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
26 # Options that are inherently 64-bit kernel only:
27 select ARCH_HAS_GIGANTIC_PAGE
28 select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
29 select ARCH_USE_CMPXCHG_LOCKREF
30 select HAVE_ARCH_SOFT_DIRTY
31 select MODULES_USE_ELF_RELA
32 select NEED_DMA_MAP_STATE
35 config FORCE_DYNAMIC_FTRACE
38 depends on FUNCTION_TRACER
41 We keep the static function tracing (!DYNAMIC_FTRACE) around
42 in order to test the non static function tracing in the
43 generic code, as other architectures still use it. But we
44 only need to keep it around for x86_64. No need to keep it
45 for x86_32. For x86_32, force DYNAMIC_FTRACE.
49 # ( Note that options that are marked 'if X86_64' could in principle be
50 # ported to 32-bit as well. )
55 # Note: keep this list sorted alphabetically
57 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
58 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
59 select ARCH_32BIT_OFF_T if X86_32
60 select ARCH_CLOCKSOURCE_INIT
61 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
62 select ARCH_HAS_DEBUG_VIRTUAL
63 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
64 select ARCH_HAS_DEVMEM_IS_ALLOWED
65 select ARCH_HAS_EARLY_DEBUG if KGDB
66 select ARCH_HAS_ELF_RANDOMIZE
67 select ARCH_HAS_FAST_MULTIPLIER
68 select ARCH_HAS_FILTER_PGPROT
69 select ARCH_HAS_FORTIFY_SOURCE
70 select ARCH_HAS_GCOV_PROFILE_ALL
71 select ARCH_HAS_KCOV if X86_64 && STACK_VALIDATION
72 select ARCH_HAS_MEM_ENCRYPT
73 select ARCH_HAS_MEMBARRIER_SYNC_CORE
74 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
75 select ARCH_HAS_PMEM_API if X86_64
76 select ARCH_HAS_PTE_DEVMAP if X86_64
77 select ARCH_HAS_PTE_SPECIAL
78 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
79 select ARCH_HAS_COPY_MC if X86_64
80 select ARCH_HAS_SET_MEMORY
81 select ARCH_HAS_SET_DIRECT_MAP
82 select ARCH_HAS_STRICT_KERNEL_RWX
83 select ARCH_HAS_STRICT_MODULE_RWX
84 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
85 select ARCH_HAS_SYSCALL_WRAPPER
86 select ARCH_HAS_UBSAN_SANITIZE_ALL
87 select ARCH_HAS_DEBUG_WX
88 select ARCH_HAVE_NMI_SAFE_CMPXCHG
89 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
90 select ARCH_MIGHT_HAVE_PC_PARPORT
91 select ARCH_MIGHT_HAVE_PC_SERIO
93 select ARCH_SUPPORTS_ACPI
94 select ARCH_SUPPORTS_ATOMIC_RMW
95 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
96 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
97 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
98 select ARCH_USE_BUILTIN_BSWAP
99 select ARCH_USE_QUEUED_RWLOCKS
100 select ARCH_USE_QUEUED_SPINLOCKS
101 select ARCH_USE_SYM_ANNOTATIONS
102 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
103 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
104 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
105 select ARCH_WANT_HUGE_PMD_SHARE
106 select ARCH_WANT_LD_ORPHAN_WARN
107 select ARCH_WANTS_THP_SWAP if X86_64
108 select BUILDTIME_TABLE_SORT
110 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
111 select CLOCKSOURCE_WATCHDOG
112 select DCACHE_WORD_ACCESS
113 select EDAC_ATOMIC_SCRUB
115 select GENERIC_CLOCKEVENTS
116 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
117 select GENERIC_CLOCKEVENTS_MIN_ADJUST
118 select GENERIC_CMOS_UPDATE
119 select GENERIC_CPU_AUTOPROBE
120 select GENERIC_CPU_VULNERABILITIES
121 select GENERIC_EARLY_IOREMAP
123 select GENERIC_FIND_FIRST_BIT
125 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
126 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
127 select GENERIC_IRQ_MIGRATION if SMP
128 select GENERIC_IRQ_PROBE
129 select GENERIC_IRQ_RESERVATION_MODE
130 select GENERIC_IRQ_SHOW
131 select GENERIC_PENDING_IRQ if SMP
132 select GENERIC_PTDUMP
133 select GENERIC_SMP_IDLE_THREAD
134 select GENERIC_STRNCPY_FROM_USER
135 select GENERIC_STRNLEN_USER
136 select GENERIC_TIME_VSYSCALL
137 select GENERIC_GETTIMEOFDAY
138 select GENERIC_VDSO_TIME_NS
139 select GUP_GET_PTE_LOW_HIGH if X86_PAE
140 select HARDIRQS_SW_RESEND
141 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
142 select HAVE_ACPI_APEI if ACPI
143 select HAVE_ACPI_APEI_NMI if ACPI
144 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
145 select HAVE_ARCH_AUDITSYSCALL
146 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
147 select HAVE_ARCH_JUMP_LABEL
148 select HAVE_ARCH_JUMP_LABEL_RELATIVE
149 select HAVE_ARCH_KASAN if X86_64
150 select HAVE_ARCH_KASAN_VMALLOC if X86_64
151 select HAVE_ARCH_KGDB
152 select HAVE_ARCH_MMAP_RND_BITS if MMU
153 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
154 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
155 select HAVE_ARCH_PREL32_RELOCATIONS
156 select HAVE_ARCH_SECCOMP_FILTER
157 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
158 select HAVE_ARCH_STACKLEAK
159 select HAVE_ARCH_TRACEHOOK
160 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
161 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
162 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
163 select HAVE_ARCH_VMAP_STACK if X86_64
164 select HAVE_ARCH_WITHIN_STACK_FRAMES
165 select HAVE_ASM_MODVERSIONS
166 select HAVE_CMPXCHG_DOUBLE
167 select HAVE_CMPXCHG_LOCAL
168 select HAVE_CONTEXT_TRACKING if X86_64
169 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
170 select HAVE_C_RECORDMCOUNT
171 select HAVE_DEBUG_KMEMLEAK
172 select HAVE_DMA_CONTIGUOUS
173 select HAVE_DYNAMIC_FTRACE
174 select HAVE_DYNAMIC_FTRACE_WITH_REGS
175 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
177 select HAVE_EFFICIENT_UNALIGNED_ACCESS
179 select HAVE_EXIT_THREAD
181 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
182 select HAVE_FTRACE_MCOUNT_RECORD
183 select HAVE_FUNCTION_GRAPH_TRACER
184 select HAVE_FUNCTION_TRACER
185 select HAVE_GCC_PLUGINS
186 select HAVE_HW_BREAKPOINT
188 select HAVE_IOREMAP_PROT
189 select HAVE_IRQ_TIME_ACCOUNTING
190 select HAVE_KERNEL_BZIP2
191 select HAVE_KERNEL_GZIP
192 select HAVE_KERNEL_LZ4
193 select HAVE_KERNEL_LZMA
194 select HAVE_KERNEL_LZO
195 select HAVE_KERNEL_XZ
196 select HAVE_KERNEL_ZSTD
198 select HAVE_KPROBES_ON_FTRACE
199 select HAVE_FUNCTION_ERROR_INJECTION
200 select HAVE_KRETPROBES
202 select HAVE_LIVEPATCH if X86_64
203 select HAVE_MIXED_BREAKPOINTS_REGS
204 select HAVE_MOD_ARCH_SPECIFIC
209 select HAVE_OPTPROBES
210 select HAVE_PCSPKR_PLATFORM
211 select HAVE_PERF_EVENTS
212 select HAVE_PERF_EVENTS_NMI
213 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
215 select HAVE_PERF_REGS
216 select HAVE_PERF_USER_STACK_DUMP
217 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
218 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
219 select HAVE_REGS_AND_STACK_ACCESS_API
220 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
221 select HAVE_FUNCTION_ARG_ACCESS_API
222 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
223 select HAVE_STACK_VALIDATION if X86_64
224 select HAVE_STATIC_CALL
225 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
227 select HAVE_SYSCALL_TRACEPOINTS
228 select HAVE_UNSTABLE_SCHED_CLOCK
229 select HAVE_USER_RETURN_NOTIFIER
230 select HAVE_GENERIC_VDSO
231 select HOTPLUG_SMT if SMP
232 select IRQ_FORCED_THREADING
233 select NEED_SG_DMA_LENGTH
234 select PCI_DOMAINS if PCI
235 select PCI_LOCKLESS_CONFIG if PCI
238 select RTC_MC146818_LIB
241 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
242 select SYSCTL_EXCEPTION_TRACE
243 select THREAD_INFO_IN_TASK
244 select USER_STACKTRACE_SUPPORT
246 select HAVE_ARCH_KCSAN if X86_64
247 select X86_FEATURE_NAMES if PROC_FS
248 select PROC_PID_ARCH_STATUS if PROC_FS
249 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
251 config INSTRUCTION_DECODER
253 depends on KPROBES || PERF_EVENTS || UPROBES
257 default "elf32-i386" if X86_32
258 default "elf64-x86-64" if X86_64
260 config LOCKDEP_SUPPORT
263 config STACKTRACE_SUPPORT
269 config ARCH_MMAP_RND_BITS_MIN
273 config ARCH_MMAP_RND_BITS_MAX
277 config ARCH_MMAP_RND_COMPAT_BITS_MIN
280 config ARCH_MMAP_RND_COMPAT_BITS_MAX
286 config GENERIC_ISA_DMA
288 depends on ISA_DMA_API
293 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
295 config GENERIC_BUG_RELATIVE_POINTERS
298 config ARCH_MAY_HAVE_PC_FDC
300 depends on ISA_DMA_API
302 config GENERIC_CALIBRATE_DELAY
305 config ARCH_HAS_CPU_RELAX
308 config ARCH_HAS_CACHE_LINE_SIZE
311 config ARCH_HAS_FILTER_PGPROT
314 config HAVE_SETUP_PER_CPU_AREA
317 config NEED_PER_CPU_EMBED_FIRST_CHUNK
320 config NEED_PER_CPU_PAGE_FIRST_CHUNK
323 config ARCH_HIBERNATION_POSSIBLE
326 config ARCH_SUSPEND_POSSIBLE
329 config ARCH_WANT_GENERAL_HUGETLB
338 config KASAN_SHADOW_OFFSET
341 default 0xdffffc0000000000
343 config HAVE_INTEL_TXT
345 depends on INTEL_IOMMU && ACPI
349 depends on X86_32 && SMP
353 depends on X86_64 && SMP
355 config X86_32_LAZY_GS
357 depends on X86_32 && !STACKPROTECTOR
359 config ARCH_SUPPORTS_UPROBES
362 config FIX_EARLYCON_MEM
365 config DYNAMIC_PHYSICAL_MASK
368 config PGTABLE_LEVELS
370 default 5 if X86_5LEVEL
375 config CC_HAS_SANE_STACKPROTECTOR
377 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
378 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
380 We have to make sure stack protector is unconditionally disabled if
381 the compiler produces broken code.
383 menu "Processor type and features"
386 bool "DMA memory allocation support" if EXPERT
389 DMA memory allocation support allows devices with less than 32-bit
390 addressing to allocate within the first 16MB of address space.
391 Disable if no such devices will be used.
396 bool "Symmetric multi-processing support"
398 This enables support for systems with more than one CPU. If you have
399 a system with only one CPU, say N. If you have a system with more
402 If you say N here, the kernel will run on uni- and multiprocessor
403 machines, but will use only one CPU of a multiprocessor machine. If
404 you say Y here, the kernel will run on many, but not all,
405 uniprocessor machines. On a uniprocessor machine, the kernel
406 will run faster if you say N here.
408 Note that if you say Y here and choose architecture "586" or
409 "Pentium" under "Processor family", the kernel will not work on 486
410 architectures. Similarly, multiprocessor kernels for the "PPro"
411 architecture may not work on all Pentium based boards.
413 People using multiprocessor machines who say Y here should also say
414 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
415 Management" code will be disabled if you say Y here.
417 See also <file:Documentation/x86/i386/IO-APIC.rst>,
418 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
419 <http://www.tldp.org/docs.html#howto>.
421 If you don't know what to do here, say N.
423 config X86_FEATURE_NAMES
424 bool "Processor feature human-readable names" if EMBEDDED
427 This option compiles in a table of x86 feature bits and corresponding
428 names. This is required to support /proc/cpuinfo and a few kernel
429 messages. You can disable this to save space, at the expense of
430 making those few kernel messages show numeric feature bits instead.
435 bool "Support x2apic"
436 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
438 This enables x2apic support on CPUs that have this feature.
440 This allows 32-bit apic IDs (so it can support very large systems),
441 and accesses the local apic via MSRs not via mmio.
443 If you don't know what to do here, say N.
446 bool "Enable MPS table" if ACPI || SFI
448 depends on X86_LOCAL_APIC
450 For old smp systems that do not have proper acpi support. Newer systems
451 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
455 depends on X86_GOLDFISH
458 bool "Avoid speculative indirect branches in kernel"
461 Compile kernel with the retpoline compiler options to guard against
462 kernel-to-user data leaks by avoiding speculative indirect
463 branches. Requires a compiler with -mindirect-branch=thunk-extern
464 support for full protection. The kernel may run slower.
466 config X86_CPU_RESCTRL
467 bool "x86 CPU resource control support"
468 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
470 select PROC_CPU_RESCTRL if PROC_FS
472 Enable x86 CPU resource control support.
474 Provide support for the allocation and monitoring of system resources
477 Intel calls this Intel Resource Director Technology
478 (Intel(R) RDT). More information about RDT can be found in the
479 Intel x86 Architecture Software Developer Manual.
481 AMD calls this AMD Platform Quality of Service (AMD QoS).
482 More information about AMD QoS can be found in the AMD64 Technology
483 Platform Quality of Service Extensions manual.
489 bool "Support for big SMP systems with more than 8 CPUs"
492 This option is needed for the systems that have more than 8 CPUs.
494 config X86_EXTENDED_PLATFORM
495 bool "Support for extended (non-PC) x86 platforms"
498 If you disable this option then the kernel will only support
499 standard PC platforms. (which covers the vast majority of
502 If you enable this option then you'll be able to select support
503 for the following (non-PC) 32 bit x86 platforms:
504 Goldfish (Android emulator)
507 SGI 320/540 (Visual Workstation)
508 STA2X11-based (e.g. Northville)
509 Moorestown MID devices
511 If you have one of these systems, or if you want to build a
512 generic distribution kernel, say Y here - otherwise say N.
516 config X86_EXTENDED_PLATFORM
517 bool "Support for extended (non-PC) x86 platforms"
520 If you disable this option then the kernel will only support
521 standard PC platforms. (which covers the vast majority of
524 If you enable this option then you'll be able to select support
525 for the following (non-PC) 64 bit x86 platforms:
530 If you have one of these systems, or if you want to build a
531 generic distribution kernel, say Y here - otherwise say N.
533 # This is an alphabetically sorted list of 64 bit extended platforms
534 # Please maintain the alphabetic order if and when there are additions
536 bool "Numascale NumaChip"
538 depends on X86_EXTENDED_PLATFORM
541 depends on X86_X2APIC
542 depends on PCI_MMCONFIG
544 Adds support for Numascale NumaChip large-SMP systems. Needed to
545 enable more than ~168 cores.
546 If you don't have one of these, you should say N here.
550 select HYPERVISOR_GUEST
552 depends on X86_64 && PCI
553 depends on X86_EXTENDED_PLATFORM
556 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
557 supposed to run on these EM64T-based machines. Only choose this option
558 if you have one of these machines.
561 bool "SGI Ultraviolet"
563 depends on X86_EXTENDED_PLATFORM
566 depends on X86_X2APIC
569 This option is needed in order to support SGI Ultraviolet systems.
570 If you don't have one of these, you should say N here.
572 # Following is an alphabetically sorted list of 32 bit extended platforms
573 # Please maintain the alphabetic order if and when there are additions
576 bool "Goldfish (Virtual Platform)"
577 depends on X86_EXTENDED_PLATFORM
579 Enable support for the Goldfish virtual platform used primarily
580 for Android development. Unless you are building for the Android
581 Goldfish emulator say N here.
584 bool "CE4100 TV platform"
586 depends on PCI_GODIRECT
587 depends on X86_IO_APIC
589 depends on X86_EXTENDED_PLATFORM
590 select X86_REBOOTFIXUPS
592 select OF_EARLY_FLATTREE
594 Select for the Intel CE media processor (CE4100) SOC.
595 This option compiles in support for the CE4100 SOC for settop
596 boxes and media devices.
599 bool "Intel MID platform support"
600 depends on X86_EXTENDED_PLATFORM
601 depends on X86_PLATFORM_DEVICES
603 depends on X86_64 || (PCI_GOANY && X86_32)
604 depends on X86_IO_APIC
610 select MFD_INTEL_MSIC
612 Select to build a kernel capable of supporting Intel MID (Mobile
613 Internet Device) platform systems which do not have the PCI legacy
614 interfaces. If you are building for a PC class system say N here.
616 Intel MID platforms are based on an Intel processor and chipset which
617 consume less power than most of the x86 derivatives.
619 config X86_INTEL_QUARK
620 bool "Intel Quark platform support"
622 depends on X86_EXTENDED_PLATFORM
623 depends on X86_PLATFORM_DEVICES
627 depends on X86_IO_APIC
632 Select to include support for Quark X1000 SoC.
633 Say Y here if you have a Quark based system such as the Arduino
634 compatible Intel Galileo.
636 config X86_INTEL_LPSS
637 bool "Intel Low Power Subsystem Support"
638 depends on X86 && ACPI && PCI
643 Select to build support for Intel Low Power Subsystem such as
644 found on Intel Lynxpoint PCH. Selecting this option enables
645 things like clock tree (common clock framework) and pincontrol
646 which are needed by the LPSS peripheral drivers.
648 config X86_AMD_PLATFORM_DEVICE
649 bool "AMD ACPI2Platform devices support"
654 Select to interpret AMD specific ACPI device to platform device
655 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
656 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
657 implemented under PINCTRL subsystem.
660 tristate "Intel SoC IOSF Sideband support for SoC platforms"
663 This option enables sideband register access support for Intel SoC
664 platforms. On these platforms the IOSF sideband is used in lieu of
665 MSR's for some register accesses, mostly but not limited to thermal
666 and power. Drivers may query the availability of this device to
667 determine if they need the sideband in order to work on these
668 platforms. The sideband is available on the following SoC products.
669 This list is not meant to be exclusive.
674 You should say Y if you are running a kernel on one of these SoC's.
676 config IOSF_MBI_DEBUG
677 bool "Enable IOSF sideband access through debugfs"
678 depends on IOSF_MBI && DEBUG_FS
680 Select this option to expose the IOSF sideband access registers (MCR,
681 MDR, MCRX) through debugfs to write and read register information from
682 different units on the SoC. This is most useful for obtaining device
683 state information for debug and analysis. As this is a general access
684 mechanism, users of this option would have specific knowledge of the
685 device they want to access.
687 If you don't require the option or are in doubt, say N.
690 bool "RDC R-321x SoC"
692 depends on X86_EXTENDED_PLATFORM
694 select X86_REBOOTFIXUPS
696 This option is needed for RDC R-321x system-on-chip, also known
698 If you don't have one of these chips, you should say N here.
700 config X86_32_NON_STANDARD
701 bool "Support non-standard 32-bit SMP architectures"
702 depends on X86_32 && SMP
703 depends on X86_EXTENDED_PLATFORM
705 This option compiles in the bigsmp and STA2X11 default
706 subarchitectures. It is intended for a generic binary
707 kernel. If you select them all, kernel will probe it one by
708 one and will fallback to default.
710 # Alphabetically sorted list of Non standard 32 bit platforms
712 config X86_SUPPORTS_MEMORY_FAILURE
714 # MCE code calls memory_failure():
716 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
717 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
718 depends on X86_64 || !SPARSEMEM
719 select ARCH_SUPPORTS_MEMORY_FAILURE
722 bool "STA2X11 Companion Chip Support"
723 depends on X86_32_NON_STANDARD && PCI
728 This adds support for boards based on the STA2X11 IO-Hub,
729 a.k.a. "ConneXt". The chip is used in place of the standard
730 PC chipset, so all "standard" peripherals are missing. If this
731 option is selected the kernel will still be able to boot on
732 standard PC machines.
735 tristate "Eurobraille/Iris poweroff module"
738 The Iris machines from EuroBraille do not have APM or ACPI support
739 to shut themselves down properly. A special I/O sequence is
740 needed to do so, which is what this module does at
743 This is only for Iris machines from EuroBraille.
747 config SCHED_OMIT_FRAME_POINTER
749 prompt "Single-depth WCHAN output"
752 Calculate simpler /proc/<PID>/wchan values. If this option
753 is disabled then wchan values will recurse back to the
754 caller function. This provides more accurate wchan values,
755 at the expense of slightly more scheduling overhead.
757 If in doubt, say "Y".
759 menuconfig HYPERVISOR_GUEST
760 bool "Linux guest support"
762 Say Y here to enable options for running Linux under various hyper-
763 visors. This option enables basic hypervisor detection and platform
766 If you say N, all options in this submenu will be skipped and
767 disabled, and Linux guest support won't be built in.
772 bool "Enable paravirtualization code"
774 This changes the kernel so it can modify itself when it is run
775 under a hypervisor, potentially improving performance significantly
776 over full virtualization. However, when run without a hypervisor
777 the kernel is theoretically slower and slightly larger.
782 config PARAVIRT_DEBUG
783 bool "paravirt-ops debugging"
784 depends on PARAVIRT && DEBUG_KERNEL
786 Enable to debug paravirt_ops internals. Specifically, BUG if
787 a paravirt_op is missing when it is called.
789 config PARAVIRT_SPINLOCKS
790 bool "Paravirtualization layer for spinlocks"
791 depends on PARAVIRT && SMP
793 Paravirtualized spinlocks allow a pvops backend to replace the
794 spinlock implementation with something virtualization-friendly
795 (for example, block the virtual CPU rather than spinning).
797 It has a minimal impact on native kernels and gives a nice performance
798 benefit on paravirtualized KVM / Xen kernels.
800 If you are unsure how to answer this question, answer Y.
802 config X86_HV_CALLBACK_VECTOR
805 source "arch/x86/xen/Kconfig"
808 bool "KVM Guest support (including kvmclock)"
810 select PARAVIRT_CLOCK
811 select ARCH_CPUIDLE_HALTPOLL
812 select X86_HV_CALLBACK_VECTOR
815 This option enables various optimizations for running under the KVM
816 hypervisor. It includes a paravirtualized clock, so that instead
817 of relying on a PIT (or probably other) emulation by the
818 underlying device model, the host provides the guest with
819 timing infrastructure such as time of day, and system time
821 config ARCH_CPUIDLE_HALTPOLL
823 prompt "Disable host haltpoll when loading haltpoll driver"
825 If virtualized under KVM, disable host haltpoll.
828 bool "Support for running PVH guests"
830 This option enables the PVH entry point for guest virtual machines
831 as specified in the x86/HVM direct boot ABI.
833 config PARAVIRT_TIME_ACCOUNTING
834 bool "Paravirtual steal time accounting"
837 Select this option to enable fine granularity task steal time
838 accounting. Time spent executing other tasks in parallel with
839 the current vCPU is discounted from the vCPU power. To account for
840 that, there can be a small performance impact.
842 If in doubt, say N here.
844 config PARAVIRT_CLOCK
847 config JAILHOUSE_GUEST
848 bool "Jailhouse non-root cell support"
849 depends on X86_64 && PCI
852 This option allows to run Linux as guest in a Jailhouse non-root
853 cell. You can leave this option disabled if you only want to start
854 Jailhouse and run Linux afterwards in the root cell.
857 bool "ACRN Guest support"
859 select X86_HV_CALLBACK_VECTOR
861 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
862 a flexible, lightweight reference open-source hypervisor, built with
863 real-time and safety-criticality in mind. It is built for embedded
864 IOT with small footprint and real-time features. More details can be
865 found in https://projectacrn.org/.
867 endif #HYPERVISOR_GUEST
869 source "arch/x86/Kconfig.cpu"
873 prompt "HPET Timer Support" if X86_32
875 Use the IA-PC HPET (High Precision Event Timer) to manage
876 time in preference to the PIT and RTC, if a HPET is
878 HPET is the next generation timer replacing legacy 8254s.
879 The HPET provides a stable time base on SMP
880 systems, unlike the TSC, but it is more expensive to access,
881 as it is off-chip. The interface used is documented
882 in the HPET spec, revision 1.
884 You can safely choose Y here. However, HPET will only be
885 activated if the platform and the BIOS support this feature.
886 Otherwise the 8254 will be used for timing services.
888 Choose N to continue using the legacy 8254 timer.
890 config HPET_EMULATE_RTC
892 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
895 def_bool y if X86_INTEL_MID
896 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
898 depends on X86_INTEL_MID && SFI
900 APB timer is the replacement for 8254, HPET on X86 MID platforms.
901 The APBT provides a stable time base on SMP
902 systems, unlike the TSC, but it is more expensive to access,
903 as it is off-chip. APB timers are always running regardless of CPU
904 C states, they are used as per CPU clockevent device when possible.
906 # Mark as expert because too many people got it wrong.
907 # The code disables itself when not needed.
910 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
911 bool "Enable DMI scanning" if EXPERT
913 Enabled scanning of DMI to identify machine quirks. Say Y
914 here unless you have verified that your setup is not
915 affected by entries in the DMI blacklist. Required by PNP
919 bool "Old AMD GART IOMMU support"
923 depends on X86_64 && PCI && AMD_NB
925 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
926 GART based hardware IOMMUs.
928 The GART supports full DMA access for devices with 32-bit access
929 limitations, on systems with more than 3 GB. This is usually needed
930 for USB, sound, many IDE/SATA chipsets and some other devices.
932 Newer systems typically have a modern AMD IOMMU, supported via
933 the CONFIG_AMD_IOMMU=y config option.
935 In normal configurations this driver is only active when needed:
936 there's more than 3 GB of memory and the system contains a
937 32-bit limited device.
942 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
943 depends on X86_64 && SMP && DEBUG_KERNEL
944 select CPUMASK_OFFSTACK
946 Enable maximum number of CPUS and NUMA Nodes for this architecture.
950 # The maximum number of CPUs supported:
952 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
953 # and which can be configured interactively in the
954 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
956 # The ranges are different on 32-bit and 64-bit kernels, depending on
957 # hardware capabilities and scalability features of the kernel.
959 # ( If MAXSMP is enabled we just use the highest possible value and disable
960 # interactive configuration. )
963 config NR_CPUS_RANGE_BEGIN
965 default NR_CPUS_RANGE_END if MAXSMP
969 config NR_CPUS_RANGE_END
972 default 64 if SMP && X86_BIGSMP
973 default 8 if SMP && !X86_BIGSMP
976 config NR_CPUS_RANGE_END
979 default 8192 if SMP && CPUMASK_OFFSTACK
980 default 512 if SMP && !CPUMASK_OFFSTACK
983 config NR_CPUS_DEFAULT
986 default 32 if X86_BIGSMP
990 config NR_CPUS_DEFAULT
993 default 8192 if MAXSMP
998 int "Maximum number of CPUs" if SMP && !MAXSMP
999 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1000 default NR_CPUS_DEFAULT
1002 This allows you to specify the maximum number of CPUs which this
1003 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1004 supported value is 8192, otherwise the maximum value is 512. The
1005 minimum value which makes sense is 2.
1007 This is purely to save memory: each supported CPU adds about 8KB
1008 to the kernel image.
1015 prompt "Multi-core scheduler support"
1018 Multi-core scheduler support improves the CPU scheduler's decision
1019 making when dealing with multi-core CPU chips at a cost of slightly
1020 increased overhead in some places. If unsure say N here.
1022 config SCHED_MC_PRIO
1023 bool "CPU core priorities scheduler support"
1024 depends on SCHED_MC && CPU_SUP_INTEL
1025 select X86_INTEL_PSTATE
1029 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1030 core ordering determined at manufacturing time, which allows
1031 certain cores to reach higher turbo frequencies (when running
1032 single threaded workloads) than others.
1034 Enabling this kernel feature teaches the scheduler about
1035 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1036 scheduler's CPU selection logic accordingly, so that higher
1037 overall system performance can be achieved.
1039 This feature will have no effect on CPUs without this feature.
1041 If unsure say Y here.
1045 depends on !SMP && X86_LOCAL_APIC
1048 bool "Local APIC support on uniprocessors" if !PCI_MSI
1050 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1052 A local APIC (Advanced Programmable Interrupt Controller) is an
1053 integrated interrupt controller in the CPU. If you have a single-CPU
1054 system which has a processor with a local APIC, you can say Y here to
1055 enable and use it. If you say Y here even though your machine doesn't
1056 have a local APIC, then the kernel will still run with no slowdown at
1057 all. The local APIC supports CPU-generated self-interrupts (timer,
1058 performance counters), and the NMI watchdog which detects hard
1061 config X86_UP_IOAPIC
1062 bool "IO-APIC support on uniprocessors"
1063 depends on X86_UP_APIC
1065 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1066 SMP-capable replacement for PC-style interrupt controllers. Most
1067 SMP systems and many recent uniprocessor systems have one.
1069 If you have a single-CPU system with an IO-APIC, you can say Y here
1070 to use it. If you say Y here even though your machine doesn't have
1071 an IO-APIC, then the kernel will still run with no slowdown at all.
1073 config X86_LOCAL_APIC
1075 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1076 select IRQ_DOMAIN_HIERARCHY
1077 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1081 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1083 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1084 bool "Reroute for broken boot IRQs"
1085 depends on X86_IO_APIC
1087 This option enables a workaround that fixes a source of
1088 spurious interrupts. This is recommended when threaded
1089 interrupt handling is used on systems where the generation of
1090 superfluous "boot interrupts" cannot be disabled.
1092 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1093 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1094 kernel does during interrupt handling). On chipsets where this
1095 boot IRQ generation cannot be disabled, this workaround keeps
1096 the original IRQ line masked so that only the equivalent "boot
1097 IRQ" is delivered to the CPUs. The workaround also tells the
1098 kernel to set up the IRQ handler on the boot IRQ line. In this
1099 way only one interrupt is delivered to the kernel. Otherwise
1100 the spurious second interrupt may cause the kernel to bring
1101 down (vital) interrupt lines.
1103 Only affects "broken" chipsets. Interrupt sharing may be
1104 increased on these systems.
1107 bool "Machine Check / overheating reporting"
1108 select GENERIC_ALLOCATOR
1111 Machine Check support allows the processor to notify the
1112 kernel if it detects a problem (e.g. overheating, data corruption).
1113 The action the kernel takes depends on the severity of the problem,
1114 ranging from warning messages to halting the machine.
1116 config X86_MCELOG_LEGACY
1117 bool "Support for deprecated /dev/mcelog character device"
1120 Enable support for /dev/mcelog which is needed by the old mcelog
1121 userspace logging daemon. Consider switching to the new generation
1124 config X86_MCE_INTEL
1126 prompt "Intel MCE features"
1127 depends on X86_MCE && X86_LOCAL_APIC
1129 Additional support for intel specific MCE features such as
1130 the thermal monitor.
1134 prompt "AMD MCE features"
1135 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1137 Additional support for AMD specific MCE features such as
1138 the DRAM Error Threshold.
1140 config X86_ANCIENT_MCE
1141 bool "Support for old Pentium 5 / WinChip machine checks"
1142 depends on X86_32 && X86_MCE
1144 Include support for machine check handling on old Pentium 5 or WinChip
1145 systems. These typically need to be enabled explicitly on the command
1148 config X86_MCE_THRESHOLD
1149 depends on X86_MCE_AMD || X86_MCE_INTEL
1152 config X86_MCE_INJECT
1153 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1154 tristate "Machine check injector support"
1156 Provide support for injecting machine checks for testing purposes.
1157 If you don't know what a machine check is and you don't do kernel
1158 QA it is safe to say n.
1160 config X86_THERMAL_VECTOR
1162 depends on X86_MCE_INTEL
1164 source "arch/x86/events/Kconfig"
1166 config X86_LEGACY_VM86
1167 bool "Legacy VM86 support"
1170 This option allows user programs to put the CPU into V8086
1171 mode, which is an 80286-era approximation of 16-bit real mode.
1173 Some very old versions of X and/or vbetool require this option
1174 for user mode setting. Similarly, DOSEMU will use it if
1175 available to accelerate real mode DOS programs. However, any
1176 recent version of DOSEMU, X, or vbetool should be fully
1177 functional even without kernel VM86 support, as they will all
1178 fall back to software emulation. Nevertheless, if you are using
1179 a 16-bit DOS program where 16-bit performance matters, vm86
1180 mode might be faster than emulation and you might want to
1183 Note that any app that works on a 64-bit kernel is unlikely to
1184 need this option, as 64-bit kernels don't, and can't, support
1185 V8086 mode. This option is also unrelated to 16-bit protected
1186 mode and is not needed to run most 16-bit programs under Wine.
1188 Enabling this option increases the complexity of the kernel
1189 and slows down exception handling a tiny bit.
1191 If unsure, say N here.
1195 default X86_LEGACY_VM86
1198 bool "Enable support for 16-bit segments" if EXPERT
1200 depends on MODIFY_LDT_SYSCALL
1202 This option is required by programs like Wine to run 16-bit
1203 protected mode legacy code on x86 processors. Disabling
1204 this option saves about 300 bytes on i386, or around 6K text
1205 plus 16K runtime memory on x86-64,
1209 depends on X86_16BIT && X86_32
1213 depends on X86_16BIT && X86_64
1215 config X86_VSYSCALL_EMULATION
1216 bool "Enable vsyscall emulation" if EXPERT
1220 This enables emulation of the legacy vsyscall page. Disabling
1221 it is roughly equivalent to booting with vsyscall=none, except
1222 that it will also disable the helpful warning if a program
1223 tries to use a vsyscall. With this option set to N, offending
1224 programs will just segfault, citing addresses of the form
1227 This option is required by many programs built before 2013, and
1228 care should be used even with newer programs if set to N.
1230 Disabling this option saves about 7K of kernel size and
1231 possibly 4K of additional runtime pagetable memory.
1233 config X86_IOPL_IOPERM
1234 bool "IOPERM and IOPL Emulation"
1237 This enables the ioperm() and iopl() syscalls which are necessary
1238 for legacy applications.
1240 Legacy IOPL support is an overbroad mechanism which allows user
1241 space aside of accessing all 65536 I/O ports also to disable
1242 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1243 capabilities and permission from potentially active security
1246 The emulation restricts the functionality of the syscall to
1247 only allowing the full range I/O port access, but prevents the
1248 ability to disable interrupts from user space which would be
1249 granted if the hardware IOPL mechanism would be used.
1252 tristate "Toshiba Laptop support"
1255 This adds a driver to safely access the System Management Mode of
1256 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1257 not work on models with a Phoenix BIOS. The System Management Mode
1258 is used to set the BIOS and power saving options on Toshiba portables.
1260 For information on utilities to make use of this driver see the
1261 Toshiba Linux utilities web site at:
1262 <http://www.buzzard.org.uk/toshiba/>.
1264 Say Y if you intend to run this kernel on a Toshiba portable.
1268 tristate "Dell i8k legacy laptop support"
1270 select SENSORS_DELL_SMM
1272 This option enables legacy /proc/i8k userspace interface in hwmon
1273 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1274 temperature and allows controlling fan speeds of Dell laptops via
1275 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1276 it reports also power and hotkey status. For fan speed control is
1277 needed userspace package i8kutils.
1279 Say Y if you intend to run this kernel on old Dell laptops or want to
1280 use userspace package i8kutils.
1283 config X86_REBOOTFIXUPS
1284 bool "Enable X86 board specific fixups for reboot"
1287 This enables chipset and/or board specific fixups to be done
1288 in order to get reboot to work correctly. This is only needed on
1289 some combinations of hardware and BIOS. The symptom, for which
1290 this config is intended, is when reboot ends with a stalled/hung
1293 Currently, the only fixup is for the Geode machines using
1294 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1296 Say Y if you want to enable the fixup. Currently, it's safe to
1297 enable this option even if you don't need it.
1301 bool "CPU microcode loading support"
1303 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1305 If you say Y here, you will be able to update the microcode on
1306 Intel and AMD processors. The Intel support is for the IA32 family,
1307 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1308 AMD support is for families 0x10 and later. You will obviously need
1309 the actual microcode binary data itself which is not shipped with
1312 The preferred method to load microcode from a detached initrd is described
1313 in Documentation/x86/microcode.rst. For that you need to enable
1314 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1315 initrd for microcode blobs.
1317 In addition, you can build the microcode into the kernel. For that you
1318 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1321 config MICROCODE_INTEL
1322 bool "Intel microcode loading support"
1323 depends on MICROCODE
1326 This options enables microcode patch loading support for Intel
1329 For the current Intel microcode data package go to
1330 <https://downloadcenter.intel.com> and search for
1331 'Linux Processor Microcode Data File'.
1333 config MICROCODE_AMD
1334 bool "AMD microcode loading support"
1335 depends on MICROCODE
1337 If you select this option, microcode patch loading support for AMD
1338 processors will be enabled.
1340 config MICROCODE_OLD_INTERFACE
1341 bool "Ancient loading interface (DEPRECATED)"
1343 depends on MICROCODE
1345 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1346 which was used by userspace tools like iucode_tool and microcode.ctl.
1347 It is inadequate because it runs too late to be able to properly
1348 load microcode on a machine and it needs special tools. Instead, you
1349 should've switched to the early loading method with the initrd or
1350 builtin microcode by now: Documentation/x86/microcode.rst
1353 tristate "/dev/cpu/*/msr - Model-specific register support"
1355 This device gives privileged processes access to the x86
1356 Model-Specific Registers (MSRs). It is a character device with
1357 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1358 MSR accesses are directed to a specific CPU on multi-processor
1362 tristate "/dev/cpu/*/cpuid - CPU information support"
1364 This device gives processes access to the x86 CPUID instruction to
1365 be executed on a specific processor. It is a character device
1366 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1370 prompt "High Memory Support"
1377 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1378 However, the address space of 32-bit x86 processors is only 4
1379 Gigabytes large. That means that, if you have a large amount of
1380 physical memory, not all of it can be "permanently mapped" by the
1381 kernel. The physical memory that's not permanently mapped is called
1384 If you are compiling a kernel which will never run on a machine with
1385 more than 1 Gigabyte total physical RAM, answer "off" here (default
1386 choice and suitable for most users). This will result in a "3GB/1GB"
1387 split: 3GB are mapped so that each process sees a 3GB virtual memory
1388 space and the remaining part of the 4GB virtual memory space is used
1389 by the kernel to permanently map as much physical memory as
1392 If the machine has between 1 and 4 Gigabytes physical RAM, then
1395 If more than 4 Gigabytes is used then answer "64GB" here. This
1396 selection turns Intel PAE (Physical Address Extension) mode on.
1397 PAE implements 3-level paging on IA32 processors. PAE is fully
1398 supported by Linux, PAE mode is implemented on all recent Intel
1399 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1400 then the kernel will not boot on CPUs that don't support PAE!
1402 The actual amount of total physical memory will either be
1403 auto detected or can be forced by using a kernel command line option
1404 such as "mem=256M". (Try "man bootparam" or see the documentation of
1405 your boot loader (lilo or loadlin) about how to pass options to the
1406 kernel at boot time.)
1408 If unsure, say "off".
1413 Select this if you have a 32-bit processor and between 1 and 4
1414 gigabytes of physical RAM.
1418 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1421 Select this if you have a 32-bit processor and more than 4
1422 gigabytes of physical RAM.
1427 prompt "Memory split" if EXPERT
1431 Select the desired split between kernel and user memory.
1433 If the address range available to the kernel is less than the
1434 physical memory installed, the remaining memory will be available
1435 as "high memory". Accessing high memory is a little more costly
1436 than low memory, as it needs to be mapped into the kernel first.
1437 Note that increasing the kernel address space limits the range
1438 available to user programs, making the address space there
1439 tighter. Selecting anything other than the default 3G/1G split
1440 will also likely make your kernel incompatible with binary-only
1443 If you are not absolutely sure what you are doing, leave this
1447 bool "3G/1G user/kernel split"
1448 config VMSPLIT_3G_OPT
1450 bool "3G/1G user/kernel split (for full 1G low memory)"
1452 bool "2G/2G user/kernel split"
1453 config VMSPLIT_2G_OPT
1455 bool "2G/2G user/kernel split (for full 2G low memory)"
1457 bool "1G/3G user/kernel split"
1462 default 0xB0000000 if VMSPLIT_3G_OPT
1463 default 0x80000000 if VMSPLIT_2G
1464 default 0x78000000 if VMSPLIT_2G_OPT
1465 default 0x40000000 if VMSPLIT_1G
1471 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1474 bool "PAE (Physical Address Extension) Support"
1475 depends on X86_32 && !HIGHMEM4G
1476 select PHYS_ADDR_T_64BIT
1479 PAE is required for NX support, and furthermore enables
1480 larger swapspace support for non-overcommit purposes. It
1481 has the cost of more pagetable lookup overhead, and also
1482 consumes more pagetable space per process.
1485 bool "Enable 5-level page tables support"
1487 select DYNAMIC_MEMORY_LAYOUT
1488 select SPARSEMEM_VMEMMAP
1491 5-level paging enables access to larger address space:
1492 upto 128 PiB of virtual address space and 4 PiB of
1493 physical address space.
1495 It will be supported by future Intel CPUs.
1497 A kernel with the option enabled can be booted on machines that
1498 support 4- or 5-level paging.
1500 See Documentation/x86/x86_64/5level-paging.rst for more
1505 config X86_DIRECT_GBPAGES
1509 Certain kernel features effectively disable kernel
1510 linear 1 GB mappings (even if the CPU otherwise
1511 supports them), so don't confuse the user by printing
1512 that we have them enabled.
1514 config X86_CPA_STATISTICS
1515 bool "Enable statistic for Change Page Attribute"
1518 Expose statistics about the Change Page Attribute mechanism, which
1519 helps to determine the effectiveness of preserving large and huge
1520 page mappings when mapping protections are changed.
1522 config AMD_MEM_ENCRYPT
1523 bool "AMD Secure Memory Encryption (SME) support"
1524 depends on X86_64 && CPU_SUP_AMD
1525 select DMA_COHERENT_POOL
1526 select DYNAMIC_PHYSICAL_MASK
1527 select ARCH_USE_MEMREMAP_PROT
1528 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1529 select INSTRUCTION_DECODER
1531 Say yes to enable support for the encryption of system memory.
1532 This requires an AMD processor that supports Secure Memory
1535 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1536 bool "Activate AMD Secure Memory Encryption (SME) by default"
1538 depends on AMD_MEM_ENCRYPT
1540 Say yes to have system memory encrypted by default if running on
1541 an AMD processor that supports Secure Memory Encryption (SME).
1543 If set to Y, then the encryption of system memory can be
1544 deactivated with the mem_encrypt=off command line option.
1546 If set to N, then the encryption of system memory can be
1547 activated with the mem_encrypt=on command line option.
1549 # Common NUMA Features
1551 bool "NUMA Memory Allocation and Scheduler Support"
1553 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1554 default y if X86_BIGSMP
1556 Enable NUMA (Non-Uniform Memory Access) support.
1558 The kernel will try to allocate memory used by a CPU on the
1559 local memory controller of the CPU and add some more
1560 NUMA awareness to the kernel.
1562 For 64-bit this is recommended if the system is Intel Core i7
1563 (or later), AMD Opteron, or EM64T NUMA.
1565 For 32-bit this is only needed if you boot a 32-bit
1566 kernel on a 64-bit NUMA platform.
1568 Otherwise, you should say N.
1572 prompt "Old style AMD Opteron NUMA detection"
1573 depends on X86_64 && NUMA && PCI
1575 Enable AMD NUMA node topology detection. You should say Y here if
1576 you have a multi processor AMD system. This uses an old method to
1577 read the NUMA configuration directly from the builtin Northbridge
1578 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1579 which also takes priority if both are compiled in.
1581 config X86_64_ACPI_NUMA
1583 prompt "ACPI NUMA detection"
1584 depends on X86_64 && NUMA && ACPI && PCI
1587 Enable ACPI SRAT based node topology detection.
1590 bool "NUMA emulation"
1593 Enable NUMA emulation. A flat machine will be split
1594 into virtual nodes when booted with "numa=fake=N", where N is the
1595 number of nodes. This is only useful for debugging.
1598 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1600 default "10" if MAXSMP
1601 default "6" if X86_64
1603 depends on NEED_MULTIPLE_NODES
1605 Specify the maximum number of NUMA Nodes available on the target
1606 system. Increases memory reserved to accommodate various tables.
1608 config ARCH_FLATMEM_ENABLE
1610 depends on X86_32 && !NUMA
1612 config ARCH_SPARSEMEM_ENABLE
1614 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1615 select SPARSEMEM_STATIC if X86_32
1616 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1618 config ARCH_SPARSEMEM_DEFAULT
1619 def_bool X86_64 || (NUMA && X86_32)
1621 config ARCH_SELECT_MEMORY_MODEL
1623 depends on ARCH_SPARSEMEM_ENABLE
1625 config ARCH_MEMORY_PROBE
1626 bool "Enable sysfs memory/probe interface"
1627 depends on X86_64 && MEMORY_HOTPLUG
1629 This option enables a sysfs memory/probe interface for testing.
1630 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1631 If you are unsure how to answer this question, answer N.
1633 config ARCH_PROC_KCORE_TEXT
1635 depends on X86_64 && PROC_KCORE
1637 config ILLEGAL_POINTER_VALUE
1640 default 0xdead000000000000 if X86_64
1642 config X86_PMEM_LEGACY_DEVICE
1645 config X86_PMEM_LEGACY
1646 tristate "Support non-standard NVDIMMs and ADR protected memory"
1647 depends on PHYS_ADDR_T_64BIT
1649 select X86_PMEM_LEGACY_DEVICE
1650 select NUMA_KEEP_MEMINFO if NUMA
1653 Treat memory marked using the non-standard e820 type of 12 as used
1654 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1655 The kernel will offer these regions to the 'pmem' driver so
1656 they can be used for persistent storage.
1661 bool "Allocate 3rd-level pagetables from highmem"
1664 The VM uses one page table entry for each page of physical memory.
1665 For systems with a lot of RAM, this can be wasteful of precious
1666 low memory. Setting this option will put user-space page table
1667 entries in high memory.
1669 config X86_CHECK_BIOS_CORRUPTION
1670 bool "Check for low memory corruption"
1672 Periodically check for memory corruption in low memory, which
1673 is suspected to be caused by BIOS. Even when enabled in the
1674 configuration, it is disabled at runtime. Enable it by
1675 setting "memory_corruption_check=1" on the kernel command
1676 line. By default it scans the low 64k of memory every 60
1677 seconds; see the memory_corruption_check_size and
1678 memory_corruption_check_period parameters in
1679 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1681 When enabled with the default parameters, this option has
1682 almost no overhead, as it reserves a relatively small amount
1683 of memory and scans it infrequently. It both detects corruption
1684 and prevents it from affecting the running system.
1686 It is, however, intended as a diagnostic tool; if repeatable
1687 BIOS-originated corruption always affects the same memory,
1688 you can use memmap= to prevent the kernel from using that
1691 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1692 bool "Set the default setting of memory_corruption_check"
1693 depends on X86_CHECK_BIOS_CORRUPTION
1696 Set whether the default state of memory_corruption_check is
1699 config X86_RESERVE_LOW
1700 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1704 Specify the amount of low memory to reserve for the BIOS.
1706 The first page contains BIOS data structures that the kernel
1707 must not use, so that page must always be reserved.
1709 By default we reserve the first 64K of physical RAM, as a
1710 number of BIOSes are known to corrupt that memory range
1711 during events such as suspend/resume or monitor cable
1712 insertion, so it must not be used by the kernel.
1714 You can set this to 4 if you are absolutely sure that you
1715 trust the BIOS to get all its memory reservations and usages
1716 right. If you know your BIOS have problems beyond the
1717 default 64K area, you can set this to 640 to avoid using the
1718 entire low memory range.
1720 If you have doubts about the BIOS (e.g. suspend/resume does
1721 not work or there's kernel crashes after certain hardware
1722 hotplug events) then you might want to enable
1723 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1724 typical corruption patterns.
1726 Leave this to the default value of 64 if you are unsure.
1728 config MATH_EMULATION
1730 depends on MODIFY_LDT_SYSCALL
1731 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1733 Linux can emulate a math coprocessor (used for floating point
1734 operations) if you don't have one. 486DX and Pentium processors have
1735 a math coprocessor built in, 486SX and 386 do not, unless you added
1736 a 487DX or 387, respectively. (The messages during boot time can
1737 give you some hints here ["man dmesg"].) Everyone needs either a
1738 coprocessor or this emulation.
1740 If you don't have a math coprocessor, you need to say Y here; if you
1741 say Y here even though you have a coprocessor, the coprocessor will
1742 be used nevertheless. (This behavior can be changed with the kernel
1743 command line option "no387", which comes handy if your coprocessor
1744 is broken. Try "man bootparam" or see the documentation of your boot
1745 loader (lilo or loadlin) about how to pass options to the kernel at
1746 boot time.) This means that it is a good idea to say Y here if you
1747 intend to use this kernel on different machines.
1749 More information about the internals of the Linux math coprocessor
1750 emulation can be found in <file:arch/x86/math-emu/README>.
1752 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1753 kernel, it won't hurt.
1757 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1759 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1760 the Memory Type Range Registers (MTRRs) may be used to control
1761 processor access to memory ranges. This is most useful if you have
1762 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1763 allows bus write transfers to be combined into a larger transfer
1764 before bursting over the PCI/AGP bus. This can increase performance
1765 of image write operations 2.5 times or more. Saying Y here creates a
1766 /proc/mtrr file which may be used to manipulate your processor's
1767 MTRRs. Typically the X server should use this.
1769 This code has a reasonably generic interface so that similar
1770 control registers on other processors can be easily supported
1773 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1774 Registers (ARRs) which provide a similar functionality to MTRRs. For
1775 these, the ARRs are used to emulate the MTRRs.
1776 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1777 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1778 write-combining. All of these processors are supported by this code
1779 and it makes sense to say Y here if you have one of them.
1781 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1782 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1783 can lead to all sorts of problems, so it's good to say Y here.
1785 You can safely say Y even if your machine doesn't have MTRRs, you'll
1786 just add about 9 KB to your kernel.
1788 See <file:Documentation/x86/mtrr.rst> for more information.
1790 config MTRR_SANITIZER
1792 prompt "MTRR cleanup support"
1795 Convert MTRR layout from continuous to discrete, so X drivers can
1796 add writeback entries.
1798 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1799 The largest mtrr entry size for a continuous block can be set with
1804 config MTRR_SANITIZER_ENABLE_DEFAULT
1805 int "MTRR cleanup enable value (0-1)"
1808 depends on MTRR_SANITIZER
1810 Enable mtrr cleanup default value
1812 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1813 int "MTRR cleanup spare reg num (0-7)"
1816 depends on MTRR_SANITIZER
1818 mtrr cleanup spare entries default, it can be changed via
1819 mtrr_spare_reg_nr=N on the kernel command line.
1823 prompt "x86 PAT support" if EXPERT
1826 Use PAT attributes to setup page level cache control.
1828 PATs are the modern equivalents of MTRRs and are much more
1829 flexible than MTRRs.
1831 Say N here if you see bootup problems (boot crash, boot hang,
1832 spontaneous reboots) or a non-working video driver.
1836 config ARCH_USES_PG_UNCACHED
1842 prompt "x86 architectural random number generator" if EXPERT
1844 Enable the x86 architectural RDRAND instruction
1845 (Intel Bull Mountain technology) to generate random numbers.
1846 If supported, this is a high bandwidth, cryptographically
1847 secure hardware random number generator.
1851 prompt "Supervisor Mode Access Prevention" if EXPERT
1853 Supervisor Mode Access Prevention (SMAP) is a security
1854 feature in newer Intel processors. There is a small
1855 performance cost if this enabled and turned on; there is
1856 also a small increase in the kernel size if this is enabled.
1862 prompt "User Mode Instruction Prevention" if EXPERT
1864 User Mode Instruction Prevention (UMIP) is a security feature in
1865 some x86 processors. If enabled, a general protection fault is
1866 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1867 executed in user mode. These instructions unnecessarily expose
1868 information about the hardware state.
1870 The vast majority of applications do not use these instructions.
1871 For the very few that do, software emulation is provided in
1872 specific cases in protected and virtual-8086 modes. Emulated
1875 config X86_INTEL_MEMORY_PROTECTION_KEYS
1876 prompt "Memory Protection Keys"
1878 # Note: only available in 64-bit mode
1879 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1880 select ARCH_USES_HIGH_VMA_FLAGS
1881 select ARCH_HAS_PKEYS
1883 Memory Protection Keys provides a mechanism for enforcing
1884 page-based protections, but without requiring modification of the
1885 page tables when an application changes protection domains.
1887 For details, see Documentation/core-api/protection-keys.rst
1892 prompt "TSX enable mode"
1893 depends on CPU_SUP_INTEL
1894 default X86_INTEL_TSX_MODE_OFF
1896 Intel's TSX (Transactional Synchronization Extensions) feature
1897 allows to optimize locking protocols through lock elision which
1898 can lead to a noticeable performance boost.
1900 On the other hand it has been shown that TSX can be exploited
1901 to form side channel attacks (e.g. TAA) and chances are there
1902 will be more of those attacks discovered in the future.
1904 Therefore TSX is not enabled by default (aka tsx=off). An admin
1905 might override this decision by tsx=on the command line parameter.
1906 Even with TSX enabled, the kernel will attempt to enable the best
1907 possible TAA mitigation setting depending on the microcode available
1908 for the particular machine.
1910 This option allows to set the default tsx mode between tsx=on, =off
1911 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1914 Say off if not sure, auto if TSX is in use but it should be used on safe
1915 platforms or on if TSX is in use and the security aspect of tsx is not
1918 config X86_INTEL_TSX_MODE_OFF
1921 TSX is disabled if possible - equals to tsx=off command line parameter.
1923 config X86_INTEL_TSX_MODE_ON
1926 TSX is always enabled on TSX capable HW - equals the tsx=on command
1929 config X86_INTEL_TSX_MODE_AUTO
1932 TSX is enabled on TSX capable HW that is believed to be safe against
1933 side channel attacks- equals the tsx=auto command line parameter.
1937 bool "Software Guard eXtensions (SGX)"
1938 depends on X86_64 && CPU_SUP_INTEL
1940 depends on CRYPTO_SHA256=y
1944 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1945 that can be used by applications to set aside private regions of code
1946 and data, referred to as enclaves. An enclave's private memory can
1947 only be accessed by code running within the enclave. Accesses from
1948 outside the enclave, including other enclaves, are disallowed by
1954 bool "EFI runtime service support"
1957 select EFI_RUNTIME_WRAPPERS
1959 This enables the kernel to use EFI runtime services that are
1960 available (such as the EFI variable services).
1962 This option is only useful on systems that have EFI firmware.
1963 In addition, you should use the latest ELILO loader available
1964 at <http://elilo.sourceforge.net> in order to take advantage
1965 of EFI runtime services. However, even with this option, the
1966 resultant kernel should continue to boot on existing non-EFI
1970 bool "EFI stub support"
1971 depends on EFI && !X86_USE_3DNOW
1972 depends on $(cc-option,-mabi=ms) || X86_32
1975 This kernel feature allows a bzImage to be loaded directly
1976 by EFI firmware without the use of a bootloader.
1978 See Documentation/admin-guide/efi-stub.rst for more information.
1981 bool "EFI mixed-mode support"
1982 depends on EFI_STUB && X86_64
1984 Enabling this feature allows a 64-bit kernel to be booted
1985 on a 32-bit firmware, provided that your CPU supports 64-bit
1988 Note that it is not possible to boot a mixed-mode enabled
1989 kernel via the EFI boot stub - a bootloader that supports
1990 the EFI handover protocol must be used.
1994 source "kernel/Kconfig.hz"
1997 bool "kexec system call"
2000 kexec is a system call that implements the ability to shutdown your
2001 current kernel, and to start another kernel. It is like a reboot
2002 but it is independent of the system firmware. And like a reboot
2003 you can start any kernel with it, not just Linux.
2005 The name comes from the similarity to the exec system call.
2007 It is an ongoing process to be certain the hardware in a machine
2008 is properly shutdown, so do not be surprised if this code does not
2009 initially work for you. As of this writing the exact hardware
2010 interface is strongly in flux, so no good recommendation can be
2014 bool "kexec file based system call"
2019 depends on CRYPTO_SHA256=y
2021 This is new version of kexec system call. This system call is
2022 file based and takes file descriptors as system call argument
2023 for kernel and initramfs as opposed to list of segments as
2024 accepted by previous system call.
2026 config ARCH_HAS_KEXEC_PURGATORY
2030 bool "Verify kernel signature during kexec_file_load() syscall"
2031 depends on KEXEC_FILE
2034 This option makes the kexec_file_load() syscall check for a valid
2035 signature of the kernel image. The image can still be loaded without
2036 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2037 there's a signature that we can check, then it must be valid.
2039 In addition to this option, you need to enable signature
2040 verification for the corresponding kernel image type being
2041 loaded in order for this to work.
2043 config KEXEC_SIG_FORCE
2044 bool "Require a valid signature in kexec_file_load() syscall"
2045 depends on KEXEC_SIG
2047 This option makes kernel signature verification mandatory for
2048 the kexec_file_load() syscall.
2050 config KEXEC_BZIMAGE_VERIFY_SIG
2051 bool "Enable bzImage signature verification support"
2052 depends on KEXEC_SIG
2053 depends on SIGNED_PE_FILE_VERIFICATION
2054 select SYSTEM_TRUSTED_KEYRING
2056 Enable bzImage signature verification support.
2059 bool "kernel crash dumps"
2060 depends on X86_64 || (X86_32 && HIGHMEM)
2062 Generate crash dump after being started by kexec.
2063 This should be normally only set in special crash dump kernels
2064 which are loaded in the main kernel with kexec-tools into
2065 a specially reserved region and then later executed after
2066 a crash by kdump/kexec. The crash dump kernel must be compiled
2067 to a memory address not used by the main kernel or BIOS using
2068 PHYSICAL_START, or it must be built as a relocatable image
2069 (CONFIG_RELOCATABLE=y).
2070 For more details see Documentation/admin-guide/kdump/kdump.rst
2074 depends on KEXEC && HIBERNATION
2076 Jump between original kernel and kexeced kernel and invoke
2077 code in physical address mode via KEXEC
2079 config PHYSICAL_START
2080 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2083 This gives the physical address where the kernel is loaded.
2085 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2086 bzImage will decompress itself to above physical address and
2087 run from there. Otherwise, bzImage will run from the address where
2088 it has been loaded by the boot loader and will ignore above physical
2091 In normal kdump cases one does not have to set/change this option
2092 as now bzImage can be compiled as a completely relocatable image
2093 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2094 address. This option is mainly useful for the folks who don't want
2095 to use a bzImage for capturing the crash dump and want to use a
2096 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2097 to be specifically compiled to run from a specific memory area
2098 (normally a reserved region) and this option comes handy.
2100 So if you are using bzImage for capturing the crash dump,
2101 leave the value here unchanged to 0x1000000 and set
2102 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2103 for capturing the crash dump change this value to start of
2104 the reserved region. In other words, it can be set based on
2105 the "X" value as specified in the "crashkernel=YM@XM"
2106 command line boot parameter passed to the panic-ed
2107 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2108 for more details about crash dumps.
2110 Usage of bzImage for capturing the crash dump is recommended as
2111 one does not have to build two kernels. Same kernel can be used
2112 as production kernel and capture kernel. Above option should have
2113 gone away after relocatable bzImage support is introduced. But it
2114 is present because there are users out there who continue to use
2115 vmlinux for dump capture. This option should go away down the
2118 Don't change this unless you know what you are doing.
2121 bool "Build a relocatable kernel"
2124 This builds a kernel image that retains relocation information
2125 so it can be loaded someplace besides the default 1MB.
2126 The relocations tend to make the kernel binary about 10% larger,
2127 but are discarded at runtime.
2129 One use is for the kexec on panic case where the recovery kernel
2130 must live at a different physical address than the primary
2133 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2134 it has been loaded at and the compile time physical address
2135 (CONFIG_PHYSICAL_START) is used as the minimum location.
2137 config RANDOMIZE_BASE
2138 bool "Randomize the address of the kernel image (KASLR)"
2139 depends on RELOCATABLE
2142 In support of Kernel Address Space Layout Randomization (KASLR),
2143 this randomizes the physical address at which the kernel image
2144 is decompressed and the virtual address where the kernel
2145 image is mapped, as a security feature that deters exploit
2146 attempts relying on knowledge of the location of kernel
2149 On 64-bit, the kernel physical and virtual addresses are
2150 randomized separately. The physical address will be anywhere
2151 between 16MB and the top of physical memory (up to 64TB). The
2152 virtual address will be randomized from 16MB up to 1GB (9 bits
2153 of entropy). Note that this also reduces the memory space
2154 available to kernel modules from 1.5GB to 1GB.
2156 On 32-bit, the kernel physical and virtual addresses are
2157 randomized together. They will be randomized from 16MB up to
2158 512MB (8 bits of entropy).
2160 Entropy is generated using the RDRAND instruction if it is
2161 supported. If RDTSC is supported, its value is mixed into
2162 the entropy pool as well. If neither RDRAND nor RDTSC are
2163 supported, then entropy is read from the i8254 timer. The
2164 usable entropy is limited by the kernel being built using
2165 2GB addressing, and that PHYSICAL_ALIGN must be at a
2166 minimum of 2MB. As a result, only 10 bits of entropy are
2167 theoretically possible, but the implementations are further
2168 limited due to memory layouts.
2172 # Relocation on x86 needs some additional build support
2173 config X86_NEED_RELOCS
2175 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2177 config PHYSICAL_ALIGN
2178 hex "Alignment value to which kernel should be aligned"
2180 range 0x2000 0x1000000 if X86_32
2181 range 0x200000 0x1000000 if X86_64
2183 This value puts the alignment restrictions on physical address
2184 where kernel is loaded and run from. Kernel is compiled for an
2185 address which meets above alignment restriction.
2187 If bootloader loads the kernel at a non-aligned address and
2188 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2189 address aligned to above value and run from there.
2191 If bootloader loads the kernel at a non-aligned address and
2192 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2193 load address and decompress itself to the address it has been
2194 compiled for and run from there. The address for which kernel is
2195 compiled already meets above alignment restrictions. Hence the
2196 end result is that kernel runs from a physical address meeting
2197 above alignment restrictions.
2199 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2200 this value must be a multiple of 0x200000.
2202 Don't change this unless you know what you are doing.
2204 config DYNAMIC_MEMORY_LAYOUT
2207 This option makes base addresses of vmalloc and vmemmap as well as
2208 __PAGE_OFFSET movable during boot.
2210 config RANDOMIZE_MEMORY
2211 bool "Randomize the kernel memory sections"
2213 depends on RANDOMIZE_BASE
2214 select DYNAMIC_MEMORY_LAYOUT
2215 default RANDOMIZE_BASE
2217 Randomizes the base virtual address of kernel memory sections
2218 (physical memory mapping, vmalloc & vmemmap). This security feature
2219 makes exploits relying on predictable memory locations less reliable.
2221 The order of allocations remains unchanged. Entropy is generated in
2222 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2223 configuration have in average 30,000 different possible virtual
2224 addresses for each memory section.
2228 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2229 hex "Physical memory mapping padding" if EXPERT
2230 depends on RANDOMIZE_MEMORY
2231 default "0xa" if MEMORY_HOTPLUG
2233 range 0x1 0x40 if MEMORY_HOTPLUG
2236 Define the padding in terabytes added to the existing physical
2237 memory size during kernel memory randomization. It is useful
2238 for memory hotplug support but reduces the entropy available for
2239 address randomization.
2241 If unsure, leave at the default value.
2247 config BOOTPARAM_HOTPLUG_CPU0
2248 bool "Set default setting of cpu0_hotpluggable"
2249 depends on HOTPLUG_CPU
2251 Set whether default state of cpu0_hotpluggable is on or off.
2253 Say Y here to enable CPU0 hotplug by default. If this switch
2254 is turned on, there is no need to give cpu0_hotplug kernel
2255 parameter and the CPU0 hotplug feature is enabled by default.
2257 Please note: there are two known CPU0 dependencies if you want
2258 to enable the CPU0 hotplug feature either by this switch or by
2259 cpu0_hotplug kernel parameter.
2261 First, resume from hibernate or suspend always starts from CPU0.
2262 So hibernate and suspend are prevented if CPU0 is offline.
2264 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2265 offline if any interrupt can not migrate out of CPU0. There may
2266 be other CPU0 dependencies.
2268 Please make sure the dependencies are under your control before
2269 you enable this feature.
2271 Say N if you don't want to enable CPU0 hotplug feature by default.
2272 You still can enable the CPU0 hotplug feature at boot by kernel
2273 parameter cpu0_hotplug.
2275 config DEBUG_HOTPLUG_CPU0
2277 prompt "Debug CPU0 hotplug"
2278 depends on HOTPLUG_CPU
2280 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2281 soon as possible and boots up userspace with CPU0 offlined. User
2282 can online CPU0 back after boot time.
2284 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2285 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2286 compilation or giving cpu0_hotplug kernel parameter at boot.
2292 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2293 depends on COMPAT_32
2295 Certain buggy versions of glibc will crash if they are
2296 presented with a 32-bit vDSO that is not mapped at the address
2297 indicated in its segment table.
2299 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2300 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2301 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2302 the only released version with the bug, but OpenSUSE 9
2303 contains a buggy "glibc 2.3.2".
2305 The symptom of the bug is that everything crashes on startup, saying:
2306 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2308 Saying Y here changes the default value of the vdso32 boot
2309 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2310 This works around the glibc bug but hurts performance.
2312 If unsure, say N: if you are compiling your own kernel, you
2313 are unlikely to be using a buggy version of glibc.
2316 prompt "vsyscall table for legacy applications"
2318 default LEGACY_VSYSCALL_XONLY
2320 Legacy user code that does not know how to find the vDSO expects
2321 to be able to issue three syscalls by calling fixed addresses in
2322 kernel space. Since this location is not randomized with ASLR,
2323 it can be used to assist security vulnerability exploitation.
2325 This setting can be changed at boot time via the kernel command
2326 line parameter vsyscall=[emulate|xonly|none].
2328 On a system with recent enough glibc (2.14 or newer) and no
2329 static binaries, you can say None without a performance penalty
2330 to improve security.
2332 If unsure, select "Emulate execution only".
2334 config LEGACY_VSYSCALL_EMULATE
2335 bool "Full emulation"
2337 The kernel traps and emulates calls into the fixed vsyscall
2338 address mapping. This makes the mapping non-executable, but
2339 it still contains readable known contents, which could be
2340 used in certain rare security vulnerability exploits. This
2341 configuration is recommended when using legacy userspace
2342 that still uses vsyscalls along with legacy binary
2343 instrumentation tools that require code to be readable.
2345 An example of this type of legacy userspace is running
2346 Pin on an old binary that still uses vsyscalls.
2348 config LEGACY_VSYSCALL_XONLY
2349 bool "Emulate execution only"
2351 The kernel traps and emulates calls into the fixed vsyscall
2352 address mapping and does not allow reads. This
2353 configuration is recommended when userspace might use the
2354 legacy vsyscall area but support for legacy binary
2355 instrumentation of legacy code is not needed. It mitigates
2356 certain uses of the vsyscall area as an ASLR-bypassing
2359 config LEGACY_VSYSCALL_NONE
2362 There will be no vsyscall mapping at all. This will
2363 eliminate any risk of ASLR bypass due to the vsyscall
2364 fixed address mapping. Attempts to use the vsyscalls
2365 will be reported to dmesg, so that either old or
2366 malicious userspace programs can be identified.
2371 bool "Built-in kernel command line"
2373 Allow for specifying boot arguments to the kernel at
2374 build time. On some systems (e.g. embedded ones), it is
2375 necessary or convenient to provide some or all of the
2376 kernel boot arguments with the kernel itself (that is,
2377 to not rely on the boot loader to provide them.)
2379 To compile command line arguments into the kernel,
2380 set this option to 'Y', then fill in the
2381 boot arguments in CONFIG_CMDLINE.
2383 Systems with fully functional boot loaders (i.e. non-embedded)
2384 should leave this option set to 'N'.
2387 string "Built-in kernel command string"
2388 depends on CMDLINE_BOOL
2391 Enter arguments here that should be compiled into the kernel
2392 image and used at boot time. If the boot loader provides a
2393 command line at boot time, it is appended to this string to
2394 form the full kernel command line, when the system boots.
2396 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2397 change this behavior.
2399 In most cases, the command line (whether built-in or provided
2400 by the boot loader) should specify the device for the root
2403 config CMDLINE_OVERRIDE
2404 bool "Built-in command line overrides boot loader arguments"
2405 depends on CMDLINE_BOOL && CMDLINE != ""
2407 Set this option to 'Y' to have the kernel ignore the boot loader
2408 command line, and use ONLY the built-in command line.
2410 This is used to work around broken boot loaders. This should
2411 be set to 'N' under normal conditions.
2413 config MODIFY_LDT_SYSCALL
2414 bool "Enable the LDT (local descriptor table)" if EXPERT
2417 Linux can allow user programs to install a per-process x86
2418 Local Descriptor Table (LDT) using the modify_ldt(2) system
2419 call. This is required to run 16-bit or segmented code such as
2420 DOSEMU or some Wine programs. It is also used by some very old
2421 threading libraries.
2423 Enabling this feature adds a small amount of overhead to
2424 context switches and increases the low-level kernel attack
2425 surface. Disabling it removes the modify_ldt(2) system call.
2427 Saying 'N' here may make sense for embedded or server kernels.
2429 source "kernel/livepatch/Kconfig"
2433 config ARCH_HAS_ADD_PAGES
2435 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2437 config ARCH_ENABLE_MEMORY_HOTPLUG
2439 depends on X86_64 || (X86_32 && HIGHMEM)
2441 config ARCH_ENABLE_MEMORY_HOTREMOVE
2443 depends on MEMORY_HOTPLUG
2445 config USE_PERCPU_NUMA_NODE_ID
2449 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2451 depends on X86_64 || X86_PAE
2453 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2455 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2457 config ARCH_ENABLE_THP_MIGRATION
2459 depends on X86_64 && TRANSPARENT_HUGEPAGE
2461 menu "Power management and ACPI options"
2463 config ARCH_HIBERNATION_HEADER
2465 depends on HIBERNATION
2467 source "kernel/power/Kconfig"
2469 source "drivers/acpi/Kconfig"
2471 source "drivers/sfi/Kconfig"
2478 tristate "APM (Advanced Power Management) BIOS support"
2479 depends on X86_32 && PM_SLEEP
2481 APM is a BIOS specification for saving power using several different
2482 techniques. This is mostly useful for battery powered laptops with
2483 APM compliant BIOSes. If you say Y here, the system time will be
2484 reset after a RESUME operation, the /proc/apm device will provide
2485 battery status information, and user-space programs will receive
2486 notification of APM "events" (e.g. battery status change).
2488 If you select "Y" here, you can disable actual use of the APM
2489 BIOS by passing the "apm=off" option to the kernel at boot time.
2491 Note that the APM support is almost completely disabled for
2492 machines with more than one CPU.
2494 In order to use APM, you will need supporting software. For location
2495 and more information, read <file:Documentation/power/apm-acpi.rst>
2496 and the Battery Powered Linux mini-HOWTO, available from
2497 <http://www.tldp.org/docs.html#howto>.
2499 This driver does not spin down disk drives (see the hdparm(8)
2500 manpage ("man 8 hdparm") for that), and it doesn't turn off
2501 VESA-compliant "green" monitors.
2503 This driver does not support the TI 4000M TravelMate and the ACER
2504 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2505 desktop machines also don't have compliant BIOSes, and this driver
2506 may cause those machines to panic during the boot phase.
2508 Generally, if you don't have a battery in your machine, there isn't
2509 much point in using this driver and you should say N. If you get
2510 random kernel OOPSes or reboots that don't seem to be related to
2511 anything, try disabling/enabling this option (or disabling/enabling
2514 Some other things you should try when experiencing seemingly random,
2517 1) make sure that you have enough swap space and that it is
2519 2) pass the "no-hlt" option to the kernel
2520 3) switch on floating point emulation in the kernel and pass
2521 the "no387" option to the kernel
2522 4) pass the "floppy=nodma" option to the kernel
2523 5) pass the "mem=4M" option to the kernel (thereby disabling
2524 all but the first 4 MB of RAM)
2525 6) make sure that the CPU is not over clocked.
2526 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2527 8) disable the cache from your BIOS settings
2528 9) install a fan for the video card or exchange video RAM
2529 10) install a better fan for the CPU
2530 11) exchange RAM chips
2531 12) exchange the motherboard.
2533 To compile this driver as a module, choose M here: the
2534 module will be called apm.
2538 config APM_IGNORE_USER_SUSPEND
2539 bool "Ignore USER SUSPEND"
2541 This option will ignore USER SUSPEND requests. On machines with a
2542 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2543 series notebooks, it is necessary to say Y because of a BIOS bug.
2545 config APM_DO_ENABLE
2546 bool "Enable PM at boot time"
2548 Enable APM features at boot time. From page 36 of the APM BIOS
2549 specification: "When disabled, the APM BIOS does not automatically
2550 power manage devices, enter the Standby State, enter the Suspend
2551 State, or take power saving steps in response to CPU Idle calls."
2552 This driver will make CPU Idle calls when Linux is idle (unless this
2553 feature is turned off -- see "Do CPU IDLE calls", below). This
2554 should always save battery power, but more complicated APM features
2555 will be dependent on your BIOS implementation. You may need to turn
2556 this option off if your computer hangs at boot time when using APM
2557 support, or if it beeps continuously instead of suspending. Turn
2558 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2559 T400CDT. This is off by default since most machines do fine without
2564 bool "Make CPU Idle calls when idle"
2566 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2567 On some machines, this can activate improved power savings, such as
2568 a slowed CPU clock rate, when the machine is idle. These idle calls
2569 are made after the idle loop has run for some length of time (e.g.,
2570 333 mS). On some machines, this will cause a hang at boot time or
2571 whenever the CPU becomes idle. (On machines with more than one CPU,
2572 this option does nothing.)
2574 config APM_DISPLAY_BLANK
2575 bool "Enable console blanking using APM"
2577 Enable console blanking using the APM. Some laptops can use this to
2578 turn off the LCD backlight when the screen blanker of the Linux
2579 virtual console blanks the screen. Note that this is only used by
2580 the virtual console screen blanker, and won't turn off the backlight
2581 when using the X Window system. This also doesn't have anything to
2582 do with your VESA-compliant power-saving monitor. Further, this
2583 option doesn't work for all laptops -- it might not turn off your
2584 backlight at all, or it might print a lot of errors to the console,
2585 especially if you are using gpm.
2587 config APM_ALLOW_INTS
2588 bool "Allow interrupts during APM BIOS calls"
2590 Normally we disable external interrupts while we are making calls to
2591 the APM BIOS as a measure to lessen the effects of a badly behaving
2592 BIOS implementation. The BIOS should reenable interrupts if it
2593 needs to. Unfortunately, some BIOSes do not -- especially those in
2594 many of the newer IBM Thinkpads. If you experience hangs when you
2595 suspend, try setting this to Y. Otherwise, say N.
2599 source "drivers/cpufreq/Kconfig"
2601 source "drivers/cpuidle/Kconfig"
2603 source "drivers/idle/Kconfig"
2608 menu "Bus options (PCI etc.)"
2611 prompt "PCI access mode"
2612 depends on X86_32 && PCI
2615 On PCI systems, the BIOS can be used to detect the PCI devices and
2616 determine their configuration. However, some old PCI motherboards
2617 have BIOS bugs and may crash if this is done. Also, some embedded
2618 PCI-based systems don't have any BIOS at all. Linux can also try to
2619 detect the PCI hardware directly without using the BIOS.
2621 With this option, you can specify how Linux should detect the
2622 PCI devices. If you choose "BIOS", the BIOS will be used,
2623 if you choose "Direct", the BIOS won't be used, and if you
2624 choose "MMConfig", then PCI Express MMCONFIG will be used.
2625 If you choose "Any", the kernel will try MMCONFIG, then the
2626 direct access method and falls back to the BIOS if that doesn't
2627 work. If unsure, go with the default, which is "Any".
2632 config PCI_GOMMCONFIG
2649 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2651 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2654 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2657 bool "Support mmconfig PCI config space access" if X86_64
2659 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2660 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2664 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2668 depends on PCI && XEN
2671 config MMCONF_FAM10H
2673 depends on X86_64 && PCI_MMCONFIG && ACPI
2675 config PCI_CNB20LE_QUIRK
2676 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2679 Read the PCI windows out of the CNB20LE host bridge. This allows
2680 PCI hotplug to work on systems with the CNB20LE chipset which do
2683 There's no public spec for this chipset, and this functionality
2684 is known to be incomplete.
2686 You should say N unless you know you need this.
2689 bool "ISA bus support on modern systems" if EXPERT
2691 Expose ISA bus device drivers and options available for selection and
2692 configuration. Enable this option if your target machine has an ISA
2693 bus. ISA is an older system, displaced by PCI and newer bus
2694 architectures -- if your target machine is modern, it probably does
2695 not have an ISA bus.
2699 # x86_64 have no ISA slots, but can have ISA-style DMA.
2701 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2704 Enables ISA-style DMA support for devices requiring such controllers.
2712 Find out whether you have ISA slots on your motherboard. ISA is the
2713 name of a bus system, i.e. the way the CPU talks to the other stuff
2714 inside your box. Other bus systems are PCI, EISA, MicroChannel
2715 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2716 newer boards don't support it. If you have ISA, say Y, otherwise N.
2719 tristate "NatSemi SCx200 support"
2721 This provides basic support for National Semiconductor's
2722 (now AMD's) Geode processors. The driver probes for the
2723 PCI-IDs of several on-chip devices, so its a good dependency
2724 for other scx200_* drivers.
2726 If compiled as a module, the driver is named scx200.
2728 config SCx200HR_TIMER
2729 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2733 This driver provides a clocksource built upon the on-chip
2734 27MHz high-resolution timer. Its also a workaround for
2735 NSC Geode SC-1100's buggy TSC, which loses time when the
2736 processor goes idle (as is done by the scheduler). The
2737 other workaround is idle=poll boot option.
2740 bool "One Laptop Per Child support"
2748 Add support for detecting the unique features of the OLPC
2752 bool "OLPC XO-1 Power Management"
2753 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2755 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2758 bool "OLPC XO-1 Real Time Clock"
2759 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2761 Add support for the XO-1 real time clock, which can be used as a
2762 programmable wakeup source.
2765 bool "OLPC XO-1 SCI extras"
2766 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2770 Add support for SCI-based features of the OLPC XO-1 laptop:
2771 - EC-driven system wakeups
2775 - AC adapter status updates
2776 - Battery status updates
2778 config OLPC_XO15_SCI
2779 bool "OLPC XO-1.5 SCI extras"
2780 depends on OLPC && ACPI
2783 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2784 - EC-driven system wakeups
2785 - AC adapter status updates
2786 - Battery status updates
2789 bool "PCEngines ALIX System Support (LED setup)"
2792 This option enables system support for the PCEngines ALIX.
2793 At present this just sets up LEDs for GPIO control on
2794 ALIX2/3/6 boards. However, other system specific setup should
2797 Note: You must still enable the drivers for GPIO and LED support
2798 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2800 Note: You have to set alix.force=1 for boards with Award BIOS.
2803 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2806 This option enables system support for the Soekris Engineering net5501.
2809 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2813 This option enables system support for the Traverse Technologies GEOS.
2816 bool "Technologic Systems TS-5500 platform support"
2818 select CHECK_SIGNATURE
2822 This option enables system support for the Technologic Systems TS-5500.
2828 depends on CPU_SUP_AMD && PCI
2831 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2833 Firmwares often provide initial graphics framebuffers so the BIOS,
2834 bootloader or kernel can show basic video-output during boot for
2835 user-guidance and debugging. Historically, x86 used the VESA BIOS
2836 Extensions and EFI-framebuffers for this, which are mostly limited
2838 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2839 framebuffers so the new generic system-framebuffer drivers can be
2840 used on x86. If the framebuffer is not compatible with the generic
2841 modes, it is advertised as fallback platform framebuffer so legacy
2842 drivers like efifb, vesafb and uvesafb can pick it up.
2843 If this option is not selected, all system framebuffers are always
2844 marked as fallback platform framebuffers as usual.
2846 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2847 not be able to pick up generic system framebuffers if this option
2848 is selected. You are highly encouraged to enable simplefb as
2849 replacement if you select this option. simplefb can correctly deal
2850 with generic system framebuffers. But you should still keep vesafb
2851 and others enabled as fallback if a system framebuffer is
2852 incompatible with simplefb.
2859 menu "Binary Emulations"
2861 config IA32_EMULATION
2862 bool "IA32 Emulation"
2864 select ARCH_WANT_OLD_COMPAT_IPC
2866 select COMPAT_BINFMT_ELF
2867 select COMPAT_OLD_SIGACTION
2869 Include code to run legacy 32-bit programs under a
2870 64-bit kernel. You should likely turn this on, unless you're
2871 100% sure that you don't have any 32-bit programs left.
2874 tristate "IA32 a.out support"
2875 depends on IA32_EMULATION
2878 Support old a.out binaries in the 32bit emulation.
2881 bool "x32 ABI for 64-bit mode"
2884 Include code to run binaries for the x32 native 32-bit ABI
2885 for 64-bit processors. An x32 process gets access to the
2886 full 64-bit register file and wide data path while leaving
2887 pointers at 32 bits for smaller memory footprint.
2889 You will need a recent binutils (2.22 or later) with
2890 elf32_x86_64 support enabled to compile a kernel with this
2895 depends on IA32_EMULATION || X86_32
2897 select OLD_SIGSUSPEND3
2901 depends on IA32_EMULATION || X86_X32
2904 config COMPAT_FOR_U64_ALIGNMENT
2907 config SYSVIPC_COMPAT
2915 config HAVE_ATOMIC_IOMAP
2919 source "drivers/firmware/Kconfig"
2921 source "arch/x86/kvm/Kconfig"
2923 source "arch/x86/Kconfig.assembler"