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_CPU_FINALIZE_INIT
64 select ARCH_HAS_DEBUG_VIRTUAL
65 select ARCH_HAS_DEVMEM_IS_ALLOWED
66 select ARCH_HAS_ELF_RANDOMIZE
67 select ARCH_HAS_FAST_MULTIPLIER
68 select ARCH_HAS_FILTER_PGPROT
69 select ARCH_HAS_FORTIFY_SOURCE
70 select ARCH_HAS_GCOV_PROFILE_ALL
71 select ARCH_HAS_KCOV if X86_64
72 select ARCH_HAS_MEM_ENCRYPT
73 select ARCH_HAS_MEMBARRIER_SYNC_CORE
74 select ARCH_HAS_PMEM_API if X86_64
75 select ARCH_HAS_PTE_DEVMAP if X86_64
76 select ARCH_HAS_PTE_SPECIAL
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 KEXEC_CORE
554 depends on X86_X2APIC
557 This option is needed in order to support SGI Ultraviolet systems.
558 If you don't have one of these, you should say N here.
560 # Following is an alphabetically sorted list of 32 bit extended platforms
561 # Please maintain the alphabetic order if and when there are additions
564 bool "Goldfish (Virtual Platform)"
565 depends on X86_EXTENDED_PLATFORM
567 Enable support for the Goldfish virtual platform used primarily
568 for Android development. Unless you are building for the Android
569 Goldfish emulator say N here.
572 bool "CE4100 TV platform"
574 depends on PCI_GODIRECT
575 depends on X86_IO_APIC
577 depends on X86_EXTENDED_PLATFORM
578 select X86_REBOOTFIXUPS
580 select OF_EARLY_FLATTREE
582 Select for the Intel CE media processor (CE4100) SOC.
583 This option compiles in support for the CE4100 SOC for settop
584 boxes and media devices.
587 bool "Intel MID platform support"
588 depends on X86_EXTENDED_PLATFORM
589 depends on X86_PLATFORM_DEVICES
591 depends on X86_64 || (PCI_GOANY && X86_32)
592 depends on X86_IO_APIC
598 select MFD_INTEL_MSIC
600 Select to build a kernel capable of supporting Intel MID (Mobile
601 Internet Device) platform systems which do not have the PCI legacy
602 interfaces. If you are building for a PC class system say N here.
604 Intel MID platforms are based on an Intel processor and chipset which
605 consume less power than most of the x86 derivatives.
607 config X86_INTEL_QUARK
608 bool "Intel Quark platform support"
610 depends on X86_EXTENDED_PLATFORM
611 depends on X86_PLATFORM_DEVICES
615 depends on X86_IO_APIC
620 Select to include support for Quark X1000 SoC.
621 Say Y here if you have a Quark based system such as the Arduino
622 compatible Intel Galileo.
624 config X86_INTEL_LPSS
625 bool "Intel Low Power Subsystem Support"
626 depends on X86 && ACPI && PCI
631 Select to build support for Intel Low Power Subsystem such as
632 found on Intel Lynxpoint PCH. Selecting this option enables
633 things like clock tree (common clock framework) and pincontrol
634 which are needed by the LPSS peripheral drivers.
636 config X86_AMD_PLATFORM_DEVICE
637 bool "AMD ACPI2Platform devices support"
642 Select to interpret AMD specific ACPI device to platform device
643 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
644 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
645 implemented under PINCTRL subsystem.
648 tristate "Intel SoC IOSF Sideband support for SoC platforms"
651 This option enables sideband register access support for Intel SoC
652 platforms. On these platforms the IOSF sideband is used in lieu of
653 MSR's for some register accesses, mostly but not limited to thermal
654 and power. Drivers may query the availability of this device to
655 determine if they need the sideband in order to work on these
656 platforms. The sideband is available on the following SoC products.
657 This list is not meant to be exclusive.
662 You should say Y if you are running a kernel on one of these SoC's.
664 config IOSF_MBI_DEBUG
665 bool "Enable IOSF sideband access through debugfs"
666 depends on IOSF_MBI && DEBUG_FS
668 Select this option to expose the IOSF sideband access registers (MCR,
669 MDR, MCRX) through debugfs to write and read register information from
670 different units on the SoC. This is most useful for obtaining device
671 state information for debug and analysis. As this is a general access
672 mechanism, users of this option would have specific knowledge of the
673 device they want to access.
675 If you don't require the option or are in doubt, say N.
678 bool "RDC R-321x SoC"
680 depends on X86_EXTENDED_PLATFORM
682 select X86_REBOOTFIXUPS
684 This option is needed for RDC R-321x system-on-chip, also known
686 If you don't have one of these chips, you should say N here.
688 config X86_32_NON_STANDARD
689 bool "Support non-standard 32-bit SMP architectures"
690 depends on X86_32 && SMP
691 depends on X86_EXTENDED_PLATFORM
693 This option compiles in the bigsmp and STA2X11 default
694 subarchitectures. It is intended for a generic binary
695 kernel. If you select them all, kernel will probe it one by
696 one and will fallback to default.
698 # Alphabetically sorted list of Non standard 32 bit platforms
700 config X86_SUPPORTS_MEMORY_FAILURE
702 # MCE code calls memory_failure():
704 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
705 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
706 depends on X86_64 || !SPARSEMEM
707 select ARCH_SUPPORTS_MEMORY_FAILURE
710 bool "STA2X11 Companion Chip Support"
711 depends on X86_32_NON_STANDARD && PCI
712 select ARCH_HAS_PHYS_TO_DMA
717 This adds support for boards based on the STA2X11 IO-Hub,
718 a.k.a. "ConneXt". The chip is used in place of the standard
719 PC chipset, so all "standard" peripherals are missing. If this
720 option is selected the kernel will still be able to boot on
721 standard PC machines.
724 tristate "Eurobraille/Iris poweroff module"
727 The Iris machines from EuroBraille do not have APM or ACPI support
728 to shut themselves down properly. A special I/O sequence is
729 needed to do so, which is what this module does at
732 This is only for Iris machines from EuroBraille.
736 config SCHED_OMIT_FRAME_POINTER
738 prompt "Single-depth WCHAN output"
741 Calculate simpler /proc/<PID>/wchan values. If this option
742 is disabled then wchan values will recurse back to the
743 caller function. This provides more accurate wchan values,
744 at the expense of slightly more scheduling overhead.
746 If in doubt, say "Y".
748 menuconfig HYPERVISOR_GUEST
749 bool "Linux guest support"
751 Say Y here to enable options for running Linux under various hyper-
752 visors. This option enables basic hypervisor detection and platform
755 If you say N, all options in this submenu will be skipped and
756 disabled, and Linux guest support won't be built in.
761 bool "Enable paravirtualization code"
763 This changes the kernel so it can modify itself when it is run
764 under a hypervisor, potentially improving performance significantly
765 over full virtualization. However, when run without a hypervisor
766 the kernel is theoretically slower and slightly larger.
771 config PARAVIRT_DEBUG
772 bool "paravirt-ops debugging"
773 depends on PARAVIRT && DEBUG_KERNEL
775 Enable to debug paravirt_ops internals. Specifically, BUG if
776 a paravirt_op is missing when it is called.
778 config PARAVIRT_SPINLOCKS
779 bool "Paravirtualization layer for spinlocks"
780 depends on PARAVIRT && SMP
782 Paravirtualized spinlocks allow a pvops backend to replace the
783 spinlock implementation with something virtualization-friendly
784 (for example, block the virtual CPU rather than spinning).
786 It has a minimal impact on native kernels and gives a nice performance
787 benefit on paravirtualized KVM / Xen kernels.
789 If you are unsure how to answer this question, answer Y.
791 config X86_HV_CALLBACK_VECTOR
794 source "arch/x86/xen/Kconfig"
797 bool "KVM Guest support (including kvmclock)"
799 select PARAVIRT_CLOCK
800 select ARCH_CPUIDLE_HALTPOLL
803 This option enables various optimizations for running under the KVM
804 hypervisor. It includes a paravirtualized clock, so that instead
805 of relying on a PIT (or probably other) emulation by the
806 underlying device model, the host provides the guest with
807 timing infrastructure such as time of day, and system time
809 config ARCH_CPUIDLE_HALTPOLL
811 prompt "Disable host haltpoll when loading haltpoll driver"
813 If virtualized under KVM, disable host haltpoll.
816 bool "Support for running PVH guests"
818 This option enables the PVH entry point for guest virtual machines
819 as specified in the x86/HVM direct boot ABI.
822 bool "Enable debug information for KVM Guests in debugfs"
823 depends on KVM_GUEST && DEBUG_FS
825 This option enables collection of various statistics for KVM guest.
826 Statistics are displayed in debugfs filesystem. Enabling this option
827 may incur significant overhead.
829 config PARAVIRT_TIME_ACCOUNTING
830 bool "Paravirtual steal time accounting"
833 Select this option to enable fine granularity task steal time
834 accounting. Time spent executing other tasks in parallel with
835 the current vCPU is discounted from the vCPU power. To account for
836 that, there can be a small performance impact.
838 If in doubt, say N here.
840 config PARAVIRT_CLOCK
843 config JAILHOUSE_GUEST
844 bool "Jailhouse non-root cell support"
845 depends on X86_64 && PCI
848 This option allows to run Linux as guest in a Jailhouse non-root
849 cell. You can leave this option disabled if you only want to start
850 Jailhouse and run Linux afterwards in the root cell.
853 bool "ACRN Guest support"
855 select X86_HV_CALLBACK_VECTOR
857 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
858 a flexible, lightweight reference open-source hypervisor, built with
859 real-time and safety-criticality in mind. It is built for embedded
860 IOT with small footprint and real-time features. More details can be
861 found in https://projectacrn.org/.
863 endif #HYPERVISOR_GUEST
865 source "arch/x86/Kconfig.cpu"
869 prompt "HPET Timer Support" if X86_32
871 Use the IA-PC HPET (High Precision Event Timer) to manage
872 time in preference to the PIT and RTC, if a HPET is
874 HPET is the next generation timer replacing legacy 8254s.
875 The HPET provides a stable time base on SMP
876 systems, unlike the TSC, but it is more expensive to access,
877 as it is off-chip. The interface used is documented
878 in the HPET spec, revision 1.
880 You can safely choose Y here. However, HPET will only be
881 activated if the platform and the BIOS support this feature.
882 Otherwise the 8254 will be used for timing services.
884 Choose N to continue using the legacy 8254 timer.
886 config HPET_EMULATE_RTC
888 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
891 def_bool y if X86_INTEL_MID
892 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
894 depends on X86_INTEL_MID && SFI
896 APB timer is the replacement for 8254, HPET on X86 MID platforms.
897 The APBT provides a stable time base on SMP
898 systems, unlike the TSC, but it is more expensive to access,
899 as it is off-chip. APB timers are always running regardless of CPU
900 C states, they are used as per CPU clockevent device when possible.
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"
918 depends on X86_64 && PCI && AMD_NB
920 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
921 GART based hardware IOMMUs.
923 The GART supports full DMA access for devices with 32-bit access
924 limitations, on systems with more than 3 GB. This is usually needed
925 for USB, sound, many IDE/SATA chipsets and some other devices.
927 Newer systems typically have a modern AMD IOMMU, supported via
928 the CONFIG_AMD_IOMMU=y config option.
930 In normal configurations this driver is only active when needed:
931 there's more than 3 GB of memory and the system contains a
932 32-bit limited device.
937 bool "IBM Calgary IOMMU support"
940 depends on X86_64 && PCI
942 Support for hardware IOMMUs in IBM's xSeries x366 and x460
943 systems. Needed to run systems with more than 3GB of memory
944 properly with 32-bit PCI devices that do not support DAC
945 (Double Address Cycle). Calgary also supports bus level
946 isolation, where all DMAs pass through the IOMMU. This
947 prevents them from going anywhere except their intended
948 destination. This catches hard-to-find kernel bugs and
949 mis-behaving drivers and devices that do not use the DMA-API
950 properly to set up their DMA buffers. The IOMMU can be
951 turned off at boot time with the iommu=off parameter.
952 Normally the kernel will make the right choice by itself.
955 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
957 prompt "Should Calgary be enabled by default?"
958 depends on CALGARY_IOMMU
960 Should Calgary be enabled by default? if you choose 'y', Calgary
961 will be used (if it exists). If you choose 'n', Calgary will not be
962 used even if it exists. If you choose 'n' and would like to use
963 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
967 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
968 depends on X86_64 && SMP && DEBUG_KERNEL
969 select CPUMASK_OFFSTACK
971 Enable maximum number of CPUS and NUMA Nodes for this architecture.
975 # The maximum number of CPUs supported:
977 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
978 # and which can be configured interactively in the
979 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
981 # The ranges are different on 32-bit and 64-bit kernels, depending on
982 # hardware capabilities and scalability features of the kernel.
984 # ( If MAXSMP is enabled we just use the highest possible value and disable
985 # interactive configuration. )
988 config NR_CPUS_RANGE_BEGIN
990 default NR_CPUS_RANGE_END if MAXSMP
994 config NR_CPUS_RANGE_END
997 default 64 if SMP && X86_BIGSMP
998 default 8 if SMP && !X86_BIGSMP
1001 config NR_CPUS_RANGE_END
1004 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
1005 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
1008 config NR_CPUS_DEFAULT
1011 default 32 if X86_BIGSMP
1015 config NR_CPUS_DEFAULT
1018 default 8192 if MAXSMP
1023 int "Maximum number of CPUs" if SMP && !MAXSMP
1024 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1025 default NR_CPUS_DEFAULT
1027 This allows you to specify the maximum number of CPUs which this
1028 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1029 supported value is 8192, otherwise the maximum value is 512. The
1030 minimum value which makes sense is 2.
1032 This is purely to save memory: each supported CPU adds about 8KB
1033 to the kernel image.
1040 prompt "Multi-core scheduler support"
1043 Multi-core scheduler support improves the CPU scheduler's decision
1044 making when dealing with multi-core CPU chips at a cost of slightly
1045 increased overhead in some places. If unsure say N here.
1047 config SCHED_MC_PRIO
1048 bool "CPU core priorities scheduler support"
1049 depends on SCHED_MC && CPU_SUP_INTEL
1050 select X86_INTEL_PSTATE
1054 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1055 core ordering determined at manufacturing time, which allows
1056 certain cores to reach higher turbo frequencies (when running
1057 single threaded workloads) than others.
1059 Enabling this kernel feature teaches the scheduler about
1060 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1061 scheduler's CPU selection logic accordingly, so that higher
1062 overall system performance can be achieved.
1064 This feature will have no effect on CPUs without this feature.
1066 If unsure say Y here.
1070 depends on !SMP && X86_LOCAL_APIC
1073 bool "Local APIC support on uniprocessors" if !PCI_MSI
1075 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1077 A local APIC (Advanced Programmable Interrupt Controller) is an
1078 integrated interrupt controller in the CPU. If you have a single-CPU
1079 system which has a processor with a local APIC, you can say Y here to
1080 enable and use it. If you say Y here even though your machine doesn't
1081 have a local APIC, then the kernel will still run with no slowdown at
1082 all. The local APIC supports CPU-generated self-interrupts (timer,
1083 performance counters), and the NMI watchdog which detects hard
1086 config X86_UP_IOAPIC
1087 bool "IO-APIC support on uniprocessors"
1088 depends on X86_UP_APIC
1090 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1091 SMP-capable replacement for PC-style interrupt controllers. Most
1092 SMP systems and many recent uniprocessor systems have one.
1094 If you have a single-CPU system with an IO-APIC, you can say Y here
1095 to use it. If you say Y here even though your machine doesn't have
1096 an IO-APIC, then the kernel will still run with no slowdown at all.
1098 config X86_LOCAL_APIC
1100 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1101 select IRQ_DOMAIN_HIERARCHY
1102 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1106 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1108 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1109 bool "Reroute for broken boot IRQs"
1110 depends on X86_IO_APIC
1112 This option enables a workaround that fixes a source of
1113 spurious interrupts. This is recommended when threaded
1114 interrupt handling is used on systems where the generation of
1115 superfluous "boot interrupts" cannot be disabled.
1117 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1118 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1119 kernel does during interrupt handling). On chipsets where this
1120 boot IRQ generation cannot be disabled, this workaround keeps
1121 the original IRQ line masked so that only the equivalent "boot
1122 IRQ" is delivered to the CPUs. The workaround also tells the
1123 kernel to set up the IRQ handler on the boot IRQ line. In this
1124 way only one interrupt is delivered to the kernel. Otherwise
1125 the spurious second interrupt may cause the kernel to bring
1126 down (vital) interrupt lines.
1128 Only affects "broken" chipsets. Interrupt sharing may be
1129 increased on these systems.
1132 bool "Machine Check / overheating reporting"
1133 select GENERIC_ALLOCATOR
1136 Machine Check support allows the processor to notify the
1137 kernel if it detects a problem (e.g. overheating, data corruption).
1138 The action the kernel takes depends on the severity of the problem,
1139 ranging from warning messages to halting the machine.
1141 config X86_MCELOG_LEGACY
1142 bool "Support for deprecated /dev/mcelog character device"
1145 Enable support for /dev/mcelog which is needed by the old mcelog
1146 userspace logging daemon. Consider switching to the new generation
1149 config X86_MCE_INTEL
1151 prompt "Intel MCE features"
1152 depends on X86_MCE && X86_LOCAL_APIC
1154 Additional support for intel specific MCE features such as
1155 the thermal monitor.
1159 prompt "AMD MCE features"
1160 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1162 Additional support for AMD specific MCE features such as
1163 the DRAM Error Threshold.
1165 config X86_ANCIENT_MCE
1166 bool "Support for old Pentium 5 / WinChip machine checks"
1167 depends on X86_32 && X86_MCE
1169 Include support for machine check handling on old Pentium 5 or WinChip
1170 systems. These typically need to be enabled explicitly on the command
1173 config X86_MCE_THRESHOLD
1174 depends on X86_MCE_AMD || X86_MCE_INTEL
1177 config X86_MCE_INJECT
1178 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1179 tristate "Machine check injector support"
1181 Provide support for injecting machine checks for testing purposes.
1182 If you don't know what a machine check is and you don't do kernel
1183 QA it is safe to say n.
1185 config X86_THERMAL_VECTOR
1187 depends on X86_MCE_INTEL
1189 source "arch/x86/events/Kconfig"
1191 config X86_LEGACY_VM86
1192 bool "Legacy VM86 support"
1195 This option allows user programs to put the CPU into V8086
1196 mode, which is an 80286-era approximation of 16-bit real mode.
1198 Some very old versions of X and/or vbetool require this option
1199 for user mode setting. Similarly, DOSEMU will use it if
1200 available to accelerate real mode DOS programs. However, any
1201 recent version of DOSEMU, X, or vbetool should be fully
1202 functional even without kernel VM86 support, as they will all
1203 fall back to software emulation. Nevertheless, if you are using
1204 a 16-bit DOS program where 16-bit performance matters, vm86
1205 mode might be faster than emulation and you might want to
1208 Note that any app that works on a 64-bit kernel is unlikely to
1209 need this option, as 64-bit kernels don't, and can't, support
1210 V8086 mode. This option is also unrelated to 16-bit protected
1211 mode and is not needed to run most 16-bit programs under Wine.
1213 Enabling this option increases the complexity of the kernel
1214 and slows down exception handling a tiny bit.
1216 If unsure, say N here.
1220 default X86_LEGACY_VM86
1223 bool "Enable support for 16-bit segments" if EXPERT
1225 depends on MODIFY_LDT_SYSCALL
1227 This option is required by programs like Wine to run 16-bit
1228 protected mode legacy code on x86 processors. Disabling
1229 this option saves about 300 bytes on i386, or around 6K text
1230 plus 16K runtime memory on x86-64,
1234 depends on X86_16BIT && X86_32
1238 depends on X86_16BIT && X86_64
1240 config X86_VSYSCALL_EMULATION
1241 bool "Enable vsyscall emulation" if EXPERT
1245 This enables emulation of the legacy vsyscall page. Disabling
1246 it is roughly equivalent to booting with vsyscall=none, except
1247 that it will also disable the helpful warning if a program
1248 tries to use a vsyscall. With this option set to N, offending
1249 programs will just segfault, citing addresses of the form
1252 This option is required by many programs built before 2013, and
1253 care should be used even with newer programs if set to N.
1255 Disabling this option saves about 7K of kernel size and
1256 possibly 4K of additional runtime pagetable memory.
1259 tristate "Toshiba Laptop support"
1262 This adds a driver to safely access the System Management Mode of
1263 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1264 not work on models with a Phoenix BIOS. The System Management Mode
1265 is used to set the BIOS and power saving options on Toshiba portables.
1267 For information on utilities to make use of this driver see the
1268 Toshiba Linux utilities web site at:
1269 <http://www.buzzard.org.uk/toshiba/>.
1271 Say Y if you intend to run this kernel on a Toshiba portable.
1275 tristate "Dell i8k legacy laptop support"
1277 select SENSORS_DELL_SMM
1279 This option enables legacy /proc/i8k userspace interface in hwmon
1280 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1281 temperature and allows controlling fan speeds of Dell laptops via
1282 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1283 it reports also power and hotkey status. For fan speed control is
1284 needed userspace package i8kutils.
1286 Say Y if you intend to run this kernel on old Dell laptops or want to
1287 use userspace package i8kutils.
1290 config X86_REBOOTFIXUPS
1291 bool "Enable X86 board specific fixups for reboot"
1294 This enables chipset and/or board specific fixups to be done
1295 in order to get reboot to work correctly. This is only needed on
1296 some combinations of hardware and BIOS. The symptom, for which
1297 this config is intended, is when reboot ends with a stalled/hung
1300 Currently, the only fixup is for the Geode machines using
1301 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1303 Say Y if you want to enable the fixup. Currently, it's safe to
1304 enable this option even if you don't need it.
1308 bool "CPU microcode loading support"
1310 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1313 If you say Y here, you will be able to update the microcode on
1314 Intel and AMD processors. The Intel support is for the IA32 family,
1315 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1316 AMD support is for families 0x10 and later. You will obviously need
1317 the actual microcode binary data itself which is not shipped with
1320 The preferred method to load microcode from a detached initrd is described
1321 in Documentation/x86/microcode.rst. For that you need to enable
1322 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1323 initrd for microcode blobs.
1325 In addition, you can build the microcode into the kernel. For that you
1326 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1329 config MICROCODE_INTEL
1330 bool "Intel microcode loading support"
1331 depends on MICROCODE
1335 This options enables microcode patch loading support for Intel
1338 For the current Intel microcode data package go to
1339 <https://downloadcenter.intel.com> and search for
1340 'Linux Processor Microcode Data File'.
1342 config MICROCODE_AMD
1343 bool "AMD microcode loading support"
1344 depends on MICROCODE
1347 If you select this option, microcode patch loading support for AMD
1348 processors will be enabled.
1350 config MICROCODE_OLD_INTERFACE
1351 bool "Ancient loading interface (DEPRECATED)"
1353 depends on MICROCODE
1355 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1356 which was used by userspace tools like iucode_tool and microcode.ctl.
1357 It is inadequate because it runs too late to be able to properly
1358 load microcode on a machine and it needs special tools. Instead, you
1359 should've switched to the early loading method with the initrd or
1360 builtin microcode by now: Documentation/x86/microcode.rst
1363 tristate "/dev/cpu/*/msr - Model-specific register support"
1365 This device gives privileged processes access to the x86
1366 Model-Specific Registers (MSRs). It is a character device with
1367 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1368 MSR accesses are directed to a specific CPU on multi-processor
1372 tristate "/dev/cpu/*/cpuid - CPU information support"
1374 This device gives processes access to the x86 CPUID instruction to
1375 be executed on a specific processor. It is a character device
1376 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1380 prompt "High Memory Support"
1387 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1388 However, the address space of 32-bit x86 processors is only 4
1389 Gigabytes large. That means that, if you have a large amount of
1390 physical memory, not all of it can be "permanently mapped" by the
1391 kernel. The physical memory that's not permanently mapped is called
1394 If you are compiling a kernel which will never run on a machine with
1395 more than 1 Gigabyte total physical RAM, answer "off" here (default
1396 choice and suitable for most users). This will result in a "3GB/1GB"
1397 split: 3GB are mapped so that each process sees a 3GB virtual memory
1398 space and the remaining part of the 4GB virtual memory space is used
1399 by the kernel to permanently map as much physical memory as
1402 If the machine has between 1 and 4 Gigabytes physical RAM, then
1405 If more than 4 Gigabytes is used then answer "64GB" here. This
1406 selection turns Intel PAE (Physical Address Extension) mode on.
1407 PAE implements 3-level paging on IA32 processors. PAE is fully
1408 supported by Linux, PAE mode is implemented on all recent Intel
1409 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1410 then the kernel will not boot on CPUs that don't support PAE!
1412 The actual amount of total physical memory will either be
1413 auto detected or can be forced by using a kernel command line option
1414 such as "mem=256M". (Try "man bootparam" or see the documentation of
1415 your boot loader (lilo or loadlin) about how to pass options to the
1416 kernel at boot time.)
1418 If unsure, say "off".
1423 Select this if you have a 32-bit processor and between 1 and 4
1424 gigabytes of physical RAM.
1428 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1431 Select this if you have a 32-bit processor and more than 4
1432 gigabytes of physical RAM.
1437 prompt "Memory split" if EXPERT
1441 Select the desired split between kernel and user memory.
1443 If the address range available to the kernel is less than the
1444 physical memory installed, the remaining memory will be available
1445 as "high memory". Accessing high memory is a little more costly
1446 than low memory, as it needs to be mapped into the kernel first.
1447 Note that increasing the kernel address space limits the range
1448 available to user programs, making the address space there
1449 tighter. Selecting anything other than the default 3G/1G split
1450 will also likely make your kernel incompatible with binary-only
1453 If you are not absolutely sure what you are doing, leave this
1457 bool "3G/1G user/kernel split"
1458 config VMSPLIT_3G_OPT
1460 bool "3G/1G user/kernel split (for full 1G low memory)"
1462 bool "2G/2G user/kernel split"
1463 config VMSPLIT_2G_OPT
1465 bool "2G/2G user/kernel split (for full 2G low memory)"
1467 bool "1G/3G user/kernel split"
1472 default 0xB0000000 if VMSPLIT_3G_OPT
1473 default 0x80000000 if VMSPLIT_2G
1474 default 0x78000000 if VMSPLIT_2G_OPT
1475 default 0x40000000 if VMSPLIT_1G
1481 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1484 bool "PAE (Physical Address Extension) Support"
1485 depends on X86_32 && !HIGHMEM4G
1486 select PHYS_ADDR_T_64BIT
1489 PAE is required for NX support, and furthermore enables
1490 larger swapspace support for non-overcommit purposes. It
1491 has the cost of more pagetable lookup overhead, and also
1492 consumes more pagetable space per process.
1495 bool "Enable 5-level page tables support"
1496 select DYNAMIC_MEMORY_LAYOUT
1497 select SPARSEMEM_VMEMMAP
1500 5-level paging enables access to larger address space:
1501 upto 128 PiB of virtual address space and 4 PiB of
1502 physical address space.
1504 It will be supported by future Intel CPUs.
1506 A kernel with the option enabled can be booted on machines that
1507 support 4- or 5-level paging.
1509 See Documentation/x86/x86_64/5level-paging.rst for more
1514 config X86_DIRECT_GBPAGES
1518 Certain kernel features effectively disable kernel
1519 linear 1 GB mappings (even if the CPU otherwise
1520 supports them), so don't confuse the user by printing
1521 that we have them enabled.
1523 config X86_CPA_STATISTICS
1524 bool "Enable statistic for Change Page Attribute"
1527 Expose statistics about the Change Page Attribute mechanims, which
1528 helps to determine the effectiveness of preserving large and huge
1529 page mappings when mapping protections are changed.
1531 config AMD_MEM_ENCRYPT
1532 bool "AMD Secure Memory Encryption (SME) support"
1533 depends on X86_64 && CPU_SUP_AMD
1534 select DYNAMIC_PHYSICAL_MASK
1535 select ARCH_USE_MEMREMAP_PROT
1536 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1538 Say yes to enable support for the encryption of system memory.
1539 This requires an AMD processor that supports Secure Memory
1542 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1543 bool "Activate AMD Secure Memory Encryption (SME) by default"
1544 depends on AMD_MEM_ENCRYPT
1546 Say yes to have system memory encrypted by default if running on
1547 an AMD processor that supports Secure Memory Encryption (SME).
1549 If set to Y, then the encryption of system memory can be
1550 deactivated with the mem_encrypt=off command line option.
1552 If set to N, then the encryption of system memory can be
1553 activated with the mem_encrypt=on command line option.
1555 # Common NUMA Features
1557 bool "Numa Memory Allocation and Scheduler Support"
1559 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1560 default y if X86_BIGSMP
1562 Enable NUMA (Non Uniform Memory Access) support.
1564 The kernel will try to allocate memory used by a CPU on the
1565 local memory controller of the CPU and add some more
1566 NUMA awareness to the kernel.
1568 For 64-bit this is recommended if the system is Intel Core i7
1569 (or later), AMD Opteron, or EM64T NUMA.
1571 For 32-bit this is only needed if you boot a 32-bit
1572 kernel on a 64-bit NUMA platform.
1574 Otherwise, you should say N.
1578 prompt "Old style AMD Opteron NUMA detection"
1579 depends on X86_64 && NUMA && PCI
1581 Enable AMD NUMA node topology detection. You should say Y here if
1582 you have a multi processor AMD system. This uses an old method to
1583 read the NUMA configuration directly from the builtin Northbridge
1584 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1585 which also takes priority if both are compiled in.
1587 config X86_64_ACPI_NUMA
1589 prompt "ACPI NUMA detection"
1590 depends on X86_64 && NUMA && ACPI && PCI
1593 Enable ACPI SRAT based node topology detection.
1595 # Some NUMA nodes have memory ranges that span
1596 # other nodes. Even though a pfn is valid and
1597 # between a node's start and end pfns, it may not
1598 # reside on that node. See memmap_init_zone()
1600 config NODES_SPAN_OTHER_NODES
1602 depends on X86_64_ACPI_NUMA
1605 bool "NUMA emulation"
1608 Enable NUMA emulation. A flat machine will be split
1609 into virtual nodes when booted with "numa=fake=N", where N is the
1610 number of nodes. This is only useful for debugging.
1613 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1615 default "10" if MAXSMP
1616 default "6" if X86_64
1618 depends on NEED_MULTIPLE_NODES
1620 Specify the maximum number of NUMA Nodes available on the target
1621 system. Increases memory reserved to accommodate various tables.
1623 config ARCH_HAVE_MEMORY_PRESENT
1625 depends on X86_32 && DISCONTIGMEM
1627 config ARCH_FLATMEM_ENABLE
1629 depends on X86_32 && !NUMA
1631 config ARCH_DISCONTIGMEM_ENABLE
1633 depends on NUMA && X86_32
1636 config ARCH_SPARSEMEM_ENABLE
1638 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1639 select SPARSEMEM_STATIC if X86_32
1640 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1642 config ARCH_SPARSEMEM_DEFAULT
1643 def_bool X86_64 || (NUMA && X86_32)
1645 config ARCH_SELECT_MEMORY_MODEL
1647 depends on ARCH_SPARSEMEM_ENABLE
1649 config ARCH_MEMORY_PROBE
1650 bool "Enable sysfs memory/probe interface"
1651 depends on X86_64 && MEMORY_HOTPLUG
1653 This option enables a sysfs memory/probe interface for testing.
1654 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1655 If you are unsure how to answer this question, answer N.
1657 config ARCH_PROC_KCORE_TEXT
1659 depends on X86_64 && PROC_KCORE
1661 config ILLEGAL_POINTER_VALUE
1664 default 0xdead000000000000 if X86_64
1666 config X86_PMEM_LEGACY_DEVICE
1669 config X86_PMEM_LEGACY
1670 tristate "Support non-standard NVDIMMs and ADR protected memory"
1671 depends on PHYS_ADDR_T_64BIT
1673 select X86_PMEM_LEGACY_DEVICE
1676 Treat memory marked using the non-standard e820 type of 12 as used
1677 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1678 The kernel will offer these regions to the 'pmem' driver so
1679 they can be used for persistent storage.
1684 bool "Allocate 3rd-level pagetables from highmem"
1687 The VM uses one page table entry for each page of physical memory.
1688 For systems with a lot of RAM, this can be wasteful of precious
1689 low memory. Setting this option will put user-space page table
1690 entries in high memory.
1692 config X86_CHECK_BIOS_CORRUPTION
1693 bool "Check for low memory corruption"
1695 Periodically check for memory corruption in low memory, which
1696 is suspected to be caused by BIOS. Even when enabled in the
1697 configuration, it is disabled at runtime. Enable it by
1698 setting "memory_corruption_check=1" on the kernel command
1699 line. By default it scans the low 64k of memory every 60
1700 seconds; see the memory_corruption_check_size and
1701 memory_corruption_check_period parameters in
1702 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1704 When enabled with the default parameters, this option has
1705 almost no overhead, as it reserves a relatively small amount
1706 of memory and scans it infrequently. It both detects corruption
1707 and prevents it from affecting the running system.
1709 It is, however, intended as a diagnostic tool; if repeatable
1710 BIOS-originated corruption always affects the same memory,
1711 you can use memmap= to prevent the kernel from using that
1714 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1715 bool "Set the default setting of memory_corruption_check"
1716 depends on X86_CHECK_BIOS_CORRUPTION
1719 Set whether the default state of memory_corruption_check is
1722 config X86_RESERVE_LOW
1723 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1727 Specify the amount of low memory to reserve for the BIOS.
1729 The first page contains BIOS data structures that the kernel
1730 must not use, so that page must always be reserved.
1732 By default we reserve the first 64K of physical RAM, as a
1733 number of BIOSes are known to corrupt that memory range
1734 during events such as suspend/resume or monitor cable
1735 insertion, so it must not be used by the kernel.
1737 You can set this to 4 if you are absolutely sure that you
1738 trust the BIOS to get all its memory reservations and usages
1739 right. If you know your BIOS have problems beyond the
1740 default 64K area, you can set this to 640 to avoid using the
1741 entire low memory range.
1743 If you have doubts about the BIOS (e.g. suspend/resume does
1744 not work or there's kernel crashes after certain hardware
1745 hotplug events) then you might want to enable
1746 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1747 typical corruption patterns.
1749 Leave this to the default value of 64 if you are unsure.
1751 config MATH_EMULATION
1753 depends on MODIFY_LDT_SYSCALL
1754 prompt "Math emulation" if X86_32
1756 Linux can emulate a math coprocessor (used for floating point
1757 operations) if you don't have one. 486DX and Pentium processors have
1758 a math coprocessor built in, 486SX and 386 do not, unless you added
1759 a 487DX or 387, respectively. (The messages during boot time can
1760 give you some hints here ["man dmesg"].) Everyone needs either a
1761 coprocessor or this emulation.
1763 If you don't have a math coprocessor, you need to say Y here; if you
1764 say Y here even though you have a coprocessor, the coprocessor will
1765 be used nevertheless. (This behavior can be changed with the kernel
1766 command line option "no387", which comes handy if your coprocessor
1767 is broken. Try "man bootparam" or see the documentation of your boot
1768 loader (lilo or loadlin) about how to pass options to the kernel at
1769 boot time.) This means that it is a good idea to say Y here if you
1770 intend to use this kernel on different machines.
1772 More information about the internals of the Linux math coprocessor
1773 emulation can be found in <file:arch/x86/math-emu/README>.
1775 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1776 kernel, it won't hurt.
1780 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1782 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1783 the Memory Type Range Registers (MTRRs) may be used to control
1784 processor access to memory ranges. This is most useful if you have
1785 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1786 allows bus write transfers to be combined into a larger transfer
1787 before bursting over the PCI/AGP bus. This can increase performance
1788 of image write operations 2.5 times or more. Saying Y here creates a
1789 /proc/mtrr file which may be used to manipulate your processor's
1790 MTRRs. Typically the X server should use this.
1792 This code has a reasonably generic interface so that similar
1793 control registers on other processors can be easily supported
1796 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1797 Registers (ARRs) which provide a similar functionality to MTRRs. For
1798 these, the ARRs are used to emulate the MTRRs.
1799 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1800 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1801 write-combining. All of these processors are supported by this code
1802 and it makes sense to say Y here if you have one of them.
1804 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1805 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1806 can lead to all sorts of problems, so it's good to say Y here.
1808 You can safely say Y even if your machine doesn't have MTRRs, you'll
1809 just add about 9 KB to your kernel.
1811 See <file:Documentation/x86/mtrr.rst> for more information.
1813 config MTRR_SANITIZER
1815 prompt "MTRR cleanup support"
1818 Convert MTRR layout from continuous to discrete, so X drivers can
1819 add writeback entries.
1821 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1822 The largest mtrr entry size for a continuous block can be set with
1827 config MTRR_SANITIZER_ENABLE_DEFAULT
1828 int "MTRR cleanup enable value (0-1)"
1831 depends on MTRR_SANITIZER
1833 Enable mtrr cleanup default value
1835 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1836 int "MTRR cleanup spare reg num (0-7)"
1839 depends on MTRR_SANITIZER
1841 mtrr cleanup spare entries default, it can be changed via
1842 mtrr_spare_reg_nr=N on the kernel command line.
1846 prompt "x86 PAT support" if EXPERT
1849 Use PAT attributes to setup page level cache control.
1851 PATs are the modern equivalents of MTRRs and are much more
1852 flexible than MTRRs.
1854 Say N here if you see bootup problems (boot crash, boot hang,
1855 spontaneous reboots) or a non-working video driver.
1859 config ARCH_USES_PG_UNCACHED
1865 prompt "x86 architectural random number generator" if EXPERT
1867 Enable the x86 architectural RDRAND instruction
1868 (Intel Bull Mountain technology) to generate random numbers.
1869 If supported, this is a high bandwidth, cryptographically
1870 secure hardware random number generator.
1874 prompt "Supervisor Mode Access Prevention" if EXPERT
1876 Supervisor Mode Access Prevention (SMAP) is a security
1877 feature in newer Intel processors. There is a small
1878 performance cost if this enabled and turned on; there is
1879 also a small increase in the kernel size if this is enabled.
1883 config X86_INTEL_UMIP
1885 depends on CPU_SUP_INTEL
1886 prompt "Intel User Mode Instruction Prevention" if EXPERT
1888 The User Mode Instruction Prevention (UMIP) is a security
1889 feature in newer Intel processors. If enabled, a general
1890 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1891 or STR instructions are executed in user mode. These instructions
1892 unnecessarily expose information about the hardware state.
1894 The vast majority of applications do not use these instructions.
1895 For the very few that do, software emulation is provided in
1896 specific cases in protected and virtual-8086 modes. Emulated
1899 config X86_INTEL_MPX
1900 prompt "Intel MPX (Memory Protection Extensions)"
1902 # Note: only available in 64-bit mode due to VMA flags shortage
1903 depends on CPU_SUP_INTEL && X86_64
1904 select ARCH_USES_HIGH_VMA_FLAGS
1906 MPX provides hardware features that can be used in
1907 conjunction with compiler-instrumented code to check
1908 memory references. It is designed to detect buffer
1909 overflow or underflow bugs.
1911 This option enables running applications which are
1912 instrumented or otherwise use MPX. It does not use MPX
1913 itself inside the kernel or to protect the kernel
1914 against bad memory references.
1916 Enabling this option will make the kernel larger:
1917 ~8k of kernel text and 36 bytes of data on a 64-bit
1918 defconfig. It adds a long to the 'mm_struct' which
1919 will increase the kernel memory overhead of each
1920 process and adds some branches to paths used during
1921 exec() and munmap().
1923 For details, see Documentation/x86/intel_mpx.rst
1927 config X86_INTEL_MEMORY_PROTECTION_KEYS
1928 prompt "Intel Memory Protection Keys"
1930 # Note: only available in 64-bit mode
1931 depends on CPU_SUP_INTEL && X86_64
1932 select ARCH_USES_HIGH_VMA_FLAGS
1933 select ARCH_HAS_PKEYS
1935 Memory Protection Keys provides a mechanism for enforcing
1936 page-based protections, but without requiring modification of the
1937 page tables when an application changes protection domains.
1939 For details, see Documentation/core-api/protection-keys.rst
1944 prompt "TSX enable mode"
1945 depends on CPU_SUP_INTEL
1946 default X86_INTEL_TSX_MODE_OFF
1948 Intel's TSX (Transactional Synchronization Extensions) feature
1949 allows to optimize locking protocols through lock elision which
1950 can lead to a noticeable performance boost.
1952 On the other hand it has been shown that TSX can be exploited
1953 to form side channel attacks (e.g. TAA) and chances are there
1954 will be more of those attacks discovered in the future.
1956 Therefore TSX is not enabled by default (aka tsx=off). An admin
1957 might override this decision by tsx=on the command line parameter.
1958 Even with TSX enabled, the kernel will attempt to enable the best
1959 possible TAA mitigation setting depending on the microcode available
1960 for the particular machine.
1962 This option allows to set the default tsx mode between tsx=on, =off
1963 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1966 Say off if not sure, auto if TSX is in use but it should be used on safe
1967 platforms or on if TSX is in use and the security aspect of tsx is not
1970 config X86_INTEL_TSX_MODE_OFF
1973 TSX is disabled if possible - equals to tsx=off command line parameter.
1975 config X86_INTEL_TSX_MODE_ON
1978 TSX is always enabled on TSX capable HW - equals the tsx=on command
1981 config X86_INTEL_TSX_MODE_AUTO
1984 TSX is enabled on TSX capable HW that is believed to be safe against
1985 side channel attacks- equals the tsx=auto command line parameter.
1989 bool "EFI runtime service support"
1992 select EFI_RUNTIME_WRAPPERS
1993 select ARCH_USE_MEMREMAP_PROT
1995 This enables the kernel to use EFI runtime services that are
1996 available (such as the EFI variable services).
1998 This option is only useful on systems that have EFI firmware.
1999 In addition, you should use the latest ELILO loader available
2000 at <http://elilo.sourceforge.net> in order to take advantage
2001 of EFI runtime services. However, even with this option, the
2002 resultant kernel should continue to boot on existing non-EFI
2006 bool "EFI stub support"
2007 depends on EFI && !X86_USE_3DNOW
2010 This kernel feature allows a bzImage to be loaded directly
2011 by EFI firmware without the use of a bootloader.
2013 See Documentation/admin-guide/efi-stub.rst for more information.
2016 bool "EFI mixed-mode support"
2017 depends on EFI_STUB && X86_64
2019 Enabling this feature allows a 64-bit kernel to be booted
2020 on a 32-bit firmware, provided that your CPU supports 64-bit
2023 Note that it is not possible to boot a mixed-mode enabled
2024 kernel via the EFI boot stub - a bootloader that supports
2025 the EFI handover protocol must be used.
2031 prompt "Enable seccomp to safely compute untrusted bytecode"
2033 This kernel feature is useful for number crunching applications
2034 that may need to compute untrusted bytecode during their
2035 execution. By using pipes or other transports made available to
2036 the process as file descriptors supporting the read/write
2037 syscalls, it's possible to isolate those applications in
2038 their own address space using seccomp. Once seccomp is
2039 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
2040 and the task is only allowed to execute a few safe syscalls
2041 defined by each seccomp mode.
2043 If unsure, say Y. Only embedded should say N here.
2045 source "kernel/Kconfig.hz"
2048 bool "kexec system call"
2051 kexec is a system call that implements the ability to shutdown your
2052 current kernel, and to start another kernel. It is like a reboot
2053 but it is independent of the system firmware. And like a reboot
2054 you can start any kernel with it, not just Linux.
2056 The name comes from the similarity to the exec system call.
2058 It is an ongoing process to be certain the hardware in a machine
2059 is properly shutdown, so do not be surprised if this code does not
2060 initially work for you. As of this writing the exact hardware
2061 interface is strongly in flux, so no good recommendation can be
2065 bool "kexec file based system call"
2070 depends on CRYPTO_SHA256=y
2072 This is new version of kexec system call. This system call is
2073 file based and takes file descriptors as system call argument
2074 for kernel and initramfs as opposed to list of segments as
2075 accepted by previous system call.
2077 config ARCH_HAS_KEXEC_PURGATORY
2081 bool "Verify kernel signature during kexec_file_load() syscall"
2082 depends on KEXEC_FILE
2085 This option makes the kexec_file_load() syscall check for a valid
2086 signature of the kernel image. The image can still be loaded without
2087 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2088 there's a signature that we can check, then it must be valid.
2090 In addition to this option, you need to enable signature
2091 verification for the corresponding kernel image type being
2092 loaded in order for this to work.
2094 config KEXEC_SIG_FORCE
2095 bool "Require a valid signature in kexec_file_load() syscall"
2096 depends on KEXEC_SIG
2098 This option makes kernel signature verification mandatory for
2099 the kexec_file_load() syscall.
2101 config KEXEC_BZIMAGE_VERIFY_SIG
2102 bool "Enable bzImage signature verification support"
2103 depends on KEXEC_SIG
2104 depends on SIGNED_PE_FILE_VERIFICATION
2105 select SYSTEM_TRUSTED_KEYRING
2107 Enable bzImage signature verification support.
2110 bool "kernel crash dumps"
2111 depends on X86_64 || (X86_32 && HIGHMEM)
2113 Generate crash dump after being started by kexec.
2114 This should be normally only set in special crash dump kernels
2115 which are loaded in the main kernel with kexec-tools into
2116 a specially reserved region and then later executed after
2117 a crash by kdump/kexec. The crash dump kernel must be compiled
2118 to a memory address not used by the main kernel or BIOS using
2119 PHYSICAL_START, or it must be built as a relocatable image
2120 (CONFIG_RELOCATABLE=y).
2121 For more details see Documentation/admin-guide/kdump/kdump.rst
2125 depends on KEXEC && HIBERNATION
2127 Jump between original kernel and kexeced kernel and invoke
2128 code in physical address mode via KEXEC
2130 config PHYSICAL_START
2131 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2134 This gives the physical address where the kernel is loaded.
2136 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2137 bzImage will decompress itself to above physical address and
2138 run from there. Otherwise, bzImage will run from the address where
2139 it has been loaded by the boot loader and will ignore above physical
2142 In normal kdump cases one does not have to set/change this option
2143 as now bzImage can be compiled as a completely relocatable image
2144 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2145 address. This option is mainly useful for the folks who don't want
2146 to use a bzImage for capturing the crash dump and want to use a
2147 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2148 to be specifically compiled to run from a specific memory area
2149 (normally a reserved region) and this option comes handy.
2151 So if you are using bzImage for capturing the crash dump,
2152 leave the value here unchanged to 0x1000000 and set
2153 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2154 for capturing the crash dump change this value to start of
2155 the reserved region. In other words, it can be set based on
2156 the "X" value as specified in the "crashkernel=YM@XM"
2157 command line boot parameter passed to the panic-ed
2158 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2159 for more details about crash dumps.
2161 Usage of bzImage for capturing the crash dump is recommended as
2162 one does not have to build two kernels. Same kernel can be used
2163 as production kernel and capture kernel. Above option should have
2164 gone away after relocatable bzImage support is introduced. But it
2165 is present because there are users out there who continue to use
2166 vmlinux for dump capture. This option should go away down the
2169 Don't change this unless you know what you are doing.
2172 bool "Build a relocatable kernel"
2175 This builds a kernel image that retains relocation information
2176 so it can be loaded someplace besides the default 1MB.
2177 The relocations tend to make the kernel binary about 10% larger,
2178 but are discarded at runtime.
2180 One use is for the kexec on panic case where the recovery kernel
2181 must live at a different physical address than the primary
2184 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2185 it has been loaded at and the compile time physical address
2186 (CONFIG_PHYSICAL_START) is used as the minimum location.
2188 config RANDOMIZE_BASE
2189 bool "Randomize the address of the kernel image (KASLR)"
2190 depends on RELOCATABLE
2193 In support of Kernel Address Space Layout Randomization (KASLR),
2194 this randomizes the physical address at which the kernel image
2195 is decompressed and the virtual address where the kernel
2196 image is mapped, as a security feature that deters exploit
2197 attempts relying on knowledge of the location of kernel
2200 On 64-bit, the kernel physical and virtual addresses are
2201 randomized separately. The physical address will be anywhere
2202 between 16MB and the top of physical memory (up to 64TB). The
2203 virtual address will be randomized from 16MB up to 1GB (9 bits
2204 of entropy). Note that this also reduces the memory space
2205 available to kernel modules from 1.5GB to 1GB.
2207 On 32-bit, the kernel physical and virtual addresses are
2208 randomized together. They will be randomized from 16MB up to
2209 512MB (8 bits of entropy).
2211 Entropy is generated using the RDRAND instruction if it is
2212 supported. If RDTSC is supported, its value is mixed into
2213 the entropy pool as well. If neither RDRAND nor RDTSC are
2214 supported, then entropy is read from the i8254 timer. The
2215 usable entropy is limited by the kernel being built using
2216 2GB addressing, and that PHYSICAL_ALIGN must be at a
2217 minimum of 2MB. As a result, only 10 bits of entropy are
2218 theoretically possible, but the implementations are further
2219 limited due to memory layouts.
2223 # Relocation on x86 needs some additional build support
2224 config X86_NEED_RELOCS
2226 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2228 config PHYSICAL_ALIGN
2229 hex "Alignment value to which kernel should be aligned"
2231 range 0x2000 0x1000000 if X86_32
2232 range 0x200000 0x1000000 if X86_64
2234 This value puts the alignment restrictions on physical address
2235 where kernel is loaded and run from. Kernel is compiled for an
2236 address which meets above alignment restriction.
2238 If bootloader loads the kernel at a non-aligned address and
2239 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2240 address aligned to above value and run from there.
2242 If bootloader loads the kernel at a non-aligned address and
2243 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2244 load address and decompress itself to the address it has been
2245 compiled for and run from there. The address for which kernel is
2246 compiled already meets above alignment restrictions. Hence the
2247 end result is that kernel runs from a physical address meeting
2248 above alignment restrictions.
2250 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2251 this value must be a multiple of 0x200000.
2253 Don't change this unless you know what you are doing.
2255 config DYNAMIC_MEMORY_LAYOUT
2258 This option makes base addresses of vmalloc and vmemmap as well as
2259 __PAGE_OFFSET movable during boot.
2261 config RANDOMIZE_MEMORY
2262 bool "Randomize the kernel memory sections"
2264 depends on RANDOMIZE_BASE
2265 select DYNAMIC_MEMORY_LAYOUT
2266 default RANDOMIZE_BASE
2268 Randomizes the base virtual address of kernel memory sections
2269 (physical memory mapping, vmalloc & vmemmap). This security feature
2270 makes exploits relying on predictable memory locations less reliable.
2272 The order of allocations remains unchanged. Entropy is generated in
2273 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2274 configuration have in average 30,000 different possible virtual
2275 addresses for each memory section.
2279 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2280 hex "Physical memory mapping padding" if EXPERT
2281 depends on RANDOMIZE_MEMORY
2282 default "0xa" if MEMORY_HOTPLUG
2284 range 0x1 0x40 if MEMORY_HOTPLUG
2287 Define the padding in terabytes added to the existing physical
2288 memory size during kernel memory randomization. It is useful
2289 for memory hotplug support but reduces the entropy available for
2290 address randomization.
2292 If unsure, leave at the default value.
2298 config BOOTPARAM_HOTPLUG_CPU0
2299 bool "Set default setting of cpu0_hotpluggable"
2300 depends on HOTPLUG_CPU
2302 Set whether default state of cpu0_hotpluggable is on or off.
2304 Say Y here to enable CPU0 hotplug by default. If this switch
2305 is turned on, there is no need to give cpu0_hotplug kernel
2306 parameter and the CPU0 hotplug feature is enabled by default.
2308 Please note: there are two known CPU0 dependencies if you want
2309 to enable the CPU0 hotplug feature either by this switch or by
2310 cpu0_hotplug kernel parameter.
2312 First, resume from hibernate or suspend always starts from CPU0.
2313 So hibernate and suspend are prevented if CPU0 is offline.
2315 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2316 offline if any interrupt can not migrate out of CPU0. There may
2317 be other CPU0 dependencies.
2319 Please make sure the dependencies are under your control before
2320 you enable this feature.
2322 Say N if you don't want to enable CPU0 hotplug feature by default.
2323 You still can enable the CPU0 hotplug feature at boot by kernel
2324 parameter cpu0_hotplug.
2326 config DEBUG_HOTPLUG_CPU0
2328 prompt "Debug CPU0 hotplug"
2329 depends on HOTPLUG_CPU
2331 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2332 soon as possible and boots up userspace with CPU0 offlined. User
2333 can online CPU0 back after boot time.
2335 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2336 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2337 compilation or giving cpu0_hotplug kernel parameter at boot.
2343 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2344 depends on COMPAT_32
2346 Certain buggy versions of glibc will crash if they are
2347 presented with a 32-bit vDSO that is not mapped at the address
2348 indicated in its segment table.
2350 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2351 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2352 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2353 the only released version with the bug, but OpenSUSE 9
2354 contains a buggy "glibc 2.3.2".
2356 The symptom of the bug is that everything crashes on startup, saying:
2357 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2359 Saying Y here changes the default value of the vdso32 boot
2360 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2361 This works around the glibc bug but hurts performance.
2363 If unsure, say N: if you are compiling your own kernel, you
2364 are unlikely to be using a buggy version of glibc.
2367 prompt "vsyscall table for legacy applications"
2369 default LEGACY_VSYSCALL_XONLY
2371 Legacy user code that does not know how to find the vDSO expects
2372 to be able to issue three syscalls by calling fixed addresses in
2373 kernel space. Since this location is not randomized with ASLR,
2374 it can be used to assist security vulnerability exploitation.
2376 This setting can be changed at boot time via the kernel command
2377 line parameter vsyscall=[emulate|xonly|none].
2379 On a system with recent enough glibc (2.14 or newer) and no
2380 static binaries, you can say None without a performance penalty
2381 to improve security.
2383 If unsure, select "Emulate execution only".
2385 config LEGACY_VSYSCALL_EMULATE
2386 bool "Full emulation"
2388 The kernel traps and emulates calls into the fixed vsyscall
2389 address mapping. This makes the mapping non-executable, but
2390 it still contains readable known contents, which could be
2391 used in certain rare security vulnerability exploits. This
2392 configuration is recommended when using legacy userspace
2393 that still uses vsyscalls along with legacy binary
2394 instrumentation tools that require code to be readable.
2396 An example of this type of legacy userspace is running
2397 Pin on an old binary that still uses vsyscalls.
2399 config LEGACY_VSYSCALL_XONLY
2400 bool "Emulate execution only"
2402 The kernel traps and emulates calls into the fixed vsyscall
2403 address mapping and does not allow reads. This
2404 configuration is recommended when userspace might use the
2405 legacy vsyscall area but support for legacy binary
2406 instrumentation of legacy code is not needed. It mitigates
2407 certain uses of the vsyscall area as an ASLR-bypassing
2410 config LEGACY_VSYSCALL_NONE
2413 There will be no vsyscall mapping at all. This will
2414 eliminate any risk of ASLR bypass due to the vsyscall
2415 fixed address mapping. Attempts to use the vsyscalls
2416 will be reported to dmesg, so that either old or
2417 malicious userspace programs can be identified.
2422 bool "Built-in kernel command line"
2424 Allow for specifying boot arguments to the kernel at
2425 build time. On some systems (e.g. embedded ones), it is
2426 necessary or convenient to provide some or all of the
2427 kernel boot arguments with the kernel itself (that is,
2428 to not rely on the boot loader to provide them.)
2430 To compile command line arguments into the kernel,
2431 set this option to 'Y', then fill in the
2432 boot arguments in CONFIG_CMDLINE.
2434 Systems with fully functional boot loaders (i.e. non-embedded)
2435 should leave this option set to 'N'.
2438 string "Built-in kernel command string"
2439 depends on CMDLINE_BOOL
2442 Enter arguments here that should be compiled into the kernel
2443 image and used at boot time. If the boot loader provides a
2444 command line at boot time, it is appended to this string to
2445 form the full kernel command line, when the system boots.
2447 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2448 change this behavior.
2450 In most cases, the command line (whether built-in or provided
2451 by the boot loader) should specify the device for the root
2454 config CMDLINE_OVERRIDE
2455 bool "Built-in command line overrides boot loader arguments"
2456 depends on CMDLINE_BOOL
2458 Set this option to 'Y' to have the kernel ignore the boot loader
2459 command line, and use ONLY the built-in command line.
2461 This is used to work around broken boot loaders. This should
2462 be set to 'N' under normal conditions.
2464 config MODIFY_LDT_SYSCALL
2465 bool "Enable the LDT (local descriptor table)" if EXPERT
2468 Linux can allow user programs to install a per-process x86
2469 Local Descriptor Table (LDT) using the modify_ldt(2) system
2470 call. This is required to run 16-bit or segmented code such as
2471 DOSEMU or some Wine programs. It is also used by some very old
2472 threading libraries.
2474 Enabling this feature adds a small amount of overhead to
2475 context switches and increases the low-level kernel attack
2476 surface. Disabling it removes the modify_ldt(2) system call.
2478 Saying 'N' here may make sense for embedded or server kernels.
2480 source "kernel/livepatch/Kconfig"
2484 config ARCH_HAS_ADD_PAGES
2486 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2488 config ARCH_ENABLE_MEMORY_HOTPLUG
2490 depends on X86_64 || (X86_32 && HIGHMEM)
2492 config ARCH_ENABLE_MEMORY_HOTREMOVE
2494 depends on MEMORY_HOTPLUG
2496 config USE_PERCPU_NUMA_NODE_ID
2500 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2502 depends on X86_64 || X86_PAE
2504 config GDS_FORCE_MITIGATION
2505 bool "Force GDS Mitigation"
2506 depends on CPU_SUP_INTEL
2509 Gather Data Sampling (GDS) is a hardware vulnerability which allows
2510 unprivileged speculative access to data which was previously stored in
2513 This option is equivalent to setting gather_data_sampling=force on the
2514 command line. The microcode mitigation is used if present, otherwise
2515 AVX is disabled as a mitigation. On affected systems that are missing
2516 the microcode any userspace code that unconditionally uses AVX will
2517 break with this option set.
2519 Setting this option on systems not vulnerable to GDS has no effect.
2523 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2525 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2527 config ARCH_ENABLE_THP_MIGRATION
2529 depends on X86_64 && TRANSPARENT_HUGEPAGE
2531 menu "Power management and ACPI options"
2533 config ARCH_HIBERNATION_HEADER
2535 depends on HIBERNATION
2537 source "kernel/power/Kconfig"
2539 source "drivers/acpi/Kconfig"
2541 source "drivers/sfi/Kconfig"
2548 tristate "APM (Advanced Power Management) BIOS support"
2549 depends on X86_32 && PM_SLEEP
2551 APM is a BIOS specification for saving power using several different
2552 techniques. This is mostly useful for battery powered laptops with
2553 APM compliant BIOSes. If you say Y here, the system time will be
2554 reset after a RESUME operation, the /proc/apm device will provide
2555 battery status information, and user-space programs will receive
2556 notification of APM "events" (e.g. battery status change).
2558 If you select "Y" here, you can disable actual use of the APM
2559 BIOS by passing the "apm=off" option to the kernel at boot time.
2561 Note that the APM support is almost completely disabled for
2562 machines with more than one CPU.
2564 In order to use APM, you will need supporting software. For location
2565 and more information, read <file:Documentation/power/apm-acpi.rst>
2566 and the Battery Powered Linux mini-HOWTO, available from
2567 <http://www.tldp.org/docs.html#howto>.
2569 This driver does not spin down disk drives (see the hdparm(8)
2570 manpage ("man 8 hdparm") for that), and it doesn't turn off
2571 VESA-compliant "green" monitors.
2573 This driver does not support the TI 4000M TravelMate and the ACER
2574 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2575 desktop machines also don't have compliant BIOSes, and this driver
2576 may cause those machines to panic during the boot phase.
2578 Generally, if you don't have a battery in your machine, there isn't
2579 much point in using this driver and you should say N. If you get
2580 random kernel OOPSes or reboots that don't seem to be related to
2581 anything, try disabling/enabling this option (or disabling/enabling
2584 Some other things you should try when experiencing seemingly random,
2587 1) make sure that you have enough swap space and that it is
2589 2) pass the "no-hlt" option to the kernel
2590 3) switch on floating point emulation in the kernel and pass
2591 the "no387" option to the kernel
2592 4) pass the "floppy=nodma" option to the kernel
2593 5) pass the "mem=4M" option to the kernel (thereby disabling
2594 all but the first 4 MB of RAM)
2595 6) make sure that the CPU is not over clocked.
2596 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2597 8) disable the cache from your BIOS settings
2598 9) install a fan for the video card or exchange video RAM
2599 10) install a better fan for the CPU
2600 11) exchange RAM chips
2601 12) exchange the motherboard.
2603 To compile this driver as a module, choose M here: the
2604 module will be called apm.
2608 config APM_IGNORE_USER_SUSPEND
2609 bool "Ignore USER SUSPEND"
2611 This option will ignore USER SUSPEND requests. On machines with a
2612 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2613 series notebooks, it is necessary to say Y because of a BIOS bug.
2615 config APM_DO_ENABLE
2616 bool "Enable PM at boot time"
2618 Enable APM features at boot time. From page 36 of the APM BIOS
2619 specification: "When disabled, the APM BIOS does not automatically
2620 power manage devices, enter the Standby State, enter the Suspend
2621 State, or take power saving steps in response to CPU Idle calls."
2622 This driver will make CPU Idle calls when Linux is idle (unless this
2623 feature is turned off -- see "Do CPU IDLE calls", below). This
2624 should always save battery power, but more complicated APM features
2625 will be dependent on your BIOS implementation. You may need to turn
2626 this option off if your computer hangs at boot time when using APM
2627 support, or if it beeps continuously instead of suspending. Turn
2628 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2629 T400CDT. This is off by default since most machines do fine without
2634 bool "Make CPU Idle calls when idle"
2636 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2637 On some machines, this can activate improved power savings, such as
2638 a slowed CPU clock rate, when the machine is idle. These idle calls
2639 are made after the idle loop has run for some length of time (e.g.,
2640 333 mS). On some machines, this will cause a hang at boot time or
2641 whenever the CPU becomes idle. (On machines with more than one CPU,
2642 this option does nothing.)
2644 config APM_DISPLAY_BLANK
2645 bool "Enable console blanking using APM"
2647 Enable console blanking using the APM. Some laptops can use this to
2648 turn off the LCD backlight when the screen blanker of the Linux
2649 virtual console blanks the screen. Note that this is only used by
2650 the virtual console screen blanker, and won't turn off the backlight
2651 when using the X Window system. This also doesn't have anything to
2652 do with your VESA-compliant power-saving monitor. Further, this
2653 option doesn't work for all laptops -- it might not turn off your
2654 backlight at all, or it might print a lot of errors to the console,
2655 especially if you are using gpm.
2657 config APM_ALLOW_INTS
2658 bool "Allow interrupts during APM BIOS calls"
2660 Normally we disable external interrupts while we are making calls to
2661 the APM BIOS as a measure to lessen the effects of a badly behaving
2662 BIOS implementation. The BIOS should reenable interrupts if it
2663 needs to. Unfortunately, some BIOSes do not -- especially those in
2664 many of the newer IBM Thinkpads. If you experience hangs when you
2665 suspend, try setting this to Y. Otherwise, say N.
2669 source "drivers/cpufreq/Kconfig"
2671 source "drivers/cpuidle/Kconfig"
2673 source "drivers/idle/Kconfig"
2678 menu "Bus options (PCI etc.)"
2681 prompt "PCI access mode"
2682 depends on X86_32 && PCI
2685 On PCI systems, the BIOS can be used to detect the PCI devices and
2686 determine their configuration. However, some old PCI motherboards
2687 have BIOS bugs and may crash if this is done. Also, some embedded
2688 PCI-based systems don't have any BIOS at all. Linux can also try to
2689 detect the PCI hardware directly without using the BIOS.
2691 With this option, you can specify how Linux should detect the
2692 PCI devices. If you choose "BIOS", the BIOS will be used,
2693 if you choose "Direct", the BIOS won't be used, and if you
2694 choose "MMConfig", then PCI Express MMCONFIG will be used.
2695 If you choose "Any", the kernel will try MMCONFIG, then the
2696 direct access method and falls back to the BIOS if that doesn't
2697 work. If unsure, go with the default, which is "Any".
2702 config PCI_GOMMCONFIG
2719 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2721 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2724 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2727 bool "Support mmconfig PCI config space access" if X86_64
2729 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2730 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2734 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2738 depends on PCI && XEN
2741 config MMCONF_FAM10H
2743 depends on X86_64 && PCI_MMCONFIG && ACPI
2745 config PCI_CNB20LE_QUIRK
2746 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2749 Read the PCI windows out of the CNB20LE host bridge. This allows
2750 PCI hotplug to work on systems with the CNB20LE chipset which do
2753 There's no public spec for this chipset, and this functionality
2754 is known to be incomplete.
2756 You should say N unless you know you need this.
2759 bool "ISA bus support on modern systems" if EXPERT
2761 Expose ISA bus device drivers and options available for selection and
2762 configuration. Enable this option if your target machine has an ISA
2763 bus. ISA is an older system, displaced by PCI and newer bus
2764 architectures -- if your target machine is modern, it probably does
2765 not have an ISA bus.
2769 # x86_64 have no ISA slots, but can have ISA-style DMA.
2771 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2774 Enables ISA-style DMA support for devices requiring such controllers.
2782 Find out whether you have ISA slots on your motherboard. ISA is the
2783 name of a bus system, i.e. the way the CPU talks to the other stuff
2784 inside your box. Other bus systems are PCI, EISA, MicroChannel
2785 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2786 newer boards don't support it. If you have ISA, say Y, otherwise N.
2789 tristate "NatSemi SCx200 support"
2791 This provides basic support for National Semiconductor's
2792 (now AMD's) Geode processors. The driver probes for the
2793 PCI-IDs of several on-chip devices, so its a good dependency
2794 for other scx200_* drivers.
2796 If compiled as a module, the driver is named scx200.
2798 config SCx200HR_TIMER
2799 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2803 This driver provides a clocksource built upon the on-chip
2804 27MHz high-resolution timer. Its also a workaround for
2805 NSC Geode SC-1100's buggy TSC, which loses time when the
2806 processor goes idle (as is done by the scheduler). The
2807 other workaround is idle=poll boot option.
2810 bool "One Laptop Per Child support"
2818 Add support for detecting the unique features of the OLPC
2822 bool "OLPC XO-1 Power Management"
2823 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2825 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2828 bool "OLPC XO-1 Real Time Clock"
2829 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2831 Add support for the XO-1 real time clock, which can be used as a
2832 programmable wakeup source.
2835 bool "OLPC XO-1 SCI extras"
2836 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2840 Add support for SCI-based features of the OLPC XO-1 laptop:
2841 - EC-driven system wakeups
2845 - AC adapter status updates
2846 - Battery status updates
2848 config OLPC_XO15_SCI
2849 bool "OLPC XO-1.5 SCI extras"
2850 depends on OLPC && ACPI
2853 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2854 - EC-driven system wakeups
2855 - AC adapter status updates
2856 - Battery status updates
2859 bool "PCEngines ALIX System Support (LED setup)"
2862 This option enables system support for the PCEngines ALIX.
2863 At present this just sets up LEDs for GPIO control on
2864 ALIX2/3/6 boards. However, other system specific setup should
2867 Note: You must still enable the drivers for GPIO and LED support
2868 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2870 Note: You have to set alix.force=1 for boards with Award BIOS.
2873 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2876 This option enables system support for the Soekris Engineering net5501.
2879 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2883 This option enables system support for the Traverse Technologies GEOS.
2886 bool "Technologic Systems TS-5500 platform support"
2888 select CHECK_SIGNATURE
2892 This option enables system support for the Technologic Systems TS-5500.
2898 depends on CPU_SUP_AMD && PCI
2901 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2903 Firmwares often provide initial graphics framebuffers so the BIOS,
2904 bootloader or kernel can show basic video-output during boot for
2905 user-guidance and debugging. Historically, x86 used the VESA BIOS
2906 Extensions and EFI-framebuffers for this, which are mostly limited
2908 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2909 framebuffers so the new generic system-framebuffer drivers can be
2910 used on x86. If the framebuffer is not compatible with the generic
2911 modes, it is advertised as fallback platform framebuffer so legacy
2912 drivers like efifb, vesafb and uvesafb can pick it up.
2913 If this option is not selected, all system framebuffers are always
2914 marked as fallback platform framebuffers as usual.
2916 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2917 not be able to pick up generic system framebuffers if this option
2918 is selected. You are highly encouraged to enable simplefb as
2919 replacement if you select this option. simplefb can correctly deal
2920 with generic system framebuffers. But you should still keep vesafb
2921 and others enabled as fallback if a system framebuffer is
2922 incompatible with simplefb.
2929 menu "Binary Emulations"
2931 config IA32_EMULATION
2932 bool "IA32 Emulation"
2934 select ARCH_WANT_OLD_COMPAT_IPC
2936 select COMPAT_BINFMT_ELF
2937 select COMPAT_OLD_SIGACTION
2939 Include code to run legacy 32-bit programs under a
2940 64-bit kernel. You should likely turn this on, unless you're
2941 100% sure that you don't have any 32-bit programs left.
2944 tristate "IA32 a.out support"
2945 depends on IA32_EMULATION
2948 Support old a.out binaries in the 32bit emulation.
2951 bool "x32 ABI for 64-bit mode"
2954 Include code to run binaries for the x32 native 32-bit ABI
2955 for 64-bit processors. An x32 process gets access to the
2956 full 64-bit register file and wide data path while leaving
2957 pointers at 32 bits for smaller memory footprint.
2959 You will need a recent binutils (2.22 or later) with
2960 elf32_x86_64 support enabled to compile a kernel with this
2965 depends on IA32_EMULATION || X86_32
2967 select OLD_SIGSUSPEND3
2971 depends on IA32_EMULATION || X86_X32
2974 config COMPAT_FOR_U64_ALIGNMENT
2977 config SYSVIPC_COMPAT
2985 config HAVE_ATOMIC_IOMAP
2989 config X86_DEV_DMA_OPS
2992 source "drivers/firmware/Kconfig"
2994 source "arch/x86/kvm/Kconfig"