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_DEBUG_VIRTUAL
73 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
74 select ARCH_HAS_DEVMEM_IS_ALLOWED
75 select ARCH_HAS_EARLY_DEBUG if KGDB
76 select ARCH_HAS_ELF_RANDOMIZE
77 select ARCH_HAS_FAST_MULTIPLIER
78 select ARCH_HAS_FILTER_PGPROT
79 select ARCH_HAS_FORTIFY_SOURCE
80 select ARCH_HAS_GCOV_PROFILE_ALL
81 select ARCH_HAS_KCOV if X86_64 && STACK_VALIDATION
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_DEBUG_WX
98 select ARCH_HAS_ZONE_DMA_SET if EXPERT
99 select ARCH_HAVE_NMI_SAFE_CMPXCHG
100 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
101 select ARCH_MIGHT_HAVE_PC_PARPORT
102 select ARCH_MIGHT_HAVE_PC_SERIO
103 select ARCH_STACKWALK
104 select ARCH_SUPPORTS_ACPI
105 select ARCH_SUPPORTS_ATOMIC_RMW
106 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
107 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
108 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
109 select ARCH_SUPPORTS_LTO_CLANG
110 select ARCH_SUPPORTS_LTO_CLANG_THIN
111 select ARCH_USE_BUILTIN_BSWAP
112 select ARCH_USE_MEMTEST
113 select ARCH_USE_QUEUED_RWLOCKS
114 select ARCH_USE_QUEUED_SPINLOCKS
115 select ARCH_USE_SYM_ANNOTATIONS
116 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
117 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
118 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
119 select ARCH_WANTS_NO_INSTR
120 select ARCH_WANT_HUGE_PMD_SHARE
121 select ARCH_WANT_LD_ORPHAN_WARN
122 select ARCH_WANTS_THP_SWAP if X86_64
123 select ARCH_HAS_PARANOID_L1D_FLUSH
124 select BUILDTIME_TABLE_SORT
126 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
127 select CLOCKSOURCE_WATCHDOG
128 select DCACHE_WORD_ACCESS
129 select DYNAMIC_SIGFRAME
130 select EDAC_ATOMIC_SCRUB
132 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
133 select GENERIC_CLOCKEVENTS_MIN_ADJUST
134 select GENERIC_CMOS_UPDATE
135 select GENERIC_CPU_AUTOPROBE
136 select GENERIC_CPU_VULNERABILITIES
137 select GENERIC_EARLY_IOREMAP
139 select GENERIC_FIND_FIRST_BIT
141 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
142 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
143 select GENERIC_IRQ_MIGRATION if SMP
144 select GENERIC_IRQ_PROBE
145 select GENERIC_IRQ_RESERVATION_MODE
146 select GENERIC_IRQ_SHOW
147 select GENERIC_PENDING_IRQ if SMP
148 select GENERIC_PTDUMP
149 select GENERIC_SMP_IDLE_THREAD
150 select GENERIC_TIME_VSYSCALL
151 select GENERIC_GETTIMEOFDAY
152 select GENERIC_VDSO_TIME_NS
153 select GUP_GET_PTE_LOW_HIGH if X86_PAE
154 select HARDIRQS_SW_RESEND
155 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
156 select HAVE_ACPI_APEI if ACPI
157 select HAVE_ACPI_APEI_NMI if ACPI
158 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
159 select HAVE_ARCH_AUDITSYSCALL
160 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
161 select HAVE_ARCH_JUMP_LABEL
162 select HAVE_ARCH_JUMP_LABEL_RELATIVE
163 select HAVE_ARCH_KASAN if X86_64
164 select HAVE_ARCH_KASAN_VMALLOC if X86_64
165 select HAVE_ARCH_KFENCE
166 select HAVE_ARCH_KGDB
167 select HAVE_ARCH_MMAP_RND_BITS if MMU
168 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
169 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
170 select HAVE_ARCH_PREL32_RELOCATIONS
171 select HAVE_ARCH_SECCOMP_FILTER
172 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
173 select HAVE_ARCH_STACKLEAK
174 select HAVE_ARCH_TRACEHOOK
175 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
176 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
177 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
178 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
179 select HAVE_ARCH_VMAP_STACK if X86_64
180 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
181 select HAVE_ARCH_WITHIN_STACK_FRAMES
182 select HAVE_ASM_MODVERSIONS
183 select HAVE_CMPXCHG_DOUBLE
184 select HAVE_CMPXCHG_LOCAL
185 select HAVE_CONTEXT_TRACKING if X86_64
186 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
187 select HAVE_C_RECORDMCOUNT
188 select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION
189 select HAVE_DEBUG_KMEMLEAK
190 select HAVE_DMA_CONTIGUOUS
191 select HAVE_DYNAMIC_FTRACE
192 select HAVE_DYNAMIC_FTRACE_WITH_REGS
193 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
194 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
195 select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
196 select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
198 select HAVE_EFFICIENT_UNALIGNED_ACCESS
200 select HAVE_EXIT_THREAD
202 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
203 select HAVE_FTRACE_MCOUNT_RECORD
204 select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
205 select HAVE_FUNCTION_TRACER
206 select HAVE_GCC_PLUGINS
207 select HAVE_HW_BREAKPOINT
208 select HAVE_IOREMAP_PROT
209 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
210 select HAVE_IRQ_TIME_ACCOUNTING
211 select HAVE_KERNEL_BZIP2
212 select HAVE_KERNEL_GZIP
213 select HAVE_KERNEL_LZ4
214 select HAVE_KERNEL_LZMA
215 select HAVE_KERNEL_LZO
216 select HAVE_KERNEL_XZ
217 select HAVE_KERNEL_ZSTD
219 select HAVE_KPROBES_ON_FTRACE
220 select HAVE_FUNCTION_ERROR_INJECTION
221 select HAVE_KRETPROBES
223 select HAVE_LIVEPATCH if X86_64
224 select HAVE_MIXED_BREAKPOINTS_REGS
225 select HAVE_MOD_ARCH_SPECIFIC
229 select HAVE_OPTPROBES
230 select HAVE_PCSPKR_PLATFORM
231 select HAVE_PERF_EVENTS
232 select HAVE_PERF_EVENTS_NMI
233 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
235 select HAVE_PERF_REGS
236 select HAVE_PERF_USER_STACK_DUMP
237 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
238 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
239 select HAVE_REGS_AND_STACK_ACCESS_API
240 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
241 select HAVE_FUNCTION_ARG_ACCESS_API
242 select HAVE_SOFTIRQ_ON_OWN_STACK
243 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
244 select HAVE_STACK_VALIDATION if X86_64
245 select HAVE_STATIC_CALL
246 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
247 select HAVE_PREEMPT_DYNAMIC
249 select HAVE_SYSCALL_TRACEPOINTS
250 select HAVE_UNSTABLE_SCHED_CLOCK
251 select HAVE_USER_RETURN_NOTIFIER
252 select HAVE_GENERIC_VDSO
253 select HOTPLUG_SMT if SMP
254 select IRQ_FORCED_THREADING
255 select NEED_SG_DMA_LENGTH
256 select PCI_DOMAINS if PCI
257 select PCI_LOCKLESS_CONFIG if PCI
260 select RTC_MC146818_LIB
263 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
264 select SYSCTL_EXCEPTION_TRACE
265 select THREAD_INFO_IN_TASK
266 select TRACE_IRQFLAGS_SUPPORT
267 select USER_STACKTRACE_SUPPORT
269 select HAVE_ARCH_KCSAN if X86_64
270 select X86_FEATURE_NAMES if PROC_FS
271 select PROC_PID_ARCH_STATUS if PROC_FS
272 select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
273 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
275 config INSTRUCTION_DECODER
277 depends on KPROBES || PERF_EVENTS || UPROBES
281 default "elf32-i386" if X86_32
282 default "elf64-x86-64" if X86_64
284 config LOCKDEP_SUPPORT
287 config STACKTRACE_SUPPORT
293 config ARCH_MMAP_RND_BITS_MIN
297 config ARCH_MMAP_RND_BITS_MAX
301 config ARCH_MMAP_RND_COMPAT_BITS_MIN
304 config ARCH_MMAP_RND_COMPAT_BITS_MAX
310 config GENERIC_ISA_DMA
312 depends on ISA_DMA_API
317 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
319 config GENERIC_BUG_RELATIVE_POINTERS
322 config ARCH_MAY_HAVE_PC_FDC
324 depends on ISA_DMA_API
326 config GENERIC_CALIBRATE_DELAY
329 config ARCH_HAS_CPU_RELAX
332 config ARCH_HAS_FILTER_PGPROT
335 config HAVE_SETUP_PER_CPU_AREA
338 config NEED_PER_CPU_EMBED_FIRST_CHUNK
341 config NEED_PER_CPU_PAGE_FIRST_CHUNK
344 config ARCH_HIBERNATION_POSSIBLE
349 default 1024 if X86_64
352 config ARCH_SUSPEND_POSSIBLE
355 config ARCH_WANT_GENERAL_HUGETLB
361 config KASAN_SHADOW_OFFSET
364 default 0xdffffc0000000000
366 config HAVE_INTEL_TXT
368 depends on INTEL_IOMMU && ACPI
372 depends on X86_32 && SMP
376 depends on X86_64 && SMP
378 config ARCH_SUPPORTS_UPROBES
381 config FIX_EARLYCON_MEM
384 config DYNAMIC_PHYSICAL_MASK
387 config PGTABLE_LEVELS
389 default 5 if X86_5LEVEL
394 config CC_HAS_SANE_STACKPROTECTOR
396 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
397 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
399 We have to make sure stack protector is unconditionally disabled if
400 the compiler produces broken code or if it does not let us control
401 the segment on 32-bit kernels.
403 menu "Processor type and features"
406 bool "Symmetric multi-processing support"
408 This enables support for systems with more than one CPU. If you have
409 a system with only one CPU, say N. If you have a system with more
412 If you say N here, the kernel will run on uni- and multiprocessor
413 machines, but will use only one CPU of a multiprocessor machine. If
414 you say Y here, the kernel will run on many, but not all,
415 uniprocessor machines. On a uniprocessor machine, the kernel
416 will run faster if you say N here.
418 Note that if you say Y here and choose architecture "586" or
419 "Pentium" under "Processor family", the kernel will not work on 486
420 architectures. Similarly, multiprocessor kernels for the "PPro"
421 architecture may not work on all Pentium based boards.
423 People using multiprocessor machines who say Y here should also say
424 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
425 Management" code will be disabled if you say Y here.
427 See also <file:Documentation/x86/i386/IO-APIC.rst>,
428 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
429 <http://www.tldp.org/docs.html#howto>.
431 If you don't know what to do here, say N.
433 config X86_FEATURE_NAMES
434 bool "Processor feature human-readable names" if EMBEDDED
437 This option compiles in a table of x86 feature bits and corresponding
438 names. This is required to support /proc/cpuinfo and a few kernel
439 messages. You can disable this to save space, at the expense of
440 making those few kernel messages show numeric feature bits instead.
445 bool "Support x2apic"
446 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
448 This enables x2apic support on CPUs that have this feature.
450 This allows 32-bit apic IDs (so it can support very large systems),
451 and accesses the local apic via MSRs not via mmio.
453 If you don't know what to do here, say N.
456 bool "Enable MPS table" if ACPI
458 depends on X86_LOCAL_APIC
460 For old smp systems that do not have proper acpi support. Newer systems
461 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
465 depends on X86_GOLDFISH
468 bool "Avoid speculative indirect branches in kernel"
471 Compile kernel with the retpoline compiler options to guard against
472 kernel-to-user data leaks by avoiding speculative indirect
473 branches. Requires a compiler with -mindirect-branch=thunk-extern
474 support for full protection. The kernel may run slower.
477 def_bool $(cc-option,-mharden-sls=all)
480 bool "Mitigate Straight-Line-Speculation"
481 depends on CC_HAS_SLS && X86_64
484 Compile the kernel with straight-line-speculation options to guard
485 against straight line speculation. The kernel image might be slightly
488 config X86_CPU_RESCTRL
489 bool "x86 CPU resource control support"
490 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
492 select PROC_CPU_RESCTRL if PROC_FS
494 Enable x86 CPU resource control support.
496 Provide support for the allocation and monitoring of system resources
499 Intel calls this Intel Resource Director Technology
500 (Intel(R) RDT). More information about RDT can be found in the
501 Intel x86 Architecture Software Developer Manual.
503 AMD calls this AMD Platform Quality of Service (AMD QoS).
504 More information about AMD QoS can be found in the AMD64 Technology
505 Platform Quality of Service Extensions manual.
511 bool "Support for big SMP systems with more than 8 CPUs"
514 This option is needed for the systems that have more than 8 CPUs.
516 config X86_EXTENDED_PLATFORM
517 bool "Support for extended (non-PC) x86 platforms"
520 If you disable this option then the kernel will only support
521 standard PC platforms. (which covers the vast majority of
524 If you enable this option then you'll be able to select support
525 for the following (non-PC) 32 bit x86 platforms:
526 Goldfish (Android emulator)
529 SGI 320/540 (Visual Workstation)
530 STA2X11-based (e.g. Northville)
531 Moorestown MID devices
533 If you have one of these systems, or if you want to build a
534 generic distribution kernel, say Y here - otherwise say N.
538 config X86_EXTENDED_PLATFORM
539 bool "Support for extended (non-PC) x86 platforms"
542 If you disable this option then the kernel will only support
543 standard PC platforms. (which covers the vast majority of
546 If you enable this option then you'll be able to select support
547 for the following (non-PC) 64 bit x86 platforms:
552 If you have one of these systems, or if you want to build a
553 generic distribution kernel, say Y here - otherwise say N.
555 # This is an alphabetically sorted list of 64 bit extended platforms
556 # Please maintain the alphabetic order if and when there are additions
558 bool "Numascale NumaChip"
560 depends on X86_EXTENDED_PLATFORM
563 depends on X86_X2APIC
564 depends on PCI_MMCONFIG
566 Adds support for Numascale NumaChip large-SMP systems. Needed to
567 enable more than ~168 cores.
568 If you don't have one of these, you should say N here.
572 select HYPERVISOR_GUEST
574 depends on X86_64 && PCI
575 depends on X86_EXTENDED_PLATFORM
578 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
579 supposed to run on these EM64T-based machines. Only choose this option
580 if you have one of these machines.
583 bool "SGI Ultraviolet"
585 depends on X86_EXTENDED_PLATFORM
588 depends on KEXEC_CORE
589 depends on X86_X2APIC
592 This option is needed in order to support SGI Ultraviolet systems.
593 If you don't have one of these, you should say N here.
595 # Following is an alphabetically sorted list of 32 bit extended platforms
596 # Please maintain the alphabetic order if and when there are additions
599 bool "Goldfish (Virtual Platform)"
600 depends on X86_EXTENDED_PLATFORM
602 Enable support for the Goldfish virtual platform used primarily
603 for Android development. Unless you are building for the Android
604 Goldfish emulator say N here.
607 bool "CE4100 TV platform"
609 depends on PCI_GODIRECT
610 depends on X86_IO_APIC
612 depends on X86_EXTENDED_PLATFORM
613 select X86_REBOOTFIXUPS
615 select OF_EARLY_FLATTREE
617 Select for the Intel CE media processor (CE4100) SOC.
618 This option compiles in support for the CE4100 SOC for settop
619 boxes and media devices.
622 bool "Intel MID platform support"
623 depends on X86_EXTENDED_PLATFORM
624 depends on X86_PLATFORM_DEVICES
626 depends on X86_64 || (PCI_GOANY && X86_32)
627 depends on X86_IO_APIC
632 Select to build a kernel capable of supporting Intel MID (Mobile
633 Internet Device) platform systems which do not have the PCI legacy
634 interfaces. If you are building for a PC class system say N here.
636 Intel MID platforms are based on an Intel processor and chipset which
637 consume less power than most of the x86 derivatives.
639 config X86_INTEL_QUARK
640 bool "Intel Quark platform support"
642 depends on X86_EXTENDED_PLATFORM
643 depends on X86_PLATFORM_DEVICES
647 depends on X86_IO_APIC
652 Select to include support for Quark X1000 SoC.
653 Say Y here if you have a Quark based system such as the Arduino
654 compatible Intel Galileo.
656 config X86_INTEL_LPSS
657 bool "Intel Low Power Subsystem Support"
658 depends on X86 && ACPI && PCI
663 Select to build support for Intel Low Power Subsystem such as
664 found on Intel Lynxpoint PCH. Selecting this option enables
665 things like clock tree (common clock framework) and pincontrol
666 which are needed by the LPSS peripheral drivers.
668 config X86_AMD_PLATFORM_DEVICE
669 bool "AMD ACPI2Platform devices support"
674 Select to interpret AMD specific ACPI device to platform device
675 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
676 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
677 implemented under PINCTRL subsystem.
680 tristate "Intel SoC IOSF Sideband support for SoC platforms"
683 This option enables sideband register access support for Intel SoC
684 platforms. On these platforms the IOSF sideband is used in lieu of
685 MSR's for some register accesses, mostly but not limited to thermal
686 and power. Drivers may query the availability of this device to
687 determine if they need the sideband in order to work on these
688 platforms. The sideband is available on the following SoC products.
689 This list is not meant to be exclusive.
694 You should say Y if you are running a kernel on one of these SoC's.
696 config IOSF_MBI_DEBUG
697 bool "Enable IOSF sideband access through debugfs"
698 depends on IOSF_MBI && DEBUG_FS
700 Select this option to expose the IOSF sideband access registers (MCR,
701 MDR, MCRX) through debugfs to write and read register information from
702 different units on the SoC. This is most useful for obtaining device
703 state information for debug and analysis. As this is a general access
704 mechanism, users of this option would have specific knowledge of the
705 device they want to access.
707 If you don't require the option or are in doubt, say N.
710 bool "RDC R-321x SoC"
712 depends on X86_EXTENDED_PLATFORM
714 select X86_REBOOTFIXUPS
716 This option is needed for RDC R-321x system-on-chip, also known
718 If you don't have one of these chips, you should say N here.
720 config X86_32_NON_STANDARD
721 bool "Support non-standard 32-bit SMP architectures"
722 depends on X86_32 && SMP
723 depends on X86_EXTENDED_PLATFORM
725 This option compiles in the bigsmp and STA2X11 default
726 subarchitectures. It is intended for a generic binary
727 kernel. If you select them all, kernel will probe it one by
728 one and will fallback to default.
730 # Alphabetically sorted list of Non standard 32 bit platforms
732 config X86_SUPPORTS_MEMORY_FAILURE
734 # MCE code calls memory_failure():
736 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
737 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
738 depends on X86_64 || !SPARSEMEM
739 select ARCH_SUPPORTS_MEMORY_FAILURE
742 bool "STA2X11 Companion Chip Support"
743 depends on X86_32_NON_STANDARD && PCI
748 This adds support for boards based on the STA2X11 IO-Hub,
749 a.k.a. "ConneXt". The chip is used in place of the standard
750 PC chipset, so all "standard" peripherals are missing. If this
751 option is selected the kernel will still be able to boot on
752 standard PC machines.
755 tristate "Eurobraille/Iris poweroff module"
758 The Iris machines from EuroBraille do not have APM or ACPI support
759 to shut themselves down properly. A special I/O sequence is
760 needed to do so, which is what this module does at
763 This is only for Iris machines from EuroBraille.
767 config SCHED_OMIT_FRAME_POINTER
769 prompt "Single-depth WCHAN output"
772 Calculate simpler /proc/<PID>/wchan values. If this option
773 is disabled then wchan values will recurse back to the
774 caller function. This provides more accurate wchan values,
775 at the expense of slightly more scheduling overhead.
777 If in doubt, say "Y".
779 menuconfig HYPERVISOR_GUEST
780 bool "Linux guest support"
782 Say Y here to enable options for running Linux under various hyper-
783 visors. This option enables basic hypervisor detection and platform
786 If you say N, all options in this submenu will be skipped and
787 disabled, and Linux guest support won't be built in.
792 bool "Enable paravirtualization code"
793 depends on HAVE_STATIC_CALL
795 This changes the kernel so it can modify itself when it is run
796 under a hypervisor, potentially improving performance significantly
797 over full virtualization. However, when run without a hypervisor
798 the kernel is theoretically slower and slightly larger.
803 config PARAVIRT_DEBUG
804 bool "paravirt-ops debugging"
805 depends on PARAVIRT && DEBUG_KERNEL
807 Enable to debug paravirt_ops internals. Specifically, BUG if
808 a paravirt_op is missing when it is called.
810 config PARAVIRT_SPINLOCKS
811 bool "Paravirtualization layer for spinlocks"
812 depends on PARAVIRT && SMP
814 Paravirtualized spinlocks allow a pvops backend to replace the
815 spinlock implementation with something virtualization-friendly
816 (for example, block the virtual CPU rather than spinning).
818 It has a minimal impact on native kernels and gives a nice performance
819 benefit on paravirtualized KVM / Xen kernels.
821 If you are unsure how to answer this question, answer Y.
823 config X86_HV_CALLBACK_VECTOR
826 source "arch/x86/xen/Kconfig"
829 bool "KVM Guest support (including kvmclock)"
831 select PARAVIRT_CLOCK
832 select ARCH_CPUIDLE_HALTPOLL
833 select X86_HV_CALLBACK_VECTOR
836 This option enables various optimizations for running under the KVM
837 hypervisor. It includes a paravirtualized clock, so that instead
838 of relying on a PIT (or probably other) emulation by the
839 underlying device model, the host provides the guest with
840 timing infrastructure such as time of day, and system time
842 config ARCH_CPUIDLE_HALTPOLL
844 prompt "Disable host haltpoll when loading haltpoll driver"
846 If virtualized under KVM, disable host haltpoll.
849 bool "Support for running PVH guests"
851 This option enables the PVH entry point for guest virtual machines
852 as specified in the x86/HVM direct boot ABI.
854 config PARAVIRT_TIME_ACCOUNTING
855 bool "Paravirtual steal time accounting"
858 Select this option to enable fine granularity task steal time
859 accounting. Time spent executing other tasks in parallel with
860 the current vCPU is discounted from the vCPU power. To account for
861 that, there can be a small performance impact.
863 If in doubt, say N here.
865 config PARAVIRT_CLOCK
868 config JAILHOUSE_GUEST
869 bool "Jailhouse non-root cell support"
870 depends on X86_64 && PCI
873 This option allows to run Linux as guest in a Jailhouse non-root
874 cell. You can leave this option disabled if you only want to start
875 Jailhouse and run Linux afterwards in the root cell.
878 bool "ACRN Guest support"
880 select X86_HV_CALLBACK_VECTOR
882 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
883 a flexible, lightweight reference open-source hypervisor, built with
884 real-time and safety-criticality in mind. It is built for embedded
885 IOT with small footprint and real-time features. More details can be
886 found in https://projectacrn.org/.
888 endif #HYPERVISOR_GUEST
890 source "arch/x86/Kconfig.cpu"
894 prompt "HPET Timer Support" if X86_32
896 Use the IA-PC HPET (High Precision Event Timer) to manage
897 time in preference to the PIT and RTC, if a HPET is
899 HPET is the next generation timer replacing legacy 8254s.
900 The HPET provides a stable time base on SMP
901 systems, unlike the TSC, but it is more expensive to access,
902 as it is off-chip. The interface used is documented
903 in the HPET spec, revision 1.
905 You can safely choose Y here. However, HPET will only be
906 activated if the platform and the BIOS support this feature.
907 Otherwise the 8254 will be used for timing services.
909 Choose N to continue using the legacy 8254 timer.
911 config HPET_EMULATE_RTC
913 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
915 # Mark as expert because too many people got it wrong.
916 # The code disables itself when not needed.
919 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
920 bool "Enable DMI scanning" if EXPERT
922 Enabled scanning of DMI to identify machine quirks. Say Y
923 here unless you have verified that your setup is not
924 affected by entries in the DMI blacklist. Required by PNP
928 bool "Old AMD GART IOMMU support"
932 depends on X86_64 && PCI && AMD_NB
934 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
935 GART based hardware IOMMUs.
937 The GART supports full DMA access for devices with 32-bit access
938 limitations, on systems with more than 3 GB. This is usually needed
939 for USB, sound, many IDE/SATA chipsets and some other devices.
941 Newer systems typically have a modern AMD IOMMU, supported via
942 the CONFIG_AMD_IOMMU=y config option.
944 In normal configurations this driver is only active when needed:
945 there's more than 3 GB of memory and the system contains a
946 32-bit limited device.
951 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
952 depends on X86_64 && SMP && DEBUG_KERNEL
953 select CPUMASK_OFFSTACK
955 Enable maximum number of CPUS and NUMA Nodes for this architecture.
959 # The maximum number of CPUs supported:
961 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
962 # and which can be configured interactively in the
963 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
965 # The ranges are different on 32-bit and 64-bit kernels, depending on
966 # hardware capabilities and scalability features of the kernel.
968 # ( If MAXSMP is enabled we just use the highest possible value and disable
969 # interactive configuration. )
972 config NR_CPUS_RANGE_BEGIN
974 default NR_CPUS_RANGE_END if MAXSMP
978 config NR_CPUS_RANGE_END
981 default 64 if SMP && X86_BIGSMP
982 default 8 if SMP && !X86_BIGSMP
985 config NR_CPUS_RANGE_END
988 default 8192 if SMP && CPUMASK_OFFSTACK
989 default 512 if SMP && !CPUMASK_OFFSTACK
992 config NR_CPUS_DEFAULT
995 default 32 if X86_BIGSMP
999 config NR_CPUS_DEFAULT
1002 default 8192 if MAXSMP
1007 int "Maximum number of CPUs" if SMP && !MAXSMP
1008 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1009 default NR_CPUS_DEFAULT
1011 This allows you to specify the maximum number of CPUs which this
1012 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1013 supported value is 8192, otherwise the maximum value is 512. The
1014 minimum value which makes sense is 2.
1016 This is purely to save memory: each supported CPU adds about 8KB
1017 to the kernel image.
1019 config SCHED_CLUSTER
1020 bool "Cluster scheduler support"
1024 Cluster scheduler support improves the CPU scheduler's decision
1025 making when dealing with machines that have clusters of CPUs.
1026 Cluster usually means a couple of CPUs which are placed closely
1027 by sharing mid-level caches, last-level cache tags or internal
1035 prompt "Multi-core scheduler support"
1038 Multi-core scheduler support improves the CPU scheduler's decision
1039 making when dealing with multi-core CPU chips at a cost of slightly
1040 increased overhead in some places. If unsure say N here.
1042 config SCHED_MC_PRIO
1043 bool "CPU core priorities scheduler support"
1044 depends on SCHED_MC && CPU_SUP_INTEL
1045 select X86_INTEL_PSTATE
1049 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1050 core ordering determined at manufacturing time, which allows
1051 certain cores to reach higher turbo frequencies (when running
1052 single threaded workloads) than others.
1054 Enabling this kernel feature teaches the scheduler about
1055 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1056 scheduler's CPU selection logic accordingly, so that higher
1057 overall system performance can be achieved.
1059 This feature will have no effect on CPUs without this feature.
1061 If unsure say Y here.
1065 depends on !SMP && X86_LOCAL_APIC
1068 bool "Local APIC support on uniprocessors" if !PCI_MSI
1070 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1072 A local APIC (Advanced Programmable Interrupt Controller) is an
1073 integrated interrupt controller in the CPU. If you have a single-CPU
1074 system which has a processor with a local APIC, you can say Y here to
1075 enable and use it. If you say Y here even though your machine doesn't
1076 have a local APIC, then the kernel will still run with no slowdown at
1077 all. The local APIC supports CPU-generated self-interrupts (timer,
1078 performance counters), and the NMI watchdog which detects hard
1081 config X86_UP_IOAPIC
1082 bool "IO-APIC support on uniprocessors"
1083 depends on X86_UP_APIC
1085 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1086 SMP-capable replacement for PC-style interrupt controllers. Most
1087 SMP systems and many recent uniprocessor systems have one.
1089 If you have a single-CPU system with an IO-APIC, you can say Y here
1090 to use it. If you say Y here even though your machine doesn't have
1091 an IO-APIC, then the kernel will still run with no slowdown at all.
1093 config X86_LOCAL_APIC
1095 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1096 select IRQ_DOMAIN_HIERARCHY
1097 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1101 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1103 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1104 bool "Reroute for broken boot IRQs"
1105 depends on X86_IO_APIC
1107 This option enables a workaround that fixes a source of
1108 spurious interrupts. This is recommended when threaded
1109 interrupt handling is used on systems where the generation of
1110 superfluous "boot interrupts" cannot be disabled.
1112 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1113 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1114 kernel does during interrupt handling). On chipsets where this
1115 boot IRQ generation cannot be disabled, this workaround keeps
1116 the original IRQ line masked so that only the equivalent "boot
1117 IRQ" is delivered to the CPUs. The workaround also tells the
1118 kernel to set up the IRQ handler on the boot IRQ line. In this
1119 way only one interrupt is delivered to the kernel. Otherwise
1120 the spurious second interrupt may cause the kernel to bring
1121 down (vital) interrupt lines.
1123 Only affects "broken" chipsets. Interrupt sharing may be
1124 increased on these systems.
1127 bool "Machine Check / overheating reporting"
1128 select GENERIC_ALLOCATOR
1131 Machine Check support allows the processor to notify the
1132 kernel if it detects a problem (e.g. overheating, data corruption).
1133 The action the kernel takes depends on the severity of the problem,
1134 ranging from warning messages to halting the machine.
1136 config X86_MCELOG_LEGACY
1137 bool "Support for deprecated /dev/mcelog character device"
1140 Enable support for /dev/mcelog which is needed by the old mcelog
1141 userspace logging daemon. Consider switching to the new generation
1144 config X86_MCE_INTEL
1146 prompt "Intel MCE features"
1147 depends on X86_MCE && X86_LOCAL_APIC
1149 Additional support for intel specific MCE features such as
1150 the thermal monitor.
1154 prompt "AMD MCE features"
1155 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1157 Additional support for AMD specific MCE features such as
1158 the DRAM Error Threshold.
1160 config X86_ANCIENT_MCE
1161 bool "Support for old Pentium 5 / WinChip machine checks"
1162 depends on X86_32 && X86_MCE
1164 Include support for machine check handling on old Pentium 5 or WinChip
1165 systems. These typically need to be enabled explicitly on the command
1168 config X86_MCE_THRESHOLD
1169 depends on X86_MCE_AMD || X86_MCE_INTEL
1172 config X86_MCE_INJECT
1173 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1174 tristate "Machine check injector support"
1176 Provide support for injecting machine checks for testing purposes.
1177 If you don't know what a machine check is and you don't do kernel
1178 QA it is safe to say n.
1180 source "arch/x86/events/Kconfig"
1182 config X86_LEGACY_VM86
1183 bool "Legacy VM86 support"
1186 This option allows user programs to put the CPU into V8086
1187 mode, which is an 80286-era approximation of 16-bit real mode.
1189 Some very old versions of X and/or vbetool require this option
1190 for user mode setting. Similarly, DOSEMU will use it if
1191 available to accelerate real mode DOS programs. However, any
1192 recent version of DOSEMU, X, or vbetool should be fully
1193 functional even without kernel VM86 support, as they will all
1194 fall back to software emulation. Nevertheless, if you are using
1195 a 16-bit DOS program where 16-bit performance matters, vm86
1196 mode might be faster than emulation and you might want to
1199 Note that any app that works on a 64-bit kernel is unlikely to
1200 need this option, as 64-bit kernels don't, and can't, support
1201 V8086 mode. This option is also unrelated to 16-bit protected
1202 mode and is not needed to run most 16-bit programs under Wine.
1204 Enabling this option increases the complexity of the kernel
1205 and slows down exception handling a tiny bit.
1207 If unsure, say N here.
1211 default X86_LEGACY_VM86
1214 bool "Enable support for 16-bit segments" if EXPERT
1216 depends on MODIFY_LDT_SYSCALL
1218 This option is required by programs like Wine to run 16-bit
1219 protected mode legacy code on x86 processors. Disabling
1220 this option saves about 300 bytes on i386, or around 6K text
1221 plus 16K runtime memory on x86-64,
1225 depends on X86_16BIT && X86_32
1229 depends on X86_16BIT && X86_64
1231 config X86_VSYSCALL_EMULATION
1232 bool "Enable vsyscall emulation" if EXPERT
1236 This enables emulation of the legacy vsyscall page. Disabling
1237 it is roughly equivalent to booting with vsyscall=none, except
1238 that it will also disable the helpful warning if a program
1239 tries to use a vsyscall. With this option set to N, offending
1240 programs will just segfault, citing addresses of the form
1243 This option is required by many programs built before 2013, and
1244 care should be used even with newer programs if set to N.
1246 Disabling this option saves about 7K of kernel size and
1247 possibly 4K of additional runtime pagetable memory.
1249 config X86_IOPL_IOPERM
1250 bool "IOPERM and IOPL Emulation"
1253 This enables the ioperm() and iopl() syscalls which are necessary
1254 for legacy applications.
1256 Legacy IOPL support is an overbroad mechanism which allows user
1257 space aside of accessing all 65536 I/O ports also to disable
1258 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1259 capabilities and permission from potentially active security
1262 The emulation restricts the functionality of the syscall to
1263 only allowing the full range I/O port access, but prevents the
1264 ability to disable interrupts from user space which would be
1265 granted if the hardware IOPL mechanism would be used.
1268 tristate "Toshiba Laptop support"
1271 This adds a driver to safely access the System Management Mode of
1272 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1273 not work on models with a Phoenix BIOS. The System Management Mode
1274 is used to set the BIOS and power saving options on Toshiba portables.
1276 For information on utilities to make use of this driver see the
1277 Toshiba Linux utilities web site at:
1278 <http://www.buzzard.org.uk/toshiba/>.
1280 Say Y if you intend to run this kernel on a Toshiba portable.
1284 tristate "Dell i8k legacy laptop support"
1287 select SENSORS_DELL_SMM
1289 This option enables legacy /proc/i8k userspace interface in hwmon
1290 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1291 temperature and allows controlling fan speeds of Dell laptops via
1292 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1293 it reports also power and hotkey status. For fan speed control is
1294 needed userspace package i8kutils.
1296 Say Y if you intend to run this kernel on old Dell laptops or want to
1297 use userspace package i8kutils.
1300 config X86_REBOOTFIXUPS
1301 bool "Enable X86 board specific fixups for reboot"
1304 This enables chipset and/or board specific fixups to be done
1305 in order to get reboot to work correctly. This is only needed on
1306 some combinations of hardware and BIOS. The symptom, for which
1307 this config is intended, is when reboot ends with a stalled/hung
1310 Currently, the only fixup is for the Geode machines using
1311 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1313 Say Y if you want to enable the fixup. Currently, it's safe to
1314 enable this option even if you don't need it.
1318 bool "CPU microcode loading support"
1320 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1322 If you say Y here, you will be able to update the microcode on
1323 Intel and AMD processors. The Intel support is for the IA32 family,
1324 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1325 AMD support is for families 0x10 and later. You will obviously need
1326 the actual microcode binary data itself which is not shipped with
1329 The preferred method to load microcode from a detached initrd is described
1330 in Documentation/x86/microcode.rst. For that you need to enable
1331 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1332 initrd for microcode blobs.
1334 In addition, you can build the microcode into the kernel. For that you
1335 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1338 config MICROCODE_INTEL
1339 bool "Intel microcode loading support"
1340 depends on MICROCODE
1343 This options enables microcode patch loading support for Intel
1346 For the current Intel microcode data package go to
1347 <https://downloadcenter.intel.com> and search for
1348 'Linux Processor Microcode Data File'.
1350 config MICROCODE_AMD
1351 bool "AMD microcode loading support"
1352 depends on MICROCODE
1354 If you select this option, microcode patch loading support for AMD
1355 processors will be enabled.
1357 config MICROCODE_OLD_INTERFACE
1358 bool "Ancient loading interface (DEPRECATED)"
1360 depends on MICROCODE
1362 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1363 which was used by userspace tools like iucode_tool and microcode.ctl.
1364 It is inadequate because it runs too late to be able to properly
1365 load microcode on a machine and it needs special tools. Instead, you
1366 should've switched to the early loading method with the initrd or
1367 builtin microcode by now: Documentation/x86/microcode.rst
1370 tristate "/dev/cpu/*/msr - Model-specific register support"
1372 This device gives privileged processes access to the x86
1373 Model-Specific Registers (MSRs). It is a character device with
1374 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1375 MSR accesses are directed to a specific CPU on multi-processor
1379 tristate "/dev/cpu/*/cpuid - CPU information support"
1381 This device gives processes access to the x86 CPUID instruction to
1382 be executed on a specific processor. It is a character device
1383 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1387 prompt "High Memory Support"
1394 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1395 However, the address space of 32-bit x86 processors is only 4
1396 Gigabytes large. That means that, if you have a large amount of
1397 physical memory, not all of it can be "permanently mapped" by the
1398 kernel. The physical memory that's not permanently mapped is called
1401 If you are compiling a kernel which will never run on a machine with
1402 more than 1 Gigabyte total physical RAM, answer "off" here (default
1403 choice and suitable for most users). This will result in a "3GB/1GB"
1404 split: 3GB are mapped so that each process sees a 3GB virtual memory
1405 space and the remaining part of the 4GB virtual memory space is used
1406 by the kernel to permanently map as much physical memory as
1409 If the machine has between 1 and 4 Gigabytes physical RAM, then
1412 If more than 4 Gigabytes is used then answer "64GB" here. This
1413 selection turns Intel PAE (Physical Address Extension) mode on.
1414 PAE implements 3-level paging on IA32 processors. PAE is fully
1415 supported by Linux, PAE mode is implemented on all recent Intel
1416 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1417 then the kernel will not boot on CPUs that don't support PAE!
1419 The actual amount of total physical memory will either be
1420 auto detected or can be forced by using a kernel command line option
1421 such as "mem=256M". (Try "man bootparam" or see the documentation of
1422 your boot loader (lilo or loadlin) about how to pass options to the
1423 kernel at boot time.)
1425 If unsure, say "off".
1430 Select this if you have a 32-bit processor and between 1 and 4
1431 gigabytes of physical RAM.
1435 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1438 Select this if you have a 32-bit processor and more than 4
1439 gigabytes of physical RAM.
1444 prompt "Memory split" if EXPERT
1448 Select the desired split between kernel and user memory.
1450 If the address range available to the kernel is less than the
1451 physical memory installed, the remaining memory will be available
1452 as "high memory". Accessing high memory is a little more costly
1453 than low memory, as it needs to be mapped into the kernel first.
1454 Note that increasing the kernel address space limits the range
1455 available to user programs, making the address space there
1456 tighter. Selecting anything other than the default 3G/1G split
1457 will also likely make your kernel incompatible with binary-only
1460 If you are not absolutely sure what you are doing, leave this
1464 bool "3G/1G user/kernel split"
1465 config VMSPLIT_3G_OPT
1467 bool "3G/1G user/kernel split (for full 1G low memory)"
1469 bool "2G/2G user/kernel split"
1470 config VMSPLIT_2G_OPT
1472 bool "2G/2G user/kernel split (for full 2G low memory)"
1474 bool "1G/3G user/kernel split"
1479 default 0xB0000000 if VMSPLIT_3G_OPT
1480 default 0x80000000 if VMSPLIT_2G
1481 default 0x78000000 if VMSPLIT_2G_OPT
1482 default 0x40000000 if VMSPLIT_1G
1488 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1491 bool "PAE (Physical Address Extension) Support"
1492 depends on X86_32 && !HIGHMEM4G
1493 select PHYS_ADDR_T_64BIT
1496 PAE is required for NX support, and furthermore enables
1497 larger swapspace support for non-overcommit purposes. It
1498 has the cost of more pagetable lookup overhead, and also
1499 consumes more pagetable space per process.
1502 bool "Enable 5-level page tables support"
1504 select DYNAMIC_MEMORY_LAYOUT
1505 select SPARSEMEM_VMEMMAP
1508 5-level paging enables access to larger address space:
1509 upto 128 PiB of virtual address space and 4 PiB of
1510 physical address space.
1512 It will be supported by future Intel CPUs.
1514 A kernel with the option enabled can be booted on machines that
1515 support 4- or 5-level paging.
1517 See Documentation/x86/x86_64/5level-paging.rst for more
1522 config X86_DIRECT_GBPAGES
1526 Certain kernel features effectively disable kernel
1527 linear 1 GB mappings (even if the CPU otherwise
1528 supports them), so don't confuse the user by printing
1529 that we have them enabled.
1531 config X86_CPA_STATISTICS
1532 bool "Enable statistic for Change Page Attribute"
1535 Expose statistics about the Change Page Attribute mechanism, which
1536 helps to determine the effectiveness of preserving large and huge
1537 page mappings when mapping protections are changed.
1539 config X86_MEM_ENCRYPT
1540 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1541 select DYNAMIC_PHYSICAL_MASK
1542 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1545 config AMD_MEM_ENCRYPT
1546 bool "AMD Secure Memory Encryption (SME) support"
1547 depends on X86_64 && CPU_SUP_AMD
1548 select DMA_COHERENT_POOL
1549 select ARCH_USE_MEMREMAP_PROT
1550 select INSTRUCTION_DECODER
1551 select ARCH_HAS_CC_PLATFORM
1552 select X86_MEM_ENCRYPT
1554 Say yes to enable support for the encryption of system memory.
1555 This requires an AMD processor that supports Secure Memory
1558 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1559 bool "Activate AMD Secure Memory Encryption (SME) by default"
1560 depends on AMD_MEM_ENCRYPT
1562 Say yes to have system memory encrypted by default if running on
1563 an AMD processor that supports Secure Memory Encryption (SME).
1565 If set to Y, then the encryption of system memory can be
1566 deactivated with the mem_encrypt=off command line option.
1568 If set to N, then the encryption of system memory can be
1569 activated with the mem_encrypt=on command line option.
1571 # Common NUMA Features
1573 bool "NUMA Memory Allocation and Scheduler Support"
1575 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1576 default y if X86_BIGSMP
1578 Enable NUMA (Non-Uniform Memory Access) support.
1580 The kernel will try to allocate memory used by a CPU on the
1581 local memory controller of the CPU and add some more
1582 NUMA awareness to the kernel.
1584 For 64-bit this is recommended if the system is Intel Core i7
1585 (or later), AMD Opteron, or EM64T NUMA.
1587 For 32-bit this is only needed if you boot a 32-bit
1588 kernel on a 64-bit NUMA platform.
1590 Otherwise, you should say N.
1594 prompt "Old style AMD Opteron NUMA detection"
1595 depends on X86_64 && NUMA && PCI
1597 Enable AMD NUMA node topology detection. You should say Y here if
1598 you have a multi processor AMD system. This uses an old method to
1599 read the NUMA configuration directly from the builtin Northbridge
1600 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1601 which also takes priority if both are compiled in.
1603 config X86_64_ACPI_NUMA
1605 prompt "ACPI NUMA detection"
1606 depends on X86_64 && NUMA && ACPI && PCI
1609 Enable ACPI SRAT based node topology detection.
1612 bool "NUMA emulation"
1615 Enable NUMA emulation. A flat machine will be split
1616 into virtual nodes when booted with "numa=fake=N", where N is the
1617 number of nodes. This is only useful for debugging.
1620 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1622 default "10" if MAXSMP
1623 default "6" if X86_64
1627 Specify the maximum number of NUMA Nodes available on the target
1628 system. Increases memory reserved to accommodate various tables.
1630 config ARCH_FLATMEM_ENABLE
1632 depends on X86_32 && !NUMA
1634 config ARCH_SPARSEMEM_ENABLE
1636 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1637 select SPARSEMEM_STATIC if X86_32
1638 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1640 config ARCH_SPARSEMEM_DEFAULT
1641 def_bool X86_64 || (NUMA && X86_32)
1643 config ARCH_SELECT_MEMORY_MODEL
1645 depends on ARCH_SPARSEMEM_ENABLE
1647 config ARCH_MEMORY_PROBE
1648 bool "Enable sysfs memory/probe interface"
1649 depends on MEMORY_HOTPLUG
1651 This option enables a sysfs memory/probe interface for testing.
1652 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1653 If you are unsure how to answer this question, answer N.
1655 config ARCH_PROC_KCORE_TEXT
1657 depends on X86_64 && PROC_KCORE
1659 config ILLEGAL_POINTER_VALUE
1662 default 0xdead000000000000 if X86_64
1664 config X86_PMEM_LEGACY_DEVICE
1667 config X86_PMEM_LEGACY
1668 tristate "Support non-standard NVDIMMs and ADR protected memory"
1669 depends on PHYS_ADDR_T_64BIT
1671 select X86_PMEM_LEGACY_DEVICE
1672 select NUMA_KEEP_MEMINFO if NUMA
1675 Treat memory marked using the non-standard e820 type of 12 as used
1676 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1677 The kernel will offer these regions to the 'pmem' driver so
1678 they can be used for persistent storage.
1683 bool "Allocate 3rd-level pagetables from highmem"
1686 The VM uses one page table entry for each page of physical memory.
1687 For systems with a lot of RAM, this can be wasteful of precious
1688 low memory. Setting this option will put user-space page table
1689 entries in high memory.
1691 config X86_CHECK_BIOS_CORRUPTION
1692 bool "Check for low memory corruption"
1694 Periodically check for memory corruption in low memory, which
1695 is suspected to be caused by BIOS. Even when enabled in the
1696 configuration, it is disabled at runtime. Enable it by
1697 setting "memory_corruption_check=1" on the kernel command
1698 line. By default it scans the low 64k of memory every 60
1699 seconds; see the memory_corruption_check_size and
1700 memory_corruption_check_period parameters in
1701 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1703 When enabled with the default parameters, this option has
1704 almost no overhead, as it reserves a relatively small amount
1705 of memory and scans it infrequently. It both detects corruption
1706 and prevents it from affecting the running system.
1708 It is, however, intended as a diagnostic tool; if repeatable
1709 BIOS-originated corruption always affects the same memory,
1710 you can use memmap= to prevent the kernel from using that
1713 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1714 bool "Set the default setting of memory_corruption_check"
1715 depends on X86_CHECK_BIOS_CORRUPTION
1718 Set whether the default state of memory_corruption_check is
1721 config MATH_EMULATION
1723 depends on MODIFY_LDT_SYSCALL
1724 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1726 Linux can emulate a math coprocessor (used for floating point
1727 operations) if you don't have one. 486DX and Pentium processors have
1728 a math coprocessor built in, 486SX and 386 do not, unless you added
1729 a 487DX or 387, respectively. (The messages during boot time can
1730 give you some hints here ["man dmesg"].) Everyone needs either a
1731 coprocessor or this emulation.
1733 If you don't have a math coprocessor, you need to say Y here; if you
1734 say Y here even though you have a coprocessor, the coprocessor will
1735 be used nevertheless. (This behavior can be changed with the kernel
1736 command line option "no387", which comes handy if your coprocessor
1737 is broken. Try "man bootparam" or see the documentation of your boot
1738 loader (lilo or loadlin) about how to pass options to the kernel at
1739 boot time.) This means that it is a good idea to say Y here if you
1740 intend to use this kernel on different machines.
1742 More information about the internals of the Linux math coprocessor
1743 emulation can be found in <file:arch/x86/math-emu/README>.
1745 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1746 kernel, it won't hurt.
1750 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1752 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1753 the Memory Type Range Registers (MTRRs) may be used to control
1754 processor access to memory ranges. This is most useful if you have
1755 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1756 allows bus write transfers to be combined into a larger transfer
1757 before bursting over the PCI/AGP bus. This can increase performance
1758 of image write operations 2.5 times or more. Saying Y here creates a
1759 /proc/mtrr file which may be used to manipulate your processor's
1760 MTRRs. Typically the X server should use this.
1762 This code has a reasonably generic interface so that similar
1763 control registers on other processors can be easily supported
1766 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1767 Registers (ARRs) which provide a similar functionality to MTRRs. For
1768 these, the ARRs are used to emulate the MTRRs.
1769 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1770 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1771 write-combining. All of these processors are supported by this code
1772 and it makes sense to say Y here if you have one of them.
1774 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1775 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1776 can lead to all sorts of problems, so it's good to say Y here.
1778 You can safely say Y even if your machine doesn't have MTRRs, you'll
1779 just add about 9 KB to your kernel.
1781 See <file:Documentation/x86/mtrr.rst> for more information.
1783 config MTRR_SANITIZER
1785 prompt "MTRR cleanup support"
1788 Convert MTRR layout from continuous to discrete, so X drivers can
1789 add writeback entries.
1791 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1792 The largest mtrr entry size for a continuous block can be set with
1797 config MTRR_SANITIZER_ENABLE_DEFAULT
1798 int "MTRR cleanup enable value (0-1)"
1801 depends on MTRR_SANITIZER
1803 Enable mtrr cleanup default value
1805 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1806 int "MTRR cleanup spare reg num (0-7)"
1809 depends on MTRR_SANITIZER
1811 mtrr cleanup spare entries default, it can be changed via
1812 mtrr_spare_reg_nr=N on the kernel command line.
1816 prompt "x86 PAT support" if EXPERT
1819 Use PAT attributes to setup page level cache control.
1821 PATs are the modern equivalents of MTRRs and are much more
1822 flexible than MTRRs.
1824 Say N here if you see bootup problems (boot crash, boot hang,
1825 spontaneous reboots) or a non-working video driver.
1829 config ARCH_USES_PG_UNCACHED
1835 prompt "x86 architectural random number generator" if EXPERT
1837 Enable the x86 architectural RDRAND instruction
1838 (Intel Bull Mountain technology) to generate random numbers.
1839 If supported, this is a high bandwidth, cryptographically
1840 secure hardware random number generator.
1844 prompt "Supervisor Mode Access Prevention" if EXPERT
1846 Supervisor Mode Access Prevention (SMAP) is a security
1847 feature in newer Intel processors. There is a small
1848 performance cost if this enabled and turned on; there is
1849 also a small increase in the kernel size if this is enabled.
1855 prompt "User Mode Instruction Prevention" if EXPERT
1857 User Mode Instruction Prevention (UMIP) is a security feature in
1858 some x86 processors. If enabled, a general protection fault is
1859 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1860 executed in user mode. These instructions unnecessarily expose
1861 information about the hardware state.
1863 The vast majority of applications do not use these instructions.
1864 For the very few that do, software emulation is provided in
1865 specific cases in protected and virtual-8086 modes. Emulated
1868 config X86_INTEL_MEMORY_PROTECTION_KEYS
1869 prompt "Memory Protection Keys"
1871 # Note: only available in 64-bit mode
1872 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1873 select ARCH_USES_HIGH_VMA_FLAGS
1874 select ARCH_HAS_PKEYS
1876 Memory Protection Keys provides a mechanism for enforcing
1877 page-based protections, but without requiring modification of the
1878 page tables when an application changes protection domains.
1880 For details, see Documentation/core-api/protection-keys.rst
1885 prompt "TSX enable mode"
1886 depends on CPU_SUP_INTEL
1887 default X86_INTEL_TSX_MODE_OFF
1889 Intel's TSX (Transactional Synchronization Extensions) feature
1890 allows to optimize locking protocols through lock elision which
1891 can lead to a noticeable performance boost.
1893 On the other hand it has been shown that TSX can be exploited
1894 to form side channel attacks (e.g. TAA) and chances are there
1895 will be more of those attacks discovered in the future.
1897 Therefore TSX is not enabled by default (aka tsx=off). An admin
1898 might override this decision by tsx=on the command line parameter.
1899 Even with TSX enabled, the kernel will attempt to enable the best
1900 possible TAA mitigation setting depending on the microcode available
1901 for the particular machine.
1903 This option allows to set the default tsx mode between tsx=on, =off
1904 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1907 Say off if not sure, auto if TSX is in use but it should be used on safe
1908 platforms or on if TSX is in use and the security aspect of tsx is not
1911 config X86_INTEL_TSX_MODE_OFF
1914 TSX is disabled if possible - equals to tsx=off command line parameter.
1916 config X86_INTEL_TSX_MODE_ON
1919 TSX is always enabled on TSX capable HW - equals the tsx=on command
1922 config X86_INTEL_TSX_MODE_AUTO
1925 TSX is enabled on TSX capable HW that is believed to be safe against
1926 side channel attacks- equals the tsx=auto command line parameter.
1930 bool "Software Guard eXtensions (SGX)"
1931 depends on X86_64 && CPU_SUP_INTEL
1933 depends on CRYPTO_SHA256=y
1936 select NUMA_KEEP_MEMINFO if NUMA
1939 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1940 that can be used by applications to set aside private regions of code
1941 and data, referred to as enclaves. An enclave's private memory can
1942 only be accessed by code running within the enclave. Accesses from
1943 outside the enclave, including other enclaves, are disallowed by
1949 bool "EFI runtime service support"
1952 select EFI_RUNTIME_WRAPPERS
1953 select ARCH_USE_MEMREMAP_PROT
1955 This enables the kernel to use EFI runtime services that are
1956 available (such as the EFI variable services).
1958 This option is only useful on systems that have EFI firmware.
1959 In addition, you should use the latest ELILO loader available
1960 at <http://elilo.sourceforge.net> in order to take advantage
1961 of EFI runtime services. However, even with this option, the
1962 resultant kernel should continue to boot on existing non-EFI
1966 bool "EFI stub support"
1968 depends on $(cc-option,-mabi=ms) || X86_32
1971 This kernel feature allows a bzImage to be loaded directly
1972 by EFI firmware without the use of a bootloader.
1974 See Documentation/admin-guide/efi-stub.rst for more information.
1977 bool "EFI mixed-mode support"
1978 depends on EFI_STUB && X86_64
1980 Enabling this feature allows a 64-bit kernel to be booted
1981 on a 32-bit firmware, provided that your CPU supports 64-bit
1984 Note that it is not possible to boot a mixed-mode enabled
1985 kernel via the EFI boot stub - a bootloader that supports
1986 the EFI handover protocol must be used.
1990 source "kernel/Kconfig.hz"
1993 bool "kexec system call"
1996 kexec is a system call that implements the ability to shutdown your
1997 current kernel, and to start another kernel. It is like a reboot
1998 but it is independent of the system firmware. And like a reboot
1999 you can start any kernel with it, not just Linux.
2001 The name comes from the similarity to the exec system call.
2003 It is an ongoing process to be certain the hardware in a machine
2004 is properly shutdown, so do not be surprised if this code does not
2005 initially work for you. As of this writing the exact hardware
2006 interface is strongly in flux, so no good recommendation can be
2010 bool "kexec file based system call"
2015 depends on CRYPTO_SHA256=y
2017 This is new version of kexec system call. This system call is
2018 file based and takes file descriptors as system call argument
2019 for kernel and initramfs as opposed to list of segments as
2020 accepted by previous system call.
2022 config ARCH_HAS_KEXEC_PURGATORY
2026 bool "Verify kernel signature during kexec_file_load() syscall"
2027 depends on KEXEC_FILE
2030 This option makes the kexec_file_load() syscall check for a valid
2031 signature of the kernel image. The image can still be loaded without
2032 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2033 there's a signature that we can check, then it must be valid.
2035 In addition to this option, you need to enable signature
2036 verification for the corresponding kernel image type being
2037 loaded in order for this to work.
2039 config KEXEC_SIG_FORCE
2040 bool "Require a valid signature in kexec_file_load() syscall"
2041 depends on KEXEC_SIG
2043 This option makes kernel signature verification mandatory for
2044 the kexec_file_load() syscall.
2046 config KEXEC_BZIMAGE_VERIFY_SIG
2047 bool "Enable bzImage signature verification support"
2048 depends on KEXEC_SIG
2049 depends on SIGNED_PE_FILE_VERIFICATION
2050 select SYSTEM_TRUSTED_KEYRING
2052 Enable bzImage signature verification support.
2055 bool "kernel crash dumps"
2056 depends on X86_64 || (X86_32 && HIGHMEM)
2058 Generate crash dump after being started by kexec.
2059 This should be normally only set in special crash dump kernels
2060 which are loaded in the main kernel with kexec-tools into
2061 a specially reserved region and then later executed after
2062 a crash by kdump/kexec. The crash dump kernel must be compiled
2063 to a memory address not used by the main kernel or BIOS using
2064 PHYSICAL_START, or it must be built as a relocatable image
2065 (CONFIG_RELOCATABLE=y).
2066 For more details see Documentation/admin-guide/kdump/kdump.rst
2070 depends on KEXEC && HIBERNATION
2072 Jump between original kernel and kexeced kernel and invoke
2073 code in physical address mode via KEXEC
2075 config PHYSICAL_START
2076 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2079 This gives the physical address where the kernel is loaded.
2081 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2082 bzImage will decompress itself to above physical address and
2083 run from there. Otherwise, bzImage will run from the address where
2084 it has been loaded by the boot loader and will ignore above physical
2087 In normal kdump cases one does not have to set/change this option
2088 as now bzImage can be compiled as a completely relocatable image
2089 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2090 address. This option is mainly useful for the folks who don't want
2091 to use a bzImage for capturing the crash dump and want to use a
2092 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2093 to be specifically compiled to run from a specific memory area
2094 (normally a reserved region) and this option comes handy.
2096 So if you are using bzImage for capturing the crash dump,
2097 leave the value here unchanged to 0x1000000 and set
2098 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2099 for capturing the crash dump change this value to start of
2100 the reserved region. In other words, it can be set based on
2101 the "X" value as specified in the "crashkernel=YM@XM"
2102 command line boot parameter passed to the panic-ed
2103 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2104 for more details about crash dumps.
2106 Usage of bzImage for capturing the crash dump is recommended as
2107 one does not have to build two kernels. Same kernel can be used
2108 as production kernel and capture kernel. Above option should have
2109 gone away after relocatable bzImage support is introduced. But it
2110 is present because there are users out there who continue to use
2111 vmlinux for dump capture. This option should go away down the
2114 Don't change this unless you know what you are doing.
2117 bool "Build a relocatable kernel"
2120 This builds a kernel image that retains relocation information
2121 so it can be loaded someplace besides the default 1MB.
2122 The relocations tend to make the kernel binary about 10% larger,
2123 but are discarded at runtime.
2125 One use is for the kexec on panic case where the recovery kernel
2126 must live at a different physical address than the primary
2129 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2130 it has been loaded at and the compile time physical address
2131 (CONFIG_PHYSICAL_START) is used as the minimum location.
2133 config RANDOMIZE_BASE
2134 bool "Randomize the address of the kernel image (KASLR)"
2135 depends on RELOCATABLE
2138 In support of Kernel Address Space Layout Randomization (KASLR),
2139 this randomizes the physical address at which the kernel image
2140 is decompressed and the virtual address where the kernel
2141 image is mapped, as a security feature that deters exploit
2142 attempts relying on knowledge of the location of kernel
2145 On 64-bit, the kernel physical and virtual addresses are
2146 randomized separately. The physical address will be anywhere
2147 between 16MB and the top of physical memory (up to 64TB). The
2148 virtual address will be randomized from 16MB up to 1GB (9 bits
2149 of entropy). Note that this also reduces the memory space
2150 available to kernel modules from 1.5GB to 1GB.
2152 On 32-bit, the kernel physical and virtual addresses are
2153 randomized together. They will be randomized from 16MB up to
2154 512MB (8 bits of entropy).
2156 Entropy is generated using the RDRAND instruction if it is
2157 supported. If RDTSC is supported, its value is mixed into
2158 the entropy pool as well. If neither RDRAND nor RDTSC are
2159 supported, then entropy is read from the i8254 timer. The
2160 usable entropy is limited by the kernel being built using
2161 2GB addressing, and that PHYSICAL_ALIGN must be at a
2162 minimum of 2MB. As a result, only 10 bits of entropy are
2163 theoretically possible, but the implementations are further
2164 limited due to memory layouts.
2168 # Relocation on x86 needs some additional build support
2169 config X86_NEED_RELOCS
2171 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2173 config PHYSICAL_ALIGN
2174 hex "Alignment value to which kernel should be aligned"
2176 range 0x2000 0x1000000 if X86_32
2177 range 0x200000 0x1000000 if X86_64
2179 This value puts the alignment restrictions on physical address
2180 where kernel is loaded and run from. Kernel is compiled for an
2181 address which meets above alignment restriction.
2183 If bootloader loads the kernel at a non-aligned address and
2184 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2185 address aligned to above value and run from there.
2187 If bootloader loads the kernel at a non-aligned address and
2188 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2189 load address and decompress itself to the address it has been
2190 compiled for and run from there. The address for which kernel is
2191 compiled already meets above alignment restrictions. Hence the
2192 end result is that kernel runs from a physical address meeting
2193 above alignment restrictions.
2195 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2196 this value must be a multiple of 0x200000.
2198 Don't change this unless you know what you are doing.
2200 config DYNAMIC_MEMORY_LAYOUT
2203 This option makes base addresses of vmalloc and vmemmap as well as
2204 __PAGE_OFFSET movable during boot.
2206 config RANDOMIZE_MEMORY
2207 bool "Randomize the kernel memory sections"
2209 depends on RANDOMIZE_BASE
2210 select DYNAMIC_MEMORY_LAYOUT
2211 default RANDOMIZE_BASE
2213 Randomizes the base virtual address of kernel memory sections
2214 (physical memory mapping, vmalloc & vmemmap). This security feature
2215 makes exploits relying on predictable memory locations less reliable.
2217 The order of allocations remains unchanged. Entropy is generated in
2218 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2219 configuration have in average 30,000 different possible virtual
2220 addresses for each memory section.
2224 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2225 hex "Physical memory mapping padding" if EXPERT
2226 depends on RANDOMIZE_MEMORY
2227 default "0xa" if MEMORY_HOTPLUG
2229 range 0x1 0x40 if MEMORY_HOTPLUG
2232 Define the padding in terabytes added to the existing physical
2233 memory size during kernel memory randomization. It is useful
2234 for memory hotplug support but reduces the entropy available for
2235 address randomization.
2237 If unsure, leave at the default value.
2243 config BOOTPARAM_HOTPLUG_CPU0
2244 bool "Set default setting of cpu0_hotpluggable"
2245 depends on HOTPLUG_CPU
2247 Set whether default state of cpu0_hotpluggable is on or off.
2249 Say Y here to enable CPU0 hotplug by default. If this switch
2250 is turned on, there is no need to give cpu0_hotplug kernel
2251 parameter and the CPU0 hotplug feature is enabled by default.
2253 Please note: there are two known CPU0 dependencies if you want
2254 to enable the CPU0 hotplug feature either by this switch or by
2255 cpu0_hotplug kernel parameter.
2257 First, resume from hibernate or suspend always starts from CPU0.
2258 So hibernate and suspend are prevented if CPU0 is offline.
2260 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2261 offline if any interrupt can not migrate out of CPU0. There may
2262 be other CPU0 dependencies.
2264 Please make sure the dependencies are under your control before
2265 you enable this feature.
2267 Say N if you don't want to enable CPU0 hotplug feature by default.
2268 You still can enable the CPU0 hotplug feature at boot by kernel
2269 parameter cpu0_hotplug.
2271 config DEBUG_HOTPLUG_CPU0
2273 prompt "Debug CPU0 hotplug"
2274 depends on HOTPLUG_CPU
2276 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2277 soon as possible and boots up userspace with CPU0 offlined. User
2278 can online CPU0 back after boot time.
2280 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2281 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2282 compilation or giving cpu0_hotplug kernel parameter at boot.
2288 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2289 depends on COMPAT_32
2291 Certain buggy versions of glibc will crash if they are
2292 presented with a 32-bit vDSO that is not mapped at the address
2293 indicated in its segment table.
2295 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2296 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2297 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2298 the only released version with the bug, but OpenSUSE 9
2299 contains a buggy "glibc 2.3.2".
2301 The symptom of the bug is that everything crashes on startup, saying:
2302 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2304 Saying Y here changes the default value of the vdso32 boot
2305 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2306 This works around the glibc bug but hurts performance.
2308 If unsure, say N: if you are compiling your own kernel, you
2309 are unlikely to be using a buggy version of glibc.
2312 prompt "vsyscall table for legacy applications"
2314 default LEGACY_VSYSCALL_XONLY
2316 Legacy user code that does not know how to find the vDSO expects
2317 to be able to issue three syscalls by calling fixed addresses in
2318 kernel space. Since this location is not randomized with ASLR,
2319 it can be used to assist security vulnerability exploitation.
2321 This setting can be changed at boot time via the kernel command
2322 line parameter vsyscall=[emulate|xonly|none].
2324 On a system with recent enough glibc (2.14 or newer) and no
2325 static binaries, you can say None without a performance penalty
2326 to improve security.
2328 If unsure, select "Emulate execution only".
2330 config LEGACY_VSYSCALL_EMULATE
2331 bool "Full emulation"
2333 The kernel traps and emulates calls into the fixed vsyscall
2334 address mapping. This makes the mapping non-executable, but
2335 it still contains readable known contents, which could be
2336 used in certain rare security vulnerability exploits. This
2337 configuration is recommended when using legacy userspace
2338 that still uses vsyscalls along with legacy binary
2339 instrumentation tools that require code to be readable.
2341 An example of this type of legacy userspace is running
2342 Pin on an old binary that still uses vsyscalls.
2344 config LEGACY_VSYSCALL_XONLY
2345 bool "Emulate execution only"
2347 The kernel traps and emulates calls into the fixed vsyscall
2348 address mapping and does not allow reads. This
2349 configuration is recommended when userspace might use the
2350 legacy vsyscall area but support for legacy binary
2351 instrumentation of legacy code is not needed. It mitigates
2352 certain uses of the vsyscall area as an ASLR-bypassing
2355 config LEGACY_VSYSCALL_NONE
2358 There will be no vsyscall mapping at all. This will
2359 eliminate any risk of ASLR bypass due to the vsyscall
2360 fixed address mapping. Attempts to use the vsyscalls
2361 will be reported to dmesg, so that either old or
2362 malicious userspace programs can be identified.
2367 bool "Built-in kernel command line"
2369 Allow for specifying boot arguments to the kernel at
2370 build time. On some systems (e.g. embedded ones), it is
2371 necessary or convenient to provide some or all of the
2372 kernel boot arguments with the kernel itself (that is,
2373 to not rely on the boot loader to provide them.)
2375 To compile command line arguments into the kernel,
2376 set this option to 'Y', then fill in the
2377 boot arguments in CONFIG_CMDLINE.
2379 Systems with fully functional boot loaders (i.e. non-embedded)
2380 should leave this option set to 'N'.
2383 string "Built-in kernel command string"
2384 depends on CMDLINE_BOOL
2387 Enter arguments here that should be compiled into the kernel
2388 image and used at boot time. If the boot loader provides a
2389 command line at boot time, it is appended to this string to
2390 form the full kernel command line, when the system boots.
2392 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2393 change this behavior.
2395 In most cases, the command line (whether built-in or provided
2396 by the boot loader) should specify the device for the root
2399 config CMDLINE_OVERRIDE
2400 bool "Built-in command line overrides boot loader arguments"
2401 depends on CMDLINE_BOOL && CMDLINE != ""
2403 Set this option to 'Y' to have the kernel ignore the boot loader
2404 command line, and use ONLY the built-in command line.
2406 This is used to work around broken boot loaders. This should
2407 be set to 'N' under normal conditions.
2409 config MODIFY_LDT_SYSCALL
2410 bool "Enable the LDT (local descriptor table)" if EXPERT
2413 Linux can allow user programs to install a per-process x86
2414 Local Descriptor Table (LDT) using the modify_ldt(2) system
2415 call. This is required to run 16-bit or segmented code such as
2416 DOSEMU or some Wine programs. It is also used by some very old
2417 threading libraries.
2419 Enabling this feature adds a small amount of overhead to
2420 context switches and increases the low-level kernel attack
2421 surface. Disabling it removes the modify_ldt(2) system call.
2423 Saying 'N' here may make sense for embedded or server kernels.
2425 config STRICT_SIGALTSTACK_SIZE
2426 bool "Enforce strict size checking for sigaltstack"
2427 depends on DYNAMIC_SIGFRAME
2429 For historical reasons MINSIGSTKSZ is a constant which became
2430 already too small with AVX512 support. Add a mechanism to
2431 enforce strict checking of the sigaltstack size against the
2432 real size of the FPU frame. This option enables the check
2433 by default. It can also be controlled via the kernel command
2434 line option 'strict_sas_size' independent of this config
2435 switch. Enabling it might break existing applications which
2436 allocate a too small sigaltstack but 'work' because they
2437 never get a signal delivered.
2439 Say 'N' unless you want to really enforce this check.
2441 source "kernel/livepatch/Kconfig"
2445 config ARCH_HAS_ADD_PAGES
2447 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2449 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2452 config USE_PERCPU_NUMA_NODE_ID
2456 menu "Power management and ACPI options"
2458 config ARCH_HIBERNATION_HEADER
2460 depends on HIBERNATION
2462 source "kernel/power/Kconfig"
2464 source "drivers/acpi/Kconfig"
2471 tristate "APM (Advanced Power Management) BIOS support"
2472 depends on X86_32 && PM_SLEEP
2474 APM is a BIOS specification for saving power using several different
2475 techniques. This is mostly useful for battery powered laptops with
2476 APM compliant BIOSes. If you say Y here, the system time will be
2477 reset after a RESUME operation, the /proc/apm device will provide
2478 battery status information, and user-space programs will receive
2479 notification of APM "events" (e.g. battery status change).
2481 If you select "Y" here, you can disable actual use of the APM
2482 BIOS by passing the "apm=off" option to the kernel at boot time.
2484 Note that the APM support is almost completely disabled for
2485 machines with more than one CPU.
2487 In order to use APM, you will need supporting software. For location
2488 and more information, read <file:Documentation/power/apm-acpi.rst>
2489 and the Battery Powered Linux mini-HOWTO, available from
2490 <http://www.tldp.org/docs.html#howto>.
2492 This driver does not spin down disk drives (see the hdparm(8)
2493 manpage ("man 8 hdparm") for that), and it doesn't turn off
2494 VESA-compliant "green" monitors.
2496 This driver does not support the TI 4000M TravelMate and the ACER
2497 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2498 desktop machines also don't have compliant BIOSes, and this driver
2499 may cause those machines to panic during the boot phase.
2501 Generally, if you don't have a battery in your machine, there isn't
2502 much point in using this driver and you should say N. If you get
2503 random kernel OOPSes or reboots that don't seem to be related to
2504 anything, try disabling/enabling this option (or disabling/enabling
2507 Some other things you should try when experiencing seemingly random,
2510 1) make sure that you have enough swap space and that it is
2512 2) pass the "no-hlt" option to the kernel
2513 3) switch on floating point emulation in the kernel and pass
2514 the "no387" option to the kernel
2515 4) pass the "floppy=nodma" option to the kernel
2516 5) pass the "mem=4M" option to the kernel (thereby disabling
2517 all but the first 4 MB of RAM)
2518 6) make sure that the CPU is not over clocked.
2519 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2520 8) disable the cache from your BIOS settings
2521 9) install a fan for the video card or exchange video RAM
2522 10) install a better fan for the CPU
2523 11) exchange RAM chips
2524 12) exchange the motherboard.
2526 To compile this driver as a module, choose M here: the
2527 module will be called apm.
2531 config APM_IGNORE_USER_SUSPEND
2532 bool "Ignore USER SUSPEND"
2534 This option will ignore USER SUSPEND requests. On machines with a
2535 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2536 series notebooks, it is necessary to say Y because of a BIOS bug.
2538 config APM_DO_ENABLE
2539 bool "Enable PM at boot time"
2541 Enable APM features at boot time. From page 36 of the APM BIOS
2542 specification: "When disabled, the APM BIOS does not automatically
2543 power manage devices, enter the Standby State, enter the Suspend
2544 State, or take power saving steps in response to CPU Idle calls."
2545 This driver will make CPU Idle calls when Linux is idle (unless this
2546 feature is turned off -- see "Do CPU IDLE calls", below). This
2547 should always save battery power, but more complicated APM features
2548 will be dependent on your BIOS implementation. You may need to turn
2549 this option off if your computer hangs at boot time when using APM
2550 support, or if it beeps continuously instead of suspending. Turn
2551 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2552 T400CDT. This is off by default since most machines do fine without
2557 bool "Make CPU Idle calls when idle"
2559 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2560 On some machines, this can activate improved power savings, such as
2561 a slowed CPU clock rate, when the machine is idle. These idle calls
2562 are made after the idle loop has run for some length of time (e.g.,
2563 333 mS). On some machines, this will cause a hang at boot time or
2564 whenever the CPU becomes idle. (On machines with more than one CPU,
2565 this option does nothing.)
2567 config APM_DISPLAY_BLANK
2568 bool "Enable console blanking using APM"
2570 Enable console blanking using the APM. Some laptops can use this to
2571 turn off the LCD backlight when the screen blanker of the Linux
2572 virtual console blanks the screen. Note that this is only used by
2573 the virtual console screen blanker, and won't turn off the backlight
2574 when using the X Window system. This also doesn't have anything to
2575 do with your VESA-compliant power-saving monitor. Further, this
2576 option doesn't work for all laptops -- it might not turn off your
2577 backlight at all, or it might print a lot of errors to the console,
2578 especially if you are using gpm.
2580 config APM_ALLOW_INTS
2581 bool "Allow interrupts during APM BIOS calls"
2583 Normally we disable external interrupts while we are making calls to
2584 the APM BIOS as a measure to lessen the effects of a badly behaving
2585 BIOS implementation. The BIOS should reenable interrupts if it
2586 needs to. Unfortunately, some BIOSes do not -- especially those in
2587 many of the newer IBM Thinkpads. If you experience hangs when you
2588 suspend, try setting this to Y. Otherwise, say N.
2592 source "drivers/cpufreq/Kconfig"
2594 source "drivers/cpuidle/Kconfig"
2596 source "drivers/idle/Kconfig"
2601 menu "Bus options (PCI etc.)"
2604 prompt "PCI access mode"
2605 depends on X86_32 && PCI
2608 On PCI systems, the BIOS can be used to detect the PCI devices and
2609 determine their configuration. However, some old PCI motherboards
2610 have BIOS bugs and may crash if this is done. Also, some embedded
2611 PCI-based systems don't have any BIOS at all. Linux can also try to
2612 detect the PCI hardware directly without using the BIOS.
2614 With this option, you can specify how Linux should detect the
2615 PCI devices. If you choose "BIOS", the BIOS will be used,
2616 if you choose "Direct", the BIOS won't be used, and if you
2617 choose "MMConfig", then PCI Express MMCONFIG will be used.
2618 If you choose "Any", the kernel will try MMCONFIG, then the
2619 direct access method and falls back to the BIOS if that doesn't
2620 work. If unsure, go with the default, which is "Any".
2625 config PCI_GOMMCONFIG
2642 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2644 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2647 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2650 bool "Support mmconfig PCI config space access" if X86_64
2652 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2653 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2657 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2661 depends on PCI && XEN
2663 config MMCONF_FAM10H
2665 depends on X86_64 && PCI_MMCONFIG && ACPI
2667 config PCI_CNB20LE_QUIRK
2668 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2671 Read the PCI windows out of the CNB20LE host bridge. This allows
2672 PCI hotplug to work on systems with the CNB20LE chipset which do
2675 There's no public spec for this chipset, and this functionality
2676 is known to be incomplete.
2678 You should say N unless you know you need this.
2681 bool "ISA bus support on modern systems" if EXPERT
2683 Expose ISA bus device drivers and options available for selection and
2684 configuration. Enable this option if your target machine has an ISA
2685 bus. ISA is an older system, displaced by PCI and newer bus
2686 architectures -- if your target machine is modern, it probably does
2687 not have an ISA bus.
2691 # x86_64 have no ISA slots, but can have ISA-style DMA.
2693 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2696 Enables ISA-style DMA support for devices requiring such controllers.
2704 Find out whether you have ISA slots on your motherboard. ISA is the
2705 name of a bus system, i.e. the way the CPU talks to the other stuff
2706 inside your box. Other bus systems are PCI, EISA, MicroChannel
2707 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2708 newer boards don't support it. If you have ISA, say Y, otherwise N.
2711 tristate "NatSemi SCx200 support"
2713 This provides basic support for National Semiconductor's
2714 (now AMD's) Geode processors. The driver probes for the
2715 PCI-IDs of several on-chip devices, so its a good dependency
2716 for other scx200_* drivers.
2718 If compiled as a module, the driver is named scx200.
2720 config SCx200HR_TIMER
2721 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2725 This driver provides a clocksource built upon the on-chip
2726 27MHz high-resolution timer. Its also a workaround for
2727 NSC Geode SC-1100's buggy TSC, which loses time when the
2728 processor goes idle (as is done by the scheduler). The
2729 other workaround is idle=poll boot option.
2732 bool "One Laptop Per Child support"
2740 Add support for detecting the unique features of the OLPC
2744 bool "OLPC XO-1 Power Management"
2745 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2747 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2750 bool "OLPC XO-1 Real Time Clock"
2751 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2753 Add support for the XO-1 real time clock, which can be used as a
2754 programmable wakeup source.
2757 bool "OLPC XO-1 SCI extras"
2758 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2762 Add support for SCI-based features of the OLPC XO-1 laptop:
2763 - EC-driven system wakeups
2767 - AC adapter status updates
2768 - Battery status updates
2770 config OLPC_XO15_SCI
2771 bool "OLPC XO-1.5 SCI extras"
2772 depends on OLPC && ACPI
2775 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2776 - EC-driven system wakeups
2777 - AC adapter status updates
2778 - Battery status updates
2781 bool "PCEngines ALIX System Support (LED setup)"
2784 This option enables system support for the PCEngines ALIX.
2785 At present this just sets up LEDs for GPIO control on
2786 ALIX2/3/6 boards. However, other system specific setup should
2789 Note: You must still enable the drivers for GPIO and LED support
2790 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2792 Note: You have to set alix.force=1 for boards with Award BIOS.
2795 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2798 This option enables system support for the Soekris Engineering net5501.
2801 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2805 This option enables system support for the Traverse Technologies GEOS.
2808 bool "Technologic Systems TS-5500 platform support"
2810 select CHECK_SIGNATURE
2814 This option enables system support for the Technologic Systems TS-5500.
2820 depends on CPU_SUP_AMD && PCI
2825 menu "Binary Emulations"
2827 config IA32_EMULATION
2828 bool "IA32 Emulation"
2830 select ARCH_WANT_OLD_COMPAT_IPC
2832 select COMPAT_OLD_SIGACTION
2834 Include code to run legacy 32-bit programs under a
2835 64-bit kernel. You should likely turn this on, unless you're
2836 100% sure that you don't have any 32-bit programs left.
2839 tristate "IA32 a.out support"
2840 depends on IA32_EMULATION
2843 Support old a.out binaries in the 32bit emulation.
2846 bool "x32 ABI for 64-bit mode"
2849 Include code to run binaries for the x32 native 32-bit ABI
2850 for 64-bit processors. An x32 process gets access to the
2851 full 64-bit register file and wide data path while leaving
2852 pointers at 32 bits for smaller memory footprint.
2854 You will need a recent binutils (2.22 or later) with
2855 elf32_x86_64 support enabled to compile a kernel with this
2860 depends on IA32_EMULATION || X86_32
2862 select OLD_SIGSUSPEND3
2866 depends on IA32_EMULATION || X86_X32
2869 config COMPAT_FOR_U64_ALIGNMENT
2872 config SYSVIPC_COMPAT
2880 config HAVE_ATOMIC_IOMAP
2884 source "arch/x86/kvm/Kconfig"
2886 source "arch/x86/Kconfig.assembler"