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
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
141 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
142 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
143 select GENERIC_IRQ_MIGRATION if SMP
144 select GENERIC_IRQ_PROBE
145 select GENERIC_IRQ_RESERVATION_MODE
146 select GENERIC_IRQ_SHOW
147 select GENERIC_PENDING_IRQ if SMP
148 select GENERIC_PTDUMP
149 select GENERIC_SMP_IDLE_THREAD
150 select GENERIC_TIME_VSYSCALL
151 select GENERIC_GETTIMEOFDAY
152 select GENERIC_VDSO_TIME_NS
153 select GUP_GET_PTE_LOW_HIGH if X86_PAE
154 select HARDIRQS_SW_RESEND
155 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
156 select HAVE_ACPI_APEI if ACPI
157 select HAVE_ACPI_APEI_NMI if ACPI
158 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
159 select HAVE_ARCH_AUDITSYSCALL
160 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
161 select HAVE_ARCH_JUMP_LABEL
162 select HAVE_ARCH_JUMP_LABEL_RELATIVE
163 select HAVE_ARCH_KASAN if X86_64
164 select HAVE_ARCH_KASAN_VMALLOC if X86_64
165 select HAVE_ARCH_KFENCE
166 select HAVE_ARCH_KGDB
167 select HAVE_ARCH_MMAP_RND_BITS if MMU
168 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
169 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
170 select HAVE_ARCH_PREL32_RELOCATIONS
171 select HAVE_ARCH_SECCOMP_FILTER
172 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
173 select HAVE_ARCH_STACKLEAK
174 select HAVE_ARCH_TRACEHOOK
175 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
176 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
177 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
178 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
179 select HAVE_ARCH_VMAP_STACK if X86_64
180 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
181 select HAVE_ARCH_WITHIN_STACK_FRAMES
182 select HAVE_ASM_MODVERSIONS
183 select HAVE_CMPXCHG_DOUBLE
184 select HAVE_CMPXCHG_LOCAL
185 select HAVE_CONTEXT_TRACKING if X86_64
186 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
187 select HAVE_C_RECORDMCOUNT
188 select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION
189 select HAVE_BUILDTIME_MCOUNT_SORT
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_SETUP_PER_CPU_AREA
244 select HAVE_SOFTIRQ_ON_OWN_STACK
245 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
246 select HAVE_STACK_VALIDATION if X86_64
247 select HAVE_STATIC_CALL
248 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
249 select HAVE_PREEMPT_DYNAMIC
251 select HAVE_SYSCALL_TRACEPOINTS
252 select HAVE_UNSTABLE_SCHED_CLOCK
253 select HAVE_USER_RETURN_NOTIFIER
254 select HAVE_GENERIC_VDSO
255 select HOTPLUG_SMT if SMP
256 select IRQ_FORCED_THREADING
257 select NEED_PER_CPU_EMBED_FIRST_CHUNK
258 select NEED_PER_CPU_PAGE_FIRST_CHUNK
259 select NEED_SG_DMA_LENGTH
260 select PCI_DOMAINS if PCI
261 select PCI_LOCKLESS_CONFIG if PCI
264 select RTC_MC146818_LIB
267 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
268 select SYSCTL_EXCEPTION_TRACE
269 select THREAD_INFO_IN_TASK
270 select TRACE_IRQFLAGS_SUPPORT
271 select USER_STACKTRACE_SUPPORT
273 select HAVE_ARCH_KCSAN if X86_64
274 select X86_FEATURE_NAMES if PROC_FS
275 select PROC_PID_ARCH_STATUS if PROC_FS
276 select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
277 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
279 config INSTRUCTION_DECODER
281 depends on KPROBES || PERF_EVENTS || UPROBES
285 default "elf32-i386" if X86_32
286 default "elf64-x86-64" if X86_64
288 config LOCKDEP_SUPPORT
291 config STACKTRACE_SUPPORT
297 config ARCH_MMAP_RND_BITS_MIN
301 config ARCH_MMAP_RND_BITS_MAX
305 config ARCH_MMAP_RND_COMPAT_BITS_MIN
308 config ARCH_MMAP_RND_COMPAT_BITS_MAX
314 config GENERIC_ISA_DMA
316 depends on ISA_DMA_API
321 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
323 config GENERIC_BUG_RELATIVE_POINTERS
326 config ARCH_MAY_HAVE_PC_FDC
328 depends on ISA_DMA_API
330 config GENERIC_CALIBRATE_DELAY
333 config ARCH_HAS_CPU_RELAX
336 config ARCH_HAS_FILTER_PGPROT
339 config ARCH_HIBERNATION_POSSIBLE
344 default 1024 if X86_64
347 config ARCH_SUSPEND_POSSIBLE
350 config ARCH_WANT_GENERAL_HUGETLB
356 config KASAN_SHADOW_OFFSET
359 default 0xdffffc0000000000
361 config HAVE_INTEL_TXT
363 depends on INTEL_IOMMU && ACPI
367 depends on X86_32 && SMP
371 depends on X86_64 && SMP
373 config ARCH_SUPPORTS_UPROBES
376 config FIX_EARLYCON_MEM
379 config DYNAMIC_PHYSICAL_MASK
382 config PGTABLE_LEVELS
384 default 5 if X86_5LEVEL
389 config CC_HAS_SANE_STACKPROTECTOR
391 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
392 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
394 We have to make sure stack protector is unconditionally disabled if
395 the compiler produces broken code or if it does not let us control
396 the segment on 32-bit kernels.
398 menu "Processor type and features"
401 bool "Symmetric multi-processing support"
403 This enables support for systems with more than one CPU. If you have
404 a system with only one CPU, say N. If you have a system with more
407 If you say N here, the kernel will run on uni- and multiprocessor
408 machines, but will use only one CPU of a multiprocessor machine. If
409 you say Y here, the kernel will run on many, but not all,
410 uniprocessor machines. On a uniprocessor machine, the kernel
411 will run faster if you say N here.
413 Note that if you say Y here and choose architecture "586" or
414 "Pentium" under "Processor family", the kernel will not work on 486
415 architectures. Similarly, multiprocessor kernels for the "PPro"
416 architecture may not work on all Pentium based boards.
418 People using multiprocessor machines who say Y here should also say
419 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
420 Management" code will be disabled if you say Y here.
422 See also <file:Documentation/x86/i386/IO-APIC.rst>,
423 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
424 <http://www.tldp.org/docs.html#howto>.
426 If you don't know what to do here, say N.
428 config X86_FEATURE_NAMES
429 bool "Processor feature human-readable names" if EMBEDDED
432 This option compiles in a table of x86 feature bits and corresponding
433 names. This is required to support /proc/cpuinfo and a few kernel
434 messages. You can disable this to save space, at the expense of
435 making those few kernel messages show numeric feature bits instead.
440 bool "Support x2apic"
441 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
443 This enables x2apic support on CPUs that have this feature.
445 This allows 32-bit apic IDs (so it can support very large systems),
446 and accesses the local apic via MSRs not via mmio.
448 If you don't know what to do here, say N.
451 bool "Enable MPS table" if ACPI
453 depends on X86_LOCAL_APIC
455 For old smp systems that do not have proper acpi support. Newer systems
456 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
460 depends on X86_GOLDFISH
463 bool "Avoid speculative indirect branches in kernel"
466 Compile kernel with the retpoline compiler options to guard against
467 kernel-to-user data leaks by avoiding speculative indirect
468 branches. Requires a compiler with -mindirect-branch=thunk-extern
469 support for full protection. The kernel may run slower.
472 def_bool $(cc-option,-mharden-sls=all)
475 bool "Mitigate Straight-Line-Speculation"
476 depends on CC_HAS_SLS && X86_64
479 Compile the kernel with straight-line-speculation options to guard
480 against straight line speculation. The kernel image might be slightly
483 config X86_CPU_RESCTRL
484 bool "x86 CPU resource control support"
485 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
487 select PROC_CPU_RESCTRL if PROC_FS
489 Enable x86 CPU resource control support.
491 Provide support for the allocation and monitoring of system resources
494 Intel calls this Intel Resource Director Technology
495 (Intel(R) RDT). More information about RDT can be found in the
496 Intel x86 Architecture Software Developer Manual.
498 AMD calls this AMD Platform Quality of Service (AMD QoS).
499 More information about AMD QoS can be found in the AMD64 Technology
500 Platform Quality of Service Extensions manual.
506 bool "Support for big SMP systems with more than 8 CPUs"
509 This option is needed for the systems that have more than 8 CPUs.
511 config X86_EXTENDED_PLATFORM
512 bool "Support for extended (non-PC) x86 platforms"
515 If you disable this option then the kernel will only support
516 standard PC platforms. (which covers the vast majority of
519 If you enable this option then you'll be able to select support
520 for the following (non-PC) 32 bit x86 platforms:
521 Goldfish (Android emulator)
524 SGI 320/540 (Visual Workstation)
525 STA2X11-based (e.g. Northville)
526 Moorestown MID devices
528 If you have one of these systems, or if you want to build a
529 generic distribution kernel, say Y here - otherwise say N.
533 config X86_EXTENDED_PLATFORM
534 bool "Support for extended (non-PC) x86 platforms"
537 If you disable this option then the kernel will only support
538 standard PC platforms. (which covers the vast majority of
541 If you enable this option then you'll be able to select support
542 for the following (non-PC) 64 bit x86 platforms:
547 If you have one of these systems, or if you want to build a
548 generic distribution kernel, say Y here - otherwise say N.
550 # This is an alphabetically sorted list of 64 bit extended platforms
551 # Please maintain the alphabetic order if and when there are additions
553 bool "Numascale NumaChip"
555 depends on X86_EXTENDED_PLATFORM
558 depends on X86_X2APIC
559 depends on PCI_MMCONFIG
561 Adds support for Numascale NumaChip large-SMP systems. Needed to
562 enable more than ~168 cores.
563 If you don't have one of these, you should say N here.
567 select HYPERVISOR_GUEST
569 depends on X86_64 && PCI
570 depends on X86_EXTENDED_PLATFORM
573 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
574 supposed to run on these EM64T-based machines. Only choose this option
575 if you have one of these machines.
578 bool "SGI Ultraviolet"
580 depends on X86_EXTENDED_PLATFORM
583 depends on KEXEC_CORE
584 depends on X86_X2APIC
587 This option is needed in order to support SGI Ultraviolet systems.
588 If you don't have one of these, you should say N here.
590 # Following is an alphabetically sorted list of 32 bit extended platforms
591 # Please maintain the alphabetic order if and when there are additions
594 bool "Goldfish (Virtual Platform)"
595 depends on X86_EXTENDED_PLATFORM
597 Enable support for the Goldfish virtual platform used primarily
598 for Android development. Unless you are building for the Android
599 Goldfish emulator say N here.
602 bool "CE4100 TV platform"
604 depends on PCI_GODIRECT
605 depends on X86_IO_APIC
607 depends on X86_EXTENDED_PLATFORM
608 select X86_REBOOTFIXUPS
610 select OF_EARLY_FLATTREE
612 Select for the Intel CE media processor (CE4100) SOC.
613 This option compiles in support for the CE4100 SOC for settop
614 boxes and media devices.
617 bool "Intel MID platform support"
618 depends on X86_EXTENDED_PLATFORM
619 depends on X86_PLATFORM_DEVICES
621 depends on X86_64 || (PCI_GOANY && X86_32)
622 depends on X86_IO_APIC
627 Select to build a kernel capable of supporting Intel MID (Mobile
628 Internet Device) platform systems which do not have the PCI legacy
629 interfaces. If you are building for a PC class system say N here.
631 Intel MID platforms are based on an Intel processor and chipset which
632 consume less power than most of the x86 derivatives.
634 config X86_INTEL_QUARK
635 bool "Intel Quark platform support"
637 depends on X86_EXTENDED_PLATFORM
638 depends on X86_PLATFORM_DEVICES
642 depends on X86_IO_APIC
647 Select to include support for Quark X1000 SoC.
648 Say Y here if you have a Quark based system such as the Arduino
649 compatible Intel Galileo.
651 config X86_INTEL_LPSS
652 bool "Intel Low Power Subsystem Support"
653 depends on X86 && ACPI && PCI
658 Select to build support for Intel Low Power Subsystem such as
659 found on Intel Lynxpoint PCH. Selecting this option enables
660 things like clock tree (common clock framework) and pincontrol
661 which are needed by the LPSS peripheral drivers.
663 config X86_AMD_PLATFORM_DEVICE
664 bool "AMD ACPI2Platform devices support"
669 Select to interpret AMD specific ACPI device to platform device
670 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
671 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
672 implemented under PINCTRL subsystem.
675 tristate "Intel SoC IOSF Sideband support for SoC platforms"
678 This option enables sideband register access support for Intel SoC
679 platforms. On these platforms the IOSF sideband is used in lieu of
680 MSR's for some register accesses, mostly but not limited to thermal
681 and power. Drivers may query the availability of this device to
682 determine if they need the sideband in order to work on these
683 platforms. The sideband is available on the following SoC products.
684 This list is not meant to be exclusive.
689 You should say Y if you are running a kernel on one of these SoC's.
691 config IOSF_MBI_DEBUG
692 bool "Enable IOSF sideband access through debugfs"
693 depends on IOSF_MBI && DEBUG_FS
695 Select this option to expose the IOSF sideband access registers (MCR,
696 MDR, MCRX) through debugfs to write and read register information from
697 different units on the SoC. This is most useful for obtaining device
698 state information for debug and analysis. As this is a general access
699 mechanism, users of this option would have specific knowledge of the
700 device they want to access.
702 If you don't require the option or are in doubt, say N.
705 bool "RDC R-321x SoC"
707 depends on X86_EXTENDED_PLATFORM
709 select X86_REBOOTFIXUPS
711 This option is needed for RDC R-321x system-on-chip, also known
713 If you don't have one of these chips, you should say N here.
715 config X86_32_NON_STANDARD
716 bool "Support non-standard 32-bit SMP architectures"
717 depends on X86_32 && SMP
718 depends on X86_EXTENDED_PLATFORM
720 This option compiles in the bigsmp and STA2X11 default
721 subarchitectures. It is intended for a generic binary
722 kernel. If you select them all, kernel will probe it one by
723 one and will fallback to default.
725 # Alphabetically sorted list of Non standard 32 bit platforms
727 config X86_SUPPORTS_MEMORY_FAILURE
729 # MCE code calls memory_failure():
731 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
732 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
733 depends on X86_64 || !SPARSEMEM
734 select ARCH_SUPPORTS_MEMORY_FAILURE
737 bool "STA2X11 Companion Chip Support"
738 depends on X86_32_NON_STANDARD && PCI
743 This adds support for boards based on the STA2X11 IO-Hub,
744 a.k.a. "ConneXt". The chip is used in place of the standard
745 PC chipset, so all "standard" peripherals are missing. If this
746 option is selected the kernel will still be able to boot on
747 standard PC machines.
750 tristate "Eurobraille/Iris poweroff module"
753 The Iris machines from EuroBraille do not have APM or ACPI support
754 to shut themselves down properly. A special I/O sequence is
755 needed to do so, which is what this module does at
758 This is only for Iris machines from EuroBraille.
762 config SCHED_OMIT_FRAME_POINTER
764 prompt "Single-depth WCHAN output"
767 Calculate simpler /proc/<PID>/wchan values. If this option
768 is disabled then wchan values will recurse back to the
769 caller function. This provides more accurate wchan values,
770 at the expense of slightly more scheduling overhead.
772 If in doubt, say "Y".
774 menuconfig HYPERVISOR_GUEST
775 bool "Linux guest support"
777 Say Y here to enable options for running Linux under various hyper-
778 visors. This option enables basic hypervisor detection and platform
781 If you say N, all options in this submenu will be skipped and
782 disabled, and Linux guest support won't be built in.
787 bool "Enable paravirtualization code"
788 depends on HAVE_STATIC_CALL
790 This changes the kernel so it can modify itself when it is run
791 under a hypervisor, potentially improving performance significantly
792 over full virtualization. However, when run without a hypervisor
793 the kernel is theoretically slower and slightly larger.
798 config PARAVIRT_DEBUG
799 bool "paravirt-ops debugging"
800 depends on PARAVIRT && DEBUG_KERNEL
802 Enable to debug paravirt_ops internals. Specifically, BUG if
803 a paravirt_op is missing when it is called.
805 config PARAVIRT_SPINLOCKS
806 bool "Paravirtualization layer for spinlocks"
807 depends on PARAVIRT && SMP
809 Paravirtualized spinlocks allow a pvops backend to replace the
810 spinlock implementation with something virtualization-friendly
811 (for example, block the virtual CPU rather than spinning).
813 It has a minimal impact on native kernels and gives a nice performance
814 benefit on paravirtualized KVM / Xen kernels.
816 If you are unsure how to answer this question, answer Y.
818 config X86_HV_CALLBACK_VECTOR
821 source "arch/x86/xen/Kconfig"
824 bool "KVM Guest support (including kvmclock)"
826 select PARAVIRT_CLOCK
827 select ARCH_CPUIDLE_HALTPOLL
828 select X86_HV_CALLBACK_VECTOR
831 This option enables various optimizations for running under the KVM
832 hypervisor. It includes a paravirtualized clock, so that instead
833 of relying on a PIT (or probably other) emulation by the
834 underlying device model, the host provides the guest with
835 timing infrastructure such as time of day, and system time
837 config ARCH_CPUIDLE_HALTPOLL
839 prompt "Disable host haltpoll when loading haltpoll driver"
841 If virtualized under KVM, disable host haltpoll.
844 bool "Support for running PVH guests"
846 This option enables the PVH entry point for guest virtual machines
847 as specified in the x86/HVM direct boot ABI.
849 config PARAVIRT_TIME_ACCOUNTING
850 bool "Paravirtual steal time accounting"
853 Select this option to enable fine granularity task steal time
854 accounting. Time spent executing other tasks in parallel with
855 the current vCPU is discounted from the vCPU power. To account for
856 that, there can be a small performance impact.
858 If in doubt, say N here.
860 config PARAVIRT_CLOCK
863 config JAILHOUSE_GUEST
864 bool "Jailhouse non-root cell support"
865 depends on X86_64 && PCI
868 This option allows to run Linux as guest in a Jailhouse non-root
869 cell. You can leave this option disabled if you only want to start
870 Jailhouse and run Linux afterwards in the root cell.
873 bool "ACRN Guest support"
875 select X86_HV_CALLBACK_VECTOR
877 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
878 a flexible, lightweight reference open-source hypervisor, built with
879 real-time and safety-criticality in mind. It is built for embedded
880 IOT with small footprint and real-time features. More details can be
881 found in https://projectacrn.org/.
883 endif #HYPERVISOR_GUEST
885 source "arch/x86/Kconfig.cpu"
889 prompt "HPET Timer Support" if X86_32
891 Use the IA-PC HPET (High Precision Event Timer) to manage
892 time in preference to the PIT and RTC, if a HPET is
894 HPET is the next generation timer replacing legacy 8254s.
895 The HPET provides a stable time base on SMP
896 systems, unlike the TSC, but it is more expensive to access,
897 as it is off-chip. The interface used is documented
898 in the HPET spec, revision 1.
900 You can safely choose Y here. However, HPET will only be
901 activated if the platform and the BIOS support this feature.
902 Otherwise the 8254 will be used for timing services.
904 Choose N to continue using the legacy 8254 timer.
906 config HPET_EMULATE_RTC
908 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
910 # Mark as expert because too many people got it wrong.
911 # The code disables itself when not needed.
914 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
915 bool "Enable DMI scanning" if EXPERT
917 Enabled scanning of DMI to identify machine quirks. Say Y
918 here unless you have verified that your setup is not
919 affected by entries in the DMI blacklist. Required by PNP
923 bool "Old AMD GART IOMMU support"
927 depends on X86_64 && PCI && AMD_NB
929 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
930 GART based hardware IOMMUs.
932 The GART supports full DMA access for devices with 32-bit access
933 limitations, on systems with more than 3 GB. This is usually needed
934 for USB, sound, many IDE/SATA chipsets and some other devices.
936 Newer systems typically have a modern AMD IOMMU, supported via
937 the CONFIG_AMD_IOMMU=y config option.
939 In normal configurations this driver is only active when needed:
940 there's more than 3 GB of memory and the system contains a
941 32-bit limited device.
946 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
947 depends on X86_64 && SMP && DEBUG_KERNEL
948 select CPUMASK_OFFSTACK
950 Enable maximum number of CPUS and NUMA Nodes for this architecture.
954 # The maximum number of CPUs supported:
956 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
957 # and which can be configured interactively in the
958 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
960 # The ranges are different on 32-bit and 64-bit kernels, depending on
961 # hardware capabilities and scalability features of the kernel.
963 # ( If MAXSMP is enabled we just use the highest possible value and disable
964 # interactive configuration. )
967 config NR_CPUS_RANGE_BEGIN
969 default NR_CPUS_RANGE_END if MAXSMP
973 config NR_CPUS_RANGE_END
976 default 64 if SMP && X86_BIGSMP
977 default 8 if SMP && !X86_BIGSMP
980 config NR_CPUS_RANGE_END
983 default 8192 if SMP && CPUMASK_OFFSTACK
984 default 512 if SMP && !CPUMASK_OFFSTACK
987 config NR_CPUS_DEFAULT
990 default 32 if X86_BIGSMP
994 config NR_CPUS_DEFAULT
997 default 8192 if MAXSMP
1002 int "Maximum number of CPUs" if SMP && !MAXSMP
1003 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1004 default NR_CPUS_DEFAULT
1006 This allows you to specify the maximum number of CPUs which this
1007 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1008 supported value is 8192, otherwise the maximum value is 512. The
1009 minimum value which makes sense is 2.
1011 This is purely to save memory: each supported CPU adds about 8KB
1012 to the kernel image.
1014 config SCHED_CLUSTER
1015 bool "Cluster scheduler support"
1019 Cluster scheduler support improves the CPU scheduler's decision
1020 making when dealing with machines that have clusters of CPUs.
1021 Cluster usually means a couple of CPUs which are placed closely
1022 by sharing mid-level caches, last-level cache tags or internal
1030 prompt "Multi-core scheduler support"
1033 Multi-core scheduler support improves the CPU scheduler's decision
1034 making when dealing with multi-core CPU chips at a cost of slightly
1035 increased overhead in some places. If unsure say N here.
1037 config SCHED_MC_PRIO
1038 bool "CPU core priorities scheduler support"
1039 depends on SCHED_MC && CPU_SUP_INTEL
1040 select X86_INTEL_PSTATE
1044 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1045 core ordering determined at manufacturing time, which allows
1046 certain cores to reach higher turbo frequencies (when running
1047 single threaded workloads) than others.
1049 Enabling this kernel feature teaches the scheduler about
1050 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1051 scheduler's CPU selection logic accordingly, so that higher
1052 overall system performance can be achieved.
1054 This feature will have no effect on CPUs without this feature.
1056 If unsure say Y here.
1060 depends on !SMP && X86_LOCAL_APIC
1063 bool "Local APIC support on uniprocessors" if !PCI_MSI
1065 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1067 A local APIC (Advanced Programmable Interrupt Controller) is an
1068 integrated interrupt controller in the CPU. If you have a single-CPU
1069 system which has a processor with a local APIC, you can say Y here to
1070 enable and use it. If you say Y here even though your machine doesn't
1071 have a local APIC, then the kernel will still run with no slowdown at
1072 all. The local APIC supports CPU-generated self-interrupts (timer,
1073 performance counters), and the NMI watchdog which detects hard
1076 config X86_UP_IOAPIC
1077 bool "IO-APIC support on uniprocessors"
1078 depends on X86_UP_APIC
1080 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1081 SMP-capable replacement for PC-style interrupt controllers. Most
1082 SMP systems and many recent uniprocessor systems have one.
1084 If you have a single-CPU system with an IO-APIC, you can say Y here
1085 to use it. If you say Y here even though your machine doesn't have
1086 an IO-APIC, then the kernel will still run with no slowdown at all.
1088 config X86_LOCAL_APIC
1090 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1091 select IRQ_DOMAIN_HIERARCHY
1092 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1096 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1098 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1099 bool "Reroute for broken boot IRQs"
1100 depends on X86_IO_APIC
1102 This option enables a workaround that fixes a source of
1103 spurious interrupts. This is recommended when threaded
1104 interrupt handling is used on systems where the generation of
1105 superfluous "boot interrupts" cannot be disabled.
1107 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1108 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1109 kernel does during interrupt handling). On chipsets where this
1110 boot IRQ generation cannot be disabled, this workaround keeps
1111 the original IRQ line masked so that only the equivalent "boot
1112 IRQ" is delivered to the CPUs. The workaround also tells the
1113 kernel to set up the IRQ handler on the boot IRQ line. In this
1114 way only one interrupt is delivered to the kernel. Otherwise
1115 the spurious second interrupt may cause the kernel to bring
1116 down (vital) interrupt lines.
1118 Only affects "broken" chipsets. Interrupt sharing may be
1119 increased on these systems.
1122 bool "Machine Check / overheating reporting"
1123 select GENERIC_ALLOCATOR
1126 Machine Check support allows the processor to notify the
1127 kernel if it detects a problem (e.g. overheating, data corruption).
1128 The action the kernel takes depends on the severity of the problem,
1129 ranging from warning messages to halting the machine.
1131 config X86_MCELOG_LEGACY
1132 bool "Support for deprecated /dev/mcelog character device"
1135 Enable support for /dev/mcelog which is needed by the old mcelog
1136 userspace logging daemon. Consider switching to the new generation
1139 config X86_MCE_INTEL
1141 prompt "Intel MCE features"
1142 depends on X86_MCE && X86_LOCAL_APIC
1144 Additional support for intel specific MCE features such as
1145 the thermal monitor.
1149 prompt "AMD MCE features"
1150 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1152 Additional support for AMD specific MCE features such as
1153 the DRAM Error Threshold.
1155 config X86_ANCIENT_MCE
1156 bool "Support for old Pentium 5 / WinChip machine checks"
1157 depends on X86_32 && X86_MCE
1159 Include support for machine check handling on old Pentium 5 or WinChip
1160 systems. These typically need to be enabled explicitly on the command
1163 config X86_MCE_THRESHOLD
1164 depends on X86_MCE_AMD || X86_MCE_INTEL
1167 config X86_MCE_INJECT
1168 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1169 tristate "Machine check injector support"
1171 Provide support for injecting machine checks for testing purposes.
1172 If you don't know what a machine check is and you don't do kernel
1173 QA it is safe to say n.
1175 source "arch/x86/events/Kconfig"
1177 config X86_LEGACY_VM86
1178 bool "Legacy VM86 support"
1181 This option allows user programs to put the CPU into V8086
1182 mode, which is an 80286-era approximation of 16-bit real mode.
1184 Some very old versions of X and/or vbetool require this option
1185 for user mode setting. Similarly, DOSEMU will use it if
1186 available to accelerate real mode DOS programs. However, any
1187 recent version of DOSEMU, X, or vbetool should be fully
1188 functional even without kernel VM86 support, as they will all
1189 fall back to software emulation. Nevertheless, if you are using
1190 a 16-bit DOS program where 16-bit performance matters, vm86
1191 mode might be faster than emulation and you might want to
1194 Note that any app that works on a 64-bit kernel is unlikely to
1195 need this option, as 64-bit kernels don't, and can't, support
1196 V8086 mode. This option is also unrelated to 16-bit protected
1197 mode and is not needed to run most 16-bit programs under Wine.
1199 Enabling this option increases the complexity of the kernel
1200 and slows down exception handling a tiny bit.
1202 If unsure, say N here.
1206 default X86_LEGACY_VM86
1209 bool "Enable support for 16-bit segments" if EXPERT
1211 depends on MODIFY_LDT_SYSCALL
1213 This option is required by programs like Wine to run 16-bit
1214 protected mode legacy code on x86 processors. Disabling
1215 this option saves about 300 bytes on i386, or around 6K text
1216 plus 16K runtime memory on x86-64,
1220 depends on X86_16BIT && X86_32
1224 depends on X86_16BIT && X86_64
1226 config X86_VSYSCALL_EMULATION
1227 bool "Enable vsyscall emulation" if EXPERT
1231 This enables emulation of the legacy vsyscall page. Disabling
1232 it is roughly equivalent to booting with vsyscall=none, except
1233 that it will also disable the helpful warning if a program
1234 tries to use a vsyscall. With this option set to N, offending
1235 programs will just segfault, citing addresses of the form
1238 This option is required by many programs built before 2013, and
1239 care should be used even with newer programs if set to N.
1241 Disabling this option saves about 7K of kernel size and
1242 possibly 4K of additional runtime pagetable memory.
1244 config X86_IOPL_IOPERM
1245 bool "IOPERM and IOPL Emulation"
1248 This enables the ioperm() and iopl() syscalls which are necessary
1249 for legacy applications.
1251 Legacy IOPL support is an overbroad mechanism which allows user
1252 space aside of accessing all 65536 I/O ports also to disable
1253 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1254 capabilities and permission from potentially active security
1257 The emulation restricts the functionality of the syscall to
1258 only allowing the full range I/O port access, but prevents the
1259 ability to disable interrupts from user space which would be
1260 granted if the hardware IOPL mechanism would be used.
1263 tristate "Toshiba Laptop support"
1266 This adds a driver to safely access the System Management Mode of
1267 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1268 not work on models with a Phoenix BIOS. The System Management Mode
1269 is used to set the BIOS and power saving options on Toshiba portables.
1271 For information on utilities to make use of this driver see the
1272 Toshiba Linux utilities web site at:
1273 <http://www.buzzard.org.uk/toshiba/>.
1275 Say Y if you intend to run this kernel on a Toshiba portable.
1279 tristate "Dell i8k legacy laptop support"
1282 select SENSORS_DELL_SMM
1284 This option enables legacy /proc/i8k userspace interface in hwmon
1285 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1286 temperature and allows controlling fan speeds of Dell laptops via
1287 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1288 it reports also power and hotkey status. For fan speed control is
1289 needed userspace package i8kutils.
1291 Say Y if you intend to run this kernel on old Dell laptops or want to
1292 use userspace package i8kutils.
1295 config X86_REBOOTFIXUPS
1296 bool "Enable X86 board specific fixups for reboot"
1299 This enables chipset and/or board specific fixups to be done
1300 in order to get reboot to work correctly. This is only needed on
1301 some combinations of hardware and BIOS. The symptom, for which
1302 this config is intended, is when reboot ends with a stalled/hung
1305 Currently, the only fixup is for the Geode machines using
1306 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1308 Say Y if you want to enable the fixup. Currently, it's safe to
1309 enable this option even if you don't need it.
1313 bool "CPU microcode loading support"
1315 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1317 If you say Y here, you will be able to update the microcode on
1318 Intel and AMD processors. The Intel support is for the IA32 family,
1319 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1320 AMD support is for families 0x10 and later. You will obviously need
1321 the actual microcode binary data itself which is not shipped with
1324 The preferred method to load microcode from a detached initrd is described
1325 in Documentation/x86/microcode.rst. For that you need to enable
1326 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1327 initrd for microcode blobs.
1329 In addition, you can build the microcode into the kernel. For that you
1330 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1333 config MICROCODE_INTEL
1334 bool "Intel microcode loading support"
1335 depends on MICROCODE
1338 This options enables microcode patch loading support for Intel
1341 For the current Intel microcode data package go to
1342 <https://downloadcenter.intel.com> and search for
1343 'Linux Processor Microcode Data File'.
1345 config MICROCODE_AMD
1346 bool "AMD microcode loading support"
1347 depends on MICROCODE
1349 If you select this option, microcode patch loading support for AMD
1350 processors will be enabled.
1352 config MICROCODE_OLD_INTERFACE
1353 bool "Ancient loading interface (DEPRECATED)"
1355 depends on MICROCODE
1357 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1358 which was used by userspace tools like iucode_tool and microcode.ctl.
1359 It is inadequate because it runs too late to be able to properly
1360 load microcode on a machine and it needs special tools. Instead, you
1361 should've switched to the early loading method with the initrd or
1362 builtin microcode by now: Documentation/x86/microcode.rst
1365 tristate "/dev/cpu/*/msr - Model-specific register support"
1367 This device gives privileged processes access to the x86
1368 Model-Specific Registers (MSRs). It is a character device with
1369 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1370 MSR accesses are directed to a specific CPU on multi-processor
1374 tristate "/dev/cpu/*/cpuid - CPU information support"
1376 This device gives processes access to the x86 CPUID instruction to
1377 be executed on a specific processor. It is a character device
1378 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1382 prompt "High Memory Support"
1389 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1390 However, the address space of 32-bit x86 processors is only 4
1391 Gigabytes large. That means that, if you have a large amount of
1392 physical memory, not all of it can be "permanently mapped" by the
1393 kernel. The physical memory that's not permanently mapped is called
1396 If you are compiling a kernel which will never run on a machine with
1397 more than 1 Gigabyte total physical RAM, answer "off" here (default
1398 choice and suitable for most users). This will result in a "3GB/1GB"
1399 split: 3GB are mapped so that each process sees a 3GB virtual memory
1400 space and the remaining part of the 4GB virtual memory space is used
1401 by the kernel to permanently map as much physical memory as
1404 If the machine has between 1 and 4 Gigabytes physical RAM, then
1407 If more than 4 Gigabytes is used then answer "64GB" here. This
1408 selection turns Intel PAE (Physical Address Extension) mode on.
1409 PAE implements 3-level paging on IA32 processors. PAE is fully
1410 supported by Linux, PAE mode is implemented on all recent Intel
1411 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1412 then the kernel will not boot on CPUs that don't support PAE!
1414 The actual amount of total physical memory will either be
1415 auto detected or can be forced by using a kernel command line option
1416 such as "mem=256M". (Try "man bootparam" or see the documentation of
1417 your boot loader (lilo or loadlin) about how to pass options to the
1418 kernel at boot time.)
1420 If unsure, say "off".
1425 Select this if you have a 32-bit processor and between 1 and 4
1426 gigabytes of physical RAM.
1430 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1433 Select this if you have a 32-bit processor and more than 4
1434 gigabytes of physical RAM.
1439 prompt "Memory split" if EXPERT
1443 Select the desired split between kernel and user memory.
1445 If the address range available to the kernel is less than the
1446 physical memory installed, the remaining memory will be available
1447 as "high memory". Accessing high memory is a little more costly
1448 than low memory, as it needs to be mapped into the kernel first.
1449 Note that increasing the kernel address space limits the range
1450 available to user programs, making the address space there
1451 tighter. Selecting anything other than the default 3G/1G split
1452 will also likely make your kernel incompatible with binary-only
1455 If you are not absolutely sure what you are doing, leave this
1459 bool "3G/1G user/kernel split"
1460 config VMSPLIT_3G_OPT
1462 bool "3G/1G user/kernel split (for full 1G low memory)"
1464 bool "2G/2G user/kernel split"
1465 config VMSPLIT_2G_OPT
1467 bool "2G/2G user/kernel split (for full 2G low memory)"
1469 bool "1G/3G user/kernel split"
1474 default 0xB0000000 if VMSPLIT_3G_OPT
1475 default 0x80000000 if VMSPLIT_2G
1476 default 0x78000000 if VMSPLIT_2G_OPT
1477 default 0x40000000 if VMSPLIT_1G
1483 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1486 bool "PAE (Physical Address Extension) Support"
1487 depends on X86_32 && !HIGHMEM4G
1488 select PHYS_ADDR_T_64BIT
1491 PAE is required for NX support, and furthermore enables
1492 larger swapspace support for non-overcommit purposes. It
1493 has the cost of more pagetable lookup overhead, and also
1494 consumes more pagetable space per process.
1497 bool "Enable 5-level page tables support"
1499 select DYNAMIC_MEMORY_LAYOUT
1500 select SPARSEMEM_VMEMMAP
1503 5-level paging enables access to larger address space:
1504 upto 128 PiB of virtual address space and 4 PiB of
1505 physical address space.
1507 It will be supported by future Intel CPUs.
1509 A kernel with the option enabled can be booted on machines that
1510 support 4- or 5-level paging.
1512 See Documentation/x86/x86_64/5level-paging.rst for more
1517 config X86_DIRECT_GBPAGES
1521 Certain kernel features effectively disable kernel
1522 linear 1 GB mappings (even if the CPU otherwise
1523 supports them), so don't confuse the user by printing
1524 that we have them enabled.
1526 config X86_CPA_STATISTICS
1527 bool "Enable statistic for Change Page Attribute"
1530 Expose statistics about the Change Page Attribute mechanism, which
1531 helps to determine the effectiveness of preserving large and huge
1532 page mappings when mapping protections are changed.
1534 config X86_MEM_ENCRYPT
1535 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1536 select DYNAMIC_PHYSICAL_MASK
1537 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1540 config AMD_MEM_ENCRYPT
1541 bool "AMD Secure Memory Encryption (SME) support"
1542 depends on X86_64 && CPU_SUP_AMD
1543 select DMA_COHERENT_POOL
1544 select ARCH_USE_MEMREMAP_PROT
1545 select INSTRUCTION_DECODER
1546 select ARCH_HAS_CC_PLATFORM
1547 select X86_MEM_ENCRYPT
1549 Say yes to enable support for the encryption of system memory.
1550 This requires an AMD processor that supports Secure Memory
1553 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1554 bool "Activate AMD Secure Memory Encryption (SME) by default"
1555 depends on AMD_MEM_ENCRYPT
1557 Say yes to have system memory encrypted by default if running on
1558 an AMD processor that supports Secure Memory Encryption (SME).
1560 If set to Y, then the encryption of system memory can be
1561 deactivated with the mem_encrypt=off command line option.
1563 If set to N, then the encryption of system memory can be
1564 activated with the mem_encrypt=on command line option.
1566 # Common NUMA Features
1568 bool "NUMA Memory Allocation and Scheduler Support"
1570 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1571 default y if X86_BIGSMP
1572 select USE_PERCPU_NUMA_NODE_ID
1574 Enable NUMA (Non-Uniform Memory Access) support.
1576 The kernel will try to allocate memory used by a CPU on the
1577 local memory controller of the CPU and add some more
1578 NUMA awareness to the kernel.
1580 For 64-bit this is recommended if the system is Intel Core i7
1581 (or later), AMD Opteron, or EM64T NUMA.
1583 For 32-bit this is only needed if you boot a 32-bit
1584 kernel on a 64-bit NUMA platform.
1586 Otherwise, you should say N.
1590 prompt "Old style AMD Opteron NUMA detection"
1591 depends on X86_64 && NUMA && PCI
1593 Enable AMD NUMA node topology detection. You should say Y here if
1594 you have a multi processor AMD system. This uses an old method to
1595 read the NUMA configuration directly from the builtin Northbridge
1596 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1597 which also takes priority if both are compiled in.
1599 config X86_64_ACPI_NUMA
1601 prompt "ACPI NUMA detection"
1602 depends on X86_64 && NUMA && ACPI && PCI
1605 Enable ACPI SRAT based node topology detection.
1608 bool "NUMA emulation"
1611 Enable NUMA emulation. A flat machine will be split
1612 into virtual nodes when booted with "numa=fake=N", where N is the
1613 number of nodes. This is only useful for debugging.
1616 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1618 default "10" if MAXSMP
1619 default "6" if X86_64
1623 Specify the maximum number of NUMA Nodes available on the target
1624 system. Increases memory reserved to accommodate various tables.
1626 config ARCH_FLATMEM_ENABLE
1628 depends on X86_32 && !NUMA
1630 config ARCH_SPARSEMEM_ENABLE
1632 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1633 select SPARSEMEM_STATIC if X86_32
1634 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1636 config ARCH_SPARSEMEM_DEFAULT
1637 def_bool X86_64 || (NUMA && X86_32)
1639 config ARCH_SELECT_MEMORY_MODEL
1641 depends on ARCH_SPARSEMEM_ENABLE
1643 config ARCH_MEMORY_PROBE
1644 bool "Enable sysfs memory/probe interface"
1645 depends on MEMORY_HOTPLUG
1647 This option enables a sysfs memory/probe interface for testing.
1648 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1649 If you are unsure how to answer this question, answer N.
1651 config ARCH_PROC_KCORE_TEXT
1653 depends on X86_64 && PROC_KCORE
1655 config ILLEGAL_POINTER_VALUE
1658 default 0xdead000000000000 if X86_64
1660 config X86_PMEM_LEGACY_DEVICE
1663 config X86_PMEM_LEGACY
1664 tristate "Support non-standard NVDIMMs and ADR protected memory"
1665 depends on PHYS_ADDR_T_64BIT
1667 select X86_PMEM_LEGACY_DEVICE
1668 select NUMA_KEEP_MEMINFO if NUMA
1671 Treat memory marked using the non-standard e820 type of 12 as used
1672 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1673 The kernel will offer these regions to the 'pmem' driver so
1674 they can be used for persistent storage.
1679 bool "Allocate 3rd-level pagetables from highmem"
1682 The VM uses one page table entry for each page of physical memory.
1683 For systems with a lot of RAM, this can be wasteful of precious
1684 low memory. Setting this option will put user-space page table
1685 entries in high memory.
1687 config X86_CHECK_BIOS_CORRUPTION
1688 bool "Check for low memory corruption"
1690 Periodically check for memory corruption in low memory, which
1691 is suspected to be caused by BIOS. Even when enabled in the
1692 configuration, it is disabled at runtime. Enable it by
1693 setting "memory_corruption_check=1" on the kernel command
1694 line. By default it scans the low 64k of memory every 60
1695 seconds; see the memory_corruption_check_size and
1696 memory_corruption_check_period parameters in
1697 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1699 When enabled with the default parameters, this option has
1700 almost no overhead, as it reserves a relatively small amount
1701 of memory and scans it infrequently. It both detects corruption
1702 and prevents it from affecting the running system.
1704 It is, however, intended as a diagnostic tool; if repeatable
1705 BIOS-originated corruption always affects the same memory,
1706 you can use memmap= to prevent the kernel from using that
1709 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1710 bool "Set the default setting of memory_corruption_check"
1711 depends on X86_CHECK_BIOS_CORRUPTION
1714 Set whether the default state of memory_corruption_check is
1717 config MATH_EMULATION
1719 depends on MODIFY_LDT_SYSCALL
1720 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1722 Linux can emulate a math coprocessor (used for floating point
1723 operations) if you don't have one. 486DX and Pentium processors have
1724 a math coprocessor built in, 486SX and 386 do not, unless you added
1725 a 487DX or 387, respectively. (The messages during boot time can
1726 give you some hints here ["man dmesg"].) Everyone needs either a
1727 coprocessor or this emulation.
1729 If you don't have a math coprocessor, you need to say Y here; if you
1730 say Y here even though you have a coprocessor, the coprocessor will
1731 be used nevertheless. (This behavior can be changed with the kernel
1732 command line option "no387", which comes handy if your coprocessor
1733 is broken. Try "man bootparam" or see the documentation of your boot
1734 loader (lilo or loadlin) about how to pass options to the kernel at
1735 boot time.) This means that it is a good idea to say Y here if you
1736 intend to use this kernel on different machines.
1738 More information about the internals of the Linux math coprocessor
1739 emulation can be found in <file:arch/x86/math-emu/README>.
1741 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1742 kernel, it won't hurt.
1746 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1748 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1749 the Memory Type Range Registers (MTRRs) may be used to control
1750 processor access to memory ranges. This is most useful if you have
1751 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1752 allows bus write transfers to be combined into a larger transfer
1753 before bursting over the PCI/AGP bus. This can increase performance
1754 of image write operations 2.5 times or more. Saying Y here creates a
1755 /proc/mtrr file which may be used to manipulate your processor's
1756 MTRRs. Typically the X server should use this.
1758 This code has a reasonably generic interface so that similar
1759 control registers on other processors can be easily supported
1762 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1763 Registers (ARRs) which provide a similar functionality to MTRRs. For
1764 these, the ARRs are used to emulate the MTRRs.
1765 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1766 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1767 write-combining. All of these processors are supported by this code
1768 and it makes sense to say Y here if you have one of them.
1770 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1771 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1772 can lead to all sorts of problems, so it's good to say Y here.
1774 You can safely say Y even if your machine doesn't have MTRRs, you'll
1775 just add about 9 KB to your kernel.
1777 See <file:Documentation/x86/mtrr.rst> for more information.
1779 config MTRR_SANITIZER
1781 prompt "MTRR cleanup support"
1784 Convert MTRR layout from continuous to discrete, so X drivers can
1785 add writeback entries.
1787 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1788 The largest mtrr entry size for a continuous block can be set with
1793 config MTRR_SANITIZER_ENABLE_DEFAULT
1794 int "MTRR cleanup enable value (0-1)"
1797 depends on MTRR_SANITIZER
1799 Enable mtrr cleanup default value
1801 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1802 int "MTRR cleanup spare reg num (0-7)"
1805 depends on MTRR_SANITIZER
1807 mtrr cleanup spare entries default, it can be changed via
1808 mtrr_spare_reg_nr=N on the kernel command line.
1812 prompt "x86 PAT support" if EXPERT
1815 Use PAT attributes to setup page level cache control.
1817 PATs are the modern equivalents of MTRRs and are much more
1818 flexible than MTRRs.
1820 Say N here if you see bootup problems (boot crash, boot hang,
1821 spontaneous reboots) or a non-working video driver.
1825 config ARCH_USES_PG_UNCACHED
1831 prompt "x86 architectural random number generator" if EXPERT
1833 Enable the x86 architectural RDRAND instruction
1834 (Intel Bull Mountain technology) to generate random numbers.
1835 If supported, this is a high bandwidth, cryptographically
1836 secure hardware random number generator.
1840 prompt "Supervisor Mode Access Prevention" if EXPERT
1842 Supervisor Mode Access Prevention (SMAP) is a security
1843 feature in newer Intel processors. There is a small
1844 performance cost if this enabled and turned on; there is
1845 also a small increase in the kernel size if this is enabled.
1851 prompt "User Mode Instruction Prevention" if EXPERT
1853 User Mode Instruction Prevention (UMIP) is a security feature in
1854 some x86 processors. If enabled, a general protection fault is
1855 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1856 executed in user mode. These instructions unnecessarily expose
1857 information about the hardware state.
1859 The vast majority of applications do not use these instructions.
1860 For the very few that do, software emulation is provided in
1861 specific cases in protected and virtual-8086 modes. Emulated
1865 # GCC >= 9 and binutils >= 2.29
1866 # Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
1868 # fentry check to work around https://reviews.llvm.org/D111108
1869 def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \
1870 (CC_IS_CLANG && $(success,echo "void a(void) {}" | $(CC) -Werror $(CLANG_FLAGS) -fcf-protection=branch -mfentry -pg -x c - -c -o /dev/null))) && \
1873 config X86_KERNEL_IBT
1874 prompt "Indirect Branch Tracking"
1876 depends on X86_64 && CC_HAS_IBT
1878 Build the kernel with support for Indirect Branch Tracking, a
1879 hardware support course-grain forward-edge Control Flow Integrity
1880 protection. It enforces that all indirect calls must land on
1881 an ENDBR instruction, as such, the compiler will instrument the
1882 code with them to make this happen.
1884 config X86_INTEL_MEMORY_PROTECTION_KEYS
1885 prompt "Memory Protection Keys"
1887 # Note: only available in 64-bit mode
1888 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1889 select ARCH_USES_HIGH_VMA_FLAGS
1890 select ARCH_HAS_PKEYS
1892 Memory Protection Keys provides a mechanism for enforcing
1893 page-based protections, but without requiring modification of the
1894 page tables when an application changes protection domains.
1896 For details, see Documentation/core-api/protection-keys.rst
1901 prompt "TSX enable mode"
1902 depends on CPU_SUP_INTEL
1903 default X86_INTEL_TSX_MODE_OFF
1905 Intel's TSX (Transactional Synchronization Extensions) feature
1906 allows to optimize locking protocols through lock elision which
1907 can lead to a noticeable performance boost.
1909 On the other hand it has been shown that TSX can be exploited
1910 to form side channel attacks (e.g. TAA) and chances are there
1911 will be more of those attacks discovered in the future.
1913 Therefore TSX is not enabled by default (aka tsx=off). An admin
1914 might override this decision by tsx=on the command line parameter.
1915 Even with TSX enabled, the kernel will attempt to enable the best
1916 possible TAA mitigation setting depending on the microcode available
1917 for the particular machine.
1919 This option allows to set the default tsx mode between tsx=on, =off
1920 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1923 Say off if not sure, auto if TSX is in use but it should be used on safe
1924 platforms or on if TSX is in use and the security aspect of tsx is not
1927 config X86_INTEL_TSX_MODE_OFF
1930 TSX is disabled if possible - equals to tsx=off command line parameter.
1932 config X86_INTEL_TSX_MODE_ON
1935 TSX is always enabled on TSX capable HW - equals the tsx=on command
1938 config X86_INTEL_TSX_MODE_AUTO
1941 TSX is enabled on TSX capable HW that is believed to be safe against
1942 side channel attacks- equals the tsx=auto command line parameter.
1946 bool "Software Guard eXtensions (SGX)"
1947 depends on X86_64 && CPU_SUP_INTEL
1949 depends on CRYPTO_SHA256=y
1952 select NUMA_KEEP_MEMINFO if NUMA
1955 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1956 that can be used by applications to set aside private regions of code
1957 and data, referred to as enclaves. An enclave's private memory can
1958 only be accessed by code running within the enclave. Accesses from
1959 outside the enclave, including other enclaves, are disallowed by
1965 bool "EFI runtime service support"
1968 select EFI_RUNTIME_WRAPPERS
1969 select ARCH_USE_MEMREMAP_PROT
1971 This enables the kernel to use EFI runtime services that are
1972 available (such as the EFI variable services).
1974 This option is only useful on systems that have EFI firmware.
1975 In addition, you should use the latest ELILO loader available
1976 at <http://elilo.sourceforge.net> in order to take advantage
1977 of EFI runtime services. However, even with this option, the
1978 resultant kernel should continue to boot on existing non-EFI
1982 bool "EFI stub support"
1984 depends on $(cc-option,-mabi=ms) || X86_32
1987 This kernel feature allows a bzImage to be loaded directly
1988 by EFI firmware without the use of a bootloader.
1990 See Documentation/admin-guide/efi-stub.rst for more information.
1993 bool "EFI mixed-mode support"
1994 depends on EFI_STUB && X86_64
1996 Enabling this feature allows a 64-bit kernel to be booted
1997 on a 32-bit firmware, provided that your CPU supports 64-bit
2000 Note that it is not possible to boot a mixed-mode enabled
2001 kernel via the EFI boot stub - a bootloader that supports
2002 the EFI handover protocol must be used.
2006 source "kernel/Kconfig.hz"
2009 bool "kexec system call"
2012 kexec is a system call that implements the ability to shutdown your
2013 current kernel, and to start another kernel. It is like a reboot
2014 but it is independent of the system firmware. And like a reboot
2015 you can start any kernel with it, not just Linux.
2017 The name comes from the similarity to the exec system call.
2019 It is an ongoing process to be certain the hardware in a machine
2020 is properly shutdown, so do not be surprised if this code does not
2021 initially work for you. As of this writing the exact hardware
2022 interface is strongly in flux, so no good recommendation can be
2026 bool "kexec file based system call"
2031 depends on CRYPTO_SHA256=y
2033 This is new version of kexec system call. This system call is
2034 file based and takes file descriptors as system call argument
2035 for kernel and initramfs as opposed to list of segments as
2036 accepted by previous system call.
2038 config ARCH_HAS_KEXEC_PURGATORY
2042 bool "Verify kernel signature during kexec_file_load() syscall"
2043 depends on KEXEC_FILE
2046 This option makes the kexec_file_load() syscall check for a valid
2047 signature of the kernel image. The image can still be loaded without
2048 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2049 there's a signature that we can check, then it must be valid.
2051 In addition to this option, you need to enable signature
2052 verification for the corresponding kernel image type being
2053 loaded in order for this to work.
2055 config KEXEC_SIG_FORCE
2056 bool "Require a valid signature in kexec_file_load() syscall"
2057 depends on KEXEC_SIG
2059 This option makes kernel signature verification mandatory for
2060 the kexec_file_load() syscall.
2062 config KEXEC_BZIMAGE_VERIFY_SIG
2063 bool "Enable bzImage signature verification support"
2064 depends on KEXEC_SIG
2065 depends on SIGNED_PE_FILE_VERIFICATION
2066 select SYSTEM_TRUSTED_KEYRING
2068 Enable bzImage signature verification support.
2071 bool "kernel crash dumps"
2072 depends on X86_64 || (X86_32 && HIGHMEM)
2074 Generate crash dump after being started by kexec.
2075 This should be normally only set in special crash dump kernels
2076 which are loaded in the main kernel with kexec-tools into
2077 a specially reserved region and then later executed after
2078 a crash by kdump/kexec. The crash dump kernel must be compiled
2079 to a memory address not used by the main kernel or BIOS using
2080 PHYSICAL_START, or it must be built as a relocatable image
2081 (CONFIG_RELOCATABLE=y).
2082 For more details see Documentation/admin-guide/kdump/kdump.rst
2086 depends on KEXEC && HIBERNATION
2088 Jump between original kernel and kexeced kernel and invoke
2089 code in physical address mode via KEXEC
2091 config PHYSICAL_START
2092 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2095 This gives the physical address where the kernel is loaded.
2097 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2098 bzImage will decompress itself to above physical address and
2099 run from there. Otherwise, bzImage will run from the address where
2100 it has been loaded by the boot loader and will ignore above physical
2103 In normal kdump cases one does not have to set/change this option
2104 as now bzImage can be compiled as a completely relocatable image
2105 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2106 address. This option is mainly useful for the folks who don't want
2107 to use a bzImage for capturing the crash dump and want to use a
2108 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2109 to be specifically compiled to run from a specific memory area
2110 (normally a reserved region) and this option comes handy.
2112 So if you are using bzImage for capturing the crash dump,
2113 leave the value here unchanged to 0x1000000 and set
2114 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2115 for capturing the crash dump change this value to start of
2116 the reserved region. In other words, it can be set based on
2117 the "X" value as specified in the "crashkernel=YM@XM"
2118 command line boot parameter passed to the panic-ed
2119 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2120 for more details about crash dumps.
2122 Usage of bzImage for capturing the crash dump is recommended as
2123 one does not have to build two kernels. Same kernel can be used
2124 as production kernel and capture kernel. Above option should have
2125 gone away after relocatable bzImage support is introduced. But it
2126 is present because there are users out there who continue to use
2127 vmlinux for dump capture. This option should go away down the
2130 Don't change this unless you know what you are doing.
2133 bool "Build a relocatable kernel"
2136 This builds a kernel image that retains relocation information
2137 so it can be loaded someplace besides the default 1MB.
2138 The relocations tend to make the kernel binary about 10% larger,
2139 but are discarded at runtime.
2141 One use is for the kexec on panic case where the recovery kernel
2142 must live at a different physical address than the primary
2145 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2146 it has been loaded at and the compile time physical address
2147 (CONFIG_PHYSICAL_START) is used as the minimum location.
2149 config RANDOMIZE_BASE
2150 bool "Randomize the address of the kernel image (KASLR)"
2151 depends on RELOCATABLE
2154 In support of Kernel Address Space Layout Randomization (KASLR),
2155 this randomizes the physical address at which the kernel image
2156 is decompressed and the virtual address where the kernel
2157 image is mapped, as a security feature that deters exploit
2158 attempts relying on knowledge of the location of kernel
2161 On 64-bit, the kernel physical and virtual addresses are
2162 randomized separately. The physical address will be anywhere
2163 between 16MB and the top of physical memory (up to 64TB). The
2164 virtual address will be randomized from 16MB up to 1GB (9 bits
2165 of entropy). Note that this also reduces the memory space
2166 available to kernel modules from 1.5GB to 1GB.
2168 On 32-bit, the kernel physical and virtual addresses are
2169 randomized together. They will be randomized from 16MB up to
2170 512MB (8 bits of entropy).
2172 Entropy is generated using the RDRAND instruction if it is
2173 supported. If RDTSC is supported, its value is mixed into
2174 the entropy pool as well. If neither RDRAND nor RDTSC are
2175 supported, then entropy is read from the i8254 timer. The
2176 usable entropy is limited by the kernel being built using
2177 2GB addressing, and that PHYSICAL_ALIGN must be at a
2178 minimum of 2MB. As a result, only 10 bits of entropy are
2179 theoretically possible, but the implementations are further
2180 limited due to memory layouts.
2184 # Relocation on x86 needs some additional build support
2185 config X86_NEED_RELOCS
2187 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2189 config PHYSICAL_ALIGN
2190 hex "Alignment value to which kernel should be aligned"
2192 range 0x2000 0x1000000 if X86_32
2193 range 0x200000 0x1000000 if X86_64
2195 This value puts the alignment restrictions on physical address
2196 where kernel is loaded and run from. Kernel is compiled for an
2197 address which meets above alignment restriction.
2199 If bootloader loads the kernel at a non-aligned address and
2200 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2201 address aligned to above value and run from there.
2203 If bootloader loads the kernel at a non-aligned address and
2204 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2205 load address and decompress itself to the address it has been
2206 compiled for and run from there. The address for which kernel is
2207 compiled already meets above alignment restrictions. Hence the
2208 end result is that kernel runs from a physical address meeting
2209 above alignment restrictions.
2211 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2212 this value must be a multiple of 0x200000.
2214 Don't change this unless you know what you are doing.
2216 config DYNAMIC_MEMORY_LAYOUT
2219 This option makes base addresses of vmalloc and vmemmap as well as
2220 __PAGE_OFFSET movable during boot.
2222 config RANDOMIZE_MEMORY
2223 bool "Randomize the kernel memory sections"
2225 depends on RANDOMIZE_BASE
2226 select DYNAMIC_MEMORY_LAYOUT
2227 default RANDOMIZE_BASE
2229 Randomizes the base virtual address of kernel memory sections
2230 (physical memory mapping, vmalloc & vmemmap). This security feature
2231 makes exploits relying on predictable memory locations less reliable.
2233 The order of allocations remains unchanged. Entropy is generated in
2234 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2235 configuration have in average 30,000 different possible virtual
2236 addresses for each memory section.
2240 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2241 hex "Physical memory mapping padding" if EXPERT
2242 depends on RANDOMIZE_MEMORY
2243 default "0xa" if MEMORY_HOTPLUG
2245 range 0x1 0x40 if MEMORY_HOTPLUG
2248 Define the padding in terabytes added to the existing physical
2249 memory size during kernel memory randomization. It is useful
2250 for memory hotplug support but reduces the entropy available for
2251 address randomization.
2253 If unsure, leave at the default value.
2259 config BOOTPARAM_HOTPLUG_CPU0
2260 bool "Set default setting of cpu0_hotpluggable"
2261 depends on HOTPLUG_CPU
2263 Set whether default state of cpu0_hotpluggable is on or off.
2265 Say Y here to enable CPU0 hotplug by default. If this switch
2266 is turned on, there is no need to give cpu0_hotplug kernel
2267 parameter and the CPU0 hotplug feature is enabled by default.
2269 Please note: there are two known CPU0 dependencies if you want
2270 to enable the CPU0 hotplug feature either by this switch or by
2271 cpu0_hotplug kernel parameter.
2273 First, resume from hibernate or suspend always starts from CPU0.
2274 So hibernate and suspend are prevented if CPU0 is offline.
2276 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2277 offline if any interrupt can not migrate out of CPU0. There may
2278 be other CPU0 dependencies.
2280 Please make sure the dependencies are under your control before
2281 you enable this feature.
2283 Say N if you don't want to enable CPU0 hotplug feature by default.
2284 You still can enable the CPU0 hotplug feature at boot by kernel
2285 parameter cpu0_hotplug.
2287 config DEBUG_HOTPLUG_CPU0
2289 prompt "Debug CPU0 hotplug"
2290 depends on HOTPLUG_CPU
2292 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2293 soon as possible and boots up userspace with CPU0 offlined. User
2294 can online CPU0 back after boot time.
2296 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2297 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2298 compilation or giving cpu0_hotplug kernel parameter at boot.
2304 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2305 depends on COMPAT_32
2307 Certain buggy versions of glibc will crash if they are
2308 presented with a 32-bit vDSO that is not mapped at the address
2309 indicated in its segment table.
2311 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2312 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2313 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2314 the only released version with the bug, but OpenSUSE 9
2315 contains a buggy "glibc 2.3.2".
2317 The symptom of the bug is that everything crashes on startup, saying:
2318 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2320 Saying Y here changes the default value of the vdso32 boot
2321 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2322 This works around the glibc bug but hurts performance.
2324 If unsure, say N: if you are compiling your own kernel, you
2325 are unlikely to be using a buggy version of glibc.
2328 prompt "vsyscall table for legacy applications"
2330 default LEGACY_VSYSCALL_XONLY
2332 Legacy user code that does not know how to find the vDSO expects
2333 to be able to issue three syscalls by calling fixed addresses in
2334 kernel space. Since this location is not randomized with ASLR,
2335 it can be used to assist security vulnerability exploitation.
2337 This setting can be changed at boot time via the kernel command
2338 line parameter vsyscall=[emulate|xonly|none].
2340 On a system with recent enough glibc (2.14 or newer) and no
2341 static binaries, you can say None without a performance penalty
2342 to improve security.
2344 If unsure, select "Emulate execution only".
2346 config LEGACY_VSYSCALL_EMULATE
2347 bool "Full emulation"
2349 The kernel traps and emulates calls into the fixed vsyscall
2350 address mapping. This makes the mapping non-executable, but
2351 it still contains readable known contents, which could be
2352 used in certain rare security vulnerability exploits. This
2353 configuration is recommended when using legacy userspace
2354 that still uses vsyscalls along with legacy binary
2355 instrumentation tools that require code to be readable.
2357 An example of this type of legacy userspace is running
2358 Pin on an old binary that still uses vsyscalls.
2360 config LEGACY_VSYSCALL_XONLY
2361 bool "Emulate execution only"
2363 The kernel traps and emulates calls into the fixed vsyscall
2364 address mapping and does not allow reads. This
2365 configuration is recommended when userspace might use the
2366 legacy vsyscall area but support for legacy binary
2367 instrumentation of legacy code is not needed. It mitigates
2368 certain uses of the vsyscall area as an ASLR-bypassing
2371 config LEGACY_VSYSCALL_NONE
2374 There will be no vsyscall mapping at all. This will
2375 eliminate any risk of ASLR bypass due to the vsyscall
2376 fixed address mapping. Attempts to use the vsyscalls
2377 will be reported to dmesg, so that either old or
2378 malicious userspace programs can be identified.
2383 bool "Built-in kernel command line"
2385 Allow for specifying boot arguments to the kernel at
2386 build time. On some systems (e.g. embedded ones), it is
2387 necessary or convenient to provide some or all of the
2388 kernel boot arguments with the kernel itself (that is,
2389 to not rely on the boot loader to provide them.)
2391 To compile command line arguments into the kernel,
2392 set this option to 'Y', then fill in the
2393 boot arguments in CONFIG_CMDLINE.
2395 Systems with fully functional boot loaders (i.e. non-embedded)
2396 should leave this option set to 'N'.
2399 string "Built-in kernel command string"
2400 depends on CMDLINE_BOOL
2403 Enter arguments here that should be compiled into the kernel
2404 image and used at boot time. If the boot loader provides a
2405 command line at boot time, it is appended to this string to
2406 form the full kernel command line, when the system boots.
2408 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2409 change this behavior.
2411 In most cases, the command line (whether built-in or provided
2412 by the boot loader) should specify the device for the root
2415 config CMDLINE_OVERRIDE
2416 bool "Built-in command line overrides boot loader arguments"
2417 depends on CMDLINE_BOOL && CMDLINE != ""
2419 Set this option to 'Y' to have the kernel ignore the boot loader
2420 command line, and use ONLY the built-in command line.
2422 This is used to work around broken boot loaders. This should
2423 be set to 'N' under normal conditions.
2425 config MODIFY_LDT_SYSCALL
2426 bool "Enable the LDT (local descriptor table)" if EXPERT
2429 Linux can allow user programs to install a per-process x86
2430 Local Descriptor Table (LDT) using the modify_ldt(2) system
2431 call. This is required to run 16-bit or segmented code such as
2432 DOSEMU or some Wine programs. It is also used by some very old
2433 threading libraries.
2435 Enabling this feature adds a small amount of overhead to
2436 context switches and increases the low-level kernel attack
2437 surface. Disabling it removes the modify_ldt(2) system call.
2439 Saying 'N' here may make sense for embedded or server kernels.
2441 config STRICT_SIGALTSTACK_SIZE
2442 bool "Enforce strict size checking for sigaltstack"
2443 depends on DYNAMIC_SIGFRAME
2445 For historical reasons MINSIGSTKSZ is a constant which became
2446 already too small with AVX512 support. Add a mechanism to
2447 enforce strict checking of the sigaltstack size against the
2448 real size of the FPU frame. This option enables the check
2449 by default. It can also be controlled via the kernel command
2450 line option 'strict_sas_size' independent of this config
2451 switch. Enabling it might break existing applications which
2452 allocate a too small sigaltstack but 'work' because they
2453 never get a signal delivered.
2455 Say 'N' unless you want to really enforce this check.
2457 source "kernel/livepatch/Kconfig"
2461 config ARCH_HAS_ADD_PAGES
2463 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2465 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2468 menu "Power management and ACPI options"
2470 config ARCH_HIBERNATION_HEADER
2472 depends on HIBERNATION
2474 source "kernel/power/Kconfig"
2476 source "drivers/acpi/Kconfig"
2483 tristate "APM (Advanced Power Management) BIOS support"
2484 depends on X86_32 && PM_SLEEP
2486 APM is a BIOS specification for saving power using several different
2487 techniques. This is mostly useful for battery powered laptops with
2488 APM compliant BIOSes. If you say Y here, the system time will be
2489 reset after a RESUME operation, the /proc/apm device will provide
2490 battery status information, and user-space programs will receive
2491 notification of APM "events" (e.g. battery status change).
2493 If you select "Y" here, you can disable actual use of the APM
2494 BIOS by passing the "apm=off" option to the kernel at boot time.
2496 Note that the APM support is almost completely disabled for
2497 machines with more than one CPU.
2499 In order to use APM, you will need supporting software. For location
2500 and more information, read <file:Documentation/power/apm-acpi.rst>
2501 and the Battery Powered Linux mini-HOWTO, available from
2502 <http://www.tldp.org/docs.html#howto>.
2504 This driver does not spin down disk drives (see the hdparm(8)
2505 manpage ("man 8 hdparm") for that), and it doesn't turn off
2506 VESA-compliant "green" monitors.
2508 This driver does not support the TI 4000M TravelMate and the ACER
2509 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2510 desktop machines also don't have compliant BIOSes, and this driver
2511 may cause those machines to panic during the boot phase.
2513 Generally, if you don't have a battery in your machine, there isn't
2514 much point in using this driver and you should say N. If you get
2515 random kernel OOPSes or reboots that don't seem to be related to
2516 anything, try disabling/enabling this option (or disabling/enabling
2519 Some other things you should try when experiencing seemingly random,
2522 1) make sure that you have enough swap space and that it is
2524 2) pass the "no-hlt" option to the kernel
2525 3) switch on floating point emulation in the kernel and pass
2526 the "no387" option to the kernel
2527 4) pass the "floppy=nodma" option to the kernel
2528 5) pass the "mem=4M" option to the kernel (thereby disabling
2529 all but the first 4 MB of RAM)
2530 6) make sure that the CPU is not over clocked.
2531 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2532 8) disable the cache from your BIOS settings
2533 9) install a fan for the video card or exchange video RAM
2534 10) install a better fan for the CPU
2535 11) exchange RAM chips
2536 12) exchange the motherboard.
2538 To compile this driver as a module, choose M here: the
2539 module will be called apm.
2543 config APM_IGNORE_USER_SUSPEND
2544 bool "Ignore USER SUSPEND"
2546 This option will ignore USER SUSPEND requests. On machines with a
2547 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2548 series notebooks, it is necessary to say Y because of a BIOS bug.
2550 config APM_DO_ENABLE
2551 bool "Enable PM at boot time"
2553 Enable APM features at boot time. From page 36 of the APM BIOS
2554 specification: "When disabled, the APM BIOS does not automatically
2555 power manage devices, enter the Standby State, enter the Suspend
2556 State, or take power saving steps in response to CPU Idle calls."
2557 This driver will make CPU Idle calls when Linux is idle (unless this
2558 feature is turned off -- see "Do CPU IDLE calls", below). This
2559 should always save battery power, but more complicated APM features
2560 will be dependent on your BIOS implementation. You may need to turn
2561 this option off if your computer hangs at boot time when using APM
2562 support, or if it beeps continuously instead of suspending. Turn
2563 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2564 T400CDT. This is off by default since most machines do fine without
2569 bool "Make CPU Idle calls when idle"
2571 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2572 On some machines, this can activate improved power savings, such as
2573 a slowed CPU clock rate, when the machine is idle. These idle calls
2574 are made after the idle loop has run for some length of time (e.g.,
2575 333 mS). On some machines, this will cause a hang at boot time or
2576 whenever the CPU becomes idle. (On machines with more than one CPU,
2577 this option does nothing.)
2579 config APM_DISPLAY_BLANK
2580 bool "Enable console blanking using APM"
2582 Enable console blanking using the APM. Some laptops can use this to
2583 turn off the LCD backlight when the screen blanker of the Linux
2584 virtual console blanks the screen. Note that this is only used by
2585 the virtual console screen blanker, and won't turn off the backlight
2586 when using the X Window system. This also doesn't have anything to
2587 do with your VESA-compliant power-saving monitor. Further, this
2588 option doesn't work for all laptops -- it might not turn off your
2589 backlight at all, or it might print a lot of errors to the console,
2590 especially if you are using gpm.
2592 config APM_ALLOW_INTS
2593 bool "Allow interrupts during APM BIOS calls"
2595 Normally we disable external interrupts while we are making calls to
2596 the APM BIOS as a measure to lessen the effects of a badly behaving
2597 BIOS implementation. The BIOS should reenable interrupts if it
2598 needs to. Unfortunately, some BIOSes do not -- especially those in
2599 many of the newer IBM Thinkpads. If you experience hangs when you
2600 suspend, try setting this to Y. Otherwise, say N.
2604 source "drivers/cpufreq/Kconfig"
2606 source "drivers/cpuidle/Kconfig"
2608 source "drivers/idle/Kconfig"
2613 menu "Bus options (PCI etc.)"
2616 prompt "PCI access mode"
2617 depends on X86_32 && PCI
2620 On PCI systems, the BIOS can be used to detect the PCI devices and
2621 determine their configuration. However, some old PCI motherboards
2622 have BIOS bugs and may crash if this is done. Also, some embedded
2623 PCI-based systems don't have any BIOS at all. Linux can also try to
2624 detect the PCI hardware directly without using the BIOS.
2626 With this option, you can specify how Linux should detect the
2627 PCI devices. If you choose "BIOS", the BIOS will be used,
2628 if you choose "Direct", the BIOS won't be used, and if you
2629 choose "MMConfig", then PCI Express MMCONFIG will be used.
2630 If you choose "Any", the kernel will try MMCONFIG, then the
2631 direct access method and falls back to the BIOS if that doesn't
2632 work. If unsure, go with the default, which is "Any".
2637 config PCI_GOMMCONFIG
2654 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2656 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2659 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2662 bool "Support mmconfig PCI config space access" if X86_64
2664 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2665 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2669 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2673 depends on PCI && XEN
2675 config MMCONF_FAM10H
2677 depends on X86_64 && PCI_MMCONFIG && ACPI
2679 config PCI_CNB20LE_QUIRK
2680 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2683 Read the PCI windows out of the CNB20LE host bridge. This allows
2684 PCI hotplug to work on systems with the CNB20LE chipset which do
2687 There's no public spec for this chipset, and this functionality
2688 is known to be incomplete.
2690 You should say N unless you know you need this.
2693 bool "ISA bus support on modern systems" if EXPERT
2695 Expose ISA bus device drivers and options available for selection and
2696 configuration. Enable this option if your target machine has an ISA
2697 bus. ISA is an older system, displaced by PCI and newer bus
2698 architectures -- if your target machine is modern, it probably does
2699 not have an ISA bus.
2703 # x86_64 have no ISA slots, but can have ISA-style DMA.
2705 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2708 Enables ISA-style DMA support for devices requiring such controllers.
2716 Find out whether you have ISA slots on your motherboard. ISA is the
2717 name of a bus system, i.e. the way the CPU talks to the other stuff
2718 inside your box. Other bus systems are PCI, EISA, MicroChannel
2719 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2720 newer boards don't support it. If you have ISA, say Y, otherwise N.
2723 tristate "NatSemi SCx200 support"
2725 This provides basic support for National Semiconductor's
2726 (now AMD's) Geode processors. The driver probes for the
2727 PCI-IDs of several on-chip devices, so its a good dependency
2728 for other scx200_* drivers.
2730 If compiled as a module, the driver is named scx200.
2732 config SCx200HR_TIMER
2733 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2737 This driver provides a clocksource built upon the on-chip
2738 27MHz high-resolution timer. Its also a workaround for
2739 NSC Geode SC-1100's buggy TSC, which loses time when the
2740 processor goes idle (as is done by the scheduler). The
2741 other workaround is idle=poll boot option.
2744 bool "One Laptop Per Child support"
2752 Add support for detecting the unique features of the OLPC
2756 bool "OLPC XO-1 Power Management"
2757 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2759 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2762 bool "OLPC XO-1 Real Time Clock"
2763 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2765 Add support for the XO-1 real time clock, which can be used as a
2766 programmable wakeup source.
2769 bool "OLPC XO-1 SCI extras"
2770 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2774 Add support for SCI-based features of the OLPC XO-1 laptop:
2775 - EC-driven system wakeups
2779 - AC adapter status updates
2780 - Battery status updates
2782 config OLPC_XO15_SCI
2783 bool "OLPC XO-1.5 SCI extras"
2784 depends on OLPC && ACPI
2787 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2788 - EC-driven system wakeups
2789 - AC adapter status updates
2790 - Battery status updates
2793 bool "PCEngines ALIX System Support (LED setup)"
2796 This option enables system support for the PCEngines ALIX.
2797 At present this just sets up LEDs for GPIO control on
2798 ALIX2/3/6 boards. However, other system specific setup should
2801 Note: You must still enable the drivers for GPIO and LED support
2802 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2804 Note: You have to set alix.force=1 for boards with Award BIOS.
2807 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2810 This option enables system support for the Soekris Engineering net5501.
2813 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2817 This option enables system support for the Traverse Technologies GEOS.
2820 bool "Technologic Systems TS-5500 platform support"
2822 select CHECK_SIGNATURE
2826 This option enables system support for the Technologic Systems TS-5500.
2832 depends on CPU_SUP_AMD && PCI
2837 menu "Binary Emulations"
2839 config IA32_EMULATION
2840 bool "IA32 Emulation"
2842 select ARCH_WANT_OLD_COMPAT_IPC
2844 select COMPAT_OLD_SIGACTION
2846 Include code to run legacy 32-bit programs under a
2847 64-bit kernel. You should likely turn this on, unless you're
2848 100% sure that you don't have any 32-bit programs left.
2851 tristate "IA32 a.out support"
2852 depends on IA32_EMULATION
2855 Support old a.out binaries in the 32bit emulation.
2858 bool "x32 ABI for 64-bit mode"
2861 Include code to run binaries for the x32 native 32-bit ABI
2862 for 64-bit processors. An x32 process gets access to the
2863 full 64-bit register file and wide data path while leaving
2864 pointers at 32 bits for smaller memory footprint.
2866 You will need a recent binutils (2.22 or later) with
2867 elf32_x86_64 support enabled to compile a kernel with this
2872 depends on IA32_EMULATION || X86_32
2874 select OLD_SIGSUSPEND3
2878 depends on IA32_EMULATION || X86_X32
2881 config COMPAT_FOR_U64_ALIGNMENT
2884 config SYSVIPC_COMPAT
2892 config HAVE_ATOMIC_IOMAP
2896 source "arch/x86/kvm/Kconfig"
2898 source "arch/x86/Kconfig.assembler"