1 # SPDX-License-Identifier: GPL-2.0
4 bool "64-bit kernel" if "$(ARCH)" = "x86"
5 default "$(ARCH)" != "i386"
7 Say yes to build a 64-bit kernel - formerly known as x86_64
8 Say no to build a 32-bit kernel - formerly known as i386
13 # Options that are inherently 32-bit kernel only:
14 select ARCH_WANT_IPC_PARSE_VERSION
16 select CLONE_BACKWARDS
17 select GENERIC_VDSO_32
18 select HAVE_DEBUG_STACKOVERFLOW
20 select MODULES_USE_ELF_REL
22 select ARCH_SPLIT_ARG64
27 # Options that are inherently 64-bit kernel only:
28 select ARCH_HAS_GIGANTIC_PAGE
29 select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
30 select ARCH_USE_CMPXCHG_LOCKREF
31 select HAVE_ARCH_SOFT_DIRTY
32 select MODULES_USE_ELF_RELA
33 select NEED_DMA_MAP_STATE
35 select ARCH_HAS_ELFCORE_COMPAT
38 config FORCE_DYNAMIC_FTRACE
41 depends on FUNCTION_TRACER
44 We keep the static function tracing (!DYNAMIC_FTRACE) around
45 in order to test the non static function tracing in the
46 generic code, as other architectures still use it. But we
47 only need to keep it around for x86_64. No need to keep it
48 for x86_32. For x86_32, force DYNAMIC_FTRACE.
52 # ( Note that options that are marked 'if X86_64' could in principle be
53 # ported to 32-bit as well. )
58 # Note: keep this list sorted alphabetically
60 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
61 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
62 select ARCH_32BIT_OFF_T if X86_32
63 select ARCH_CLOCKSOURCE_INIT
64 select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
65 select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
66 select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
67 select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
68 select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE)
69 select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
70 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
71 select ARCH_HAS_CACHE_LINE_SIZE
72 select ARCH_HAS_CURRENT_STACK_POINTER
73 select ARCH_HAS_DEBUG_VIRTUAL
74 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
75 select ARCH_HAS_DEVMEM_IS_ALLOWED
76 select ARCH_HAS_EARLY_DEBUG if KGDB
77 select ARCH_HAS_ELF_RANDOMIZE
78 select ARCH_HAS_FAST_MULTIPLIER
79 select ARCH_HAS_FORTIFY_SOURCE
80 select ARCH_HAS_GCOV_PROFILE_ALL
81 select ARCH_HAS_KCOV if X86_64
82 select ARCH_HAS_MEM_ENCRYPT
83 select ARCH_HAS_MEMBARRIER_SYNC_CORE
84 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
85 select ARCH_HAS_PMEM_API if X86_64
86 select ARCH_HAS_PTE_DEVMAP if X86_64
87 select ARCH_HAS_PTE_SPECIAL
88 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
89 select ARCH_HAS_COPY_MC if X86_64
90 select ARCH_HAS_SET_MEMORY
91 select ARCH_HAS_SET_DIRECT_MAP
92 select ARCH_HAS_STRICT_KERNEL_RWX
93 select ARCH_HAS_STRICT_MODULE_RWX
94 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
95 select ARCH_HAS_SYSCALL_WRAPPER
96 select ARCH_HAS_UBSAN_SANITIZE_ALL
97 select ARCH_HAS_VM_GET_PAGE_PROT
98 select ARCH_HAS_DEBUG_WX
99 select ARCH_HAS_ZONE_DMA_SET if EXPERT
100 select ARCH_HAVE_NMI_SAFE_CMPXCHG
101 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
102 select ARCH_MIGHT_HAVE_PC_PARPORT
103 select ARCH_MIGHT_HAVE_PC_SERIO
104 select ARCH_STACKWALK
105 select ARCH_SUPPORTS_ACPI
106 select ARCH_SUPPORTS_ATOMIC_RMW
107 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
108 select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64
109 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
110 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
111 select ARCH_SUPPORTS_LTO_CLANG
112 select ARCH_SUPPORTS_LTO_CLANG_THIN
113 select ARCH_USE_BUILTIN_BSWAP
114 select ARCH_USE_MEMTEST
115 select ARCH_USE_QUEUED_RWLOCKS
116 select ARCH_USE_QUEUED_SPINLOCKS
117 select ARCH_USE_SYM_ANNOTATIONS
118 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
119 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
120 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
121 select ARCH_WANTS_NO_INSTR
122 select ARCH_WANT_GENERAL_HUGETLB
123 select ARCH_WANT_HUGE_PMD_SHARE
124 select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP if X86_64
125 select ARCH_WANT_LD_ORPHAN_WARN
126 select ARCH_WANTS_THP_SWAP if X86_64
127 select ARCH_HAS_PARANOID_L1D_FLUSH
128 select BUILDTIME_TABLE_SORT
130 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
131 select CLOCKSOURCE_WATCHDOG
132 select DCACHE_WORD_ACCESS
133 select DYNAMIC_SIGFRAME
134 select EDAC_ATOMIC_SCRUB
136 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
137 select GENERIC_CLOCKEVENTS_MIN_ADJUST
138 select GENERIC_CMOS_UPDATE
139 select GENERIC_CPU_AUTOPROBE
140 select GENERIC_CPU_VULNERABILITIES
141 select GENERIC_EARLY_IOREMAP
144 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
145 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
146 select GENERIC_IRQ_MIGRATION if SMP
147 select GENERIC_IRQ_PROBE
148 select GENERIC_IRQ_RESERVATION_MODE
149 select GENERIC_IRQ_SHOW
150 select GENERIC_PENDING_IRQ if SMP
151 select GENERIC_PTDUMP
152 select GENERIC_SMP_IDLE_THREAD
153 select GENERIC_TIME_VSYSCALL
154 select GENERIC_GETTIMEOFDAY
155 select GENERIC_VDSO_TIME_NS
156 select GUP_GET_PTE_LOW_HIGH if X86_PAE
157 select HARDIRQS_SW_RESEND
158 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
159 select HAVE_ACPI_APEI if ACPI
160 select HAVE_ACPI_APEI_NMI if ACPI
161 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
162 select HAVE_ARCH_AUDITSYSCALL
163 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
164 select HAVE_ARCH_HUGE_VMALLOC if X86_64
165 select HAVE_ARCH_JUMP_LABEL
166 select HAVE_ARCH_JUMP_LABEL_RELATIVE
167 select HAVE_ARCH_KASAN if X86_64
168 select HAVE_ARCH_KASAN_VMALLOC if X86_64
169 select HAVE_ARCH_KFENCE
170 select HAVE_ARCH_KGDB
171 select HAVE_ARCH_MMAP_RND_BITS if MMU
172 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
173 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
174 select HAVE_ARCH_PREL32_RELOCATIONS
175 select HAVE_ARCH_SECCOMP_FILTER
176 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
177 select HAVE_ARCH_STACKLEAK
178 select HAVE_ARCH_TRACEHOOK
179 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
180 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
181 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
182 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
183 select HAVE_ARCH_VMAP_STACK if X86_64
184 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
185 select HAVE_ARCH_WITHIN_STACK_FRAMES
186 select HAVE_ASM_MODVERSIONS
187 select HAVE_CMPXCHG_DOUBLE
188 select HAVE_CMPXCHG_LOCAL
189 select HAVE_CONTEXT_TRACKING if X86_64
190 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
191 select HAVE_C_RECORDMCOUNT
192 select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
193 select HAVE_BUILDTIME_MCOUNT_SORT
194 select HAVE_DEBUG_KMEMLEAK
195 select HAVE_DMA_CONTIGUOUS
196 select HAVE_DYNAMIC_FTRACE
197 select HAVE_DYNAMIC_FTRACE_WITH_REGS
198 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
199 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
200 select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
201 select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
203 select HAVE_EFFICIENT_UNALIGNED_ACCESS
205 select HAVE_EXIT_THREAD
207 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
208 select HAVE_FTRACE_MCOUNT_RECORD
209 select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
210 select HAVE_FUNCTION_TRACER
211 select HAVE_GCC_PLUGINS
212 select HAVE_HW_BREAKPOINT
213 select HAVE_IOREMAP_PROT
214 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
215 select HAVE_IRQ_TIME_ACCOUNTING
216 select HAVE_JUMP_LABEL_HACK if HAVE_OBJTOOL
217 select HAVE_KERNEL_BZIP2
218 select HAVE_KERNEL_GZIP
219 select HAVE_KERNEL_LZ4
220 select HAVE_KERNEL_LZMA
221 select HAVE_KERNEL_LZO
222 select HAVE_KERNEL_XZ
223 select HAVE_KERNEL_ZSTD
225 select HAVE_KPROBES_ON_FTRACE
226 select HAVE_FUNCTION_ERROR_INJECTION
227 select HAVE_KRETPROBES
230 select HAVE_LIVEPATCH if X86_64
231 select HAVE_MIXED_BREAKPOINTS_REGS
232 select HAVE_MOD_ARCH_SPECIFIC
235 select HAVE_NOINSTR_HACK if HAVE_OBJTOOL
237 select HAVE_NOINSTR_VALIDATION if HAVE_OBJTOOL
238 select HAVE_OBJTOOL if X86_64
239 select HAVE_OPTPROBES
240 select HAVE_PCSPKR_PLATFORM
241 select HAVE_PERF_EVENTS
242 select HAVE_PERF_EVENTS_NMI
243 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
245 select HAVE_PERF_REGS
246 select HAVE_PERF_USER_STACK_DUMP
247 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
248 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
249 select HAVE_REGS_AND_STACK_ACCESS_API
250 select HAVE_RELIABLE_STACKTRACE if UNWINDER_ORC || STACK_VALIDATION
251 select HAVE_FUNCTION_ARG_ACCESS_API
252 select HAVE_SETUP_PER_CPU_AREA
253 select HAVE_SOFTIRQ_ON_OWN_STACK
254 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
255 select HAVE_STACK_VALIDATION if HAVE_OBJTOOL
256 select HAVE_STATIC_CALL
257 select HAVE_STATIC_CALL_INLINE if HAVE_OBJTOOL
258 select HAVE_PREEMPT_DYNAMIC_CALL
260 select HAVE_SYSCALL_TRACEPOINTS
261 select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
262 select HAVE_UNSTABLE_SCHED_CLOCK
263 select HAVE_USER_RETURN_NOTIFIER
264 select HAVE_GENERIC_VDSO
265 select HOTPLUG_SMT if SMP
266 select IRQ_FORCED_THREADING
267 select NEED_PER_CPU_EMBED_FIRST_CHUNK
268 select NEED_PER_CPU_PAGE_FIRST_CHUNK
269 select NEED_SG_DMA_LENGTH
270 select PCI_DOMAINS if PCI
271 select PCI_LOCKLESS_CONFIG if PCI
274 select RTC_MC146818_LIB
277 select SYSCTL_EXCEPTION_TRACE
278 select THREAD_INFO_IN_TASK
279 select TRACE_IRQFLAGS_SUPPORT
280 select USER_STACKTRACE_SUPPORT
282 select HAVE_ARCH_KCSAN if X86_64
283 select X86_FEATURE_NAMES if PROC_FS
284 select PROC_PID_ARCH_STATUS if PROC_FS
285 select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
286 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
288 config INSTRUCTION_DECODER
290 depends on KPROBES || PERF_EVENTS || UPROBES
294 default "elf32-i386" if X86_32
295 default "elf64-x86-64" if X86_64
297 config LOCKDEP_SUPPORT
300 config STACKTRACE_SUPPORT
306 config ARCH_MMAP_RND_BITS_MIN
310 config ARCH_MMAP_RND_BITS_MAX
314 config ARCH_MMAP_RND_COMPAT_BITS_MIN
317 config ARCH_MMAP_RND_COMPAT_BITS_MAX
323 config GENERIC_ISA_DMA
325 depends on ISA_DMA_API
330 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
332 config GENERIC_BUG_RELATIVE_POINTERS
335 config ARCH_MAY_HAVE_PC_FDC
337 depends on ISA_DMA_API
339 config GENERIC_CALIBRATE_DELAY
342 config ARCH_HAS_CPU_RELAX
345 config ARCH_HIBERNATION_POSSIBLE
350 default 1024 if X86_64
353 config ARCH_SUSPEND_POSSIBLE
359 config KASAN_SHADOW_OFFSET
362 default 0xdffffc0000000000
364 config HAVE_INTEL_TXT
366 depends on INTEL_IOMMU && ACPI
370 depends on X86_32 && SMP
374 depends on X86_64 && SMP
376 config ARCH_SUPPORTS_UPROBES
379 config FIX_EARLYCON_MEM
382 config DYNAMIC_PHYSICAL_MASK
385 config PGTABLE_LEVELS
387 default 5 if X86_5LEVEL
392 config CC_HAS_SANE_STACKPROTECTOR
394 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
395 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
397 We have to make sure stack protector is unconditionally disabled if
398 the compiler produces broken code or if it does not let us control
399 the segment on 32-bit kernels.
401 menu "Processor type and features"
404 bool "Symmetric multi-processing support"
406 This enables support for systems with more than one CPU. If you have
407 a system with only one CPU, say N. If you have a system with more
410 If you say N here, the kernel will run on uni- and multiprocessor
411 machines, but will use only one CPU of a multiprocessor machine. If
412 you say Y here, the kernel will run on many, but not all,
413 uniprocessor machines. On a uniprocessor machine, the kernel
414 will run faster if you say N here.
416 Note that if you say Y here and choose architecture "586" or
417 "Pentium" under "Processor family", the kernel will not work on 486
418 architectures. Similarly, multiprocessor kernels for the "PPro"
419 architecture may not work on all Pentium based boards.
421 People using multiprocessor machines who say Y here should also say
422 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
423 Management" code will be disabled if you say Y here.
425 See also <file:Documentation/x86/i386/IO-APIC.rst>,
426 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
427 <http://www.tldp.org/docs.html#howto>.
429 If you don't know what to do here, say N.
431 config X86_FEATURE_NAMES
432 bool "Processor feature human-readable names" if EMBEDDED
435 This option compiles in a table of x86 feature bits and corresponding
436 names. This is required to support /proc/cpuinfo and a few kernel
437 messages. You can disable this to save space, at the expense of
438 making those few kernel messages show numeric feature bits instead.
443 bool "Support x2apic"
444 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
446 This enables x2apic support on CPUs that have this feature.
448 This allows 32-bit apic IDs (so it can support very large systems),
449 and accesses the local apic via MSRs not via mmio.
451 If you don't know what to do here, say N.
454 bool "Enable MPS table" if ACPI
456 depends on X86_LOCAL_APIC
458 For old smp systems that do not have proper acpi support. Newer systems
459 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
463 depends on X86_GOLDFISH
466 bool "Avoid speculative indirect branches in kernel"
467 select OBJTOOL if HAVE_OBJTOOL
470 Compile kernel with the retpoline compiler options to guard against
471 kernel-to-user data leaks by avoiding speculative indirect
472 branches. Requires a compiler with -mindirect-branch=thunk-extern
473 support for full protection. The kernel may run slower.
476 def_bool $(cc-option,-mharden-sls=all)
479 bool "Mitigate Straight-Line-Speculation"
480 depends on CC_HAS_SLS && X86_64
481 select OBJTOOL if HAVE_OBJTOOL
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 config INTEL_TDX_GUEST
889 bool "Intel TDX (Trust Domain Extensions) - Guest Support"
890 depends on X86_64 && CPU_SUP_INTEL
891 depends on X86_X2APIC
892 select ARCH_HAS_CC_PLATFORM
893 select X86_MEM_ENCRYPT
896 Support running as a guest under Intel TDX. Without this support,
897 the guest kernel can not boot or run under TDX.
898 TDX includes memory encryption and integrity capabilities
899 which protect the confidentiality and integrity of guest
900 memory contents and CPU state. TDX guests are protected from
901 some attacks from the VMM.
903 endif # HYPERVISOR_GUEST
905 source "arch/x86/Kconfig.cpu"
909 prompt "HPET Timer Support" if X86_32
911 Use the IA-PC HPET (High Precision Event Timer) to manage
912 time in preference to the PIT and RTC, if a HPET is
914 HPET is the next generation timer replacing legacy 8254s.
915 The HPET provides a stable time base on SMP
916 systems, unlike the TSC, but it is more expensive to access,
917 as it is off-chip. The interface used is documented
918 in the HPET spec, revision 1.
920 You can safely choose Y here. However, HPET will only be
921 activated if the platform and the BIOS support this feature.
922 Otherwise the 8254 will be used for timing services.
924 Choose N to continue using the legacy 8254 timer.
926 config HPET_EMULATE_RTC
928 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
930 # Mark as expert because too many people got it wrong.
931 # The code disables itself when not needed.
934 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
935 bool "Enable DMI scanning" if EXPERT
937 Enabled scanning of DMI to identify machine quirks. Say Y
938 here unless you have verified that your setup is not
939 affected by entries in the DMI blacklist. Required by PNP
943 bool "Old AMD GART IOMMU support"
947 depends on X86_64 && PCI && AMD_NB
949 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
950 GART based hardware IOMMUs.
952 The GART supports full DMA access for devices with 32-bit access
953 limitations, on systems with more than 3 GB. This is usually needed
954 for USB, sound, many IDE/SATA chipsets and some other devices.
956 Newer systems typically have a modern AMD IOMMU, supported via
957 the CONFIG_AMD_IOMMU=y config option.
959 In normal configurations this driver is only active when needed:
960 there's more than 3 GB of memory and the system contains a
961 32-bit limited device.
965 config BOOT_VESA_SUPPORT
968 If true, at least one selected framebuffer driver can take advantage
969 of VESA video modes set at an early boot stage via the vga= parameter.
972 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
973 depends on X86_64 && SMP && DEBUG_KERNEL
974 select CPUMASK_OFFSTACK
976 Enable maximum number of CPUS and NUMA Nodes for this architecture.
980 # The maximum number of CPUs supported:
982 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
983 # and which can be configured interactively in the
984 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
986 # The ranges are different on 32-bit and 64-bit kernels, depending on
987 # hardware capabilities and scalability features of the kernel.
989 # ( If MAXSMP is enabled we just use the highest possible value and disable
990 # interactive configuration. )
993 config NR_CPUS_RANGE_BEGIN
995 default NR_CPUS_RANGE_END if MAXSMP
999 config NR_CPUS_RANGE_END
1002 default 64 if SMP && X86_BIGSMP
1003 default 8 if SMP && !X86_BIGSMP
1006 config NR_CPUS_RANGE_END
1009 default 8192 if SMP && CPUMASK_OFFSTACK
1010 default 512 if SMP && !CPUMASK_OFFSTACK
1013 config NR_CPUS_DEFAULT
1016 default 32 if X86_BIGSMP
1020 config NR_CPUS_DEFAULT
1023 default 8192 if MAXSMP
1028 int "Maximum number of CPUs" if SMP && !MAXSMP
1029 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1030 default NR_CPUS_DEFAULT
1032 This allows you to specify the maximum number of CPUs which this
1033 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1034 supported value is 8192, otherwise the maximum value is 512. The
1035 minimum value which makes sense is 2.
1037 This is purely to save memory: each supported CPU adds about 8KB
1038 to the kernel image.
1040 config SCHED_CLUSTER
1041 bool "Cluster scheduler support"
1045 Cluster scheduler support improves the CPU scheduler's decision
1046 making when dealing with machines that have clusters of CPUs.
1047 Cluster usually means a couple of CPUs which are placed closely
1048 by sharing mid-level caches, last-level cache tags or internal
1056 prompt "Multi-core scheduler support"
1059 Multi-core scheduler support improves the CPU scheduler's decision
1060 making when dealing with multi-core CPU chips at a cost of slightly
1061 increased overhead in some places. If unsure say N here.
1063 config SCHED_MC_PRIO
1064 bool "CPU core priorities scheduler support"
1065 depends on SCHED_MC && CPU_SUP_INTEL
1066 select X86_INTEL_PSTATE
1070 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1071 core ordering determined at manufacturing time, which allows
1072 certain cores to reach higher turbo frequencies (when running
1073 single threaded workloads) than others.
1075 Enabling this kernel feature teaches the scheduler about
1076 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1077 scheduler's CPU selection logic accordingly, so that higher
1078 overall system performance can be achieved.
1080 This feature will have no effect on CPUs without this feature.
1082 If unsure say Y here.
1086 depends on !SMP && X86_LOCAL_APIC
1089 bool "Local APIC support on uniprocessors" if !PCI_MSI
1091 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1093 A local APIC (Advanced Programmable Interrupt Controller) is an
1094 integrated interrupt controller in the CPU. If you have a single-CPU
1095 system which has a processor with a local APIC, you can say Y here to
1096 enable and use it. If you say Y here even though your machine doesn't
1097 have a local APIC, then the kernel will still run with no slowdown at
1098 all. The local APIC supports CPU-generated self-interrupts (timer,
1099 performance counters), and the NMI watchdog which detects hard
1102 config X86_UP_IOAPIC
1103 bool "IO-APIC support on uniprocessors"
1104 depends on X86_UP_APIC
1106 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1107 SMP-capable replacement for PC-style interrupt controllers. Most
1108 SMP systems and many recent uniprocessor systems have one.
1110 If you have a single-CPU system with an IO-APIC, you can say Y here
1111 to use it. If you say Y here even though your machine doesn't have
1112 an IO-APIC, then the kernel will still run with no slowdown at all.
1114 config X86_LOCAL_APIC
1116 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1117 select IRQ_DOMAIN_HIERARCHY
1118 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1122 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1124 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1125 bool "Reroute for broken boot IRQs"
1126 depends on X86_IO_APIC
1128 This option enables a workaround that fixes a source of
1129 spurious interrupts. This is recommended when threaded
1130 interrupt handling is used on systems where the generation of
1131 superfluous "boot interrupts" cannot be disabled.
1133 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1134 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1135 kernel does during interrupt handling). On chipsets where this
1136 boot IRQ generation cannot be disabled, this workaround keeps
1137 the original IRQ line masked so that only the equivalent "boot
1138 IRQ" is delivered to the CPUs. The workaround also tells the
1139 kernel to set up the IRQ handler on the boot IRQ line. In this
1140 way only one interrupt is delivered to the kernel. Otherwise
1141 the spurious second interrupt may cause the kernel to bring
1142 down (vital) interrupt lines.
1144 Only affects "broken" chipsets. Interrupt sharing may be
1145 increased on these systems.
1148 bool "Machine Check / overheating reporting"
1149 select GENERIC_ALLOCATOR
1152 Machine Check support allows the processor to notify the
1153 kernel if it detects a problem (e.g. overheating, data corruption).
1154 The action the kernel takes depends on the severity of the problem,
1155 ranging from warning messages to halting the machine.
1157 config X86_MCELOG_LEGACY
1158 bool "Support for deprecated /dev/mcelog character device"
1161 Enable support for /dev/mcelog which is needed by the old mcelog
1162 userspace logging daemon. Consider switching to the new generation
1165 config X86_MCE_INTEL
1167 prompt "Intel MCE features"
1168 depends on X86_MCE && X86_LOCAL_APIC
1170 Additional support for intel specific MCE features such as
1171 the thermal monitor.
1175 prompt "AMD MCE features"
1176 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1178 Additional support for AMD specific MCE features such as
1179 the DRAM Error Threshold.
1181 config X86_ANCIENT_MCE
1182 bool "Support for old Pentium 5 / WinChip machine checks"
1183 depends on X86_32 && X86_MCE
1185 Include support for machine check handling on old Pentium 5 or WinChip
1186 systems. These typically need to be enabled explicitly on the command
1189 config X86_MCE_THRESHOLD
1190 depends on X86_MCE_AMD || X86_MCE_INTEL
1193 config X86_MCE_INJECT
1194 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1195 tristate "Machine check injector support"
1197 Provide support for injecting machine checks for testing purposes.
1198 If you don't know what a machine check is and you don't do kernel
1199 QA it is safe to say n.
1201 source "arch/x86/events/Kconfig"
1203 config X86_LEGACY_VM86
1204 bool "Legacy VM86 support"
1207 This option allows user programs to put the CPU into V8086
1208 mode, which is an 80286-era approximation of 16-bit real mode.
1210 Some very old versions of X and/or vbetool require this option
1211 for user mode setting. Similarly, DOSEMU will use it if
1212 available to accelerate real mode DOS programs. However, any
1213 recent version of DOSEMU, X, or vbetool should be fully
1214 functional even without kernel VM86 support, as they will all
1215 fall back to software emulation. Nevertheless, if you are using
1216 a 16-bit DOS program where 16-bit performance matters, vm86
1217 mode might be faster than emulation and you might want to
1220 Note that any app that works on a 64-bit kernel is unlikely to
1221 need this option, as 64-bit kernels don't, and can't, support
1222 V8086 mode. This option is also unrelated to 16-bit protected
1223 mode and is not needed to run most 16-bit programs under Wine.
1225 Enabling this option increases the complexity of the kernel
1226 and slows down exception handling a tiny bit.
1228 If unsure, say N here.
1232 default X86_LEGACY_VM86
1235 bool "Enable support for 16-bit segments" if EXPERT
1237 depends on MODIFY_LDT_SYSCALL
1239 This option is required by programs like Wine to run 16-bit
1240 protected mode legacy code on x86 processors. Disabling
1241 this option saves about 300 bytes on i386, or around 6K text
1242 plus 16K runtime memory on x86-64,
1246 depends on X86_16BIT && X86_32
1250 depends on X86_16BIT && X86_64
1252 config X86_VSYSCALL_EMULATION
1253 bool "Enable vsyscall emulation" if EXPERT
1257 This enables emulation of the legacy vsyscall page. Disabling
1258 it is roughly equivalent to booting with vsyscall=none, except
1259 that it will also disable the helpful warning if a program
1260 tries to use a vsyscall. With this option set to N, offending
1261 programs will just segfault, citing addresses of the form
1264 This option is required by many programs built before 2013, and
1265 care should be used even with newer programs if set to N.
1267 Disabling this option saves about 7K of kernel size and
1268 possibly 4K of additional runtime pagetable memory.
1270 config X86_IOPL_IOPERM
1271 bool "IOPERM and IOPL Emulation"
1274 This enables the ioperm() and iopl() syscalls which are necessary
1275 for legacy applications.
1277 Legacy IOPL support is an overbroad mechanism which allows user
1278 space aside of accessing all 65536 I/O ports also to disable
1279 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1280 capabilities and permission from potentially active security
1283 The emulation restricts the functionality of the syscall to
1284 only allowing the full range I/O port access, but prevents the
1285 ability to disable interrupts from user space which would be
1286 granted if the hardware IOPL mechanism would be used.
1289 tristate "Toshiba Laptop support"
1292 This adds a driver to safely access the System Management Mode of
1293 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1294 not work on models with a Phoenix BIOS. The System Management Mode
1295 is used to set the BIOS and power saving options on Toshiba portables.
1297 For information on utilities to make use of this driver see the
1298 Toshiba Linux utilities web site at:
1299 <http://www.buzzard.org.uk/toshiba/>.
1301 Say Y if you intend to run this kernel on a Toshiba portable.
1304 config X86_REBOOTFIXUPS
1305 bool "Enable X86 board specific fixups for reboot"
1308 This enables chipset and/or board specific fixups to be done
1309 in order to get reboot to work correctly. This is only needed on
1310 some combinations of hardware and BIOS. The symptom, for which
1311 this config is intended, is when reboot ends with a stalled/hung
1314 Currently, the only fixup is for the Geode machines using
1315 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1317 Say Y if you want to enable the fixup. Currently, it's safe to
1318 enable this option even if you don't need it.
1322 bool "CPU microcode loading support"
1324 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1326 If you say Y here, you will be able to update the microcode on
1327 Intel and AMD processors. The Intel support is for the IA32 family,
1328 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1329 AMD support is for families 0x10 and later. You will obviously need
1330 the actual microcode binary data itself which is not shipped with
1333 The preferred method to load microcode from a detached initrd is described
1334 in Documentation/x86/microcode.rst. For that you need to enable
1335 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1336 initrd for microcode blobs.
1338 In addition, you can build the microcode into the kernel. For that you
1339 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1342 config MICROCODE_INTEL
1343 bool "Intel microcode loading support"
1344 depends on CPU_SUP_INTEL && MICROCODE
1347 This options enables microcode patch loading support for Intel
1350 For the current Intel microcode data package go to
1351 <https://downloadcenter.intel.com> and search for
1352 'Linux Processor Microcode Data File'.
1354 config MICROCODE_AMD
1355 bool "AMD microcode loading support"
1356 depends on CPU_SUP_AMD && MICROCODE
1358 If you select this option, microcode patch loading support for AMD
1359 processors will be enabled.
1361 config MICROCODE_LATE_LOADING
1362 bool "Late microcode loading (DANGEROUS)"
1364 depends on MICROCODE
1366 Loading microcode late, when the system is up and executing instructions
1367 is a tricky business and should be avoided if possible. Just the sequence
1368 of synchronizing all cores and SMT threads is one fragile dance which does
1369 not guarantee that cores might not softlock after the loading. Therefore,
1370 use this at your own risk. Late loading taints the kernel too.
1373 tristate "/dev/cpu/*/msr - Model-specific register support"
1375 This device gives privileged processes access to the x86
1376 Model-Specific Registers (MSRs). It is a character device with
1377 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1378 MSR accesses are directed to a specific CPU on multi-processor
1382 tristate "/dev/cpu/*/cpuid - CPU information support"
1384 This device gives processes access to the x86 CPUID instruction to
1385 be executed on a specific processor. It is a character device
1386 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1390 prompt "High Memory Support"
1397 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1398 However, the address space of 32-bit x86 processors is only 4
1399 Gigabytes large. That means that, if you have a large amount of
1400 physical memory, not all of it can be "permanently mapped" by the
1401 kernel. The physical memory that's not permanently mapped is called
1404 If you are compiling a kernel which will never run on a machine with
1405 more than 1 Gigabyte total physical RAM, answer "off" here (default
1406 choice and suitable for most users). This will result in a "3GB/1GB"
1407 split: 3GB are mapped so that each process sees a 3GB virtual memory
1408 space and the remaining part of the 4GB virtual memory space is used
1409 by the kernel to permanently map as much physical memory as
1412 If the machine has between 1 and 4 Gigabytes physical RAM, then
1415 If more than 4 Gigabytes is used then answer "64GB" here. This
1416 selection turns Intel PAE (Physical Address Extension) mode on.
1417 PAE implements 3-level paging on IA32 processors. PAE is fully
1418 supported by Linux, PAE mode is implemented on all recent Intel
1419 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1420 then the kernel will not boot on CPUs that don't support PAE!
1422 The actual amount of total physical memory will either be
1423 auto detected or can be forced by using a kernel command line option
1424 such as "mem=256M". (Try "man bootparam" or see the documentation of
1425 your boot loader (lilo or loadlin) about how to pass options to the
1426 kernel at boot time.)
1428 If unsure, say "off".
1433 Select this if you have a 32-bit processor and between 1 and 4
1434 gigabytes of physical RAM.
1438 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1441 Select this if you have a 32-bit processor and more than 4
1442 gigabytes of physical RAM.
1447 prompt "Memory split" if EXPERT
1451 Select the desired split between kernel and user memory.
1453 If the address range available to the kernel is less than the
1454 physical memory installed, the remaining memory will be available
1455 as "high memory". Accessing high memory is a little more costly
1456 than low memory, as it needs to be mapped into the kernel first.
1457 Note that increasing the kernel address space limits the range
1458 available to user programs, making the address space there
1459 tighter. Selecting anything other than the default 3G/1G split
1460 will also likely make your kernel incompatible with binary-only
1463 If you are not absolutely sure what you are doing, leave this
1467 bool "3G/1G user/kernel split"
1468 config VMSPLIT_3G_OPT
1470 bool "3G/1G user/kernel split (for full 1G low memory)"
1472 bool "2G/2G user/kernel split"
1473 config VMSPLIT_2G_OPT
1475 bool "2G/2G user/kernel split (for full 2G low memory)"
1477 bool "1G/3G user/kernel split"
1482 default 0xB0000000 if VMSPLIT_3G_OPT
1483 default 0x80000000 if VMSPLIT_2G
1484 default 0x78000000 if VMSPLIT_2G_OPT
1485 default 0x40000000 if VMSPLIT_1G
1491 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1494 bool "PAE (Physical Address Extension) Support"
1495 depends on X86_32 && !HIGHMEM4G
1496 select PHYS_ADDR_T_64BIT
1499 PAE is required for NX support, and furthermore enables
1500 larger swapspace support for non-overcommit purposes. It
1501 has the cost of more pagetable lookup overhead, and also
1502 consumes more pagetable space per process.
1505 bool "Enable 5-level page tables support"
1507 select DYNAMIC_MEMORY_LAYOUT
1508 select SPARSEMEM_VMEMMAP
1511 5-level paging enables access to larger address space:
1512 upto 128 PiB of virtual address space and 4 PiB of
1513 physical address space.
1515 It will be supported by future Intel CPUs.
1517 A kernel with the option enabled can be booted on machines that
1518 support 4- or 5-level paging.
1520 See Documentation/x86/x86_64/5level-paging.rst for more
1525 config X86_DIRECT_GBPAGES
1529 Certain kernel features effectively disable kernel
1530 linear 1 GB mappings (even if the CPU otherwise
1531 supports them), so don't confuse the user by printing
1532 that we have them enabled.
1534 config X86_CPA_STATISTICS
1535 bool "Enable statistic for Change Page Attribute"
1538 Expose statistics about the Change Page Attribute mechanism, which
1539 helps to determine the effectiveness of preserving large and huge
1540 page mappings when mapping protections are changed.
1542 config X86_MEM_ENCRYPT
1543 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1544 select DYNAMIC_PHYSICAL_MASK
1545 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1548 config AMD_MEM_ENCRYPT
1549 bool "AMD Secure Memory Encryption (SME) support"
1550 depends on X86_64 && CPU_SUP_AMD
1551 select DMA_COHERENT_POOL
1552 select ARCH_USE_MEMREMAP_PROT
1553 select INSTRUCTION_DECODER
1554 select ARCH_HAS_CC_PLATFORM
1555 select X86_MEM_ENCRYPT
1557 Say yes to enable support for the encryption of system memory.
1558 This requires an AMD processor that supports Secure Memory
1561 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1562 bool "Activate AMD Secure Memory Encryption (SME) by default"
1563 depends on AMD_MEM_ENCRYPT
1565 Say yes to have system memory encrypted by default if running on
1566 an AMD processor that supports Secure Memory Encryption (SME).
1568 If set to Y, then the encryption of system memory can be
1569 deactivated with the mem_encrypt=off command line option.
1571 If set to N, then the encryption of system memory can be
1572 activated with the mem_encrypt=on command line option.
1574 # Common NUMA Features
1576 bool "NUMA Memory Allocation and Scheduler Support"
1578 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1579 default y if X86_BIGSMP
1580 select USE_PERCPU_NUMA_NODE_ID
1582 Enable NUMA (Non-Uniform Memory Access) support.
1584 The kernel will try to allocate memory used by a CPU on the
1585 local memory controller of the CPU and add some more
1586 NUMA awareness to the kernel.
1588 For 64-bit this is recommended if the system is Intel Core i7
1589 (or later), AMD Opteron, or EM64T NUMA.
1591 For 32-bit this is only needed if you boot a 32-bit
1592 kernel on a 64-bit NUMA platform.
1594 Otherwise, you should say N.
1598 prompt "Old style AMD Opteron NUMA detection"
1599 depends on X86_64 && NUMA && PCI
1601 Enable AMD NUMA node topology detection. You should say Y here if
1602 you have a multi processor AMD system. This uses an old method to
1603 read the NUMA configuration directly from the builtin Northbridge
1604 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1605 which also takes priority if both are compiled in.
1607 config X86_64_ACPI_NUMA
1609 prompt "ACPI NUMA detection"
1610 depends on X86_64 && NUMA && ACPI && PCI
1613 Enable ACPI SRAT based node topology detection.
1616 bool "NUMA emulation"
1619 Enable NUMA emulation. A flat machine will be split
1620 into virtual nodes when booted with "numa=fake=N", where N is the
1621 number of nodes. This is only useful for debugging.
1624 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1626 default "10" if MAXSMP
1627 default "6" if X86_64
1631 Specify the maximum number of NUMA Nodes available on the target
1632 system. Increases memory reserved to accommodate various tables.
1634 config ARCH_FLATMEM_ENABLE
1636 depends on X86_32 && !NUMA
1638 config ARCH_SPARSEMEM_ENABLE
1640 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1641 select SPARSEMEM_STATIC if X86_32
1642 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1644 config ARCH_SPARSEMEM_DEFAULT
1645 def_bool X86_64 || (NUMA && X86_32)
1647 config ARCH_SELECT_MEMORY_MODEL
1649 depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE
1651 config ARCH_MEMORY_PROBE
1652 bool "Enable sysfs memory/probe interface"
1653 depends on MEMORY_HOTPLUG
1655 This option enables a sysfs memory/probe interface for testing.
1656 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1657 If you are unsure how to answer this question, answer N.
1659 config ARCH_PROC_KCORE_TEXT
1661 depends on X86_64 && PROC_KCORE
1663 config ILLEGAL_POINTER_VALUE
1666 default 0xdead000000000000 if X86_64
1668 config X86_PMEM_LEGACY_DEVICE
1671 config X86_PMEM_LEGACY
1672 tristate "Support non-standard NVDIMMs and ADR protected memory"
1673 depends on PHYS_ADDR_T_64BIT
1675 select X86_PMEM_LEGACY_DEVICE
1676 select NUMA_KEEP_MEMINFO if NUMA
1679 Treat memory marked using the non-standard e820 type of 12 as used
1680 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1681 The kernel will offer these regions to the 'pmem' driver so
1682 they can be used for persistent storage.
1687 bool "Allocate 3rd-level pagetables from highmem"
1690 The VM uses one page table entry for each page of physical memory.
1691 For systems with a lot of RAM, this can be wasteful of precious
1692 low memory. Setting this option will put user-space page table
1693 entries in high memory.
1695 config X86_CHECK_BIOS_CORRUPTION
1696 bool "Check for low memory corruption"
1698 Periodically check for memory corruption in low memory, which
1699 is suspected to be caused by BIOS. Even when enabled in the
1700 configuration, it is disabled at runtime. Enable it by
1701 setting "memory_corruption_check=1" on the kernel command
1702 line. By default it scans the low 64k of memory every 60
1703 seconds; see the memory_corruption_check_size and
1704 memory_corruption_check_period parameters in
1705 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1707 When enabled with the default parameters, this option has
1708 almost no overhead, as it reserves a relatively small amount
1709 of memory and scans it infrequently. It both detects corruption
1710 and prevents it from affecting the running system.
1712 It is, however, intended as a diagnostic tool; if repeatable
1713 BIOS-originated corruption always affects the same memory,
1714 you can use memmap= to prevent the kernel from using that
1717 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1718 bool "Set the default setting of memory_corruption_check"
1719 depends on X86_CHECK_BIOS_CORRUPTION
1722 Set whether the default state of memory_corruption_check is
1725 config MATH_EMULATION
1727 depends on MODIFY_LDT_SYSCALL
1728 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1730 Linux can emulate a math coprocessor (used for floating point
1731 operations) if you don't have one. 486DX and Pentium processors have
1732 a math coprocessor built in, 486SX and 386 do not, unless you added
1733 a 487DX or 387, respectively. (The messages during boot time can
1734 give you some hints here ["man dmesg"].) Everyone needs either a
1735 coprocessor or this emulation.
1737 If you don't have a math coprocessor, you need to say Y here; if you
1738 say Y here even though you have a coprocessor, the coprocessor will
1739 be used nevertheless. (This behavior can be changed with the kernel
1740 command line option "no387", which comes handy if your coprocessor
1741 is broken. Try "man bootparam" or see the documentation of your boot
1742 loader (lilo or loadlin) about how to pass options to the kernel at
1743 boot time.) This means that it is a good idea to say Y here if you
1744 intend to use this kernel on different machines.
1746 More information about the internals of the Linux math coprocessor
1747 emulation can be found in <file:arch/x86/math-emu/README>.
1749 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1750 kernel, it won't hurt.
1754 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1756 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1757 the Memory Type Range Registers (MTRRs) may be used to control
1758 processor access to memory ranges. This is most useful if you have
1759 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1760 allows bus write transfers to be combined into a larger transfer
1761 before bursting over the PCI/AGP bus. This can increase performance
1762 of image write operations 2.5 times or more. Saying Y here creates a
1763 /proc/mtrr file which may be used to manipulate your processor's
1764 MTRRs. Typically the X server should use this.
1766 This code has a reasonably generic interface so that similar
1767 control registers on other processors can be easily supported
1770 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1771 Registers (ARRs) which provide a similar functionality to MTRRs. For
1772 these, the ARRs are used to emulate the MTRRs.
1773 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1774 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1775 write-combining. All of these processors are supported by this code
1776 and it makes sense to say Y here if you have one of them.
1778 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1779 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1780 can lead to all sorts of problems, so it's good to say Y here.
1782 You can safely say Y even if your machine doesn't have MTRRs, you'll
1783 just add about 9 KB to your kernel.
1785 See <file:Documentation/x86/mtrr.rst> for more information.
1787 config MTRR_SANITIZER
1789 prompt "MTRR cleanup support"
1792 Convert MTRR layout from continuous to discrete, so X drivers can
1793 add writeback entries.
1795 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1796 The largest mtrr entry size for a continuous block can be set with
1801 config MTRR_SANITIZER_ENABLE_DEFAULT
1802 int "MTRR cleanup enable value (0-1)"
1805 depends on MTRR_SANITIZER
1807 Enable mtrr cleanup default value
1809 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1810 int "MTRR cleanup spare reg num (0-7)"
1813 depends on MTRR_SANITIZER
1815 mtrr cleanup spare entries default, it can be changed via
1816 mtrr_spare_reg_nr=N on the kernel command line.
1820 prompt "x86 PAT support" if EXPERT
1823 Use PAT attributes to setup page level cache control.
1825 PATs are the modern equivalents of MTRRs and are much more
1826 flexible than MTRRs.
1828 Say N here if you see bootup problems (boot crash, boot hang,
1829 spontaneous reboots) or a non-working video driver.
1833 config ARCH_USES_PG_UNCACHED
1839 prompt "x86 architectural random number generator" if EXPERT
1841 Enable the x86 architectural RDRAND instruction
1842 (Intel Bull Mountain technology) to generate random numbers.
1843 If supported, this is a high bandwidth, cryptographically
1844 secure hardware random number generator.
1848 prompt "User Mode Instruction Prevention" if EXPERT
1850 User Mode Instruction Prevention (UMIP) is a security feature in
1851 some x86 processors. If enabled, a general protection fault is
1852 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1853 executed in user mode. These instructions unnecessarily expose
1854 information about the hardware state.
1856 The vast majority of applications do not use these instructions.
1857 For the very few that do, software emulation is provided in
1858 specific cases in protected and virtual-8086 modes. Emulated
1862 # GCC >= 9 and binutils >= 2.29
1863 # Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
1865 # https://github.com/llvm/llvm-project/commit/e0b89df2e0f0130881bf6c39bf31d7f6aac00e0f
1866 # https://github.com/llvm/llvm-project/commit/dfcf69770bc522b9e411c66454934a37c1f35332
1867 def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \
1868 (CC_IS_CLANG && CLANG_VERSION >= 140000)) && \
1871 config X86_KERNEL_IBT
1872 prompt "Indirect Branch Tracking"
1874 depends on X86_64 && CC_HAS_IBT && HAVE_OBJTOOL
1875 # https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
1876 depends on !LD_IS_LLD || LLD_VERSION >= 140000
1879 Build the kernel with support for Indirect Branch Tracking, a
1880 hardware support course-grain forward-edge Control Flow Integrity
1881 protection. It enforces that all indirect calls must land on
1882 an ENDBR instruction, as such, the compiler will instrument the
1883 code with them to make this happen.
1885 In addition to building the kernel with IBT, seal all functions that
1886 are not indirect call targets, avoiding them ever becoming one.
1888 This requires LTO like objtool runs and will slow down the build. It
1889 does significantly reduce the number of ENDBR instructions in the
1892 config X86_INTEL_MEMORY_PROTECTION_KEYS
1893 prompt "Memory Protection Keys"
1895 # Note: only available in 64-bit mode
1896 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1897 select ARCH_USES_HIGH_VMA_FLAGS
1898 select ARCH_HAS_PKEYS
1900 Memory Protection Keys provides a mechanism for enforcing
1901 page-based protections, but without requiring modification of the
1902 page tables when an application changes protection domains.
1904 For details, see Documentation/core-api/protection-keys.rst
1909 prompt "TSX enable mode"
1910 depends on CPU_SUP_INTEL
1911 default X86_INTEL_TSX_MODE_OFF
1913 Intel's TSX (Transactional Synchronization Extensions) feature
1914 allows to optimize locking protocols through lock elision which
1915 can lead to a noticeable performance boost.
1917 On the other hand it has been shown that TSX can be exploited
1918 to form side channel attacks (e.g. TAA) and chances are there
1919 will be more of those attacks discovered in the future.
1921 Therefore TSX is not enabled by default (aka tsx=off). An admin
1922 might override this decision by tsx=on the command line parameter.
1923 Even with TSX enabled, the kernel will attempt to enable the best
1924 possible TAA mitigation setting depending on the microcode available
1925 for the particular machine.
1927 This option allows to set the default tsx mode between tsx=on, =off
1928 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1931 Say off if not sure, auto if TSX is in use but it should be used on safe
1932 platforms or on if TSX is in use and the security aspect of tsx is not
1935 config X86_INTEL_TSX_MODE_OFF
1938 TSX is disabled if possible - equals to tsx=off command line parameter.
1940 config X86_INTEL_TSX_MODE_ON
1943 TSX is always enabled on TSX capable HW - equals the tsx=on command
1946 config X86_INTEL_TSX_MODE_AUTO
1949 TSX is enabled on TSX capable HW that is believed to be safe against
1950 side channel attacks- equals the tsx=auto command line parameter.
1954 bool "Software Guard eXtensions (SGX)"
1955 depends on X86_64 && CPU_SUP_INTEL
1957 depends on CRYPTO_SHA256=y
1960 select NUMA_KEEP_MEMINFO if NUMA
1963 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1964 that can be used by applications to set aside private regions of code
1965 and data, referred to as enclaves. An enclave's private memory can
1966 only be accessed by code running within the enclave. Accesses from
1967 outside the enclave, including other enclaves, are disallowed by
1973 bool "EFI runtime service support"
1976 select EFI_RUNTIME_WRAPPERS
1977 select ARCH_USE_MEMREMAP_PROT
1979 This enables the kernel to use EFI runtime services that are
1980 available (such as the EFI variable services).
1982 This option is only useful on systems that have EFI firmware.
1983 In addition, you should use the latest ELILO loader available
1984 at <http://elilo.sourceforge.net> in order to take advantage
1985 of EFI runtime services. However, even with this option, the
1986 resultant kernel should continue to boot on existing non-EFI
1990 bool "EFI stub support"
1992 depends on $(cc-option,-mabi=ms) || X86_32
1995 This kernel feature allows a bzImage to be loaded directly
1996 by EFI firmware without the use of a bootloader.
1998 See Documentation/admin-guide/efi-stub.rst for more information.
2001 bool "EFI mixed-mode support"
2002 depends on EFI_STUB && X86_64
2004 Enabling this feature allows a 64-bit kernel to be booted
2005 on a 32-bit firmware, provided that your CPU supports 64-bit
2008 Note that it is not possible to boot a mixed-mode enabled
2009 kernel via the EFI boot stub - a bootloader that supports
2010 the EFI handover protocol must be used.
2014 source "kernel/Kconfig.hz"
2017 bool "kexec system call"
2020 kexec is a system call that implements the ability to shutdown your
2021 current kernel, and to start another kernel. It is like a reboot
2022 but it is independent of the system firmware. And like a reboot
2023 you can start any kernel with it, not just Linux.
2025 The name comes from the similarity to the exec system call.
2027 It is an ongoing process to be certain the hardware in a machine
2028 is properly shutdown, so do not be surprised if this code does not
2029 initially work for you. As of this writing the exact hardware
2030 interface is strongly in flux, so no good recommendation can be
2034 bool "kexec file based system call"
2039 depends on CRYPTO_SHA256=y
2041 This is new version of kexec system call. This system call is
2042 file based and takes file descriptors as system call argument
2043 for kernel and initramfs as opposed to list of segments as
2044 accepted by previous system call.
2046 config ARCH_HAS_KEXEC_PURGATORY
2050 bool "Verify kernel signature during kexec_file_load() syscall"
2051 depends on KEXEC_FILE
2054 This option makes the kexec_file_load() syscall check for a valid
2055 signature of the kernel image. The image can still be loaded without
2056 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2057 there's a signature that we can check, then it must be valid.
2059 In addition to this option, you need to enable signature
2060 verification for the corresponding kernel image type being
2061 loaded in order for this to work.
2063 config KEXEC_SIG_FORCE
2064 bool "Require a valid signature in kexec_file_load() syscall"
2065 depends on KEXEC_SIG
2067 This option makes kernel signature verification mandatory for
2068 the kexec_file_load() syscall.
2070 config KEXEC_BZIMAGE_VERIFY_SIG
2071 bool "Enable bzImage signature verification support"
2072 depends on KEXEC_SIG
2073 depends on SIGNED_PE_FILE_VERIFICATION
2074 select SYSTEM_TRUSTED_KEYRING
2076 Enable bzImage signature verification support.
2079 bool "kernel crash dumps"
2080 depends on X86_64 || (X86_32 && HIGHMEM)
2082 Generate crash dump after being started by kexec.
2083 This should be normally only set in special crash dump kernels
2084 which are loaded in the main kernel with kexec-tools into
2085 a specially reserved region and then later executed after
2086 a crash by kdump/kexec. The crash dump kernel must be compiled
2087 to a memory address not used by the main kernel or BIOS using
2088 PHYSICAL_START, or it must be built as a relocatable image
2089 (CONFIG_RELOCATABLE=y).
2090 For more details see Documentation/admin-guide/kdump/kdump.rst
2094 depends on KEXEC && HIBERNATION
2096 Jump between original kernel and kexeced kernel and invoke
2097 code in physical address mode via KEXEC
2099 config PHYSICAL_START
2100 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2103 This gives the physical address where the kernel is loaded.
2105 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2106 bzImage will decompress itself to above physical address and
2107 run from there. Otherwise, bzImage will run from the address where
2108 it has been loaded by the boot loader and will ignore above physical
2111 In normal kdump cases one does not have to set/change this option
2112 as now bzImage can be compiled as a completely relocatable image
2113 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2114 address. This option is mainly useful for the folks who don't want
2115 to use a bzImage for capturing the crash dump and want to use a
2116 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2117 to be specifically compiled to run from a specific memory area
2118 (normally a reserved region) and this option comes handy.
2120 So if you are using bzImage for capturing the crash dump,
2121 leave the value here unchanged to 0x1000000 and set
2122 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2123 for capturing the crash dump change this value to start of
2124 the reserved region. In other words, it can be set based on
2125 the "X" value as specified in the "crashkernel=YM@XM"
2126 command line boot parameter passed to the panic-ed
2127 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2128 for more details about crash dumps.
2130 Usage of bzImage for capturing the crash dump is recommended as
2131 one does not have to build two kernels. Same kernel can be used
2132 as production kernel and capture kernel. Above option should have
2133 gone away after relocatable bzImage support is introduced. But it
2134 is present because there are users out there who continue to use
2135 vmlinux for dump capture. This option should go away down the
2138 Don't change this unless you know what you are doing.
2141 bool "Build a relocatable kernel"
2144 This builds a kernel image that retains relocation information
2145 so it can be loaded someplace besides the default 1MB.
2146 The relocations tend to make the kernel binary about 10% larger,
2147 but are discarded at runtime.
2149 One use is for the kexec on panic case where the recovery kernel
2150 must live at a different physical address than the primary
2153 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2154 it has been loaded at and the compile time physical address
2155 (CONFIG_PHYSICAL_START) is used as the minimum location.
2157 config RANDOMIZE_BASE
2158 bool "Randomize the address of the kernel image (KASLR)"
2159 depends on RELOCATABLE
2162 In support of Kernel Address Space Layout Randomization (KASLR),
2163 this randomizes the physical address at which the kernel image
2164 is decompressed and the virtual address where the kernel
2165 image is mapped, as a security feature that deters exploit
2166 attempts relying on knowledge of the location of kernel
2169 On 64-bit, the kernel physical and virtual addresses are
2170 randomized separately. The physical address will be anywhere
2171 between 16MB and the top of physical memory (up to 64TB). The
2172 virtual address will be randomized from 16MB up to 1GB (9 bits
2173 of entropy). Note that this also reduces the memory space
2174 available to kernel modules from 1.5GB to 1GB.
2176 On 32-bit, the kernel physical and virtual addresses are
2177 randomized together. They will be randomized from 16MB up to
2178 512MB (8 bits of entropy).
2180 Entropy is generated using the RDRAND instruction if it is
2181 supported. If RDTSC is supported, its value is mixed into
2182 the entropy pool as well. If neither RDRAND nor RDTSC are
2183 supported, then entropy is read from the i8254 timer. The
2184 usable entropy is limited by the kernel being built using
2185 2GB addressing, and that PHYSICAL_ALIGN must be at a
2186 minimum of 2MB. As a result, only 10 bits of entropy are
2187 theoretically possible, but the implementations are further
2188 limited due to memory layouts.
2192 # Relocation on x86 needs some additional build support
2193 config X86_NEED_RELOCS
2195 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2197 config PHYSICAL_ALIGN
2198 hex "Alignment value to which kernel should be aligned"
2200 range 0x2000 0x1000000 if X86_32
2201 range 0x200000 0x1000000 if X86_64
2203 This value puts the alignment restrictions on physical address
2204 where kernel is loaded and run from. Kernel is compiled for an
2205 address which meets above alignment restriction.
2207 If bootloader loads the kernel at a non-aligned address and
2208 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2209 address aligned to above value and run from there.
2211 If bootloader loads the kernel at a non-aligned address and
2212 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2213 load address and decompress itself to the address it has been
2214 compiled for and run from there. The address for which kernel is
2215 compiled already meets above alignment restrictions. Hence the
2216 end result is that kernel runs from a physical address meeting
2217 above alignment restrictions.
2219 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2220 this value must be a multiple of 0x200000.
2222 Don't change this unless you know what you are doing.
2224 config DYNAMIC_MEMORY_LAYOUT
2227 This option makes base addresses of vmalloc and vmemmap as well as
2228 __PAGE_OFFSET movable during boot.
2230 config RANDOMIZE_MEMORY
2231 bool "Randomize the kernel memory sections"
2233 depends on RANDOMIZE_BASE
2234 select DYNAMIC_MEMORY_LAYOUT
2235 default RANDOMIZE_BASE
2237 Randomizes the base virtual address of kernel memory sections
2238 (physical memory mapping, vmalloc & vmemmap). This security feature
2239 makes exploits relying on predictable memory locations less reliable.
2241 The order of allocations remains unchanged. Entropy is generated in
2242 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2243 configuration have in average 30,000 different possible virtual
2244 addresses for each memory section.
2248 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2249 hex "Physical memory mapping padding" if EXPERT
2250 depends on RANDOMIZE_MEMORY
2251 default "0xa" if MEMORY_HOTPLUG
2253 range 0x1 0x40 if MEMORY_HOTPLUG
2256 Define the padding in terabytes added to the existing physical
2257 memory size during kernel memory randomization. It is useful
2258 for memory hotplug support but reduces the entropy available for
2259 address randomization.
2261 If unsure, leave at the default value.
2267 config BOOTPARAM_HOTPLUG_CPU0
2268 bool "Set default setting of cpu0_hotpluggable"
2269 depends on HOTPLUG_CPU
2271 Set whether default state of cpu0_hotpluggable is on or off.
2273 Say Y here to enable CPU0 hotplug by default. If this switch
2274 is turned on, there is no need to give cpu0_hotplug kernel
2275 parameter and the CPU0 hotplug feature is enabled by default.
2277 Please note: there are two known CPU0 dependencies if you want
2278 to enable the CPU0 hotplug feature either by this switch or by
2279 cpu0_hotplug kernel parameter.
2281 First, resume from hibernate or suspend always starts from CPU0.
2282 So hibernate and suspend are prevented if CPU0 is offline.
2284 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2285 offline if any interrupt can not migrate out of CPU0. There may
2286 be other CPU0 dependencies.
2288 Please make sure the dependencies are under your control before
2289 you enable this feature.
2291 Say N if you don't want to enable CPU0 hotplug feature by default.
2292 You still can enable the CPU0 hotplug feature at boot by kernel
2293 parameter cpu0_hotplug.
2295 config DEBUG_HOTPLUG_CPU0
2297 prompt "Debug CPU0 hotplug"
2298 depends on HOTPLUG_CPU
2300 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2301 soon as possible and boots up userspace with CPU0 offlined. User
2302 can online CPU0 back after boot time.
2304 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2305 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2306 compilation or giving cpu0_hotplug kernel parameter at boot.
2312 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2313 depends on COMPAT_32
2315 Certain buggy versions of glibc will crash if they are
2316 presented with a 32-bit vDSO that is not mapped at the address
2317 indicated in its segment table.
2319 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2320 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2321 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2322 the only released version with the bug, but OpenSUSE 9
2323 contains a buggy "glibc 2.3.2".
2325 The symptom of the bug is that everything crashes on startup, saying:
2326 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2328 Saying Y here changes the default value of the vdso32 boot
2329 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2330 This works around the glibc bug but hurts performance.
2332 If unsure, say N: if you are compiling your own kernel, you
2333 are unlikely to be using a buggy version of glibc.
2336 prompt "vsyscall table for legacy applications"
2338 default LEGACY_VSYSCALL_XONLY
2340 Legacy user code that does not know how to find the vDSO expects
2341 to be able to issue three syscalls by calling fixed addresses in
2342 kernel space. Since this location is not randomized with ASLR,
2343 it can be used to assist security vulnerability exploitation.
2345 This setting can be changed at boot time via the kernel command
2346 line parameter vsyscall=[emulate|xonly|none]. Emulate mode
2347 is deprecated and can only be enabled using the kernel command
2350 On a system with recent enough glibc (2.14 or newer) and no
2351 static binaries, you can say None without a performance penalty
2352 to improve security.
2354 If unsure, select "Emulate execution only".
2356 config LEGACY_VSYSCALL_XONLY
2357 bool "Emulate execution only"
2359 The kernel traps and emulates calls into the fixed vsyscall
2360 address mapping and does not allow reads. This
2361 configuration is recommended when userspace might use the
2362 legacy vsyscall area but support for legacy binary
2363 instrumentation of legacy code is not needed. It mitigates
2364 certain uses of the vsyscall area as an ASLR-bypassing
2367 config LEGACY_VSYSCALL_NONE
2370 There will be no vsyscall mapping at all. This will
2371 eliminate any risk of ASLR bypass due to the vsyscall
2372 fixed address mapping. Attempts to use the vsyscalls
2373 will be reported to dmesg, so that either old or
2374 malicious userspace programs can be identified.
2379 bool "Built-in kernel command line"
2381 Allow for specifying boot arguments to the kernel at
2382 build time. On some systems (e.g. embedded ones), it is
2383 necessary or convenient to provide some or all of the
2384 kernel boot arguments with the kernel itself (that is,
2385 to not rely on the boot loader to provide them.)
2387 To compile command line arguments into the kernel,
2388 set this option to 'Y', then fill in the
2389 boot arguments in CONFIG_CMDLINE.
2391 Systems with fully functional boot loaders (i.e. non-embedded)
2392 should leave this option set to 'N'.
2395 string "Built-in kernel command string"
2396 depends on CMDLINE_BOOL
2399 Enter arguments here that should be compiled into the kernel
2400 image and used at boot time. If the boot loader provides a
2401 command line at boot time, it is appended to this string to
2402 form the full kernel command line, when the system boots.
2404 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2405 change this behavior.
2407 In most cases, the command line (whether built-in or provided
2408 by the boot loader) should specify the device for the root
2411 config CMDLINE_OVERRIDE
2412 bool "Built-in command line overrides boot loader arguments"
2413 depends on CMDLINE_BOOL && CMDLINE != ""
2415 Set this option to 'Y' to have the kernel ignore the boot loader
2416 command line, and use ONLY the built-in command line.
2418 This is used to work around broken boot loaders. This should
2419 be set to 'N' under normal conditions.
2421 config MODIFY_LDT_SYSCALL
2422 bool "Enable the LDT (local descriptor table)" if EXPERT
2425 Linux can allow user programs to install a per-process x86
2426 Local Descriptor Table (LDT) using the modify_ldt(2) system
2427 call. This is required to run 16-bit or segmented code such as
2428 DOSEMU or some Wine programs. It is also used by some very old
2429 threading libraries.
2431 Enabling this feature adds a small amount of overhead to
2432 context switches and increases the low-level kernel attack
2433 surface. Disabling it removes the modify_ldt(2) system call.
2435 Saying 'N' here may make sense for embedded or server kernels.
2437 config STRICT_SIGALTSTACK_SIZE
2438 bool "Enforce strict size checking for sigaltstack"
2439 depends on DYNAMIC_SIGFRAME
2441 For historical reasons MINSIGSTKSZ is a constant which became
2442 already too small with AVX512 support. Add a mechanism to
2443 enforce strict checking of the sigaltstack size against the
2444 real size of the FPU frame. This option enables the check
2445 by default. It can also be controlled via the kernel command
2446 line option 'strict_sas_size' independent of this config
2447 switch. Enabling it might break existing applications which
2448 allocate a too small sigaltstack but 'work' because they
2449 never get a signal delivered.
2451 Say 'N' unless you want to really enforce this check.
2453 source "kernel/livepatch/Kconfig"
2457 config ARCH_HAS_ADD_PAGES
2459 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2461 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2464 menu "Power management and ACPI options"
2466 config ARCH_HIBERNATION_HEADER
2468 depends on HIBERNATION
2470 source "kernel/power/Kconfig"
2472 source "drivers/acpi/Kconfig"
2479 tristate "APM (Advanced Power Management) BIOS support"
2480 depends on X86_32 && PM_SLEEP
2482 APM is a BIOS specification for saving power using several different
2483 techniques. This is mostly useful for battery powered laptops with
2484 APM compliant BIOSes. If you say Y here, the system time will be
2485 reset after a RESUME operation, the /proc/apm device will provide
2486 battery status information, and user-space programs will receive
2487 notification of APM "events" (e.g. battery status change).
2489 If you select "Y" here, you can disable actual use of the APM
2490 BIOS by passing the "apm=off" option to the kernel at boot time.
2492 Note that the APM support is almost completely disabled for
2493 machines with more than one CPU.
2495 In order to use APM, you will need supporting software. For location
2496 and more information, read <file:Documentation/power/apm-acpi.rst>
2497 and the Battery Powered Linux mini-HOWTO, available from
2498 <http://www.tldp.org/docs.html#howto>.
2500 This driver does not spin down disk drives (see the hdparm(8)
2501 manpage ("man 8 hdparm") for that), and it doesn't turn off
2502 VESA-compliant "green" monitors.
2504 This driver does not support the TI 4000M TravelMate and the ACER
2505 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2506 desktop machines also don't have compliant BIOSes, and this driver
2507 may cause those machines to panic during the boot phase.
2509 Generally, if you don't have a battery in your machine, there isn't
2510 much point in using this driver and you should say N. If you get
2511 random kernel OOPSes or reboots that don't seem to be related to
2512 anything, try disabling/enabling this option (or disabling/enabling
2515 Some other things you should try when experiencing seemingly random,
2518 1) make sure that you have enough swap space and that it is
2520 2) pass the "no-hlt" option to the kernel
2521 3) switch on floating point emulation in the kernel and pass
2522 the "no387" option to the kernel
2523 4) pass the "floppy=nodma" option to the kernel
2524 5) pass the "mem=4M" option to the kernel (thereby disabling
2525 all but the first 4 MB of RAM)
2526 6) make sure that the CPU is not over clocked.
2527 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2528 8) disable the cache from your BIOS settings
2529 9) install a fan for the video card or exchange video RAM
2530 10) install a better fan for the CPU
2531 11) exchange RAM chips
2532 12) exchange the motherboard.
2534 To compile this driver as a module, choose M here: the
2535 module will be called apm.
2539 config APM_IGNORE_USER_SUSPEND
2540 bool "Ignore USER SUSPEND"
2542 This option will ignore USER SUSPEND requests. On machines with a
2543 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2544 series notebooks, it is necessary to say Y because of a BIOS bug.
2546 config APM_DO_ENABLE
2547 bool "Enable PM at boot time"
2549 Enable APM features at boot time. From page 36 of the APM BIOS
2550 specification: "When disabled, the APM BIOS does not automatically
2551 power manage devices, enter the Standby State, enter the Suspend
2552 State, or take power saving steps in response to CPU Idle calls."
2553 This driver will make CPU Idle calls when Linux is idle (unless this
2554 feature is turned off -- see "Do CPU IDLE calls", below). This
2555 should always save battery power, but more complicated APM features
2556 will be dependent on your BIOS implementation. You may need to turn
2557 this option off if your computer hangs at boot time when using APM
2558 support, or if it beeps continuously instead of suspending. Turn
2559 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2560 T400CDT. This is off by default since most machines do fine without
2565 bool "Make CPU Idle calls when idle"
2567 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2568 On some machines, this can activate improved power savings, such as
2569 a slowed CPU clock rate, when the machine is idle. These idle calls
2570 are made after the idle loop has run for some length of time (e.g.,
2571 333 mS). On some machines, this will cause a hang at boot time or
2572 whenever the CPU becomes idle. (On machines with more than one CPU,
2573 this option does nothing.)
2575 config APM_DISPLAY_BLANK
2576 bool "Enable console blanking using APM"
2578 Enable console blanking using the APM. Some laptops can use this to
2579 turn off the LCD backlight when the screen blanker of the Linux
2580 virtual console blanks the screen. Note that this is only used by
2581 the virtual console screen blanker, and won't turn off the backlight
2582 when using the X Window system. This also doesn't have anything to
2583 do with your VESA-compliant power-saving monitor. Further, this
2584 option doesn't work for all laptops -- it might not turn off your
2585 backlight at all, or it might print a lot of errors to the console,
2586 especially if you are using gpm.
2588 config APM_ALLOW_INTS
2589 bool "Allow interrupts during APM BIOS calls"
2591 Normally we disable external interrupts while we are making calls to
2592 the APM BIOS as a measure to lessen the effects of a badly behaving
2593 BIOS implementation. The BIOS should reenable interrupts if it
2594 needs to. Unfortunately, some BIOSes do not -- especially those in
2595 many of the newer IBM Thinkpads. If you experience hangs when you
2596 suspend, try setting this to Y. Otherwise, say N.
2600 source "drivers/cpufreq/Kconfig"
2602 source "drivers/cpuidle/Kconfig"
2604 source "drivers/idle/Kconfig"
2608 menu "Bus options (PCI etc.)"
2611 prompt "PCI access mode"
2612 depends on X86_32 && PCI
2615 On PCI systems, the BIOS can be used to detect the PCI devices and
2616 determine their configuration. However, some old PCI motherboards
2617 have BIOS bugs and may crash if this is done. Also, some embedded
2618 PCI-based systems don't have any BIOS at all. Linux can also try to
2619 detect the PCI hardware directly without using the BIOS.
2621 With this option, you can specify how Linux should detect the
2622 PCI devices. If you choose "BIOS", the BIOS will be used,
2623 if you choose "Direct", the BIOS won't be used, and if you
2624 choose "MMConfig", then PCI Express MMCONFIG will be used.
2625 If you choose "Any", the kernel will try MMCONFIG, then the
2626 direct access method and falls back to the BIOS if that doesn't
2627 work. If unsure, go with the default, which is "Any".
2632 config PCI_GOMMCONFIG
2649 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2651 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2654 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2657 bool "Support mmconfig PCI config space access" if X86_64
2659 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2660 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2664 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2668 depends on PCI && XEN
2670 config MMCONF_FAM10H
2672 depends on X86_64 && PCI_MMCONFIG && ACPI
2674 config PCI_CNB20LE_QUIRK
2675 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2678 Read the PCI windows out of the CNB20LE host bridge. This allows
2679 PCI hotplug to work on systems with the CNB20LE chipset which do
2682 There's no public spec for this chipset, and this functionality
2683 is known to be incomplete.
2685 You should say N unless you know you need this.
2688 bool "ISA bus support on modern systems" if EXPERT
2690 Expose ISA bus device drivers and options available for selection and
2691 configuration. Enable this option if your target machine has an ISA
2692 bus. ISA is an older system, displaced by PCI and newer bus
2693 architectures -- if your target machine is modern, it probably does
2694 not have an ISA bus.
2698 # x86_64 have no ISA slots, but can have ISA-style DMA.
2700 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2703 Enables ISA-style DMA support for devices requiring such controllers.
2711 Find out whether you have ISA slots on your motherboard. ISA is the
2712 name of a bus system, i.e. the way the CPU talks to the other stuff
2713 inside your box. Other bus systems are PCI, EISA, MicroChannel
2714 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2715 newer boards don't support it. If you have ISA, say Y, otherwise N.
2718 tristate "NatSemi SCx200 support"
2720 This provides basic support for National Semiconductor's
2721 (now AMD's) Geode processors. The driver probes for the
2722 PCI-IDs of several on-chip devices, so its a good dependency
2723 for other scx200_* drivers.
2725 If compiled as a module, the driver is named scx200.
2727 config SCx200HR_TIMER
2728 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2732 This driver provides a clocksource built upon the on-chip
2733 27MHz high-resolution timer. Its also a workaround for
2734 NSC Geode SC-1100's buggy TSC, which loses time when the
2735 processor goes idle (as is done by the scheduler). The
2736 other workaround is idle=poll boot option.
2739 bool "One Laptop Per Child support"
2747 Add support for detecting the unique features of the OLPC
2751 bool "OLPC XO-1 Power Management"
2752 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2754 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2757 bool "OLPC XO-1 Real Time Clock"
2758 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2760 Add support for the XO-1 real time clock, which can be used as a
2761 programmable wakeup source.
2764 bool "OLPC XO-1 SCI extras"
2765 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2769 Add support for SCI-based features of the OLPC XO-1 laptop:
2770 - EC-driven system wakeups
2774 - AC adapter status updates
2775 - Battery status updates
2777 config OLPC_XO15_SCI
2778 bool "OLPC XO-1.5 SCI extras"
2779 depends on OLPC && ACPI
2782 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2783 - EC-driven system wakeups
2784 - AC adapter status updates
2785 - Battery status updates
2788 bool "PCEngines ALIX System Support (LED setup)"
2791 This option enables system support for the PCEngines ALIX.
2792 At present this just sets up LEDs for GPIO control on
2793 ALIX2/3/6 boards. However, other system specific setup should
2796 Note: You must still enable the drivers for GPIO and LED support
2797 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2799 Note: You have to set alix.force=1 for boards with Award BIOS.
2802 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2805 This option enables system support for the Soekris Engineering net5501.
2808 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2812 This option enables system support for the Traverse Technologies GEOS.
2815 bool "Technologic Systems TS-5500 platform support"
2817 select CHECK_SIGNATURE
2821 This option enables system support for the Technologic Systems TS-5500.
2827 depends on CPU_SUP_AMD && PCI
2831 menu "Binary Emulations"
2833 config IA32_EMULATION
2834 bool "IA32 Emulation"
2836 select ARCH_WANT_OLD_COMPAT_IPC
2838 select COMPAT_OLD_SIGACTION
2840 Include code to run legacy 32-bit programs under a
2841 64-bit kernel. You should likely turn this on, unless you're
2842 100% sure that you don't have any 32-bit programs left.
2845 bool "x32 ABI for 64-bit mode"
2847 # llvm-objcopy does not convert x86_64 .note.gnu.property or
2848 # compressed debug sections to x86_x32 properly:
2849 # https://github.com/ClangBuiltLinux/linux/issues/514
2850 # https://github.com/ClangBuiltLinux/linux/issues/1141
2851 depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
2853 Include code to run binaries for the x32 native 32-bit ABI
2854 for 64-bit processors. An x32 process gets access to the
2855 full 64-bit register file and wide data path while leaving
2856 pointers at 32 bits for smaller memory footprint.
2860 depends on IA32_EMULATION || X86_32
2862 select OLD_SIGSUSPEND3
2866 depends on IA32_EMULATION || X86_X32_ABI
2868 config COMPAT_FOR_U64_ALIGNMENT
2874 config HAVE_ATOMIC_IOMAP
2878 source "arch/x86/kvm/Kconfig"
2880 source "arch/x86/Kconfig.assembler"