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 GENERIC_VDSO_32
18 select HAVE_DEBUG_STACKOVERFLOW
20 select MODULES_USE_ELF_REL
22 select ARCH_SPLIT_ARG64
27 # Options that are inherently 64-bit kernel only:
28 select ARCH_HAS_GIGANTIC_PAGE
29 select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
30 select ARCH_USE_CMPXCHG_LOCKREF
31 select HAVE_ARCH_SOFT_DIRTY
32 select MODULES_USE_ELF_RELA
33 select NEED_DMA_MAP_STATE
35 select ARCH_HAS_ELFCORE_COMPAT
37 config FORCE_DYNAMIC_FTRACE
40 depends on FUNCTION_TRACER
43 We keep the static function tracing (!DYNAMIC_FTRACE) around
44 in order to test the non static function tracing in the
45 generic code, as other architectures still use it. But we
46 only need to keep it around for x86_64. No need to keep it
47 for x86_32. For x86_32, force DYNAMIC_FTRACE.
51 # ( Note that options that are marked 'if X86_64' could in principle be
52 # ported to 32-bit as well. )
57 # Note: keep this list sorted alphabetically
59 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
60 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
61 select ARCH_32BIT_OFF_T if X86_32
62 select ARCH_CLOCKSOURCE_INIT
63 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
64 select ARCH_HAS_DEBUG_VIRTUAL
65 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
66 select ARCH_HAS_DEVMEM_IS_ALLOWED
67 select ARCH_HAS_EARLY_DEBUG if KGDB
68 select ARCH_HAS_ELF_RANDOMIZE
69 select ARCH_HAS_FAST_MULTIPLIER
70 select ARCH_HAS_FILTER_PGPROT
71 select ARCH_HAS_FORTIFY_SOURCE
72 select ARCH_HAS_GCOV_PROFILE_ALL
73 select ARCH_HAS_KCOV if X86_64 && STACK_VALIDATION
74 select ARCH_HAS_MEM_ENCRYPT
75 select ARCH_HAS_MEMBARRIER_SYNC_CORE
76 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
77 select ARCH_HAS_PMEM_API if X86_64
78 select ARCH_HAS_PTE_DEVMAP if X86_64
79 select ARCH_HAS_PTE_SPECIAL
80 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
81 select ARCH_HAS_COPY_MC if X86_64
82 select ARCH_HAS_SET_MEMORY
83 select ARCH_HAS_SET_DIRECT_MAP
84 select ARCH_HAS_STRICT_KERNEL_RWX
85 select ARCH_HAS_STRICT_MODULE_RWX
86 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
87 select ARCH_HAS_SYSCALL_WRAPPER
88 select ARCH_HAS_UBSAN_SANITIZE_ALL
89 select ARCH_HAS_DEBUG_WX
90 select ARCH_HAVE_NMI_SAFE_CMPXCHG
91 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
92 select ARCH_MIGHT_HAVE_PC_PARPORT
93 select ARCH_MIGHT_HAVE_PC_SERIO
95 select ARCH_SUPPORTS_ACPI
96 select ARCH_SUPPORTS_ATOMIC_RMW
97 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
98 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
99 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
100 select ARCH_SUPPORTS_LTO_CLANG if X86_64
101 select ARCH_SUPPORTS_LTO_CLANG_THIN if X86_64
102 select ARCH_USE_BUILTIN_BSWAP
103 select ARCH_USE_MEMTEST
104 select ARCH_USE_QUEUED_RWLOCKS
105 select ARCH_USE_QUEUED_SPINLOCKS
106 select ARCH_USE_SYM_ANNOTATIONS
107 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
108 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
109 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
110 select ARCH_WANT_HUGE_PMD_SHARE
111 select ARCH_WANT_LD_ORPHAN_WARN
112 select ARCH_WANTS_THP_SWAP if X86_64
113 select BUILDTIME_TABLE_SORT
115 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
116 select CLOCKSOURCE_WATCHDOG
117 select DCACHE_WORD_ACCESS
118 select EDAC_ATOMIC_SCRUB
120 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
121 select GENERIC_CLOCKEVENTS_MIN_ADJUST
122 select GENERIC_CMOS_UPDATE
123 select GENERIC_CPU_AUTOPROBE
124 select GENERIC_CPU_VULNERABILITIES
125 select GENERIC_EARLY_IOREMAP
127 select GENERIC_FIND_FIRST_BIT
129 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
130 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
131 select GENERIC_IRQ_MIGRATION if SMP
132 select GENERIC_IRQ_PROBE
133 select GENERIC_IRQ_RESERVATION_MODE
134 select GENERIC_IRQ_SHOW
135 select GENERIC_PENDING_IRQ if SMP
136 select GENERIC_PTDUMP
137 select GENERIC_SMP_IDLE_THREAD
138 select GENERIC_STRNCPY_FROM_USER
139 select GENERIC_STRNLEN_USER
140 select GENERIC_TIME_VSYSCALL
141 select GENERIC_GETTIMEOFDAY
142 select GENERIC_VDSO_TIME_NS
143 select GUP_GET_PTE_LOW_HIGH if X86_PAE
144 select HARDIRQS_SW_RESEND
145 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
146 select HAVE_ACPI_APEI if ACPI
147 select HAVE_ACPI_APEI_NMI if ACPI
148 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
149 select HAVE_ARCH_AUDITSYSCALL
150 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
151 select HAVE_ARCH_JUMP_LABEL
152 select HAVE_ARCH_JUMP_LABEL_RELATIVE
153 select HAVE_ARCH_KASAN if X86_64
154 select HAVE_ARCH_KASAN_VMALLOC if X86_64
155 select HAVE_ARCH_KFENCE
156 select HAVE_ARCH_KGDB
157 select HAVE_ARCH_MMAP_RND_BITS if MMU
158 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
159 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
160 select HAVE_ARCH_PREL32_RELOCATIONS
161 select HAVE_ARCH_SECCOMP_FILTER
162 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
163 select HAVE_ARCH_STACKLEAK
164 select HAVE_ARCH_TRACEHOOK
165 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
166 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
167 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
168 select HAVE_ARCH_VMAP_STACK if X86_64
169 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
170 select HAVE_ARCH_WITHIN_STACK_FRAMES
171 select HAVE_ASM_MODVERSIONS
172 select HAVE_CMPXCHG_DOUBLE
173 select HAVE_CMPXCHG_LOCAL
174 select HAVE_CONTEXT_TRACKING if X86_64
175 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
176 select HAVE_C_RECORDMCOUNT
177 select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION
178 select HAVE_DEBUG_KMEMLEAK
179 select HAVE_DMA_CONTIGUOUS
180 select HAVE_DYNAMIC_FTRACE
181 select HAVE_DYNAMIC_FTRACE_WITH_REGS
182 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
183 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
185 select HAVE_EFFICIENT_UNALIGNED_ACCESS
187 select HAVE_EXIT_THREAD
189 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
190 select HAVE_FTRACE_MCOUNT_RECORD
191 select HAVE_FUNCTION_GRAPH_TRACER
192 select HAVE_FUNCTION_TRACER
193 select HAVE_GCC_PLUGINS
194 select HAVE_HW_BREAKPOINT
196 select HAVE_IOREMAP_PROT
197 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
198 select HAVE_IRQ_TIME_ACCOUNTING
199 select HAVE_KERNEL_BZIP2
200 select HAVE_KERNEL_GZIP
201 select HAVE_KERNEL_LZ4
202 select HAVE_KERNEL_LZMA
203 select HAVE_KERNEL_LZO
204 select HAVE_KERNEL_XZ
205 select HAVE_KERNEL_ZSTD
207 select HAVE_KPROBES_ON_FTRACE
208 select HAVE_FUNCTION_ERROR_INJECTION
209 select HAVE_KRETPROBES
211 select HAVE_LIVEPATCH if X86_64
212 select HAVE_MIXED_BREAKPOINTS_REGS
213 select HAVE_MOD_ARCH_SPECIFIC
217 select HAVE_OPTPROBES
218 select HAVE_PCSPKR_PLATFORM
219 select HAVE_PERF_EVENTS
220 select HAVE_PERF_EVENTS_NMI
221 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
223 select HAVE_PERF_REGS
224 select HAVE_PERF_USER_STACK_DUMP
225 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
226 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
227 select HAVE_REGS_AND_STACK_ACCESS_API
228 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
229 select HAVE_FUNCTION_ARG_ACCESS_API
230 select HAVE_SOFTIRQ_ON_OWN_STACK
231 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
232 select HAVE_STACK_VALIDATION if X86_64
233 select HAVE_STATIC_CALL
234 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
235 select HAVE_PREEMPT_DYNAMIC
237 select HAVE_SYSCALL_TRACEPOINTS
238 select HAVE_UNSTABLE_SCHED_CLOCK
239 select HAVE_USER_RETURN_NOTIFIER
240 select HAVE_GENERIC_VDSO
241 select HOTPLUG_SMT if SMP
242 select IRQ_FORCED_THREADING
243 select NEED_SG_DMA_LENGTH
244 select PCI_DOMAINS if PCI
245 select PCI_LOCKLESS_CONFIG if PCI
248 select RTC_MC146818_LIB
251 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
252 select SYSCTL_EXCEPTION_TRACE
253 select THREAD_INFO_IN_TASK
254 select USER_STACKTRACE_SUPPORT
256 select HAVE_ARCH_KCSAN if X86_64
257 select X86_FEATURE_NAMES if PROC_FS
258 select PROC_PID_ARCH_STATUS if PROC_FS
259 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
261 config INSTRUCTION_DECODER
263 depends on KPROBES || PERF_EVENTS || UPROBES
267 default "elf32-i386" if X86_32
268 default "elf64-x86-64" if X86_64
270 config LOCKDEP_SUPPORT
273 config STACKTRACE_SUPPORT
279 config ARCH_MMAP_RND_BITS_MIN
283 config ARCH_MMAP_RND_BITS_MAX
287 config ARCH_MMAP_RND_COMPAT_BITS_MIN
290 config ARCH_MMAP_RND_COMPAT_BITS_MAX
296 config GENERIC_ISA_DMA
298 depends on ISA_DMA_API
303 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
305 config GENERIC_BUG_RELATIVE_POINTERS
308 config ARCH_MAY_HAVE_PC_FDC
310 depends on ISA_DMA_API
312 config GENERIC_CALIBRATE_DELAY
315 config ARCH_HAS_CPU_RELAX
318 config ARCH_HAS_CACHE_LINE_SIZE
321 config ARCH_HAS_FILTER_PGPROT
324 config HAVE_SETUP_PER_CPU_AREA
327 config NEED_PER_CPU_EMBED_FIRST_CHUNK
330 config NEED_PER_CPU_PAGE_FIRST_CHUNK
333 config ARCH_HIBERNATION_POSSIBLE
336 config ARCH_SUSPEND_POSSIBLE
339 config ARCH_WANT_GENERAL_HUGETLB
348 config KASAN_SHADOW_OFFSET
351 default 0xdffffc0000000000
353 config HAVE_INTEL_TXT
355 depends on INTEL_IOMMU && ACPI
359 depends on X86_32 && SMP
363 depends on X86_64 && SMP
365 config ARCH_SUPPORTS_UPROBES
368 config FIX_EARLYCON_MEM
371 config DYNAMIC_PHYSICAL_MASK
374 config PGTABLE_LEVELS
376 default 5 if X86_5LEVEL
381 config CC_HAS_SANE_STACKPROTECTOR
383 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
384 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
386 We have to make sure stack protector is unconditionally disabled if
387 the compiler produces broken code or if it does not let us control
388 the segment on 32-bit kernels.
390 menu "Processor type and features"
393 bool "DMA memory allocation support" if EXPERT
396 DMA memory allocation support allows devices with less than 32-bit
397 addressing to allocate within the first 16MB of address space.
398 Disable if no such devices will be used.
403 bool "Symmetric multi-processing support"
405 This enables support for systems with more than one CPU. If you have
406 a system with only one CPU, say N. If you have a system with more
409 If you say N here, the kernel will run on uni- and multiprocessor
410 machines, but will use only one CPU of a multiprocessor machine. If
411 you say Y here, the kernel will run on many, but not all,
412 uniprocessor machines. On a uniprocessor machine, the kernel
413 will run faster if you say N here.
415 Note that if you say Y here and choose architecture "586" or
416 "Pentium" under "Processor family", the kernel will not work on 486
417 architectures. Similarly, multiprocessor kernels for the "PPro"
418 architecture may not work on all Pentium based boards.
420 People using multiprocessor machines who say Y here should also say
421 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
422 Management" code will be disabled if you say Y here.
424 See also <file:Documentation/x86/i386/IO-APIC.rst>,
425 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
426 <http://www.tldp.org/docs.html#howto>.
428 If you don't know what to do here, say N.
430 config X86_FEATURE_NAMES
431 bool "Processor feature human-readable names" if EMBEDDED
434 This option compiles in a table of x86 feature bits and corresponding
435 names. This is required to support /proc/cpuinfo and a few kernel
436 messages. You can disable this to save space, at the expense of
437 making those few kernel messages show numeric feature bits instead.
442 bool "Support x2apic"
443 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
445 This enables x2apic support on CPUs that have this feature.
447 This allows 32-bit apic IDs (so it can support very large systems),
448 and accesses the local apic via MSRs not via mmio.
450 If you don't know what to do here, say N.
453 bool "Enable MPS table" if ACPI
455 depends on X86_LOCAL_APIC
457 For old smp systems that do not have proper acpi support. Newer systems
458 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
462 depends on X86_GOLDFISH
465 bool "Avoid speculative indirect branches in kernel"
468 Compile kernel with the retpoline compiler options to guard against
469 kernel-to-user data leaks by avoiding speculative indirect
470 branches. Requires a compiler with -mindirect-branch=thunk-extern
471 support for full protection. The kernel may run slower.
473 config X86_CPU_RESCTRL
474 bool "x86 CPU resource control support"
475 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
477 select PROC_CPU_RESCTRL if PROC_FS
479 Enable x86 CPU resource control support.
481 Provide support for the allocation and monitoring of system resources
484 Intel calls this Intel Resource Director Technology
485 (Intel(R) RDT). More information about RDT can be found in the
486 Intel x86 Architecture Software Developer Manual.
488 AMD calls this AMD Platform Quality of Service (AMD QoS).
489 More information about AMD QoS can be found in the AMD64 Technology
490 Platform Quality of Service Extensions manual.
496 bool "Support for big SMP systems with more than 8 CPUs"
499 This option is needed for the systems that have more than 8 CPUs.
501 config X86_EXTENDED_PLATFORM
502 bool "Support for extended (non-PC) x86 platforms"
505 If you disable this option then the kernel will only support
506 standard PC platforms. (which covers the vast majority of
509 If you enable this option then you'll be able to select support
510 for the following (non-PC) 32 bit x86 platforms:
511 Goldfish (Android emulator)
514 SGI 320/540 (Visual Workstation)
515 STA2X11-based (e.g. Northville)
516 Moorestown MID devices
518 If you have one of these systems, or if you want to build a
519 generic distribution kernel, say Y here - otherwise say N.
523 config X86_EXTENDED_PLATFORM
524 bool "Support for extended (non-PC) x86 platforms"
527 If you disable this option then the kernel will only support
528 standard PC platforms. (which covers the vast majority of
531 If you enable this option then you'll be able to select support
532 for the following (non-PC) 64 bit x86 platforms:
537 If you have one of these systems, or if you want to build a
538 generic distribution kernel, say Y here - otherwise say N.
540 # This is an alphabetically sorted list of 64 bit extended platforms
541 # Please maintain the alphabetic order if and when there are additions
543 bool "Numascale NumaChip"
545 depends on X86_EXTENDED_PLATFORM
548 depends on X86_X2APIC
549 depends on PCI_MMCONFIG
551 Adds support for Numascale NumaChip large-SMP systems. Needed to
552 enable more than ~168 cores.
553 If you don't have one of these, you should say N here.
557 select HYPERVISOR_GUEST
559 depends on X86_64 && PCI
560 depends on X86_EXTENDED_PLATFORM
563 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
564 supposed to run on these EM64T-based machines. Only choose this option
565 if you have one of these machines.
568 bool "SGI Ultraviolet"
570 depends on X86_EXTENDED_PLATFORM
573 depends on KEXEC_CORE
574 depends on X86_X2APIC
577 This option is needed in order to support SGI Ultraviolet systems.
578 If you don't have one of these, you should say N here.
580 # Following is an alphabetically sorted list of 32 bit extended platforms
581 # Please maintain the alphabetic order if and when there are additions
584 bool "Goldfish (Virtual Platform)"
585 depends on X86_EXTENDED_PLATFORM
587 Enable support for the Goldfish virtual platform used primarily
588 for Android development. Unless you are building for the Android
589 Goldfish emulator say N here.
592 bool "CE4100 TV platform"
594 depends on PCI_GODIRECT
595 depends on X86_IO_APIC
597 depends on X86_EXTENDED_PLATFORM
598 select X86_REBOOTFIXUPS
600 select OF_EARLY_FLATTREE
602 Select for the Intel CE media processor (CE4100) SOC.
603 This option compiles in support for the CE4100 SOC for settop
604 boxes and media devices.
607 bool "Intel MID platform support"
608 depends on X86_EXTENDED_PLATFORM
609 depends on X86_PLATFORM_DEVICES
611 depends on X86_64 || (PCI_GOANY && X86_32)
612 depends on X86_IO_APIC
617 select MFD_INTEL_MSIC
619 Select to build a kernel capable of supporting Intel MID (Mobile
620 Internet Device) platform systems which do not have the PCI legacy
621 interfaces. If you are building for a PC class system say N here.
623 Intel MID platforms are based on an Intel processor and chipset which
624 consume less power than most of the x86 derivatives.
626 config X86_INTEL_QUARK
627 bool "Intel Quark platform support"
629 depends on X86_EXTENDED_PLATFORM
630 depends on X86_PLATFORM_DEVICES
634 depends on X86_IO_APIC
639 Select to include support for Quark X1000 SoC.
640 Say Y here if you have a Quark based system such as the Arduino
641 compatible Intel Galileo.
643 config X86_INTEL_LPSS
644 bool "Intel Low Power Subsystem Support"
645 depends on X86 && ACPI && PCI
650 Select to build support for Intel Low Power Subsystem such as
651 found on Intel Lynxpoint PCH. Selecting this option enables
652 things like clock tree (common clock framework) and pincontrol
653 which are needed by the LPSS peripheral drivers.
655 config X86_AMD_PLATFORM_DEVICE
656 bool "AMD ACPI2Platform devices support"
661 Select to interpret AMD specific ACPI device to platform device
662 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
663 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
664 implemented under PINCTRL subsystem.
667 tristate "Intel SoC IOSF Sideband support for SoC platforms"
670 This option enables sideband register access support for Intel SoC
671 platforms. On these platforms the IOSF sideband is used in lieu of
672 MSR's for some register accesses, mostly but not limited to thermal
673 and power. Drivers may query the availability of this device to
674 determine if they need the sideband in order to work on these
675 platforms. The sideband is available on the following SoC products.
676 This list is not meant to be exclusive.
681 You should say Y if you are running a kernel on one of these SoC's.
683 config IOSF_MBI_DEBUG
684 bool "Enable IOSF sideband access through debugfs"
685 depends on IOSF_MBI && DEBUG_FS
687 Select this option to expose the IOSF sideband access registers (MCR,
688 MDR, MCRX) through debugfs to write and read register information from
689 different units on the SoC. This is most useful for obtaining device
690 state information for debug and analysis. As this is a general access
691 mechanism, users of this option would have specific knowledge of the
692 device they want to access.
694 If you don't require the option or are in doubt, say N.
697 bool "RDC R-321x SoC"
699 depends on X86_EXTENDED_PLATFORM
701 select X86_REBOOTFIXUPS
703 This option is needed for RDC R-321x system-on-chip, also known
705 If you don't have one of these chips, you should say N here.
707 config X86_32_NON_STANDARD
708 bool "Support non-standard 32-bit SMP architectures"
709 depends on X86_32 && SMP
710 depends on X86_EXTENDED_PLATFORM
712 This option compiles in the bigsmp and STA2X11 default
713 subarchitectures. It is intended for a generic binary
714 kernel. If you select them all, kernel will probe it one by
715 one and will fallback to default.
717 # Alphabetically sorted list of Non standard 32 bit platforms
719 config X86_SUPPORTS_MEMORY_FAILURE
721 # MCE code calls memory_failure():
723 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
724 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
725 depends on X86_64 || !SPARSEMEM
726 select ARCH_SUPPORTS_MEMORY_FAILURE
729 bool "STA2X11 Companion Chip Support"
730 depends on X86_32_NON_STANDARD && PCI
735 This adds support for boards based on the STA2X11 IO-Hub,
736 a.k.a. "ConneXt". The chip is used in place of the standard
737 PC chipset, so all "standard" peripherals are missing. If this
738 option is selected the kernel will still be able to boot on
739 standard PC machines.
742 tristate "Eurobraille/Iris poweroff module"
745 The Iris machines from EuroBraille do not have APM or ACPI support
746 to shut themselves down properly. A special I/O sequence is
747 needed to do so, which is what this module does at
750 This is only for Iris machines from EuroBraille.
754 config SCHED_OMIT_FRAME_POINTER
756 prompt "Single-depth WCHAN output"
759 Calculate simpler /proc/<PID>/wchan values. If this option
760 is disabled then wchan values will recurse back to the
761 caller function. This provides more accurate wchan values,
762 at the expense of slightly more scheduling overhead.
764 If in doubt, say "Y".
766 menuconfig HYPERVISOR_GUEST
767 bool "Linux guest support"
769 Say Y here to enable options for running Linux under various hyper-
770 visors. This option enables basic hypervisor detection and platform
773 If you say N, all options in this submenu will be skipped and
774 disabled, and Linux guest support won't be built in.
779 bool "Enable paravirtualization code"
780 depends on HAVE_STATIC_CALL
782 This changes the kernel so it can modify itself when it is run
783 under a hypervisor, potentially improving performance significantly
784 over full virtualization. However, when run without a hypervisor
785 the kernel is theoretically slower and slightly larger.
790 config PARAVIRT_DEBUG
791 bool "paravirt-ops debugging"
792 depends on PARAVIRT && DEBUG_KERNEL
794 Enable to debug paravirt_ops internals. Specifically, BUG if
795 a paravirt_op is missing when it is called.
797 config PARAVIRT_SPINLOCKS
798 bool "Paravirtualization layer for spinlocks"
799 depends on PARAVIRT && SMP
801 Paravirtualized spinlocks allow a pvops backend to replace the
802 spinlock implementation with something virtualization-friendly
803 (for example, block the virtual CPU rather than spinning).
805 It has a minimal impact on native kernels and gives a nice performance
806 benefit on paravirtualized KVM / Xen kernels.
808 If you are unsure how to answer this question, answer Y.
810 config X86_HV_CALLBACK_VECTOR
813 source "arch/x86/xen/Kconfig"
816 bool "KVM Guest support (including kvmclock)"
818 select PARAVIRT_CLOCK
819 select ARCH_CPUIDLE_HALTPOLL
820 select X86_HV_CALLBACK_VECTOR
823 This option enables various optimizations for running under the KVM
824 hypervisor. It includes a paravirtualized clock, so that instead
825 of relying on a PIT (or probably other) emulation by the
826 underlying device model, the host provides the guest with
827 timing infrastructure such as time of day, and system time
829 config ARCH_CPUIDLE_HALTPOLL
831 prompt "Disable host haltpoll when loading haltpoll driver"
833 If virtualized under KVM, disable host haltpoll.
836 bool "Support for running PVH guests"
838 This option enables the PVH entry point for guest virtual machines
839 as specified in the x86/HVM direct boot ABI.
841 config PARAVIRT_TIME_ACCOUNTING
842 bool "Paravirtual steal time accounting"
845 Select this option to enable fine granularity task steal time
846 accounting. Time spent executing other tasks in parallel with
847 the current vCPU is discounted from the vCPU power. To account for
848 that, there can be a small performance impact.
850 If in doubt, say N here.
852 config PARAVIRT_CLOCK
855 config JAILHOUSE_GUEST
856 bool "Jailhouse non-root cell support"
857 depends on X86_64 && PCI
860 This option allows to run Linux as guest in a Jailhouse non-root
861 cell. You can leave this option disabled if you only want to start
862 Jailhouse and run Linux afterwards in the root cell.
865 bool "ACRN Guest support"
867 select X86_HV_CALLBACK_VECTOR
869 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
870 a flexible, lightweight reference open-source hypervisor, built with
871 real-time and safety-criticality in mind. It is built for embedded
872 IOT with small footprint and real-time features. More details can be
873 found in https://projectacrn.org/.
875 endif #HYPERVISOR_GUEST
877 source "arch/x86/Kconfig.cpu"
881 prompt "HPET Timer Support" if X86_32
883 Use the IA-PC HPET (High Precision Event Timer) to manage
884 time in preference to the PIT and RTC, if a HPET is
886 HPET is the next generation timer replacing legacy 8254s.
887 The HPET provides a stable time base on SMP
888 systems, unlike the TSC, but it is more expensive to access,
889 as it is off-chip. The interface used is documented
890 in the HPET spec, revision 1.
892 You can safely choose Y here. However, HPET will only be
893 activated if the platform and the BIOS support this feature.
894 Otherwise the 8254 will be used for timing services.
896 Choose N to continue using the legacy 8254 timer.
898 config HPET_EMULATE_RTC
900 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
902 # Mark as expert because too many people got it wrong.
903 # The code disables itself when not needed.
906 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
907 bool "Enable DMI scanning" if EXPERT
909 Enabled scanning of DMI to identify machine quirks. Say Y
910 here unless you have verified that your setup is not
911 affected by entries in the DMI blacklist. Required by PNP
915 bool "Old AMD GART IOMMU support"
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 source "arch/x86/events/Kconfig"
1158 config X86_LEGACY_VM86
1159 bool "Legacy VM86 support"
1162 This option allows user programs to put the CPU into V8086
1163 mode, which is an 80286-era approximation of 16-bit real mode.
1165 Some very old versions of X and/or vbetool require this option
1166 for user mode setting. Similarly, DOSEMU will use it if
1167 available to accelerate real mode DOS programs. However, any
1168 recent version of DOSEMU, X, or vbetool should be fully
1169 functional even without kernel VM86 support, as they will all
1170 fall back to software emulation. Nevertheless, if you are using
1171 a 16-bit DOS program where 16-bit performance matters, vm86
1172 mode might be faster than emulation and you might want to
1175 Note that any app that works on a 64-bit kernel is unlikely to
1176 need this option, as 64-bit kernels don't, and can't, support
1177 V8086 mode. This option is also unrelated to 16-bit protected
1178 mode and is not needed to run most 16-bit programs under Wine.
1180 Enabling this option increases the complexity of the kernel
1181 and slows down exception handling a tiny bit.
1183 If unsure, say N here.
1187 default X86_LEGACY_VM86
1190 bool "Enable support for 16-bit segments" if EXPERT
1192 depends on MODIFY_LDT_SYSCALL
1194 This option is required by programs like Wine to run 16-bit
1195 protected mode legacy code on x86 processors. Disabling
1196 this option saves about 300 bytes on i386, or around 6K text
1197 plus 16K runtime memory on x86-64,
1201 depends on X86_16BIT && X86_32
1205 depends on X86_16BIT && X86_64
1207 config X86_VSYSCALL_EMULATION
1208 bool "Enable vsyscall emulation" if EXPERT
1212 This enables emulation of the legacy vsyscall page. Disabling
1213 it is roughly equivalent to booting with vsyscall=none, except
1214 that it will also disable the helpful warning if a program
1215 tries to use a vsyscall. With this option set to N, offending
1216 programs will just segfault, citing addresses of the form
1219 This option is required by many programs built before 2013, and
1220 care should be used even with newer programs if set to N.
1222 Disabling this option saves about 7K of kernel size and
1223 possibly 4K of additional runtime pagetable memory.
1225 config X86_IOPL_IOPERM
1226 bool "IOPERM and IOPL Emulation"
1229 This enables the ioperm() and iopl() syscalls which are necessary
1230 for legacy applications.
1232 Legacy IOPL support is an overbroad mechanism which allows user
1233 space aside of accessing all 65536 I/O ports also to disable
1234 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1235 capabilities and permission from potentially active security
1238 The emulation restricts the functionality of the syscall to
1239 only allowing the full range I/O port access, but prevents the
1240 ability to disable interrupts from user space which would be
1241 granted if the hardware IOPL mechanism would be used.
1244 tristate "Toshiba Laptop support"
1247 This adds a driver to safely access the System Management Mode of
1248 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1249 not work on models with a Phoenix BIOS. The System Management Mode
1250 is used to set the BIOS and power saving options on Toshiba portables.
1252 For information on utilities to make use of this driver see the
1253 Toshiba Linux utilities web site at:
1254 <http://www.buzzard.org.uk/toshiba/>.
1256 Say Y if you intend to run this kernel on a Toshiba portable.
1260 tristate "Dell i8k legacy laptop support"
1262 select SENSORS_DELL_SMM
1264 This option enables legacy /proc/i8k userspace interface in hwmon
1265 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1266 temperature and allows controlling fan speeds of Dell laptops via
1267 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1268 it reports also power and hotkey status. For fan speed control is
1269 needed userspace package i8kutils.
1271 Say Y if you intend to run this kernel on old Dell laptops or want to
1272 use userspace package i8kutils.
1275 config X86_REBOOTFIXUPS
1276 bool "Enable X86 board specific fixups for reboot"
1279 This enables chipset and/or board specific fixups to be done
1280 in order to get reboot to work correctly. This is only needed on
1281 some combinations of hardware and BIOS. The symptom, for which
1282 this config is intended, is when reboot ends with a stalled/hung
1285 Currently, the only fixup is for the Geode machines using
1286 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1288 Say Y if you want to enable the fixup. Currently, it's safe to
1289 enable this option even if you don't need it.
1293 bool "CPU microcode loading support"
1295 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1297 If you say Y here, you will be able to update the microcode on
1298 Intel and AMD processors. The Intel support is for the IA32 family,
1299 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1300 AMD support is for families 0x10 and later. You will obviously need
1301 the actual microcode binary data itself which is not shipped with
1304 The preferred method to load microcode from a detached initrd is described
1305 in Documentation/x86/microcode.rst. For that you need to enable
1306 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1307 initrd for microcode blobs.
1309 In addition, you can build the microcode into the kernel. For that you
1310 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1313 config MICROCODE_INTEL
1314 bool "Intel microcode loading support"
1315 depends on MICROCODE
1318 This options enables microcode patch loading support for Intel
1321 For the current Intel microcode data package go to
1322 <https://downloadcenter.intel.com> and search for
1323 'Linux Processor Microcode Data File'.
1325 config MICROCODE_AMD
1326 bool "AMD microcode loading support"
1327 depends on MICROCODE
1329 If you select this option, microcode patch loading support for AMD
1330 processors will be enabled.
1332 config MICROCODE_OLD_INTERFACE
1333 bool "Ancient loading interface (DEPRECATED)"
1335 depends on MICROCODE
1337 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1338 which was used by userspace tools like iucode_tool and microcode.ctl.
1339 It is inadequate because it runs too late to be able to properly
1340 load microcode on a machine and it needs special tools. Instead, you
1341 should've switched to the early loading method with the initrd or
1342 builtin microcode by now: Documentation/x86/microcode.rst
1345 tristate "/dev/cpu/*/msr - Model-specific register support"
1347 This device gives privileged processes access to the x86
1348 Model-Specific Registers (MSRs). It is a character device with
1349 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1350 MSR accesses are directed to a specific CPU on multi-processor
1354 tristate "/dev/cpu/*/cpuid - CPU information support"
1356 This device gives processes access to the x86 CPUID instruction to
1357 be executed on a specific processor. It is a character device
1358 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1362 prompt "High Memory Support"
1369 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1370 However, the address space of 32-bit x86 processors is only 4
1371 Gigabytes large. That means that, if you have a large amount of
1372 physical memory, not all of it can be "permanently mapped" by the
1373 kernel. The physical memory that's not permanently mapped is called
1376 If you are compiling a kernel which will never run on a machine with
1377 more than 1 Gigabyte total physical RAM, answer "off" here (default
1378 choice and suitable for most users). This will result in a "3GB/1GB"
1379 split: 3GB are mapped so that each process sees a 3GB virtual memory
1380 space and the remaining part of the 4GB virtual memory space is used
1381 by the kernel to permanently map as much physical memory as
1384 If the machine has between 1 and 4 Gigabytes physical RAM, then
1387 If more than 4 Gigabytes is used then answer "64GB" here. This
1388 selection turns Intel PAE (Physical Address Extension) mode on.
1389 PAE implements 3-level paging on IA32 processors. PAE is fully
1390 supported by Linux, PAE mode is implemented on all recent Intel
1391 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1392 then the kernel will not boot on CPUs that don't support PAE!
1394 The actual amount of total physical memory will either be
1395 auto detected or can be forced by using a kernel command line option
1396 such as "mem=256M". (Try "man bootparam" or see the documentation of
1397 your boot loader (lilo or loadlin) about how to pass options to the
1398 kernel at boot time.)
1400 If unsure, say "off".
1405 Select this if you have a 32-bit processor and between 1 and 4
1406 gigabytes of physical RAM.
1410 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1413 Select this if you have a 32-bit processor and more than 4
1414 gigabytes of physical RAM.
1419 prompt "Memory split" if EXPERT
1423 Select the desired split between kernel and user memory.
1425 If the address range available to the kernel is less than the
1426 physical memory installed, the remaining memory will be available
1427 as "high memory". Accessing high memory is a little more costly
1428 than low memory, as it needs to be mapped into the kernel first.
1429 Note that increasing the kernel address space limits the range
1430 available to user programs, making the address space there
1431 tighter. Selecting anything other than the default 3G/1G split
1432 will also likely make your kernel incompatible with binary-only
1435 If you are not absolutely sure what you are doing, leave this
1439 bool "3G/1G user/kernel split"
1440 config VMSPLIT_3G_OPT
1442 bool "3G/1G user/kernel split (for full 1G low memory)"
1444 bool "2G/2G user/kernel split"
1445 config VMSPLIT_2G_OPT
1447 bool "2G/2G user/kernel split (for full 2G low memory)"
1449 bool "1G/3G user/kernel split"
1454 default 0xB0000000 if VMSPLIT_3G_OPT
1455 default 0x80000000 if VMSPLIT_2G
1456 default 0x78000000 if VMSPLIT_2G_OPT
1457 default 0x40000000 if VMSPLIT_1G
1463 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1466 bool "PAE (Physical Address Extension) Support"
1467 depends on X86_32 && !HIGHMEM4G
1468 select PHYS_ADDR_T_64BIT
1471 PAE is required for NX support, and furthermore enables
1472 larger swapspace support for non-overcommit purposes. It
1473 has the cost of more pagetable lookup overhead, and also
1474 consumes more pagetable space per process.
1477 bool "Enable 5-level page tables support"
1479 select DYNAMIC_MEMORY_LAYOUT
1480 select SPARSEMEM_VMEMMAP
1483 5-level paging enables access to larger address space:
1484 upto 128 PiB of virtual address space and 4 PiB of
1485 physical address space.
1487 It will be supported by future Intel CPUs.
1489 A kernel with the option enabled can be booted on machines that
1490 support 4- or 5-level paging.
1492 See Documentation/x86/x86_64/5level-paging.rst for more
1497 config X86_DIRECT_GBPAGES
1501 Certain kernel features effectively disable kernel
1502 linear 1 GB mappings (even if the CPU otherwise
1503 supports them), so don't confuse the user by printing
1504 that we have them enabled.
1506 config X86_CPA_STATISTICS
1507 bool "Enable statistic for Change Page Attribute"
1510 Expose statistics about the Change Page Attribute mechanism, which
1511 helps to determine the effectiveness of preserving large and huge
1512 page mappings when mapping protections are changed.
1514 config AMD_MEM_ENCRYPT
1515 bool "AMD Secure Memory Encryption (SME) support"
1516 depends on X86_64 && CPU_SUP_AMD
1517 select DMA_COHERENT_POOL
1518 select DYNAMIC_PHYSICAL_MASK
1519 select ARCH_USE_MEMREMAP_PROT
1520 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1521 select INSTRUCTION_DECODER
1522 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1524 Say yes to enable support for the encryption of system memory.
1525 This requires an AMD processor that supports Secure Memory
1528 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1529 bool "Activate AMD Secure Memory Encryption (SME) by default"
1531 depends on AMD_MEM_ENCRYPT
1533 Say yes to have system memory encrypted by default if running on
1534 an AMD processor that supports Secure Memory Encryption (SME).
1536 If set to Y, then the encryption of system memory can be
1537 deactivated with the mem_encrypt=off command line option.
1539 If set to N, then the encryption of system memory can be
1540 activated with the mem_encrypt=on command line option.
1542 # Common NUMA Features
1544 bool "NUMA Memory Allocation and Scheduler Support"
1546 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1547 default y if X86_BIGSMP
1549 Enable NUMA (Non-Uniform Memory Access) support.
1551 The kernel will try to allocate memory used by a CPU on the
1552 local memory controller of the CPU and add some more
1553 NUMA awareness to the kernel.
1555 For 64-bit this is recommended if the system is Intel Core i7
1556 (or later), AMD Opteron, or EM64T NUMA.
1558 For 32-bit this is only needed if you boot a 32-bit
1559 kernel on a 64-bit NUMA platform.
1561 Otherwise, you should say N.
1565 prompt "Old style AMD Opteron NUMA detection"
1566 depends on X86_64 && NUMA && PCI
1568 Enable AMD NUMA node topology detection. You should say Y here if
1569 you have a multi processor AMD system. This uses an old method to
1570 read the NUMA configuration directly from the builtin Northbridge
1571 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1572 which also takes priority if both are compiled in.
1574 config X86_64_ACPI_NUMA
1576 prompt "ACPI NUMA detection"
1577 depends on X86_64 && NUMA && ACPI && PCI
1580 Enable ACPI SRAT based node topology detection.
1583 bool "NUMA emulation"
1586 Enable NUMA emulation. A flat machine will be split
1587 into virtual nodes when booted with "numa=fake=N", where N is the
1588 number of nodes. This is only useful for debugging.
1591 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1593 default "10" if MAXSMP
1594 default "6" if X86_64
1596 depends on NEED_MULTIPLE_NODES
1598 Specify the maximum number of NUMA Nodes available on the target
1599 system. Increases memory reserved to accommodate various tables.
1601 config ARCH_FLATMEM_ENABLE
1603 depends on X86_32 && !NUMA
1605 config ARCH_SPARSEMEM_ENABLE
1607 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1608 select SPARSEMEM_STATIC if X86_32
1609 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1611 config ARCH_SPARSEMEM_DEFAULT
1612 def_bool X86_64 || (NUMA && X86_32)
1614 config ARCH_SELECT_MEMORY_MODEL
1616 depends on ARCH_SPARSEMEM_ENABLE
1618 config ARCH_MEMORY_PROBE
1619 bool "Enable sysfs memory/probe interface"
1620 depends on X86_64 && MEMORY_HOTPLUG
1622 This option enables a sysfs memory/probe interface for testing.
1623 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1624 If you are unsure how to answer this question, answer N.
1626 config ARCH_PROC_KCORE_TEXT
1628 depends on X86_64 && PROC_KCORE
1630 config ILLEGAL_POINTER_VALUE
1633 default 0xdead000000000000 if X86_64
1635 config X86_PMEM_LEGACY_DEVICE
1638 config X86_PMEM_LEGACY
1639 tristate "Support non-standard NVDIMMs and ADR protected memory"
1640 depends on PHYS_ADDR_T_64BIT
1642 select X86_PMEM_LEGACY_DEVICE
1643 select NUMA_KEEP_MEMINFO if NUMA
1646 Treat memory marked using the non-standard e820 type of 12 as used
1647 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1648 The kernel will offer these regions to the 'pmem' driver so
1649 they can be used for persistent storage.
1654 bool "Allocate 3rd-level pagetables from highmem"
1657 The VM uses one page table entry for each page of physical memory.
1658 For systems with a lot of RAM, this can be wasteful of precious
1659 low memory. Setting this option will put user-space page table
1660 entries in high memory.
1662 config X86_CHECK_BIOS_CORRUPTION
1663 bool "Check for low memory corruption"
1665 Periodically check for memory corruption in low memory, which
1666 is suspected to be caused by BIOS. Even when enabled in the
1667 configuration, it is disabled at runtime. Enable it by
1668 setting "memory_corruption_check=1" on the kernel command
1669 line. By default it scans the low 64k of memory every 60
1670 seconds; see the memory_corruption_check_size and
1671 memory_corruption_check_period parameters in
1672 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1674 When enabled with the default parameters, this option has
1675 almost no overhead, as it reserves a relatively small amount
1676 of memory and scans it infrequently. It both detects corruption
1677 and prevents it from affecting the running system.
1679 It is, however, intended as a diagnostic tool; if repeatable
1680 BIOS-originated corruption always affects the same memory,
1681 you can use memmap= to prevent the kernel from using that
1684 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1685 bool "Set the default setting of memory_corruption_check"
1686 depends on X86_CHECK_BIOS_CORRUPTION
1689 Set whether the default state of memory_corruption_check is
1692 config X86_RESERVE_LOW
1693 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1697 Specify the amount of low memory to reserve for the BIOS.
1699 The first page contains BIOS data structures that the kernel
1700 must not use, so that page must always be reserved.
1702 By default we reserve the first 64K of physical RAM, as a
1703 number of BIOSes are known to corrupt that memory range
1704 during events such as suspend/resume or monitor cable
1705 insertion, so it must not be used by the kernel.
1707 You can set this to 4 if you are absolutely sure that you
1708 trust the BIOS to get all its memory reservations and usages
1709 right. If you know your BIOS have problems beyond the
1710 default 64K area, you can set this to 640 to avoid using the
1711 entire low memory range.
1713 If you have doubts about the BIOS (e.g. suspend/resume does
1714 not work or there's kernel crashes after certain hardware
1715 hotplug events) then you might want to enable
1716 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1717 typical corruption patterns.
1719 Leave this to the default value of 64 if you are unsure.
1721 config MATH_EMULATION
1723 depends on MODIFY_LDT_SYSCALL
1724 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1726 Linux can emulate a math coprocessor (used for floating point
1727 operations) if you don't have one. 486DX and Pentium processors have
1728 a math coprocessor built in, 486SX and 386 do not, unless you added
1729 a 487DX or 387, respectively. (The messages during boot time can
1730 give you some hints here ["man dmesg"].) Everyone needs either a
1731 coprocessor or this emulation.
1733 If you don't have a math coprocessor, you need to say Y here; if you
1734 say Y here even though you have a coprocessor, the coprocessor will
1735 be used nevertheless. (This behavior can be changed with the kernel
1736 command line option "no387", which comes handy if your coprocessor
1737 is broken. Try "man bootparam" or see the documentation of your boot
1738 loader (lilo or loadlin) about how to pass options to the kernel at
1739 boot time.) This means that it is a good idea to say Y here if you
1740 intend to use this kernel on different machines.
1742 More information about the internals of the Linux math coprocessor
1743 emulation can be found in <file:arch/x86/math-emu/README>.
1745 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1746 kernel, it won't hurt.
1750 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1752 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1753 the Memory Type Range Registers (MTRRs) may be used to control
1754 processor access to memory ranges. This is most useful if you have
1755 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1756 allows bus write transfers to be combined into a larger transfer
1757 before bursting over the PCI/AGP bus. This can increase performance
1758 of image write operations 2.5 times or more. Saying Y here creates a
1759 /proc/mtrr file which may be used to manipulate your processor's
1760 MTRRs. Typically the X server should use this.
1762 This code has a reasonably generic interface so that similar
1763 control registers on other processors can be easily supported
1766 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1767 Registers (ARRs) which provide a similar functionality to MTRRs. For
1768 these, the ARRs are used to emulate the MTRRs.
1769 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1770 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1771 write-combining. All of these processors are supported by this code
1772 and it makes sense to say Y here if you have one of them.
1774 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1775 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1776 can lead to all sorts of problems, so it's good to say Y here.
1778 You can safely say Y even if your machine doesn't have MTRRs, you'll
1779 just add about 9 KB to your kernel.
1781 See <file:Documentation/x86/mtrr.rst> for more information.
1783 config MTRR_SANITIZER
1785 prompt "MTRR cleanup support"
1788 Convert MTRR layout from continuous to discrete, so X drivers can
1789 add writeback entries.
1791 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1792 The largest mtrr entry size for a continuous block can be set with
1797 config MTRR_SANITIZER_ENABLE_DEFAULT
1798 int "MTRR cleanup enable value (0-1)"
1801 depends on MTRR_SANITIZER
1803 Enable mtrr cleanup default value
1805 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1806 int "MTRR cleanup spare reg num (0-7)"
1809 depends on MTRR_SANITIZER
1811 mtrr cleanup spare entries default, it can be changed via
1812 mtrr_spare_reg_nr=N on the kernel command line.
1816 prompt "x86 PAT support" if EXPERT
1819 Use PAT attributes to setup page level cache control.
1821 PATs are the modern equivalents of MTRRs and are much more
1822 flexible than MTRRs.
1824 Say N here if you see bootup problems (boot crash, boot hang,
1825 spontaneous reboots) or a non-working video driver.
1829 config ARCH_USES_PG_UNCACHED
1835 prompt "x86 architectural random number generator" if EXPERT
1837 Enable the x86 architectural RDRAND instruction
1838 (Intel Bull Mountain technology) to generate random numbers.
1839 If supported, this is a high bandwidth, cryptographically
1840 secure hardware random number generator.
1844 prompt "Supervisor Mode Access Prevention" if EXPERT
1846 Supervisor Mode Access Prevention (SMAP) is a security
1847 feature in newer Intel processors. There is a small
1848 performance cost if this enabled and turned on; there is
1849 also a small increase in the kernel size if this is enabled.
1855 prompt "User Mode Instruction Prevention" if EXPERT
1857 User Mode Instruction Prevention (UMIP) is a security feature in
1858 some x86 processors. If enabled, a general protection fault is
1859 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1860 executed in user mode. These instructions unnecessarily expose
1861 information about the hardware state.
1863 The vast majority of applications do not use these instructions.
1864 For the very few that do, software emulation is provided in
1865 specific cases in protected and virtual-8086 modes. Emulated
1868 config X86_INTEL_MEMORY_PROTECTION_KEYS
1869 prompt "Memory Protection Keys"
1871 # Note: only available in 64-bit mode
1872 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1873 select ARCH_USES_HIGH_VMA_FLAGS
1874 select ARCH_HAS_PKEYS
1876 Memory Protection Keys provides a mechanism for enforcing
1877 page-based protections, but without requiring modification of the
1878 page tables when an application changes protection domains.
1880 For details, see Documentation/core-api/protection-keys.rst
1885 prompt "TSX enable mode"
1886 depends on CPU_SUP_INTEL
1887 default X86_INTEL_TSX_MODE_OFF
1889 Intel's TSX (Transactional Synchronization Extensions) feature
1890 allows to optimize locking protocols through lock elision which
1891 can lead to a noticeable performance boost.
1893 On the other hand it has been shown that TSX can be exploited
1894 to form side channel attacks (e.g. TAA) and chances are there
1895 will be more of those attacks discovered in the future.
1897 Therefore TSX is not enabled by default (aka tsx=off). An admin
1898 might override this decision by tsx=on the command line parameter.
1899 Even with TSX enabled, the kernel will attempt to enable the best
1900 possible TAA mitigation setting depending on the microcode available
1901 for the particular machine.
1903 This option allows to set the default tsx mode between tsx=on, =off
1904 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1907 Say off if not sure, auto if TSX is in use but it should be used on safe
1908 platforms or on if TSX is in use and the security aspect of tsx is not
1911 config X86_INTEL_TSX_MODE_OFF
1914 TSX is disabled if possible - equals to tsx=off command line parameter.
1916 config X86_INTEL_TSX_MODE_ON
1919 TSX is always enabled on TSX capable HW - equals the tsx=on command
1922 config X86_INTEL_TSX_MODE_AUTO
1925 TSX is enabled on TSX capable HW that is believed to be safe against
1926 side channel attacks- equals the tsx=auto command line parameter.
1930 bool "Software Guard eXtensions (SGX)"
1931 depends on X86_64 && CPU_SUP_INTEL
1933 depends on CRYPTO_SHA256=y
1936 select NUMA_KEEP_MEMINFO if NUMA
1938 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1939 that can be used by applications to set aside private regions of code
1940 and data, referred to as enclaves. An enclave's private memory can
1941 only be accessed by code running within the enclave. Accesses from
1942 outside the enclave, including other enclaves, are disallowed by
1948 bool "EFI runtime service support"
1951 select EFI_RUNTIME_WRAPPERS
1953 This enables the kernel to use EFI runtime services that are
1954 available (such as the EFI variable services).
1956 This option is only useful on systems that have EFI firmware.
1957 In addition, you should use the latest ELILO loader available
1958 at <http://elilo.sourceforge.net> in order to take advantage
1959 of EFI runtime services. However, even with this option, the
1960 resultant kernel should continue to boot on existing non-EFI
1964 bool "EFI stub support"
1965 depends on EFI && !X86_USE_3DNOW
1966 depends on $(cc-option,-mabi=ms) || X86_32
1969 This kernel feature allows a bzImage to be loaded directly
1970 by EFI firmware without the use of a bootloader.
1972 See Documentation/admin-guide/efi-stub.rst for more information.
1975 bool "EFI mixed-mode support"
1976 depends on EFI_STUB && X86_64
1978 Enabling this feature allows a 64-bit kernel to be booted
1979 on a 32-bit firmware, provided that your CPU supports 64-bit
1982 Note that it is not possible to boot a mixed-mode enabled
1983 kernel via the EFI boot stub - a bootloader that supports
1984 the EFI handover protocol must be used.
1988 source "kernel/Kconfig.hz"
1991 bool "kexec system call"
1994 kexec is a system call that implements the ability to shutdown your
1995 current kernel, and to start another kernel. It is like a reboot
1996 but it is independent of the system firmware. And like a reboot
1997 you can start any kernel with it, not just Linux.
1999 The name comes from the similarity to the exec system call.
2001 It is an ongoing process to be certain the hardware in a machine
2002 is properly shutdown, so do not be surprised if this code does not
2003 initially work for you. As of this writing the exact hardware
2004 interface is strongly in flux, so no good recommendation can be
2008 bool "kexec file based system call"
2013 depends on CRYPTO_SHA256=y
2015 This is new version of kexec system call. This system call is
2016 file based and takes file descriptors as system call argument
2017 for kernel and initramfs as opposed to list of segments as
2018 accepted by previous system call.
2020 config ARCH_HAS_KEXEC_PURGATORY
2024 bool "Verify kernel signature during kexec_file_load() syscall"
2025 depends on KEXEC_FILE
2028 This option makes the kexec_file_load() syscall check for a valid
2029 signature of the kernel image. The image can still be loaded without
2030 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2031 there's a signature that we can check, then it must be valid.
2033 In addition to this option, you need to enable signature
2034 verification for the corresponding kernel image type being
2035 loaded in order for this to work.
2037 config KEXEC_SIG_FORCE
2038 bool "Require a valid signature in kexec_file_load() syscall"
2039 depends on KEXEC_SIG
2041 This option makes kernel signature verification mandatory for
2042 the kexec_file_load() syscall.
2044 config KEXEC_BZIMAGE_VERIFY_SIG
2045 bool "Enable bzImage signature verification support"
2046 depends on KEXEC_SIG
2047 depends on SIGNED_PE_FILE_VERIFICATION
2048 select SYSTEM_TRUSTED_KEYRING
2050 Enable bzImage signature verification support.
2053 bool "kernel crash dumps"
2054 depends on X86_64 || (X86_32 && HIGHMEM)
2056 Generate crash dump after being started by kexec.
2057 This should be normally only set in special crash dump kernels
2058 which are loaded in the main kernel with kexec-tools into
2059 a specially reserved region and then later executed after
2060 a crash by kdump/kexec. The crash dump kernel must be compiled
2061 to a memory address not used by the main kernel or BIOS using
2062 PHYSICAL_START, or it must be built as a relocatable image
2063 (CONFIG_RELOCATABLE=y).
2064 For more details see Documentation/admin-guide/kdump/kdump.rst
2068 depends on KEXEC && HIBERNATION
2070 Jump between original kernel and kexeced kernel and invoke
2071 code in physical address mode via KEXEC
2073 config PHYSICAL_START
2074 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2077 This gives the physical address where the kernel is loaded.
2079 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2080 bzImage will decompress itself to above physical address and
2081 run from there. Otherwise, bzImage will run from the address where
2082 it has been loaded by the boot loader and will ignore above physical
2085 In normal kdump cases one does not have to set/change this option
2086 as now bzImage can be compiled as a completely relocatable image
2087 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2088 address. This option is mainly useful for the folks who don't want
2089 to use a bzImage for capturing the crash dump and want to use a
2090 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2091 to be specifically compiled to run from a specific memory area
2092 (normally a reserved region) and this option comes handy.
2094 So if you are using bzImage for capturing the crash dump,
2095 leave the value here unchanged to 0x1000000 and set
2096 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2097 for capturing the crash dump change this value to start of
2098 the reserved region. In other words, it can be set based on
2099 the "X" value as specified in the "crashkernel=YM@XM"
2100 command line boot parameter passed to the panic-ed
2101 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2102 for more details about crash dumps.
2104 Usage of bzImage for capturing the crash dump is recommended as
2105 one does not have to build two kernels. Same kernel can be used
2106 as production kernel and capture kernel. Above option should have
2107 gone away after relocatable bzImage support is introduced. But it
2108 is present because there are users out there who continue to use
2109 vmlinux for dump capture. This option should go away down the
2112 Don't change this unless you know what you are doing.
2115 bool "Build a relocatable kernel"
2118 This builds a kernel image that retains relocation information
2119 so it can be loaded someplace besides the default 1MB.
2120 The relocations tend to make the kernel binary about 10% larger,
2121 but are discarded at runtime.
2123 One use is for the kexec on panic case where the recovery kernel
2124 must live at a different physical address than the primary
2127 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2128 it has been loaded at and the compile time physical address
2129 (CONFIG_PHYSICAL_START) is used as the minimum location.
2131 config RANDOMIZE_BASE
2132 bool "Randomize the address of the kernel image (KASLR)"
2133 depends on RELOCATABLE
2136 In support of Kernel Address Space Layout Randomization (KASLR),
2137 this randomizes the physical address at which the kernel image
2138 is decompressed and the virtual address where the kernel
2139 image is mapped, as a security feature that deters exploit
2140 attempts relying on knowledge of the location of kernel
2143 On 64-bit, the kernel physical and virtual addresses are
2144 randomized separately. The physical address will be anywhere
2145 between 16MB and the top of physical memory (up to 64TB). The
2146 virtual address will be randomized from 16MB up to 1GB (9 bits
2147 of entropy). Note that this also reduces the memory space
2148 available to kernel modules from 1.5GB to 1GB.
2150 On 32-bit, the kernel physical and virtual addresses are
2151 randomized together. They will be randomized from 16MB up to
2152 512MB (8 bits of entropy).
2154 Entropy is generated using the RDRAND instruction if it is
2155 supported. If RDTSC is supported, its value is mixed into
2156 the entropy pool as well. If neither RDRAND nor RDTSC are
2157 supported, then entropy is read from the i8254 timer. The
2158 usable entropy is limited by the kernel being built using
2159 2GB addressing, and that PHYSICAL_ALIGN must be at a
2160 minimum of 2MB. As a result, only 10 bits of entropy are
2161 theoretically possible, but the implementations are further
2162 limited due to memory layouts.
2166 # Relocation on x86 needs some additional build support
2167 config X86_NEED_RELOCS
2169 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2171 config PHYSICAL_ALIGN
2172 hex "Alignment value to which kernel should be aligned"
2174 range 0x2000 0x1000000 if X86_32
2175 range 0x200000 0x1000000 if X86_64
2177 This value puts the alignment restrictions on physical address
2178 where kernel is loaded and run from. Kernel is compiled for an
2179 address which meets above alignment restriction.
2181 If bootloader loads the kernel at a non-aligned address and
2182 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2183 address aligned to above value and run from there.
2185 If bootloader loads the kernel at a non-aligned address and
2186 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2187 load address and decompress itself to the address it has been
2188 compiled for and run from there. The address for which kernel is
2189 compiled already meets above alignment restrictions. Hence the
2190 end result is that kernel runs from a physical address meeting
2191 above alignment restrictions.
2193 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2194 this value must be a multiple of 0x200000.
2196 Don't change this unless you know what you are doing.
2198 config DYNAMIC_MEMORY_LAYOUT
2201 This option makes base addresses of vmalloc and vmemmap as well as
2202 __PAGE_OFFSET movable during boot.
2204 config RANDOMIZE_MEMORY
2205 bool "Randomize the kernel memory sections"
2207 depends on RANDOMIZE_BASE
2208 select DYNAMIC_MEMORY_LAYOUT
2209 default RANDOMIZE_BASE
2211 Randomizes the base virtual address of kernel memory sections
2212 (physical memory mapping, vmalloc & vmemmap). This security feature
2213 makes exploits relying on predictable memory locations less reliable.
2215 The order of allocations remains unchanged. Entropy is generated in
2216 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2217 configuration have in average 30,000 different possible virtual
2218 addresses for each memory section.
2222 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2223 hex "Physical memory mapping padding" if EXPERT
2224 depends on RANDOMIZE_MEMORY
2225 default "0xa" if MEMORY_HOTPLUG
2227 range 0x1 0x40 if MEMORY_HOTPLUG
2230 Define the padding in terabytes added to the existing physical
2231 memory size during kernel memory randomization. It is useful
2232 for memory hotplug support but reduces the entropy available for
2233 address randomization.
2235 If unsure, leave at the default value.
2241 config BOOTPARAM_HOTPLUG_CPU0
2242 bool "Set default setting of cpu0_hotpluggable"
2243 depends on HOTPLUG_CPU
2245 Set whether default state of cpu0_hotpluggable is on or off.
2247 Say Y here to enable CPU0 hotplug by default. If this switch
2248 is turned on, there is no need to give cpu0_hotplug kernel
2249 parameter and the CPU0 hotplug feature is enabled by default.
2251 Please note: there are two known CPU0 dependencies if you want
2252 to enable the CPU0 hotplug feature either by this switch or by
2253 cpu0_hotplug kernel parameter.
2255 First, resume from hibernate or suspend always starts from CPU0.
2256 So hibernate and suspend are prevented if CPU0 is offline.
2258 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2259 offline if any interrupt can not migrate out of CPU0. There may
2260 be other CPU0 dependencies.
2262 Please make sure the dependencies are under your control before
2263 you enable this feature.
2265 Say N if you don't want to enable CPU0 hotplug feature by default.
2266 You still can enable the CPU0 hotplug feature at boot by kernel
2267 parameter cpu0_hotplug.
2269 config DEBUG_HOTPLUG_CPU0
2271 prompt "Debug CPU0 hotplug"
2272 depends on HOTPLUG_CPU
2274 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2275 soon as possible and boots up userspace with CPU0 offlined. User
2276 can online CPU0 back after boot time.
2278 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2279 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2280 compilation or giving cpu0_hotplug kernel parameter at boot.
2286 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2287 depends on COMPAT_32
2289 Certain buggy versions of glibc will crash if they are
2290 presented with a 32-bit vDSO that is not mapped at the address
2291 indicated in its segment table.
2293 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2294 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2295 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2296 the only released version with the bug, but OpenSUSE 9
2297 contains a buggy "glibc 2.3.2".
2299 The symptom of the bug is that everything crashes on startup, saying:
2300 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2302 Saying Y here changes the default value of the vdso32 boot
2303 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2304 This works around the glibc bug but hurts performance.
2306 If unsure, say N: if you are compiling your own kernel, you
2307 are unlikely to be using a buggy version of glibc.
2310 prompt "vsyscall table for legacy applications"
2312 default LEGACY_VSYSCALL_XONLY
2314 Legacy user code that does not know how to find the vDSO expects
2315 to be able to issue three syscalls by calling fixed addresses in
2316 kernel space. Since this location is not randomized with ASLR,
2317 it can be used to assist security vulnerability exploitation.
2319 This setting can be changed at boot time via the kernel command
2320 line parameter vsyscall=[emulate|xonly|none].
2322 On a system with recent enough glibc (2.14 or newer) and no
2323 static binaries, you can say None without a performance penalty
2324 to improve security.
2326 If unsure, select "Emulate execution only".
2328 config LEGACY_VSYSCALL_EMULATE
2329 bool "Full emulation"
2331 The kernel traps and emulates calls into the fixed vsyscall
2332 address mapping. This makes the mapping non-executable, but
2333 it still contains readable known contents, which could be
2334 used in certain rare security vulnerability exploits. This
2335 configuration is recommended when using legacy userspace
2336 that still uses vsyscalls along with legacy binary
2337 instrumentation tools that require code to be readable.
2339 An example of this type of legacy userspace is running
2340 Pin on an old binary that still uses vsyscalls.
2342 config LEGACY_VSYSCALL_XONLY
2343 bool "Emulate execution only"
2345 The kernel traps and emulates calls into the fixed vsyscall
2346 address mapping and does not allow reads. This
2347 configuration is recommended when userspace might use the
2348 legacy vsyscall area but support for legacy binary
2349 instrumentation of legacy code is not needed. It mitigates
2350 certain uses of the vsyscall area as an ASLR-bypassing
2353 config LEGACY_VSYSCALL_NONE
2356 There will be no vsyscall mapping at all. This will
2357 eliminate any risk of ASLR bypass due to the vsyscall
2358 fixed address mapping. Attempts to use the vsyscalls
2359 will be reported to dmesg, so that either old or
2360 malicious userspace programs can be identified.
2365 bool "Built-in kernel command line"
2367 Allow for specifying boot arguments to the kernel at
2368 build time. On some systems (e.g. embedded ones), it is
2369 necessary or convenient to provide some or all of the
2370 kernel boot arguments with the kernel itself (that is,
2371 to not rely on the boot loader to provide them.)
2373 To compile command line arguments into the kernel,
2374 set this option to 'Y', then fill in the
2375 boot arguments in CONFIG_CMDLINE.
2377 Systems with fully functional boot loaders (i.e. non-embedded)
2378 should leave this option set to 'N'.
2381 string "Built-in kernel command string"
2382 depends on CMDLINE_BOOL
2385 Enter arguments here that should be compiled into the kernel
2386 image and used at boot time. If the boot loader provides a
2387 command line at boot time, it is appended to this string to
2388 form the full kernel command line, when the system boots.
2390 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2391 change this behavior.
2393 In most cases, the command line (whether built-in or provided
2394 by the boot loader) should specify the device for the root
2397 config CMDLINE_OVERRIDE
2398 bool "Built-in command line overrides boot loader arguments"
2399 depends on CMDLINE_BOOL && CMDLINE != ""
2401 Set this option to 'Y' to have the kernel ignore the boot loader
2402 command line, and use ONLY the built-in command line.
2404 This is used to work around broken boot loaders. This should
2405 be set to 'N' under normal conditions.
2407 config MODIFY_LDT_SYSCALL
2408 bool "Enable the LDT (local descriptor table)" if EXPERT
2411 Linux can allow user programs to install a per-process x86
2412 Local Descriptor Table (LDT) using the modify_ldt(2) system
2413 call. This is required to run 16-bit or segmented code such as
2414 DOSEMU or some Wine programs. It is also used by some very old
2415 threading libraries.
2417 Enabling this feature adds a small amount of overhead to
2418 context switches and increases the low-level kernel attack
2419 surface. Disabling it removes the modify_ldt(2) system call.
2421 Saying 'N' here may make sense for embedded or server kernels.
2423 source "kernel/livepatch/Kconfig"
2427 config ARCH_HAS_ADD_PAGES
2429 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2431 config ARCH_ENABLE_MEMORY_HOTPLUG
2433 depends on X86_64 || (X86_32 && HIGHMEM)
2435 config ARCH_ENABLE_MEMORY_HOTREMOVE
2437 depends on MEMORY_HOTPLUG
2439 config USE_PERCPU_NUMA_NODE_ID
2443 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2445 depends on X86_64 || X86_PAE
2447 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2449 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2451 config ARCH_ENABLE_THP_MIGRATION
2453 depends on X86_64 && TRANSPARENT_HUGEPAGE
2455 menu "Power management and ACPI options"
2457 config ARCH_HIBERNATION_HEADER
2459 depends on HIBERNATION
2461 source "kernel/power/Kconfig"
2463 source "drivers/acpi/Kconfig"
2470 tristate "APM (Advanced Power Management) BIOS support"
2471 depends on X86_32 && PM_SLEEP
2473 APM is a BIOS specification for saving power using several different
2474 techniques. This is mostly useful for battery powered laptops with
2475 APM compliant BIOSes. If you say Y here, the system time will be
2476 reset after a RESUME operation, the /proc/apm device will provide
2477 battery status information, and user-space programs will receive
2478 notification of APM "events" (e.g. battery status change).
2480 If you select "Y" here, you can disable actual use of the APM
2481 BIOS by passing the "apm=off" option to the kernel at boot time.
2483 Note that the APM support is almost completely disabled for
2484 machines with more than one CPU.
2486 In order to use APM, you will need supporting software. For location
2487 and more information, read <file:Documentation/power/apm-acpi.rst>
2488 and the Battery Powered Linux mini-HOWTO, available from
2489 <http://www.tldp.org/docs.html#howto>.
2491 This driver does not spin down disk drives (see the hdparm(8)
2492 manpage ("man 8 hdparm") for that), and it doesn't turn off
2493 VESA-compliant "green" monitors.
2495 This driver does not support the TI 4000M TravelMate and the ACER
2496 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2497 desktop machines also don't have compliant BIOSes, and this driver
2498 may cause those machines to panic during the boot phase.
2500 Generally, if you don't have a battery in your machine, there isn't
2501 much point in using this driver and you should say N. If you get
2502 random kernel OOPSes or reboots that don't seem to be related to
2503 anything, try disabling/enabling this option (or disabling/enabling
2506 Some other things you should try when experiencing seemingly random,
2509 1) make sure that you have enough swap space and that it is
2511 2) pass the "no-hlt" option to the kernel
2512 3) switch on floating point emulation in the kernel and pass
2513 the "no387" option to the kernel
2514 4) pass the "floppy=nodma" option to the kernel
2515 5) pass the "mem=4M" option to the kernel (thereby disabling
2516 all but the first 4 MB of RAM)
2517 6) make sure that the CPU is not over clocked.
2518 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2519 8) disable the cache from your BIOS settings
2520 9) install a fan for the video card or exchange video RAM
2521 10) install a better fan for the CPU
2522 11) exchange RAM chips
2523 12) exchange the motherboard.
2525 To compile this driver as a module, choose M here: the
2526 module will be called apm.
2530 config APM_IGNORE_USER_SUSPEND
2531 bool "Ignore USER SUSPEND"
2533 This option will ignore USER SUSPEND requests. On machines with a
2534 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2535 series notebooks, it is necessary to say Y because of a BIOS bug.
2537 config APM_DO_ENABLE
2538 bool "Enable PM at boot time"
2540 Enable APM features at boot time. From page 36 of the APM BIOS
2541 specification: "When disabled, the APM BIOS does not automatically
2542 power manage devices, enter the Standby State, enter the Suspend
2543 State, or take power saving steps in response to CPU Idle calls."
2544 This driver will make CPU Idle calls when Linux is idle (unless this
2545 feature is turned off -- see "Do CPU IDLE calls", below). This
2546 should always save battery power, but more complicated APM features
2547 will be dependent on your BIOS implementation. You may need to turn
2548 this option off if your computer hangs at boot time when using APM
2549 support, or if it beeps continuously instead of suspending. Turn
2550 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2551 T400CDT. This is off by default since most machines do fine without
2556 bool "Make CPU Idle calls when idle"
2558 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2559 On some machines, this can activate improved power savings, such as
2560 a slowed CPU clock rate, when the machine is idle. These idle calls
2561 are made after the idle loop has run for some length of time (e.g.,
2562 333 mS). On some machines, this will cause a hang at boot time or
2563 whenever the CPU becomes idle. (On machines with more than one CPU,
2564 this option does nothing.)
2566 config APM_DISPLAY_BLANK
2567 bool "Enable console blanking using APM"
2569 Enable console blanking using the APM. Some laptops can use this to
2570 turn off the LCD backlight when the screen blanker of the Linux
2571 virtual console blanks the screen. Note that this is only used by
2572 the virtual console screen blanker, and won't turn off the backlight
2573 when using the X Window system. This also doesn't have anything to
2574 do with your VESA-compliant power-saving monitor. Further, this
2575 option doesn't work for all laptops -- it might not turn off your
2576 backlight at all, or it might print a lot of errors to the console,
2577 especially if you are using gpm.
2579 config APM_ALLOW_INTS
2580 bool "Allow interrupts during APM BIOS calls"
2582 Normally we disable external interrupts while we are making calls to
2583 the APM BIOS as a measure to lessen the effects of a badly behaving
2584 BIOS implementation. The BIOS should reenable interrupts if it
2585 needs to. Unfortunately, some BIOSes do not -- especially those in
2586 many of the newer IBM Thinkpads. If you experience hangs when you
2587 suspend, try setting this to Y. Otherwise, say N.
2591 source "drivers/cpufreq/Kconfig"
2593 source "drivers/cpuidle/Kconfig"
2595 source "drivers/idle/Kconfig"
2600 menu "Bus options (PCI etc.)"
2603 prompt "PCI access mode"
2604 depends on X86_32 && PCI
2607 On PCI systems, the BIOS can be used to detect the PCI devices and
2608 determine their configuration. However, some old PCI motherboards
2609 have BIOS bugs and may crash if this is done. Also, some embedded
2610 PCI-based systems don't have any BIOS at all. Linux can also try to
2611 detect the PCI hardware directly without using the BIOS.
2613 With this option, you can specify how Linux should detect the
2614 PCI devices. If you choose "BIOS", the BIOS will be used,
2615 if you choose "Direct", the BIOS won't be used, and if you
2616 choose "MMConfig", then PCI Express MMCONFIG will be used.
2617 If you choose "Any", the kernel will try MMCONFIG, then the
2618 direct access method and falls back to the BIOS if that doesn't
2619 work. If unsure, go with the default, which is "Any".
2624 config PCI_GOMMCONFIG
2641 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2643 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2646 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2649 bool "Support mmconfig PCI config space access" if X86_64
2651 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2652 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2656 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2660 depends on PCI && XEN
2663 config MMCONF_FAM10H
2665 depends on X86_64 && PCI_MMCONFIG && ACPI
2667 config PCI_CNB20LE_QUIRK
2668 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2671 Read the PCI windows out of the CNB20LE host bridge. This allows
2672 PCI hotplug to work on systems with the CNB20LE chipset which do
2675 There's no public spec for this chipset, and this functionality
2676 is known to be incomplete.
2678 You should say N unless you know you need this.
2681 bool "ISA bus support on modern systems" if EXPERT
2683 Expose ISA bus device drivers and options available for selection and
2684 configuration. Enable this option if your target machine has an ISA
2685 bus. ISA is an older system, displaced by PCI and newer bus
2686 architectures -- if your target machine is modern, it probably does
2687 not have an ISA bus.
2691 # x86_64 have no ISA slots, but can have ISA-style DMA.
2693 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2696 Enables ISA-style DMA support for devices requiring such controllers.
2704 Find out whether you have ISA slots on your motherboard. ISA is the
2705 name of a bus system, i.e. the way the CPU talks to the other stuff
2706 inside your box. Other bus systems are PCI, EISA, MicroChannel
2707 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2708 newer boards don't support it. If you have ISA, say Y, otherwise N.
2711 tristate "NatSemi SCx200 support"
2713 This provides basic support for National Semiconductor's
2714 (now AMD's) Geode processors. The driver probes for the
2715 PCI-IDs of several on-chip devices, so its a good dependency
2716 for other scx200_* drivers.
2718 If compiled as a module, the driver is named scx200.
2720 config SCx200HR_TIMER
2721 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2725 This driver provides a clocksource built upon the on-chip
2726 27MHz high-resolution timer. Its also a workaround for
2727 NSC Geode SC-1100's buggy TSC, which loses time when the
2728 processor goes idle (as is done by the scheduler). The
2729 other workaround is idle=poll boot option.
2732 bool "One Laptop Per Child support"
2740 Add support for detecting the unique features of the OLPC
2744 bool "OLPC XO-1 Power Management"
2745 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2747 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2750 bool "OLPC XO-1 Real Time Clock"
2751 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2753 Add support for the XO-1 real time clock, which can be used as a
2754 programmable wakeup source.
2757 bool "OLPC XO-1 SCI extras"
2758 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2762 Add support for SCI-based features of the OLPC XO-1 laptop:
2763 - EC-driven system wakeups
2767 - AC adapter status updates
2768 - Battery status updates
2770 config OLPC_XO15_SCI
2771 bool "OLPC XO-1.5 SCI extras"
2772 depends on OLPC && ACPI
2775 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2776 - EC-driven system wakeups
2777 - AC adapter status updates
2778 - Battery status updates
2781 bool "PCEngines ALIX System Support (LED setup)"
2784 This option enables system support for the PCEngines ALIX.
2785 At present this just sets up LEDs for GPIO control on
2786 ALIX2/3/6 boards. However, other system specific setup should
2789 Note: You must still enable the drivers for GPIO and LED support
2790 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2792 Note: You have to set alix.force=1 for boards with Award BIOS.
2795 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2798 This option enables system support for the Soekris Engineering net5501.
2801 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2805 This option enables system support for the Traverse Technologies GEOS.
2808 bool "Technologic Systems TS-5500 platform support"
2810 select CHECK_SIGNATURE
2814 This option enables system support for the Technologic Systems TS-5500.
2820 depends on CPU_SUP_AMD && PCI
2823 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2825 Firmwares often provide initial graphics framebuffers so the BIOS,
2826 bootloader or kernel can show basic video-output during boot for
2827 user-guidance and debugging. Historically, x86 used the VESA BIOS
2828 Extensions and EFI-framebuffers for this, which are mostly limited
2830 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2831 framebuffers so the new generic system-framebuffer drivers can be
2832 used on x86. If the framebuffer is not compatible with the generic
2833 modes, it is advertised as fallback platform framebuffer so legacy
2834 drivers like efifb, vesafb and uvesafb can pick it up.
2835 If this option is not selected, all system framebuffers are always
2836 marked as fallback platform framebuffers as usual.
2838 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2839 not be able to pick up generic system framebuffers if this option
2840 is selected. You are highly encouraged to enable simplefb as
2841 replacement if you select this option. simplefb can correctly deal
2842 with generic system framebuffers. But you should still keep vesafb
2843 and others enabled as fallback if a system framebuffer is
2844 incompatible with simplefb.
2851 menu "Binary Emulations"
2853 config IA32_EMULATION
2854 bool "IA32 Emulation"
2856 select ARCH_WANT_OLD_COMPAT_IPC
2858 select COMPAT_OLD_SIGACTION
2860 Include code to run legacy 32-bit programs under a
2861 64-bit kernel. You should likely turn this on, unless you're
2862 100% sure that you don't have any 32-bit programs left.
2865 tristate "IA32 a.out support"
2866 depends on IA32_EMULATION
2869 Support old a.out binaries in the 32bit emulation.
2872 bool "x32 ABI for 64-bit mode"
2875 Include code to run binaries for the x32 native 32-bit ABI
2876 for 64-bit processors. An x32 process gets access to the
2877 full 64-bit register file and wide data path while leaving
2878 pointers at 32 bits for smaller memory footprint.
2880 You will need a recent binutils (2.22 or later) with
2881 elf32_x86_64 support enabled to compile a kernel with this
2886 depends on IA32_EMULATION || X86_32
2888 select OLD_SIGSUSPEND3
2892 depends on IA32_EMULATION || X86_X32
2895 config COMPAT_FOR_U64_ALIGNMENT
2898 config SYSVIPC_COMPAT
2906 config HAVE_ATOMIC_IOMAP
2910 source "drivers/firmware/Kconfig"
2912 source "arch/x86/kvm/Kconfig"
2914 source "arch/x86/Kconfig.assembler"