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 endif #HYPERVISOR_GUEST
883 source "arch/x86/Kconfig.cpu"
887 prompt "HPET Timer Support" if X86_32
889 Use the IA-PC HPET (High Precision Event Timer) to manage
890 time in preference to the PIT and RTC, if a HPET is
892 HPET is the next generation timer replacing legacy 8254s.
893 The HPET provides a stable time base on SMP
894 systems, unlike the TSC, but it is more expensive to access,
895 as it is off-chip. The interface used is documented
896 in the HPET spec, revision 1.
898 You can safely choose Y here. However, HPET will only be
899 activated if the platform and the BIOS support this feature.
900 Otherwise the 8254 will be used for timing services.
902 Choose N to continue using the legacy 8254 timer.
904 config HPET_EMULATE_RTC
906 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
908 # Mark as expert because too many people got it wrong.
909 # The code disables itself when not needed.
912 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
913 bool "Enable DMI scanning" if EXPERT
915 Enabled scanning of DMI to identify machine quirks. Say Y
916 here unless you have verified that your setup is not
917 affected by entries in the DMI blacklist. Required by PNP
921 bool "Old AMD GART IOMMU support"
925 depends on X86_64 && PCI && AMD_NB
927 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
928 GART based hardware IOMMUs.
930 The GART supports full DMA access for devices with 32-bit access
931 limitations, on systems with more than 3 GB. This is usually needed
932 for USB, sound, many IDE/SATA chipsets and some other devices.
934 Newer systems typically have a modern AMD IOMMU, supported via
935 the CONFIG_AMD_IOMMU=y config option.
937 In normal configurations this driver is only active when needed:
938 there's more than 3 GB of memory and the system contains a
939 32-bit limited device.
944 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
945 depends on X86_64 && SMP && DEBUG_KERNEL
946 select CPUMASK_OFFSTACK
948 Enable maximum number of CPUS and NUMA Nodes for this architecture.
952 # The maximum number of CPUs supported:
954 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
955 # and which can be configured interactively in the
956 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
958 # The ranges are different on 32-bit and 64-bit kernels, depending on
959 # hardware capabilities and scalability features of the kernel.
961 # ( If MAXSMP is enabled we just use the highest possible value and disable
962 # interactive configuration. )
965 config NR_CPUS_RANGE_BEGIN
967 default NR_CPUS_RANGE_END if MAXSMP
971 config NR_CPUS_RANGE_END
974 default 64 if SMP && X86_BIGSMP
975 default 8 if SMP && !X86_BIGSMP
978 config NR_CPUS_RANGE_END
981 default 8192 if SMP && CPUMASK_OFFSTACK
982 default 512 if SMP && !CPUMASK_OFFSTACK
985 config NR_CPUS_DEFAULT
988 default 32 if X86_BIGSMP
992 config NR_CPUS_DEFAULT
995 default 8192 if MAXSMP
1000 int "Maximum number of CPUs" if SMP && !MAXSMP
1001 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1002 default NR_CPUS_DEFAULT
1004 This allows you to specify the maximum number of CPUs which this
1005 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1006 supported value is 8192, otherwise the maximum value is 512. The
1007 minimum value which makes sense is 2.
1009 This is purely to save memory: each supported CPU adds about 8KB
1010 to the kernel image.
1012 config SCHED_CLUSTER
1013 bool "Cluster scheduler support"
1017 Cluster scheduler support improves the CPU scheduler's decision
1018 making when dealing with machines that have clusters of CPUs.
1019 Cluster usually means a couple of CPUs which are placed closely
1020 by sharing mid-level caches, last-level cache tags or internal
1028 prompt "Multi-core scheduler support"
1031 Multi-core scheduler support improves the CPU scheduler's decision
1032 making when dealing with multi-core CPU chips at a cost of slightly
1033 increased overhead in some places. If unsure say N here.
1035 config SCHED_MC_PRIO
1036 bool "CPU core priorities scheduler support"
1037 depends on SCHED_MC && CPU_SUP_INTEL
1038 select X86_INTEL_PSTATE
1042 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1043 core ordering determined at manufacturing time, which allows
1044 certain cores to reach higher turbo frequencies (when running
1045 single threaded workloads) than others.
1047 Enabling this kernel feature teaches the scheduler about
1048 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1049 scheduler's CPU selection logic accordingly, so that higher
1050 overall system performance can be achieved.
1052 This feature will have no effect on CPUs without this feature.
1054 If unsure say Y here.
1058 depends on !SMP && X86_LOCAL_APIC
1061 bool "Local APIC support on uniprocessors" if !PCI_MSI
1063 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1065 A local APIC (Advanced Programmable Interrupt Controller) is an
1066 integrated interrupt controller in the CPU. If you have a single-CPU
1067 system which has a processor with a local APIC, you can say Y here to
1068 enable and use it. If you say Y here even though your machine doesn't
1069 have a local APIC, then the kernel will still run with no slowdown at
1070 all. The local APIC supports CPU-generated self-interrupts (timer,
1071 performance counters), and the NMI watchdog which detects hard
1074 config X86_UP_IOAPIC
1075 bool "IO-APIC support on uniprocessors"
1076 depends on X86_UP_APIC
1078 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1079 SMP-capable replacement for PC-style interrupt controllers. Most
1080 SMP systems and many recent uniprocessor systems have one.
1082 If you have a single-CPU system with an IO-APIC, you can say Y here
1083 to use it. If you say Y here even though your machine doesn't have
1084 an IO-APIC, then the kernel will still run with no slowdown at all.
1086 config X86_LOCAL_APIC
1088 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1089 select IRQ_DOMAIN_HIERARCHY
1090 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1094 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1096 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1097 bool "Reroute for broken boot IRQs"
1098 depends on X86_IO_APIC
1100 This option enables a workaround that fixes a source of
1101 spurious interrupts. This is recommended when threaded
1102 interrupt handling is used on systems where the generation of
1103 superfluous "boot interrupts" cannot be disabled.
1105 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1106 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1107 kernel does during interrupt handling). On chipsets where this
1108 boot IRQ generation cannot be disabled, this workaround keeps
1109 the original IRQ line masked so that only the equivalent "boot
1110 IRQ" is delivered to the CPUs. The workaround also tells the
1111 kernel to set up the IRQ handler on the boot IRQ line. In this
1112 way only one interrupt is delivered to the kernel. Otherwise
1113 the spurious second interrupt may cause the kernel to bring
1114 down (vital) interrupt lines.
1116 Only affects "broken" chipsets. Interrupt sharing may be
1117 increased on these systems.
1120 bool "Machine Check / overheating reporting"
1121 select GENERIC_ALLOCATOR
1124 Machine Check support allows the processor to notify the
1125 kernel if it detects a problem (e.g. overheating, data corruption).
1126 The action the kernel takes depends on the severity of the problem,
1127 ranging from warning messages to halting the machine.
1129 config X86_MCELOG_LEGACY
1130 bool "Support for deprecated /dev/mcelog character device"
1133 Enable support for /dev/mcelog which is needed by the old mcelog
1134 userspace logging daemon. Consider switching to the new generation
1137 config X86_MCE_INTEL
1139 prompt "Intel MCE features"
1140 depends on X86_MCE && X86_LOCAL_APIC
1142 Additional support for intel specific MCE features such as
1143 the thermal monitor.
1147 prompt "AMD MCE features"
1148 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1150 Additional support for AMD specific MCE features such as
1151 the DRAM Error Threshold.
1153 config X86_ANCIENT_MCE
1154 bool "Support for old Pentium 5 / WinChip machine checks"
1155 depends on X86_32 && X86_MCE
1157 Include support for machine check handling on old Pentium 5 or WinChip
1158 systems. These typically need to be enabled explicitly on the command
1161 config X86_MCE_THRESHOLD
1162 depends on X86_MCE_AMD || X86_MCE_INTEL
1165 config X86_MCE_INJECT
1166 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1167 tristate "Machine check injector support"
1169 Provide support for injecting machine checks for testing purposes.
1170 If you don't know what a machine check is and you don't do kernel
1171 QA it is safe to say n.
1173 source "arch/x86/events/Kconfig"
1175 config X86_LEGACY_VM86
1176 bool "Legacy VM86 support"
1179 This option allows user programs to put the CPU into V8086
1180 mode, which is an 80286-era approximation of 16-bit real mode.
1182 Some very old versions of X and/or vbetool require this option
1183 for user mode setting. Similarly, DOSEMU will use it if
1184 available to accelerate real mode DOS programs. However, any
1185 recent version of DOSEMU, X, or vbetool should be fully
1186 functional even without kernel VM86 support, as they will all
1187 fall back to software emulation. Nevertheless, if you are using
1188 a 16-bit DOS program where 16-bit performance matters, vm86
1189 mode might be faster than emulation and you might want to
1192 Note that any app that works on a 64-bit kernel is unlikely to
1193 need this option, as 64-bit kernels don't, and can't, support
1194 V8086 mode. This option is also unrelated to 16-bit protected
1195 mode and is not needed to run most 16-bit programs under Wine.
1197 Enabling this option increases the complexity of the kernel
1198 and slows down exception handling a tiny bit.
1200 If unsure, say N here.
1204 default X86_LEGACY_VM86
1207 bool "Enable support for 16-bit segments" if EXPERT
1209 depends on MODIFY_LDT_SYSCALL
1211 This option is required by programs like Wine to run 16-bit
1212 protected mode legacy code on x86 processors. Disabling
1213 this option saves about 300 bytes on i386, or around 6K text
1214 plus 16K runtime memory on x86-64,
1218 depends on X86_16BIT && X86_32
1222 depends on X86_16BIT && X86_64
1224 config X86_VSYSCALL_EMULATION
1225 bool "Enable vsyscall emulation" if EXPERT
1229 This enables emulation of the legacy vsyscall page. Disabling
1230 it is roughly equivalent to booting with vsyscall=none, except
1231 that it will also disable the helpful warning if a program
1232 tries to use a vsyscall. With this option set to N, offending
1233 programs will just segfault, citing addresses of the form
1236 This option is required by many programs built before 2013, and
1237 care should be used even with newer programs if set to N.
1239 Disabling this option saves about 7K of kernel size and
1240 possibly 4K of additional runtime pagetable memory.
1242 config X86_IOPL_IOPERM
1243 bool "IOPERM and IOPL Emulation"
1246 This enables the ioperm() and iopl() syscalls which are necessary
1247 for legacy applications.
1249 Legacy IOPL support is an overbroad mechanism which allows user
1250 space aside of accessing all 65536 I/O ports also to disable
1251 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1252 capabilities and permission from potentially active security
1255 The emulation restricts the functionality of the syscall to
1256 only allowing the full range I/O port access, but prevents the
1257 ability to disable interrupts from user space which would be
1258 granted if the hardware IOPL mechanism would be used.
1261 tristate "Toshiba Laptop support"
1264 This adds a driver to safely access the System Management Mode of
1265 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1266 not work on models with a Phoenix BIOS. The System Management Mode
1267 is used to set the BIOS and power saving options on Toshiba portables.
1269 For information on utilities to make use of this driver see the
1270 Toshiba Linux utilities web site at:
1271 <http://www.buzzard.org.uk/toshiba/>.
1273 Say Y if you intend to run this kernel on a Toshiba portable.
1276 config X86_REBOOTFIXUPS
1277 bool "Enable X86 board specific fixups for reboot"
1280 This enables chipset and/or board specific fixups to be done
1281 in order to get reboot to work correctly. This is only needed on
1282 some combinations of hardware and BIOS. The symptom, for which
1283 this config is intended, is when reboot ends with a stalled/hung
1286 Currently, the only fixup is for the Geode machines using
1287 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1289 Say Y if you want to enable the fixup. Currently, it's safe to
1290 enable this option even if you don't need it.
1294 bool "CPU microcode loading support"
1296 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1298 If you say Y here, you will be able to update the microcode on
1299 Intel and AMD processors. The Intel support is for the IA32 family,
1300 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1301 AMD support is for families 0x10 and later. You will obviously need
1302 the actual microcode binary data itself which is not shipped with
1305 The preferred method to load microcode from a detached initrd is described
1306 in Documentation/x86/microcode.rst. For that you need to enable
1307 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1308 initrd for microcode blobs.
1310 In addition, you can build the microcode into the kernel. For that you
1311 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1314 config MICROCODE_INTEL
1315 bool "Intel microcode loading support"
1316 depends on MICROCODE
1319 This options enables microcode patch loading support for Intel
1322 For the current Intel microcode data package go to
1323 <https://downloadcenter.intel.com> and search for
1324 'Linux Processor Microcode Data File'.
1326 config MICROCODE_AMD
1327 bool "AMD microcode loading support"
1328 depends on MICROCODE
1330 If you select this option, microcode patch loading support for AMD
1331 processors will be enabled.
1333 config MICROCODE_OLD_INTERFACE
1334 bool "Ancient loading interface (DEPRECATED)"
1336 depends on MICROCODE
1338 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1339 which was used by userspace tools like iucode_tool and microcode.ctl.
1340 It is inadequate because it runs too late to be able to properly
1341 load microcode on a machine and it needs special tools. Instead, you
1342 should've switched to the early loading method with the initrd or
1343 builtin microcode by now: Documentation/x86/microcode.rst
1346 tristate "/dev/cpu/*/msr - Model-specific register support"
1348 This device gives privileged processes access to the x86
1349 Model-Specific Registers (MSRs). It is a character device with
1350 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1351 MSR accesses are directed to a specific CPU on multi-processor
1355 tristate "/dev/cpu/*/cpuid - CPU information support"
1357 This device gives processes access to the x86 CPUID instruction to
1358 be executed on a specific processor. It is a character device
1359 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1363 prompt "High Memory Support"
1370 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1371 However, the address space of 32-bit x86 processors is only 4
1372 Gigabytes large. That means that, if you have a large amount of
1373 physical memory, not all of it can be "permanently mapped" by the
1374 kernel. The physical memory that's not permanently mapped is called
1377 If you are compiling a kernel which will never run on a machine with
1378 more than 1 Gigabyte total physical RAM, answer "off" here (default
1379 choice and suitable for most users). This will result in a "3GB/1GB"
1380 split: 3GB are mapped so that each process sees a 3GB virtual memory
1381 space and the remaining part of the 4GB virtual memory space is used
1382 by the kernel to permanently map as much physical memory as
1385 If the machine has between 1 and 4 Gigabytes physical RAM, then
1388 If more than 4 Gigabytes is used then answer "64GB" here. This
1389 selection turns Intel PAE (Physical Address Extension) mode on.
1390 PAE implements 3-level paging on IA32 processors. PAE is fully
1391 supported by Linux, PAE mode is implemented on all recent Intel
1392 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1393 then the kernel will not boot on CPUs that don't support PAE!
1395 The actual amount of total physical memory will either be
1396 auto detected or can be forced by using a kernel command line option
1397 such as "mem=256M". (Try "man bootparam" or see the documentation of
1398 your boot loader (lilo or loadlin) about how to pass options to the
1399 kernel at boot time.)
1401 If unsure, say "off".
1406 Select this if you have a 32-bit processor and between 1 and 4
1407 gigabytes of physical RAM.
1411 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1414 Select this if you have a 32-bit processor and more than 4
1415 gigabytes of physical RAM.
1420 prompt "Memory split" if EXPERT
1424 Select the desired split between kernel and user memory.
1426 If the address range available to the kernel is less than the
1427 physical memory installed, the remaining memory will be available
1428 as "high memory". Accessing high memory is a little more costly
1429 than low memory, as it needs to be mapped into the kernel first.
1430 Note that increasing the kernel address space limits the range
1431 available to user programs, making the address space there
1432 tighter. Selecting anything other than the default 3G/1G split
1433 will also likely make your kernel incompatible with binary-only
1436 If you are not absolutely sure what you are doing, leave this
1440 bool "3G/1G user/kernel split"
1441 config VMSPLIT_3G_OPT
1443 bool "3G/1G user/kernel split (for full 1G low memory)"
1445 bool "2G/2G user/kernel split"
1446 config VMSPLIT_2G_OPT
1448 bool "2G/2G user/kernel split (for full 2G low memory)"
1450 bool "1G/3G user/kernel split"
1455 default 0xB0000000 if VMSPLIT_3G_OPT
1456 default 0x80000000 if VMSPLIT_2G
1457 default 0x78000000 if VMSPLIT_2G_OPT
1458 default 0x40000000 if VMSPLIT_1G
1464 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1467 bool "PAE (Physical Address Extension) Support"
1468 depends on X86_32 && !HIGHMEM4G
1469 select PHYS_ADDR_T_64BIT
1472 PAE is required for NX support, and furthermore enables
1473 larger swapspace support for non-overcommit purposes. It
1474 has the cost of more pagetable lookup overhead, and also
1475 consumes more pagetable space per process.
1478 bool "Enable 5-level page tables support"
1480 select DYNAMIC_MEMORY_LAYOUT
1481 select SPARSEMEM_VMEMMAP
1484 5-level paging enables access to larger address space:
1485 upto 128 PiB of virtual address space and 4 PiB of
1486 physical address space.
1488 It will be supported by future Intel CPUs.
1490 A kernel with the option enabled can be booted on machines that
1491 support 4- or 5-level paging.
1493 See Documentation/x86/x86_64/5level-paging.rst for more
1498 config X86_DIRECT_GBPAGES
1502 Certain kernel features effectively disable kernel
1503 linear 1 GB mappings (even if the CPU otherwise
1504 supports them), so don't confuse the user by printing
1505 that we have them enabled.
1507 config X86_CPA_STATISTICS
1508 bool "Enable statistic for Change Page Attribute"
1511 Expose statistics about the Change Page Attribute mechanism, which
1512 helps to determine the effectiveness of preserving large and huge
1513 page mappings when mapping protections are changed.
1515 config X86_MEM_ENCRYPT
1516 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1517 select DYNAMIC_PHYSICAL_MASK
1518 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1521 config AMD_MEM_ENCRYPT
1522 bool "AMD Secure Memory Encryption (SME) support"
1523 depends on X86_64 && CPU_SUP_AMD
1524 select DMA_COHERENT_POOL
1525 select ARCH_USE_MEMREMAP_PROT
1526 select INSTRUCTION_DECODER
1527 select ARCH_HAS_CC_PLATFORM
1528 select X86_MEM_ENCRYPT
1530 Say yes to enable support for the encryption of system memory.
1531 This requires an AMD processor that supports Secure Memory
1534 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1535 bool "Activate AMD Secure Memory Encryption (SME) by default"
1536 depends on AMD_MEM_ENCRYPT
1538 Say yes to have system memory encrypted by default if running on
1539 an AMD processor that supports Secure Memory Encryption (SME).
1541 If set to Y, then the encryption of system memory can be
1542 deactivated with the mem_encrypt=off command line option.
1544 If set to N, then the encryption of system memory can be
1545 activated with the mem_encrypt=on command line option.
1547 # Common NUMA Features
1549 bool "NUMA Memory Allocation and Scheduler Support"
1551 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1552 default y if X86_BIGSMP
1553 select USE_PERCPU_NUMA_NODE_ID
1555 Enable NUMA (Non-Uniform Memory Access) support.
1557 The kernel will try to allocate memory used by a CPU on the
1558 local memory controller of the CPU and add some more
1559 NUMA awareness to the kernel.
1561 For 64-bit this is recommended if the system is Intel Core i7
1562 (or later), AMD Opteron, or EM64T NUMA.
1564 For 32-bit this is only needed if you boot a 32-bit
1565 kernel on a 64-bit NUMA platform.
1567 Otherwise, you should say N.
1571 prompt "Old style AMD Opteron NUMA detection"
1572 depends on X86_64 && NUMA && PCI
1574 Enable AMD NUMA node topology detection. You should say Y here if
1575 you have a multi processor AMD system. This uses an old method to
1576 read the NUMA configuration directly from the builtin Northbridge
1577 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1578 which also takes priority if both are compiled in.
1580 config X86_64_ACPI_NUMA
1582 prompt "ACPI NUMA detection"
1583 depends on X86_64 && NUMA && ACPI && PCI
1586 Enable ACPI SRAT based node topology detection.
1589 bool "NUMA emulation"
1592 Enable NUMA emulation. A flat machine will be split
1593 into virtual nodes when booted with "numa=fake=N", where N is the
1594 number of nodes. This is only useful for debugging.
1597 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1599 default "10" if MAXSMP
1600 default "6" if X86_64
1604 Specify the maximum number of NUMA Nodes available on the target
1605 system. Increases memory reserved to accommodate various tables.
1607 config ARCH_FLATMEM_ENABLE
1609 depends on X86_32 && !NUMA
1611 config ARCH_SPARSEMEM_ENABLE
1613 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1614 select SPARSEMEM_STATIC if X86_32
1615 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1617 config ARCH_SPARSEMEM_DEFAULT
1618 def_bool X86_64 || (NUMA && X86_32)
1620 config ARCH_SELECT_MEMORY_MODEL
1622 depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE
1624 config ARCH_MEMORY_PROBE
1625 bool "Enable sysfs memory/probe interface"
1626 depends on MEMORY_HOTPLUG
1628 This option enables a sysfs memory/probe interface for testing.
1629 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1630 If you are unsure how to answer this question, answer N.
1632 config ARCH_PROC_KCORE_TEXT
1634 depends on X86_64 && PROC_KCORE
1636 config ILLEGAL_POINTER_VALUE
1639 default 0xdead000000000000 if X86_64
1641 config X86_PMEM_LEGACY_DEVICE
1644 config X86_PMEM_LEGACY
1645 tristate "Support non-standard NVDIMMs and ADR protected memory"
1646 depends on PHYS_ADDR_T_64BIT
1648 select X86_PMEM_LEGACY_DEVICE
1649 select NUMA_KEEP_MEMINFO if NUMA
1652 Treat memory marked using the non-standard e820 type of 12 as used
1653 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1654 The kernel will offer these regions to the 'pmem' driver so
1655 they can be used for persistent storage.
1660 bool "Allocate 3rd-level pagetables from highmem"
1663 The VM uses one page table entry for each page of physical memory.
1664 For systems with a lot of RAM, this can be wasteful of precious
1665 low memory. Setting this option will put user-space page table
1666 entries in high memory.
1668 config X86_CHECK_BIOS_CORRUPTION
1669 bool "Check for low memory corruption"
1671 Periodically check for memory corruption in low memory, which
1672 is suspected to be caused by BIOS. Even when enabled in the
1673 configuration, it is disabled at runtime. Enable it by
1674 setting "memory_corruption_check=1" on the kernel command
1675 line. By default it scans the low 64k of memory every 60
1676 seconds; see the memory_corruption_check_size and
1677 memory_corruption_check_period parameters in
1678 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1680 When enabled with the default parameters, this option has
1681 almost no overhead, as it reserves a relatively small amount
1682 of memory and scans it infrequently. It both detects corruption
1683 and prevents it from affecting the running system.
1685 It is, however, intended as a diagnostic tool; if repeatable
1686 BIOS-originated corruption always affects the same memory,
1687 you can use memmap= to prevent the kernel from using that
1690 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1691 bool "Set the default setting of memory_corruption_check"
1692 depends on X86_CHECK_BIOS_CORRUPTION
1695 Set whether the default state of memory_corruption_check is
1698 config MATH_EMULATION
1700 depends on MODIFY_LDT_SYSCALL
1701 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1703 Linux can emulate a math coprocessor (used for floating point
1704 operations) if you don't have one. 486DX and Pentium processors have
1705 a math coprocessor built in, 486SX and 386 do not, unless you added
1706 a 487DX or 387, respectively. (The messages during boot time can
1707 give you some hints here ["man dmesg"].) Everyone needs either a
1708 coprocessor or this emulation.
1710 If you don't have a math coprocessor, you need to say Y here; if you
1711 say Y here even though you have a coprocessor, the coprocessor will
1712 be used nevertheless. (This behavior can be changed with the kernel
1713 command line option "no387", which comes handy if your coprocessor
1714 is broken. Try "man bootparam" or see the documentation of your boot
1715 loader (lilo or loadlin) about how to pass options to the kernel at
1716 boot time.) This means that it is a good idea to say Y here if you
1717 intend to use this kernel on different machines.
1719 More information about the internals of the Linux math coprocessor
1720 emulation can be found in <file:arch/x86/math-emu/README>.
1722 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1723 kernel, it won't hurt.
1727 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1729 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1730 the Memory Type Range Registers (MTRRs) may be used to control
1731 processor access to memory ranges. This is most useful if you have
1732 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1733 allows bus write transfers to be combined into a larger transfer
1734 before bursting over the PCI/AGP bus. This can increase performance
1735 of image write operations 2.5 times or more. Saying Y here creates a
1736 /proc/mtrr file which may be used to manipulate your processor's
1737 MTRRs. Typically the X server should use this.
1739 This code has a reasonably generic interface so that similar
1740 control registers on other processors can be easily supported
1743 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1744 Registers (ARRs) which provide a similar functionality to MTRRs. For
1745 these, the ARRs are used to emulate the MTRRs.
1746 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1747 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1748 write-combining. All of these processors are supported by this code
1749 and it makes sense to say Y here if you have one of them.
1751 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1752 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1753 can lead to all sorts of problems, so it's good to say Y here.
1755 You can safely say Y even if your machine doesn't have MTRRs, you'll
1756 just add about 9 KB to your kernel.
1758 See <file:Documentation/x86/mtrr.rst> for more information.
1760 config MTRR_SANITIZER
1762 prompt "MTRR cleanup support"
1765 Convert MTRR layout from continuous to discrete, so X drivers can
1766 add writeback entries.
1768 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1769 The largest mtrr entry size for a continuous block can be set with
1774 config MTRR_SANITIZER_ENABLE_DEFAULT
1775 int "MTRR cleanup enable value (0-1)"
1778 depends on MTRR_SANITIZER
1780 Enable mtrr cleanup default value
1782 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1783 int "MTRR cleanup spare reg num (0-7)"
1786 depends on MTRR_SANITIZER
1788 mtrr cleanup spare entries default, it can be changed via
1789 mtrr_spare_reg_nr=N on the kernel command line.
1793 prompt "x86 PAT support" if EXPERT
1796 Use PAT attributes to setup page level cache control.
1798 PATs are the modern equivalents of MTRRs and are much more
1799 flexible than MTRRs.
1801 Say N here if you see bootup problems (boot crash, boot hang,
1802 spontaneous reboots) or a non-working video driver.
1806 config ARCH_USES_PG_UNCACHED
1812 prompt "x86 architectural random number generator" if EXPERT
1814 Enable the x86 architectural RDRAND instruction
1815 (Intel Bull Mountain technology) to generate random numbers.
1816 If supported, this is a high bandwidth, cryptographically
1817 secure hardware random number generator.
1821 prompt "Supervisor Mode Access Prevention" if EXPERT
1823 Supervisor Mode Access Prevention (SMAP) is a security
1824 feature in newer Intel processors. There is a small
1825 performance cost if this enabled and turned on; there is
1826 also a small increase in the kernel size if this is enabled.
1832 prompt "User Mode Instruction Prevention" if EXPERT
1834 User Mode Instruction Prevention (UMIP) is a security feature in
1835 some x86 processors. If enabled, a general protection fault is
1836 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1837 executed in user mode. These instructions unnecessarily expose
1838 information about the hardware state.
1840 The vast majority of applications do not use these instructions.
1841 For the very few that do, software emulation is provided in
1842 specific cases in protected and virtual-8086 modes. Emulated
1846 # GCC >= 9 and binutils >= 2.29
1847 # Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
1849 # https://github.com/llvm/llvm-project/commit/e0b89df2e0f0130881bf6c39bf31d7f6aac00e0f
1850 # https://github.com/llvm/llvm-project/commit/dfcf69770bc522b9e411c66454934a37c1f35332
1851 def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \
1852 (CC_IS_CLANG && CLANG_VERSION >= 140000)) && \
1855 config X86_KERNEL_IBT
1856 prompt "Indirect Branch Tracking"
1858 depends on X86_64 && CC_HAS_IBT && STACK_VALIDATION
1859 # https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
1860 depends on !LD_IS_LLD || LLD_VERSION >= 140000
1862 Build the kernel with support for Indirect Branch Tracking, a
1863 hardware support course-grain forward-edge Control Flow Integrity
1864 protection. It enforces that all indirect calls must land on
1865 an ENDBR instruction, as such, the compiler will instrument the
1866 code with them to make this happen.
1868 In addition to building the kernel with IBT, seal all functions that
1869 are not indirect call targets, avoiding them ever becoming one.
1871 This requires LTO like objtool runs and will slow down the build. It
1872 does significantly reduce the number of ENDBR instructions in the
1875 config X86_INTEL_MEMORY_PROTECTION_KEYS
1876 prompt "Memory Protection Keys"
1878 # Note: only available in 64-bit mode
1879 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1880 select ARCH_USES_HIGH_VMA_FLAGS
1881 select ARCH_HAS_PKEYS
1883 Memory Protection Keys provides a mechanism for enforcing
1884 page-based protections, but without requiring modification of the
1885 page tables when an application changes protection domains.
1887 For details, see Documentation/core-api/protection-keys.rst
1892 prompt "TSX enable mode"
1893 depends on CPU_SUP_INTEL
1894 default X86_INTEL_TSX_MODE_OFF
1896 Intel's TSX (Transactional Synchronization Extensions) feature
1897 allows to optimize locking protocols through lock elision which
1898 can lead to a noticeable performance boost.
1900 On the other hand it has been shown that TSX can be exploited
1901 to form side channel attacks (e.g. TAA) and chances are there
1902 will be more of those attacks discovered in the future.
1904 Therefore TSX is not enabled by default (aka tsx=off). An admin
1905 might override this decision by tsx=on the command line parameter.
1906 Even with TSX enabled, the kernel will attempt to enable the best
1907 possible TAA mitigation setting depending on the microcode available
1908 for the particular machine.
1910 This option allows to set the default tsx mode between tsx=on, =off
1911 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1914 Say off if not sure, auto if TSX is in use but it should be used on safe
1915 platforms or on if TSX is in use and the security aspect of tsx is not
1918 config X86_INTEL_TSX_MODE_OFF
1921 TSX is disabled if possible - equals to tsx=off command line parameter.
1923 config X86_INTEL_TSX_MODE_ON
1926 TSX is always enabled on TSX capable HW - equals the tsx=on command
1929 config X86_INTEL_TSX_MODE_AUTO
1932 TSX is enabled on TSX capable HW that is believed to be safe against
1933 side channel attacks- equals the tsx=auto command line parameter.
1937 bool "Software Guard eXtensions (SGX)"
1938 depends on X86_64 && CPU_SUP_INTEL
1940 depends on CRYPTO_SHA256=y
1943 select NUMA_KEEP_MEMINFO if NUMA
1946 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1947 that can be used by applications to set aside private regions of code
1948 and data, referred to as enclaves. An enclave's private memory can
1949 only be accessed by code running within the enclave. Accesses from
1950 outside the enclave, including other enclaves, are disallowed by
1956 bool "EFI runtime service support"
1959 select EFI_RUNTIME_WRAPPERS
1960 select ARCH_USE_MEMREMAP_PROT
1962 This enables the kernel to use EFI runtime services that are
1963 available (such as the EFI variable services).
1965 This option is only useful on systems that have EFI firmware.
1966 In addition, you should use the latest ELILO loader available
1967 at <http://elilo.sourceforge.net> in order to take advantage
1968 of EFI runtime services. However, even with this option, the
1969 resultant kernel should continue to boot on existing non-EFI
1973 bool "EFI stub support"
1975 depends on $(cc-option,-mabi=ms) || X86_32
1978 This kernel feature allows a bzImage to be loaded directly
1979 by EFI firmware without the use of a bootloader.
1981 See Documentation/admin-guide/efi-stub.rst for more information.
1984 bool "EFI mixed-mode support"
1985 depends on EFI_STUB && X86_64
1987 Enabling this feature allows a 64-bit kernel to be booted
1988 on a 32-bit firmware, provided that your CPU supports 64-bit
1991 Note that it is not possible to boot a mixed-mode enabled
1992 kernel via the EFI boot stub - a bootloader that supports
1993 the EFI handover protocol must be used.
1997 source "kernel/Kconfig.hz"
2000 bool "kexec system call"
2003 kexec is a system call that implements the ability to shutdown your
2004 current kernel, and to start another kernel. It is like a reboot
2005 but it is independent of the system firmware. And like a reboot
2006 you can start any kernel with it, not just Linux.
2008 The name comes from the similarity to the exec system call.
2010 It is an ongoing process to be certain the hardware in a machine
2011 is properly shutdown, so do not be surprised if this code does not
2012 initially work for you. As of this writing the exact hardware
2013 interface is strongly in flux, so no good recommendation can be
2017 bool "kexec file based system call"
2022 depends on CRYPTO_SHA256=y
2024 This is new version of kexec system call. This system call is
2025 file based and takes file descriptors as system call argument
2026 for kernel and initramfs as opposed to list of segments as
2027 accepted by previous system call.
2029 config ARCH_HAS_KEXEC_PURGATORY
2033 bool "Verify kernel signature during kexec_file_load() syscall"
2034 depends on KEXEC_FILE
2037 This option makes the kexec_file_load() syscall check for a valid
2038 signature of the kernel image. The image can still be loaded without
2039 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2040 there's a signature that we can check, then it must be valid.
2042 In addition to this option, you need to enable signature
2043 verification for the corresponding kernel image type being
2044 loaded in order for this to work.
2046 config KEXEC_SIG_FORCE
2047 bool "Require a valid signature in kexec_file_load() syscall"
2048 depends on KEXEC_SIG
2050 This option makes kernel signature verification mandatory for
2051 the kexec_file_load() syscall.
2053 config KEXEC_BZIMAGE_VERIFY_SIG
2054 bool "Enable bzImage signature verification support"
2055 depends on KEXEC_SIG
2056 depends on SIGNED_PE_FILE_VERIFICATION
2057 select SYSTEM_TRUSTED_KEYRING
2059 Enable bzImage signature verification support.
2062 bool "kernel crash dumps"
2063 depends on X86_64 || (X86_32 && HIGHMEM)
2065 Generate crash dump after being started by kexec.
2066 This should be normally only set in special crash dump kernels
2067 which are loaded in the main kernel with kexec-tools into
2068 a specially reserved region and then later executed after
2069 a crash by kdump/kexec. The crash dump kernel must be compiled
2070 to a memory address not used by the main kernel or BIOS using
2071 PHYSICAL_START, or it must be built as a relocatable image
2072 (CONFIG_RELOCATABLE=y).
2073 For more details see Documentation/admin-guide/kdump/kdump.rst
2077 depends on KEXEC && HIBERNATION
2079 Jump between original kernel and kexeced kernel and invoke
2080 code in physical address mode via KEXEC
2082 config PHYSICAL_START
2083 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2086 This gives the physical address where the kernel is loaded.
2088 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2089 bzImage will decompress itself to above physical address and
2090 run from there. Otherwise, bzImage will run from the address where
2091 it has been loaded by the boot loader and will ignore above physical
2094 In normal kdump cases one does not have to set/change this option
2095 as now bzImage can be compiled as a completely relocatable image
2096 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2097 address. This option is mainly useful for the folks who don't want
2098 to use a bzImage for capturing the crash dump and want to use a
2099 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2100 to be specifically compiled to run from a specific memory area
2101 (normally a reserved region) and this option comes handy.
2103 So if you are using bzImage for capturing the crash dump,
2104 leave the value here unchanged to 0x1000000 and set
2105 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2106 for capturing the crash dump change this value to start of
2107 the reserved region. In other words, it can be set based on
2108 the "X" value as specified in the "crashkernel=YM@XM"
2109 command line boot parameter passed to the panic-ed
2110 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2111 for more details about crash dumps.
2113 Usage of bzImage for capturing the crash dump is recommended as
2114 one does not have to build two kernels. Same kernel can be used
2115 as production kernel and capture kernel. Above option should have
2116 gone away after relocatable bzImage support is introduced. But it
2117 is present because there are users out there who continue to use
2118 vmlinux for dump capture. This option should go away down the
2121 Don't change this unless you know what you are doing.
2124 bool "Build a relocatable kernel"
2127 This builds a kernel image that retains relocation information
2128 so it can be loaded someplace besides the default 1MB.
2129 The relocations tend to make the kernel binary about 10% larger,
2130 but are discarded at runtime.
2132 One use is for the kexec on panic case where the recovery kernel
2133 must live at a different physical address than the primary
2136 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2137 it has been loaded at and the compile time physical address
2138 (CONFIG_PHYSICAL_START) is used as the minimum location.
2140 config RANDOMIZE_BASE
2141 bool "Randomize the address of the kernel image (KASLR)"
2142 depends on RELOCATABLE
2145 In support of Kernel Address Space Layout Randomization (KASLR),
2146 this randomizes the physical address at which the kernel image
2147 is decompressed and the virtual address where the kernel
2148 image is mapped, as a security feature that deters exploit
2149 attempts relying on knowledge of the location of kernel
2152 On 64-bit, the kernel physical and virtual addresses are
2153 randomized separately. The physical address will be anywhere
2154 between 16MB and the top of physical memory (up to 64TB). The
2155 virtual address will be randomized from 16MB up to 1GB (9 bits
2156 of entropy). Note that this also reduces the memory space
2157 available to kernel modules from 1.5GB to 1GB.
2159 On 32-bit, the kernel physical and virtual addresses are
2160 randomized together. They will be randomized from 16MB up to
2161 512MB (8 bits of entropy).
2163 Entropy is generated using the RDRAND instruction if it is
2164 supported. If RDTSC is supported, its value is mixed into
2165 the entropy pool as well. If neither RDRAND nor RDTSC are
2166 supported, then entropy is read from the i8254 timer. The
2167 usable entropy is limited by the kernel being built using
2168 2GB addressing, and that PHYSICAL_ALIGN must be at a
2169 minimum of 2MB. As a result, only 10 bits of entropy are
2170 theoretically possible, but the implementations are further
2171 limited due to memory layouts.
2175 # Relocation on x86 needs some additional build support
2176 config X86_NEED_RELOCS
2178 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2180 config PHYSICAL_ALIGN
2181 hex "Alignment value to which kernel should be aligned"
2183 range 0x2000 0x1000000 if X86_32
2184 range 0x200000 0x1000000 if X86_64
2186 This value puts the alignment restrictions on physical address
2187 where kernel is loaded and run from. Kernel is compiled for an
2188 address which meets above alignment restriction.
2190 If bootloader loads the kernel at a non-aligned address and
2191 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2192 address aligned to above value and run from there.
2194 If bootloader loads the kernel at a non-aligned address and
2195 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2196 load address and decompress itself to the address it has been
2197 compiled for and run from there. The address for which kernel is
2198 compiled already meets above alignment restrictions. Hence the
2199 end result is that kernel runs from a physical address meeting
2200 above alignment restrictions.
2202 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2203 this value must be a multiple of 0x200000.
2205 Don't change this unless you know what you are doing.
2207 config DYNAMIC_MEMORY_LAYOUT
2210 This option makes base addresses of vmalloc and vmemmap as well as
2211 __PAGE_OFFSET movable during boot.
2213 config RANDOMIZE_MEMORY
2214 bool "Randomize the kernel memory sections"
2216 depends on RANDOMIZE_BASE
2217 select DYNAMIC_MEMORY_LAYOUT
2218 default RANDOMIZE_BASE
2220 Randomizes the base virtual address of kernel memory sections
2221 (physical memory mapping, vmalloc & vmemmap). This security feature
2222 makes exploits relying on predictable memory locations less reliable.
2224 The order of allocations remains unchanged. Entropy is generated in
2225 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2226 configuration have in average 30,000 different possible virtual
2227 addresses for each memory section.
2231 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2232 hex "Physical memory mapping padding" if EXPERT
2233 depends on RANDOMIZE_MEMORY
2234 default "0xa" if MEMORY_HOTPLUG
2236 range 0x1 0x40 if MEMORY_HOTPLUG
2239 Define the padding in terabytes added to the existing physical
2240 memory size during kernel memory randomization. It is useful
2241 for memory hotplug support but reduces the entropy available for
2242 address randomization.
2244 If unsure, leave at the default value.
2250 config BOOTPARAM_HOTPLUG_CPU0
2251 bool "Set default setting of cpu0_hotpluggable"
2252 depends on HOTPLUG_CPU
2254 Set whether default state of cpu0_hotpluggable is on or off.
2256 Say Y here to enable CPU0 hotplug by default. If this switch
2257 is turned on, there is no need to give cpu0_hotplug kernel
2258 parameter and the CPU0 hotplug feature is enabled by default.
2260 Please note: there are two known CPU0 dependencies if you want
2261 to enable the CPU0 hotplug feature either by this switch or by
2262 cpu0_hotplug kernel parameter.
2264 First, resume from hibernate or suspend always starts from CPU0.
2265 So hibernate and suspend are prevented if CPU0 is offline.
2267 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2268 offline if any interrupt can not migrate out of CPU0. There may
2269 be other CPU0 dependencies.
2271 Please make sure the dependencies are under your control before
2272 you enable this feature.
2274 Say N if you don't want to enable CPU0 hotplug feature by default.
2275 You still can enable the CPU0 hotplug feature at boot by kernel
2276 parameter cpu0_hotplug.
2278 config DEBUG_HOTPLUG_CPU0
2280 prompt "Debug CPU0 hotplug"
2281 depends on HOTPLUG_CPU
2283 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2284 soon as possible and boots up userspace with CPU0 offlined. User
2285 can online CPU0 back after boot time.
2287 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2288 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2289 compilation or giving cpu0_hotplug kernel parameter at boot.
2295 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2296 depends on COMPAT_32
2298 Certain buggy versions of glibc will crash if they are
2299 presented with a 32-bit vDSO that is not mapped at the address
2300 indicated in its segment table.
2302 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2303 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2304 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2305 the only released version with the bug, but OpenSUSE 9
2306 contains a buggy "glibc 2.3.2".
2308 The symptom of the bug is that everything crashes on startup, saying:
2309 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2311 Saying Y here changes the default value of the vdso32 boot
2312 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2313 This works around the glibc bug but hurts performance.
2315 If unsure, say N: if you are compiling your own kernel, you
2316 are unlikely to be using a buggy version of glibc.
2319 prompt "vsyscall table for legacy applications"
2321 default LEGACY_VSYSCALL_XONLY
2323 Legacy user code that does not know how to find the vDSO expects
2324 to be able to issue three syscalls by calling fixed addresses in
2325 kernel space. Since this location is not randomized with ASLR,
2326 it can be used to assist security vulnerability exploitation.
2328 This setting can be changed at boot time via the kernel command
2329 line parameter vsyscall=[emulate|xonly|none].
2331 On a system with recent enough glibc (2.14 or newer) and no
2332 static binaries, you can say None without a performance penalty
2333 to improve security.
2335 If unsure, select "Emulate execution only".
2337 config LEGACY_VSYSCALL_EMULATE
2338 bool "Full emulation"
2340 The kernel traps and emulates calls into the fixed vsyscall
2341 address mapping. This makes the mapping non-executable, but
2342 it still contains readable known contents, which could be
2343 used in certain rare security vulnerability exploits. This
2344 configuration is recommended when using legacy userspace
2345 that still uses vsyscalls along with legacy binary
2346 instrumentation tools that require code to be readable.
2348 An example of this type of legacy userspace is running
2349 Pin on an old binary that still uses vsyscalls.
2351 config LEGACY_VSYSCALL_XONLY
2352 bool "Emulate execution only"
2354 The kernel traps and emulates calls into the fixed vsyscall
2355 address mapping and does not allow reads. This
2356 configuration is recommended when userspace might use the
2357 legacy vsyscall area but support for legacy binary
2358 instrumentation of legacy code is not needed. It mitigates
2359 certain uses of the vsyscall area as an ASLR-bypassing
2362 config LEGACY_VSYSCALL_NONE
2365 There will be no vsyscall mapping at all. This will
2366 eliminate any risk of ASLR bypass due to the vsyscall
2367 fixed address mapping. Attempts to use the vsyscalls
2368 will be reported to dmesg, so that either old or
2369 malicious userspace programs can be identified.
2374 bool "Built-in kernel command line"
2376 Allow for specifying boot arguments to the kernel at
2377 build time. On some systems (e.g. embedded ones), it is
2378 necessary or convenient to provide some or all of the
2379 kernel boot arguments with the kernel itself (that is,
2380 to not rely on the boot loader to provide them.)
2382 To compile command line arguments into the kernel,
2383 set this option to 'Y', then fill in the
2384 boot arguments in CONFIG_CMDLINE.
2386 Systems with fully functional boot loaders (i.e. non-embedded)
2387 should leave this option set to 'N'.
2390 string "Built-in kernel command string"
2391 depends on CMDLINE_BOOL
2394 Enter arguments here that should be compiled into the kernel
2395 image and used at boot time. If the boot loader provides a
2396 command line at boot time, it is appended to this string to
2397 form the full kernel command line, when the system boots.
2399 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2400 change this behavior.
2402 In most cases, the command line (whether built-in or provided
2403 by the boot loader) should specify the device for the root
2406 config CMDLINE_OVERRIDE
2407 bool "Built-in command line overrides boot loader arguments"
2408 depends on CMDLINE_BOOL && CMDLINE != ""
2410 Set this option to 'Y' to have the kernel ignore the boot loader
2411 command line, and use ONLY the built-in command line.
2413 This is used to work around broken boot loaders. This should
2414 be set to 'N' under normal conditions.
2416 config MODIFY_LDT_SYSCALL
2417 bool "Enable the LDT (local descriptor table)" if EXPERT
2420 Linux can allow user programs to install a per-process x86
2421 Local Descriptor Table (LDT) using the modify_ldt(2) system
2422 call. This is required to run 16-bit or segmented code such as
2423 DOSEMU or some Wine programs. It is also used by some very old
2424 threading libraries.
2426 Enabling this feature adds a small amount of overhead to
2427 context switches and increases the low-level kernel attack
2428 surface. Disabling it removes the modify_ldt(2) system call.
2430 Saying 'N' here may make sense for embedded or server kernels.
2432 config STRICT_SIGALTSTACK_SIZE
2433 bool "Enforce strict size checking for sigaltstack"
2434 depends on DYNAMIC_SIGFRAME
2436 For historical reasons MINSIGSTKSZ is a constant which became
2437 already too small with AVX512 support. Add a mechanism to
2438 enforce strict checking of the sigaltstack size against the
2439 real size of the FPU frame. This option enables the check
2440 by default. It can also be controlled via the kernel command
2441 line option 'strict_sas_size' independent of this config
2442 switch. Enabling it might break existing applications which
2443 allocate a too small sigaltstack but 'work' because they
2444 never get a signal delivered.
2446 Say 'N' unless you want to really enforce this check.
2448 source "kernel/livepatch/Kconfig"
2452 config ARCH_HAS_ADD_PAGES
2454 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2456 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2459 menu "Power management and ACPI options"
2461 config ARCH_HIBERNATION_HEADER
2463 depends on HIBERNATION
2465 source "kernel/power/Kconfig"
2467 source "drivers/acpi/Kconfig"
2474 tristate "APM (Advanced Power Management) BIOS support"
2475 depends on X86_32 && PM_SLEEP
2477 APM is a BIOS specification for saving power using several different
2478 techniques. This is mostly useful for battery powered laptops with
2479 APM compliant BIOSes. If you say Y here, the system time will be
2480 reset after a RESUME operation, the /proc/apm device will provide
2481 battery status information, and user-space programs will receive
2482 notification of APM "events" (e.g. battery status change).
2484 If you select "Y" here, you can disable actual use of the APM
2485 BIOS by passing the "apm=off" option to the kernel at boot time.
2487 Note that the APM support is almost completely disabled for
2488 machines with more than one CPU.
2490 In order to use APM, you will need supporting software. For location
2491 and more information, read <file:Documentation/power/apm-acpi.rst>
2492 and the Battery Powered Linux mini-HOWTO, available from
2493 <http://www.tldp.org/docs.html#howto>.
2495 This driver does not spin down disk drives (see the hdparm(8)
2496 manpage ("man 8 hdparm") for that), and it doesn't turn off
2497 VESA-compliant "green" monitors.
2499 This driver does not support the TI 4000M TravelMate and the ACER
2500 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2501 desktop machines also don't have compliant BIOSes, and this driver
2502 may cause those machines to panic during the boot phase.
2504 Generally, if you don't have a battery in your machine, there isn't
2505 much point in using this driver and you should say N. If you get
2506 random kernel OOPSes or reboots that don't seem to be related to
2507 anything, try disabling/enabling this option (or disabling/enabling
2510 Some other things you should try when experiencing seemingly random,
2513 1) make sure that you have enough swap space and that it is
2515 2) pass the "no-hlt" option to the kernel
2516 3) switch on floating point emulation in the kernel and pass
2517 the "no387" option to the kernel
2518 4) pass the "floppy=nodma" option to the kernel
2519 5) pass the "mem=4M" option to the kernel (thereby disabling
2520 all but the first 4 MB of RAM)
2521 6) make sure that the CPU is not over clocked.
2522 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2523 8) disable the cache from your BIOS settings
2524 9) install a fan for the video card or exchange video RAM
2525 10) install a better fan for the CPU
2526 11) exchange RAM chips
2527 12) exchange the motherboard.
2529 To compile this driver as a module, choose M here: the
2530 module will be called apm.
2534 config APM_IGNORE_USER_SUSPEND
2535 bool "Ignore USER SUSPEND"
2537 This option will ignore USER SUSPEND requests. On machines with a
2538 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2539 series notebooks, it is necessary to say Y because of a BIOS bug.
2541 config APM_DO_ENABLE
2542 bool "Enable PM at boot time"
2544 Enable APM features at boot time. From page 36 of the APM BIOS
2545 specification: "When disabled, the APM BIOS does not automatically
2546 power manage devices, enter the Standby State, enter the Suspend
2547 State, or take power saving steps in response to CPU Idle calls."
2548 This driver will make CPU Idle calls when Linux is idle (unless this
2549 feature is turned off -- see "Do CPU IDLE calls", below). This
2550 should always save battery power, but more complicated APM features
2551 will be dependent on your BIOS implementation. You may need to turn
2552 this option off if your computer hangs at boot time when using APM
2553 support, or if it beeps continuously instead of suspending. Turn
2554 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2555 T400CDT. This is off by default since most machines do fine without
2560 bool "Make CPU Idle calls when idle"
2562 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2563 On some machines, this can activate improved power savings, such as
2564 a slowed CPU clock rate, when the machine is idle. These idle calls
2565 are made after the idle loop has run for some length of time (e.g.,
2566 333 mS). On some machines, this will cause a hang at boot time or
2567 whenever the CPU becomes idle. (On machines with more than one CPU,
2568 this option does nothing.)
2570 config APM_DISPLAY_BLANK
2571 bool "Enable console blanking using APM"
2573 Enable console blanking using the APM. Some laptops can use this to
2574 turn off the LCD backlight when the screen blanker of the Linux
2575 virtual console blanks the screen. Note that this is only used by
2576 the virtual console screen blanker, and won't turn off the backlight
2577 when using the X Window system. This also doesn't have anything to
2578 do with your VESA-compliant power-saving monitor. Further, this
2579 option doesn't work for all laptops -- it might not turn off your
2580 backlight at all, or it might print a lot of errors to the console,
2581 especially if you are using gpm.
2583 config APM_ALLOW_INTS
2584 bool "Allow interrupts during APM BIOS calls"
2586 Normally we disable external interrupts while we are making calls to
2587 the APM BIOS as a measure to lessen the effects of a badly behaving
2588 BIOS implementation. The BIOS should reenable interrupts if it
2589 needs to. Unfortunately, some BIOSes do not -- especially those in
2590 many of the newer IBM Thinkpads. If you experience hangs when you
2591 suspend, try setting this to Y. Otherwise, say N.
2595 source "drivers/cpufreq/Kconfig"
2597 source "drivers/cpuidle/Kconfig"
2599 source "drivers/idle/Kconfig"
2604 menu "Bus options (PCI etc.)"
2607 prompt "PCI access mode"
2608 depends on X86_32 && PCI
2611 On PCI systems, the BIOS can be used to detect the PCI devices and
2612 determine their configuration. However, some old PCI motherboards
2613 have BIOS bugs and may crash if this is done. Also, some embedded
2614 PCI-based systems don't have any BIOS at all. Linux can also try to
2615 detect the PCI hardware directly without using the BIOS.
2617 With this option, you can specify how Linux should detect the
2618 PCI devices. If you choose "BIOS", the BIOS will be used,
2619 if you choose "Direct", the BIOS won't be used, and if you
2620 choose "MMConfig", then PCI Express MMCONFIG will be used.
2621 If you choose "Any", the kernel will try MMCONFIG, then the
2622 direct access method and falls back to the BIOS if that doesn't
2623 work. If unsure, go with the default, which is "Any".
2628 config PCI_GOMMCONFIG
2645 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2647 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2650 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2653 bool "Support mmconfig PCI config space access" if X86_64
2655 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2656 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2660 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2664 depends on PCI && XEN
2666 config MMCONF_FAM10H
2668 depends on X86_64 && PCI_MMCONFIG && ACPI
2670 config PCI_CNB20LE_QUIRK
2671 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2674 Read the PCI windows out of the CNB20LE host bridge. This allows
2675 PCI hotplug to work on systems with the CNB20LE chipset which do
2678 There's no public spec for this chipset, and this functionality
2679 is known to be incomplete.
2681 You should say N unless you know you need this.
2684 bool "ISA bus support on modern systems" if EXPERT
2686 Expose ISA bus device drivers and options available for selection and
2687 configuration. Enable this option if your target machine has an ISA
2688 bus. ISA is an older system, displaced by PCI and newer bus
2689 architectures -- if your target machine is modern, it probably does
2690 not have an ISA bus.
2694 # x86_64 have no ISA slots, but can have ISA-style DMA.
2696 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2699 Enables ISA-style DMA support for devices requiring such controllers.
2707 Find out whether you have ISA slots on your motherboard. ISA is the
2708 name of a bus system, i.e. the way the CPU talks to the other stuff
2709 inside your box. Other bus systems are PCI, EISA, MicroChannel
2710 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2711 newer boards don't support it. If you have ISA, say Y, otherwise N.
2714 tristate "NatSemi SCx200 support"
2716 This provides basic support for National Semiconductor's
2717 (now AMD's) Geode processors. The driver probes for the
2718 PCI-IDs of several on-chip devices, so its a good dependency
2719 for other scx200_* drivers.
2721 If compiled as a module, the driver is named scx200.
2723 config SCx200HR_TIMER
2724 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2728 This driver provides a clocksource built upon the on-chip
2729 27MHz high-resolution timer. Its also a workaround for
2730 NSC Geode SC-1100's buggy TSC, which loses time when the
2731 processor goes idle (as is done by the scheduler). The
2732 other workaround is idle=poll boot option.
2735 bool "One Laptop Per Child support"
2743 Add support for detecting the unique features of the OLPC
2747 bool "OLPC XO-1 Power Management"
2748 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2750 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2753 bool "OLPC XO-1 Real Time Clock"
2754 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2756 Add support for the XO-1 real time clock, which can be used as a
2757 programmable wakeup source.
2760 bool "OLPC XO-1 SCI extras"
2761 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2765 Add support for SCI-based features of the OLPC XO-1 laptop:
2766 - EC-driven system wakeups
2770 - AC adapter status updates
2771 - Battery status updates
2773 config OLPC_XO15_SCI
2774 bool "OLPC XO-1.5 SCI extras"
2775 depends on OLPC && ACPI
2778 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2779 - EC-driven system wakeups
2780 - AC adapter status updates
2781 - Battery status updates
2784 bool "PCEngines ALIX System Support (LED setup)"
2787 This option enables system support for the PCEngines ALIX.
2788 At present this just sets up LEDs for GPIO control on
2789 ALIX2/3/6 boards. However, other system specific setup should
2792 Note: You must still enable the drivers for GPIO and LED support
2793 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2795 Note: You have to set alix.force=1 for boards with Award BIOS.
2798 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2801 This option enables system support for the Soekris Engineering net5501.
2804 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2808 This option enables system support for the Traverse Technologies GEOS.
2811 bool "Technologic Systems TS-5500 platform support"
2813 select CHECK_SIGNATURE
2817 This option enables system support for the Technologic Systems TS-5500.
2823 depends on CPU_SUP_AMD && PCI
2828 menu "Binary Emulations"
2830 config IA32_EMULATION
2831 bool "IA32 Emulation"
2833 select ARCH_WANT_OLD_COMPAT_IPC
2835 select COMPAT_OLD_SIGACTION
2837 Include code to run legacy 32-bit programs under a
2838 64-bit kernel. You should likely turn this on, unless you're
2839 100% sure that you don't have any 32-bit programs left.
2842 tristate "IA32 a.out support"
2843 depends on IA32_EMULATION
2846 Support old a.out binaries in the 32bit emulation.
2849 bool "x32 ABI for 64-bit mode"
2851 # llvm-objcopy does not convert x86_64 .note.gnu.property or
2852 # compressed debug sections to x86_x32 properly:
2853 # https://github.com/ClangBuiltLinux/linux/issues/514
2854 # https://github.com/ClangBuiltLinux/linux/issues/1141
2855 depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
2857 Include code to run binaries for the x32 native 32-bit ABI
2858 for 64-bit processors. An x32 process gets access to the
2859 full 64-bit register file and wide data path while leaving
2860 pointers at 32 bits for smaller memory footprint.
2864 depends on IA32_EMULATION || X86_32
2866 select OLD_SIGSUSPEND3
2870 depends on IA32_EMULATION || X86_X32_ABI
2873 config COMPAT_FOR_U64_ALIGNMENT
2876 config SYSVIPC_COMPAT
2884 config HAVE_ATOMIC_IOMAP
2888 source "arch/x86/kvm/Kconfig"
2890 source "arch/x86/Kconfig.assembler"