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_WANT_DEFAULT_BPF_JIT if X86_64
97 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
98 select ARCH_WANT_HUGE_PMD_SHARE
99 select ARCH_WANTS_THP_SWAP if X86_64
100 select BUILDTIME_TABLE_SORT
102 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
103 select CLOCKSOURCE_WATCHDOG
104 select DCACHE_WORD_ACCESS
105 select EDAC_ATOMIC_SCRUB
107 select GENERIC_CLOCKEVENTS
108 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
109 select GENERIC_CLOCKEVENTS_MIN_ADJUST
110 select GENERIC_CMOS_UPDATE
111 select GENERIC_CPU_AUTOPROBE
112 select GENERIC_CPU_VULNERABILITIES
113 select GENERIC_EARLY_IOREMAP
114 select GENERIC_FIND_FIRST_BIT
116 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
117 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
118 select GENERIC_IRQ_MIGRATION if SMP
119 select GENERIC_IRQ_PROBE
120 select GENERIC_IRQ_RESERVATION_MODE
121 select GENERIC_IRQ_SHOW
122 select GENERIC_PENDING_IRQ if SMP
123 select GENERIC_PTDUMP
124 select GENERIC_SMP_IDLE_THREAD
125 select GENERIC_STRNCPY_FROM_USER
126 select GENERIC_STRNLEN_USER
127 select GENERIC_TIME_VSYSCALL
128 select GENERIC_GETTIMEOFDAY
129 select GENERIC_VDSO_TIME_NS
130 select GUP_GET_PTE_LOW_HIGH if X86_PAE
131 select HARDIRQS_SW_RESEND
132 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
133 select HAVE_ACPI_APEI if ACPI
134 select HAVE_ACPI_APEI_NMI if ACPI
135 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
136 select HAVE_ARCH_AUDITSYSCALL
137 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
138 select HAVE_ARCH_JUMP_LABEL
139 select HAVE_ARCH_JUMP_LABEL_RELATIVE
140 select HAVE_ARCH_KASAN if X86_64
141 select HAVE_ARCH_KASAN_VMALLOC if X86_64
142 select HAVE_ARCH_KGDB
143 select HAVE_ARCH_MMAP_RND_BITS if MMU
144 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
145 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
146 select HAVE_ARCH_PREL32_RELOCATIONS
147 select HAVE_ARCH_SECCOMP_FILTER
148 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
149 select HAVE_ARCH_STACKLEAK
150 select HAVE_ARCH_TRACEHOOK
151 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
152 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
153 select HAVE_ARCH_VMAP_STACK if X86_64
154 select HAVE_ARCH_WITHIN_STACK_FRAMES
155 select HAVE_ASM_MODVERSIONS
156 select HAVE_CMPXCHG_DOUBLE
157 select HAVE_CMPXCHG_LOCAL
158 select HAVE_CONTEXT_TRACKING if X86_64
159 select HAVE_COPY_THREAD_TLS
160 select HAVE_C_RECORDMCOUNT
161 select HAVE_DEBUG_KMEMLEAK
162 select HAVE_DMA_CONTIGUOUS
163 select HAVE_DYNAMIC_FTRACE
164 select HAVE_DYNAMIC_FTRACE_WITH_REGS
165 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
167 select HAVE_EFFICIENT_UNALIGNED_ACCESS
169 select HAVE_EXIT_THREAD
171 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
172 select HAVE_FTRACE_MCOUNT_RECORD
173 select HAVE_FUNCTION_GRAPH_TRACER
174 select HAVE_FUNCTION_TRACER
175 select HAVE_GCC_PLUGINS
176 select HAVE_HW_BREAKPOINT
178 select HAVE_IOREMAP_PROT
179 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
180 select HAVE_IRQ_TIME_ACCOUNTING
181 select HAVE_KERNEL_BZIP2
182 select HAVE_KERNEL_GZIP
183 select HAVE_KERNEL_LZ4
184 select HAVE_KERNEL_LZMA
185 select HAVE_KERNEL_LZO
186 select HAVE_KERNEL_XZ
188 select HAVE_KPROBES_ON_FTRACE
189 select HAVE_FUNCTION_ERROR_INJECTION
190 select HAVE_KRETPROBES
192 select HAVE_LIVEPATCH if X86_64
193 select HAVE_MEMBLOCK_NODE_MAP
194 select HAVE_MIXED_BREAKPOINTS_REGS
195 select HAVE_MOD_ARCH_SPECIFIC
199 select HAVE_OPTPROBES
200 select HAVE_PCSPKR_PLATFORM
201 select HAVE_PERF_EVENTS
202 select HAVE_PERF_EVENTS_NMI
203 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
205 select HAVE_PERF_REGS
206 select HAVE_PERF_USER_STACK_DUMP
207 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
208 select HAVE_REGS_AND_STACK_ACCESS_API
209 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
210 select HAVE_FUNCTION_ARG_ACCESS_API
211 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
212 select HAVE_STACK_VALIDATION if X86_64
214 select HAVE_SYSCALL_TRACEPOINTS
215 select HAVE_UNSTABLE_SCHED_CLOCK
216 select HAVE_USER_RETURN_NOTIFIER
217 select HAVE_GENERIC_VDSO
218 select HOTPLUG_SMT if SMP
219 select IRQ_FORCED_THREADING
220 select NEED_SG_DMA_LENGTH
221 select PCI_DOMAINS if PCI
222 select PCI_LOCKLESS_CONFIG if PCI
225 select RTC_MC146818_LIB
228 select SYSCTL_EXCEPTION_TRACE
229 select THREAD_INFO_IN_TASK
230 select USER_STACKTRACE_SUPPORT
232 select X86_FEATURE_NAMES if PROC_FS
233 select PROC_PID_ARCH_STATUS if PROC_FS
235 config INSTRUCTION_DECODER
237 depends on KPROBES || PERF_EVENTS || UPROBES
241 default "elf32-i386" if X86_32
242 default "elf64-x86-64" if X86_64
244 config ARCH_DEFCONFIG
246 default "arch/x86/configs/i386_defconfig" if X86_32
247 default "arch/x86/configs/x86_64_defconfig" if X86_64
249 config LOCKDEP_SUPPORT
252 config STACKTRACE_SUPPORT
258 config ARCH_MMAP_RND_BITS_MIN
262 config ARCH_MMAP_RND_BITS_MAX
266 config ARCH_MMAP_RND_COMPAT_BITS_MIN
269 config ARCH_MMAP_RND_COMPAT_BITS_MAX
275 config GENERIC_ISA_DMA
277 depends on ISA_DMA_API
282 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
284 config GENERIC_BUG_RELATIVE_POINTERS
287 config ARCH_MAY_HAVE_PC_FDC
289 depends on ISA_DMA_API
291 config GENERIC_CALIBRATE_DELAY
294 config ARCH_HAS_CPU_RELAX
297 config ARCH_HAS_CACHE_LINE_SIZE
300 config ARCH_HAS_FILTER_PGPROT
303 config HAVE_SETUP_PER_CPU_AREA
306 config NEED_PER_CPU_EMBED_FIRST_CHUNK
309 config NEED_PER_CPU_PAGE_FIRST_CHUNK
312 config ARCH_HIBERNATION_POSSIBLE
315 config ARCH_SUSPEND_POSSIBLE
318 config ARCH_WANT_GENERAL_HUGETLB
327 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
330 config KASAN_SHADOW_OFFSET
333 default 0xdffffc0000000000
335 config HAVE_INTEL_TXT
337 depends on INTEL_IOMMU && ACPI
341 depends on X86_32 && SMP
345 depends on X86_64 && SMP
347 config X86_32_LAZY_GS
349 depends on X86_32 && !STACKPROTECTOR
351 config ARCH_SUPPORTS_UPROBES
354 config FIX_EARLYCON_MEM
357 config DYNAMIC_PHYSICAL_MASK
360 config PGTABLE_LEVELS
362 default 5 if X86_5LEVEL
367 config CC_HAS_SANE_STACKPROTECTOR
369 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
370 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
372 We have to make sure stack protector is unconditionally disabled if
373 the compiler produces broken code.
375 menu "Processor type and features"
378 bool "DMA memory allocation support" if EXPERT
381 DMA memory allocation support allows devices with less than 32-bit
382 addressing to allocate within the first 16MB of address space.
383 Disable if no such devices will be used.
388 bool "Symmetric multi-processing support"
390 This enables support for systems with more than one CPU. If you have
391 a system with only one CPU, say N. If you have a system with more
394 If you say N here, the kernel will run on uni- and multiprocessor
395 machines, but will use only one CPU of a multiprocessor machine. If
396 you say Y here, the kernel will run on many, but not all,
397 uniprocessor machines. On a uniprocessor machine, the kernel
398 will run faster if you say N here.
400 Note that if you say Y here and choose architecture "586" or
401 "Pentium" under "Processor family", the kernel will not work on 486
402 architectures. Similarly, multiprocessor kernels for the "PPro"
403 architecture may not work on all Pentium based boards.
405 People using multiprocessor machines who say Y here should also say
406 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
407 Management" code will be disabled if you say Y here.
409 See also <file:Documentation/x86/i386/IO-APIC.rst>,
410 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
411 <http://www.tldp.org/docs.html#howto>.
413 If you don't know what to do here, say N.
415 config X86_FEATURE_NAMES
416 bool "Processor feature human-readable names" if EMBEDDED
419 This option compiles in a table of x86 feature bits and corresponding
420 names. This is required to support /proc/cpuinfo and a few kernel
421 messages. You can disable this to save space, at the expense of
422 making those few kernel messages show numeric feature bits instead.
427 bool "Support x2apic"
428 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
430 This enables x2apic support on CPUs that have this feature.
432 This allows 32-bit apic IDs (so it can support very large systems),
433 and accesses the local apic via MSRs not via mmio.
435 If you don't know what to do here, say N.
438 bool "Enable MPS table" if ACPI || SFI
440 depends on X86_LOCAL_APIC
442 For old smp systems that do not have proper acpi support. Newer systems
443 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
447 depends on X86_GOLDFISH
450 bool "Avoid speculative indirect branches in kernel"
452 select STACK_VALIDATION if HAVE_STACK_VALIDATION
454 Compile kernel with the retpoline compiler options to guard against
455 kernel-to-user data leaks by avoiding speculative indirect
456 branches. Requires a compiler with -mindirect-branch=thunk-extern
457 support for full protection. The kernel may run slower.
459 config X86_CPU_RESCTRL
460 bool "x86 CPU resource control support"
461 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
463 select PROC_CPU_RESCTRL if PROC_FS
465 Enable x86 CPU resource control support.
467 Provide support for the allocation and monitoring of system resources
470 Intel calls this Intel Resource Director Technology
471 (Intel(R) RDT). More information about RDT can be found in the
472 Intel x86 Architecture Software Developer Manual.
474 AMD calls this AMD Platform Quality of Service (AMD QoS).
475 More information about AMD QoS can be found in the AMD64 Technology
476 Platform Quality of Service Extensions manual.
482 bool "Support for big SMP systems with more than 8 CPUs"
485 This option is needed for the systems that have more than 8 CPUs.
487 config X86_EXTENDED_PLATFORM
488 bool "Support for extended (non-PC) x86 platforms"
491 If you disable this option then the kernel will only support
492 standard PC platforms. (which covers the vast majority of
495 If you enable this option then you'll be able to select support
496 for the following (non-PC) 32 bit x86 platforms:
497 Goldfish (Android emulator)
500 SGI 320/540 (Visual Workstation)
501 STA2X11-based (e.g. Northville)
502 Moorestown MID devices
504 If you have one of these systems, or if you want to build a
505 generic distribution kernel, say Y here - otherwise say N.
509 config X86_EXTENDED_PLATFORM
510 bool "Support for extended (non-PC) x86 platforms"
513 If you disable this option then the kernel will only support
514 standard PC platforms. (which covers the vast majority of
517 If you enable this option then you'll be able to select support
518 for the following (non-PC) 64 bit x86 platforms:
523 If you have one of these systems, or if you want to build a
524 generic distribution kernel, say Y here - otherwise say N.
526 # This is an alphabetically sorted list of 64 bit extended platforms
527 # Please maintain the alphabetic order if and when there are additions
529 bool "Numascale NumaChip"
531 depends on X86_EXTENDED_PLATFORM
534 depends on X86_X2APIC
535 depends on PCI_MMCONFIG
537 Adds support for Numascale NumaChip large-SMP systems. Needed to
538 enable more than ~168 cores.
539 If you don't have one of these, you should say N here.
543 select HYPERVISOR_GUEST
545 depends on X86_64 && PCI
546 depends on X86_EXTENDED_PLATFORM
549 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
550 supposed to run on these EM64T-based machines. Only choose this option
551 if you have one of these machines.
554 bool "SGI Ultraviolet"
556 depends on X86_EXTENDED_PLATFORM
559 depends on X86_X2APIC
562 This option is needed in order to support SGI Ultraviolet systems.
563 If you don't have one of these, you should say N here.
565 # Following is an alphabetically sorted list of 32 bit extended platforms
566 # Please maintain the alphabetic order if and when there are additions
569 bool "Goldfish (Virtual Platform)"
570 depends on X86_EXTENDED_PLATFORM
572 Enable support for the Goldfish virtual platform used primarily
573 for Android development. Unless you are building for the Android
574 Goldfish emulator say N here.
577 bool "CE4100 TV platform"
579 depends on PCI_GODIRECT
580 depends on X86_IO_APIC
582 depends on X86_EXTENDED_PLATFORM
583 select X86_REBOOTFIXUPS
585 select OF_EARLY_FLATTREE
587 Select for the Intel CE media processor (CE4100) SOC.
588 This option compiles in support for the CE4100 SOC for settop
589 boxes and media devices.
592 bool "Intel MID platform support"
593 depends on X86_EXTENDED_PLATFORM
594 depends on X86_PLATFORM_DEVICES
596 depends on X86_64 || (PCI_GOANY && X86_32)
597 depends on X86_IO_APIC
603 select MFD_INTEL_MSIC
605 Select to build a kernel capable of supporting Intel MID (Mobile
606 Internet Device) platform systems which do not have the PCI legacy
607 interfaces. If you are building for a PC class system say N here.
609 Intel MID platforms are based on an Intel processor and chipset which
610 consume less power than most of the x86 derivatives.
612 config X86_INTEL_QUARK
613 bool "Intel Quark platform support"
615 depends on X86_EXTENDED_PLATFORM
616 depends on X86_PLATFORM_DEVICES
620 depends on X86_IO_APIC
625 Select to include support for Quark X1000 SoC.
626 Say Y here if you have a Quark based system such as the Arduino
627 compatible Intel Galileo.
629 config X86_INTEL_LPSS
630 bool "Intel Low Power Subsystem Support"
631 depends on X86 && ACPI && PCI
636 Select to build support for Intel Low Power Subsystem such as
637 found on Intel Lynxpoint PCH. Selecting this option enables
638 things like clock tree (common clock framework) and pincontrol
639 which are needed by the LPSS peripheral drivers.
641 config X86_AMD_PLATFORM_DEVICE
642 bool "AMD ACPI2Platform devices support"
647 Select to interpret AMD specific ACPI device to platform device
648 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
649 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
650 implemented under PINCTRL subsystem.
653 tristate "Intel SoC IOSF Sideband support for SoC platforms"
656 This option enables sideband register access support for Intel SoC
657 platforms. On these platforms the IOSF sideband is used in lieu of
658 MSR's for some register accesses, mostly but not limited to thermal
659 and power. Drivers may query the availability of this device to
660 determine if they need the sideband in order to work on these
661 platforms. The sideband is available on the following SoC products.
662 This list is not meant to be exclusive.
667 You should say Y if you are running a kernel on one of these SoC's.
669 config IOSF_MBI_DEBUG
670 bool "Enable IOSF sideband access through debugfs"
671 depends on IOSF_MBI && DEBUG_FS
673 Select this option to expose the IOSF sideband access registers (MCR,
674 MDR, MCRX) through debugfs to write and read register information from
675 different units on the SoC. This is most useful for obtaining device
676 state information for debug and analysis. As this is a general access
677 mechanism, users of this option would have specific knowledge of the
678 device they want to access.
680 If you don't require the option or are in doubt, say N.
683 bool "RDC R-321x SoC"
685 depends on X86_EXTENDED_PLATFORM
687 select X86_REBOOTFIXUPS
689 This option is needed for RDC R-321x system-on-chip, also known
691 If you don't have one of these chips, you should say N here.
693 config X86_32_NON_STANDARD
694 bool "Support non-standard 32-bit SMP architectures"
695 depends on X86_32 && SMP
696 depends on X86_EXTENDED_PLATFORM
698 This option compiles in the bigsmp and STA2X11 default
699 subarchitectures. It is intended for a generic binary
700 kernel. If you select them all, kernel will probe it one by
701 one and will fallback to default.
703 # Alphabetically sorted list of Non standard 32 bit platforms
705 config X86_SUPPORTS_MEMORY_FAILURE
707 # MCE code calls memory_failure():
709 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
710 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
711 depends on X86_64 || !SPARSEMEM
712 select ARCH_SUPPORTS_MEMORY_FAILURE
715 bool "STA2X11 Companion Chip Support"
716 depends on X86_32_NON_STANDARD && PCI
721 This adds support for boards based on the STA2X11 IO-Hub,
722 a.k.a. "ConneXt". The chip is used in place of the standard
723 PC chipset, so all "standard" peripherals are missing. If this
724 option is selected the kernel will still be able to boot on
725 standard PC machines.
728 tristate "Eurobraille/Iris poweroff module"
731 The Iris machines from EuroBraille do not have APM or ACPI support
732 to shut themselves down properly. A special I/O sequence is
733 needed to do so, which is what this module does at
736 This is only for Iris machines from EuroBraille.
740 config SCHED_OMIT_FRAME_POINTER
742 prompt "Single-depth WCHAN output"
745 Calculate simpler /proc/<PID>/wchan values. If this option
746 is disabled then wchan values will recurse back to the
747 caller function. This provides more accurate wchan values,
748 at the expense of slightly more scheduling overhead.
750 If in doubt, say "Y".
752 menuconfig HYPERVISOR_GUEST
753 bool "Linux guest support"
755 Say Y here to enable options for running Linux under various hyper-
756 visors. This option enables basic hypervisor detection and platform
759 If you say N, all options in this submenu will be skipped and
760 disabled, and Linux guest support won't be built in.
765 bool "Enable paravirtualization code"
767 This changes the kernel so it can modify itself when it is run
768 under a hypervisor, potentially improving performance significantly
769 over full virtualization. However, when run without a hypervisor
770 the kernel is theoretically slower and slightly larger.
775 config PARAVIRT_DEBUG
776 bool "paravirt-ops debugging"
777 depends on PARAVIRT && DEBUG_KERNEL
779 Enable to debug paravirt_ops internals. Specifically, BUG if
780 a paravirt_op is missing when it is called.
782 config PARAVIRT_SPINLOCKS
783 bool "Paravirtualization layer for spinlocks"
784 depends on PARAVIRT && SMP
786 Paravirtualized spinlocks allow a pvops backend to replace the
787 spinlock implementation with something virtualization-friendly
788 (for example, block the virtual CPU rather than spinning).
790 It has a minimal impact on native kernels and gives a nice performance
791 benefit on paravirtualized KVM / Xen kernels.
793 If you are unsure how to answer this question, answer Y.
795 config X86_HV_CALLBACK_VECTOR
798 source "arch/x86/xen/Kconfig"
801 bool "KVM Guest support (including kvmclock)"
803 select PARAVIRT_CLOCK
804 select ARCH_CPUIDLE_HALTPOLL
807 This option enables various optimizations for running under the KVM
808 hypervisor. It includes a paravirtualized clock, so that instead
809 of relying on a PIT (or probably other) emulation by the
810 underlying device model, the host provides the guest with
811 timing infrastructure such as time of day, and system time
813 config ARCH_CPUIDLE_HALTPOLL
815 prompt "Disable host haltpoll when loading haltpoll driver"
817 If virtualized under KVM, disable host haltpoll.
820 bool "Support for running PVH guests"
822 This option enables the PVH entry point for guest virtual machines
823 as specified in the x86/HVM direct boot ABI.
826 bool "Enable debug information for KVM Guests in debugfs"
827 depends on KVM_GUEST && DEBUG_FS
829 This option enables collection of various statistics for KVM guest.
830 Statistics are displayed in debugfs filesystem. Enabling this option
831 may incur significant overhead.
833 config PARAVIRT_TIME_ACCOUNTING
834 bool "Paravirtual steal time accounting"
837 Select this option to enable fine granularity task steal time
838 accounting. Time spent executing other tasks in parallel with
839 the current vCPU is discounted from the vCPU power. To account for
840 that, there can be a small performance impact.
842 If in doubt, say N here.
844 config PARAVIRT_CLOCK
847 config JAILHOUSE_GUEST
848 bool "Jailhouse non-root cell support"
849 depends on X86_64 && PCI
852 This option allows to run Linux as guest in a Jailhouse non-root
853 cell. You can leave this option disabled if you only want to start
854 Jailhouse and run Linux afterwards in the root cell.
857 bool "ACRN Guest support"
859 select X86_HV_CALLBACK_VECTOR
861 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
862 a flexible, lightweight reference open-source hypervisor, built with
863 real-time and safety-criticality in mind. It is built for embedded
864 IOT with small footprint and real-time features. More details can be
865 found in https://projectacrn.org/.
867 endif #HYPERVISOR_GUEST
869 source "arch/x86/Kconfig.cpu"
873 prompt "HPET Timer Support" if X86_32
875 Use the IA-PC HPET (High Precision Event Timer) to manage
876 time in preference to the PIT and RTC, if a HPET is
878 HPET is the next generation timer replacing legacy 8254s.
879 The HPET provides a stable time base on SMP
880 systems, unlike the TSC, but it is more expensive to access,
881 as it is off-chip. The interface used is documented
882 in the HPET spec, revision 1.
884 You can safely choose Y here. However, HPET will only be
885 activated if the platform and the BIOS support this feature.
886 Otherwise the 8254 will be used for timing services.
888 Choose N to continue using the legacy 8254 timer.
890 config HPET_EMULATE_RTC
892 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
895 def_bool y if X86_INTEL_MID
896 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
898 depends on X86_INTEL_MID && SFI
900 APB timer is the replacement for 8254, HPET on X86 MID platforms.
901 The APBT provides a stable time base on SMP
902 systems, unlike the TSC, but it is more expensive to access,
903 as it is off-chip. APB timers are always running regardless of CPU
904 C states, they are used as per CPU clockevent device when possible.
906 # Mark as expert because too many people got it wrong.
907 # The code disables itself when not needed.
910 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
911 bool "Enable DMI scanning" if EXPERT
913 Enabled scanning of DMI to identify machine quirks. Say Y
914 here unless you have verified that your setup is not
915 affected by entries in the DMI blacklist. Required by PNP
919 bool "Old AMD GART IOMMU support"
922 depends on X86_64 && PCI && AMD_NB
924 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
925 GART based hardware IOMMUs.
927 The GART supports full DMA access for devices with 32-bit access
928 limitations, on systems with more than 3 GB. This is usually needed
929 for USB, sound, many IDE/SATA chipsets and some other devices.
931 Newer systems typically have a modern AMD IOMMU, supported via
932 the CONFIG_AMD_IOMMU=y config option.
934 In normal configurations this driver is only active when needed:
935 there's more than 3 GB of memory and the system contains a
936 32-bit limited device.
941 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
942 depends on X86_64 && SMP && DEBUG_KERNEL
943 select CPUMASK_OFFSTACK
945 Enable maximum number of CPUS and NUMA Nodes for this architecture.
949 # The maximum number of CPUs supported:
951 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
952 # and which can be configured interactively in the
953 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
955 # The ranges are different on 32-bit and 64-bit kernels, depending on
956 # hardware capabilities and scalability features of the kernel.
958 # ( If MAXSMP is enabled we just use the highest possible value and disable
959 # interactive configuration. )
962 config NR_CPUS_RANGE_BEGIN
964 default NR_CPUS_RANGE_END if MAXSMP
968 config NR_CPUS_RANGE_END
971 default 64 if SMP && X86_BIGSMP
972 default 8 if SMP && !X86_BIGSMP
975 config NR_CPUS_RANGE_END
978 default 8192 if SMP && CPUMASK_OFFSTACK
979 default 512 if SMP && !CPUMASK_OFFSTACK
982 config NR_CPUS_DEFAULT
985 default 32 if X86_BIGSMP
989 config NR_CPUS_DEFAULT
992 default 8192 if MAXSMP
997 int "Maximum number of CPUs" if SMP && !MAXSMP
998 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
999 default NR_CPUS_DEFAULT
1001 This allows you to specify the maximum number of CPUs which this
1002 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1003 supported value is 8192, otherwise the maximum value is 512. The
1004 minimum value which makes sense is 2.
1006 This is purely to save memory: each supported CPU adds about 8KB
1007 to the kernel image.
1014 prompt "Multi-core scheduler support"
1017 Multi-core scheduler support improves the CPU scheduler's decision
1018 making when dealing with multi-core CPU chips at a cost of slightly
1019 increased overhead in some places. If unsure say N here.
1021 config SCHED_MC_PRIO
1022 bool "CPU core priorities scheduler support"
1023 depends on SCHED_MC && CPU_SUP_INTEL
1024 select X86_INTEL_PSTATE
1028 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1029 core ordering determined at manufacturing time, which allows
1030 certain cores to reach higher turbo frequencies (when running
1031 single threaded workloads) than others.
1033 Enabling this kernel feature teaches the scheduler about
1034 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1035 scheduler's CPU selection logic accordingly, so that higher
1036 overall system performance can be achieved.
1038 This feature will have no effect on CPUs without this feature.
1040 If unsure say Y here.
1044 depends on !SMP && X86_LOCAL_APIC
1047 bool "Local APIC support on uniprocessors" if !PCI_MSI
1049 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1051 A local APIC (Advanced Programmable Interrupt Controller) is an
1052 integrated interrupt controller in the CPU. If you have a single-CPU
1053 system which has a processor with a local APIC, you can say Y here to
1054 enable and use it. If you say Y here even though your machine doesn't
1055 have a local APIC, then the kernel will still run with no slowdown at
1056 all. The local APIC supports CPU-generated self-interrupts (timer,
1057 performance counters), and the NMI watchdog which detects hard
1060 config X86_UP_IOAPIC
1061 bool "IO-APIC support on uniprocessors"
1062 depends on X86_UP_APIC
1064 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1065 SMP-capable replacement for PC-style interrupt controllers. Most
1066 SMP systems and many recent uniprocessor systems have one.
1068 If you have a single-CPU system with an IO-APIC, you can say Y here
1069 to use it. If you say Y here even though your machine doesn't have
1070 an IO-APIC, then the kernel will still run with no slowdown at all.
1072 config X86_LOCAL_APIC
1074 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1075 select IRQ_DOMAIN_HIERARCHY
1076 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1080 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1082 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1083 bool "Reroute for broken boot IRQs"
1084 depends on X86_IO_APIC
1086 This option enables a workaround that fixes a source of
1087 spurious interrupts. This is recommended when threaded
1088 interrupt handling is used on systems where the generation of
1089 superfluous "boot interrupts" cannot be disabled.
1091 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1092 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1093 kernel does during interrupt handling). On chipsets where this
1094 boot IRQ generation cannot be disabled, this workaround keeps
1095 the original IRQ line masked so that only the equivalent "boot
1096 IRQ" is delivered to the CPUs. The workaround also tells the
1097 kernel to set up the IRQ handler on the boot IRQ line. In this
1098 way only one interrupt is delivered to the kernel. Otherwise
1099 the spurious second interrupt may cause the kernel to bring
1100 down (vital) interrupt lines.
1102 Only affects "broken" chipsets. Interrupt sharing may be
1103 increased on these systems.
1106 bool "Machine Check / overheating reporting"
1107 select GENERIC_ALLOCATOR
1110 Machine Check support allows the processor to notify the
1111 kernel if it detects a problem (e.g. overheating, data corruption).
1112 The action the kernel takes depends on the severity of the problem,
1113 ranging from warning messages to halting the machine.
1115 config X86_MCELOG_LEGACY
1116 bool "Support for deprecated /dev/mcelog character device"
1119 Enable support for /dev/mcelog which is needed by the old mcelog
1120 userspace logging daemon. Consider switching to the new generation
1123 config X86_MCE_INTEL
1125 prompt "Intel MCE features"
1126 depends on X86_MCE && X86_LOCAL_APIC
1128 Additional support for intel specific MCE features such as
1129 the thermal monitor.
1133 prompt "AMD MCE features"
1134 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1136 Additional support for AMD specific MCE features such as
1137 the DRAM Error Threshold.
1139 config X86_ANCIENT_MCE
1140 bool "Support for old Pentium 5 / WinChip machine checks"
1141 depends on X86_32 && X86_MCE
1143 Include support for machine check handling on old Pentium 5 or WinChip
1144 systems. These typically need to be enabled explicitly on the command
1147 config X86_MCE_THRESHOLD
1148 depends on X86_MCE_AMD || X86_MCE_INTEL
1151 config X86_MCE_INJECT
1152 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1153 tristate "Machine check injector support"
1155 Provide support for injecting machine checks for testing purposes.
1156 If you don't know what a machine check is and you don't do kernel
1157 QA it is safe to say n.
1159 config X86_THERMAL_VECTOR
1161 depends on X86_MCE_INTEL
1163 source "arch/x86/events/Kconfig"
1165 config X86_LEGACY_VM86
1166 bool "Legacy VM86 support"
1169 This option allows user programs to put the CPU into V8086
1170 mode, which is an 80286-era approximation of 16-bit real mode.
1172 Some very old versions of X and/or vbetool require this option
1173 for user mode setting. Similarly, DOSEMU will use it if
1174 available to accelerate real mode DOS programs. However, any
1175 recent version of DOSEMU, X, or vbetool should be fully
1176 functional even without kernel VM86 support, as they will all
1177 fall back to software emulation. Nevertheless, if you are using
1178 a 16-bit DOS program where 16-bit performance matters, vm86
1179 mode might be faster than emulation and you might want to
1182 Note that any app that works on a 64-bit kernel is unlikely to
1183 need this option, as 64-bit kernels don't, and can't, support
1184 V8086 mode. This option is also unrelated to 16-bit protected
1185 mode and is not needed to run most 16-bit programs under Wine.
1187 Enabling this option increases the complexity of the kernel
1188 and slows down exception handling a tiny bit.
1190 If unsure, say N here.
1194 default X86_LEGACY_VM86
1197 bool "Enable support for 16-bit segments" if EXPERT
1199 depends on MODIFY_LDT_SYSCALL
1201 This option is required by programs like Wine to run 16-bit
1202 protected mode legacy code on x86 processors. Disabling
1203 this option saves about 300 bytes on i386, or around 6K text
1204 plus 16K runtime memory on x86-64,
1208 depends on X86_16BIT && X86_32
1212 depends on X86_16BIT && X86_64
1214 config X86_VSYSCALL_EMULATION
1215 bool "Enable vsyscall emulation" if EXPERT
1219 This enables emulation of the legacy vsyscall page. Disabling
1220 it is roughly equivalent to booting with vsyscall=none, except
1221 that it will also disable the helpful warning if a program
1222 tries to use a vsyscall. With this option set to N, offending
1223 programs will just segfault, citing addresses of the form
1226 This option is required by many programs built before 2013, and
1227 care should be used even with newer programs if set to N.
1229 Disabling this option saves about 7K of kernel size and
1230 possibly 4K of additional runtime pagetable memory.
1232 config X86_IOPL_IOPERM
1233 bool "IOPERM and IOPL Emulation"
1236 This enables the ioperm() and iopl() syscalls which are necessary
1237 for legacy applications.
1239 Legacy IOPL support is an overbroad mechanism which allows user
1240 space aside of accessing all 65536 I/O ports also to disable
1241 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1242 capabilities and permission from potentially active security
1245 The emulation restricts the functionality of the syscall to
1246 only allowing the full range I/O port access, but prevents the
1247 ability to disable interrupts from user space which would be
1248 granted if the hardware IOPL mechanism would be used.
1251 tristate "Toshiba Laptop support"
1254 This adds a driver to safely access the System Management Mode of
1255 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1256 not work on models with a Phoenix BIOS. The System Management Mode
1257 is used to set the BIOS and power saving options on Toshiba portables.
1259 For information on utilities to make use of this driver see the
1260 Toshiba Linux utilities web site at:
1261 <http://www.buzzard.org.uk/toshiba/>.
1263 Say Y if you intend to run this kernel on a Toshiba portable.
1267 tristate "Dell i8k legacy laptop support"
1269 select SENSORS_DELL_SMM
1271 This option enables legacy /proc/i8k userspace interface in hwmon
1272 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1273 temperature and allows controlling fan speeds of Dell laptops via
1274 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1275 it reports also power and hotkey status. For fan speed control is
1276 needed userspace package i8kutils.
1278 Say Y if you intend to run this kernel on old Dell laptops or want to
1279 use userspace package i8kutils.
1282 config X86_REBOOTFIXUPS
1283 bool "Enable X86 board specific fixups for reboot"
1286 This enables chipset and/or board specific fixups to be done
1287 in order to get reboot to work correctly. This is only needed on
1288 some combinations of hardware and BIOS. The symptom, for which
1289 this config is intended, is when reboot ends with a stalled/hung
1292 Currently, the only fixup is for the Geode machines using
1293 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1295 Say Y if you want to enable the fixup. Currently, it's safe to
1296 enable this option even if you don't need it.
1300 bool "CPU microcode loading support"
1302 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1305 If you say Y here, you will be able to update the microcode on
1306 Intel and AMD processors. The Intel support is for the IA32 family,
1307 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1308 AMD support is for families 0x10 and later. You will obviously need
1309 the actual microcode binary data itself which is not shipped with
1312 The preferred method to load microcode from a detached initrd is described
1313 in Documentation/x86/microcode.rst. For that you need to enable
1314 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1315 initrd for microcode blobs.
1317 In addition, you can build the microcode into the kernel. For that you
1318 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1321 config MICROCODE_INTEL
1322 bool "Intel microcode loading support"
1323 depends on MICROCODE
1327 This options enables microcode patch loading support for Intel
1330 For the current Intel microcode data package go to
1331 <https://downloadcenter.intel.com> and search for
1332 'Linux Processor Microcode Data File'.
1334 config MICROCODE_AMD
1335 bool "AMD microcode loading support"
1336 depends on MICROCODE
1339 If you select this option, microcode patch loading support for AMD
1340 processors will be enabled.
1342 config MICROCODE_OLD_INTERFACE
1343 bool "Ancient loading interface (DEPRECATED)"
1345 depends on MICROCODE
1347 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1348 which was used by userspace tools like iucode_tool and microcode.ctl.
1349 It is inadequate because it runs too late to be able to properly
1350 load microcode on a machine and it needs special tools. Instead, you
1351 should've switched to the early loading method with the initrd or
1352 builtin microcode by now: Documentation/x86/microcode.rst
1355 tristate "/dev/cpu/*/msr - Model-specific register support"
1357 This device gives privileged processes access to the x86
1358 Model-Specific Registers (MSRs). It is a character device with
1359 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1360 MSR accesses are directed to a specific CPU on multi-processor
1364 tristate "/dev/cpu/*/cpuid - CPU information support"
1366 This device gives processes access to the x86 CPUID instruction to
1367 be executed on a specific processor. It is a character device
1368 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1372 prompt "High Memory Support"
1379 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1380 However, the address space of 32-bit x86 processors is only 4
1381 Gigabytes large. That means that, if you have a large amount of
1382 physical memory, not all of it can be "permanently mapped" by the
1383 kernel. The physical memory that's not permanently mapped is called
1386 If you are compiling a kernel which will never run on a machine with
1387 more than 1 Gigabyte total physical RAM, answer "off" here (default
1388 choice and suitable for most users). This will result in a "3GB/1GB"
1389 split: 3GB are mapped so that each process sees a 3GB virtual memory
1390 space and the remaining part of the 4GB virtual memory space is used
1391 by the kernel to permanently map as much physical memory as
1394 If the machine has between 1 and 4 Gigabytes physical RAM, then
1397 If more than 4 Gigabytes is used then answer "64GB" here. This
1398 selection turns Intel PAE (Physical Address Extension) mode on.
1399 PAE implements 3-level paging on IA32 processors. PAE is fully
1400 supported by Linux, PAE mode is implemented on all recent Intel
1401 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1402 then the kernel will not boot on CPUs that don't support PAE!
1404 The actual amount of total physical memory will either be
1405 auto detected or can be forced by using a kernel command line option
1406 such as "mem=256M". (Try "man bootparam" or see the documentation of
1407 your boot loader (lilo or loadlin) about how to pass options to the
1408 kernel at boot time.)
1410 If unsure, say "off".
1415 Select this if you have a 32-bit processor and between 1 and 4
1416 gigabytes of physical RAM.
1420 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1423 Select this if you have a 32-bit processor and more than 4
1424 gigabytes of physical RAM.
1429 prompt "Memory split" if EXPERT
1433 Select the desired split between kernel and user memory.
1435 If the address range available to the kernel is less than the
1436 physical memory installed, the remaining memory will be available
1437 as "high memory". Accessing high memory is a little more costly
1438 than low memory, as it needs to be mapped into the kernel first.
1439 Note that increasing the kernel address space limits the range
1440 available to user programs, making the address space there
1441 tighter. Selecting anything other than the default 3G/1G split
1442 will also likely make your kernel incompatible with binary-only
1445 If you are not absolutely sure what you are doing, leave this
1449 bool "3G/1G user/kernel split"
1450 config VMSPLIT_3G_OPT
1452 bool "3G/1G user/kernel split (for full 1G low memory)"
1454 bool "2G/2G user/kernel split"
1455 config VMSPLIT_2G_OPT
1457 bool "2G/2G user/kernel split (for full 2G low memory)"
1459 bool "1G/3G user/kernel split"
1464 default 0xB0000000 if VMSPLIT_3G_OPT
1465 default 0x80000000 if VMSPLIT_2G
1466 default 0x78000000 if VMSPLIT_2G_OPT
1467 default 0x40000000 if VMSPLIT_1G
1473 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1476 bool "PAE (Physical Address Extension) Support"
1477 depends on X86_32 && !HIGHMEM4G
1478 select PHYS_ADDR_T_64BIT
1481 PAE is required for NX support, and furthermore enables
1482 larger swapspace support for non-overcommit purposes. It
1483 has the cost of more pagetable lookup overhead, and also
1484 consumes more pagetable space per process.
1487 bool "Enable 5-level page tables support"
1489 select DYNAMIC_MEMORY_LAYOUT
1490 select SPARSEMEM_VMEMMAP
1493 5-level paging enables access to larger address space:
1494 upto 128 PiB of virtual address space and 4 PiB of
1495 physical address space.
1497 It will be supported by future Intel CPUs.
1499 A kernel with the option enabled can be booted on machines that
1500 support 4- or 5-level paging.
1502 See Documentation/x86/x86_64/5level-paging.rst for more
1507 config X86_DIRECT_GBPAGES
1511 Certain kernel features effectively disable kernel
1512 linear 1 GB mappings (even if the CPU otherwise
1513 supports them), so don't confuse the user by printing
1514 that we have them enabled.
1516 config X86_CPA_STATISTICS
1517 bool "Enable statistic for Change Page Attribute"
1520 Expose statistics about the Change Page Attribute mechanism, which
1521 helps to determine the effectiveness of preserving large and huge
1522 page mappings when mapping protections are changed.
1524 config AMD_MEM_ENCRYPT
1525 bool "AMD Secure Memory Encryption (SME) support"
1526 depends on X86_64 && CPU_SUP_AMD
1527 select DYNAMIC_PHYSICAL_MASK
1528 select ARCH_USE_MEMREMAP_PROT
1529 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1531 Say yes to enable support for the encryption of system memory.
1532 This requires an AMD processor that supports Secure Memory
1535 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1536 bool "Activate AMD Secure Memory Encryption (SME) by default"
1538 depends on AMD_MEM_ENCRYPT
1540 Say yes to have system memory encrypted by default if running on
1541 an AMD processor that supports Secure Memory Encryption (SME).
1543 If set to Y, then the encryption of system memory can be
1544 deactivated with the mem_encrypt=off command line option.
1546 If set to N, then the encryption of system memory can be
1547 activated with the mem_encrypt=on command line option.
1549 # Common NUMA Features
1551 bool "NUMA Memory Allocation and Scheduler Support"
1553 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1554 default y if X86_BIGSMP
1556 Enable NUMA (Non-Uniform Memory Access) support.
1558 The kernel will try to allocate memory used by a CPU on the
1559 local memory controller of the CPU and add some more
1560 NUMA awareness to the kernel.
1562 For 64-bit this is recommended if the system is Intel Core i7
1563 (or later), AMD Opteron, or EM64T NUMA.
1565 For 32-bit this is only needed if you boot a 32-bit
1566 kernel on a 64-bit NUMA platform.
1568 Otherwise, you should say N.
1572 prompt "Old style AMD Opteron NUMA detection"
1573 depends on X86_64 && NUMA && PCI
1575 Enable AMD NUMA node topology detection. You should say Y here if
1576 you have a multi processor AMD system. This uses an old method to
1577 read the NUMA configuration directly from the builtin Northbridge
1578 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1579 which also takes priority if both are compiled in.
1581 config X86_64_ACPI_NUMA
1583 prompt "ACPI NUMA detection"
1584 depends on X86_64 && NUMA && ACPI && PCI
1587 Enable ACPI SRAT based node topology detection.
1589 # Some NUMA nodes have memory ranges that span
1590 # other nodes. Even though a pfn is valid and
1591 # between a node's start and end pfns, it may not
1592 # reside on that node. See memmap_init_zone()
1594 config NODES_SPAN_OTHER_NODES
1596 depends on X86_64_ACPI_NUMA
1599 bool "NUMA emulation"
1602 Enable NUMA emulation. A flat machine will be split
1603 into virtual nodes when booted with "numa=fake=N", where N is the
1604 number of nodes. This is only useful for debugging.
1607 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1609 default "10" if MAXSMP
1610 default "6" if X86_64
1612 depends on NEED_MULTIPLE_NODES
1614 Specify the maximum number of NUMA Nodes available on the target
1615 system. Increases memory reserved to accommodate various tables.
1617 config ARCH_HAVE_MEMORY_PRESENT
1619 depends on X86_32 && DISCONTIGMEM
1621 config ARCH_FLATMEM_ENABLE
1623 depends on X86_32 && !NUMA
1625 config ARCH_DISCONTIGMEM_ENABLE
1627 depends on NUMA && X86_32
1630 config ARCH_SPARSEMEM_ENABLE
1632 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1633 select SPARSEMEM_STATIC if X86_32
1634 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1636 config ARCH_SPARSEMEM_DEFAULT
1637 def_bool X86_64 || (NUMA && X86_32)
1639 config ARCH_SELECT_MEMORY_MODEL
1641 depends on ARCH_SPARSEMEM_ENABLE
1643 config ARCH_MEMORY_PROBE
1644 bool "Enable sysfs memory/probe interface"
1645 depends on X86_64 && MEMORY_HOTPLUG
1647 This option enables a sysfs memory/probe interface for testing.
1648 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1649 If you are unsure how to answer this question, answer N.
1651 config ARCH_PROC_KCORE_TEXT
1653 depends on X86_64 && PROC_KCORE
1655 config ILLEGAL_POINTER_VALUE
1658 default 0xdead000000000000 if X86_64
1660 config X86_PMEM_LEGACY_DEVICE
1663 config X86_PMEM_LEGACY
1664 tristate "Support non-standard NVDIMMs and ADR protected memory"
1665 depends on PHYS_ADDR_T_64BIT
1667 select X86_PMEM_LEGACY_DEVICE
1670 Treat memory marked using the non-standard e820 type of 12 as used
1671 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1672 The kernel will offer these regions to the 'pmem' driver so
1673 they can be used for persistent storage.
1678 bool "Allocate 3rd-level pagetables from highmem"
1681 The VM uses one page table entry for each page of physical memory.
1682 For systems with a lot of RAM, this can be wasteful of precious
1683 low memory. Setting this option will put user-space page table
1684 entries in high memory.
1686 config X86_CHECK_BIOS_CORRUPTION
1687 bool "Check for low memory corruption"
1689 Periodically check for memory corruption in low memory, which
1690 is suspected to be caused by BIOS. Even when enabled in the
1691 configuration, it is disabled at runtime. Enable it by
1692 setting "memory_corruption_check=1" on the kernel command
1693 line. By default it scans the low 64k of memory every 60
1694 seconds; see the memory_corruption_check_size and
1695 memory_corruption_check_period parameters in
1696 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1698 When enabled with the default parameters, this option has
1699 almost no overhead, as it reserves a relatively small amount
1700 of memory and scans it infrequently. It both detects corruption
1701 and prevents it from affecting the running system.
1703 It is, however, intended as a diagnostic tool; if repeatable
1704 BIOS-originated corruption always affects the same memory,
1705 you can use memmap= to prevent the kernel from using that
1708 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1709 bool "Set the default setting of memory_corruption_check"
1710 depends on X86_CHECK_BIOS_CORRUPTION
1713 Set whether the default state of memory_corruption_check is
1716 config X86_RESERVE_LOW
1717 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1721 Specify the amount of low memory to reserve for the BIOS.
1723 The first page contains BIOS data structures that the kernel
1724 must not use, so that page must always be reserved.
1726 By default we reserve the first 64K of physical RAM, as a
1727 number of BIOSes are known to corrupt that memory range
1728 during events such as suspend/resume or monitor cable
1729 insertion, so it must not be used by the kernel.
1731 You can set this to 4 if you are absolutely sure that you
1732 trust the BIOS to get all its memory reservations and usages
1733 right. If you know your BIOS have problems beyond the
1734 default 64K area, you can set this to 640 to avoid using the
1735 entire low memory range.
1737 If you have doubts about the BIOS (e.g. suspend/resume does
1738 not work or there's kernel crashes after certain hardware
1739 hotplug events) then you might want to enable
1740 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1741 typical corruption patterns.
1743 Leave this to the default value of 64 if you are unsure.
1745 config MATH_EMULATION
1747 depends on MODIFY_LDT_SYSCALL
1748 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1750 Linux can emulate a math coprocessor (used for floating point
1751 operations) if you don't have one. 486DX and Pentium processors have
1752 a math coprocessor built in, 486SX and 386 do not, unless you added
1753 a 487DX or 387, respectively. (The messages during boot time can
1754 give you some hints here ["man dmesg"].) Everyone needs either a
1755 coprocessor or this emulation.
1757 If you don't have a math coprocessor, you need to say Y here; if you
1758 say Y here even though you have a coprocessor, the coprocessor will
1759 be used nevertheless. (This behavior can be changed with the kernel
1760 command line option "no387", which comes handy if your coprocessor
1761 is broken. Try "man bootparam" or see the documentation of your boot
1762 loader (lilo or loadlin) about how to pass options to the kernel at
1763 boot time.) This means that it is a good idea to say Y here if you
1764 intend to use this kernel on different machines.
1766 More information about the internals of the Linux math coprocessor
1767 emulation can be found in <file:arch/x86/math-emu/README>.
1769 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1770 kernel, it won't hurt.
1774 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1776 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1777 the Memory Type Range Registers (MTRRs) may be used to control
1778 processor access to memory ranges. This is most useful if you have
1779 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1780 allows bus write transfers to be combined into a larger transfer
1781 before bursting over the PCI/AGP bus. This can increase performance
1782 of image write operations 2.5 times or more. Saying Y here creates a
1783 /proc/mtrr file which may be used to manipulate your processor's
1784 MTRRs. Typically the X server should use this.
1786 This code has a reasonably generic interface so that similar
1787 control registers on other processors can be easily supported
1790 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1791 Registers (ARRs) which provide a similar functionality to MTRRs. For
1792 these, the ARRs are used to emulate the MTRRs.
1793 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1794 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1795 write-combining. All of these processors are supported by this code
1796 and it makes sense to say Y here if you have one of them.
1798 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1799 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1800 can lead to all sorts of problems, so it's good to say Y here.
1802 You can safely say Y even if your machine doesn't have MTRRs, you'll
1803 just add about 9 KB to your kernel.
1805 See <file:Documentation/x86/mtrr.rst> for more information.
1807 config MTRR_SANITIZER
1809 prompt "MTRR cleanup support"
1812 Convert MTRR layout from continuous to discrete, so X drivers can
1813 add writeback entries.
1815 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1816 The largest mtrr entry size for a continuous block can be set with
1821 config MTRR_SANITIZER_ENABLE_DEFAULT
1822 int "MTRR cleanup enable value (0-1)"
1825 depends on MTRR_SANITIZER
1827 Enable mtrr cleanup default value
1829 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1830 int "MTRR cleanup spare reg num (0-7)"
1833 depends on MTRR_SANITIZER
1835 mtrr cleanup spare entries default, it can be changed via
1836 mtrr_spare_reg_nr=N on the kernel command line.
1840 prompt "x86 PAT support" if EXPERT
1843 Use PAT attributes to setup page level cache control.
1845 PATs are the modern equivalents of MTRRs and are much more
1846 flexible than MTRRs.
1848 Say N here if you see bootup problems (boot crash, boot hang,
1849 spontaneous reboots) or a non-working video driver.
1853 config ARCH_USES_PG_UNCACHED
1859 prompt "x86 architectural random number generator" if EXPERT
1861 Enable the x86 architectural RDRAND instruction
1862 (Intel Bull Mountain technology) to generate random numbers.
1863 If supported, this is a high bandwidth, cryptographically
1864 secure hardware random number generator.
1868 prompt "Supervisor Mode Access Prevention" if EXPERT
1870 Supervisor Mode Access Prevention (SMAP) is a security
1871 feature in newer Intel processors. There is a small
1872 performance cost if this enabled and turned on; there is
1873 also a small increase in the kernel size if this is enabled.
1879 depends on CPU_SUP_INTEL || CPU_SUP_AMD
1880 prompt "User Mode Instruction Prevention" if EXPERT
1882 User Mode Instruction Prevention (UMIP) is a security feature in
1883 some x86 processors. If enabled, a general protection fault is
1884 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1885 executed in user mode. These instructions unnecessarily expose
1886 information about the hardware state.
1888 The vast majority of applications do not use these instructions.
1889 For the very few that do, software emulation is provided in
1890 specific cases in protected and virtual-8086 modes. Emulated
1893 config X86_INTEL_MEMORY_PROTECTION_KEYS
1894 prompt "Intel Memory Protection Keys"
1896 # Note: only available in 64-bit mode
1897 depends on CPU_SUP_INTEL && X86_64
1898 select ARCH_USES_HIGH_VMA_FLAGS
1899 select ARCH_HAS_PKEYS
1901 Memory Protection Keys provides a mechanism for enforcing
1902 page-based protections, but without requiring modification of the
1903 page tables when an application changes protection domains.
1905 For details, see Documentation/core-api/protection-keys.rst
1910 prompt "TSX enable mode"
1911 depends on CPU_SUP_INTEL
1912 default X86_INTEL_TSX_MODE_OFF
1914 Intel's TSX (Transactional Synchronization Extensions) feature
1915 allows to optimize locking protocols through lock elision which
1916 can lead to a noticeable performance boost.
1918 On the other hand it has been shown that TSX can be exploited
1919 to form side channel attacks (e.g. TAA) and chances are there
1920 will be more of those attacks discovered in the future.
1922 Therefore TSX is not enabled by default (aka tsx=off). An admin
1923 might override this decision by tsx=on the command line parameter.
1924 Even with TSX enabled, the kernel will attempt to enable the best
1925 possible TAA mitigation setting depending on the microcode available
1926 for the particular machine.
1928 This option allows to set the default tsx mode between tsx=on, =off
1929 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1932 Say off if not sure, auto if TSX is in use but it should be used on safe
1933 platforms or on if TSX is in use and the security aspect of tsx is not
1936 config X86_INTEL_TSX_MODE_OFF
1939 TSX is disabled if possible - equals to tsx=off command line parameter.
1941 config X86_INTEL_TSX_MODE_ON
1944 TSX is always enabled on TSX capable HW - equals the tsx=on command
1947 config X86_INTEL_TSX_MODE_AUTO
1950 TSX is enabled on TSX capable HW that is believed to be safe against
1951 side channel attacks- equals the tsx=auto command line parameter.
1955 bool "EFI runtime service support"
1958 select EFI_RUNTIME_WRAPPERS
1960 This enables the kernel to use EFI runtime services that are
1961 available (such as the EFI variable services).
1963 This option is only useful on systems that have EFI firmware.
1964 In addition, you should use the latest ELILO loader available
1965 at <http://elilo.sourceforge.net> in order to take advantage
1966 of EFI runtime services. However, even with this option, the
1967 resultant kernel should continue to boot on existing non-EFI
1971 bool "EFI stub support"
1972 depends on EFI && !X86_USE_3DNOW
1973 depends on $(cc-option,-mabi=ms) || X86_32
1976 This kernel feature allows a bzImage to be loaded directly
1977 by EFI firmware without the use of a bootloader.
1979 See Documentation/admin-guide/efi-stub.rst for more information.
1982 bool "EFI mixed-mode support"
1983 depends on EFI_STUB && X86_64
1985 Enabling this feature allows a 64-bit kernel to be booted
1986 on a 32-bit firmware, provided that your CPU supports 64-bit
1989 Note that it is not possible to boot a mixed-mode enabled
1990 kernel via the EFI boot stub - a bootloader that supports
1991 the EFI handover protocol must be used.
1997 prompt "Enable seccomp to safely compute untrusted bytecode"
1999 This kernel feature is useful for number crunching applications
2000 that may need to compute untrusted bytecode during their
2001 execution. By using pipes or other transports made available to
2002 the process as file descriptors supporting the read/write
2003 syscalls, it's possible to isolate those applications in
2004 their own address space using seccomp. Once seccomp is
2005 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
2006 and the task is only allowed to execute a few safe syscalls
2007 defined by each seccomp mode.
2009 If unsure, say Y. Only embedded should say N here.
2011 source "kernel/Kconfig.hz"
2014 bool "kexec system call"
2017 kexec is a system call that implements the ability to shutdown your
2018 current kernel, and to start another kernel. It is like a reboot
2019 but it is independent of the system firmware. And like a reboot
2020 you can start any kernel with it, not just Linux.
2022 The name comes from the similarity to the exec system call.
2024 It is an ongoing process to be certain the hardware in a machine
2025 is properly shutdown, so do not be surprised if this code does not
2026 initially work for you. As of this writing the exact hardware
2027 interface is strongly in flux, so no good recommendation can be
2031 bool "kexec file based system call"
2036 depends on CRYPTO_SHA256=y
2038 This is new version of kexec system call. This system call is
2039 file based and takes file descriptors as system call argument
2040 for kernel and initramfs as opposed to list of segments as
2041 accepted by previous system call.
2043 config ARCH_HAS_KEXEC_PURGATORY
2047 bool "Verify kernel signature during kexec_file_load() syscall"
2048 depends on KEXEC_FILE
2051 This option makes the kexec_file_load() syscall check for a valid
2052 signature of the kernel image. The image can still be loaded without
2053 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2054 there's a signature that we can check, then it must be valid.
2056 In addition to this option, you need to enable signature
2057 verification for the corresponding kernel image type being
2058 loaded in order for this to work.
2060 config KEXEC_SIG_FORCE
2061 bool "Require a valid signature in kexec_file_load() syscall"
2062 depends on KEXEC_SIG
2064 This option makes kernel signature verification mandatory for
2065 the kexec_file_load() syscall.
2067 config KEXEC_BZIMAGE_VERIFY_SIG
2068 bool "Enable bzImage signature verification support"
2069 depends on KEXEC_SIG
2070 depends on SIGNED_PE_FILE_VERIFICATION
2071 select SYSTEM_TRUSTED_KEYRING
2073 Enable bzImage signature verification support.
2076 bool "kernel crash dumps"
2077 depends on X86_64 || (X86_32 && HIGHMEM)
2079 Generate crash dump after being started by kexec.
2080 This should be normally only set in special crash dump kernels
2081 which are loaded in the main kernel with kexec-tools into
2082 a specially reserved region and then later executed after
2083 a crash by kdump/kexec. The crash dump kernel must be compiled
2084 to a memory address not used by the main kernel or BIOS using
2085 PHYSICAL_START, or it must be built as a relocatable image
2086 (CONFIG_RELOCATABLE=y).
2087 For more details see Documentation/admin-guide/kdump/kdump.rst
2091 depends on KEXEC && HIBERNATION
2093 Jump between original kernel and kexeced kernel and invoke
2094 code in physical address mode via KEXEC
2096 config PHYSICAL_START
2097 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2100 This gives the physical address where the kernel is loaded.
2102 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2103 bzImage will decompress itself to above physical address and
2104 run from there. Otherwise, bzImage will run from the address where
2105 it has been loaded by the boot loader and will ignore above physical
2108 In normal kdump cases one does not have to set/change this option
2109 as now bzImage can be compiled as a completely relocatable image
2110 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2111 address. This option is mainly useful for the folks who don't want
2112 to use a bzImage for capturing the crash dump and want to use a
2113 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2114 to be specifically compiled to run from a specific memory area
2115 (normally a reserved region) and this option comes handy.
2117 So if you are using bzImage for capturing the crash dump,
2118 leave the value here unchanged to 0x1000000 and set
2119 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2120 for capturing the crash dump change this value to start of
2121 the reserved region. In other words, it can be set based on
2122 the "X" value as specified in the "crashkernel=YM@XM"
2123 command line boot parameter passed to the panic-ed
2124 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2125 for more details about crash dumps.
2127 Usage of bzImage for capturing the crash dump is recommended as
2128 one does not have to build two kernels. Same kernel can be used
2129 as production kernel and capture kernel. Above option should have
2130 gone away after relocatable bzImage support is introduced. But it
2131 is present because there are users out there who continue to use
2132 vmlinux for dump capture. This option should go away down the
2135 Don't change this unless you know what you are doing.
2138 bool "Build a relocatable kernel"
2141 This builds a kernel image that retains relocation information
2142 so it can be loaded someplace besides the default 1MB.
2143 The relocations tend to make the kernel binary about 10% larger,
2144 but are discarded at runtime.
2146 One use is for the kexec on panic case where the recovery kernel
2147 must live at a different physical address than the primary
2150 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2151 it has been loaded at and the compile time physical address
2152 (CONFIG_PHYSICAL_START) is used as the minimum location.
2154 config RANDOMIZE_BASE
2155 bool "Randomize the address of the kernel image (KASLR)"
2156 depends on RELOCATABLE
2159 In support of Kernel Address Space Layout Randomization (KASLR),
2160 this randomizes the physical address at which the kernel image
2161 is decompressed and the virtual address where the kernel
2162 image is mapped, as a security feature that deters exploit
2163 attempts relying on knowledge of the location of kernel
2166 On 64-bit, the kernel physical and virtual addresses are
2167 randomized separately. The physical address will be anywhere
2168 between 16MB and the top of physical memory (up to 64TB). The
2169 virtual address will be randomized from 16MB up to 1GB (9 bits
2170 of entropy). Note that this also reduces the memory space
2171 available to kernel modules from 1.5GB to 1GB.
2173 On 32-bit, the kernel physical and virtual addresses are
2174 randomized together. They will be randomized from 16MB up to
2175 512MB (8 bits of entropy).
2177 Entropy is generated using the RDRAND instruction if it is
2178 supported. If RDTSC is supported, its value is mixed into
2179 the entropy pool as well. If neither RDRAND nor RDTSC are
2180 supported, then entropy is read from the i8254 timer. The
2181 usable entropy is limited by the kernel being built using
2182 2GB addressing, and that PHYSICAL_ALIGN must be at a
2183 minimum of 2MB. As a result, only 10 bits of entropy are
2184 theoretically possible, but the implementations are further
2185 limited due to memory layouts.
2189 # Relocation on x86 needs some additional build support
2190 config X86_NEED_RELOCS
2192 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2194 config PHYSICAL_ALIGN
2195 hex "Alignment value to which kernel should be aligned"
2197 range 0x2000 0x1000000 if X86_32
2198 range 0x200000 0x1000000 if X86_64
2200 This value puts the alignment restrictions on physical address
2201 where kernel is loaded and run from. Kernel is compiled for an
2202 address which meets above alignment restriction.
2204 If bootloader loads the kernel at a non-aligned address and
2205 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2206 address aligned to above value and run from there.
2208 If bootloader loads the kernel at a non-aligned address and
2209 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2210 load address and decompress itself to the address it has been
2211 compiled for and run from there. The address for which kernel is
2212 compiled already meets above alignment restrictions. Hence the
2213 end result is that kernel runs from a physical address meeting
2214 above alignment restrictions.
2216 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2217 this value must be a multiple of 0x200000.
2219 Don't change this unless you know what you are doing.
2221 config DYNAMIC_MEMORY_LAYOUT
2224 This option makes base addresses of vmalloc and vmemmap as well as
2225 __PAGE_OFFSET movable during boot.
2227 config RANDOMIZE_MEMORY
2228 bool "Randomize the kernel memory sections"
2230 depends on RANDOMIZE_BASE
2231 select DYNAMIC_MEMORY_LAYOUT
2232 default RANDOMIZE_BASE
2234 Randomizes the base virtual address of kernel memory sections
2235 (physical memory mapping, vmalloc & vmemmap). This security feature
2236 makes exploits relying on predictable memory locations less reliable.
2238 The order of allocations remains unchanged. Entropy is generated in
2239 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2240 configuration have in average 30,000 different possible virtual
2241 addresses for each memory section.
2245 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2246 hex "Physical memory mapping padding" if EXPERT
2247 depends on RANDOMIZE_MEMORY
2248 default "0xa" if MEMORY_HOTPLUG
2250 range 0x1 0x40 if MEMORY_HOTPLUG
2253 Define the padding in terabytes added to the existing physical
2254 memory size during kernel memory randomization. It is useful
2255 for memory hotplug support but reduces the entropy available for
2256 address randomization.
2258 If unsure, leave at the default value.
2264 config BOOTPARAM_HOTPLUG_CPU0
2265 bool "Set default setting of cpu0_hotpluggable"
2266 depends on HOTPLUG_CPU
2268 Set whether default state of cpu0_hotpluggable is on or off.
2270 Say Y here to enable CPU0 hotplug by default. If this switch
2271 is turned on, there is no need to give cpu0_hotplug kernel
2272 parameter and the CPU0 hotplug feature is enabled by default.
2274 Please note: there are two known CPU0 dependencies if you want
2275 to enable the CPU0 hotplug feature either by this switch or by
2276 cpu0_hotplug kernel parameter.
2278 First, resume from hibernate or suspend always starts from CPU0.
2279 So hibernate and suspend are prevented if CPU0 is offline.
2281 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2282 offline if any interrupt can not migrate out of CPU0. There may
2283 be other CPU0 dependencies.
2285 Please make sure the dependencies are under your control before
2286 you enable this feature.
2288 Say N if you don't want to enable CPU0 hotplug feature by default.
2289 You still can enable the CPU0 hotplug feature at boot by kernel
2290 parameter cpu0_hotplug.
2292 config DEBUG_HOTPLUG_CPU0
2294 prompt "Debug CPU0 hotplug"
2295 depends on HOTPLUG_CPU
2297 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2298 soon as possible and boots up userspace with CPU0 offlined. User
2299 can online CPU0 back after boot time.
2301 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2302 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2303 compilation or giving cpu0_hotplug kernel parameter at boot.
2309 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2310 depends on COMPAT_32
2312 Certain buggy versions of glibc will crash if they are
2313 presented with a 32-bit vDSO that is not mapped at the address
2314 indicated in its segment table.
2316 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2317 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2318 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2319 the only released version with the bug, but OpenSUSE 9
2320 contains a buggy "glibc 2.3.2".
2322 The symptom of the bug is that everything crashes on startup, saying:
2323 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2325 Saying Y here changes the default value of the vdso32 boot
2326 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2327 This works around the glibc bug but hurts performance.
2329 If unsure, say N: if you are compiling your own kernel, you
2330 are unlikely to be using a buggy version of glibc.
2333 prompt "vsyscall table for legacy applications"
2335 default LEGACY_VSYSCALL_XONLY
2337 Legacy user code that does not know how to find the vDSO expects
2338 to be able to issue three syscalls by calling fixed addresses in
2339 kernel space. Since this location is not randomized with ASLR,
2340 it can be used to assist security vulnerability exploitation.
2342 This setting can be changed at boot time via the kernel command
2343 line parameter vsyscall=[emulate|xonly|none].
2345 On a system with recent enough glibc (2.14 or newer) and no
2346 static binaries, you can say None without a performance penalty
2347 to improve security.
2349 If unsure, select "Emulate execution only".
2351 config LEGACY_VSYSCALL_EMULATE
2352 bool "Full emulation"
2354 The kernel traps and emulates calls into the fixed vsyscall
2355 address mapping. This makes the mapping non-executable, but
2356 it still contains readable known contents, which could be
2357 used in certain rare security vulnerability exploits. This
2358 configuration is recommended when using legacy userspace
2359 that still uses vsyscalls along with legacy binary
2360 instrumentation tools that require code to be readable.
2362 An example of this type of legacy userspace is running
2363 Pin on an old binary that still uses vsyscalls.
2365 config LEGACY_VSYSCALL_XONLY
2366 bool "Emulate execution only"
2368 The kernel traps and emulates calls into the fixed vsyscall
2369 address mapping and does not allow reads. This
2370 configuration is recommended when userspace might use the
2371 legacy vsyscall area but support for legacy binary
2372 instrumentation of legacy code is not needed. It mitigates
2373 certain uses of the vsyscall area as an ASLR-bypassing
2376 config LEGACY_VSYSCALL_NONE
2379 There will be no vsyscall mapping at all. This will
2380 eliminate any risk of ASLR bypass due to the vsyscall
2381 fixed address mapping. Attempts to use the vsyscalls
2382 will be reported to dmesg, so that either old or
2383 malicious userspace programs can be identified.
2388 bool "Built-in kernel command line"
2390 Allow for specifying boot arguments to the kernel at
2391 build time. On some systems (e.g. embedded ones), it is
2392 necessary or convenient to provide some or all of the
2393 kernel boot arguments with the kernel itself (that is,
2394 to not rely on the boot loader to provide them.)
2396 To compile command line arguments into the kernel,
2397 set this option to 'Y', then fill in the
2398 boot arguments in CONFIG_CMDLINE.
2400 Systems with fully functional boot loaders (i.e. non-embedded)
2401 should leave this option set to 'N'.
2404 string "Built-in kernel command string"
2405 depends on CMDLINE_BOOL
2408 Enter arguments here that should be compiled into the kernel
2409 image and used at boot time. If the boot loader provides a
2410 command line at boot time, it is appended to this string to
2411 form the full kernel command line, when the system boots.
2413 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2414 change this behavior.
2416 In most cases, the command line (whether built-in or provided
2417 by the boot loader) should specify the device for the root
2420 config CMDLINE_OVERRIDE
2421 bool "Built-in command line overrides boot loader arguments"
2422 depends on CMDLINE_BOOL
2424 Set this option to 'Y' to have the kernel ignore the boot loader
2425 command line, and use ONLY the built-in command line.
2427 This is used to work around broken boot loaders. This should
2428 be set to 'N' under normal conditions.
2430 config MODIFY_LDT_SYSCALL
2431 bool "Enable the LDT (local descriptor table)" if EXPERT
2434 Linux can allow user programs to install a per-process x86
2435 Local Descriptor Table (LDT) using the modify_ldt(2) system
2436 call. This is required to run 16-bit or segmented code such as
2437 DOSEMU or some Wine programs. It is also used by some very old
2438 threading libraries.
2440 Enabling this feature adds a small amount of overhead to
2441 context switches and increases the low-level kernel attack
2442 surface. Disabling it removes the modify_ldt(2) system call.
2444 Saying 'N' here may make sense for embedded or server kernels.
2446 source "kernel/livepatch/Kconfig"
2450 config ARCH_HAS_ADD_PAGES
2452 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2454 config ARCH_ENABLE_MEMORY_HOTPLUG
2456 depends on X86_64 || (X86_32 && HIGHMEM)
2458 config ARCH_ENABLE_MEMORY_HOTREMOVE
2460 depends on MEMORY_HOTPLUG
2462 config USE_PERCPU_NUMA_NODE_ID
2466 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2468 depends on X86_64 || X86_PAE
2470 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2472 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2474 config ARCH_ENABLE_THP_MIGRATION
2476 depends on X86_64 && TRANSPARENT_HUGEPAGE
2478 menu "Power management and ACPI options"
2480 config ARCH_HIBERNATION_HEADER
2482 depends on HIBERNATION
2484 source "kernel/power/Kconfig"
2486 source "drivers/acpi/Kconfig"
2488 source "drivers/sfi/Kconfig"
2495 tristate "APM (Advanced Power Management) BIOS support"
2496 depends on X86_32 && PM_SLEEP
2498 APM is a BIOS specification for saving power using several different
2499 techniques. This is mostly useful for battery powered laptops with
2500 APM compliant BIOSes. If you say Y here, the system time will be
2501 reset after a RESUME operation, the /proc/apm device will provide
2502 battery status information, and user-space programs will receive
2503 notification of APM "events" (e.g. battery status change).
2505 If you select "Y" here, you can disable actual use of the APM
2506 BIOS by passing the "apm=off" option to the kernel at boot time.
2508 Note that the APM support is almost completely disabled for
2509 machines with more than one CPU.
2511 In order to use APM, you will need supporting software. For location
2512 and more information, read <file:Documentation/power/apm-acpi.rst>
2513 and the Battery Powered Linux mini-HOWTO, available from
2514 <http://www.tldp.org/docs.html#howto>.
2516 This driver does not spin down disk drives (see the hdparm(8)
2517 manpage ("man 8 hdparm") for that), and it doesn't turn off
2518 VESA-compliant "green" monitors.
2520 This driver does not support the TI 4000M TravelMate and the ACER
2521 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2522 desktop machines also don't have compliant BIOSes, and this driver
2523 may cause those machines to panic during the boot phase.
2525 Generally, if you don't have a battery in your machine, there isn't
2526 much point in using this driver and you should say N. If you get
2527 random kernel OOPSes or reboots that don't seem to be related to
2528 anything, try disabling/enabling this option (or disabling/enabling
2531 Some other things you should try when experiencing seemingly random,
2534 1) make sure that you have enough swap space and that it is
2536 2) pass the "no-hlt" option to the kernel
2537 3) switch on floating point emulation in the kernel and pass
2538 the "no387" option to the kernel
2539 4) pass the "floppy=nodma" option to the kernel
2540 5) pass the "mem=4M" option to the kernel (thereby disabling
2541 all but the first 4 MB of RAM)
2542 6) make sure that the CPU is not over clocked.
2543 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2544 8) disable the cache from your BIOS settings
2545 9) install a fan for the video card or exchange video RAM
2546 10) install a better fan for the CPU
2547 11) exchange RAM chips
2548 12) exchange the motherboard.
2550 To compile this driver as a module, choose M here: the
2551 module will be called apm.
2555 config APM_IGNORE_USER_SUSPEND
2556 bool "Ignore USER SUSPEND"
2558 This option will ignore USER SUSPEND requests. On machines with a
2559 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2560 series notebooks, it is necessary to say Y because of a BIOS bug.
2562 config APM_DO_ENABLE
2563 bool "Enable PM at boot time"
2565 Enable APM features at boot time. From page 36 of the APM BIOS
2566 specification: "When disabled, the APM BIOS does not automatically
2567 power manage devices, enter the Standby State, enter the Suspend
2568 State, or take power saving steps in response to CPU Idle calls."
2569 This driver will make CPU Idle calls when Linux is idle (unless this
2570 feature is turned off -- see "Do CPU IDLE calls", below). This
2571 should always save battery power, but more complicated APM features
2572 will be dependent on your BIOS implementation. You may need to turn
2573 this option off if your computer hangs at boot time when using APM
2574 support, or if it beeps continuously instead of suspending. Turn
2575 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2576 T400CDT. This is off by default since most machines do fine without
2581 bool "Make CPU Idle calls when idle"
2583 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2584 On some machines, this can activate improved power savings, such as
2585 a slowed CPU clock rate, when the machine is idle. These idle calls
2586 are made after the idle loop has run for some length of time (e.g.,
2587 333 mS). On some machines, this will cause a hang at boot time or
2588 whenever the CPU becomes idle. (On machines with more than one CPU,
2589 this option does nothing.)
2591 config APM_DISPLAY_BLANK
2592 bool "Enable console blanking using APM"
2594 Enable console blanking using the APM. Some laptops can use this to
2595 turn off the LCD backlight when the screen blanker of the Linux
2596 virtual console blanks the screen. Note that this is only used by
2597 the virtual console screen blanker, and won't turn off the backlight
2598 when using the X Window system. This also doesn't have anything to
2599 do with your VESA-compliant power-saving monitor. Further, this
2600 option doesn't work for all laptops -- it might not turn off your
2601 backlight at all, or it might print a lot of errors to the console,
2602 especially if you are using gpm.
2604 config APM_ALLOW_INTS
2605 bool "Allow interrupts during APM BIOS calls"
2607 Normally we disable external interrupts while we are making calls to
2608 the APM BIOS as a measure to lessen the effects of a badly behaving
2609 BIOS implementation. The BIOS should reenable interrupts if it
2610 needs to. Unfortunately, some BIOSes do not -- especially those in
2611 many of the newer IBM Thinkpads. If you experience hangs when you
2612 suspend, try setting this to Y. Otherwise, say N.
2616 source "drivers/cpufreq/Kconfig"
2618 source "drivers/cpuidle/Kconfig"
2620 source "drivers/idle/Kconfig"
2625 menu "Bus options (PCI etc.)"
2628 prompt "PCI access mode"
2629 depends on X86_32 && PCI
2632 On PCI systems, the BIOS can be used to detect the PCI devices and
2633 determine their configuration. However, some old PCI motherboards
2634 have BIOS bugs and may crash if this is done. Also, some embedded
2635 PCI-based systems don't have any BIOS at all. Linux can also try to
2636 detect the PCI hardware directly without using the BIOS.
2638 With this option, you can specify how Linux should detect the
2639 PCI devices. If you choose "BIOS", the BIOS will be used,
2640 if you choose "Direct", the BIOS won't be used, and if you
2641 choose "MMConfig", then PCI Express MMCONFIG will be used.
2642 If you choose "Any", the kernel will try MMCONFIG, then the
2643 direct access method and falls back to the BIOS if that doesn't
2644 work. If unsure, go with the default, which is "Any".
2649 config PCI_GOMMCONFIG
2666 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2668 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2671 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2674 bool "Support mmconfig PCI config space access" if X86_64
2676 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2677 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2681 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2685 depends on PCI && XEN
2688 config MMCONF_FAM10H
2690 depends on X86_64 && PCI_MMCONFIG && ACPI
2692 config PCI_CNB20LE_QUIRK
2693 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2696 Read the PCI windows out of the CNB20LE host bridge. This allows
2697 PCI hotplug to work on systems with the CNB20LE chipset which do
2700 There's no public spec for this chipset, and this functionality
2701 is known to be incomplete.
2703 You should say N unless you know you need this.
2706 bool "ISA bus support on modern systems" if EXPERT
2708 Expose ISA bus device drivers and options available for selection and
2709 configuration. Enable this option if your target machine has an ISA
2710 bus. ISA is an older system, displaced by PCI and newer bus
2711 architectures -- if your target machine is modern, it probably does
2712 not have an ISA bus.
2716 # x86_64 have no ISA slots, but can have ISA-style DMA.
2718 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2721 Enables ISA-style DMA support for devices requiring such controllers.
2729 Find out whether you have ISA slots on your motherboard. ISA is the
2730 name of a bus system, i.e. the way the CPU talks to the other stuff
2731 inside your box. Other bus systems are PCI, EISA, MicroChannel
2732 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2733 newer boards don't support it. If you have ISA, say Y, otherwise N.
2736 tristate "NatSemi SCx200 support"
2738 This provides basic support for National Semiconductor's
2739 (now AMD's) Geode processors. The driver probes for the
2740 PCI-IDs of several on-chip devices, so its a good dependency
2741 for other scx200_* drivers.
2743 If compiled as a module, the driver is named scx200.
2745 config SCx200HR_TIMER
2746 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2750 This driver provides a clocksource built upon the on-chip
2751 27MHz high-resolution timer. Its also a workaround for
2752 NSC Geode SC-1100's buggy TSC, which loses time when the
2753 processor goes idle (as is done by the scheduler). The
2754 other workaround is idle=poll boot option.
2757 bool "One Laptop Per Child support"
2765 Add support for detecting the unique features of the OLPC
2769 bool "OLPC XO-1 Power Management"
2770 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2772 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2775 bool "OLPC XO-1 Real Time Clock"
2776 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2778 Add support for the XO-1 real time clock, which can be used as a
2779 programmable wakeup source.
2782 bool "OLPC XO-1 SCI extras"
2783 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2787 Add support for SCI-based features of the OLPC XO-1 laptop:
2788 - EC-driven system wakeups
2792 - AC adapter status updates
2793 - Battery status updates
2795 config OLPC_XO15_SCI
2796 bool "OLPC XO-1.5 SCI extras"
2797 depends on OLPC && ACPI
2800 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2801 - EC-driven system wakeups
2802 - AC adapter status updates
2803 - Battery status updates
2806 bool "PCEngines ALIX System Support (LED setup)"
2809 This option enables system support for the PCEngines ALIX.
2810 At present this just sets up LEDs for GPIO control on
2811 ALIX2/3/6 boards. However, other system specific setup should
2814 Note: You must still enable the drivers for GPIO and LED support
2815 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2817 Note: You have to set alix.force=1 for boards with Award BIOS.
2820 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2823 This option enables system support for the Soekris Engineering net5501.
2826 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2830 This option enables system support for the Traverse Technologies GEOS.
2833 bool "Technologic Systems TS-5500 platform support"
2835 select CHECK_SIGNATURE
2839 This option enables system support for the Technologic Systems TS-5500.
2845 depends on CPU_SUP_AMD && PCI
2848 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2850 Firmwares often provide initial graphics framebuffers so the BIOS,
2851 bootloader or kernel can show basic video-output during boot for
2852 user-guidance and debugging. Historically, x86 used the VESA BIOS
2853 Extensions and EFI-framebuffers for this, which are mostly limited
2855 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2856 framebuffers so the new generic system-framebuffer drivers can be
2857 used on x86. If the framebuffer is not compatible with the generic
2858 modes, it is advertised as fallback platform framebuffer so legacy
2859 drivers like efifb, vesafb and uvesafb can pick it up.
2860 If this option is not selected, all system framebuffers are always
2861 marked as fallback platform framebuffers as usual.
2863 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2864 not be able to pick up generic system framebuffers if this option
2865 is selected. You are highly encouraged to enable simplefb as
2866 replacement if you select this option. simplefb can correctly deal
2867 with generic system framebuffers. But you should still keep vesafb
2868 and others enabled as fallback if a system framebuffer is
2869 incompatible with simplefb.
2876 menu "Binary Emulations"
2878 config IA32_EMULATION
2879 bool "IA32 Emulation"
2881 select ARCH_WANT_OLD_COMPAT_IPC
2883 select COMPAT_BINFMT_ELF
2884 select COMPAT_OLD_SIGACTION
2886 Include code to run legacy 32-bit programs under a
2887 64-bit kernel. You should likely turn this on, unless you're
2888 100% sure that you don't have any 32-bit programs left.
2891 tristate "IA32 a.out support"
2892 depends on IA32_EMULATION
2895 Support old a.out binaries in the 32bit emulation.
2898 bool "x32 ABI for 64-bit mode"
2901 Include code to run binaries for the x32 native 32-bit ABI
2902 for 64-bit processors. An x32 process gets access to the
2903 full 64-bit register file and wide data path while leaving
2904 pointers at 32 bits for smaller memory footprint.
2906 You will need a recent binutils (2.22 or later) with
2907 elf32_x86_64 support enabled to compile a kernel with this
2912 depends on IA32_EMULATION || X86_32
2914 select OLD_SIGSUSPEND3
2918 depends on IA32_EMULATION || X86_X32
2921 config COMPAT_FOR_U64_ALIGNMENT
2924 config SYSVIPC_COMPAT
2932 config HAVE_ATOMIC_IOMAP
2936 source "drivers/firmware/Kconfig"
2938 source "arch/x86/kvm/Kconfig"