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
33 select ARCH_HAS_SYSCALL_WRAPPER
35 config FORCE_DYNAMIC_FTRACE
38 depends on FUNCTION_TRACER
41 We keep the static function tracing (!DYNAMIC_FTRACE) around
42 in order to test the non static function tracing in the
43 generic code, as other architectures still use it. But we
44 only need to keep it around for x86_64. No need to keep it
45 for x86_32. For x86_32, force DYNAMIC_FTRACE.
49 # ( Note that options that are marked 'if X86_64' could in principle be
50 # ported to 32-bit as well. )
55 # Note: keep this list sorted alphabetically
57 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
58 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
59 select ARCH_32BIT_OFF_T if X86_32
60 select ARCH_CLOCKSOURCE_DATA
61 select ARCH_CLOCKSOURCE_INIT
62 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
63 select ARCH_HAS_DEBUG_VIRTUAL
64 select ARCH_HAS_DEVMEM_IS_ALLOWED
65 select ARCH_HAS_ELF_RANDOMIZE
66 select ARCH_HAS_FAST_MULTIPLIER
67 select ARCH_HAS_FILTER_PGPROT
68 select ARCH_HAS_FORTIFY_SOURCE
69 select ARCH_HAS_GCOV_PROFILE_ALL
70 select ARCH_HAS_KCOV if X86_64
71 select ARCH_HAS_MEM_ENCRYPT
72 select ARCH_HAS_MEMBARRIER_SYNC_CORE
73 select ARCH_HAS_PMEM_API if X86_64
74 select ARCH_HAS_PTE_DEVMAP if X86_64
75 select ARCH_HAS_PTE_SPECIAL
76 select ARCH_HAS_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 GENERIC_VDSO_TIME_NS
128 select GUP_GET_PTE_LOW_HIGH if X86_PAE
129 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
130 select HAVE_ACPI_APEI if ACPI
131 select HAVE_ACPI_APEI_NMI if ACPI
132 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
133 select HAVE_ARCH_AUDITSYSCALL
134 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
135 select HAVE_ARCH_JUMP_LABEL
136 select HAVE_ARCH_JUMP_LABEL_RELATIVE
137 select HAVE_ARCH_KASAN if X86_64
138 select HAVE_ARCH_KASAN_VMALLOC if X86_64
139 select HAVE_ARCH_KGDB
140 select HAVE_ARCH_MMAP_RND_BITS if MMU
141 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
142 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
143 select HAVE_ARCH_PREL32_RELOCATIONS
144 select HAVE_ARCH_SECCOMP_FILTER
145 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
146 select HAVE_ARCH_STACKLEAK
147 select HAVE_ARCH_TRACEHOOK
148 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
149 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
150 select HAVE_ARCH_VMAP_STACK if X86_64
151 select HAVE_ARCH_WITHIN_STACK_FRAMES
152 select HAVE_ASM_MODVERSIONS
153 select HAVE_CMPXCHG_DOUBLE
154 select HAVE_CMPXCHG_LOCAL
155 select HAVE_CONTEXT_TRACKING if X86_64
156 select HAVE_COPY_THREAD_TLS
157 select HAVE_C_RECORDMCOUNT
158 select HAVE_DEBUG_KMEMLEAK
159 select HAVE_DMA_CONTIGUOUS
160 select HAVE_DYNAMIC_FTRACE
161 select HAVE_DYNAMIC_FTRACE_WITH_REGS
162 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
164 select HAVE_EFFICIENT_UNALIGNED_ACCESS
166 select HAVE_EXIT_THREAD
168 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
169 select HAVE_FTRACE_MCOUNT_RECORD
170 select HAVE_FUNCTION_GRAPH_TRACER
171 select HAVE_FUNCTION_TRACER
172 select HAVE_GCC_PLUGINS
173 select HAVE_HW_BREAKPOINT
175 select HAVE_IOREMAP_PROT
176 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
177 select HAVE_IRQ_TIME_ACCOUNTING
178 select HAVE_KERNEL_BZIP2
179 select HAVE_KERNEL_GZIP
180 select HAVE_KERNEL_LZ4
181 select HAVE_KERNEL_LZMA
182 select HAVE_KERNEL_LZO
183 select HAVE_KERNEL_XZ
185 select HAVE_KPROBES_ON_FTRACE
186 select HAVE_FUNCTION_ERROR_INJECTION
187 select HAVE_KRETPROBES
189 select HAVE_LIVEPATCH if X86_64
190 select HAVE_MEMBLOCK_NODE_MAP
191 select HAVE_MIXED_BREAKPOINTS_REGS
192 select HAVE_MOD_ARCH_SPECIFIC
196 select HAVE_OPTPROBES
197 select HAVE_PCSPKR_PLATFORM
198 select HAVE_PERF_EVENTS
199 select HAVE_PERF_EVENTS_NMI
200 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
202 select HAVE_PERF_REGS
203 select HAVE_PERF_USER_STACK_DUMP
204 select HAVE_RCU_TABLE_FREE if PARAVIRT
205 select HAVE_REGS_AND_STACK_ACCESS_API
206 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
207 select HAVE_FUNCTION_ARG_ACCESS_API
208 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
209 select HAVE_STACK_VALIDATION if X86_64
211 select HAVE_SYSCALL_TRACEPOINTS
212 select HAVE_UNSTABLE_SCHED_CLOCK
213 select HAVE_USER_RETURN_NOTIFIER
214 select HAVE_GENERIC_VDSO
215 select HOTPLUG_SMT if SMP
216 select IRQ_FORCED_THREADING
217 select NEED_SG_DMA_LENGTH
218 select PCI_DOMAINS if PCI
219 select PCI_LOCKLESS_CONFIG if PCI
222 select RTC_MC146818_LIB
225 select SYSCTL_EXCEPTION_TRACE
226 select THREAD_INFO_IN_TASK
227 select USER_STACKTRACE_SUPPORT
229 select X86_FEATURE_NAMES if PROC_FS
230 select PROC_PID_ARCH_STATUS if PROC_FS
232 config INSTRUCTION_DECODER
234 depends on KPROBES || PERF_EVENTS || UPROBES
238 default "elf32-i386" if X86_32
239 default "elf64-x86-64" if X86_64
241 config ARCH_DEFCONFIG
243 default "arch/x86/configs/i386_defconfig" if X86_32
244 default "arch/x86/configs/x86_64_defconfig" if X86_64
246 config LOCKDEP_SUPPORT
249 config STACKTRACE_SUPPORT
255 config ARCH_MMAP_RND_BITS_MIN
259 config ARCH_MMAP_RND_BITS_MAX
263 config ARCH_MMAP_RND_COMPAT_BITS_MIN
266 config ARCH_MMAP_RND_COMPAT_BITS_MAX
272 config GENERIC_ISA_DMA
274 depends on ISA_DMA_API
279 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
281 config GENERIC_BUG_RELATIVE_POINTERS
284 config ARCH_MAY_HAVE_PC_FDC
286 depends on ISA_DMA_API
288 config GENERIC_CALIBRATE_DELAY
291 config ARCH_HAS_CPU_RELAX
294 config ARCH_HAS_CACHE_LINE_SIZE
297 config ARCH_HAS_FILTER_PGPROT
300 config HAVE_SETUP_PER_CPU_AREA
303 config NEED_PER_CPU_EMBED_FIRST_CHUNK
306 config NEED_PER_CPU_PAGE_FIRST_CHUNK
309 config ARCH_HIBERNATION_POSSIBLE
312 config ARCH_SUSPEND_POSSIBLE
315 config ARCH_WANT_GENERAL_HUGETLB
324 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
327 config KASAN_SHADOW_OFFSET
330 default 0xdffffc0000000000
332 config HAVE_INTEL_TXT
334 depends on INTEL_IOMMU && ACPI
338 depends on X86_32 && SMP
342 depends on X86_64 && SMP
344 config X86_32_LAZY_GS
346 depends on X86_32 && !STACKPROTECTOR
348 config ARCH_SUPPORTS_UPROBES
351 config FIX_EARLYCON_MEM
354 config DYNAMIC_PHYSICAL_MASK
357 config PGTABLE_LEVELS
359 default 5 if X86_5LEVEL
364 config CC_HAS_SANE_STACKPROTECTOR
366 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
367 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
369 We have to make sure stack protector is unconditionally disabled if
370 the compiler produces broken code.
372 menu "Processor type and features"
375 bool "DMA memory allocation support" if EXPERT
378 DMA memory allocation support allows devices with less than 32-bit
379 addressing to allocate within the first 16MB of address space.
380 Disable if no such devices will be used.
385 bool "Symmetric multi-processing support"
387 This enables support for systems with more than one CPU. If you have
388 a system with only one CPU, say N. If you have a system with more
391 If you say N here, the kernel will run on uni- and multiprocessor
392 machines, but will use only one CPU of a multiprocessor machine. If
393 you say Y here, the kernel will run on many, but not all,
394 uniprocessor machines. On a uniprocessor machine, the kernel
395 will run faster if you say N here.
397 Note that if you say Y here and choose architecture "586" or
398 "Pentium" under "Processor family", the kernel will not work on 486
399 architectures. Similarly, multiprocessor kernels for the "PPro"
400 architecture may not work on all Pentium based boards.
402 People using multiprocessor machines who say Y here should also say
403 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
404 Management" code will be disabled if you say Y here.
406 See also <file:Documentation/x86/i386/IO-APIC.rst>,
407 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
408 <http://www.tldp.org/docs.html#howto>.
410 If you don't know what to do here, say N.
412 config X86_FEATURE_NAMES
413 bool "Processor feature human-readable names" if EMBEDDED
416 This option compiles in a table of x86 feature bits and corresponding
417 names. This is required to support /proc/cpuinfo and a few kernel
418 messages. You can disable this to save space, at the expense of
419 making those few kernel messages show numeric feature bits instead.
424 bool "Support x2apic"
425 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
427 This enables x2apic support on CPUs that have this feature.
429 This allows 32-bit apic IDs (so it can support very large systems),
430 and accesses the local apic via MSRs not via mmio.
432 If you don't know what to do here, say N.
435 bool "Enable MPS table" if ACPI || SFI
437 depends on X86_LOCAL_APIC
439 For old smp systems that do not have proper acpi support. Newer systems
440 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
444 depends on X86_GOLDFISH
447 bool "Avoid speculative indirect branches in kernel"
449 select STACK_VALIDATION if HAVE_STACK_VALIDATION
451 Compile kernel with the retpoline compiler options to guard against
452 kernel-to-user data leaks by avoiding speculative indirect
453 branches. Requires a compiler with -mindirect-branch=thunk-extern
454 support for full protection. The kernel may run slower.
456 config X86_CPU_RESCTRL
457 bool "x86 CPU resource control support"
458 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
461 Enable x86 CPU resource control support.
463 Provide support for the allocation and monitoring of system resources
466 Intel calls this Intel Resource Director Technology
467 (Intel(R) RDT). More information about RDT can be found in the
468 Intel x86 Architecture Software Developer Manual.
470 AMD calls this AMD Platform Quality of Service (AMD QoS).
471 More information about AMD QoS can be found in the AMD64 Technology
472 Platform Quality of Service Extensions manual.
478 bool "Support for big SMP systems with more than 8 CPUs"
481 This option is needed for the systems that have more than 8 CPUs
483 config X86_EXTENDED_PLATFORM
484 bool "Support for extended (non-PC) x86 platforms"
487 If you disable this option then the kernel will only support
488 standard PC platforms. (which covers the vast majority of
491 If you enable this option then you'll be able to select support
492 for the following (non-PC) 32 bit x86 platforms:
493 Goldfish (Android emulator)
496 SGI 320/540 (Visual Workstation)
497 STA2X11-based (e.g. Northville)
498 Moorestown MID devices
500 If you have one of these systems, or if you want to build a
501 generic distribution kernel, say Y here - otherwise say N.
505 config X86_EXTENDED_PLATFORM
506 bool "Support for extended (non-PC) x86 platforms"
509 If you disable this option then the kernel will only support
510 standard PC platforms. (which covers the vast majority of
513 If you enable this option then you'll be able to select support
514 for the following (non-PC) 64 bit x86 platforms:
519 If you have one of these systems, or if you want to build a
520 generic distribution kernel, say Y here - otherwise say N.
522 # This is an alphabetically sorted list of 64 bit extended platforms
523 # Please maintain the alphabetic order if and when there are additions
525 bool "Numascale NumaChip"
527 depends on X86_EXTENDED_PLATFORM
530 depends on X86_X2APIC
531 depends on PCI_MMCONFIG
533 Adds support for Numascale NumaChip large-SMP systems. Needed to
534 enable more than ~168 cores.
535 If you don't have one of these, you should say N here.
539 select HYPERVISOR_GUEST
541 depends on X86_64 && PCI
542 depends on X86_EXTENDED_PLATFORM
545 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
546 supposed to run on these EM64T-based machines. Only choose this option
547 if you have one of these machines.
550 bool "SGI Ultraviolet"
552 depends on X86_EXTENDED_PLATFORM
555 depends on X86_X2APIC
558 This option is needed in order to support SGI Ultraviolet systems.
559 If you don't have one of these, you should say N here.
561 # Following is an alphabetically sorted list of 32 bit extended platforms
562 # Please maintain the alphabetic order if and when there are additions
565 bool "Goldfish (Virtual Platform)"
566 depends on X86_EXTENDED_PLATFORM
568 Enable support for the Goldfish virtual platform used primarily
569 for Android development. Unless you are building for the Android
570 Goldfish emulator say N here.
573 bool "CE4100 TV platform"
575 depends on PCI_GODIRECT
576 depends on X86_IO_APIC
578 depends on X86_EXTENDED_PLATFORM
579 select X86_REBOOTFIXUPS
581 select OF_EARLY_FLATTREE
583 Select for the Intel CE media processor (CE4100) SOC.
584 This option compiles in support for the CE4100 SOC for settop
585 boxes and media devices.
588 bool "Intel MID platform support"
589 depends on X86_EXTENDED_PLATFORM
590 depends on X86_PLATFORM_DEVICES
592 depends on X86_64 || (PCI_GOANY && X86_32)
593 depends on X86_IO_APIC
599 select MFD_INTEL_MSIC
601 Select to build a kernel capable of supporting Intel MID (Mobile
602 Internet Device) platform systems which do not have the PCI legacy
603 interfaces. If you are building for a PC class system say N here.
605 Intel MID platforms are based on an Intel processor and chipset which
606 consume less power than most of the x86 derivatives.
608 config X86_INTEL_QUARK
609 bool "Intel Quark platform support"
611 depends on X86_EXTENDED_PLATFORM
612 depends on X86_PLATFORM_DEVICES
616 depends on X86_IO_APIC
621 Select to include support for Quark X1000 SoC.
622 Say Y here if you have a Quark based system such as the Arduino
623 compatible Intel Galileo.
625 config X86_INTEL_LPSS
626 bool "Intel Low Power Subsystem Support"
627 depends on X86 && ACPI && PCI
632 Select to build support for Intel Low Power Subsystem such as
633 found on Intel Lynxpoint PCH. Selecting this option enables
634 things like clock tree (common clock framework) and pincontrol
635 which are needed by the LPSS peripheral drivers.
637 config X86_AMD_PLATFORM_DEVICE
638 bool "AMD ACPI2Platform devices support"
643 Select to interpret AMD specific ACPI device to platform device
644 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
645 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
646 implemented under PINCTRL subsystem.
649 tristate "Intel SoC IOSF Sideband support for SoC platforms"
652 This option enables sideband register access support for Intel SoC
653 platforms. On these platforms the IOSF sideband is used in lieu of
654 MSR's for some register accesses, mostly but not limited to thermal
655 and power. Drivers may query the availability of this device to
656 determine if they need the sideband in order to work on these
657 platforms. The sideband is available on the following SoC products.
658 This list is not meant to be exclusive.
663 You should say Y if you are running a kernel on one of these SoC's.
665 config IOSF_MBI_DEBUG
666 bool "Enable IOSF sideband access through debugfs"
667 depends on IOSF_MBI && DEBUG_FS
669 Select this option to expose the IOSF sideband access registers (MCR,
670 MDR, MCRX) through debugfs to write and read register information from
671 different units on the SoC. This is most useful for obtaining device
672 state information for debug and analysis. As this is a general access
673 mechanism, users of this option would have specific knowledge of the
674 device they want to access.
676 If you don't require the option or are in doubt, say N.
679 bool "RDC R-321x SoC"
681 depends on X86_EXTENDED_PLATFORM
683 select X86_REBOOTFIXUPS
685 This option is needed for RDC R-321x system-on-chip, also known
687 If you don't have one of these chips, you should say N here.
689 config X86_32_NON_STANDARD
690 bool "Support non-standard 32-bit SMP architectures"
691 depends on X86_32 && SMP
692 depends on X86_EXTENDED_PLATFORM
694 This option compiles in the bigsmp and STA2X11 default
695 subarchitectures. It is intended for a generic binary
696 kernel. If you select them all, kernel will probe it one by
697 one and will fallback to default.
699 # Alphabetically sorted list of Non standard 32 bit platforms
701 config X86_SUPPORTS_MEMORY_FAILURE
703 # MCE code calls memory_failure():
705 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
706 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
707 depends on X86_64 || !SPARSEMEM
708 select ARCH_SUPPORTS_MEMORY_FAILURE
711 bool "STA2X11 Companion Chip Support"
712 depends on X86_32_NON_STANDARD && PCI
717 This adds support for boards based on the STA2X11 IO-Hub,
718 a.k.a. "ConneXt". The chip is used in place of the standard
719 PC chipset, so all "standard" peripherals are missing. If this
720 option is selected the kernel will still be able to boot on
721 standard PC machines.
724 tristate "Eurobraille/Iris poweroff module"
727 The Iris machines from EuroBraille do not have APM or ACPI support
728 to shut themselves down properly. A special I/O sequence is
729 needed to do so, which is what this module does at
732 This is only for Iris machines from EuroBraille.
736 config SCHED_OMIT_FRAME_POINTER
738 prompt "Single-depth WCHAN output"
741 Calculate simpler /proc/<PID>/wchan values. If this option
742 is disabled then wchan values will recurse back to the
743 caller function. This provides more accurate wchan values,
744 at the expense of slightly more scheduling overhead.
746 If in doubt, say "Y".
748 menuconfig HYPERVISOR_GUEST
749 bool "Linux guest support"
751 Say Y here to enable options for running Linux under various hyper-
752 visors. This option enables basic hypervisor detection and platform
755 If you say N, all options in this submenu will be skipped and
756 disabled, and Linux guest support won't be built in.
761 bool "Enable paravirtualization code"
763 This changes the kernel so it can modify itself when it is run
764 under a hypervisor, potentially improving performance significantly
765 over full virtualization. However, when run without a hypervisor
766 the kernel is theoretically slower and slightly larger.
771 config PARAVIRT_DEBUG
772 bool "paravirt-ops debugging"
773 depends on PARAVIRT && DEBUG_KERNEL
775 Enable to debug paravirt_ops internals. Specifically, BUG if
776 a paravirt_op is missing when it is called.
778 config PARAVIRT_SPINLOCKS
779 bool "Paravirtualization layer for spinlocks"
780 depends on PARAVIRT && SMP
782 Paravirtualized spinlocks allow a pvops backend to replace the
783 spinlock implementation with something virtualization-friendly
784 (for example, block the virtual CPU rather than spinning).
786 It has a minimal impact on native kernels and gives a nice performance
787 benefit on paravirtualized KVM / Xen kernels.
789 If you are unsure how to answer this question, answer Y.
791 config X86_HV_CALLBACK_VECTOR
794 source "arch/x86/xen/Kconfig"
797 bool "KVM Guest support (including kvmclock)"
799 select PARAVIRT_CLOCK
800 select ARCH_CPUIDLE_HALTPOLL
803 This option enables various optimizations for running under the KVM
804 hypervisor. It includes a paravirtualized clock, so that instead
805 of relying on a PIT (or probably other) emulation by the
806 underlying device model, the host provides the guest with
807 timing infrastructure such as time of day, and system time
809 config ARCH_CPUIDLE_HALTPOLL
811 prompt "Disable host haltpoll when loading haltpoll driver"
813 If virtualized under KVM, disable host haltpoll.
816 bool "Support for running PVH guests"
818 This option enables the PVH entry point for guest virtual machines
819 as specified in the x86/HVM direct boot ABI.
822 bool "Enable debug information for KVM Guests in debugfs"
823 depends on KVM_GUEST && DEBUG_FS
825 This option enables collection of various statistics for KVM guest.
826 Statistics are displayed in debugfs filesystem. Enabling this option
827 may incur significant overhead.
829 config PARAVIRT_TIME_ACCOUNTING
830 bool "Paravirtual steal time accounting"
833 Select this option to enable fine granularity task steal time
834 accounting. Time spent executing other tasks in parallel with
835 the current vCPU is discounted from the vCPU power. To account for
836 that, there can be a small performance impact.
838 If in doubt, say N here.
840 config PARAVIRT_CLOCK
843 config JAILHOUSE_GUEST
844 bool "Jailhouse non-root cell support"
845 depends on X86_64 && PCI
848 This option allows to run Linux as guest in a Jailhouse non-root
849 cell. You can leave this option disabled if you only want to start
850 Jailhouse and run Linux afterwards in the root cell.
853 bool "ACRN Guest support"
855 select X86_HV_CALLBACK_VECTOR
857 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
858 a flexible, lightweight reference open-source hypervisor, built with
859 real-time and safety-criticality in mind. It is built for embedded
860 IOT with small footprint and real-time features. More details can be
861 found in https://projectacrn.org/.
863 endif #HYPERVISOR_GUEST
865 source "arch/x86/Kconfig.cpu"
869 prompt "HPET Timer Support" if X86_32
871 Use the IA-PC HPET (High Precision Event Timer) to manage
872 time in preference to the PIT and RTC, if a HPET is
874 HPET is the next generation timer replacing legacy 8254s.
875 The HPET provides a stable time base on SMP
876 systems, unlike the TSC, but it is more expensive to access,
877 as it is off-chip. The interface used is documented
878 in the HPET spec, revision 1.
880 You can safely choose Y here. However, HPET will only be
881 activated if the platform and the BIOS support this feature.
882 Otherwise the 8254 will be used for timing services.
884 Choose N to continue using the legacy 8254 timer.
886 config HPET_EMULATE_RTC
888 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
891 def_bool y if X86_INTEL_MID
892 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
894 depends on X86_INTEL_MID && SFI
896 APB timer is the replacement for 8254, HPET on X86 MID platforms.
897 The APBT provides a stable time base on SMP
898 systems, unlike the TSC, but it is more expensive to access,
899 as it is off-chip. APB timers are always running regardless of CPU
900 C states, they are used as per CPU clockevent device when possible.
902 # Mark as expert because too many people got it wrong.
903 # The code disables itself when not needed.
906 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
907 bool "Enable DMI scanning" if EXPERT
909 Enabled scanning of DMI to identify machine quirks. Say Y
910 here unless you have verified that your setup is not
911 affected by entries in the DMI blacklist. Required by PNP
915 bool "Old AMD GART IOMMU support"
918 depends on X86_64 && PCI && AMD_NB
920 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
921 GART based hardware IOMMUs.
923 The GART supports full DMA access for devices with 32-bit access
924 limitations, on systems with more than 3 GB. This is usually needed
925 for USB, sound, many IDE/SATA chipsets and some other devices.
927 Newer systems typically have a modern AMD IOMMU, supported via
928 the CONFIG_AMD_IOMMU=y config option.
930 In normal configurations this driver is only active when needed:
931 there's more than 3 GB of memory and the system contains a
932 32-bit limited device.
937 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
938 depends on X86_64 && SMP && DEBUG_KERNEL
939 select CPUMASK_OFFSTACK
941 Enable maximum number of CPUS and NUMA Nodes for this architecture.
945 # The maximum number of CPUs supported:
947 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
948 # and which can be configured interactively in the
949 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
951 # The ranges are different on 32-bit and 64-bit kernels, depending on
952 # hardware capabilities and scalability features of the kernel.
954 # ( If MAXSMP is enabled we just use the highest possible value and disable
955 # interactive configuration. )
958 config NR_CPUS_RANGE_BEGIN
960 default NR_CPUS_RANGE_END if MAXSMP
964 config NR_CPUS_RANGE_END
967 default 64 if SMP && X86_BIGSMP
968 default 8 if SMP && !X86_BIGSMP
971 config NR_CPUS_RANGE_END
974 default 8192 if SMP && CPUMASK_OFFSTACK
975 default 512 if SMP && !CPUMASK_OFFSTACK
978 config NR_CPUS_DEFAULT
981 default 32 if X86_BIGSMP
985 config NR_CPUS_DEFAULT
988 default 8192 if MAXSMP
993 int "Maximum number of CPUs" if SMP && !MAXSMP
994 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
995 default NR_CPUS_DEFAULT
997 This allows you to specify the maximum number of CPUs which this
998 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
999 supported value is 8192, otherwise the maximum value is 512. The
1000 minimum value which makes sense is 2.
1002 This is purely to save memory: each supported CPU adds about 8KB
1003 to the kernel image.
1010 prompt "Multi-core scheduler support"
1013 Multi-core scheduler support improves the CPU scheduler's decision
1014 making when dealing with multi-core CPU chips at a cost of slightly
1015 increased overhead in some places. If unsure say N here.
1017 config SCHED_MC_PRIO
1018 bool "CPU core priorities scheduler support"
1019 depends on SCHED_MC && CPU_SUP_INTEL
1020 select X86_INTEL_PSTATE
1024 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1025 core ordering determined at manufacturing time, which allows
1026 certain cores to reach higher turbo frequencies (when running
1027 single threaded workloads) than others.
1029 Enabling this kernel feature teaches the scheduler about
1030 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1031 scheduler's CPU selection logic accordingly, so that higher
1032 overall system performance can be achieved.
1034 This feature will have no effect on CPUs without this feature.
1036 If unsure say Y here.
1040 depends on !SMP && X86_LOCAL_APIC
1043 bool "Local APIC support on uniprocessors" if !PCI_MSI
1045 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1047 A local APIC (Advanced Programmable Interrupt Controller) is an
1048 integrated interrupt controller in the CPU. If you have a single-CPU
1049 system which has a processor with a local APIC, you can say Y here to
1050 enable and use it. If you say Y here even though your machine doesn't
1051 have a local APIC, then the kernel will still run with no slowdown at
1052 all. The local APIC supports CPU-generated self-interrupts (timer,
1053 performance counters), and the NMI watchdog which detects hard
1056 config X86_UP_IOAPIC
1057 bool "IO-APIC support on uniprocessors"
1058 depends on X86_UP_APIC
1060 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1061 SMP-capable replacement for PC-style interrupt controllers. Most
1062 SMP systems and many recent uniprocessor systems have one.
1064 If you have a single-CPU system with an IO-APIC, you can say Y here
1065 to use it. If you say Y here even though your machine doesn't have
1066 an IO-APIC, then the kernel will still run with no slowdown at all.
1068 config X86_LOCAL_APIC
1070 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1071 select IRQ_DOMAIN_HIERARCHY
1072 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1076 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1078 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1079 bool "Reroute for broken boot IRQs"
1080 depends on X86_IO_APIC
1082 This option enables a workaround that fixes a source of
1083 spurious interrupts. This is recommended when threaded
1084 interrupt handling is used on systems where the generation of
1085 superfluous "boot interrupts" cannot be disabled.
1087 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1088 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1089 kernel does during interrupt handling). On chipsets where this
1090 boot IRQ generation cannot be disabled, this workaround keeps
1091 the original IRQ line masked so that only the equivalent "boot
1092 IRQ" is delivered to the CPUs. The workaround also tells the
1093 kernel to set up the IRQ handler on the boot IRQ line. In this
1094 way only one interrupt is delivered to the kernel. Otherwise
1095 the spurious second interrupt may cause the kernel to bring
1096 down (vital) interrupt lines.
1098 Only affects "broken" chipsets. Interrupt sharing may be
1099 increased on these systems.
1102 bool "Machine Check / overheating reporting"
1103 select GENERIC_ALLOCATOR
1106 Machine Check support allows the processor to notify the
1107 kernel if it detects a problem (e.g. overheating, data corruption).
1108 The action the kernel takes depends on the severity of the problem,
1109 ranging from warning messages to halting the machine.
1111 config X86_MCELOG_LEGACY
1112 bool "Support for deprecated /dev/mcelog character device"
1115 Enable support for /dev/mcelog which is needed by the old mcelog
1116 userspace logging daemon. Consider switching to the new generation
1119 config X86_MCE_INTEL
1121 prompt "Intel MCE features"
1122 depends on X86_MCE && X86_LOCAL_APIC
1124 Additional support for intel specific MCE features such as
1125 the thermal monitor.
1129 prompt "AMD MCE features"
1130 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1132 Additional support for AMD specific MCE features such as
1133 the DRAM Error Threshold.
1135 config X86_ANCIENT_MCE
1136 bool "Support for old Pentium 5 / WinChip machine checks"
1137 depends on X86_32 && X86_MCE
1139 Include support for machine check handling on old Pentium 5 or WinChip
1140 systems. These typically need to be enabled explicitly on the command
1143 config X86_MCE_THRESHOLD
1144 depends on X86_MCE_AMD || X86_MCE_INTEL
1147 config X86_MCE_INJECT
1148 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1149 tristate "Machine check injector support"
1151 Provide support for injecting machine checks for testing purposes.
1152 If you don't know what a machine check is and you don't do kernel
1153 QA it is safe to say n.
1155 config X86_THERMAL_VECTOR
1157 depends on X86_MCE_INTEL
1159 source "arch/x86/events/Kconfig"
1161 config X86_LEGACY_VM86
1162 bool "Legacy VM86 support"
1165 This option allows user programs to put the CPU into V8086
1166 mode, which is an 80286-era approximation of 16-bit real mode.
1168 Some very old versions of X and/or vbetool require this option
1169 for user mode setting. Similarly, DOSEMU will use it if
1170 available to accelerate real mode DOS programs. However, any
1171 recent version of DOSEMU, X, or vbetool should be fully
1172 functional even without kernel VM86 support, as they will all
1173 fall back to software emulation. Nevertheless, if you are using
1174 a 16-bit DOS program where 16-bit performance matters, vm86
1175 mode might be faster than emulation and you might want to
1178 Note that any app that works on a 64-bit kernel is unlikely to
1179 need this option, as 64-bit kernels don't, and can't, support
1180 V8086 mode. This option is also unrelated to 16-bit protected
1181 mode and is not needed to run most 16-bit programs under Wine.
1183 Enabling this option increases the complexity of the kernel
1184 and slows down exception handling a tiny bit.
1186 If unsure, say N here.
1190 default X86_LEGACY_VM86
1193 bool "Enable support for 16-bit segments" if EXPERT
1195 depends on MODIFY_LDT_SYSCALL
1197 This option is required by programs like Wine to run 16-bit
1198 protected mode legacy code on x86 processors. Disabling
1199 this option saves about 300 bytes on i386, or around 6K text
1200 plus 16K runtime memory on x86-64,
1204 depends on X86_16BIT && X86_32
1208 depends on X86_16BIT && X86_64
1210 config X86_VSYSCALL_EMULATION
1211 bool "Enable vsyscall emulation" if EXPERT
1215 This enables emulation of the legacy vsyscall page. Disabling
1216 it is roughly equivalent to booting with vsyscall=none, except
1217 that it will also disable the helpful warning if a program
1218 tries to use a vsyscall. With this option set to N, offending
1219 programs will just segfault, citing addresses of the form
1222 This option is required by many programs built before 2013, and
1223 care should be used even with newer programs if set to N.
1225 Disabling this option saves about 7K of kernel size and
1226 possibly 4K of additional runtime pagetable memory.
1228 config X86_IOPL_IOPERM
1229 bool "IOPERM and IOPL Emulation"
1232 This enables the ioperm() and iopl() syscalls which are necessary
1233 for legacy applications.
1235 Legacy IOPL support is an overbroad mechanism which allows user
1236 space aside of accessing all 65536 I/O ports also to disable
1237 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1238 capabilities and permission from potentially active security
1241 The emulation restricts the functionality of the syscall to
1242 only allowing the full range I/O port access, but prevents the
1243 ability to disable interrupts from user space which would be
1244 granted if the hardware IOPL mechanism would be used.
1247 tristate "Toshiba Laptop support"
1250 This adds a driver to safely access the System Management Mode of
1251 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1252 not work on models with a Phoenix BIOS. The System Management Mode
1253 is used to set the BIOS and power saving options on Toshiba portables.
1255 For information on utilities to make use of this driver see the
1256 Toshiba Linux utilities web site at:
1257 <http://www.buzzard.org.uk/toshiba/>.
1259 Say Y if you intend to run this kernel on a Toshiba portable.
1263 tristate "Dell i8k legacy laptop support"
1265 select SENSORS_DELL_SMM
1267 This option enables legacy /proc/i8k userspace interface in hwmon
1268 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1269 temperature and allows controlling fan speeds of Dell laptops via
1270 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1271 it reports also power and hotkey status. For fan speed control is
1272 needed userspace package i8kutils.
1274 Say Y if you intend to run this kernel on old Dell laptops or want to
1275 use userspace package i8kutils.
1278 config X86_REBOOTFIXUPS
1279 bool "Enable X86 board specific fixups for reboot"
1282 This enables chipset and/or board specific fixups to be done
1283 in order to get reboot to work correctly. This is only needed on
1284 some combinations of hardware and BIOS. The symptom, for which
1285 this config is intended, is when reboot ends with a stalled/hung
1288 Currently, the only fixup is for the Geode machines using
1289 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1291 Say Y if you want to enable the fixup. Currently, it's safe to
1292 enable this option even if you don't need it.
1296 bool "CPU microcode loading support"
1298 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1301 If you say Y here, you will be able to update the microcode on
1302 Intel and AMD processors. The Intel support is for the IA32 family,
1303 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1304 AMD support is for families 0x10 and later. You will obviously need
1305 the actual microcode binary data itself which is not shipped with
1308 The preferred method to load microcode from a detached initrd is described
1309 in Documentation/x86/microcode.rst. For that you need to enable
1310 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1311 initrd for microcode blobs.
1313 In addition, you can build the microcode into the kernel. For that you
1314 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1317 config MICROCODE_INTEL
1318 bool "Intel microcode loading support"
1319 depends on MICROCODE
1323 This options enables microcode patch loading support for Intel
1326 For the current Intel microcode data package go to
1327 <https://downloadcenter.intel.com> and search for
1328 'Linux Processor Microcode Data File'.
1330 config MICROCODE_AMD
1331 bool "AMD microcode loading support"
1332 depends on MICROCODE
1335 If you select this option, microcode patch loading support for AMD
1336 processors will be enabled.
1338 config MICROCODE_OLD_INTERFACE
1339 bool "Ancient loading interface (DEPRECATED)"
1341 depends on MICROCODE
1343 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1344 which was used by userspace tools like iucode_tool and microcode.ctl.
1345 It is inadequate because it runs too late to be able to properly
1346 load microcode on a machine and it needs special tools. Instead, you
1347 should've switched to the early loading method with the initrd or
1348 builtin microcode by now: Documentation/x86/microcode.rst
1351 tristate "/dev/cpu/*/msr - Model-specific register support"
1353 This device gives privileged processes access to the x86
1354 Model-Specific Registers (MSRs). It is a character device with
1355 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1356 MSR accesses are directed to a specific CPU on multi-processor
1360 tristate "/dev/cpu/*/cpuid - CPU information support"
1362 This device gives processes access to the x86 CPUID instruction to
1363 be executed on a specific processor. It is a character device
1364 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1368 prompt "High Memory Support"
1375 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1376 However, the address space of 32-bit x86 processors is only 4
1377 Gigabytes large. That means that, if you have a large amount of
1378 physical memory, not all of it can be "permanently mapped" by the
1379 kernel. The physical memory that's not permanently mapped is called
1382 If you are compiling a kernel which will never run on a machine with
1383 more than 1 Gigabyte total physical RAM, answer "off" here (default
1384 choice and suitable for most users). This will result in a "3GB/1GB"
1385 split: 3GB are mapped so that each process sees a 3GB virtual memory
1386 space and the remaining part of the 4GB virtual memory space is used
1387 by the kernel to permanently map as much physical memory as
1390 If the machine has between 1 and 4 Gigabytes physical RAM, then
1393 If more than 4 Gigabytes is used then answer "64GB" here. This
1394 selection turns Intel PAE (Physical Address Extension) mode on.
1395 PAE implements 3-level paging on IA32 processors. PAE is fully
1396 supported by Linux, PAE mode is implemented on all recent Intel
1397 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1398 then the kernel will not boot on CPUs that don't support PAE!
1400 The actual amount of total physical memory will either be
1401 auto detected or can be forced by using a kernel command line option
1402 such as "mem=256M". (Try "man bootparam" or see the documentation of
1403 your boot loader (lilo or loadlin) about how to pass options to the
1404 kernel at boot time.)
1406 If unsure, say "off".
1411 Select this if you have a 32-bit processor and between 1 and 4
1412 gigabytes of physical RAM.
1416 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1419 Select this if you have a 32-bit processor and more than 4
1420 gigabytes of physical RAM.
1425 prompt "Memory split" if EXPERT
1429 Select the desired split between kernel and user memory.
1431 If the address range available to the kernel is less than the
1432 physical memory installed, the remaining memory will be available
1433 as "high memory". Accessing high memory is a little more costly
1434 than low memory, as it needs to be mapped into the kernel first.
1435 Note that increasing the kernel address space limits the range
1436 available to user programs, making the address space there
1437 tighter. Selecting anything other than the default 3G/1G split
1438 will also likely make your kernel incompatible with binary-only
1441 If you are not absolutely sure what you are doing, leave this
1445 bool "3G/1G user/kernel split"
1446 config VMSPLIT_3G_OPT
1448 bool "3G/1G user/kernel split (for full 1G low memory)"
1450 bool "2G/2G user/kernel split"
1451 config VMSPLIT_2G_OPT
1453 bool "2G/2G user/kernel split (for full 2G low memory)"
1455 bool "1G/3G user/kernel split"
1460 default 0xB0000000 if VMSPLIT_3G_OPT
1461 default 0x80000000 if VMSPLIT_2G
1462 default 0x78000000 if VMSPLIT_2G_OPT
1463 default 0x40000000 if VMSPLIT_1G
1469 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1472 bool "PAE (Physical Address Extension) Support"
1473 depends on X86_32 && !HIGHMEM4G
1474 select PHYS_ADDR_T_64BIT
1477 PAE is required for NX support, and furthermore enables
1478 larger swapspace support for non-overcommit purposes. It
1479 has the cost of more pagetable lookup overhead, and also
1480 consumes more pagetable space per process.
1483 bool "Enable 5-level page tables support"
1485 select DYNAMIC_MEMORY_LAYOUT
1486 select SPARSEMEM_VMEMMAP
1489 5-level paging enables access to larger address space:
1490 upto 128 PiB of virtual address space and 4 PiB of
1491 physical address space.
1493 It will be supported by future Intel CPUs.
1495 A kernel with the option enabled can be booted on machines that
1496 support 4- or 5-level paging.
1498 See Documentation/x86/x86_64/5level-paging.rst for more
1503 config X86_DIRECT_GBPAGES
1507 Certain kernel features effectively disable kernel
1508 linear 1 GB mappings (even if the CPU otherwise
1509 supports them), so don't confuse the user by printing
1510 that we have them enabled.
1512 config X86_CPA_STATISTICS
1513 bool "Enable statistic for Change Page Attribute"
1516 Expose statistics about the Change Page Attribute mechanims, which
1517 helps to determine the effectiveness of preserving large and huge
1518 page mappings when mapping protections are changed.
1520 config AMD_MEM_ENCRYPT
1521 bool "AMD Secure Memory Encryption (SME) support"
1522 depends on X86_64 && CPU_SUP_AMD
1523 select DYNAMIC_PHYSICAL_MASK
1524 select ARCH_USE_MEMREMAP_PROT
1525 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1527 Say yes to enable support for the encryption of system memory.
1528 This requires an AMD processor that supports Secure Memory
1531 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1532 bool "Activate AMD Secure Memory Encryption (SME) by default"
1534 depends on AMD_MEM_ENCRYPT
1536 Say yes to have system memory encrypted by default if running on
1537 an AMD processor that supports Secure Memory Encryption (SME).
1539 If set to Y, then the encryption of system memory can be
1540 deactivated with the mem_encrypt=off command line option.
1542 If set to N, then the encryption of system memory can be
1543 activated with the mem_encrypt=on command line option.
1545 # Common NUMA Features
1547 bool "Numa Memory Allocation and Scheduler Support"
1549 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1550 default y if X86_BIGSMP
1552 Enable NUMA (Non Uniform Memory Access) support.
1554 The kernel will try to allocate memory used by a CPU on the
1555 local memory controller of the CPU and add some more
1556 NUMA awareness to the kernel.
1558 For 64-bit this is recommended if the system is Intel Core i7
1559 (or later), AMD Opteron, or EM64T NUMA.
1561 For 32-bit this is only needed if you boot a 32-bit
1562 kernel on a 64-bit NUMA platform.
1564 Otherwise, you should say N.
1568 prompt "Old style AMD Opteron NUMA detection"
1569 depends on X86_64 && NUMA && PCI
1571 Enable AMD NUMA node topology detection. You should say Y here if
1572 you have a multi processor AMD system. This uses an old method to
1573 read the NUMA configuration directly from the builtin Northbridge
1574 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1575 which also takes priority if both are compiled in.
1577 config X86_64_ACPI_NUMA
1579 prompt "ACPI NUMA detection"
1580 depends on X86_64 && NUMA && ACPI && PCI
1583 Enable ACPI SRAT based node topology detection.
1585 # Some NUMA nodes have memory ranges that span
1586 # other nodes. Even though a pfn is valid and
1587 # between a node's start and end pfns, it may not
1588 # reside on that node. See memmap_init_zone()
1590 config NODES_SPAN_OTHER_NODES
1592 depends on X86_64_ACPI_NUMA
1595 bool "NUMA emulation"
1598 Enable NUMA emulation. A flat machine will be split
1599 into virtual nodes when booted with "numa=fake=N", where N is the
1600 number of nodes. This is only useful for debugging.
1603 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1605 default "10" if MAXSMP
1606 default "6" if X86_64
1608 depends on NEED_MULTIPLE_NODES
1610 Specify the maximum number of NUMA Nodes available on the target
1611 system. Increases memory reserved to accommodate various tables.
1613 config ARCH_HAVE_MEMORY_PRESENT
1615 depends on X86_32 && DISCONTIGMEM
1617 config ARCH_FLATMEM_ENABLE
1619 depends on X86_32 && !NUMA
1621 config ARCH_DISCONTIGMEM_ENABLE
1623 depends on NUMA && X86_32
1626 config ARCH_SPARSEMEM_ENABLE
1628 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1629 select SPARSEMEM_STATIC if X86_32
1630 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1632 config ARCH_SPARSEMEM_DEFAULT
1633 def_bool X86_64 || (NUMA && X86_32)
1635 config ARCH_SELECT_MEMORY_MODEL
1637 depends on ARCH_SPARSEMEM_ENABLE
1639 config ARCH_MEMORY_PROBE
1640 bool "Enable sysfs memory/probe interface"
1641 depends on X86_64 && MEMORY_HOTPLUG
1643 This option enables a sysfs memory/probe interface for testing.
1644 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1645 If you are unsure how to answer this question, answer N.
1647 config ARCH_PROC_KCORE_TEXT
1649 depends on X86_64 && PROC_KCORE
1651 config ILLEGAL_POINTER_VALUE
1654 default 0xdead000000000000 if X86_64
1656 config X86_PMEM_LEGACY_DEVICE
1659 config X86_PMEM_LEGACY
1660 tristate "Support non-standard NVDIMMs and ADR protected memory"
1661 depends on PHYS_ADDR_T_64BIT
1663 select X86_PMEM_LEGACY_DEVICE
1666 Treat memory marked using the non-standard e820 type of 12 as used
1667 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1668 The kernel will offer these regions to the 'pmem' driver so
1669 they can be used for persistent storage.
1674 bool "Allocate 3rd-level pagetables from highmem"
1677 The VM uses one page table entry for each page of physical memory.
1678 For systems with a lot of RAM, this can be wasteful of precious
1679 low memory. Setting this option will put user-space page table
1680 entries in high memory.
1682 config X86_CHECK_BIOS_CORRUPTION
1683 bool "Check for low memory corruption"
1685 Periodically check for memory corruption in low memory, which
1686 is suspected to be caused by BIOS. Even when enabled in the
1687 configuration, it is disabled at runtime. Enable it by
1688 setting "memory_corruption_check=1" on the kernel command
1689 line. By default it scans the low 64k of memory every 60
1690 seconds; see the memory_corruption_check_size and
1691 memory_corruption_check_period parameters in
1692 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1694 When enabled with the default parameters, this option has
1695 almost no overhead, as it reserves a relatively small amount
1696 of memory and scans it infrequently. It both detects corruption
1697 and prevents it from affecting the running system.
1699 It is, however, intended as a diagnostic tool; if repeatable
1700 BIOS-originated corruption always affects the same memory,
1701 you can use memmap= to prevent the kernel from using that
1704 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1705 bool "Set the default setting of memory_corruption_check"
1706 depends on X86_CHECK_BIOS_CORRUPTION
1709 Set whether the default state of memory_corruption_check is
1712 config X86_RESERVE_LOW
1713 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1717 Specify the amount of low memory to reserve for the BIOS.
1719 The first page contains BIOS data structures that the kernel
1720 must not use, so that page must always be reserved.
1722 By default we reserve the first 64K of physical RAM, as a
1723 number of BIOSes are known to corrupt that memory range
1724 during events such as suspend/resume or monitor cable
1725 insertion, so it must not be used by the kernel.
1727 You can set this to 4 if you are absolutely sure that you
1728 trust the BIOS to get all its memory reservations and usages
1729 right. If you know your BIOS have problems beyond the
1730 default 64K area, you can set this to 640 to avoid using the
1731 entire low memory range.
1733 If you have doubts about the BIOS (e.g. suspend/resume does
1734 not work or there's kernel crashes after certain hardware
1735 hotplug events) then you might want to enable
1736 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1737 typical corruption patterns.
1739 Leave this to the default value of 64 if you are unsure.
1741 config MATH_EMULATION
1743 depends on MODIFY_LDT_SYSCALL
1744 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1746 Linux can emulate a math coprocessor (used for floating point
1747 operations) if you don't have one. 486DX and Pentium processors have
1748 a math coprocessor built in, 486SX and 386 do not, unless you added
1749 a 487DX or 387, respectively. (The messages during boot time can
1750 give you some hints here ["man dmesg"].) Everyone needs either a
1751 coprocessor or this emulation.
1753 If you don't have a math coprocessor, you need to say Y here; if you
1754 say Y here even though you have a coprocessor, the coprocessor will
1755 be used nevertheless. (This behavior can be changed with the kernel
1756 command line option "no387", which comes handy if your coprocessor
1757 is broken. Try "man bootparam" or see the documentation of your boot
1758 loader (lilo or loadlin) about how to pass options to the kernel at
1759 boot time.) This means that it is a good idea to say Y here if you
1760 intend to use this kernel on different machines.
1762 More information about the internals of the Linux math coprocessor
1763 emulation can be found in <file:arch/x86/math-emu/README>.
1765 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1766 kernel, it won't hurt.
1770 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1772 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1773 the Memory Type Range Registers (MTRRs) may be used to control
1774 processor access to memory ranges. This is most useful if you have
1775 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1776 allows bus write transfers to be combined into a larger transfer
1777 before bursting over the PCI/AGP bus. This can increase performance
1778 of image write operations 2.5 times or more. Saying Y here creates a
1779 /proc/mtrr file which may be used to manipulate your processor's
1780 MTRRs. Typically the X server should use this.
1782 This code has a reasonably generic interface so that similar
1783 control registers on other processors can be easily supported
1786 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1787 Registers (ARRs) which provide a similar functionality to MTRRs. For
1788 these, the ARRs are used to emulate the MTRRs.
1789 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1790 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1791 write-combining. All of these processors are supported by this code
1792 and it makes sense to say Y here if you have one of them.
1794 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1795 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1796 can lead to all sorts of problems, so it's good to say Y here.
1798 You can safely say Y even if your machine doesn't have MTRRs, you'll
1799 just add about 9 KB to your kernel.
1801 See <file:Documentation/x86/mtrr.rst> for more information.
1803 config MTRR_SANITIZER
1805 prompt "MTRR cleanup support"
1808 Convert MTRR layout from continuous to discrete, so X drivers can
1809 add writeback entries.
1811 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1812 The largest mtrr entry size for a continuous block can be set with
1817 config MTRR_SANITIZER_ENABLE_DEFAULT
1818 int "MTRR cleanup enable value (0-1)"
1821 depends on MTRR_SANITIZER
1823 Enable mtrr cleanup default value
1825 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1826 int "MTRR cleanup spare reg num (0-7)"
1829 depends on MTRR_SANITIZER
1831 mtrr cleanup spare entries default, it can be changed via
1832 mtrr_spare_reg_nr=N on the kernel command line.
1836 prompt "x86 PAT support" if EXPERT
1839 Use PAT attributes to setup page level cache control.
1841 PATs are the modern equivalents of MTRRs and are much more
1842 flexible than MTRRs.
1844 Say N here if you see bootup problems (boot crash, boot hang,
1845 spontaneous reboots) or a non-working video driver.
1849 config ARCH_USES_PG_UNCACHED
1855 prompt "x86 architectural random number generator" if EXPERT
1857 Enable the x86 architectural RDRAND instruction
1858 (Intel Bull Mountain technology) to generate random numbers.
1859 If supported, this is a high bandwidth, cryptographically
1860 secure hardware random number generator.
1864 prompt "Supervisor Mode Access Prevention" if EXPERT
1866 Supervisor Mode Access Prevention (SMAP) is a security
1867 feature in newer Intel processors. There is a small
1868 performance cost if this enabled and turned on; there is
1869 also a small increase in the kernel size if this is enabled.
1875 depends on CPU_SUP_INTEL || CPU_SUP_AMD
1876 prompt "User Mode Instruction Prevention" if EXPERT
1878 User Mode Instruction Prevention (UMIP) is a security feature in
1879 some x86 processors. If enabled, a general protection fault is
1880 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1881 executed in user mode. These instructions unnecessarily expose
1882 information about the hardware state.
1884 The vast majority of applications do not use these instructions.
1885 For the very few that do, software emulation is provided in
1886 specific cases in protected and virtual-8086 modes. Emulated
1889 config X86_INTEL_MPX
1890 prompt "Intel MPX (Memory Protection Extensions)"
1892 # Note: only available in 64-bit mode due to VMA flags shortage
1893 depends on CPU_SUP_INTEL && X86_64
1894 select ARCH_USES_HIGH_VMA_FLAGS
1896 MPX provides hardware features that can be used in
1897 conjunction with compiler-instrumented code to check
1898 memory references. It is designed to detect buffer
1899 overflow or underflow bugs.
1901 This option enables running applications which are
1902 instrumented or otherwise use MPX. It does not use MPX
1903 itself inside the kernel or to protect the kernel
1904 against bad memory references.
1906 Enabling this option will make the kernel larger:
1907 ~8k of kernel text and 36 bytes of data on a 64-bit
1908 defconfig. It adds a long to the 'mm_struct' which
1909 will increase the kernel memory overhead of each
1910 process and adds some branches to paths used during
1911 exec() and munmap().
1913 For details, see Documentation/x86/intel_mpx.rst
1917 config X86_INTEL_MEMORY_PROTECTION_KEYS
1918 prompt "Intel Memory Protection Keys"
1920 # Note: only available in 64-bit mode
1921 depends on CPU_SUP_INTEL && X86_64
1922 select ARCH_USES_HIGH_VMA_FLAGS
1923 select ARCH_HAS_PKEYS
1925 Memory Protection Keys provides a mechanism for enforcing
1926 page-based protections, but without requiring modification of the
1927 page tables when an application changes protection domains.
1929 For details, see Documentation/core-api/protection-keys.rst
1934 prompt "TSX enable mode"
1935 depends on CPU_SUP_INTEL
1936 default X86_INTEL_TSX_MODE_OFF
1938 Intel's TSX (Transactional Synchronization Extensions) feature
1939 allows to optimize locking protocols through lock elision which
1940 can lead to a noticeable performance boost.
1942 On the other hand it has been shown that TSX can be exploited
1943 to form side channel attacks (e.g. TAA) and chances are there
1944 will be more of those attacks discovered in the future.
1946 Therefore TSX is not enabled by default (aka tsx=off). An admin
1947 might override this decision by tsx=on the command line parameter.
1948 Even with TSX enabled, the kernel will attempt to enable the best
1949 possible TAA mitigation setting depending on the microcode available
1950 for the particular machine.
1952 This option allows to set the default tsx mode between tsx=on, =off
1953 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1956 Say off if not sure, auto if TSX is in use but it should be used on safe
1957 platforms or on if TSX is in use and the security aspect of tsx is not
1960 config X86_INTEL_TSX_MODE_OFF
1963 TSX is disabled if possible - equals to tsx=off command line parameter.
1965 config X86_INTEL_TSX_MODE_ON
1968 TSX is always enabled on TSX capable HW - equals the tsx=on command
1971 config X86_INTEL_TSX_MODE_AUTO
1974 TSX is enabled on TSX capable HW that is believed to be safe against
1975 side channel attacks- equals the tsx=auto command line parameter.
1979 bool "EFI runtime service support"
1982 select EFI_RUNTIME_WRAPPERS
1984 This enables the kernel to use EFI runtime services that are
1985 available (such as the EFI variable services).
1987 This option is only useful on systems that have EFI firmware.
1988 In addition, you should use the latest ELILO loader available
1989 at <http://elilo.sourceforge.net> in order to take advantage
1990 of EFI runtime services. However, even with this option, the
1991 resultant kernel should continue to boot on existing non-EFI
1995 bool "EFI stub support"
1996 depends on EFI && !X86_USE_3DNOW
1999 This kernel feature allows a bzImage to be loaded directly
2000 by EFI firmware without the use of a bootloader.
2002 See Documentation/admin-guide/efi-stub.rst for more information.
2005 bool "EFI mixed-mode support"
2006 depends on EFI_STUB && X86_64
2008 Enabling this feature allows a 64-bit kernel to be booted
2009 on a 32-bit firmware, provided that your CPU supports 64-bit
2012 Note that it is not possible to boot a mixed-mode enabled
2013 kernel via the EFI boot stub - a bootloader that supports
2014 the EFI handover protocol must be used.
2020 prompt "Enable seccomp to safely compute untrusted bytecode"
2022 This kernel feature is useful for number crunching applications
2023 that may need to compute untrusted bytecode during their
2024 execution. By using pipes or other transports made available to
2025 the process as file descriptors supporting the read/write
2026 syscalls, it's possible to isolate those applications in
2027 their own address space using seccomp. Once seccomp is
2028 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
2029 and the task is only allowed to execute a few safe syscalls
2030 defined by each seccomp mode.
2032 If unsure, say Y. Only embedded should say N here.
2034 source "kernel/Kconfig.hz"
2037 bool "kexec system call"
2040 kexec is a system call that implements the ability to shutdown your
2041 current kernel, and to start another kernel. It is like a reboot
2042 but it is independent of the system firmware. And like a reboot
2043 you can start any kernel with it, not just Linux.
2045 The name comes from the similarity to the exec system call.
2047 It is an ongoing process to be certain the hardware in a machine
2048 is properly shutdown, so do not be surprised if this code does not
2049 initially work for you. As of this writing the exact hardware
2050 interface is strongly in flux, so no good recommendation can be
2054 bool "kexec file based system call"
2059 depends on CRYPTO_SHA256=y
2061 This is new version of kexec system call. This system call is
2062 file based and takes file descriptors as system call argument
2063 for kernel and initramfs as opposed to list of segments as
2064 accepted by previous system call.
2066 config ARCH_HAS_KEXEC_PURGATORY
2070 bool "Verify kernel signature during kexec_file_load() syscall"
2071 depends on KEXEC_FILE
2074 This option makes the kexec_file_load() syscall check for a valid
2075 signature of the kernel image. The image can still be loaded without
2076 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2077 there's a signature that we can check, then it must be valid.
2079 In addition to this option, you need to enable signature
2080 verification for the corresponding kernel image type being
2081 loaded in order for this to work.
2083 config KEXEC_SIG_FORCE
2084 bool "Require a valid signature in kexec_file_load() syscall"
2085 depends on KEXEC_SIG
2087 This option makes kernel signature verification mandatory for
2088 the kexec_file_load() syscall.
2090 config KEXEC_BZIMAGE_VERIFY_SIG
2091 bool "Enable bzImage signature verification support"
2092 depends on KEXEC_SIG
2093 depends on SIGNED_PE_FILE_VERIFICATION
2094 select SYSTEM_TRUSTED_KEYRING
2096 Enable bzImage signature verification support.
2099 bool "kernel crash dumps"
2100 depends on X86_64 || (X86_32 && HIGHMEM)
2102 Generate crash dump after being started by kexec.
2103 This should be normally only set in special crash dump kernels
2104 which are loaded in the main kernel with kexec-tools into
2105 a specially reserved region and then later executed after
2106 a crash by kdump/kexec. The crash dump kernel must be compiled
2107 to a memory address not used by the main kernel or BIOS using
2108 PHYSICAL_START, or it must be built as a relocatable image
2109 (CONFIG_RELOCATABLE=y).
2110 For more details see Documentation/admin-guide/kdump/kdump.rst
2114 depends on KEXEC && HIBERNATION
2116 Jump between original kernel and kexeced kernel and invoke
2117 code in physical address mode via KEXEC
2119 config PHYSICAL_START
2120 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2123 This gives the physical address where the kernel is loaded.
2125 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2126 bzImage will decompress itself to above physical address and
2127 run from there. Otherwise, bzImage will run from the address where
2128 it has been loaded by the boot loader and will ignore above physical
2131 In normal kdump cases one does not have to set/change this option
2132 as now bzImage can be compiled as a completely relocatable image
2133 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2134 address. This option is mainly useful for the folks who don't want
2135 to use a bzImage for capturing the crash dump and want to use a
2136 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2137 to be specifically compiled to run from a specific memory area
2138 (normally a reserved region) and this option comes handy.
2140 So if you are using bzImage for capturing the crash dump,
2141 leave the value here unchanged to 0x1000000 and set
2142 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2143 for capturing the crash dump change this value to start of
2144 the reserved region. In other words, it can be set based on
2145 the "X" value as specified in the "crashkernel=YM@XM"
2146 command line boot parameter passed to the panic-ed
2147 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2148 for more details about crash dumps.
2150 Usage of bzImage for capturing the crash dump is recommended as
2151 one does not have to build two kernels. Same kernel can be used
2152 as production kernel and capture kernel. Above option should have
2153 gone away after relocatable bzImage support is introduced. But it
2154 is present because there are users out there who continue to use
2155 vmlinux for dump capture. This option should go away down the
2158 Don't change this unless you know what you are doing.
2161 bool "Build a relocatable kernel"
2164 This builds a kernel image that retains relocation information
2165 so it can be loaded someplace besides the default 1MB.
2166 The relocations tend to make the kernel binary about 10% larger,
2167 but are discarded at runtime.
2169 One use is for the kexec on panic case where the recovery kernel
2170 must live at a different physical address than the primary
2173 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2174 it has been loaded at and the compile time physical address
2175 (CONFIG_PHYSICAL_START) is used as the minimum location.
2177 config RANDOMIZE_BASE
2178 bool "Randomize the address of the kernel image (KASLR)"
2179 depends on RELOCATABLE
2182 In support of Kernel Address Space Layout Randomization (KASLR),
2183 this randomizes the physical address at which the kernel image
2184 is decompressed and the virtual address where the kernel
2185 image is mapped, as a security feature that deters exploit
2186 attempts relying on knowledge of the location of kernel
2189 On 64-bit, the kernel physical and virtual addresses are
2190 randomized separately. The physical address will be anywhere
2191 between 16MB and the top of physical memory (up to 64TB). The
2192 virtual address will be randomized from 16MB up to 1GB (9 bits
2193 of entropy). Note that this also reduces the memory space
2194 available to kernel modules from 1.5GB to 1GB.
2196 On 32-bit, the kernel physical and virtual addresses are
2197 randomized together. They will be randomized from 16MB up to
2198 512MB (8 bits of entropy).
2200 Entropy is generated using the RDRAND instruction if it is
2201 supported. If RDTSC is supported, its value is mixed into
2202 the entropy pool as well. If neither RDRAND nor RDTSC are
2203 supported, then entropy is read from the i8254 timer. The
2204 usable entropy is limited by the kernel being built using
2205 2GB addressing, and that PHYSICAL_ALIGN must be at a
2206 minimum of 2MB. As a result, only 10 bits of entropy are
2207 theoretically possible, but the implementations are further
2208 limited due to memory layouts.
2212 # Relocation on x86 needs some additional build support
2213 config X86_NEED_RELOCS
2215 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2217 config PHYSICAL_ALIGN
2218 hex "Alignment value to which kernel should be aligned"
2220 range 0x2000 0x1000000 if X86_32
2221 range 0x200000 0x1000000 if X86_64
2223 This value puts the alignment restrictions on physical address
2224 where kernel is loaded and run from. Kernel is compiled for an
2225 address which meets above alignment restriction.
2227 If bootloader loads the kernel at a non-aligned address and
2228 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2229 address aligned to above value and run from there.
2231 If bootloader loads the kernel at a non-aligned address and
2232 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2233 load address and decompress itself to the address it has been
2234 compiled for and run from there. The address for which kernel is
2235 compiled already meets above alignment restrictions. Hence the
2236 end result is that kernel runs from a physical address meeting
2237 above alignment restrictions.
2239 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2240 this value must be a multiple of 0x200000.
2242 Don't change this unless you know what you are doing.
2244 config DYNAMIC_MEMORY_LAYOUT
2247 This option makes base addresses of vmalloc and vmemmap as well as
2248 __PAGE_OFFSET movable during boot.
2250 config RANDOMIZE_MEMORY
2251 bool "Randomize the kernel memory sections"
2253 depends on RANDOMIZE_BASE
2254 select DYNAMIC_MEMORY_LAYOUT
2255 default RANDOMIZE_BASE
2257 Randomizes the base virtual address of kernel memory sections
2258 (physical memory mapping, vmalloc & vmemmap). This security feature
2259 makes exploits relying on predictable memory locations less reliable.
2261 The order of allocations remains unchanged. Entropy is generated in
2262 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2263 configuration have in average 30,000 different possible virtual
2264 addresses for each memory section.
2268 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2269 hex "Physical memory mapping padding" if EXPERT
2270 depends on RANDOMIZE_MEMORY
2271 default "0xa" if MEMORY_HOTPLUG
2273 range 0x1 0x40 if MEMORY_HOTPLUG
2276 Define the padding in terabytes added to the existing physical
2277 memory size during kernel memory randomization. It is useful
2278 for memory hotplug support but reduces the entropy available for
2279 address randomization.
2281 If unsure, leave at the default value.
2287 config BOOTPARAM_HOTPLUG_CPU0
2288 bool "Set default setting of cpu0_hotpluggable"
2289 depends on HOTPLUG_CPU
2291 Set whether default state of cpu0_hotpluggable is on or off.
2293 Say Y here to enable CPU0 hotplug by default. If this switch
2294 is turned on, there is no need to give cpu0_hotplug kernel
2295 parameter and the CPU0 hotplug feature is enabled by default.
2297 Please note: there are two known CPU0 dependencies if you want
2298 to enable the CPU0 hotplug feature either by this switch or by
2299 cpu0_hotplug kernel parameter.
2301 First, resume from hibernate or suspend always starts from CPU0.
2302 So hibernate and suspend are prevented if CPU0 is offline.
2304 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2305 offline if any interrupt can not migrate out of CPU0. There may
2306 be other CPU0 dependencies.
2308 Please make sure the dependencies are under your control before
2309 you enable this feature.
2311 Say N if you don't want to enable CPU0 hotplug feature by default.
2312 You still can enable the CPU0 hotplug feature at boot by kernel
2313 parameter cpu0_hotplug.
2315 config DEBUG_HOTPLUG_CPU0
2317 prompt "Debug CPU0 hotplug"
2318 depends on HOTPLUG_CPU
2320 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2321 soon as possible and boots up userspace with CPU0 offlined. User
2322 can online CPU0 back after boot time.
2324 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2325 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2326 compilation or giving cpu0_hotplug kernel parameter at boot.
2332 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2333 depends on COMPAT_32
2335 Certain buggy versions of glibc will crash if they are
2336 presented with a 32-bit vDSO that is not mapped at the address
2337 indicated in its segment table.
2339 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2340 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2341 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2342 the only released version with the bug, but OpenSUSE 9
2343 contains a buggy "glibc 2.3.2".
2345 The symptom of the bug is that everything crashes on startup, saying:
2346 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2348 Saying Y here changes the default value of the vdso32 boot
2349 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2350 This works around the glibc bug but hurts performance.
2352 If unsure, say N: if you are compiling your own kernel, you
2353 are unlikely to be using a buggy version of glibc.
2356 prompt "vsyscall table for legacy applications"
2358 default LEGACY_VSYSCALL_XONLY
2360 Legacy user code that does not know how to find the vDSO expects
2361 to be able to issue three syscalls by calling fixed addresses in
2362 kernel space. Since this location is not randomized with ASLR,
2363 it can be used to assist security vulnerability exploitation.
2365 This setting can be changed at boot time via the kernel command
2366 line parameter vsyscall=[emulate|xonly|none].
2368 On a system with recent enough glibc (2.14 or newer) and no
2369 static binaries, you can say None without a performance penalty
2370 to improve security.
2372 If unsure, select "Emulate execution only".
2374 config LEGACY_VSYSCALL_EMULATE
2375 bool "Full emulation"
2377 The kernel traps and emulates calls into the fixed vsyscall
2378 address mapping. This makes the mapping non-executable, but
2379 it still contains readable known contents, which could be
2380 used in certain rare security vulnerability exploits. This
2381 configuration is recommended when using legacy userspace
2382 that still uses vsyscalls along with legacy binary
2383 instrumentation tools that require code to be readable.
2385 An example of this type of legacy userspace is running
2386 Pin on an old binary that still uses vsyscalls.
2388 config LEGACY_VSYSCALL_XONLY
2389 bool "Emulate execution only"
2391 The kernel traps and emulates calls into the fixed vsyscall
2392 address mapping and does not allow reads. This
2393 configuration is recommended when userspace might use the
2394 legacy vsyscall area but support for legacy binary
2395 instrumentation of legacy code is not needed. It mitigates
2396 certain uses of the vsyscall area as an ASLR-bypassing
2399 config LEGACY_VSYSCALL_NONE
2402 There will be no vsyscall mapping at all. This will
2403 eliminate any risk of ASLR bypass due to the vsyscall
2404 fixed address mapping. Attempts to use the vsyscalls
2405 will be reported to dmesg, so that either old or
2406 malicious userspace programs can be identified.
2411 bool "Built-in kernel command line"
2413 Allow for specifying boot arguments to the kernel at
2414 build time. On some systems (e.g. embedded ones), it is
2415 necessary or convenient to provide some or all of the
2416 kernel boot arguments with the kernel itself (that is,
2417 to not rely on the boot loader to provide them.)
2419 To compile command line arguments into the kernel,
2420 set this option to 'Y', then fill in the
2421 boot arguments in CONFIG_CMDLINE.
2423 Systems with fully functional boot loaders (i.e. non-embedded)
2424 should leave this option set to 'N'.
2427 string "Built-in kernel command string"
2428 depends on CMDLINE_BOOL
2431 Enter arguments here that should be compiled into the kernel
2432 image and used at boot time. If the boot loader provides a
2433 command line at boot time, it is appended to this string to
2434 form the full kernel command line, when the system boots.
2436 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2437 change this behavior.
2439 In most cases, the command line (whether built-in or provided
2440 by the boot loader) should specify the device for the root
2443 config CMDLINE_OVERRIDE
2444 bool "Built-in command line overrides boot loader arguments"
2445 depends on CMDLINE_BOOL
2447 Set this option to 'Y' to have the kernel ignore the boot loader
2448 command line, and use ONLY the built-in command line.
2450 This is used to work around broken boot loaders. This should
2451 be set to 'N' under normal conditions.
2453 config MODIFY_LDT_SYSCALL
2454 bool "Enable the LDT (local descriptor table)" if EXPERT
2457 Linux can allow user programs to install a per-process x86
2458 Local Descriptor Table (LDT) using the modify_ldt(2) system
2459 call. This is required to run 16-bit or segmented code such as
2460 DOSEMU or some Wine programs. It is also used by some very old
2461 threading libraries.
2463 Enabling this feature adds a small amount of overhead to
2464 context switches and increases the low-level kernel attack
2465 surface. Disabling it removes the modify_ldt(2) system call.
2467 Saying 'N' here may make sense for embedded or server kernels.
2469 source "kernel/livepatch/Kconfig"
2473 config ARCH_HAS_ADD_PAGES
2475 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2477 config ARCH_ENABLE_MEMORY_HOTPLUG
2479 depends on X86_64 || (X86_32 && HIGHMEM)
2481 config ARCH_ENABLE_MEMORY_HOTREMOVE
2483 depends on MEMORY_HOTPLUG
2485 config USE_PERCPU_NUMA_NODE_ID
2489 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2491 depends on X86_64 || X86_PAE
2493 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2495 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2497 config ARCH_ENABLE_THP_MIGRATION
2499 depends on X86_64 && TRANSPARENT_HUGEPAGE
2501 menu "Power management and ACPI options"
2503 config ARCH_HIBERNATION_HEADER
2505 depends on HIBERNATION
2507 source "kernel/power/Kconfig"
2509 source "drivers/acpi/Kconfig"
2511 source "drivers/sfi/Kconfig"
2518 tristate "APM (Advanced Power Management) BIOS support"
2519 depends on X86_32 && PM_SLEEP
2521 APM is a BIOS specification for saving power using several different
2522 techniques. This is mostly useful for battery powered laptops with
2523 APM compliant BIOSes. If you say Y here, the system time will be
2524 reset after a RESUME operation, the /proc/apm device will provide
2525 battery status information, and user-space programs will receive
2526 notification of APM "events" (e.g. battery status change).
2528 If you select "Y" here, you can disable actual use of the APM
2529 BIOS by passing the "apm=off" option to the kernel at boot time.
2531 Note that the APM support is almost completely disabled for
2532 machines with more than one CPU.
2534 In order to use APM, you will need supporting software. For location
2535 and more information, read <file:Documentation/power/apm-acpi.rst>
2536 and the Battery Powered Linux mini-HOWTO, available from
2537 <http://www.tldp.org/docs.html#howto>.
2539 This driver does not spin down disk drives (see the hdparm(8)
2540 manpage ("man 8 hdparm") for that), and it doesn't turn off
2541 VESA-compliant "green" monitors.
2543 This driver does not support the TI 4000M TravelMate and the ACER
2544 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2545 desktop machines also don't have compliant BIOSes, and this driver
2546 may cause those machines to panic during the boot phase.
2548 Generally, if you don't have a battery in your machine, there isn't
2549 much point in using this driver and you should say N. If you get
2550 random kernel OOPSes or reboots that don't seem to be related to
2551 anything, try disabling/enabling this option (or disabling/enabling
2554 Some other things you should try when experiencing seemingly random,
2557 1) make sure that you have enough swap space and that it is
2559 2) pass the "no-hlt" option to the kernel
2560 3) switch on floating point emulation in the kernel and pass
2561 the "no387" option to the kernel
2562 4) pass the "floppy=nodma" option to the kernel
2563 5) pass the "mem=4M" option to the kernel (thereby disabling
2564 all but the first 4 MB of RAM)
2565 6) make sure that the CPU is not over clocked.
2566 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2567 8) disable the cache from your BIOS settings
2568 9) install a fan for the video card or exchange video RAM
2569 10) install a better fan for the CPU
2570 11) exchange RAM chips
2571 12) exchange the motherboard.
2573 To compile this driver as a module, choose M here: the
2574 module will be called apm.
2578 config APM_IGNORE_USER_SUSPEND
2579 bool "Ignore USER SUSPEND"
2581 This option will ignore USER SUSPEND requests. On machines with a
2582 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2583 series notebooks, it is necessary to say Y because of a BIOS bug.
2585 config APM_DO_ENABLE
2586 bool "Enable PM at boot time"
2588 Enable APM features at boot time. From page 36 of the APM BIOS
2589 specification: "When disabled, the APM BIOS does not automatically
2590 power manage devices, enter the Standby State, enter the Suspend
2591 State, or take power saving steps in response to CPU Idle calls."
2592 This driver will make CPU Idle calls when Linux is idle (unless this
2593 feature is turned off -- see "Do CPU IDLE calls", below). This
2594 should always save battery power, but more complicated APM features
2595 will be dependent on your BIOS implementation. You may need to turn
2596 this option off if your computer hangs at boot time when using APM
2597 support, or if it beeps continuously instead of suspending. Turn
2598 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2599 T400CDT. This is off by default since most machines do fine without
2604 bool "Make CPU Idle calls when idle"
2606 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2607 On some machines, this can activate improved power savings, such as
2608 a slowed CPU clock rate, when the machine is idle. These idle calls
2609 are made after the idle loop has run for some length of time (e.g.,
2610 333 mS). On some machines, this will cause a hang at boot time or
2611 whenever the CPU becomes idle. (On machines with more than one CPU,
2612 this option does nothing.)
2614 config APM_DISPLAY_BLANK
2615 bool "Enable console blanking using APM"
2617 Enable console blanking using the APM. Some laptops can use this to
2618 turn off the LCD backlight when the screen blanker of the Linux
2619 virtual console blanks the screen. Note that this is only used by
2620 the virtual console screen blanker, and won't turn off the backlight
2621 when using the X Window system. This also doesn't have anything to
2622 do with your VESA-compliant power-saving monitor. Further, this
2623 option doesn't work for all laptops -- it might not turn off your
2624 backlight at all, or it might print a lot of errors to the console,
2625 especially if you are using gpm.
2627 config APM_ALLOW_INTS
2628 bool "Allow interrupts during APM BIOS calls"
2630 Normally we disable external interrupts while we are making calls to
2631 the APM BIOS as a measure to lessen the effects of a badly behaving
2632 BIOS implementation. The BIOS should reenable interrupts if it
2633 needs to. Unfortunately, some BIOSes do not -- especially those in
2634 many of the newer IBM Thinkpads. If you experience hangs when you
2635 suspend, try setting this to Y. Otherwise, say N.
2639 source "drivers/cpufreq/Kconfig"
2641 source "drivers/cpuidle/Kconfig"
2643 source "drivers/idle/Kconfig"
2648 menu "Bus options (PCI etc.)"
2651 prompt "PCI access mode"
2652 depends on X86_32 && PCI
2655 On PCI systems, the BIOS can be used to detect the PCI devices and
2656 determine their configuration. However, some old PCI motherboards
2657 have BIOS bugs and may crash if this is done. Also, some embedded
2658 PCI-based systems don't have any BIOS at all. Linux can also try to
2659 detect the PCI hardware directly without using the BIOS.
2661 With this option, you can specify how Linux should detect the
2662 PCI devices. If you choose "BIOS", the BIOS will be used,
2663 if you choose "Direct", the BIOS won't be used, and if you
2664 choose "MMConfig", then PCI Express MMCONFIG will be used.
2665 If you choose "Any", the kernel will try MMCONFIG, then the
2666 direct access method and falls back to the BIOS if that doesn't
2667 work. If unsure, go with the default, which is "Any".
2672 config PCI_GOMMCONFIG
2689 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2691 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2694 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2697 bool "Support mmconfig PCI config space access" if X86_64
2699 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2700 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2704 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2708 depends on PCI && XEN
2711 config MMCONF_FAM10H
2713 depends on X86_64 && PCI_MMCONFIG && ACPI
2715 config PCI_CNB20LE_QUIRK
2716 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2719 Read the PCI windows out of the CNB20LE host bridge. This allows
2720 PCI hotplug to work on systems with the CNB20LE chipset which do
2723 There's no public spec for this chipset, and this functionality
2724 is known to be incomplete.
2726 You should say N unless you know you need this.
2729 bool "ISA bus support on modern systems" if EXPERT
2731 Expose ISA bus device drivers and options available for selection and
2732 configuration. Enable this option if your target machine has an ISA
2733 bus. ISA is an older system, displaced by PCI and newer bus
2734 architectures -- if your target machine is modern, it probably does
2735 not have an ISA bus.
2739 # x86_64 have no ISA slots, but can have ISA-style DMA.
2741 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2744 Enables ISA-style DMA support for devices requiring such controllers.
2752 Find out whether you have ISA slots on your motherboard. ISA is the
2753 name of a bus system, i.e. the way the CPU talks to the other stuff
2754 inside your box. Other bus systems are PCI, EISA, MicroChannel
2755 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2756 newer boards don't support it. If you have ISA, say Y, otherwise N.
2759 tristate "NatSemi SCx200 support"
2761 This provides basic support for National Semiconductor's
2762 (now AMD's) Geode processors. The driver probes for the
2763 PCI-IDs of several on-chip devices, so its a good dependency
2764 for other scx200_* drivers.
2766 If compiled as a module, the driver is named scx200.
2768 config SCx200HR_TIMER
2769 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2773 This driver provides a clocksource built upon the on-chip
2774 27MHz high-resolution timer. Its also a workaround for
2775 NSC Geode SC-1100's buggy TSC, which loses time when the
2776 processor goes idle (as is done by the scheduler). The
2777 other workaround is idle=poll boot option.
2780 bool "One Laptop Per Child support"
2788 Add support for detecting the unique features of the OLPC
2792 bool "OLPC XO-1 Power Management"
2793 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2795 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2798 bool "OLPC XO-1 Real Time Clock"
2799 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2801 Add support for the XO-1 real time clock, which can be used as a
2802 programmable wakeup source.
2805 bool "OLPC XO-1 SCI extras"
2806 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2810 Add support for SCI-based features of the OLPC XO-1 laptop:
2811 - EC-driven system wakeups
2815 - AC adapter status updates
2816 - Battery status updates
2818 config OLPC_XO15_SCI
2819 bool "OLPC XO-1.5 SCI extras"
2820 depends on OLPC && ACPI
2823 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2824 - EC-driven system wakeups
2825 - AC adapter status updates
2826 - Battery status updates
2829 bool "PCEngines ALIX System Support (LED setup)"
2832 This option enables system support for the PCEngines ALIX.
2833 At present this just sets up LEDs for GPIO control on
2834 ALIX2/3/6 boards. However, other system specific setup should
2837 Note: You must still enable the drivers for GPIO and LED support
2838 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2840 Note: You have to set alix.force=1 for boards with Award BIOS.
2843 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2846 This option enables system support for the Soekris Engineering net5501.
2849 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2853 This option enables system support for the Traverse Technologies GEOS.
2856 bool "Technologic Systems TS-5500 platform support"
2858 select CHECK_SIGNATURE
2862 This option enables system support for the Technologic Systems TS-5500.
2868 depends on CPU_SUP_AMD && PCI
2871 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2873 Firmwares often provide initial graphics framebuffers so the BIOS,
2874 bootloader or kernel can show basic video-output during boot for
2875 user-guidance and debugging. Historically, x86 used the VESA BIOS
2876 Extensions and EFI-framebuffers for this, which are mostly limited
2878 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2879 framebuffers so the new generic system-framebuffer drivers can be
2880 used on x86. If the framebuffer is not compatible with the generic
2881 modes, it is advertised as fallback platform framebuffer so legacy
2882 drivers like efifb, vesafb and uvesafb can pick it up.
2883 If this option is not selected, all system framebuffers are always
2884 marked as fallback platform framebuffers as usual.
2886 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2887 not be able to pick up generic system framebuffers if this option
2888 is selected. You are highly encouraged to enable simplefb as
2889 replacement if you select this option. simplefb can correctly deal
2890 with generic system framebuffers. But you should still keep vesafb
2891 and others enabled as fallback if a system framebuffer is
2892 incompatible with simplefb.
2899 menu "Binary Emulations"
2901 config IA32_EMULATION
2902 bool "IA32 Emulation"
2904 select ARCH_WANT_OLD_COMPAT_IPC
2906 select COMPAT_BINFMT_ELF
2907 select COMPAT_OLD_SIGACTION
2909 Include code to run legacy 32-bit programs under a
2910 64-bit kernel. You should likely turn this on, unless you're
2911 100% sure that you don't have any 32-bit programs left.
2914 tristate "IA32 a.out support"
2915 depends on IA32_EMULATION
2918 Support old a.out binaries in the 32bit emulation.
2921 bool "x32 ABI for 64-bit mode"
2924 Include code to run binaries for the x32 native 32-bit ABI
2925 for 64-bit processors. An x32 process gets access to the
2926 full 64-bit register file and wide data path while leaving
2927 pointers at 32 bits for smaller memory footprint.
2929 You will need a recent binutils (2.22 or later) with
2930 elf32_x86_64 support enabled to compile a kernel with this
2935 depends on IA32_EMULATION || X86_32
2937 select OLD_SIGSUSPEND3
2941 depends on IA32_EMULATION || X86_X32
2944 config COMPAT_FOR_U64_ALIGNMENT
2947 config SYSVIPC_COMPAT
2955 config HAVE_ATOMIC_IOMAP
2959 config X86_DEV_DMA_OPS
2962 source "drivers/firmware/Kconfig"
2964 source "arch/x86/kvm/Kconfig"