1 # SPDX-License-Identifier: GPL-2.0
4 bool "64-bit kernel" if "$(ARCH)" = "x86"
5 default "$(ARCH)" != "i386"
7 Say yes to build a 64-bit kernel - formerly known as x86_64
8 Say no to build a 32-bit kernel - formerly known as i386
13 # Options that are inherently 32-bit kernel only:
14 select ARCH_WANT_IPC_PARSE_VERSION
16 select CLONE_BACKWARDS
17 select HAVE_DEBUG_STACKOVERFLOW
18 select MODULES_USE_ELF_REL
20 select GENERIC_VDSO_32
25 # Options that are inherently 64-bit kernel only:
26 select ARCH_HAS_GIGANTIC_PAGE
27 select ARCH_SUPPORTS_INT128
28 select ARCH_USE_CMPXCHG_LOCKREF
29 select HAVE_ARCH_SOFT_DIRTY
30 select MODULES_USE_ELF_RELA
31 select NEED_DMA_MAP_STATE
33 select ARCH_HAS_SYSCALL_WRAPPER
35 config FORCE_DYNAMIC_FTRACE
38 depends on FUNCTION_TRACER
41 We keep the static function tracing (!DYNAMIC_FTRACE) around
42 in order to test the non static function tracing in the
43 generic code, as other architectures still use it. But we
44 only need to keep it around for x86_64. No need to keep it
45 for x86_32. For x86_32, force DYNAMIC_FTRACE.
49 # ( Note that options that are marked 'if X86_64' could in principle be
50 # ported to 32-bit as well. )
55 # Note: keep this list sorted alphabetically
57 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
58 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
59 select ARCH_32BIT_OFF_T if X86_32
60 select ARCH_CLOCKSOURCE_DATA
61 select ARCH_CLOCKSOURCE_INIT
62 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
63 select ARCH_HAS_DEBUG_VIRTUAL
64 select ARCH_HAS_DEVMEM_IS_ALLOWED
65 select ARCH_HAS_ELF_RANDOMIZE
66 select ARCH_HAS_FAST_MULTIPLIER
67 select ARCH_HAS_FILTER_PGPROT
68 select ARCH_HAS_FORTIFY_SOURCE
69 select ARCH_HAS_GCOV_PROFILE_ALL
70 select ARCH_HAS_KCOV if X86_64
71 select ARCH_HAS_MEMBARRIER_SYNC_CORE
72 select ARCH_HAS_PMEM_API if X86_64
73 select ARCH_HAS_PTE_DEVMAP if X86_64
74 select ARCH_HAS_PTE_SPECIAL
75 select ARCH_HAS_REFCOUNT
76 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
77 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
78 select ARCH_HAS_SET_MEMORY
79 select ARCH_HAS_SET_DIRECT_MAP
80 select ARCH_HAS_STRICT_KERNEL_RWX
81 select ARCH_HAS_STRICT_MODULE_RWX
82 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
83 select ARCH_HAS_UBSAN_SANITIZE_ALL
84 select ARCH_HAVE_NMI_SAFE_CMPXCHG
85 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
86 select ARCH_MIGHT_HAVE_PC_PARPORT
87 select ARCH_MIGHT_HAVE_PC_SERIO
89 select ARCH_SUPPORTS_ACPI
90 select ARCH_SUPPORTS_ATOMIC_RMW
91 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
92 select ARCH_USE_BUILTIN_BSWAP
93 select ARCH_USE_QUEUED_RWLOCKS
94 select ARCH_USE_QUEUED_SPINLOCKS
95 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
96 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
97 select ARCH_WANT_HUGE_PMD_SHARE
98 select ARCH_WANTS_THP_SWAP if X86_64
99 select BUILDTIME_EXTABLE_SORT
101 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
102 select CLOCKSOURCE_WATCHDOG
103 select DCACHE_WORD_ACCESS
104 select EDAC_ATOMIC_SCRUB
106 select GENERIC_CLOCKEVENTS
107 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
108 select GENERIC_CLOCKEVENTS_MIN_ADJUST
109 select GENERIC_CMOS_UPDATE
110 select GENERIC_CPU_AUTOPROBE
111 select GENERIC_CPU_VULNERABILITIES
112 select GENERIC_EARLY_IOREMAP
113 select GENERIC_FIND_FIRST_BIT
115 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
116 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
117 select GENERIC_IRQ_MIGRATION if SMP
118 select GENERIC_IRQ_PROBE
119 select GENERIC_IRQ_RESERVATION_MODE
120 select GENERIC_IRQ_SHOW
121 select GENERIC_PENDING_IRQ if SMP
122 select GENERIC_SMP_IDLE_THREAD
123 select GENERIC_STRNCPY_FROM_USER
124 select GENERIC_STRNLEN_USER
125 select GENERIC_TIME_VSYSCALL
126 select GENERIC_GETTIMEOFDAY
127 select GUP_GET_PTE_LOW_HIGH if X86_PAE
128 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
129 select HAVE_ACPI_APEI if ACPI
130 select HAVE_ACPI_APEI_NMI if ACPI
131 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
132 select HAVE_ARCH_AUDITSYSCALL
133 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
134 select HAVE_ARCH_JUMP_LABEL
135 select HAVE_ARCH_JUMP_LABEL_RELATIVE
136 select HAVE_ARCH_KASAN if X86_64
137 select HAVE_ARCH_KGDB
138 select HAVE_ARCH_MMAP_RND_BITS if MMU
139 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
140 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
141 select HAVE_ARCH_PREL32_RELOCATIONS
142 select HAVE_ARCH_SECCOMP_FILTER
143 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
144 select HAVE_ARCH_STACKLEAK
145 select HAVE_ARCH_TRACEHOOK
146 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
147 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
148 select HAVE_ARCH_VMAP_STACK if X86_64
149 select HAVE_ARCH_WITHIN_STACK_FRAMES
150 select HAVE_CMPXCHG_DOUBLE
151 select HAVE_CMPXCHG_LOCAL
152 select HAVE_CONTEXT_TRACKING if X86_64
153 select HAVE_COPY_THREAD_TLS
154 select HAVE_C_RECORDMCOUNT
155 select HAVE_DEBUG_KMEMLEAK
156 select HAVE_DMA_CONTIGUOUS
157 select HAVE_DYNAMIC_FTRACE
158 select HAVE_DYNAMIC_FTRACE_WITH_REGS
160 select HAVE_EFFICIENT_UNALIGNED_ACCESS
162 select HAVE_EXIT_THREAD
164 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
165 select HAVE_FTRACE_MCOUNT_RECORD
166 select HAVE_FUNCTION_GRAPH_TRACER
167 select HAVE_FUNCTION_TRACER
168 select HAVE_GCC_PLUGINS
169 select HAVE_HW_BREAKPOINT
171 select HAVE_IOREMAP_PROT
172 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
173 select HAVE_IRQ_TIME_ACCOUNTING
174 select HAVE_KERNEL_BZIP2
175 select HAVE_KERNEL_GZIP
176 select HAVE_KERNEL_LZ4
177 select HAVE_KERNEL_LZMA
178 select HAVE_KERNEL_LZO
179 select HAVE_KERNEL_XZ
181 select HAVE_KPROBES_ON_FTRACE
182 select HAVE_FUNCTION_ERROR_INJECTION
183 select HAVE_KRETPROBES
185 select HAVE_LIVEPATCH if X86_64
186 select HAVE_MEMBLOCK_NODE_MAP
187 select HAVE_MIXED_BREAKPOINTS_REGS
188 select HAVE_MOD_ARCH_SPECIFIC
192 select HAVE_OPTPROBES
193 select HAVE_PCSPKR_PLATFORM
194 select HAVE_PERF_EVENTS
195 select HAVE_PERF_EVENTS_NMI
196 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
198 select HAVE_PERF_REGS
199 select HAVE_PERF_USER_STACK_DUMP
200 select HAVE_RCU_TABLE_FREE if PARAVIRT
201 select HAVE_REGS_AND_STACK_ACCESS_API
202 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
203 select HAVE_FUNCTION_ARG_ACCESS_API
204 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
205 select HAVE_STACK_VALIDATION if X86_64
207 select HAVE_SYSCALL_TRACEPOINTS
208 select HAVE_UNSTABLE_SCHED_CLOCK
209 select HAVE_USER_RETURN_NOTIFIER
210 select HAVE_GENERIC_VDSO
211 select HOTPLUG_SMT if SMP
212 select IRQ_FORCED_THREADING
213 select NEED_SG_DMA_LENGTH
214 select PCI_DOMAINS if PCI
215 select PCI_LOCKLESS_CONFIG if PCI
218 select RTC_MC146818_LIB
221 select SYSCTL_EXCEPTION_TRACE
222 select THREAD_INFO_IN_TASK
223 select USER_STACKTRACE_SUPPORT
225 select X86_FEATURE_NAMES if PROC_FS
226 select PROC_PID_ARCH_STATUS if PROC_FS
228 config INSTRUCTION_DECODER
230 depends on KPROBES || PERF_EVENTS || UPROBES
234 default "elf32-i386" if X86_32
235 default "elf64-x86-64" if X86_64
237 config ARCH_DEFCONFIG
239 default "arch/x86/configs/i386_defconfig" if X86_32
240 default "arch/x86/configs/x86_64_defconfig" if X86_64
242 config LOCKDEP_SUPPORT
245 config STACKTRACE_SUPPORT
251 config ARCH_MMAP_RND_BITS_MIN
255 config ARCH_MMAP_RND_BITS_MAX
259 config ARCH_MMAP_RND_COMPAT_BITS_MIN
262 config ARCH_MMAP_RND_COMPAT_BITS_MAX
268 config GENERIC_ISA_DMA
270 depends on ISA_DMA_API
275 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
277 config GENERIC_BUG_RELATIVE_POINTERS
280 config ARCH_MAY_HAVE_PC_FDC
282 depends on ISA_DMA_API
284 config GENERIC_CALIBRATE_DELAY
287 config ARCH_HAS_CPU_RELAX
290 config ARCH_HAS_CACHE_LINE_SIZE
293 config ARCH_HAS_FILTER_PGPROT
296 config HAVE_SETUP_PER_CPU_AREA
299 config NEED_PER_CPU_EMBED_FIRST_CHUNK
302 config NEED_PER_CPU_PAGE_FIRST_CHUNK
305 config ARCH_HIBERNATION_POSSIBLE
308 config ARCH_SUSPEND_POSSIBLE
311 config ARCH_WANT_GENERAL_HUGETLB
320 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
323 config KASAN_SHADOW_OFFSET
326 default 0xdffffc0000000000
328 config HAVE_INTEL_TXT
330 depends on INTEL_IOMMU && ACPI
334 depends on X86_32 && SMP
338 depends on X86_64 && SMP
340 config X86_32_LAZY_GS
342 depends on X86_32 && !STACKPROTECTOR
344 config ARCH_SUPPORTS_UPROBES
347 config FIX_EARLYCON_MEM
350 config DYNAMIC_PHYSICAL_MASK
353 config PGTABLE_LEVELS
355 default 5 if X86_5LEVEL
360 config CC_HAS_SANE_STACKPROTECTOR
362 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
363 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
365 We have to make sure stack protector is unconditionally disabled if
366 the compiler produces broken code.
368 menu "Processor type and features"
371 bool "DMA memory allocation support" if EXPERT
374 DMA memory allocation support allows devices with less than 32-bit
375 addressing to allocate within the first 16MB of address space.
376 Disable if no such devices will be used.
381 bool "Symmetric multi-processing support"
383 This enables support for systems with more than one CPU. If you have
384 a system with only one CPU, say N. If you have a system with more
387 If you say N here, the kernel will run on uni- and multiprocessor
388 machines, but will use only one CPU of a multiprocessor machine. If
389 you say Y here, the kernel will run on many, but not all,
390 uniprocessor machines. On a uniprocessor machine, the kernel
391 will run faster if you say N here.
393 Note that if you say Y here and choose architecture "586" or
394 "Pentium" under "Processor family", the kernel will not work on 486
395 architectures. Similarly, multiprocessor kernels for the "PPro"
396 architecture may not work on all Pentium based boards.
398 People using multiprocessor machines who say Y here should also say
399 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
400 Management" code will be disabled if you say Y here.
402 See also <file:Documentation/x86/i386/IO-APIC.rst>,
403 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
404 <http://www.tldp.org/docs.html#howto>.
406 If you don't know what to do here, say N.
408 config X86_FEATURE_NAMES
409 bool "Processor feature human-readable names" if EMBEDDED
412 This option compiles in a table of x86 feature bits and corresponding
413 names. This is required to support /proc/cpuinfo and a few kernel
414 messages. You can disable this to save space, at the expense of
415 making those few kernel messages show numeric feature bits instead.
420 bool "Support x2apic"
421 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
423 This enables x2apic support on CPUs that have this feature.
425 This allows 32-bit apic IDs (so it can support very large systems),
426 and accesses the local apic via MSRs not via mmio.
428 If you don't know what to do here, say N.
431 bool "Enable MPS table" if ACPI || SFI
433 depends on X86_LOCAL_APIC
435 For old smp systems that do not have proper acpi support. Newer systems
436 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
440 depends on X86_GOLDFISH
443 bool "Avoid speculative indirect branches in kernel"
445 select STACK_VALIDATION if HAVE_STACK_VALIDATION
447 Compile kernel with the retpoline compiler options to guard against
448 kernel-to-user data leaks by avoiding speculative indirect
449 branches. Requires a compiler with -mindirect-branch=thunk-extern
450 support for full protection. The kernel may run slower.
452 config X86_CPU_RESCTRL
453 bool "x86 CPU resource control support"
454 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
457 Enable x86 CPU resource control support.
459 Provide support for the allocation and monitoring of system resources
462 Intel calls this Intel Resource Director Technology
463 (Intel(R) RDT). More information about RDT can be found in the
464 Intel x86 Architecture Software Developer Manual.
466 AMD calls this AMD Platform Quality of Service (AMD QoS).
467 More information about AMD QoS can be found in the AMD64 Technology
468 Platform Quality of Service Extensions manual.
474 bool "Support for big SMP systems with more than 8 CPUs"
477 This option is needed for the systems that have more than 8 CPUs
479 config X86_EXTENDED_PLATFORM
480 bool "Support for extended (non-PC) x86 platforms"
483 If you disable this option then the kernel will only support
484 standard PC platforms. (which covers the vast majority of
487 If you enable this option then you'll be able to select support
488 for the following (non-PC) 32 bit x86 platforms:
489 Goldfish (Android emulator)
492 SGI 320/540 (Visual Workstation)
493 STA2X11-based (e.g. Northville)
494 Moorestown MID devices
496 If you have one of these systems, or if you want to build a
497 generic distribution kernel, say Y here - otherwise say N.
501 config X86_EXTENDED_PLATFORM
502 bool "Support for extended (non-PC) x86 platforms"
505 If you disable this option then the kernel will only support
506 standard PC platforms. (which covers the vast majority of
509 If you enable this option then you'll be able to select support
510 for the following (non-PC) 64 bit x86 platforms:
515 If you have one of these systems, or if you want to build a
516 generic distribution kernel, say Y here - otherwise say N.
518 # This is an alphabetically sorted list of 64 bit extended platforms
519 # Please maintain the alphabetic order if and when there are additions
521 bool "Numascale NumaChip"
523 depends on X86_EXTENDED_PLATFORM
526 depends on X86_X2APIC
527 depends on PCI_MMCONFIG
529 Adds support for Numascale NumaChip large-SMP systems. Needed to
530 enable more than ~168 cores.
531 If you don't have one of these, you should say N here.
535 select HYPERVISOR_GUEST
537 depends on X86_64 && PCI
538 depends on X86_EXTENDED_PLATFORM
541 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
542 supposed to run on these EM64T-based machines. Only choose this option
543 if you have one of these machines.
546 bool "SGI Ultraviolet"
548 depends on X86_EXTENDED_PLATFORM
551 depends on X86_X2APIC
554 This option is needed in order to support SGI Ultraviolet systems.
555 If you don't have one of these, you should say N here.
557 # Following is an alphabetically sorted list of 32 bit extended platforms
558 # Please maintain the alphabetic order if and when there are additions
561 bool "Goldfish (Virtual Platform)"
562 depends on X86_EXTENDED_PLATFORM
564 Enable support for the Goldfish virtual platform used primarily
565 for Android development. Unless you are building for the Android
566 Goldfish emulator say N here.
569 bool "CE4100 TV platform"
571 depends on PCI_GODIRECT
572 depends on X86_IO_APIC
574 depends on X86_EXTENDED_PLATFORM
575 select X86_REBOOTFIXUPS
577 select OF_EARLY_FLATTREE
579 Select for the Intel CE media processor (CE4100) SOC.
580 This option compiles in support for the CE4100 SOC for settop
581 boxes and media devices.
584 bool "Intel MID platform support"
585 depends on X86_EXTENDED_PLATFORM
586 depends on X86_PLATFORM_DEVICES
588 depends on X86_64 || (PCI_GOANY && X86_32)
589 depends on X86_IO_APIC
595 select MFD_INTEL_MSIC
597 Select to build a kernel capable of supporting Intel MID (Mobile
598 Internet Device) platform systems which do not have the PCI legacy
599 interfaces. If you are building for a PC class system say N here.
601 Intel MID platforms are based on an Intel processor and chipset which
602 consume less power than most of the x86 derivatives.
604 config X86_INTEL_QUARK
605 bool "Intel Quark platform support"
607 depends on X86_EXTENDED_PLATFORM
608 depends on X86_PLATFORM_DEVICES
612 depends on X86_IO_APIC
617 Select to include support for Quark X1000 SoC.
618 Say Y here if you have a Quark based system such as the Arduino
619 compatible Intel Galileo.
621 config X86_INTEL_LPSS
622 bool "Intel Low Power Subsystem Support"
623 depends on X86 && ACPI && PCI
628 Select to build support for Intel Low Power Subsystem such as
629 found on Intel Lynxpoint PCH. Selecting this option enables
630 things like clock tree (common clock framework) and pincontrol
631 which are needed by the LPSS peripheral drivers.
633 config X86_AMD_PLATFORM_DEVICE
634 bool "AMD ACPI2Platform devices support"
639 Select to interpret AMD specific ACPI device to platform device
640 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
641 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
642 implemented under PINCTRL subsystem.
645 tristate "Intel SoC IOSF Sideband support for SoC platforms"
648 This option enables sideband register access support for Intel SoC
649 platforms. On these platforms the IOSF sideband is used in lieu of
650 MSR's for some register accesses, mostly but not limited to thermal
651 and power. Drivers may query the availability of this device to
652 determine if they need the sideband in order to work on these
653 platforms. The sideband is available on the following SoC products.
654 This list is not meant to be exclusive.
659 You should say Y if you are running a kernel on one of these SoC's.
661 config IOSF_MBI_DEBUG
662 bool "Enable IOSF sideband access through debugfs"
663 depends on IOSF_MBI && DEBUG_FS
665 Select this option to expose the IOSF sideband access registers (MCR,
666 MDR, MCRX) through debugfs to write and read register information from
667 different units on the SoC. This is most useful for obtaining device
668 state information for debug and analysis. As this is a general access
669 mechanism, users of this option would have specific knowledge of the
670 device they want to access.
672 If you don't require the option or are in doubt, say N.
675 bool "RDC R-321x SoC"
677 depends on X86_EXTENDED_PLATFORM
679 select X86_REBOOTFIXUPS
681 This option is needed for RDC R-321x system-on-chip, also known
683 If you don't have one of these chips, you should say N here.
685 config X86_32_NON_STANDARD
686 bool "Support non-standard 32-bit SMP architectures"
687 depends on X86_32 && SMP
688 depends on X86_EXTENDED_PLATFORM
690 This option compiles in the bigsmp and STA2X11 default
691 subarchitectures. It is intended for a generic binary
692 kernel. If you select them all, kernel will probe it one by
693 one and will fallback to default.
695 # Alphabetically sorted list of Non standard 32 bit platforms
697 config X86_SUPPORTS_MEMORY_FAILURE
699 # MCE code calls memory_failure():
701 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
702 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
703 depends on X86_64 || !SPARSEMEM
704 select ARCH_SUPPORTS_MEMORY_FAILURE
707 bool "STA2X11 Companion Chip Support"
708 depends on X86_32_NON_STANDARD && PCI
709 select ARCH_HAS_PHYS_TO_DMA
714 This adds support for boards based on the STA2X11 IO-Hub,
715 a.k.a. "ConneXt". The chip is used in place of the standard
716 PC chipset, so all "standard" peripherals are missing. If this
717 option is selected the kernel will still be able to boot on
718 standard PC machines.
721 tristate "Eurobraille/Iris poweroff module"
724 The Iris machines from EuroBraille do not have APM or ACPI support
725 to shut themselves down properly. A special I/O sequence is
726 needed to do so, which is what this module does at
729 This is only for Iris machines from EuroBraille.
733 config SCHED_OMIT_FRAME_POINTER
735 prompt "Single-depth WCHAN output"
738 Calculate simpler /proc/<PID>/wchan values. If this option
739 is disabled then wchan values will recurse back to the
740 caller function. This provides more accurate wchan values,
741 at the expense of slightly more scheduling overhead.
743 If in doubt, say "Y".
745 menuconfig HYPERVISOR_GUEST
746 bool "Linux guest support"
748 Say Y here to enable options for running Linux under various hyper-
749 visors. This option enables basic hypervisor detection and platform
752 If you say N, all options in this submenu will be skipped and
753 disabled, and Linux guest support won't be built in.
758 bool "Enable paravirtualization code"
760 This changes the kernel so it can modify itself when it is run
761 under a hypervisor, potentially improving performance significantly
762 over full virtualization. However, when run without a hypervisor
763 the kernel is theoretically slower and slightly larger.
768 config PARAVIRT_DEBUG
769 bool "paravirt-ops debugging"
770 depends on PARAVIRT && DEBUG_KERNEL
772 Enable to debug paravirt_ops internals. Specifically, BUG if
773 a paravirt_op is missing when it is called.
775 config PARAVIRT_SPINLOCKS
776 bool "Paravirtualization layer for spinlocks"
777 depends on PARAVIRT && SMP
779 Paravirtualized spinlocks allow a pvops backend to replace the
780 spinlock implementation with something virtualization-friendly
781 (for example, block the virtual CPU rather than spinning).
783 It has a minimal impact on native kernels and gives a nice performance
784 benefit on paravirtualized KVM / Xen kernels.
786 If you are unsure how to answer this question, answer Y.
788 config X86_HV_CALLBACK_VECTOR
791 source "arch/x86/xen/Kconfig"
794 bool "KVM Guest support (including kvmclock)"
796 select PARAVIRT_CLOCK
797 select ARCH_CPUIDLE_HALTPOLL
800 This option enables various optimizations for running under the KVM
801 hypervisor. It includes a paravirtualized clock, so that instead
802 of relying on a PIT (or probably other) emulation by the
803 underlying device model, the host provides the guest with
804 timing infrastructure such as time of day, and system time
806 config ARCH_CPUIDLE_HALTPOLL
808 prompt "Disable host haltpoll when loading haltpoll driver"
810 If virtualized under KVM, disable host haltpoll.
813 bool "Support for running PVH guests"
815 This option enables the PVH entry point for guest virtual machines
816 as specified in the x86/HVM direct boot ABI.
819 bool "Enable debug information for KVM Guests in debugfs"
820 depends on KVM_GUEST && DEBUG_FS
822 This option enables collection of various statistics for KVM guest.
823 Statistics are displayed in debugfs filesystem. Enabling this option
824 may incur significant overhead.
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 "IBM Calgary IOMMU support"
937 depends on X86_64 && PCI
939 Support for hardware IOMMUs in IBM's xSeries x366 and x460
940 systems. Needed to run systems with more than 3GB of memory
941 properly with 32-bit PCI devices that do not support DAC
942 (Double Address Cycle). Calgary also supports bus level
943 isolation, where all DMAs pass through the IOMMU. This
944 prevents them from going anywhere except their intended
945 destination. This catches hard-to-find kernel bugs and
946 mis-behaving drivers and devices that do not use the DMA-API
947 properly to set up their DMA buffers. The IOMMU can be
948 turned off at boot time with the iommu=off parameter.
949 Normally the kernel will make the right choice by itself.
952 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
954 prompt "Should Calgary be enabled by default?"
955 depends on CALGARY_IOMMU
957 Should Calgary be enabled by default? if you choose 'y', Calgary
958 will be used (if it exists). If you choose 'n', Calgary will not be
959 used even if it exists. If you choose 'n' and would like to use
960 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
964 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
965 depends on X86_64 && SMP && DEBUG_KERNEL
966 select CPUMASK_OFFSTACK
968 Enable maximum number of CPUS and NUMA Nodes for this architecture.
972 # The maximum number of CPUs supported:
974 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
975 # and which can be configured interactively in the
976 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
978 # The ranges are different on 32-bit and 64-bit kernels, depending on
979 # hardware capabilities and scalability features of the kernel.
981 # ( If MAXSMP is enabled we just use the highest possible value and disable
982 # interactive configuration. )
985 config NR_CPUS_RANGE_BEGIN
987 default NR_CPUS_RANGE_END if MAXSMP
991 config NR_CPUS_RANGE_END
994 default 64 if SMP && X86_BIGSMP
995 default 8 if SMP && !X86_BIGSMP
998 config NR_CPUS_RANGE_END
1001 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
1002 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
1005 config NR_CPUS_DEFAULT
1008 default 32 if X86_BIGSMP
1012 config NR_CPUS_DEFAULT
1015 default 8192 if MAXSMP
1020 int "Maximum number of CPUs" if SMP && !MAXSMP
1021 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1022 default NR_CPUS_DEFAULT
1024 This allows you to specify the maximum number of CPUs which this
1025 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1026 supported value is 8192, otherwise the maximum value is 512. The
1027 minimum value which makes sense is 2.
1029 This is purely to save memory: each supported CPU adds about 8KB
1030 to the kernel image.
1037 prompt "Multi-core scheduler support"
1040 Multi-core scheduler support improves the CPU scheduler's decision
1041 making when dealing with multi-core CPU chips at a cost of slightly
1042 increased overhead in some places. If unsure say N here.
1044 config SCHED_MC_PRIO
1045 bool "CPU core priorities scheduler support"
1046 depends on SCHED_MC && CPU_SUP_INTEL
1047 select X86_INTEL_PSTATE
1051 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1052 core ordering determined at manufacturing time, which allows
1053 certain cores to reach higher turbo frequencies (when running
1054 single threaded workloads) than others.
1056 Enabling this kernel feature teaches the scheduler about
1057 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1058 scheduler's CPU selection logic accordingly, so that higher
1059 overall system performance can be achieved.
1061 This feature will have no effect on CPUs without this feature.
1063 If unsure say Y here.
1067 depends on !SMP && X86_LOCAL_APIC
1070 bool "Local APIC support on uniprocessors" if !PCI_MSI
1072 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1074 A local APIC (Advanced Programmable Interrupt Controller) is an
1075 integrated interrupt controller in the CPU. If you have a single-CPU
1076 system which has a processor with a local APIC, you can say Y here to
1077 enable and use it. If you say Y here even though your machine doesn't
1078 have a local APIC, then the kernel will still run with no slowdown at
1079 all. The local APIC supports CPU-generated self-interrupts (timer,
1080 performance counters), and the NMI watchdog which detects hard
1083 config X86_UP_IOAPIC
1084 bool "IO-APIC support on uniprocessors"
1085 depends on X86_UP_APIC
1087 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1088 SMP-capable replacement for PC-style interrupt controllers. Most
1089 SMP systems and many recent uniprocessor systems have one.
1091 If you have a single-CPU system with an IO-APIC, you can say Y here
1092 to use it. If you say Y here even though your machine doesn't have
1093 an IO-APIC, then the kernel will still run with no slowdown at all.
1095 config X86_LOCAL_APIC
1097 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1098 select IRQ_DOMAIN_HIERARCHY
1099 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1103 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1105 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1106 bool "Reroute for broken boot IRQs"
1107 depends on X86_IO_APIC
1109 This option enables a workaround that fixes a source of
1110 spurious interrupts. This is recommended when threaded
1111 interrupt handling is used on systems where the generation of
1112 superfluous "boot interrupts" cannot be disabled.
1114 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1115 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1116 kernel does during interrupt handling). On chipsets where this
1117 boot IRQ generation cannot be disabled, this workaround keeps
1118 the original IRQ line masked so that only the equivalent "boot
1119 IRQ" is delivered to the CPUs. The workaround also tells the
1120 kernel to set up the IRQ handler on the boot IRQ line. In this
1121 way only one interrupt is delivered to the kernel. Otherwise
1122 the spurious second interrupt may cause the kernel to bring
1123 down (vital) interrupt lines.
1125 Only affects "broken" chipsets. Interrupt sharing may be
1126 increased on these systems.
1129 bool "Machine Check / overheating reporting"
1130 select GENERIC_ALLOCATOR
1133 Machine Check support allows the processor to notify the
1134 kernel if it detects a problem (e.g. overheating, data corruption).
1135 The action the kernel takes depends on the severity of the problem,
1136 ranging from warning messages to halting the machine.
1138 config X86_MCELOG_LEGACY
1139 bool "Support for deprecated /dev/mcelog character device"
1142 Enable support for /dev/mcelog which is needed by the old mcelog
1143 userspace logging daemon. Consider switching to the new generation
1146 config X86_MCE_INTEL
1148 prompt "Intel MCE features"
1149 depends on X86_MCE && X86_LOCAL_APIC
1151 Additional support for intel specific MCE features such as
1152 the thermal monitor.
1156 prompt "AMD MCE features"
1157 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1159 Additional support for AMD specific MCE features such as
1160 the DRAM Error Threshold.
1162 config X86_ANCIENT_MCE
1163 bool "Support for old Pentium 5 / WinChip machine checks"
1164 depends on X86_32 && X86_MCE
1166 Include support for machine check handling on old Pentium 5 or WinChip
1167 systems. These typically need to be enabled explicitly on the command
1170 config X86_MCE_THRESHOLD
1171 depends on X86_MCE_AMD || X86_MCE_INTEL
1174 config X86_MCE_INJECT
1175 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1176 tristate "Machine check injector support"
1178 Provide support for injecting machine checks for testing purposes.
1179 If you don't know what a machine check is and you don't do kernel
1180 QA it is safe to say n.
1182 config X86_THERMAL_VECTOR
1184 depends on X86_MCE_INTEL
1186 source "arch/x86/events/Kconfig"
1188 config X86_LEGACY_VM86
1189 bool "Legacy VM86 support"
1192 This option allows user programs to put the CPU into V8086
1193 mode, which is an 80286-era approximation of 16-bit real mode.
1195 Some very old versions of X and/or vbetool require this option
1196 for user mode setting. Similarly, DOSEMU will use it if
1197 available to accelerate real mode DOS programs. However, any
1198 recent version of DOSEMU, X, or vbetool should be fully
1199 functional even without kernel VM86 support, as they will all
1200 fall back to software emulation. Nevertheless, if you are using
1201 a 16-bit DOS program where 16-bit performance matters, vm86
1202 mode might be faster than emulation and you might want to
1205 Note that any app that works on a 64-bit kernel is unlikely to
1206 need this option, as 64-bit kernels don't, and can't, support
1207 V8086 mode. This option is also unrelated to 16-bit protected
1208 mode and is not needed to run most 16-bit programs under Wine.
1210 Enabling this option increases the complexity of the kernel
1211 and slows down exception handling a tiny bit.
1213 If unsure, say N here.
1217 default X86_LEGACY_VM86
1220 bool "Enable support for 16-bit segments" if EXPERT
1222 depends on MODIFY_LDT_SYSCALL
1224 This option is required by programs like Wine to run 16-bit
1225 protected mode legacy code on x86 processors. Disabling
1226 this option saves about 300 bytes on i386, or around 6K text
1227 plus 16K runtime memory on x86-64,
1231 depends on X86_16BIT && X86_32
1235 depends on X86_16BIT && X86_64
1237 config X86_VSYSCALL_EMULATION
1238 bool "Enable vsyscall emulation" if EXPERT
1242 This enables emulation of the legacy vsyscall page. Disabling
1243 it is roughly equivalent to booting with vsyscall=none, except
1244 that it will also disable the helpful warning if a program
1245 tries to use a vsyscall. With this option set to N, offending
1246 programs will just segfault, citing addresses of the form
1249 This option is required by many programs built before 2013, and
1250 care should be used even with newer programs if set to N.
1252 Disabling this option saves about 7K of kernel size and
1253 possibly 4K of additional runtime pagetable memory.
1256 tristate "Toshiba Laptop support"
1259 This adds a driver to safely access the System Management Mode of
1260 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1261 not work on models with a Phoenix BIOS. The System Management Mode
1262 is used to set the BIOS and power saving options on Toshiba portables.
1264 For information on utilities to make use of this driver see the
1265 Toshiba Linux utilities web site at:
1266 <http://www.buzzard.org.uk/toshiba/>.
1268 Say Y if you intend to run this kernel on a Toshiba portable.
1272 tristate "Dell i8k legacy laptop support"
1274 select SENSORS_DELL_SMM
1276 This option enables legacy /proc/i8k userspace interface in hwmon
1277 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1278 temperature and allows controlling fan speeds of Dell laptops via
1279 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1280 it reports also power and hotkey status. For fan speed control is
1281 needed userspace package i8kutils.
1283 Say Y if you intend to run this kernel on old Dell laptops or want to
1284 use userspace package i8kutils.
1287 config X86_REBOOTFIXUPS
1288 bool "Enable X86 board specific fixups for reboot"
1291 This enables chipset and/or board specific fixups to be done
1292 in order to get reboot to work correctly. This is only needed on
1293 some combinations of hardware and BIOS. The symptom, for which
1294 this config is intended, is when reboot ends with a stalled/hung
1297 Currently, the only fixup is for the Geode machines using
1298 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1300 Say Y if you want to enable the fixup. Currently, it's safe to
1301 enable this option even if you don't need it.
1305 bool "CPU microcode loading support"
1307 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1310 If you say Y here, you will be able to update the microcode on
1311 Intel and AMD processors. The Intel support is for the IA32 family,
1312 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1313 AMD support is for families 0x10 and later. You will obviously need
1314 the actual microcode binary data itself which is not shipped with
1317 The preferred method to load microcode from a detached initrd is described
1318 in Documentation/x86/microcode.rst. For that you need to enable
1319 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1320 initrd for microcode blobs.
1322 In addition, you can build the microcode into the kernel. For that you
1323 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1326 config MICROCODE_INTEL
1327 bool "Intel microcode loading support"
1328 depends on MICROCODE
1332 This options enables microcode patch loading support for Intel
1335 For the current Intel microcode data package go to
1336 <https://downloadcenter.intel.com> and search for
1337 'Linux Processor Microcode Data File'.
1339 config MICROCODE_AMD
1340 bool "AMD microcode loading support"
1341 depends on MICROCODE
1344 If you select this option, microcode patch loading support for AMD
1345 processors will be enabled.
1347 config MICROCODE_OLD_INTERFACE
1348 bool "Ancient loading interface (DEPRECATED)"
1350 depends on MICROCODE
1352 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1353 which was used by userspace tools like iucode_tool and microcode.ctl.
1354 It is inadequate because it runs too late to be able to properly
1355 load microcode on a machine and it needs special tools. Instead, you
1356 should've switched to the early loading method with the initrd or
1357 builtin microcode by now: Documentation/x86/microcode.rst
1360 tristate "/dev/cpu/*/msr - Model-specific register support"
1362 This device gives privileged processes access to the x86
1363 Model-Specific Registers (MSRs). It is a character device with
1364 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1365 MSR accesses are directed to a specific CPU on multi-processor
1369 tristate "/dev/cpu/*/cpuid - CPU information support"
1371 This device gives processes access to the x86 CPUID instruction to
1372 be executed on a specific processor. It is a character device
1373 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1377 prompt "High Memory Support"
1384 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1385 However, the address space of 32-bit x86 processors is only 4
1386 Gigabytes large. That means that, if you have a large amount of
1387 physical memory, not all of it can be "permanently mapped" by the
1388 kernel. The physical memory that's not permanently mapped is called
1391 If you are compiling a kernel which will never run on a machine with
1392 more than 1 Gigabyte total physical RAM, answer "off" here (default
1393 choice and suitable for most users). This will result in a "3GB/1GB"
1394 split: 3GB are mapped so that each process sees a 3GB virtual memory
1395 space and the remaining part of the 4GB virtual memory space is used
1396 by the kernel to permanently map as much physical memory as
1399 If the machine has between 1 and 4 Gigabytes physical RAM, then
1402 If more than 4 Gigabytes is used then answer "64GB" here. This
1403 selection turns Intel PAE (Physical Address Extension) mode on.
1404 PAE implements 3-level paging on IA32 processors. PAE is fully
1405 supported by Linux, PAE mode is implemented on all recent Intel
1406 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1407 then the kernel will not boot on CPUs that don't support PAE!
1409 The actual amount of total physical memory will either be
1410 auto detected or can be forced by using a kernel command line option
1411 such as "mem=256M". (Try "man bootparam" or see the documentation of
1412 your boot loader (lilo or loadlin) about how to pass options to the
1413 kernel at boot time.)
1415 If unsure, say "off".
1420 Select this if you have a 32-bit processor and between 1 and 4
1421 gigabytes of physical RAM.
1425 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1428 Select this if you have a 32-bit processor and more than 4
1429 gigabytes of physical RAM.
1434 prompt "Memory split" if EXPERT
1438 Select the desired split between kernel and user memory.
1440 If the address range available to the kernel is less than the
1441 physical memory installed, the remaining memory will be available
1442 as "high memory". Accessing high memory is a little more costly
1443 than low memory, as it needs to be mapped into the kernel first.
1444 Note that increasing the kernel address space limits the range
1445 available to user programs, making the address space there
1446 tighter. Selecting anything other than the default 3G/1G split
1447 will also likely make your kernel incompatible with binary-only
1450 If you are not absolutely sure what you are doing, leave this
1454 bool "3G/1G user/kernel split"
1455 config VMSPLIT_3G_OPT
1457 bool "3G/1G user/kernel split (for full 1G low memory)"
1459 bool "2G/2G user/kernel split"
1460 config VMSPLIT_2G_OPT
1462 bool "2G/2G user/kernel split (for full 2G low memory)"
1464 bool "1G/3G user/kernel split"
1469 default 0xB0000000 if VMSPLIT_3G_OPT
1470 default 0x80000000 if VMSPLIT_2G
1471 default 0x78000000 if VMSPLIT_2G_OPT
1472 default 0x40000000 if VMSPLIT_1G
1478 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1481 bool "PAE (Physical Address Extension) Support"
1482 depends on X86_32 && !HIGHMEM4G
1483 select PHYS_ADDR_T_64BIT
1486 PAE is required for NX support, and furthermore enables
1487 larger swapspace support for non-overcommit purposes. It
1488 has the cost of more pagetable lookup overhead, and also
1489 consumes more pagetable space per process.
1492 bool "Enable 5-level page tables support"
1493 select DYNAMIC_MEMORY_LAYOUT
1494 select SPARSEMEM_VMEMMAP
1497 5-level paging enables access to larger address space:
1498 upto 128 PiB of virtual address space and 4 PiB of
1499 physical address space.
1501 It will be supported by future Intel CPUs.
1503 A kernel with the option enabled can be booted on machines that
1504 support 4- or 5-level paging.
1506 See Documentation/x86/x86_64/5level-paging.rst for more
1511 config X86_DIRECT_GBPAGES
1515 Certain kernel features effectively disable kernel
1516 linear 1 GB mappings (even if the CPU otherwise
1517 supports them), so don't confuse the user by printing
1518 that we have them enabled.
1520 config X86_CPA_STATISTICS
1521 bool "Enable statistic for Change Page Attribute"
1524 Expose statistics about the Change Page Attribute mechanims, which
1525 helps to determine the effectiveness of preserving large and huge
1526 page mappings when mapping protections are changed.
1528 config ARCH_HAS_MEM_ENCRYPT
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"
1545 depends on AMD_MEM_ENCRYPT
1547 Say yes to have system memory encrypted by default if running on
1548 an AMD processor that supports Secure Memory Encryption (SME).
1550 If set to Y, then the encryption of system memory can be
1551 deactivated with the mem_encrypt=off command line option.
1553 If set to N, then the encryption of system memory can be
1554 activated with the mem_encrypt=on command line option.
1556 # Common NUMA Features
1558 bool "Numa Memory Allocation and Scheduler Support"
1560 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1561 default y if X86_BIGSMP
1563 Enable NUMA (Non Uniform Memory Access) support.
1565 The kernel will try to allocate memory used by a CPU on the
1566 local memory controller of the CPU and add some more
1567 NUMA awareness to the kernel.
1569 For 64-bit this is recommended if the system is Intel Core i7
1570 (or later), AMD Opteron, or EM64T NUMA.
1572 For 32-bit this is only needed if you boot a 32-bit
1573 kernel on a 64-bit NUMA platform.
1575 Otherwise, you should say N.
1579 prompt "Old style AMD Opteron NUMA detection"
1580 depends on X86_64 && NUMA && PCI
1582 Enable AMD NUMA node topology detection. You should say Y here if
1583 you have a multi processor AMD system. This uses an old method to
1584 read the NUMA configuration directly from the builtin Northbridge
1585 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1586 which also takes priority if both are compiled in.
1588 config X86_64_ACPI_NUMA
1590 prompt "ACPI NUMA detection"
1591 depends on X86_64 && NUMA && ACPI && PCI
1594 Enable ACPI SRAT based node topology detection.
1596 # Some NUMA nodes have memory ranges that span
1597 # other nodes. Even though a pfn is valid and
1598 # between a node's start and end pfns, it may not
1599 # reside on that node. See memmap_init_zone()
1601 config NODES_SPAN_OTHER_NODES
1603 depends on X86_64_ACPI_NUMA
1606 bool "NUMA emulation"
1609 Enable NUMA emulation. A flat machine will be split
1610 into virtual nodes when booted with "numa=fake=N", where N is the
1611 number of nodes. This is only useful for debugging.
1614 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1616 default "10" if MAXSMP
1617 default "6" if X86_64
1619 depends on NEED_MULTIPLE_NODES
1621 Specify the maximum number of NUMA Nodes available on the target
1622 system. Increases memory reserved to accommodate various tables.
1624 config ARCH_HAVE_MEMORY_PRESENT
1626 depends on X86_32 && DISCONTIGMEM
1628 config ARCH_FLATMEM_ENABLE
1630 depends on X86_32 && !NUMA
1632 config ARCH_DISCONTIGMEM_ENABLE
1634 depends on NUMA && X86_32
1637 config ARCH_SPARSEMEM_ENABLE
1639 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1640 select SPARSEMEM_STATIC if X86_32
1641 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1643 config ARCH_SPARSEMEM_DEFAULT
1644 def_bool X86_64 || (NUMA && X86_32)
1646 config ARCH_SELECT_MEMORY_MODEL
1648 depends on ARCH_SPARSEMEM_ENABLE
1650 config ARCH_MEMORY_PROBE
1651 bool "Enable sysfs memory/probe interface"
1652 depends on X86_64 && MEMORY_HOTPLUG
1654 This option enables a sysfs memory/probe interface for testing.
1655 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1656 If you are unsure how to answer this question, answer N.
1658 config ARCH_PROC_KCORE_TEXT
1660 depends on X86_64 && PROC_KCORE
1662 config ILLEGAL_POINTER_VALUE
1665 default 0xdead000000000000 if X86_64
1667 config X86_PMEM_LEGACY_DEVICE
1670 config X86_PMEM_LEGACY
1671 tristate "Support non-standard NVDIMMs and ADR protected memory"
1672 depends on PHYS_ADDR_T_64BIT
1674 select X86_PMEM_LEGACY_DEVICE
1677 Treat memory marked using the non-standard e820 type of 12 as used
1678 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1679 The kernel will offer these regions to the 'pmem' driver so
1680 they can be used for persistent storage.
1685 bool "Allocate 3rd-level pagetables from highmem"
1688 The VM uses one page table entry for each page of physical memory.
1689 For systems with a lot of RAM, this can be wasteful of precious
1690 low memory. Setting this option will put user-space page table
1691 entries in high memory.
1693 config X86_CHECK_BIOS_CORRUPTION
1694 bool "Check for low memory corruption"
1696 Periodically check for memory corruption in low memory, which
1697 is suspected to be caused by BIOS. Even when enabled in the
1698 configuration, it is disabled at runtime. Enable it by
1699 setting "memory_corruption_check=1" on the kernel command
1700 line. By default it scans the low 64k of memory every 60
1701 seconds; see the memory_corruption_check_size and
1702 memory_corruption_check_period parameters in
1703 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1705 When enabled with the default parameters, this option has
1706 almost no overhead, as it reserves a relatively small amount
1707 of memory and scans it infrequently. It both detects corruption
1708 and prevents it from affecting the running system.
1710 It is, however, intended as a diagnostic tool; if repeatable
1711 BIOS-originated corruption always affects the same memory,
1712 you can use memmap= to prevent the kernel from using that
1715 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1716 bool "Set the default setting of memory_corruption_check"
1717 depends on X86_CHECK_BIOS_CORRUPTION
1720 Set whether the default state of memory_corruption_check is
1723 config X86_RESERVE_LOW
1724 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1728 Specify the amount of low memory to reserve for the BIOS.
1730 The first page contains BIOS data structures that the kernel
1731 must not use, so that page must always be reserved.
1733 By default we reserve the first 64K of physical RAM, as a
1734 number of BIOSes are known to corrupt that memory range
1735 during events such as suspend/resume or monitor cable
1736 insertion, so it must not be used by the kernel.
1738 You can set this to 4 if you are absolutely sure that you
1739 trust the BIOS to get all its memory reservations and usages
1740 right. If you know your BIOS have problems beyond the
1741 default 64K area, you can set this to 640 to avoid using the
1742 entire low memory range.
1744 If you have doubts about the BIOS (e.g. suspend/resume does
1745 not work or there's kernel crashes after certain hardware
1746 hotplug events) then you might want to enable
1747 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1748 typical corruption patterns.
1750 Leave this to the default value of 64 if you are unsure.
1752 config MATH_EMULATION
1754 depends on MODIFY_LDT_SYSCALL
1755 prompt "Math emulation" if X86_32
1757 Linux can emulate a math coprocessor (used for floating point
1758 operations) if you don't have one. 486DX and Pentium processors have
1759 a math coprocessor built in, 486SX and 386 do not, unless you added
1760 a 487DX or 387, respectively. (The messages during boot time can
1761 give you some hints here ["man dmesg"].) Everyone needs either a
1762 coprocessor or this emulation.
1764 If you don't have a math coprocessor, you need to say Y here; if you
1765 say Y here even though you have a coprocessor, the coprocessor will
1766 be used nevertheless. (This behavior can be changed with the kernel
1767 command line option "no387", which comes handy if your coprocessor
1768 is broken. Try "man bootparam" or see the documentation of your boot
1769 loader (lilo or loadlin) about how to pass options to the kernel at
1770 boot time.) This means that it is a good idea to say Y here if you
1771 intend to use this kernel on different machines.
1773 More information about the internals of the Linux math coprocessor
1774 emulation can be found in <file:arch/x86/math-emu/README>.
1776 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1777 kernel, it won't hurt.
1781 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1783 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1784 the Memory Type Range Registers (MTRRs) may be used to control
1785 processor access to memory ranges. This is most useful if you have
1786 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1787 allows bus write transfers to be combined into a larger transfer
1788 before bursting over the PCI/AGP bus. This can increase performance
1789 of image write operations 2.5 times or more. Saying Y here creates a
1790 /proc/mtrr file which may be used to manipulate your processor's
1791 MTRRs. Typically the X server should use this.
1793 This code has a reasonably generic interface so that similar
1794 control registers on other processors can be easily supported
1797 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1798 Registers (ARRs) which provide a similar functionality to MTRRs. For
1799 these, the ARRs are used to emulate the MTRRs.
1800 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1801 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1802 write-combining. All of these processors are supported by this code
1803 and it makes sense to say Y here if you have one of them.
1805 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1806 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1807 can lead to all sorts of problems, so it's good to say Y here.
1809 You can safely say Y even if your machine doesn't have MTRRs, you'll
1810 just add about 9 KB to your kernel.
1812 See <file:Documentation/x86/mtrr.rst> for more information.
1814 config MTRR_SANITIZER
1816 prompt "MTRR cleanup support"
1819 Convert MTRR layout from continuous to discrete, so X drivers can
1820 add writeback entries.
1822 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1823 The largest mtrr entry size for a continuous block can be set with
1828 config MTRR_SANITIZER_ENABLE_DEFAULT
1829 int "MTRR cleanup enable value (0-1)"
1832 depends on MTRR_SANITIZER
1834 Enable mtrr cleanup default value
1836 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1837 int "MTRR cleanup spare reg num (0-7)"
1840 depends on MTRR_SANITIZER
1842 mtrr cleanup spare entries default, it can be changed via
1843 mtrr_spare_reg_nr=N on the kernel command line.
1847 prompt "x86 PAT support" if EXPERT
1850 Use PAT attributes to setup page level cache control.
1852 PATs are the modern equivalents of MTRRs and are much more
1853 flexible than MTRRs.
1855 Say N here if you see bootup problems (boot crash, boot hang,
1856 spontaneous reboots) or a non-working video driver.
1860 config ARCH_USES_PG_UNCACHED
1866 prompt "x86 architectural random number generator" if EXPERT
1868 Enable the x86 architectural RDRAND instruction
1869 (Intel Bull Mountain technology) to generate random numbers.
1870 If supported, this is a high bandwidth, cryptographically
1871 secure hardware random number generator.
1875 prompt "Supervisor Mode Access Prevention" if EXPERT
1877 Supervisor Mode Access Prevention (SMAP) is a security
1878 feature in newer Intel processors. There is a small
1879 performance cost if this enabled and turned on; there is
1880 also a small increase in the kernel size if this is enabled.
1884 config X86_INTEL_UMIP
1886 depends on CPU_SUP_INTEL
1887 prompt "Intel User Mode Instruction Prevention" if EXPERT
1889 The User Mode Instruction Prevention (UMIP) is a security
1890 feature in newer Intel processors. If enabled, a general
1891 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1892 or STR instructions are executed in user mode. These instructions
1893 unnecessarily expose information about the hardware state.
1895 The vast majority of applications do not use these instructions.
1896 For the very few that do, software emulation is provided in
1897 specific cases in protected and virtual-8086 modes. Emulated
1900 config X86_INTEL_MPX
1901 prompt "Intel MPX (Memory Protection Extensions)"
1903 # Note: only available in 64-bit mode due to VMA flags shortage
1904 depends on CPU_SUP_INTEL && X86_64
1905 select ARCH_USES_HIGH_VMA_FLAGS
1907 MPX provides hardware features that can be used in
1908 conjunction with compiler-instrumented code to check
1909 memory references. It is designed to detect buffer
1910 overflow or underflow bugs.
1912 This option enables running applications which are
1913 instrumented or otherwise use MPX. It does not use MPX
1914 itself inside the kernel or to protect the kernel
1915 against bad memory references.
1917 Enabling this option will make the kernel larger:
1918 ~8k of kernel text and 36 bytes of data on a 64-bit
1919 defconfig. It adds a long to the 'mm_struct' which
1920 will increase the kernel memory overhead of each
1921 process and adds some branches to paths used during
1922 exec() and munmap().
1924 For details, see Documentation/x86/intel_mpx.rst
1928 config X86_INTEL_MEMORY_PROTECTION_KEYS
1929 prompt "Intel Memory Protection Keys"
1931 # Note: only available in 64-bit mode
1932 depends on CPU_SUP_INTEL && X86_64
1933 select ARCH_USES_HIGH_VMA_FLAGS
1934 select ARCH_HAS_PKEYS
1936 Memory Protection Keys provides a mechanism for enforcing
1937 page-based protections, but without requiring modification of the
1938 page tables when an application changes protection domains.
1940 For details, see Documentation/core-api/protection-keys.rst
1945 bool "EFI runtime service support"
1948 select EFI_RUNTIME_WRAPPERS
1950 This enables the kernel to use EFI runtime services that are
1951 available (such as the EFI variable services).
1953 This option is only useful on systems that have EFI firmware.
1954 In addition, you should use the latest ELILO loader available
1955 at <http://elilo.sourceforge.net> in order to take advantage
1956 of EFI runtime services. However, even with this option, the
1957 resultant kernel should continue to boot on existing non-EFI
1961 bool "EFI stub support"
1962 depends on EFI && !X86_USE_3DNOW
1965 This kernel feature allows a bzImage to be loaded directly
1966 by EFI firmware without the use of a bootloader.
1968 See Documentation/admin-guide/efi-stub.rst for more information.
1971 bool "EFI mixed-mode support"
1972 depends on EFI_STUB && X86_64
1974 Enabling this feature allows a 64-bit kernel to be booted
1975 on a 32-bit firmware, provided that your CPU supports 64-bit
1978 Note that it is not possible to boot a mixed-mode enabled
1979 kernel via the EFI boot stub - a bootloader that supports
1980 the EFI handover protocol must be used.
1986 prompt "Enable seccomp to safely compute untrusted bytecode"
1988 This kernel feature is useful for number crunching applications
1989 that may need to compute untrusted bytecode during their
1990 execution. By using pipes or other transports made available to
1991 the process as file descriptors supporting the read/write
1992 syscalls, it's possible to isolate those applications in
1993 their own address space using seccomp. Once seccomp is
1994 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1995 and the task is only allowed to execute a few safe syscalls
1996 defined by each seccomp mode.
1998 If unsure, say Y. Only embedded should say N here.
2000 source "kernel/Kconfig.hz"
2003 bool "kexec system call"
2006 kexec is a system call that implements the ability to shutdown your
2007 current kernel, and to start another kernel. It is like a reboot
2008 but it is independent of the system firmware. And like a reboot
2009 you can start any kernel with it, not just Linux.
2011 The name comes from the similarity to the exec system call.
2013 It is an ongoing process to be certain the hardware in a machine
2014 is properly shutdown, so do not be surprised if this code does not
2015 initially work for you. As of this writing the exact hardware
2016 interface is strongly in flux, so no good recommendation can be
2020 bool "kexec file based system call"
2025 depends on CRYPTO_SHA256=y
2027 This is new version of kexec system call. This system call is
2028 file based and takes file descriptors as system call argument
2029 for kernel and initramfs as opposed to list of segments as
2030 accepted by previous system call.
2032 config ARCH_HAS_KEXEC_PURGATORY
2035 config KEXEC_VERIFY_SIG
2036 bool "Verify kernel signature during kexec_file_load() syscall"
2037 depends on KEXEC_FILE
2039 This option makes kernel signature verification mandatory for
2040 the kexec_file_load() syscall.
2042 In addition to that option, you need to enable signature
2043 verification for the corresponding kernel image type being
2044 loaded in order for this to work.
2046 config KEXEC_BZIMAGE_VERIFY_SIG
2047 bool "Enable bzImage signature verification support"
2048 depends on KEXEC_VERIFY_SIG
2049 depends on SIGNED_PE_FILE_VERIFICATION
2050 select SYSTEM_TRUSTED_KEYRING
2052 Enable bzImage signature verification support.
2055 bool "kernel crash dumps"
2056 depends on X86_64 || (X86_32 && HIGHMEM)
2058 Generate crash dump after being started by kexec.
2059 This should be normally only set in special crash dump kernels
2060 which are loaded in the main kernel with kexec-tools into
2061 a specially reserved region and then later executed after
2062 a crash by kdump/kexec. The crash dump kernel must be compiled
2063 to a memory address not used by the main kernel or BIOS using
2064 PHYSICAL_START, or it must be built as a relocatable image
2065 (CONFIG_RELOCATABLE=y).
2066 For more details see Documentation/admin-guide/kdump/kdump.rst
2070 depends on KEXEC && HIBERNATION
2072 Jump between original kernel and kexeced kernel and invoke
2073 code in physical address mode via KEXEC
2075 config PHYSICAL_START
2076 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2079 This gives the physical address where the kernel is loaded.
2081 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2082 bzImage will decompress itself to above physical address and
2083 run from there. Otherwise, bzImage will run from the address where
2084 it has been loaded by the boot loader and will ignore above physical
2087 In normal kdump cases one does not have to set/change this option
2088 as now bzImage can be compiled as a completely relocatable image
2089 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2090 address. This option is mainly useful for the folks who don't want
2091 to use a bzImage for capturing the crash dump and want to use a
2092 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2093 to be specifically compiled to run from a specific memory area
2094 (normally a reserved region) and this option comes handy.
2096 So if you are using bzImage for capturing the crash dump,
2097 leave the value here unchanged to 0x1000000 and set
2098 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2099 for capturing the crash dump change this value to start of
2100 the reserved region. In other words, it can be set based on
2101 the "X" value as specified in the "crashkernel=YM@XM"
2102 command line boot parameter passed to the panic-ed
2103 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2104 for more details about crash dumps.
2106 Usage of bzImage for capturing the crash dump is recommended as
2107 one does not have to build two kernels. Same kernel can be used
2108 as production kernel and capture kernel. Above option should have
2109 gone away after relocatable bzImage support is introduced. But it
2110 is present because there are users out there who continue to use
2111 vmlinux for dump capture. This option should go away down the
2114 Don't change this unless you know what you are doing.
2117 bool "Build a relocatable kernel"
2120 This builds a kernel image that retains relocation information
2121 so it can be loaded someplace besides the default 1MB.
2122 The relocations tend to make the kernel binary about 10% larger,
2123 but are discarded at runtime.
2125 One use is for the kexec on panic case where the recovery kernel
2126 must live at a different physical address than the primary
2129 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2130 it has been loaded at and the compile time physical address
2131 (CONFIG_PHYSICAL_START) is used as the minimum location.
2133 config RANDOMIZE_BASE
2134 bool "Randomize the address of the kernel image (KASLR)"
2135 depends on RELOCATABLE
2138 In support of Kernel Address Space Layout Randomization (KASLR),
2139 this randomizes the physical address at which the kernel image
2140 is decompressed and the virtual address where the kernel
2141 image is mapped, as a security feature that deters exploit
2142 attempts relying on knowledge of the location of kernel
2145 On 64-bit, the kernel physical and virtual addresses are
2146 randomized separately. The physical address will be anywhere
2147 between 16MB and the top of physical memory (up to 64TB). The
2148 virtual address will be randomized from 16MB up to 1GB (9 bits
2149 of entropy). Note that this also reduces the memory space
2150 available to kernel modules from 1.5GB to 1GB.
2152 On 32-bit, the kernel physical and virtual addresses are
2153 randomized together. They will be randomized from 16MB up to
2154 512MB (8 bits of entropy).
2156 Entropy is generated using the RDRAND instruction if it is
2157 supported. If RDTSC is supported, its value is mixed into
2158 the entropy pool as well. If neither RDRAND nor RDTSC are
2159 supported, then entropy is read from the i8254 timer. The
2160 usable entropy is limited by the kernel being built using
2161 2GB addressing, and that PHYSICAL_ALIGN must be at a
2162 minimum of 2MB. As a result, only 10 bits of entropy are
2163 theoretically possible, but the implementations are further
2164 limited due to memory layouts.
2168 # Relocation on x86 needs some additional build support
2169 config X86_NEED_RELOCS
2171 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2173 config PHYSICAL_ALIGN
2174 hex "Alignment value to which kernel should be aligned"
2176 range 0x2000 0x1000000 if X86_32
2177 range 0x200000 0x1000000 if X86_64
2179 This value puts the alignment restrictions on physical address
2180 where kernel is loaded and run from. Kernel is compiled for an
2181 address which meets above alignment restriction.
2183 If bootloader loads the kernel at a non-aligned address and
2184 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2185 address aligned to above value and run from there.
2187 If bootloader loads the kernel at a non-aligned address and
2188 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2189 load address and decompress itself to the address it has been
2190 compiled for and run from there. The address for which kernel is
2191 compiled already meets above alignment restrictions. Hence the
2192 end result is that kernel runs from a physical address meeting
2193 above alignment restrictions.
2195 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2196 this value must be a multiple of 0x200000.
2198 Don't change this unless you know what you are doing.
2200 config DYNAMIC_MEMORY_LAYOUT
2203 This option makes base addresses of vmalloc and vmemmap as well as
2204 __PAGE_OFFSET movable during boot.
2206 config RANDOMIZE_MEMORY
2207 bool "Randomize the kernel memory sections"
2209 depends on RANDOMIZE_BASE
2210 select DYNAMIC_MEMORY_LAYOUT
2211 default RANDOMIZE_BASE
2213 Randomizes the base virtual address of kernel memory sections
2214 (physical memory mapping, vmalloc & vmemmap). This security feature
2215 makes exploits relying on predictable memory locations less reliable.
2217 The order of allocations remains unchanged. Entropy is generated in
2218 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2219 configuration have in average 30,000 different possible virtual
2220 addresses for each memory section.
2224 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2225 hex "Physical memory mapping padding" if EXPERT
2226 depends on RANDOMIZE_MEMORY
2227 default "0xa" if MEMORY_HOTPLUG
2229 range 0x1 0x40 if MEMORY_HOTPLUG
2232 Define the padding in terabytes added to the existing physical
2233 memory size during kernel memory randomization. It is useful
2234 for memory hotplug support but reduces the entropy available for
2235 address randomization.
2237 If unsure, leave at the default value.
2243 config BOOTPARAM_HOTPLUG_CPU0
2244 bool "Set default setting of cpu0_hotpluggable"
2245 depends on HOTPLUG_CPU
2247 Set whether default state of cpu0_hotpluggable is on or off.
2249 Say Y here to enable CPU0 hotplug by default. If this switch
2250 is turned on, there is no need to give cpu0_hotplug kernel
2251 parameter and the CPU0 hotplug feature is enabled by default.
2253 Please note: there are two known CPU0 dependencies if you want
2254 to enable the CPU0 hotplug feature either by this switch or by
2255 cpu0_hotplug kernel parameter.
2257 First, resume from hibernate or suspend always starts from CPU0.
2258 So hibernate and suspend are prevented if CPU0 is offline.
2260 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2261 offline if any interrupt can not migrate out of CPU0. There may
2262 be other CPU0 dependencies.
2264 Please make sure the dependencies are under your control before
2265 you enable this feature.
2267 Say N if you don't want to enable CPU0 hotplug feature by default.
2268 You still can enable the CPU0 hotplug feature at boot by kernel
2269 parameter cpu0_hotplug.
2271 config DEBUG_HOTPLUG_CPU0
2273 prompt "Debug CPU0 hotplug"
2274 depends on HOTPLUG_CPU
2276 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2277 soon as possible and boots up userspace with CPU0 offlined. User
2278 can online CPU0 back after boot time.
2280 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2281 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2282 compilation or giving cpu0_hotplug kernel parameter at boot.
2288 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2289 depends on COMPAT_32
2291 Certain buggy versions of glibc will crash if they are
2292 presented with a 32-bit vDSO that is not mapped at the address
2293 indicated in its segment table.
2295 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2296 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2297 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2298 the only released version with the bug, but OpenSUSE 9
2299 contains a buggy "glibc 2.3.2".
2301 The symptom of the bug is that everything crashes on startup, saying:
2302 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2304 Saying Y here changes the default value of the vdso32 boot
2305 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2306 This works around the glibc bug but hurts performance.
2308 If unsure, say N: if you are compiling your own kernel, you
2309 are unlikely to be using a buggy version of glibc.
2312 prompt "vsyscall table for legacy applications"
2314 default LEGACY_VSYSCALL_XONLY
2316 Legacy user code that does not know how to find the vDSO expects
2317 to be able to issue three syscalls by calling fixed addresses in
2318 kernel space. Since this location is not randomized with ASLR,
2319 it can be used to assist security vulnerability exploitation.
2321 This setting can be changed at boot time via the kernel command
2322 line parameter vsyscall=[emulate|xonly|none].
2324 On a system with recent enough glibc (2.14 or newer) and no
2325 static binaries, you can say None without a performance penalty
2326 to improve security.
2328 If unsure, select "Emulate execution only".
2330 config LEGACY_VSYSCALL_EMULATE
2331 bool "Full emulation"
2333 The kernel traps and emulates calls into the fixed vsyscall
2334 address mapping. This makes the mapping non-executable, but
2335 it still contains readable known contents, which could be
2336 used in certain rare security vulnerability exploits. This
2337 configuration is recommended when using legacy userspace
2338 that still uses vsyscalls along with legacy binary
2339 instrumentation tools that require code to be readable.
2341 An example of this type of legacy userspace is running
2342 Pin on an old binary that still uses vsyscalls.
2344 config LEGACY_VSYSCALL_XONLY
2345 bool "Emulate execution only"
2347 The kernel traps and emulates calls into the fixed vsyscall
2348 address mapping and does not allow reads. This
2349 configuration is recommended when userspace might use the
2350 legacy vsyscall area but support for legacy binary
2351 instrumentation of legacy code is not needed. It mitigates
2352 certain uses of the vsyscall area as an ASLR-bypassing
2355 config LEGACY_VSYSCALL_NONE
2358 There will be no vsyscall mapping at all. This will
2359 eliminate any risk of ASLR bypass due to the vsyscall
2360 fixed address mapping. Attempts to use the vsyscalls
2361 will be reported to dmesg, so that either old or
2362 malicious userspace programs can be identified.
2367 bool "Built-in kernel command line"
2369 Allow for specifying boot arguments to the kernel at
2370 build time. On some systems (e.g. embedded ones), it is
2371 necessary or convenient to provide some or all of the
2372 kernel boot arguments with the kernel itself (that is,
2373 to not rely on the boot loader to provide them.)
2375 To compile command line arguments into the kernel,
2376 set this option to 'Y', then fill in the
2377 boot arguments in CONFIG_CMDLINE.
2379 Systems with fully functional boot loaders (i.e. non-embedded)
2380 should leave this option set to 'N'.
2383 string "Built-in kernel command string"
2384 depends on CMDLINE_BOOL
2387 Enter arguments here that should be compiled into the kernel
2388 image and used at boot time. If the boot loader provides a
2389 command line at boot time, it is appended to this string to
2390 form the full kernel command line, when the system boots.
2392 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2393 change this behavior.
2395 In most cases, the command line (whether built-in or provided
2396 by the boot loader) should specify the device for the root
2399 config CMDLINE_OVERRIDE
2400 bool "Built-in command line overrides boot loader arguments"
2401 depends on CMDLINE_BOOL
2403 Set this option to 'Y' to have the kernel ignore the boot loader
2404 command line, and use ONLY the built-in command line.
2406 This is used to work around broken boot loaders. This should
2407 be set to 'N' under normal conditions.
2409 config MODIFY_LDT_SYSCALL
2410 bool "Enable the LDT (local descriptor table)" if EXPERT
2413 Linux can allow user programs to install a per-process x86
2414 Local Descriptor Table (LDT) using the modify_ldt(2) system
2415 call. This is required to run 16-bit or segmented code such as
2416 DOSEMU or some Wine programs. It is also used by some very old
2417 threading libraries.
2419 Enabling this feature adds a small amount of overhead to
2420 context switches and increases the low-level kernel attack
2421 surface. Disabling it removes the modify_ldt(2) system call.
2423 Saying 'N' here may make sense for embedded or server kernels.
2425 source "kernel/livepatch/Kconfig"
2429 config ARCH_HAS_ADD_PAGES
2431 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2433 config ARCH_ENABLE_MEMORY_HOTPLUG
2435 depends on X86_64 || (X86_32 && HIGHMEM)
2437 config ARCH_ENABLE_MEMORY_HOTREMOVE
2439 depends on MEMORY_HOTPLUG
2441 config USE_PERCPU_NUMA_NODE_ID
2445 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2447 depends on X86_64 || X86_PAE
2449 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2451 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2453 config ARCH_ENABLE_THP_MIGRATION
2455 depends on X86_64 && TRANSPARENT_HUGEPAGE
2457 menu "Power management and ACPI options"
2459 config ARCH_HIBERNATION_HEADER
2461 depends on HIBERNATION
2463 source "kernel/power/Kconfig"
2465 source "drivers/acpi/Kconfig"
2467 source "drivers/sfi/Kconfig"
2474 tristate "APM (Advanced Power Management) BIOS support"
2475 depends on X86_32 && PM_SLEEP
2477 APM is a BIOS specification for saving power using several different
2478 techniques. This is mostly useful for battery powered laptops with
2479 APM compliant BIOSes. If you say Y here, the system time will be
2480 reset after a RESUME operation, the /proc/apm device will provide
2481 battery status information, and user-space programs will receive
2482 notification of APM "events" (e.g. battery status change).
2484 If you select "Y" here, you can disable actual use of the APM
2485 BIOS by passing the "apm=off" option to the kernel at boot time.
2487 Note that the APM support is almost completely disabled for
2488 machines with more than one CPU.
2490 In order to use APM, you will need supporting software. For location
2491 and more information, read <file:Documentation/power/apm-acpi.rst>
2492 and the Battery Powered Linux mini-HOWTO, available from
2493 <http://www.tldp.org/docs.html#howto>.
2495 This driver does not spin down disk drives (see the hdparm(8)
2496 manpage ("man 8 hdparm") for that), and it doesn't turn off
2497 VESA-compliant "green" monitors.
2499 This driver does not support the TI 4000M TravelMate and the ACER
2500 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2501 desktop machines also don't have compliant BIOSes, and this driver
2502 may cause those machines to panic during the boot phase.
2504 Generally, if you don't have a battery in your machine, there isn't
2505 much point in using this driver and you should say N. If you get
2506 random kernel OOPSes or reboots that don't seem to be related to
2507 anything, try disabling/enabling this option (or disabling/enabling
2510 Some other things you should try when experiencing seemingly random,
2513 1) make sure that you have enough swap space and that it is
2515 2) pass the "no-hlt" option to the kernel
2516 3) switch on floating point emulation in the kernel and pass
2517 the "no387" option to the kernel
2518 4) pass the "floppy=nodma" option to the kernel
2519 5) pass the "mem=4M" option to the kernel (thereby disabling
2520 all but the first 4 MB of RAM)
2521 6) make sure that the CPU is not over clocked.
2522 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2523 8) disable the cache from your BIOS settings
2524 9) install a fan for the video card or exchange video RAM
2525 10) install a better fan for the CPU
2526 11) exchange RAM chips
2527 12) exchange the motherboard.
2529 To compile this driver as a module, choose M here: the
2530 module will be called apm.
2534 config APM_IGNORE_USER_SUSPEND
2535 bool "Ignore USER SUSPEND"
2537 This option will ignore USER SUSPEND requests. On machines with a
2538 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2539 series notebooks, it is necessary to say Y because of a BIOS bug.
2541 config APM_DO_ENABLE
2542 bool "Enable PM at boot time"
2544 Enable APM features at boot time. From page 36 of the APM BIOS
2545 specification: "When disabled, the APM BIOS does not automatically
2546 power manage devices, enter the Standby State, enter the Suspend
2547 State, or take power saving steps in response to CPU Idle calls."
2548 This driver will make CPU Idle calls when Linux is idle (unless this
2549 feature is turned off -- see "Do CPU IDLE calls", below). This
2550 should always save battery power, but more complicated APM features
2551 will be dependent on your BIOS implementation. You may need to turn
2552 this option off if your computer hangs at boot time when using APM
2553 support, or if it beeps continuously instead of suspending. Turn
2554 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2555 T400CDT. This is off by default since most machines do fine without
2560 bool "Make CPU Idle calls when idle"
2562 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2563 On some machines, this can activate improved power savings, such as
2564 a slowed CPU clock rate, when the machine is idle. These idle calls
2565 are made after the idle loop has run for some length of time (e.g.,
2566 333 mS). On some machines, this will cause a hang at boot time or
2567 whenever the CPU becomes idle. (On machines with more than one CPU,
2568 this option does nothing.)
2570 config APM_DISPLAY_BLANK
2571 bool "Enable console blanking using APM"
2573 Enable console blanking using the APM. Some laptops can use this to
2574 turn off the LCD backlight when the screen blanker of the Linux
2575 virtual console blanks the screen. Note that this is only used by
2576 the virtual console screen blanker, and won't turn off the backlight
2577 when using the X Window system. This also doesn't have anything to
2578 do with your VESA-compliant power-saving monitor. Further, this
2579 option doesn't work for all laptops -- it might not turn off your
2580 backlight at all, or it might print a lot of errors to the console,
2581 especially if you are using gpm.
2583 config APM_ALLOW_INTS
2584 bool "Allow interrupts during APM BIOS calls"
2586 Normally we disable external interrupts while we are making calls to
2587 the APM BIOS as a measure to lessen the effects of a badly behaving
2588 BIOS implementation. The BIOS should reenable interrupts if it
2589 needs to. Unfortunately, some BIOSes do not -- especially those in
2590 many of the newer IBM Thinkpads. If you experience hangs when you
2591 suspend, try setting this to Y. Otherwise, say N.
2595 source "drivers/cpufreq/Kconfig"
2597 source "drivers/cpuidle/Kconfig"
2599 source "drivers/idle/Kconfig"
2604 menu "Bus options (PCI etc.)"
2607 prompt "PCI access mode"
2608 depends on X86_32 && PCI
2611 On PCI systems, the BIOS can be used to detect the PCI devices and
2612 determine their configuration. However, some old PCI motherboards
2613 have BIOS bugs and may crash if this is done. Also, some embedded
2614 PCI-based systems don't have any BIOS at all. Linux can also try to
2615 detect the PCI hardware directly without using the BIOS.
2617 With this option, you can specify how Linux should detect the
2618 PCI devices. If you choose "BIOS", the BIOS will be used,
2619 if you choose "Direct", the BIOS won't be used, and if you
2620 choose "MMConfig", then PCI Express MMCONFIG will be used.
2621 If you choose "Any", the kernel will try MMCONFIG, then the
2622 direct access method and falls back to the BIOS if that doesn't
2623 work. If unsure, go with the default, which is "Any".
2628 config PCI_GOMMCONFIG
2645 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2647 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2650 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2653 bool "Support mmconfig PCI config space access" if X86_64
2655 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2656 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2660 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2664 depends on PCI && XEN
2667 config MMCONF_FAM10H
2669 depends on X86_64 && PCI_MMCONFIG && ACPI
2671 config PCI_CNB20LE_QUIRK
2672 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2675 Read the PCI windows out of the CNB20LE host bridge. This allows
2676 PCI hotplug to work on systems with the CNB20LE chipset which do
2679 There's no public spec for this chipset, and this functionality
2680 is known to be incomplete.
2682 You should say N unless you know you need this.
2685 bool "ISA bus support on modern systems" if EXPERT
2687 Expose ISA bus device drivers and options available for selection and
2688 configuration. Enable this option if your target machine has an ISA
2689 bus. ISA is an older system, displaced by PCI and newer bus
2690 architectures -- if your target machine is modern, it probably does
2691 not have an ISA bus.
2695 # x86_64 have no ISA slots, but can have ISA-style DMA.
2697 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2700 Enables ISA-style DMA support for devices requiring such controllers.
2708 Find out whether you have ISA slots on your motherboard. ISA is the
2709 name of a bus system, i.e. the way the CPU talks to the other stuff
2710 inside your box. Other bus systems are PCI, EISA, MicroChannel
2711 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2712 newer boards don't support it. If you have ISA, say Y, otherwise N.
2715 tristate "NatSemi SCx200 support"
2717 This provides basic support for National Semiconductor's
2718 (now AMD's) Geode processors. The driver probes for the
2719 PCI-IDs of several on-chip devices, so its a good dependency
2720 for other scx200_* drivers.
2722 If compiled as a module, the driver is named scx200.
2724 config SCx200HR_TIMER
2725 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2729 This driver provides a clocksource built upon the on-chip
2730 27MHz high-resolution timer. Its also a workaround for
2731 NSC Geode SC-1100's buggy TSC, which loses time when the
2732 processor goes idle (as is done by the scheduler). The
2733 other workaround is idle=poll boot option.
2736 bool "One Laptop Per Child support"
2744 Add support for detecting the unique features of the OLPC
2748 bool "OLPC XO-1 Power Management"
2749 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2751 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2754 bool "OLPC XO-1 Real Time Clock"
2755 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2757 Add support for the XO-1 real time clock, which can be used as a
2758 programmable wakeup source.
2761 bool "OLPC XO-1 SCI extras"
2762 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2766 Add support for SCI-based features of the OLPC XO-1 laptop:
2767 - EC-driven system wakeups
2771 - AC adapter status updates
2772 - Battery status updates
2774 config OLPC_XO15_SCI
2775 bool "OLPC XO-1.5 SCI extras"
2776 depends on OLPC && ACPI
2779 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2780 - EC-driven system wakeups
2781 - AC adapter status updates
2782 - Battery status updates
2785 bool "PCEngines ALIX System Support (LED setup)"
2788 This option enables system support for the PCEngines ALIX.
2789 At present this just sets up LEDs for GPIO control on
2790 ALIX2/3/6 boards. However, other system specific setup should
2793 Note: You must still enable the drivers for GPIO and LED support
2794 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2796 Note: You have to set alix.force=1 for boards with Award BIOS.
2799 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2802 This option enables system support for the Soekris Engineering net5501.
2805 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2809 This option enables system support for the Traverse Technologies GEOS.
2812 bool "Technologic Systems TS-5500 platform support"
2814 select CHECK_SIGNATURE
2818 This option enables system support for the Technologic Systems TS-5500.
2824 depends on CPU_SUP_AMD && PCI
2827 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2829 Firmwares often provide initial graphics framebuffers so the BIOS,
2830 bootloader or kernel can show basic video-output during boot for
2831 user-guidance and debugging. Historically, x86 used the VESA BIOS
2832 Extensions and EFI-framebuffers for this, which are mostly limited
2834 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2835 framebuffers so the new generic system-framebuffer drivers can be
2836 used on x86. If the framebuffer is not compatible with the generic
2837 modes, it is advertised as fallback platform framebuffer so legacy
2838 drivers like efifb, vesafb and uvesafb can pick it up.
2839 If this option is not selected, all system framebuffers are always
2840 marked as fallback platform framebuffers as usual.
2842 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2843 not be able to pick up generic system framebuffers if this option
2844 is selected. You are highly encouraged to enable simplefb as
2845 replacement if you select this option. simplefb can correctly deal
2846 with generic system framebuffers. But you should still keep vesafb
2847 and others enabled as fallback if a system framebuffer is
2848 incompatible with simplefb.
2855 menu "Binary Emulations"
2857 config IA32_EMULATION
2858 bool "IA32 Emulation"
2860 select ARCH_WANT_OLD_COMPAT_IPC
2862 select COMPAT_BINFMT_ELF
2863 select COMPAT_OLD_SIGACTION
2865 Include code to run legacy 32-bit programs under a
2866 64-bit kernel. You should likely turn this on, unless you're
2867 100% sure that you don't have any 32-bit programs left.
2870 tristate "IA32 a.out support"
2871 depends on IA32_EMULATION
2874 Support old a.out binaries in the 32bit emulation.
2877 bool "x32 ABI for 64-bit mode"
2880 Include code to run binaries for the x32 native 32-bit ABI
2881 for 64-bit processors. An x32 process gets access to the
2882 full 64-bit register file and wide data path while leaving
2883 pointers at 32 bits for smaller memory footprint.
2885 You will need a recent binutils (2.22 or later) with
2886 elf32_x86_64 support enabled to compile a kernel with this
2891 depends on IA32_EMULATION || X86_32
2893 select OLD_SIGSUSPEND3
2897 depends on IA32_EMULATION || X86_X32
2900 config COMPAT_FOR_U64_ALIGNMENT
2903 config SYSVIPC_COMPAT
2911 config HAVE_ATOMIC_IOMAP
2915 config X86_DEV_DMA_OPS
2918 source "drivers/firmware/Kconfig"
2920 source "arch/x86/kvm/Kconfig"