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_PAGE_TABLE_CHECK if X86_64
108 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
109 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
110 select ARCH_SUPPORTS_LTO_CLANG
111 select ARCH_SUPPORTS_LTO_CLANG_THIN
112 select ARCH_USE_BUILTIN_BSWAP
113 select ARCH_USE_MEMTEST
114 select ARCH_USE_QUEUED_RWLOCKS
115 select ARCH_USE_QUEUED_SPINLOCKS
116 select ARCH_USE_SYM_ANNOTATIONS
117 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
118 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
119 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
120 select ARCH_WANTS_NO_INSTR
121 select ARCH_WANT_HUGE_PMD_SHARE
122 select ARCH_WANT_LD_ORPHAN_WARN
123 select ARCH_WANTS_THP_SWAP if X86_64
124 select ARCH_HAS_PARANOID_L1D_FLUSH
125 select BUILDTIME_TABLE_SORT
127 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
128 select CLOCKSOURCE_WATCHDOG
129 select DCACHE_WORD_ACCESS
130 select DYNAMIC_SIGFRAME
131 select EDAC_ATOMIC_SCRUB
133 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
134 select GENERIC_CLOCKEVENTS_MIN_ADJUST
135 select GENERIC_CMOS_UPDATE
136 select GENERIC_CPU_AUTOPROBE
137 select GENERIC_CPU_VULNERABILITIES
138 select GENERIC_EARLY_IOREMAP
140 select GENERIC_FIND_FIRST_BIT
142 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
143 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
144 select GENERIC_IRQ_MIGRATION if SMP
145 select GENERIC_IRQ_PROBE
146 select GENERIC_IRQ_RESERVATION_MODE
147 select GENERIC_IRQ_SHOW
148 select GENERIC_PENDING_IRQ if SMP
149 select GENERIC_PTDUMP
150 select GENERIC_SMP_IDLE_THREAD
151 select GENERIC_TIME_VSYSCALL
152 select GENERIC_GETTIMEOFDAY
153 select GENERIC_VDSO_TIME_NS
154 select GUP_GET_PTE_LOW_HIGH if X86_PAE
155 select HARDIRQS_SW_RESEND
156 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
157 select HAVE_ACPI_APEI if ACPI
158 select HAVE_ACPI_APEI_NMI if ACPI
159 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
160 select HAVE_ARCH_AUDITSYSCALL
161 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
162 select HAVE_ARCH_JUMP_LABEL
163 select HAVE_ARCH_JUMP_LABEL_RELATIVE
164 select HAVE_ARCH_KASAN if X86_64
165 select HAVE_ARCH_KASAN_VMALLOC if X86_64
166 select HAVE_ARCH_KFENCE
167 select HAVE_ARCH_KGDB
168 select HAVE_ARCH_MMAP_RND_BITS if MMU
169 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
170 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
171 select HAVE_ARCH_PREL32_RELOCATIONS
172 select HAVE_ARCH_SECCOMP_FILTER
173 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
174 select HAVE_ARCH_STACKLEAK
175 select HAVE_ARCH_TRACEHOOK
176 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
177 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
178 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
179 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
180 select HAVE_ARCH_VMAP_STACK if X86_64
181 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
182 select HAVE_ARCH_WITHIN_STACK_FRAMES
183 select HAVE_ASM_MODVERSIONS
184 select HAVE_CMPXCHG_DOUBLE
185 select HAVE_CMPXCHG_LOCAL
186 select HAVE_CONTEXT_TRACKING if X86_64
187 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
188 select HAVE_C_RECORDMCOUNT
189 select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION
190 select HAVE_DEBUG_KMEMLEAK
191 select HAVE_DMA_CONTIGUOUS
192 select HAVE_DYNAMIC_FTRACE
193 select HAVE_DYNAMIC_FTRACE_WITH_REGS
194 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
195 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
196 select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
197 select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
199 select HAVE_EFFICIENT_UNALIGNED_ACCESS
201 select HAVE_EXIT_THREAD
203 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
204 select HAVE_FTRACE_MCOUNT_RECORD
205 select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
206 select HAVE_FUNCTION_TRACER
207 select HAVE_GCC_PLUGINS
208 select HAVE_HW_BREAKPOINT
209 select HAVE_IOREMAP_PROT
210 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
211 select HAVE_IRQ_TIME_ACCOUNTING
212 select HAVE_KERNEL_BZIP2
213 select HAVE_KERNEL_GZIP
214 select HAVE_KERNEL_LZ4
215 select HAVE_KERNEL_LZMA
216 select HAVE_KERNEL_LZO
217 select HAVE_KERNEL_XZ
218 select HAVE_KERNEL_ZSTD
220 select HAVE_KPROBES_ON_FTRACE
221 select HAVE_FUNCTION_ERROR_INJECTION
222 select HAVE_KRETPROBES
224 select HAVE_LIVEPATCH if X86_64
225 select HAVE_MIXED_BREAKPOINTS_REGS
226 select HAVE_MOD_ARCH_SPECIFIC
230 select HAVE_OPTPROBES
231 select HAVE_PCSPKR_PLATFORM
232 select HAVE_PERF_EVENTS
233 select HAVE_PERF_EVENTS_NMI
234 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
236 select HAVE_PERF_REGS
237 select HAVE_PERF_USER_STACK_DUMP
238 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
239 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
240 select HAVE_REGS_AND_STACK_ACCESS_API
241 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
242 select HAVE_FUNCTION_ARG_ACCESS_API
243 select HAVE_SOFTIRQ_ON_OWN_STACK
244 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
245 select HAVE_STACK_VALIDATION if X86_64
246 select HAVE_STATIC_CALL
247 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
248 select HAVE_PREEMPT_DYNAMIC
250 select HAVE_SYSCALL_TRACEPOINTS
251 select HAVE_UNSTABLE_SCHED_CLOCK
252 select HAVE_USER_RETURN_NOTIFIER
253 select HAVE_GENERIC_VDSO
254 select HOTPLUG_SMT if SMP
255 select IRQ_FORCED_THREADING
256 select NEED_SG_DMA_LENGTH
257 select PCI_DOMAINS if PCI
258 select PCI_LOCKLESS_CONFIG if PCI
261 select RTC_MC146818_LIB
264 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
265 select SYSCTL_EXCEPTION_TRACE
266 select THREAD_INFO_IN_TASK
267 select TRACE_IRQFLAGS_SUPPORT
268 select USER_STACKTRACE_SUPPORT
270 select HAVE_ARCH_KCSAN if X86_64
271 select X86_FEATURE_NAMES if PROC_FS
272 select PROC_PID_ARCH_STATUS if PROC_FS
273 select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
274 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
276 config INSTRUCTION_DECODER
278 depends on KPROBES || PERF_EVENTS || UPROBES
282 default "elf32-i386" if X86_32
283 default "elf64-x86-64" if X86_64
285 config LOCKDEP_SUPPORT
288 config STACKTRACE_SUPPORT
294 config ARCH_MMAP_RND_BITS_MIN
298 config ARCH_MMAP_RND_BITS_MAX
302 config ARCH_MMAP_RND_COMPAT_BITS_MIN
305 config ARCH_MMAP_RND_COMPAT_BITS_MAX
311 config GENERIC_ISA_DMA
313 depends on ISA_DMA_API
318 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
320 config GENERIC_BUG_RELATIVE_POINTERS
323 config ARCH_MAY_HAVE_PC_FDC
325 depends on ISA_DMA_API
327 config GENERIC_CALIBRATE_DELAY
330 config ARCH_HAS_CPU_RELAX
333 config ARCH_HAS_FILTER_PGPROT
336 config HAVE_SETUP_PER_CPU_AREA
339 config NEED_PER_CPU_EMBED_FIRST_CHUNK
342 config NEED_PER_CPU_PAGE_FIRST_CHUNK
345 config ARCH_HIBERNATION_POSSIBLE
350 default 1024 if X86_64
353 config ARCH_SUSPEND_POSSIBLE
356 config ARCH_WANT_GENERAL_HUGETLB
362 config KASAN_SHADOW_OFFSET
365 default 0xdffffc0000000000
367 config HAVE_INTEL_TXT
369 depends on INTEL_IOMMU && ACPI
373 depends on X86_32 && SMP
377 depends on X86_64 && SMP
379 config ARCH_SUPPORTS_UPROBES
382 config FIX_EARLYCON_MEM
385 config DYNAMIC_PHYSICAL_MASK
388 config PGTABLE_LEVELS
390 default 5 if X86_5LEVEL
395 config CC_HAS_SANE_STACKPROTECTOR
397 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
398 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
400 We have to make sure stack protector is unconditionally disabled if
401 the compiler produces broken code or if it does not let us control
402 the segment on 32-bit kernels.
404 menu "Processor type and features"
407 bool "Symmetric multi-processing support"
409 This enables support for systems with more than one CPU. If you have
410 a system with only one CPU, say N. If you have a system with more
413 If you say N here, the kernel will run on uni- and multiprocessor
414 machines, but will use only one CPU of a multiprocessor machine. If
415 you say Y here, the kernel will run on many, but not all,
416 uniprocessor machines. On a uniprocessor machine, the kernel
417 will run faster if you say N here.
419 Note that if you say Y here and choose architecture "586" or
420 "Pentium" under "Processor family", the kernel will not work on 486
421 architectures. Similarly, multiprocessor kernels for the "PPro"
422 architecture may not work on all Pentium based boards.
424 People using multiprocessor machines who say Y here should also say
425 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
426 Management" code will be disabled if you say Y here.
428 See also <file:Documentation/x86/i386/IO-APIC.rst>,
429 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
430 <http://www.tldp.org/docs.html#howto>.
432 If you don't know what to do here, say N.
434 config X86_FEATURE_NAMES
435 bool "Processor feature human-readable names" if EMBEDDED
438 This option compiles in a table of x86 feature bits and corresponding
439 names. This is required to support /proc/cpuinfo and a few kernel
440 messages. You can disable this to save space, at the expense of
441 making those few kernel messages show numeric feature bits instead.
446 bool "Support x2apic"
447 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
449 This enables x2apic support on CPUs that have this feature.
451 This allows 32-bit apic IDs (so it can support very large systems),
452 and accesses the local apic via MSRs not via mmio.
454 If you don't know what to do here, say N.
457 bool "Enable MPS table" if ACPI
459 depends on X86_LOCAL_APIC
461 For old smp systems that do not have proper acpi support. Newer systems
462 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
466 depends on X86_GOLDFISH
469 bool "Avoid speculative indirect branches in kernel"
472 Compile kernel with the retpoline compiler options to guard against
473 kernel-to-user data leaks by avoiding speculative indirect
474 branches. Requires a compiler with -mindirect-branch=thunk-extern
475 support for full protection. The kernel may run slower.
478 def_bool $(cc-option,-mharden-sls=all)
481 bool "Mitigate Straight-Line-Speculation"
482 depends on CC_HAS_SLS && X86_64
485 Compile the kernel with straight-line-speculation options to guard
486 against straight line speculation. The kernel image might be slightly
489 config X86_CPU_RESCTRL
490 bool "x86 CPU resource control support"
491 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
493 select PROC_CPU_RESCTRL if PROC_FS
495 Enable x86 CPU resource control support.
497 Provide support for the allocation and monitoring of system resources
500 Intel calls this Intel Resource Director Technology
501 (Intel(R) RDT). More information about RDT can be found in the
502 Intel x86 Architecture Software Developer Manual.
504 AMD calls this AMD Platform Quality of Service (AMD QoS).
505 More information about AMD QoS can be found in the AMD64 Technology
506 Platform Quality of Service Extensions manual.
512 bool "Support for big SMP systems with more than 8 CPUs"
515 This option is needed for the systems that have more than 8 CPUs.
517 config X86_EXTENDED_PLATFORM
518 bool "Support for extended (non-PC) x86 platforms"
521 If you disable this option then the kernel will only support
522 standard PC platforms. (which covers the vast majority of
525 If you enable this option then you'll be able to select support
526 for the following (non-PC) 32 bit x86 platforms:
527 Goldfish (Android emulator)
530 SGI 320/540 (Visual Workstation)
531 STA2X11-based (e.g. Northville)
532 Moorestown MID devices
534 If you have one of these systems, or if you want to build a
535 generic distribution kernel, say Y here - otherwise say N.
539 config X86_EXTENDED_PLATFORM
540 bool "Support for extended (non-PC) x86 platforms"
543 If you disable this option then the kernel will only support
544 standard PC platforms. (which covers the vast majority of
547 If you enable this option then you'll be able to select support
548 for the following (non-PC) 64 bit x86 platforms:
553 If you have one of these systems, or if you want to build a
554 generic distribution kernel, say Y here - otherwise say N.
556 # This is an alphabetically sorted list of 64 bit extended platforms
557 # Please maintain the alphabetic order if and when there are additions
559 bool "Numascale NumaChip"
561 depends on X86_EXTENDED_PLATFORM
564 depends on X86_X2APIC
565 depends on PCI_MMCONFIG
567 Adds support for Numascale NumaChip large-SMP systems. Needed to
568 enable more than ~168 cores.
569 If you don't have one of these, you should say N here.
573 select HYPERVISOR_GUEST
575 depends on X86_64 && PCI
576 depends on X86_EXTENDED_PLATFORM
579 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
580 supposed to run on these EM64T-based machines. Only choose this option
581 if you have one of these machines.
584 bool "SGI Ultraviolet"
586 depends on X86_EXTENDED_PLATFORM
589 depends on KEXEC_CORE
590 depends on X86_X2APIC
593 This option is needed in order to support SGI Ultraviolet systems.
594 If you don't have one of these, you should say N here.
596 # Following is an alphabetically sorted list of 32 bit extended platforms
597 # Please maintain the alphabetic order if and when there are additions
600 bool "Goldfish (Virtual Platform)"
601 depends on X86_EXTENDED_PLATFORM
603 Enable support for the Goldfish virtual platform used primarily
604 for Android development. Unless you are building for the Android
605 Goldfish emulator say N here.
608 bool "CE4100 TV platform"
610 depends on PCI_GODIRECT
611 depends on X86_IO_APIC
613 depends on X86_EXTENDED_PLATFORM
614 select X86_REBOOTFIXUPS
616 select OF_EARLY_FLATTREE
618 Select for the Intel CE media processor (CE4100) SOC.
619 This option compiles in support for the CE4100 SOC for settop
620 boxes and media devices.
623 bool "Intel MID platform support"
624 depends on X86_EXTENDED_PLATFORM
625 depends on X86_PLATFORM_DEVICES
627 depends on X86_64 || (PCI_GOANY && X86_32)
628 depends on X86_IO_APIC
633 Select to build a kernel capable of supporting Intel MID (Mobile
634 Internet Device) platform systems which do not have the PCI legacy
635 interfaces. If you are building for a PC class system say N here.
637 Intel MID platforms are based on an Intel processor and chipset which
638 consume less power than most of the x86 derivatives.
640 config X86_INTEL_QUARK
641 bool "Intel Quark platform support"
643 depends on X86_EXTENDED_PLATFORM
644 depends on X86_PLATFORM_DEVICES
648 depends on X86_IO_APIC
653 Select to include support for Quark X1000 SoC.
654 Say Y here if you have a Quark based system such as the Arduino
655 compatible Intel Galileo.
657 config X86_INTEL_LPSS
658 bool "Intel Low Power Subsystem Support"
659 depends on X86 && ACPI && PCI
664 Select to build support for Intel Low Power Subsystem such as
665 found on Intel Lynxpoint PCH. Selecting this option enables
666 things like clock tree (common clock framework) and pincontrol
667 which are needed by the LPSS peripheral drivers.
669 config X86_AMD_PLATFORM_DEVICE
670 bool "AMD ACPI2Platform devices support"
675 Select to interpret AMD specific ACPI device to platform device
676 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
677 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
678 implemented under PINCTRL subsystem.
681 tristate "Intel SoC IOSF Sideband support for SoC platforms"
684 This option enables sideband register access support for Intel SoC
685 platforms. On these platforms the IOSF sideband is used in lieu of
686 MSR's for some register accesses, mostly but not limited to thermal
687 and power. Drivers may query the availability of this device to
688 determine if they need the sideband in order to work on these
689 platforms. The sideband is available on the following SoC products.
690 This list is not meant to be exclusive.
695 You should say Y if you are running a kernel on one of these SoC's.
697 config IOSF_MBI_DEBUG
698 bool "Enable IOSF sideband access through debugfs"
699 depends on IOSF_MBI && DEBUG_FS
701 Select this option to expose the IOSF sideband access registers (MCR,
702 MDR, MCRX) through debugfs to write and read register information from
703 different units on the SoC. This is most useful for obtaining device
704 state information for debug and analysis. As this is a general access
705 mechanism, users of this option would have specific knowledge of the
706 device they want to access.
708 If you don't require the option or are in doubt, say N.
711 bool "RDC R-321x SoC"
713 depends on X86_EXTENDED_PLATFORM
715 select X86_REBOOTFIXUPS
717 This option is needed for RDC R-321x system-on-chip, also known
719 If you don't have one of these chips, you should say N here.
721 config X86_32_NON_STANDARD
722 bool "Support non-standard 32-bit SMP architectures"
723 depends on X86_32 && SMP
724 depends on X86_EXTENDED_PLATFORM
726 This option compiles in the bigsmp and STA2X11 default
727 subarchitectures. It is intended for a generic binary
728 kernel. If you select them all, kernel will probe it one by
729 one and will fallback to default.
731 # Alphabetically sorted list of Non standard 32 bit platforms
733 config X86_SUPPORTS_MEMORY_FAILURE
735 # MCE code calls memory_failure():
737 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
738 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
739 depends on X86_64 || !SPARSEMEM
740 select ARCH_SUPPORTS_MEMORY_FAILURE
743 bool "STA2X11 Companion Chip Support"
744 depends on X86_32_NON_STANDARD && PCI
749 This adds support for boards based on the STA2X11 IO-Hub,
750 a.k.a. "ConneXt". The chip is used in place of the standard
751 PC chipset, so all "standard" peripherals are missing. If this
752 option is selected the kernel will still be able to boot on
753 standard PC machines.
756 tristate "Eurobraille/Iris poweroff module"
759 The Iris machines from EuroBraille do not have APM or ACPI support
760 to shut themselves down properly. A special I/O sequence is
761 needed to do so, which is what this module does at
764 This is only for Iris machines from EuroBraille.
768 config SCHED_OMIT_FRAME_POINTER
770 prompt "Single-depth WCHAN output"
773 Calculate simpler /proc/<PID>/wchan values. If this option
774 is disabled then wchan values will recurse back to the
775 caller function. This provides more accurate wchan values,
776 at the expense of slightly more scheduling overhead.
778 If in doubt, say "Y".
780 menuconfig HYPERVISOR_GUEST
781 bool "Linux guest support"
783 Say Y here to enable options for running Linux under various hyper-
784 visors. This option enables basic hypervisor detection and platform
787 If you say N, all options in this submenu will be skipped and
788 disabled, and Linux guest support won't be built in.
793 bool "Enable paravirtualization code"
794 depends on HAVE_STATIC_CALL
796 This changes the kernel so it can modify itself when it is run
797 under a hypervisor, potentially improving performance significantly
798 over full virtualization. However, when run without a hypervisor
799 the kernel is theoretically slower and slightly larger.
804 config PARAVIRT_DEBUG
805 bool "paravirt-ops debugging"
806 depends on PARAVIRT && DEBUG_KERNEL
808 Enable to debug paravirt_ops internals. Specifically, BUG if
809 a paravirt_op is missing when it is called.
811 config PARAVIRT_SPINLOCKS
812 bool "Paravirtualization layer for spinlocks"
813 depends on PARAVIRT && SMP
815 Paravirtualized spinlocks allow a pvops backend to replace the
816 spinlock implementation with something virtualization-friendly
817 (for example, block the virtual CPU rather than spinning).
819 It has a minimal impact on native kernels and gives a nice performance
820 benefit on paravirtualized KVM / Xen kernels.
822 If you are unsure how to answer this question, answer Y.
824 config X86_HV_CALLBACK_VECTOR
827 source "arch/x86/xen/Kconfig"
830 bool "KVM Guest support (including kvmclock)"
832 select PARAVIRT_CLOCK
833 select ARCH_CPUIDLE_HALTPOLL
834 select X86_HV_CALLBACK_VECTOR
837 This option enables various optimizations for running under the KVM
838 hypervisor. It includes a paravirtualized clock, so that instead
839 of relying on a PIT (or probably other) emulation by the
840 underlying device model, the host provides the guest with
841 timing infrastructure such as time of day, and system time
843 config ARCH_CPUIDLE_HALTPOLL
845 prompt "Disable host haltpoll when loading haltpoll driver"
847 If virtualized under KVM, disable host haltpoll.
850 bool "Support for running PVH guests"
852 This option enables the PVH entry point for guest virtual machines
853 as specified in the x86/HVM direct boot ABI.
855 config PARAVIRT_TIME_ACCOUNTING
856 bool "Paravirtual steal time accounting"
859 Select this option to enable fine granularity task steal time
860 accounting. Time spent executing other tasks in parallel with
861 the current vCPU is discounted from the vCPU power. To account for
862 that, there can be a small performance impact.
864 If in doubt, say N here.
866 config PARAVIRT_CLOCK
869 config JAILHOUSE_GUEST
870 bool "Jailhouse non-root cell support"
871 depends on X86_64 && PCI
874 This option allows to run Linux as guest in a Jailhouse non-root
875 cell. You can leave this option disabled if you only want to start
876 Jailhouse and run Linux afterwards in the root cell.
879 bool "ACRN Guest support"
881 select X86_HV_CALLBACK_VECTOR
883 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
884 a flexible, lightweight reference open-source hypervisor, built with
885 real-time and safety-criticality in mind. It is built for embedded
886 IOT with small footprint and real-time features. More details can be
887 found in https://projectacrn.org/.
889 endif #HYPERVISOR_GUEST
891 source "arch/x86/Kconfig.cpu"
895 prompt "HPET Timer Support" if X86_32
897 Use the IA-PC HPET (High Precision Event Timer) to manage
898 time in preference to the PIT and RTC, if a HPET is
900 HPET is the next generation timer replacing legacy 8254s.
901 The HPET provides a stable time base on SMP
902 systems, unlike the TSC, but it is more expensive to access,
903 as it is off-chip. The interface used is documented
904 in the HPET spec, revision 1.
906 You can safely choose Y here. However, HPET will only be
907 activated if the platform and the BIOS support this feature.
908 Otherwise the 8254 will be used for timing services.
910 Choose N to continue using the legacy 8254 timer.
912 config HPET_EMULATE_RTC
914 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
916 # Mark as expert because too many people got it wrong.
917 # The code disables itself when not needed.
920 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
921 bool "Enable DMI scanning" if EXPERT
923 Enabled scanning of DMI to identify machine quirks. Say Y
924 here unless you have verified that your setup is not
925 affected by entries in the DMI blacklist. Required by PNP
929 bool "Old AMD GART IOMMU support"
933 depends on X86_64 && PCI && AMD_NB
935 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
936 GART based hardware IOMMUs.
938 The GART supports full DMA access for devices with 32-bit access
939 limitations, on systems with more than 3 GB. This is usually needed
940 for USB, sound, many IDE/SATA chipsets and some other devices.
942 Newer systems typically have a modern AMD IOMMU, supported via
943 the CONFIG_AMD_IOMMU=y config option.
945 In normal configurations this driver is only active when needed:
946 there's more than 3 GB of memory and the system contains a
947 32-bit limited device.
952 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
953 depends on X86_64 && SMP && DEBUG_KERNEL
954 select CPUMASK_OFFSTACK
956 Enable maximum number of CPUS and NUMA Nodes for this architecture.
960 # The maximum number of CPUs supported:
962 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
963 # and which can be configured interactively in the
964 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
966 # The ranges are different on 32-bit and 64-bit kernels, depending on
967 # hardware capabilities and scalability features of the kernel.
969 # ( If MAXSMP is enabled we just use the highest possible value and disable
970 # interactive configuration. )
973 config NR_CPUS_RANGE_BEGIN
975 default NR_CPUS_RANGE_END if MAXSMP
979 config NR_CPUS_RANGE_END
982 default 64 if SMP && X86_BIGSMP
983 default 8 if SMP && !X86_BIGSMP
986 config NR_CPUS_RANGE_END
989 default 8192 if SMP && CPUMASK_OFFSTACK
990 default 512 if SMP && !CPUMASK_OFFSTACK
993 config NR_CPUS_DEFAULT
996 default 32 if X86_BIGSMP
1000 config NR_CPUS_DEFAULT
1003 default 8192 if MAXSMP
1008 int "Maximum number of CPUs" if SMP && !MAXSMP
1009 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1010 default NR_CPUS_DEFAULT
1012 This allows you to specify the maximum number of CPUs which this
1013 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1014 supported value is 8192, otherwise the maximum value is 512. The
1015 minimum value which makes sense is 2.
1017 This is purely to save memory: each supported CPU adds about 8KB
1018 to the kernel image.
1020 config SCHED_CLUSTER
1021 bool "Cluster scheduler support"
1025 Cluster scheduler support improves the CPU scheduler's decision
1026 making when dealing with machines that have clusters of CPUs.
1027 Cluster usually means a couple of CPUs which are placed closely
1028 by sharing mid-level caches, last-level cache tags or internal
1036 prompt "Multi-core scheduler support"
1039 Multi-core scheduler support improves the CPU scheduler's decision
1040 making when dealing with multi-core CPU chips at a cost of slightly
1041 increased overhead in some places. If unsure say N here.
1043 config SCHED_MC_PRIO
1044 bool "CPU core priorities scheduler support"
1045 depends on SCHED_MC && CPU_SUP_INTEL
1046 select X86_INTEL_PSTATE
1050 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1051 core ordering determined at manufacturing time, which allows
1052 certain cores to reach higher turbo frequencies (when running
1053 single threaded workloads) than others.
1055 Enabling this kernel feature teaches the scheduler about
1056 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1057 scheduler's CPU selection logic accordingly, so that higher
1058 overall system performance can be achieved.
1060 This feature will have no effect on CPUs without this feature.
1062 If unsure say Y here.
1066 depends on !SMP && X86_LOCAL_APIC
1069 bool "Local APIC support on uniprocessors" if !PCI_MSI
1071 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1073 A local APIC (Advanced Programmable Interrupt Controller) is an
1074 integrated interrupt controller in the CPU. If you have a single-CPU
1075 system which has a processor with a local APIC, you can say Y here to
1076 enable and use it. If you say Y here even though your machine doesn't
1077 have a local APIC, then the kernel will still run with no slowdown at
1078 all. The local APIC supports CPU-generated self-interrupts (timer,
1079 performance counters), and the NMI watchdog which detects hard
1082 config X86_UP_IOAPIC
1083 bool "IO-APIC support on uniprocessors"
1084 depends on X86_UP_APIC
1086 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1087 SMP-capable replacement for PC-style interrupt controllers. Most
1088 SMP systems and many recent uniprocessor systems have one.
1090 If you have a single-CPU system with an IO-APIC, you can say Y here
1091 to use it. If you say Y here even though your machine doesn't have
1092 an IO-APIC, then the kernel will still run with no slowdown at all.
1094 config X86_LOCAL_APIC
1096 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1097 select IRQ_DOMAIN_HIERARCHY
1098 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1102 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1104 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1105 bool "Reroute for broken boot IRQs"
1106 depends on X86_IO_APIC
1108 This option enables a workaround that fixes a source of
1109 spurious interrupts. This is recommended when threaded
1110 interrupt handling is used on systems where the generation of
1111 superfluous "boot interrupts" cannot be disabled.
1113 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1114 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1115 kernel does during interrupt handling). On chipsets where this
1116 boot IRQ generation cannot be disabled, this workaround keeps
1117 the original IRQ line masked so that only the equivalent "boot
1118 IRQ" is delivered to the CPUs. The workaround also tells the
1119 kernel to set up the IRQ handler on the boot IRQ line. In this
1120 way only one interrupt is delivered to the kernel. Otherwise
1121 the spurious second interrupt may cause the kernel to bring
1122 down (vital) interrupt lines.
1124 Only affects "broken" chipsets. Interrupt sharing may be
1125 increased on these systems.
1128 bool "Machine Check / overheating reporting"
1129 select GENERIC_ALLOCATOR
1132 Machine Check support allows the processor to notify the
1133 kernel if it detects a problem (e.g. overheating, data corruption).
1134 The action the kernel takes depends on the severity of the problem,
1135 ranging from warning messages to halting the machine.
1137 config X86_MCELOG_LEGACY
1138 bool "Support for deprecated /dev/mcelog character device"
1141 Enable support for /dev/mcelog which is needed by the old mcelog
1142 userspace logging daemon. Consider switching to the new generation
1145 config X86_MCE_INTEL
1147 prompt "Intel MCE features"
1148 depends on X86_MCE && X86_LOCAL_APIC
1150 Additional support for intel specific MCE features such as
1151 the thermal monitor.
1155 prompt "AMD MCE features"
1156 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1158 Additional support for AMD specific MCE features such as
1159 the DRAM Error Threshold.
1161 config X86_ANCIENT_MCE
1162 bool "Support for old Pentium 5 / WinChip machine checks"
1163 depends on X86_32 && X86_MCE
1165 Include support for machine check handling on old Pentium 5 or WinChip
1166 systems. These typically need to be enabled explicitly on the command
1169 config X86_MCE_THRESHOLD
1170 depends on X86_MCE_AMD || X86_MCE_INTEL
1173 config X86_MCE_INJECT
1174 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1175 tristate "Machine check injector support"
1177 Provide support for injecting machine checks for testing purposes.
1178 If you don't know what a machine check is and you don't do kernel
1179 QA it is safe to say n.
1181 source "arch/x86/events/Kconfig"
1183 config X86_LEGACY_VM86
1184 bool "Legacy VM86 support"
1187 This option allows user programs to put the CPU into V8086
1188 mode, which is an 80286-era approximation of 16-bit real mode.
1190 Some very old versions of X and/or vbetool require this option
1191 for user mode setting. Similarly, DOSEMU will use it if
1192 available to accelerate real mode DOS programs. However, any
1193 recent version of DOSEMU, X, or vbetool should be fully
1194 functional even without kernel VM86 support, as they will all
1195 fall back to software emulation. Nevertheless, if you are using
1196 a 16-bit DOS program where 16-bit performance matters, vm86
1197 mode might be faster than emulation and you might want to
1200 Note that any app that works on a 64-bit kernel is unlikely to
1201 need this option, as 64-bit kernels don't, and can't, support
1202 V8086 mode. This option is also unrelated to 16-bit protected
1203 mode and is not needed to run most 16-bit programs under Wine.
1205 Enabling this option increases the complexity of the kernel
1206 and slows down exception handling a tiny bit.
1208 If unsure, say N here.
1212 default X86_LEGACY_VM86
1215 bool "Enable support for 16-bit segments" if EXPERT
1217 depends on MODIFY_LDT_SYSCALL
1219 This option is required by programs like Wine to run 16-bit
1220 protected mode legacy code on x86 processors. Disabling
1221 this option saves about 300 bytes on i386, or around 6K text
1222 plus 16K runtime memory on x86-64,
1226 depends on X86_16BIT && X86_32
1230 depends on X86_16BIT && X86_64
1232 config X86_VSYSCALL_EMULATION
1233 bool "Enable vsyscall emulation" if EXPERT
1237 This enables emulation of the legacy vsyscall page. Disabling
1238 it is roughly equivalent to booting with vsyscall=none, except
1239 that it will also disable the helpful warning if a program
1240 tries to use a vsyscall. With this option set to N, offending
1241 programs will just segfault, citing addresses of the form
1244 This option is required by many programs built before 2013, and
1245 care should be used even with newer programs if set to N.
1247 Disabling this option saves about 7K of kernel size and
1248 possibly 4K of additional runtime pagetable memory.
1250 config X86_IOPL_IOPERM
1251 bool "IOPERM and IOPL Emulation"
1254 This enables the ioperm() and iopl() syscalls which are necessary
1255 for legacy applications.
1257 Legacy IOPL support is an overbroad mechanism which allows user
1258 space aside of accessing all 65536 I/O ports also to disable
1259 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1260 capabilities and permission from potentially active security
1263 The emulation restricts the functionality of the syscall to
1264 only allowing the full range I/O port access, but prevents the
1265 ability to disable interrupts from user space which would be
1266 granted if the hardware IOPL mechanism would be used.
1269 tristate "Toshiba Laptop support"
1272 This adds a driver to safely access the System Management Mode of
1273 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1274 not work on models with a Phoenix BIOS. The System Management Mode
1275 is used to set the BIOS and power saving options on Toshiba portables.
1277 For information on utilities to make use of this driver see the
1278 Toshiba Linux utilities web site at:
1279 <http://www.buzzard.org.uk/toshiba/>.
1281 Say Y if you intend to run this kernel on a Toshiba portable.
1285 tristate "Dell i8k legacy laptop support"
1288 select SENSORS_DELL_SMM
1290 This option enables legacy /proc/i8k userspace interface in hwmon
1291 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1292 temperature and allows controlling fan speeds of Dell laptops via
1293 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1294 it reports also power and hotkey status. For fan speed control is
1295 needed userspace package i8kutils.
1297 Say Y if you intend to run this kernel on old Dell laptops or want to
1298 use userspace package i8kutils.
1301 config X86_REBOOTFIXUPS
1302 bool "Enable X86 board specific fixups for reboot"
1305 This enables chipset and/or board specific fixups to be done
1306 in order to get reboot to work correctly. This is only needed on
1307 some combinations of hardware and BIOS. The symptom, for which
1308 this config is intended, is when reboot ends with a stalled/hung
1311 Currently, the only fixup is for the Geode machines using
1312 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1314 Say Y if you want to enable the fixup. Currently, it's safe to
1315 enable this option even if you don't need it.
1319 bool "CPU microcode loading support"
1321 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1323 If you say Y here, you will be able to update the microcode on
1324 Intel and AMD processors. The Intel support is for the IA32 family,
1325 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1326 AMD support is for families 0x10 and later. You will obviously need
1327 the actual microcode binary data itself which is not shipped with
1330 The preferred method to load microcode from a detached initrd is described
1331 in Documentation/x86/microcode.rst. For that you need to enable
1332 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1333 initrd for microcode blobs.
1335 In addition, you can build the microcode into the kernel. For that you
1336 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1339 config MICROCODE_INTEL
1340 bool "Intel microcode loading support"
1341 depends on MICROCODE
1344 This options enables microcode patch loading support for Intel
1347 For the current Intel microcode data package go to
1348 <https://downloadcenter.intel.com> and search for
1349 'Linux Processor Microcode Data File'.
1351 config MICROCODE_AMD
1352 bool "AMD microcode loading support"
1353 depends on MICROCODE
1355 If you select this option, microcode patch loading support for AMD
1356 processors will be enabled.
1358 config MICROCODE_OLD_INTERFACE
1359 bool "Ancient loading interface (DEPRECATED)"
1361 depends on MICROCODE
1363 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1364 which was used by userspace tools like iucode_tool and microcode.ctl.
1365 It is inadequate because it runs too late to be able to properly
1366 load microcode on a machine and it needs special tools. Instead, you
1367 should've switched to the early loading method with the initrd or
1368 builtin microcode by now: Documentation/x86/microcode.rst
1371 tristate "/dev/cpu/*/msr - Model-specific register support"
1373 This device gives privileged processes access to the x86
1374 Model-Specific Registers (MSRs). It is a character device with
1375 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1376 MSR accesses are directed to a specific CPU on multi-processor
1380 tristate "/dev/cpu/*/cpuid - CPU information support"
1382 This device gives processes access to the x86 CPUID instruction to
1383 be executed on a specific processor. It is a character device
1384 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1388 prompt "High Memory Support"
1395 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1396 However, the address space of 32-bit x86 processors is only 4
1397 Gigabytes large. That means that, if you have a large amount of
1398 physical memory, not all of it can be "permanently mapped" by the
1399 kernel. The physical memory that's not permanently mapped is called
1402 If you are compiling a kernel which will never run on a machine with
1403 more than 1 Gigabyte total physical RAM, answer "off" here (default
1404 choice and suitable for most users). This will result in a "3GB/1GB"
1405 split: 3GB are mapped so that each process sees a 3GB virtual memory
1406 space and the remaining part of the 4GB virtual memory space is used
1407 by the kernel to permanently map as much physical memory as
1410 If the machine has between 1 and 4 Gigabytes physical RAM, then
1413 If more than 4 Gigabytes is used then answer "64GB" here. This
1414 selection turns Intel PAE (Physical Address Extension) mode on.
1415 PAE implements 3-level paging on IA32 processors. PAE is fully
1416 supported by Linux, PAE mode is implemented on all recent Intel
1417 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1418 then the kernel will not boot on CPUs that don't support PAE!
1420 The actual amount of total physical memory will either be
1421 auto detected or can be forced by using a kernel command line option
1422 such as "mem=256M". (Try "man bootparam" or see the documentation of
1423 your boot loader (lilo or loadlin) about how to pass options to the
1424 kernel at boot time.)
1426 If unsure, say "off".
1431 Select this if you have a 32-bit processor and between 1 and 4
1432 gigabytes of physical RAM.
1436 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1439 Select this if you have a 32-bit processor and more than 4
1440 gigabytes of physical RAM.
1445 prompt "Memory split" if EXPERT
1449 Select the desired split between kernel and user memory.
1451 If the address range available to the kernel is less than the
1452 physical memory installed, the remaining memory will be available
1453 as "high memory". Accessing high memory is a little more costly
1454 than low memory, as it needs to be mapped into the kernel first.
1455 Note that increasing the kernel address space limits the range
1456 available to user programs, making the address space there
1457 tighter. Selecting anything other than the default 3G/1G split
1458 will also likely make your kernel incompatible with binary-only
1461 If you are not absolutely sure what you are doing, leave this
1465 bool "3G/1G user/kernel split"
1466 config VMSPLIT_3G_OPT
1468 bool "3G/1G user/kernel split (for full 1G low memory)"
1470 bool "2G/2G user/kernel split"
1471 config VMSPLIT_2G_OPT
1473 bool "2G/2G user/kernel split (for full 2G low memory)"
1475 bool "1G/3G user/kernel split"
1480 default 0xB0000000 if VMSPLIT_3G_OPT
1481 default 0x80000000 if VMSPLIT_2G
1482 default 0x78000000 if VMSPLIT_2G_OPT
1483 default 0x40000000 if VMSPLIT_1G
1489 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1492 bool "PAE (Physical Address Extension) Support"
1493 depends on X86_32 && !HIGHMEM4G
1494 select PHYS_ADDR_T_64BIT
1497 PAE is required for NX support, and furthermore enables
1498 larger swapspace support for non-overcommit purposes. It
1499 has the cost of more pagetable lookup overhead, and also
1500 consumes more pagetable space per process.
1503 bool "Enable 5-level page tables support"
1505 select DYNAMIC_MEMORY_LAYOUT
1506 select SPARSEMEM_VMEMMAP
1509 5-level paging enables access to larger address space:
1510 upto 128 PiB of virtual address space and 4 PiB of
1511 physical address space.
1513 It will be supported by future Intel CPUs.
1515 A kernel with the option enabled can be booted on machines that
1516 support 4- or 5-level paging.
1518 See Documentation/x86/x86_64/5level-paging.rst for more
1523 config X86_DIRECT_GBPAGES
1527 Certain kernel features effectively disable kernel
1528 linear 1 GB mappings (even if the CPU otherwise
1529 supports them), so don't confuse the user by printing
1530 that we have them enabled.
1532 config X86_CPA_STATISTICS
1533 bool "Enable statistic for Change Page Attribute"
1536 Expose statistics about the Change Page Attribute mechanism, which
1537 helps to determine the effectiveness of preserving large and huge
1538 page mappings when mapping protections are changed.
1540 config X86_MEM_ENCRYPT
1541 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1542 select DYNAMIC_PHYSICAL_MASK
1543 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1546 config AMD_MEM_ENCRYPT
1547 bool "AMD Secure Memory Encryption (SME) support"
1548 depends on X86_64 && CPU_SUP_AMD
1549 select DMA_COHERENT_POOL
1550 select ARCH_USE_MEMREMAP_PROT
1551 select INSTRUCTION_DECODER
1552 select ARCH_HAS_CC_PLATFORM
1553 select X86_MEM_ENCRYPT
1555 Say yes to enable support for the encryption of system memory.
1556 This requires an AMD processor that supports Secure Memory
1559 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1560 bool "Activate AMD Secure Memory Encryption (SME) by default"
1561 depends on AMD_MEM_ENCRYPT
1563 Say yes to have system memory encrypted by default if running on
1564 an AMD processor that supports Secure Memory Encryption (SME).
1566 If set to Y, then the encryption of system memory can be
1567 deactivated with the mem_encrypt=off command line option.
1569 If set to N, then the encryption of system memory can be
1570 activated with the mem_encrypt=on command line option.
1572 # Common NUMA Features
1574 bool "NUMA Memory Allocation and Scheduler Support"
1576 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1577 default y if X86_BIGSMP
1579 Enable NUMA (Non-Uniform Memory Access) support.
1581 The kernel will try to allocate memory used by a CPU on the
1582 local memory controller of the CPU and add some more
1583 NUMA awareness to the kernel.
1585 For 64-bit this is recommended if the system is Intel Core i7
1586 (or later), AMD Opteron, or EM64T NUMA.
1588 For 32-bit this is only needed if you boot a 32-bit
1589 kernel on a 64-bit NUMA platform.
1591 Otherwise, you should say N.
1595 prompt "Old style AMD Opteron NUMA detection"
1596 depends on X86_64 && NUMA && PCI
1598 Enable AMD NUMA node topology detection. You should say Y here if
1599 you have a multi processor AMD system. This uses an old method to
1600 read the NUMA configuration directly from the builtin Northbridge
1601 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1602 which also takes priority if both are compiled in.
1604 config X86_64_ACPI_NUMA
1606 prompt "ACPI NUMA detection"
1607 depends on X86_64 && NUMA && ACPI && PCI
1610 Enable ACPI SRAT based node topology detection.
1613 bool "NUMA emulation"
1616 Enable NUMA emulation. A flat machine will be split
1617 into virtual nodes when booted with "numa=fake=N", where N is the
1618 number of nodes. This is only useful for debugging.
1621 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1623 default "10" if MAXSMP
1624 default "6" if X86_64
1628 Specify the maximum number of NUMA Nodes available on the target
1629 system. Increases memory reserved to accommodate various tables.
1631 config ARCH_FLATMEM_ENABLE
1633 depends on X86_32 && !NUMA
1635 config ARCH_SPARSEMEM_ENABLE
1637 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1638 select SPARSEMEM_STATIC if X86_32
1639 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1641 config ARCH_SPARSEMEM_DEFAULT
1642 def_bool X86_64 || (NUMA && X86_32)
1644 config ARCH_SELECT_MEMORY_MODEL
1646 depends on ARCH_SPARSEMEM_ENABLE
1648 config ARCH_MEMORY_PROBE
1649 bool "Enable sysfs memory/probe interface"
1650 depends on MEMORY_HOTPLUG
1652 This option enables a sysfs memory/probe interface for testing.
1653 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1654 If you are unsure how to answer this question, answer N.
1656 config ARCH_PROC_KCORE_TEXT
1658 depends on X86_64 && PROC_KCORE
1660 config ILLEGAL_POINTER_VALUE
1663 default 0xdead000000000000 if X86_64
1665 config X86_PMEM_LEGACY_DEVICE
1668 config X86_PMEM_LEGACY
1669 tristate "Support non-standard NVDIMMs and ADR protected memory"
1670 depends on PHYS_ADDR_T_64BIT
1672 select X86_PMEM_LEGACY_DEVICE
1673 select NUMA_KEEP_MEMINFO if NUMA
1676 Treat memory marked using the non-standard e820 type of 12 as used
1677 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1678 The kernel will offer these regions to the 'pmem' driver so
1679 they can be used for persistent storage.
1684 bool "Allocate 3rd-level pagetables from highmem"
1687 The VM uses one page table entry for each page of physical memory.
1688 For systems with a lot of RAM, this can be wasteful of precious
1689 low memory. Setting this option will put user-space page table
1690 entries in high memory.
1692 config X86_CHECK_BIOS_CORRUPTION
1693 bool "Check for low memory corruption"
1695 Periodically check for memory corruption in low memory, which
1696 is suspected to be caused by BIOS. Even when enabled in the
1697 configuration, it is disabled at runtime. Enable it by
1698 setting "memory_corruption_check=1" on the kernel command
1699 line. By default it scans the low 64k of memory every 60
1700 seconds; see the memory_corruption_check_size and
1701 memory_corruption_check_period parameters in
1702 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1704 When enabled with the default parameters, this option has
1705 almost no overhead, as it reserves a relatively small amount
1706 of memory and scans it infrequently. It both detects corruption
1707 and prevents it from affecting the running system.
1709 It is, however, intended as a diagnostic tool; if repeatable
1710 BIOS-originated corruption always affects the same memory,
1711 you can use memmap= to prevent the kernel from using that
1714 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1715 bool "Set the default setting of memory_corruption_check"
1716 depends on X86_CHECK_BIOS_CORRUPTION
1719 Set whether the default state of memory_corruption_check is
1722 config MATH_EMULATION
1724 depends on MODIFY_LDT_SYSCALL
1725 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1727 Linux can emulate a math coprocessor (used for floating point
1728 operations) if you don't have one. 486DX and Pentium processors have
1729 a math coprocessor built in, 486SX and 386 do not, unless you added
1730 a 487DX or 387, respectively. (The messages during boot time can
1731 give you some hints here ["man dmesg"].) Everyone needs either a
1732 coprocessor or this emulation.
1734 If you don't have a math coprocessor, you need to say Y here; if you
1735 say Y here even though you have a coprocessor, the coprocessor will
1736 be used nevertheless. (This behavior can be changed with the kernel
1737 command line option "no387", which comes handy if your coprocessor
1738 is broken. Try "man bootparam" or see the documentation of your boot
1739 loader (lilo or loadlin) about how to pass options to the kernel at
1740 boot time.) This means that it is a good idea to say Y here if you
1741 intend to use this kernel on different machines.
1743 More information about the internals of the Linux math coprocessor
1744 emulation can be found in <file:arch/x86/math-emu/README>.
1746 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1747 kernel, it won't hurt.
1751 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1753 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1754 the Memory Type Range Registers (MTRRs) may be used to control
1755 processor access to memory ranges. This is most useful if you have
1756 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1757 allows bus write transfers to be combined into a larger transfer
1758 before bursting over the PCI/AGP bus. This can increase performance
1759 of image write operations 2.5 times or more. Saying Y here creates a
1760 /proc/mtrr file which may be used to manipulate your processor's
1761 MTRRs. Typically the X server should use this.
1763 This code has a reasonably generic interface so that similar
1764 control registers on other processors can be easily supported
1767 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1768 Registers (ARRs) which provide a similar functionality to MTRRs. For
1769 these, the ARRs are used to emulate the MTRRs.
1770 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1771 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1772 write-combining. All of these processors are supported by this code
1773 and it makes sense to say Y here if you have one of them.
1775 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1776 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1777 can lead to all sorts of problems, so it's good to say Y here.
1779 You can safely say Y even if your machine doesn't have MTRRs, you'll
1780 just add about 9 KB to your kernel.
1782 See <file:Documentation/x86/mtrr.rst> for more information.
1784 config MTRR_SANITIZER
1786 prompt "MTRR cleanup support"
1789 Convert MTRR layout from continuous to discrete, so X drivers can
1790 add writeback entries.
1792 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1793 The largest mtrr entry size for a continuous block can be set with
1798 config MTRR_SANITIZER_ENABLE_DEFAULT
1799 int "MTRR cleanup enable value (0-1)"
1802 depends on MTRR_SANITIZER
1804 Enable mtrr cleanup default value
1806 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1807 int "MTRR cleanup spare reg num (0-7)"
1810 depends on MTRR_SANITIZER
1812 mtrr cleanup spare entries default, it can be changed via
1813 mtrr_spare_reg_nr=N on the kernel command line.
1817 prompt "x86 PAT support" if EXPERT
1820 Use PAT attributes to setup page level cache control.
1822 PATs are the modern equivalents of MTRRs and are much more
1823 flexible than MTRRs.
1825 Say N here if you see bootup problems (boot crash, boot hang,
1826 spontaneous reboots) or a non-working video driver.
1830 config ARCH_USES_PG_UNCACHED
1836 prompt "x86 architectural random number generator" if EXPERT
1838 Enable the x86 architectural RDRAND instruction
1839 (Intel Bull Mountain technology) to generate random numbers.
1840 If supported, this is a high bandwidth, cryptographically
1841 secure hardware random number generator.
1845 prompt "Supervisor Mode Access Prevention" if EXPERT
1847 Supervisor Mode Access Prevention (SMAP) is a security
1848 feature in newer Intel processors. There is a small
1849 performance cost if this enabled and turned on; there is
1850 also a small increase in the kernel size if this is enabled.
1856 prompt "User Mode Instruction Prevention" if EXPERT
1858 User Mode Instruction Prevention (UMIP) is a security feature in
1859 some x86 processors. If enabled, a general protection fault is
1860 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1861 executed in user mode. These instructions unnecessarily expose
1862 information about the hardware state.
1864 The vast majority of applications do not use these instructions.
1865 For the very few that do, software emulation is provided in
1866 specific cases in protected and virtual-8086 modes. Emulated
1869 config X86_INTEL_MEMORY_PROTECTION_KEYS
1870 prompt "Memory Protection Keys"
1872 # Note: only available in 64-bit mode
1873 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1874 select ARCH_USES_HIGH_VMA_FLAGS
1875 select ARCH_HAS_PKEYS
1877 Memory Protection Keys provides a mechanism for enforcing
1878 page-based protections, but without requiring modification of the
1879 page tables when an application changes protection domains.
1881 For details, see Documentation/core-api/protection-keys.rst
1886 prompt "TSX enable mode"
1887 depends on CPU_SUP_INTEL
1888 default X86_INTEL_TSX_MODE_OFF
1890 Intel's TSX (Transactional Synchronization Extensions) feature
1891 allows to optimize locking protocols through lock elision which
1892 can lead to a noticeable performance boost.
1894 On the other hand it has been shown that TSX can be exploited
1895 to form side channel attacks (e.g. TAA) and chances are there
1896 will be more of those attacks discovered in the future.
1898 Therefore TSX is not enabled by default (aka tsx=off). An admin
1899 might override this decision by tsx=on the command line parameter.
1900 Even with TSX enabled, the kernel will attempt to enable the best
1901 possible TAA mitigation setting depending on the microcode available
1902 for the particular machine.
1904 This option allows to set the default tsx mode between tsx=on, =off
1905 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1908 Say off if not sure, auto if TSX is in use but it should be used on safe
1909 platforms or on if TSX is in use and the security aspect of tsx is not
1912 config X86_INTEL_TSX_MODE_OFF
1915 TSX is disabled if possible - equals to tsx=off command line parameter.
1917 config X86_INTEL_TSX_MODE_ON
1920 TSX is always enabled on TSX capable HW - equals the tsx=on command
1923 config X86_INTEL_TSX_MODE_AUTO
1926 TSX is enabled on TSX capable HW that is believed to be safe against
1927 side channel attacks- equals the tsx=auto command line parameter.
1931 bool "Software Guard eXtensions (SGX)"
1932 depends on X86_64 && CPU_SUP_INTEL
1934 depends on CRYPTO_SHA256=y
1937 select NUMA_KEEP_MEMINFO if NUMA
1940 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1941 that can be used by applications to set aside private regions of code
1942 and data, referred to as enclaves. An enclave's private memory can
1943 only be accessed by code running within the enclave. Accesses from
1944 outside the enclave, including other enclaves, are disallowed by
1950 bool "EFI runtime service support"
1953 select EFI_RUNTIME_WRAPPERS
1954 select ARCH_USE_MEMREMAP_PROT
1956 This enables the kernel to use EFI runtime services that are
1957 available (such as the EFI variable services).
1959 This option is only useful on systems that have EFI firmware.
1960 In addition, you should use the latest ELILO loader available
1961 at <http://elilo.sourceforge.net> in order to take advantage
1962 of EFI runtime services. However, even with this option, the
1963 resultant kernel should continue to boot on existing non-EFI
1967 bool "EFI stub support"
1969 depends on $(cc-option,-mabi=ms) || X86_32
1972 This kernel feature allows a bzImage to be loaded directly
1973 by EFI firmware without the use of a bootloader.
1975 See Documentation/admin-guide/efi-stub.rst for more information.
1978 bool "EFI mixed-mode support"
1979 depends on EFI_STUB && X86_64
1981 Enabling this feature allows a 64-bit kernel to be booted
1982 on a 32-bit firmware, provided that your CPU supports 64-bit
1985 Note that it is not possible to boot a mixed-mode enabled
1986 kernel via the EFI boot stub - a bootloader that supports
1987 the EFI handover protocol must be used.
1991 source "kernel/Kconfig.hz"
1994 bool "kexec system call"
1997 kexec is a system call that implements the ability to shutdown your
1998 current kernel, and to start another kernel. It is like a reboot
1999 but it is independent of the system firmware. And like a reboot
2000 you can start any kernel with it, not just Linux.
2002 The name comes from the similarity to the exec system call.
2004 It is an ongoing process to be certain the hardware in a machine
2005 is properly shutdown, so do not be surprised if this code does not
2006 initially work for you. As of this writing the exact hardware
2007 interface is strongly in flux, so no good recommendation can be
2011 bool "kexec file based system call"
2016 depends on CRYPTO_SHA256=y
2018 This is new version of kexec system call. This system call is
2019 file based and takes file descriptors as system call argument
2020 for kernel and initramfs as opposed to list of segments as
2021 accepted by previous system call.
2023 config ARCH_HAS_KEXEC_PURGATORY
2027 bool "Verify kernel signature during kexec_file_load() syscall"
2028 depends on KEXEC_FILE
2031 This option makes the kexec_file_load() syscall check for a valid
2032 signature of the kernel image. The image can still be loaded without
2033 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2034 there's a signature that we can check, then it must be valid.
2036 In addition to this option, you need to enable signature
2037 verification for the corresponding kernel image type being
2038 loaded in order for this to work.
2040 config KEXEC_SIG_FORCE
2041 bool "Require a valid signature in kexec_file_load() syscall"
2042 depends on KEXEC_SIG
2044 This option makes kernel signature verification mandatory for
2045 the kexec_file_load() syscall.
2047 config KEXEC_BZIMAGE_VERIFY_SIG
2048 bool "Enable bzImage signature verification support"
2049 depends on KEXEC_SIG
2050 depends on SIGNED_PE_FILE_VERIFICATION
2051 select SYSTEM_TRUSTED_KEYRING
2053 Enable bzImage signature verification support.
2056 bool "kernel crash dumps"
2057 depends on X86_64 || (X86_32 && HIGHMEM)
2059 Generate crash dump after being started by kexec.
2060 This should be normally only set in special crash dump kernels
2061 which are loaded in the main kernel with kexec-tools into
2062 a specially reserved region and then later executed after
2063 a crash by kdump/kexec. The crash dump kernel must be compiled
2064 to a memory address not used by the main kernel or BIOS using
2065 PHYSICAL_START, or it must be built as a relocatable image
2066 (CONFIG_RELOCATABLE=y).
2067 For more details see Documentation/admin-guide/kdump/kdump.rst
2071 depends on KEXEC && HIBERNATION
2073 Jump between original kernel and kexeced kernel and invoke
2074 code in physical address mode via KEXEC
2076 config PHYSICAL_START
2077 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2080 This gives the physical address where the kernel is loaded.
2082 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2083 bzImage will decompress itself to above physical address and
2084 run from there. Otherwise, bzImage will run from the address where
2085 it has been loaded by the boot loader and will ignore above physical
2088 In normal kdump cases one does not have to set/change this option
2089 as now bzImage can be compiled as a completely relocatable image
2090 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2091 address. This option is mainly useful for the folks who don't want
2092 to use a bzImage for capturing the crash dump and want to use a
2093 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2094 to be specifically compiled to run from a specific memory area
2095 (normally a reserved region) and this option comes handy.
2097 So if you are using bzImage for capturing the crash dump,
2098 leave the value here unchanged to 0x1000000 and set
2099 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2100 for capturing the crash dump change this value to start of
2101 the reserved region. In other words, it can be set based on
2102 the "X" value as specified in the "crashkernel=YM@XM"
2103 command line boot parameter passed to the panic-ed
2104 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2105 for more details about crash dumps.
2107 Usage of bzImage for capturing the crash dump is recommended as
2108 one does not have to build two kernels. Same kernel can be used
2109 as production kernel and capture kernel. Above option should have
2110 gone away after relocatable bzImage support is introduced. But it
2111 is present because there are users out there who continue to use
2112 vmlinux for dump capture. This option should go away down the
2115 Don't change this unless you know what you are doing.
2118 bool "Build a relocatable kernel"
2121 This builds a kernel image that retains relocation information
2122 so it can be loaded someplace besides the default 1MB.
2123 The relocations tend to make the kernel binary about 10% larger,
2124 but are discarded at runtime.
2126 One use is for the kexec on panic case where the recovery kernel
2127 must live at a different physical address than the primary
2130 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2131 it has been loaded at and the compile time physical address
2132 (CONFIG_PHYSICAL_START) is used as the minimum location.
2134 config RANDOMIZE_BASE
2135 bool "Randomize the address of the kernel image (KASLR)"
2136 depends on RELOCATABLE
2139 In support of Kernel Address Space Layout Randomization (KASLR),
2140 this randomizes the physical address at which the kernel image
2141 is decompressed and the virtual address where the kernel
2142 image is mapped, as a security feature that deters exploit
2143 attempts relying on knowledge of the location of kernel
2146 On 64-bit, the kernel physical and virtual addresses are
2147 randomized separately. The physical address will be anywhere
2148 between 16MB and the top of physical memory (up to 64TB). The
2149 virtual address will be randomized from 16MB up to 1GB (9 bits
2150 of entropy). Note that this also reduces the memory space
2151 available to kernel modules from 1.5GB to 1GB.
2153 On 32-bit, the kernel physical and virtual addresses are
2154 randomized together. They will be randomized from 16MB up to
2155 512MB (8 bits of entropy).
2157 Entropy is generated using the RDRAND instruction if it is
2158 supported. If RDTSC is supported, its value is mixed into
2159 the entropy pool as well. If neither RDRAND nor RDTSC are
2160 supported, then entropy is read from the i8254 timer. The
2161 usable entropy is limited by the kernel being built using
2162 2GB addressing, and that PHYSICAL_ALIGN must be at a
2163 minimum of 2MB. As a result, only 10 bits of entropy are
2164 theoretically possible, but the implementations are further
2165 limited due to memory layouts.
2169 # Relocation on x86 needs some additional build support
2170 config X86_NEED_RELOCS
2172 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2174 config PHYSICAL_ALIGN
2175 hex "Alignment value to which kernel should be aligned"
2177 range 0x2000 0x1000000 if X86_32
2178 range 0x200000 0x1000000 if X86_64
2180 This value puts the alignment restrictions on physical address
2181 where kernel is loaded and run from. Kernel is compiled for an
2182 address which meets above alignment restriction.
2184 If bootloader loads the kernel at a non-aligned address and
2185 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2186 address aligned to above value and run from there.
2188 If bootloader loads the kernel at a non-aligned address and
2189 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2190 load address and decompress itself to the address it has been
2191 compiled for and run from there. The address for which kernel is
2192 compiled already meets above alignment restrictions. Hence the
2193 end result is that kernel runs from a physical address meeting
2194 above alignment restrictions.
2196 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2197 this value must be a multiple of 0x200000.
2199 Don't change this unless you know what you are doing.
2201 config DYNAMIC_MEMORY_LAYOUT
2204 This option makes base addresses of vmalloc and vmemmap as well as
2205 __PAGE_OFFSET movable during boot.
2207 config RANDOMIZE_MEMORY
2208 bool "Randomize the kernel memory sections"
2210 depends on RANDOMIZE_BASE
2211 select DYNAMIC_MEMORY_LAYOUT
2212 default RANDOMIZE_BASE
2214 Randomizes the base virtual address of kernel memory sections
2215 (physical memory mapping, vmalloc & vmemmap). This security feature
2216 makes exploits relying on predictable memory locations less reliable.
2218 The order of allocations remains unchanged. Entropy is generated in
2219 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2220 configuration have in average 30,000 different possible virtual
2221 addresses for each memory section.
2225 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2226 hex "Physical memory mapping padding" if EXPERT
2227 depends on RANDOMIZE_MEMORY
2228 default "0xa" if MEMORY_HOTPLUG
2230 range 0x1 0x40 if MEMORY_HOTPLUG
2233 Define the padding in terabytes added to the existing physical
2234 memory size during kernel memory randomization. It is useful
2235 for memory hotplug support but reduces the entropy available for
2236 address randomization.
2238 If unsure, leave at the default value.
2244 config BOOTPARAM_HOTPLUG_CPU0
2245 bool "Set default setting of cpu0_hotpluggable"
2246 depends on HOTPLUG_CPU
2248 Set whether default state of cpu0_hotpluggable is on or off.
2250 Say Y here to enable CPU0 hotplug by default. If this switch
2251 is turned on, there is no need to give cpu0_hotplug kernel
2252 parameter and the CPU0 hotplug feature is enabled by default.
2254 Please note: there are two known CPU0 dependencies if you want
2255 to enable the CPU0 hotplug feature either by this switch or by
2256 cpu0_hotplug kernel parameter.
2258 First, resume from hibernate or suspend always starts from CPU0.
2259 So hibernate and suspend are prevented if CPU0 is offline.
2261 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2262 offline if any interrupt can not migrate out of CPU0. There may
2263 be other CPU0 dependencies.
2265 Please make sure the dependencies are under your control before
2266 you enable this feature.
2268 Say N if you don't want to enable CPU0 hotplug feature by default.
2269 You still can enable the CPU0 hotplug feature at boot by kernel
2270 parameter cpu0_hotplug.
2272 config DEBUG_HOTPLUG_CPU0
2274 prompt "Debug CPU0 hotplug"
2275 depends on HOTPLUG_CPU
2277 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2278 soon as possible and boots up userspace with CPU0 offlined. User
2279 can online CPU0 back after boot time.
2281 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2282 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2283 compilation or giving cpu0_hotplug kernel parameter at boot.
2289 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2290 depends on COMPAT_32
2292 Certain buggy versions of glibc will crash if they are
2293 presented with a 32-bit vDSO that is not mapped at the address
2294 indicated in its segment table.
2296 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2297 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2298 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2299 the only released version with the bug, but OpenSUSE 9
2300 contains a buggy "glibc 2.3.2".
2302 The symptom of the bug is that everything crashes on startup, saying:
2303 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2305 Saying Y here changes the default value of the vdso32 boot
2306 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2307 This works around the glibc bug but hurts performance.
2309 If unsure, say N: if you are compiling your own kernel, you
2310 are unlikely to be using a buggy version of glibc.
2313 prompt "vsyscall table for legacy applications"
2315 default LEGACY_VSYSCALL_XONLY
2317 Legacy user code that does not know how to find the vDSO expects
2318 to be able to issue three syscalls by calling fixed addresses in
2319 kernel space. Since this location is not randomized with ASLR,
2320 it can be used to assist security vulnerability exploitation.
2322 This setting can be changed at boot time via the kernel command
2323 line parameter vsyscall=[emulate|xonly|none].
2325 On a system with recent enough glibc (2.14 or newer) and no
2326 static binaries, you can say None without a performance penalty
2327 to improve security.
2329 If unsure, select "Emulate execution only".
2331 config LEGACY_VSYSCALL_EMULATE
2332 bool "Full emulation"
2334 The kernel traps and emulates calls into the fixed vsyscall
2335 address mapping. This makes the mapping non-executable, but
2336 it still contains readable known contents, which could be
2337 used in certain rare security vulnerability exploits. This
2338 configuration is recommended when using legacy userspace
2339 that still uses vsyscalls along with legacy binary
2340 instrumentation tools that require code to be readable.
2342 An example of this type of legacy userspace is running
2343 Pin on an old binary that still uses vsyscalls.
2345 config LEGACY_VSYSCALL_XONLY
2346 bool "Emulate execution only"
2348 The kernel traps and emulates calls into the fixed vsyscall
2349 address mapping and does not allow reads. This
2350 configuration is recommended when userspace might use the
2351 legacy vsyscall area but support for legacy binary
2352 instrumentation of legacy code is not needed. It mitigates
2353 certain uses of the vsyscall area as an ASLR-bypassing
2356 config LEGACY_VSYSCALL_NONE
2359 There will be no vsyscall mapping at all. This will
2360 eliminate any risk of ASLR bypass due to the vsyscall
2361 fixed address mapping. Attempts to use the vsyscalls
2362 will be reported to dmesg, so that either old or
2363 malicious userspace programs can be identified.
2368 bool "Built-in kernel command line"
2370 Allow for specifying boot arguments to the kernel at
2371 build time. On some systems (e.g. embedded ones), it is
2372 necessary or convenient to provide some or all of the
2373 kernel boot arguments with the kernel itself (that is,
2374 to not rely on the boot loader to provide them.)
2376 To compile command line arguments into the kernel,
2377 set this option to 'Y', then fill in the
2378 boot arguments in CONFIG_CMDLINE.
2380 Systems with fully functional boot loaders (i.e. non-embedded)
2381 should leave this option set to 'N'.
2384 string "Built-in kernel command string"
2385 depends on CMDLINE_BOOL
2388 Enter arguments here that should be compiled into the kernel
2389 image and used at boot time. If the boot loader provides a
2390 command line at boot time, it is appended to this string to
2391 form the full kernel command line, when the system boots.
2393 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2394 change this behavior.
2396 In most cases, the command line (whether built-in or provided
2397 by the boot loader) should specify the device for the root
2400 config CMDLINE_OVERRIDE
2401 bool "Built-in command line overrides boot loader arguments"
2402 depends on CMDLINE_BOOL && CMDLINE != ""
2404 Set this option to 'Y' to have the kernel ignore the boot loader
2405 command line, and use ONLY the built-in command line.
2407 This is used to work around broken boot loaders. This should
2408 be set to 'N' under normal conditions.
2410 config MODIFY_LDT_SYSCALL
2411 bool "Enable the LDT (local descriptor table)" if EXPERT
2414 Linux can allow user programs to install a per-process x86
2415 Local Descriptor Table (LDT) using the modify_ldt(2) system
2416 call. This is required to run 16-bit or segmented code such as
2417 DOSEMU or some Wine programs. It is also used by some very old
2418 threading libraries.
2420 Enabling this feature adds a small amount of overhead to
2421 context switches and increases the low-level kernel attack
2422 surface. Disabling it removes the modify_ldt(2) system call.
2424 Saying 'N' here may make sense for embedded or server kernels.
2426 config STRICT_SIGALTSTACK_SIZE
2427 bool "Enforce strict size checking for sigaltstack"
2428 depends on DYNAMIC_SIGFRAME
2430 For historical reasons MINSIGSTKSZ is a constant which became
2431 already too small with AVX512 support. Add a mechanism to
2432 enforce strict checking of the sigaltstack size against the
2433 real size of the FPU frame. This option enables the check
2434 by default. It can also be controlled via the kernel command
2435 line option 'strict_sas_size' independent of this config
2436 switch. Enabling it might break existing applications which
2437 allocate a too small sigaltstack but 'work' because they
2438 never get a signal delivered.
2440 Say 'N' unless you want to really enforce this check.
2442 source "kernel/livepatch/Kconfig"
2446 config ARCH_HAS_ADD_PAGES
2448 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2450 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2453 config USE_PERCPU_NUMA_NODE_ID
2457 menu "Power management and ACPI options"
2459 config ARCH_HIBERNATION_HEADER
2461 depends on HIBERNATION
2463 source "kernel/power/Kconfig"
2465 source "drivers/acpi/Kconfig"
2472 tristate "APM (Advanced Power Management) BIOS support"
2473 depends on X86_32 && PM_SLEEP
2475 APM is a BIOS specification for saving power using several different
2476 techniques. This is mostly useful for battery powered laptops with
2477 APM compliant BIOSes. If you say Y here, the system time will be
2478 reset after a RESUME operation, the /proc/apm device will provide
2479 battery status information, and user-space programs will receive
2480 notification of APM "events" (e.g. battery status change).
2482 If you select "Y" here, you can disable actual use of the APM
2483 BIOS by passing the "apm=off" option to the kernel at boot time.
2485 Note that the APM support is almost completely disabled for
2486 machines with more than one CPU.
2488 In order to use APM, you will need supporting software. For location
2489 and more information, read <file:Documentation/power/apm-acpi.rst>
2490 and the Battery Powered Linux mini-HOWTO, available from
2491 <http://www.tldp.org/docs.html#howto>.
2493 This driver does not spin down disk drives (see the hdparm(8)
2494 manpage ("man 8 hdparm") for that), and it doesn't turn off
2495 VESA-compliant "green" monitors.
2497 This driver does not support the TI 4000M TravelMate and the ACER
2498 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2499 desktop machines also don't have compliant BIOSes, and this driver
2500 may cause those machines to panic during the boot phase.
2502 Generally, if you don't have a battery in your machine, there isn't
2503 much point in using this driver and you should say N. If you get
2504 random kernel OOPSes or reboots that don't seem to be related to
2505 anything, try disabling/enabling this option (or disabling/enabling
2508 Some other things you should try when experiencing seemingly random,
2511 1) make sure that you have enough swap space and that it is
2513 2) pass the "no-hlt" option to the kernel
2514 3) switch on floating point emulation in the kernel and pass
2515 the "no387" option to the kernel
2516 4) pass the "floppy=nodma" option to the kernel
2517 5) pass the "mem=4M" option to the kernel (thereby disabling
2518 all but the first 4 MB of RAM)
2519 6) make sure that the CPU is not over clocked.
2520 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2521 8) disable the cache from your BIOS settings
2522 9) install a fan for the video card or exchange video RAM
2523 10) install a better fan for the CPU
2524 11) exchange RAM chips
2525 12) exchange the motherboard.
2527 To compile this driver as a module, choose M here: the
2528 module will be called apm.
2532 config APM_IGNORE_USER_SUSPEND
2533 bool "Ignore USER SUSPEND"
2535 This option will ignore USER SUSPEND requests. On machines with a
2536 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2537 series notebooks, it is necessary to say Y because of a BIOS bug.
2539 config APM_DO_ENABLE
2540 bool "Enable PM at boot time"
2542 Enable APM features at boot time. From page 36 of the APM BIOS
2543 specification: "When disabled, the APM BIOS does not automatically
2544 power manage devices, enter the Standby State, enter the Suspend
2545 State, or take power saving steps in response to CPU Idle calls."
2546 This driver will make CPU Idle calls when Linux is idle (unless this
2547 feature is turned off -- see "Do CPU IDLE calls", below). This
2548 should always save battery power, but more complicated APM features
2549 will be dependent on your BIOS implementation. You may need to turn
2550 this option off if your computer hangs at boot time when using APM
2551 support, or if it beeps continuously instead of suspending. Turn
2552 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2553 T400CDT. This is off by default since most machines do fine without
2558 bool "Make CPU Idle calls when idle"
2560 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2561 On some machines, this can activate improved power savings, such as
2562 a slowed CPU clock rate, when the machine is idle. These idle calls
2563 are made after the idle loop has run for some length of time (e.g.,
2564 333 mS). On some machines, this will cause a hang at boot time or
2565 whenever the CPU becomes idle. (On machines with more than one CPU,
2566 this option does nothing.)
2568 config APM_DISPLAY_BLANK
2569 bool "Enable console blanking using APM"
2571 Enable console blanking using the APM. Some laptops can use this to
2572 turn off the LCD backlight when the screen blanker of the Linux
2573 virtual console blanks the screen. Note that this is only used by
2574 the virtual console screen blanker, and won't turn off the backlight
2575 when using the X Window system. This also doesn't have anything to
2576 do with your VESA-compliant power-saving monitor. Further, this
2577 option doesn't work for all laptops -- it might not turn off your
2578 backlight at all, or it might print a lot of errors to the console,
2579 especially if you are using gpm.
2581 config APM_ALLOW_INTS
2582 bool "Allow interrupts during APM BIOS calls"
2584 Normally we disable external interrupts while we are making calls to
2585 the APM BIOS as a measure to lessen the effects of a badly behaving
2586 BIOS implementation. The BIOS should reenable interrupts if it
2587 needs to. Unfortunately, some BIOSes do not -- especially those in
2588 many of the newer IBM Thinkpads. If you experience hangs when you
2589 suspend, try setting this to Y. Otherwise, say N.
2593 source "drivers/cpufreq/Kconfig"
2595 source "drivers/cpuidle/Kconfig"
2597 source "drivers/idle/Kconfig"
2602 menu "Bus options (PCI etc.)"
2605 prompt "PCI access mode"
2606 depends on X86_32 && PCI
2609 On PCI systems, the BIOS can be used to detect the PCI devices and
2610 determine their configuration. However, some old PCI motherboards
2611 have BIOS bugs and may crash if this is done. Also, some embedded
2612 PCI-based systems don't have any BIOS at all. Linux can also try to
2613 detect the PCI hardware directly without using the BIOS.
2615 With this option, you can specify how Linux should detect the
2616 PCI devices. If you choose "BIOS", the BIOS will be used,
2617 if you choose "Direct", the BIOS won't be used, and if you
2618 choose "MMConfig", then PCI Express MMCONFIG will be used.
2619 If you choose "Any", the kernel will try MMCONFIG, then the
2620 direct access method and falls back to the BIOS if that doesn't
2621 work. If unsure, go with the default, which is "Any".
2626 config PCI_GOMMCONFIG
2643 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2645 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2648 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2651 bool "Support mmconfig PCI config space access" if X86_64
2653 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2654 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2658 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2662 depends on PCI && XEN
2664 config MMCONF_FAM10H
2666 depends on X86_64 && PCI_MMCONFIG && ACPI
2668 config PCI_CNB20LE_QUIRK
2669 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2672 Read the PCI windows out of the CNB20LE host bridge. This allows
2673 PCI hotplug to work on systems with the CNB20LE chipset which do
2676 There's no public spec for this chipset, and this functionality
2677 is known to be incomplete.
2679 You should say N unless you know you need this.
2682 bool "ISA bus support on modern systems" if EXPERT
2684 Expose ISA bus device drivers and options available for selection and
2685 configuration. Enable this option if your target machine has an ISA
2686 bus. ISA is an older system, displaced by PCI and newer bus
2687 architectures -- if your target machine is modern, it probably does
2688 not have an ISA bus.
2692 # x86_64 have no ISA slots, but can have ISA-style DMA.
2694 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2697 Enables ISA-style DMA support for devices requiring such controllers.
2705 Find out whether you have ISA slots on your motherboard. ISA is the
2706 name of a bus system, i.e. the way the CPU talks to the other stuff
2707 inside your box. Other bus systems are PCI, EISA, MicroChannel
2708 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2709 newer boards don't support it. If you have ISA, say Y, otherwise N.
2712 tristate "NatSemi SCx200 support"
2714 This provides basic support for National Semiconductor's
2715 (now AMD's) Geode processors. The driver probes for the
2716 PCI-IDs of several on-chip devices, so its a good dependency
2717 for other scx200_* drivers.
2719 If compiled as a module, the driver is named scx200.
2721 config SCx200HR_TIMER
2722 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2726 This driver provides a clocksource built upon the on-chip
2727 27MHz high-resolution timer. Its also a workaround for
2728 NSC Geode SC-1100's buggy TSC, which loses time when the
2729 processor goes idle (as is done by the scheduler). The
2730 other workaround is idle=poll boot option.
2733 bool "One Laptop Per Child support"
2741 Add support for detecting the unique features of the OLPC
2745 bool "OLPC XO-1 Power Management"
2746 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2748 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2751 bool "OLPC XO-1 Real Time Clock"
2752 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2754 Add support for the XO-1 real time clock, which can be used as a
2755 programmable wakeup source.
2758 bool "OLPC XO-1 SCI extras"
2759 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2763 Add support for SCI-based features of the OLPC XO-1 laptop:
2764 - EC-driven system wakeups
2768 - AC adapter status updates
2769 - Battery status updates
2771 config OLPC_XO15_SCI
2772 bool "OLPC XO-1.5 SCI extras"
2773 depends on OLPC && ACPI
2776 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2777 - EC-driven system wakeups
2778 - AC adapter status updates
2779 - Battery status updates
2782 bool "PCEngines ALIX System Support (LED setup)"
2785 This option enables system support for the PCEngines ALIX.
2786 At present this just sets up LEDs for GPIO control on
2787 ALIX2/3/6 boards. However, other system specific setup should
2790 Note: You must still enable the drivers for GPIO and LED support
2791 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2793 Note: You have to set alix.force=1 for boards with Award BIOS.
2796 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2799 This option enables system support for the Soekris Engineering net5501.
2802 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2806 This option enables system support for the Traverse Technologies GEOS.
2809 bool "Technologic Systems TS-5500 platform support"
2811 select CHECK_SIGNATURE
2815 This option enables system support for the Technologic Systems TS-5500.
2821 depends on CPU_SUP_AMD && PCI
2826 menu "Binary Emulations"
2828 config IA32_EMULATION
2829 bool "IA32 Emulation"
2831 select ARCH_WANT_OLD_COMPAT_IPC
2833 select COMPAT_OLD_SIGACTION
2835 Include code to run legacy 32-bit programs under a
2836 64-bit kernel. You should likely turn this on, unless you're
2837 100% sure that you don't have any 32-bit programs left.
2840 tristate "IA32 a.out support"
2841 depends on IA32_EMULATION
2844 Support old a.out binaries in the 32bit emulation.
2847 bool "x32 ABI for 64-bit mode"
2850 Include code to run binaries for the x32 native 32-bit ABI
2851 for 64-bit processors. An x32 process gets access to the
2852 full 64-bit register file and wide data path while leaving
2853 pointers at 32 bits for smaller memory footprint.
2855 You will need a recent binutils (2.22 or later) with
2856 elf32_x86_64 support enabled to compile a kernel with this
2861 depends on IA32_EMULATION || X86_32
2863 select OLD_SIGSUSPEND3
2867 depends on IA32_EMULATION || X86_X32
2870 config COMPAT_FOR_U64_ALIGNMENT
2873 config SYSVIPC_COMPAT
2881 config HAVE_ATOMIC_IOMAP
2885 source "arch/x86/kvm/Kconfig"
2887 source "arch/x86/Kconfig.assembler"