bit programs left.
2864 tristate "IA32 a.out support"
2865 depends on IA32_EMULATION
2868 Support old a.out binaries in the 32bit emulation.
2871 bool "x32 ABI for 64-bit mode"
2874 Include code to run binaries for the x32 native 32-bit ABI
2875 for 64-bit processors. An x32 process gets access to the
2876 full 64-bit register file and wide data path while leaving
2877 pointers at 32 bits for smaller memory footprint.
2879 You will need a recent binutils (2.22 or later) with
2880 elf32_x86_64 support enabled to compile a kernel with this
2885 depends on IA32_EMULATION || X86_32
2887 select OLD_SIGSUSPEND3
2891 depends on IA32_EMULATION || X86_X32
2894 config COMPAT_FOR_U64_ALIGNMENT
2897 config SYSVIPC_COMPAT
2905 config HAVE_ATOMIC_IOMAP
2909 source "drivers/firmware/Kconfig"
2911 source "arch/x86/kvm/Kconfig"
2913 source "arch/x86/Kconfig.assembler"