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_FORTIFY_SOURCE
80 select ARCH_HAS_GCOV_PROFILE_ALL
81 select ARCH_HAS_KCOV if X86_64
82 select ARCH_HAS_MEM_ENCRYPT
83 select ARCH_HAS_MEMBARRIER_SYNC_CORE
84 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
85 select ARCH_HAS_PMEM_API if X86_64
86 select ARCH_HAS_PTE_DEVMAP if X86_64
87 select ARCH_HAS_PTE_SPECIAL
88 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
89 select ARCH_HAS_COPY_MC if X86_64
90 select ARCH_HAS_SET_MEMORY
91 select ARCH_HAS_SET_DIRECT_MAP
92 select ARCH_HAS_STRICT_KERNEL_RWX
93 select ARCH_HAS_STRICT_MODULE_RWX
94 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
95 select ARCH_HAS_SYSCALL_WRAPPER
96 select ARCH_HAS_UBSAN_SANITIZE_ALL
97 select ARCH_HAS_VM_GET_PAGE_PROT
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_HUGETLB_PAGE_OPTIMIZE_VMEMMAP if X86_64
125 select ARCH_WANT_LD_ORPHAN_WARN
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_HUGE_VMALLOC if X86_64
165 select HAVE_ARCH_JUMP_LABEL
166 select HAVE_ARCH_JUMP_LABEL_RELATIVE
167 select HAVE_ARCH_KASAN if X86_64
168 select HAVE_ARCH_KASAN_VMALLOC if X86_64
169 select HAVE_ARCH_KFENCE
170 select HAVE_ARCH_KGDB
171 select HAVE_ARCH_MMAP_RND_BITS if MMU
172 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
173 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
174 select HAVE_ARCH_PREL32_RELOCATIONS
175 select HAVE_ARCH_SECCOMP_FILTER
176 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
177 select HAVE_ARCH_STACKLEAK
178 select HAVE_ARCH_TRACEHOOK
179 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
180 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
181 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
182 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
183 select HAVE_ARCH_VMAP_STACK if X86_64
184 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
185 select HAVE_ARCH_WITHIN_STACK_FRAMES
186 select HAVE_ASM_MODVERSIONS
187 select HAVE_CMPXCHG_DOUBLE
188 select HAVE_CMPXCHG_LOCAL
189 select HAVE_CONTEXT_TRACKING if X86_64
190 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
191 select HAVE_C_RECORDMCOUNT
192 select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
193 select HAVE_BUILDTIME_MCOUNT_SORT
194 select HAVE_DEBUG_KMEMLEAK
195 select HAVE_DMA_CONTIGUOUS
196 select HAVE_DYNAMIC_FTRACE
197 select HAVE_DYNAMIC_FTRACE_WITH_REGS
198 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
199 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
200 select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
201 select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
203 select HAVE_EFFICIENT_UNALIGNED_ACCESS
205 select HAVE_EXIT_THREAD
207 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
208 select HAVE_FTRACE_MCOUNT_RECORD
209 select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
210 select HAVE_FUNCTION_TRACER
211 select HAVE_GCC_PLUGINS
212 select HAVE_HW_BREAKPOINT
213 select HAVE_IOREMAP_PROT
214 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
215 select HAVE_IRQ_TIME_ACCOUNTING
216 select HAVE_JUMP_LABEL_HACK if HAVE_OBJTOOL
217 select HAVE_KERNEL_BZIP2
218 select HAVE_KERNEL_GZIP
219 select HAVE_KERNEL_LZ4
220 select HAVE_KERNEL_LZMA
221 select HAVE_KERNEL_LZO
222 select HAVE_KERNEL_XZ
223 select HAVE_KERNEL_ZSTD
225 select HAVE_KPROBES_ON_FTRACE
226 select HAVE_FUNCTION_ERROR_INJECTION
227 select HAVE_KRETPROBES
230 select HAVE_LIVEPATCH if X86_64
231 select HAVE_MIXED_BREAKPOINTS_REGS
232 select HAVE_MOD_ARCH_SPECIFIC
235 select HAVE_NOINSTR_HACK if HAVE_OBJTOOL
237 select HAVE_NOINSTR_VALIDATION if HAVE_OBJTOOL
238 select HAVE_OBJTOOL if X86_64
239 select HAVE_OPTPROBES
240 select HAVE_PCSPKR_PLATFORM
241 select HAVE_PERF_EVENTS
242 select HAVE_PERF_EVENTS_NMI
243 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
245 select HAVE_PERF_REGS
246 select HAVE_PERF_USER_STACK_DUMP
247 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
248 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
249 select HAVE_REGS_AND_STACK_ACCESS_API
250 select HAVE_RELIABLE_STACKTRACE if UNWINDER_ORC || STACK_VALIDATION
251 select HAVE_FUNCTION_ARG_ACCESS_API
252 select HAVE_SETUP_PER_CPU_AREA
253 select HAVE_SOFTIRQ_ON_OWN_STACK
254 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
255 select HAVE_STACK_VALIDATION if HAVE_OBJTOOL
256 select HAVE_STATIC_CALL
257 select HAVE_STATIC_CALL_INLINE if HAVE_OBJTOOL
258 select HAVE_PREEMPT_DYNAMIC_CALL
260 select HAVE_SYSCALL_TRACEPOINTS
261 select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
262 select HAVE_UNSTABLE_SCHED_CLOCK
263 select HAVE_USER_RETURN_NOTIFIER
264 select HAVE_GENERIC_VDSO
265 select HOTPLUG_SMT if SMP
266 select IRQ_FORCED_THREADING
267 select NEED_PER_CPU_EMBED_FIRST_CHUNK
268 select NEED_PER_CPU_PAGE_FIRST_CHUNK
269 select NEED_SG_DMA_LENGTH
270 select PCI_DOMAINS if PCI
271 select PCI_LOCKLESS_CONFIG if PCI
274 select RTC_MC146818_LIB
277 select SYSCTL_EXCEPTION_TRACE
278 select THREAD_INFO_IN_TASK
279 select TRACE_IRQFLAGS_SUPPORT
280 select USER_STACKTRACE_SUPPORT
281 select HAVE_ARCH_KCSAN if X86_64
282 select X86_FEATURE_NAMES if PROC_FS
283 select PROC_PID_ARCH_STATUS if PROC_FS
284 select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
285 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
287 config INSTRUCTION_DECODER
289 depends on KPROBES || PERF_EVENTS || UPROBES
293 default "elf32-i386" if X86_32
294 default "elf64-x86-64" if X86_64
296 config LOCKDEP_SUPPORT
299 config STACKTRACE_SUPPORT
305 config ARCH_MMAP_RND_BITS_MIN
309 config ARCH_MMAP_RND_BITS_MAX
313 config ARCH_MMAP_RND_COMPAT_BITS_MIN
316 config ARCH_MMAP_RND_COMPAT_BITS_MAX
322 config GENERIC_ISA_DMA
324 depends on ISA_DMA_API
329 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
331 config GENERIC_BUG_RELATIVE_POINTERS
334 config ARCH_MAY_HAVE_PC_FDC
336 depends on ISA_DMA_API
338 config GENERIC_CALIBRATE_DELAY
341 config ARCH_HAS_CPU_RELAX
344 config ARCH_HIBERNATION_POSSIBLE
349 default 1024 if X86_64
352 config ARCH_SUSPEND_POSSIBLE
358 config KASAN_SHADOW_OFFSET
361 default 0xdffffc0000000000
363 config HAVE_INTEL_TXT
365 depends on INTEL_IOMMU && ACPI
369 depends on X86_32 && SMP
373 depends on X86_64 && SMP
375 config ARCH_SUPPORTS_UPROBES
378 config FIX_EARLYCON_MEM
381 config DYNAMIC_PHYSICAL_MASK
384 config PGTABLE_LEVELS
386 default 5 if X86_5LEVEL
391 config CC_HAS_SANE_STACKPROTECTOR
393 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
394 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
396 We have to make sure stack protector is unconditionally disabled if
397 the compiler produces broken code or if it does not let us control
398 the segment on 32-bit kernels.
400 menu "Processor type and features"
403 bool "Symmetric multi-processing support"
405 This enables support for systems with more than one CPU. If you have
406 a system with only one CPU, say N. If you have a system with more
409 If you say N here, the kernel will run on uni- and multiprocessor
410 machines, but will use only one CPU of a multiprocessor machine. If
411 you say Y here, the kernel will run on many, but not all,
412 uniprocessor machines. On a uniprocessor machine, the kernel
413 will run faster if you say N here.
415 Note that if you say Y here and choose architecture "586" or
416 "Pentium" under "Processor family", the kernel will not work on 486
417 architectures. Similarly, multiprocessor kernels for the "PPro"
418 architecture may not work on all Pentium based boards.
420 People using multiprocessor machines who say Y here should also say
421 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
422 Management" code will be disabled if you say Y here.
424 See also <file:Documentation/x86/i386/IO-APIC.rst>,
425 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
426 <http://www.tldp.org/docs.html#howto>.
428 If you don't know what to do here, say N.
430 config X86_FEATURE_NAMES
431 bool "Processor feature human-readable names" if EMBEDDED
434 This option compiles in a table of x86 feature bits and corresponding
435 names. This is required to support /proc/cpuinfo and a few kernel
436 messages. You can disable this to save space, at the expense of
437 making those few kernel messages show numeric feature bits instead.
442 bool "Support x2apic"
443 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
445 This enables x2apic support on CPUs that have this feature.
447 This allows 32-bit apic IDs (so it can support very large systems),
448 and accesses the local apic via MSRs not via mmio.
450 If you don't know what to do here, say N.
453 bool "Enable MPS table" if ACPI
455 depends on X86_LOCAL_APIC
457 For old smp systems that do not have proper acpi support. Newer systems
458 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
462 depends on X86_GOLDFISH
465 bool "Avoid speculative indirect branches in kernel"
466 select OBJTOOL if HAVE_OBJTOOL
469 Compile kernel with the retpoline compiler options to guard against
470 kernel-to-user data leaks by avoiding speculative indirect
471 branches. Requires a compiler with -mindirect-branch=thunk-extern
472 support for full protection. The kernel may run slower.
475 def_bool $(cc-option,-mharden-sls=all)
478 bool "Mitigate Straight-Line-Speculation"
479 depends on CC_HAS_SLS && X86_64
480 select OBJTOOL if HAVE_OBJTOOL
483 Compile the kernel with straight-line-speculation options to guard
484 against straight line speculation. The kernel image might be slightly
487 config X86_CPU_RESCTRL
488 bool "x86 CPU resource control support"
489 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
491 select PROC_CPU_RESCTRL if PROC_FS
493 Enable x86 CPU resource control support.
495 Provide support for the allocation and monitoring of system resources
498 Intel calls this Intel Resource Director Technology
499 (Intel(R) RDT). More information about RDT can be found in the
500 Intel x86 Architecture Software Developer Manual.
502 AMD calls this AMD Platform Quality of Service (AMD QoS).
503 More information about AMD QoS can be found in the AMD64 Technology
504 Platform Quality of Service Extensions manual.
510 bool "Support for big SMP systems with more than 8 CPUs"
513 This option is needed for the systems that have more than 8 CPUs.
515 config X86_EXTENDED_PLATFORM
516 bool "Support for extended (non-PC) x86 platforms"
519 If you disable this option then the kernel will only support
520 standard PC platforms. (which covers the vast majority of
523 If you enable this option then you'll be able to select support
524 for the following (non-PC) 32 bit x86 platforms:
525 Goldfish (Android emulator)
528 SGI 320/540 (Visual Workstation)
529 STA2X11-based (e.g. Northville)
530 Moorestown MID devices
532 If you have one of these systems, or if you want to build a
533 generic distribution kernel, say Y here - otherwise say N.
537 config X86_EXTENDED_PLATFORM
538 bool "Support for extended (non-PC) x86 platforms"
541 If you disable this option then the kernel will only support
542 standard PC platforms. (which covers the vast majority of
545 If you enable this option then you'll be able to select support
546 for the following (non-PC) 64 bit x86 platforms:
551 If you have one of these systems, or if you want to build a
552 generic distribution kernel, say Y here - otherwise say N.
554 # This is an alphabetically sorted list of 64 bit extended platforms
555 # Please maintain the alphabetic order if and when there are additions
557 bool "Numascale NumaChip"
559 depends on X86_EXTENDED_PLATFORM
562 depends on X86_X2APIC
563 depends on PCI_MMCONFIG
565 Adds support for Numascale NumaChip large-SMP systems. Needed to
566 enable more than ~168 cores.
567 If you don't have one of these, you should say N here.
571 select HYPERVISOR_GUEST
573 depends on X86_64 && PCI
574 depends on X86_EXTENDED_PLATFORM
577 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
578 supposed to run on these EM64T-based machines. Only choose this option
579 if you have one of these machines.
582 bool "SGI Ultraviolet"
584 depends on X86_EXTENDED_PLATFORM
587 depends on KEXEC_CORE
588 depends on X86_X2APIC
591 This option is needed in order to support SGI Ultraviolet systems.
592 If you don't have one of these, you should say N here.
594 # Following is an alphabetically sorted list of 32 bit extended platforms
595 # Please maintain the alphabetic order if and when there are additions
598 bool "Goldfish (Virtual Platform)"
599 depends on X86_EXTENDED_PLATFORM
601 Enable support for the Goldfish virtual platform used primarily
602 for Android development. Unless you are building for the Android
603 Goldfish emulator say N here.
606 bool "CE4100 TV platform"
608 depends on PCI_GODIRECT
609 depends on X86_IO_APIC
611 depends on X86_EXTENDED_PLATFORM
612 select X86_REBOOTFIXUPS
614 select OF_EARLY_FLATTREE
616 Select for the Intel CE media processor (CE4100) SOC.
617 This option compiles in support for the CE4100 SOC for settop
618 boxes and media devices.
621 bool "Intel MID platform support"
622 depends on X86_EXTENDED_PLATFORM
623 depends on X86_PLATFORM_DEVICES
625 depends on X86_64 || (PCI_GOANY && X86_32)
626 depends on X86_IO_APIC
631 Select to build a kernel capable of supporting Intel MID (Mobile
632 Internet Device) platform systems which do not have the PCI legacy
633 interfaces. If you are building for a PC class system say N here.
635 Intel MID platforms are based on an Intel processor and chipset which
636 consume less power than most of the x86 derivatives.
638 config X86_INTEL_QUARK
639 bool "Intel Quark platform support"
641 depends on X86_EXTENDED_PLATFORM
642 depends on X86_PLATFORM_DEVICES
646 depends on X86_IO_APIC
651 Select to include support for Quark X1000 SoC.
652 Say Y here if you have a Quark based system such as the Arduino
653 compatible Intel Galileo.
655 config X86_INTEL_LPSS
656 bool "Intel Low Power Subsystem Support"
657 depends on X86 && ACPI && PCI
662 Select to build support for Intel Low Power Subsystem such as
663 found on Intel Lynxpoint PCH. Selecting this option enables
664 things like clock tree (common clock framework) and pincontrol
665 which are needed by the LPSS peripheral drivers.
667 config X86_AMD_PLATFORM_DEVICE
668 bool "AMD ACPI2Platform devices support"
673 Select to interpret AMD specific ACPI device to platform device
674 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
675 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
676 implemented under PINCTRL subsystem.
679 tristate "Intel SoC IOSF Sideband support for SoC platforms"
682 This option enables sideband register access support for Intel SoC
683 platforms. On these platforms the IOSF sideband is used in lieu of
684 MSR's for some register accesses, mostly but not limited to thermal
685 and power. Drivers may query the availability of this device to
686 determine if they need the sideband in order to work on these
687 platforms. The sideband is available on the following SoC products.
688 This list is not meant to be exclusive.
693 You should say Y if you are running a kernel on one of these SoC's.
695 config IOSF_MBI_DEBUG
696 bool "Enable IOSF sideband access through debugfs"
697 depends on IOSF_MBI && DEBUG_FS
699 Select this option to expose the IOSF sideband access registers (MCR,
700 MDR, MCRX) through debugfs to write and read register information from
701 different units on the SoC. This is most useful for obtaining device
702 state information for debug and analysis. As this is a general access
703 mechanism, users of this option would have specific knowledge of the
704 device they want to access.
706 If you don't require the option or are in doubt, say N.
709 bool "RDC R-321x SoC"
711 depends on X86_EXTENDED_PLATFORM
713 select X86_REBOOTFIXUPS
715 This option is needed for RDC R-321x system-on-chip, also known
717 If you don't have one of these chips, you should say N here.
719 config X86_32_NON_STANDARD
720 bool "Support non-standard 32-bit SMP architectures"
721 depends on X86_32 && SMP
722 depends on X86_EXTENDED_PLATFORM
724 This option compiles in the bigsmp and STA2X11 default
725 subarchitectures. It is intended for a generic binary
726 kernel. If you select them all, kernel will probe it one by
727 one and will fallback to default.
729 # Alphabetically sorted list of Non standard 32 bit platforms
731 config X86_SUPPORTS_MEMORY_FAILURE
733 # MCE code calls memory_failure():
735 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
736 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
737 depends on X86_64 || !SPARSEMEM
738 select ARCH_SUPPORTS_MEMORY_FAILURE
741 bool "STA2X11 Companion Chip Support"
742 depends on X86_32_NON_STANDARD && PCI
747 This adds support for boards based on the STA2X11 IO-Hub,
748 a.k.a. "ConneXt". The chip is used in place of the standard
749 PC chipset, so all "standard" peripherals are missing. If this
750 option is selected the kernel will still be able to boot on
751 standard PC machines.
754 tristate "Eurobraille/Iris poweroff module"
757 The Iris machines from EuroBraille do not have APM or ACPI support
758 to shut themselves down properly. A special I/O sequence is
759 needed to do so, which is what this module does at
762 This is only for Iris machines from EuroBraille.
766 config SCHED_OMIT_FRAME_POINTER
768 prompt "Single-depth WCHAN output"
771 Calculate simpler /proc/<PID>/wchan values. If this option
772 is disabled then wchan values will recurse back to the
773 caller function. This provides more accurate wchan values,
774 at the expense of slightly more scheduling overhead.
776 If in doubt, say "Y".
778 menuconfig HYPERVISOR_GUEST
779 bool "Linux guest support"
781 Say Y here to enable options for running Linux under various hyper-
782 visors. This option enables basic hypervisor detection and platform
785 If you say N, all options in this submenu will be skipped and
786 disabled, and Linux guest support won't be built in.
791 bool "Enable paravirtualization code"
792 depends on HAVE_STATIC_CALL
794 This changes the kernel so it can modify itself when it is run
795 under a hypervisor, potentially improving performance significantly
796 over full virtualization. However, when run without a hypervisor
797 the kernel is theoretically slower and slightly larger.
802 config PARAVIRT_DEBUG
803 bool "paravirt-ops debugging"
804 depends on PARAVIRT && DEBUG_KERNEL
806 Enable to debug paravirt_ops internals. Specifically, BUG if
807 a paravirt_op is missing when it is called.
809 config PARAVIRT_SPINLOCKS
810 bool "Paravirtualization layer for spinlocks"
811 depends on PARAVIRT && SMP
813 Paravirtualized spinlocks allow a pvops backend to replace the
814 spinlock implementation with something virtualization-friendly
815 (for example, block the virtual CPU rather than spinning).
817 It has a minimal impact on native kernels and gives a nice performance
818 benefit on paravirtualized KVM / Xen kernels.
820 If you are unsure how to answer this question, answer Y.
822 config X86_HV_CALLBACK_VECTOR
825 source "arch/x86/xen/Kconfig"
828 bool "KVM Guest support (including kvmclock)"
830 select PARAVIRT_CLOCK
831 select ARCH_CPUIDLE_HALTPOLL
832 select X86_HV_CALLBACK_VECTOR
835 This option enables various optimizations for running under the KVM
836 hypervisor. It includes a paravirtualized clock, so that instead
837 of relying on a PIT (or probably other) emulation by the
838 underlying device model, the host provides the guest with
839 timing infrastructure such as time of day, and system time
841 config ARCH_CPUIDLE_HALTPOLL
843 prompt "Disable host haltpoll when loading haltpoll driver"
845 If virtualized under KVM, disable host haltpoll.
848 bool "Support for running PVH guests"
850 This option enables the PVH entry point for guest virtual machines
851 as specified in the x86/HVM direct boot ABI.
853 config PARAVIRT_TIME_ACCOUNTING
854 bool "Paravirtual steal time accounting"
857 Select this option to enable fine granularity task steal time
858 accounting. Time spent executing other tasks in parallel with
859 the current vCPU is discounted from the vCPU power. To account for
860 that, there can be a small performance impact.
862 If in doubt, say N here.
864 config PARAVIRT_CLOCK
867 config JAILHOUSE_GUEST
868 bool "Jailhouse non-root cell support"
869 depends on X86_64 && PCI
872 This option allows to run Linux as guest in a Jailhouse non-root
873 cell. You can leave this option disabled if you only want to start
874 Jailhouse and run Linux afterwards in the root cell.
877 bool "ACRN Guest support"
879 select X86_HV_CALLBACK_VECTOR
881 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
882 a flexible, lightweight reference open-source hypervisor, built with
883 real-time and safety-criticality in mind. It is built for embedded
884 IOT with small footprint and real-time features. More details can be
885 found in https://projectacrn.org/.
887 config INTEL_TDX_GUEST
888 bool "Intel TDX (Trust Domain Extensions) - Guest Support"
889 depends on X86_64 && CPU_SUP_INTEL
890 depends on X86_X2APIC
891 select ARCH_HAS_CC_PLATFORM
892 select X86_MEM_ENCRYPT
895 Support running as a guest under Intel TDX. Without this support,
896 the guest kernel can not boot or run under TDX.
897 TDX includes memory encryption and integrity capabilities
898 which protect the confidentiality and integrity of guest
899 memory contents and CPU state. TDX guests are protected from
900 some attacks from the VMM.
902 endif # HYPERVISOR_GUEST
904 source "arch/x86/Kconfig.cpu"
908 prompt "HPET Timer Support" if X86_32
910 Use the IA-PC HPET (High Precision Event Timer) to manage
911 time in preference to the PIT and RTC, if a HPET is
913 HPET is the next generation timer replacing legacy 8254s.
914 The HPET provides a stable time base on SMP
915 systems, unlike the TSC, but it is more expensive to access,
916 as it is off-chip. The interface used is documented
917 in the HPET spec, revision 1.
919 You can safely choose Y here. However, HPET will only be
920 activated if the platform and the BIOS support this feature.
921 Otherwise the 8254 will be used for timing services.
923 Choose N to continue using the legacy 8254 timer.
925 config HPET_EMULATE_RTC
927 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
929 # Mark as expert because too many people got it wrong.
930 # The code disables itself when not needed.
933 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
934 bool "Enable DMI scanning" if EXPERT
936 Enabled scanning of DMI to identify machine quirks. Say Y
937 here unless you have verified that your setup is not
938 affected by entries in the DMI blacklist. Required by PNP
942 bool "Old AMD GART IOMMU support"
946 depends on X86_64 && PCI && AMD_NB
948 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
949 GART based hardware IOMMUs.
951 The GART supports full DMA access for devices with 32-bit access
952 limitations, on systems with more than 3 GB. This is usually needed
953 for USB, sound, many IDE/SATA chipsets and some other devices.
955 Newer systems typically have a modern AMD IOMMU, supported via
956 the CONFIG_AMD_IOMMU=y config option.
958 In normal configurations this driver is only active when needed:
959 there's more than 3 GB of memory and the system contains a
960 32-bit limited device.
964 config BOOT_VESA_SUPPORT
967 If true, at least one selected framebuffer driver can take advantage
968 of VESA video modes set at an early boot stage via the vga= parameter.
971 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
972 depends on X86_64 && SMP && DEBUG_KERNEL
973 select CPUMASK_OFFSTACK
975 Enable maximum number of CPUS and NUMA Nodes for this architecture.
979 # The maximum number of CPUs supported:
981 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
982 # and which can be configured interactively in the
983 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
985 # The ranges are different on 32-bit and 64-bit kernels, depending on
986 # hardware capabilities and scalability features of the kernel.
988 # ( If MAXSMP is enabled we just use the highest possible value and disable
989 # interactive configuration. )
992 config NR_CPUS_RANGE_BEGIN
994 default NR_CPUS_RANGE_END if MAXSMP
998 config NR_CPUS_RANGE_END
1001 default 64 if SMP && X86_BIGSMP
1002 default 8 if SMP && !X86_BIGSMP
1005 config NR_CPUS_RANGE_END
1008 default 8192 if SMP && CPUMASK_OFFSTACK
1009 default 512 if SMP && !CPUMASK_OFFSTACK
1012 config NR_CPUS_DEFAULT
1015 default 32 if X86_BIGSMP
1019 config NR_CPUS_DEFAULT
1022 default 8192 if MAXSMP
1027 int "Maximum number of CPUs" if SMP && !MAXSMP
1028 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1029 default NR_CPUS_DEFAULT
1031 This allows you to specify the maximum number of CPUs which this
1032 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1033 supported value is 8192, otherwise the maximum value is 512. The
1034 minimum value which makes sense is 2.
1036 This is purely to save memory: each supported CPU adds about 8KB
1037 to the kernel image.
1039 config SCHED_CLUSTER
1040 bool "Cluster scheduler support"
1044 Cluster scheduler support improves the CPU scheduler's decision
1045 making when dealing with machines that have clusters of CPUs.
1046 Cluster usually means a couple of CPUs which are placed closely
1047 by sharing mid-level caches, last-level cache tags or internal
1055 prompt "Multi-core scheduler support"
1058 Multi-core scheduler support improves the CPU scheduler's decision
1059 making when dealing with multi-core CPU chips at a cost of slightly
1060 increased overhead in some places. If unsure say N here.
1062 config SCHED_MC_PRIO
1063 bool "CPU core priorities scheduler support"
1064 depends on SCHED_MC && CPU_SUP_INTEL
1065 select X86_INTEL_PSTATE
1069 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1070 core ordering determined at manufacturing time, which allows
1071 certain cores to reach higher turbo frequencies (when running
1072 single threaded workloads) than others.
1074 Enabling this kernel feature teaches the scheduler about
1075 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1076 scheduler's CPU selection logic accordingly, so that higher
1077 overall system performance can be achieved.
1079 This feature will have no effect on CPUs without this feature.
1081 If unsure say Y here.
1085 depends on !SMP && X86_LOCAL_APIC
1088 bool "Local APIC support on uniprocessors" if !PCI_MSI
1090 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1092 A local APIC (Advanced Programmable Interrupt Controller) is an
1093 integrated interrupt controller in the CPU. If you have a single-CPU
1094 system which has a processor with a local APIC, you can say Y here to
1095 enable and use it. If you say Y here even though your machine doesn't
1096 have a local APIC, then the kernel will still run with no slowdown at
1097 all. The local APIC supports CPU-generated self-interrupts (timer,
1098 performance counters), and the NMI watchdog which detects hard
1101 config X86_UP_IOAPIC
1102 bool "IO-APIC support on uniprocessors"
1103 depends on X86_UP_APIC
1105 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1106 SMP-capable replacement for PC-style interrupt controllers. Most
1107 SMP systems and many recent uniprocessor systems have one.
1109 If you have a single-CPU system with an IO-APIC, you can say Y here
1110 to use it. If you say Y here even though your machine doesn't have
1111 an IO-APIC, then the kernel will still run with no slowdown at all.
1113 config X86_LOCAL_APIC
1115 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1116 select IRQ_DOMAIN_HIERARCHY
1117 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1121 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1123 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1124 bool "Reroute for broken boot IRQs"
1125 depends on X86_IO_APIC
1127 This option enables a workaround that fixes a source of
1128 spurious interrupts. This is recommended when threaded
1129 interrupt handling is used on systems where the generation of
1130 superfluous "boot interrupts" cannot be disabled.
1132 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1133 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1134 kernel does during interrupt handling). On chipsets where this
1135 boot IRQ generation cannot be disabled, this workaround keeps
1136 the original IRQ line masked so that only the equivalent "boot
1137 IRQ" is delivered to the CPUs. The workaround also tells the
1138 kernel to set up the IRQ handler on the boot IRQ line. In this
1139 way only one interrupt is delivered to the kernel. Otherwise
1140 the spurious second interrupt may cause the kernel to bring
1141 down (vital) interrupt lines.
1143 Only affects "broken" chipsets. Interrupt sharing may be
1144 increased on these systems.
1147 bool "Machine Check / overheating reporting"
1148 select GENERIC_ALLOCATOR
1151 Machine Check support allows the processor to notify the
1152 kernel if it detects a problem (e.g. overheating, data corruption).
1153 The action the kernel takes depends on the severity of the problem,
1154 ranging from warning messages to halting the machine.
1156 config X86_MCELOG_LEGACY
1157 bool "Support for deprecated /dev/mcelog character device"
1160 Enable support for /dev/mcelog which is needed by the old mcelog
1161 userspace logging daemon. Consider switching to the new generation
1164 config X86_MCE_INTEL
1166 prompt "Intel MCE features"
1167 depends on X86_MCE && X86_LOCAL_APIC
1169 Additional support for intel specific MCE features such as
1170 the thermal monitor.
1174 prompt "AMD MCE features"
1175 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1177 Additional support for AMD specific MCE features such as
1178 the DRAM Error Threshold.
1180 config X86_ANCIENT_MCE
1181 bool "Support for old Pentium 5 / WinChip machine checks"
1182 depends on X86_32 && X86_MCE
1184 Include support for machine check handling on old Pentium 5 or WinChip
1185 systems. These typically need to be enabled explicitly on the command
1188 config X86_MCE_THRESHOLD
1189 depends on X86_MCE_AMD || X86_MCE_INTEL
1192 config X86_MCE_INJECT
1193 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1194 tristate "Machine check injector support"
1196 Provide support for injecting machine checks for testing purposes.
1197 If you don't know what a machine check is and you don't do kernel
1198 QA it is safe to say n.
1200 source "arch/x86/events/Kconfig"
1202 config X86_LEGACY_VM86
1203 bool "Legacy VM86 support"
1206 This option allows user programs to put the CPU into V8086
1207 mode, which is an 80286-era approximation of 16-bit real mode.
1209 Some very old versions of X and/or vbetool require this option
1210 for user mode setting. Similarly, DOSEMU will use it if
1211 available to accelerate real mode DOS programs. However, any
1212 recent version of DOSEMU, X, or vbetool should be fully
1213 functional even without kernel VM86 support, as they will all
1214 fall back to software emulation. Nevertheless, if you are using
1215 a 16-bit DOS program where 16-bit performance matters, vm86
1216 mode might be faster than emulation and you might want to
1219 Note that any app that works on a 64-bit kernel is unlikely to
1220 need this option, as 64-bit kernels don't, and can't, support
1221 V8086 mode. This option is also unrelated to 16-bit protected
1222 mode and is not needed to run most 16-bit programs under Wine.
1224 Enabling this option increases the complexity of the kernel
1225 and slows down exception handling a tiny bit.
1227 If unsure, say N here.
1231 default X86_LEGACY_VM86
1234 bool "Enable support for 16-bit segments" if EXPERT
1236 depends on MODIFY_LDT_SYSCALL
1238 This option is required by programs like Wine to run 16-bit
1239 protected mode legacy code on x86 processors. Disabling
1240 this option saves about 300 bytes on i386, or around 6K text
1241 plus 16K runtime memory on x86-64,
1245 depends on X86_16BIT && X86_32
1249 depends on X86_16BIT && X86_64
1251 config X86_VSYSCALL_EMULATION
1252 bool "Enable vsyscall emulation" if EXPERT
1256 This enables emulation of the legacy vsyscall page. Disabling
1257 it is roughly equivalent to booting with vsyscall=none, except
1258 that it will also disable the helpful warning if a program
1259 tries to use a vsyscall. With this option set to N, offending
1260 programs will just segfault, citing addresses of the form
1263 This option is required by many programs built before 2013, and
1264 care should be used even with newer programs if set to N.
1266 Disabling this option saves about 7K of kernel size and
1267 possibly 4K of additional runtime pagetable memory.
1269 config X86_IOPL_IOPERM
1270 bool "IOPERM and IOPL Emulation"
1273 This enables the ioperm() and iopl() syscalls which are necessary
1274 for legacy applications.
1276 Legacy IOPL support is an overbroad mechanism which allows user
1277 space aside of accessing all 65536 I/O ports also to disable
1278 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1279 capabilities and permission from potentially active security
1282 The emulation restricts the functionality of the syscall to
1283 only allowing the full range I/O port access, but prevents the
1284 ability to disable interrupts from user space which would be
1285 granted if the hardware IOPL mechanism would be used.
1288 tristate "Toshiba Laptop support"
1291 This adds a driver to safely access the System Management Mode of
1292 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1293 not work on models with a Phoenix BIOS. The System Management Mode
1294 is used to set the BIOS and power saving options on Toshiba portables.
1296 For information on utilities to make use of this driver see the
1297 Toshiba Linux utilities web site at:
1298 <http://www.buzzard.org.uk/toshiba/>.
1300 Say Y if you intend to run this kernel on a Toshiba portable.
1303 config X86_REBOOTFIXUPS
1304 bool "Enable X86 board specific fixups for reboot"
1307 This enables chipset and/or board specific fixups to be done
1308 in order to get reboot to work correctly. This is only needed on
1309 some combinations of hardware and BIOS. The symptom, for which
1310 this config is intended, is when reboot ends with a stalled/hung
1313 Currently, the only fixup is for the Geode machines using
1314 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1316 Say Y if you want to enable the fixup. Currently, it's safe to
1317 enable this option even if you don't need it.
1321 bool "CPU microcode loading support"
1323 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1325 If you say Y here, you will be able to update the microcode on
1326 Intel and AMD processors. The Intel support is for the IA32 family,
1327 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1328 AMD support is for families 0x10 and later. You will obviously need
1329 the actual microcode binary data itself which is not shipped with
1332 The preferred method to load microcode from a detached initrd is described
1333 in Documentation/x86/microcode.rst. For that you need to enable
1334 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1335 initrd for microcode blobs.
1337 In addition, you can build the microcode into the kernel. For that you
1338 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1341 config MICROCODE_INTEL
1342 bool "Intel microcode loading support"
1343 depends on CPU_SUP_INTEL && MICROCODE
1346 This options enables microcode patch loading support for Intel
1349 For the current Intel microcode data package go to
1350 <https://downloadcenter.intel.com> and search for
1351 'Linux Processor Microcode Data File'.
1353 config MICROCODE_AMD
1354 bool "AMD microcode loading support"
1355 depends on CPU_SUP_AMD && MICROCODE
1357 If you select this option, microcode patch loading support for AMD
1358 processors will be enabled.
1360 config MICROCODE_LATE_LOADING
1361 bool "Late microcode loading (DANGEROUS)"
1363 depends on MICROCODE
1365 Loading microcode late, when the system is up and executing instructions
1366 is a tricky business and should be avoided if possible. Just the sequence
1367 of synchronizing all cores and SMT threads is one fragile dance which does
1368 not guarantee that cores might not softlock after the loading. Therefore,
1369 use this at your own risk. Late loading taints the kernel too.
1372 tristate "/dev/cpu/*/msr - Model-specific register support"
1374 This device gives privileged processes access to the x86
1375 Model-Specific Registers (MSRs). It is a character device with
1376 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1377 MSR accesses are directed to a specific CPU on multi-processor
1381 tristate "/dev/cpu/*/cpuid - CPU information support"
1383 This device gives processes access to the x86 CPUID instruction to
1384 be executed on a specific processor. It is a character device
1385 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1389 prompt "High Memory Support"
1396 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1397 However, the address space of 32-bit x86 processors is only 4
1398 Gigabytes large. That means that, if you have a large amount of
1399 physical memory, not all of it can be "permanently mapped" by the
1400 kernel. The physical memory that's not permanently mapped is called
1403 If you are compiling a kernel which will never run on a machine with
1404 more than 1 Gigabyte total physical RAM, answer "off" here (default
1405 choice and suitable for most users). This will result in a "3GB/1GB"
1406 split: 3GB are mapped so that each process sees a 3GB virtual memory
1407 space and the remaining part of the 4GB virtual memory space is used
1408 by the kernel to permanently map as much physical memory as
1411 If the machine has between 1 and 4 Gigabytes physical RAM, then
1414 If more than 4 Gigabytes is used then answer "64GB" here. This
1415 selection turns Intel PAE (Physical Address Extension) mode on.
1416 PAE implements 3-level paging on IA32 processors. PAE is fully
1417 supported by Linux, PAE mode is implemented on all recent Intel
1418 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1419 then the kernel will not boot on CPUs that don't support PAE!
1421 The actual amount of total physical memory will either be
1422 auto detected or can be forced by using a kernel command line option
1423 such as "mem=256M". (Try "man bootparam" or see the documentation of
1424 your boot loader (lilo or loadlin) about how to pass options to the
1425 kernel at boot time.)
1427 If unsure, say "off".
1432 Select this if you have a 32-bit processor and between 1 and 4
1433 gigabytes of physical RAM.
1437 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1440 Select this if you have a 32-bit processor and more than 4
1441 gigabytes of physical RAM.
1446 prompt "Memory split" if EXPERT
1450 Select the desired split between kernel and user memory.
1452 If the address range available to the kernel is less than the
1453 physical memory installed, the remaining memory will be available
1454 as "high memory". Accessing high memory is a little more costly
1455 than low memory, as it needs to be mapped into the kernel first.
1456 Note that increasing the kernel address space limits the range
1457 available to user programs, making the address space there
1458 tighter. Selecting anything other than the default 3G/1G split
1459 will also likely make your kernel incompatible with binary-only
1462 If you are not absolutely sure what you are doing, leave this
1466 bool "3G/1G user/kernel split"
1467 config VMSPLIT_3G_OPT
1469 bool "3G/1G user/kernel split (for full 1G low memory)"
1471 bool "2G/2G user/kernel split"
1472 config VMSPLIT_2G_OPT
1474 bool "2G/2G user/kernel split (for full 2G low memory)"
1476 bool "1G/3G user/kernel split"
1481 default 0xB0000000 if VMSPLIT_3G_OPT
1482 default 0x80000000 if VMSPLIT_2G
1483 default 0x78000000 if VMSPLIT_2G_OPT
1484 default 0x40000000 if VMSPLIT_1G
1490 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1493 bool "PAE (Physical Address Extension) Support"
1494 depends on X86_32 && !HIGHMEM4G
1495 select PHYS_ADDR_T_64BIT
1498 PAE is required for NX support, and furthermore enables
1499 larger swapspace support for non-overcommit purposes. It
1500 has the cost of more pagetable lookup overhead, and also
1501 consumes more pagetable space per process.
1504 bool "Enable 5-level page tables support"
1506 select DYNAMIC_MEMORY_LAYOUT
1507 select SPARSEMEM_VMEMMAP
1510 5-level paging enables access to larger address space:
1511 upto 128 PiB of virtual address space and 4 PiB of
1512 physical address space.
1514 It will be supported by future Intel CPUs.
1516 A kernel with the option enabled can be booted on machines that
1517 support 4- or 5-level paging.
1519 See Documentation/x86/x86_64/5level-paging.rst for more
1524 config X86_DIRECT_GBPAGES
1528 Certain kernel features effectively disable kernel
1529 linear 1 GB mappings (even if the CPU otherwise
1530 supports them), so don't confuse the user by printing
1531 that we have them enabled.
1533 config X86_CPA_STATISTICS
1534 bool "Enable statistic for Change Page Attribute"
1537 Expose statistics about the Change Page Attribute mechanism, which
1538 helps to determine the effectiveness of preserving large and huge
1539 page mappings when mapping protections are changed.
1541 config X86_MEM_ENCRYPT
1542 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1543 select DYNAMIC_PHYSICAL_MASK
1546 config AMD_MEM_ENCRYPT
1547 bool "AMD Secure Memory Encryption (SME) support"
1548 depends on X86_64 && CPU_SUP_AMD
1549 select DMA_COHERENT_POOL
1550 select ARCH_USE_MEMREMAP_PROT
1551 select INSTRUCTION_DECODER
1552 select ARCH_HAS_CC_PLATFORM
1553 select X86_MEM_ENCRYPT
1555 Say yes to enable support for the encryption of system memory.
1556 This requires an AMD processor that supports Secure Memory
1559 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1560 bool "Activate AMD Secure Memory Encryption (SME) by default"
1561 depends on AMD_MEM_ENCRYPT
1563 Say yes to have system memory encrypted by default if running on
1564 an AMD processor that supports Secure Memory Encryption (SME).
1566 If set to Y, then the encryption of system memory can be
1567 deactivated with the mem_encrypt=off command line option.
1569 If set to N, then the encryption of system memory can be
1570 activated with the mem_encrypt=on command line option.
1572 # Common NUMA Features
1574 bool "NUMA Memory Allocation and Scheduler Support"
1576 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1577 default y if X86_BIGSMP
1578 select USE_PERCPU_NUMA_NODE_ID
1580 Enable NUMA (Non-Uniform Memory Access) support.
1582 The kernel will try to allocate memory used by a CPU on the
1583 local memory controller of the CPU and add some more
1584 NUMA awareness to the kernel.
1586 For 64-bit this is recommended if the system is Intel Core i7
1587 (or later), AMD Opteron, or EM64T NUMA.
1589 For 32-bit this is only needed if you boot a 32-bit
1590 kernel on a 64-bit NUMA platform.
1592 Otherwise, you should say N.
1596 prompt "Old style AMD Opteron NUMA detection"
1597 depends on X86_64 && NUMA && PCI
1599 Enable AMD NUMA node topology detection. You should say Y here if
1600 you have a multi processor AMD system. This uses an old method to
1601 read the NUMA configuration directly from the builtin Northbridge
1602 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1603 which also takes priority if both are compiled in.
1605 config X86_64_ACPI_NUMA
1607 prompt "ACPI NUMA detection"
1608 depends on X86_64 && NUMA && ACPI && PCI
1611 Enable ACPI SRAT based node topology detection.
1614 bool "NUMA emulation"
1617 Enable NUMA emulation. A flat machine will be split
1618 into virtual nodes when booted with "numa=fake=N", where N is the
1619 number of nodes. This is only useful for debugging.
1622 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1624 default "10" if MAXSMP
1625 default "6" if X86_64
1629 Specify the maximum number of NUMA Nodes available on the target
1630 system. Increases memory reserved to accommodate various tables.
1632 config ARCH_FLATMEM_ENABLE
1634 depends on X86_32 && !NUMA
1636 config ARCH_SPARSEMEM_ENABLE
1638 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1639 select SPARSEMEM_STATIC if X86_32
1640 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1642 config ARCH_SPARSEMEM_DEFAULT
1643 def_bool X86_64 || (NUMA && X86_32)
1645 config ARCH_SELECT_MEMORY_MODEL
1647 depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE
1649 config ARCH_MEMORY_PROBE
1650 bool "Enable sysfs memory/probe interface"
1651 depends on MEMORY_HOTPLUG
1653 This option enables a sysfs memory/probe interface for testing.
1654 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1655 If you are unsure how to answer this question, answer N.
1657 config ARCH_PROC_KCORE_TEXT
1659 depends on X86_64 && PROC_KCORE
1661 config ILLEGAL_POINTER_VALUE
1664 default 0xdead000000000000 if X86_64
1666 config X86_PMEM_LEGACY_DEVICE
1669 config X86_PMEM_LEGACY
1670 tristate "Support non-standard NVDIMMs and ADR protected memory"
1671 depends on PHYS_ADDR_T_64BIT
1673 select X86_PMEM_LEGACY_DEVICE
1674 select NUMA_KEEP_MEMINFO if NUMA
1677 Treat memory marked using the non-standard e820 type of 12 as used
1678 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1679 The kernel will offer these regions to the 'pmem' driver so
1680 they can be used for persistent storage.
1685 bool "Allocate 3rd-level pagetables from highmem"
1688 The VM uses one page table entry for each page of physical memory.
1689 For systems with a lot of RAM, this can be wasteful of precious
1690 low memory. Setting this option will put user-space page table
1691 entries in high memory.
1693 config X86_CHECK_BIOS_CORRUPTION
1694 bool "Check for low memory corruption"
1696 Periodically check for memory corruption in low memory, which
1697 is suspected to be caused by BIOS. Even when enabled in the
1698 configuration, it is disabled at runtime. Enable it by
1699 setting "memory_corruption_check=1" on the kernel command
1700 line. By default it scans the low 64k of memory every 60
1701 seconds; see the memory_corruption_check_size and
1702 memory_corruption_check_period parameters in
1703 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1705 When enabled with the default parameters, this option has
1706 almost no overhead, as it reserves a relatively small amount
1707 of memory and scans it infrequently. It both detects corruption
1708 and prevents it from affecting the running system.
1710 It is, however, intended as a diagnostic tool; if repeatable
1711 BIOS-originated corruption always affects the same memory,
1712 you can use memmap= to prevent the kernel from using that
1715 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1716 bool "Set the default setting of memory_corruption_check"
1717 depends on X86_CHECK_BIOS_CORRUPTION
1720 Set whether the default state of memory_corruption_check is
1723 config MATH_EMULATION
1725 depends on MODIFY_LDT_SYSCALL
1726 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1728 Linux can emulate a math coprocessor (used for floating point
1729 operations) if you don't have one. 486DX and Pentium processors have
1730 a math coprocessor built in, 486SX and 386 do not, unless you added
1731 a 487DX or 387, respectively. (The messages during boot time can
1732 give you some hints here ["man dmesg"].) Everyone needs either a
1733 coprocessor or this emulation.
1735 If you don't have a math coprocessor, you need to say Y here; if you
1736 say Y here even though you have a coprocessor, the coprocessor will
1737 be used nevertheless. (This behavior can be changed with the kernel
1738 command line option "no387", which comes handy if your coprocessor
1739 is broken. Try "man bootparam" or see the documentation of your boot
1740 loader (lilo or loadlin) about how to pass options to the kernel at
1741 boot time.) This means that it is a good idea to say Y here if you
1742 intend to use this kernel on different machines.
1744 More information about the internals of the Linux math coprocessor
1745 emulation can be found in <file:arch/x86/math-emu/README>.
1747 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1748 kernel, it won't hurt.
1752 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1754 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1755 the Memory Type Range Registers (MTRRs) may be used to control
1756 processor access to memory ranges. This is most useful if you have
1757 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1758 allows bus write transfers to be combined into a larger transfer
1759 before bursting over the PCI/AGP bus. This can increase performance
1760 of image write operations 2.5 times or more. Saying Y here creates a
1761 /proc/mtrr file which may be used to manipulate your processor's
1762 MTRRs. Typically the X server should use this.
1764 This code has a reasonably generic interface so that similar
1765 control registers on other processors can be easily supported
1768 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1769 Registers (ARRs) which provide a similar functionality to MTRRs. For
1770 these, the ARRs are used to emulate the MTRRs.
1771 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1772 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1773 write-combining. All of these processors are supported by this code
1774 and it makes sense to say Y here if you have one of them.
1776 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1777 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1778 can lead to all sorts of problems, so it's good to say Y here.
1780 You can safely say Y even if your machine doesn't have MTRRs, you'll
1781 just add about 9 KB to your kernel.
1783 See <file:Documentation/x86/mtrr.rst> for more information.
1785 config MTRR_SANITIZER
1787 prompt "MTRR cleanup support"
1790 Convert MTRR layout from continuous to discrete, so X drivers can
1791 add writeback entries.
1793 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1794 The largest mtrr entry size for a continuous block can be set with
1799 config MTRR_SANITIZER_ENABLE_DEFAULT
1800 int "MTRR cleanup enable value (0-1)"
1803 depends on MTRR_SANITIZER
1805 Enable mtrr cleanup default value
1807 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1808 int "MTRR cleanup spare reg num (0-7)"
1811 depends on MTRR_SANITIZER
1813 mtrr cleanup spare entries default, it can be changed via
1814 mtrr_spare_reg_nr=N on the kernel command line.
1818 prompt "x86 PAT support" if EXPERT
1821 Use PAT attributes to setup page level cache control.
1823 PATs are the modern equivalents of MTRRs and are much more
1824 flexible than MTRRs.
1826 Say N here if you see bootup problems (boot crash, boot hang,
1827 spontaneous reboots) or a non-working video driver.
1831 config ARCH_USES_PG_UNCACHED
1837 prompt "x86 architectural random number generator" if EXPERT
1839 Enable the x86 architectural RDRAND instruction
1840 (Intel Bull Mountain technology) to generate random numbers.
1841 If supported, this is a high bandwidth, cryptographically
1842 secure hardware random number generator.
1846 prompt "User Mode Instruction Prevention" if EXPERT
1848 User Mode Instruction Prevention (UMIP) is a security feature in
1849 some x86 processors. If enabled, a general protection fault is
1850 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1851 executed in user mode. These instructions unnecessarily expose
1852 information about the hardware state.
1854 The vast majority of applications do not use these instructions.
1855 For the very few that do, software emulation is provided in
1856 specific cases in protected and virtual-8086 modes. Emulated
1860 # GCC >= 9 and binutils >= 2.29
1861 # Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
1863 # https://github.com/llvm/llvm-project/commit/e0b89df2e0f0130881bf6c39bf31d7f6aac00e0f
1864 # https://github.com/llvm/llvm-project/commit/dfcf69770bc522b9e411c66454934a37c1f35332
1865 def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \
1866 (CC_IS_CLANG && CLANG_VERSION >= 140000)) && \
1869 config X86_KERNEL_IBT
1870 prompt "Indirect Branch Tracking"
1872 depends on X86_64 && CC_HAS_IBT && HAVE_OBJTOOL
1873 # https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
1874 depends on !LD_IS_LLD || LLD_VERSION >= 140000
1877 Build the kernel with support for Indirect Branch Tracking, a
1878 hardware support course-grain forward-edge Control Flow Integrity
1879 protection. It enforces that all indirect calls must land on
1880 an ENDBR instruction, as such, the compiler will instrument the
1881 code with them to make this happen.
1883 In addition to building the kernel with IBT, seal all functions that
1884 are not indirect call targets, avoiding them ever becoming one.
1886 This requires LTO like objtool runs and will slow down the build. It
1887 does significantly reduce the number of ENDBR instructions in the
1890 config X86_INTEL_MEMORY_PROTECTION_KEYS
1891 prompt "Memory Protection Keys"
1893 # Note: only available in 64-bit mode
1894 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1895 select ARCH_USES_HIGH_VMA_FLAGS
1896 select ARCH_HAS_PKEYS
1898 Memory Protection Keys provides a mechanism for enforcing
1899 page-based protections, but without requiring modification of the
1900 page tables when an application changes protection domains.
1902 For details, see Documentation/core-api/protection-keys.rst
1907 prompt "TSX enable mode"
1908 depends on CPU_SUP_INTEL
1909 default X86_INTEL_TSX_MODE_OFF
1911 Intel's TSX (Transactional Synchronization Extensions) feature
1912 allows to optimize locking protocols through lock elision which
1913 can lead to a noticeable performance boost.
1915 On the other hand it has been shown that TSX can be exploited
1916 to form side channel attacks (e.g. TAA) and chances are there
1917 will be more of those attacks discovered in the future.
1919 Therefore TSX is not enabled by default (aka tsx=off). An admin
1920 might override this decision by tsx=on the command line parameter.
1921 Even with TSX enabled, the kernel will attempt to enable the best
1922 possible TAA mitigation setting depending on the microcode available
1923 for the particular machine.
1925 This option allows to set the default tsx mode between tsx=on, =off
1926 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1929 Say off if not sure, auto if TSX is in use but it should be used on safe
1930 platforms or on if TSX is in use and the security aspect of tsx is not
1933 config X86_INTEL_TSX_MODE_OFF
1936 TSX is disabled if possible - equals to tsx=off command line parameter.
1938 config X86_INTEL_TSX_MODE_ON
1941 TSX is always enabled on TSX capable HW - equals the tsx=on command
1944 config X86_INTEL_TSX_MODE_AUTO
1947 TSX is enabled on TSX capable HW that is believed to be safe against
1948 side channel attacks- equals the tsx=auto command line parameter.
1952 bool "Software Guard eXtensions (SGX)"
1953 depends on X86_64 && CPU_SUP_INTEL
1955 depends on CRYPTO_SHA256=y
1958 select NUMA_KEEP_MEMINFO if NUMA
1961 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1962 that can be used by applications to set aside private regions of code
1963 and data, referred to as enclaves. An enclave's private memory can
1964 only be accessed by code running within the enclave. Accesses from
1965 outside the enclave, including other enclaves, are disallowed by
1971 bool "EFI runtime service support"
1974 select EFI_RUNTIME_WRAPPERS
1975 select ARCH_USE_MEMREMAP_PROT
1977 This enables the kernel to use EFI runtime services that are
1978 available (such as the EFI variable services).
1980 This option is only useful on systems that have EFI firmware.
1981 In addition, you should use the latest ELILO loader available
1982 at <http://elilo.sourceforge.net> in order to take advantage
1983 of EFI runtime services. However, even with this option, the
1984 resultant kernel should continue to boot on existing non-EFI
1988 bool "EFI stub support"
1990 depends on $(cc-option,-mabi=ms) || X86_32
1993 This kernel feature allows a bzImage to be loaded directly
1994 by EFI firmware without the use of a bootloader.
1996 See Documentation/admin-guide/efi-stub.rst for more information.
1999 bool "EFI mixed-mode support"
2000 depends on EFI_STUB && X86_64
2002 Enabling this feature allows a 64-bit kernel to be booted
2003 on a 32-bit firmware, provided that your CPU supports 64-bit
2006 Note that it is not possible to boot a mixed-mode enabled
2007 kernel via the EFI boot stub - a bootloader that supports
2008 the EFI handover protocol must be used.
2012 source "kernel/Kconfig.hz"
2015 bool "kexec system call"
2018 kexec is a system call that implements the ability to shutdown your
2019 current kernel, and to start another kernel. It is like a reboot
2020 but it is independent of the system firmware. And like a reboot
2021 you can start any kernel with it, not just Linux.
2023 The name comes from the similarity to the exec system call.
2025 It is an ongoing process to be certain the hardware in a machine
2026 is properly shutdown, so do not be surprised if this code does not
2027 initially work for you. As of this writing the exact hardware
2028 interface is strongly in flux, so no good recommendation can be
2032 bool "kexec file based system call"
2037 depends on CRYPTO_SHA256=y
2039 This is new version of kexec system call. This system call is
2040 file based and takes file descriptors as system call argument
2041 for kernel and initramfs as opposed to list of segments as
2042 accepted by previous system call.
2044 config ARCH_HAS_KEXEC_PURGATORY
2048 bool "Verify kernel signature during kexec_file_load() syscall"
2049 depends on KEXEC_FILE
2052 This option makes the kexec_file_load() syscall check for a valid
2053 signature of the kernel image. The image can still be loaded without
2054 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2055 there's a signature that we can check, then it must be valid.
2057 In addition to this option, you need to enable signature
2058 verification for the corresponding kernel image type being
2059 loaded in order for this to work.
2061 config KEXEC_SIG_FORCE
2062 bool "Require a valid signature in kexec_file_load() syscall"
2063 depends on KEXEC_SIG
2065 This option makes kernel signature verification mandatory for
2066 the kexec_file_load() syscall.
2068 config KEXEC_BZIMAGE_VERIFY_SIG
2069 bool "Enable bzImage signature verification support"
2070 depends on KEXEC_SIG
2071 depends on SIGNED_PE_FILE_VERIFICATION
2072 select SYSTEM_TRUSTED_KEYRING
2074 Enable bzImage signature verification support.
2077 bool "kernel crash dumps"
2078 depends on X86_64 || (X86_32 && HIGHMEM)
2080 Generate crash dump after being started by kexec.
2081 This should be normally only set in special crash dump kernels
2082 which are loaded in the main kernel with kexec-tools into
2083 a specially reserved region and then later executed after
2084 a crash by kdump/kexec. The crash dump kernel must be compiled
2085 to a memory address not used by the main kernel or BIOS using
2086 PHYSICAL_START, or it must be built as a relocatable image
2087 (CONFIG_RELOCATABLE=y).
2088 For more details see Documentation/admin-guide/kdump/kdump.rst
2092 depends on KEXEC && HIBERNATION
2094 Jump between original kernel and kexeced kernel and invoke
2095 code in physical address mode via KEXEC
2097 config PHYSICAL_START
2098 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2101 This gives the physical address where the kernel is loaded.
2103 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2104 bzImage will decompress itself to above physical address and
2105 run from there. Otherwise, bzImage will run from the address where
2106 it has been loaded by the boot loader and will ignore above physical
2109 In normal kdump cases one does not have to set/change this option
2110 as now bzImage can be compiled as a completely relocatable image
2111 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2112 address. This option is mainly useful for the folks who don't want
2113 to use a bzImage for capturing the crash dump and want to use a
2114 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2115 to be specifically compiled to run from a specific memory area
2116 (normally a reserved region) and this option comes handy.
2118 So if you are using bzImage for capturing the crash dump,
2119 leave the value here unchanged to 0x1000000 and set
2120 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2121 for capturing the crash dump change this value to start of
2122 the reserved region. In other words, it can be set based on
2123 the "X" value as specified in the "crashkernel=YM@XM"
2124 command line boot parameter passed to the panic-ed
2125 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2126 for more details about crash dumps.
2128 Usage of bzImage for capturing the crash dump is recommended as
2129 one does not have to build two kernels. Same kernel can be used
2130 as production kernel and capture kernel. Above option should have
2131 gone away after relocatable bzImage support is introduced. But it
2132 is present because there are users out there who continue to use
2133 vmlinux for dump capture. This option should go away down the
2136 Don't change this unless you know what you are doing.
2139 bool "Build a relocatable kernel"
2142 This builds a kernel image that retains relocation information
2143 so it can be loaded someplace besides the default 1MB.
2144 The relocations tend to make the kernel binary about 10% larger,
2145 but are discarded at runtime.
2147 One use is for the kexec on panic case where the recovery kernel
2148 must live at a different physical address than the primary
2151 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2152 it has been loaded at and the compile time physical address
2153 (CONFIG_PHYSICAL_START) is used as the minimum location.
2155 config RANDOMIZE_BASE
2156 bool "Randomize the address of the kernel image (KASLR)"
2157 depends on RELOCATABLE
2160 In support of Kernel Address Space Layout Randomization (KASLR),
2161 this randomizes the physical address at which the kernel image
2162 is decompressed and the virtual address where the kernel
2163 image is mapped, as a security feature that deters exploit
2164 attempts relying on knowledge of the location of kernel
2167 On 64-bit, the kernel physical and virtual addresses are
2168 randomized separately. The physical address will be anywhere
2169 between 16MB and the top of physical memory (up to 64TB). The
2170 virtual address will be randomized from 16MB up to 1GB (9 bits
2171 of entropy). Note that this also reduces the memory space
2172 available to kernel modules from 1.5GB to 1GB.
2174 On 32-bit, the kernel physical and virtual addresses are
2175 randomized together. They will be randomized from 16MB up to
2176 512MB (8 bits of entropy).
2178 Entropy is generated using the RDRAND instruction if it is
2179 supported. If RDTSC is supported, its value is mixed into
2180 the entropy pool as well. If neither RDRAND nor RDTSC are
2181 supported, then entropy is read from the i8254 timer. The
2182 usable entropy is limited by the kernel being built using
2183 2GB addressing, and that PHYSICAL_ALIGN must be at a
2184 minimum of 2MB. As a result, only 10 bits of entropy are
2185 theoretically possible, but the implementations are further
2186 limited due to memory layouts.
2190 # Relocation on x86 needs some additional build support
2191 config X86_NEED_RELOCS
2193 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2195 config PHYSICAL_ALIGN
2196 hex "Alignment value to which kernel should be aligned"
2198 range 0x2000 0x1000000 if X86_32
2199 range 0x200000 0x1000000 if X86_64
2201 This value puts the alignment restrictions on physical address
2202 where kernel is loaded and run from. Kernel is compiled for an
2203 address which meets above alignment restriction.
2205 If bootloader loads the kernel at a non-aligned address and
2206 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2207 address aligned to above value and run from there.
2209 If bootloader loads the kernel at a non-aligned address and
2210 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2211 load address and decompress itself to the address it has been
2212 compiled for and run from there. The address for which kernel is
2213 compiled already meets above alignment restrictions. Hence the
2214 end result is that kernel runs from a physical address meeting
2215 above alignment restrictions.
2217 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2218 this value must be a multiple of 0x200000.
2220 Don't change this unless you know what you are doing.
2222 config DYNAMIC_MEMORY_LAYOUT
2225 This option makes base addresses of vmalloc and vmemmap as well as
2226 __PAGE_OFFSET movable during boot.
2228 config RANDOMIZE_MEMORY
2229 bool "Randomize the kernel memory sections"
2231 depends on RANDOMIZE_BASE
2232 select DYNAMIC_MEMORY_LAYOUT
2233 default RANDOMIZE_BASE
2235 Randomizes the base virtual address of kernel memory sections
2236 (physical memory mapping, vmalloc & vmemmap). This security feature
2237 makes exploits relying on predictable memory locations less reliable.
2239 The order of allocations remains unchanged. Entropy is generated in
2240 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2241 configuration have in average 30,000 different possible virtual
2242 addresses for each memory section.
2246 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2247 hex "Physical memory mapping padding" if EXPERT
2248 depends on RANDOMIZE_MEMORY
2249 default "0xa" if MEMORY_HOTPLUG
2251 range 0x1 0x40 if MEMORY_HOTPLUG
2254 Define the padding in terabytes added to the existing physical
2255 memory size during kernel memory randomization. It is useful
2256 for memory hotplug support but reduces the entropy available for
2257 address randomization.
2259 If unsure, leave at the default value.
2265 config BOOTPARAM_HOTPLUG_CPU0
2266 bool "Set default setting of cpu0_hotpluggable"
2267 depends on HOTPLUG_CPU
2269 Set whether default state of cpu0_hotpluggable is on or off.
2271 Say Y here to enable CPU0 hotplug by default. If this switch
2272 is turned on, there is no need to give cpu0_hotplug kernel
2273 parameter and the CPU0 hotplug feature is enabled by default.
2275 Please note: there are two known CPU0 dependencies if you want
2276 to enable the CPU0 hotplug feature either by this switch or by
2277 cpu0_hotplug kernel parameter.
2279 First, resume from hibernate or suspend always starts from CPU0.
2280 So hibernate and suspend are prevented if CPU0 is offline.
2282 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2283 offline if any interrupt can not migrate out of CPU0. There may
2284 be other CPU0 dependencies.
2286 Please make sure the dependencies are under your control before
2287 you enable this feature.
2289 Say N if you don't want to enable CPU0 hotplug feature by default.
2290 You still can enable the CPU0 hotplug feature at boot by kernel
2291 parameter cpu0_hotplug.
2293 config DEBUG_HOTPLUG_CPU0
2295 prompt "Debug CPU0 hotplug"
2296 depends on HOTPLUG_CPU
2298 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2299 soon as possible and boots up userspace with CPU0 offlined. User
2300 can online CPU0 back after boot time.
2302 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2303 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2304 compilation or giving cpu0_hotplug kernel parameter at boot.
2310 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2311 depends on COMPAT_32
2313 Certain buggy versions of glibc will crash if they are
2314 presented with a 32-bit vDSO that is not mapped at the address
2315 indicated in its segment table.
2317 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2318 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2319 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2320 the only released version with the bug, but OpenSUSE 9
2321 contains a buggy "glibc 2.3.2".
2323 The symptom of the bug is that everything crashes on startup, saying:
2324 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2326 Saying Y here changes the default value of the vdso32 boot
2327 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2328 This works around the glibc bug but hurts performance.
2330 If unsure, say N: if you are compiling your own kernel, you
2331 are unlikely to be using a buggy version of glibc.
2334 prompt "vsyscall table for legacy applications"
2336 default LEGACY_VSYSCALL_XONLY
2338 Legacy user code that does not know how to find the vDSO expects
2339 to be able to issue three syscalls by calling fixed addresses in
2340 kernel space. Since this location is not randomized with ASLR,
2341 it can be used to assist security vulnerability exploitation.
2343 This setting can be changed at boot time via the kernel command
2344 line parameter vsyscall=[emulate|xonly|none]. Emulate mode
2345 is deprecated and can only be enabled using the kernel command
2348 On a system with recent enough glibc (2.14 or newer) and no
2349 static binaries, you can say None without a performance penalty
2350 to improve security.
2352 If unsure, select "Emulate execution only".
2354 config LEGACY_VSYSCALL_XONLY
2355 bool "Emulate execution only"
2357 The kernel traps and emulates calls into the fixed vsyscall
2358 address mapping and does not allow reads. This
2359 configuration is recommended when userspace might use the
2360 legacy vsyscall area but support for legacy binary
2361 instrumentation of legacy code is not needed. It mitigates
2362 certain uses of the vsyscall area as an ASLR-bypassing
2365 config LEGACY_VSYSCALL_NONE
2368 There will be no vsyscall mapping at all. This will
2369 eliminate any risk of ASLR bypass due to the vsyscall
2370 fixed address mapping. Attempts to use the vsyscalls
2371 will be reported to dmesg, so that either old or
2372 malicious userspace programs can be identified.
2377 bool "Built-in kernel command line"
2379 Allow for specifying boot arguments to the kernel at
2380 build time. On some systems (e.g. embedded ones), it is
2381 necessary or convenient to provide some or all of the
2382 kernel boot arguments with the kernel itself (that is,
2383 to not rely on the boot loader to provide them.)
2385 To compile command line arguments into the kernel,
2386 set this option to 'Y', then fill in the
2387 boot arguments in CONFIG_CMDLINE.
2389 Systems with fully functional boot loaders (i.e. non-embedded)
2390 should leave this option set to 'N'.
2393 string "Built-in kernel command string"
2394 depends on CMDLINE_BOOL
2397 Enter arguments here that should be compiled into the kernel
2398 image and used at boot time. If the boot loader provides a
2399 command line at boot time, it is appended to this string to
2400 form the full kernel command line, when the system boots.
2402 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2403 change this behavior.
2405 In most cases, the command line (whether built-in or provided
2406 by the boot loader) should specify the device for the root
2409 config CMDLINE_OVERRIDE
2410 bool "Built-in command line overrides boot loader arguments"
2411 depends on CMDLINE_BOOL && CMDLINE != ""
2413 Set this option to 'Y' to have the kernel ignore the boot loader
2414 command line, and use ONLY the built-in command line.
2416 This is used to work around broken boot loaders. This should
2417 be set to 'N' under normal conditions.
2419 config MODIFY_LDT_SYSCALL
2420 bool "Enable the LDT (local descriptor table)" if EXPERT
2423 Linux can allow user programs to install a per-process x86
2424 Local Descriptor Table (LDT) using the modify_ldt(2) system
2425 call. This is required to run 16-bit or segmented code such as
2426 DOSEMU or some Wine programs. It is also used by some very old
2427 threading libraries.
2429 Enabling this feature adds a small amount of overhead to
2430 context switches and increases the low-level kernel attack
2431 surface. Disabling it removes the modify_ldt(2) system call.
2433 Saying 'N' here may make sense for embedded or server kernels.
2435 config STRICT_SIGALTSTACK_SIZE
2436 bool "Enforce strict size checking for sigaltstack"
2437 depends on DYNAMIC_SIGFRAME
2439 For historical reasons MINSIGSTKSZ is a constant which became
2440 already too small with AVX512 support. Add a mechanism to
2441 enforce strict checking of the sigaltstack size against the
2442 real size of the FPU frame. This option enables the check
2443 by default. It can also be controlled via the kernel command
2444 line option 'strict_sas_size' independent of this config
2445 switch. Enabling it might break existing applications which
2446 allocate a too small sigaltstack but 'work' because they
2447 never get a signal delivered.
2449 Say 'N' unless you want to really enforce this check.
2451 source "kernel/livepatch/Kconfig"
2455 config ARCH_HAS_ADD_PAGES
2457 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2459 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2462 menu "Power management and ACPI options"
2464 config ARCH_HIBERNATION_HEADER
2466 depends on HIBERNATION
2468 source "kernel/power/Kconfig"
2470 source "drivers/acpi/Kconfig"
2477 tristate "APM (Advanced Power Management) BIOS support"
2478 depends on X86_32 && PM_SLEEP
2480 APM is a BIOS specification for saving power using several different
2481 techniques. This is mostly useful for battery powered laptops with
2482 APM compliant BIOSes. If you say Y here, the system time will be
2483 reset after a RESUME operation, the /proc/apm device will provide
2484 battery status information, and user-space programs will receive
2485 notification of APM "events" (e.g. battery status change).
2487 If you select "Y" here, you can disable actual use of the APM
2488 BIOS by passing the "apm=off" option to the kernel at boot time.
2490 Note that the APM support is almost completely disabled for
2491 machines with more than one CPU.
2493 In order to use APM, you will need supporting software. For location
2494 and more information, read <file:Documentation/power/apm-acpi.rst>
2495 and the Battery Powered Linux mini-HOWTO, available from
2496 <http://www.tldp.org/docs.html#howto>.
2498 This driver does not spin down disk drives (see the hdparm(8)
2499 manpage ("man 8 hdparm") for that), and it doesn't turn off
2500 VESA-compliant "green" monitors.
2502 This driver does not support the TI 4000M TravelMate and the ACER
2503 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2504 desktop machines also don't have compliant BIOSes, and this driver
2505 may cause those machines to panic during the boot phase.
2507 Generally, if you don't have a battery in your machine, there isn't
2508 much point in using this driver and you should say N. If you get
2509 random kernel OOPSes or reboots that don't seem to be related to
2510 anything, try disabling/enabling this option (or disabling/enabling
2513 Some other things you should try when experiencing seemingly random,
2516 1) make sure that you have enough swap space and that it is
2518 2) pass the "no-hlt" option to the kernel
2519 3) switch on floating point emulation in the kernel and pass
2520 the "no387" option to the kernel
2521 4) pass the "floppy=nodma" option to the kernel
2522 5) pass the "mem=4M" option to the kernel (thereby disabling
2523 all but the first 4 MB of RAM)
2524 6) make sure that the CPU is not over clocked.
2525 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2526 8) disable the cache from your BIOS settings
2527 9) install a fan for the video card or exchange video RAM
2528 10) install a better fan for the CPU
2529 11) exchange RAM chips
2530 12) exchange the motherboard.
2532 To compile this driver as a module, choose M here: the
2533 module will be called apm.
2537 config APM_IGNORE_USER_SUSPEND
2538 bool "Ignore USER SUSPEND"
2540 This option will ignore USER SUSPEND requests. On machines with a
2541 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2542 series notebooks, it is necessary to say Y because of a BIOS bug.
2544 config APM_DO_ENABLE
2545 bool "Enable PM at boot time"
2547 Enable APM features at boot time. From page 36 of the APM BIOS
2548 specification: "When disabled, the APM BIOS does not automatically
2549 power manage devices, enter the Standby State, enter the Suspend
2550 State, or take power saving steps in response to CPU Idle calls."
2551 This driver will make CPU Idle calls when Linux is idle (unless this
2552 feature is turned off -- see "Do CPU IDLE calls", below). This
2553 should always save battery power, but more complicated APM features
2554 will be dependent on your BIOS implementation. You may need to turn
2555 this option off if your computer hangs at boot time when using APM
2556 support, or if it beeps continuously instead of suspending. Turn
2557 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2558 T400CDT. This is off by default since most machines do fine without
2563 bool "Make CPU Idle calls when idle"
2565 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2566 On some machines, this can activate improved power savings, such as
2567 a slowed CPU clock rate, when the machine is idle. These idle calls
2568 are made after the idle loop has run for some length of time (e.g.,
2569 333 mS). On some machines, this will cause a hang at boot time or
2570 whenever the CPU becomes idle. (On machines with more than one CPU,
2571 this option does nothing.)
2573 config APM_DISPLAY_BLANK
2574 bool "Enable console blanking using APM"
2576 Enable console blanking using the APM. Some laptops can use this to
2577 turn off the LCD backlight when the screen blanker of the Linux
2578 virtual console blanks the screen. Note that this is only used by
2579 the virtual console screen blanker, and won't turn off the backlight
2580 when using the X Window system. This also doesn't have anything to
2581 do with your VESA-compliant power-saving monitor. Further, this
2582 option doesn't work for all laptops -- it might not turn off your
2583 backlight at all, or it might print a lot of errors to the console,
2584 especially if you are using gpm.
2586 config APM_ALLOW_INTS
2587 bool "Allow interrupts during APM BIOS calls"
2589 Normally we disable external interrupts while we are making calls to
2590 the APM BIOS as a measure to lessen the effects of a badly behaving
2591 BIOS implementation. The BIOS should reenable interrupts if it
2592 needs to. Unfortunately, some BIOSes do not -- especially those in
2593 many of the newer IBM Thinkpads. If you experience hangs when you
2594 suspend, try setting this to Y. Otherwise, say N.
2598 source "drivers/cpufreq/Kconfig"
2600 source "drivers/cpuidle/Kconfig"
2602 source "drivers/idle/Kconfig"
2606 menu "Bus options (PCI etc.)"
2609 prompt "PCI access mode"
2610 depends on X86_32 && PCI
2613 On PCI systems, the BIOS can be used to detect the PCI devices and
2614 determine their configuration. However, some old PCI motherboards
2615 have BIOS bugs and may crash if this is done. Also, some embedded
2616 PCI-based systems don't have any BIOS at all. Linux can also try to
2617 detect the PCI hardware directly without using the BIOS.
2619 With this option, you can specify how Linux should detect the
2620 PCI devices. If you choose "BIOS", the BIOS will be used,
2621 if you choose "Direct", the BIOS won't be used, and if you
2622 choose "MMConfig", then PCI Express MMCONFIG will be used.
2623 If you choose "Any", the kernel will try MMCONFIG, then the
2624 direct access method and falls back to the BIOS if that doesn't
2625 work. If unsure, go with the default, which is "Any".
2630 config PCI_GOMMCONFIG
2647 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2649 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2652 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2655 bool "Support mmconfig PCI config space access" if X86_64
2657 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2658 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2662 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2666 depends on PCI && XEN
2668 config MMCONF_FAM10H
2670 depends on X86_64 && PCI_MMCONFIG && ACPI
2672 config PCI_CNB20LE_QUIRK
2673 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2676 Read the PCI windows out of the CNB20LE host bridge. This allows
2677 PCI hotplug to work on systems with the CNB20LE chipset which do
2680 There's no public spec for this chipset, and this functionality
2681 is known to be incomplete.
2683 You should say N unless you know you need this.
2686 bool "ISA bus support on modern systems" if EXPERT
2688 Expose ISA bus device drivers and options available for selection and
2689 configuration. Enable this option if your target machine has an ISA
2690 bus. ISA is an older system, displaced by PCI and newer bus
2691 architectures -- if your target machine is modern, it probably does
2692 not have an ISA bus.
2696 # x86_64 have no ISA slots, but can have ISA-style DMA.
2698 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2701 Enables ISA-style DMA support for devices requiring such controllers.
2709 Find out whether you have ISA slots on your motherboard. ISA is the
2710 name of a bus system, i.e. the way the CPU talks to the other stuff
2711 inside your box. Other bus systems are PCI, EISA, MicroChannel
2712 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2713 newer boards don't support it. If you have ISA, say Y, otherwise N.
2716 tristate "NatSemi SCx200 support"
2718 This provides basic support for National Semiconductor's
2719 (now AMD's) Geode processors. The driver probes for the
2720 PCI-IDs of several on-chip devices, so its a good dependency
2721 for other scx200_* drivers.
2723 If compiled as a module, the driver is named scx200.
2725 config SCx200HR_TIMER
2726 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2730 This driver provides a clocksource built upon the on-chip
2731 27MHz high-resolution timer. Its also a workaround for
2732 NSC Geode SC-1100's buggy TSC, which loses time when the
2733 processor goes idle (as is done by the scheduler). The
2734 other workaround is idle=poll boot option.
2737 bool "One Laptop Per Child support"
2745 Add support for detecting the unique features of the OLPC
2749 bool "OLPC XO-1 Power Management"
2750 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2752 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2755 bool "OLPC XO-1 Real Time Clock"
2756 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2758 Add support for the XO-1 real time clock, which can be used as a
2759 programmable wakeup source.
2762 bool "OLPC XO-1 SCI extras"
2763 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2767 Add support for SCI-based features of the OLPC XO-1 laptop:
2768 - EC-driven system wakeups
2772 - AC adapter status updates
2773 - Battery status updates
2775 config OLPC_XO15_SCI
2776 bool "OLPC XO-1.5 SCI extras"
2777 depends on OLPC && ACPI
2780 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2781 - EC-driven system wakeups
2782 - AC adapter status updates
2783 - Battery status updates
2786 bool "PCEngines ALIX System Support (LED setup)"
2789 This option enables system support for the PCEngines ALIX.
2790 At present this just sets up LEDs for GPIO control on
2791 ALIX2/3/6 boards. However, other system specific setup should
2794 Note: You must still enable the drivers for GPIO and LED support
2795 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2797 Note: You have to set alix.force=1 for boards with Award BIOS.
2800 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2803 This option enables system support for the Soekris Engineering net5501.
2806 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2810 This option enables system support for the Traverse Technologies GEOS.
2813 bool "Technologic Systems TS-5500 platform support"
2815 select CHECK_SIGNATURE
2819 This option enables system support for the Technologic Systems TS-5500.
2825 depends on CPU_SUP_AMD && PCI
2829 menu "Binary Emulations"
2831 config IA32_EMULATION
2832 bool "IA32 Emulation"
2834 select ARCH_WANT_OLD_COMPAT_IPC
2836 select COMPAT_OLD_SIGACTION
2838 Include code to run legacy 32-bit programs under a
2839 64-bit kernel. You should likely turn this on, unless you're
2840 100% sure that you don't have any 32-bit programs left.
2843 bool "x32 ABI for 64-bit mode"
2845 # llvm-objcopy does not convert x86_64 .note.gnu.property or
2846 # compressed debug sections to x86_x32 properly:
2847 # https://github.com/ClangBuiltLinux/linux/issues/514
2848 # https://github.com/ClangBuiltLinux/linux/issues/1141
2849 depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
2851 Include code to run binaries for the x32 native 32-bit ABI
2852 for 64-bit processors. An x32 process gets access to the
2853 full 64-bit register file and wide data path while leaving
2854 pointers at 32 bits for smaller memory footprint.
2858 depends on IA32_EMULATION || X86_32
2860 select OLD_SIGSUSPEND3
2864 depends on IA32_EMULATION || X86_X32_ABI
2866 config COMPAT_FOR_U64_ALIGNMENT
2872 config HAVE_ATOMIC_IOMAP
2876 source "arch/x86/kvm/Kconfig"
2878 source "arch/x86/Kconfig.assembler"