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 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_KASAN_VMALLOC if X86_64
138 select HAVE_ARCH_KGDB
139 select HAVE_ARCH_MMAP_RND_BITS if MMU
140 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
141 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
142 select HAVE_ARCH_PREL32_RELOCATIONS
143 select HAVE_ARCH_SECCOMP_FILTER
144 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
145 select HAVE_ARCH_STACKLEAK
146 select HAVE_ARCH_TRACEHOOK
147 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
148 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
149 select HAVE_ARCH_VMAP_STACK if X86_64
150 select HAVE_ARCH_WITHIN_STACK_FRAMES
151 select HAVE_ASM_MODVERSIONS
152 select HAVE_CMPXCHG_DOUBLE
153 select HAVE_CMPXCHG_LOCAL
154 select HAVE_CONTEXT_TRACKING if X86_64
155 select HAVE_COPY_THREAD_TLS
156 select HAVE_C_RECORDMCOUNT
157 select HAVE_DEBUG_KMEMLEAK
158 select HAVE_DMA_CONTIGUOUS
159 select HAVE_DYNAMIC_FTRACE
160 select HAVE_DYNAMIC_FTRACE_WITH_REGS
161 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
163 select HAVE_EFFICIENT_UNALIGNED_ACCESS
165 select HAVE_EXIT_THREAD
167 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
168 select HAVE_FTRACE_MCOUNT_RECORD
169 select HAVE_FUNCTION_GRAPH_TRACER
170 select HAVE_FUNCTION_TRACER
171 select HAVE_GCC_PLUGINS
172 select HAVE_HW_BREAKPOINT
174 select HAVE_IOREMAP_PROT
175 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
176 select HAVE_IRQ_TIME_ACCOUNTING
177 select HAVE_KERNEL_BZIP2
178 select HAVE_KERNEL_GZIP
179 select HAVE_KERNEL_LZ4
180 select HAVE_KERNEL_LZMA
181 select HAVE_KERNEL_LZO
182 select HAVE_KERNEL_XZ
184 select HAVE_KPROBES_ON_FTRACE
185 select HAVE_FUNCTION_ERROR_INJECTION
186 select HAVE_KRETPROBES
188 select HAVE_LIVEPATCH if X86_64
189 select HAVE_MEMBLOCK_NODE_MAP
190 select HAVE_MIXED_BREAKPOINTS_REGS
191 select HAVE_MOD_ARCH_SPECIFIC
195 select HAVE_OPTPROBES
196 select HAVE_PCSPKR_PLATFORM
197 select HAVE_PERF_EVENTS
198 select HAVE_PERF_EVENTS_NMI
199 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
201 select HAVE_PERF_REGS
202 select HAVE_PERF_USER_STACK_DUMP
203 select HAVE_RCU_TABLE_FREE if PARAVIRT
204 select HAVE_REGS_AND_STACK_ACCESS_API
205 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
206 select HAVE_FUNCTION_ARG_ACCESS_API
207 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
208 select HAVE_STACK_VALIDATION if X86_64
210 select HAVE_SYSCALL_TRACEPOINTS
211 select HAVE_UNSTABLE_SCHED_CLOCK
212 select HAVE_USER_RETURN_NOTIFIER
213 select HAVE_GENERIC_VDSO
214 select HOTPLUG_SMT if SMP
215 select IRQ_FORCED_THREADING
216 select NEED_SG_DMA_LENGTH
217 select PCI_DOMAINS if PCI
218 select PCI_LOCKLESS_CONFIG if PCI
221 select RTC_MC146818_LIB
224 select SYSCTL_EXCEPTION_TRACE
225 select THREAD_INFO_IN_TASK
226 select USER_STACKTRACE_SUPPORT
228 select X86_FEATURE_NAMES if PROC_FS
229 select PROC_PID_ARCH_STATUS if PROC_FS
231 config INSTRUCTION_DECODER
233 depends on KPROBES || PERF_EVENTS || UPROBES
237 default "elf32-i386" if X86_32
238 default "elf64-x86-64" if X86_64
240 config ARCH_DEFCONFIG
242 default "arch/x86/configs/i386_defconfig" if X86_32
243 default "arch/x86/configs/x86_64_defconfig" if X86_64
245 config LOCKDEP_SUPPORT
248 config STACKTRACE_SUPPORT
254 config ARCH_MMAP_RND_BITS_MIN
258 config ARCH_MMAP_RND_BITS_MAX
262 config ARCH_MMAP_RND_COMPAT_BITS_MIN
265 config ARCH_MMAP_RND_COMPAT_BITS_MAX
271 config GENERIC_ISA_DMA
273 depends on ISA_DMA_API
278 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
280 config GENERIC_BUG_RELATIVE_POINTERS
283 config ARCH_MAY_HAVE_PC_FDC
285 depends on ISA_DMA_API
287 config GENERIC_CALIBRATE_DELAY
290 config ARCH_HAS_CPU_RELAX
293 config ARCH_HAS_CACHE_LINE_SIZE
296 config ARCH_HAS_FILTER_PGPROT
299 config HAVE_SETUP_PER_CPU_AREA
302 config NEED_PER_CPU_EMBED_FIRST_CHUNK
305 config NEED_PER_CPU_PAGE_FIRST_CHUNK
308 config ARCH_HIBERNATION_POSSIBLE
311 config ARCH_SUSPEND_POSSIBLE
314 config ARCH_WANT_GENERAL_HUGETLB
323 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
326 config KASAN_SHADOW_OFFSET
329 default 0xdffffc0000000000
331 config HAVE_INTEL_TXT
333 depends on INTEL_IOMMU && ACPI
337 depends on X86_32 && SMP
341 depends on X86_64 && SMP
343 config X86_32_LAZY_GS
345 depends on X86_32 && !STACKPROTECTOR
347 config ARCH_SUPPORTS_UPROBES
350 config FIX_EARLYCON_MEM
353 config DYNAMIC_PHYSICAL_MASK
356 config PGTABLE_LEVELS
358 default 5 if X86_5LEVEL
363 config CC_HAS_SANE_STACKPROTECTOR
365 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
366 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
368 We have to make sure stack protector is unconditionally disabled if
369 the compiler produces broken code.
371 menu "Processor type and features"
374 bool "DMA memory allocation support" if EXPERT
377 DMA memory allocation support allows devices with less than 32-bit
378 addressing to allocate within the first 16MB of address space.
379 Disable if no such devices will be used.
384 bool "Symmetric multi-processing support"
386 This enables support for systems with more than one CPU. If you have
387 a system with only one CPU, say N. If you have a system with more
390 If you say N here, the kernel will run on uni- and multiprocessor
391 machines, but will use only one CPU of a multiprocessor machine. If
392 you say Y here, the kernel will run on many, but not all,
393 uniprocessor machines. On a uniprocessor machine, the kernel
394 will run faster if you say N here.
396 Note that if you say Y here and choose architecture "586" or
397 "Pentium" under "Processor family", the kernel will not work on 486
398 architectures. Similarly, multiprocessor kernels for the "PPro"
399 architecture may not work on all Pentium based boards.
401 People using multiprocessor machines who say Y here should also say
402 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
403 Management" code will be disabled if you say Y here.
405 See also <file:Documentation/x86/i386/IO-APIC.rst>,
406 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
407 <http://www.tldp.org/docs.html#howto>.
409 If you don't know what to do here, say N.
411 config X86_FEATURE_NAMES
412 bool "Processor feature human-readable names" if EMBEDDED
415 This option compiles in a table of x86 feature bits and corresponding
416 names. This is required to support /proc/cpuinfo and a few kernel
417 messages. You can disable this to save space, at the expense of
418 making those few kernel messages show numeric feature bits instead.
423 bool "Support x2apic"
424 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
426 This enables x2apic support on CPUs that have this feature.
428 This allows 32-bit apic IDs (so it can support very large systems),
429 and accesses the local apic via MSRs not via mmio.
431 If you don't know what to do here, say N.
434 bool "Enable MPS table" if ACPI || SFI
436 depends on X86_LOCAL_APIC
438 For old smp systems that do not have proper acpi support. Newer systems
439 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
443 depends on X86_GOLDFISH
446 bool "Avoid speculative indirect branches in kernel"
448 select STACK_VALIDATION if HAVE_STACK_VALIDATION
450 Compile kernel with the retpoline compiler options to guard against
451 kernel-to-user data leaks by avoiding speculative indirect
452 branches. Requires a compiler with -mindirect-branch=thunk-extern
453 support for full protection. The kernel may run slower.
455 config X86_CPU_RESCTRL
456 bool "x86 CPU resource control support"
457 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
460 Enable x86 CPU resource control support.
462 Provide support for the allocation and monitoring of system resources
465 Intel calls this Intel Resource Director Technology
466 (Intel(R) RDT). More information about RDT can be found in the
467 Intel x86 Architecture Software Developer Manual.
469 AMD calls this AMD Platform Quality of Service (AMD QoS).
470 More information about AMD QoS can be found in the AMD64 Technology
471 Platform Quality of Service Extensions manual.
477 bool "Support for big SMP systems with more than 8 CPUs"
480 This option is needed for the systems that have more than 8 CPUs
482 config X86_EXTENDED_PLATFORM
483 bool "Support for extended (non-PC) x86 platforms"
486 If you disable this option then the kernel will only support
487 standard PC platforms. (which covers the vast majority of
490 If you enable this option then you'll be able to select support
491 for the following (non-PC) 32 bit x86 platforms:
492 Goldfish (Android emulator)
495 SGI 320/540 (Visual Workstation)
496 STA2X11-based (e.g. Northville)
497 Moorestown MID devices
499 If you have one of these systems, or if you want to build a
500 generic distribution kernel, say Y here - otherwise say N.
504 config X86_EXTENDED_PLATFORM
505 bool "Support for extended (non-PC) x86 platforms"
508 If you disable this option then the kernel will only support
509 standard PC platforms. (which covers the vast majority of
512 If you enable this option then you'll be able to select support
513 for the following (non-PC) 64 bit x86 platforms:
518 If you have one of these systems, or if you want to build a
519 generic distribution kernel, say Y here - otherwise say N.
521 # This is an alphabetically sorted list of 64 bit extended platforms
522 # Please maintain the alphabetic order if and when there are additions
524 bool "Numascale NumaChip"
526 depends on X86_EXTENDED_PLATFORM
529 depends on X86_X2APIC
530 depends on PCI_MMCONFIG
532 Adds support for Numascale NumaChip large-SMP systems. Needed to
533 enable more than ~168 cores.
534 If you don't have one of these, you should say N here.
538 select HYPERVISOR_GUEST
540 depends on X86_64 && PCI
541 depends on X86_EXTENDED_PLATFORM
544 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
545 supposed to run on these EM64T-based machines. Only choose this option
546 if you have one of these machines.
549 bool "SGI Ultraviolet"
551 depends on X86_EXTENDED_PLATFORM
554 depends on X86_X2APIC
557 This option is needed in order to support SGI Ultraviolet systems.
558 If you don't have one of these, you should say N here.
560 # Following is an alphabetically sorted list of 32 bit extended platforms
561 # Please maintain the alphabetic order if and when there are additions
564 bool "Goldfish (Virtual Platform)"
565 depends on X86_EXTENDED_PLATFORM
567 Enable support for the Goldfish virtual platform used primarily
568 for Android development. Unless you are building for the Android
569 Goldfish emulator say N here.
572 bool "CE4100 TV platform"
574 depends on PCI_GODIRECT
575 depends on X86_IO_APIC
577 depends on X86_EXTENDED_PLATFORM
578 select X86_REBOOTFIXUPS
580 select OF_EARLY_FLATTREE
582 Select for the Intel CE media processor (CE4100) SOC.
583 This option compiles in support for the CE4100 SOC for settop
584 boxes and media devices.
587 bool "Intel MID platform support"
588 depends on X86_EXTENDED_PLATFORM
589 depends on X86_PLATFORM_DEVICES
591 depends on X86_64 || (PCI_GOANY && X86_32)
592 depends on X86_IO_APIC
598 select MFD_INTEL_MSIC
600 Select to build a kernel capable of supporting Intel MID (Mobile
601 Internet Device) platform systems which do not have the PCI legacy
602 interfaces. If you are building for a PC class system say N here.
604 Intel MID platforms are based on an Intel processor and chipset which
605 consume less power than most of the x86 derivatives.
607 config X86_INTEL_QUARK
608 bool "Intel Quark platform support"
610 depends on X86_EXTENDED_PLATFORM
611 depends on X86_PLATFORM_DEVICES
615 depends on X86_IO_APIC
620 Select to include support for Quark X1000 SoC.
621 Say Y here if you have a Quark based system such as the Arduino
622 compatible Intel Galileo.
624 config X86_INTEL_LPSS
625 bool "Intel Low Power Subsystem Support"
626 depends on X86 && ACPI && PCI
631 Select to build support for Intel Low Power Subsystem such as
632 found on Intel Lynxpoint PCH. Selecting this option enables
633 things like clock tree (common clock framework) and pincontrol
634 which are needed by the LPSS peripheral drivers.
636 config X86_AMD_PLATFORM_DEVICE
637 bool "AMD ACPI2Platform devices support"
642 Select to interpret AMD specific ACPI device to platform device
643 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
644 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
645 implemented under PINCTRL subsystem.
648 tristate "Intel SoC IOSF Sideband support for SoC platforms"
651 This option enables sideband register access support for Intel SoC
652 platforms. On these platforms the IOSF sideband is used in lieu of
653 MSR's for some register accesses, mostly but not limited to thermal
654 and power. Drivers may query the availability of this device to
655 determine if they need the sideband in order to work on these
656 platforms. The sideband is available on the following SoC products.
657 This list is not meant to be exclusive.
662 You should say Y if you are running a kernel on one of these SoC's.
664 config IOSF_MBI_DEBUG
665 bool "Enable IOSF sideband access through debugfs"
666 depends on IOSF_MBI && DEBUG_FS
668 Select this option to expose the IOSF sideband access registers (MCR,
669 MDR, MCRX) through debugfs to write and read register information from
670 different units on the SoC. This is most useful for obtaining device
671 state information for debug and analysis. As this is a general access
672 mechanism, users of this option would have specific knowledge of the
673 device they want to access.
675 If you don't require the option or are in doubt, say N.
678 bool "RDC R-321x SoC"
680 depends on X86_EXTENDED_PLATFORM
682 select X86_REBOOTFIXUPS
684 This option is needed for RDC R-321x system-on-chip, also known
686 If you don't have one of these chips, you should say N here.
688 config X86_32_NON_STANDARD
689 bool "Support non-standard 32-bit SMP architectures"
690 depends on X86_32 && SMP
691 depends on X86_EXTENDED_PLATFORM
693 This option compiles in the bigsmp and STA2X11 default
694 subarchitectures. It is intended for a generic binary
695 kernel. If you select them all, kernel will probe it one by
696 one and will fallback to default.
698 # Alphabetically sorted list of Non standard 32 bit platforms
700 config X86_SUPPORTS_MEMORY_FAILURE
702 # MCE code calls memory_failure():
704 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
705 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
706 depends on X86_64 || !SPARSEMEM
707 select ARCH_SUPPORTS_MEMORY_FAILURE
710 bool "STA2X11 Companion Chip Support"
711 depends on X86_32_NON_STANDARD && PCI
716 This adds support for boards based on the STA2X11 IO-Hub,
717 a.k.a. "ConneXt". The chip is used in place of the standard
718 PC chipset, so all "standard" peripherals are missing. If this
719 option is selected the kernel will still be able to boot on
720 standard PC machines.
723 tristate "Eurobraille/Iris poweroff module"
726 The Iris machines from EuroBraille do not have APM or ACPI support
727 to shut themselves down properly. A special I/O sequence is
728 needed to do so, which is what this module does at
731 This is only for Iris machines from EuroBraille.
735 config SCHED_OMIT_FRAME_POINTER
737 prompt "Single-depth WCHAN output"
740 Calculate simpler /proc/<PID>/wchan values. If this option
741 is disabled then wchan values will recurse back to the
742 caller function. This provides more accurate wchan values,
743 at the expense of slightly more scheduling overhead.
745 If in doubt, say "Y".
747 menuconfig HYPERVISOR_GUEST
748 bool "Linux guest support"
750 Say Y here to enable options for running Linux under various hyper-
751 visors. This option enables basic hypervisor detection and platform
754 If you say N, all options in this submenu will be skipped and
755 disabled, and Linux guest support won't be built in.
760 bool "Enable paravirtualization code"
762 This changes the kernel so it can modify itself when it is run
763 under a hypervisor, potentially improving performance significantly
764 over full virtualization. However, when run without a hypervisor
765 the kernel is theoretically slower and slightly larger.
770 config PARAVIRT_DEBUG
771 bool "paravirt-ops debugging"
772 depends on PARAVIRT && DEBUG_KERNEL
774 Enable to debug paravirt_ops internals. Specifically, BUG if
775 a paravirt_op is missing when it is called.
777 config PARAVIRT_SPINLOCKS
778 bool "Paravirtualization layer for spinlocks"
779 depends on PARAVIRT && SMP
781 Paravirtualized spinlocks allow a pvops backend to replace the
782 spinlock implementation with something virtualization-friendly
783 (for example, block the virtual CPU rather than spinning).
785 It has a minimal impact on native kernels and gives a nice performance
786 benefit on paravirtualized KVM / Xen kernels.
788 If you are unsure how to answer this question, answer Y.
790 config X86_HV_CALLBACK_VECTOR
793 source "arch/x86/xen/Kconfig"
796 bool "KVM Guest support (including kvmclock)"
798 select PARAVIRT_CLOCK
799 select ARCH_CPUIDLE_HALTPOLL
802 This option enables various optimizations for running under the KVM
803 hypervisor. It includes a paravirtualized clock, so that instead
804 of relying on a PIT (or probably other) emulation by the
805 underlying device model, the host provides the guest with
806 timing infrastructure such as time of day, and system time
808 config ARCH_CPUIDLE_HALTPOLL
810 prompt "Disable host haltpoll when loading haltpoll driver"
812 If virtualized under KVM, disable host haltpoll.
815 bool "Support for running PVH guests"
817 This option enables the PVH entry point for guest virtual machines
818 as specified in the x86/HVM direct boot ABI.
821 bool "Enable debug information for KVM Guests in debugfs"
822 depends on KVM_GUEST && DEBUG_FS
824 This option enables collection of various statistics for KVM guest.
825 Statistics are displayed in debugfs filesystem. Enabling this option
826 may incur significant overhead.
828 config PARAVIRT_TIME_ACCOUNTING
829 bool "Paravirtual steal time accounting"
832 Select this option to enable fine granularity task steal time
833 accounting. Time spent executing other tasks in parallel with
834 the current vCPU is discounted from the vCPU power. To account for
835 that, there can be a small performance impact.
837 If in doubt, say N here.
839 config PARAVIRT_CLOCK
842 config JAILHOUSE_GUEST
843 bool "Jailhouse non-root cell support"
844 depends on X86_64 && PCI
847 This option allows to run Linux as guest in a Jailhouse non-root
848 cell. You can leave this option disabled if you only want to start
849 Jailhouse and run Linux afterwards in the root cell.
852 bool "ACRN Guest support"
854 select X86_HV_CALLBACK_VECTOR
856 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
857 a flexible, lightweight reference open-source hypervisor, built with
858 real-time and safety-criticality in mind. It is built for embedded
859 IOT with small footprint and real-time features. More details can be
860 found in https://projectacrn.org/.
862 endif #HYPERVISOR_GUEST
864 source "arch/x86/Kconfig.cpu"
868 prompt "HPET Timer Support" if X86_32
870 Use the IA-PC HPET (High Precision Event Timer) to manage
871 time in preference to the PIT and RTC, if a HPET is
873 HPET is the next generation timer replacing legacy 8254s.
874 The HPET provides a stable time base on SMP
875 systems, unlike the TSC, but it is more expensive to access,
876 as it is off-chip. The interface used is documented
877 in the HPET spec, revision 1.
879 You can safely choose Y here. However, HPET will only be
880 activated if the platform and the BIOS support this feature.
881 Otherwise the 8254 will be used for timing services.
883 Choose N to continue using the legacy 8254 timer.
885 config HPET_EMULATE_RTC
887 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
890 def_bool y if X86_INTEL_MID
891 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
893 depends on X86_INTEL_MID && SFI
895 APB timer is the replacement for 8254, HPET on X86 MID platforms.
896 The APBT provides a stable time base on SMP
897 systems, unlike the TSC, but it is more expensive to access,
898 as it is off-chip. APB timers are always running regardless of CPU
899 C states, they are used as per CPU clockevent device when possible.
901 # Mark as expert because too many people got it wrong.
902 # The code disables itself when not needed.
905 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
906 bool "Enable DMI scanning" if EXPERT
908 Enabled scanning of DMI to identify machine quirks. Say Y
909 here unless you have verified that your setup is not
910 affected by entries in the DMI blacklist. Required by PNP
914 bool "Old AMD GART IOMMU support"
917 depends on X86_64 && PCI && AMD_NB
919 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
920 GART based hardware IOMMUs.
922 The GART supports full DMA access for devices with 32-bit access
923 limitations, on systems with more than 3 GB. This is usually needed
924 for USB, sound, many IDE/SATA chipsets and some other devices.
926 Newer systems typically have a modern AMD IOMMU, supported via
927 the CONFIG_AMD_IOMMU=y config option.
929 In normal configurations this driver is only active when needed:
930 there's more than 3 GB of memory and the system contains a
931 32-bit limited device.
936 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
937 depends on X86_64 && SMP && DEBUG_KERNEL
938 select CPUMASK_OFFSTACK
940 Enable maximum number of CPUS and NUMA Nodes for this architecture.
944 # The maximum number of CPUs supported:
946 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
947 # and which can be configured interactively in the
948 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
950 # The ranges are different on 32-bit and 64-bit kernels, depending on
951 # hardware capabilities and scalability features of the kernel.
953 # ( If MAXSMP is enabled we just use the highest possible value and disable
954 # interactive configuration. )
957 config NR_CPUS_RANGE_BEGIN
959 default NR_CPUS_RANGE_END if MAXSMP
963 config NR_CPUS_RANGE_END
966 default 64 if SMP && X86_BIGSMP
967 default 8 if SMP && !X86_BIGSMP
970 config NR_CPUS_RANGE_END
973 default 8192 if SMP && CPUMASK_OFFSTACK
974 default 512 if SMP && !CPUMASK_OFFSTACK
977 config NR_CPUS_DEFAULT
980 default 32 if X86_BIGSMP
984 config NR_CPUS_DEFAULT
987 default 8192 if MAXSMP
992 int "Maximum number of CPUs" if SMP && !MAXSMP
993 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
994 default NR_CPUS_DEFAULT
996 This allows you to specify the maximum number of CPUs which this
997 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
998 supported value is 8192, otherwise the maximum value is 512. The
999 minimum value which makes sense is 2.
1001 This is purely to save memory: each supported CPU adds about 8KB
1002 to the kernel image.
1009 prompt "Multi-core scheduler support"
1012 Multi-core scheduler support improves the CPU scheduler's decision
1013 making when dealing with multi-core CPU chips at a cost of slightly
1014 increased overhead in some places. If unsure say N here.
1016 config SCHED_MC_PRIO
1017 bool "CPU core priorities scheduler support"
1018 depends on SCHED_MC && CPU_SUP_INTEL
1019 select X86_INTEL_PSTATE
1023 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1024 core ordering determined at manufacturing time, which allows
1025 certain cores to reach higher turbo frequencies (when running
1026 single threaded workloads) than others.
1028 Enabling this kernel feature teaches the scheduler about
1029 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1030 scheduler's CPU selection logic accordingly, so that higher
1031 overall system performance can be achieved.
1033 This feature will have no effect on CPUs without this feature.
1035 If unsure say Y here.
1039 depends on !SMP && X86_LOCAL_APIC
1042 bool "Local APIC support on uniprocessors" if !PCI_MSI
1044 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1046 A local APIC (Advanced Programmable Interrupt Controller) is an
1047 integrated interrupt controller in the CPU. If you have a single-CPU
1048 system which has a processor with a local APIC, you can say Y here to
1049 enable and use it. If you say Y here even though your machine doesn't
1050 have a local APIC, then the kernel will still run with no slowdown at
1051 all. The local APIC supports CPU-generated self-interrupts (timer,
1052 performance counters), and the NMI watchdog which detects hard
1055 config X86_UP_IOAPIC
1056 bool "IO-APIC support on uniprocessors"
1057 depends on X86_UP_APIC
1059 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1060 SMP-capable replacement for PC-style interrupt controllers. Most
1061 SMP systems and many recent uniprocessor systems have one.
1063 If you have a single-CPU system with an IO-APIC, you can say Y here
1064 to use it. If you say Y here even though your machine doesn't have
1065 an IO-APIC, then the kernel will still run with no slowdown at all.
1067 config X86_LOCAL_APIC
1069 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1070 select IRQ_DOMAIN_HIERARCHY
1071 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1075 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1077 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1078 bool "Reroute for broken boot IRQs"
1079 depends on X86_IO_APIC
1081 This option enables a workaround that fixes a source of
1082 spurious interrupts. This is recommended when threaded
1083 interrupt handling is used on systems where the generation of
1084 superfluous "boot interrupts" cannot be disabled.
1086 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1087 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1088 kernel does during interrupt handling). On chipsets where this
1089 boot IRQ generation cannot be disabled, this workaround keeps
1090 the original IRQ line masked so that only the equivalent "boot
1091 IRQ" is delivered to the CPUs. The workaround also tells the
1092 kernel to set up the IRQ handler on the boot IRQ line. In this
1093 way only one interrupt is delivered to the kernel. Otherwise
1094 the spurious second interrupt may cause the kernel to bring
1095 down (vital) interrupt lines.
1097 Only affects "broken" chipsets. Interrupt sharing may be
1098 increased on these systems.
1101 bool "Machine Check / overheating reporting"
1102 select GENERIC_ALLOCATOR
1105 Machine Check support allows the processor to notify the
1106 kernel if it detects a problem (e.g. overheating, data corruption).
1107 The action the kernel takes depends on the severity of the problem,
1108 ranging from warning messages to halting the machine.
1110 config X86_MCELOG_LEGACY
1111 bool "Support for deprecated /dev/mcelog character device"
1114 Enable support for /dev/mcelog which is needed by the old mcelog
1115 userspace logging daemon. Consider switching to the new generation
1118 config X86_MCE_INTEL
1120 prompt "Intel MCE features"
1121 depends on X86_MCE && X86_LOCAL_APIC
1123 Additional support for intel specific MCE features such as
1124 the thermal monitor.
1128 prompt "AMD MCE features"
1129 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1131 Additional support for AMD specific MCE features such as
1132 the DRAM Error Threshold.
1134 config X86_ANCIENT_MCE
1135 bool "Support for old Pentium 5 / WinChip machine checks"
1136 depends on X86_32 && X86_MCE
1138 Include support for machine check handling on old Pentium 5 or WinChip
1139 systems. These typically need to be enabled explicitly on the command
1142 config X86_MCE_THRESHOLD
1143 depends on X86_MCE_AMD || X86_MCE_INTEL
1146 config X86_MCE_INJECT
1147 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1148 tristate "Machine check injector support"
1150 Provide support for injecting machine checks for testing purposes.
1151 If you don't know what a machine check is and you don't do kernel
1152 QA it is safe to say n.
1154 config X86_THERMAL_VECTOR
1156 depends on X86_MCE_INTEL
1158 source "arch/x86/events/Kconfig"
1160 config X86_LEGACY_VM86
1161 bool "Legacy VM86 support"
1164 This option allows user programs to put the CPU into V8086
1165 mode, which is an 80286-era approximation of 16-bit real mode.
1167 Some very old versions of X and/or vbetool require this option
1168 for user mode setting. Similarly, DOSEMU will use it if
1169 available to accelerate real mode DOS programs. However, any
1170 recent version of DOSEMU, X, or vbetool should be fully
1171 functional even without kernel VM86 support, as they will all
1172 fall back to software emulation. Nevertheless, if you are using
1173 a 16-bit DOS program where 16-bit performance matters, vm86
1174 mode might be faster than emulation and you might want to
1177 Note that any app that works on a 64-bit kernel is unlikely to
1178 need this option, as 64-bit kernels don't, and can't, support
1179 V8086 mode. This option is also unrelated to 16-bit protected
1180 mode and is not needed to run most 16-bit programs under Wine.
1182 Enabling this option increases the complexity of the kernel
1183 and slows down exception handling a tiny bit.
1185 If unsure, say N here.
1189 default X86_LEGACY_VM86
1192 bool "Enable support for 16-bit segments" if EXPERT
1194 depends on MODIFY_LDT_SYSCALL
1196 This option is required by programs like Wine to run 16-bit
1197 protected mode legacy code on x86 processors. Disabling
1198 this option saves about 300 bytes on i386, or around 6K text
1199 plus 16K runtime memory on x86-64,
1203 depends on X86_16BIT && X86_32
1207 depends on X86_16BIT && X86_64
1209 config X86_VSYSCALL_EMULATION
1210 bool "Enable vsyscall emulation" if EXPERT
1214 This enables emulation of the legacy vsyscall page. Disabling
1215 it is roughly equivalent to booting with vsyscall=none, except
1216 that it will also disable the helpful warning if a program
1217 tries to use a vsyscall. With this option set to N, offending
1218 programs will just segfault, citing addresses of the form
1221 This option is required by many programs built before 2013, and
1222 care should be used even with newer programs if set to N.
1224 Disabling this option saves about 7K of kernel size and
1225 possibly 4K of additional runtime pagetable memory.
1227 config X86_IOPL_IOPERM
1228 bool "IOPERM and IOPL Emulation"
1231 This enables the ioperm() and iopl() syscalls which are necessary
1232 for legacy applications.
1234 Legacy IOPL support is an overbroad mechanism which allows user
1235 space aside of accessing all 65536 I/O ports also to disable
1236 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1237 capabilities and permission from potentially active security
1240 The emulation restricts the functionality of the syscall to
1241 only allowing the full range I/O port access, but prevents the
1242 ability to disable interrupts from user space which would be
1243 granted if the hardware IOPL mechanism would be used.
1246 tristate "Toshiba Laptop support"
1249 This adds a driver to safely access the System Management Mode of
1250 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1251 not work on models with a Phoenix BIOS. The System Management Mode
1252 is used to set the BIOS and power saving options on Toshiba portables.
1254 For information on utilities to make use of this driver see the
1255 Toshiba Linux utilities web site at:
1256 <http://www.buzzard.org.uk/toshiba/>.
1258 Say Y if you intend to run this kernel on a Toshiba portable.
1262 tristate "Dell i8k legacy laptop support"
1264 select SENSORS_DELL_SMM
1266 This option enables legacy /proc/i8k userspace interface in hwmon
1267 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1268 temperature and allows controlling fan speeds of Dell laptops via
1269 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1270 it reports also power and hotkey status. For fan speed control is
1271 needed userspace package i8kutils.
1273 Say Y if you intend to run this kernel on old Dell laptops or want to
1274 use userspace package i8kutils.
1277 config X86_REBOOTFIXUPS
1278 bool "Enable X86 board specific fixups for reboot"
1281 This enables chipset and/or board specific fixups to be done
1282 in order to get reboot to work correctly. This is only needed on
1283 some combinations of hardware and BIOS. The symptom, for which
1284 this config is intended, is when reboot ends with a stalled/hung
1287 Currently, the only fixup is for the Geode machines using
1288 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1290 Say Y if you want to enable the fixup. Currently, it's safe to
1291 enable this option even if you don't need it.
1295 bool "CPU microcode loading support"
1297 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1300 If you say Y here, you will be able to update the microcode on
1301 Intel and AMD processors. The Intel support is for the IA32 family,
1302 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1303 AMD support is for families 0x10 and later. You will obviously need
1304 the actual microcode binary data itself which is not shipped with
1307 The preferred method to load microcode from a detached initrd is described
1308 in Documentation/x86/microcode.rst. For that you need to enable
1309 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1310 initrd for microcode blobs.
1312 In addition, you can build the microcode into the kernel. For that you
1313 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1316 config MICROCODE_INTEL
1317 bool "Intel microcode loading support"
1318 depends on MICROCODE
1322 This options enables microcode patch loading support for Intel
1325 For the current Intel microcode data package go to
1326 <https://downloadcenter.intel.com> and search for
1327 'Linux Processor Microcode Data File'.
1329 config MICROCODE_AMD
1330 bool "AMD microcode loading support"
1331 depends on MICROCODE
1334 If you select this option, microcode patch loading support for AMD
1335 processors will be enabled.
1337 config MICROCODE_OLD_INTERFACE
1338 bool "Ancient loading interface (DEPRECATED)"
1340 depends on MICROCODE
1342 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1343 which was used by userspace tools like iucode_tool and microcode.ctl.
1344 It is inadequate because it runs too late to be able to properly
1345 load microcode on a machine and it needs special tools. Instead, you
1346 should've switched to the early loading method with the initrd or
1347 builtin microcode by now: Documentation/x86/microcode.rst
1350 tristate "/dev/cpu/*/msr - Model-specific register support"
1352 This device gives privileged processes access to the x86
1353 Model-Specific Registers (MSRs). It is a character device with
1354 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1355 MSR accesses are directed to a specific CPU on multi-processor
1359 tristate "/dev/cpu/*/cpuid - CPU information support"
1361 This device gives processes access to the x86 CPUID instruction to
1362 be executed on a specific processor. It is a character device
1363 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1367 prompt "High Memory Support"
1374 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1375 However, the address space of 32-bit x86 processors is only 4
1376 Gigabytes large. That means that, if you have a large amount of
1377 physical memory, not all of it can be "permanently mapped" by the
1378 kernel. The physical memory that's not permanently mapped is called
1381 If you are compiling a kernel which will never run on a machine with
1382 more than 1 Gigabyte total physical RAM, answer "off" here (default
1383 choice and suitable for most users). This will result in a "3GB/1GB"
1384 split: 3GB are mapped so that each process sees a 3GB virtual memory
1385 space and the remaining part of the 4GB virtual memory space is used
1386 by the kernel to permanently map as much physical memory as
1389 If the machine has between 1 and 4 Gigabytes physical RAM, then
1392 If more than 4 Gigabytes is used then answer "64GB" here. This
1393 selection turns Intel PAE (Physical Address Extension) mode on.
1394 PAE implements 3-level paging on IA32 processors. PAE is fully
1395 supported by Linux, PAE mode is implemented on all recent Intel
1396 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1397 then the kernel will not boot on CPUs that don't support PAE!
1399 The actual amount of total physical memory will either be
1400 auto detected or can be forced by using a kernel command line option
1401 such as "mem=256M". (Try "man bootparam" or see the documentation of
1402 your boot loader (lilo or loadlin) about how to pass options to the
1403 kernel at boot time.)
1405 If unsure, say "off".
1410 Select this if you have a 32-bit processor and between 1 and 4
1411 gigabytes of physical RAM.
1415 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1418 Select this if you have a 32-bit processor and more than 4
1419 gigabytes of physical RAM.
1424 prompt "Memory split" if EXPERT
1428 Select the desired split between kernel and user memory.
1430 If the address range available to the kernel is less than the
1431 physical memory installed, the remaining memory will be available
1432 as "high memory". Accessing high memory is a little more costly
1433 than low memory, as it needs to be mapped into the kernel first.
1434 Note that increasing the kernel address space limits the range
1435 available to user programs, making the address space there
1436 tighter. Selecting anything other than the default 3G/1G split
1437 will also likely make your kernel incompatible with binary-only
1440 If you are not absolutely sure what you are doing, leave this
1444 bool "3G/1G user/kernel split"
1445 config VMSPLIT_3G_OPT
1447 bool "3G/1G user/kernel split (for full 1G low memory)"
1449 bool "2G/2G user/kernel split"
1450 config VMSPLIT_2G_OPT
1452 bool "2G/2G user/kernel split (for full 2G low memory)"
1454 bool "1G/3G user/kernel split"
1459 default 0xB0000000 if VMSPLIT_3G_OPT
1460 default 0x80000000 if VMSPLIT_2G
1461 default 0x78000000 if VMSPLIT_2G_OPT
1462 default 0x40000000 if VMSPLIT_1G
1468 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1471 bool "PAE (Physical Address Extension) Support"
1472 depends on X86_32 && !HIGHMEM4G
1473 select PHYS_ADDR_T_64BIT
1476 PAE is required for NX support, and furthermore enables
1477 larger swapspace support for non-overcommit purposes. It
1478 has the cost of more pagetable lookup overhead, and also
1479 consumes more pagetable space per process.
1482 bool "Enable 5-level page tables support"
1484 select DYNAMIC_MEMORY_LAYOUT
1485 select SPARSEMEM_VMEMMAP
1488 5-level paging enables access to larger address space:
1489 upto 128 PiB of virtual address space and 4 PiB of
1490 physical address space.
1492 It will be supported by future Intel CPUs.
1494 A kernel with the option enabled can be booted on machines that
1495 support 4- or 5-level paging.
1497 See Documentation/x86/x86_64/5level-paging.rst for more
1502 config X86_DIRECT_GBPAGES
1506 Certain kernel features effectively disable kernel
1507 linear 1 GB mappings (even if the CPU otherwise
1508 supports them), so don't confuse the user by printing
1509 that we have them enabled.
1511 config X86_CPA_STATISTICS
1512 bool "Enable statistic for Change Page Attribute"
1515 Expose statistics about the Change Page Attribute mechanims, which
1516 helps to determine the effectiveness of preserving large and huge
1517 page mappings when mapping protections are changed.
1519 config AMD_MEM_ENCRYPT
1520 bool "AMD Secure Memory Encryption (SME) support"
1521 depends on X86_64 && CPU_SUP_AMD
1522 select DYNAMIC_PHYSICAL_MASK
1523 select ARCH_USE_MEMREMAP_PROT
1524 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1526 Say yes to enable support for the encryption of system memory.
1527 This requires an AMD processor that supports Secure Memory
1530 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1531 bool "Activate AMD Secure Memory Encryption (SME) by default"
1533 depends on AMD_MEM_ENCRYPT
1535 Say yes to have system memory encrypted by default if running on
1536 an AMD processor that supports Secure Memory Encryption (SME).
1538 If set to Y, then the encryption of system memory can be
1539 deactivated with the mem_encrypt=off command line option.
1541 If set to N, then the encryption of system memory can be
1542 activated with the mem_encrypt=on command line option.
1544 # Common NUMA Features
1546 bool "Numa Memory Allocation and Scheduler Support"
1548 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1549 default y if X86_BIGSMP
1551 Enable NUMA (Non Uniform Memory Access) support.
1553 The kernel will try to allocate memory used by a CPU on the
1554 local memory controller of the CPU and add some more
1555 NUMA awareness to the kernel.
1557 For 64-bit this is recommended if the system is Intel Core i7
1558 (or later), AMD Opteron, or EM64T NUMA.
1560 For 32-bit this is only needed if you boot a 32-bit
1561 kernel on a 64-bit NUMA platform.
1563 Otherwise, you should say N.
1567 prompt "Old style AMD Opteron NUMA detection"
1568 depends on X86_64 && NUMA && PCI
1570 Enable AMD NUMA node topology detection. You should say Y here if
1571 you have a multi processor AMD system. This uses an old method to
1572 read the NUMA configuration directly from the builtin Northbridge
1573 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1574 which also takes priority if both are compiled in.
1576 config X86_64_ACPI_NUMA
1578 prompt "ACPI NUMA detection"
1579 depends on X86_64 && NUMA && ACPI && PCI
1582 Enable ACPI SRAT based node topology detection.
1584 # Some NUMA nodes have memory ranges that span
1585 # other nodes. Even though a pfn is valid and
1586 # between a node's start and end pfns, it may not
1587 # reside on that node. See memmap_init_zone()
1589 config NODES_SPAN_OTHER_NODES
1591 depends on X86_64_ACPI_NUMA
1594 bool "NUMA emulation"
1597 Enable NUMA emulation. A flat machine will be split
1598 into virtual nodes when booted with "numa=fake=N", where N is the
1599 number of nodes. This is only useful for debugging.
1602 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1604 default "10" if MAXSMP
1605 default "6" if X86_64
1607 depends on NEED_MULTIPLE_NODES
1609 Specify the maximum number of NUMA Nodes available on the target
1610 system. Increases memory reserved to accommodate various tables.
1612 config ARCH_HAVE_MEMORY_PRESENT
1614 depends on X86_32 && DISCONTIGMEM
1616 config ARCH_FLATMEM_ENABLE
1618 depends on X86_32 && !NUMA
1620 config ARCH_DISCONTIGMEM_ENABLE
1622 depends on NUMA && X86_32
1625 config ARCH_SPARSEMEM_ENABLE
1627 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1628 select SPARSEMEM_STATIC if X86_32
1629 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1631 config ARCH_SPARSEMEM_DEFAULT
1632 def_bool X86_64 || (NUMA && X86_32)
1634 config ARCH_SELECT_MEMORY_MODEL
1636 depends on ARCH_SPARSEMEM_ENABLE
1638 config ARCH_MEMORY_PROBE
1639 bool "Enable sysfs memory/probe interface"
1640 depends on X86_64 && MEMORY_HOTPLUG
1642 This option enables a sysfs memory/probe interface for testing.
1643 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1644 If you are unsure how to answer this question, answer N.
1646 config ARCH_PROC_KCORE_TEXT
1648 depends on X86_64 && PROC_KCORE
1650 config ILLEGAL_POINTER_VALUE
1653 default 0xdead000000000000 if X86_64
1655 config X86_PMEM_LEGACY_DEVICE
1658 config X86_PMEM_LEGACY
1659 tristate "Support non-standard NVDIMMs and ADR protected memory"
1660 depends on PHYS_ADDR_T_64BIT
1662 select X86_PMEM_LEGACY_DEVICE
1665 Treat memory marked using the non-standard e820 type of 12 as used
1666 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1667 The kernel will offer these regions to the 'pmem' driver so
1668 they can be used for persistent storage.
1673 bool "Allocate 3rd-level pagetables from highmem"
1676 The VM uses one page table entry for each page of physical memory.
1677 For systems with a lot of RAM, this can be wasteful of precious
1678 low memory. Setting this option will put user-space page table
1679 entries in high memory.
1681 config X86_CHECK_BIOS_CORRUPTION
1682 bool "Check for low memory corruption"
1684 Periodically check for memory corruption in low memory, which
1685 is suspected to be caused by BIOS. Even when enabled in the
1686 configuration, it is disabled at runtime. Enable it by
1687 setting "memory_corruption_check=1" on the kernel command
1688 line. By default it scans the low 64k of memory every 60
1689 seconds; see the memory_corruption_check_size and
1690 memory_corruption_check_period parameters in
1691 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1693 When enabled with the default parameters, this option has
1694 almost no overhead, as it reserves a relatively small amount
1695 of memory and scans it infrequently. It both detects corruption
1696 and prevents it from affecting the running system.
1698 It is, however, intended as a diagnostic tool; if repeatable
1699 BIOS-originated corruption always affects the same memory,
1700 you can use memmap= to prevent the kernel from using that
1703 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1704 bool "Set the default setting of memory_corruption_check"
1705 depends on X86_CHECK_BIOS_CORRUPTION
1708 Set whether the default state of memory_corruption_check is
1711 config X86_RESERVE_LOW
1712 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1716 Specify the amount of low memory to reserve for the BIOS.
1718 The first page contains BIOS data structures that the kernel
1719 must not use, so that page must always be reserved.
1721 By default we reserve the first 64K of physical RAM, as a
1722 number of BIOSes are known to corrupt that memory range
1723 during events such as suspend/resume or monitor cable
1724 insertion, so it must not be used by the kernel.
1726 You can set this to 4 if you are absolutely sure that you
1727 trust the BIOS to get all its memory reservations and usages
1728 right. If you know your BIOS have problems beyond the
1729 default 64K area, you can set this to 640 to avoid using the
1730 entire low memory range.
1732 If you have doubts about the BIOS (e.g. suspend/resume does
1733 not work or there's kernel crashes after certain hardware
1734 hotplug events) then you might want to enable
1735 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1736 typical corruption patterns.
1738 Leave this to the default value of 64 if you are unsure.
1740 config MATH_EMULATION
1742 depends on MODIFY_LDT_SYSCALL
1743 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1745 Linux can emulate a math coprocessor (used for floating point
1746 operations) if you don't have one. 486DX and Pentium processors have
1747 a math coprocessor built in, 486SX and 386 do not, unless you added
1748 a 487DX or 387, respectively. (The messages during boot time can
1749 give you some hints here ["man dmesg"].) Everyone needs either a
1750 coprocessor or this emulation.
1752 If you don't have a math coprocessor, you need to say Y here; if you
1753 say Y here even though you have a coprocessor, the coprocessor will
1754 be used nevertheless. (This behavior can be changed with the kernel
1755 command line option "no387", which comes handy if your coprocessor
1756 is broken. Try "man bootparam" or see the documentation of your boot
1757 loader (lilo or loadlin) about how to pass options to the kernel at
1758 boot time.) This means that it is a good idea to say Y here if you
1759 intend to use this kernel on different machines.
1761 More information about the internals of the Linux math coprocessor
1762 emulation can be found in <file:arch/x86/math-emu/README>.
1764 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1765 kernel, it won't hurt.
1769 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1771 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1772 the Memory Type Range Registers (MTRRs) may be used to control
1773 processor access to memory ranges. This is most useful if you have
1774 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1775 allows bus write transfers to be combined into a larger transfer
1776 before bursting over the PCI/AGP bus. This can increase performance
1777 of image write operations 2.5 times or more. Saying Y here creates a
1778 /proc/mtrr file which may be used to manipulate your processor's
1779 MTRRs. Typically the X server should use this.
1781 This code has a reasonably generic interface so that similar
1782 control registers on other processors can be easily supported
1785 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1786 Registers (ARRs) which provide a similar functionality to MTRRs. For
1787 these, the ARRs are used to emulate the MTRRs.
1788 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1789 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1790 write-combining. All of these processors are supported by this code
1791 and it makes sense to say Y here if you have one of them.
1793 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1794 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1795 can lead to all sorts of problems, so it's good to say Y here.
1797 You can safely say Y even if your machine doesn't have MTRRs, you'll
1798 just add about 9 KB to your kernel.
1800 See <file:Documentation/x86/mtrr.rst> for more information.
1802 config MTRR_SANITIZER
1804 prompt "MTRR cleanup support"
1807 Convert MTRR layout from continuous to discrete, so X drivers can
1808 add writeback entries.
1810 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1811 The largest mtrr entry size for a continuous block can be set with
1816 config MTRR_SANITIZER_ENABLE_DEFAULT
1817 int "MTRR cleanup enable value (0-1)"
1820 depends on MTRR_SANITIZER
1822 Enable mtrr cleanup default value
1824 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1825 int "MTRR cleanup spare reg num (0-7)"
1828 depends on MTRR_SANITIZER
1830 mtrr cleanup spare entries default, it can be changed via
1831 mtrr_spare_reg_nr=N on the kernel command line.
1835 prompt "x86 PAT support" if EXPERT
1838 Use PAT attributes to setup page level cache control.
1840 PATs are the modern equivalents of MTRRs and are much more
1841 flexible than MTRRs.
1843 Say N here if you see bootup problems (boot crash, boot hang,
1844 spontaneous reboots) or a non-working video driver.
1848 config ARCH_USES_PG_UNCACHED
1854 prompt "x86 architectural random number generator" if EXPERT
1856 Enable the x86 architectural RDRAND instruction
1857 (Intel Bull Mountain technology) to generate random numbers.
1858 If supported, this is a high bandwidth, cryptographically
1859 secure hardware random number generator.
1863 prompt "Supervisor Mode Access Prevention" if EXPERT
1865 Supervisor Mode Access Prevention (SMAP) is a security
1866 feature in newer Intel processors. There is a small
1867 performance cost if this enabled and turned on; there is
1868 also a small increase in the kernel size if this is enabled.
1874 depends on CPU_SUP_INTEL || CPU_SUP_AMD
1875 prompt "User Mode Instruction Prevention" if EXPERT
1877 User Mode Instruction Prevention (UMIP) is a security feature in
1878 some x86 processors. If enabled, a general protection fault is
1879 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1880 executed in user mode. These instructions unnecessarily expose
1881 information about the hardware state.
1883 The vast majority of applications do not use these instructions.
1884 For the very few that do, software emulation is provided in
1885 specific cases in protected and virtual-8086 modes. Emulated
1888 config X86_INTEL_MPX
1889 prompt "Intel MPX (Memory Protection Extensions)"
1891 # Note: only available in 64-bit mode due to VMA flags shortage
1892 depends on CPU_SUP_INTEL && X86_64
1893 select ARCH_USES_HIGH_VMA_FLAGS
1895 MPX provides hardware features that can be used in
1896 conjunction with compiler-instrumented code to check
1897 memory references. It is designed to detect buffer
1898 overflow or underflow bugs.
1900 This option enables running applications which are
1901 instrumented or otherwise use MPX. It does not use MPX
1902 itself inside the kernel or to protect the kernel
1903 against bad memory references.
1905 Enabling this option will make the kernel larger:
1906 ~8k of kernel text and 36 bytes of data on a 64-bit
1907 defconfig. It adds a long to the 'mm_struct' which
1908 will increase the kernel memory overhead of each
1909 process and adds some branches to paths used during
1910 exec() and munmap().
1912 For details, see Documentation/x86/intel_mpx.rst
1916 config X86_INTEL_MEMORY_PROTECTION_KEYS
1917 prompt "Intel Memory Protection Keys"
1919 # Note: only available in 64-bit mode
1920 depends on CPU_SUP_INTEL && X86_64
1921 select ARCH_USES_HIGH_VMA_FLAGS
1922 select ARCH_HAS_PKEYS
1924 Memory Protection Keys provides a mechanism for enforcing
1925 page-based protections, but without requiring modification of the
1926 page tables when an application changes protection domains.
1928 For details, see Documentation/core-api/protection-keys.rst
1933 prompt "TSX enable mode"
1934 depends on CPU_SUP_INTEL
1935 default X86_INTEL_TSX_MODE_OFF
1937 Intel's TSX (Transactional Synchronization Extensions) feature
1938 allows to optimize locking protocols through lock elision which
1939 can lead to a noticeable performance boost.
1941 On the other hand it has been shown that TSX can be exploited
1942 to form side channel attacks (e.g. TAA) and chances are there
1943 will be more of those attacks discovered in the future.
1945 Therefore TSX is not enabled by default (aka tsx=off). An admin
1946 might override this decision by tsx=on the command line parameter.
1947 Even with TSX enabled, the kernel will attempt to enable the best
1948 possible TAA mitigation setting depending on the microcode available
1949 for the particular machine.
1951 This option allows to set the default tsx mode between tsx=on, =off
1952 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1955 Say off if not sure, auto if TSX is in use but it should be used on safe
1956 platforms or on if TSX is in use and the security aspect of tsx is not
1959 config X86_INTEL_TSX_MODE_OFF
1962 TSX is disabled if possible - equals to tsx=off command line parameter.
1964 config X86_INTEL_TSX_MODE_ON
1967 TSX is always enabled on TSX capable HW - equals the tsx=on command
1970 config X86_INTEL_TSX_MODE_AUTO
1973 TSX is enabled on TSX capable HW that is believed to be safe against
1974 side channel attacks- equals the tsx=auto command line parameter.
1978 bool "EFI runtime service support"
1981 select EFI_RUNTIME_WRAPPERS
1983 This enables the kernel to use EFI runtime services that are
1984 available (such as the EFI variable services).
1986 This option is only useful on systems that have EFI firmware.
1987 In addition, you should use the latest ELILO loader available
1988 at <http://elilo.sourceforge.net> in order to take advantage
1989 of EFI runtime services. However, even with this option, the
1990 resultant kernel should continue to boot on existing non-EFI
1994 bool "EFI stub support"
1995 depends on EFI && !X86_USE_3DNOW
1998 This kernel feature allows a bzImage to be loaded directly
1999 by EFI firmware without the use of a bootloader.
2001 See Documentation/admin-guide/efi-stub.rst for more information.
2004 bool "EFI mixed-mode support"
2005 depends on EFI_STUB && X86_64
2007 Enabling this feature allows a 64-bit kernel to be booted
2008 on a 32-bit firmware, provided that your CPU supports 64-bit
2011 Note that it is not possible to boot a mixed-mode enabled
2012 kernel via the EFI boot stub - a bootloader that supports
2013 the EFI handover protocol must be used.
2019 prompt "Enable seccomp to safely compute untrusted bytecode"
2021 This kernel feature is useful for number crunching applications
2022 that may need to compute untrusted bytecode during their
2023 execution. By using pipes or other transports made available to
2024 the process as file descriptors supporting the read/write
2025 syscalls, it's possible to isolate those applications in
2026 their own address space using seccomp. Once seccomp is
2027 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
2028 and the task is only allowed to execute a few safe syscalls
2029 defined by each seccomp mode.
2031 If unsure, say Y. Only embedded should say N here.
2033 source "kernel/Kconfig.hz"
2036 bool "kexec system call"
2039 kexec is a system call that implements the ability to shutdown your
2040 current kernel, and to start another kernel. It is like a reboot
2041 but it is independent of the system firmware. And like a reboot
2042 you can start any kernel with it, not just Linux.
2044 The name comes from the similarity to the exec system call.
2046 It is an ongoing process to be certain the hardware in a machine
2047 is properly shutdown, so do not be surprised if this code does not
2048 initially work for you. As of this writing the exact hardware
2049 interface is strongly in flux, so no good recommendation can be
2053 bool "kexec file based system call"
2058 depends on CRYPTO_SHA256=y
2060 This is new version of kexec system call. This system call is
2061 file based and takes file descriptors as system call argument
2062 for kernel and initramfs as opposed to list of segments as
2063 accepted by previous system call.
2065 config ARCH_HAS_KEXEC_PURGATORY
2069 bool "Verify kernel signature during kexec_file_load() syscall"
2070 depends on KEXEC_FILE
2073 This option makes the kexec_file_load() syscall check for a valid
2074 signature of the kernel image. The image can still be loaded without
2075 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2076 there's a signature that we can check, then it must be valid.
2078 In addition to this option, you need to enable signature
2079 verification for the corresponding kernel image type being
2080 loaded in order for this to work.
2082 config KEXEC_SIG_FORCE
2083 bool "Require a valid signature in kexec_file_load() syscall"
2084 depends on KEXEC_SIG
2086 This option makes kernel signature verification mandatory for
2087 the kexec_file_load() syscall.
2089 config KEXEC_BZIMAGE_VERIFY_SIG
2090 bool "Enable bzImage signature verification support"
2091 depends on KEXEC_SIG
2092 depends on SIGNED_PE_FILE_VERIFICATION
2093 select SYSTEM_TRUSTED_KEYRING
2095 Enable bzImage signature verification support.
2098 bool "kernel crash dumps"
2099 depends on X86_64 || (X86_32 && HIGHMEM)
2101 Generate crash dump after being started by kexec.
2102 This should be normally only set in special crash dump kernels
2103 which are loaded in the main kernel with kexec-tools into
2104 a specially reserved region and then later executed after
2105 a crash by kdump/kexec. The crash dump kernel must be compiled
2106 to a memory address not used by the main kernel or BIOS using
2107 PHYSICAL_START, or it must be built as a relocatable image
2108 (CONFIG_RELOCATABLE=y).
2109 For more details see Documentation/admin-guide/kdump/kdump.rst
2113 depends on KEXEC && HIBERNATION
2115 Jump between original kernel and kexeced kernel and invoke
2116 code in physical address mode via KEXEC
2118 config PHYSICAL_START
2119 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2122 This gives the physical address where the kernel is loaded.
2124 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2125 bzImage will decompress itself to above physical address and
2126 run from there. Otherwise, bzImage will run from the address where
2127 it has been loaded by the boot loader and will ignore above physical
2130 In normal kdump cases one does not have to set/change this option
2131 as now bzImage can be compiled as a completely relocatable image
2132 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2133 address. This option is mainly useful for the folks who don't want
2134 to use a bzImage for capturing the crash dump and want to use a
2135 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2136 to be specifically compiled to run from a specific memory area
2137 (normally a reserved region) and this option comes handy.
2139 So if you are using bzImage for capturing the crash dump,
2140 leave the value here unchanged to 0x1000000 and set
2141 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2142 for capturing the crash dump change this value to start of
2143 the reserved region. In other words, it can be set based on
2144 the "X" value as specified in the "crashkernel=YM@XM"
2145 command line boot parameter passed to the panic-ed
2146 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2147 for more details about crash dumps.
2149 Usage of bzImage for capturing the crash dump is recommended as
2150 one does not have to build two kernels. Same kernel can be used
2151 as production kernel and capture kernel. Above option should have
2152 gone away after relocatable bzImage support is introduced. But it
2153 is present because there are users out there who continue to use
2154 vmlinux for dump capture. This option should go away down the
2157 Don't change this unless you know what you are doing.
2160 bool "Build a relocatable kernel"
2163 This builds a kernel image that retains relocation information
2164 so it can be loaded someplace besides the default 1MB.
2165 The relocations tend to make the kernel binary about 10% larger,
2166 but are discarded at runtime.
2168 One use is for the kexec on panic case where the recovery kernel
2169 must live at a different physical address than the primary
2172 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2173 it has been loaded at and the compile time physical address
2174 (CONFIG_PHYSICAL_START) is used as the minimum location.
2176 config RANDOMIZE_BASE
2177 bool "Randomize the address of the kernel image (KASLR)"
2178 depends on RELOCATABLE
2181 In support of Kernel Address Space Layout Randomization (KASLR),
2182 this randomizes the physical address at which the kernel image
2183 is decompressed and the virtual address where the kernel
2184 image is mapped, as a security feature that deters exploit
2185 attempts relying on knowledge of the location of kernel
2188 On 64-bit, the kernel physical and virtual addresses are
2189 randomized separately. The physical address will be anywhere
2190 between 16MB and the top of physical memory (up to 64TB). The
2191 virtual address will be randomized from 16MB up to 1GB (9 bits
2192 of entropy). Note that this also reduces the memory space
2193 available to kernel modules from 1.5GB to 1GB.
2195 On 32-bit, the kernel physical and virtual addresses are
2196 randomized together. They will be randomized from 16MB up to
2197 512MB (8 bits of entropy).
2199 Entropy is generated using the RDRAND instruction if it is
2200 supported. If RDTSC is supported, its value is mixed into
2201 the entropy pool as well. If neither RDRAND nor RDTSC are
2202 supported, then entropy is read from the i8254 timer. The
2203 usable entropy is limited by the kernel being built using
2204 2GB addressing, and that PHYSICAL_ALIGN must be at a
2205 minimum of 2MB. As a result, only 10 bits of entropy are
2206 theoretically possible, but the implementations are further
2207 limited due to memory layouts.
2211 # Relocation on x86 needs some additional build support
2212 config X86_NEED_RELOCS
2214 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2216 config PHYSICAL_ALIGN
2217 hex "Alignment value to which kernel should be aligned"
2219 range 0x2000 0x1000000 if X86_32
2220 range 0x200000 0x1000000 if X86_64
2222 This value puts the alignment restrictions on physical address
2223 where kernel is loaded and run from. Kernel is compiled for an
2224 address which meets above alignment restriction.
2226 If bootloader loads the kernel at a non-aligned address and
2227 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2228 address aligned to above value and run from there.
2230 If bootloader loads the kernel at a non-aligned address and
2231 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2232 load address and decompress itself to the address it has been
2233 compiled for and run from there. The address for which kernel is
2234 compiled already meets above alignment restrictions. Hence the
2235 end result is that kernel runs from a physical address meeting
2236 above alignment restrictions.
2238 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2239 this value must be a multiple of 0x200000.
2241 Don't change this unless you know what you are doing.
2243 config DYNAMIC_MEMORY_LAYOUT
2246 This option makes base addresses of vmalloc and vmemmap as well as
2247 __PAGE_OFFSET movable during boot.
2249 config RANDOMIZE_MEMORY
2250 bool "Randomize the kernel memory sections"
2252 depends on RANDOMIZE_BASE
2253 select DYNAMIC_MEMORY_LAYOUT
2254 default RANDOMIZE_BASE
2256 Randomizes the base virtual address of kernel memory sections
2257 (physical memory mapping, vmalloc & vmemmap). This security feature
2258 makes exploits relying on predictable memory locations less reliable.
2260 The order of allocations remains unchanged. Entropy is generated in
2261 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2262 configuration have in average 30,000 different possible virtual
2263 addresses for each memory section.
2267 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2268 hex "Physical memory mapping padding" if EXPERT
2269 depends on RANDOMIZE_MEMORY
2270 default "0xa" if MEMORY_HOTPLUG
2272 range 0x1 0x40 if MEMORY_HOTPLUG
2275 Define the padding in terabytes added to the existing physical
2276 memory size during kernel memory randomization. It is useful
2277 for memory hotplug support but reduces the entropy available for
2278 address randomization.
2280 If unsure, leave at the default value.
2286 config BOOTPARAM_HOTPLUG_CPU0
2287 bool "Set default setting of cpu0_hotpluggable"
2288 depends on HOTPLUG_CPU
2290 Set whether default state of cpu0_hotpluggable is on or off.
2292 Say Y here to enable CPU0 hotplug by default. If this switch
2293 is turned on, there is no need to give cpu0_hotplug kernel
2294 parameter and the CPU0 hotplug feature is enabled by default.
2296 Please note: there are two known CPU0 dependencies if you want
2297 to enable the CPU0 hotplug feature either by this switch or by
2298 cpu0_hotplug kernel parameter.
2300 First, resume from hibernate or suspend always starts from CPU0.
2301 So hibernate and suspend are prevented if CPU0 is offline.
2303 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2304 offline if any interrupt can not migrate out of CPU0. There may
2305 be other CPU0 dependencies.
2307 Please make sure the dependencies are under your control before
2308 you enable this feature.
2310 Say N if you don't want to enable CPU0 hotplug feature by default.
2311 You still can enable the CPU0 hotplug feature at boot by kernel
2312 parameter cpu0_hotplug.
2314 config DEBUG_HOTPLUG_CPU0
2316 prompt "Debug CPU0 hotplug"
2317 depends on HOTPLUG_CPU
2319 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2320 soon as possible and boots up userspace with CPU0 offlined. User
2321 can online CPU0 back after boot time.
2323 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2324 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2325 compilation or giving cpu0_hotplug kernel parameter at boot.
2331 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2332 depends on COMPAT_32
2334 Certain buggy versions of glibc will crash if they are
2335 presented with a 32-bit vDSO that is not mapped at the address
2336 indicated in its segment table.
2338 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2339 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2340 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2341 the only released version with the bug, but OpenSUSE 9
2342 contains a buggy "glibc 2.3.2".
2344 The symptom of the bug is that everything crashes on startup, saying:
2345 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2347 Saying Y here changes the default value of the vdso32 boot
2348 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2349 This works around the glibc bug but hurts performance.
2351 If unsure, say N: if you are compiling your own kernel, you
2352 are unlikely to be using a buggy version of glibc.
2355 prompt "vsyscall table for legacy applications"
2357 default LEGACY_VSYSCALL_XONLY
2359 Legacy user code that does not know how to find the vDSO expects
2360 to be able to issue three syscalls by calling fixed addresses in
2361 kernel space. Since this location is not randomized with ASLR,
2362 it can be used to assist security vulnerability exploitation.
2364 This setting can be changed at boot time via the kernel command
2365 line parameter vsyscall=[emulate|xonly|none].
2367 On a system with recent enough glibc (2.14 or newer) and no
2368 static binaries, you can say None without a performance penalty
2369 to improve security.
2371 If unsure, select "Emulate execution only".
2373 config LEGACY_VSYSCALL_EMULATE
2374 bool "Full emulation"
2376 The kernel traps and emulates calls into the fixed vsyscall
2377 address mapping. This makes the mapping non-executable, but
2378 it still contains readable known contents, which could be
2379 used in certain rare security vulnerability exploits. This
2380 configuration is recommended when using legacy userspace
2381 that still uses vsyscalls along with legacy binary
2382 instrumentation tools that require code to be readable.
2384 An example of this type of legacy userspace is running
2385 Pin on an old binary that still uses vsyscalls.
2387 config LEGACY_VSYSCALL_XONLY
2388 bool "Emulate execution only"
2390 The kernel traps and emulates calls into the fixed vsyscall
2391 address mapping and does not allow reads. This
2392 configuration is recommended when userspace might use the
2393 legacy vsyscall area but support for legacy binary
2394 instrumentation of legacy code is not needed. It mitigates
2395 certain uses of the vsyscall area as an ASLR-bypassing
2398 config LEGACY_VSYSCALL_NONE
2401 There will be no vsyscall mapping at all. This will
2402 eliminate any risk of ASLR bypass due to the vsyscall
2403 fixed address mapping. Attempts to use the vsyscalls
2404 will be reported to dmesg, so that either old or
2405 malicious userspace programs can be identified.
2410 bool "Built-in kernel command line"
2412 Allow for specifying boot arguments to the kernel at
2413 build time. On some systems (e.g. embedded ones), it is
2414 necessary or convenient to provide some or all of the
2415 kernel boot arguments with the kernel itself (that is,
2416 to not rely on the boot loader to provide them.)
2418 To compile command line arguments into the kernel,
2419 set this option to 'Y', then fill in the
2420 boot arguments in CONFIG_CMDLINE.
2422 Systems with fully functional boot loaders (i.e. non-embedded)
2423 should leave this option set to 'N'.
2426 string "Built-in kernel command string"
2427 depends on CMDLINE_BOOL
2430 Enter arguments here that should be compiled into the kernel
2431 image and used at boot time. If the boot loader provides a
2432 command line at boot time, it is appended to this string to
2433 form the full kernel command line, when the system boots.
2435 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2436 change this behavior.
2438 In most cases, the command line (whether built-in or provided
2439 by the boot loader) should specify the device for the root
2442 config CMDLINE_OVERRIDE
2443 bool "Built-in command line overrides boot loader arguments"
2444 depends on CMDLINE_BOOL
2446 Set this option to 'Y' to have the kernel ignore the boot loader
2447 command line, and use ONLY the built-in command line.
2449 This is used to work around broken boot loaders. This should
2450 be set to 'N' under normal conditions.
2452 config MODIFY_LDT_SYSCALL
2453 bool "Enable the LDT (local descriptor table)" if EXPERT
2456 Linux can allow user programs to install a per-process x86
2457 Local Descriptor Table (LDT) using the modify_ldt(2) system
2458 call. This is required to run 16-bit or segmented code such as
2459 DOSEMU or some Wine programs. It is also used by some very old
2460 threading libraries.
2462 Enabling this feature adds a small amount of overhead to
2463 context switches and increases the low-level kernel attack
2464 surface. Disabling it removes the modify_ldt(2) system call.
2466 Saying 'N' here may make sense for embedded or server kernels.
2468 source "kernel/livepatch/Kconfig"
2472 config ARCH_HAS_ADD_PAGES
2474 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2476 config ARCH_ENABLE_MEMORY_HOTPLUG
2478 depends on X86_64 || (X86_32 && HIGHMEM)
2480 config ARCH_ENABLE_MEMORY_HOTREMOVE
2482 depends on MEMORY_HOTPLUG
2484 config USE_PERCPU_NUMA_NODE_ID
2488 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2490 depends on X86_64 || X86_PAE
2492 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2494 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2496 config ARCH_ENABLE_THP_MIGRATION
2498 depends on X86_64 && TRANSPARENT_HUGEPAGE
2500 menu "Power management and ACPI options"
2502 config ARCH_HIBERNATION_HEADER
2504 depends on HIBERNATION
2506 source "kernel/power/Kconfig"
2508 source "drivers/acpi/Kconfig"
2510 source "drivers/sfi/Kconfig"
2517 tristate "APM (Advanced Power Management) BIOS support"
2518 depends on X86_32 && PM_SLEEP
2520 APM is a BIOS specification for saving power using several different
2521 techniques. This is mostly useful for battery powered laptops with
2522 APM compliant BIOSes. If you say Y here, the system time will be
2523 reset after a RESUME operation, the /proc/apm device will provide
2524 battery status information, and user-space programs will receive
2525 notification of APM "events" (e.g. battery status change).
2527 If you select "Y" here, you can disable actual use of the APM
2528 BIOS by passing the "apm=off" option to the kernel at boot time.
2530 Note that the APM support is almost completely disabled for
2531 machines with more than one CPU.
2533 In order to use APM, you will need supporting software. For location
2534 and more information, read <file:Documentation/power/apm-acpi.rst>
2535 and the Battery Powered Linux mini-HOWTO, available from
2536 <http://www.tldp.org/docs.html#howto>.
2538 This driver does not spin down disk drives (see the hdparm(8)
2539 manpage ("man 8 hdparm") for that), and it doesn't turn off
2540 VESA-compliant "green" monitors.
2542 This driver does not support the TI 4000M TravelMate and the ACER
2543 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2544 desktop machines also don't have compliant BIOSes, and this driver
2545 may cause those machines to panic during the boot phase.
2547 Generally, if you don't have a battery in your machine, there isn't
2548 much point in using this driver and you should say N. If you get
2549 random kernel OOPSes or reboots that don't seem to be related to
2550 anything, try disabling/enabling this option (or disabling/enabling
2553 Some other things you should try when experiencing seemingly random,
2556 1) make sure that you have enough swap space and that it is
2558 2) pass the "no-hlt" option to the kernel
2559 3) switch on floating point emulation in the kernel and pass
2560 the "no387" option to the kernel
2561 4) pass the "floppy=nodma" option to the kernel
2562 5) pass the "mem=4M" option to the kernel (thereby disabling
2563 all but the first 4 MB of RAM)
2564 6) make sure that the CPU is not over clocked.
2565 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2566 8) disable the cache from your BIOS settings
2567 9) install a fan for the video card or exchange video RAM
2568 10) install a better fan for the CPU
2569 11) exchange RAM chips
2570 12) exchange the motherboard.
2572 To compile this driver as a module, choose M here: the
2573 module will be called apm.
2577 config APM_IGNORE_USER_SUSPEND
2578 bool "Ignore USER SUSPEND"
2580 This option will ignore USER SUSPEND requests. On machines with a
2581 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2582 series notebooks, it is necessary to say Y because of a BIOS bug.
2584 config APM_DO_ENABLE
2585 bool "Enable PM at boot time"
2587 Enable APM features at boot time. From page 36 of the APM BIOS
2588 specification: "When disabled, the APM BIOS does not automatically
2589 power manage devices, enter the Standby State, enter the Suspend
2590 State, or take power saving steps in response to CPU Idle calls."
2591 This driver will make CPU Idle calls when Linux is idle (unless this
2592 feature is turned off -- see "Do CPU IDLE calls", below). This
2593 should always save battery power, but more complicated APM features
2594 will be dependent on your BIOS implementation. You may need to turn
2595 this option off if your computer hangs at boot time when using APM
2596 support, or if it beeps continuously instead of suspending. Turn
2597 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2598 T400CDT. This is off by default since most machines do fine without
2603 bool "Make CPU Idle calls when idle"
2605 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2606 On some machines, this can activate improved power savings, such as
2607 a slowed CPU clock rate, when the machine is idle. These idle calls
2608 are made after the idle loop has run for some length of time (e.g.,
2609 333 mS). On some machines, this will cause a hang at boot time or
2610 whenever the CPU becomes idle. (On machines with more than one CPU,
2611 this option does nothing.)
2613 config APM_DISPLAY_BLANK
2614 bool "Enable console blanking using APM"
2616 Enable console blanking using the APM. Some laptops can use this to
2617 turn off the LCD backlight when the screen blanker of the Linux
2618 virtual console blanks the screen. Note that this is only used by
2619 the virtual console screen blanker, and won't turn off the backlight
2620 when using the X Window system. This also doesn't have anything to
2621 do with your VESA-compliant power-saving monitor. Further, this
2622 option doesn't work for all laptops -- it might not turn off your
2623 backlight at all, or it might print a lot of errors to the console,
2624 especially if you are using gpm.
2626 config APM_ALLOW_INTS
2627 bool "Allow interrupts during APM BIOS calls"
2629 Normally we disable external interrupts while we are making calls to
2630 the APM BIOS as a measure to lessen the effects of a badly behaving
2631 BIOS implementation. The BIOS should reenable interrupts if it
2632 needs to. Unfortunately, some BIOSes do not -- especially those in
2633 many of the newer IBM Thinkpads. If you experience hangs when you
2634 suspend, try setting this to Y. Otherwise, say N.
2638 source "drivers/cpufreq/Kconfig"
2640 source "drivers/cpuidle/Kconfig"
2642 source "drivers/idle/Kconfig"
2647 menu "Bus options (PCI etc.)"
2650 prompt "PCI access mode"
2651 depends on X86_32 && PCI
2654 On PCI systems, the BIOS can be used to detect the PCI devices and
2655 determine their configuration. However, some old PCI motherboards
2656 have BIOS bugs and may crash if this is done. Also, some embedded
2657 PCI-based systems don't have any BIOS at all. Linux can also try to
2658 detect the PCI hardware directly without using the BIOS.
2660 With this option, you can specify how Linux should detect the
2661 PCI devices. If you choose "BIOS", the BIOS will be used,
2662 if you choose "Direct", the BIOS won't be used, and if you
2663 choose "MMConfig", then PCI Express MMCONFIG will be used.
2664 If you choose "Any", the kernel will try MMCONFIG, then the
2665 direct access method and falls back to the BIOS if that doesn't
2666 work. If unsure, go with the default, which is "Any".
2671 config PCI_GOMMCONFIG
2688 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2690 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2693 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2696 bool "Support mmconfig PCI config space access" if X86_64
2698 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2699 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2703 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2707 depends on PCI && XEN
2710 config MMCONF_FAM10H
2712 depends on X86_64 && PCI_MMCONFIG && ACPI
2714 config PCI_CNB20LE_QUIRK
2715 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2718 Read the PCI windows out of the CNB20LE host bridge. This allows
2719 PCI hotplug to work on systems with the CNB20LE chipset which do
2722 There's no public spec for this chipset, and this functionality
2723 is known to be incomplete.
2725 You should say N unless you know you need this.
2728 bool "ISA bus support on modern systems" if EXPERT
2730 Expose ISA bus device drivers and options available for selection and
2731 configuration. Enable this option if your target machine has an ISA
2732 bus. ISA is an older system, displaced by PCI and newer bus
2733 architectures -- if your target machine is modern, it probably does
2734 not have an ISA bus.
2738 # x86_64 have no ISA slots, but can have ISA-style DMA.
2740 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2743 Enables ISA-style DMA support for devices requiring such controllers.
2751 Find out whether you have ISA slots on your motherboard. ISA is the
2752 name of a bus system, i.e. the way the CPU talks to the other stuff
2753 inside your box. Other bus systems are PCI, EISA, MicroChannel
2754 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2755 newer boards don't support it. If you have ISA, say Y, otherwise N.
2758 tristate "NatSemi SCx200 support"
2760 This provides basic support for National Semiconductor's
2761 (now AMD's) Geode processors. The driver probes for the
2762 PCI-IDs of several on-chip devices, so its a good dependency
2763 for other scx200_* drivers.
2765 If compiled as a module, the driver is named scx200.
2767 config SCx200HR_TIMER
2768 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2772 This driver provides a clocksource built upon the on-chip
2773 27MHz high-resolution timer. Its also a workaround for
2774 NSC Geode SC-1100's buggy TSC, which loses time when the
2775 processor goes idle (as is done by the scheduler). The
2776 other workaround is idle=poll boot option.
2779 bool "One Laptop Per Child support"
2787 Add support for detecting the unique features of the OLPC
2791 bool "OLPC XO-1 Power Management"
2792 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2794 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2797 bool "OLPC XO-1 Real Time Clock"
2798 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2800 Add support for the XO-1 real time clock, which can be used as a
2801 programmable wakeup source.
2804 bool "OLPC XO-1 SCI extras"
2805 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2809 Add support for SCI-based features of the OLPC XO-1 laptop:
2810 - EC-driven system wakeups
2814 - AC adapter status updates
2815 - Battery status updates
2817 config OLPC_XO15_SCI
2818 bool "OLPC XO-1.5 SCI extras"
2819 depends on OLPC && ACPI
2822 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2823 - EC-driven system wakeups
2824 - AC adapter status updates
2825 - Battery status updates
2828 bool "PCEngines ALIX System Support (LED setup)"
2831 This option enables system support for the PCEngines ALIX.
2832 At present this just sets up LEDs for GPIO control on
2833 ALIX2/3/6 boards. However, other system specific setup should
2836 Note: You must still enable the drivers for GPIO and LED support
2837 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2839 Note: You have to set alix.force=1 for boards with Award BIOS.
2842 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2845 This option enables system support for the Soekris Engineering net5501.
2848 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2852 This option enables system support for the Traverse Technologies GEOS.
2855 bool "Technologic Systems TS-5500 platform support"
2857 select CHECK_SIGNATURE
2861 This option enables system support for the Technologic Systems TS-5500.
2867 depends on CPU_SUP_AMD && PCI
2870 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2872 Firmwares often provide initial graphics framebuffers so the BIOS,
2873 bootloader or kernel can show basic video-output during boot for
2874 user-guidance and debugging. Historically, x86 used the VESA BIOS
2875 Extensions and EFI-framebuffers for this, which are mostly limited
2877 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2878 framebuffers so the new generic system-framebuffer drivers can be
2879 used on x86. If the framebuffer is not compatible with the generic
2880 modes, it is advertised as fallback platform framebuffer so legacy
2881 drivers like efifb, vesafb and uvesafb can pick it up.
2882 If this option is not selected, all system framebuffers are always
2883 marked as fallback platform framebuffers as usual.
2885 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2886 not be able to pick up generic system framebuffers if this option
2887 is selected. You are highly encouraged to enable simplefb as
2888 replacement if you select this option. simplefb can correctly deal
2889 with generic system framebuffers. But you should still keep vesafb
2890 and others enabled as fallback if a system framebuffer is
2891 incompatible with simplefb.
2898 menu "Binary Emulations"
2900 config IA32_EMULATION
2901 bool "IA32 Emulation"
2903 select ARCH_WANT_OLD_COMPAT_IPC
2905 select COMPAT_BINFMT_ELF
2906 select COMPAT_OLD_SIGACTION
2908 Include code to run legacy 32-bit programs under a
2909 64-bit kernel. You should likely turn this on, unless you're
2910 100% sure that you don't have any 32-bit programs left.
2913 tristate "IA32 a.out support"
2914 depends on IA32_EMULATION
2917 Support old a.out binaries in the 32bit emulation.
2920 bool "x32 ABI for 64-bit mode"
2923 Include code to run binaries for the x32 native 32-bit ABI
2924 for 64-bit processors. An x32 process gets access to the
2925 full 64-bit register file and wide data path while leaving
2926 pointers at 32 bits for smaller memory footprint.
2928 You will need a recent binutils (2.22 or later) with
2929 elf32_x86_64 support enabled to compile a kernel with this
2934 depends on IA32_EMULATION || X86_32
2936 select OLD_SIGSUSPEND3
2940 depends on IA32_EMULATION || X86_X32
2943 config COMPAT_FOR_U64_ALIGNMENT
2946 config SYSVIPC_COMPAT
2954 config HAVE_ATOMIC_IOMAP
2958 config X86_DEV_DMA_OPS
2961 source "drivers/firmware/Kconfig"
2963 source "arch/x86/kvm/Kconfig"