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
38 config FORCE_DYNAMIC_FTRACE
41 depends on FUNCTION_TRACER
44 We keep the static function tracing (!DYNAMIC_FTRACE) around
45 in order to test the non static function tracing in the
46 generic code, as other architectures still use it. But we
47 only need to keep it around for x86_64. No need to keep it
48 for x86_32. For x86_32, force DYNAMIC_FTRACE.
52 # ( Note that options that are marked 'if X86_64' could in principle be
53 # ported to 32-bit as well. )
58 # Note: keep this list sorted alphabetically
60 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
61 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
62 select ARCH_32BIT_OFF_T if X86_32
63 select ARCH_CLOCKSOURCE_INIT
64 select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
65 select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
66 select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
67 select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
68 select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE)
69 select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
70 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
71 select ARCH_HAS_CACHE_LINE_SIZE
72 select ARCH_HAS_CURRENT_STACK_POINTER
73 select ARCH_HAS_DEBUG_VIRTUAL
74 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
75 select ARCH_HAS_DEVMEM_IS_ALLOWED
76 select ARCH_HAS_EARLY_DEBUG if KGDB
77 select ARCH_HAS_ELF_RANDOMIZE
78 select ARCH_HAS_FAST_MULTIPLIER
79 select ARCH_HAS_FILTER_PGPROT
80 select ARCH_HAS_FORTIFY_SOURCE
81 select ARCH_HAS_GCOV_PROFILE_ALL
82 select ARCH_HAS_KCOV if X86_64
83 select ARCH_HAS_MEM_ENCRYPT
84 select ARCH_HAS_MEMBARRIER_SYNC_CORE
85 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
86 select ARCH_HAS_PMEM_API if X86_64
87 select ARCH_HAS_PTE_DEVMAP if X86_64
88 select ARCH_HAS_PTE_SPECIAL
89 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
90 select ARCH_HAS_COPY_MC if X86_64
91 select ARCH_HAS_SET_MEMORY
92 select ARCH_HAS_SET_DIRECT_MAP
93 select ARCH_HAS_STRICT_KERNEL_RWX
94 select ARCH_HAS_STRICT_MODULE_RWX
95 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
96 select ARCH_HAS_SYSCALL_WRAPPER
97 select ARCH_HAS_UBSAN_SANITIZE_ALL
98 select ARCH_HAS_DEBUG_WX
99 select ARCH_HAS_ZONE_DMA_SET if EXPERT
100 select ARCH_HAVE_NMI_SAFE_CMPXCHG
101 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
102 select ARCH_MIGHT_HAVE_PC_PARPORT
103 select ARCH_MIGHT_HAVE_PC_SERIO
104 select ARCH_STACKWALK
105 select ARCH_SUPPORTS_ACPI
106 select ARCH_SUPPORTS_ATOMIC_RMW
107 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
108 select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64
109 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
110 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
111 select ARCH_SUPPORTS_LTO_CLANG
112 select ARCH_SUPPORTS_LTO_CLANG_THIN
113 select ARCH_USE_BUILTIN_BSWAP
114 select ARCH_USE_MEMTEST
115 select ARCH_USE_QUEUED_RWLOCKS
116 select ARCH_USE_QUEUED_SPINLOCKS
117 select ARCH_USE_SYM_ANNOTATIONS
118 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
119 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
120 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
121 select ARCH_WANTS_NO_INSTR
122 select ARCH_WANT_GENERAL_HUGETLB
123 select ARCH_WANT_HUGE_PMD_SHARE
124 select ARCH_WANT_LD_ORPHAN_WARN
125 select ARCH_WANTS_RT_DELAYED_SIGNALS
126 select ARCH_WANTS_THP_SWAP if X86_64
127 select ARCH_HAS_PARANOID_L1D_FLUSH
128 select BUILDTIME_TABLE_SORT
130 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
131 select CLOCKSOURCE_WATCHDOG
132 select DCACHE_WORD_ACCESS
133 select DYNAMIC_SIGFRAME
134 select EDAC_ATOMIC_SCRUB
136 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
137 select GENERIC_CLOCKEVENTS_MIN_ADJUST
138 select GENERIC_CMOS_UPDATE
139 select GENERIC_CPU_AUTOPROBE
140 select GENERIC_CPU_VULNERABILITIES
141 select GENERIC_EARLY_IOREMAP
144 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
145 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
146 select GENERIC_IRQ_MIGRATION if SMP
147 select GENERIC_IRQ_PROBE
148 select GENERIC_IRQ_RESERVATION_MODE
149 select GENERIC_IRQ_SHOW
150 select GENERIC_PENDING_IRQ if SMP
151 select GENERIC_PTDUMP
152 select GENERIC_SMP_IDLE_THREAD
153 select GENERIC_TIME_VSYSCALL
154 select GENERIC_GETTIMEOFDAY
155 select GENERIC_VDSO_TIME_NS
156 select GUP_GET_PTE_LOW_HIGH if X86_PAE
157 select HARDIRQS_SW_RESEND
158 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
159 select HAVE_ACPI_APEI if ACPI
160 select HAVE_ACPI_APEI_NMI if ACPI
161 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
162 select HAVE_ARCH_AUDITSYSCALL
163 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
164 select HAVE_ARCH_JUMP_LABEL
165 select HAVE_ARCH_JUMP_LABEL_RELATIVE
166 select HAVE_ARCH_KASAN if X86_64
167 select HAVE_ARCH_KASAN_VMALLOC if X86_64
168 select HAVE_ARCH_KFENCE
169 select HAVE_ARCH_KGDB
170 select HAVE_ARCH_MMAP_RND_BITS if MMU
171 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
172 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
173 select HAVE_ARCH_PREL32_RELOCATIONS
174 select HAVE_ARCH_SECCOMP_FILTER
175 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
176 select HAVE_ARCH_STACKLEAK
177 select HAVE_ARCH_TRACEHOOK
178 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
179 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
180 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
181 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
182 select HAVE_ARCH_VMAP_STACK if X86_64
183 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
184 select HAVE_ARCH_WITHIN_STACK_FRAMES
185 select HAVE_ASM_MODVERSIONS
186 select HAVE_CMPXCHG_DOUBLE
187 select HAVE_CMPXCHG_LOCAL
188 select HAVE_CONTEXT_TRACKING if X86_64
189 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
190 select HAVE_C_RECORDMCOUNT
191 select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION
192 select HAVE_BUILDTIME_MCOUNT_SORT
193 select HAVE_DEBUG_KMEMLEAK
194 select HAVE_DMA_CONTIGUOUS
195 select HAVE_DYNAMIC_FTRACE
196 select HAVE_DYNAMIC_FTRACE_WITH_REGS
197 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
198 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
199 select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
200 select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
202 select HAVE_EFFICIENT_UNALIGNED_ACCESS
204 select HAVE_EXIT_THREAD
206 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
207 select HAVE_FTRACE_MCOUNT_RECORD
208 select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
209 select HAVE_FUNCTION_TRACER
210 select HAVE_GCC_PLUGINS
211 select HAVE_HW_BREAKPOINT
212 select HAVE_IOREMAP_PROT
213 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
214 select HAVE_IRQ_TIME_ACCOUNTING
215 select HAVE_KERNEL_BZIP2
216 select HAVE_KERNEL_GZIP
217 select HAVE_KERNEL_LZ4
218 select HAVE_KERNEL_LZMA
219 select HAVE_KERNEL_LZO
220 select HAVE_KERNEL_XZ
221 select HAVE_KERNEL_ZSTD
223 select HAVE_KPROBES_ON_FTRACE
224 select HAVE_FUNCTION_ERROR_INJECTION
225 select HAVE_KRETPROBES
227 select HAVE_LIVEPATCH if X86_64
228 select HAVE_MIXED_BREAKPOINTS_REGS
229 select HAVE_MOD_ARCH_SPECIFIC
233 select HAVE_OPTPROBES
234 select HAVE_PCSPKR_PLATFORM
235 select HAVE_PERF_EVENTS
236 select HAVE_PERF_EVENTS_NMI
237 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
239 select HAVE_PERF_REGS
240 select HAVE_PERF_USER_STACK_DUMP
241 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
242 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
243 select HAVE_REGS_AND_STACK_ACCESS_API
244 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
245 select HAVE_FUNCTION_ARG_ACCESS_API
246 select HAVE_SETUP_PER_CPU_AREA
247 select HAVE_SOFTIRQ_ON_OWN_STACK
248 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
249 select HAVE_STACK_VALIDATION if X86_64
250 select HAVE_STATIC_CALL
251 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
252 select HAVE_PREEMPT_DYNAMIC_CALL
254 select HAVE_SYSCALL_TRACEPOINTS
255 select HAVE_UNSTABLE_SCHED_CLOCK
256 select HAVE_USER_RETURN_NOTIFIER
257 select HAVE_GENERIC_VDSO
258 select HOTPLUG_SMT if SMP
259 select IRQ_FORCED_THREADING
260 select NEED_PER_CPU_EMBED_FIRST_CHUNK
261 select NEED_PER_CPU_PAGE_FIRST_CHUNK
262 select NEED_SG_DMA_LENGTH
263 select PCI_DOMAINS if PCI
264 select PCI_LOCKLESS_CONFIG if PCI
267 select RTC_MC146818_LIB
270 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
271 select SYSCTL_EXCEPTION_TRACE
272 select THREAD_INFO_IN_TASK
273 select TRACE_IRQFLAGS_SUPPORT
274 select USER_STACKTRACE_SUPPORT
276 select HAVE_ARCH_KCSAN if X86_64
277 select X86_FEATURE_NAMES if PROC_FS
278 select PROC_PID_ARCH_STATUS if PROC_FS
279 select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
280 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
282 config INSTRUCTION_DECODER
284 depends on KPROBES || PERF_EVENTS || UPROBES
288 default "elf32-i386" if X86_32
289 default "elf64-x86-64" if X86_64
291 config LOCKDEP_SUPPORT
294 config STACKTRACE_SUPPORT
300 config ARCH_MMAP_RND_BITS_MIN
304 config ARCH_MMAP_RND_BITS_MAX
308 config ARCH_MMAP_RND_COMPAT_BITS_MIN
311 config ARCH_MMAP_RND_COMPAT_BITS_MAX
317 config GENERIC_ISA_DMA
319 depends on ISA_DMA_API
324 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
326 config GENERIC_BUG_RELATIVE_POINTERS
329 config ARCH_MAY_HAVE_PC_FDC
331 depends on ISA_DMA_API
333 config GENERIC_CALIBRATE_DELAY
336 config ARCH_HAS_CPU_RELAX
339 config ARCH_HAS_FILTER_PGPROT
342 config ARCH_HIBERNATION_POSSIBLE
347 default 1024 if X86_64
350 config ARCH_SUSPEND_POSSIBLE
356 config KASAN_SHADOW_OFFSET
359 default 0xdffffc0000000000
361 config HAVE_INTEL_TXT
363 depends on INTEL_IOMMU && ACPI
367 depends on X86_32 && SMP
371 depends on X86_64 && SMP
373 config ARCH_SUPPORTS_UPROBES
376 config FIX_EARLYCON_MEM
379 config DYNAMIC_PHYSICAL_MASK
382 config PGTABLE_LEVELS
384 default 5 if X86_5LEVEL
389 config CC_HAS_SANE_STACKPROTECTOR
391 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
392 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
394 We have to make sure stack protector is unconditionally disabled if
395 the compiler produces broken code or if it does not let us control
396 the segment on 32-bit kernels.
398 menu "Processor type and features"
401 bool "Symmetric multi-processing support"
403 This enables support for systems with more than one CPU. If you have
404 a system with only one CPU, say N. If you have a system with more
407 If you say N here, the kernel will run on uni- and multiprocessor
408 machines, but will use only one CPU of a multiprocessor machine. If
409 you say Y here, the kernel will run on many, but not all,
410 uniprocessor machines. On a uniprocessor machine, the kernel
411 will run faster if you say N here.
413 Note that if you say Y here and choose architecture "586" or
414 "Pentium" under "Processor family", the kernel will not work on 486
415 architectures. Similarly, multiprocessor kernels for the "PPro"
416 architecture may not work on all Pentium based boards.
418 People using multiprocessor machines who say Y here should also say
419 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
420 Management" code will be disabled if you say Y here.
422 See also <file:Documentation/x86/i386/IO-APIC.rst>,
423 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
424 <http://www.tldp.org/docs.html#howto>.
426 If you don't know what to do here, say N.
428 config X86_FEATURE_NAMES
429 bool "Processor feature human-readable names" if EMBEDDED
432 This option compiles in a table of x86 feature bits and corresponding
433 names. This is required to support /proc/cpuinfo and a few kernel
434 messages. You can disable this to save space, at the expense of
435 making those few kernel messages show numeric feature bits instead.
440 bool "Support x2apic"
441 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
443 This enables x2apic support on CPUs that have this feature.
445 This allows 32-bit apic IDs (so it can support very large systems),
446 and accesses the local apic via MSRs not via mmio.
448 If you don't know what to do here, say N.
451 bool "Enable MPS table" if ACPI
453 depends on X86_LOCAL_APIC
455 For old smp systems that do not have proper acpi support. Newer systems
456 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
460 depends on X86_GOLDFISH
463 bool "Avoid speculative indirect branches in kernel"
466 Compile kernel with the retpoline compiler options to guard against
467 kernel-to-user data leaks by avoiding speculative indirect
468 branches. Requires a compiler with -mindirect-branch=thunk-extern
469 support for full protection. The kernel may run slower.
472 def_bool $(cc-option,-mharden-sls=all)
475 bool "Mitigate Straight-Line-Speculation"
476 depends on CC_HAS_SLS && X86_64
479 Compile the kernel with straight-line-speculation options to guard
480 against straight line speculation. The kernel image might be slightly
483 config X86_CPU_RESCTRL
484 bool "x86 CPU resource control support"
485 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
487 select PROC_CPU_RESCTRL if PROC_FS
489 Enable x86 CPU resource control support.
491 Provide support for the allocation and monitoring of system resources
494 Intel calls this Intel Resource Director Technology
495 (Intel(R) RDT). More information about RDT can be found in the
496 Intel x86 Architecture Software Developer Manual.
498 AMD calls this AMD Platform Quality of Service (AMD QoS).
499 More information about AMD QoS can be found in the AMD64 Technology
500 Platform Quality of Service Extensions manual.
506 bool "Support for big SMP systems with more than 8 CPUs"
509 This option is needed for the systems that have more than 8 CPUs.
511 config X86_EXTENDED_PLATFORM
512 bool "Support for extended (non-PC) x86 platforms"
515 If you disable this option then the kernel will only support
516 standard PC platforms. (which covers the vast majority of
519 If you enable this option then you'll be able to select support
520 for the following (non-PC) 32 bit x86 platforms:
521 Goldfish (Android emulator)
524 SGI 320/540 (Visual Workstation)
525 STA2X11-based (e.g. Northville)
526 Moorestown MID devices
528 If you have one of these systems, or if you want to build a
529 generic distribution kernel, say Y here - otherwise say N.
533 config X86_EXTENDED_PLATFORM
534 bool "Support for extended (non-PC) x86 platforms"
537 If you disable this option then the kernel will only support
538 standard PC platforms. (which covers the vast majority of
541 If you enable this option then you'll be able to select support
542 for the following (non-PC) 64 bit x86 platforms:
547 If you have one of these systems, or if you want to build a
548 generic distribution kernel, say Y here - otherwise say N.
550 # This is an alphabetically sorted list of 64 bit extended platforms
551 # Please maintain the alphabetic order if and when there are additions
553 bool "Numascale NumaChip"
555 depends on X86_EXTENDED_PLATFORM
558 depends on X86_X2APIC
559 depends on PCI_MMCONFIG
561 Adds support for Numascale NumaChip large-SMP systems. Needed to
562 enable more than ~168 cores.
563 If you don't have one of these, you should say N here.
567 select HYPERVISOR_GUEST
569 depends on X86_64 && PCI
570 depends on X86_EXTENDED_PLATFORM
573 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
574 supposed to run on these EM64T-based machines. Only choose this option
575 if you have one of these machines.
578 bool "SGI Ultraviolet"
580 depends on X86_EXTENDED_PLATFORM
583 depends on KEXEC_CORE
584 depends on X86_X2APIC
587 This option is needed in order to support SGI Ultraviolet systems.
588 If you don't have one of these, you should say N here.
590 # Following is an alphabetically sorted list of 32 bit extended platforms
591 # Please maintain the alphabetic order if and when there are additions
594 bool "Goldfish (Virtual Platform)"
595 depends on X86_EXTENDED_PLATFORM
597 Enable support for the Goldfish virtual platform used primarily
598 for Android development. Unless you are building for the Android
599 Goldfish emulator say N here.
602 bool "CE4100 TV platform"
604 depends on PCI_GODIRECT
605 depends on X86_IO_APIC
607 depends on X86_EXTENDED_PLATFORM
608 select X86_REBOOTFIXUPS
610 select OF_EARLY_FLATTREE
612 Select for the Intel CE media processor (CE4100) SOC.
613 This option compiles in support for the CE4100 SOC for settop
614 boxes and media devices.
617 bool "Intel MID platform support"
618 depends on X86_EXTENDED_PLATFORM
619 depends on X86_PLATFORM_DEVICES
621 depends on X86_64 || (PCI_GOANY && X86_32)
622 depends on X86_IO_APIC
627 Select to build a kernel capable of supporting Intel MID (Mobile
628 Internet Device) platform systems which do not have the PCI legacy
629 interfaces. If you are building for a PC class system say N here.
631 Intel MID platforms are based on an Intel processor and chipset which
632 consume less power than most of the x86 derivatives.
634 config X86_INTEL_QUARK
635 bool "Intel Quark platform support"
637 depends on X86_EXTENDED_PLATFORM
638 depends on X86_PLATFORM_DEVICES
642 depends on X86_IO_APIC
647 Select to include support for Quark X1000 SoC.
648 Say Y here if you have a Quark based system such as the Arduino
649 compatible Intel Galileo.
651 config X86_INTEL_LPSS
652 bool "Intel Low Power Subsystem Support"
653 depends on X86 && ACPI && PCI
658 Select to build support for Intel Low Power Subsystem such as
659 found on Intel Lynxpoint PCH. Selecting this option enables
660 things like clock tree (common clock framework) and pincontrol
661 which are needed by the LPSS peripheral drivers.
663 config X86_AMD_PLATFORM_DEVICE
664 bool "AMD ACPI2Platform devices support"
669 Select to interpret AMD specific ACPI device to platform device
670 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
671 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
672 implemented under PINCTRL subsystem.
675 tristate "Intel SoC IOSF Sideband support for SoC platforms"
678 This option enables sideband register access support for Intel SoC
679 platforms. On these platforms the IOSF sideband is used in lieu of
680 MSR's for some register accesses, mostly but not limited to thermal
681 and power. Drivers may query the availability of this device to
682 determine if they need the sideband in order to work on these
683 platforms. The sideband is available on the following SoC products.
684 This list is not meant to be exclusive.
689 You should say Y if you are running a kernel on one of these SoC's.
691 config IOSF_MBI_DEBUG
692 bool "Enable IOSF sideband access through debugfs"
693 depends on IOSF_MBI && DEBUG_FS
695 Select this option to expose the IOSF sideband access registers (MCR,
696 MDR, MCRX) through debugfs to write and read register information from
697 different units on the SoC. This is most useful for obtaining device
698 state information for debug and analysis. As this is a general access
699 mechanism, users of this option would have specific knowledge of the
700 device they want to access.
702 If you don't require the option or are in doubt, say N.
705 bool "RDC R-321x SoC"
707 depends on X86_EXTENDED_PLATFORM
709 select X86_REBOOTFIXUPS
711 This option is needed for RDC R-321x system-on-chip, also known
713 If you don't have one of these chips, you should say N here.
715 config X86_32_NON_STANDARD
716 bool "Support non-standard 32-bit SMP architectures"
717 depends on X86_32 && SMP
718 depends on X86_EXTENDED_PLATFORM
720 This option compiles in the bigsmp and STA2X11 default
721 subarchitectures. It is intended for a generic binary
722 kernel. If you select them all, kernel will probe it one by
723 one and will fallback to default.
725 # Alphabetically sorted list of Non standard 32 bit platforms
727 config X86_SUPPORTS_MEMORY_FAILURE
729 # MCE code calls memory_failure():
731 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
732 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
733 depends on X86_64 || !SPARSEMEM
734 select ARCH_SUPPORTS_MEMORY_FAILURE
737 bool "STA2X11 Companion Chip Support"
738 depends on X86_32_NON_STANDARD && PCI
743 This adds support for boards based on the STA2X11 IO-Hub,
744 a.k.a. "ConneXt". The chip is used in place of the standard
745 PC chipset, so all "standard" peripherals are missing. If this
746 option is selected the kernel will still be able to boot on
747 standard PC machines.
750 tristate "Eurobraille/Iris poweroff module"
753 The Iris machines from EuroBraille do not have APM or ACPI support
754 to shut themselves down properly. A special I/O sequence is
755 needed to do so, which is what this module does at
758 This is only for Iris machines from EuroBraille.
762 config SCHED_OMIT_FRAME_POINTER
764 prompt "Single-depth WCHAN output"
767 Calculate simpler /proc/<PID>/wchan values. If this option
768 is disabled then wchan values will recurse back to the
769 caller function. This provides more accurate wchan values,
770 at the expense of slightly more scheduling overhead.
772 If in doubt, say "Y".
774 menuconfig HYPERVISOR_GUEST
775 bool "Linux guest support"
777 Say Y here to enable options for running Linux under various hyper-
778 visors. This option enables basic hypervisor detection and platform
781 If you say N, all options in this submenu will be skipped and
782 disabled, and Linux guest support won't be built in.
787 bool "Enable paravirtualization code"
788 depends on HAVE_STATIC_CALL
790 This changes the kernel so it can modify itself when it is run
791 under a hypervisor, potentially improving performance significantly
792 over full virtualization. However, when run without a hypervisor
793 the kernel is theoretically slower and slightly larger.
798 config PARAVIRT_DEBUG
799 bool "paravirt-ops debugging"
800 depends on PARAVIRT && DEBUG_KERNEL
802 Enable to debug paravirt_ops internals. Specifically, BUG if
803 a paravirt_op is missing when it is called.
805 config PARAVIRT_SPINLOCKS
806 bool "Paravirtualization layer for spinlocks"
807 depends on PARAVIRT && SMP
809 Paravirtualized spinlocks allow a pvops backend to replace the
810 spinlock implementation with something virtualization-friendly
811 (for example, block the virtual CPU rather than spinning).
813 It has a minimal impact on native kernels and gives a nice performance
814 benefit on paravirtualized KVM / Xen kernels.
816 If you are unsure how to answer this question, answer Y.
818 config X86_HV_CALLBACK_VECTOR
821 source "arch/x86/xen/Kconfig"
824 bool "KVM Guest support (including kvmclock)"
826 select PARAVIRT_CLOCK
827 select ARCH_CPUIDLE_HALTPOLL
828 select X86_HV_CALLBACK_VECTOR
831 This option enables various optimizations for running under the KVM
832 hypervisor. It includes a paravirtualized clock, so that instead
833 of relying on a PIT (or probably other) emulation by the
834 underlying device model, the host provides the guest with
835 timing infrastructure such as time of day, and system time
837 config ARCH_CPUIDLE_HALTPOLL
839 prompt "Disable host haltpoll when loading haltpoll driver"
841 If virtualized under KVM, disable host haltpoll.
844 bool "Support for running PVH guests"
846 This option enables the PVH entry point for guest virtual machines
847 as specified in the x86/HVM direct boot ABI.
849 config PARAVIRT_TIME_ACCOUNTING
850 bool "Paravirtual steal time accounting"
853 Select this option to enable fine granularity task steal time
854 accounting. Time spent executing other tasks in parallel with
855 the current vCPU is discounted from the vCPU power. To account for
856 that, there can be a small performance impact.
858 If in doubt, say N here.
860 config PARAVIRT_CLOCK
863 config JAILHOUSE_GUEST
864 bool "Jailhouse non-root cell support"
865 depends on X86_64 && PCI
868 This option allows to run Linux as guest in a Jailhouse non-root
869 cell. You can leave this option disabled if you only want to start
870 Jailhouse and run Linux afterwards in the root cell.
873 bool "ACRN Guest support"
875 select X86_HV_CALLBACK_VECTOR
877 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
878 a flexible, lightweight reference open-source hypervisor, built with
879 real-time and safety-criticality in mind. It is built for embedded
880 IOT with small footprint and real-time features. More details can be
881 found in https://projectacrn.org/.
883 endif #HYPERVISOR_GUEST
885 source "arch/x86/Kconfig.cpu"
889 prompt "HPET Timer Support" if X86_32
891 Use the IA-PC HPET (High Precision Event Timer) to manage
892 time in preference to the PIT and RTC, if a HPET is
894 HPET is the next generation timer replacing legacy 8254s.
895 The HPET provides a stable time base on SMP
896 systems, unlike the TSC, but it is more expensive to access,
897 as it is off-chip. The interface used is documented
898 in the HPET spec, revision 1.
900 You can safely choose Y here. However, HPET will only be
901 activated if the platform and the BIOS support this feature.
902 Otherwise the 8254 will be used for timing services.
904 Choose N to continue using the legacy 8254 timer.
906 config HPET_EMULATE_RTC
908 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
910 # Mark as expert because too many people got it wrong.
911 # The code disables itself when not needed.
914 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
915 bool "Enable DMI scanning" if EXPERT
917 Enabled scanning of DMI to identify machine quirks. Say Y
918 here unless you have verified that your setup is not
919 affected by entries in the DMI blacklist. Required by PNP
923 bool "Old AMD GART IOMMU support"
927 depends on X86_64 && PCI && AMD_NB
929 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
930 GART based hardware IOMMUs.
932 The GART supports full DMA access for devices with 32-bit access
933 limitations, on systems with more than 3 GB. This is usually needed
934 for USB, sound, many IDE/SATA chipsets and some other devices.
936 Newer systems typically have a modern AMD IOMMU, supported via
937 the CONFIG_AMD_IOMMU=y config option.
939 In normal configurations this driver is only active when needed:
940 there's more than 3 GB of memory and the system contains a
941 32-bit limited device.
946 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
947 depends on X86_64 && SMP && DEBUG_KERNEL
948 select CPUMASK_OFFSTACK
950 Enable maximum number of CPUS and NUMA Nodes for this architecture.
954 # The maximum number of CPUs supported:
956 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
957 # and which can be configured interactively in the
958 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
960 # The ranges are different on 32-bit and 64-bit kernels, depending on
961 # hardware capabilities and scalability features of the kernel.
963 # ( If MAXSMP is enabled we just use the highest possible value and disable
964 # interactive configuration. )
967 config NR_CPUS_RANGE_BEGIN
969 default NR_CPUS_RANGE_END if MAXSMP
973 config NR_CPUS_RANGE_END
976 default 64 if SMP && X86_BIGSMP
977 default 8 if SMP && !X86_BIGSMP
980 config NR_CPUS_RANGE_END
983 default 8192 if SMP && CPUMASK_OFFSTACK
984 default 512 if SMP && !CPUMASK_OFFSTACK
987 config NR_CPUS_DEFAULT
990 default 32 if X86_BIGSMP
994 config NR_CPUS_DEFAULT
997 default 8192 if MAXSMP
1002 int "Maximum number of CPUs" if SMP && !MAXSMP
1003 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1004 default NR_CPUS_DEFAULT
1006 This allows you to specify the maximum number of CPUs which this
1007 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1008 supported value is 8192, otherwise the maximum value is 512. The
1009 minimum value which makes sense is 2.
1011 This is purely to save memory: each supported CPU adds about 8KB
1012 to the kernel image.
1014 config SCHED_CLUSTER
1015 bool "Cluster scheduler support"
1019 Cluster scheduler support improves the CPU scheduler's decision
1020 making when dealing with machines that have clusters of CPUs.
1021 Cluster usually means a couple of CPUs which are placed closely
1022 by sharing mid-level caches, last-level cache tags or internal
1030 prompt "Multi-core scheduler support"
1033 Multi-core scheduler support improves the CPU scheduler's decision
1034 making when dealing with multi-core CPU chips at a cost of slightly
1035 increased overhead in some places. If unsure say N here.
1037 config SCHED_MC_PRIO
1038 bool "CPU core priorities scheduler support"
1039 depends on SCHED_MC && CPU_SUP_INTEL
1040 select X86_INTEL_PSTATE
1044 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1045 core ordering determined at manufacturing time, which allows
1046 certain cores to reach higher turbo frequencies (when running
1047 single threaded workloads) than others.
1049 Enabling this kernel feature teaches the scheduler about
1050 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1051 scheduler's CPU selection logic accordingly, so that higher
1052 overall system performance can be achieved.
1054 This feature will have no effect on CPUs without this feature.
1056 If unsure say Y here.
1060 depends on !SMP && X86_LOCAL_APIC
1063 bool "Local APIC support on uniprocessors" if !PCI_MSI
1065 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1067 A local APIC (Advanced Programmable Interrupt Controller) is an
1068 integrated interrupt controller in the CPU. If you have a single-CPU
1069 system which has a processor with a local APIC, you can say Y here to
1070 enable and use it. If you say Y here even though your machine doesn't
1071 have a local APIC, then the kernel will still run with no slowdown at
1072 all. The local APIC supports CPU-generated self-interrupts (timer,
1073 performance counters), and the NMI watchdog which detects hard
1076 config X86_UP_IOAPIC
1077 bool "IO-APIC support on uniprocessors"
1078 depends on X86_UP_APIC
1080 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1081 SMP-capable replacement for PC-style interrupt controllers. Most
1082 SMP systems and many recent uniprocessor systems have one.
1084 If you have a single-CPU system with an IO-APIC, you can say Y here
1085 to use it. If you say Y here even though your machine doesn't have
1086 an IO-APIC, then the kernel will still run with no slowdown at all.
1088 config X86_LOCAL_APIC
1090 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1091 select IRQ_DOMAIN_HIERARCHY
1092 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1096 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1098 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1099 bool "Reroute for broken boot IRQs"
1100 depends on X86_IO_APIC
1102 This option enables a workaround that fixes a source of
1103 spurious interrupts. This is recommended when threaded
1104 interrupt handling is used on systems where the generation of
1105 superfluous "boot interrupts" cannot be disabled.
1107 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1108 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1109 kernel does during interrupt handling). On chipsets where this
1110 boot IRQ generation cannot be disabled, this workaround keeps
1111 the original IRQ line masked so that only the equivalent "boot
1112 IRQ" is delivered to the CPUs. The workaround also tells the
1113 kernel to set up the IRQ handler on the boot IRQ line. In this
1114 way only one interrupt is delivered to the kernel. Otherwise
1115 the spurious second interrupt may cause the kernel to bring
1116 down (vital) interrupt lines.
1118 Only affects "broken" chipsets. Interrupt sharing may be
1119 increased on these systems.
1122 bool "Machine Check / overheating reporting"
1123 select GENERIC_ALLOCATOR
1126 Machine Check support allows the processor to notify the
1127 kernel if it detects a problem (e.g. overheating, data corruption).
1128 The action the kernel takes depends on the severity of the problem,
1129 ranging from warning messages to halting the machine.
1131 config X86_MCELOG_LEGACY
1132 bool "Support for deprecated /dev/mcelog character device"
1135 Enable support for /dev/mcelog which is needed by the old mcelog
1136 userspace logging daemon. Consider switching to the new generation
1139 config X86_MCE_INTEL
1141 prompt "Intel MCE features"
1142 depends on X86_MCE && X86_LOCAL_APIC
1144 Additional support for intel specific MCE features such as
1145 the thermal monitor.
1149 prompt "AMD MCE features"
1150 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1152 Additional support for AMD specific MCE features such as
1153 the DRAM Error Threshold.
1155 config X86_ANCIENT_MCE
1156 bool "Support for old Pentium 5 / WinChip machine checks"
1157 depends on X86_32 && X86_MCE
1159 Include support for machine check handling on old Pentium 5 or WinChip
1160 systems. These typically need to be enabled explicitly on the command
1163 config X86_MCE_THRESHOLD
1164 depends on X86_MCE_AMD || X86_MCE_INTEL
1167 config X86_MCE_INJECT
1168 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1169 tristate "Machine check injector support"
1171 Provide support for injecting machine checks for testing purposes.
1172 If you don't know what a machine check is and you don't do kernel
1173 QA it is safe to say n.
1175 source "arch/x86/events/Kconfig"
1177 config X86_LEGACY_VM86
1178 bool "Legacy VM86 support"
1181 This option allows user programs to put the CPU into V8086
1182 mode, which is an 80286-era approximation of 16-bit real mode.
1184 Some very old versions of X and/or vbetool require this option
1185 for user mode setting. Similarly, DOSEMU will use it if
1186 available to accelerate real mode DOS programs. However, any
1187 recent version of DOSEMU, X, or vbetool should be fully
1188 functional even without kernel VM86 support, as they will all
1189 fall back to software emulation. Nevertheless, if you are using
1190 a 16-bit DOS program where 16-bit performance matters, vm86
1191 mode might be faster than emulation and you might want to
1194 Note that any app that works on a 64-bit kernel is unlikely to
1195 need this option, as 64-bit kernels don't, and can't, support
1196 V8086 mode. This option is also unrelated to 16-bit protected
1197 mode and is not needed to run most 16-bit programs under Wine.
1199 Enabling this option increases the complexity of the kernel
1200 and slows down exception handling a tiny bit.
1202 If unsure, say N here.
1206 default X86_LEGACY_VM86
1209 bool "Enable support for 16-bit segments" if EXPERT
1211 depends on MODIFY_LDT_SYSCALL
1213 This option is required by programs like Wine to run 16-bit
1214 protected mode legacy code on x86 processors. Disabling
1215 this option saves about 300 bytes on i386, or around 6K text
1216 plus 16K runtime memory on x86-64,
1220 depends on X86_16BIT && X86_32
1224 depends on X86_16BIT && X86_64
1226 config X86_VSYSCALL_EMULATION
1227 bool "Enable vsyscall emulation" if EXPERT
1231 This enables emulation of the legacy vsyscall page. Disabling
1232 it is roughly equivalent to booting with vsyscall=none, except
1233 that it will also disable the helpful warning if a program
1234 tries to use a vsyscall. With this option set to N, offending
1235 programs will just segfault, citing addresses of the form
1238 This option is required by many programs built before 2013, and
1239 care should be used even with newer programs if set to N.
1241 Disabling this option saves about 7K of kernel size and
1242 possibly 4K of additional runtime pagetable memory.
1244 config X86_IOPL_IOPERM
1245 bool "IOPERM and IOPL Emulation"
1248 This enables the ioperm() and iopl() syscalls which are necessary
1249 for legacy applications.
1251 Legacy IOPL support is an overbroad mechanism which allows user
1252 space aside of accessing all 65536 I/O ports also to disable
1253 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1254 capabilities and permission from potentially active security
1257 The emulation restricts the functionality of the syscall to
1258 only allowing the full range I/O port access, but prevents the
1259 ability to disable interrupts from user space which would be
1260 granted if the hardware IOPL mechanism would be used.
1263 tristate "Toshiba Laptop support"
1266 This adds a driver to safely access the System Management Mode of
1267 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1268 not work on models with a Phoenix BIOS. The System Management Mode
1269 is used to set the BIOS and power saving options on Toshiba portables.
1271 For information on utilities to make use of this driver see the
1272 Toshiba Linux utilities web site at:
1273 <http://www.buzzard.org.uk/toshiba/>.
1275 Say Y if you intend to run this kernel on a Toshiba portable.
1278 config X86_REBOOTFIXUPS
1279 bool "Enable X86 board specific fixups for reboot"
1282 This enables chipset and/or board specific fixups to be done
1283 in order to get reboot to work correctly. This is only needed on
1284 some combinations of hardware and BIOS. The symptom, for which
1285 this config is intended, is when reboot ends with a stalled/hung
1288 Currently, the only fixup is for the Geode machines using
1289 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1291 Say Y if you want to enable the fixup. Currently, it's safe to
1292 enable this option even if you don't need it.
1296 bool "CPU microcode loading support"
1298 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1300 If you say Y here, you will be able to update the microcode on
1301 Intel and AMD processors. The Intel support is for the IA32 family,
1302 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1303 AMD support is for families 0x10 and later. You will obviously need
1304 the actual microcode binary data itself which is not shipped with
1307 The preferred method to load microcode from a detached initrd is described
1308 in Documentation/x86/microcode.rst. For that you need to enable
1309 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1310 initrd for microcode blobs.
1312 In addition, you can build the microcode into the kernel. For that you
1313 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1316 config MICROCODE_INTEL
1317 bool "Intel microcode loading support"
1318 depends on MICROCODE
1321 This options enables microcode patch loading support for Intel
1324 For the current Intel microcode data package go to
1325 <https://downloadcenter.intel.com> and search for
1326 'Linux Processor Microcode Data File'.
1328 config MICROCODE_AMD
1329 bool "AMD microcode loading support"
1330 depends on MICROCODE
1332 If you select this option, microcode patch loading support for AMD
1333 processors will be enabled.
1335 config MICROCODE_OLD_INTERFACE
1336 bool "Ancient loading interface (DEPRECATED)"
1338 depends on MICROCODE
1340 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1341 which was used by userspace tools like iucode_tool and microcode.ctl.
1342 It is inadequate because it runs too late to be able to properly
1343 load microcode on a machine and it needs special tools. Instead, you
1344 should've switched to the early loading method with the initrd or
1345 builtin microcode by now: Documentation/x86/microcode.rst
1348 tristate "/dev/cpu/*/msr - Model-specific register support"
1350 This device gives privileged processes access to the x86
1351 Model-Specific Registers (MSRs). It is a character device with
1352 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1353 MSR accesses are directed to a specific CPU on multi-processor
1357 tristate "/dev/cpu/*/cpuid - CPU information support"
1359 This device gives processes access to the x86 CPUID instruction to
1360 be executed on a specific processor. It is a character device
1361 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1365 prompt "High Memory Support"
1372 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1373 However, the address space of 32-bit x86 processors is only 4
1374 Gigabytes large. That means that, if you have a large amount of
1375 physical memory, not all of it can be "permanently mapped" by the
1376 kernel. The physical memory that's not permanently mapped is called
1379 If you are compiling a kernel which will never run on a machine with
1380 more than 1 Gigabyte total physical RAM, answer "off" here (default
1381 choice and suitable for most users). This will result in a "3GB/1GB"
1382 split: 3GB are mapped so that each process sees a 3GB virtual memory
1383 space and the remaining part of the 4GB virtual memory space is used
1384 by the kernel to permanently map as much physical memory as
1387 If the machine has between 1 and 4 Gigabytes physical RAM, then
1390 If more than 4 Gigabytes is used then answer "64GB" here. This
1391 selection turns Intel PAE (Physical Address Extension) mode on.
1392 PAE implements 3-level paging on IA32 processors. PAE is fully
1393 supported by Linux, PAE mode is implemented on all recent Intel
1394 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1395 then the kernel will not boot on CPUs that don't support PAE!
1397 The actual amount of total physical memory will either be
1398 auto detected or can be forced by using a kernel command line option
1399 such as "mem=256M". (Try "man bootparam" or see the documentation of
1400 your boot loader (lilo or loadlin) about how to pass options to the
1401 kernel at boot time.)
1403 If unsure, say "off".
1408 Select this if you have a 32-bit processor and between 1 and 4
1409 gigabytes of physical RAM.
1413 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1416 Select this if you have a 32-bit processor and more than 4
1417 gigabytes of physical RAM.
1422 prompt "Memory split" if EXPERT
1426 Select the desired split between kernel and user memory.
1428 If the address range available to the kernel is less than the
1429 physical memory installed, the remaining memory will be available
1430 as "high memory". Accessing high memory is a little more costly
1431 than low memory, as it needs to be mapped into the kernel first.
1432 Note that increasing the kernel address space limits the range
1433 available to user programs, making the address space there
1434 tighter. Selecting anything other than the default 3G/1G split
1435 will also likely make your kernel incompatible with binary-only
1438 If you are not absolutely sure what you are doing, leave this
1442 bool "3G/1G user/kernel split"
1443 config VMSPLIT_3G_OPT
1445 bool "3G/1G user/kernel split (for full 1G low memory)"
1447 bool "2G/2G user/kernel split"
1448 config VMSPLIT_2G_OPT
1450 bool "2G/2G user/kernel split (for full 2G low memory)"
1452 bool "1G/3G user/kernel split"
1457 default 0xB0000000 if VMSPLIT_3G_OPT
1458 default 0x80000000 if VMSPLIT_2G
1459 default 0x78000000 if VMSPLIT_2G_OPT
1460 default 0x40000000 if VMSPLIT_1G
1466 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1469 bool "PAE (Physical Address Extension) Support"
1470 depends on X86_32 && !HIGHMEM4G
1471 select PHYS_ADDR_T_64BIT
1474 PAE is required for NX support, and furthermore enables
1475 larger swapspace support for non-overcommit purposes. It
1476 has the cost of more pagetable lookup overhead, and also
1477 consumes more pagetable space per process.
1480 bool "Enable 5-level page tables support"
1482 select DYNAMIC_MEMORY_LAYOUT
1483 select SPARSEMEM_VMEMMAP
1486 5-level paging enables access to larger address space:
1487 upto 128 PiB of virtual address space and 4 PiB of
1488 physical address space.
1490 It will be supported by future Intel CPUs.
1492 A kernel with the option enabled can be booted on machines that
1493 support 4- or 5-level paging.
1495 See Documentation/x86/x86_64/5level-paging.rst for more
1500 config X86_DIRECT_GBPAGES
1504 Certain kernel features effectively disable kernel
1505 linear 1 GB mappings (even if the CPU otherwise
1506 supports them), so don't confuse the user by printing
1507 that we have them enabled.
1509 config X86_CPA_STATISTICS
1510 bool "Enable statistic for Change Page Attribute"
1513 Expose statistics about the Change Page Attribute mechanism, which
1514 helps to determine the effectiveness of preserving large and huge
1515 page mappings when mapping protections are changed.
1517 config X86_MEM_ENCRYPT
1518 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1519 select DYNAMIC_PHYSICAL_MASK
1520 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1523 config AMD_MEM_ENCRYPT
1524 bool "AMD Secure Memory Encryption (SME) support"
1525 depends on X86_64 && CPU_SUP_AMD
1526 select DMA_COHERENT_POOL
1527 select ARCH_USE_MEMREMAP_PROT
1528 select INSTRUCTION_DECODER
1529 select ARCH_HAS_CC_PLATFORM
1530 select X86_MEM_ENCRYPT
1532 Say yes to enable support for the encryption of system memory.
1533 This requires an AMD processor that supports Secure Memory
1536 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1537 bool "Activate AMD Secure Memory Encryption (SME) by default"
1538 depends on AMD_MEM_ENCRYPT
1540 Say yes to have system memory encrypted by default if running on
1541 an AMD processor that supports Secure Memory Encryption (SME).
1543 If set to Y, then the encryption of system memory can be
1544 deactivated with the mem_encrypt=off command line option.
1546 If set to N, then the encryption of system memory can be
1547 activated with the mem_encrypt=on command line option.
1549 # Common NUMA Features
1551 bool "NUMA Memory Allocation and Scheduler Support"
1553 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1554 default y if X86_BIGSMP
1555 select USE_PERCPU_NUMA_NODE_ID
1557 Enable NUMA (Non-Uniform Memory Access) support.
1559 The kernel will try to allocate memory used by a CPU on the
1560 local memory controller of the CPU and add some more
1561 NUMA awareness to the kernel.
1563 For 64-bit this is recommended if the system is Intel Core i7
1564 (or later), AMD Opteron, or EM64T NUMA.
1566 For 32-bit this is only needed if you boot a 32-bit
1567 kernel on a 64-bit NUMA platform.
1569 Otherwise, you should say N.
1573 prompt "Old style AMD Opteron NUMA detection"
1574 depends on X86_64 && NUMA && PCI
1576 Enable AMD NUMA node topology detection. You should say Y here if
1577 you have a multi processor AMD system. This uses an old method to
1578 read the NUMA configuration directly from the builtin Northbridge
1579 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1580 which also takes priority if both are compiled in.
1582 config X86_64_ACPI_NUMA
1584 prompt "ACPI NUMA detection"
1585 depends on X86_64 && NUMA && ACPI && PCI
1588 Enable ACPI SRAT based node topology detection.
1591 bool "NUMA emulation"
1594 Enable NUMA emulation. A flat machine will be split
1595 into virtual nodes when booted with "numa=fake=N", where N is the
1596 number of nodes. This is only useful for debugging.
1599 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1601 default "10" if MAXSMP
1602 default "6" if X86_64
1606 Specify the maximum number of NUMA Nodes available on the target
1607 system. Increases memory reserved to accommodate various tables.
1609 config ARCH_FLATMEM_ENABLE
1611 depends on X86_32 && !NUMA
1613 config ARCH_SPARSEMEM_ENABLE
1615 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1616 select SPARSEMEM_STATIC if X86_32
1617 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1619 config ARCH_SPARSEMEM_DEFAULT
1620 def_bool X86_64 || (NUMA && X86_32)
1622 config ARCH_SELECT_MEMORY_MODEL
1624 depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE
1626 config ARCH_MEMORY_PROBE
1627 bool "Enable sysfs memory/probe interface"
1628 depends on MEMORY_HOTPLUG
1630 This option enables a sysfs memory/probe interface for testing.
1631 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1632 If you are unsure how to answer this question, answer N.
1634 config ARCH_PROC_KCORE_TEXT
1636 depends on X86_64 && PROC_KCORE
1638 config ILLEGAL_POINTER_VALUE
1641 default 0xdead000000000000 if X86_64
1643 config X86_PMEM_LEGACY_DEVICE
1646 config X86_PMEM_LEGACY
1647 tristate "Support non-standard NVDIMMs and ADR protected memory"
1648 depends on PHYS_ADDR_T_64BIT
1650 select X86_PMEM_LEGACY_DEVICE
1651 select NUMA_KEEP_MEMINFO if NUMA
1654 Treat memory marked using the non-standard e820 type of 12 as used
1655 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1656 The kernel will offer these regions to the 'pmem' driver so
1657 they can be used for persistent storage.
1662 bool "Allocate 3rd-level pagetables from highmem"
1665 The VM uses one page table entry for each page of physical memory.
1666 For systems with a lot of RAM, this can be wasteful of precious
1667 low memory. Setting this option will put user-space page table
1668 entries in high memory.
1670 config X86_CHECK_BIOS_CORRUPTION
1671 bool "Check for low memory corruption"
1673 Periodically check for memory corruption in low memory, which
1674 is suspected to be caused by BIOS. Even when enabled in the
1675 configuration, it is disabled at runtime. Enable it by
1676 setting "memory_corruption_check=1" on the kernel command
1677 line. By default it scans the low 64k of memory every 60
1678 seconds; see the memory_corruption_check_size and
1679 memory_corruption_check_period parameters in
1680 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1682 When enabled with the default parameters, this option has
1683 almost no overhead, as it reserves a relatively small amount
1684 of memory and scans it infrequently. It both detects corruption
1685 and prevents it from affecting the running system.
1687 It is, however, intended as a diagnostic tool; if repeatable
1688 BIOS-originated corruption always affects the same memory,
1689 you can use memmap= to prevent the kernel from using that
1692 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1693 bool "Set the default setting of memory_corruption_check"
1694 depends on X86_CHECK_BIOS_CORRUPTION
1697 Set whether the default state of memory_corruption_check is
1700 config MATH_EMULATION
1702 depends on MODIFY_LDT_SYSCALL
1703 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1705 Linux can emulate a math coprocessor (used for floating point
1706 operations) if you don't have one. 486DX and Pentium processors have
1707 a math coprocessor built in, 486SX and 386 do not, unless you added
1708 a 487DX or 387, respectively. (The messages during boot time can
1709 give you some hints here ["man dmesg"].) Everyone needs either a
1710 coprocessor or this emulation.
1712 If you don't have a math coprocessor, you need to say Y here; if you
1713 say Y here even though you have a coprocessor, the coprocessor will
1714 be used nevertheless. (This behavior can be changed with the kernel
1715 command line option "no387", which comes handy if your coprocessor
1716 is broken. Try "man bootparam" or see the documentation of your boot
1717 loader (lilo or loadlin) about how to pass options to the kernel at
1718 boot time.) This means that it is a good idea to say Y here if you
1719 intend to use this kernel on different machines.
1721 More information about the internals of the Linux math coprocessor
1722 emulation can be found in <file:arch/x86/math-emu/README>.
1724 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1725 kernel, it won't hurt.
1729 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1731 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1732 the Memory Type Range Registers (MTRRs) may be used to control
1733 processor access to memory ranges. This is most useful if you have
1734 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1735 allows bus write transfers to be combined into a larger transfer
1736 before bursting over the PCI/AGP bus. This can increase performance
1737 of image write operations 2.5 times or more. Saying Y here creates a
1738 /proc/mtrr file which may be used to manipulate your processor's
1739 MTRRs. Typically the X server should use this.
1741 This code has a reasonably generic interface so that similar
1742 control registers on other processors can be easily supported
1745 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1746 Registers (ARRs) which provide a similar functionality to MTRRs. For
1747 these, the ARRs are used to emulate the MTRRs.
1748 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1749 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1750 write-combining. All of these processors are supported by this code
1751 and it makes sense to say Y here if you have one of them.
1753 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1754 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1755 can lead to all sorts of problems, so it's good to say Y here.
1757 You can safely say Y even if your machine doesn't have MTRRs, you'll
1758 just add about 9 KB to your kernel.
1760 See <file:Documentation/x86/mtrr.rst> for more information.
1762 config MTRR_SANITIZER
1764 prompt "MTRR cleanup support"
1767 Convert MTRR layout from continuous to discrete, so X drivers can
1768 add writeback entries.
1770 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1771 The largest mtrr entry size for a continuous block can be set with
1776 config MTRR_SANITIZER_ENABLE_DEFAULT
1777 int "MTRR cleanup enable value (0-1)"
1780 depends on MTRR_SANITIZER
1782 Enable mtrr cleanup default value
1784 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1785 int "MTRR cleanup spare reg num (0-7)"
1788 depends on MTRR_SANITIZER
1790 mtrr cleanup spare entries default, it can be changed via
1791 mtrr_spare_reg_nr=N on the kernel command line.
1795 prompt "x86 PAT support" if EXPERT
1798 Use PAT attributes to setup page level cache control.
1800 PATs are the modern equivalents of MTRRs and are much more
1801 flexible than MTRRs.
1803 Say N here if you see bootup problems (boot crash, boot hang,
1804 spontaneous reboots) or a non-working video driver.
1808 config ARCH_USES_PG_UNCACHED
1814 prompt "x86 architectural random number generator" if EXPERT
1816 Enable the x86 architectural RDRAND instruction
1817 (Intel Bull Mountain technology) to generate random numbers.
1818 If supported, this is a high bandwidth, cryptographically
1819 secure hardware random number generator.
1823 prompt "Supervisor Mode Access Prevention" if EXPERT
1825 Supervisor Mode Access Prevention (SMAP) is a security
1826 feature in newer Intel processors. There is a small
1827 performance cost if this enabled and turned on; there is
1828 also a small increase in the kernel size if this is enabled.
1834 prompt "User Mode Instruction Prevention" if EXPERT
1836 User Mode Instruction Prevention (UMIP) is a security feature in
1837 some x86 processors. If enabled, a general protection fault is
1838 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1839 executed in user mode. These instructions unnecessarily expose
1840 information about the hardware state.
1842 The vast majority of applications do not use these instructions.
1843 For the very few that do, software emulation is provided in
1844 specific cases in protected and virtual-8086 modes. Emulated
1847 config X86_INTEL_MEMORY_PROTECTION_KEYS
1848 prompt "Memory Protection Keys"
1850 # Note: only available in 64-bit mode
1851 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1852 select ARCH_USES_HIGH_VMA_FLAGS
1853 select ARCH_HAS_PKEYS
1855 Memory Protection Keys provides a mechanism for enforcing
1856 page-based protections, but without requiring modification of the
1857 page tables when an application changes protection domains.
1859 For details, see Documentation/core-api/protection-keys.rst
1864 prompt "TSX enable mode"
1865 depends on CPU_SUP_INTEL
1866 default X86_INTEL_TSX_MODE_OFF
1868 Intel's TSX (Transactional Synchronization Extensions) feature
1869 allows to optimize locking protocols through lock elision which
1870 can lead to a noticeable performance boost.
1872 On the other hand it has been shown that TSX can be exploited
1873 to form side channel attacks (e.g. TAA) and chances are there
1874 will be more of those attacks discovered in the future.
1876 Therefore TSX is not enabled by default (aka tsx=off). An admin
1877 might override this decision by tsx=on the command line parameter.
1878 Even with TSX enabled, the kernel will attempt to enable the best
1879 possible TAA mitigation setting depending on the microcode available
1880 for the particular machine.
1882 This option allows to set the default tsx mode between tsx=on, =off
1883 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1886 Say off if not sure, auto if TSX is in use but it should be used on safe
1887 platforms or on if TSX is in use and the security aspect of tsx is not
1890 config X86_INTEL_TSX_MODE_OFF
1893 TSX is disabled if possible - equals to tsx=off command line parameter.
1895 config X86_INTEL_TSX_MODE_ON
1898 TSX is always enabled on TSX capable HW - equals the tsx=on command
1901 config X86_INTEL_TSX_MODE_AUTO
1904 TSX is enabled on TSX capable HW that is believed to be safe against
1905 side channel attacks- equals the tsx=auto command line parameter.
1909 bool "Software Guard eXtensions (SGX)"
1910 depends on X86_64 && CPU_SUP_INTEL
1912 depends on CRYPTO_SHA256=y
1915 select NUMA_KEEP_MEMINFO if NUMA
1918 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1919 that can be used by applications to set aside private regions of code
1920 and data, referred to as enclaves. An enclave's private memory can
1921 only be accessed by code running within the enclave. Accesses from
1922 outside the enclave, including other enclaves, are disallowed by
1928 bool "EFI runtime service support"
1931 select EFI_RUNTIME_WRAPPERS
1932 select ARCH_USE_MEMREMAP_PROT
1934 This enables the kernel to use EFI runtime services that are
1935 available (such as the EFI variable services).
1937 This option is only useful on systems that have EFI firmware.
1938 In addition, you should use the latest ELILO loader available
1939 at <http://elilo.sourceforge.net> in order to take advantage
1940 of EFI runtime services. However, even with this option, the
1941 resultant kernel should continue to boot on existing non-EFI
1945 bool "EFI stub support"
1947 depends on $(cc-option,-mabi=ms) || X86_32
1950 This kernel feature allows a bzImage to be loaded directly
1951 by EFI firmware without the use of a bootloader.
1953 See Documentation/admin-guide/efi-stub.rst for more information.
1956 bool "EFI mixed-mode support"
1957 depends on EFI_STUB && X86_64
1959 Enabling this feature allows a 64-bit kernel to be booted
1960 on a 32-bit firmware, provided that your CPU supports 64-bit
1963 Note that it is not possible to boot a mixed-mode enabled
1964 kernel via the EFI boot stub - a bootloader that supports
1965 the EFI handover protocol must be used.
1969 source "kernel/Kconfig.hz"
1972 bool "kexec system call"
1975 kexec is a system call that implements the ability to shutdown your
1976 current kernel, and to start another kernel. It is like a reboot
1977 but it is independent of the system firmware. And like a reboot
1978 you can start any kernel with it, not just Linux.
1980 The name comes from the similarity to the exec system call.
1982 It is an ongoing process to be certain the hardware in a machine
1983 is properly shutdown, so do not be surprised if this code does not
1984 initially work for you. As of this writing the exact hardware
1985 interface is strongly in flux, so no good recommendation can be
1989 bool "kexec file based system call"
1994 depends on CRYPTO_SHA256=y
1996 This is new version of kexec system call. This system call is
1997 file based and takes file descriptors as system call argument
1998 for kernel and initramfs as opposed to list of segments as
1999 accepted by previous system call.
2001 config ARCH_HAS_KEXEC_PURGATORY
2005 bool "Verify kernel signature during kexec_file_load() syscall"
2006 depends on KEXEC_FILE
2009 This option makes the kexec_file_load() syscall check for a valid
2010 signature of the kernel image. The image can still be loaded without
2011 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2012 there's a signature that we can check, then it must be valid.
2014 In addition to this option, you need to enable signature
2015 verification for the corresponding kernel image type being
2016 loaded in order for this to work.
2018 config KEXEC_SIG_FORCE
2019 bool "Require a valid signature in kexec_file_load() syscall"
2020 depends on KEXEC_SIG
2022 This option makes kernel signature verification mandatory for
2023 the kexec_file_load() syscall.
2025 config KEXEC_BZIMAGE_VERIFY_SIG
2026 bool "Enable bzImage signature verification support"
2027 depends on KEXEC_SIG
2028 depends on SIGNED_PE_FILE_VERIFICATION
2029 select SYSTEM_TRUSTED_KEYRING
2031 Enable bzImage signature verification support.
2034 bool "kernel crash dumps"
2035 depends on X86_64 || (X86_32 && HIGHMEM)
2037 Generate crash dump after being started by kexec.
2038 This should be normally only set in special crash dump kernels
2039 which are loaded in the main kernel with kexec-tools into
2040 a specially reserved region and then later executed after
2041 a crash by kdump/kexec. The crash dump kernel must be compiled
2042 to a memory address not used by the main kernel or BIOS using
2043 PHYSICAL_START, or it must be built as a relocatable image
2044 (CONFIG_RELOCATABLE=y).
2045 For more details see Documentation/admin-guide/kdump/kdump.rst
2049 depends on KEXEC && HIBERNATION
2051 Jump between original kernel and kexeced kernel and invoke
2052 code in physical address mode via KEXEC
2054 config PHYSICAL_START
2055 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2058 This gives the physical address where the kernel is loaded.
2060 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2061 bzImage will decompress itself to above physical address and
2062 run from there. Otherwise, bzImage will run from the address where
2063 it has been loaded by the boot loader and will ignore above physical
2066 In normal kdump cases one does not have to set/change this option
2067 as now bzImage can be compiled as a completely relocatable image
2068 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2069 address. This option is mainly useful for the folks who don't want
2070 to use a bzImage for capturing the crash dump and want to use a
2071 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2072 to be specifically compiled to run from a specific memory area
2073 (normally a reserved region) and this option comes handy.
2075 So if you are using bzImage for capturing the crash dump,
2076 leave the value here unchanged to 0x1000000 and set
2077 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2078 for capturing the crash dump change this value to start of
2079 the reserved region. In other words, it can be set based on
2080 the "X" value as specified in the "crashkernel=YM@XM"
2081 command line boot parameter passed to the panic-ed
2082 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2083 for more details about crash dumps.
2085 Usage of bzImage for capturing the crash dump is recommended as
2086 one does not have to build two kernels. Same kernel can be used
2087 as production kernel and capture kernel. Above option should have
2088 gone away after relocatable bzImage support is introduced. But it
2089 is present because there are users out there who continue to use
2090 vmlinux for dump capture. This option should go away down the
2093 Don't change this unless you know what you are doing.
2096 bool "Build a relocatable kernel"
2099 This builds a kernel image that retains relocation information
2100 so it can be loaded someplace besides the default 1MB.
2101 The relocations tend to make the kernel binary about 10% larger,
2102 but are discarded at runtime.
2104 One use is for the kexec on panic case where the recovery kernel
2105 must live at a different physical address than the primary
2108 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2109 it has been loaded at and the compile time physical address
2110 (CONFIG_PHYSICAL_START) is used as the minimum location.
2112 config RANDOMIZE_BASE
2113 bool "Randomize the address of the kernel image (KASLR)"
2114 depends on RELOCATABLE
2117 In support of Kernel Address Space Layout Randomization (KASLR),
2118 this randomizes the physical address at which the kernel image
2119 is decompressed and the virtual address where the kernel
2120 image is mapped, as a security feature that deters exploit
2121 attempts relying on knowledge of the location of kernel
2124 On 64-bit, the kernel physical and virtual addresses are
2125 randomized separately. The physical address will be anywhere
2126 between 16MB and the top of physical memory (up to 64TB). The
2127 virtual address will be randomized from 16MB up to 1GB (9 bits
2128 of entropy). Note that this also reduces the memory space
2129 available to kernel modules from 1.5GB to 1GB.
2131 On 32-bit, the kernel physical and virtual addresses are
2132 randomized together. They will be randomized from 16MB up to
2133 512MB (8 bits of entropy).
2135 Entropy is generated using the RDRAND instruction if it is
2136 supported. If RDTSC is supported, its value is mixed into
2137 the entropy pool as well. If neither RDRAND nor RDTSC are
2138 supported, then entropy is read from the i8254 timer. The
2139 usable entropy is limited by the kernel being built using
2140 2GB addressing, and that PHYSICAL_ALIGN must be at a
2141 minimum of 2MB. As a result, only 10 bits of entropy are
2142 theoretically possible, but the implementations are further
2143 limited due to memory layouts.
2147 # Relocation on x86 needs some additional build support
2148 config X86_NEED_RELOCS
2150 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2152 config PHYSICAL_ALIGN
2153 hex "Alignment value to which kernel should be aligned"
2155 range 0x2000 0x1000000 if X86_32
2156 range 0x200000 0x1000000 if X86_64
2158 This value puts the alignment restrictions on physical address
2159 where kernel is loaded and run from. Kernel is compiled for an
2160 address which meets above alignment restriction.
2162 If bootloader loads the kernel at a non-aligned address and
2163 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2164 address aligned to above value and run from there.
2166 If bootloader loads the kernel at a non-aligned address and
2167 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2168 load address and decompress itself to the address it has been
2169 compiled for and run from there. The address for which kernel is
2170 compiled already meets above alignment restrictions. Hence the
2171 end result is that kernel runs from a physical address meeting
2172 above alignment restrictions.
2174 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2175 this value must be a multiple of 0x200000.
2177 Don't change this unless you know what you are doing.
2179 config DYNAMIC_MEMORY_LAYOUT
2182 This option makes base addresses of vmalloc and vmemmap as well as
2183 __PAGE_OFFSET movable during boot.
2185 config RANDOMIZE_MEMORY
2186 bool "Randomize the kernel memory sections"
2188 depends on RANDOMIZE_BASE
2189 select DYNAMIC_MEMORY_LAYOUT
2190 default RANDOMIZE_BASE
2192 Randomizes the base virtual address of kernel memory sections
2193 (physical memory mapping, vmalloc & vmemmap). This security feature
2194 makes exploits relying on predictable memory locations less reliable.
2196 The order of allocations remains unchanged. Entropy is generated in
2197 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2198 configuration have in average 30,000 different possible virtual
2199 addresses for each memory section.
2203 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2204 hex "Physical memory mapping padding" if EXPERT
2205 depends on RANDOMIZE_MEMORY
2206 default "0xa" if MEMORY_HOTPLUG
2208 range 0x1 0x40 if MEMORY_HOTPLUG
2211 Define the padding in terabytes added to the existing physical
2212 memory size during kernel memory randomization. It is useful
2213 for memory hotplug support but reduces the entropy available for
2214 address randomization.
2216 If unsure, leave at the default value.
2222 config BOOTPARAM_HOTPLUG_CPU0
2223 bool "Set default setting of cpu0_hotpluggable"
2224 depends on HOTPLUG_CPU
2226 Set whether default state of cpu0_hotpluggable is on or off.
2228 Say Y here to enable CPU0 hotplug by default. If this switch
2229 is turned on, there is no need to give cpu0_hotplug kernel
2230 parameter and the CPU0 hotplug feature is enabled by default.
2232 Please note: there are two known CPU0 dependencies if you want
2233 to enable the CPU0 hotplug feature either by this switch or by
2234 cpu0_hotplug kernel parameter.
2236 First, resume from hibernate or suspend always starts from CPU0.
2237 So hibernate and suspend are prevented if CPU0 is offline.
2239 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2240 offline if any interrupt can not migrate out of CPU0. There may
2241 be other CPU0 dependencies.
2243 Please make sure the dependencies are under your control before
2244 you enable this feature.
2246 Say N if you don't want to enable CPU0 hotplug feature by default.
2247 You still can enable the CPU0 hotplug feature at boot by kernel
2248 parameter cpu0_hotplug.
2250 config DEBUG_HOTPLUG_CPU0
2252 prompt "Debug CPU0 hotplug"
2253 depends on HOTPLUG_CPU
2255 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2256 soon as possible and boots up userspace with CPU0 offlined. User
2257 can online CPU0 back after boot time.
2259 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2260 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2261 compilation or giving cpu0_hotplug kernel parameter at boot.
2267 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2268 depends on COMPAT_32
2270 Certain buggy versions of glibc will crash if they are
2271 presented with a 32-bit vDSO that is not mapped at the address
2272 indicated in its segment table.
2274 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2275 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2276 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2277 the only released version with the bug, but OpenSUSE 9
2278 contains a buggy "glibc 2.3.2".
2280 The symptom of the bug is that everything crashes on startup, saying:
2281 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2283 Saying Y here changes the default value of the vdso32 boot
2284 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2285 This works around the glibc bug but hurts performance.
2287 If unsure, say N: if you are compiling your own kernel, you
2288 are unlikely to be using a buggy version of glibc.
2291 prompt "vsyscall table for legacy applications"
2293 default LEGACY_VSYSCALL_XONLY
2295 Legacy user code that does not know how to find the vDSO expects
2296 to be able to issue three syscalls by calling fixed addresses in
2297 kernel space. Since this location is not randomized with ASLR,
2298 it can be used to assist security vulnerability exploitation.
2300 This setting can be changed at boot time via the kernel command
2301 line parameter vsyscall=[emulate|xonly|none].
2303 On a system with recent enough glibc (2.14 or newer) and no
2304 static binaries, you can say None without a performance penalty
2305 to improve security.
2307 If unsure, select "Emulate execution only".
2309 config LEGACY_VSYSCALL_EMULATE
2310 bool "Full emulation"
2312 The kernel traps and emulates calls into the fixed vsyscall
2313 address mapping. This makes the mapping non-executable, but
2314 it still contains readable known contents, which could be
2315 used in certain rare security vulnerability exploits. This
2316 configuration is recommended when using legacy userspace
2317 that still uses vsyscalls along with legacy binary
2318 instrumentation tools that require code to be readable.
2320 An example of this type of legacy userspace is running
2321 Pin on an old binary that still uses vsyscalls.
2323 config LEGACY_VSYSCALL_XONLY
2324 bool "Emulate execution only"
2326 The kernel traps and emulates calls into the fixed vsyscall
2327 address mapping and does not allow reads. This
2328 configuration is recommended when userspace might use the
2329 legacy vsyscall area but support for legacy binary
2330 instrumentation of legacy code is not needed. It mitigates
2331 certain uses of the vsyscall area as an ASLR-bypassing
2334 config LEGACY_VSYSCALL_NONE
2337 There will be no vsyscall mapping at all. This will
2338 eliminate any risk of ASLR bypass due to the vsyscall
2339 fixed address mapping. Attempts to use the vsyscalls
2340 will be reported to dmesg, so that either old or
2341 malicious userspace programs can be identified.
2346 bool "Built-in kernel command line"
2348 Allow for specifying boot arguments to the kernel at
2349 build time. On some systems (e.g. embedded ones), it is
2350 necessary or convenient to provide some or all of the
2351 kernel boot arguments with the kernel itself (that is,
2352 to not rely on the boot loader to provide them.)
2354 To compile command line arguments into the kernel,
2355 set this option to 'Y', then fill in the
2356 boot arguments in CONFIG_CMDLINE.
2358 Systems with fully functional boot loaders (i.e. non-embedded)
2359 should leave this option set to 'N'.
2362 string "Built-in kernel command string"
2363 depends on CMDLINE_BOOL
2366 Enter arguments here that should be compiled into the kernel
2367 image and used at boot time. If the boot loader provides a
2368 command line at boot time, it is appended to this string to
2369 form the full kernel command line, when the system boots.
2371 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2372 change this behavior.
2374 In most cases, the command line (whether built-in or provided
2375 by the boot loader) should specify the device for the root
2378 config CMDLINE_OVERRIDE
2379 bool "Built-in command line overrides boot loader arguments"
2380 depends on CMDLINE_BOOL && CMDLINE != ""
2382 Set this option to 'Y' to have the kernel ignore the boot loader
2383 command line, and use ONLY the built-in command line.
2385 This is used to work around broken boot loaders. This should
2386 be set to 'N' under normal conditions.
2388 config MODIFY_LDT_SYSCALL
2389 bool "Enable the LDT (local descriptor table)" if EXPERT
2392 Linux can allow user programs to install a per-process x86
2393 Local Descriptor Table (LDT) using the modify_ldt(2) system
2394 call. This is required to run 16-bit or segmented code such as
2395 DOSEMU or some Wine programs. It is also used by some very old
2396 threading libraries.
2398 Enabling this feature adds a small amount of overhead to
2399 context switches and increases the low-level kernel attack
2400 surface. Disabling it removes the modify_ldt(2) system call.
2402 Saying 'N' here may make sense for embedded or server kernels.
2404 config STRICT_SIGALTSTACK_SIZE
2405 bool "Enforce strict size checking for sigaltstack"
2406 depends on DYNAMIC_SIGFRAME
2408 For historical reasons MINSIGSTKSZ is a constant which became
2409 already too small with AVX512 support. Add a mechanism to
2410 enforce strict checking of the sigaltstack size against the
2411 real size of the FPU frame. This option enables the check
2412 by default. It can also be controlled via the kernel command
2413 line option 'strict_sas_size' independent of this config
2414 switch. Enabling it might break existing applications which
2415 allocate a too small sigaltstack but 'work' because they
2416 never get a signal delivered.
2418 Say 'N' unless you want to really enforce this check.
2420 source "kernel/livepatch/Kconfig"
2424 config ARCH_HAS_ADD_PAGES
2426 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2428 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2431 menu "Power management and ACPI options"
2433 config ARCH_HIBERNATION_HEADER
2435 depends on HIBERNATION
2437 source "kernel/power/Kconfig"
2439 source "drivers/acpi/Kconfig"
2446 tristate "APM (Advanced Power Management) BIOS support"
2447 depends on X86_32 && PM_SLEEP
2449 APM is a BIOS specification for saving power using several different
2450 techniques. This is mostly useful for battery powered laptops with
2451 APM compliant BIOSes. If you say Y here, the system time will be
2452 reset after a RESUME operation, the /proc/apm device will provide
2453 battery status information, and user-space programs will receive
2454 notification of APM "events" (e.g. battery status change).
2456 If you select "Y" here, you can disable actual use of the APM
2457 BIOS by passing the "apm=off" option to the kernel at boot time.
2459 Note that the APM support is almost completely disabled for
2460 machines with more than one CPU.
2462 In order to use APM, you will need supporting software. For location
2463 and more information, read <file:Documentation/power/apm-acpi.rst>
2464 and the Battery Powered Linux mini-HOWTO, available from
2465 <http://www.tldp.org/docs.html#howto>.
2467 This driver does not spin down disk drives (see the hdparm(8)
2468 manpage ("man 8 hdparm") for that), and it doesn't turn off
2469 VESA-compliant "green" monitors.
2471 This driver does not support the TI 4000M TravelMate and the ACER
2472 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2473 desktop machines also don't have compliant BIOSes, and this driver
2474 may cause those machines to panic during the boot phase.
2476 Generally, if you don't have a battery in your machine, there isn't
2477 much point in using this driver and you should say N. If you get
2478 random kernel OOPSes or reboots that don't seem to be related to
2479 anything, try disabling/enabling this option (or disabling/enabling
2482 Some other things you should try when experiencing seemingly random,
2485 1) make sure that you have enough swap space and that it is
2487 2) pass the "no-hlt" option to the kernel
2488 3) switch on floating point emulation in the kernel and pass
2489 the "no387" option to the kernel
2490 4) pass the "floppy=nodma" option to the kernel
2491 5) pass the "mem=4M" option to the kernel (thereby disabling
2492 all but the first 4 MB of RAM)
2493 6) make sure that the CPU is not over clocked.
2494 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2495 8) disable the cache from your BIOS settings
2496 9) install a fan for the video card or exchange video RAM
2497 10) install a better fan for the CPU
2498 11) exchange RAM chips
2499 12) exchange the motherboard.
2501 To compile this driver as a module, choose M here: the
2502 module will be called apm.
2506 config APM_IGNORE_USER_SUSPEND
2507 bool "Ignore USER SUSPEND"
2509 This option will ignore USER SUSPEND requests. On machines with a
2510 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2511 series notebooks, it is necessary to say Y because of a BIOS bug.
2513 config APM_DO_ENABLE
2514 bool "Enable PM at boot time"
2516 Enable APM features at boot time. From page 36 of the APM BIOS
2517 specification: "When disabled, the APM BIOS does not automatically
2518 power manage devices, enter the Standby State, enter the Suspend
2519 State, or take power saving steps in response to CPU Idle calls."
2520 This driver will make CPU Idle calls when Linux is idle (unless this
2521 feature is turned off -- see "Do CPU IDLE calls", below). This
2522 should always save battery power, but more complicated APM features
2523 will be dependent on your BIOS implementation. You may need to turn
2524 this option off if your computer hangs at boot time when using APM
2525 support, or if it beeps continuously instead of suspending. Turn
2526 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2527 T400CDT. This is off by default since most machines do fine without
2532 bool "Make CPU Idle calls when idle"
2534 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2535 On some machines, this can activate improved power savings, such as
2536 a slowed CPU clock rate, when the machine is idle. These idle calls
2537 are made after the idle loop has run for some length of time (e.g.,
2538 333 mS). On some machines, this will cause a hang at boot time or
2539 whenever the CPU becomes idle. (On machines with more than one CPU,
2540 this option does nothing.)
2542 config APM_DISPLAY_BLANK
2543 bool "Enable console blanking using APM"
2545 Enable console blanking using the APM. Some laptops can use this to
2546 turn off the LCD backlight when the screen blanker of the Linux
2547 virtual console blanks the screen. Note that this is only used by
2548 the virtual console screen blanker, and won't turn off the backlight
2549 when using the X Window system. This also doesn't have anything to
2550 do with your VESA-compliant power-saving monitor. Further, this
2551 option doesn't work for all laptops -- it might not turn off your
2552 backlight at all, or it might print a lot of errors to the console,
2553 especially if you are using gpm.
2555 config APM_ALLOW_INTS
2556 bool "Allow interrupts during APM BIOS calls"
2558 Normally we disable external interrupts while we are making calls to
2559 the APM BIOS as a measure to lessen the effects of a badly behaving
2560 BIOS implementation. The BIOS should reenable interrupts if it
2561 needs to. Unfortunately, some BIOSes do not -- especially those in
2562 many of the newer IBM Thinkpads. If you experience hangs when you
2563 suspend, try setting this to Y. Otherwise, say N.
2567 source "drivers/cpufreq/Kconfig"
2569 source "drivers/cpuidle/Kconfig"
2571 source "drivers/idle/Kconfig"
2576 menu "Bus options (PCI etc.)"
2579 prompt "PCI access mode"
2580 depends on X86_32 && PCI
2583 On PCI systems, the BIOS can be used to detect the PCI devices and
2584 determine their configuration. However, some old PCI motherboards
2585 have BIOS bugs and may crash if this is done. Also, some embedded
2586 PCI-based systems don't have any BIOS at all. Linux can also try to
2587 detect the PCI hardware directly without using the BIOS.
2589 With this option, you can specify how Linux should detect the
2590 PCI devices. If you choose "BIOS", the BIOS will be used,
2591 if you choose "Direct", the BIOS won't be used, and if you
2592 choose "MMConfig", then PCI Express MMCONFIG will be used.
2593 If you choose "Any", the kernel will try MMCONFIG, then the
2594 direct access method and falls back to the BIOS if that doesn't
2595 work. If unsure, go with the default, which is "Any".
2600 config PCI_GOMMCONFIG
2617 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2619 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2622 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2625 bool "Support mmconfig PCI config space access" if X86_64
2627 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2628 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2632 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2636 depends on PCI && XEN
2638 config MMCONF_FAM10H
2640 depends on X86_64 && PCI_MMCONFIG && ACPI
2642 config PCI_CNB20LE_QUIRK
2643 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2646 Read the PCI windows out of the CNB20LE host bridge. This allows
2647 PCI hotplug to work on systems with the CNB20LE chipset which do
2650 There's no public spec for this chipset, and this functionality
2651 is known to be incomplete.
2653 You should say N unless you know you need this.
2656 bool "ISA bus support on modern systems" if EXPERT
2658 Expose ISA bus device drivers and options available for selection and
2659 configuration. Enable this option if your target machine has an ISA
2660 bus. ISA is an older system, displaced by PCI and newer bus
2661 architectures -- if your target machine is modern, it probably does
2662 not have an ISA bus.
2666 # x86_64 have no ISA slots, but can have ISA-style DMA.
2668 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2671 Enables ISA-style DMA support for devices requiring such controllers.
2679 Find out whether you have ISA slots on your motherboard. ISA is the
2680 name of a bus system, i.e. the way the CPU talks to the other stuff
2681 inside your box. Other bus systems are PCI, EISA, MicroChannel
2682 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2683 newer boards don't support it. If you have ISA, say Y, otherwise N.
2686 tristate "NatSemi SCx200 support"
2688 This provides basic support for National Semiconductor's
2689 (now AMD's) Geode processors. The driver probes for the
2690 PCI-IDs of several on-chip devices, so its a good dependency
2691 for other scx200_* drivers.
2693 If compiled as a module, the driver is named scx200.
2695 config SCx200HR_TIMER
2696 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2700 This driver provides a clocksource built upon the on-chip
2701 27MHz high-resolution timer. Its also a workaround for
2702 NSC Geode SC-1100's buggy TSC, which loses time when the
2703 processor goes idle (as is done by the scheduler). The
2704 other workaround is idle=poll boot option.
2707 bool "One Laptop Per Child support"
2715 Add support for detecting the unique features of the OLPC
2719 bool "OLPC XO-1 Power Management"
2720 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2722 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2725 bool "OLPC XO-1 Real Time Clock"
2726 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2728 Add support for the XO-1 real time clock, which can be used as a
2729 programmable wakeup source.
2732 bool "OLPC XO-1 SCI extras"
2733 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2737 Add support for SCI-based features of the OLPC XO-1 laptop:
2738 - EC-driven system wakeups
2742 - AC adapter status updates
2743 - Battery status updates
2745 config OLPC_XO15_SCI
2746 bool "OLPC XO-1.5 SCI extras"
2747 depends on OLPC && ACPI
2750 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2751 - EC-driven system wakeups
2752 - AC adapter status updates
2753 - Battery status updates
2756 bool "PCEngines ALIX System Support (LED setup)"
2759 This option enables system support for the PCEngines ALIX.
2760 At present this just sets up LEDs for GPIO control on
2761 ALIX2/3/6 boards. However, other system specific setup should
2764 Note: You must still enable the drivers for GPIO and LED support
2765 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2767 Note: You have to set alix.force=1 for boards with Award BIOS.
2770 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2773 This option enables system support for the Soekris Engineering net5501.
2776 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2780 This option enables system support for the Traverse Technologies GEOS.
2783 bool "Technologic Systems TS-5500 platform support"
2785 select CHECK_SIGNATURE
2789 This option enables system support for the Technologic Systems TS-5500.
2795 depends on CPU_SUP_AMD && PCI
2800 menu "Binary Emulations"
2802 config IA32_EMULATION
2803 bool "IA32 Emulation"
2805 select ARCH_WANT_OLD_COMPAT_IPC
2807 select COMPAT_OLD_SIGACTION
2809 Include code to run legacy 32-bit programs under a
2810 64-bit kernel. You should likely turn this on, unless you're
2811 100% sure that you don't have any 32-bit programs left.
2814 tristate "IA32 a.out support"
2815 depends on IA32_EMULATION
2818 Support old a.out binaries in the 32bit emulation.
2821 bool "x32 ABI for 64-bit mode"
2824 Include code to run binaries for the x32 native 32-bit ABI
2825 for 64-bit processors. An x32 process gets access to the
2826 full 64-bit register file and wide data path while leaving
2827 pointers at 32 bits for smaller memory footprint.
2829 You will need a recent binutils (2.22 or later) with
2830 elf32_x86_64 support enabled to compile a kernel with this
2835 depends on IA32_EMULATION || X86_32
2837 select OLD_SIGSUSPEND3
2841 depends on IA32_EMULATION || X86_X32
2844 config COMPAT_FOR_U64_ALIGNMENT
2847 config SYSVIPC_COMPAT
2855 config HAVE_ATOMIC_IOMAP
2859 source "arch/x86/kvm/Kconfig"
2861 source "arch/x86/Kconfig.assembler"