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
37 config FORCE_DYNAMIC_FTRACE
40 depends on FUNCTION_TRACER
43 We keep the static function tracing (!DYNAMIC_FTRACE) around
44 in order to test the non static function tracing in the
45 generic code, as other architectures still use it. But we
46 only need to keep it around for x86_64. No need to keep it
47 for x86_32. For x86_32, force DYNAMIC_FTRACE.
51 # ( Note that options that are marked 'if X86_64' could in principle be
52 # ported to 32-bit as well. )
57 # Note: keep this list sorted alphabetically
59 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
60 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
61 select ARCH_32BIT_OFF_T if X86_32
62 select ARCH_CLOCKSOURCE_INIT
63 select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64 || (X86_32 && HIGHMEM)
64 select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
65 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
66 select ARCH_HAS_CACHE_LINE_SIZE
67 select ARCH_HAS_DEBUG_VIRTUAL
68 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
69 select ARCH_HAS_DEVMEM_IS_ALLOWED
70 select ARCH_HAS_EARLY_DEBUG if KGDB
71 select ARCH_HAS_ELF_RANDOMIZE
72 select ARCH_HAS_FAST_MULTIPLIER
73 select ARCH_HAS_FILTER_PGPROT
74 select ARCH_HAS_FORTIFY_SOURCE
75 select ARCH_HAS_GCOV_PROFILE_ALL
76 select ARCH_HAS_KCOV if X86_64 && STACK_VALIDATION
77 select ARCH_HAS_MEM_ENCRYPT
78 select ARCH_HAS_MEMBARRIER_SYNC_CORE
79 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
80 select ARCH_HAS_PMEM_API if X86_64
81 select ARCH_HAS_PTE_DEVMAP if X86_64
82 select ARCH_HAS_PTE_SPECIAL
83 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
84 select ARCH_HAS_COPY_MC if X86_64
85 select ARCH_HAS_SET_MEMORY
86 select ARCH_HAS_SET_DIRECT_MAP
87 select ARCH_HAS_STRICT_KERNEL_RWX
88 select ARCH_HAS_STRICT_MODULE_RWX
89 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
90 select ARCH_HAS_SYSCALL_WRAPPER
91 select ARCH_HAS_UBSAN_SANITIZE_ALL
92 select ARCH_HAS_DEBUG_WX
93 select ARCH_HAVE_NMI_SAFE_CMPXCHG
94 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
95 select ARCH_MIGHT_HAVE_PC_PARPORT
96 select ARCH_MIGHT_HAVE_PC_SERIO
98 select ARCH_SUPPORTS_ACPI
99 select ARCH_SUPPORTS_ATOMIC_RMW
100 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
101 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
102 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
103 select ARCH_SUPPORTS_LTO_CLANG if X86_64
104 select ARCH_SUPPORTS_LTO_CLANG_THIN if X86_64
105 select ARCH_USE_BUILTIN_BSWAP
106 select ARCH_USE_MEMTEST
107 select ARCH_USE_QUEUED_RWLOCKS
108 select ARCH_USE_QUEUED_SPINLOCKS
109 select ARCH_USE_SYM_ANNOTATIONS
110 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
111 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
112 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
113 select ARCH_WANT_HUGE_PMD_SHARE
114 select ARCH_WANT_LD_ORPHAN_WARN
115 select ARCH_WANTS_THP_SWAP if X86_64
116 select BUILDTIME_TABLE_SORT
118 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
119 select CLOCKSOURCE_WATCHDOG
120 select DCACHE_WORD_ACCESS
121 select EDAC_ATOMIC_SCRUB
123 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
124 select GENERIC_CLOCKEVENTS_MIN_ADJUST
125 select GENERIC_CMOS_UPDATE
126 select GENERIC_CPU_AUTOPROBE
127 select GENERIC_CPU_VULNERABILITIES
128 select GENERIC_EARLY_IOREMAP
130 select GENERIC_FIND_FIRST_BIT
132 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
133 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
134 select GENERIC_IRQ_MIGRATION if SMP
135 select GENERIC_IRQ_PROBE
136 select GENERIC_IRQ_RESERVATION_MODE
137 select GENERIC_IRQ_SHOW
138 select GENERIC_PENDING_IRQ if SMP
139 select GENERIC_PTDUMP
140 select GENERIC_SMP_IDLE_THREAD
141 select GENERIC_STRNCPY_FROM_USER
142 select GENERIC_STRNLEN_USER
143 select GENERIC_TIME_VSYSCALL
144 select GENERIC_GETTIMEOFDAY
145 select GENERIC_VDSO_TIME_NS
146 select GUP_GET_PTE_LOW_HIGH if X86_PAE
147 select HARDIRQS_SW_RESEND
148 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
149 select HAVE_ACPI_APEI if ACPI
150 select HAVE_ACPI_APEI_NMI if ACPI
151 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
152 select HAVE_ARCH_AUDITSYSCALL
153 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
154 select HAVE_ARCH_JUMP_LABEL
155 select HAVE_ARCH_JUMP_LABEL_RELATIVE
156 select HAVE_ARCH_KASAN if X86_64
157 select HAVE_ARCH_KASAN_VMALLOC if X86_64
158 select HAVE_ARCH_KFENCE
159 select HAVE_ARCH_KGDB
160 select HAVE_ARCH_MMAP_RND_BITS if MMU
161 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
162 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
163 select HAVE_ARCH_PREL32_RELOCATIONS
164 select HAVE_ARCH_SECCOMP_FILTER
165 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
166 select HAVE_ARCH_STACKLEAK
167 select HAVE_ARCH_TRACEHOOK
168 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
169 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
170 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
171 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
172 select HAVE_ARCH_VMAP_STACK if X86_64
173 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
174 select HAVE_ARCH_WITHIN_STACK_FRAMES
175 select HAVE_ASM_MODVERSIONS
176 select HAVE_CMPXCHG_DOUBLE
177 select HAVE_CMPXCHG_LOCAL
178 select HAVE_CONTEXT_TRACKING if X86_64
179 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
180 select HAVE_C_RECORDMCOUNT
181 select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION
182 select HAVE_DEBUG_KMEMLEAK
183 select HAVE_DMA_CONTIGUOUS
184 select HAVE_DYNAMIC_FTRACE
185 select HAVE_DYNAMIC_FTRACE_WITH_REGS
186 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
187 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
189 select HAVE_EFFICIENT_UNALIGNED_ACCESS
191 select HAVE_EXIT_THREAD
193 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
194 select HAVE_FTRACE_MCOUNT_RECORD
195 select HAVE_FUNCTION_GRAPH_TRACER
196 select HAVE_FUNCTION_TRACER
197 select HAVE_GCC_PLUGINS
198 select HAVE_HW_BREAKPOINT
200 select HAVE_IOREMAP_PROT
201 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
202 select HAVE_IRQ_TIME_ACCOUNTING
203 select HAVE_KERNEL_BZIP2
204 select HAVE_KERNEL_GZIP
205 select HAVE_KERNEL_LZ4
206 select HAVE_KERNEL_LZMA
207 select HAVE_KERNEL_LZO
208 select HAVE_KERNEL_XZ
209 select HAVE_KERNEL_ZSTD
211 select HAVE_KPROBES_ON_FTRACE
212 select HAVE_FUNCTION_ERROR_INJECTION
213 select HAVE_KRETPROBES
215 select HAVE_LIVEPATCH if X86_64
216 select HAVE_MIXED_BREAKPOINTS_REGS
217 select HAVE_MOD_ARCH_SPECIFIC
221 select HAVE_OPTPROBES
222 select HAVE_PCSPKR_PLATFORM
223 select HAVE_PERF_EVENTS
224 select HAVE_PERF_EVENTS_NMI
225 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
227 select HAVE_PERF_REGS
228 select HAVE_PERF_USER_STACK_DUMP
229 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
230 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
231 select HAVE_REGS_AND_STACK_ACCESS_API
232 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
233 select HAVE_FUNCTION_ARG_ACCESS_API
234 select HAVE_SOFTIRQ_ON_OWN_STACK
235 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
236 select HAVE_STACK_VALIDATION if X86_64
237 select HAVE_STATIC_CALL
238 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
239 select HAVE_PREEMPT_DYNAMIC
241 select HAVE_SYSCALL_TRACEPOINTS
242 select HAVE_UNSTABLE_SCHED_CLOCK
243 select HAVE_USER_RETURN_NOTIFIER
244 select HAVE_GENERIC_VDSO
245 select HOTPLUG_SMT if SMP
246 select IRQ_FORCED_THREADING
247 select NEED_SG_DMA_LENGTH
248 select PCI_DOMAINS if PCI
249 select PCI_LOCKLESS_CONFIG if PCI
252 select RTC_MC146818_LIB
255 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
256 select SYSCTL_EXCEPTION_TRACE
257 select THREAD_INFO_IN_TASK
258 select USER_STACKTRACE_SUPPORT
260 select HAVE_ARCH_KCSAN if X86_64
261 select X86_FEATURE_NAMES if PROC_FS
262 select PROC_PID_ARCH_STATUS if PROC_FS
263 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
265 config INSTRUCTION_DECODER
267 depends on KPROBES || PERF_EVENTS || UPROBES
271 default "elf32-i386" if X86_32
272 default "elf64-x86-64" if X86_64
274 config LOCKDEP_SUPPORT
277 config STACKTRACE_SUPPORT
283 config ARCH_MMAP_RND_BITS_MIN
287 config ARCH_MMAP_RND_BITS_MAX
291 config ARCH_MMAP_RND_COMPAT_BITS_MIN
294 config ARCH_MMAP_RND_COMPAT_BITS_MAX
300 config GENERIC_ISA_DMA
302 depends on ISA_DMA_API
307 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
309 config GENERIC_BUG_RELATIVE_POINTERS
312 config ARCH_MAY_HAVE_PC_FDC
314 depends on ISA_DMA_API
316 config GENERIC_CALIBRATE_DELAY
319 config ARCH_HAS_CPU_RELAX
322 config ARCH_HAS_FILTER_PGPROT
325 config HAVE_SETUP_PER_CPU_AREA
328 config NEED_PER_CPU_EMBED_FIRST_CHUNK
331 config NEED_PER_CPU_PAGE_FIRST_CHUNK
334 config ARCH_HIBERNATION_POSSIBLE
337 config ARCH_SUSPEND_POSSIBLE
340 config ARCH_WANT_GENERAL_HUGETLB
349 config KASAN_SHADOW_OFFSET
352 default 0xdffffc0000000000
354 config HAVE_INTEL_TXT
356 depends on INTEL_IOMMU && ACPI
360 depends on X86_32 && SMP
364 depends on X86_64 && SMP
366 config ARCH_SUPPORTS_UPROBES
369 config FIX_EARLYCON_MEM
372 config DYNAMIC_PHYSICAL_MASK
375 config PGTABLE_LEVELS
377 default 5 if X86_5LEVEL
382 config CC_HAS_SANE_STACKPROTECTOR
384 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
385 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
387 We have to make sure stack protector is unconditionally disabled if
388 the compiler produces broken code or if it does not let us control
389 the segment on 32-bit kernels.
391 menu "Processor type and features"
394 bool "DMA memory allocation support" if EXPERT
397 DMA memory allocation support allows devices with less than 32-bit
398 addressing to allocate within the first 16MB of address space.
399 Disable if no such devices will be used.
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"
469 Compile kernel with the retpoline compiler options to guard against
470 kernel-to-user data leaks by avoiding speculative indirect
471 branches. Requires a compiler with -mindirect-branch=thunk-extern
472 support for full protection. The kernel may run slower.
474 config X86_CPU_RESCTRL
475 bool "x86 CPU resource control support"
476 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
478 select PROC_CPU_RESCTRL if PROC_FS
480 Enable x86 CPU resource control support.
482 Provide support for the allocation and monitoring of system resources
485 Intel calls this Intel Resource Director Technology
486 (Intel(R) RDT). More information about RDT can be found in the
487 Intel x86 Architecture Software Developer Manual.
489 AMD calls this AMD Platform Quality of Service (AMD QoS).
490 More information about AMD QoS can be found in the AMD64 Technology
491 Platform Quality of Service Extensions manual.
497 bool "Support for big SMP systems with more than 8 CPUs"
500 This option is needed for the systems that have more than 8 CPUs.
502 config X86_EXTENDED_PLATFORM
503 bool "Support for extended (non-PC) x86 platforms"
506 If you disable this option then the kernel will only support
507 standard PC platforms. (which covers the vast majority of
510 If you enable this option then you'll be able to select support
511 for the following (non-PC) 32 bit x86 platforms:
512 Goldfish (Android emulator)
515 SGI 320/540 (Visual Workstation)
516 STA2X11-based (e.g. Northville)
517 Moorestown MID devices
519 If you have one of these systems, or if you want to build a
520 generic distribution kernel, say Y here - otherwise say N.
524 config X86_EXTENDED_PLATFORM
525 bool "Support for extended (non-PC) x86 platforms"
528 If you disable this option then the kernel will only support
529 standard PC platforms. (which covers the vast majority of
532 If you enable this option then you'll be able to select support
533 for the following (non-PC) 64 bit x86 platforms:
538 If you have one of these systems, or if you want to build a
539 generic distribution kernel, say Y here - otherwise say N.
541 # This is an alphabetically sorted list of 64 bit extended platforms
542 # Please maintain the alphabetic order if and when there are additions
544 bool "Numascale NumaChip"
546 depends on X86_EXTENDED_PLATFORM
549 depends on X86_X2APIC
550 depends on PCI_MMCONFIG
552 Adds support for Numascale NumaChip large-SMP systems. Needed to
553 enable more than ~168 cores.
554 If you don't have one of these, you should say N here.
558 select HYPERVISOR_GUEST
560 depends on X86_64 && PCI
561 depends on X86_EXTENDED_PLATFORM
564 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
565 supposed to run on these EM64T-based machines. Only choose this option
566 if you have one of these machines.
569 bool "SGI Ultraviolet"
571 depends on X86_EXTENDED_PLATFORM
574 depends on KEXEC_CORE
575 depends on X86_X2APIC
578 This option is needed in order to support SGI Ultraviolet systems.
579 If you don't have one of these, you should say N here.
581 # Following is an alphabetically sorted list of 32 bit extended platforms
582 # Please maintain the alphabetic order if and when there are additions
585 bool "Goldfish (Virtual Platform)"
586 depends on X86_EXTENDED_PLATFORM
588 Enable support for the Goldfish virtual platform used primarily
589 for Android development. Unless you are building for the Android
590 Goldfish emulator say N here.
593 bool "CE4100 TV platform"
595 depends on PCI_GODIRECT
596 depends on X86_IO_APIC
598 depends on X86_EXTENDED_PLATFORM
599 select X86_REBOOTFIXUPS
601 select OF_EARLY_FLATTREE
603 Select for the Intel CE media processor (CE4100) SOC.
604 This option compiles in support for the CE4100 SOC for settop
605 boxes and media devices.
608 bool "Intel MID platform support"
609 depends on X86_EXTENDED_PLATFORM
610 depends on X86_PLATFORM_DEVICES
612 depends on X86_64 || (PCI_GOANY && X86_32)
613 depends on X86_IO_APIC
618 select MFD_INTEL_MSIC
620 Select to build a kernel capable of supporting Intel MID (Mobile
621 Internet Device) platform systems which do not have the PCI legacy
622 interfaces. If you are building for a PC class system say N here.
624 Intel MID platforms are based on an Intel processor and chipset which
625 consume less power than most of the x86 derivatives.
627 config X86_INTEL_QUARK
628 bool "Intel Quark platform support"
630 depends on X86_EXTENDED_PLATFORM
631 depends on X86_PLATFORM_DEVICES
635 depends on X86_IO_APIC
640 Select to include support for Quark X1000 SoC.
641 Say Y here if you have a Quark based system such as the Arduino
642 compatible Intel Galileo.
644 config X86_INTEL_LPSS
645 bool "Intel Low Power Subsystem Support"
646 depends on X86 && ACPI && PCI
651 Select to build support for Intel Low Power Subsystem such as
652 found on Intel Lynxpoint PCH. Selecting this option enables
653 things like clock tree (common clock framework) and pincontrol
654 which are needed by the LPSS peripheral drivers.
656 config X86_AMD_PLATFORM_DEVICE
657 bool "AMD ACPI2Platform devices support"
662 Select to interpret AMD specific ACPI device to platform device
663 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
664 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
665 implemented under PINCTRL subsystem.
668 tristate "Intel SoC IOSF Sideband support for SoC platforms"
671 This option enables sideband register access support for Intel SoC
672 platforms. On these platforms the IOSF sideband is used in lieu of
673 MSR's for some register accesses, mostly but not limited to thermal
674 and power. Drivers may query the availability of this device to
675 determine if they need the sideband in order to work on these
676 platforms. The sideband is available on the following SoC products.
677 This list is not meant to be exclusive.
682 You should say Y if you are running a kernel on one of these SoC's.
684 config IOSF_MBI_DEBUG
685 bool "Enable IOSF sideband access through debugfs"
686 depends on IOSF_MBI && DEBUG_FS
688 Select this option to expose the IOSF sideband access registers (MCR,
689 MDR, MCRX) through debugfs to write and read register information from
690 different units on the SoC. This is most useful for obtaining device
691 state information for debug and analysis. As this is a general access
692 mechanism, users of this option would have specific knowledge of the
693 device they want to access.
695 If you don't require the option or are in doubt, say N.
698 bool "RDC R-321x SoC"
700 depends on X86_EXTENDED_PLATFORM
702 select X86_REBOOTFIXUPS
704 This option is needed for RDC R-321x system-on-chip, also known
706 If you don't have one of these chips, you should say N here.
708 config X86_32_NON_STANDARD
709 bool "Support non-standard 32-bit SMP architectures"
710 depends on X86_32 && SMP
711 depends on X86_EXTENDED_PLATFORM
713 This option compiles in the bigsmp and STA2X11 default
714 subarchitectures. It is intended for a generic binary
715 kernel. If you select them all, kernel will probe it one by
716 one and will fallback to default.
718 # Alphabetically sorted list of Non standard 32 bit platforms
720 config X86_SUPPORTS_MEMORY_FAILURE
722 # MCE code calls memory_failure():
724 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
725 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
726 depends on X86_64 || !SPARSEMEM
727 select ARCH_SUPPORTS_MEMORY_FAILURE
730 bool "STA2X11 Companion Chip Support"
731 depends on X86_32_NON_STANDARD && PCI
736 This adds support for boards based on the STA2X11 IO-Hub,
737 a.k.a. "ConneXt". The chip is used in place of the standard
738 PC chipset, so all "standard" peripherals are missing. If this
739 option is selected the kernel will still be able to boot on
740 standard PC machines.
743 tristate "Eurobraille/Iris poweroff module"
746 The Iris machines from EuroBraille do not have APM or ACPI support
747 to shut themselves down properly. A special I/O sequence is
748 needed to do so, which is what this module does at
751 This is only for Iris machines from EuroBraille.
755 config SCHED_OMIT_FRAME_POINTER
757 prompt "Single-depth WCHAN output"
760 Calculate simpler /proc/<PID>/wchan values. If this option
761 is disabled then wchan values will recurse back to the
762 caller function. This provides more accurate wchan values,
763 at the expense of slightly more scheduling overhead.
765 If in doubt, say "Y".
767 menuconfig HYPERVISOR_GUEST
768 bool "Linux guest support"
770 Say Y here to enable options for running Linux under various hyper-
771 visors. This option enables basic hypervisor detection and platform
774 If you say N, all options in this submenu will be skipped and
775 disabled, and Linux guest support won't be built in.
780 bool "Enable paravirtualization code"
781 depends on HAVE_STATIC_CALL
783 This changes the kernel so it can modify itself when it is run
784 under a hypervisor, potentially improving performance significantly
785 over full virtualization. However, when run without a hypervisor
786 the kernel is theoretically slower and slightly larger.
791 config PARAVIRT_DEBUG
792 bool "paravirt-ops debugging"
793 depends on PARAVIRT && DEBUG_KERNEL
795 Enable to debug paravirt_ops internals. Specifically, BUG if
796 a paravirt_op is missing when it is called.
798 config PARAVIRT_SPINLOCKS
799 bool "Paravirtualization layer for spinlocks"
800 depends on PARAVIRT && SMP
802 Paravirtualized spinlocks allow a pvops backend to replace the
803 spinlock implementation with something virtualization-friendly
804 (for example, block the virtual CPU rather than spinning).
806 It has a minimal impact on native kernels and gives a nice performance
807 benefit on paravirtualized KVM / Xen kernels.
809 If you are unsure how to answer this question, answer Y.
811 config X86_HV_CALLBACK_VECTOR
814 source "arch/x86/xen/Kconfig"
817 bool "KVM Guest support (including kvmclock)"
819 select PARAVIRT_CLOCK
820 select ARCH_CPUIDLE_HALTPOLL
821 select X86_HV_CALLBACK_VECTOR
824 This option enables various optimizations for running under the KVM
825 hypervisor. It includes a paravirtualized clock, so that instead
826 of relying on a PIT (or probably other) emulation by the
827 underlying device model, the host provides the guest with
828 timing infrastructure such as time of day, and system time
830 config ARCH_CPUIDLE_HALTPOLL
832 prompt "Disable host haltpoll when loading haltpoll driver"
834 If virtualized under KVM, disable host haltpoll.
837 bool "Support for running PVH guests"
839 This option enables the PVH entry point for guest virtual machines
840 as specified in the x86/HVM direct boot ABI.
842 config PARAVIRT_TIME_ACCOUNTING
843 bool "Paravirtual steal time accounting"
846 Select this option to enable fine granularity task steal time
847 accounting. Time spent executing other tasks in parallel with
848 the current vCPU is discounted from the vCPU power. To account for
849 that, there can be a small performance impact.
851 If in doubt, say N here.
853 config PARAVIRT_CLOCK
856 config JAILHOUSE_GUEST
857 bool "Jailhouse non-root cell support"
858 depends on X86_64 && PCI
861 This option allows to run Linux as guest in a Jailhouse non-root
862 cell. You can leave this option disabled if you only want to start
863 Jailhouse and run Linux afterwards in the root cell.
866 bool "ACRN Guest support"
868 select X86_HV_CALLBACK_VECTOR
870 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
871 a flexible, lightweight reference open-source hypervisor, built with
872 real-time and safety-criticality in mind. It is built for embedded
873 IOT with small footprint and real-time features. More details can be
874 found in https://projectacrn.org/.
876 endif #HYPERVISOR_GUEST
878 source "arch/x86/Kconfig.cpu"
882 prompt "HPET Timer Support" if X86_32
884 Use the IA-PC HPET (High Precision Event Timer) to manage
885 time in preference to the PIT and RTC, if a HPET is
887 HPET is the next generation timer replacing legacy 8254s.
888 The HPET provides a stable time base on SMP
889 systems, unlike the TSC, but it is more expensive to access,
890 as it is off-chip. The interface used is documented
891 in the HPET spec, revision 1.
893 You can safely choose Y here. However, HPET will only be
894 activated if the platform and the BIOS support this feature.
895 Otherwise the 8254 will be used for timing services.
897 Choose N to continue using the legacy 8254 timer.
899 config HPET_EMULATE_RTC
901 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
903 # Mark as expert because too many people got it wrong.
904 # The code disables itself when not needed.
907 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
908 bool "Enable DMI scanning" if EXPERT
910 Enabled scanning of DMI to identify machine quirks. Say Y
911 here unless you have verified that your setup is not
912 affected by entries in the DMI blacklist. Required by PNP
916 bool "Old AMD GART IOMMU support"
920 depends on X86_64 && PCI && AMD_NB
922 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
923 GART based hardware IOMMUs.
925 The GART supports full DMA access for devices with 32-bit access
926 limitations, on systems with more than 3 GB. This is usually needed
927 for USB, sound, many IDE/SATA chipsets and some other devices.
929 Newer systems typically have a modern AMD IOMMU, supported via
930 the CONFIG_AMD_IOMMU=y config option.
932 In normal configurations this driver is only active when needed:
933 there's more than 3 GB of memory and the system contains a
934 32-bit limited device.
939 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
940 depends on X86_64 && SMP && DEBUG_KERNEL
941 select CPUMASK_OFFSTACK
943 Enable maximum number of CPUS and NUMA Nodes for this architecture.
947 # The maximum number of CPUs supported:
949 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
950 # and which can be configured interactively in the
951 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
953 # The ranges are different on 32-bit and 64-bit kernels, depending on
954 # hardware capabilities and scalability features of the kernel.
956 # ( If MAXSMP is enabled we just use the highest possible value and disable
957 # interactive configuration. )
960 config NR_CPUS_RANGE_BEGIN
962 default NR_CPUS_RANGE_END if MAXSMP
966 config NR_CPUS_RANGE_END
969 default 64 if SMP && X86_BIGSMP
970 default 8 if SMP && !X86_BIGSMP
973 config NR_CPUS_RANGE_END
976 default 8192 if SMP && CPUMASK_OFFSTACK
977 default 512 if SMP && !CPUMASK_OFFSTACK
980 config NR_CPUS_DEFAULT
983 default 32 if X86_BIGSMP
987 config NR_CPUS_DEFAULT
990 default 8192 if MAXSMP
995 int "Maximum number of CPUs" if SMP && !MAXSMP
996 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
997 default NR_CPUS_DEFAULT
999 This allows you to specify the maximum number of CPUs which this
1000 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1001 supported value is 8192, otherwise the maximum value is 512. The
1002 minimum value which makes sense is 2.
1004 This is purely to save memory: each supported CPU adds about 8KB
1005 to the kernel image.
1012 prompt "Multi-core scheduler support"
1015 Multi-core scheduler support improves the CPU scheduler's decision
1016 making when dealing with multi-core CPU chips at a cost of slightly
1017 increased overhead in some places. If unsure say N here.
1019 config SCHED_MC_PRIO
1020 bool "CPU core priorities scheduler support"
1021 depends on SCHED_MC && CPU_SUP_INTEL
1022 select X86_INTEL_PSTATE
1026 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1027 core ordering determined at manufacturing time, which allows
1028 certain cores to reach higher turbo frequencies (when running
1029 single threaded workloads) than others.
1031 Enabling this kernel feature teaches the scheduler about
1032 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1033 scheduler's CPU selection logic accordingly, so that higher
1034 overall system performance can be achieved.
1036 This feature will have no effect on CPUs without this feature.
1038 If unsure say Y here.
1042 depends on !SMP && X86_LOCAL_APIC
1045 bool "Local APIC support on uniprocessors" if !PCI_MSI
1047 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1049 A local APIC (Advanced Programmable Interrupt Controller) is an
1050 integrated interrupt controller in the CPU. If you have a single-CPU
1051 system which has a processor with a local APIC, you can say Y here to
1052 enable and use it. If you say Y here even though your machine doesn't
1053 have a local APIC, then the kernel will still run with no slowdown at
1054 all. The local APIC supports CPU-generated self-interrupts (timer,
1055 performance counters), and the NMI watchdog which detects hard
1058 config X86_UP_IOAPIC
1059 bool "IO-APIC support on uniprocessors"
1060 depends on X86_UP_APIC
1062 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1063 SMP-capable replacement for PC-style interrupt controllers. Most
1064 SMP systems and many recent uniprocessor systems have one.
1066 If you have a single-CPU system with an IO-APIC, you can say Y here
1067 to use it. If you say Y here even though your machine doesn't have
1068 an IO-APIC, then the kernel will still run with no slowdown at all.
1070 config X86_LOCAL_APIC
1072 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1073 select IRQ_DOMAIN_HIERARCHY
1074 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1078 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1080 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1081 bool "Reroute for broken boot IRQs"
1082 depends on X86_IO_APIC
1084 This option enables a workaround that fixes a source of
1085 spurious interrupts. This is recommended when threaded
1086 interrupt handling is used on systems where the generation of
1087 superfluous "boot interrupts" cannot be disabled.
1089 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1090 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1091 kernel does during interrupt handling). On chipsets where this
1092 boot IRQ generation cannot be disabled, this workaround keeps
1093 the original IRQ line masked so that only the equivalent "boot
1094 IRQ" is delivered to the CPUs. The workaround also tells the
1095 kernel to set up the IRQ handler on the boot IRQ line. In this
1096 way only one interrupt is delivered to the kernel. Otherwise
1097 the spurious second interrupt may cause the kernel to bring
1098 down (vital) interrupt lines.
1100 Only affects "broken" chipsets. Interrupt sharing may be
1101 increased on these systems.
1104 bool "Machine Check / overheating reporting"
1105 select GENERIC_ALLOCATOR
1108 Machine Check support allows the processor to notify the
1109 kernel if it detects a problem (e.g. overheating, data corruption).
1110 The action the kernel takes depends on the severity of the problem,
1111 ranging from warning messages to halting the machine.
1113 config X86_MCELOG_LEGACY
1114 bool "Support for deprecated /dev/mcelog character device"
1117 Enable support for /dev/mcelog which is needed by the old mcelog
1118 userspace logging daemon. Consider switching to the new generation
1121 config X86_MCE_INTEL
1123 prompt "Intel MCE features"
1124 depends on X86_MCE && X86_LOCAL_APIC
1126 Additional support for intel specific MCE features such as
1127 the thermal monitor.
1131 prompt "AMD MCE features"
1132 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1134 Additional support for AMD specific MCE features such as
1135 the DRAM Error Threshold.
1137 config X86_ANCIENT_MCE
1138 bool "Support for old Pentium 5 / WinChip machine checks"
1139 depends on X86_32 && X86_MCE
1141 Include support for machine check handling on old Pentium 5 or WinChip
1142 systems. These typically need to be enabled explicitly on the command
1145 config X86_MCE_THRESHOLD
1146 depends on X86_MCE_AMD || X86_MCE_INTEL
1149 config X86_MCE_INJECT
1150 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1151 tristate "Machine check injector support"
1153 Provide support for injecting machine checks for testing purposes.
1154 If you don't know what a machine check is and you don't do kernel
1155 QA it is safe to say n.
1157 source "arch/x86/events/Kconfig"
1159 config X86_LEGACY_VM86
1160 bool "Legacy VM86 support"
1163 This option allows user programs to put the CPU into V8086
1164 mode, which is an 80286-era approximation of 16-bit real mode.
1166 Some very old versions of X and/or vbetool require this option
1167 for user mode setting. Similarly, DOSEMU will use it if
1168 available to accelerate real mode DOS programs. However, any
1169 recent version of DOSEMU, X, or vbetool should be fully
1170 functional even without kernel VM86 support, as they will all
1171 fall back to software emulation. Nevertheless, if you are using
1172 a 16-bit DOS program where 16-bit performance matters, vm86
1173 mode might be faster than emulation and you might want to
1176 Note that any app that works on a 64-bit kernel is unlikely to
1177 need this option, as 64-bit kernels don't, and can't, support
1178 V8086 mode. This option is also unrelated to 16-bit protected
1179 mode and is not needed to run most 16-bit programs under Wine.
1181 Enabling this option increases the complexity of the kernel
1182 and slows down exception handling a tiny bit.
1184 If unsure, say N here.
1188 default X86_LEGACY_VM86
1191 bool "Enable support for 16-bit segments" if EXPERT
1193 depends on MODIFY_LDT_SYSCALL
1195 This option is required by programs like Wine to run 16-bit
1196 protected mode legacy code on x86 processors. Disabling
1197 this option saves about 300 bytes on i386, or around 6K text
1198 plus 16K runtime memory on x86-64,
1202 depends on X86_16BIT && X86_32
1206 depends on X86_16BIT && X86_64
1208 config X86_VSYSCALL_EMULATION
1209 bool "Enable vsyscall emulation" if EXPERT
1213 This enables emulation of the legacy vsyscall page. Disabling
1214 it is roughly equivalent to booting with vsyscall=none, except
1215 that it will also disable the helpful warning if a program
1216 tries to use a vsyscall. With this option set to N, offending
1217 programs will just segfault, citing addresses of the form
1220 This option is required by many programs built before 2013, and
1221 care should be used even with newer programs if set to N.
1223 Disabling this option saves about 7K of kernel size and
1224 possibly 4K of additional runtime pagetable memory.
1226 config X86_IOPL_IOPERM
1227 bool "IOPERM and IOPL Emulation"
1230 This enables the ioperm() and iopl() syscalls which are necessary
1231 for legacy applications.
1233 Legacy IOPL support is an overbroad mechanism which allows user
1234 space aside of accessing all 65536 I/O ports also to disable
1235 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1236 capabilities and permission from potentially active security
1239 The emulation restricts the functionality of the syscall to
1240 only allowing the full range I/O port access, but prevents the
1241 ability to disable interrupts from user space which would be
1242 granted if the hardware IOPL mechanism would be used.
1245 tristate "Toshiba Laptop support"
1248 This adds a driver to safely access the System Management Mode of
1249 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1250 not work on models with a Phoenix BIOS. The System Management Mode
1251 is used to set the BIOS and power saving options on Toshiba portables.
1253 For information on utilities to make use of this driver see the
1254 Toshiba Linux utilities web site at:
1255 <http://www.buzzard.org.uk/toshiba/>.
1257 Say Y if you intend to run this kernel on a Toshiba portable.
1261 tristate "Dell i8k legacy laptop support"
1263 select SENSORS_DELL_SMM
1265 This option enables legacy /proc/i8k userspace interface in hwmon
1266 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1267 temperature and allows controlling fan speeds of Dell laptops via
1268 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1269 it reports also power and hotkey status. For fan speed control is
1270 needed userspace package i8kutils.
1272 Say Y if you intend to run this kernel on old Dell laptops or want to
1273 use userspace package i8kutils.
1276 config X86_REBOOTFIXUPS
1277 bool "Enable X86 board specific fixups for reboot"
1280 This enables chipset and/or board specific fixups to be done
1281 in order to get reboot to work correctly. This is only needed on
1282 some combinations of hardware and BIOS. The symptom, for which
1283 this config is intended, is when reboot ends with a stalled/hung
1286 Currently, the only fixup is for the Geode machines using
1287 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1289 Say Y if you want to enable the fixup. Currently, it's safe to
1290 enable this option even if you don't need it.
1294 bool "CPU microcode loading support"
1296 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1298 If you say Y here, you will be able to update the microcode on
1299 Intel and AMD processors. The Intel support is for the IA32 family,
1300 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1301 AMD support is for families 0x10 and later. You will obviously need
1302 the actual microcode binary data itself which is not shipped with
1305 The preferred method to load microcode from a detached initrd is described
1306 in Documentation/x86/microcode.rst. For that you need to enable
1307 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1308 initrd for microcode blobs.
1310 In addition, you can build the microcode into the kernel. For that you
1311 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1314 config MICROCODE_INTEL
1315 bool "Intel microcode loading support"
1316 depends on MICROCODE
1319 This options enables microcode patch loading support for Intel
1322 For the current Intel microcode data package go to
1323 <https://downloadcenter.intel.com> and search for
1324 'Linux Processor Microcode Data File'.
1326 config MICROCODE_AMD
1327 bool "AMD microcode loading support"
1328 depends on MICROCODE
1330 If you select this option, microcode patch loading support for AMD
1331 processors will be enabled.
1333 config MICROCODE_OLD_INTERFACE
1334 bool "Ancient loading interface (DEPRECATED)"
1336 depends on MICROCODE
1338 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1339 which was used by userspace tools like iucode_tool and microcode.ctl.
1340 It is inadequate because it runs too late to be able to properly
1341 load microcode on a machine and it needs special tools. Instead, you
1342 should've switched to the early loading method with the initrd or
1343 builtin microcode by now: Documentation/x86/microcode.rst
1346 tristate "/dev/cpu/*/msr - Model-specific register support"
1348 This device gives privileged processes access to the x86
1349 Model-Specific Registers (MSRs). It is a character device with
1350 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1351 MSR accesses are directed to a specific CPU on multi-processor
1355 tristate "/dev/cpu/*/cpuid - CPU information support"
1357 This device gives processes access to the x86 CPUID instruction to
1358 be executed on a specific processor. It is a character device
1359 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1363 prompt "High Memory Support"
1370 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1371 However, the address space of 32-bit x86 processors is only 4
1372 Gigabytes large. That means that, if you have a large amount of
1373 physical memory, not all of it can be "permanently mapped" by the
1374 kernel. The physical memory that's not permanently mapped is called
1377 If you are compiling a kernel which will never run on a machine with
1378 more than 1 Gigabyte total physical RAM, answer "off" here (default
1379 choice and suitable for most users). This will result in a "3GB/1GB"
1380 split: 3GB are mapped so that each process sees a 3GB virtual memory
1381 space and the remaining part of the 4GB virtual memory space is used
1382 by the kernel to permanently map as much physical memory as
1385 If the machine has between 1 and 4 Gigabytes physical RAM, then
1388 If more than 4 Gigabytes is used then answer "64GB" here. This
1389 selection turns Intel PAE (Physical Address Extension) mode on.
1390 PAE implements 3-level paging on IA32 processors. PAE is fully
1391 supported by Linux, PAE mode is implemented on all recent Intel
1392 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1393 then the kernel will not boot on CPUs that don't support PAE!
1395 The actual amount of total physical memory will either be
1396 auto detected or can be forced by using a kernel command line option
1397 such as "mem=256M". (Try "man bootparam" or see the documentation of
1398 your boot loader (lilo or loadlin) about how to pass options to the
1399 kernel at boot time.)
1401 If unsure, say "off".
1406 Select this if you have a 32-bit processor and between 1 and 4
1407 gigabytes of physical RAM.
1411 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1414 Select this if you have a 32-bit processor and more than 4
1415 gigabytes of physical RAM.
1420 prompt "Memory split" if EXPERT
1424 Select the desired split between kernel and user memory.
1426 If the address range available to the kernel is less than the
1427 physical memory installed, the remaining memory will be available
1428 as "high memory". Accessing high memory is a little more costly
1429 than low memory, as it needs to be mapped into the kernel first.
1430 Note that increasing the kernel address space limits the range
1431 available to user programs, making the address space there
1432 tighter. Selecting anything other than the default 3G/1G split
1433 will also likely make your kernel incompatible with binary-only
1436 If you are not absolutely sure what you are doing, leave this
1440 bool "3G/1G user/kernel split"
1441 config VMSPLIT_3G_OPT
1443 bool "3G/1G user/kernel split (for full 1G low memory)"
1445 bool "2G/2G user/kernel split"
1446 config VMSPLIT_2G_OPT
1448 bool "2G/2G user/kernel split (for full 2G low memory)"
1450 bool "1G/3G user/kernel split"
1455 default 0xB0000000 if VMSPLIT_3G_OPT
1456 default 0x80000000 if VMSPLIT_2G
1457 default 0x78000000 if VMSPLIT_2G_OPT
1458 default 0x40000000 if VMSPLIT_1G
1464 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1467 bool "PAE (Physical Address Extension) Support"
1468 depends on X86_32 && !HIGHMEM4G
1469 select PHYS_ADDR_T_64BIT
1472 PAE is required for NX support, and furthermore enables
1473 larger swapspace support for non-overcommit purposes. It
1474 has the cost of more pagetable lookup overhead, and also
1475 consumes more pagetable space per process.
1478 bool "Enable 5-level page tables support"
1480 select DYNAMIC_MEMORY_LAYOUT
1481 select SPARSEMEM_VMEMMAP
1484 5-level paging enables access to larger address space:
1485 upto 128 PiB of virtual address space and 4 PiB of
1486 physical address space.
1488 It will be supported by future Intel CPUs.
1490 A kernel with the option enabled can be booted on machines that
1491 support 4- or 5-level paging.
1493 See Documentation/x86/x86_64/5level-paging.rst for more
1498 config X86_DIRECT_GBPAGES
1502 Certain kernel features effectively disable kernel
1503 linear 1 GB mappings (even if the CPU otherwise
1504 supports them), so don't confuse the user by printing
1505 that we have them enabled.
1507 config X86_CPA_STATISTICS
1508 bool "Enable statistic for Change Page Attribute"
1511 Expose statistics about the Change Page Attribute mechanism, which
1512 helps to determine the effectiveness of preserving large and huge
1513 page mappings when mapping protections are changed.
1515 config AMD_MEM_ENCRYPT
1516 bool "AMD Secure Memory Encryption (SME) support"
1517 depends on X86_64 && CPU_SUP_AMD
1518 select DMA_COHERENT_POOL
1519 select DYNAMIC_PHYSICAL_MASK
1520 select ARCH_USE_MEMREMAP_PROT
1521 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1522 select INSTRUCTION_DECODER
1523 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1525 Say yes to enable support for the encryption of system memory.
1526 This requires an AMD processor that supports Secure Memory
1529 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1530 bool "Activate AMD Secure Memory Encryption (SME) by default"
1532 depends on AMD_MEM_ENCRYPT
1534 Say yes to have system memory encrypted by default if running on
1535 an AMD processor that supports Secure Memory Encryption (SME).
1537 If set to Y, then the encryption of system memory can be
1538 deactivated with the mem_encrypt=off command line option.
1540 If set to N, then the encryption of system memory can be
1541 activated with the mem_encrypt=on command line option.
1543 # Common NUMA Features
1545 bool "NUMA Memory Allocation and Scheduler Support"
1547 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1548 default y if X86_BIGSMP
1550 Enable NUMA (Non-Uniform Memory Access) support.
1552 The kernel will try to allocate memory used by a CPU on the
1553 local memory controller of the CPU and add some more
1554 NUMA awareness to the kernel.
1556 For 64-bit this is recommended if the system is Intel Core i7
1557 (or later), AMD Opteron, or EM64T NUMA.
1559 For 32-bit this is only needed if you boot a 32-bit
1560 kernel on a 64-bit NUMA platform.
1562 Otherwise, you should say N.
1566 prompt "Old style AMD Opteron NUMA detection"
1567 depends on X86_64 && NUMA && PCI
1569 Enable AMD NUMA node topology detection. You should say Y here if
1570 you have a multi processor AMD system. This uses an old method to
1571 read the NUMA configuration directly from the builtin Northbridge
1572 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1573 which also takes priority if both are compiled in.
1575 config X86_64_ACPI_NUMA
1577 prompt "ACPI NUMA detection"
1578 depends on X86_64 && NUMA && ACPI && PCI
1581 Enable ACPI SRAT based node topology detection.
1584 bool "NUMA emulation"
1587 Enable NUMA emulation. A flat machine will be split
1588 into virtual nodes when booted with "numa=fake=N", where N is the
1589 number of nodes. This is only useful for debugging.
1592 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1594 default "10" if MAXSMP
1595 default "6" if X86_64
1597 depends on NEED_MULTIPLE_NODES
1599 Specify the maximum number of NUMA Nodes available on the target
1600 system. Increases memory reserved to accommodate various tables.
1602 config ARCH_FLATMEM_ENABLE
1604 depends on X86_32 && !NUMA
1606 config ARCH_SPARSEMEM_ENABLE
1608 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1609 select SPARSEMEM_STATIC if X86_32
1610 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1612 config ARCH_SPARSEMEM_DEFAULT
1613 def_bool X86_64 || (NUMA && X86_32)
1615 config ARCH_SELECT_MEMORY_MODEL
1617 depends on ARCH_SPARSEMEM_ENABLE
1619 config ARCH_MEMORY_PROBE
1620 bool "Enable sysfs memory/probe interface"
1621 depends on X86_64 && MEMORY_HOTPLUG
1623 This option enables a sysfs memory/probe interface for testing.
1624 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1625 If you are unsure how to answer this question, answer N.
1627 config ARCH_PROC_KCORE_TEXT
1629 depends on X86_64 && PROC_KCORE
1631 config ILLEGAL_POINTER_VALUE
1634 default 0xdead000000000000 if X86_64
1636 config X86_PMEM_LEGACY_DEVICE
1639 config X86_PMEM_LEGACY
1640 tristate "Support non-standard NVDIMMs and ADR protected memory"
1641 depends on PHYS_ADDR_T_64BIT
1643 select X86_PMEM_LEGACY_DEVICE
1644 select NUMA_KEEP_MEMINFO if NUMA
1647 Treat memory marked using the non-standard e820 type of 12 as used
1648 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1649 The kernel will offer these regions to the 'pmem' driver so
1650 they can be used for persistent storage.
1655 bool "Allocate 3rd-level pagetables from highmem"
1658 The VM uses one page table entry for each page of physical memory.
1659 For systems with a lot of RAM, this can be wasteful of precious
1660 low memory. Setting this option will put user-space page table
1661 entries in high memory.
1663 config X86_CHECK_BIOS_CORRUPTION
1664 bool "Check for low memory corruption"
1666 Periodically check for memory corruption in low memory, which
1667 is suspected to be caused by BIOS. Even when enabled in the
1668 configuration, it is disabled at runtime. Enable it by
1669 setting "memory_corruption_check=1" on the kernel command
1670 line. By default it scans the low 64k of memory every 60
1671 seconds; see the memory_corruption_check_size and
1672 memory_corruption_check_period parameters in
1673 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1675 When enabled with the default parameters, this option has
1676 almost no overhead, as it reserves a relatively small amount
1677 of memory and scans it infrequently. It both detects corruption
1678 and prevents it from affecting the running system.
1680 It is, however, intended as a diagnostic tool; if repeatable
1681 BIOS-originated corruption always affects the same memory,
1682 you can use memmap= to prevent the kernel from using that
1685 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1686 bool "Set the default setting of memory_corruption_check"
1687 depends on X86_CHECK_BIOS_CORRUPTION
1690 Set whether the default state of memory_corruption_check is
1693 config X86_RESERVE_LOW
1694 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1698 Specify the amount of low memory to reserve for the BIOS.
1700 The first page contains BIOS data structures that the kernel
1701 must not use, so that page must always be reserved.
1703 By default we reserve the first 64K of physical RAM, as a
1704 number of BIOSes are known to corrupt that memory range
1705 during events such as suspend/resume or monitor cable
1706 insertion, so it must not be used by the kernel.
1708 You can set this to 4 if you are absolutely sure that you
1709 trust the BIOS to get all its memory reservations and usages
1710 right. If you know your BIOS have problems beyond the
1711 default 64K area, you can set this to 640 to avoid using the
1712 entire low memory range.
1714 If you have doubts about the BIOS (e.g. suspend/resume does
1715 not work or there's kernel crashes after certain hardware
1716 hotplug events) then you might want to enable
1717 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1718 typical corruption patterns.
1720 Leave this to the default value of 64 if you are unsure.
1722 config MATH_EMULATION
1724 depends on MODIFY_LDT_SYSCALL
1725 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1727 Linux can emulate a math coprocessor (used for floating point
1728 operations) if you don't have one. 486DX and Pentium processors have
1729 a math coprocessor built in, 486SX and 386 do not, unless you added
1730 a 487DX or 387, respectively. (The messages during boot time can
1731 give you some hints here ["man dmesg"].) Everyone needs either a
1732 coprocessor or this emulation.
1734 If you don't have a math coprocessor, you need to say Y here; if you
1735 say Y here even though you have a coprocessor, the coprocessor will
1736 be used nevertheless. (This behavior can be changed with the kernel
1737 command line option "no387", which comes handy if your coprocessor
1738 is broken. Try "man bootparam" or see the documentation of your boot
1739 loader (lilo or loadlin) about how to pass options to the kernel at
1740 boot time.) This means that it is a good idea to say Y here if you
1741 intend to use this kernel on different machines.
1743 More information about the internals of the Linux math coprocessor
1744 emulation can be found in <file:arch/x86/math-emu/README>.
1746 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1747 kernel, it won't hurt.
1751 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1753 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1754 the Memory Type Range Registers (MTRRs) may be used to control
1755 processor access to memory ranges. This is most useful if you have
1756 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1757 allows bus write transfers to be combined into a larger transfer
1758 before bursting over the PCI/AGP bus. This can increase performance
1759 of image write operations 2.5 times or more. Saying Y here creates a
1760 /proc/mtrr file which may be used to manipulate your processor's
1761 MTRRs. Typically the X server should use this.
1763 This code has a reasonably generic interface so that similar
1764 control registers on other processors can be easily supported
1767 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1768 Registers (ARRs) which provide a similar functionality to MTRRs. For
1769 these, the ARRs are used to emulate the MTRRs.
1770 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1771 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1772 write-combining. All of these processors are supported by this code
1773 and it makes sense to say Y here if you have one of them.
1775 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1776 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1777 can lead to all sorts of problems, so it's good to say Y here.
1779 You can safely say Y even if your machine doesn't have MTRRs, you'll
1780 just add about 9 KB to your kernel.
1782 See <file:Documentation/x86/mtrr.rst> for more information.
1784 config MTRR_SANITIZER
1786 prompt "MTRR cleanup support"
1789 Convert MTRR layout from continuous to discrete, so X drivers can
1790 add writeback entries.
1792 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1793 The largest mtrr entry size for a continuous block can be set with
1798 config MTRR_SANITIZER_ENABLE_DEFAULT
1799 int "MTRR cleanup enable value (0-1)"
1802 depends on MTRR_SANITIZER
1804 Enable mtrr cleanup default value
1806 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1807 int "MTRR cleanup spare reg num (0-7)"
1810 depends on MTRR_SANITIZER
1812 mtrr cleanup spare entries default, it can be changed via
1813 mtrr_spare_reg_nr=N on the kernel command line.
1817 prompt "x86 PAT support" if EXPERT
1820 Use PAT attributes to setup page level cache control.
1822 PATs are the modern equivalents of MTRRs and are much more
1823 flexible than MTRRs.
1825 Say N here if you see bootup problems (boot crash, boot hang,
1826 spontaneous reboots) or a non-working video driver.
1830 config ARCH_USES_PG_UNCACHED
1836 prompt "x86 architectural random number generator" if EXPERT
1838 Enable the x86 architectural RDRAND instruction
1839 (Intel Bull Mountain technology) to generate random numbers.
1840 If supported, this is a high bandwidth, cryptographically
1841 secure hardware random number generator.
1845 prompt "Supervisor Mode Access Prevention" if EXPERT
1847 Supervisor Mode Access Prevention (SMAP) is a security
1848 feature in newer Intel processors. There is a small
1849 performance cost if this enabled and turned on; there is
1850 also a small increase in the kernel size if this is enabled.
1856 prompt "User Mode Instruction Prevention" if EXPERT
1858 User Mode Instruction Prevention (UMIP) is a security feature in
1859 some x86 processors. If enabled, a general protection fault is
1860 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1861 executed in user mode. These instructions unnecessarily expose
1862 information about the hardware state.
1864 The vast majority of applications do not use these instructions.
1865 For the very few that do, software emulation is provided in
1866 specific cases in protected and virtual-8086 modes. Emulated
1869 config X86_INTEL_MEMORY_PROTECTION_KEYS
1870 prompt "Memory Protection Keys"
1872 # Note: only available in 64-bit mode
1873 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1874 select ARCH_USES_HIGH_VMA_FLAGS
1875 select ARCH_HAS_PKEYS
1877 Memory Protection Keys provides a mechanism for enforcing
1878 page-based protections, but without requiring modification of the
1879 page tables when an application changes protection domains.
1881 For details, see Documentation/core-api/protection-keys.rst
1886 prompt "TSX enable mode"
1887 depends on CPU_SUP_INTEL
1888 default X86_INTEL_TSX_MODE_OFF
1890 Intel's TSX (Transactional Synchronization Extensions) feature
1891 allows to optimize locking protocols through lock elision which
1892 can lead to a noticeable performance boost.
1894 On the other hand it has been shown that TSX can be exploited
1895 to form side channel attacks (e.g. TAA) and chances are there
1896 will be more of those attacks discovered in the future.
1898 Therefore TSX is not enabled by default (aka tsx=off). An admin
1899 might override this decision by tsx=on the command line parameter.
1900 Even with TSX enabled, the kernel will attempt to enable the best
1901 possible TAA mitigation setting depending on the microcode available
1902 for the particular machine.
1904 This option allows to set the default tsx mode between tsx=on, =off
1905 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1908 Say off if not sure, auto if TSX is in use but it should be used on safe
1909 platforms or on if TSX is in use and the security aspect of tsx is not
1912 config X86_INTEL_TSX_MODE_OFF
1915 TSX is disabled if possible - equals to tsx=off command line parameter.
1917 config X86_INTEL_TSX_MODE_ON
1920 TSX is always enabled on TSX capable HW - equals the tsx=on command
1923 config X86_INTEL_TSX_MODE_AUTO
1926 TSX is enabled on TSX capable HW that is believed to be safe against
1927 side channel attacks- equals the tsx=auto command line parameter.
1931 bool "Software Guard eXtensions (SGX)"
1932 depends on X86_64 && CPU_SUP_INTEL
1934 depends on CRYPTO_SHA256=y
1937 select NUMA_KEEP_MEMINFO if NUMA
1939 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1940 that can be used by applications to set aside private regions of code
1941 and data, referred to as enclaves. An enclave's private memory can
1942 only be accessed by code running within the enclave. Accesses from
1943 outside the enclave, including other enclaves, are disallowed by
1949 bool "EFI runtime service support"
1952 select EFI_RUNTIME_WRAPPERS
1954 This enables the kernel to use EFI runtime services that are
1955 available (such as the EFI variable services).
1957 This option is only useful on systems that have EFI firmware.
1958 In addition, you should use the latest ELILO loader available
1959 at <http://elilo.sourceforge.net> in order to take advantage
1960 of EFI runtime services. However, even with this option, the
1961 resultant kernel should continue to boot on existing non-EFI
1965 bool "EFI stub support"
1966 depends on EFI && !X86_USE_3DNOW
1967 depends on $(cc-option,-mabi=ms) || X86_32
1970 This kernel feature allows a bzImage to be loaded directly
1971 by EFI firmware without the use of a bootloader.
1973 See Documentation/admin-guide/efi-stub.rst for more information.
1976 bool "EFI mixed-mode support"
1977 depends on EFI_STUB && X86_64
1979 Enabling this feature allows a 64-bit kernel to be booted
1980 on a 32-bit firmware, provided that your CPU supports 64-bit
1983 Note that it is not possible to boot a mixed-mode enabled
1984 kernel via the EFI boot stub - a bootloader that supports
1985 the EFI handover protocol must be used.
1989 source "kernel/Kconfig.hz"
1992 bool "kexec system call"
1995 kexec is a system call that implements the ability to shutdown your
1996 current kernel, and to start another kernel. It is like a reboot
1997 but it is independent of the system firmware. And like a reboot
1998 you can start any kernel with it, not just Linux.
2000 The name comes from the similarity to the exec system call.
2002 It is an ongoing process to be certain the hardware in a machine
2003 is properly shutdown, so do not be surprised if this code does not
2004 initially work for you. As of this writing the exact hardware
2005 interface is strongly in flux, so no good recommendation can be
2009 bool "kexec file based system call"
2014 depends on CRYPTO_SHA256=y
2016 This is new version of kexec system call. This system call is
2017 file based and takes file descriptors as system call argument
2018 for kernel and initramfs as opposed to list of segments as
2019 accepted by previous system call.
2021 config ARCH_HAS_KEXEC_PURGATORY
2025 bool "Verify kernel signature during kexec_file_load() syscall"
2026 depends on KEXEC_FILE
2029 This option makes the kexec_file_load() syscall check for a valid
2030 signature of the kernel image. The image can still be loaded without
2031 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2032 there's a signature that we can check, then it must be valid.
2034 In addition to this option, you need to enable signature
2035 verification for the corresponding kernel image type being
2036 loaded in order for this to work.
2038 config KEXEC_SIG_FORCE
2039 bool "Require a valid signature in kexec_file_load() syscall"
2040 depends on KEXEC_SIG
2042 This option makes kernel signature verification mandatory for
2043 the kexec_file_load() syscall.
2045 config KEXEC_BZIMAGE_VERIFY_SIG
2046 bool "Enable bzImage signature verification support"
2047 depends on KEXEC_SIG
2048 depends on SIGNED_PE_FILE_VERIFICATION
2049 select SYSTEM_TRUSTED_KEYRING
2051 Enable bzImage signature verification support.
2054 bool "kernel crash dumps"
2055 depends on X86_64 || (X86_32 && HIGHMEM)
2057 Generate crash dump after being started by kexec.
2058 This should be normally only set in special crash dump kernels
2059 which are loaded in the main kernel with kexec-tools into
2060 a specially reserved region and then later executed after
2061 a crash by kdump/kexec. The crash dump kernel must be compiled
2062 to a memory address not used by the main kernel or BIOS using
2063 PHYSICAL_START, or it must be built as a relocatable image
2064 (CONFIG_RELOCATABLE=y).
2065 For more details see Documentation/admin-guide/kdump/kdump.rst
2069 depends on KEXEC && HIBERNATION
2071 Jump between original kernel and kexeced kernel and invoke
2072 code in physical address mode via KEXEC
2074 config PHYSICAL_START
2075 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2078 This gives the physical address where the kernel is loaded.
2080 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2081 bzImage will decompress itself to above physical address and
2082 run from there. Otherwise, bzImage will run from the address where
2083 it has been loaded by the boot loader and will ignore above physical
2086 In normal kdump cases one does not have to set/change this option
2087 as now bzImage can be compiled as a completely relocatable image
2088 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2089 address. This option is mainly useful for the folks who don't want
2090 to use a bzImage for capturing the crash dump and want to use a
2091 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2092 to be specifically compiled to run from a specific memory area
2093 (normally a reserved region) and this option comes handy.
2095 So if you are using bzImage for capturing the crash dump,
2096 leave the value here unchanged to 0x1000000 and set
2097 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2098 for capturing the crash dump change this value to start of
2099 the reserved region. In other words, it can be set based on
2100 the "X" value as specified in the "crashkernel=YM@XM"
2101 command line boot parameter passed to the panic-ed
2102 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2103 for more details about crash dumps.
2105 Usage of bzImage for capturing the crash dump is recommended as
2106 one does not have to build two kernels. Same kernel can be used
2107 as production kernel and capture kernel. Above option should have
2108 gone away after relocatable bzImage support is introduced. But it
2109 is present because there are users out there who continue to use
2110 vmlinux for dump capture. This option should go away down the
2113 Don't change this unless you know what you are doing.
2116 bool "Build a relocatable kernel"
2119 This builds a kernel image that retains relocation information
2120 so it can be loaded someplace besides the default 1MB.
2121 The relocations tend to make the kernel binary about 10% larger,
2122 but are discarded at runtime.
2124 One use is for the kexec on panic case where the recovery kernel
2125 must live at a different physical address than the primary
2128 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2129 it has been loaded at and the compile time physical address
2130 (CONFIG_PHYSICAL_START) is used as the minimum location.
2132 config RANDOMIZE_BASE
2133 bool "Randomize the address of the kernel image (KASLR)"
2134 depends on RELOCATABLE
2137 In support of Kernel Address Space Layout Randomization (KASLR),
2138 this randomizes the physical address at which the kernel image
2139 is decompressed and the virtual address where the kernel
2140 image is mapped, as a security feature that deters exploit
2141 attempts relying on knowledge of the location of kernel
2144 On 64-bit, the kernel physical and virtual addresses are
2145 randomized separately. The physical address will be anywhere
2146 between 16MB and the top of physical memory (up to 64TB). The
2147 virtual address will be randomized from 16MB up to 1GB (9 bits
2148 of entropy). Note that this also reduces the memory space
2149 available to kernel modules from 1.5GB to 1GB.
2151 On 32-bit, the kernel physical and virtual addresses are
2152 randomized together. They will be randomized from 16MB up to
2153 512MB (8 bits of entropy).
2155 Entropy is generated using the RDRAND instruction if it is
2156 supported. If RDTSC is supported, its value is mixed into
2157 the entropy pool as well. If neither RDRAND nor RDTSC are
2158 supported, then entropy is read from the i8254 timer. The
2159 usable entropy is limited by the kernel being built using
2160 2GB addressing, and that PHYSICAL_ALIGN must be at a
2161 minimum of 2MB. As a result, only 10 bits of entropy are
2162 theoretically possible, but the implementations are further
2163 limited due to memory layouts.
2167 # Relocation on x86 needs some additional build support
2168 config X86_NEED_RELOCS
2170 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2172 config PHYSICAL_ALIGN
2173 hex "Alignment value to which kernel should be aligned"
2175 range 0x2000 0x1000000 if X86_32
2176 range 0x200000 0x1000000 if X86_64
2178 This value puts the alignment restrictions on physical address
2179 where kernel is loaded and run from. Kernel is compiled for an
2180 address which meets above alignment restriction.
2182 If bootloader loads the kernel at a non-aligned address and
2183 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2184 address aligned to above value and run from there.
2186 If bootloader loads the kernel at a non-aligned address and
2187 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2188 load address and decompress itself to the address it has been
2189 compiled for and run from there. The address for which kernel is
2190 compiled already meets above alignment restrictions. Hence the
2191 end result is that kernel runs from a physical address meeting
2192 above alignment restrictions.
2194 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2195 this value must be a multiple of 0x200000.
2197 Don't change this unless you know what you are doing.
2199 config DYNAMIC_MEMORY_LAYOUT
2202 This option makes base addresses of vmalloc and vmemmap as well as
2203 __PAGE_OFFSET movable during boot.
2205 config RANDOMIZE_MEMORY
2206 bool "Randomize the kernel memory sections"
2208 depends on RANDOMIZE_BASE
2209 select DYNAMIC_MEMORY_LAYOUT
2210 default RANDOMIZE_BASE
2212 Randomizes the base virtual address of kernel memory sections
2213 (physical memory mapping, vmalloc & vmemmap). This security feature
2214 makes exploits relying on predictable memory locations less reliable.
2216 The order of allocations remains unchanged. Entropy is generated in
2217 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2218 configuration have in average 30,000 different possible virtual
2219 addresses for each memory section.
2223 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2224 hex "Physical memory mapping padding" if EXPERT
2225 depends on RANDOMIZE_MEMORY
2226 default "0xa" if MEMORY_HOTPLUG
2228 range 0x1 0x40 if MEMORY_HOTPLUG
2231 Define the padding in terabytes added to the existing physical
2232 memory size during kernel memory randomization. It is useful
2233 for memory hotplug support but reduces the entropy available for
2234 address randomization.
2236 If unsure, leave at the default value.
2242 config BOOTPARAM_HOTPLUG_CPU0
2243 bool "Set default setting of cpu0_hotpluggable"
2244 depends on HOTPLUG_CPU
2246 Set whether default state of cpu0_hotpluggable is on or off.
2248 Say Y here to enable CPU0 hotplug by default. If this switch
2249 is turned on, there is no need to give cpu0_hotplug kernel
2250 parameter and the CPU0 hotplug feature is enabled by default.
2252 Please note: there are two known CPU0 dependencies if you want
2253 to enable the CPU0 hotplug feature either by this switch or by
2254 cpu0_hotplug kernel parameter.
2256 First, resume from hibernate or suspend always starts from CPU0.
2257 So hibernate and suspend are prevented if CPU0 is offline.
2259 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2260 offline if any interrupt can not migrate out of CPU0. There may
2261 be other CPU0 dependencies.
2263 Please make sure the dependencies are under your control before
2264 you enable this feature.
2266 Say N if you don't want to enable CPU0 hotplug feature by default.
2267 You still can enable the CPU0 hotplug feature at boot by kernel
2268 parameter cpu0_hotplug.
2270 config DEBUG_HOTPLUG_CPU0
2272 prompt "Debug CPU0 hotplug"
2273 depends on HOTPLUG_CPU
2275 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2276 soon as possible and boots up userspace with CPU0 offlined. User
2277 can online CPU0 back after boot time.
2279 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2280 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2281 compilation or giving cpu0_hotplug kernel parameter at boot.
2287 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2288 depends on COMPAT_32
2290 Certain buggy versions of glibc will crash if they are
2291 presented with a 32-bit vDSO that is not mapped at the address
2292 indicated in its segment table.
2294 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2295 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2296 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2297 the only released version with the bug, but OpenSUSE 9
2298 contains a buggy "glibc 2.3.2".
2300 The symptom of the bug is that everything crashes on startup, saying:
2301 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2303 Saying Y here changes the default value of the vdso32 boot
2304 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2305 This works around the glibc bug but hurts performance.
2307 If unsure, say N: if you are compiling your own kernel, you
2308 are unlikely to be using a buggy version of glibc.
2311 prompt "vsyscall table for legacy applications"
2313 default LEGACY_VSYSCALL_XONLY
2315 Legacy user code that does not know how to find the vDSO expects
2316 to be able to issue three syscalls by calling fixed addresses in
2317 kernel space. Since this location is not randomized with ASLR,
2318 it can be used to assist security vulnerability exploitation.
2320 This setting can be changed at boot time via the kernel command
2321 line parameter vsyscall=[emulate|xonly|none].
2323 On a system with recent enough glibc (2.14 or newer) and no
2324 static binaries, you can say None without a performance penalty
2325 to improve security.
2327 If unsure, select "Emulate execution only".
2329 config LEGACY_VSYSCALL_EMULATE
2330 bool "Full emulation"
2332 The kernel traps and emulates calls into the fixed vsyscall
2333 address mapping. This makes the mapping non-executable, but
2334 it still contains readable known contents, which could be
2335 used in certain rare security vulnerability exploits. This
2336 configuration is recommended when using legacy userspace
2337 that still uses vsyscalls along with legacy binary
2338 instrumentation tools that require code to be readable.
2340 An example of this type of legacy userspace is running
2341 Pin on an old binary that still uses vsyscalls.
2343 config LEGACY_VSYSCALL_XONLY
2344 bool "Emulate execution only"
2346 The kernel traps and emulates calls into the fixed vsyscall
2347 address mapping and does not allow reads. This
2348 configuration is recommended when userspace might use the
2349 legacy vsyscall area but support for legacy binary
2350 instrumentation of legacy code is not needed. It mitigates
2351 certain uses of the vsyscall area as an ASLR-bypassing
2354 config LEGACY_VSYSCALL_NONE
2357 There will be no vsyscall mapping at all. This will
2358 eliminate any risk of ASLR bypass due to the vsyscall
2359 fixed address mapping. Attempts to use the vsyscalls
2360 will be reported to dmesg, so that either old or
2361 malicious userspace programs can be identified.
2366 bool "Built-in kernel command line"
2368 Allow for specifying boot arguments to the kernel at
2369 build time. On some systems (e.g. embedded ones), it is
2370 necessary or convenient to provide some or all of the
2371 kernel boot arguments with the kernel itself (that is,
2372 to not rely on the boot loader to provide them.)
2374 To compile command line arguments into the kernel,
2375 set this option to 'Y', then fill in the
2376 boot arguments in CONFIG_CMDLINE.
2378 Systems with fully functional boot loaders (i.e. non-embedded)
2379 should leave this option set to 'N'.
2382 string "Built-in kernel command string"
2383 depends on CMDLINE_BOOL
2386 Enter arguments here that should be compiled into the kernel
2387 image and used at boot time. If the boot loader provides a
2388 command line at boot time, it is appended to this string to
2389 form the full kernel command line, when the system boots.
2391 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2392 change this behavior.
2394 In most cases, the command line (whether built-in or provided
2395 by the boot loader) should specify the device for the root
2398 config CMDLINE_OVERRIDE
2399 bool "Built-in command line overrides boot loader arguments"
2400 depends on CMDLINE_BOOL && CMDLINE != ""
2402 Set this option to 'Y' to have the kernel ignore the boot loader
2403 command line, and use ONLY the built-in command line.
2405 This is used to work around broken boot loaders. This should
2406 be set to 'N' under normal conditions.
2408 config MODIFY_LDT_SYSCALL
2409 bool "Enable the LDT (local descriptor table)" if EXPERT
2412 Linux can allow user programs to install a per-process x86
2413 Local Descriptor Table (LDT) using the modify_ldt(2) system
2414 call. This is required to run 16-bit or segmented code such as
2415 DOSEMU or some Wine programs. It is also used by some very old
2416 threading libraries.
2418 Enabling this feature adds a small amount of overhead to
2419 context switches and increases the low-level kernel attack
2420 surface. Disabling it removes the modify_ldt(2) system call.
2422 Saying 'N' here may make sense for embedded or server kernels.
2424 source "kernel/livepatch/Kconfig"
2428 config ARCH_HAS_ADD_PAGES
2430 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2432 config USE_PERCPU_NUMA_NODE_ID
2436 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2438 depends on X86_64 || X86_PAE
2440 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2442 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2444 config ARCH_ENABLE_THP_MIGRATION
2446 depends on X86_64 && TRANSPARENT_HUGEPAGE
2448 menu "Power management and ACPI options"
2450 config ARCH_HIBERNATION_HEADER
2452 depends on HIBERNATION
2454 source "kernel/power/Kconfig"
2456 source "drivers/acpi/Kconfig"
2463 tristate "APM (Advanced Power Management) BIOS support"
2464 depends on X86_32 && PM_SLEEP
2466 APM is a BIOS specification for saving power using several different
2467 techniques. This is mostly useful for battery powered laptops with
2468 APM compliant BIOSes. If you say Y here, the system time will be
2469 reset after a RESUME operation, the /proc/apm device will provide
2470 battery status information, and user-space programs will receive
2471 notification of APM "events" (e.g. battery status change).
2473 If you select "Y" here, you can disable actual use of the APM
2474 BIOS by passing the "apm=off" option to the kernel at boot time.
2476 Note that the APM support is almost completely disabled for
2477 machines with more than one CPU.
2479 In order to use APM, you will need supporting software. For location
2480 and more information, read <file:Documentation/power/apm-acpi.rst>
2481 and the Battery Powered Linux mini-HOWTO, available from
2482 <http://www.tldp.org/docs.html#howto>.
2484 This driver does not spin down disk drives (see the hdparm(8)
2485 manpage ("man 8 hdparm") for that), and it doesn't turn off
2486 VESA-compliant "green" monitors.
2488 This driver does not support the TI 4000M TravelMate and the ACER
2489 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2490 desktop machines also don't have compliant BIOSes, and this driver
2491 may cause those machines to panic during the boot phase.
2493 Generally, if you don't have a battery in your machine, there isn't
2494 much point in using this driver and you should say N. If you get
2495 random kernel OOPSes or reboots that don't seem to be related to
2496 anything, try disabling/enabling this option (or disabling/enabling
2499 Some other things you should try when experiencing seemingly random,
2502 1) make sure that you have enough swap space and that it is
2504 2) pass the "no-hlt" option to the kernel
2505 3) switch on floating point emulation in the kernel and pass
2506 the "no387" option to the kernel
2507 4) pass the "floppy=nodma" option to the kernel
2508 5) pass the "mem=4M" option to the kernel (thereby disabling
2509 all but the first 4 MB of RAM)
2510 6) make sure that the CPU is not over clocked.
2511 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2512 8) disable the cache from your BIOS settings
2513 9) install a fan for the video card or exchange video RAM
2514 10) install a better fan for the CPU
2515 11) exchange RAM chips
2516 12) exchange the motherboard.
2518 To compile this driver as a module, choose M here: the
2519 module will be called apm.
2523 config APM_IGNORE_USER_SUSPEND
2524 bool "Ignore USER SUSPEND"
2526 This option will ignore USER SUSPEND requests. On machines with a
2527 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2528 series notebooks, it is necessary to say Y because of a BIOS bug.
2530 config APM_DO_ENABLE
2531 bool "Enable PM at boot time"
2533 Enable APM features at boot time. From page 36 of the APM BIOS
2534 specification: "When disabled, the APM BIOS does not automatically
2535 power manage devices, enter the Standby State, enter the Suspend
2536 State, or take power saving steps in response to CPU Idle calls."
2537 This driver will make CPU Idle calls when Linux is idle (unless this
2538 feature is turned off -- see "Do CPU IDLE calls", below). This
2539 should always save battery power, but more complicated APM features
2540 will be dependent on your BIOS implementation. You may need to turn
2541 this option off if your computer hangs at boot time when using APM
2542 support, or if it beeps continuously instead of suspending. Turn
2543 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2544 T400CDT. This is off by default since most machines do fine without
2549 bool "Make CPU Idle calls when idle"
2551 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2552 On some machines, this can activate improved power savings, such as
2553 a slowed CPU clock rate, when the machine is idle. These idle calls
2554 are made after the idle loop has run for some length of time (e.g.,
2555 333 mS). On some machines, this will cause a hang at boot time or
2556 whenever the CPU becomes idle. (On machines with more than one CPU,
2557 this option does nothing.)
2559 config APM_DISPLAY_BLANK
2560 bool "Enable console blanking using APM"
2562 Enable console blanking using the APM. Some laptops can use this to
2563 turn off the LCD backlight when the screen blanker of the Linux
2564 virtual console blanks the screen. Note that this is only used by
2565 the virtual console screen blanker, and won't turn off the backlight
2566 when using the X Window system. This also doesn't have anything to
2567 do with your VESA-compliant power-saving monitor. Further, this
2568 option doesn't work for all laptops -- it might not turn off your
2569 backlight at all, or it might print a lot of errors to the console,
2570 especially if you are using gpm.
2572 config APM_ALLOW_INTS
2573 bool "Allow interrupts during APM BIOS calls"
2575 Normally we disable external interrupts while we are making calls to
2576 the APM BIOS as a measure to lessen the effects of a badly behaving
2577 BIOS implementation. The BIOS should reenable interrupts if it
2578 needs to. Unfortunately, some BIOSes do not -- especially those in
2579 many of the newer IBM Thinkpads. If you experience hangs when you
2580 suspend, try setting this to Y. Otherwise, say N.
2584 source "drivers/cpufreq/Kconfig"
2586 source "drivers/cpuidle/Kconfig"
2588 source "drivers/idle/Kconfig"
2593 menu "Bus options (PCI etc.)"
2596 prompt "PCI access mode"
2597 depends on X86_32 && PCI
2600 On PCI systems, the BIOS can be used to detect the PCI devices and
2601 determine their configuration. However, some old PCI motherboards
2602 have BIOS bugs and may crash if this is done. Also, some embedded
2603 PCI-based systems don't have any BIOS at all. Linux can also try to
2604 detect the PCI hardware directly without using the BIOS.
2606 With this option, you can specify how Linux should detect the
2607 PCI devices. If you choose "BIOS", the BIOS will be used,
2608 if you choose "Direct", the BIOS won't be used, and if you
2609 choose "MMConfig", then PCI Express MMCONFIG will be used.
2610 If you choose "Any", the kernel will try MMCONFIG, then the
2611 direct access method and falls back to the BIOS if that doesn't
2612 work. If unsure, go with the default, which is "Any".
2617 config PCI_GOMMCONFIG
2634 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2636 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2639 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2642 bool "Support mmconfig PCI config space access" if X86_64
2644 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2645 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2649 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2653 depends on PCI && XEN
2656 config MMCONF_FAM10H
2658 depends on X86_64 && PCI_MMCONFIG && ACPI
2660 config PCI_CNB20LE_QUIRK
2661 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2664 Read the PCI windows out of the CNB20LE host bridge. This allows
2665 PCI hotplug to work on systems with the CNB20LE chipset which do
2668 There's no public spec for this chipset, and this functionality
2669 is known to be incomplete.
2671 You should say N unless you know you need this.
2674 bool "ISA bus support on modern systems" if EXPERT
2676 Expose ISA bus device drivers and options available for selection and
2677 configuration. Enable this option if your target machine has an ISA
2678 bus. ISA is an older system, displaced by PCI and newer bus
2679 architectures -- if your target machine is modern, it probably does
2680 not have an ISA bus.
2684 # x86_64 have no ISA slots, but can have ISA-style DMA.
2686 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2689 Enables ISA-style DMA support for devices requiring such controllers.
2697 Find out whether you have ISA slots on your motherboard. ISA is the
2698 name of a bus system, i.e. the way the CPU talks to the other stuff
2699 inside your box. Other bus systems are PCI, EISA, MicroChannel
2700 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2701 newer boards don't support it. If you have ISA, say Y, otherwise N.
2704 tristate "NatSemi SCx200 support"
2706 This provides basic support for National Semiconductor's
2707 (now AMD's) Geode processors. The driver probes for the
2708 PCI-IDs of several on-chip devices, so its a good dependency
2709 for other scx200_* drivers.
2711 If compiled as a module, the driver is named scx200.
2713 config SCx200HR_TIMER
2714 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2718 This driver provides a clocksource built upon the on-chip
2719 27MHz high-resolution timer. Its also a workaround for
2720 NSC Geode SC-1100's buggy TSC, which loses time when the
2721 processor goes idle (as is done by the scheduler). The
2722 other workaround is idle=poll boot option.
2725 bool "One Laptop Per Child support"
2733 Add support for detecting the unique features of the OLPC
2737 bool "OLPC XO-1 Power Management"
2738 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2740 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2743 bool "OLPC XO-1 Real Time Clock"
2744 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2746 Add support for the XO-1 real time clock, which can be used as a
2747 programmable wakeup source.
2750 bool "OLPC XO-1 SCI extras"
2751 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2755 Add support for SCI-based features of the OLPC XO-1 laptop:
2756 - EC-driven system wakeups
2760 - AC adapter status updates
2761 - Battery status updates
2763 config OLPC_XO15_SCI
2764 bool "OLPC XO-1.5 SCI extras"
2765 depends on OLPC && ACPI
2768 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2769 - EC-driven system wakeups
2770 - AC adapter status updates
2771 - Battery status updates
2774 bool "PCEngines ALIX System Support (LED setup)"
2777 This option enables system support for the PCEngines ALIX.
2778 At present this just sets up LEDs for GPIO control on
2779 ALIX2/3/6 boards. However, other system specific setup should
2782 Note: You must still enable the drivers for GPIO and LED support
2783 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2785 Note: You have to set alix.force=1 for boards with Award BIOS.
2788 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2791 This option enables system support for the Soekris Engineering net5501.
2794 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2798 This option enables system support for the Traverse Technologies GEOS.
2801 bool "Technologic Systems TS-5500 platform support"
2803 select CHECK_SIGNATURE
2807 This option enables system support for the Technologic Systems TS-5500.
2813 depends on CPU_SUP_AMD && PCI
2816 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2818 Firmwares often provide initial graphics framebuffers so the BIOS,
2819 bootloader or kernel can show basic video-output during boot for
2820 user-guidance and debugging. Historically, x86 used the VESA BIOS
2821 Extensions and EFI-framebuffers for this, which are mostly limited
2823 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2824 framebuffers so the new generic system-framebuffer drivers can be
2825 used on x86. If the framebuffer is not compatible with the generic
2826 modes, it is advertised as fallback platform framebuffer so legacy
2827 drivers like efifb, vesafb and uvesafb can pick it up.
2828 If this option is not selected, all system framebuffers are always
2829 marked as fallback platform framebuffers as usual.
2831 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2832 not be able to pick up generic system framebuffers if this option
2833 is selected. You are highly encouraged to enable simplefb as
2834 replacement if you select this option. simplefb can correctly deal
2835 with generic system framebuffers. But you should still keep vesafb
2836 and others enabled as fallback if a system framebuffer is
2837 incompatible with simplefb.
2844 menu "Binary Emulations"
2846 config IA32_EMULATION
2847 bool "IA32 Emulation"
2849 select ARCH_WANT_OLD_COMPAT_IPC
2851 select COMPAT_OLD_SIGACTION
2853 Include code to run legacy 32-bit programs under a
2854 64-bit kernel. You should likely turn this on, unless you're
2855 100% sure that you don't have any 32-bit programs left.
2858 tristate "IA32 a.out support"
2859 depends on IA32_EMULATION
2862 Support old a.out binaries in the 32bit emulation.
2865 bool "x32 ABI for 64-bit mode"
2868 Include code to run binaries for the x32 native 32-bit ABI
2869 for 64-bit processors. An x32 process gets access to the
2870 full 64-bit register file and wide data path while leaving
2871 pointers at 32 bits for smaller memory footprint.
2873 You will need a recent binutils (2.22 or later) with
2874 elf32_x86_64 support enabled to compile a kernel with this
2879 depends on IA32_EMULATION || X86_32
2881 select OLD_SIGSUSPEND3
2885 depends on IA32_EMULATION || X86_X32
2888 config COMPAT_FOR_U64_ALIGNMENT
2891 config SYSVIPC_COMPAT
2899 config HAVE_ATOMIC_IOMAP
2903 source "drivers/firmware/Kconfig"
2905 source "arch/x86/kvm/Kconfig"
2907 source "arch/x86/Kconfig.assembler"