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 HAVE_DEBUG_STACKOVERFLOW
18 select MODULES_USE_ELF_REL
20 select GENERIC_VDSO_32
25 # Options that are inherently 64-bit kernel only:
26 select ARCH_HAS_GIGANTIC_PAGE
27 select ARCH_SUPPORTS_INT128
28 select ARCH_USE_CMPXCHG_LOCKREF
29 select HAVE_ARCH_SOFT_DIRTY
30 select MODULES_USE_ELF_RELA
31 select NEED_DMA_MAP_STATE
33 select ARCH_HAS_SYSCALL_WRAPPER
35 config FORCE_DYNAMIC_FTRACE
38 depends on FUNCTION_TRACER
41 We keep the static function tracing (!DYNAMIC_FTRACE) around
42 in order to test the non static function tracing in the
43 generic code, as other architectures still use it. But we
44 only need to keep it around for x86_64. No need to keep it
45 for x86_32. For x86_32, force DYNAMIC_FTRACE.
49 # ( Note that options that are marked 'if X86_64' could in principle be
50 # ported to 32-bit as well. )
55 # Note: keep this list sorted alphabetically
57 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
58 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
59 select ARCH_32BIT_OFF_T if X86_32
60 select ARCH_CLOCKSOURCE_DATA
61 select ARCH_CLOCKSOURCE_INIT
62 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
63 select ARCH_HAS_DEBUG_VIRTUAL
64 select ARCH_HAS_DEVMEM_IS_ALLOWED
65 select ARCH_HAS_ELF_RANDOMIZE
66 select ARCH_HAS_FAST_MULTIPLIER
67 select ARCH_HAS_FILTER_PGPROT
68 select ARCH_HAS_FORTIFY_SOURCE
69 select ARCH_HAS_GCOV_PROFILE_ALL
70 select ARCH_HAS_KCOV if X86_64
71 select ARCH_HAS_MEM_ENCRYPT
72 select ARCH_HAS_MEMBARRIER_SYNC_CORE
73 select ARCH_HAS_PMEM_API if X86_64
74 select ARCH_HAS_PTE_DEVMAP if X86_64
75 select ARCH_HAS_PTE_SPECIAL
76 select ARCH_HAS_REFCOUNT
77 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
78 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
79 select ARCH_HAS_SET_MEMORY
80 select ARCH_HAS_SET_DIRECT_MAP
81 select ARCH_HAS_STRICT_KERNEL_RWX
82 select ARCH_HAS_STRICT_MODULE_RWX
83 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
84 select ARCH_HAS_UBSAN_SANITIZE_ALL
85 select ARCH_HAVE_NMI_SAFE_CMPXCHG
86 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
87 select ARCH_MIGHT_HAVE_PC_PARPORT
88 select ARCH_MIGHT_HAVE_PC_SERIO
90 select ARCH_SUPPORTS_ACPI
91 select ARCH_SUPPORTS_ATOMIC_RMW
92 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
93 select ARCH_USE_BUILTIN_BSWAP
94 select ARCH_USE_QUEUED_RWLOCKS
95 select ARCH_USE_QUEUED_SPINLOCKS
96 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
97 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
98 select ARCH_WANT_HUGE_PMD_SHARE
99 select ARCH_WANTS_THP_SWAP if X86_64
100 select BUILDTIME_EXTABLE_SORT
102 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
103 select CLOCKSOURCE_WATCHDOG
104 select DCACHE_WORD_ACCESS
105 select EDAC_ATOMIC_SCRUB
107 select GENERIC_CLOCKEVENTS
108 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
109 select GENERIC_CLOCKEVENTS_MIN_ADJUST
110 select GENERIC_CMOS_UPDATE
111 select GENERIC_CPU_AUTOPROBE
112 select GENERIC_CPU_VULNERABILITIES
113 select GENERIC_EARLY_IOREMAP
114 select GENERIC_FIND_FIRST_BIT
116 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
117 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
118 select GENERIC_IRQ_MIGRATION if SMP
119 select GENERIC_IRQ_PROBE
120 select GENERIC_IRQ_RESERVATION_MODE
121 select GENERIC_IRQ_SHOW
122 select GENERIC_PENDING_IRQ if SMP
123 select GENERIC_SMP_IDLE_THREAD
124 select GENERIC_STRNCPY_FROM_USER
125 select GENERIC_STRNLEN_USER
126 select GENERIC_TIME_VSYSCALL
127 select GENERIC_GETTIMEOFDAY
128 select GUP_GET_PTE_LOW_HIGH if X86_PAE
129 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
130 select HAVE_ACPI_APEI if ACPI
131 select HAVE_ACPI_APEI_NMI if ACPI
132 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
133 select HAVE_ARCH_AUDITSYSCALL
134 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
135 select HAVE_ARCH_JUMP_LABEL
136 select HAVE_ARCH_JUMP_LABEL_RELATIVE
137 select HAVE_ARCH_KASAN if X86_64
138 select HAVE_ARCH_KGDB
139 select HAVE_ARCH_MMAP_RND_BITS if MMU
140 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
141 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
142 select HAVE_ARCH_PREL32_RELOCATIONS
143 select HAVE_ARCH_SECCOMP_FILTER
144 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
145 select HAVE_ARCH_STACKLEAK
146 select HAVE_ARCH_TRACEHOOK
147 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
148 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
149 select HAVE_ARCH_VMAP_STACK if X86_64
150 select HAVE_ARCH_WITHIN_STACK_FRAMES
151 select HAVE_ASM_MODVERSIONS
152 select HAVE_CMPXCHG_DOUBLE
153 select HAVE_CMPXCHG_LOCAL
154 select HAVE_CONTEXT_TRACKING if X86_64
155 select HAVE_COPY_THREAD_TLS
156 select HAVE_C_RECORDMCOUNT
157 select HAVE_DEBUG_KMEMLEAK
158 select HAVE_DMA_CONTIGUOUS
159 select HAVE_DYNAMIC_FTRACE
160 select HAVE_DYNAMIC_FTRACE_WITH_REGS
162 select HAVE_EFFICIENT_UNALIGNED_ACCESS
164 select HAVE_EXIT_THREAD
166 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
167 select HAVE_FTRACE_MCOUNT_RECORD
168 select HAVE_FUNCTION_GRAPH_TRACER
169 select HAVE_FUNCTION_TRACER
170 select HAVE_GCC_PLUGINS
171 select HAVE_HW_BREAKPOINT
173 select HAVE_IOREMAP_PROT
174 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
175 select HAVE_IRQ_TIME_ACCOUNTING
176 select HAVE_KERNEL_BZIP2
177 select HAVE_KERNEL_GZIP
178 select HAVE_KERNEL_LZ4
179 select HAVE_KERNEL_LZMA
180 select HAVE_KERNEL_LZO
181 select HAVE_KERNEL_XZ
183 select HAVE_KPROBES_ON_FTRACE
184 select HAVE_FUNCTION_ERROR_INJECTION
185 select HAVE_KRETPROBES
187 select HAVE_LIVEPATCH if X86_64
188 select HAVE_MEMBLOCK_NODE_MAP
189 select HAVE_MIXED_BREAKPOINTS_REGS
190 select HAVE_MOD_ARCH_SPECIFIC
194 select HAVE_OPTPROBES
195 select HAVE_PCSPKR_PLATFORM
196 select HAVE_PERF_EVENTS
197 select HAVE_PERF_EVENTS_NMI
198 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
200 select HAVE_PERF_REGS
201 select HAVE_PERF_USER_STACK_DUMP
202 select HAVE_RCU_TABLE_FREE if PARAVIRT
203 select HAVE_REGS_AND_STACK_ACCESS_API
204 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
205 select HAVE_FUNCTION_ARG_ACCESS_API
206 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
207 select HAVE_STACK_VALIDATION if X86_64
209 select HAVE_SYSCALL_TRACEPOINTS
210 select HAVE_UNSTABLE_SCHED_CLOCK
211 select HAVE_USER_RETURN_NOTIFIER
212 select HAVE_GENERIC_VDSO
213 select HOTPLUG_SMT if SMP
214 select IRQ_FORCED_THREADING
215 select NEED_SG_DMA_LENGTH
216 select PCI_DOMAINS if PCI
217 select PCI_LOCKLESS_CONFIG if PCI
220 select RTC_MC146818_LIB
223 select SYSCTL_EXCEPTION_TRACE
224 select THREAD_INFO_IN_TASK
225 select USER_STACKTRACE_SUPPORT
227 select X86_FEATURE_NAMES if PROC_FS
228 select PROC_PID_ARCH_STATUS if PROC_FS
230 config INSTRUCTION_DECODER
232 depends on KPROBES || PERF_EVENTS || UPROBES
236 default "elf32-i386" if X86_32
237 default "elf64-x86-64" if X86_64
239 config ARCH_DEFCONFIG
241 default "arch/x86/configs/i386_defconfig" if X86_32
242 default "arch/x86/configs/x86_64_defconfig" if X86_64
244 config LOCKDEP_SUPPORT
247 config STACKTRACE_SUPPORT
253 config ARCH_MMAP_RND_BITS_MIN
257 config ARCH_MMAP_RND_BITS_MAX
261 config ARCH_MMAP_RND_COMPAT_BITS_MIN
264 config ARCH_MMAP_RND_COMPAT_BITS_MAX
270 config GENERIC_ISA_DMA
272 depends on ISA_DMA_API
277 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
279 config GENERIC_BUG_RELATIVE_POINTERS
282 config ARCH_MAY_HAVE_PC_FDC
284 depends on ISA_DMA_API
286 config GENERIC_CALIBRATE_DELAY
289 config ARCH_HAS_CPU_RELAX
292 config ARCH_HAS_CACHE_LINE_SIZE
295 config ARCH_HAS_FILTER_PGPROT
298 config HAVE_SETUP_PER_CPU_AREA
301 config NEED_PER_CPU_EMBED_FIRST_CHUNK
304 config NEED_PER_CPU_PAGE_FIRST_CHUNK
307 config ARCH_HIBERNATION_POSSIBLE
310 config ARCH_SUSPEND_POSSIBLE
313 config ARCH_WANT_GENERAL_HUGETLB
322 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
325 config KASAN_SHADOW_OFFSET
328 default 0xdffffc0000000000
330 config HAVE_INTEL_TXT
332 depends on INTEL_IOMMU && ACPI
336 depends on X86_32 && SMP
340 depends on X86_64 && SMP
342 config X86_32_LAZY_GS
344 depends on X86_32 && !STACKPROTECTOR
346 config ARCH_SUPPORTS_UPROBES
349 config FIX_EARLYCON_MEM
352 config DYNAMIC_PHYSICAL_MASK
355 config PGTABLE_LEVELS
357 default 5 if X86_5LEVEL
362 config CC_HAS_SANE_STACKPROTECTOR
364 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
365 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
367 We have to make sure stack protector is unconditionally disabled if
368 the compiler produces broken code.
370 menu "Processor type and features"
373 bool "DMA memory allocation support" if EXPERT
376 DMA memory allocation support allows devices with less than 32-bit
377 addressing to allocate within the first 16MB of address space.
378 Disable if no such devices will be used.
383 bool "Symmetric multi-processing support"
385 This enables support for systems with more than one CPU. If you have
386 a system with only one CPU, say N. If you have a system with more
389 If you say N here, the kernel will run on uni- and multiprocessor
390 machines, but will use only one CPU of a multiprocessor machine. If
391 you say Y here, the kernel will run on many, but not all,
392 uniprocessor machines. On a uniprocessor machine, the kernel
393 will run faster if you say N here.
395 Note that if you say Y here and choose architecture "586" or
396 "Pentium" under "Processor family", the kernel will not work on 486
397 architectures. Similarly, multiprocessor kernels for the "PPro"
398 architecture may not work on all Pentium based boards.
400 People using multiprocessor machines who say Y here should also say
401 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
402 Management" code will be disabled if you say Y here.
404 See also <file:Documentation/x86/i386/IO-APIC.rst>,
405 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
406 <http://www.tldp.org/docs.html#howto>.
408 If you don't know what to do here, say N.
410 config X86_FEATURE_NAMES
411 bool "Processor feature human-readable names" if EMBEDDED
414 This option compiles in a table of x86 feature bits and corresponding
415 names. This is required to support /proc/cpuinfo and a few kernel
416 messages. You can disable this to save space, at the expense of
417 making those few kernel messages show numeric feature bits instead.
422 bool "Support x2apic"
423 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
425 This enables x2apic support on CPUs that have this feature.
427 This allows 32-bit apic IDs (so it can support very large systems),
428 and accesses the local apic via MSRs not via mmio.
430 If you don't know what to do here, say N.
433 bool "Enable MPS table" if ACPI || SFI
435 depends on X86_LOCAL_APIC
437 For old smp systems that do not have proper acpi support. Newer systems
438 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
442 depends on X86_GOLDFISH
445 bool "Avoid speculative indirect branches in kernel"
447 select STACK_VALIDATION if HAVE_STACK_VALIDATION
449 Compile kernel with the retpoline compiler options to guard against
450 kernel-to-user data leaks by avoiding speculative indirect
451 branches. Requires a compiler with -mindirect-branch=thunk-extern
452 support for full protection. The kernel may run slower.
454 config X86_CPU_RESCTRL
455 bool "x86 CPU resource control support"
456 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
459 Enable x86 CPU resource control support.
461 Provide support for the allocation and monitoring of system resources
464 Intel calls this Intel Resource Director Technology
465 (Intel(R) RDT). More information about RDT can be found in the
466 Intel x86 Architecture Software Developer Manual.
468 AMD calls this AMD Platform Quality of Service (AMD QoS).
469 More information about AMD QoS can be found in the AMD64 Technology
470 Platform Quality of Service Extensions manual.
476 bool "Support for big SMP systems with more than 8 CPUs"
479 This option is needed for the systems that have more than 8 CPUs
481 config X86_EXTENDED_PLATFORM
482 bool "Support for extended (non-PC) x86 platforms"
485 If you disable this option then the kernel will only support
486 standard PC platforms. (which covers the vast majority of
489 If you enable this option then you'll be able to select support
490 for the following (non-PC) 32 bit x86 platforms:
491 Goldfish (Android emulator)
494 SGI 320/540 (Visual Workstation)
495 STA2X11-based (e.g. Northville)
496 Moorestown MID devices
498 If you have one of these systems, or if you want to build a
499 generic distribution kernel, say Y here - otherwise say N.
503 config X86_EXTENDED_PLATFORM
504 bool "Support for extended (non-PC) x86 platforms"
507 If you disable this option then the kernel will only support
508 standard PC platforms. (which covers the vast majority of
511 If you enable this option then you'll be able to select support
512 for the following (non-PC) 64 bit x86 platforms:
517 If you have one of these systems, or if you want to build a
518 generic distribution kernel, say Y here - otherwise say N.
520 # This is an alphabetically sorted list of 64 bit extended platforms
521 # Please maintain the alphabetic order if and when there are additions
523 bool "Numascale NumaChip"
525 depends on X86_EXTENDED_PLATFORM
528 depends on X86_X2APIC
529 depends on PCI_MMCONFIG
531 Adds support for Numascale NumaChip large-SMP systems. Needed to
532 enable more than ~168 cores.
533 If you don't have one of these, you should say N here.
537 select HYPERVISOR_GUEST
539 depends on X86_64 && PCI
540 depends on X86_EXTENDED_PLATFORM
543 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
544 supposed to run on these EM64T-based machines. Only choose this option
545 if you have one of these machines.
548 bool "SGI Ultraviolet"
550 depends on X86_EXTENDED_PLATFORM
553 depends on X86_X2APIC
556 This option is needed in order to support SGI Ultraviolet systems.
557 If you don't have one of these, you should say N here.
559 # Following is an alphabetically sorted list of 32 bit extended platforms
560 # Please maintain the alphabetic order if and when there are additions
563 bool "Goldfish (Virtual Platform)"
564 depends on X86_EXTENDED_PLATFORM
566 Enable support for the Goldfish virtual platform used primarily
567 for Android development. Unless you are building for the Android
568 Goldfish emulator say N here.
571 bool "CE4100 TV platform"
573 depends on PCI_GODIRECT
574 depends on X86_IO_APIC
576 depends on X86_EXTENDED_PLATFORM
577 select X86_REBOOTFIXUPS
579 select OF_EARLY_FLATTREE
581 Select for the Intel CE media processor (CE4100) SOC.
582 This option compiles in support for the CE4100 SOC for settop
583 boxes and media devices.
586 bool "Intel MID platform support"
587 depends on X86_EXTENDED_PLATFORM
588 depends on X86_PLATFORM_DEVICES
590 depends on X86_64 || (PCI_GOANY && X86_32)
591 depends on X86_IO_APIC
597 select MFD_INTEL_MSIC
599 Select to build a kernel capable of supporting Intel MID (Mobile
600 Internet Device) platform systems which do not have the PCI legacy
601 interfaces. If you are building for a PC class system say N here.
603 Intel MID platforms are based on an Intel processor and chipset which
604 consume less power than most of the x86 derivatives.
606 config X86_INTEL_QUARK
607 bool "Intel Quark platform support"
609 depends on X86_EXTENDED_PLATFORM
610 depends on X86_PLATFORM_DEVICES
614 depends on X86_IO_APIC
619 Select to include support for Quark X1000 SoC.
620 Say Y here if you have a Quark based system such as the Arduino
621 compatible Intel Galileo.
623 config X86_INTEL_LPSS
624 bool "Intel Low Power Subsystem Support"
625 depends on X86 && ACPI && PCI
630 Select to build support for Intel Low Power Subsystem such as
631 found on Intel Lynxpoint PCH. Selecting this option enables
632 things like clock tree (common clock framework) and pincontrol
633 which are needed by the LPSS peripheral drivers.
635 config X86_AMD_PLATFORM_DEVICE
636 bool "AMD ACPI2Platform devices support"
641 Select to interpret AMD specific ACPI device to platform device
642 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
643 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
644 implemented under PINCTRL subsystem.
647 tristate "Intel SoC IOSF Sideband support for SoC platforms"
650 This option enables sideband register access support for Intel SoC
651 platforms. On these platforms the IOSF sideband is used in lieu of
652 MSR's for some register accesses, mostly but not limited to thermal
653 and power. Drivers may query the availability of this device to
654 determine if they need the sideband in order to work on these
655 platforms. The sideband is available on the following SoC products.
656 This list is not meant to be exclusive.
661 You should say Y if you are running a kernel on one of these SoC's.
663 config IOSF_MBI_DEBUG
664 bool "Enable IOSF sideband access through debugfs"
665 depends on IOSF_MBI && DEBUG_FS
667 Select this option to expose the IOSF sideband access registers (MCR,
668 MDR, MCRX) through debugfs to write and read register information from
669 different units on the SoC. This is most useful for obtaining device
670 state information for debug and analysis. As this is a general access
671 mechanism, users of this option would have specific knowledge of the
672 device they want to access.
674 If you don't require the option or are in doubt, say N.
677 bool "RDC R-321x SoC"
679 depends on X86_EXTENDED_PLATFORM
681 select X86_REBOOTFIXUPS
683 This option is needed for RDC R-321x system-on-chip, also known
685 If you don't have one of these chips, you should say N here.
687 config X86_32_NON_STANDARD
688 bool "Support non-standard 32-bit SMP architectures"
689 depends on X86_32 && SMP
690 depends on X86_EXTENDED_PLATFORM
692 This option compiles in the bigsmp and STA2X11 default
693 subarchitectures. It is intended for a generic binary
694 kernel. If you select them all, kernel will probe it one by
695 one and will fallback to default.
697 # Alphabetically sorted list of Non standard 32 bit platforms
699 config X86_SUPPORTS_MEMORY_FAILURE
701 # MCE code calls memory_failure():
703 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
704 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
705 depends on X86_64 || !SPARSEMEM
706 select ARCH_SUPPORTS_MEMORY_FAILURE
709 bool "STA2X11 Companion Chip Support"
710 depends on X86_32_NON_STANDARD && PCI
711 select ARCH_HAS_PHYS_TO_DMA
716 This adds support for boards based on the STA2X11 IO-Hub,
717 a.k.a. "ConneXt". The chip is used in place of the standard
718 PC chipset, so all "standard" peripherals are missing. If this
719 option is selected the kernel will still be able to boot on
720 standard PC machines.
723 tristate "Eurobraille/Iris poweroff module"
726 The Iris machines from EuroBraille do not have APM or ACPI support
727 to shut themselves down properly. A special I/O sequence is
728 needed to do so, which is what this module does at
731 This is only for Iris machines from EuroBraille.
735 config SCHED_OMIT_FRAME_POINTER
737 prompt "Single-depth WCHAN output"
740 Calculate simpler /proc/<PID>/wchan values. If this option
741 is disabled then wchan values will recurse back to the
742 caller function. This provides more accurate wchan values,
743 at the expense of slightly more scheduling overhead.
745 If in doubt, say "Y".
747 menuconfig HYPERVISOR_GUEST
748 bool "Linux guest support"
750 Say Y here to enable options for running Linux under various hyper-
751 visors. This option enables basic hypervisor detection and platform
754 If you say N, all options in this submenu will be skipped and
755 disabled, and Linux guest support won't be built in.
760 bool "Enable paravirtualization code"
762 This changes the kernel so it can modify itself when it is run
763 under a hypervisor, potentially improving performance significantly
764 over full virtualization. However, when run without a hypervisor
765 the kernel is theoretically slower and slightly larger.
770 config PARAVIRT_DEBUG
771 bool "paravirt-ops debugging"
772 depends on PARAVIRT && DEBUG_KERNEL
774 Enable to debug paravirt_ops internals. Specifically, BUG if
775 a paravirt_op is missing when it is called.
777 config PARAVIRT_SPINLOCKS
778 bool "Paravirtualization layer for spinlocks"
779 depends on PARAVIRT && SMP
781 Paravirtualized spinlocks allow a pvops backend to replace the
782 spinlock implementation with something virtualization-friendly
783 (for example, block the virtual CPU rather than spinning).
785 It has a minimal impact on native kernels and gives a nice performance
786 benefit on paravirtualized KVM / Xen kernels.
788 If you are unsure how to answer this question, answer Y.
790 config X86_HV_CALLBACK_VECTOR
793 source "arch/x86/xen/Kconfig"
796 bool "KVM Guest support (including kvmclock)"
798 select PARAVIRT_CLOCK
799 select ARCH_CPUIDLE_HALTPOLL
802 This option enables various optimizations for running under the KVM
803 hypervisor. It includes a paravirtualized clock, so that instead
804 of relying on a PIT (or probably other) emulation by the
805 underlying device model, the host provides the guest with
806 timing infrastructure such as time of day, and system time
808 config ARCH_CPUIDLE_HALTPOLL
810 prompt "Disable host haltpoll when loading haltpoll driver"
812 If virtualized under KVM, disable host haltpoll.
815 bool "Support for running PVH guests"
817 This option enables the PVH entry point for guest virtual machines
818 as specified in the x86/HVM direct boot ABI.
821 bool "Enable debug information for KVM Guests in debugfs"
822 depends on KVM_GUEST && DEBUG_FS
824 This option enables collection of various statistics for KVM guest.
825 Statistics are displayed in debugfs filesystem. Enabling this option
826 may incur significant overhead.
828 config PARAVIRT_TIME_ACCOUNTING
829 bool "Paravirtual steal time accounting"
832 Select this option to enable fine granularity task steal time
833 accounting. Time spent executing other tasks in parallel with
834 the current vCPU is discounted from the vCPU power. To account for
835 that, there can be a small performance impact.
837 If in doubt, say N here.
839 config PARAVIRT_CLOCK
842 config JAILHOUSE_GUEST
843 bool "Jailhouse non-root cell support"
844 depends on X86_64 && PCI
847 This option allows to run Linux as guest in a Jailhouse non-root
848 cell. You can leave this option disabled if you only want to start
849 Jailhouse and run Linux afterwards in the root cell.
852 bool "ACRN Guest support"
854 select X86_HV_CALLBACK_VECTOR
856 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
857 a flexible, lightweight reference open-source hypervisor, built with
858 real-time and safety-criticality in mind. It is built for embedded
859 IOT with small footprint and real-time features. More details can be
860 found in https://projectacrn.org/.
862 endif #HYPERVISOR_GUEST
864 source "arch/x86/Kconfig.cpu"
868 prompt "HPET Timer Support" if X86_32
870 Use the IA-PC HPET (High Precision Event Timer) to manage
871 time in preference to the PIT and RTC, if a HPET is
873 HPET is the next generation timer replacing legacy 8254s.
874 The HPET provides a stable time base on SMP
875 systems, unlike the TSC, but it is more expensive to access,
876 as it is off-chip. The interface used is documented
877 in the HPET spec, revision 1.
879 You can safely choose Y here. However, HPET will only be
880 activated if the platform and the BIOS support this feature.
881 Otherwise the 8254 will be used for timing services.
883 Choose N to continue using the legacy 8254 timer.
885 config HPET_EMULATE_RTC
887 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
890 def_bool y if X86_INTEL_MID
891 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
893 depends on X86_INTEL_MID && SFI
895 APB timer is the replacement for 8254, HPET on X86 MID platforms.
896 The APBT provides a stable time base on SMP
897 systems, unlike the TSC, but it is more expensive to access,
898 as it is off-chip. APB timers are always running regardless of CPU
899 C states, they are used as per CPU clockevent device when possible.
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"
917 depends on X86_64 && PCI && AMD_NB
919 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
920 GART based hardware IOMMUs.
922 The GART supports full DMA access for devices with 32-bit access
923 limitations, on systems with more than 3 GB. This is usually needed
924 for USB, sound, many IDE/SATA chipsets and some other devices.
926 Newer systems typically have a modern AMD IOMMU, supported via
927 the CONFIG_AMD_IOMMU=y config option.
929 In normal configurations this driver is only active when needed:
930 there's more than 3 GB of memory and the system contains a
931 32-bit limited device.
936 bool "IBM Calgary IOMMU support"
939 depends on X86_64 && PCI
941 Support for hardware IOMMUs in IBM's xSeries x366 and x460
942 systems. Needed to run systems with more than 3GB of memory
943 properly with 32-bit PCI devices that do not support DAC
944 (Double Address Cycle). Calgary also supports bus level
945 isolation, where all DMAs pass through the IOMMU. This
946 prevents them from going anywhere except their intended
947 destination. This catches hard-to-find kernel bugs and
948 mis-behaving drivers and devices that do not use the DMA-API
949 properly to set up their DMA buffers. The IOMMU can be
950 turned off at boot time with the iommu=off parameter.
951 Normally the kernel will make the right choice by itself.
954 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
956 prompt "Should Calgary be enabled by default?"
957 depends on CALGARY_IOMMU
959 Should Calgary be enabled by default? if you choose 'y', Calgary
960 will be used (if it exists). If you choose 'n', Calgary will not be
961 used even if it exists. If you choose 'n' and would like to use
962 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
966 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
967 depends on X86_64 && SMP && DEBUG_KERNEL
968 select CPUMASK_OFFSTACK
970 Enable maximum number of CPUS and NUMA Nodes for this architecture.
974 # The maximum number of CPUs supported:
976 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
977 # and which can be configured interactively in the
978 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
980 # The ranges are different on 32-bit and 64-bit kernels, depending on
981 # hardware capabilities and scalability features of the kernel.
983 # ( If MAXSMP is enabled we just use the highest possible value and disable
984 # interactive configuration. )
987 config NR_CPUS_RANGE_BEGIN
989 default NR_CPUS_RANGE_END if MAXSMP
993 config NR_CPUS_RANGE_END
996 default 64 if SMP && X86_BIGSMP
997 default 8 if SMP && !X86_BIGSMP
1000 config NR_CPUS_RANGE_END
1003 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
1004 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
1007 config NR_CPUS_DEFAULT
1010 default 32 if X86_BIGSMP
1014 config NR_CPUS_DEFAULT
1017 default 8192 if MAXSMP
1022 int "Maximum number of CPUs" if SMP && !MAXSMP
1023 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1024 default NR_CPUS_DEFAULT
1026 This allows you to specify the maximum number of CPUs which this
1027 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1028 supported value is 8192, otherwise the maximum value is 512. The
1029 minimum value which makes sense is 2.
1031 This is purely to save memory: each supported CPU adds about 8KB
1032 to the kernel image.
1039 prompt "Multi-core scheduler support"
1042 Multi-core scheduler support improves the CPU scheduler's decision
1043 making when dealing with multi-core CPU chips at a cost of slightly
1044 increased overhead in some places. If unsure say N here.
1046 config SCHED_MC_PRIO
1047 bool "CPU core priorities scheduler support"
1048 depends on SCHED_MC && CPU_SUP_INTEL
1049 select X86_INTEL_PSTATE
1053 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1054 core ordering determined at manufacturing time, which allows
1055 certain cores to reach higher turbo frequencies (when running
1056 single threaded workloads) than others.
1058 Enabling this kernel feature teaches the scheduler about
1059 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1060 scheduler's CPU selection logic accordingly, so that higher
1061 overall system performance can be achieved.
1063 This feature will have no effect on CPUs without this feature.
1065 If unsure say Y here.
1069 depends on !SMP && X86_LOCAL_APIC
1072 bool "Local APIC support on uniprocessors" if !PCI_MSI
1074 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1076 A local APIC (Advanced Programmable Interrupt Controller) is an
1077 integrated interrupt controller in the CPU. If you have a single-CPU
1078 system which has a processor with a local APIC, you can say Y here to
1079 enable and use it. If you say Y here even though your machine doesn't
1080 have a local APIC, then the kernel will still run with no slowdown at
1081 all. The local APIC supports CPU-generated self-interrupts (timer,
1082 performance counters), and the NMI watchdog which detects hard
1085 config X86_UP_IOAPIC
1086 bool "IO-APIC support on uniprocessors"
1087 depends on X86_UP_APIC
1089 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1090 SMP-capable replacement for PC-style interrupt controllers. Most
1091 SMP systems and many recent uniprocessor systems have one.
1093 If you have a single-CPU system with an IO-APIC, you can say Y here
1094 to use it. If you say Y here even though your machine doesn't have
1095 an IO-APIC, then the kernel will still run with no slowdown at all.
1097 config X86_LOCAL_APIC
1099 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1100 select IRQ_DOMAIN_HIERARCHY
1101 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1105 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1107 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1108 bool "Reroute for broken boot IRQs"
1109 depends on X86_IO_APIC
1111 This option enables a workaround that fixes a source of
1112 spurious interrupts. This is recommended when threaded
1113 interrupt handling is used on systems where the generation of
1114 superfluous "boot interrupts" cannot be disabled.
1116 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1117 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1118 kernel does during interrupt handling). On chipsets where this
1119 boot IRQ generation cannot be disabled, this workaround keeps
1120 the original IRQ line masked so that only the equivalent "boot
1121 IRQ" is delivered to the CPUs. The workaround also tells the
1122 kernel to set up the IRQ handler on the boot IRQ line. In this
1123 way only one interrupt is delivered to the kernel. Otherwise
1124 the spurious second interrupt may cause the kernel to bring
1125 down (vital) interrupt lines.
1127 Only affects "broken" chipsets. Interrupt sharing may be
1128 increased on these systems.
1131 bool "Machine Check / overheating reporting"
1132 select GENERIC_ALLOCATOR
1135 Machine Check support allows the processor to notify the
1136 kernel if it detects a problem (e.g. overheating, data corruption).
1137 The action the kernel takes depends on the severity of the problem,
1138 ranging from warning messages to halting the machine.
1140 config X86_MCELOG_LEGACY
1141 bool "Support for deprecated /dev/mcelog character device"
1144 Enable support for /dev/mcelog which is needed by the old mcelog
1145 userspace logging daemon. Consider switching to the new generation
1148 config X86_MCE_INTEL
1150 prompt "Intel MCE features"
1151 depends on X86_MCE && X86_LOCAL_APIC
1153 Additional support for intel specific MCE features such as
1154 the thermal monitor.
1158 prompt "AMD MCE features"
1159 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1161 Additional support for AMD specific MCE features such as
1162 the DRAM Error Threshold.
1164 config X86_ANCIENT_MCE
1165 bool "Support for old Pentium 5 / WinChip machine checks"
1166 depends on X86_32 && X86_MCE
1168 Include support for machine check handling on old Pentium 5 or WinChip
1169 systems. These typically need to be enabled explicitly on the command
1172 config X86_MCE_THRESHOLD
1173 depends on X86_MCE_AMD || X86_MCE_INTEL
1176 config X86_MCE_INJECT
1177 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1178 tristate "Machine check injector support"
1180 Provide support for injecting machine checks for testing purposes.
1181 If you don't know what a machine check is and you don't do kernel
1182 QA it is safe to say n.
1184 config X86_THERMAL_VECTOR
1186 depends on X86_MCE_INTEL
1188 source "arch/x86/events/Kconfig"
1190 config X86_LEGACY_VM86
1191 bool "Legacy VM86 support"
1194 This option allows user programs to put the CPU into V8086
1195 mode, which is an 80286-era approximation of 16-bit real mode.
1197 Some very old versions of X and/or vbetool require this option
1198 for user mode setting. Similarly, DOSEMU will use it if
1199 available to accelerate real mode DOS programs. However, any
1200 recent version of DOSEMU, X, or vbetool should be fully
1201 functional even without kernel VM86 support, as they will all
1202 fall back to software emulation. Nevertheless, if you are using
1203 a 16-bit DOS program where 16-bit performance matters, vm86
1204 mode might be faster than emulation and you might want to
1207 Note that any app that works on a 64-bit kernel is unlikely to
1208 need this option, as 64-bit kernels don't, and can't, support
1209 V8086 mode. This option is also unrelated to 16-bit protected
1210 mode and is not needed to run most 16-bit programs under Wine.
1212 Enabling this option increases the complexity of the kernel
1213 and slows down exception handling a tiny bit.
1215 If unsure, say N here.
1219 default X86_LEGACY_VM86
1222 bool "Enable support for 16-bit segments" if EXPERT
1224 depends on MODIFY_LDT_SYSCALL
1226 This option is required by programs like Wine to run 16-bit
1227 protected mode legacy code on x86 processors. Disabling
1228 this option saves about 300 bytes on i386, or around 6K text
1229 plus 16K runtime memory on x86-64,
1233 depends on X86_16BIT && X86_32
1237 depends on X86_16BIT && X86_64
1239 config X86_VSYSCALL_EMULATION
1240 bool "Enable vsyscall emulation" if EXPERT
1244 This enables emulation of the legacy vsyscall page. Disabling
1245 it is roughly equivalent to booting with vsyscall=none, except
1246 that it will also disable the helpful warning if a program
1247 tries to use a vsyscall. With this option set to N, offending
1248 programs will just segfault, citing addresses of the form
1251 This option is required by many programs built before 2013, and
1252 care should be used even with newer programs if set to N.
1254 Disabling this option saves about 7K of kernel size and
1255 possibly 4K of additional runtime pagetable memory.
1259 default X86_IOPL_EMULATION
1261 config X86_IOPL_EMULATION
1262 bool "IOPL Emulation"
1264 Legacy IOPL support is an overbroad mechanism which allows user
1265 space aside of accessing all 65536 I/O ports also to disable
1266 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1267 capabilities and permission from potentially active security
1270 The emulation restricts the functionality of the syscall to
1271 only allowing the full range I/O port access, but prevents the
1272 ability to disable interrupts from user space.
1274 config X86_IOPL_LEGACY
1277 Allow the full IOPL permissions, i.e. user space access to all
1278 65536 I/O ports and also the ability to disable interrupts, which
1279 is overbroad and can result in system lockups.
1281 config X86_IOPL_NONE
1284 Disable the IOPL permission syscall. That's the safest option as
1285 no sane application should depend on this functionality.
1290 tristate "Toshiba Laptop support"
1293 This adds a driver to safely access the System Management Mode of
1294 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1295 not work on models with a Phoenix BIOS. The System Management Mode
1296 is used to set the BIOS and power saving options on Toshiba portables.
1298 For information on utilities to make use of this driver see the
1299 Toshiba Linux utilities web site at:
1300 <http://www.buzzard.org.uk/toshiba/>.
1302 Say Y if you intend to run this kernel on a Toshiba portable.
1306 tristate "Dell i8k legacy laptop support"
1308 select SENSORS_DELL_SMM
1310 This option enables legacy /proc/i8k userspace interface in hwmon
1311 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1312 temperature and allows controlling fan speeds of Dell laptops via
1313 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1314 it reports also power and hotkey status. For fan speed control is
1315 needed userspace package i8kutils.
1317 Say Y if you intend to run this kernel on old Dell laptops or want to
1318 use userspace package i8kutils.
1321 config X86_REBOOTFIXUPS
1322 bool "Enable X86 board specific fixups for reboot"
1325 This enables chipset and/or board specific fixups to be done
1326 in order to get reboot to work correctly. This is only needed on
1327 some combinations of hardware and BIOS. The symptom, for which
1328 this config is intended, is when reboot ends with a stalled/hung
1331 Currently, the only fixup is for the Geode machines using
1332 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1334 Say Y if you want to enable the fixup. Currently, it's safe to
1335 enable this option even if you don't need it.
1339 bool "CPU microcode loading support"
1341 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1344 If you say Y here, you will be able to update the microcode on
1345 Intel and AMD processors. The Intel support is for the IA32 family,
1346 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1347 AMD support is for families 0x10 and later. You will obviously need
1348 the actual microcode binary data itself which is not shipped with
1351 The preferred method to load microcode from a detached initrd is described
1352 in Documentation/x86/microcode.rst. For that you need to enable
1353 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1354 initrd for microcode blobs.
1356 In addition, you can build the microcode into the kernel. For that you
1357 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1360 config MICROCODE_INTEL
1361 bool "Intel microcode loading support"
1362 depends on MICROCODE
1366 This options enables microcode patch loading support for Intel
1369 For the current Intel microcode data package go to
1370 <https://downloadcenter.intel.com> and search for
1371 'Linux Processor Microcode Data File'.
1373 config MICROCODE_AMD
1374 bool "AMD microcode loading support"
1375 depends on MICROCODE
1378 If you select this option, microcode patch loading support for AMD
1379 processors will be enabled.
1381 config MICROCODE_OLD_INTERFACE
1382 bool "Ancient loading interface (DEPRECATED)"
1384 depends on MICROCODE
1386 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1387 which was used by userspace tools like iucode_tool and microcode.ctl.
1388 It is inadequate because it runs too late to be able to properly
1389 load microcode on a machine and it needs special tools. Instead, you
1390 should've switched to the early loading method with the initrd or
1391 builtin microcode by now: Documentation/x86/microcode.rst
1394 tristate "/dev/cpu/*/msr - Model-specific register support"
1396 This device gives privileged processes access to the x86
1397 Model-Specific Registers (MSRs). It is a character device with
1398 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1399 MSR accesses are directed to a specific CPU on multi-processor
1403 tristate "/dev/cpu/*/cpuid - CPU information support"
1405 This device gives processes access to the x86 CPUID instruction to
1406 be executed on a specific processor. It is a character device
1407 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1411 prompt "High Memory Support"
1418 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1419 However, the address space of 32-bit x86 processors is only 4
1420 Gigabytes large. That means that, if you have a large amount of
1421 physical memory, not all of it can be "permanently mapped" by the
1422 kernel. The physical memory that's not permanently mapped is called
1425 If you are compiling a kernel which will never run on a machine with
1426 more than 1 Gigabyte total physical RAM, answer "off" here (default
1427 choice and suitable for most users). This will result in a "3GB/1GB"
1428 split: 3GB are mapped so that each process sees a 3GB virtual memory
1429 space and the remaining part of the 4GB virtual memory space is used
1430 by the kernel to permanently map as much physical memory as
1433 If the machine has between 1 and 4 Gigabytes physical RAM, then
1436 If more than 4 Gigabytes is used then answer "64GB" here. This
1437 selection turns Intel PAE (Physical Address Extension) mode on.
1438 PAE implements 3-level paging on IA32 processors. PAE is fully
1439 supported by Linux, PAE mode is implemented on all recent Intel
1440 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1441 then the kernel will not boot on CPUs that don't support PAE!
1443 The actual amount of total physical memory will either be
1444 auto detected or can be forced by using a kernel command line option
1445 such as "mem=256M". (Try "man bootparam" or see the documentation of
1446 your boot loader (lilo or loadlin) about how to pass options to the
1447 kernel at boot time.)
1449 If unsure, say "off".
1454 Select this if you have a 32-bit processor and between 1 and 4
1455 gigabytes of physical RAM.
1459 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1462 Select this if you have a 32-bit processor and more than 4
1463 gigabytes of physical RAM.
1468 prompt "Memory split" if EXPERT
1472 Select the desired split between kernel and user memory.
1474 If the address range available to the kernel is less than the
1475 physical memory installed, the remaining memory will be available
1476 as "high memory". Accessing high memory is a little more costly
1477 than low memory, as it needs to be mapped into the kernel first.
1478 Note that increasing the kernel address space limits the range
1479 available to user programs, making the address space there
1480 tighter. Selecting anything other than the default 3G/1G split
1481 will also likely make your kernel incompatible with binary-only
1484 If you are not absolutely sure what you are doing, leave this
1488 bool "3G/1G user/kernel split"
1489 config VMSPLIT_3G_OPT
1491 bool "3G/1G user/kernel split (for full 1G low memory)"
1493 bool "2G/2G user/kernel split"
1494 config VMSPLIT_2G_OPT
1496 bool "2G/2G user/kernel split (for full 2G low memory)"
1498 bool "1G/3G user/kernel split"
1503 default 0xB0000000 if VMSPLIT_3G_OPT
1504 default 0x80000000 if VMSPLIT_2G
1505 default 0x78000000 if VMSPLIT_2G_OPT
1506 default 0x40000000 if VMSPLIT_1G
1512 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1515 bool "PAE (Physical Address Extension) Support"
1516 depends on X86_32 && !HIGHMEM4G
1517 select PHYS_ADDR_T_64BIT
1520 PAE is required for NX support, and furthermore enables
1521 larger swapspace support for non-overcommit purposes. It
1522 has the cost of more pagetable lookup overhead, and also
1523 consumes more pagetable space per process.
1526 bool "Enable 5-level page tables support"
1527 select DYNAMIC_MEMORY_LAYOUT
1528 select SPARSEMEM_VMEMMAP
1531 5-level paging enables access to larger address space:
1532 upto 128 PiB of virtual address space and 4 PiB of
1533 physical address space.
1535 It will be supported by future Intel CPUs.
1537 A kernel with the option enabled can be booted on machines that
1538 support 4- or 5-level paging.
1540 See Documentation/x86/x86_64/5level-paging.rst for more
1545 config X86_DIRECT_GBPAGES
1549 Certain kernel features effectively disable kernel
1550 linear 1 GB mappings (even if the CPU otherwise
1551 supports them), so don't confuse the user by printing
1552 that we have them enabled.
1554 config X86_CPA_STATISTICS
1555 bool "Enable statistic for Change Page Attribute"
1558 Expose statistics about the Change Page Attribute mechanims, which
1559 helps to determine the effectiveness of preserving large and huge
1560 page mappings when mapping protections are changed.
1562 config AMD_MEM_ENCRYPT
1563 bool "AMD Secure Memory Encryption (SME) support"
1564 depends on X86_64 && CPU_SUP_AMD
1565 select DYNAMIC_PHYSICAL_MASK
1566 select ARCH_USE_MEMREMAP_PROT
1567 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1569 Say yes to enable support for the encryption of system memory.
1570 This requires an AMD processor that supports Secure Memory
1573 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1574 bool "Activate AMD Secure Memory Encryption (SME) by default"
1576 depends on AMD_MEM_ENCRYPT
1578 Say yes to have system memory encrypted by default if running on
1579 an AMD processor that supports Secure Memory Encryption (SME).
1581 If set to Y, then the encryption of system memory can be
1582 deactivated with the mem_encrypt=off command line option.
1584 If set to N, then the encryption of system memory can be
1585 activated with the mem_encrypt=on command line option.
1587 # Common NUMA Features
1589 bool "Numa Memory Allocation and Scheduler Support"
1591 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1592 default y if X86_BIGSMP
1594 Enable NUMA (Non Uniform Memory Access) support.
1596 The kernel will try to allocate memory used by a CPU on the
1597 local memory controller of the CPU and add some more
1598 NUMA awareness to the kernel.
1600 For 64-bit this is recommended if the system is Intel Core i7
1601 (or later), AMD Opteron, or EM64T NUMA.
1603 For 32-bit this is only needed if you boot a 32-bit
1604 kernel on a 64-bit NUMA platform.
1606 Otherwise, you should say N.
1610 prompt "Old style AMD Opteron NUMA detection"
1611 depends on X86_64 && NUMA && PCI
1613 Enable AMD NUMA node topology detection. You should say Y here if
1614 you have a multi processor AMD system. This uses an old method to
1615 read the NUMA configuration directly from the builtin Northbridge
1616 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1617 which also takes priority if both are compiled in.
1619 config X86_64_ACPI_NUMA
1621 prompt "ACPI NUMA detection"
1622 depends on X86_64 && NUMA && ACPI && PCI
1625 Enable ACPI SRAT based node topology detection.
1627 # Some NUMA nodes have memory ranges that span
1628 # other nodes. Even though a pfn is valid and
1629 # between a node's start and end pfns, it may not
1630 # reside on that node. See memmap_init_zone()
1632 config NODES_SPAN_OTHER_NODES
1634 depends on X86_64_ACPI_NUMA
1637 bool "NUMA emulation"
1640 Enable NUMA emulation. A flat machine will be split
1641 into virtual nodes when booted with "numa=fake=N", where N is the
1642 number of nodes. This is only useful for debugging.
1645 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1647 default "10" if MAXSMP
1648 default "6" if X86_64
1650 depends on NEED_MULTIPLE_NODES
1652 Specify the maximum number of NUMA Nodes available on the target
1653 system. Increases memory reserved to accommodate various tables.
1655 config ARCH_HAVE_MEMORY_PRESENT
1657 depends on X86_32 && DISCONTIGMEM
1659 config ARCH_FLATMEM_ENABLE
1661 depends on X86_32 && !NUMA
1663 config ARCH_DISCONTIGMEM_ENABLE
1665 depends on NUMA && X86_32
1668 config ARCH_SPARSEMEM_ENABLE
1670 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1671 select SPARSEMEM_STATIC if X86_32
1672 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1674 config ARCH_SPARSEMEM_DEFAULT
1675 def_bool X86_64 || (NUMA && X86_32)
1677 config ARCH_SELECT_MEMORY_MODEL
1679 depends on ARCH_SPARSEMEM_ENABLE
1681 config ARCH_MEMORY_PROBE
1682 bool "Enable sysfs memory/probe interface"
1683 depends on X86_64 && MEMORY_HOTPLUG
1685 This option enables a sysfs memory/probe interface for testing.
1686 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1687 If you are unsure how to answer this question, answer N.
1689 config ARCH_PROC_KCORE_TEXT
1691 depends on X86_64 && PROC_KCORE
1693 config ILLEGAL_POINTER_VALUE
1696 default 0xdead000000000000 if X86_64
1698 config X86_PMEM_LEGACY_DEVICE
1701 config X86_PMEM_LEGACY
1702 tristate "Support non-standard NVDIMMs and ADR protected memory"
1703 depends on PHYS_ADDR_T_64BIT
1705 select X86_PMEM_LEGACY_DEVICE
1708 Treat memory marked using the non-standard e820 type of 12 as used
1709 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1710 The kernel will offer these regions to the 'pmem' driver so
1711 they can be used for persistent storage.
1716 bool "Allocate 3rd-level pagetables from highmem"
1719 The VM uses one page table entry for each page of physical memory.
1720 For systems with a lot of RAM, this can be wasteful of precious
1721 low memory. Setting this option will put user-space page table
1722 entries in high memory.
1724 config X86_CHECK_BIOS_CORRUPTION
1725 bool "Check for low memory corruption"
1727 Periodically check for memory corruption in low memory, which
1728 is suspected to be caused by BIOS. Even when enabled in the
1729 configuration, it is disabled at runtime. Enable it by
1730 setting "memory_corruption_check=1" on the kernel command
1731 line. By default it scans the low 64k of memory every 60
1732 seconds; see the memory_corruption_check_size and
1733 memory_corruption_check_period parameters in
1734 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1736 When enabled with the default parameters, this option has
1737 almost no overhead, as it reserves a relatively small amount
1738 of memory and scans it infrequently. It both detects corruption
1739 and prevents it from affecting the running system.
1741 It is, however, intended as a diagnostic tool; if repeatable
1742 BIOS-originated corruption always affects the same memory,
1743 you can use memmap= to prevent the kernel from using that
1746 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1747 bool "Set the default setting of memory_corruption_check"
1748 depends on X86_CHECK_BIOS_CORRUPTION
1751 Set whether the default state of memory_corruption_check is
1754 config X86_RESERVE_LOW
1755 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1759 Specify the amount of low memory to reserve for the BIOS.
1761 The first page contains BIOS data structures that the kernel
1762 must not use, so that page must always be reserved.
1764 By default we reserve the first 64K of physical RAM, as a
1765 number of BIOSes are known to corrupt that memory range
1766 during events such as suspend/resume or monitor cable
1767 insertion, so it must not be used by the kernel.
1769 You can set this to 4 if you are absolutely sure that you
1770 trust the BIOS to get all its memory reservations and usages
1771 right. If you know your BIOS have problems beyond the
1772 default 64K area, you can set this to 640 to avoid using the
1773 entire low memory range.
1775 If you have doubts about the BIOS (e.g. suspend/resume does
1776 not work or there's kernel crashes after certain hardware
1777 hotplug events) then you might want to enable
1778 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1779 typical corruption patterns.
1781 Leave this to the default value of 64 if you are unsure.
1783 config MATH_EMULATION
1785 depends on MODIFY_LDT_SYSCALL
1786 prompt "Math emulation" if X86_32
1788 Linux can emulate a math coprocessor (used for floating point
1789 operations) if you don't have one. 486DX and Pentium processors have
1790 a math coprocessor built in, 486SX and 386 do not, unless you added
1791 a 487DX or 387, respectively. (The messages during boot time can
1792 give you some hints here ["man dmesg"].) Everyone needs either a
1793 coprocessor or this emulation.
1795 If you don't have a math coprocessor, you need to say Y here; if you
1796 say Y here even though you have a coprocessor, the coprocessor will
1797 be used nevertheless. (This behavior can be changed with the kernel
1798 command line option "no387", which comes handy if your coprocessor
1799 is broken. Try "man bootparam" or see the documentation of your boot
1800 loader (lilo or loadlin) about how to pass options to the kernel at
1801 boot time.) This means that it is a good idea to say Y here if you
1802 intend to use this kernel on different machines.
1804 More information about the internals of the Linux math coprocessor
1805 emulation can be found in <file:arch/x86/math-emu/README>.
1807 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1808 kernel, it won't hurt.
1812 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1814 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1815 the Memory Type Range Registers (MTRRs) may be used to control
1816 processor access to memory ranges. This is most useful if you have
1817 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1818 allows bus write transfers to be combined into a larger transfer
1819 before bursting over the PCI/AGP bus. This can increase performance
1820 of image write operations 2.5 times or more. Saying Y here creates a
1821 /proc/mtrr file which may be used to manipulate your processor's
1822 MTRRs. Typically the X server should use this.
1824 This code has a reasonably generic interface so that similar
1825 control registers on other processors can be easily supported
1828 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1829 Registers (ARRs) which provide a similar functionality to MTRRs. For
1830 these, the ARRs are used to emulate the MTRRs.
1831 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1832 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1833 write-combining. All of these processors are supported by this code
1834 and it makes sense to say Y here if you have one of them.
1836 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1837 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1838 can lead to all sorts of problems, so it's good to say Y here.
1840 You can safely say Y even if your machine doesn't have MTRRs, you'll
1841 just add about 9 KB to your kernel.
1843 See <file:Documentation/x86/mtrr.rst> for more information.
1845 config MTRR_SANITIZER
1847 prompt "MTRR cleanup support"
1850 Convert MTRR layout from continuous to discrete, so X drivers can
1851 add writeback entries.
1853 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1854 The largest mtrr entry size for a continuous block can be set with
1859 config MTRR_SANITIZER_ENABLE_DEFAULT
1860 int "MTRR cleanup enable value (0-1)"
1863 depends on MTRR_SANITIZER
1865 Enable mtrr cleanup default value
1867 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1868 int "MTRR cleanup spare reg num (0-7)"
1871 depends on MTRR_SANITIZER
1873 mtrr cleanup spare entries default, it can be changed via
1874 mtrr_spare_reg_nr=N on the kernel command line.
1878 prompt "x86 PAT support" if EXPERT
1881 Use PAT attributes to setup page level cache control.
1883 PATs are the modern equivalents of MTRRs and are much more
1884 flexible than MTRRs.
1886 Say N here if you see bootup problems (boot crash, boot hang,
1887 spontaneous reboots) or a non-working video driver.
1891 config ARCH_USES_PG_UNCACHED
1897 prompt "x86 architectural random number generator" if EXPERT
1899 Enable the x86 architectural RDRAND instruction
1900 (Intel Bull Mountain technology) to generate random numbers.
1901 If supported, this is a high bandwidth, cryptographically
1902 secure hardware random number generator.
1906 prompt "Supervisor Mode Access Prevention" if EXPERT
1908 Supervisor Mode Access Prevention (SMAP) is a security
1909 feature in newer Intel processors. There is a small
1910 performance cost if this enabled and turned on; there is
1911 also a small increase in the kernel size if this is enabled.
1915 config X86_INTEL_UMIP
1917 depends on CPU_SUP_INTEL
1918 prompt "Intel User Mode Instruction Prevention" if EXPERT
1920 The User Mode Instruction Prevention (UMIP) is a security
1921 feature in newer Intel processors. If enabled, a general
1922 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1923 or STR instructions are executed in user mode. These instructions
1924 unnecessarily expose information about the hardware state.
1926 The vast majority of applications do not use these instructions.
1927 For the very few that do, software emulation is provided in
1928 specific cases in protected and virtual-8086 modes. Emulated
1931 config X86_INTEL_MPX
1932 prompt "Intel MPX (Memory Protection Extensions)"
1934 # Note: only available in 64-bit mode due to VMA flags shortage
1935 depends on CPU_SUP_INTEL && X86_64
1936 select ARCH_USES_HIGH_VMA_FLAGS
1938 MPX provides hardware features that can be used in
1939 conjunction with compiler-instrumented code to check
1940 memory references. It is designed to detect buffer
1941 overflow or underflow bugs.
1943 This option enables running applications which are
1944 instrumented or otherwise use MPX. It does not use MPX
1945 itself inside the kernel or to protect the kernel
1946 against bad memory references.
1948 Enabling this option will make the kernel larger:
1949 ~8k of kernel text and 36 bytes of data on a 64-bit
1950 defconfig. It adds a long to the 'mm_struct' which
1951 will increase the kernel memory overhead of each
1952 process and adds some branches to paths used during
1953 exec() and munmap().
1955 For details, see Documentation/x86/intel_mpx.rst
1959 config X86_INTEL_MEMORY_PROTECTION_KEYS
1960 prompt "Intel Memory Protection Keys"
1962 # Note: only available in 64-bit mode
1963 depends on CPU_SUP_INTEL && X86_64
1964 select ARCH_USES_HIGH_VMA_FLAGS
1965 select ARCH_HAS_PKEYS
1967 Memory Protection Keys provides a mechanism for enforcing
1968 page-based protections, but without requiring modification of the
1969 page tables when an application changes protection domains.
1971 For details, see Documentation/core-api/protection-keys.rst
1976 bool "EFI runtime service support"
1979 select EFI_RUNTIME_WRAPPERS
1981 This enables the kernel to use EFI runtime services that are
1982 available (such as the EFI variable services).
1984 This option is only useful on systems that have EFI firmware.
1985 In addition, you should use the latest ELILO loader available
1986 at <http://elilo.sourceforge.net> in order to take advantage
1987 of EFI runtime services. However, even with this option, the
1988 resultant kernel should continue to boot on existing non-EFI
1992 bool "EFI stub support"
1993 depends on EFI && !X86_USE_3DNOW
1996 This kernel feature allows a bzImage to be loaded directly
1997 by EFI firmware without the use of a bootloader.
1999 See Documentation/admin-guide/efi-stub.rst for more information.
2002 bool "EFI mixed-mode support"
2003 depends on EFI_STUB && X86_64
2005 Enabling this feature allows a 64-bit kernel to be booted
2006 on a 32-bit firmware, provided that your CPU supports 64-bit
2009 Note that it is not possible to boot a mixed-mode enabled
2010 kernel via the EFI boot stub - a bootloader that supports
2011 the EFI handover protocol must be used.
2017 prompt "Enable seccomp to safely compute untrusted bytecode"
2019 This kernel feature is useful for number crunching applications
2020 that may need to compute untrusted bytecode during their
2021 execution. By using pipes or other transports made available to
2022 the process as file descriptors supporting the read/write
2023 syscalls, it's possible to isolate those applications in
2024 their own address space using seccomp. Once seccomp is
2025 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
2026 and the task is only allowed to execute a few safe syscalls
2027 defined by each seccomp mode.
2029 If unsure, say Y. Only embedded should say N here.
2031 source "kernel/Kconfig.hz"
2034 bool "kexec system call"
2037 kexec is a system call that implements the ability to shutdown your
2038 current kernel, and to start another kernel. It is like a reboot
2039 but it is independent of the system firmware. And like a reboot
2040 you can start any kernel with it, not just Linux.
2042 The name comes from the similarity to the exec system call.
2044 It is an ongoing process to be certain the hardware in a machine
2045 is properly shutdown, so do not be surprised if this code does not
2046 initially work for you. As of this writing the exact hardware
2047 interface is strongly in flux, so no good recommendation can be
2051 bool "kexec file based system call"
2056 depends on CRYPTO_SHA256=y
2058 This is new version of kexec system call. This system call is
2059 file based and takes file descriptors as system call argument
2060 for kernel and initramfs as opposed to list of segments as
2061 accepted by previous system call.
2063 config ARCH_HAS_KEXEC_PURGATORY
2067 bool "Verify kernel signature during kexec_file_load() syscall"
2068 depends on KEXEC_FILE
2071 This option makes the kexec_file_load() syscall check for a valid
2072 signature of the kernel image. The image can still be loaded without
2073 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2074 there's a signature that we can check, then it must be valid.
2076 In addition to this option, you need to enable signature
2077 verification for the corresponding kernel image type being
2078 loaded in order for this to work.
2080 config KEXEC_SIG_FORCE
2081 bool "Require a valid signature in kexec_file_load() syscall"
2082 depends on KEXEC_SIG
2084 This option makes kernel signature verification mandatory for
2085 the kexec_file_load() syscall.
2087 config KEXEC_BZIMAGE_VERIFY_SIG
2088 bool "Enable bzImage signature verification support"
2089 depends on KEXEC_SIG
2090 depends on SIGNED_PE_FILE_VERIFICATION
2091 select SYSTEM_TRUSTED_KEYRING
2093 Enable bzImage signature verification support.
2096 bool "kernel crash dumps"
2097 depends on X86_64 || (X86_32 && HIGHMEM)
2099 Generate crash dump after being started by kexec.
2100 This should be normally only set in special crash dump kernels
2101 which are loaded in the main kernel with kexec-tools into
2102 a specially reserved region and then later executed after
2103 a crash by kdump/kexec. The crash dump kernel must be compiled
2104 to a memory address not used by the main kernel or BIOS using
2105 PHYSICAL_START, or it must be built as a relocatable image
2106 (CONFIG_RELOCATABLE=y).
2107 For more details see Documentation/admin-guide/kdump/kdump.rst
2111 depends on KEXEC && HIBERNATION
2113 Jump between original kernel and kexeced kernel and invoke
2114 code in physical address mode via KEXEC
2116 config PHYSICAL_START
2117 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2120 This gives the physical address where the kernel is loaded.
2122 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2123 bzImage will decompress itself to above physical address and
2124 run from there. Otherwise, bzImage will run from the address where
2125 it has been loaded by the boot loader and will ignore above physical
2128 In normal kdump cases one does not have to set/change this option
2129 as now bzImage can be compiled as a completely relocatable image
2130 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2131 address. This option is mainly useful for the folks who don't want
2132 to use a bzImage for capturing the crash dump and want to use a
2133 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2134 to be specifically compiled to run from a specific memory area
2135 (normally a reserved region) and this option comes handy.
2137 So if you are using bzImage for capturing the crash dump,
2138 leave the value here unchanged to 0x1000000 and set
2139 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2140 for capturing the crash dump change this value to start of
2141 the reserved region. In other words, it can be set based on
2142 the "X" value as specified in the "crashkernel=YM@XM"
2143 command line boot parameter passed to the panic-ed
2144 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2145 for more details about crash dumps.
2147 Usage of bzImage for capturing the crash dump is recommended as
2148 one does not have to build two kernels. Same kernel can be used
2149 as production kernel and capture kernel. Above option should have
2150 gone away after relocatable bzImage support is introduced. But it
2151 is present because there are users out there who continue to use
2152 vmlinux for dump capture. This option should go away down the
2155 Don't change this unless you know what you are doing.
2158 bool "Build a relocatable kernel"
2161 This builds a kernel image that retains relocation information
2162 so it can be loaded someplace besides the default 1MB.
2163 The relocations tend to make the kernel binary about 10% larger,
2164 but are discarded at runtime.
2166 One use is for the kexec on panic case where the recovery kernel
2167 must live at a different physical address than the primary
2170 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2171 it has been loaded at and the compile time physical address
2172 (CONFIG_PHYSICAL_START) is used as the minimum location.
2174 config RANDOMIZE_BASE
2175 bool "Randomize the address of the kernel image (KASLR)"
2176 depends on RELOCATABLE
2179 In support of Kernel Address Space Layout Randomization (KASLR),
2180 this randomizes the physical address at which the kernel image
2181 is decompressed and the virtual address where the kernel
2182 image is mapped, as a security feature that deters exploit
2183 attempts relying on knowledge of the location of kernel
2186 On 64-bit, the kernel physical and virtual addresses are
2187 randomized separately. The physical address will be anywhere
2188 between 16MB and the top of physical memory (up to 64TB). The
2189 virtual address will be randomized from 16MB up to 1GB (9 bits
2190 of entropy). Note that this also reduces the memory space
2191 available to kernel modules from 1.5GB to 1GB.
2193 On 32-bit, the kernel physical and virtual addresses are
2194 randomized together. They will be randomized from 16MB up to
2195 512MB (8 bits of entropy).
2197 Entropy is generated using the RDRAND instruction if it is
2198 supported. If RDTSC is supported, its value is mixed into
2199 the entropy pool as well. If neither RDRAND nor RDTSC are
2200 supported, then entropy is read from the i8254 timer. The
2201 usable entropy is limited by the kernel being built using
2202 2GB addressing, and that PHYSICAL_ALIGN must be at a
2203 minimum of 2MB. As a result, only 10 bits of entropy are
2204 theoretically possible, but the implementations are further
2205 limited due to memory layouts.
2209 # Relocation on x86 needs some additional build support
2210 config X86_NEED_RELOCS
2212 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2214 config PHYSICAL_ALIGN
2215 hex "Alignment value to which kernel should be aligned"
2217 range 0x2000 0x1000000 if X86_32
2218 range 0x200000 0x1000000 if X86_64
2220 This value puts the alignment restrictions on physical address
2221 where kernel is loaded and run from. Kernel is compiled for an
2222 address which meets above alignment restriction.
2224 If bootloader loads the kernel at a non-aligned address and
2225 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2226 address aligned to above value and run from there.
2228 If bootloader loads the kernel at a non-aligned address and
2229 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2230 load address and decompress itself to the address it has been
2231 compiled for and run from there. The address for which kernel is
2232 compiled already meets above alignment restrictions. Hence the
2233 end result is that kernel runs from a physical address meeting
2234 above alignment restrictions.
2236 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2237 this value must be a multiple of 0x200000.
2239 Don't change this unless you know what you are doing.
2241 config DYNAMIC_MEMORY_LAYOUT
2244 This option makes base addresses of vmalloc and vmemmap as well as
2245 __PAGE_OFFSET movable during boot.
2247 config RANDOMIZE_MEMORY
2248 bool "Randomize the kernel memory sections"
2250 depends on RANDOMIZE_BASE
2251 select DYNAMIC_MEMORY_LAYOUT
2252 default RANDOMIZE_BASE
2254 Randomizes the base virtual address of kernel memory sections
2255 (physical memory mapping, vmalloc & vmemmap). This security feature
2256 makes exploits relying on predictable memory locations less reliable.
2258 The order of allocations remains unchanged. Entropy is generated in
2259 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2260 configuration have in average 30,000 different possible virtual
2261 addresses for each memory section.
2265 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2266 hex "Physical memory mapping padding" if EXPERT
2267 depends on RANDOMIZE_MEMORY
2268 default "0xa" if MEMORY_HOTPLUG
2270 range 0x1 0x40 if MEMORY_HOTPLUG
2273 Define the padding in terabytes added to the existing physical
2274 memory size during kernel memory randomization. It is useful
2275 for memory hotplug support but reduces the entropy available for
2276 address randomization.
2278 If unsure, leave at the default value.
2284 config BOOTPARAM_HOTPLUG_CPU0
2285 bool "Set default setting of cpu0_hotpluggable"
2286 depends on HOTPLUG_CPU
2288 Set whether default state of cpu0_hotpluggable is on or off.
2290 Say Y here to enable CPU0 hotplug by default. If this switch
2291 is turned on, there is no need to give cpu0_hotplug kernel
2292 parameter and the CPU0 hotplug feature is enabled by default.
2294 Please note: there are two known CPU0 dependencies if you want
2295 to enable the CPU0 hotplug feature either by this switch or by
2296 cpu0_hotplug kernel parameter.
2298 First, resume from hibernate or suspend always starts from CPU0.
2299 So hibernate and suspend are prevented if CPU0 is offline.
2301 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2302 offline if any interrupt can not migrate out of CPU0. There may
2303 be other CPU0 dependencies.
2305 Please make sure the dependencies are under your control before
2306 you enable this feature.
2308 Say N if you don't want to enable CPU0 hotplug feature by default.
2309 You still can enable the CPU0 hotplug feature at boot by kernel
2310 parameter cpu0_hotplug.
2312 config DEBUG_HOTPLUG_CPU0
2314 prompt "Debug CPU0 hotplug"
2315 depends on HOTPLUG_CPU
2317 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2318 soon as possible and boots up userspace with CPU0 offlined. User
2319 can online CPU0 back after boot time.
2321 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2322 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2323 compilation or giving cpu0_hotplug kernel parameter at boot.
2329 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2330 depends on COMPAT_32
2332 Certain buggy versions of glibc will crash if they are
2333 presented with a 32-bit vDSO that is not mapped at the address
2334 indicated in its segment table.
2336 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2337 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2338 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2339 the only released version with the bug, but OpenSUSE 9
2340 contains a buggy "glibc 2.3.2".
2342 The symptom of the bug is that everything crashes on startup, saying:
2343 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2345 Saying Y here changes the default value of the vdso32 boot
2346 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2347 This works around the glibc bug but hurts performance.
2349 If unsure, say N: if you are compiling your own kernel, you
2350 are unlikely to be using a buggy version of glibc.
2353 prompt "vsyscall table for legacy applications"
2355 default LEGACY_VSYSCALL_XONLY
2357 Legacy user code that does not know how to find the vDSO expects
2358 to be able to issue three syscalls by calling fixed addresses in
2359 kernel space. Since this location is not randomized with ASLR,
2360 it can be used to assist security vulnerability exploitation.
2362 This setting can be changed at boot time via the kernel command
2363 line parameter vsyscall=[emulate|xonly|none].
2365 On a system with recent enough glibc (2.14 or newer) and no
2366 static binaries, you can say None without a performance penalty
2367 to improve security.
2369 If unsure, select "Emulate execution only".
2371 config LEGACY_VSYSCALL_EMULATE
2372 bool "Full emulation"
2374 The kernel traps and emulates calls into the fixed vsyscall
2375 address mapping. This makes the mapping non-executable, but
2376 it still contains readable known contents, which could be
2377 used in certain rare security vulnerability exploits. This
2378 configuration is recommended when using legacy userspace
2379 that still uses vsyscalls along with legacy binary
2380 instrumentation tools that require code to be readable.
2382 An example of this type of legacy userspace is running
2383 Pin on an old binary that still uses vsyscalls.
2385 config LEGACY_VSYSCALL_XONLY
2386 bool "Emulate execution only"
2388 The kernel traps and emulates calls into the fixed vsyscall
2389 address mapping and does not allow reads. This
2390 configuration is recommended when userspace might use the
2391 legacy vsyscall area but support for legacy binary
2392 instrumentation of legacy code is not needed. It mitigates
2393 certain uses of the vsyscall area as an ASLR-bypassing
2396 config LEGACY_VSYSCALL_NONE
2399 There will be no vsyscall mapping at all. This will
2400 eliminate any risk of ASLR bypass due to the vsyscall
2401 fixed address mapping. Attempts to use the vsyscalls
2402 will be reported to dmesg, so that either old or
2403 malicious userspace programs can be identified.
2408 bool "Built-in kernel command line"
2410 Allow for specifying boot arguments to the kernel at
2411 build time. On some systems (e.g. embedded ones), it is
2412 necessary or convenient to provide some or all of the
2413 kernel boot arguments with the kernel itself (that is,
2414 to not rely on the boot loader to provide them.)
2416 To compile command line arguments into the kernel,
2417 set this option to 'Y', then fill in the
2418 boot arguments in CONFIG_CMDLINE.
2420 Systems with fully functional boot loaders (i.e. non-embedded)
2421 should leave this option set to 'N'.
2424 string "Built-in kernel command string"
2425 depends on CMDLINE_BOOL
2428 Enter arguments here that should be compiled into the kernel
2429 image and used at boot time. If the boot loader provides a
2430 command line at boot time, it is appended to this string to
2431 form the full kernel command line, when the system boots.
2433 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2434 change this behavior.
2436 In most cases, the command line (whether built-in or provided
2437 by the boot loader) should specify the device for the root
2440 config CMDLINE_OVERRIDE
2441 bool "Built-in command line overrides boot loader arguments"
2442 depends on CMDLINE_BOOL
2444 Set this option to 'Y' to have the kernel ignore the boot loader
2445 command line, and use ONLY the built-in command line.
2447 This is used to work around broken boot loaders. This should
2448 be set to 'N' under normal conditions.
2450 config MODIFY_LDT_SYSCALL
2451 bool "Enable the LDT (local descriptor table)" if EXPERT
2454 Linux can allow user programs to install a per-process x86
2455 Local Descriptor Table (LDT) using the modify_ldt(2) system
2456 call. This is required to run 16-bit or segmented code such as
2457 DOSEMU or some Wine programs. It is also used by some very old
2458 threading libraries.
2460 Enabling this feature adds a small amount of overhead to
2461 context switches and increases the low-level kernel attack
2462 surface. Disabling it removes the modify_ldt(2) system call.
2464 Saying 'N' here may make sense for embedded or server kernels.
2466 source "kernel/livepatch/Kconfig"
2470 config ARCH_HAS_ADD_PAGES
2472 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2474 config ARCH_ENABLE_MEMORY_HOTPLUG
2476 depends on X86_64 || (X86_32 && HIGHMEM)
2478 config ARCH_ENABLE_MEMORY_HOTREMOVE
2480 depends on MEMORY_HOTPLUG
2482 config USE_PERCPU_NUMA_NODE_ID
2486 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2488 depends on X86_64 || X86_PAE
2490 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2492 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2494 config ARCH_ENABLE_THP_MIGRATION
2496 depends on X86_64 && TRANSPARENT_HUGEPAGE
2498 menu "Power management and ACPI options"
2500 config ARCH_HIBERNATION_HEADER
2502 depends on HIBERNATION
2504 source "kernel/power/Kconfig"
2506 source "drivers/acpi/Kconfig"
2508 source "drivers/sfi/Kconfig"
2515 tristate "APM (Advanced Power Management) BIOS support"
2516 depends on X86_32 && PM_SLEEP
2518 APM is a BIOS specification for saving power using several different
2519 techniques. This is mostly useful for battery powered laptops with
2520 APM compliant BIOSes. If you say Y here, the system time will be
2521 reset after a RESUME operation, the /proc/apm device will provide
2522 battery status information, and user-space programs will receive
2523 notification of APM "events" (e.g. battery status change).
2525 If you select "Y" here, you can disable actual use of the APM
2526 BIOS by passing the "apm=off" option to the kernel at boot time.
2528 Note that the APM support is almost completely disabled for
2529 machines with more than one CPU.
2531 In order to use APM, you will need supporting software. For location
2532 and more information, read <file:Documentation/power/apm-acpi.rst>
2533 and the Battery Powered Linux mini-HOWTO, available from
2534 <http://www.tldp.org/docs.html#howto>.
2536 This driver does not spin down disk drives (see the hdparm(8)
2537 manpage ("man 8 hdparm") for that), and it doesn't turn off
2538 VESA-compliant "green" monitors.
2540 This driver does not support the TI 4000M TravelMate and the ACER
2541 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2542 desktop machines also don't have compliant BIOSes, and this driver
2543 may cause those machines to panic during the boot phase.
2545 Generally, if you don't have a battery in your machine, there isn't
2546 much point in using this driver and you should say N. If you get
2547 random kernel OOPSes or reboots that don't seem to be related to
2548 anything, try disabling/enabling this option (or disabling/enabling
2551 Some other things you should try when experiencing seemingly random,
2554 1) make sure that you have enough swap space and that it is
2556 2) pass the "no-hlt" option to the kernel
2557 3) switch on floating point emulation in the kernel and pass
2558 the "no387" option to the kernel
2559 4) pass the "floppy=nodma" option to the kernel
2560 5) pass the "mem=4M" option to the kernel (thereby disabling
2561 all but the first 4 MB of RAM)
2562 6) make sure that the CPU is not over clocked.
2563 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2564 8) disable the cache from your BIOS settings
2565 9) install a fan for the video card or exchange video RAM
2566 10) install a better fan for the CPU
2567 11) exchange RAM chips
2568 12) exchange the motherboard.
2570 To compile this driver as a module, choose M here: the
2571 module will be called apm.
2575 config APM_IGNORE_USER_SUSPEND
2576 bool "Ignore USER SUSPEND"
2578 This option will ignore USER SUSPEND requests. On machines with a
2579 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2580 series notebooks, it is necessary to say Y because of a BIOS bug.
2582 config APM_DO_ENABLE
2583 bool "Enable PM at boot time"
2585 Enable APM features at boot time. From page 36 of the APM BIOS
2586 specification: "When disabled, the APM BIOS does not automatically
2587 power manage devices, enter the Standby State, enter the Suspend
2588 State, or take power saving steps in response to CPU Idle calls."
2589 This driver will make CPU Idle calls when Linux is idle (unless this
2590 feature is turned off -- see "Do CPU IDLE calls", below). This
2591 should always save battery power, but more complicated APM features
2592 will be dependent on your BIOS implementation. You may need to turn
2593 this option off if your computer hangs at boot time when using APM
2594 support, or if it beeps continuously instead of suspending. Turn
2595 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2596 T400CDT. This is off by default since most machines do fine without
2601 bool "Make CPU Idle calls when idle"
2603 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2604 On some machines, this can activate improved power savings, such as
2605 a slowed CPU clock rate, when the machine is idle. These idle calls
2606 are made after the idle loop has run for some length of time (e.g.,
2607 333 mS). On some machines, this will cause a hang at boot time or
2608 whenever the CPU becomes idle. (On machines with more than one CPU,
2609 this option does nothing.)
2611 config APM_DISPLAY_BLANK
2612 bool "Enable console blanking using APM"
2614 Enable console blanking using the APM. Some laptops can use this to
2615 turn off the LCD backlight when the screen blanker of the Linux
2616 virtual console blanks the screen. Note that this is only used by
2617 the virtual console screen blanker, and won't turn off the backlight
2618 when using the X Window system. This also doesn't have anything to
2619 do with your VESA-compliant power-saving monitor. Further, this
2620 option doesn't work for all laptops -- it might not turn off your
2621 backlight at all, or it might print a lot of errors to the console,
2622 especially if you are using gpm.
2624 config APM_ALLOW_INTS
2625 bool "Allow interrupts during APM BIOS calls"
2627 Normally we disable external interrupts while we are making calls to
2628 the APM BIOS as a measure to lessen the effects of a badly behaving
2629 BIOS implementation. The BIOS should reenable interrupts if it
2630 needs to. Unfortunately, some BIOSes do not -- especially those in
2631 many of the newer IBM Thinkpads. If you experience hangs when you
2632 suspend, try setting this to Y. Otherwise, say N.
2636 source "drivers/cpufreq/Kconfig"
2638 source "drivers/cpuidle/Kconfig"
2640 source "drivers/idle/Kconfig"
2645 menu "Bus options (PCI etc.)"
2648 prompt "PCI access mode"
2649 depends on X86_32 && PCI
2652 On PCI systems, the BIOS can be used to detect the PCI devices and
2653 determine their configuration. However, some old PCI motherboards
2654 have BIOS bugs and may crash if this is done. Also, some embedded
2655 PCI-based systems don't have any BIOS at all. Linux can also try to
2656 detect the PCI hardware directly without using the BIOS.
2658 With this option, you can specify how Linux should detect the
2659 PCI devices. If you choose "BIOS", the BIOS will be used,
2660 if you choose "Direct", the BIOS won't be used, and if you
2661 choose "MMConfig", then PCI Express MMCONFIG will be used.
2662 If you choose "Any", the kernel will try MMCONFIG, then the
2663 direct access method and falls back to the BIOS if that doesn't
2664 work. If unsure, go with the default, which is "Any".
2669 config PCI_GOMMCONFIG
2686 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2688 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2691 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2694 bool "Support mmconfig PCI config space access" if X86_64
2696 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2697 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2701 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2705 depends on PCI && XEN
2708 config MMCONF_FAM10H
2710 depends on X86_64 && PCI_MMCONFIG && ACPI
2712 config PCI_CNB20LE_QUIRK
2713 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2716 Read the PCI windows out of the CNB20LE host bridge. This allows
2717 PCI hotplug to work on systems with the CNB20LE chipset which do
2720 There's no public spec for this chipset, and this functionality
2721 is known to be incomplete.
2723 You should say N unless you know you need this.
2726 bool "ISA bus support on modern systems" if EXPERT
2728 Expose ISA bus device drivers and options available for selection and
2729 configuration. Enable this option if your target machine has an ISA
2730 bus. ISA is an older system, displaced by PCI and newer bus
2731 architectures -- if your target machine is modern, it probably does
2732 not have an ISA bus.
2736 # x86_64 have no ISA slots, but can have ISA-style DMA.
2738 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2741 Enables ISA-style DMA support for devices requiring such controllers.
2749 Find out whether you have ISA slots on your motherboard. ISA is the
2750 name of a bus system, i.e. the way the CPU talks to the other stuff
2751 inside your box. Other bus systems are PCI, EISA, MicroChannel
2752 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2753 newer boards don't support it. If you have ISA, say Y, otherwise N.
2756 tristate "NatSemi SCx200 support"
2758 This provides basic support for National Semiconductor's
2759 (now AMD's) Geode processors. The driver probes for the
2760 PCI-IDs of several on-chip devices, so its a good dependency
2761 for other scx200_* drivers.
2763 If compiled as a module, the driver is named scx200.
2765 config SCx200HR_TIMER
2766 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2770 This driver provides a clocksource built upon the on-chip
2771 27MHz high-resolution timer. Its also a workaround for
2772 NSC Geode SC-1100's buggy TSC, which loses time when the
2773 processor goes idle (as is done by the scheduler). The
2774 other workaround is idle=poll boot option.
2777 bool "One Laptop Per Child support"
2785 Add support for detecting the unique features of the OLPC
2789 bool "OLPC XO-1 Power Management"
2790 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2792 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2795 bool "OLPC XO-1 Real Time Clock"
2796 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2798 Add support for the XO-1 real time clock, which can be used as a
2799 programmable wakeup source.
2802 bool "OLPC XO-1 SCI extras"
2803 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2807 Add support for SCI-based features of the OLPC XO-1 laptop:
2808 - EC-driven system wakeups
2812 - AC adapter status updates
2813 - Battery status updates
2815 config OLPC_XO15_SCI
2816 bool "OLPC XO-1.5 SCI extras"
2817 depends on OLPC && ACPI
2820 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2821 - EC-driven system wakeups
2822 - AC adapter status updates
2823 - Battery status updates
2826 bool "PCEngines ALIX System Support (LED setup)"
2829 This option enables system support for the PCEngines ALIX.
2830 At present this just sets up LEDs for GPIO control on
2831 ALIX2/3/6 boards. However, other system specific setup should
2834 Note: You must still enable the drivers for GPIO and LED support
2835 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2837 Note: You have to set alix.force=1 for boards with Award BIOS.
2840 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2843 This option enables system support for the Soekris Engineering net5501.
2846 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2850 This option enables system support for the Traverse Technologies GEOS.
2853 bool "Technologic Systems TS-5500 platform support"
2855 select CHECK_SIGNATURE
2859 This option enables system support for the Technologic Systems TS-5500.
2865 depends on CPU_SUP_AMD && PCI
2868 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2870 Firmwares often provide initial graphics framebuffers so the BIOS,
2871 bootloader or kernel can show basic video-output during boot for
2872 user-guidance and debugging. Historically, x86 used the VESA BIOS
2873 Extensions and EFI-framebuffers for this, which are mostly limited
2875 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2876 framebuffers so the new generic system-framebuffer drivers can be
2877 used on x86. If the framebuffer is not compatible with the generic
2878 modes, it is advertised as fallback platform framebuffer so legacy
2879 drivers like efifb, vesafb and uvesafb can pick it up.
2880 If this option is not selected, all system framebuffers are always
2881 marked as fallback platform framebuffers as usual.
2883 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2884 not be able to pick up generic system framebuffers if this option
2885 is selected. You are highly encouraged to enable simplefb as
2886 replacement if you select this option. simplefb can correctly deal
2887 with generic system framebuffers. But you should still keep vesafb
2888 and others enabled as fallback if a system framebuffer is
2889 incompatible with simplefb.
2896 menu "Binary Emulations"
2898 config IA32_EMULATION
2899 bool "IA32 Emulation"
2901 select ARCH_WANT_OLD_COMPAT_IPC
2903 select COMPAT_BINFMT_ELF
2904 select COMPAT_OLD_SIGACTION
2906 Include code to run legacy 32-bit programs under a
2907 64-bit kernel. You should likely turn this on, unless you're
2908 100% sure that you don't have any 32-bit programs left.
2911 tristate "IA32 a.out support"
2912 depends on IA32_EMULATION
2915 Support old a.out binaries in the 32bit emulation.
2918 bool "x32 ABI for 64-bit mode"
2921 Include code to run binaries for the x32 native 32-bit ABI
2922 for 64-bit processors. An x32 process gets access to the
2923 full 64-bit register file and wide data path while leaving
2924 pointers at 32 bits for smaller memory footprint.
2926 You will need a recent binutils (2.22 or later) with
2927 elf32_x86_64 support enabled to compile a kernel with this
2932 depends on IA32_EMULATION || X86_32
2934 select OLD_SIGSUSPEND3
2938 depends on IA32_EMULATION || X86_X32
2941 config COMPAT_FOR_U64_ALIGNMENT
2944 config SYSVIPC_COMPAT
2952 config HAVE_ATOMIC_IOMAP
2956 config X86_DEV_DMA_OPS
2959 source "drivers/firmware/Kconfig"
2961 source "arch/x86/kvm/Kconfig"