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 if CC_HAS_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
34 config FORCE_DYNAMIC_FTRACE
37 depends on FUNCTION_TRACER
40 We keep the static function tracing (!DYNAMIC_FTRACE) around
41 in order to test the non static function tracing in the
42 generic code, as other architectures still use it. But we
43 only need to keep it around for x86_64. No need to keep it
44 for x86_32. For x86_32, force DYNAMIC_FTRACE.
48 # ( Note that options that are marked 'if X86_64' could in principle be
49 # ported to 32-bit as well. )
54 # Note: keep this list sorted alphabetically
56 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
57 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
58 select ARCH_32BIT_OFF_T if X86_32
59 select ARCH_CLOCKSOURCE_INIT
60 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
61 select ARCH_HAS_DEBUG_VIRTUAL
62 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
63 select ARCH_HAS_DEVMEM_IS_ALLOWED
64 select ARCH_HAS_EARLY_DEBUG if KGDB
65 select ARCH_HAS_ELF_RANDOMIZE
66 select ARCH_HAS_FAST_MULTIPLIER
67 select ARCH_HAS_FILTER_PGPROT
68 select ARCH_HAS_FORTIFY_SOURCE
69 select ARCH_HAS_GCOV_PROFILE_ALL
70 select ARCH_HAS_KCOV if X86_64
71 select ARCH_HAS_MEM_ENCRYPT
72 select ARCH_HAS_MEMBARRIER_SYNC_CORE
73 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
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_SYSCALL_WRAPPER
85 select ARCH_HAS_UBSAN_SANITIZE_ALL
86 select ARCH_HAS_DEBUG_WX
87 select ARCH_HAVE_NMI_SAFE_CMPXCHG
88 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
89 select ARCH_MIGHT_HAVE_PC_PARPORT
90 select ARCH_MIGHT_HAVE_PC_SERIO
92 select ARCH_SUPPORTS_ACPI
93 select ARCH_SUPPORTS_ATOMIC_RMW
94 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
95 select ARCH_USE_BUILTIN_BSWAP
96 select ARCH_USE_QUEUED_RWLOCKS
97 select ARCH_USE_QUEUED_SPINLOCKS
98 select ARCH_USE_SYM_ANNOTATIONS
99 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
100 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
101 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
102 select ARCH_WANT_HUGE_PMD_SHARE
103 select ARCH_WANTS_THP_SWAP if X86_64
104 select BUILDTIME_TABLE_SORT
106 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
107 select CLOCKSOURCE_WATCHDOG
108 select DCACHE_WORD_ACCESS
109 select EDAC_ATOMIC_SCRUB
111 select GENERIC_CLOCKEVENTS
112 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
113 select GENERIC_CLOCKEVENTS_MIN_ADJUST
114 select GENERIC_CMOS_UPDATE
115 select GENERIC_CPU_AUTOPROBE
116 select GENERIC_CPU_VULNERABILITIES
117 select GENERIC_EARLY_IOREMAP
118 select GENERIC_FIND_FIRST_BIT
120 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
121 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
122 select GENERIC_IRQ_MIGRATION if SMP
123 select GENERIC_IRQ_PROBE
124 select GENERIC_IRQ_RESERVATION_MODE
125 select GENERIC_IRQ_SHOW
126 select GENERIC_PENDING_IRQ if SMP
127 select GENERIC_PTDUMP
128 select GENERIC_SMP_IDLE_THREAD
129 select GENERIC_STRNCPY_FROM_USER
130 select GENERIC_STRNLEN_USER
131 select GENERIC_TIME_VSYSCALL
132 select GENERIC_GETTIMEOFDAY
133 select GENERIC_VDSO_TIME_NS
134 select GUP_GET_PTE_LOW_HIGH if X86_PAE
135 select HARDIRQS_SW_RESEND
136 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
137 select HAVE_ACPI_APEI if ACPI
138 select HAVE_ACPI_APEI_NMI if ACPI
139 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
140 select HAVE_ARCH_AUDITSYSCALL
141 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
142 select HAVE_ARCH_JUMP_LABEL
143 select HAVE_ARCH_JUMP_LABEL_RELATIVE
144 select HAVE_ARCH_KASAN if X86_64
145 select HAVE_ARCH_KASAN_VMALLOC if X86_64
146 select HAVE_ARCH_KGDB
147 select HAVE_ARCH_MMAP_RND_BITS if MMU
148 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
149 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
150 select HAVE_ARCH_PREL32_RELOCATIONS
151 select HAVE_ARCH_SECCOMP_FILTER
152 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
153 select HAVE_ARCH_STACKLEAK
154 select HAVE_ARCH_TRACEHOOK
155 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
156 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
157 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
158 select HAVE_ARCH_VMAP_STACK if X86_64
159 select HAVE_ARCH_WITHIN_STACK_FRAMES
160 select HAVE_ASM_MODVERSIONS
161 select HAVE_CMPXCHG_DOUBLE
162 select HAVE_CMPXCHG_LOCAL
163 select HAVE_CONTEXT_TRACKING if X86_64
164 select HAVE_COPY_THREAD_TLS
165 select HAVE_C_RECORDMCOUNT
166 select HAVE_DEBUG_KMEMLEAK
167 select HAVE_DMA_CONTIGUOUS
168 select HAVE_DYNAMIC_FTRACE
169 select HAVE_DYNAMIC_FTRACE_WITH_REGS
170 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
172 select HAVE_EFFICIENT_UNALIGNED_ACCESS
174 select HAVE_EXIT_THREAD
176 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
177 select HAVE_FTRACE_MCOUNT_RECORD
178 select HAVE_FUNCTION_GRAPH_TRACER
179 select HAVE_FUNCTION_TRACER
180 select HAVE_GCC_PLUGINS
181 select HAVE_HW_BREAKPOINT
183 select HAVE_IOREMAP_PROT
184 select HAVE_IRQ_TIME_ACCOUNTING
185 select HAVE_KERNEL_BZIP2
186 select HAVE_KERNEL_GZIP
187 select HAVE_KERNEL_LZ4
188 select HAVE_KERNEL_LZMA
189 select HAVE_KERNEL_LZO
190 select HAVE_KERNEL_XZ
192 select HAVE_KPROBES_ON_FTRACE
193 select HAVE_FUNCTION_ERROR_INJECTION
194 select HAVE_KRETPROBES
196 select HAVE_LIVEPATCH if X86_64
197 select HAVE_MIXED_BREAKPOINTS_REGS
198 select HAVE_MOD_ARCH_SPECIFIC
202 select HAVE_OPTPROBES
203 select HAVE_PCSPKR_PLATFORM
204 select HAVE_PERF_EVENTS
205 select HAVE_PERF_EVENTS_NMI
206 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
208 select HAVE_PERF_REGS
209 select HAVE_PERF_USER_STACK_DUMP
210 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
211 select HAVE_REGS_AND_STACK_ACCESS_API
212 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
213 select HAVE_FUNCTION_ARG_ACCESS_API
214 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
215 select HAVE_STACK_VALIDATION if X86_64
217 select HAVE_SYSCALL_TRACEPOINTS
218 select HAVE_UNSTABLE_SCHED_CLOCK
219 select HAVE_USER_RETURN_NOTIFIER
220 select HAVE_GENERIC_VDSO
221 select HOTPLUG_SMT if SMP
222 select IRQ_FORCED_THREADING
223 select NEED_SG_DMA_LENGTH
224 select PCI_DOMAINS if PCI
225 select PCI_LOCKLESS_CONFIG if PCI
228 select RTC_MC146818_LIB
231 select SYSCTL_EXCEPTION_TRACE
232 select THREAD_INFO_IN_TASK
233 select USER_STACKTRACE_SUPPORT
235 select HAVE_ARCH_KCSAN if X86_64
236 select X86_FEATURE_NAMES if PROC_FS
237 select PROC_PID_ARCH_STATUS if PROC_FS
238 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
240 config INSTRUCTION_DECODER
242 depends on KPROBES || PERF_EVENTS || UPROBES
246 default "elf32-i386" if X86_32
247 default "elf64-x86-64" if X86_64
249 config LOCKDEP_SUPPORT
252 config STACKTRACE_SUPPORT
258 config ARCH_MMAP_RND_BITS_MIN
262 config ARCH_MMAP_RND_BITS_MAX
266 config ARCH_MMAP_RND_COMPAT_BITS_MIN
269 config ARCH_MMAP_RND_COMPAT_BITS_MAX
275 config GENERIC_ISA_DMA
277 depends on ISA_DMA_API
282 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
284 config GENERIC_BUG_RELATIVE_POINTERS
287 config ARCH_MAY_HAVE_PC_FDC
289 depends on ISA_DMA_API
291 config GENERIC_CALIBRATE_DELAY
294 config ARCH_HAS_CPU_RELAX
297 config ARCH_HAS_CACHE_LINE_SIZE
300 config ARCH_HAS_FILTER_PGPROT
303 config HAVE_SETUP_PER_CPU_AREA
306 config NEED_PER_CPU_EMBED_FIRST_CHUNK
309 config NEED_PER_CPU_PAGE_FIRST_CHUNK
312 config ARCH_HIBERNATION_POSSIBLE
315 config ARCH_SUSPEND_POSSIBLE
318 config ARCH_WANT_GENERAL_HUGETLB
327 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
330 config KASAN_SHADOW_OFFSET
333 default 0xdffffc0000000000
335 config HAVE_INTEL_TXT
337 depends on INTEL_IOMMU && ACPI
341 depends on X86_32 && SMP
345 depends on X86_64 && SMP
347 config X86_32_LAZY_GS
349 depends on X86_32 && !STACKPROTECTOR
351 config ARCH_SUPPORTS_UPROBES
354 config FIX_EARLYCON_MEM
357 config DYNAMIC_PHYSICAL_MASK
360 config PGTABLE_LEVELS
362 default 5 if X86_5LEVEL
367 config CC_HAS_SANE_STACKPROTECTOR
369 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
370 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
372 We have to make sure stack protector is unconditionally disabled if
373 the compiler produces broken code.
375 menu "Processor type and features"
378 bool "DMA memory allocation support" if EXPERT
381 DMA memory allocation support allows devices with less than 32-bit
382 addressing to allocate within the first 16MB of address space.
383 Disable if no such devices will be used.
388 bool "Symmetric multi-processing support"
390 This enables support for systems with more than one CPU. If you have
391 a system with only one CPU, say N. If you have a system with more
394 If you say N here, the kernel will run on uni- and multiprocessor
395 machines, but will use only one CPU of a multiprocessor machine. If
396 you say Y here, the kernel will run on many, but not all,
397 uniprocessor machines. On a uniprocessor machine, the kernel
398 will run faster if you say N here.
400 Note that if you say Y here and choose architecture "586" or
401 "Pentium" under "Processor family", the kernel will not work on 486
402 architectures. Similarly, multiprocessor kernels for the "PPro"
403 architecture may not work on all Pentium based boards.
405 People using multiprocessor machines who say Y here should also say
406 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
407 Management" code will be disabled if you say Y here.
409 See also <file:Documentation/x86/i386/IO-APIC.rst>,
410 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
411 <http://www.tldp.org/docs.html#howto>.
413 If you don't know what to do here, say N.
415 config X86_FEATURE_NAMES
416 bool "Processor feature human-readable names" if EMBEDDED
419 This option compiles in a table of x86 feature bits and corresponding
420 names. This is required to support /proc/cpuinfo and a few kernel
421 messages. You can disable this to save space, at the expense of
422 making those few kernel messages show numeric feature bits instead.
427 bool "Support x2apic"
428 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
430 This enables x2apic support on CPUs that have this feature.
432 This allows 32-bit apic IDs (so it can support very large systems),
433 and accesses the local apic via MSRs not via mmio.
435 If you don't know what to do here, say N.
438 bool "Enable MPS table" if ACPI || SFI
440 depends on X86_LOCAL_APIC
442 For old smp systems that do not have proper acpi support. Newer systems
443 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
447 depends on X86_GOLDFISH
450 bool "Avoid speculative indirect branches in kernel"
452 select STACK_VALIDATION if HAVE_STACK_VALIDATION
454 Compile kernel with the retpoline compiler options to guard against
455 kernel-to-user data leaks by avoiding speculative indirect
456 branches. Requires a compiler with -mindirect-branch=thunk-extern
457 support for full protection. The kernel may run slower.
459 config X86_CPU_RESCTRL
460 bool "x86 CPU resource control support"
461 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
463 select PROC_CPU_RESCTRL if PROC_FS
465 Enable x86 CPU resource control support.
467 Provide support for the allocation and monitoring of system resources
470 Intel calls this Intel Resource Director Technology
471 (Intel(R) RDT). More information about RDT can be found in the
472 Intel x86 Architecture Software Developer Manual.
474 AMD calls this AMD Platform Quality of Service (AMD QoS).
475 More information about AMD QoS can be found in the AMD64 Technology
476 Platform Quality of Service Extensions manual.
482 bool "Support for big SMP systems with more than 8 CPUs"
485 This option is needed for the systems that have more than 8 CPUs.
487 config X86_EXTENDED_PLATFORM
488 bool "Support for extended (non-PC) x86 platforms"
491 If you disable this option then the kernel will only support
492 standard PC platforms. (which covers the vast majority of
495 If you enable this option then you'll be able to select support
496 for the following (non-PC) 32 bit x86 platforms:
497 Goldfish (Android emulator)
500 SGI 320/540 (Visual Workstation)
501 STA2X11-based (e.g. Northville)
502 Moorestown MID devices
504 If you have one of these systems, or if you want to build a
505 generic distribution kernel, say Y here - otherwise say N.
509 config X86_EXTENDED_PLATFORM
510 bool "Support for extended (non-PC) x86 platforms"
513 If you disable this option then the kernel will only support
514 standard PC platforms. (which covers the vast majority of
517 If you enable this option then you'll be able to select support
518 for the following (non-PC) 64 bit x86 platforms:
523 If you have one of these systems, or if you want to build a
524 generic distribution kernel, say Y here - otherwise say N.
526 # This is an alphabetically sorted list of 64 bit extended platforms
527 # Please maintain the alphabetic order if and when there are additions
529 bool "Numascale NumaChip"
531 depends on X86_EXTENDED_PLATFORM
534 depends on X86_X2APIC
535 depends on PCI_MMCONFIG
537 Adds support for Numascale NumaChip large-SMP systems. Needed to
538 enable more than ~168 cores.
539 If you don't have one of these, you should say N here.
543 select HYPERVISOR_GUEST
545 depends on X86_64 && PCI
546 depends on X86_EXTENDED_PLATFORM
549 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
550 supposed to run on these EM64T-based machines. Only choose this option
551 if you have one of these machines.
554 bool "SGI Ultraviolet"
556 depends on X86_EXTENDED_PLATFORM
559 depends on X86_X2APIC
562 This option is needed in order to support SGI Ultraviolet systems.
563 If you don't have one of these, you should say N here.
565 # Following is an alphabetically sorted list of 32 bit extended platforms
566 # Please maintain the alphabetic order if and when there are additions
569 bool "Goldfish (Virtual Platform)"
570 depends on X86_EXTENDED_PLATFORM
572 Enable support for the Goldfish virtual platform used primarily
573 for Android development. Unless you are building for the Android
574 Goldfish emulator say N here.
577 bool "CE4100 TV platform"
579 depends on PCI_GODIRECT
580 depends on X86_IO_APIC
582 depends on X86_EXTENDED_PLATFORM
583 select X86_REBOOTFIXUPS
585 select OF_EARLY_FLATTREE
587 Select for the Intel CE media processor (CE4100) SOC.
588 This option compiles in support for the CE4100 SOC for settop
589 boxes and media devices.
592 bool "Intel MID platform support"
593 depends on X86_EXTENDED_PLATFORM
594 depends on X86_PLATFORM_DEVICES
596 depends on X86_64 || (PCI_GOANY && X86_32)
597 depends on X86_IO_APIC
603 select MFD_INTEL_MSIC
605 Select to build a kernel capable of supporting Intel MID (Mobile
606 Internet Device) platform systems which do not have the PCI legacy
607 interfaces. If you are building for a PC class system say N here.
609 Intel MID platforms are based on an Intel processor and chipset which
610 consume less power than most of the x86 derivatives.
612 config X86_INTEL_QUARK
613 bool "Intel Quark platform support"
615 depends on X86_EXTENDED_PLATFORM
616 depends on X86_PLATFORM_DEVICES
620 depends on X86_IO_APIC
625 Select to include support for Quark X1000 SoC.
626 Say Y here if you have a Quark based system such as the Arduino
627 compatible Intel Galileo.
629 config X86_INTEL_LPSS
630 bool "Intel Low Power Subsystem Support"
631 depends on X86 && ACPI && PCI
636 Select to build support for Intel Low Power Subsystem such as
637 found on Intel Lynxpoint PCH. Selecting this option enables
638 things like clock tree (common clock framework) and pincontrol
639 which are needed by the LPSS peripheral drivers.
641 config X86_AMD_PLATFORM_DEVICE
642 bool "AMD ACPI2Platform devices support"
647 Select to interpret AMD specific ACPI device to platform device
648 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
649 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
650 implemented under PINCTRL subsystem.
653 tristate "Intel SoC IOSF Sideband support for SoC platforms"
656 This option enables sideband register access support for Intel SoC
657 platforms. On these platforms the IOSF sideband is used in lieu of
658 MSR's for some register accesses, mostly but not limited to thermal
659 and power. Drivers may query the availability of this device to
660 determine if they need the sideband in order to work on these
661 platforms. The sideband is available on the following SoC products.
662 This list is not meant to be exclusive.
667 You should say Y if you are running a kernel on one of these SoC's.
669 config IOSF_MBI_DEBUG
670 bool "Enable IOSF sideband access through debugfs"
671 depends on IOSF_MBI && DEBUG_FS
673 Select this option to expose the IOSF sideband access registers (MCR,
674 MDR, MCRX) through debugfs to write and read register information from
675 different units on the SoC. This is most useful for obtaining device
676 state information for debug and analysis. As this is a general access
677 mechanism, users of this option would have specific knowledge of the
678 device they want to access.
680 If you don't require the option or are in doubt, say N.
683 bool "RDC R-321x SoC"
685 depends on X86_EXTENDED_PLATFORM
687 select X86_REBOOTFIXUPS
689 This option is needed for RDC R-321x system-on-chip, also known
691 If you don't have one of these chips, you should say N here.
693 config X86_32_NON_STANDARD
694 bool "Support non-standard 32-bit SMP architectures"
695 depends on X86_32 && SMP
696 depends on X86_EXTENDED_PLATFORM
698 This option compiles in the bigsmp and STA2X11 default
699 subarchitectures. It is intended for a generic binary
700 kernel. If you select them all, kernel will probe it one by
701 one and will fallback to default.
703 # Alphabetically sorted list of Non standard 32 bit platforms
705 config X86_SUPPORTS_MEMORY_FAILURE
707 # MCE code calls memory_failure():
709 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
710 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
711 depends on X86_64 || !SPARSEMEM
712 select ARCH_SUPPORTS_MEMORY_FAILURE
715 bool "STA2X11 Companion Chip Support"
716 depends on X86_32_NON_STANDARD && PCI
721 This adds support for boards based on the STA2X11 IO-Hub,
722 a.k.a. "ConneXt". The chip is used in place of the standard
723 PC chipset, so all "standard" peripherals are missing. If this
724 option is selected the kernel will still be able to boot on
725 standard PC machines.
728 tristate "Eurobraille/Iris poweroff module"
731 The Iris machines from EuroBraille do not have APM or ACPI support
732 to shut themselves down properly. A special I/O sequence is
733 needed to do so, which is what this module does at
736 This is only for Iris machines from EuroBraille.
740 config SCHED_OMIT_FRAME_POINTER
742 prompt "Single-depth WCHAN output"
745 Calculate simpler /proc/<PID>/wchan values. If this option
746 is disabled then wchan values will recurse back to the
747 caller function. This provides more accurate wchan values,
748 at the expense of slightly more scheduling overhead.
750 If in doubt, say "Y".
752 menuconfig HYPERVISOR_GUEST
753 bool "Linux guest support"
755 Say Y here to enable options for running Linux under various hyper-
756 visors. This option enables basic hypervisor detection and platform
759 If you say N, all options in this submenu will be skipped and
760 disabled, and Linux guest support won't be built in.
765 bool "Enable paravirtualization code"
767 This changes the kernel so it can modify itself when it is run
768 under a hypervisor, potentially improving performance significantly
769 over full virtualization. However, when run without a hypervisor
770 the kernel is theoretically slower and slightly larger.
775 config PARAVIRT_DEBUG
776 bool "paravirt-ops debugging"
777 depends on PARAVIRT && DEBUG_KERNEL
779 Enable to debug paravirt_ops internals. Specifically, BUG if
780 a paravirt_op is missing when it is called.
782 config PARAVIRT_SPINLOCKS
783 bool "Paravirtualization layer for spinlocks"
784 depends on PARAVIRT && SMP
786 Paravirtualized spinlocks allow a pvops backend to replace the
787 spinlock implementation with something virtualization-friendly
788 (for example, block the virtual CPU rather than spinning).
790 It has a minimal impact on native kernels and gives a nice performance
791 benefit on paravirtualized KVM / Xen kernels.
793 If you are unsure how to answer this question, answer Y.
795 config X86_HV_CALLBACK_VECTOR
798 source "arch/x86/xen/Kconfig"
801 bool "KVM Guest support (including kvmclock)"
803 select PARAVIRT_CLOCK
804 select ARCH_CPUIDLE_HALTPOLL
805 select X86_HV_CALLBACK_VECTOR
808 This option enables various optimizations for running under the KVM
809 hypervisor. It includes a paravirtualized clock, so that instead
810 of relying on a PIT (or probably other) emulation by the
811 underlying device model, the host provides the guest with
812 timing infrastructure such as time of day, and system time
814 config ARCH_CPUIDLE_HALTPOLL
816 prompt "Disable host haltpoll when loading haltpoll driver"
818 If virtualized under KVM, disable host haltpoll.
821 bool "Support for running PVH guests"
823 This option enables the PVH entry point for guest virtual machines
824 as specified in the x86/HVM direct boot ABI.
826 config PARAVIRT_TIME_ACCOUNTING
827 bool "Paravirtual steal time accounting"
830 Select this option to enable fine granularity task steal time
831 accounting. Time spent executing other tasks in parallel with
832 the current vCPU is discounted from the vCPU power. To account for
833 that, there can be a small performance impact.
835 If in doubt, say N here.
837 config PARAVIRT_CLOCK
840 config JAILHOUSE_GUEST
841 bool "Jailhouse non-root cell support"
842 depends on X86_64 && PCI
845 This option allows to run Linux as guest in a Jailhouse non-root
846 cell. You can leave this option disabled if you only want to start
847 Jailhouse and run Linux afterwards in the root cell.
850 bool "ACRN Guest support"
852 select X86_HV_CALLBACK_VECTOR
854 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
855 a flexible, lightweight reference open-source hypervisor, built with
856 real-time and safety-criticality in mind. It is built for embedded
857 IOT with small footprint and real-time features. More details can be
858 found in https://projectacrn.org/.
860 endif #HYPERVISOR_GUEST
862 source "arch/x86/Kconfig.cpu"
866 prompt "HPET Timer Support" if X86_32
868 Use the IA-PC HPET (High Precision Event Timer) to manage
869 time in preference to the PIT and RTC, if a HPET is
871 HPET is the next generation timer replacing legacy 8254s.
872 The HPET provides a stable time base on SMP
873 systems, unlike the TSC, but it is more expensive to access,
874 as it is off-chip. The interface used is documented
875 in the HPET spec, revision 1.
877 You can safely choose Y here. However, HPET will only be
878 activated if the platform and the BIOS support this feature.
879 Otherwise the 8254 will be used for timing services.
881 Choose N to continue using the legacy 8254 timer.
883 config HPET_EMULATE_RTC
885 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
888 def_bool y if X86_INTEL_MID
889 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
891 depends on X86_INTEL_MID && SFI
893 APB timer is the replacement for 8254, HPET on X86 MID platforms.
894 The APBT provides a stable time base on SMP
895 systems, unlike the TSC, but it is more expensive to access,
896 as it is off-chip. APB timers are always running regardless of CPU
897 C states, they are used as per CPU clockevent device when possible.
899 # Mark as expert because too many people got it wrong.
900 # The code disables itself when not needed.
903 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
904 bool "Enable DMI scanning" if EXPERT
906 Enabled scanning of DMI to identify machine quirks. Say Y
907 here unless you have verified that your setup is not
908 affected by entries in the DMI blacklist. Required by PNP
912 bool "Old AMD GART IOMMU support"
915 depends on X86_64 && PCI && AMD_NB
917 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
918 GART based hardware IOMMUs.
920 The GART supports full DMA access for devices with 32-bit access
921 limitations, on systems with more than 3 GB. This is usually needed
922 for USB, sound, many IDE/SATA chipsets and some other devices.
924 Newer systems typically have a modern AMD IOMMU, supported via
925 the CONFIG_AMD_IOMMU=y config option.
927 In normal configurations this driver is only active when needed:
928 there's more than 3 GB of memory and the system contains a
929 32-bit limited device.
934 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
935 depends on X86_64 && SMP && DEBUG_KERNEL
936 select CPUMASK_OFFSTACK
938 Enable maximum number of CPUS and NUMA Nodes for this architecture.
942 # The maximum number of CPUs supported:
944 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
945 # and which can be configured interactively in the
946 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
948 # The ranges are different on 32-bit and 64-bit kernels, depending on
949 # hardware capabilities and scalability features of the kernel.
951 # ( If MAXSMP is enabled we just use the highest possible value and disable
952 # interactive configuration. )
955 config NR_CPUS_RANGE_BEGIN
957 default NR_CPUS_RANGE_END if MAXSMP
961 config NR_CPUS_RANGE_END
964 default 64 if SMP && X86_BIGSMP
965 default 8 if SMP && !X86_BIGSMP
968 config NR_CPUS_RANGE_END
971 default 8192 if SMP && CPUMASK_OFFSTACK
972 default 512 if SMP && !CPUMASK_OFFSTACK
975 config NR_CPUS_DEFAULT
978 default 32 if X86_BIGSMP
982 config NR_CPUS_DEFAULT
985 default 8192 if MAXSMP
990 int "Maximum number of CPUs" if SMP && !MAXSMP
991 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
992 default NR_CPUS_DEFAULT
994 This allows you to specify the maximum number of CPUs which this
995 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
996 supported value is 8192, otherwise the maximum value is 512. The
997 minimum value which makes sense is 2.
999 This is purely to save memory: each supported CPU adds about 8KB
1000 to the kernel image.
1007 prompt "Multi-core scheduler support"
1010 Multi-core scheduler support improves the CPU scheduler's decision
1011 making when dealing with multi-core CPU chips at a cost of slightly
1012 increased overhead in some places. If unsure say N here.
1014 config SCHED_MC_PRIO
1015 bool "CPU core priorities scheduler support"
1016 depends on SCHED_MC && CPU_SUP_INTEL
1017 select X86_INTEL_PSTATE
1021 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1022 core ordering determined at manufacturing time, which allows
1023 certain cores to reach higher turbo frequencies (when running
1024 single threaded workloads) than others.
1026 Enabling this kernel feature teaches the scheduler about
1027 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1028 scheduler's CPU selection logic accordingly, so that higher
1029 overall system performance can be achieved.
1031 This feature will have no effect on CPUs without this feature.
1033 If unsure say Y here.
1037 depends on !SMP && X86_LOCAL_APIC
1040 bool "Local APIC support on uniprocessors" if !PCI_MSI
1042 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1044 A local APIC (Advanced Programmable Interrupt Controller) is an
1045 integrated interrupt controller in the CPU. If you have a single-CPU
1046 system which has a processor with a local APIC, you can say Y here to
1047 enable and use it. If you say Y here even though your machine doesn't
1048 have a local APIC, then the kernel will still run with no slowdown at
1049 all. The local APIC supports CPU-generated self-interrupts (timer,
1050 performance counters), and the NMI watchdog which detects hard
1053 config X86_UP_IOAPIC
1054 bool "IO-APIC support on uniprocessors"
1055 depends on X86_UP_APIC
1057 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1058 SMP-capable replacement for PC-style interrupt controllers. Most
1059 SMP systems and many recent uniprocessor systems have one.
1061 If you have a single-CPU system with an IO-APIC, you can say Y here
1062 to use it. If you say Y here even though your machine doesn't have
1063 an IO-APIC, then the kernel will still run with no slowdown at all.
1065 config X86_LOCAL_APIC
1067 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1068 select IRQ_DOMAIN_HIERARCHY
1069 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1073 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1075 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1076 bool "Reroute for broken boot IRQs"
1077 depends on X86_IO_APIC
1079 This option enables a workaround that fixes a source of
1080 spurious interrupts. This is recommended when threaded
1081 interrupt handling is used on systems where the generation of
1082 superfluous "boot interrupts" cannot be disabled.
1084 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1085 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1086 kernel does during interrupt handling). On chipsets where this
1087 boot IRQ generation cannot be disabled, this workaround keeps
1088 the original IRQ line masked so that only the equivalent "boot
1089 IRQ" is delivered to the CPUs. The workaround also tells the
1090 kernel to set up the IRQ handler on the boot IRQ line. In this
1091 way only one interrupt is delivered to the kernel. Otherwise
1092 the spurious second interrupt may cause the kernel to bring
1093 down (vital) interrupt lines.
1095 Only affects "broken" chipsets. Interrupt sharing may be
1096 increased on these systems.
1099 bool "Machine Check / overheating reporting"
1100 select GENERIC_ALLOCATOR
1103 Machine Check support allows the processor to notify the
1104 kernel if it detects a problem (e.g. overheating, data corruption).
1105 The action the kernel takes depends on the severity of the problem,
1106 ranging from warning messages to halting the machine.
1108 config X86_MCELOG_LEGACY
1109 bool "Support for deprecated /dev/mcelog character device"
1112 Enable support for /dev/mcelog which is needed by the old mcelog
1113 userspace logging daemon. Consider switching to the new generation
1116 config X86_MCE_INTEL
1118 prompt "Intel MCE features"
1119 depends on X86_MCE && X86_LOCAL_APIC
1121 Additional support for intel specific MCE features such as
1122 the thermal monitor.
1126 prompt "AMD MCE features"
1127 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1129 Additional support for AMD specific MCE features such as
1130 the DRAM Error Threshold.
1132 config X86_ANCIENT_MCE
1133 bool "Support for old Pentium 5 / WinChip machine checks"
1134 depends on X86_32 && X86_MCE
1136 Include support for machine check handling on old Pentium 5 or WinChip
1137 systems. These typically need to be enabled explicitly on the command
1140 config X86_MCE_THRESHOLD
1141 depends on X86_MCE_AMD || X86_MCE_INTEL
1144 config X86_MCE_INJECT
1145 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1146 tristate "Machine check injector support"
1148 Provide support for injecting machine checks for testing purposes.
1149 If you don't know what a machine check is and you don't do kernel
1150 QA it is safe to say n.
1152 config X86_THERMAL_VECTOR
1154 depends on X86_MCE_INTEL
1156 source "arch/x86/events/Kconfig"
1158 config X86_LEGACY_VM86
1159 bool "Legacy VM86 support"
1162 This option allows user programs to put the CPU into V8086
1163 mode, which is an 80286-era approximation of 16-bit real mode.
1165 Some very old versions of X and/or vbetool require this option
1166 for user mode setting. Similarly, DOSEMU will use it if
1167 available to accelerate real mode DOS programs. However, any
1168 recent version of DOSEMU, X, or vbetool should be fully
1169 functional even without kernel VM86 support, as they will all
1170 fall back to software emulation. Nevertheless, if you are using
1171 a 16-bit DOS program where 16-bit performance matters, vm86
1172 mode might be faster than emulation and you might want to
1175 Note that any app that works on a 64-bit kernel is unlikely to
1176 need this option, as 64-bit kernels don't, and can't, support
1177 V8086 mode. This option is also unrelated to 16-bit protected
1178 mode and is not needed to run most 16-bit programs under Wine.
1180 Enabling this option increases the complexity of the kernel
1181 and slows down exception handling a tiny bit.
1183 If unsure, say N here.
1187 default X86_LEGACY_VM86
1190 bool "Enable support for 16-bit segments" if EXPERT
1192 depends on MODIFY_LDT_SYSCALL
1194 This option is required by programs like Wine to run 16-bit
1195 protected mode legacy code on x86 processors. Disabling
1196 this option saves about 300 bytes on i386, or around 6K text
1197 plus 16K runtime memory on x86-64,
1201 depends on X86_16BIT && X86_32
1205 depends on X86_16BIT && X86_64
1207 config X86_VSYSCALL_EMULATION
1208 bool "Enable vsyscall emulation" if EXPERT
1212 This enables emulation of the legacy vsyscall page. Disabling
1213 it is roughly equivalent to booting with vsyscall=none, except
1214 that it will also disable the helpful warning if a program
1215 tries to use a vsyscall. With this option set to N, offending
1216 programs will just segfault, citing addresses of the form
1219 This option is required by many programs built before 2013, and
1220 care should be used even with newer programs if set to N.
1222 Disabling this option saves about 7K of kernel size and
1223 possibly 4K of additional runtime pagetable memory.
1225 config X86_IOPL_IOPERM
1226 bool "IOPERM and IOPL Emulation"
1229 This enables the ioperm() and iopl() syscalls which are necessary
1230 for legacy applications.
1232 Legacy IOPL support is an overbroad mechanism which allows user
1233 space aside of accessing all 65536 I/O ports also to disable
1234 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1235 capabilities and permission from potentially active security
1238 The emulation restricts the functionality of the syscall to
1239 only allowing the full range I/O port access, but prevents the
1240 ability to disable interrupts from user space which would be
1241 granted if the hardware IOPL mechanism would be used.
1244 tristate "Toshiba Laptop support"
1247 This adds a driver to safely access the System Management Mode of
1248 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1249 not work on models with a Phoenix BIOS. The System Management Mode
1250 is used to set the BIOS and power saving options on Toshiba portables.
1252 For information on utilities to make use of this driver see the
1253 Toshiba Linux utilities web site at:
1254 <http://www.buzzard.org.uk/toshiba/>.
1256 Say Y if you intend to run this kernel on a Toshiba portable.
1260 tristate "Dell i8k legacy laptop support"
1262 select SENSORS_DELL_SMM
1264 This option enables legacy /proc/i8k userspace interface in hwmon
1265 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1266 temperature and allows controlling fan speeds of Dell laptops via
1267 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1268 it reports also power and hotkey status. For fan speed control is
1269 needed userspace package i8kutils.
1271 Say Y if you intend to run this kernel on old Dell laptops or want to
1272 use userspace package i8kutils.
1275 config X86_REBOOTFIXUPS
1276 bool "Enable X86 board specific fixups for reboot"
1279 This enables chipset and/or board specific fixups to be done
1280 in order to get reboot to work correctly. This is only needed on
1281 some combinations of hardware and BIOS. The symptom, for which
1282 this config is intended, is when reboot ends with a stalled/hung
1285 Currently, the only fixup is for the Geode machines using
1286 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1288 Say Y if you want to enable the fixup. Currently, it's safe to
1289 enable this option even if you don't need it.
1293 bool "CPU microcode loading support"
1295 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1298 If you say Y here, you will be able to update the microcode on
1299 Intel and AMD processors. The Intel support is for the IA32 family,
1300 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1301 AMD support is for families 0x10 and later. You will obviously need
1302 the actual microcode binary data itself which is not shipped with
1305 The preferred method to load microcode from a detached initrd is described
1306 in Documentation/x86/microcode.rst. For that you need to enable
1307 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1308 initrd for microcode blobs.
1310 In addition, you can build the microcode into the kernel. For that you
1311 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1314 config MICROCODE_INTEL
1315 bool "Intel microcode loading support"
1316 depends on MICROCODE
1320 This options enables microcode patch loading support for Intel
1323 For the current Intel microcode data package go to
1324 <https://downloadcenter.intel.com> and search for
1325 'Linux Processor Microcode Data File'.
1327 config MICROCODE_AMD
1328 bool "AMD microcode loading support"
1329 depends on MICROCODE
1332 If you select this option, microcode patch loading support for AMD
1333 processors will be enabled.
1335 config MICROCODE_OLD_INTERFACE
1336 bool "Ancient loading interface (DEPRECATED)"
1338 depends on MICROCODE
1340 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1341 which was used by userspace tools like iucode_tool and microcode.ctl.
1342 It is inadequate because it runs too late to be able to properly
1343 load microcode on a machine and it needs special tools. Instead, you
1344 should've switched to the early loading method with the initrd or
1345 builtin microcode by now: Documentation/x86/microcode.rst
1348 tristate "/dev/cpu/*/msr - Model-specific register support"
1350 This device gives privileged processes access to the x86
1351 Model-Specific Registers (MSRs). It is a character device with
1352 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1353 MSR accesses are directed to a specific CPU on multi-processor
1357 tristate "/dev/cpu/*/cpuid - CPU information support"
1359 This device gives processes access to the x86 CPUID instruction to
1360 be executed on a specific processor. It is a character device
1361 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1365 prompt "High Memory Support"
1372 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1373 However, the address space of 32-bit x86 processors is only 4
1374 Gigabytes large. That means that, if you have a large amount of
1375 physical memory, not all of it can be "permanently mapped" by the
1376 kernel. The physical memory that's not permanently mapped is called
1379 If you are compiling a kernel which will never run on a machine with
1380 more than 1 Gigabyte total physical RAM, answer "off" here (default
1381 choice and suitable for most users). This will result in a "3GB/1GB"
1382 split: 3GB are mapped so that each process sees a 3GB virtual memory
1383 space and the remaining part of the 4GB virtual memory space is used
1384 by the kernel to permanently map as much physical memory as
1387 If the machine has between 1 and 4 Gigabytes physical RAM, then
1390 If more than 4 Gigabytes is used then answer "64GB" here. This
1391 selection turns Intel PAE (Physical Address Extension) mode on.
1392 PAE implements 3-level paging on IA32 processors. PAE is fully
1393 supported by Linux, PAE mode is implemented on all recent Intel
1394 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1395 then the kernel will not boot on CPUs that don't support PAE!
1397 The actual amount of total physical memory will either be
1398 auto detected or can be forced by using a kernel command line option
1399 such as "mem=256M". (Try "man bootparam" or see the documentation of
1400 your boot loader (lilo or loadlin) about how to pass options to the
1401 kernel at boot time.)
1403 If unsure, say "off".
1408 Select this if you have a 32-bit processor and between 1 and 4
1409 gigabytes of physical RAM.
1413 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1416 Select this if you have a 32-bit processor and more than 4
1417 gigabytes of physical RAM.
1422 prompt "Memory split" if EXPERT
1426 Select the desired split between kernel and user memory.
1428 If the address range available to the kernel is less than the
1429 physical memory installed, the remaining memory will be available
1430 as "high memory". Accessing high memory is a little more costly
1431 than low memory, as it needs to be mapped into the kernel first.
1432 Note that increasing the kernel address space limits the range
1433 available to user programs, making the address space there
1434 tighter. Selecting anything other than the default 3G/1G split
1435 will also likely make your kernel incompatible with binary-only
1438 If you are not absolutely sure what you are doing, leave this
1442 bool "3G/1G user/kernel split"
1443 config VMSPLIT_3G_OPT
1445 bool "3G/1G user/kernel split (for full 1G low memory)"
1447 bool "2G/2G user/kernel split"
1448 config VMSPLIT_2G_OPT
1450 bool "2G/2G user/kernel split (for full 2G low memory)"
1452 bool "1G/3G user/kernel split"
1457 default 0xB0000000 if VMSPLIT_3G_OPT
1458 default 0x80000000 if VMSPLIT_2G
1459 default 0x78000000 if VMSPLIT_2G_OPT
1460 default 0x40000000 if VMSPLIT_1G
1466 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1469 bool "PAE (Physical Address Extension) Support"
1470 depends on X86_32 && !HIGHMEM4G
1471 select PHYS_ADDR_T_64BIT
1474 PAE is required for NX support, and furthermore enables
1475 larger swapspace support for non-overcommit purposes. It
1476 has the cost of more pagetable lookup overhead, and also
1477 consumes more pagetable space per process.
1480 bool "Enable 5-level page tables support"
1482 select DYNAMIC_MEMORY_LAYOUT
1483 select SPARSEMEM_VMEMMAP
1486 5-level paging enables access to larger address space:
1487 upto 128 PiB of virtual address space and 4 PiB of
1488 physical address space.
1490 It will be supported by future Intel CPUs.
1492 A kernel with the option enabled can be booted on machines that
1493 support 4- or 5-level paging.
1495 See Documentation/x86/x86_64/5level-paging.rst for more
1500 config X86_DIRECT_GBPAGES
1504 Certain kernel features effectively disable kernel
1505 linear 1 GB mappings (even if the CPU otherwise
1506 supports them), so don't confuse the user by printing
1507 that we have them enabled.
1509 config X86_CPA_STATISTICS
1510 bool "Enable statistic for Change Page Attribute"
1513 Expose statistics about the Change Page Attribute mechanism, which
1514 helps to determine the effectiveness of preserving large and huge
1515 page mappings when mapping protections are changed.
1517 config AMD_MEM_ENCRYPT
1518 bool "AMD Secure Memory Encryption (SME) support"
1519 depends on X86_64 && CPU_SUP_AMD
1520 select DMA_COHERENT_POOL
1521 select DYNAMIC_PHYSICAL_MASK
1522 select ARCH_USE_MEMREMAP_PROT
1523 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1525 Say yes to enable support for the encryption of system memory.
1526 This requires an AMD processor that supports Secure Memory
1529 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1530 bool "Activate AMD Secure Memory Encryption (SME) by default"
1532 depends on AMD_MEM_ENCRYPT
1534 Say yes to have system memory encrypted by default if running on
1535 an AMD processor that supports Secure Memory Encryption (SME).
1537 If set to Y, then the encryption of system memory can be
1538 deactivated with the mem_encrypt=off command line option.
1540 If set to N, then the encryption of system memory can be
1541 activated with the mem_encrypt=on command line option.
1543 # Common NUMA Features
1545 bool "NUMA Memory Allocation and Scheduler Support"
1547 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1548 default y if X86_BIGSMP
1550 Enable NUMA (Non-Uniform Memory Access) support.
1552 The kernel will try to allocate memory used by a CPU on the
1553 local memory controller of the CPU and add some more
1554 NUMA awareness to the kernel.
1556 For 64-bit this is recommended if the system is Intel Core i7
1557 (or later), AMD Opteron, or EM64T NUMA.
1559 For 32-bit this is only needed if you boot a 32-bit
1560 kernel on a 64-bit NUMA platform.
1562 Otherwise, you should say N.
1566 prompt "Old style AMD Opteron NUMA detection"
1567 depends on X86_64 && NUMA && PCI
1569 Enable AMD NUMA node topology detection. You should say Y here if
1570 you have a multi processor AMD system. This uses an old method to
1571 read the NUMA configuration directly from the builtin Northbridge
1572 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1573 which also takes priority if both are compiled in.
1575 config X86_64_ACPI_NUMA
1577 prompt "ACPI NUMA detection"
1578 depends on X86_64 && NUMA && ACPI && PCI
1581 Enable ACPI SRAT based node topology detection.
1584 bool "NUMA emulation"
1587 Enable NUMA emulation. A flat machine will be split
1588 into virtual nodes when booted with "numa=fake=N", where N is the
1589 number of nodes. This is only useful for debugging.
1592 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1594 default "10" if MAXSMP
1595 default "6" if X86_64
1597 depends on NEED_MULTIPLE_NODES
1599 Specify the maximum number of NUMA Nodes available on the target
1600 system. Increases memory reserved to accommodate various tables.
1602 config ARCH_FLATMEM_ENABLE
1604 depends on X86_32 && !NUMA
1606 config ARCH_SPARSEMEM_ENABLE
1608 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1609 select SPARSEMEM_STATIC if X86_32
1610 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1612 config ARCH_SPARSEMEM_DEFAULT
1613 def_bool X86_64 || (NUMA && X86_32)
1615 config ARCH_SELECT_MEMORY_MODEL
1617 depends on ARCH_SPARSEMEM_ENABLE
1619 config ARCH_MEMORY_PROBE
1620 bool "Enable sysfs memory/probe interface"
1621 depends on X86_64 && MEMORY_HOTPLUG
1623 This option enables a sysfs memory/probe interface for testing.
1624 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1625 If you are unsure how to answer this question, answer N.
1627 config ARCH_PROC_KCORE_TEXT
1629 depends on X86_64 && PROC_KCORE
1631 config ILLEGAL_POINTER_VALUE
1634 default 0xdead000000000000 if X86_64
1636 config X86_PMEM_LEGACY_DEVICE
1639 config X86_PMEM_LEGACY
1640 tristate "Support non-standard NVDIMMs and ADR protected memory"
1641 depends on PHYS_ADDR_T_64BIT
1643 select X86_PMEM_LEGACY_DEVICE
1644 select NUMA_KEEP_MEMINFO if NUMA
1647 Treat memory marked using the non-standard e820 type of 12 as used
1648 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1649 The kernel will offer these regions to the 'pmem' driver so
1650 they can be used for persistent storage.
1655 bool "Allocate 3rd-level pagetables from highmem"
1658 The VM uses one page table entry for each page of physical memory.
1659 For systems with a lot of RAM, this can be wasteful of precious
1660 low memory. Setting this option will put user-space page table
1661 entries in high memory.
1663 config X86_CHECK_BIOS_CORRUPTION
1664 bool "Check for low memory corruption"
1666 Periodically check for memory corruption in low memory, which
1667 is suspected to be caused by BIOS. Even when enabled in the
1668 configuration, it is disabled at runtime. Enable it by
1669 setting "memory_corruption_check=1" on the kernel command
1670 line. By default it scans the low 64k of memory every 60
1671 seconds; see the memory_corruption_check_size and
1672 memory_corruption_check_period parameters in
1673 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1675 When enabled with the default parameters, this option has
1676 almost no overhead, as it reserves a relatively small amount
1677 of memory and scans it infrequently. It both detects corruption
1678 and prevents it from affecting the running system.
1680 It is, however, intended as a diagnostic tool; if repeatable
1681 BIOS-originated corruption always affects the same memory,
1682 you can use memmap= to prevent the kernel from using that
1685 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1686 bool "Set the default setting of memory_corruption_check"
1687 depends on X86_CHECK_BIOS_CORRUPTION
1690 Set whether the default state of memory_corruption_check is
1693 config X86_RESERVE_LOW
1694 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1698 Specify the amount of low memory to reserve for the BIOS.
1700 The first page contains BIOS data structures that the kernel
1701 must not use, so that page must always be reserved.
1703 By default we reserve the first 64K of physical RAM, as a
1704 number of BIOSes are known to corrupt that memory range
1705 during events such as suspend/resume or monitor cable
1706 insertion, so it must not be used by the kernel.
1708 You can set this to 4 if you are absolutely sure that you
1709 trust the BIOS to get all its memory reservations and usages
1710 right. If you know your BIOS have problems beyond the
1711 default 64K area, you can set this to 640 to avoid using the
1712 entire low memory range.
1714 If you have doubts about the BIOS (e.g. suspend/resume does
1715 not work or there's kernel crashes after certain hardware
1716 hotplug events) then you might want to enable
1717 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1718 typical corruption patterns.
1720 Leave this to the default value of 64 if you are unsure.
1722 config MATH_EMULATION
1724 depends on MODIFY_LDT_SYSCALL
1725 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1727 Linux can emulate a math coprocessor (used for floating point
1728 operations) if you don't have one. 486DX and Pentium processors have
1729 a math coprocessor built in, 486SX and 386 do not, unless you added
1730 a 487DX or 387, respectively. (The messages during boot time can
1731 give you some hints here ["man dmesg"].) Everyone needs either a
1732 coprocessor or this emulation.
1734 If you don't have a math coprocessor, you need to say Y here; if you
1735 say Y here even though you have a coprocessor, the coprocessor will
1736 be used nevertheless. (This behavior can be changed with the kernel
1737 command line option "no387", which comes handy if your coprocessor
1738 is broken. Try "man bootparam" or see the documentation of your boot
1739 loader (lilo or loadlin) about how to pass options to the kernel at
1740 boot time.) This means that it is a good idea to say Y here if you
1741 intend to use this kernel on different machines.
1743 More information about the internals of the Linux math coprocessor
1744 emulation can be found in <file:arch/x86/math-emu/README>.
1746 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1747 kernel, it won't hurt.
1751 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1753 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1754 the Memory Type Range Registers (MTRRs) may be used to control
1755 processor access to memory ranges. This is most useful if you have
1756 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1757 allows bus write transfers to be combined into a larger transfer
1758 before bursting over the PCI/AGP bus. This can increase performance
1759 of image write operations 2.5 times or more. Saying Y here creates a
1760 /proc/mtrr file which may be used to manipulate your processor's
1761 MTRRs. Typically the X server should use this.
1763 This code has a reasonably generic interface so that similar
1764 control registers on other processors can be easily supported
1767 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1768 Registers (ARRs) which provide a similar functionality to MTRRs. For
1769 these, the ARRs are used to emulate the MTRRs.
1770 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1771 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1772 write-combining. All of these processors are supported by this code
1773 and it makes sense to say Y here if you have one of them.
1775 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1776 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1777 can lead to all sorts of problems, so it's good to say Y here.
1779 You can safely say Y even if your machine doesn't have MTRRs, you'll
1780 just add about 9 KB to your kernel.
1782 See <file:Documentation/x86/mtrr.rst> for more information.
1784 config MTRR_SANITIZER
1786 prompt "MTRR cleanup support"
1789 Convert MTRR layout from continuous to discrete, so X drivers can
1790 add writeback entries.
1792 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1793 The largest mtrr entry size for a continuous block can be set with
1798 config MTRR_SANITIZER_ENABLE_DEFAULT
1799 int "MTRR cleanup enable value (0-1)"
1802 depends on MTRR_SANITIZER
1804 Enable mtrr cleanup default value
1806 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1807 int "MTRR cleanup spare reg num (0-7)"
1810 depends on MTRR_SANITIZER
1812 mtrr cleanup spare entries default, it can be changed via
1813 mtrr_spare_reg_nr=N on the kernel command line.
1817 prompt "x86 PAT support" if EXPERT
1820 Use PAT attributes to setup page level cache control.
1822 PATs are the modern equivalents of MTRRs and are much more
1823 flexible than MTRRs.
1825 Say N here if you see bootup problems (boot crash, boot hang,
1826 spontaneous reboots) or a non-working video driver.
1830 config ARCH_USES_PG_UNCACHED
1836 prompt "x86 architectural random number generator" if EXPERT
1838 Enable the x86 architectural RDRAND instruction
1839 (Intel Bull Mountain technology) to generate random numbers.
1840 If supported, this is a high bandwidth, cryptographically
1841 secure hardware random number generator.
1845 prompt "Supervisor Mode Access Prevention" if EXPERT
1847 Supervisor Mode Access Prevention (SMAP) is a security
1848 feature in newer Intel processors. There is a small
1849 performance cost if this enabled and turned on; there is
1850 also a small increase in the kernel size if this is enabled.
1856 prompt "User Mode Instruction Prevention" if EXPERT
1858 User Mode Instruction Prevention (UMIP) is a security feature in
1859 some x86 processors. If enabled, a general protection fault is
1860 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1861 executed in user mode. These instructions unnecessarily expose
1862 information about the hardware state.
1864 The vast majority of applications do not use these instructions.
1865 For the very few that do, software emulation is provided in
1866 specific cases in protected and virtual-8086 modes. Emulated
1869 config X86_INTEL_MEMORY_PROTECTION_KEYS
1870 prompt "Memory Protection Keys"
1872 # Note: only available in 64-bit mode
1873 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1874 select ARCH_USES_HIGH_VMA_FLAGS
1875 select ARCH_HAS_PKEYS
1877 Memory Protection Keys provides a mechanism for enforcing
1878 page-based protections, but without requiring modification of the
1879 page tables when an application changes protection domains.
1881 For details, see Documentation/core-api/protection-keys.rst
1886 prompt "TSX enable mode"
1887 depends on CPU_SUP_INTEL
1888 default X86_INTEL_TSX_MODE_OFF
1890 Intel's TSX (Transactional Synchronization Extensions) feature
1891 allows to optimize locking protocols through lock elision which
1892 can lead to a noticeable performance boost.
1894 On the other hand it has been shown that TSX can be exploited
1895 to form side channel attacks (e.g. TAA) and chances are there
1896 will be more of those attacks discovered in the future.
1898 Therefore TSX is not enabled by default (aka tsx=off). An admin
1899 might override this decision by tsx=on the command line parameter.
1900 Even with TSX enabled, the kernel will attempt to enable the best
1901 possible TAA mitigation setting depending on the microcode available
1902 for the particular machine.
1904 This option allows to set the default tsx mode between tsx=on, =off
1905 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1908 Say off if not sure, auto if TSX is in use but it should be used on safe
1909 platforms or on if TSX is in use and the security aspect of tsx is not
1912 config X86_INTEL_TSX_MODE_OFF
1915 TSX is disabled if possible - equals to tsx=off command line parameter.
1917 config X86_INTEL_TSX_MODE_ON
1920 TSX is always enabled on TSX capable HW - equals the tsx=on command
1923 config X86_INTEL_TSX_MODE_AUTO
1926 TSX is enabled on TSX capable HW that is believed to be safe against
1927 side channel attacks- equals the tsx=auto command line parameter.
1931 bool "EFI runtime service support"
1934 select EFI_RUNTIME_WRAPPERS
1936 This enables the kernel to use EFI runtime services that are
1937 available (such as the EFI variable services).
1939 This option is only useful on systems that have EFI firmware.
1940 In addition, you should use the latest ELILO loader available
1941 at <http://elilo.sourceforge.net> in order to take advantage
1942 of EFI runtime services. However, even with this option, the
1943 resultant kernel should continue to boot on existing non-EFI
1947 bool "EFI stub support"
1948 depends on EFI && !X86_USE_3DNOW
1949 depends on $(cc-option,-mabi=ms) || X86_32
1952 This kernel feature allows a bzImage to be loaded directly
1953 by EFI firmware without the use of a bootloader.
1955 See Documentation/admin-guide/efi-stub.rst for more information.
1958 bool "EFI mixed-mode support"
1959 depends on EFI_STUB && X86_64
1961 Enabling this feature allows a 64-bit kernel to be booted
1962 on a 32-bit firmware, provided that your CPU supports 64-bit
1965 Note that it is not possible to boot a mixed-mode enabled
1966 kernel via the EFI boot stub - a bootloader that supports
1967 the EFI handover protocol must be used.
1973 prompt "Enable seccomp to safely compute untrusted bytecode"
1975 This kernel feature is useful for number crunching applications
1976 that may need to compute untrusted bytecode during their
1977 execution. By using pipes or other transports made available to
1978 the process as file descriptors supporting the read/write
1979 syscalls, it's possible to isolate those applications in
1980 their own address space using seccomp. Once seccomp is
1981 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1982 and the task is only allowed to execute a few safe syscalls
1983 defined by each seccomp mode.
1985 If unsure, say Y. Only embedded should say N here.
1987 source "kernel/Kconfig.hz"
1990 bool "kexec system call"
1993 kexec is a system call that implements the ability to shutdown your
1994 current kernel, and to start another kernel. It is like a reboot
1995 but it is independent of the system firmware. And like a reboot
1996 you can start any kernel with it, not just Linux.
1998 The name comes from the similarity to the exec system call.
2000 It is an ongoing process to be certain the hardware in a machine
2001 is properly shutdown, so do not be surprised if this code does not
2002 initially work for you. As of this writing the exact hardware
2003 interface is strongly in flux, so no good recommendation can be
2007 bool "kexec file based system call"
2012 depends on CRYPTO_SHA256=y
2014 This is new version of kexec system call. This system call is
2015 file based and takes file descriptors as system call argument
2016 for kernel and initramfs as opposed to list of segments as
2017 accepted by previous system call.
2019 config ARCH_HAS_KEXEC_PURGATORY
2023 bool "Verify kernel signature during kexec_file_load() syscall"
2024 depends on KEXEC_FILE
2027 This option makes the kexec_file_load() syscall check for a valid
2028 signature of the kernel image. The image can still be loaded without
2029 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2030 there's a signature that we can check, then it must be valid.
2032 In addition to this option, you need to enable signature
2033 verification for the corresponding kernel image type being
2034 loaded in order for this to work.
2036 config KEXEC_SIG_FORCE
2037 bool "Require a valid signature in kexec_file_load() syscall"
2038 depends on KEXEC_SIG
2040 This option makes kernel signature verification mandatory for
2041 the kexec_file_load() syscall.
2043 config KEXEC_BZIMAGE_VERIFY_SIG
2044 bool "Enable bzImage signature verification support"
2045 depends on KEXEC_SIG
2046 depends on SIGNED_PE_FILE_VERIFICATION
2047 select SYSTEM_TRUSTED_KEYRING
2049 Enable bzImage signature verification support.
2052 bool "kernel crash dumps"
2053 depends on X86_64 || (X86_32 && HIGHMEM)
2055 Generate crash dump after being started by kexec.
2056 This should be normally only set in special crash dump kernels
2057 which are loaded in the main kernel with kexec-tools into
2058 a specially reserved region and then later executed after
2059 a crash by kdump/kexec. The crash dump kernel must be compiled
2060 to a memory address not used by the main kernel or BIOS using
2061 PHYSICAL_START, or it must be built as a relocatable image
2062 (CONFIG_RELOCATABLE=y).
2063 For more details see Documentation/admin-guide/kdump/kdump.rst
2067 depends on KEXEC && HIBERNATION
2069 Jump between original kernel and kexeced kernel and invoke
2070 code in physical address mode via KEXEC
2072 config PHYSICAL_START
2073 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2076 This gives the physical address where the kernel is loaded.
2078 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2079 bzImage will decompress itself to above physical address and
2080 run from there. Otherwise, bzImage will run from the address where
2081 it has been loaded by the boot loader and will ignore above physical
2084 In normal kdump cases one does not have to set/change this option
2085 as now bzImage can be compiled as a completely relocatable image
2086 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2087 address. This option is mainly useful for the folks who don't want
2088 to use a bzImage for capturing the crash dump and want to use a
2089 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2090 to be specifically compiled to run from a specific memory area
2091 (normally a reserved region) and this option comes handy.
2093 So if you are using bzImage for capturing the crash dump,
2094 leave the value here unchanged to 0x1000000 and set
2095 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2096 for capturing the crash dump change this value to start of
2097 the reserved region. In other words, it can be set based on
2098 the "X" value as specified in the "crashkernel=YM@XM"
2099 command line boot parameter passed to the panic-ed
2100 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2101 for more details about crash dumps.
2103 Usage of bzImage for capturing the crash dump is recommended as
2104 one does not have to build two kernels. Same kernel can be used
2105 as production kernel and capture kernel. Above option should have
2106 gone away after relocatable bzImage support is introduced. But it
2107 is present because there are users out there who continue to use
2108 vmlinux for dump capture. This option should go away down the
2111 Don't change this unless you know what you are doing.
2114 bool "Build a relocatable kernel"
2117 This builds a kernel image that retains relocation information
2118 so it can be loaded someplace besides the default 1MB.
2119 The relocations tend to make the kernel binary about 10% larger,
2120 but are discarded at runtime.
2122 One use is for the kexec on panic case where the recovery kernel
2123 must live at a different physical address than the primary
2126 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2127 it has been loaded at and the compile time physical address
2128 (CONFIG_PHYSICAL_START) is used as the minimum location.
2130 config RANDOMIZE_BASE
2131 bool "Randomize the address of the kernel image (KASLR)"
2132 depends on RELOCATABLE
2135 In support of Kernel Address Space Layout Randomization (KASLR),
2136 this randomizes the physical address at which the kernel image
2137 is decompressed and the virtual address where the kernel
2138 image is mapped, as a security feature that deters exploit
2139 attempts relying on knowledge of the location of kernel
2142 On 64-bit, the kernel physical and virtual addresses are
2143 randomized separately. The physical address will be anywhere
2144 between 16MB and the top of physical memory (up to 64TB). The
2145 virtual address will be randomized from 16MB up to 1GB (9 bits
2146 of entropy). Note that this also reduces the memory space
2147 available to kernel modules from 1.5GB to 1GB.
2149 On 32-bit, the kernel physical and virtual addresses are
2150 randomized together. They will be randomized from 16MB up to
2151 512MB (8 bits of entropy).
2153 Entropy is generated using the RDRAND instruction if it is
2154 supported. If RDTSC is supported, its value is mixed into
2155 the entropy pool as well. If neither RDRAND nor RDTSC are
2156 supported, then entropy is read from the i8254 timer. The
2157 usable entropy is limited by the kernel being built using
2158 2GB addressing, and that PHYSICAL_ALIGN must be at a
2159 minimum of 2MB. As a result, only 10 bits of entropy are
2160 theoretically possible, but the implementations are further
2161 limited due to memory layouts.
2165 # Relocation on x86 needs some additional build support
2166 config X86_NEED_RELOCS
2168 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2170 config PHYSICAL_ALIGN
2171 hex "Alignment value to which kernel should be aligned"
2173 range 0x2000 0x1000000 if X86_32
2174 range 0x200000 0x1000000 if X86_64
2176 This value puts the alignment restrictions on physical address
2177 where kernel is loaded and run from. Kernel is compiled for an
2178 address which meets above alignment restriction.
2180 If bootloader loads the kernel at a non-aligned address and
2181 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2182 address aligned to above value and run from there.
2184 If bootloader loads the kernel at a non-aligned address and
2185 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2186 load address and decompress itself to the address it has been
2187 compiled for and run from there. The address for which kernel is
2188 compiled already meets above alignment restrictions. Hence the
2189 end result is that kernel runs from a physical address meeting
2190 above alignment restrictions.
2192 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2193 this value must be a multiple of 0x200000.
2195 Don't change this unless you know what you are doing.
2197 config DYNAMIC_MEMORY_LAYOUT
2200 This option makes base addresses of vmalloc and vmemmap as well as
2201 __PAGE_OFFSET movable during boot.
2203 config RANDOMIZE_MEMORY
2204 bool "Randomize the kernel memory sections"
2206 depends on RANDOMIZE_BASE
2207 select DYNAMIC_MEMORY_LAYOUT
2208 default RANDOMIZE_BASE
2210 Randomizes the base virtual address of kernel memory sections
2211 (physical memory mapping, vmalloc & vmemmap). This security feature
2212 makes exploits relying on predictable memory locations less reliable.
2214 The order of allocations remains unchanged. Entropy is generated in
2215 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2216 configuration have in average 30,000 different possible virtual
2217 addresses for each memory section.
2221 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2222 hex "Physical memory mapping padding" if EXPERT
2223 depends on RANDOMIZE_MEMORY
2224 default "0xa" if MEMORY_HOTPLUG
2226 range 0x1 0x40 if MEMORY_HOTPLUG
2229 Define the padding in terabytes added to the existing physical
2230 memory size during kernel memory randomization. It is useful
2231 for memory hotplug support but reduces the entropy available for
2232 address randomization.
2234 If unsure, leave at the default value.
2240 config BOOTPARAM_HOTPLUG_CPU0
2241 bool "Set default setting of cpu0_hotpluggable"
2242 depends on HOTPLUG_CPU
2244 Set whether default state of cpu0_hotpluggable is on or off.
2246 Say Y here to enable CPU0 hotplug by default. If this switch
2247 is turned on, there is no need to give cpu0_hotplug kernel
2248 parameter and the CPU0 hotplug feature is enabled by default.
2250 Please note: there are two known CPU0 dependencies if you want
2251 to enable the CPU0 hotplug feature either by this switch or by
2252 cpu0_hotplug kernel parameter.
2254 First, resume from hibernate or suspend always starts from CPU0.
2255 So hibernate and suspend are prevented if CPU0 is offline.
2257 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2258 offline if any interrupt can not migrate out of CPU0. There may
2259 be other CPU0 dependencies.
2261 Please make sure the dependencies are under your control before
2262 you enable this feature.
2264 Say N if you don't want to enable CPU0 hotplug feature by default.
2265 You still can enable the CPU0 hotplug feature at boot by kernel
2266 parameter cpu0_hotplug.
2268 config DEBUG_HOTPLUG_CPU0
2270 prompt "Debug CPU0 hotplug"
2271 depends on HOTPLUG_CPU
2273 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2274 soon as possible and boots up userspace with CPU0 offlined. User
2275 can online CPU0 back after boot time.
2277 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2278 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2279 compilation or giving cpu0_hotplug kernel parameter at boot.
2285 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2286 depends on COMPAT_32
2288 Certain buggy versions of glibc will crash if they are
2289 presented with a 32-bit vDSO that is not mapped at the address
2290 indicated in its segment table.
2292 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2293 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2294 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2295 the only released version with the bug, but OpenSUSE 9
2296 contains a buggy "glibc 2.3.2".
2298 The symptom of the bug is that everything crashes on startup, saying:
2299 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2301 Saying Y here changes the default value of the vdso32 boot
2302 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2303 This works around the glibc bug but hurts performance.
2305 If unsure, say N: if you are compiling your own kernel, you
2306 are unlikely to be using a buggy version of glibc.
2309 prompt "vsyscall table for legacy applications"
2311 default LEGACY_VSYSCALL_XONLY
2313 Legacy user code that does not know how to find the vDSO expects
2314 to be able to issue three syscalls by calling fixed addresses in
2315 kernel space. Since this location is not randomized with ASLR,
2316 it can be used to assist security vulnerability exploitation.
2318 This setting can be changed at boot time via the kernel command
2319 line parameter vsyscall=[emulate|xonly|none].
2321 On a system with recent enough glibc (2.14 or newer) and no
2322 static binaries, you can say None without a performance penalty
2323 to improve security.
2325 If unsure, select "Emulate execution only".
2327 config LEGACY_VSYSCALL_EMULATE
2328 bool "Full emulation"
2330 The kernel traps and emulates calls into the fixed vsyscall
2331 address mapping. This makes the mapping non-executable, but
2332 it still contains readable known contents, which could be
2333 used in certain rare security vulnerability exploits. This
2334 configuration is recommended when using legacy userspace
2335 that still uses vsyscalls along with legacy binary
2336 instrumentation tools that require code to be readable.
2338 An example of this type of legacy userspace is running
2339 Pin on an old binary that still uses vsyscalls.
2341 config LEGACY_VSYSCALL_XONLY
2342 bool "Emulate execution only"
2344 The kernel traps and emulates calls into the fixed vsyscall
2345 address mapping and does not allow reads. This
2346 configuration is recommended when userspace might use the
2347 legacy vsyscall area but support for legacy binary
2348 instrumentation of legacy code is not needed. It mitigates
2349 certain uses of the vsyscall area as an ASLR-bypassing
2352 config LEGACY_VSYSCALL_NONE
2355 There will be no vsyscall mapping at all. This will
2356 eliminate any risk of ASLR bypass due to the vsyscall
2357 fixed address mapping. Attempts to use the vsyscalls
2358 will be reported to dmesg, so that either old or
2359 malicious userspace programs can be identified.
2364 bool "Built-in kernel command line"
2366 Allow for specifying boot arguments to the kernel at
2367 build time. On some systems (e.g. embedded ones), it is
2368 necessary or convenient to provide some or all of the
2369 kernel boot arguments with the kernel itself (that is,
2370 to not rely on the boot loader to provide them.)
2372 To compile command line arguments into the kernel,
2373 set this option to 'Y', then fill in the
2374 boot arguments in CONFIG_CMDLINE.
2376 Systems with fully functional boot loaders (i.e. non-embedded)
2377 should leave this option set to 'N'.
2380 string "Built-in kernel command string"
2381 depends on CMDLINE_BOOL
2384 Enter arguments here that should be compiled into the kernel
2385 image and used at boot time. If the boot loader provides a
2386 command line at boot time, it is appended to this string to
2387 form the full kernel command line, when the system boots.
2389 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2390 change this behavior.
2392 In most cases, the command line (whether built-in or provided
2393 by the boot loader) should specify the device for the root
2396 config CMDLINE_OVERRIDE
2397 bool "Built-in command line overrides boot loader arguments"
2398 depends on CMDLINE_BOOL && CMDLINE != ""
2400 Set this option to 'Y' to have the kernel ignore the boot loader
2401 command line, and use ONLY the built-in command line.
2403 This is used to work around broken boot loaders. This should
2404 be set to 'N' under normal conditions.
2406 config MODIFY_LDT_SYSCALL
2407 bool "Enable the LDT (local descriptor table)" if EXPERT
2410 Linux can allow user programs to install a per-process x86
2411 Local Descriptor Table (LDT) using the modify_ldt(2) system
2412 call. This is required to run 16-bit or segmented code such as
2413 DOSEMU or some Wine programs. It is also used by some very old
2414 threading libraries.
2416 Enabling this feature adds a small amount of overhead to
2417 context switches and increases the low-level kernel attack
2418 surface. Disabling it removes the modify_ldt(2) system call.
2420 Saying 'N' here may make sense for embedded or server kernels.
2422 source "kernel/livepatch/Kconfig"
2426 config ARCH_HAS_ADD_PAGES
2428 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2430 config ARCH_ENABLE_MEMORY_HOTPLUG
2432 depends on X86_64 || (X86_32 && HIGHMEM)
2434 config ARCH_ENABLE_MEMORY_HOTREMOVE
2436 depends on MEMORY_HOTPLUG
2438 config USE_PERCPU_NUMA_NODE_ID
2442 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2444 depends on X86_64 || X86_PAE
2446 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2448 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2450 config ARCH_ENABLE_THP_MIGRATION
2452 depends on X86_64 && TRANSPARENT_HUGEPAGE
2454 menu "Power management and ACPI options"
2456 config ARCH_HIBERNATION_HEADER
2458 depends on HIBERNATION
2460 source "kernel/power/Kconfig"
2462 source "drivers/acpi/Kconfig"
2464 source "drivers/sfi/Kconfig"
2471 tristate "APM (Advanced Power Management) BIOS support"
2472 depends on X86_32 && PM_SLEEP
2474 APM is a BIOS specification for saving power using several different
2475 techniques. This is mostly useful for battery powered laptops with
2476 APM compliant BIOSes. If you say Y here, the system time will be
2477 reset after a RESUME operation, the /proc/apm device will provide
2478 battery status information, and user-space programs will receive
2479 notification of APM "events" (e.g. battery status change).
2481 If you select "Y" here, you can disable actual use of the APM
2482 BIOS by passing the "apm=off" option to the kernel at boot time.
2484 Note that the APM support is almost completely disabled for
2485 machines with more than one CPU.
2487 In order to use APM, you will need supporting software. For location
2488 and more information, read <file:Documentation/power/apm-acpi.rst>
2489 and the Battery Powered Linux mini-HOWTO, available from
2490 <http://www.tldp.org/docs.html#howto>.
2492 This driver does not spin down disk drives (see the hdparm(8)
2493 manpage ("man 8 hdparm") for that), and it doesn't turn off
2494 VESA-compliant "green" monitors.
2496 This driver does not support the TI 4000M TravelMate and the ACER
2497 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2498 desktop machines also don't have compliant BIOSes, and this driver
2499 may cause those machines to panic during the boot phase.
2501 Generally, if you don't have a battery in your machine, there isn't
2502 much point in using this driver and you should say N. If you get
2503 random kernel OOPSes or reboots that don't seem to be related to
2504 anything, try disabling/enabling this option (or disabling/enabling
2507 Some other things you should try when experiencing seemingly random,
2510 1) make sure that you have enough swap space and that it is
2512 2) pass the "no-hlt" option to the kernel
2513 3) switch on floating point emulation in the kernel and pass
2514 the "no387" option to the kernel
2515 4) pass the "floppy=nodma" option to the kernel
2516 5) pass the "mem=4M" option to the kernel (thereby disabling
2517 all but the first 4 MB of RAM)
2518 6) make sure that the CPU is not over clocked.
2519 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2520 8) disable the cache from your BIOS settings
2521 9) install a fan for the video card or exchange video RAM
2522 10) install a better fan for the CPU
2523 11) exchange RAM chips
2524 12) exchange the motherboard.
2526 To compile this driver as a module, choose M here: the
2527 module will be called apm.
2531 config APM_IGNORE_USER_SUSPEND
2532 bool "Ignore USER SUSPEND"
2534 This option will ignore USER SUSPEND requests. On machines with a
2535 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2536 series notebooks, it is necessary to say Y because of a BIOS bug.
2538 config APM_DO_ENABLE
2539 bool "Enable PM at boot time"
2541 Enable APM features at boot time. From page 36 of the APM BIOS
2542 specification: "When disabled, the APM BIOS does not automatically
2543 power manage devices, enter the Standby State, enter the Suspend
2544 State, or take power saving steps in response to CPU Idle calls."
2545 This driver will make CPU Idle calls when Linux is idle (unless this
2546 feature is turned off -- see "Do CPU IDLE calls", below). This
2547 should always save battery power, but more complicated APM features
2548 will be dependent on your BIOS implementation. You may need to turn
2549 this option off if your computer hangs at boot time when using APM
2550 support, or if it beeps continuously instead of suspending. Turn
2551 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2552 T400CDT. This is off by default since most machines do fine without
2557 bool "Make CPU Idle calls when idle"
2559 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2560 On some machines, this can activate improved power savings, such as
2561 a slowed CPU clock rate, when the machine is idle. These idle calls
2562 are made after the idle loop has run for some length of time (e.g.,
2563 333 mS). On some machines, this will cause a hang at boot time or
2564 whenever the CPU becomes idle. (On machines with more than one CPU,
2565 this option does nothing.)
2567 config APM_DISPLAY_BLANK
2568 bool "Enable console blanking using APM"
2570 Enable console blanking using the APM. Some laptops can use this to
2571 turn off the LCD backlight when the screen blanker of the Linux
2572 virtual console blanks the screen. Note that this is only used by
2573 the virtual console screen blanker, and won't turn off the backlight
2574 when using the X Window system. This also doesn't have anything to
2575 do with your VESA-compliant power-saving monitor. Further, this
2576 option doesn't work for all laptops -- it might not turn off your
2577 backlight at all, or it might print a lot of errors to the console,
2578 especially if you are using gpm.
2580 config APM_ALLOW_INTS
2581 bool "Allow interrupts during APM BIOS calls"
2583 Normally we disable external interrupts while we are making calls to
2584 the APM BIOS as a measure to lessen the effects of a badly behaving
2585 BIOS implementation. The BIOS should reenable interrupts if it
2586 needs to. Unfortunately, some BIOSes do not -- especially those in
2587 many of the newer IBM Thinkpads. If you experience hangs when you
2588 suspend, try setting this to Y. Otherwise, say N.
2592 source "drivers/cpufreq/Kconfig"
2594 source "drivers/cpuidle/Kconfig"
2596 source "drivers/idle/Kconfig"
2601 menu "Bus options (PCI etc.)"
2604 prompt "PCI access mode"
2605 depends on X86_32 && PCI
2608 On PCI systems, the BIOS can be used to detect the PCI devices and
2609 determine their configuration. However, some old PCI motherboards
2610 have BIOS bugs and may crash if this is done. Also, some embedded
2611 PCI-based systems don't have any BIOS at all. Linux can also try to
2612 detect the PCI hardware directly without using the BIOS.
2614 With this option, you can specify how Linux should detect the
2615 PCI devices. If you choose "BIOS", the BIOS will be used,
2616 if you choose "Direct", the BIOS won't be used, and if you
2617 choose "MMConfig", then PCI Express MMCONFIG will be used.
2618 If you choose "Any", the kernel will try MMCONFIG, then the
2619 direct access method and falls back to the BIOS if that doesn't
2620 work. If unsure, go with the default, which is "Any".
2625 config PCI_GOMMCONFIG
2642 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2644 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2647 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2650 bool "Support mmconfig PCI config space access" if X86_64
2652 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2653 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2657 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2661 depends on PCI && XEN
2664 config MMCONF_FAM10H
2666 depends on X86_64 && PCI_MMCONFIG && ACPI
2668 config PCI_CNB20LE_QUIRK
2669 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2672 Read the PCI windows out of the CNB20LE host bridge. This allows
2673 PCI hotplug to work on systems with the CNB20LE chipset which do
2676 There's no public spec for this chipset, and this functionality
2677 is known to be incomplete.
2679 You should say N unless you know you need this.
2682 bool "ISA bus support on modern systems" if EXPERT
2684 Expose ISA bus device drivers and options available for selection and
2685 configuration. Enable this option if your target machine has an ISA
2686 bus. ISA is an older system, displaced by PCI and newer bus
2687 architectures -- if your target machine is modern, it probably does
2688 not have an ISA bus.
2692 # x86_64 have no ISA slots, but can have ISA-style DMA.
2694 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2697 Enables ISA-style DMA support for devices requiring such controllers.
2705 Find out whether you have ISA slots on your motherboard. ISA is the
2706 name of a bus system, i.e. the way the CPU talks to the other stuff
2707 inside your box. Other bus systems are PCI, EISA, MicroChannel
2708 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2709 newer boards don't support it. If you have ISA, say Y, otherwise N.
2712 tristate "NatSemi SCx200 support"
2714 This provides basic support for National Semiconductor's
2715 (now AMD's) Geode processors. The driver probes for the
2716 PCI-IDs of several on-chip devices, so its a good dependency
2717 for other scx200_* drivers.
2719 If compiled as a module, the driver is named scx200.
2721 config SCx200HR_TIMER
2722 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2726 This driver provides a clocksource built upon the on-chip
2727 27MHz high-resolution timer. Its also a workaround for
2728 NSC Geode SC-1100's buggy TSC, which loses time when the
2729 processor goes idle (as is done by the scheduler). The
2730 other workaround is idle=poll boot option.
2733 bool "One Laptop Per Child support"
2741 Add support for detecting the unique features of the OLPC
2745 bool "OLPC XO-1 Power Management"
2746 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2748 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2751 bool "OLPC XO-1 Real Time Clock"
2752 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2754 Add support for the XO-1 real time clock, which can be used as a
2755 programmable wakeup source.
2758 bool "OLPC XO-1 SCI extras"
2759 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2763 Add support for SCI-based features of the OLPC XO-1 laptop:
2764 - EC-driven system wakeups
2768 - AC adapter status updates
2769 - Battery status updates
2771 config OLPC_XO15_SCI
2772 bool "OLPC XO-1.5 SCI extras"
2773 depends on OLPC && ACPI
2776 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2777 - EC-driven system wakeups
2778 - AC adapter status updates
2779 - Battery status updates
2782 bool "PCEngines ALIX System Support (LED setup)"
2785 This option enables system support for the PCEngines ALIX.
2786 At present this just sets up LEDs for GPIO control on
2787 ALIX2/3/6 boards. However, other system specific setup should
2790 Note: You must still enable the drivers for GPIO and LED support
2791 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2793 Note: You have to set alix.force=1 for boards with Award BIOS.
2796 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2799 This option enables system support for the Soekris Engineering net5501.
2802 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2806 This option enables system support for the Traverse Technologies GEOS.
2809 bool "Technologic Systems TS-5500 platform support"
2811 select CHECK_SIGNATURE
2815 This option enables system support for the Technologic Systems TS-5500.
2821 depends on CPU_SUP_AMD && PCI
2824 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2826 Firmwares often provide initial graphics framebuffers so the BIOS,
2827 bootloader or kernel can show basic video-output during boot for
2828 user-guidance and debugging. Historically, x86 used the VESA BIOS
2829 Extensions and EFI-framebuffers for this, which are mostly limited
2831 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2832 framebuffers so the new generic system-framebuffer drivers can be
2833 used on x86. If the framebuffer is not compatible with the generic
2834 modes, it is advertised as fallback platform framebuffer so legacy
2835 drivers like efifb, vesafb and uvesafb can pick it up.
2836 If this option is not selected, all system framebuffers are always
2837 marked as fallback platform framebuffers as usual.
2839 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2840 not be able to pick up generic system framebuffers if this option
2841 is selected. You are highly encouraged to enable simplefb as
2842 replacement if you select this option. simplefb can correctly deal
2843 with generic system framebuffers. But you should still keep vesafb
2844 and others enabled as fallback if a system framebuffer is
2845 incompatible with simplefb.
2852 menu "Binary Emulations"
2854 config IA32_EMULATION
2855 bool "IA32 Emulation"
2857 select ARCH_WANT_OLD_COMPAT_IPC
2859 select COMPAT_BINFMT_ELF
2860 select COMPAT_OLD_SIGACTION
2862 Include code to run legacy 32-bit programs under a
2863 64-bit kernel. You should likely turn this on, unless you're
2864 100% sure that you don't have any 32-bit programs left.
2867 tristate "IA32 a.out support"
2868 depends on IA32_EMULATION
2871 Support old a.out binaries in the 32bit emulation.
2874 bool "x32 ABI for 64-bit mode"
2877 Include code to run binaries for the x32 native 32-bit ABI
2878 for 64-bit processors. An x32 process gets access to the
2879 full 64-bit register file and wide data path while leaving
2880 pointers at 32 bits for smaller memory footprint.
2882 You will need a recent binutils (2.22 or later) with
2883 elf32_x86_64 support enabled to compile a kernel with this
2888 depends on IA32_EMULATION || X86_32
2890 select OLD_SIGSUSPEND3
2894 depends on IA32_EMULATION || X86_X32
2897 config COMPAT_FOR_U64_ALIGNMENT
2900 config SYSVIPC_COMPAT
2908 config HAVE_ATOMIC_IOMAP
2912 source "drivers/firmware/Kconfig"
2914 source "arch/x86/kvm/Kconfig"
2916 source "arch/x86/Kconfig.assembler"