1 # SPDX-License-Identifier: GPL-2.0
4 bool "64-bit kernel" if "$(ARCH)" = "x86"
5 default "$(ARCH)" != "i386"
7 Say yes to build a 64-bit kernel - formerly known as x86_64
8 Say no to build a 32-bit kernel - formerly known as i386
13 # Options that are inherently 32-bit kernel only:
14 select ARCH_WANT_IPC_PARSE_VERSION
16 select CLONE_BACKWARDS
17 select HAVE_DEBUG_STACKOVERFLOW
18 select MODULES_USE_ELF_REL
20 select GENERIC_VDSO_32
25 # Options that are inherently 64-bit kernel only:
26 select ARCH_HAS_GIGANTIC_PAGE
27 select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
28 select ARCH_USE_CMPXCHG_LOCKREF
29 select HAVE_ARCH_SOFT_DIRTY
30 select MODULES_USE_ELF_RELA
31 select NEED_DMA_MAP_STATE
34 config FORCE_DYNAMIC_FTRACE
37 depends on FUNCTION_TRACER
40 We keep the static function tracing (!DYNAMIC_FTRACE) around
41 in order to test the non static function tracing in the
42 generic code, as other architectures still use it. But we
43 only need to keep it around for x86_64. No need to keep it
44 for x86_32. For x86_32, force DYNAMIC_FTRACE.
48 # ( Note that options that are marked 'if X86_64' could in principle be
49 # ported to 32-bit as well. )
54 # Note: keep this list sorted alphabetically
56 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
57 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
58 select ARCH_32BIT_OFF_T if X86_32
59 select ARCH_CLOCKSOURCE_INIT
60 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
61 select ARCH_HAS_DEBUG_VIRTUAL
62 select ARCH_HAS_DEVMEM_IS_ALLOWED
63 select ARCH_HAS_ELF_RANDOMIZE
64 select ARCH_HAS_FAST_MULTIPLIER
65 select ARCH_HAS_FILTER_PGPROT
66 select ARCH_HAS_FORTIFY_SOURCE
67 select ARCH_HAS_GCOV_PROFILE_ALL
68 select ARCH_HAS_KCOV if X86_64
69 select ARCH_HAS_MEM_ENCRYPT
70 select ARCH_HAS_MEMBARRIER_SYNC_CORE
71 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
72 select ARCH_HAS_PMEM_API if X86_64
73 select ARCH_HAS_PTE_DEVMAP if X86_64
74 select ARCH_HAS_PTE_SPECIAL
75 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
76 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
77 select ARCH_HAS_SET_MEMORY
78 select ARCH_HAS_SET_DIRECT_MAP
79 select ARCH_HAS_STRICT_KERNEL_RWX
80 select ARCH_HAS_STRICT_MODULE_RWX
81 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
82 select ARCH_HAS_SYSCALL_WRAPPER
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_USERFAULTFD_WP if X86_64 && USERFAULTFD
154 select HAVE_ARCH_VMAP_STACK if X86_64
155 select HAVE_ARCH_WITHIN_STACK_FRAMES
156 select HAVE_ASM_MODVERSIONS
157 select HAVE_CMPXCHG_DOUBLE
158 select HAVE_CMPXCHG_LOCAL
159 select HAVE_CONTEXT_TRACKING if X86_64
160 select HAVE_COPY_THREAD_TLS
161 select HAVE_C_RECORDMCOUNT
162 select HAVE_DEBUG_KMEMLEAK
163 select HAVE_DMA_CONTIGUOUS
164 select HAVE_DYNAMIC_FTRACE
165 select HAVE_DYNAMIC_FTRACE_WITH_REGS
166 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
168 select HAVE_EFFICIENT_UNALIGNED_ACCESS
170 select HAVE_EXIT_THREAD
172 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
173 select HAVE_FTRACE_MCOUNT_RECORD
174 select HAVE_FUNCTION_GRAPH_TRACER
175 select HAVE_FUNCTION_TRACER
176 select HAVE_GCC_PLUGINS
177 select HAVE_HW_BREAKPOINT
179 select HAVE_IOREMAP_PROT
180 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
181 select HAVE_IRQ_TIME_ACCOUNTING
182 select HAVE_KERNEL_BZIP2
183 select HAVE_KERNEL_GZIP
184 select HAVE_KERNEL_LZ4
185 select HAVE_KERNEL_LZMA
186 select HAVE_KERNEL_LZO
187 select HAVE_KERNEL_XZ
189 select HAVE_KPROBES_ON_FTRACE
190 select HAVE_FUNCTION_ERROR_INJECTION
191 select HAVE_KRETPROBES
193 select HAVE_LIVEPATCH if X86_64
194 select HAVE_MEMBLOCK_NODE_MAP
195 select HAVE_MIXED_BREAKPOINTS_REGS
196 select HAVE_MOD_ARCH_SPECIFIC
200 select HAVE_OPTPROBES
201 select HAVE_PCSPKR_PLATFORM
202 select HAVE_PERF_EVENTS
203 select HAVE_PERF_EVENTS_NMI
204 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
206 select HAVE_PERF_REGS
207 select HAVE_PERF_USER_STACK_DUMP
208 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
209 select HAVE_REGS_AND_STACK_ACCESS_API
210 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
211 select HAVE_FUNCTION_ARG_ACCESS_API
212 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
213 select HAVE_STACK_VALIDATION if X86_64
215 select HAVE_SYSCALL_TRACEPOINTS
216 select HAVE_UNSTABLE_SCHED_CLOCK
217 select HAVE_USER_RETURN_NOTIFIER
218 select HAVE_GENERIC_VDSO
219 select HOTPLUG_SMT if SMP
220 select IRQ_FORCED_THREADING
221 select NEED_SG_DMA_LENGTH
222 select PCI_DOMAINS if PCI
223 select PCI_LOCKLESS_CONFIG if PCI
226 select RTC_MC146818_LIB
229 select SYSCTL_EXCEPTION_TRACE
230 select THREAD_INFO_IN_TASK
231 select USER_STACKTRACE_SUPPORT
233 select X86_FEATURE_NAMES if PROC_FS
234 select PROC_PID_ARCH_STATUS if PROC_FS
235 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
237 config INSTRUCTION_DECODER
239 depends on KPROBES || PERF_EVENTS || UPROBES
243 default "elf32-i386" if X86_32
244 default "elf64-x86-64" if X86_64
246 config LOCKDEP_SUPPORT
249 config STACKTRACE_SUPPORT
255 config ARCH_MMAP_RND_BITS_MIN
259 config ARCH_MMAP_RND_BITS_MAX
263 config ARCH_MMAP_RND_COMPAT_BITS_MIN
266 config ARCH_MMAP_RND_COMPAT_BITS_MAX
272 config GENERIC_ISA_DMA
274 depends on ISA_DMA_API
279 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
281 config GENERIC_BUG_RELATIVE_POINTERS
284 config ARCH_MAY_HAVE_PC_FDC
286 depends on ISA_DMA_API
288 config GENERIC_CALIBRATE_DELAY
291 config ARCH_HAS_CPU_RELAX
294 config ARCH_HAS_CACHE_LINE_SIZE
297 config ARCH_HAS_FILTER_PGPROT
300 config HAVE_SETUP_PER_CPU_AREA
303 config NEED_PER_CPU_EMBED_FIRST_CHUNK
306 config NEED_PER_CPU_PAGE_FIRST_CHUNK
309 config ARCH_HIBERNATION_POSSIBLE
312 config ARCH_SUSPEND_POSSIBLE
315 config ARCH_WANT_GENERAL_HUGETLB
324 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
327 config KASAN_SHADOW_OFFSET
330 default 0xdffffc0000000000
332 config HAVE_INTEL_TXT
334 depends on INTEL_IOMMU && ACPI
338 depends on X86_32 && SMP
342 depends on X86_64 && SMP
344 config X86_32_LAZY_GS
346 depends on X86_32 && !STACKPROTECTOR
348 config ARCH_SUPPORTS_UPROBES
351 config FIX_EARLYCON_MEM
354 config DYNAMIC_PHYSICAL_MASK
357 config PGTABLE_LEVELS
359 default 5 if X86_5LEVEL
364 config CC_HAS_SANE_STACKPROTECTOR
366 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
367 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
369 We have to make sure stack protector is unconditionally disabled if
370 the compiler produces broken code.
372 menu "Processor type and features"
375 bool "DMA memory allocation support" if EXPERT
378 DMA memory allocation support allows devices with less than 32-bit
379 addressing to allocate within the first 16MB of address space.
380 Disable if no such devices will be used.
385 bool "Symmetric multi-processing support"
387 This enables support for systems with more than one CPU. If you have
388 a system with only one CPU, say N. If you have a system with more
391 If you say N here, the kernel will run on uni- and multiprocessor
392 machines, but will use only one CPU of a multiprocessor machine. If
393 you say Y here, the kernel will run on many, but not all,
394 uniprocessor machines. On a uniprocessor machine, the kernel
395 will run faster if you say N here.
397 Note that if you say Y here and choose architecture "586" or
398 "Pentium" under "Processor family", the kernel will not work on 486
399 architectures. Similarly, multiprocessor kernels for the "PPro"
400 architecture may not work on all Pentium based boards.
402 People using multiprocessor machines who say Y here should also say
403 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
404 Management" code will be disabled if you say Y here.
406 See also <file:Documentation/x86/i386/IO-APIC.rst>,
407 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
408 <http://www.tldp.org/docs.html#howto>.
410 If you don't know what to do here, say N.
412 config X86_FEATURE_NAMES
413 bool "Processor feature human-readable names" if EMBEDDED
416 This option compiles in a table of x86 feature bits and corresponding
417 names. This is required to support /proc/cpuinfo and a few kernel
418 messages. You can disable this to save space, at the expense of
419 making those few kernel messages show numeric feature bits instead.
424 bool "Support x2apic"
425 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
427 This enables x2apic support on CPUs that have this feature.
429 This allows 32-bit apic IDs (so it can support very large systems),
430 and accesses the local apic via MSRs not via mmio.
432 If you don't know what to do here, say N.
435 bool "Enable MPS table" if ACPI || SFI
437 depends on X86_LOCAL_APIC
439 For old smp systems that do not have proper acpi support. Newer systems
440 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
444 depends on X86_GOLDFISH
447 bool "Avoid speculative indirect branches in kernel"
449 select STACK_VALIDATION if HAVE_STACK_VALIDATION
451 Compile kernel with the retpoline compiler options to guard against
452 kernel-to-user data leaks by avoiding speculative indirect
453 branches. Requires a compiler with -mindirect-branch=thunk-extern
454 support for full protection. The kernel may run slower.
456 config X86_CPU_RESCTRL
457 bool "x86 CPU resource control support"
458 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
460 select PROC_CPU_RESCTRL if PROC_FS
462 Enable x86 CPU resource control support.
464 Provide support for the allocation and monitoring of system resources
467 Intel calls this Intel Resource Director Technology
468 (Intel(R) RDT). More information about RDT can be found in the
469 Intel x86 Architecture Software Developer Manual.
471 AMD calls this AMD Platform Quality of Service (AMD QoS).
472 More information about AMD QoS can be found in the AMD64 Technology
473 Platform Quality of Service Extensions manual.
479 bool "Support for big SMP systems with more than 8 CPUs"
482 This option is needed for the systems that have more than 8 CPUs.
484 config X86_EXTENDED_PLATFORM
485 bool "Support for extended (non-PC) x86 platforms"
488 If you disable this option then the kernel will only support
489 standard PC platforms. (which covers the vast majority of
492 If you enable this option then you'll be able to select support
493 for the following (non-PC) 32 bit x86 platforms:
494 Goldfish (Android emulator)
497 SGI 320/540 (Visual Workstation)
498 STA2X11-based (e.g. Northville)
499 Moorestown MID devices
501 If you have one of these systems, or if you want to build a
502 generic distribution kernel, say Y here - otherwise say N.
506 config X86_EXTENDED_PLATFORM
507 bool "Support for extended (non-PC) x86 platforms"
510 If you disable this option then the kernel will only support
511 standard PC platforms. (which covers the vast majority of
514 If you enable this option then you'll be able to select support
515 for the following (non-PC) 64 bit x86 platforms:
520 If you have one of these systems, or if you want to build a
521 generic distribution kernel, say Y here - otherwise say N.
523 # This is an alphabetically sorted list of 64 bit extended platforms
524 # Please maintain the alphabetic order if and when there are additions
526 bool "Numascale NumaChip"
528 depends on X86_EXTENDED_PLATFORM
531 depends on X86_X2APIC
532 depends on PCI_MMCONFIG
534 Adds support for Numascale NumaChip large-SMP systems. Needed to
535 enable more than ~168 cores.
536 If you don't have one of these, you should say N here.
540 select HYPERVISOR_GUEST
542 depends on X86_64 && PCI
543 depends on X86_EXTENDED_PLATFORM
546 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
547 supposed to run on these EM64T-based machines. Only choose this option
548 if you have one of these machines.
551 bool "SGI Ultraviolet"
553 depends on X86_EXTENDED_PLATFORM
556 depends on X86_X2APIC
559 This option is needed in order to support SGI Ultraviolet systems.
560 If you don't have one of these, you should say N here.
562 # Following is an alphabetically sorted list of 32 bit extended platforms
563 # Please maintain the alphabetic order if and when there are additions
566 bool "Goldfish (Virtual Platform)"
567 depends on X86_EXTENDED_PLATFORM
569 Enable support for the Goldfish virtual platform used primarily
570 for Android development. Unless you are building for the Android
571 Goldfish emulator say N here.
574 bool "CE4100 TV platform"
576 depends on PCI_GODIRECT
577 depends on X86_IO_APIC
579 depends on X86_EXTENDED_PLATFORM
580 select X86_REBOOTFIXUPS
582 select OF_EARLY_FLATTREE
584 Select for the Intel CE media processor (CE4100) SOC.
585 This option compiles in support for the CE4100 SOC for settop
586 boxes and media devices.
589 bool "Intel MID platform support"
590 depends on X86_EXTENDED_PLATFORM
591 depends on X86_PLATFORM_DEVICES
593 depends on X86_64 || (PCI_GOANY && X86_32)
594 depends on X86_IO_APIC
600 select MFD_INTEL_MSIC
602 Select to build a kernel capable of supporting Intel MID (Mobile
603 Internet Device) platform systems which do not have the PCI legacy
604 interfaces. If you are building for a PC class system say N here.
606 Intel MID platforms are based on an Intel processor and chipset which
607 consume less power than most of the x86 derivatives.
609 config X86_INTEL_QUARK
610 bool "Intel Quark platform support"
612 depends on X86_EXTENDED_PLATFORM
613 depends on X86_PLATFORM_DEVICES
617 depends on X86_IO_APIC
622 Select to include support for Quark X1000 SoC.
623 Say Y here if you have a Quark based system such as the Arduino
624 compatible Intel Galileo.
626 config X86_INTEL_LPSS
627 bool "Intel Low Power Subsystem Support"
628 depends on X86 && ACPI && PCI
633 Select to build support for Intel Low Power Subsystem such as
634 found on Intel Lynxpoint PCH. Selecting this option enables
635 things like clock tree (common clock framework) and pincontrol
636 which are needed by the LPSS peripheral drivers.
638 config X86_AMD_PLATFORM_DEVICE
639 bool "AMD ACPI2Platform devices support"
644 Select to interpret AMD specific ACPI device to platform device
645 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
646 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
647 implemented under PINCTRL subsystem.
650 tristate "Intel SoC IOSF Sideband support for SoC platforms"
653 This option enables sideband register access support for Intel SoC
654 platforms. On these platforms the IOSF sideband is used in lieu of
655 MSR's for some register accesses, mostly but not limited to thermal
656 and power. Drivers may query the availability of this device to
657 determine if they need the sideband in order to work on these
658 platforms. The sideband is available on the following SoC products.
659 This list is not meant to be exclusive.
664 You should say Y if you are running a kernel on one of these SoC's.
666 config IOSF_MBI_DEBUG
667 bool "Enable IOSF sideband access through debugfs"
668 depends on IOSF_MBI && DEBUG_FS
670 Select this option to expose the IOSF sideband access registers (MCR,
671 MDR, MCRX) through debugfs to write and read register information from
672 different units on the SoC. This is most useful for obtaining device
673 state information for debug and analysis. As this is a general access
674 mechanism, users of this option would have specific knowledge of the
675 device they want to access.
677 If you don't require the option or are in doubt, say N.
680 bool "RDC R-321x SoC"
682 depends on X86_EXTENDED_PLATFORM
684 select X86_REBOOTFIXUPS
686 This option is needed for RDC R-321x system-on-chip, also known
688 If you don't have one of these chips, you should say N here.
690 config X86_32_NON_STANDARD
691 bool "Support non-standard 32-bit SMP architectures"
692 depends on X86_32 && SMP
693 depends on X86_EXTENDED_PLATFORM
695 This option compiles in the bigsmp and STA2X11 default
696 subarchitectures. It is intended for a generic binary
697 kernel. If you select them all, kernel will probe it one by
698 one and will fallback to default.
700 # Alphabetically sorted list of Non standard 32 bit platforms
702 config X86_SUPPORTS_MEMORY_FAILURE
704 # MCE code calls memory_failure():
706 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
707 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
708 depends on X86_64 || !SPARSEMEM
709 select ARCH_SUPPORTS_MEMORY_FAILURE
712 bool "STA2X11 Companion Chip Support"
713 depends on X86_32_NON_STANDARD && PCI
718 This adds support for boards based on the STA2X11 IO-Hub,
719 a.k.a. "ConneXt". The chip is used in place of the standard
720 PC chipset, so all "standard" peripherals are missing. If this
721 option is selected the kernel will still be able to boot on
722 standard PC machines.
725 tristate "Eurobraille/Iris poweroff module"
728 The Iris machines from EuroBraille do not have APM or ACPI support
729 to shut themselves down properly. A special I/O sequence is
730 needed to do so, which is what this module does at
733 This is only for Iris machines from EuroBraille.
737 config SCHED_OMIT_FRAME_POINTER
739 prompt "Single-depth WCHAN output"
742 Calculate simpler /proc/<PID>/wchan values. If this option
743 is disabled then wchan values will recurse back to the
744 caller function. This provides more accurate wchan values,
745 at the expense of slightly more scheduling overhead.
747 If in doubt, say "Y".
749 menuconfig HYPERVISOR_GUEST
750 bool "Linux guest support"
752 Say Y here to enable options for running Linux under various hyper-
753 visors. This option enables basic hypervisor detection and platform
756 If you say N, all options in this submenu will be skipped and
757 disabled, and Linux guest support won't be built in.
762 bool "Enable paravirtualization code"
764 This changes the kernel so it can modify itself when it is run
765 under a hypervisor, potentially improving performance significantly
766 over full virtualization. However, when run without a hypervisor
767 the kernel is theoretically slower and slightly larger.
772 config PARAVIRT_DEBUG
773 bool "paravirt-ops debugging"
774 depends on PARAVIRT && DEBUG_KERNEL
776 Enable to debug paravirt_ops internals. Specifically, BUG if
777 a paravirt_op is missing when it is called.
779 config PARAVIRT_SPINLOCKS
780 bool "Paravirtualization layer for spinlocks"
781 depends on PARAVIRT && SMP
783 Paravirtualized spinlocks allow a pvops backend to replace the
784 spinlock implementation with something virtualization-friendly
785 (for example, block the virtual CPU rather than spinning).
787 It has a minimal impact on native kernels and gives a nice performance
788 benefit on paravirtualized KVM / Xen kernels.
790 If you are unsure how to answer this question, answer Y.
792 config X86_HV_CALLBACK_VECTOR
795 source "arch/x86/xen/Kconfig"
798 bool "KVM Guest support (including kvmclock)"
800 select PARAVIRT_CLOCK
801 select ARCH_CPUIDLE_HALTPOLL
804 This option enables various optimizations for running under the KVM
805 hypervisor. It includes a paravirtualized clock, so that instead
806 of relying on a PIT (or probably other) emulation by the
807 underlying device model, the host provides the guest with
808 timing infrastructure such as time of day, and system time
810 config ARCH_CPUIDLE_HALTPOLL
812 prompt "Disable host haltpoll when loading haltpoll driver"
814 If virtualized under KVM, disable host haltpoll.
817 bool "Support for running PVH guests"
819 This option enables the PVH entry point for guest virtual machines
820 as specified in the x86/HVM direct boot ABI.
823 bool "Enable debug information for KVM Guests in debugfs"
824 depends on KVM_GUEST && DEBUG_FS
826 This option enables collection of various statistics for KVM guest.
827 Statistics are displayed in debugfs filesystem. Enabling this option
828 may incur significant overhead.
830 config PARAVIRT_TIME_ACCOUNTING
831 bool "Paravirtual steal time accounting"
834 Select this option to enable fine granularity task steal time
835 accounting. Time spent executing other tasks in parallel with
836 the current vCPU is discounted from the vCPU power. To account for
837 that, there can be a small performance impact.
839 If in doubt, say N here.
841 config PARAVIRT_CLOCK
844 config JAILHOUSE_GUEST
845 bool "Jailhouse non-root cell support"
846 depends on X86_64 && PCI
849 This option allows to run Linux as guest in a Jailhouse non-root
850 cell. You can leave this option disabled if you only want to start
851 Jailhouse and run Linux afterwards in the root cell.
854 bool "ACRN Guest support"
856 select X86_HV_CALLBACK_VECTOR
858 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
859 a flexible, lightweight reference open-source hypervisor, built with
860 real-time and safety-criticality in mind. It is built for embedded
861 IOT with small footprint and real-time features. More details can be
862 found in https://projectacrn.org/.
864 endif #HYPERVISOR_GUEST
866 source "arch/x86/Kconfig.cpu"
870 prompt "HPET Timer Support" if X86_32
872 Use the IA-PC HPET (High Precision Event Timer) to manage
873 time in preference to the PIT and RTC, if a HPET is
875 HPET is the next generation timer replacing legacy 8254s.
876 The HPET provides a stable time base on SMP
877 systems, unlike the TSC, but it is more expensive to access,
878 as it is off-chip. The interface used is documented
879 in the HPET spec, revision 1.
881 You can safely choose Y here. However, HPET will only be
882 activated if the platform and the BIOS support this feature.
883 Otherwise the 8254 will be used for timing services.
885 Choose N to continue using the legacy 8254 timer.
887 config HPET_EMULATE_RTC
889 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
892 def_bool y if X86_INTEL_MID
893 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
895 depends on X86_INTEL_MID && SFI
897 APB timer is the replacement for 8254, HPET on X86 MID platforms.
898 The APBT provides a stable time base on SMP
899 systems, unlike the TSC, but it is more expensive to access,
900 as it is off-chip. APB timers are always running regardless of CPU
901 C states, they are used as per CPU clockevent device when possible.
903 # Mark as expert because too many people got it wrong.
904 # The code disables itself when not needed.
907 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
908 bool "Enable DMI scanning" if EXPERT
910 Enabled scanning of DMI to identify machine quirks. Say Y
911 here unless you have verified that your setup is not
912 affected by entries in the DMI blacklist. Required by PNP
916 bool "Old AMD GART IOMMU support"
919 depends on X86_64 && PCI && AMD_NB
921 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
922 GART based hardware IOMMUs.
924 The GART supports full DMA access for devices with 32-bit access
925 limitations, on systems with more than 3 GB. This is usually needed
926 for USB, sound, many IDE/SATA chipsets and some other devices.
928 Newer systems typically have a modern AMD IOMMU, supported via
929 the CONFIG_AMD_IOMMU=y config option.
931 In normal configurations this driver is only active when needed:
932 there's more than 3 GB of memory and the system contains a
933 32-bit limited device.
938 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
939 depends on X86_64 && SMP && DEBUG_KERNEL
940 select CPUMASK_OFFSTACK
942 Enable maximum number of CPUS and NUMA Nodes for this architecture.
946 # The maximum number of CPUs supported:
948 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
949 # and which can be configured interactively in the
950 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
952 # The ranges are different on 32-bit and 64-bit kernels, depending on
953 # hardware capabilities and scalability features of the kernel.
955 # ( If MAXSMP is enabled we just use the highest possible value and disable
956 # interactive configuration. )
959 config NR_CPUS_RANGE_BEGIN
961 default NR_CPUS_RANGE_END if MAXSMP
965 config NR_CPUS_RANGE_END
968 default 64 if SMP && X86_BIGSMP
969 default 8 if SMP && !X86_BIGSMP
972 config NR_CPUS_RANGE_END
975 default 8192 if SMP && CPUMASK_OFFSTACK
976 default 512 if SMP && !CPUMASK_OFFSTACK
979 config NR_CPUS_DEFAULT
982 default 32 if X86_BIGSMP
986 config NR_CPUS_DEFAULT
989 default 8192 if MAXSMP
994 int "Maximum number of CPUs" if SMP && !MAXSMP
995 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
996 default NR_CPUS_DEFAULT
998 This allows you to specify the maximum number of CPUs which this
999 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1000 supported value is 8192, otherwise the maximum value is 512. The
1001 minimum value which makes sense is 2.
1003 This is purely to save memory: each supported CPU adds about 8KB
1004 to the kernel image.
1011 prompt "Multi-core scheduler support"
1014 Multi-core scheduler support improves the CPU scheduler's decision
1015 making when dealing with multi-core CPU chips at a cost of slightly
1016 increased overhead in some places. If unsure say N here.
1018 config SCHED_MC_PRIO
1019 bool "CPU core priorities scheduler support"
1020 depends on SCHED_MC && CPU_SUP_INTEL
1021 select X86_INTEL_PSTATE
1025 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1026 core ordering determined at manufacturing time, which allows
1027 certain cores to reach higher turbo frequencies (when running
1028 single threaded workloads) than others.
1030 Enabling this kernel feature teaches the scheduler about
1031 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1032 scheduler's CPU selection logic accordingly, so that higher
1033 overall system performance can be achieved.
1035 This feature will have no effect on CPUs without this feature.
1037 If unsure say Y here.
1041 depends on !SMP && X86_LOCAL_APIC
1044 bool "Local APIC support on uniprocessors" if !PCI_MSI
1046 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1048 A local APIC (Advanced Programmable Interrupt Controller) is an
1049 integrated interrupt controller in the CPU. If you have a single-CPU
1050 system which has a processor with a local APIC, you can say Y here to
1051 enable and use it. If you say Y here even though your machine doesn't
1052 have a local APIC, then the kernel will still run with no slowdown at
1053 all. The local APIC supports CPU-generated self-interrupts (timer,
1054 performance counters), and the NMI watchdog which detects hard
1057 config X86_UP_IOAPIC
1058 bool "IO-APIC support on uniprocessors"
1059 depends on X86_UP_APIC
1061 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1062 SMP-capable replacement for PC-style interrupt controllers. Most
1063 SMP systems and many recent uniprocessor systems have one.
1065 If you have a single-CPU system with an IO-APIC, you can say Y here
1066 to use it. If you say Y here even though your machine doesn't have
1067 an IO-APIC, then the kernel will still run with no slowdown at all.
1069 config X86_LOCAL_APIC
1071 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1072 select IRQ_DOMAIN_HIERARCHY
1073 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1077 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1079 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1080 bool "Reroute for broken boot IRQs"
1081 depends on X86_IO_APIC
1083 This option enables a workaround that fixes a source of
1084 spurious interrupts. This is recommended when threaded
1085 interrupt handling is used on systems where the generation of
1086 superfluous "boot interrupts" cannot be disabled.
1088 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1089 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1090 kernel does during interrupt handling). On chipsets where this
1091 boot IRQ generation cannot be disabled, this workaround keeps
1092 the original IRQ line masked so that only the equivalent "boot
1093 IRQ" is delivered to the CPUs. The workaround also tells the
1094 kernel to set up the IRQ handler on the boot IRQ line. In this
1095 way only one interrupt is delivered to the kernel. Otherwise
1096 the spurious second interrupt may cause the kernel to bring
1097 down (vital) interrupt lines.
1099 Only affects "broken" chipsets. Interrupt sharing may be
1100 increased on these systems.
1103 bool "Machine Check / overheating reporting"
1104 select GENERIC_ALLOCATOR
1107 Machine Check support allows the processor to notify the
1108 kernel if it detects a problem (e.g. overheating, data corruption).
1109 The action the kernel takes depends on the severity of the problem,
1110 ranging from warning messages to halting the machine.
1112 config X86_MCELOG_LEGACY
1113 bool "Support for deprecated /dev/mcelog character device"
1116 Enable support for /dev/mcelog which is needed by the old mcelog
1117 userspace logging daemon. Consider switching to the new generation
1120 config X86_MCE_INTEL
1122 prompt "Intel MCE features"
1123 depends on X86_MCE && X86_LOCAL_APIC
1125 Additional support for intel specific MCE features such as
1126 the thermal monitor.
1130 prompt "AMD MCE features"
1131 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1133 Additional support for AMD specific MCE features such as
1134 the DRAM Error Threshold.
1136 config X86_ANCIENT_MCE
1137 bool "Support for old Pentium 5 / WinChip machine checks"
1138 depends on X86_32 && X86_MCE
1140 Include support for machine check handling on old Pentium 5 or WinChip
1141 systems. These typically need to be enabled explicitly on the command
1144 config X86_MCE_THRESHOLD
1145 depends on X86_MCE_AMD || X86_MCE_INTEL
1148 config X86_MCE_INJECT
1149 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1150 tristate "Machine check injector support"
1152 Provide support for injecting machine checks for testing purposes.
1153 If you don't know what a machine check is and you don't do kernel
1154 QA it is safe to say n.
1156 config X86_THERMAL_VECTOR
1158 depends on X86_MCE_INTEL
1160 source "arch/x86/events/Kconfig"
1162 config X86_LEGACY_VM86
1163 bool "Legacy VM86 support"
1166 This option allows user programs to put the CPU into V8086
1167 mode, which is an 80286-era approximation of 16-bit real mode.
1169 Some very old versions of X and/or vbetool require this option
1170 for user mode setting. Similarly, DOSEMU will use it if
1171 available to accelerate real mode DOS programs. However, any
1172 recent version of DOSEMU, X, or vbetool should be fully
1173 functional even without kernel VM86 support, as they will all
1174 fall back to software emulation. Nevertheless, if you are using
1175 a 16-bit DOS program where 16-bit performance matters, vm86
1176 mode might be faster than emulation and you might want to
1179 Note that any app that works on a 64-bit kernel is unlikely to
1180 need this option, as 64-bit kernels don't, and can't, support
1181 V8086 mode. This option is also unrelated to 16-bit protected
1182 mode and is not needed to run most 16-bit programs under Wine.
1184 Enabling this option increases the complexity of the kernel
1185 and slows down exception handling a tiny bit.
1187 If unsure, say N here.
1191 default X86_LEGACY_VM86
1194 bool "Enable support for 16-bit segments" if EXPERT
1196 depends on MODIFY_LDT_SYSCALL
1198 This option is required by programs like Wine to run 16-bit
1199 protected mode legacy code on x86 processors. Disabling
1200 this option saves about 300 bytes on i386, or around 6K text
1201 plus 16K runtime memory on x86-64,
1205 depends on X86_16BIT && X86_32
1209 depends on X86_16BIT && X86_64
1211 config X86_VSYSCALL_EMULATION
1212 bool "Enable vsyscall emulation" if EXPERT
1216 This enables emulation of the legacy vsyscall page. Disabling
1217 it is roughly equivalent to booting with vsyscall=none, except
1218 that it will also disable the helpful warning if a program
1219 tries to use a vsyscall. With this option set to N, offending
1220 programs will just segfault, citing addresses of the form
1223 This option is required by many programs built before 2013, and
1224 care should be used even with newer programs if set to N.
1226 Disabling this option saves about 7K of kernel size and
1227 possibly 4K of additional runtime pagetable memory.
1229 config X86_IOPL_IOPERM
1230 bool "IOPERM and IOPL Emulation"
1233 This enables the ioperm() and iopl() syscalls which are necessary
1234 for legacy applications.
1236 Legacy IOPL support is an overbroad mechanism which allows user
1237 space aside of accessing all 65536 I/O ports also to disable
1238 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1239 capabilities and permission from potentially active security
1242 The emulation restricts the functionality of the syscall to
1243 only allowing the full range I/O port access, but prevents the
1244 ability to disable interrupts from user space which would be
1245 granted if the hardware IOPL mechanism would be used.
1248 tristate "Toshiba Laptop support"
1251 This adds a driver to safely access the System Management Mode of
1252 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1253 not work on models with a Phoenix BIOS. The System Management Mode
1254 is used to set the BIOS and power saving options on Toshiba portables.
1256 For information on utilities to make use of this driver see the
1257 Toshiba Linux utilities web site at:
1258 <http://www.buzzard.org.uk/toshiba/>.
1260 Say Y if you intend to run this kernel on a Toshiba portable.
1264 tristate "Dell i8k legacy laptop support"
1266 select SENSORS_DELL_SMM
1268 This option enables legacy /proc/i8k userspace interface in hwmon
1269 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1270 temperature and allows controlling fan speeds of Dell laptops via
1271 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1272 it reports also power and hotkey status. For fan speed control is
1273 needed userspace package i8kutils.
1275 Say Y if you intend to run this kernel on old Dell laptops or want to
1276 use userspace package i8kutils.
1279 config X86_REBOOTFIXUPS
1280 bool "Enable X86 board specific fixups for reboot"
1283 This enables chipset and/or board specific fixups to be done
1284 in order to get reboot to work correctly. This is only needed on
1285 some combinations of hardware and BIOS. The symptom, for which
1286 this config is intended, is when reboot ends with a stalled/hung
1289 Currently, the only fixup is for the Geode machines using
1290 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1292 Say Y if you want to enable the fixup. Currently, it's safe to
1293 enable this option even if you don't need it.
1297 bool "CPU microcode loading support"
1299 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1302 If you say Y here, you will be able to update the microcode on
1303 Intel and AMD processors. The Intel support is for the IA32 family,
1304 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1305 AMD support is for families 0x10 and later. You will obviously need
1306 the actual microcode binary data itself which is not shipped with
1309 The preferred method to load microcode from a detached initrd is described
1310 in Documentation/x86/microcode.rst. For that you need to enable
1311 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1312 initrd for microcode blobs.
1314 In addition, you can build the microcode into the kernel. For that you
1315 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1318 config MICROCODE_INTEL
1319 bool "Intel microcode loading support"
1320 depends on MICROCODE
1324 This options enables microcode patch loading support for Intel
1327 For the current Intel microcode data package go to
1328 <https://downloadcenter.intel.com> and search for
1329 'Linux Processor Microcode Data File'.
1331 config MICROCODE_AMD
1332 bool "AMD microcode loading support"
1333 depends on MICROCODE
1336 If you select this option, microcode patch loading support for AMD
1337 processors will be enabled.
1339 config MICROCODE_OLD_INTERFACE
1340 bool "Ancient loading interface (DEPRECATED)"
1342 depends on MICROCODE
1344 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1345 which was used by userspace tools like iucode_tool and microcode.ctl.
1346 It is inadequate because it runs too late to be able to properly
1347 load microcode on a machine and it needs special tools. Instead, you
1348 should've switched to the early loading method with the initrd or
1349 builtin microcode by now: Documentation/x86/microcode.rst
1352 tristate "/dev/cpu/*/msr - Model-specific register support"
1354 This device gives privileged processes access to the x86
1355 Model-Specific Registers (MSRs). It is a character device with
1356 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1357 MSR accesses are directed to a specific CPU on multi-processor
1361 tristate "/dev/cpu/*/cpuid - CPU information support"
1363 This device gives processes access to the x86 CPUID instruction to
1364 be executed on a specific processor. It is a character device
1365 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1369 prompt "High Memory Support"
1376 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1377 However, the address space of 32-bit x86 processors is only 4
1378 Gigabytes large. That means that, if you have a large amount of
1379 physical memory, not all of it can be "permanently mapped" by the
1380 kernel. The physical memory that's not permanently mapped is called
1383 If you are compiling a kernel which will never run on a machine with
1384 more than 1 Gigabyte total physical RAM, answer "off" here (default
1385 choice and suitable for most users). This will result in a "3GB/1GB"
1386 split: 3GB are mapped so that each process sees a 3GB virtual memory
1387 space and the remaining part of the 4GB virtual memory space is used
1388 by the kernel to permanently map as much physical memory as
1391 If the machine has between 1 and 4 Gigabytes physical RAM, then
1394 If more than 4 Gigabytes is used then answer "64GB" here. This
1395 selection turns Intel PAE (Physical Address Extension) mode on.
1396 PAE implements 3-level paging on IA32 processors. PAE is fully
1397 supported by Linux, PAE mode is implemented on all recent Intel
1398 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1399 then the kernel will not boot on CPUs that don't support PAE!
1401 The actual amount of total physical memory will either be
1402 auto detected or can be forced by using a kernel command line option
1403 such as "mem=256M". (Try "man bootparam" or see the documentation of
1404 your boot loader (lilo or loadlin) about how to pass options to the
1405 kernel at boot time.)
1407 If unsure, say "off".
1412 Select this if you have a 32-bit processor and between 1 and 4
1413 gigabytes of physical RAM.
1417 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1420 Select this if you have a 32-bit processor and more than 4
1421 gigabytes of physical RAM.
1426 prompt "Memory split" if EXPERT
1430 Select the desired split between kernel and user memory.
1432 If the address range available to the kernel is less than the
1433 physical memory installed, the remaining memory will be available
1434 as "high memory". Accessing high memory is a little more costly
1435 than low memory, as it needs to be mapped into the kernel first.
1436 Note that increasing the kernel address space limits the range
1437 available to user programs, making the address space there
1438 tighter. Selecting anything other than the default 3G/1G split
1439 will also likely make your kernel incompatible with binary-only
1442 If you are not absolutely sure what you are doing, leave this
1446 bool "3G/1G user/kernel split"
1447 config VMSPLIT_3G_OPT
1449 bool "3G/1G user/kernel split (for full 1G low memory)"
1451 bool "2G/2G user/kernel split"
1452 config VMSPLIT_2G_OPT
1454 bool "2G/2G user/kernel split (for full 2G low memory)"
1456 bool "1G/3G user/kernel split"
1461 default 0xB0000000 if VMSPLIT_3G_OPT
1462 default 0x80000000 if VMSPLIT_2G
1463 default 0x78000000 if VMSPLIT_2G_OPT
1464 default 0x40000000 if VMSPLIT_1G
1470 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1473 bool "PAE (Physical Address Extension) Support"
1474 depends on X86_32 && !HIGHMEM4G
1475 select PHYS_ADDR_T_64BIT
1478 PAE is required for NX support, and furthermore enables
1479 larger swapspace support for non-overcommit purposes. It
1480 has the cost of more pagetable lookup overhead, and also
1481 consumes more pagetable space per process.
1484 bool "Enable 5-level page tables support"
1486 select DYNAMIC_MEMORY_LAYOUT
1487 select SPARSEMEM_VMEMMAP
1490 5-level paging enables access to larger address space:
1491 upto 128 PiB of virtual address space and 4 PiB of
1492 physical address space.
1494 It will be supported by future Intel CPUs.
1496 A kernel with the option enabled can be booted on machines that
1497 support 4- or 5-level paging.
1499 See Documentation/x86/x86_64/5level-paging.rst for more
1504 config X86_DIRECT_GBPAGES
1508 Certain kernel features effectively disable kernel
1509 linear 1 GB mappings (even if the CPU otherwise
1510 supports them), so don't confuse the user by printing
1511 that we have them enabled.
1513 config X86_CPA_STATISTICS
1514 bool "Enable statistic for Change Page Attribute"
1517 Expose statistics about the Change Page Attribute mechanism, which
1518 helps to determine the effectiveness of preserving large and huge
1519 page mappings when mapping protections are changed.
1521 config AMD_MEM_ENCRYPT
1522 bool "AMD Secure Memory Encryption (SME) support"
1523 depends on X86_64 && CPU_SUP_AMD
1524 select DYNAMIC_PHYSICAL_MASK
1525 select ARCH_USE_MEMREMAP_PROT
1526 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1528 Say yes to enable support for the encryption of system memory.
1529 This requires an AMD processor that supports Secure Memory
1532 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1533 bool "Activate AMD Secure Memory Encryption (SME) by default"
1535 depends on AMD_MEM_ENCRYPT
1537 Say yes to have system memory encrypted by default if running on
1538 an AMD processor that supports Secure Memory Encryption (SME).
1540 If set to Y, then the encryption of system memory can be
1541 deactivated with the mem_encrypt=off command line option.
1543 If set to N, then the encryption of system memory can be
1544 activated with the mem_encrypt=on command line option.
1546 # Common NUMA Features
1548 bool "NUMA Memory Allocation and Scheduler Support"
1550 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1551 default y if X86_BIGSMP
1553 Enable NUMA (Non-Uniform Memory Access) support.
1555 The kernel will try to allocate memory used by a CPU on the
1556 local memory controller of the CPU and add some more
1557 NUMA awareness to the kernel.
1559 For 64-bit this is recommended if the system is Intel Core i7
1560 (or later), AMD Opteron, or EM64T NUMA.
1562 For 32-bit this is only needed if you boot a 32-bit
1563 kernel on a 64-bit NUMA platform.
1565 Otherwise, you should say N.
1569 prompt "Old style AMD Opteron NUMA detection"
1570 depends on X86_64 && NUMA && PCI
1572 Enable AMD NUMA node topology detection. You should say Y here if
1573 you have a multi processor AMD system. This uses an old method to
1574 read the NUMA configuration directly from the builtin Northbridge
1575 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1576 which also takes priority if both are compiled in.
1578 config X86_64_ACPI_NUMA
1580 prompt "ACPI NUMA detection"
1581 depends on X86_64 && NUMA && ACPI && PCI
1584 Enable ACPI SRAT based node topology detection.
1586 # Some NUMA nodes have memory ranges that span
1587 # other nodes. Even though a pfn is valid and
1588 # between a node's start and end pfns, it may not
1589 # reside on that node. See memmap_init_zone()
1591 config NODES_SPAN_OTHER_NODES
1593 depends on X86_64_ACPI_NUMA
1596 bool "NUMA emulation"
1599 Enable NUMA emulation. A flat machine will be split
1600 into virtual nodes when booted with "numa=fake=N", where N is the
1601 number of nodes. This is only useful for debugging.
1604 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1606 default "10" if MAXSMP
1607 default "6" if X86_64
1609 depends on NEED_MULTIPLE_NODES
1611 Specify the maximum number of NUMA Nodes available on the target
1612 system. Increases memory reserved to accommodate various tables.
1614 config ARCH_HAVE_MEMORY_PRESENT
1616 depends on X86_32 && DISCONTIGMEM
1618 config ARCH_FLATMEM_ENABLE
1620 depends on X86_32 && !NUMA
1622 config ARCH_DISCONTIGMEM_ENABLE
1624 depends on NUMA && X86_32
1627 config ARCH_SPARSEMEM_ENABLE
1629 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1630 select SPARSEMEM_STATIC if X86_32
1631 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1633 config ARCH_SPARSEMEM_DEFAULT
1634 def_bool X86_64 || (NUMA && X86_32)
1636 config ARCH_SELECT_MEMORY_MODEL
1638 depends on ARCH_SPARSEMEM_ENABLE
1640 config ARCH_MEMORY_PROBE
1641 bool "Enable sysfs memory/probe interface"
1642 depends on X86_64 && MEMORY_HOTPLUG
1644 This option enables a sysfs memory/probe interface for testing.
1645 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1646 If you are unsure how to answer this question, answer N.
1648 config ARCH_PROC_KCORE_TEXT
1650 depends on X86_64 && PROC_KCORE
1652 config ILLEGAL_POINTER_VALUE
1655 default 0xdead000000000000 if X86_64
1657 config X86_PMEM_LEGACY_DEVICE
1660 config X86_PMEM_LEGACY
1661 tristate "Support non-standard NVDIMMs and ADR protected memory"
1662 depends on PHYS_ADDR_T_64BIT
1664 select X86_PMEM_LEGACY_DEVICE
1665 select NUMA_KEEP_MEMINFO if NUMA
1668 Treat memory marked using the non-standard e820 type of 12 as used
1669 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1670 The kernel will offer these regions to the 'pmem' driver so
1671 they can be used for persistent storage.
1676 bool "Allocate 3rd-level pagetables from highmem"
1679 The VM uses one page table entry for each page of physical memory.
1680 For systems with a lot of RAM, this can be wasteful of precious
1681 low memory. Setting this option will put user-space page table
1682 entries in high memory.
1684 config X86_CHECK_BIOS_CORRUPTION
1685 bool "Check for low memory corruption"
1687 Periodically check for memory corruption in low memory, which
1688 is suspected to be caused by BIOS. Even when enabled in the
1689 configuration, it is disabled at runtime. Enable it by
1690 setting "memory_corruption_check=1" on the kernel command
1691 line. By default it scans the low 64k of memory every 60
1692 seconds; see the memory_corruption_check_size and
1693 memory_corruption_check_period parameters in
1694 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1696 When enabled with the default parameters, this option has
1697 almost no overhead, as it reserves a relatively small amount
1698 of memory and scans it infrequently. It both detects corruption
1699 and prevents it from affecting the running system.
1701 It is, however, intended as a diagnostic tool; if repeatable
1702 BIOS-originated corruption always affects the same memory,
1703 you can use memmap= to prevent the kernel from using that
1706 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1707 bool "Set the default setting of memory_corruption_check"
1708 depends on X86_CHECK_BIOS_CORRUPTION
1711 Set whether the default state of memory_corruption_check is
1714 config X86_RESERVE_LOW
1715 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1719 Specify the amount of low memory to reserve for the BIOS.
1721 The first page contains BIOS data structures that the kernel
1722 must not use, so that page must always be reserved.
1724 By default we reserve the first 64K of physical RAM, as a
1725 number of BIOSes are known to corrupt that memory range
1726 during events such as suspend/resume or monitor cable
1727 insertion, so it must not be used by the kernel.
1729 You can set this to 4 if you are absolutely sure that you
1730 trust the BIOS to get all its memory reservations and usages
1731 right. If you know your BIOS have problems beyond the
1732 default 64K area, you can set this to 640 to avoid using the
1733 entire low memory range.
1735 If you have doubts about the BIOS (e.g. suspend/resume does
1736 not work or there's kernel crashes after certain hardware
1737 hotplug events) then you might want to enable
1738 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1739 typical corruption patterns.
1741 Leave this to the default value of 64 if you are unsure.
1743 config MATH_EMULATION
1745 depends on MODIFY_LDT_SYSCALL
1746 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1748 Linux can emulate a math coprocessor (used for floating point
1749 operations) if you don't have one. 486DX and Pentium processors have
1750 a math coprocessor built in, 486SX and 386 do not, unless you added
1751 a 487DX or 387, respectively. (The messages during boot time can
1752 give you some hints here ["man dmesg"].) Everyone needs either a
1753 coprocessor or this emulation.
1755 If you don't have a math coprocessor, you need to say Y here; if you
1756 say Y here even though you have a coprocessor, the coprocessor will
1757 be used nevertheless. (This behavior can be changed with the kernel
1758 command line option "no387", which comes handy if your coprocessor
1759 is broken. Try "man bootparam" or see the documentation of your boot
1760 loader (lilo or loadlin) about how to pass options to the kernel at
1761 boot time.) This means that it is a good idea to say Y here if you
1762 intend to use this kernel on different machines.
1764 More information about the internals of the Linux math coprocessor
1765 emulation can be found in <file:arch/x86/math-emu/README>.
1767 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1768 kernel, it won't hurt.
1772 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1774 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1775 the Memory Type Range Registers (MTRRs) may be used to control
1776 processor access to memory ranges. This is most useful if you have
1777 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1778 allows bus write transfers to be combined into a larger transfer
1779 before bursting over the PCI/AGP bus. This can increase performance
1780 of image write operations 2.5 times or more. Saying Y here creates a
1781 /proc/mtrr file which may be used to manipulate your processor's
1782 MTRRs. Typically the X server should use this.
1784 This code has a reasonably generic interface so that similar
1785 control registers on other processors can be easily supported
1788 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1789 Registers (ARRs) which provide a similar functionality to MTRRs. For
1790 these, the ARRs are used to emulate the MTRRs.
1791 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1792 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1793 write-combining. All of these processors are supported by this code
1794 and it makes sense to say Y here if you have one of them.
1796 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1797 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1798 can lead to all sorts of problems, so it's good to say Y here.
1800 You can safely say Y even if your machine doesn't have MTRRs, you'll
1801 just add about 9 KB to your kernel.
1803 See <file:Documentation/x86/mtrr.rst> for more information.
1805 config MTRR_SANITIZER
1807 prompt "MTRR cleanup support"
1810 Convert MTRR layout from continuous to discrete, so X drivers can
1811 add writeback entries.
1813 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1814 The largest mtrr entry size for a continuous block can be set with
1819 config MTRR_SANITIZER_ENABLE_DEFAULT
1820 int "MTRR cleanup enable value (0-1)"
1823 depends on MTRR_SANITIZER
1825 Enable mtrr cleanup default value
1827 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1828 int "MTRR cleanup spare reg num (0-7)"
1831 depends on MTRR_SANITIZER
1833 mtrr cleanup spare entries default, it can be changed via
1834 mtrr_spare_reg_nr=N on the kernel command line.
1838 prompt "x86 PAT support" if EXPERT
1841 Use PAT attributes to setup page level cache control.
1843 PATs are the modern equivalents of MTRRs and are much more
1844 flexible than MTRRs.
1846 Say N here if you see bootup problems (boot crash, boot hang,
1847 spontaneous reboots) or a non-working video driver.
1851 config ARCH_USES_PG_UNCACHED
1857 prompt "x86 architectural random number generator" if EXPERT
1859 Enable the x86 architectural RDRAND instruction
1860 (Intel Bull Mountain technology) to generate random numbers.
1861 If supported, this is a high bandwidth, cryptographically
1862 secure hardware random number generator.
1866 prompt "Supervisor Mode Access Prevention" if EXPERT
1868 Supervisor Mode Access Prevention (SMAP) is a security
1869 feature in newer Intel processors. There is a small
1870 performance cost if this enabled and turned on; there is
1871 also a small increase in the kernel size if this is enabled.
1877 prompt "User Mode Instruction Prevention" if EXPERT
1879 User Mode Instruction Prevention (UMIP) is a security feature in
1880 some x86 processors. If enabled, a general protection fault is
1881 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1882 executed in user mode. These instructions unnecessarily expose
1883 information about the hardware state.
1885 The vast majority of applications do not use these instructions.
1886 For the very few that do, software emulation is provided in
1887 specific cases in protected and virtual-8086 modes. Emulated
1890 config X86_INTEL_MEMORY_PROTECTION_KEYS
1891 prompt "Intel Memory Protection Keys"
1893 # Note: only available in 64-bit mode
1894 depends on CPU_SUP_INTEL && X86_64
1895 select ARCH_USES_HIGH_VMA_FLAGS
1896 select ARCH_HAS_PKEYS
1898 Memory Protection Keys provides a mechanism for enforcing
1899 page-based protections, but without requiring modification of the
1900 page tables when an application changes protection domains.
1902 For details, see Documentation/core-api/protection-keys.rst
1907 prompt "TSX enable mode"
1908 depends on CPU_SUP_INTEL
1909 default X86_INTEL_TSX_MODE_OFF
1911 Intel's TSX (Transactional Synchronization Extensions) feature
1912 allows to optimize locking protocols through lock elision which
1913 can lead to a noticeable performance boost.
1915 On the other hand it has been shown that TSX can be exploited
1916 to form side channel attacks (e.g. TAA) and chances are there
1917 will be more of those attacks discovered in the future.
1919 Therefore TSX is not enabled by default (aka tsx=off). An admin
1920 might override this decision by tsx=on the command line parameter.
1921 Even with TSX enabled, the kernel will attempt to enable the best
1922 possible TAA mitigation setting depending on the microcode available
1923 for the particular machine.
1925 This option allows to set the default tsx mode between tsx=on, =off
1926 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1929 Say off if not sure, auto if TSX is in use but it should be used on safe
1930 platforms or on if TSX is in use and the security aspect of tsx is not
1933 config X86_INTEL_TSX_MODE_OFF
1936 TSX is disabled if possible - equals to tsx=off command line parameter.
1938 config X86_INTEL_TSX_MODE_ON
1941 TSX is always enabled on TSX capable HW - equals the tsx=on command
1944 config X86_INTEL_TSX_MODE_AUTO
1947 TSX is enabled on TSX capable HW that is believed to be safe against
1948 side channel attacks- equals the tsx=auto command line parameter.
1952 bool "EFI runtime service support"
1955 select EFI_RUNTIME_WRAPPERS
1957 This enables the kernel to use EFI runtime services that are
1958 available (such as the EFI variable services).
1960 This option is only useful on systems that have EFI firmware.
1961 In addition, you should use the latest ELILO loader available
1962 at <http://elilo.sourceforge.net> in order to take advantage
1963 of EFI runtime services. However, even with this option, the
1964 resultant kernel should continue to boot on existing non-EFI
1968 bool "EFI stub support"
1969 depends on EFI && !X86_USE_3DNOW
1970 depends on $(cc-option,-mabi=ms) || X86_32
1973 This kernel feature allows a bzImage to be loaded directly
1974 by EFI firmware without the use of a bootloader.
1976 See Documentation/admin-guide/efi-stub.rst for more information.
1979 bool "EFI mixed-mode support"
1980 depends on EFI_STUB && X86_64
1982 Enabling this feature allows a 64-bit kernel to be booted
1983 on a 32-bit firmware, provided that your CPU supports 64-bit
1986 Note that it is not possible to boot a mixed-mode enabled
1987 kernel via the EFI boot stub - a bootloader that supports
1988 the EFI handover protocol must be used.
1994 prompt "Enable seccomp to safely compute untrusted bytecode"
1996 This kernel feature is useful for number crunching applications
1997 that may need to compute untrusted bytecode during their
1998 execution. By using pipes or other transports made available to
1999 the process as file descriptors supporting the read/write
2000 syscalls, it's possible to isolate those applications in
2001 their own address space using seccomp. Once seccomp is
2002 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
2003 and the task is only allowed to execute a few safe syscalls
2004 defined by each seccomp mode.
2006 If unsure, say Y. Only embedded should say N here.
2008 source "kernel/Kconfig.hz"
2011 bool "kexec system call"
2014 kexec is a system call that implements the ability to shutdown your
2015 current kernel, and to start another kernel. It is like a reboot
2016 but it is independent of the system firmware. And like a reboot
2017 you can start any kernel with it, not just Linux.
2019 The name comes from the similarity to the exec system call.
2021 It is an ongoing process to be certain the hardware in a machine
2022 is properly shutdown, so do not be surprised if this code does not
2023 initially work for you. As of this writing the exact hardware
2024 interface is strongly in flux, so no good recommendation can be
2028 bool "kexec file based system call"
2033 depends on CRYPTO_SHA256=y
2035 This is new version of kexec system call. This system call is
2036 file based and takes file descriptors as system call argument
2037 for kernel and initramfs as opposed to list of segments as
2038 accepted by previous system call.
2040 config ARCH_HAS_KEXEC_PURGATORY
2044 bool "Verify kernel signature during kexec_file_load() syscall"
2045 depends on KEXEC_FILE
2048 This option makes the kexec_file_load() syscall check for a valid
2049 signature of the kernel image. The image can still be loaded without
2050 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2051 there's a signature that we can check, then it must be valid.
2053 In addition to this option, you need to enable signature
2054 verification for the corresponding kernel image type being
2055 loaded in order for this to work.
2057 config KEXEC_SIG_FORCE
2058 bool "Require a valid signature in kexec_file_load() syscall"
2059 depends on KEXEC_SIG
2061 This option makes kernel signature verification mandatory for
2062 the kexec_file_load() syscall.
2064 config KEXEC_BZIMAGE_VERIFY_SIG
2065 bool "Enable bzImage signature verification support"
2066 depends on KEXEC_SIG
2067 depends on SIGNED_PE_FILE_VERIFICATION
2068 select SYSTEM_TRUSTED_KEYRING
2070 Enable bzImage signature verification support.
2073 bool "kernel crash dumps"
2074 depends on X86_64 || (X86_32 && HIGHMEM)
2076 Generate crash dump after being started by kexec.
2077 This should be normally only set in special crash dump kernels
2078 which are loaded in the main kernel with kexec-tools into
2079 a specially reserved region and then later executed after
2080 a crash by kdump/kexec. The crash dump kernel must be compiled
2081 to a memory address not used by the main kernel or BIOS using
2082 PHYSICAL_START, or it must be built as a relocatable image
2083 (CONFIG_RELOCATABLE=y).
2084 For more details see Documentation/admin-guide/kdump/kdump.rst
2088 depends on KEXEC && HIBERNATION
2090 Jump between original kernel and kexeced kernel and invoke
2091 code in physical address mode via KEXEC
2093 config PHYSICAL_START
2094 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2097 This gives the physical address where the kernel is loaded.
2099 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2100 bzImage will decompress itself to above physical address and
2101 run from there. Otherwise, bzImage will run from the address where
2102 it has been loaded by the boot loader and will ignore above physical
2105 In normal kdump cases one does not have to set/change this option
2106 as now bzImage can be compiled as a completely relocatable image
2107 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2108 address. This option is mainly useful for the folks who don't want
2109 to use a bzImage for capturing the crash dump and want to use a
2110 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2111 to be specifically compiled to run from a specific memory area
2112 (normally a reserved region) and this option comes handy.
2114 So if you are using bzImage for capturing the crash dump,
2115 leave the value here unchanged to 0x1000000 and set
2116 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2117 for capturing the crash dump change this value to start of
2118 the reserved region. In other words, it can be set based on
2119 the "X" value as specified in the "crashkernel=YM@XM"
2120 command line boot parameter passed to the panic-ed
2121 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2122 for more details about crash dumps.
2124 Usage of bzImage for capturing the crash dump is recommended as
2125 one does not have to build two kernels. Same kernel can be used
2126 as production kernel and capture kernel. Above option should have
2127 gone away after relocatable bzImage support is introduced. But it
2128 is present because there are users out there who continue to use
2129 vmlinux for dump capture. This option should go away down the
2132 Don't change this unless you know what you are doing.
2135 bool "Build a relocatable kernel"
2138 This builds a kernel image that retains relocation information
2139 so it can be loaded someplace besides the default 1MB.
2140 The relocations tend to make the kernel binary about 10% larger,
2141 but are discarded at runtime.
2143 One use is for the kexec on panic case where the recovery kernel
2144 must live at a different physical address than the primary
2147 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2148 it has been loaded at and the compile time physical address
2149 (CONFIG_PHYSICAL_START) is used as the minimum location.
2151 config RANDOMIZE_BASE
2152 bool "Randomize the address of the kernel image (KASLR)"
2153 depends on RELOCATABLE
2156 In support of Kernel Address Space Layout Randomization (KASLR),
2157 this randomizes the physical address at which the kernel image
2158 is decompressed and the virtual address where the kernel
2159 image is mapped, as a security feature that deters exploit
2160 attempts relying on knowledge of the location of kernel
2163 On 64-bit, the kernel physical and virtual addresses are
2164 randomized separately. The physical address will be anywhere
2165 between 16MB and the top of physical memory (up to 64TB). The
2166 virtual address will be randomized from 16MB up to 1GB (9 bits
2167 of entropy). Note that this also reduces the memory space
2168 available to kernel modules from 1.5GB to 1GB.
2170 On 32-bit, the kernel physical and virtual addresses are
2171 randomized together. They will be randomized from 16MB up to
2172 512MB (8 bits of entropy).
2174 Entropy is generated using the RDRAND instruction if it is
2175 supported. If RDTSC is supported, its value is mixed into
2176 the entropy pool as well. If neither RDRAND nor RDTSC are
2177 supported, then entropy is read from the i8254 timer. The
2178 usable entropy is limited by the kernel being built using
2179 2GB addressing, and that PHYSICAL_ALIGN must be at a
2180 minimum of 2MB. As a result, only 10 bits of entropy are
2181 theoretically possible, but the implementations are further
2182 limited due to memory layouts.
2186 # Relocation on x86 needs some additional build support
2187 config X86_NEED_RELOCS
2189 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2191 config PHYSICAL_ALIGN
2192 hex "Alignment value to which kernel should be aligned"
2194 range 0x2000 0x1000000 if X86_32
2195 range 0x200000 0x1000000 if X86_64
2197 This value puts the alignment restrictions on physical address
2198 where kernel is loaded and run from. Kernel is compiled for an
2199 address which meets above alignment restriction.
2201 If bootloader loads the kernel at a non-aligned address and
2202 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2203 address aligned to above value and run from there.
2205 If bootloader loads the kernel at a non-aligned address and
2206 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2207 load address and decompress itself to the address it has been
2208 compiled for and run from there. The address for which kernel is
2209 compiled already meets above alignment restrictions. Hence the
2210 end result is that kernel runs from a physical address meeting
2211 above alignment restrictions.
2213 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2214 this value must be a multiple of 0x200000.
2216 Don't change this unless you know what you are doing.
2218 config DYNAMIC_MEMORY_LAYOUT
2221 This option makes base addresses of vmalloc and vmemmap as well as
2222 __PAGE_OFFSET movable during boot.
2224 config RANDOMIZE_MEMORY
2225 bool "Randomize the kernel memory sections"
2227 depends on RANDOMIZE_BASE
2228 select DYNAMIC_MEMORY_LAYOUT
2229 default RANDOMIZE_BASE
2231 Randomizes the base virtual address of kernel memory sections
2232 (physical memory mapping, vmalloc & vmemmap). This security feature
2233 makes exploits relying on predictable memory locations less reliable.
2235 The order of allocations remains unchanged. Entropy is generated in
2236 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2237 configuration have in average 30,000 different possible virtual
2238 addresses for each memory section.
2242 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2243 hex "Physical memory mapping padding" if EXPERT
2244 depends on RANDOMIZE_MEMORY
2245 default "0xa" if MEMORY_HOTPLUG
2247 range 0x1 0x40 if MEMORY_HOTPLUG
2250 Define the padding in terabytes added to the existing physical
2251 memory size during kernel memory randomization. It is useful
2252 for memory hotplug support but reduces the entropy available for
2253 address randomization.
2255 If unsure, leave at the default value.
2261 config BOOTPARAM_HOTPLUG_CPU0
2262 bool "Set default setting of cpu0_hotpluggable"
2263 depends on HOTPLUG_CPU
2265 Set whether default state of cpu0_hotpluggable is on or off.
2267 Say Y here to enable CPU0 hotplug by default. If this switch
2268 is turned on, there is no need to give cpu0_hotplug kernel
2269 parameter and the CPU0 hotplug feature is enabled by default.
2271 Please note: there are two known CPU0 dependencies if you want
2272 to enable the CPU0 hotplug feature either by this switch or by
2273 cpu0_hotplug kernel parameter.
2275 First, resume from hibernate or suspend always starts from CPU0.
2276 So hibernate and suspend are prevented if CPU0 is offline.
2278 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2279 offline if any interrupt can not migrate out of CPU0. There may
2280 be other CPU0 dependencies.
2282 Please make sure the dependencies are under your control before
2283 you enable this feature.
2285 Say N if you don't want to enable CPU0 hotplug feature by default.
2286 You still can enable the CPU0 hotplug feature at boot by kernel
2287 parameter cpu0_hotplug.
2289 config DEBUG_HOTPLUG_CPU0
2291 prompt "Debug CPU0 hotplug"
2292 depends on HOTPLUG_CPU
2294 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2295 soon as possible and boots up userspace with CPU0 offlined. User
2296 can online CPU0 back after boot time.
2298 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2299 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2300 compilation or giving cpu0_hotplug kernel parameter at boot.
2306 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2307 depends on COMPAT_32
2309 Certain buggy versions of glibc will crash if they are
2310 presented with a 32-bit vDSO that is not mapped at the address
2311 indicated in its segment table.
2313 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2314 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2315 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2316 the only released version with the bug, but OpenSUSE 9
2317 contains a buggy "glibc 2.3.2".
2319 The symptom of the bug is that everything crashes on startup, saying:
2320 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2322 Saying Y here changes the default value of the vdso32 boot
2323 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2324 This works around the glibc bug but hurts performance.
2326 If unsure, say N: if you are compiling your own kernel, you
2327 are unlikely to be using a buggy version of glibc.
2330 prompt "vsyscall table for legacy applications"
2332 default LEGACY_VSYSCALL_XONLY
2334 Legacy user code that does not know how to find the vDSO expects
2335 to be able to issue three syscalls by calling fixed addresses in
2336 kernel space. Since this location is not randomized with ASLR,
2337 it can be used to assist security vulnerability exploitation.
2339 This setting can be changed at boot time via the kernel command
2340 line parameter vsyscall=[emulate|xonly|none].
2342 On a system with recent enough glibc (2.14 or newer) and no
2343 static binaries, you can say None without a performance penalty
2344 to improve security.
2346 If unsure, select "Emulate execution only".
2348 config LEGACY_VSYSCALL_EMULATE
2349 bool "Full emulation"
2351 The kernel traps and emulates calls into the fixed vsyscall
2352 address mapping. This makes the mapping non-executable, but
2353 it still contains readable known contents, which could be
2354 used in certain rare security vulnerability exploits. This
2355 configuration is recommended when using legacy userspace
2356 that still uses vsyscalls along with legacy binary
2357 instrumentation tools that require code to be readable.
2359 An example of this type of legacy userspace is running
2360 Pin on an old binary that still uses vsyscalls.
2362 config LEGACY_VSYSCALL_XONLY
2363 bool "Emulate execution only"
2365 The kernel traps and emulates calls into the fixed vsyscall
2366 address mapping and does not allow reads. This
2367 configuration is recommended when userspace might use the
2368 legacy vsyscall area but support for legacy binary
2369 instrumentation of legacy code is not needed. It mitigates
2370 certain uses of the vsyscall area as an ASLR-bypassing
2373 config LEGACY_VSYSCALL_NONE
2376 There will be no vsyscall mapping at all. This will
2377 eliminate any risk of ASLR bypass due to the vsyscall
2378 fixed address mapping. Attempts to use the vsyscalls
2379 will be reported to dmesg, so that either old or
2380 malicious userspace programs can be identified.
2385 bool "Built-in kernel command line"
2387 Allow for specifying boot arguments to the kernel at
2388 build time. On some systems (e.g. embedded ones), it is
2389 necessary or convenient to provide some or all of the
2390 kernel boot arguments with the kernel itself (that is,
2391 to not rely on the boot loader to provide them.)
2393 To compile command line arguments into the kernel,
2394 set this option to 'Y', then fill in the
2395 boot arguments in CONFIG_CMDLINE.
2397 Systems with fully functional boot loaders (i.e. non-embedded)
2398 should leave this option set to 'N'.
2401 string "Built-in kernel command string"
2402 depends on CMDLINE_BOOL
2405 Enter arguments here that should be compiled into the kernel
2406 image and used at boot time. If the boot loader provides a
2407 command line at boot time, it is appended to this string to
2408 form the full kernel command line, when the system boots.
2410 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2411 change this behavior.
2413 In most cases, the command line (whether built-in or provided
2414 by the boot loader) should specify the device for the root
2417 config CMDLINE_OVERRIDE
2418 bool "Built-in command line overrides boot loader arguments"
2419 depends on CMDLINE_BOOL && CMDLINE != ""
2421 Set this option to 'Y' to have the kernel ignore the boot loader
2422 command line, and use ONLY the built-in command line.
2424 This is used to work around broken boot loaders. This should
2425 be set to 'N' under normal conditions.
2427 config MODIFY_LDT_SYSCALL
2428 bool "Enable the LDT (local descriptor table)" if EXPERT
2431 Linux can allow user programs to install a per-process x86
2432 Local Descriptor Table (LDT) using the modify_ldt(2) system
2433 call. This is required to run 16-bit or segmented code such as
2434 DOSEMU or some Wine programs. It is also used by some very old
2435 threading libraries.
2437 Enabling this feature adds a small amount of overhead to
2438 context switches and increases the low-level kernel attack
2439 surface. Disabling it removes the modify_ldt(2) system call.
2441 Saying 'N' here may make sense for embedded or server kernels.
2443 source "kernel/livepatch/Kconfig"
2447 config ARCH_HAS_ADD_PAGES
2449 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2451 config ARCH_ENABLE_MEMORY_HOTPLUG
2453 depends on X86_64 || (X86_32 && HIGHMEM)
2455 config ARCH_ENABLE_MEMORY_HOTREMOVE
2457 depends on MEMORY_HOTPLUG
2459 config USE_PERCPU_NUMA_NODE_ID
2463 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2465 depends on X86_64 || X86_PAE
2467 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2469 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2471 config ARCH_ENABLE_THP_MIGRATION
2473 depends on X86_64 && TRANSPARENT_HUGEPAGE
2475 menu "Power management and ACPI options"
2477 config ARCH_HIBERNATION_HEADER
2479 depends on HIBERNATION
2481 source "kernel/power/Kconfig"
2483 source "drivers/acpi/Kconfig"
2485 source "drivers/sfi/Kconfig"
2492 tristate "APM (Advanced Power Management) BIOS support"
2493 depends on X86_32 && PM_SLEEP
2495 APM is a BIOS specification for saving power using several different
2496 techniques. This is mostly useful for battery powered laptops with
2497 APM compliant BIOSes. If you say Y here, the system time will be
2498 reset after a RESUME operation, the /proc/apm device will provide
2499 battery status information, and user-space programs will receive
2500 notification of APM "events" (e.g. battery status change).
2502 If you select "Y" here, you can disable actual use of the APM
2503 BIOS by passing the "apm=off" option to the kernel at boot time.
2505 Note that the APM support is almost completely disabled for
2506 machines with more than one CPU.
2508 In order to use APM, you will need supporting software. For location
2509 and more information, read <file:Documentation/power/apm-acpi.rst>
2510 and the Battery Powered Linux mini-HOWTO, available from
2511 <http://www.tldp.org/docs.html#howto>.
2513 This driver does not spin down disk drives (see the hdparm(8)
2514 manpage ("man 8 hdparm") for that), and it doesn't turn off
2515 VESA-compliant "green" monitors.
2517 This driver does not support the TI 4000M TravelMate and the ACER
2518 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2519 desktop machines also don't have compliant BIOSes, and this driver
2520 may cause those machines to panic during the boot phase.
2522 Generally, if you don't have a battery in your machine, there isn't
2523 much point in using this driver and you should say N. If you get
2524 random kernel OOPSes or reboots that don't seem to be related to
2525 anything, try disabling/enabling this option (or disabling/enabling
2528 Some other things you should try when experiencing seemingly random,
2531 1) make sure that you have enough swap space and that it is
2533 2) pass the "no-hlt" option to the kernel
2534 3) switch on floating point emulation in the kernel and pass
2535 the "no387" option to the kernel
2536 4) pass the "floppy=nodma" option to the kernel
2537 5) pass the "mem=4M" option to the kernel (thereby disabling
2538 all but the first 4 MB of RAM)
2539 6) make sure that the CPU is not over clocked.
2540 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2541 8) disable the cache from your BIOS settings
2542 9) install a fan for the video card or exchange video RAM
2543 10) install a better fan for the CPU
2544 11) exchange RAM chips
2545 12) exchange the motherboard.
2547 To compile this driver as a module, choose M here: the
2548 module will be called apm.
2552 config APM_IGNORE_USER_SUSPEND
2553 bool "Ignore USER SUSPEND"
2555 This option will ignore USER SUSPEND requests. On machines with a
2556 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2557 series notebooks, it is necessary to say Y because of a BIOS bug.
2559 config APM_DO_ENABLE
2560 bool "Enable PM at boot time"
2562 Enable APM features at boot time. From page 36 of the APM BIOS
2563 specification: "When disabled, the APM BIOS does not automatically
2564 power manage devices, enter the Standby State, enter the Suspend
2565 State, or take power saving steps in response to CPU Idle calls."
2566 This driver will make CPU Idle calls when Linux is idle (unless this
2567 feature is turned off -- see "Do CPU IDLE calls", below). This
2568 should always save battery power, but more complicated APM features
2569 will be dependent on your BIOS implementation. You may need to turn
2570 this option off if your computer hangs at boot time when using APM
2571 support, or if it beeps continuously instead of suspending. Turn
2572 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2573 T400CDT. This is off by default since most machines do fine without
2578 bool "Make CPU Idle calls when idle"
2580 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2581 On some machines, this can activate improved power savings, such as
2582 a slowed CPU clock rate, when the machine is idle. These idle calls
2583 are made after the idle loop has run for some length of time (e.g.,
2584 333 mS). On some machines, this will cause a hang at boot time or
2585 whenever the CPU becomes idle. (On machines with more than one CPU,
2586 this option does nothing.)
2588 config APM_DISPLAY_BLANK
2589 bool "Enable console blanking using APM"
2591 Enable console blanking using the APM. Some laptops can use this to
2592 turn off the LCD backlight when the screen blanker of the Linux
2593 virtual console blanks the screen. Note that this is only used by
2594 the virtual console screen blanker, and won't turn off the backlight
2595 when using the X Window system. This also doesn't have anything to
2596 do with your VESA-compliant power-saving monitor. Further, this
2597 option doesn't work for all laptops -- it might not turn off your
2598 backlight at all, or it might print a lot of errors to the console,
2599 especially if you are using gpm.
2601 config APM_ALLOW_INTS
2602 bool "Allow interrupts during APM BIOS calls"
2604 Normally we disable external interrupts while we are making calls to
2605 the APM BIOS as a measure to lessen the effects of a badly behaving
2606 BIOS implementation. The BIOS should reenable interrupts if it
2607 needs to. Unfortunately, some BIOSes do not -- especially those in
2608 many of the newer IBM Thinkpads. If you experience hangs when you
2609 suspend, try setting this to Y. Otherwise, say N.
2613 source "drivers/cpufreq/Kconfig"
2615 source "drivers/cpuidle/Kconfig"
2617 source "drivers/idle/Kconfig"
2622 menu "Bus options (PCI etc.)"
2625 prompt "PCI access mode"
2626 depends on X86_32 && PCI
2629 On PCI systems, the BIOS can be used to detect the PCI devices and
2630 determine their configuration. However, some old PCI motherboards
2631 have BIOS bugs and may crash if this is done. Also, some embedded
2632 PCI-based systems don't have any BIOS at all. Linux can also try to
2633 detect the PCI hardware directly without using the BIOS.
2635 With this option, you can specify how Linux should detect the
2636 PCI devices. If you choose "BIOS", the BIOS will be used,
2637 if you choose "Direct", the BIOS won't be used, and if you
2638 choose "MMConfig", then PCI Express MMCONFIG will be used.
2639 If you choose "Any", the kernel will try MMCONFIG, then the
2640 direct access method and falls back to the BIOS if that doesn't
2641 work. If unsure, go with the default, which is "Any".
2646 config PCI_GOMMCONFIG
2663 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2665 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2668 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2671 bool "Support mmconfig PCI config space access" if X86_64
2673 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2674 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2678 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2682 depends on PCI && XEN
2685 config MMCONF_FAM10H
2687 depends on X86_64 && PCI_MMCONFIG && ACPI
2689 config PCI_CNB20LE_QUIRK
2690 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2693 Read the PCI windows out of the CNB20LE host bridge. This allows
2694 PCI hotplug to work on systems with the CNB20LE chipset which do
2697 There's no public spec for this chipset, and this functionality
2698 is known to be incomplete.
2700 You should say N unless you know you need this.
2703 bool "ISA bus support on modern systems" if EXPERT
2705 Expose ISA bus device drivers and options available for selection and
2706 configuration. Enable this option if your target machine has an ISA
2707 bus. ISA is an older system, displaced by PCI and newer bus
2708 architectures -- if your target machine is modern, it probably does
2709 not have an ISA bus.
2713 # x86_64 have no ISA slots, but can have ISA-style DMA.
2715 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2718 Enables ISA-style DMA support for devices requiring such controllers.
2726 Find out whether you have ISA slots on your motherboard. ISA is the
2727 name of a bus system, i.e. the way the CPU talks to the other stuff
2728 inside your box. Other bus systems are PCI, EISA, MicroChannel
2729 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2730 newer boards don't support it. If you have ISA, say Y, otherwise N.
2733 tristate "NatSemi SCx200 support"
2735 This provides basic support for National Semiconductor's
2736 (now AMD's) Geode processors. The driver probes for the
2737 PCI-IDs of several on-chip devices, so its a good dependency
2738 for other scx200_* drivers.
2740 If compiled as a module, the driver is named scx200.
2742 config SCx200HR_TIMER
2743 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2747 This driver provides a clocksource built upon the on-chip
2748 27MHz high-resolution timer. Its also a workaround for
2749 NSC Geode SC-1100's buggy TSC, which loses time when the
2750 processor goes idle (as is done by the scheduler). The
2751 other workaround is idle=poll boot option.
2754 bool "One Laptop Per Child support"
2762 Add support for detecting the unique features of the OLPC
2766 bool "OLPC XO-1 Power Management"
2767 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2769 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2772 bool "OLPC XO-1 Real Time Clock"
2773 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2775 Add support for the XO-1 real time clock, which can be used as a
2776 programmable wakeup source.
2779 bool "OLPC XO-1 SCI extras"
2780 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2784 Add support for SCI-based features of the OLPC XO-1 laptop:
2785 - EC-driven system wakeups
2789 - AC adapter status updates
2790 - Battery status updates
2792 config OLPC_XO15_SCI
2793 bool "OLPC XO-1.5 SCI extras"
2794 depends on OLPC && ACPI
2797 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2798 - EC-driven system wakeups
2799 - AC adapter status updates
2800 - Battery status updates
2803 bool "PCEngines ALIX System Support (LED setup)"
2806 This option enables system support for the PCEngines ALIX.
2807 At present this just sets up LEDs for GPIO control on
2808 ALIX2/3/6 boards. However, other system specific setup should
2811 Note: You must still enable the drivers for GPIO and LED support
2812 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2814 Note: You have to set alix.force=1 for boards with Award BIOS.
2817 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2820 This option enables system support for the Soekris Engineering net5501.
2823 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2827 This option enables system support for the Traverse Technologies GEOS.
2830 bool "Technologic Systems TS-5500 platform support"
2832 select CHECK_SIGNATURE
2836 This option enables system support for the Technologic Systems TS-5500.
2842 depends on CPU_SUP_AMD && PCI
2845 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2847 Firmwares often provide initial graphics framebuffers so the BIOS,
2848 bootloader or kernel can show basic video-output during boot for
2849 user-guidance and debugging. Historically, x86 used the VESA BIOS
2850 Extensions and EFI-framebuffers for this, which are mostly limited
2852 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2853 framebuffers so the new generic system-framebuffer drivers can be
2854 used on x86. If the framebuffer is not compatible with the generic
2855 modes, it is advertised as fallback platform framebuffer so legacy
2856 drivers like efifb, vesafb and uvesafb can pick it up.
2857 If this option is not selected, all system framebuffers are always
2858 marked as fallback platform framebuffers as usual.
2860 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2861 not be able to pick up generic system framebuffers if this option
2862 is selected. You are highly encouraged to enable simplefb as
2863 replacement if you select this option. simplefb can correctly deal
2864 with generic system framebuffers. But you should still keep vesafb
2865 and others enabled as fallback if a system framebuffer is
2866 incompatible with simplefb.
2873 menu "Binary Emulations"
2875 config IA32_EMULATION
2876 bool "IA32 Emulation"
2878 select ARCH_WANT_OLD_COMPAT_IPC
2880 select COMPAT_BINFMT_ELF
2881 select COMPAT_OLD_SIGACTION
2883 Include code to run legacy 32-bit programs under a
2884 64-bit kernel. You should likely turn this on, unless you're
2885 100% sure that you don't have any 32-bit programs left.
2888 tristate "IA32 a.out support"
2889 depends on IA32_EMULATION
2892 Support old a.out binaries in the 32bit emulation.
2895 bool "x32 ABI for 64-bit mode"
2898 Include code to run binaries for the x32 native 32-bit ABI
2899 for 64-bit processors. An x32 process gets access to the
2900 full 64-bit register file and wide data path while leaving
2901 pointers at 32 bits for smaller memory footprint.
2903 You will need a recent binutils (2.22 or later) with
2904 elf32_x86_64 support enabled to compile a kernel with this
2909 depends on IA32_EMULATION || X86_32
2911 select OLD_SIGSUSPEND3
2915 depends on IA32_EMULATION || X86_X32
2918 config COMPAT_FOR_U64_ALIGNMENT
2921 config SYSVIPC_COMPAT
2929 config HAVE_ATOMIC_IOMAP
2933 source "drivers/firmware/Kconfig"
2935 source "arch/x86/kvm/Kconfig"
2937 source "arch/x86/Kconfig.assembler"