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_THP_SWAP if X86_64
126 select ARCH_HAS_PARANOID_L1D_FLUSH
127 select BUILDTIME_TABLE_SORT
129 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
130 select CLOCKSOURCE_WATCHDOG
131 select DCACHE_WORD_ACCESS
132 select DYNAMIC_SIGFRAME
133 select EDAC_ATOMIC_SCRUB
135 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
136 select GENERIC_CLOCKEVENTS_MIN_ADJUST
137 select GENERIC_CMOS_UPDATE
138 select GENERIC_CPU_AUTOPROBE
139 select GENERIC_CPU_VULNERABILITIES
140 select GENERIC_EARLY_IOREMAP
143 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
144 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
145 select GENERIC_IRQ_MIGRATION if SMP
146 select GENERIC_IRQ_PROBE
147 select GENERIC_IRQ_RESERVATION_MODE
148 select GENERIC_IRQ_SHOW
149 select GENERIC_PENDING_IRQ if SMP
150 select GENERIC_PTDUMP
151 select GENERIC_SMP_IDLE_THREAD
152 select GENERIC_TIME_VSYSCALL
153 select GENERIC_GETTIMEOFDAY
154 select GENERIC_VDSO_TIME_NS
155 select GUP_GET_PTE_LOW_HIGH if X86_PAE
156 select HARDIRQS_SW_RESEND
157 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
158 select HAVE_ACPI_APEI if ACPI
159 select HAVE_ACPI_APEI_NMI if ACPI
160 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
161 select HAVE_ARCH_AUDITSYSCALL
162 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
163 select HAVE_ARCH_HUGE_VMALLOC if X86_64
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
228 select HAVE_LIVEPATCH if X86_64
229 select HAVE_MIXED_BREAKPOINTS_REGS
230 select HAVE_MOD_ARCH_SPECIFIC
234 select HAVE_OPTPROBES
235 select HAVE_PCSPKR_PLATFORM
236 select HAVE_PERF_EVENTS
237 select HAVE_PERF_EVENTS_NMI
238 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
240 select HAVE_PERF_REGS
241 select HAVE_PERF_USER_STACK_DUMP
242 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
243 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
244 select HAVE_REGS_AND_STACK_ACCESS_API
245 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
246 select HAVE_FUNCTION_ARG_ACCESS_API
247 select HAVE_SETUP_PER_CPU_AREA
248 select HAVE_SOFTIRQ_ON_OWN_STACK
249 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
250 select HAVE_STACK_VALIDATION if X86_64
251 select HAVE_STATIC_CALL
252 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
253 select HAVE_PREEMPT_DYNAMIC_CALL
255 select HAVE_SYSCALL_TRACEPOINTS
256 select HAVE_UNSTABLE_SCHED_CLOCK
257 select HAVE_USER_RETURN_NOTIFIER
258 select HAVE_GENERIC_VDSO
259 select HOTPLUG_SMT if SMP
260 select IRQ_FORCED_THREADING
261 select NEED_PER_CPU_EMBED_FIRST_CHUNK
262 select NEED_PER_CPU_PAGE_FIRST_CHUNK
263 select NEED_SG_DMA_LENGTH
264 select PCI_DOMAINS if PCI
265 select PCI_LOCKLESS_CONFIG if PCI
268 select RTC_MC146818_LIB
271 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
272 select SYSCTL_EXCEPTION_TRACE
273 select THREAD_INFO_IN_TASK
274 select TRACE_IRQFLAGS_SUPPORT
275 select USER_STACKTRACE_SUPPORT
277 select HAVE_ARCH_KCSAN if X86_64
278 select X86_FEATURE_NAMES if PROC_FS
279 select PROC_PID_ARCH_STATUS if PROC_FS
280 select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
281 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
283 config INSTRUCTION_DECODER
285 depends on KPROBES || PERF_EVENTS || UPROBES
289 default "elf32-i386" if X86_32
290 default "elf64-x86-64" if X86_64
292 config LOCKDEP_SUPPORT
295 config STACKTRACE_SUPPORT
301 config ARCH_MMAP_RND_BITS_MIN
305 config ARCH_MMAP_RND_BITS_MAX
309 config ARCH_MMAP_RND_COMPAT_BITS_MIN
312 config ARCH_MMAP_RND_COMPAT_BITS_MAX
318 config GENERIC_ISA_DMA
320 depends on ISA_DMA_API
325 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
327 config GENERIC_BUG_RELATIVE_POINTERS
330 config ARCH_MAY_HAVE_PC_FDC
332 depends on ISA_DMA_API
334 config GENERIC_CALIBRATE_DELAY
337 config ARCH_HAS_CPU_RELAX
340 config ARCH_HIBERNATION_POSSIBLE
345 default 1024 if X86_64
348 config ARCH_SUSPEND_POSSIBLE
354 config KASAN_SHADOW_OFFSET
357 default 0xdffffc0000000000
359 config HAVE_INTEL_TXT
361 depends on INTEL_IOMMU && ACPI
365 depends on X86_32 && SMP
369 depends on X86_64 && SMP
371 config ARCH_SUPPORTS_UPROBES
374 config FIX_EARLYCON_MEM
377 config DYNAMIC_PHYSICAL_MASK
380 config PGTABLE_LEVELS
382 default 5 if X86_5LEVEL
387 config CC_HAS_SANE_STACKPROTECTOR
389 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
390 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
392 We have to make sure stack protector is unconditionally disabled if
393 the compiler produces broken code or if it does not let us control
394 the segment on 32-bit kernels.
396 menu "Processor type and features"
399 bool "Symmetric multi-processing support"
401 This enables support for systems with more than one CPU. If you have
402 a system with only one CPU, say N. If you have a system with more
405 If you say N here, the kernel will run on uni- and multiprocessor
406 machines, but will use only one CPU of a multiprocessor machine. If
407 you say Y here, the kernel will run on many, but not all,
408 uniprocessor machines. On a uniprocessor machine, the kernel
409 will run faster if you say N here.
411 Note that if you say Y here and choose architecture "586" or
412 "Pentium" under "Processor family", the kernel will not work on 486
413 architectures. Similarly, multiprocessor kernels for the "PPro"
414 architecture may not work on all Pentium based boards.
416 People using multiprocessor machines who say Y here should also say
417 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
418 Management" code will be disabled if you say Y here.
420 See also <file:Documentation/x86/i386/IO-APIC.rst>,
421 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
422 <http://www.tldp.org/docs.html#howto>.
424 If you don't know what to do here, say N.
426 config X86_FEATURE_NAMES
427 bool "Processor feature human-readable names" if EMBEDDED
430 This option compiles in a table of x86 feature bits and corresponding
431 names. This is required to support /proc/cpuinfo and a few kernel
432 messages. You can disable this to save space, at the expense of
433 making those few kernel messages show numeric feature bits instead.
438 bool "Support x2apic"
439 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
441 This enables x2apic support on CPUs that have this feature.
443 This allows 32-bit apic IDs (so it can support very large systems),
444 and accesses the local apic via MSRs not via mmio.
446 If you don't know what to do here, say N.
449 bool "Enable MPS table" if ACPI
451 depends on X86_LOCAL_APIC
453 For old smp systems that do not have proper acpi support. Newer systems
454 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
458 depends on X86_GOLDFISH
461 bool "Avoid speculative indirect branches in kernel"
464 Compile kernel with the retpoline compiler options to guard against
465 kernel-to-user data leaks by avoiding speculative indirect
466 branches. Requires a compiler with -mindirect-branch=thunk-extern
467 support for full protection. The kernel may run slower.
470 def_bool $(cc-option,-mharden-sls=all)
473 bool "Mitigate Straight-Line-Speculation"
474 depends on CC_HAS_SLS && X86_64
477 Compile the kernel with straight-line-speculation options to guard
478 against straight line speculation. The kernel image might be slightly
481 config X86_CPU_RESCTRL
482 bool "x86 CPU resource control support"
483 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
485 select PROC_CPU_RESCTRL if PROC_FS
487 Enable x86 CPU resource control support.
489 Provide support for the allocation and monitoring of system resources
492 Intel calls this Intel Resource Director Technology
493 (Intel(R) RDT). More information about RDT can be found in the
494 Intel x86 Architecture Software Developer Manual.
496 AMD calls this AMD Platform Quality of Service (AMD QoS).
497 More information about AMD QoS can be found in the AMD64 Technology
498 Platform Quality of Service Extensions manual.
504 bool "Support for big SMP systems with more than 8 CPUs"
507 This option is needed for the systems that have more than 8 CPUs.
509 config X86_EXTENDED_PLATFORM
510 bool "Support for extended (non-PC) x86 platforms"
513 If you disable this option then the kernel will only support
514 standard PC platforms. (which covers the vast majority of
517 If you enable this option then you'll be able to select support
518 for the following (non-PC) 32 bit x86 platforms:
519 Goldfish (Android emulator)
522 SGI 320/540 (Visual Workstation)
523 STA2X11-based (e.g. Northville)
524 Moorestown MID devices
526 If you have one of these systems, or if you want to build a
527 generic distribution kernel, say Y here - otherwise say N.
531 config X86_EXTENDED_PLATFORM
532 bool "Support for extended (non-PC) x86 platforms"
535 If you disable this option then the kernel will only support
536 standard PC platforms. (which covers the vast majority of
539 If you enable this option then you'll be able to select support
540 for the following (non-PC) 64 bit x86 platforms:
545 If you have one of these systems, or if you want to build a
546 generic distribution kernel, say Y here - otherwise say N.
548 # This is an alphabetically sorted list of 64 bit extended platforms
549 # Please maintain the alphabetic order if and when there are additions
551 bool "Numascale NumaChip"
553 depends on X86_EXTENDED_PLATFORM
556 depends on X86_X2APIC
557 depends on PCI_MMCONFIG
559 Adds support for Numascale NumaChip large-SMP systems. Needed to
560 enable more than ~168 cores.
561 If you don't have one of these, you should say N here.
565 select HYPERVISOR_GUEST
567 depends on X86_64 && PCI
568 depends on X86_EXTENDED_PLATFORM
571 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
572 supposed to run on these EM64T-based machines. Only choose this option
573 if you have one of these machines.
576 bool "SGI Ultraviolet"
578 depends on X86_EXTENDED_PLATFORM
581 depends on KEXEC_CORE
582 depends on X86_X2APIC
585 This option is needed in order to support SGI Ultraviolet systems.
586 If you don't have one of these, you should say N here.
588 # Following is an alphabetically sorted list of 32 bit extended platforms
589 # Please maintain the alphabetic order if and when there are additions
592 bool "Goldfish (Virtual Platform)"
593 depends on X86_EXTENDED_PLATFORM
595 Enable support for the Goldfish virtual platform used primarily
596 for Android development. Unless you are building for the Android
597 Goldfish emulator say N here.
600 bool "CE4100 TV platform"
602 depends on PCI_GODIRECT
603 depends on X86_IO_APIC
605 depends on X86_EXTENDED_PLATFORM
606 select X86_REBOOTFIXUPS
608 select OF_EARLY_FLATTREE
610 Select for the Intel CE media processor (CE4100) SOC.
611 This option compiles in support for the CE4100 SOC for settop
612 boxes and media devices.
615 bool "Intel MID platform support"
616 depends on X86_EXTENDED_PLATFORM
617 depends on X86_PLATFORM_DEVICES
619 depends on X86_64 || (PCI_GOANY && X86_32)
620 depends on X86_IO_APIC
625 Select to build a kernel capable of supporting Intel MID (Mobile
626 Internet Device) platform systems which do not have the PCI legacy
627 interfaces. If you are building for a PC class system say N here.
629 Intel MID platforms are based on an Intel processor and chipset which
630 consume less power than most of the x86 derivatives.
632 config X86_INTEL_QUARK
633 bool "Intel Quark platform support"
635 depends on X86_EXTENDED_PLATFORM
636 depends on X86_PLATFORM_DEVICES
640 depends on X86_IO_APIC
645 Select to include support for Quark X1000 SoC.
646 Say Y here if you have a Quark based system such as the Arduino
647 compatible Intel Galileo.
649 config X86_INTEL_LPSS
650 bool "Intel Low Power Subsystem Support"
651 depends on X86 && ACPI && PCI
656 Select to build support for Intel Low Power Subsystem such as
657 found on Intel Lynxpoint PCH. Selecting this option enables
658 things like clock tree (common clock framework) and pincontrol
659 which are needed by the LPSS peripheral drivers.
661 config X86_AMD_PLATFORM_DEVICE
662 bool "AMD ACPI2Platform devices support"
667 Select to interpret AMD specific ACPI device to platform device
668 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
669 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
670 implemented under PINCTRL subsystem.
673 tristate "Intel SoC IOSF Sideband support for SoC platforms"
676 This option enables sideband register access support for Intel SoC
677 platforms. On these platforms the IOSF sideband is used in lieu of
678 MSR's for some register accesses, mostly but not limited to thermal
679 and power. Drivers may query the availability of this device to
680 determine if they need the sideband in order to work on these
681 platforms. The sideband is available on the following SoC products.
682 This list is not meant to be exclusive.
687 You should say Y if you are running a kernel on one of these SoC's.
689 config IOSF_MBI_DEBUG
690 bool "Enable IOSF sideband access through debugfs"
691 depends on IOSF_MBI && DEBUG_FS
693 Select this option to expose the IOSF sideband access registers (MCR,
694 MDR, MCRX) through debugfs to write and read register information from
695 different units on the SoC. This is most useful for obtaining device
696 state information for debug and analysis. As this is a general access
697 mechanism, users of this option would have specific knowledge of the
698 device they want to access.
700 If you don't require the option or are in doubt, say N.
703 bool "RDC R-321x SoC"
705 depends on X86_EXTENDED_PLATFORM
707 select X86_REBOOTFIXUPS
709 This option is needed for RDC R-321x system-on-chip, also known
711 If you don't have one of these chips, you should say N here.
713 config X86_32_NON_STANDARD
714 bool "Support non-standard 32-bit SMP architectures"
715 depends on X86_32 && SMP
716 depends on X86_EXTENDED_PLATFORM
718 This option compiles in the bigsmp and STA2X11 default
719 subarchitectures. It is intended for a generic binary
720 kernel. If you select them all, kernel will probe it one by
721 one and will fallback to default.
723 # Alphabetically sorted list of Non standard 32 bit platforms
725 config X86_SUPPORTS_MEMORY_FAILURE
727 # MCE code calls memory_failure():
729 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
730 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
731 depends on X86_64 || !SPARSEMEM
732 select ARCH_SUPPORTS_MEMORY_FAILURE
735 bool "STA2X11 Companion Chip Support"
736 depends on X86_32_NON_STANDARD && PCI
741 This adds support for boards based on the STA2X11 IO-Hub,
742 a.k.a. "ConneXt". The chip is used in place of the standard
743 PC chipset, so all "standard" peripherals are missing. If this
744 option is selected the kernel will still be able to boot on
745 standard PC machines.
748 tristate "Eurobraille/Iris poweroff module"
751 The Iris machines from EuroBraille do not have APM or ACPI support
752 to shut themselves down properly. A special I/O sequence is
753 needed to do so, which is what this module does at
756 This is only for Iris machines from EuroBraille.
760 config SCHED_OMIT_FRAME_POINTER
762 prompt "Single-depth WCHAN output"
765 Calculate simpler /proc/<PID>/wchan values. If this option
766 is disabled then wchan values will recurse back to the
767 caller function. This provides more accurate wchan values,
768 at the expense of slightly more scheduling overhead.
770 If in doubt, say "Y".
772 menuconfig HYPERVISOR_GUEST
773 bool "Linux guest support"
775 Say Y here to enable options for running Linux under various hyper-
776 visors. This option enables basic hypervisor detection and platform
779 If you say N, all options in this submenu will be skipped and
780 disabled, and Linux guest support won't be built in.
785 bool "Enable paravirtualization code"
786 depends on HAVE_STATIC_CALL
788 This changes the kernel so it can modify itself when it is run
789 under a hypervisor, potentially improving performance significantly
790 over full virtualization. However, when run without a hypervisor
791 the kernel is theoretically slower and slightly larger.
796 config PARAVIRT_DEBUG
797 bool "paravirt-ops debugging"
798 depends on PARAVIRT && DEBUG_KERNEL
800 Enable to debug paravirt_ops internals. Specifically, BUG if
801 a paravirt_op is missing when it is called.
803 config PARAVIRT_SPINLOCKS
804 bool "Paravirtualization layer for spinlocks"
805 depends on PARAVIRT && SMP
807 Paravirtualized spinlocks allow a pvops backend to replace the
808 spinlock implementation with something virtualization-friendly
809 (for example, block the virtual CPU rather than spinning).
811 It has a minimal impact on native kernels and gives a nice performance
812 benefit on paravirtualized KVM / Xen kernels.
814 If you are unsure how to answer this question, answer Y.
816 config X86_HV_CALLBACK_VECTOR
819 source "arch/x86/xen/Kconfig"
822 bool "KVM Guest support (including kvmclock)"
824 select PARAVIRT_CLOCK
825 select ARCH_CPUIDLE_HALTPOLL
826 select X86_HV_CALLBACK_VECTOR
829 This option enables various optimizations for running under the KVM
830 hypervisor. It includes a paravirtualized clock, so that instead
831 of relying on a PIT (or probably other) emulation by the
832 underlying device model, the host provides the guest with
833 timing infrastructure such as time of day, and system time
835 config ARCH_CPUIDLE_HALTPOLL
837 prompt "Disable host haltpoll when loading haltpoll driver"
839 If virtualized under KVM, disable host haltpoll.
842 bool "Support for running PVH guests"
844 This option enables the PVH entry point for guest virtual machines
845 as specified in the x86/HVM direct boot ABI.
847 config PARAVIRT_TIME_ACCOUNTING
848 bool "Paravirtual steal time accounting"
851 Select this option to enable fine granularity task steal time
852 accounting. Time spent executing other tasks in parallel with
853 the current vCPU is discounted from the vCPU power. To account for
854 that, there can be a small performance impact.
856 If in doubt, say N here.
858 config PARAVIRT_CLOCK
861 config JAILHOUSE_GUEST
862 bool "Jailhouse non-root cell support"
863 depends on X86_64 && PCI
866 This option allows to run Linux as guest in a Jailhouse non-root
867 cell. You can leave this option disabled if you only want to start
868 Jailhouse and run Linux afterwards in the root cell.
871 bool "ACRN Guest support"
873 select X86_HV_CALLBACK_VECTOR
875 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
876 a flexible, lightweight reference open-source hypervisor, built with
877 real-time and safety-criticality in mind. It is built for embedded
878 IOT with small footprint and real-time features. More details can be
879 found in https://projectacrn.org/.
881 config INTEL_TDX_GUEST
882 bool "Intel TDX (Trust Domain Extensions) - Guest Support"
883 depends on X86_64 && CPU_SUP_INTEL
884 depends on X86_X2APIC
885 select ARCH_HAS_CC_PLATFORM
886 select X86_MEM_ENCRYPT
889 Support running as a guest under Intel TDX. Without this support,
890 the guest kernel can not boot or run under TDX.
891 TDX includes memory encryption and integrity capabilities
892 which protect the confidentiality and integrity of guest
893 memory contents and CPU state. TDX guests are protected from
894 some attacks from the VMM.
896 endif #HYPERVISOR_GUEST
898 source "arch/x86/Kconfig.cpu"
902 prompt "HPET Timer Support" if X86_32
904 Use the IA-PC HPET (High Precision Event Timer) to manage
905 time in preference to the PIT and RTC, if a HPET is
907 HPET is the next generation timer replacing legacy 8254s.
908 The HPET provides a stable time base on SMP
909 systems, unlike the TSC, but it is more expensive to access,
910 as it is off-chip. The interface used is documented
911 in the HPET spec, revision 1.
913 You can safely choose Y here. However, HPET will only be
914 activated if the platform and the BIOS support this feature.
915 Otherwise the 8254 will be used for timing services.
917 Choose N to continue using the legacy 8254 timer.
919 config HPET_EMULATE_RTC
921 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
923 # Mark as expert because too many people got it wrong.
924 # The code disables itself when not needed.
927 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
928 bool "Enable DMI scanning" if EXPERT
930 Enabled scanning of DMI to identify machine quirks. Say Y
931 here unless you have verified that your setup is not
932 affected by entries in the DMI blacklist. Required by PNP
936 bool "Old AMD GART IOMMU support"
940 depends on X86_64 && PCI && AMD_NB
942 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
943 GART based hardware IOMMUs.
945 The GART supports full DMA access for devices with 32-bit access
946 limitations, on systems with more than 3 GB. This is usually needed
947 for USB, sound, many IDE/SATA chipsets and some other devices.
949 Newer systems typically have a modern AMD IOMMU, supported via
950 the CONFIG_AMD_IOMMU=y config option.
952 In normal configurations this driver is only active when needed:
953 there's more than 3 GB of memory and the system contains a
954 32-bit limited device.
959 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
960 depends on X86_64 && SMP && DEBUG_KERNEL
961 select CPUMASK_OFFSTACK
963 Enable maximum number of CPUS and NUMA Nodes for this architecture.
967 # The maximum number of CPUs supported:
969 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
970 # and which can be configured interactively in the
971 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
973 # The ranges are different on 32-bit and 64-bit kernels, depending on
974 # hardware capabilities and scalability features of the kernel.
976 # ( If MAXSMP is enabled we just use the highest possible value and disable
977 # interactive configuration. )
980 config NR_CPUS_RANGE_BEGIN
982 default NR_CPUS_RANGE_END if MAXSMP
986 config NR_CPUS_RANGE_END
989 default 64 if SMP && X86_BIGSMP
990 default 8 if SMP && !X86_BIGSMP
993 config NR_CPUS_RANGE_END
996 default 8192 if SMP && CPUMASK_OFFSTACK
997 default 512 if SMP && !CPUMASK_OFFSTACK
1000 config NR_CPUS_DEFAULT
1003 default 32 if X86_BIGSMP
1007 config NR_CPUS_DEFAULT
1010 default 8192 if MAXSMP
1015 int "Maximum number of CPUs" if SMP && !MAXSMP
1016 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1017 default NR_CPUS_DEFAULT
1019 This allows you to specify the maximum number of CPUs which this
1020 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1021 supported value is 8192, otherwise the maximum value is 512. The
1022 minimum value which makes sense is 2.
1024 This is purely to save memory: each supported CPU adds about 8KB
1025 to the kernel image.
1027 config SCHED_CLUSTER
1028 bool "Cluster scheduler support"
1032 Cluster scheduler support improves the CPU scheduler's decision
1033 making when dealing with machines that have clusters of CPUs.
1034 Cluster usually means a couple of CPUs which are placed closely
1035 by sharing mid-level caches, last-level cache tags or internal
1043 prompt "Multi-core scheduler support"
1046 Multi-core scheduler support improves the CPU scheduler's decision
1047 making when dealing with multi-core CPU chips at a cost of slightly
1048 increased overhead in some places. If unsure say N here.
1050 config SCHED_MC_PRIO
1051 bool "CPU core priorities scheduler support"
1052 depends on SCHED_MC && CPU_SUP_INTEL
1053 select X86_INTEL_PSTATE
1057 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1058 core ordering determined at manufacturing time, which allows
1059 certain cores to reach higher turbo frequencies (when running
1060 single threaded workloads) than others.
1062 Enabling this kernel feature teaches the scheduler about
1063 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1064 scheduler's CPU selection logic accordingly, so that higher
1065 overall system performance can be achieved.
1067 This feature will have no effect on CPUs without this feature.
1069 If unsure say Y here.
1073 depends on !SMP && X86_LOCAL_APIC
1076 bool "Local APIC support on uniprocessors" if !PCI_MSI
1078 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1080 A local APIC (Advanced Programmable Interrupt Controller) is an
1081 integrated interrupt controller in the CPU. If you have a single-CPU
1082 system which has a processor with a local APIC, you can say Y here to
1083 enable and use it. If you say Y here even though your machine doesn't
1084 have a local APIC, then the kernel will still run with no slowdown at
1085 all. The local APIC supports CPU-generated self-interrupts (timer,
1086 performance counters), and the NMI watchdog which detects hard
1089 config X86_UP_IOAPIC
1090 bool "IO-APIC support on uniprocessors"
1091 depends on X86_UP_APIC
1093 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1094 SMP-capable replacement for PC-style interrupt controllers. Most
1095 SMP systems and many recent uniprocessor systems have one.
1097 If you have a single-CPU system with an IO-APIC, you can say Y here
1098 to use it. If you say Y here even though your machine doesn't have
1099 an IO-APIC, then the kernel will still run with no slowdown at all.
1101 config X86_LOCAL_APIC
1103 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1104 select IRQ_DOMAIN_HIERARCHY
1105 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1109 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1111 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1112 bool "Reroute for broken boot IRQs"
1113 depends on X86_IO_APIC
1115 This option enables a workaround that fixes a source of
1116 spurious interrupts. This is recommended when threaded
1117 interrupt handling is used on systems where the generation of
1118 superfluous "boot interrupts" cannot be disabled.
1120 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1121 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1122 kernel does during interrupt handling). On chipsets where this
1123 boot IRQ generation cannot be disabled, this workaround keeps
1124 the original IRQ line masked so that only the equivalent "boot
1125 IRQ" is delivered to the CPUs. The workaround also tells the
1126 kernel to set up the IRQ handler on the boot IRQ line. In this
1127 way only one interrupt is delivered to the kernel. Otherwise
1128 the spurious second interrupt may cause the kernel to bring
1129 down (vital) interrupt lines.
1131 Only affects "broken" chipsets. Interrupt sharing may be
1132 increased on these systems.
1135 bool "Machine Check / overheating reporting"
1136 select GENERIC_ALLOCATOR
1139 Machine Check support allows the processor to notify the
1140 kernel if it detects a problem (e.g. overheating, data corruption).
1141 The action the kernel takes depends on the severity of the problem,
1142 ranging from warning messages to halting the machine.
1144 config X86_MCELOG_LEGACY
1145 bool "Support for deprecated /dev/mcelog character device"
1148 Enable support for /dev/mcelog which is needed by the old mcelog
1149 userspace logging daemon. Consider switching to the new generation
1152 config X86_MCE_INTEL
1154 prompt "Intel MCE features"
1155 depends on X86_MCE && X86_LOCAL_APIC
1157 Additional support for intel specific MCE features such as
1158 the thermal monitor.
1162 prompt "AMD MCE features"
1163 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1165 Additional support for AMD specific MCE features such as
1166 the DRAM Error Threshold.
1168 config X86_ANCIENT_MCE
1169 bool "Support for old Pentium 5 / WinChip machine checks"
1170 depends on X86_32 && X86_MCE
1172 Include support for machine check handling on old Pentium 5 or WinChip
1173 systems. These typically need to be enabled explicitly on the command
1176 config X86_MCE_THRESHOLD
1177 depends on X86_MCE_AMD || X86_MCE_INTEL
1180 config X86_MCE_INJECT
1181 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1182 tristate "Machine check injector support"
1184 Provide support for injecting machine checks for testing purposes.
1185 If you don't know what a machine check is and you don't do kernel
1186 QA it is safe to say n.
1188 source "arch/x86/events/Kconfig"
1190 config X86_LEGACY_VM86
1191 bool "Legacy VM86 support"
1194 This option allows user programs to put the CPU into V8086
1195 mode, which is an 80286-era approximation of 16-bit real mode.
1197 Some very old versions of X and/or vbetool require this option
1198 for user mode setting. Similarly, DOSEMU will use it if
1199 available to accelerate real mode DOS programs. However, any
1200 recent version of DOSEMU, X, or vbetool should be fully
1201 functional even without kernel VM86 support, as they will all
1202 fall back to software emulation. Nevertheless, if you are using
1203 a 16-bit DOS program where 16-bit performance matters, vm86
1204 mode might be faster than emulation and you might want to
1207 Note that any app that works on a 64-bit kernel is unlikely to
1208 need this option, as 64-bit kernels don't, and can't, support
1209 V8086 mode. This option is also unrelated to 16-bit protected
1210 mode and is not needed to run most 16-bit programs under Wine.
1212 Enabling this option increases the complexity of the kernel
1213 and slows down exception handling a tiny bit.
1215 If unsure, say N here.
1219 default X86_LEGACY_VM86
1222 bool "Enable support for 16-bit segments" if EXPERT
1224 depends on MODIFY_LDT_SYSCALL
1226 This option is required by programs like Wine to run 16-bit
1227 protected mode legacy code on x86 processors. Disabling
1228 this option saves about 300 bytes on i386, or around 6K text
1229 plus 16K runtime memory on x86-64,
1233 depends on X86_16BIT && X86_32
1237 depends on X86_16BIT && X86_64
1239 config X86_VSYSCALL_EMULATION
1240 bool "Enable vsyscall emulation" if EXPERT
1244 This enables emulation of the legacy vsyscall page. Disabling
1245 it is roughly equivalent to booting with vsyscall=none, except
1246 that it will also disable the helpful warning if a program
1247 tries to use a vsyscall. With this option set to N, offending
1248 programs will just segfault, citing addresses of the form
1251 This option is required by many programs built before 2013, and
1252 care should be used even with newer programs if set to N.
1254 Disabling this option saves about 7K of kernel size and
1255 possibly 4K of additional runtime pagetable memory.
1257 config X86_IOPL_IOPERM
1258 bool "IOPERM and IOPL Emulation"
1261 This enables the ioperm() and iopl() syscalls which are necessary
1262 for legacy applications.
1264 Legacy IOPL support is an overbroad mechanism which allows user
1265 space aside of accessing all 65536 I/O ports also to disable
1266 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1267 capabilities and permission from potentially active security
1270 The emulation restricts the functionality of the syscall to
1271 only allowing the full range I/O port access, but prevents the
1272 ability to disable interrupts from user space which would be
1273 granted if the hardware IOPL mechanism would be used.
1276 tristate "Toshiba Laptop support"
1279 This adds a driver to safely access the System Management Mode of
1280 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1281 not work on models with a Phoenix BIOS. The System Management Mode
1282 is used to set the BIOS and power saving options on Toshiba portables.
1284 For information on utilities to make use of this driver see the
1285 Toshiba Linux utilities web site at:
1286 <http://www.buzzard.org.uk/toshiba/>.
1288 Say Y if you intend to run this kernel on a Toshiba portable.
1291 config X86_REBOOTFIXUPS
1292 bool "Enable X86 board specific fixups for reboot"
1295 This enables chipset and/or board specific fixups to be done
1296 in order to get reboot to work correctly. This is only needed on
1297 some combinations of hardware and BIOS. The symptom, for which
1298 this config is intended, is when reboot ends with a stalled/hung
1301 Currently, the only fixup is for the Geode machines using
1302 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1304 Say Y if you want to enable the fixup. Currently, it's safe to
1305 enable this option even if you don't need it.
1309 bool "CPU microcode loading support"
1311 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1313 If you say Y here, you will be able to update the microcode on
1314 Intel and AMD processors. The Intel support is for the IA32 family,
1315 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1316 AMD support is for families 0x10 and later. You will obviously need
1317 the actual microcode binary data itself which is not shipped with
1320 The preferred method to load microcode from a detached initrd is described
1321 in Documentation/x86/microcode.rst. For that you need to enable
1322 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1323 initrd for microcode blobs.
1325 In addition, you can build the microcode into the kernel. For that you
1326 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1329 config MICROCODE_INTEL
1330 bool "Intel microcode loading support"
1331 depends on CPU_SUP_INTEL && MICROCODE
1334 This options enables microcode patch loading support for Intel
1337 For the current Intel microcode data package go to
1338 <https://downloadcenter.intel.com> and search for
1339 'Linux Processor Microcode Data File'.
1341 config MICROCODE_AMD
1342 bool "AMD microcode loading support"
1343 depends on CPU_SUP_AMD && MICROCODE
1345 If you select this option, microcode patch loading support for AMD
1346 processors will be enabled.
1348 config MICROCODE_OLD_INTERFACE
1349 bool "Ancient loading interface (DEPRECATED)"
1351 depends on MICROCODE
1353 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1354 which was used by userspace tools like iucode_tool and microcode.ctl.
1355 It is inadequate because it runs too late to be able to properly
1356 load microcode on a machine and it needs special tools. Instead, you
1357 should've switched to the early loading method with the initrd or
1358 builtin microcode by now: Documentation/x86/microcode.rst
1361 tristate "/dev/cpu/*/msr - Model-specific register support"
1363 This device gives privileged processes access to the x86
1364 Model-Specific Registers (MSRs). It is a character device with
1365 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1366 MSR accesses are directed to a specific CPU on multi-processor
1370 tristate "/dev/cpu/*/cpuid - CPU information support"
1372 This device gives processes access to the x86 CPUID instruction to
1373 be executed on a specific processor. It is a character device
1374 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1378 prompt "High Memory Support"
1385 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1386 However, the address space of 32-bit x86 processors is only 4
1387 Gigabytes large. That means that, if you have a large amount of
1388 physical memory, not all of it can be "permanently mapped" by the
1389 kernel. The physical memory that's not permanently mapped is called
1392 If you are compiling a kernel which will never run on a machine with
1393 more than 1 Gigabyte total physical RAM, answer "off" here (default
1394 choice and suitable for most users). This will result in a "3GB/1GB"
1395 split: 3GB are mapped so that each process sees a 3GB virtual memory
1396 space and the remaining part of the 4GB virtual memory space is used
1397 by the kernel to permanently map as much physical memory as
1400 If the machine has between 1 and 4 Gigabytes physical RAM, then
1403 If more than 4 Gigabytes is used then answer "64GB" here. This
1404 selection turns Intel PAE (Physical Address Extension) mode on.
1405 PAE implements 3-level paging on IA32 processors. PAE is fully
1406 supported by Linux, PAE mode is implemented on all recent Intel
1407 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1408 then the kernel will not boot on CPUs that don't support PAE!
1410 The actual amount of total physical memory will either be
1411 auto detected or can be forced by using a kernel command line option
1412 such as "mem=256M". (Try "man bootparam" or see the documentation of
1413 your boot loader (lilo or loadlin) about how to pass options to the
1414 kernel at boot time.)
1416 If unsure, say "off".
1421 Select this if you have a 32-bit processor and between 1 and 4
1422 gigabytes of physical RAM.
1426 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1429 Select this if you have a 32-bit processor and more than 4
1430 gigabytes of physical RAM.
1435 prompt "Memory split" if EXPERT
1439 Select the desired split between kernel and user memory.
1441 If the address range available to the kernel is less than the
1442 physical memory installed, the remaining memory will be available
1443 as "high memory". Accessing high memory is a little more costly
1444 than low memory, as it needs to be mapped into the kernel first.
1445 Note that increasing the kernel address space limits the range
1446 available to user programs, making the address space there
1447 tighter. Selecting anything other than the default 3G/1G split
1448 will also likely make your kernel incompatible with binary-only
1451 If you are not absolutely sure what you are doing, leave this
1455 bool "3G/1G user/kernel split"
1456 config VMSPLIT_3G_OPT
1458 bool "3G/1G user/kernel split (for full 1G low memory)"
1460 bool "2G/2G user/kernel split"
1461 config VMSPLIT_2G_OPT
1463 bool "2G/2G user/kernel split (for full 2G low memory)"
1465 bool "1G/3G user/kernel split"
1470 default 0xB0000000 if VMSPLIT_3G_OPT
1471 default 0x80000000 if VMSPLIT_2G
1472 default 0x78000000 if VMSPLIT_2G_OPT
1473 default 0x40000000 if VMSPLIT_1G
1479 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1482 bool "PAE (Physical Address Extension) Support"
1483 depends on X86_32 && !HIGHMEM4G
1484 select PHYS_ADDR_T_64BIT
1487 PAE is required for NX support, and furthermore enables
1488 larger swapspace support for non-overcommit purposes. It
1489 has the cost of more pagetable lookup overhead, and also
1490 consumes more pagetable space per process.
1493 bool "Enable 5-level page tables support"
1495 select DYNAMIC_MEMORY_LAYOUT
1496 select SPARSEMEM_VMEMMAP
1499 5-level paging enables access to larger address space:
1500 upto 128 PiB of virtual address space and 4 PiB of
1501 physical address space.
1503 It will be supported by future Intel CPUs.
1505 A kernel with the option enabled can be booted on machines that
1506 support 4- or 5-level paging.
1508 See Documentation/x86/x86_64/5level-paging.rst for more
1513 config X86_DIRECT_GBPAGES
1517 Certain kernel features effectively disable kernel
1518 linear 1 GB mappings (even if the CPU otherwise
1519 supports them), so don't confuse the user by printing
1520 that we have them enabled.
1522 config X86_CPA_STATISTICS
1523 bool "Enable statistic for Change Page Attribute"
1526 Expose statistics about the Change Page Attribute mechanism, which
1527 helps to determine the effectiveness of preserving large and huge
1528 page mappings when mapping protections are changed.
1530 config X86_MEM_ENCRYPT
1531 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1532 select DYNAMIC_PHYSICAL_MASK
1533 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1536 config AMD_MEM_ENCRYPT
1537 bool "AMD Secure Memory Encryption (SME) support"
1538 depends on X86_64 && CPU_SUP_AMD
1539 select DMA_COHERENT_POOL
1540 select ARCH_USE_MEMREMAP_PROT
1541 select INSTRUCTION_DECODER
1542 select ARCH_HAS_CC_PLATFORM
1543 select X86_MEM_ENCRYPT
1545 Say yes to enable support for the encryption of system memory.
1546 This requires an AMD processor that supports Secure Memory
1549 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1550 bool "Activate AMD Secure Memory Encryption (SME) by default"
1551 depends on AMD_MEM_ENCRYPT
1553 Say yes to have system memory encrypted by default if running on
1554 an AMD processor that supports Secure Memory Encryption (SME).
1556 If set to Y, then the encryption of system memory can be
1557 deactivated with the mem_encrypt=off command line option.
1559 If set to N, then the encryption of system memory can be
1560 activated with the mem_encrypt=on command line option.
1562 # Common NUMA Features
1564 bool "NUMA Memory Allocation and Scheduler Support"
1566 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1567 default y if X86_BIGSMP
1568 select USE_PERCPU_NUMA_NODE_ID
1570 Enable NUMA (Non-Uniform Memory Access) support.
1572 The kernel will try to allocate memory used by a CPU on the
1573 local memory controller of the CPU and add some more
1574 NUMA awareness to the kernel.
1576 For 64-bit this is recommended if the system is Intel Core i7
1577 (or later), AMD Opteron, or EM64T NUMA.
1579 For 32-bit this is only needed if you boot a 32-bit
1580 kernel on a 64-bit NUMA platform.
1582 Otherwise, you should say N.
1586 prompt "Old style AMD Opteron NUMA detection"
1587 depends on X86_64 && NUMA && PCI
1589 Enable AMD NUMA node topology detection. You should say Y here if
1590 you have a multi processor AMD system. This uses an old method to
1591 read the NUMA configuration directly from the builtin Northbridge
1592 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1593 which also takes priority if both are compiled in.
1595 config X86_64_ACPI_NUMA
1597 prompt "ACPI NUMA detection"
1598 depends on X86_64 && NUMA && ACPI && PCI
1601 Enable ACPI SRAT based node topology detection.
1604 bool "NUMA emulation"
1607 Enable NUMA emulation. A flat machine will be split
1608 into virtual nodes when booted with "numa=fake=N", where N is the
1609 number of nodes. This is only useful for debugging.
1612 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1614 default "10" if MAXSMP
1615 default "6" if X86_64
1619 Specify the maximum number of NUMA Nodes available on the target
1620 system. Increases memory reserved to accommodate various tables.
1622 config ARCH_FLATMEM_ENABLE
1624 depends on X86_32 && !NUMA
1626 config ARCH_SPARSEMEM_ENABLE
1628 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1629 select SPARSEMEM_STATIC if X86_32
1630 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1632 config ARCH_SPARSEMEM_DEFAULT
1633 def_bool X86_64 || (NUMA && X86_32)
1635 config ARCH_SELECT_MEMORY_MODEL
1637 depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE
1639 config ARCH_MEMORY_PROBE
1640 bool "Enable sysfs memory/probe interface"
1641 depends on MEMORY_HOTPLUG
1643 This option enables a sysfs memory/probe interface for testing.
1644 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1645 If you are unsure how to answer this question, answer N.
1647 config ARCH_PROC_KCORE_TEXT
1649 depends on X86_64 && PROC_KCORE
1651 config ILLEGAL_POINTER_VALUE
1654 default 0xdead000000000000 if X86_64
1656 config X86_PMEM_LEGACY_DEVICE
1659 config X86_PMEM_LEGACY
1660 tristate "Support non-standard NVDIMMs and ADR protected memory"
1661 depends on PHYS_ADDR_T_64BIT
1663 select X86_PMEM_LEGACY_DEVICE
1664 select NUMA_KEEP_MEMINFO if NUMA
1667 Treat memory marked using the non-standard e820 type of 12 as used
1668 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1669 The kernel will offer these regions to the 'pmem' driver so
1670 they can be used for persistent storage.
1675 bool "Allocate 3rd-level pagetables from highmem"
1678 The VM uses one page table entry for each page of physical memory.
1679 For systems with a lot of RAM, this can be wasteful of precious
1680 low memory. Setting this option will put user-space page table
1681 entries in high memory.
1683 config X86_CHECK_BIOS_CORRUPTION
1684 bool "Check for low memory corruption"
1686 Periodically check for memory corruption in low memory, which
1687 is suspected to be caused by BIOS. Even when enabled in the
1688 configuration, it is disabled at runtime. Enable it by
1689 setting "memory_corruption_check=1" on the kernel command
1690 line. By default it scans the low 64k of memory every 60
1691 seconds; see the memory_corruption_check_size and
1692 memory_corruption_check_period parameters in
1693 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1695 When enabled with the default parameters, this option has
1696 almost no overhead, as it reserves a relatively small amount
1697 of memory and scans it infrequently. It both detects corruption
1698 and prevents it from affecting the running system.
1700 It is, however, intended as a diagnostic tool; if repeatable
1701 BIOS-originated corruption always affects the same memory,
1702 you can use memmap= to prevent the kernel from using that
1705 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1706 bool "Set the default setting of memory_corruption_check"
1707 depends on X86_CHECK_BIOS_CORRUPTION
1710 Set whether the default state of memory_corruption_check is
1713 config MATH_EMULATION
1715 depends on MODIFY_LDT_SYSCALL
1716 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1718 Linux can emulate a math coprocessor (used for floating point
1719 operations) if you don't have one. 486DX and Pentium processors have
1720 a math coprocessor built in, 486SX and 386 do not, unless you added
1721 a 487DX or 387, respectively. (The messages during boot time can
1722 give you some hints here ["man dmesg"].) Everyone needs either a
1723 coprocessor or this emulation.
1725 If you don't have a math coprocessor, you need to say Y here; if you
1726 say Y here even though you have a coprocessor, the coprocessor will
1727 be used nevertheless. (This behavior can be changed with the kernel
1728 command line option "no387", which comes handy if your coprocessor
1729 is broken. Try "man bootparam" or see the documentation of your boot
1730 loader (lilo or loadlin) about how to pass options to the kernel at
1731 boot time.) This means that it is a good idea to say Y here if you
1732 intend to use this kernel on different machines.
1734 More information about the internals of the Linux math coprocessor
1735 emulation can be found in <file:arch/x86/math-emu/README>.
1737 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1738 kernel, it won't hurt.
1742 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1744 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1745 the Memory Type Range Registers (MTRRs) may be used to control
1746 processor access to memory ranges. This is most useful if you have
1747 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1748 allows bus write transfers to be combined into a larger transfer
1749 before bursting over the PCI/AGP bus. This can increase performance
1750 of image write operations 2.5 times or more. Saying Y here creates a
1751 /proc/mtrr file which may be used to manipulate your processor's
1752 MTRRs. Typically the X server should use this.
1754 This code has a reasonably generic interface so that similar
1755 control registers on other processors can be easily supported
1758 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1759 Registers (ARRs) which provide a similar functionality to MTRRs. For
1760 these, the ARRs are used to emulate the MTRRs.
1761 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1762 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1763 write-combining. All of these processors are supported by this code
1764 and it makes sense to say Y here if you have one of them.
1766 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1767 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1768 can lead to all sorts of problems, so it's good to say Y here.
1770 You can safely say Y even if your machine doesn't have MTRRs, you'll
1771 just add about 9 KB to your kernel.
1773 See <file:Documentation/x86/mtrr.rst> for more information.
1775 config MTRR_SANITIZER
1777 prompt "MTRR cleanup support"
1780 Convert MTRR layout from continuous to discrete, so X drivers can
1781 add writeback entries.
1783 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1784 The largest mtrr entry size for a continuous block can be set with
1789 config MTRR_SANITIZER_ENABLE_DEFAULT
1790 int "MTRR cleanup enable value (0-1)"
1793 depends on MTRR_SANITIZER
1795 Enable mtrr cleanup default value
1797 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1798 int "MTRR cleanup spare reg num (0-7)"
1801 depends on MTRR_SANITIZER
1803 mtrr cleanup spare entries default, it can be changed via
1804 mtrr_spare_reg_nr=N on the kernel command line.
1808 prompt "x86 PAT support" if EXPERT
1811 Use PAT attributes to setup page level cache control.
1813 PATs are the modern equivalents of MTRRs and are much more
1814 flexible than MTRRs.
1816 Say N here if you see bootup problems (boot crash, boot hang,
1817 spontaneous reboots) or a non-working video driver.
1821 config ARCH_USES_PG_UNCACHED
1827 prompt "x86 architectural random number generator" if EXPERT
1829 Enable the x86 architectural RDRAND instruction
1830 (Intel Bull Mountain technology) to generate random numbers.
1831 If supported, this is a high bandwidth, cryptographically
1832 secure hardware random number generator.
1836 prompt "User Mode Instruction Prevention" if EXPERT
1838 User Mode Instruction Prevention (UMIP) is a security feature in
1839 some x86 processors. If enabled, a general protection fault is
1840 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1841 executed in user mode. These instructions unnecessarily expose
1842 information about the hardware state.
1844 The vast majority of applications do not use these instructions.
1845 For the very few that do, software emulation is provided in
1846 specific cases in protected and virtual-8086 modes. Emulated
1850 # GCC >= 9 and binutils >= 2.29
1851 # Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
1853 # https://github.com/llvm/llvm-project/commit/e0b89df2e0f0130881bf6c39bf31d7f6aac00e0f
1854 # https://github.com/llvm/llvm-project/commit/dfcf69770bc522b9e411c66454934a37c1f35332
1855 def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \
1856 (CC_IS_CLANG && CLANG_VERSION >= 140000)) && \
1859 config X86_KERNEL_IBT
1860 prompt "Indirect Branch Tracking"
1862 depends on X86_64 && CC_HAS_IBT && STACK_VALIDATION
1863 # https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
1864 depends on !LD_IS_LLD || LLD_VERSION >= 140000
1866 Build the kernel with support for Indirect Branch Tracking, a
1867 hardware support course-grain forward-edge Control Flow Integrity
1868 protection. It enforces that all indirect calls must land on
1869 an ENDBR instruction, as such, the compiler will instrument the
1870 code with them to make this happen.
1872 In addition to building the kernel with IBT, seal all functions that
1873 are not indirect call targets, avoiding them ever becoming one.
1875 This requires LTO like objtool runs and will slow down the build. It
1876 does significantly reduce the number of ENDBR instructions in the
1879 config X86_INTEL_MEMORY_PROTECTION_KEYS
1880 prompt "Memory Protection Keys"
1882 # Note: only available in 64-bit mode
1883 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1884 select ARCH_USES_HIGH_VMA_FLAGS
1885 select ARCH_HAS_PKEYS
1887 Memory Protection Keys provides a mechanism for enforcing
1888 page-based protections, but without requiring modification of the
1889 page tables when an application changes protection domains.
1891 For details, see Documentation/core-api/protection-keys.rst
1896 prompt "TSX enable mode"
1897 depends on CPU_SUP_INTEL
1898 default X86_INTEL_TSX_MODE_OFF
1900 Intel's TSX (Transactional Synchronization Extensions) feature
1901 allows to optimize locking protocols through lock elision which
1902 can lead to a noticeable performance boost.
1904 On the other hand it has been shown that TSX can be exploited
1905 to form side channel attacks (e.g. TAA) and chances are there
1906 will be more of those attacks discovered in the future.
1908 Therefore TSX is not enabled by default (aka tsx=off). An admin
1909 might override this decision by tsx=on the command line parameter.
1910 Even with TSX enabled, the kernel will attempt to enable the best
1911 possible TAA mitigation setting depending on the microcode available
1912 for the particular machine.
1914 This option allows to set the default tsx mode between tsx=on, =off
1915 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1918 Say off if not sure, auto if TSX is in use but it should be used on safe
1919 platforms or on if TSX is in use and the security aspect of tsx is not
1922 config X86_INTEL_TSX_MODE_OFF
1925 TSX is disabled if possible - equals to tsx=off command line parameter.
1927 config X86_INTEL_TSX_MODE_ON
1930 TSX is always enabled on TSX capable HW - equals the tsx=on command
1933 config X86_INTEL_TSX_MODE_AUTO
1936 TSX is enabled on TSX capable HW that is believed to be safe against
1937 side channel attacks- equals the tsx=auto command line parameter.
1941 bool "Software Guard eXtensions (SGX)"
1942 depends on X86_64 && CPU_SUP_INTEL
1944 depends on CRYPTO_SHA256=y
1947 select NUMA_KEEP_MEMINFO if NUMA
1950 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1951 that can be used by applications to set aside private regions of code
1952 and data, referred to as enclaves. An enclave's private memory can
1953 only be accessed by code running within the enclave. Accesses from
1954 outside the enclave, including other enclaves, are disallowed by
1960 bool "EFI runtime service support"
1963 select EFI_RUNTIME_WRAPPERS
1964 select ARCH_USE_MEMREMAP_PROT
1966 This enables the kernel to use EFI runtime services that are
1967 available (such as the EFI variable services).
1969 This option is only useful on systems that have EFI firmware.
1970 In addition, you should use the latest ELILO loader available
1971 at <http://elilo.sourceforge.net> in order to take advantage
1972 of EFI runtime services. However, even with this option, the
1973 resultant kernel should continue to boot on existing non-EFI
1977 bool "EFI stub support"
1979 depends on $(cc-option,-mabi=ms) || X86_32
1982 This kernel feature allows a bzImage to be loaded directly
1983 by EFI firmware without the use of a bootloader.
1985 See Documentation/admin-guide/efi-stub.rst for more information.
1988 bool "EFI mixed-mode support"
1989 depends on EFI_STUB && X86_64
1991 Enabling this feature allows a 64-bit kernel to be booted
1992 on a 32-bit firmware, provided that your CPU supports 64-bit
1995 Note that it is not possible to boot a mixed-mode enabled
1996 kernel via the EFI boot stub - a bootloader that supports
1997 the EFI handover protocol must be used.
2001 source "kernel/Kconfig.hz"
2004 bool "kexec system call"
2007 kexec is a system call that implements the ability to shutdown your
2008 current kernel, and to start another kernel. It is like a reboot
2009 but it is independent of the system firmware. And like a reboot
2010 you can start any kernel with it, not just Linux.
2012 The name comes from the similarity to the exec system call.
2014 It is an ongoing process to be certain the hardware in a machine
2015 is properly shutdown, so do not be surprised if this code does not
2016 initially work for you. As of this writing the exact hardware
2017 interface is strongly in flux, so no good recommendation can be
2021 bool "kexec file based system call"
2026 depends on CRYPTO_SHA256=y
2028 This is new version of kexec system call. This system call is
2029 file based and takes file descriptors as system call argument
2030 for kernel and initramfs as opposed to list of segments as
2031 accepted by previous system call.
2033 config ARCH_HAS_KEXEC_PURGATORY
2037 bool "Verify kernel signature during kexec_file_load() syscall"
2038 depends on KEXEC_FILE
2041 This option makes the kexec_file_load() syscall check for a valid
2042 signature of the kernel image. The image can still be loaded without
2043 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2044 there's a signature that we can check, then it must be valid.
2046 In addition to this option, you need to enable signature
2047 verification for the corresponding kernel image type being
2048 loaded in order for this to work.
2050 config KEXEC_SIG_FORCE
2051 bool "Require a valid signature in kexec_file_load() syscall"
2052 depends on KEXEC_SIG
2054 This option makes kernel signature verification mandatory for
2055 the kexec_file_load() syscall.
2057 config KEXEC_BZIMAGE_VERIFY_SIG
2058 bool "Enable bzImage signature verification support"
2059 depends on KEXEC_SIG
2060 depends on SIGNED_PE_FILE_VERIFICATION
2061 select SYSTEM_TRUSTED_KEYRING
2063 Enable bzImage signature verification support.
2066 bool "kernel crash dumps"
2067 depends on X86_64 || (X86_32 && HIGHMEM)
2069 Generate crash dump after being started by kexec.
2070 This should be normally only set in special crash dump kernels
2071 which are loaded in the main kernel with kexec-tools into
2072 a specially reserved region and then later executed after
2073 a crash by kdump/kexec. The crash dump kernel must be compiled
2074 to a memory address not used by the main kernel or BIOS using
2075 PHYSICAL_START, or it must be built as a relocatable image
2076 (CONFIG_RELOCATABLE=y).
2077 For more details see Documentation/admin-guide/kdump/kdump.rst
2081 depends on KEXEC && HIBERNATION
2083 Jump between original kernel and kexeced kernel and invoke
2084 code in physical address mode via KEXEC
2086 config PHYSICAL_START
2087 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2090 This gives the physical address where the kernel is loaded.
2092 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2093 bzImage will decompress itself to above physical address and
2094 run from there. Otherwise, bzImage will run from the address where
2095 it has been loaded by the boot loader and will ignore above physical
2098 In normal kdump cases one does not have to set/change this option
2099 as now bzImage can be compiled as a completely relocatable image
2100 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2101 address. This option is mainly useful for the folks who don't want
2102 to use a bzImage for capturing the crash dump and want to use a
2103 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2104 to be specifically compiled to run from a specific memory area
2105 (normally a reserved region) and this option comes handy.
2107 So if you are using bzImage for capturing the crash dump,
2108 leave the value here unchanged to 0x1000000 and set
2109 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2110 for capturing the crash dump change this value to start of
2111 the reserved region. In other words, it can be set based on
2112 the "X" value as specified in the "crashkernel=YM@XM"
2113 command line boot parameter passed to the panic-ed
2114 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2115 for more details about crash dumps.
2117 Usage of bzImage for capturing the crash dump is recommended as
2118 one does not have to build two kernels. Same kernel can be used
2119 as production kernel and capture kernel. Above option should have
2120 gone away after relocatable bzImage support is introduced. But it
2121 is present because there are users out there who continue to use
2122 vmlinux for dump capture. This option should go away down the
2125 Don't change this unless you know what you are doing.
2128 bool "Build a relocatable kernel"
2131 This builds a kernel image that retains relocation information
2132 so it can be loaded someplace besides the default 1MB.
2133 The relocations tend to make the kernel binary about 10% larger,
2134 but are discarded at runtime.
2136 One use is for the kexec on panic case where the recovery kernel
2137 must live at a different physical address than the primary
2140 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2141 it has been loaded at and the compile time physical address
2142 (CONFIG_PHYSICAL_START) is used as the minimum location.
2144 config RANDOMIZE_BASE
2145 bool "Randomize the address of the kernel image (KASLR)"
2146 depends on RELOCATABLE
2149 In support of Kernel Address Space Layout Randomization (KASLR),
2150 this randomizes the physical address at which the kernel image
2151 is decompressed and the virtual address where the kernel
2152 image is mapped, as a security feature that deters exploit
2153 attempts relying on knowledge of the location of kernel
2156 On 64-bit, the kernel physical and virtual addresses are
2157 randomized separately. The physical address will be anywhere
2158 between 16MB and the top of physical memory (up to 64TB). The
2159 virtual address will be randomized from 16MB up to 1GB (9 bits
2160 of entropy). Note that this also reduces the memory space
2161 available to kernel modules from 1.5GB to 1GB.
2163 On 32-bit, the kernel physical and virtual addresses are
2164 randomized together. They will be randomized from 16MB up to
2165 512MB (8 bits of entropy).
2167 Entropy is generated using the RDRAND instruction if it is
2168 supported. If RDTSC is supported, its value is mixed into
2169 the entropy pool as well. If neither RDRAND nor RDTSC are
2170 supported, then entropy is read from the i8254 timer. The
2171 usable entropy is limited by the kernel being built using
2172 2GB addressing, and that PHYSICAL_ALIGN must be at a
2173 minimum of 2MB. As a result, only 10 bits of entropy are
2174 theoretically possible, but the implementations are further
2175 limited due to memory layouts.
2179 # Relocation on x86 needs some additional build support
2180 config X86_NEED_RELOCS
2182 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2184 config PHYSICAL_ALIGN
2185 hex "Alignment value to which kernel should be aligned"
2187 range 0x2000 0x1000000 if X86_32
2188 range 0x200000 0x1000000 if X86_64
2190 This value puts the alignment restrictions on physical address
2191 where kernel is loaded and run from. Kernel is compiled for an
2192 address which meets above alignment restriction.
2194 If bootloader loads the kernel at a non-aligned address and
2195 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2196 address aligned to above value and run from there.
2198 If bootloader loads the kernel at a non-aligned address and
2199 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2200 load address and decompress itself to the address it has been
2201 compiled for and run from there. The address for which kernel is
2202 compiled already meets above alignment restrictions. Hence the
2203 end result is that kernel runs from a physical address meeting
2204 above alignment restrictions.
2206 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2207 this value must be a multiple of 0x200000.
2209 Don't change this unless you know what you are doing.
2211 config DYNAMIC_MEMORY_LAYOUT
2214 This option makes base addresses of vmalloc and vmemmap as well as
2215 __PAGE_OFFSET movable during boot.
2217 config RANDOMIZE_MEMORY
2218 bool "Randomize the kernel memory sections"
2220 depends on RANDOMIZE_BASE
2221 select DYNAMIC_MEMORY_LAYOUT
2222 default RANDOMIZE_BASE
2224 Randomizes the base virtual address of kernel memory sections
2225 (physical memory mapping, vmalloc & vmemmap). This security feature
2226 makes exploits relying on predictable memory locations less reliable.
2228 The order of allocations remains unchanged. Entropy is generated in
2229 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2230 configuration have in average 30,000 different possible virtual
2231 addresses for each memory section.
2235 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2236 hex "Physical memory mapping padding" if EXPERT
2237 depends on RANDOMIZE_MEMORY
2238 default "0xa" if MEMORY_HOTPLUG
2240 range 0x1 0x40 if MEMORY_HOTPLUG
2243 Define the padding in terabytes added to the existing physical
2244 memory size during kernel memory randomization. It is useful
2245 for memory hotplug support but reduces the entropy available for
2246 address randomization.
2248 If unsure, leave at the default value.
2254 config BOOTPARAM_HOTPLUG_CPU0
2255 bool "Set default setting of cpu0_hotpluggable"
2256 depends on HOTPLUG_CPU
2258 Set whether default state of cpu0_hotpluggable is on or off.
2260 Say Y here to enable CPU0 hotplug by default. If this switch
2261 is turned on, there is no need to give cpu0_hotplug kernel
2262 parameter and the CPU0 hotplug feature is enabled by default.
2264 Please note: there are two known CPU0 dependencies if you want
2265 to enable the CPU0 hotplug feature either by this switch or by
2266 cpu0_hotplug kernel parameter.
2268 First, resume from hibernate or suspend always starts from CPU0.
2269 So hibernate and suspend are prevented if CPU0 is offline.
2271 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2272 offline if any interrupt can not migrate out of CPU0. There may
2273 be other CPU0 dependencies.
2275 Please make sure the dependencies are under your control before
2276 you enable this feature.
2278 Say N if you don't want to enable CPU0 hotplug feature by default.
2279 You still can enable the CPU0 hotplug feature at boot by kernel
2280 parameter cpu0_hotplug.
2282 config DEBUG_HOTPLUG_CPU0
2284 prompt "Debug CPU0 hotplug"
2285 depends on HOTPLUG_CPU
2287 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2288 soon as possible and boots up userspace with CPU0 offlined. User
2289 can online CPU0 back after boot time.
2291 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2292 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2293 compilation or giving cpu0_hotplug kernel parameter at boot.
2299 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2300 depends on COMPAT_32
2302 Certain buggy versions of glibc will crash if they are
2303 presented with a 32-bit vDSO that is not mapped at the address
2304 indicated in its segment table.
2306 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2307 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2308 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2309 the only released version with the bug, but OpenSUSE 9
2310 contains a buggy "glibc 2.3.2".
2312 The symptom of the bug is that everything crashes on startup, saying:
2313 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2315 Saying Y here changes the default value of the vdso32 boot
2316 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2317 This works around the glibc bug but hurts performance.
2319 If unsure, say N: if you are compiling your own kernel, you
2320 are unlikely to be using a buggy version of glibc.
2323 prompt "vsyscall table for legacy applications"
2325 default LEGACY_VSYSCALL_XONLY
2327 Legacy user code that does not know how to find the vDSO expects
2328 to be able to issue three syscalls by calling fixed addresses in
2329 kernel space. Since this location is not randomized with ASLR,
2330 it can be used to assist security vulnerability exploitation.
2332 This setting can be changed at boot time via the kernel command
2333 line parameter vsyscall=[emulate|xonly|none].
2335 On a system with recent enough glibc (2.14 or newer) and no
2336 static binaries, you can say None without a performance penalty
2337 to improve security.
2339 If unsure, select "Emulate execution only".
2341 config LEGACY_VSYSCALL_EMULATE
2342 bool "Full emulation"
2344 The kernel traps and emulates calls into the fixed vsyscall
2345 address mapping. This makes the mapping non-executable, but
2346 it still contains readable known contents, which could be
2347 used in certain rare security vulnerability exploits. This
2348 configuration is recommended when using legacy userspace
2349 that still uses vsyscalls along with legacy binary
2350 instrumentation tools that require code to be readable.
2352 An example of this type of legacy userspace is running
2353 Pin on an old binary that still uses vsyscalls.
2355 config LEGACY_VSYSCALL_XONLY
2356 bool "Emulate execution only"
2358 The kernel traps and emulates calls into the fixed vsyscall
2359 address mapping and does not allow reads. This
2360 configuration is recommended when userspace might use the
2361 legacy vsyscall area but support for legacy binary
2362 instrumentation of legacy code is not needed. It mitigates
2363 certain uses of the vsyscall area as an ASLR-bypassing
2366 config LEGACY_VSYSCALL_NONE
2369 There will be no vsyscall mapping at all. This will
2370 eliminate any risk of ASLR bypass due to the vsyscall
2371 fixed address mapping. Attempts to use the vsyscalls
2372 will be reported to dmesg, so that either old or
2373 malicious userspace programs can be identified.
2378 bool "Built-in kernel command line"
2380 Allow for specifying boot arguments to the kernel at
2381 build time. On some systems (e.g. embedded ones), it is
2382 necessary or convenient to provide some or all of the
2383 kernel boot arguments with the kernel itself (that is,
2384 to not rely on the boot loader to provide them.)
2386 To compile command line arguments into the kernel,
2387 set this option to 'Y', then fill in the
2388 boot arguments in CONFIG_CMDLINE.
2390 Systems with fully functional boot loaders (i.e. non-embedded)
2391 should leave this option set to 'N'.
2394 string "Built-in kernel command string"
2395 depends on CMDLINE_BOOL
2398 Enter arguments here that should be compiled into the kernel
2399 image and used at boot time. If the boot loader provides a
2400 command line at boot time, it is appended to this string to
2401 form the full kernel command line, when the system boots.
2403 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2404 change this behavior.
2406 In most cases, the command line (whether built-in or provided
2407 by the boot loader) should specify the device for the root
2410 config CMDLINE_OVERRIDE
2411 bool "Built-in command line overrides boot loader arguments"
2412 depends on CMDLINE_BOOL && CMDLINE != ""
2414 Set this option to 'Y' to have the kernel ignore the boot loader
2415 command line, and use ONLY the built-in command line.
2417 This is used to work around broken boot loaders. This should
2418 be set to 'N' under normal conditions.
2420 config MODIFY_LDT_SYSCALL
2421 bool "Enable the LDT (local descriptor table)" if EXPERT
2424 Linux can allow user programs to install a per-process x86
2425 Local Descriptor Table (LDT) using the modify_ldt(2) system
2426 call. This is required to run 16-bit or segmented code such as
2427 DOSEMU or some Wine programs. It is also used by some very old
2428 threading libraries.
2430 Enabling this feature adds a small amount of overhead to
2431 context switches and increases the low-level kernel attack
2432 surface. Disabling it removes the modify_ldt(2) system call.
2434 Saying 'N' here may make sense for embedded or server kernels.
2436 config STRICT_SIGALTSTACK_SIZE
2437 bool "Enforce strict size checking for sigaltstack"
2438 depends on DYNAMIC_SIGFRAME
2440 For historical reasons MINSIGSTKSZ is a constant which became
2441 already too small with AVX512 support. Add a mechanism to
2442 enforce strict checking of the sigaltstack size against the
2443 real size of the FPU frame. This option enables the check
2444 by default. It can also be controlled via the kernel command
2445 line option 'strict_sas_size' independent of this config
2446 switch. Enabling it might break existing applications which
2447 allocate a too small sigaltstack but 'work' because they
2448 never get a signal delivered.
2450 Say 'N' unless you want to really enforce this check.
2452 source "kernel/livepatch/Kconfig"
2456 config ARCH_HAS_ADD_PAGES
2458 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2460 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2463 menu "Power management and ACPI options"
2465 config ARCH_HIBERNATION_HEADER
2467 depends on HIBERNATION
2469 source "kernel/power/Kconfig"
2471 source "drivers/acpi/Kconfig"
2478 tristate "APM (Advanced Power Management) BIOS support"
2479 depends on X86_32 && PM_SLEEP
2481 APM is a BIOS specification for saving power using several different
2482 techniques. This is mostly useful for battery powered laptops with
2483 APM compliant BIOSes. If you say Y here, the system time will be
2484 reset after a RESUME operation, the /proc/apm device will provide
2485 battery status information, and user-space programs will receive
2486 notification of APM "events" (e.g. battery status change).
2488 If you select "Y" here, you can disable actual use of the APM
2489 BIOS by passing the "apm=off" option to the kernel at boot time.
2491 Note that the APM support is almost completely disabled for
2492 machines with more than one CPU.
2494 In order to use APM, you will need supporting software. For location
2495 and more information, read <file:Documentation/power/apm-acpi.rst>
2496 and the Battery Powered Linux mini-HOWTO, available from
2497 <http://www.tldp.org/docs.html#howto>.
2499 This driver does not spin down disk drives (see the hdparm(8)
2500 manpage ("man 8 hdparm") for that), and it doesn't turn off
2501 VESA-compliant "green" monitors.
2503 This driver does not support the TI 4000M TravelMate and the ACER
2504 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2505 desktop machines also don't have compliant BIOSes, and this driver
2506 may cause those machines to panic during the boot phase.
2508 Generally, if you don't have a battery in your machine, there isn't
2509 much point in using this driver and you should say N. If you get
2510 random kernel OOPSes or reboots that don't seem to be related to
2511 anything, try disabling/enabling this option (or disabling/enabling
2514 Some other things you should try when experiencing seemingly random,
2517 1) make sure that you have enough swap space and that it is
2519 2) pass the "no-hlt" option to the kernel
2520 3) switch on floating point emulation in the kernel and pass
2521 the "no387" option to the kernel
2522 4) pass the "floppy=nodma" option to the kernel
2523 5) pass the "mem=4M" option to the kernel (thereby disabling
2524 all but the first 4 MB of RAM)
2525 6) make sure that the CPU is not over clocked.
2526 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2527 8) disable the cache from your BIOS settings
2528 9) install a fan for the video card or exchange video RAM
2529 10) install a better fan for the CPU
2530 11) exchange RAM chips
2531 12) exchange the motherboard.
2533 To compile this driver as a module, choose M here: the
2534 module will be called apm.
2538 config APM_IGNORE_USER_SUSPEND
2539 bool "Ignore USER SUSPEND"
2541 This option will ignore USER SUSPEND requests. On machines with a
2542 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2543 series notebooks, it is necessary to say Y because of a BIOS bug.
2545 config APM_DO_ENABLE
2546 bool "Enable PM at boot time"
2548 Enable APM features at boot time. From page 36 of the APM BIOS
2549 specification: "When disabled, the APM BIOS does not automatically
2550 power manage devices, enter the Standby State, enter the Suspend
2551 State, or take power saving steps in response to CPU Idle calls."
2552 This driver will make CPU Idle calls when Linux is idle (unless this
2553 feature is turned off -- see "Do CPU IDLE calls", below). This
2554 should always save battery power, but more complicated APM features
2555 will be dependent on your BIOS implementation. You may need to turn
2556 this option off if your computer hangs at boot time when using APM
2557 support, or if it beeps continuously instead of suspending. Turn
2558 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2559 T400CDT. This is off by default since most machines do fine without
2564 bool "Make CPU Idle calls when idle"
2566 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2567 On some machines, this can activate improved power savings, such as
2568 a slowed CPU clock rate, when the machine is idle. These idle calls
2569 are made after the idle loop has run for some length of time (e.g.,
2570 333 mS). On some machines, this will cause a hang at boot time or
2571 whenever the CPU becomes idle. (On machines with more than one CPU,
2572 this option does nothing.)
2574 config APM_DISPLAY_BLANK
2575 bool "Enable console blanking using APM"
2577 Enable console blanking using the APM. Some laptops can use this to
2578 turn off the LCD backlight when the screen blanker of the Linux
2579 virtual console blanks the screen. Note that this is only used by
2580 the virtual console screen blanker, and won't turn off the backlight
2581 when using the X Window system. This also doesn't have anything to
2582 do with your VESA-compliant power-saving monitor. Further, this
2583 option doesn't work for all laptops -- it might not turn off your
2584 backlight at all, or it might print a lot of errors to the console,
2585 especially if you are using gpm.
2587 config APM_ALLOW_INTS
2588 bool "Allow interrupts during APM BIOS calls"
2590 Normally we disable external interrupts while we are making calls to
2591 the APM BIOS as a measure to lessen the effects of a badly behaving
2592 BIOS implementation. The BIOS should reenable interrupts if it
2593 needs to. Unfortunately, some BIOSes do not -- especially those in
2594 many of the newer IBM Thinkpads. If you experience hangs when you
2595 suspend, try setting this to Y. Otherwise, say N.
2599 source "drivers/cpufreq/Kconfig"
2601 source "drivers/cpuidle/Kconfig"
2603 source "drivers/idle/Kconfig"
2608 menu "Bus options (PCI etc.)"
2611 prompt "PCI access mode"
2612 depends on X86_32 && PCI
2615 On PCI systems, the BIOS can be used to detect the PCI devices and
2616 determine their configuration. However, some old PCI motherboards
2617 have BIOS bugs and may crash if this is done. Also, some embedded
2618 PCI-based systems don't have any BIOS at all. Linux can also try to
2619 detect the PCI hardware directly without using the BIOS.
2621 With this option, you can specify how Linux should detect the
2622 PCI devices. If you choose "BIOS", the BIOS will be used,
2623 if you choose "Direct", the BIOS won't be used, and if you
2624 choose "MMConfig", then PCI Express MMCONFIG will be used.
2625 If you choose "Any", the kernel will try MMCONFIG, then the
2626 direct access method and falls back to the BIOS if that doesn't
2627 work. If unsure, go with the default, which is "Any".
2632 config PCI_GOMMCONFIG
2649 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2651 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2654 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2657 bool "Support mmconfig PCI config space access" if X86_64
2659 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2660 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2664 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2668 depends on PCI && XEN
2670 config MMCONF_FAM10H
2672 depends on X86_64 && PCI_MMCONFIG && ACPI
2674 config PCI_CNB20LE_QUIRK
2675 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2678 Read the PCI windows out of the CNB20LE host bridge. This allows
2679 PCI hotplug to work on systems with the CNB20LE chipset which do
2682 There's no public spec for this chipset, and this functionality
2683 is known to be incomplete.
2685 You should say N unless you know you need this.
2688 bool "ISA bus support on modern systems" if EXPERT
2690 Expose ISA bus device drivers and options available for selection and
2691 configuration. Enable this option if your target machine has an ISA
2692 bus. ISA is an older system, displaced by PCI and newer bus
2693 architectures -- if your target machine is modern, it probably does
2694 not have an ISA bus.
2698 # x86_64 have no ISA slots, but can have ISA-style DMA.
2700 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2703 Enables ISA-style DMA support for devices requiring such controllers.
2711 Find out whether you have ISA slots on your motherboard. ISA is the
2712 name of a bus system, i.e. the way the CPU talks to the other stuff
2713 inside your box. Other bus systems are PCI, EISA, MicroChannel
2714 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2715 newer boards don't support it. If you have ISA, say Y, otherwise N.
2718 tristate "NatSemi SCx200 support"
2720 This provides basic support for National Semiconductor's
2721 (now AMD's) Geode processors. The driver probes for the
2722 PCI-IDs of several on-chip devices, so its a good dependency
2723 for other scx200_* drivers.
2725 If compiled as a module, the driver is named scx200.
2727 config SCx200HR_TIMER
2728 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2732 This driver provides a clocksource built upon the on-chip
2733 27MHz high-resolution timer. Its also a workaround for
2734 NSC Geode SC-1100's buggy TSC, which loses time when the
2735 processor goes idle (as is done by the scheduler). The
2736 other workaround is idle=poll boot option.
2739 bool "One Laptop Per Child support"
2747 Add support for detecting the unique features of the OLPC
2751 bool "OLPC XO-1 Power Management"
2752 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2754 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2757 bool "OLPC XO-1 Real Time Clock"
2758 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2760 Add support for the XO-1 real time clock, which can be used as a
2761 programmable wakeup source.
2764 bool "OLPC XO-1 SCI extras"
2765 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2769 Add support for SCI-based features of the OLPC XO-1 laptop:
2770 - EC-driven system wakeups
2774 - AC adapter status updates
2775 - Battery status updates
2777 config OLPC_XO15_SCI
2778 bool "OLPC XO-1.5 SCI extras"
2779 depends on OLPC && ACPI
2782 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2783 - EC-driven system wakeups
2784 - AC adapter status updates
2785 - Battery status updates
2788 bool "PCEngines ALIX System Support (LED setup)"
2791 This option enables system support for the PCEngines ALIX.
2792 At present this just sets up LEDs for GPIO control on
2793 ALIX2/3/6 boards. However, other system specific setup should
2796 Note: You must still enable the drivers for GPIO and LED support
2797 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2799 Note: You have to set alix.force=1 for boards with Award BIOS.
2802 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2805 This option enables system support for the Soekris Engineering net5501.
2808 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2812 This option enables system support for the Traverse Technologies GEOS.
2815 bool "Technologic Systems TS-5500 platform support"
2817 select CHECK_SIGNATURE
2821 This option enables system support for the Technologic Systems TS-5500.
2827 depends on CPU_SUP_AMD && PCI
2832 menu "Binary Emulations"
2834 config IA32_EMULATION
2835 bool "IA32 Emulation"
2837 select ARCH_WANT_OLD_COMPAT_IPC
2839 select COMPAT_OLD_SIGACTION
2841 Include code to run legacy 32-bit programs under a
2842 64-bit kernel. You should likely turn this on, unless you're
2843 100% sure that you don't have any 32-bit programs left.
2846 bool "x32 ABI for 64-bit mode"
2848 # llvm-objcopy does not convert x86_64 .note.gnu.property or
2849 # compressed debug sections to x86_x32 properly:
2850 # https://github.com/ClangBuiltLinux/linux/issues/514
2851 # https://github.com/ClangBuiltLinux/linux/issues/1141
2852 depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
2854 Include code to run binaries for the x32 native 32-bit ABI
2855 for 64-bit processors. An x32 process gets access to the
2856 full 64-bit register file and wide data path while leaving
2857 pointers at 32 bits for smaller memory footprint.
2861 depends on IA32_EMULATION || X86_32
2863 select OLD_SIGSUSPEND3
2867 depends on IA32_EMULATION || X86_X32_ABI
2870 config COMPAT_FOR_U64_ALIGNMENT
2873 config SYSVIPC_COMPAT
2881 config HAVE_ATOMIC_IOMAP
2885 source "arch/x86/kvm/Kconfig"
2887 source "arch/x86/Kconfig.assembler"