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 HAVE_DEBUG_STACKOVERFLOW
18 select MODULES_USE_ELF_REL
20 select GENERIC_VDSO_32
25 # Options that are inherently 64-bit kernel only:
26 select ARCH_HAS_GIGANTIC_PAGE
27 select ARCH_SUPPORTS_INT128
28 select ARCH_USE_CMPXCHG_LOCKREF
29 select HAVE_ARCH_SOFT_DIRTY
30 select MODULES_USE_ELF_RELA
31 select NEED_DMA_MAP_STATE
33 select ARCH_HAS_SYSCALL_WRAPPER
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_DATA
61 select ARCH_CLOCKSOURCE_INIT
62 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
63 select ARCH_HAS_DEBUG_VIRTUAL
64 select ARCH_HAS_DEVMEM_IS_ALLOWED
65 select ARCH_HAS_ELF_RANDOMIZE
66 select ARCH_HAS_FAST_MULTIPLIER
67 select ARCH_HAS_FILTER_PGPROT
68 select ARCH_HAS_FORTIFY_SOURCE
69 select ARCH_HAS_GCOV_PROFILE_ALL
70 select ARCH_HAS_KCOV if X86_64
71 select ARCH_HAS_MEMBARRIER_SYNC_CORE
72 select ARCH_HAS_PMEM_API if X86_64
73 select ARCH_HAS_PTE_SPECIAL
74 select ARCH_HAS_REFCOUNT
75 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
76 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
77 select ARCH_HAS_SET_MEMORY
78 select ARCH_HAS_SET_DIRECT_MAP
79 select ARCH_HAS_STRICT_KERNEL_RWX
80 select ARCH_HAS_STRICT_MODULE_RWX
81 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
82 select ARCH_HAS_UBSAN_SANITIZE_ALL
83 select ARCH_HAS_ZONE_DEVICE if X86_64
84 select ARCH_HAVE_NMI_SAFE_CMPXCHG
85 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
86 select ARCH_MIGHT_HAVE_PC_PARPORT
87 select ARCH_MIGHT_HAVE_PC_SERIO
89 select ARCH_SUPPORTS_ACPI
90 select ARCH_SUPPORTS_ATOMIC_RMW
91 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
92 select ARCH_USE_BUILTIN_BSWAP
93 select ARCH_USE_QUEUED_RWLOCKS
94 select ARCH_USE_QUEUED_SPINLOCKS
95 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
96 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
97 select ARCH_WANTS_THP_SWAP if X86_64
98 select BUILDTIME_EXTABLE_SORT
100 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
101 select CLOCKSOURCE_WATCHDOG
102 select DCACHE_WORD_ACCESS
103 select EDAC_ATOMIC_SCRUB
105 select GENERIC_CLOCKEVENTS
106 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
107 select GENERIC_CLOCKEVENTS_MIN_ADJUST
108 select GENERIC_CMOS_UPDATE
109 select GENERIC_CPU_AUTOPROBE
110 select GENERIC_CPU_VULNERABILITIES
111 select GENERIC_EARLY_IOREMAP
112 select GENERIC_FIND_FIRST_BIT
114 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
115 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
116 select GENERIC_IRQ_MIGRATION if SMP
117 select GENERIC_IRQ_PROBE
118 select GENERIC_IRQ_RESERVATION_MODE
119 select GENERIC_IRQ_SHOW
120 select GENERIC_PENDING_IRQ if SMP
121 select GENERIC_SMP_IDLE_THREAD
122 select GENERIC_STRNCPY_FROM_USER
123 select GENERIC_STRNLEN_USER
124 select GENERIC_TIME_VSYSCALL
125 select GENERIC_GETTIMEOFDAY
126 select GUP_GET_PTE_LOW_HIGH if X86_PAE
127 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
128 select HAVE_ACPI_APEI if ACPI
129 select HAVE_ACPI_APEI_NMI if ACPI
130 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
131 select HAVE_ARCH_AUDITSYSCALL
132 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
133 select HAVE_ARCH_JUMP_LABEL
134 select HAVE_ARCH_JUMP_LABEL_RELATIVE
135 select HAVE_ARCH_KASAN if X86_64
136 select HAVE_ARCH_KGDB
137 select HAVE_ARCH_MMAP_RND_BITS if MMU
138 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
139 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
140 select HAVE_ARCH_PREL32_RELOCATIONS
141 select HAVE_ARCH_SECCOMP_FILTER
142 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
143 select HAVE_ARCH_STACKLEAK
144 select HAVE_ARCH_TRACEHOOK
145 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
146 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
147 select HAVE_ARCH_VMAP_STACK if X86_64
148 select HAVE_ARCH_WITHIN_STACK_FRAMES
149 select HAVE_CMPXCHG_DOUBLE
150 select HAVE_CMPXCHG_LOCAL
151 select HAVE_CONTEXT_TRACKING if X86_64
152 select HAVE_COPY_THREAD_TLS
153 select HAVE_C_RECORDMCOUNT
154 select HAVE_DEBUG_KMEMLEAK
155 select HAVE_DMA_CONTIGUOUS
156 select HAVE_DYNAMIC_FTRACE
157 select HAVE_DYNAMIC_FTRACE_WITH_REGS
159 select HAVE_EFFICIENT_UNALIGNED_ACCESS
161 select HAVE_EXIT_THREAD
163 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
164 select HAVE_FTRACE_MCOUNT_RECORD
165 select HAVE_FUNCTION_GRAPH_TRACER
166 select HAVE_FUNCTION_TRACER
167 select HAVE_GCC_PLUGINS
168 select HAVE_HW_BREAKPOINT
170 select HAVE_IOREMAP_PROT
171 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
172 select HAVE_IRQ_TIME_ACCOUNTING
173 select HAVE_KERNEL_BZIP2
174 select HAVE_KERNEL_GZIP
175 select HAVE_KERNEL_LZ4
176 select HAVE_KERNEL_LZMA
177 select HAVE_KERNEL_LZO
178 select HAVE_KERNEL_XZ
180 select HAVE_KPROBES_ON_FTRACE
181 select HAVE_FUNCTION_ERROR_INJECTION
182 select HAVE_KRETPROBES
184 select HAVE_LIVEPATCH if X86_64
185 select HAVE_MEMBLOCK_NODE_MAP
186 select HAVE_MIXED_BREAKPOINTS_REGS
187 select HAVE_MOD_ARCH_SPECIFIC
191 select HAVE_OPTPROBES
192 select HAVE_PCSPKR_PLATFORM
193 select HAVE_PERF_EVENTS
194 select HAVE_PERF_EVENTS_NMI
195 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
197 select HAVE_PERF_REGS
198 select HAVE_PERF_USER_STACK_DUMP
199 select HAVE_RCU_TABLE_FREE if PARAVIRT
200 select HAVE_REGS_AND_STACK_ACCESS_API
201 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
202 select HAVE_FUNCTION_ARG_ACCESS_API
203 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
204 select HAVE_STACK_VALIDATION if X86_64
206 select HAVE_SYSCALL_TRACEPOINTS
207 select HAVE_UNSTABLE_SCHED_CLOCK
208 select HAVE_USER_RETURN_NOTIFIER
209 select HAVE_GENERIC_VDSO
210 select HOTPLUG_SMT if SMP
211 select IRQ_FORCED_THREADING
212 select NEED_SG_DMA_LENGTH
213 select PCI_DOMAINS if PCI
214 select PCI_LOCKLESS_CONFIG if PCI
217 select RTC_MC146818_LIB
220 select SYSCTL_EXCEPTION_TRACE
221 select THREAD_INFO_IN_TASK
222 select USER_STACKTRACE_SUPPORT
224 select X86_FEATURE_NAMES if PROC_FS
225 select PROC_PID_ARCH_STATUS if PROC_FS
227 config INSTRUCTION_DECODER
229 depends on KPROBES || PERF_EVENTS || UPROBES
233 default "elf32-i386" if X86_32
234 default "elf64-x86-64" if X86_64
236 config ARCH_DEFCONFIG
238 default "arch/x86/configs/i386_defconfig" if X86_32
239 default "arch/x86/configs/x86_64_defconfig" if X86_64
241 config LOCKDEP_SUPPORT
244 config STACKTRACE_SUPPORT
250 config ARCH_MMAP_RND_BITS_MIN
254 config ARCH_MMAP_RND_BITS_MAX
258 config ARCH_MMAP_RND_COMPAT_BITS_MIN
261 config ARCH_MMAP_RND_COMPAT_BITS_MAX
267 config GENERIC_ISA_DMA
269 depends on ISA_DMA_API
274 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
276 config GENERIC_BUG_RELATIVE_POINTERS
279 config ARCH_MAY_HAVE_PC_FDC
281 depends on ISA_DMA_API
283 config GENERIC_CALIBRATE_DELAY
286 config ARCH_HAS_CPU_RELAX
289 config ARCH_HAS_CACHE_LINE_SIZE
292 config ARCH_HAS_FILTER_PGPROT
295 config HAVE_SETUP_PER_CPU_AREA
298 config NEED_PER_CPU_EMBED_FIRST_CHUNK
301 config NEED_PER_CPU_PAGE_FIRST_CHUNK
304 config ARCH_HIBERNATION_POSSIBLE
307 config ARCH_SUSPEND_POSSIBLE
310 config ARCH_WANT_HUGE_PMD_SHARE
313 config ARCH_WANT_GENERAL_HUGETLB
322 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
325 config KASAN_SHADOW_OFFSET
328 default 0xdffffc0000000000
330 config HAVE_INTEL_TXT
332 depends on INTEL_IOMMU && ACPI
336 depends on X86_32 && SMP
340 depends on X86_64 && SMP
342 config X86_32_LAZY_GS
344 depends on X86_32 && !STACKPROTECTOR
346 config ARCH_SUPPORTS_UPROBES
349 config FIX_EARLYCON_MEM
352 config DYNAMIC_PHYSICAL_MASK
355 config PGTABLE_LEVELS
357 default 5 if X86_5LEVEL
362 config CC_HAS_SANE_STACKPROTECTOR
364 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
365 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
367 We have to make sure stack protector is unconditionally disabled if
368 the compiler produces broken code.
370 menu "Processor type and features"
373 bool "DMA memory allocation support" if EXPERT
376 DMA memory allocation support allows devices with less than 32-bit
377 addressing to allocate within the first 16MB of address space.
378 Disable if no such devices will be used.
383 bool "Symmetric multi-processing support"
385 This enables support for systems with more than one CPU. If you have
386 a system with only one CPU, say N. If you have a system with more
389 If you say N here, the kernel will run on uni- and multiprocessor
390 machines, but will use only one CPU of a multiprocessor machine. If
391 you say Y here, the kernel will run on many, but not all,
392 uniprocessor machines. On a uniprocessor machine, the kernel
393 will run faster if you say N here.
395 Note that if you say Y here and choose architecture "586" or
396 "Pentium" under "Processor family", the kernel will not work on 486
397 architectures. Similarly, multiprocessor kernels for the "PPro"
398 architecture may not work on all Pentium based boards.
400 People using multiprocessor machines who say Y here should also say
401 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
402 Management" code will be disabled if you say Y here.
404 See also <file:Documentation/x86/i386/IO-APIC.rst>,
405 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
406 <http://www.tldp.org/docs.html#howto>.
408 If you don't know what to do here, say N.
410 config X86_FEATURE_NAMES
411 bool "Processor feature human-readable names" if EMBEDDED
414 This option compiles in a table of x86 feature bits and corresponding
415 names. This is required to support /proc/cpuinfo and a few kernel
416 messages. You can disable this to save space, at the expense of
417 making those few kernel messages show numeric feature bits instead.
422 bool "Support x2apic"
423 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
425 This enables x2apic support on CPUs that have this feature.
427 This allows 32-bit apic IDs (so it can support very large systems),
428 and accesses the local apic via MSRs not via mmio.
430 If you don't know what to do here, say N.
433 bool "Enable MPS table" if ACPI || SFI
435 depends on X86_LOCAL_APIC
437 For old smp systems that do not have proper acpi support. Newer systems
438 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
442 depends on X86_GOLDFISH
445 bool "Avoid speculative indirect branches in kernel"
447 select STACK_VALIDATION if HAVE_STACK_VALIDATION
449 Compile kernel with the retpoline compiler options to guard against
450 kernel-to-user data leaks by avoiding speculative indirect
451 branches. Requires a compiler with -mindirect-branch=thunk-extern
452 support for full protection. The kernel may run slower.
454 config X86_CPU_RESCTRL
455 bool "x86 CPU resource control support"
456 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
459 Enable x86 CPU resource control support.
461 Provide support for the allocation and monitoring of system resources
464 Intel calls this Intel Resource Director Technology
465 (Intel(R) RDT). More information about RDT can be found in the
466 Intel x86 Architecture Software Developer Manual.
468 AMD calls this AMD Platform Quality of Service (AMD QoS).
469 More information about AMD QoS can be found in the AMD64 Technology
470 Platform Quality of Service Extensions manual.
476 bool "Support for big SMP systems with more than 8 CPUs"
479 This option is needed for the systems that have more than 8 CPUs
481 config X86_EXTENDED_PLATFORM
482 bool "Support for extended (non-PC) x86 platforms"
485 If you disable this option then the kernel will only support
486 standard PC platforms. (which covers the vast majority of
489 If you enable this option then you'll be able to select support
490 for the following (non-PC) 32 bit x86 platforms:
491 Goldfish (Android emulator)
494 SGI 320/540 (Visual Workstation)
495 STA2X11-based (e.g. Northville)
496 Moorestown MID devices
498 If you have one of these systems, or if you want to build a
499 generic distribution kernel, say Y here - otherwise say N.
503 config X86_EXTENDED_PLATFORM
504 bool "Support for extended (non-PC) x86 platforms"
507 If you disable this option then the kernel will only support
508 standard PC platforms. (which covers the vast majority of
511 If you enable this option then you'll be able to select support
512 for the following (non-PC) 64 bit x86 platforms:
517 If you have one of these systems, or if you want to build a
518 generic distribution kernel, say Y here - otherwise say N.
520 # This is an alphabetically sorted list of 64 bit extended platforms
521 # Please maintain the alphabetic order if and when there are additions
523 bool "Numascale NumaChip"
525 depends on X86_EXTENDED_PLATFORM
528 depends on X86_X2APIC
529 depends on PCI_MMCONFIG
531 Adds support for Numascale NumaChip large-SMP systems. Needed to
532 enable more than ~168 cores.
533 If you don't have one of these, you should say N here.
537 select HYPERVISOR_GUEST
539 depends on X86_64 && PCI
540 depends on X86_EXTENDED_PLATFORM
543 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
544 supposed to run on these EM64T-based machines. Only choose this option
545 if you have one of these machines.
548 bool "SGI Ultraviolet"
550 depends on X86_EXTENDED_PLATFORM
553 depends on X86_X2APIC
556 This option is needed in order to support SGI Ultraviolet systems.
557 If you don't have one of these, you should say N here.
559 # Following is an alphabetically sorted list of 32 bit extended platforms
560 # Please maintain the alphabetic order if and when there are additions
563 bool "Goldfish (Virtual Platform)"
564 depends on X86_EXTENDED_PLATFORM
566 Enable support for the Goldfish virtual platform used primarily
567 for Android development. Unless you are building for the Android
568 Goldfish emulator say N here.
571 bool "CE4100 TV platform"
573 depends on PCI_GODIRECT
574 depends on X86_IO_APIC
576 depends on X86_EXTENDED_PLATFORM
577 select X86_REBOOTFIXUPS
579 select OF_EARLY_FLATTREE
581 Select for the Intel CE media processor (CE4100) SOC.
582 This option compiles in support for the CE4100 SOC for settop
583 boxes and media devices.
586 bool "Intel MID platform support"
587 depends on X86_EXTENDED_PLATFORM
588 depends on X86_PLATFORM_DEVICES
590 depends on X86_64 || (PCI_GOANY && X86_32)
591 depends on X86_IO_APIC
597 select MFD_INTEL_MSIC
599 Select to build a kernel capable of supporting Intel MID (Mobile
600 Internet Device) platform systems which do not have the PCI legacy
601 interfaces. If you are building for a PC class system say N here.
603 Intel MID platforms are based on an Intel processor and chipset which
604 consume less power than most of the x86 derivatives.
606 config X86_INTEL_QUARK
607 bool "Intel Quark platform support"
609 depends on X86_EXTENDED_PLATFORM
610 depends on X86_PLATFORM_DEVICES
614 depends on X86_IO_APIC
619 Select to include support for Quark X1000 SoC.
620 Say Y here if you have a Quark based system such as the Arduino
621 compatible Intel Galileo.
623 config X86_INTEL_LPSS
624 bool "Intel Low Power Subsystem Support"
625 depends on X86 && ACPI && PCI
630 Select to build support for Intel Low Power Subsystem such as
631 found on Intel Lynxpoint PCH. Selecting this option enables
632 things like clock tree (common clock framework) and pincontrol
633 which are needed by the LPSS peripheral drivers.
635 config X86_AMD_PLATFORM_DEVICE
636 bool "AMD ACPI2Platform devices support"
641 Select to interpret AMD specific ACPI device to platform device
642 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
643 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
644 implemented under PINCTRL subsystem.
647 tristate "Intel SoC IOSF Sideband support for SoC platforms"
650 This option enables sideband register access support for Intel SoC
651 platforms. On these platforms the IOSF sideband is used in lieu of
652 MSR's for some register accesses, mostly but not limited to thermal
653 and power. Drivers may query the availability of this device to
654 determine if they need the sideband in order to work on these
655 platforms. The sideband is available on the following SoC products.
656 This list is not meant to be exclusive.
661 You should say Y if you are running a kernel on one of these SoC's.
663 config IOSF_MBI_DEBUG
664 bool "Enable IOSF sideband access through debugfs"
665 depends on IOSF_MBI && DEBUG_FS
667 Select this option to expose the IOSF sideband access registers (MCR,
668 MDR, MCRX) through debugfs to write and read register information from
669 different units on the SoC. This is most useful for obtaining device
670 state information for debug and analysis. As this is a general access
671 mechanism, users of this option would have specific knowledge of the
672 device they want to access.
674 If you don't require the option or are in doubt, say N.
677 bool "RDC R-321x SoC"
679 depends on X86_EXTENDED_PLATFORM
681 select X86_REBOOTFIXUPS
683 This option is needed for RDC R-321x system-on-chip, also known
685 If you don't have one of these chips, you should say N here.
687 config X86_32_NON_STANDARD
688 bool "Support non-standard 32-bit SMP architectures"
689 depends on X86_32 && SMP
690 depends on X86_EXTENDED_PLATFORM
692 This option compiles in the bigsmp and STA2X11 default
693 subarchitectures. It is intended for a generic binary
694 kernel. If you select them all, kernel will probe it one by
695 one and will fallback to default.
697 # Alphabetically sorted list of Non standard 32 bit platforms
699 config X86_SUPPORTS_MEMORY_FAILURE
701 # MCE code calls memory_failure():
703 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
704 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
705 depends on X86_64 || !SPARSEMEM
706 select ARCH_SUPPORTS_MEMORY_FAILURE
709 bool "STA2X11 Companion Chip Support"
710 depends on X86_32_NON_STANDARD && PCI
711 select ARCH_HAS_PHYS_TO_DMA
716 This adds support for boards based on the STA2X11 IO-Hub,
717 a.k.a. "ConneXt". The chip is used in place of the standard
718 PC chipset, so all "standard" peripherals are missing. If this
719 option is selected the kernel will still be able to boot on
720 standard PC machines.
723 tristate "Eurobraille/Iris poweroff module"
726 The Iris machines from EuroBraille do not have APM or ACPI support
727 to shut themselves down properly. A special I/O sequence is
728 needed to do so, which is what this module does at
731 This is only for Iris machines from EuroBraille.
735 config SCHED_OMIT_FRAME_POINTER
737 prompt "Single-depth WCHAN output"
740 Calculate simpler /proc/<PID>/wchan values. If this option
741 is disabled then wchan values will recurse back to the
742 caller function. This provides more accurate wchan values,
743 at the expense of slightly more scheduling overhead.
745 If in doubt, say "Y".
747 menuconfig HYPERVISOR_GUEST
748 bool "Linux guest support"
750 Say Y here to enable options for running Linux under various hyper-
751 visors. This option enables basic hypervisor detection and platform
754 If you say N, all options in this submenu will be skipped and
755 disabled, and Linux guest support won't be built in.
760 bool "Enable paravirtualization code"
762 This changes the kernel so it can modify itself when it is run
763 under a hypervisor, potentially improving performance significantly
764 over full virtualization. However, when run without a hypervisor
765 the kernel is theoretically slower and slightly larger.
770 config PARAVIRT_DEBUG
771 bool "paravirt-ops debugging"
772 depends on PARAVIRT && DEBUG_KERNEL
774 Enable to debug paravirt_ops internals. Specifically, BUG if
775 a paravirt_op is missing when it is called.
777 config PARAVIRT_SPINLOCKS
778 bool "Paravirtualization layer for spinlocks"
779 depends on PARAVIRT && SMP
781 Paravirtualized spinlocks allow a pvops backend to replace the
782 spinlock implementation with something virtualization-friendly
783 (for example, block the virtual CPU rather than spinning).
785 It has a minimal impact on native kernels and gives a nice performance
786 benefit on paravirtualized KVM / Xen kernels.
788 If you are unsure how to answer this question, answer Y.
790 config X86_HV_CALLBACK_VECTOR
793 source "arch/x86/xen/Kconfig"
796 bool "KVM Guest support (including kvmclock)"
798 select PARAVIRT_CLOCK
801 This option enables various optimizations for running under the KVM
802 hypervisor. It includes a paravirtualized clock, so that instead
803 of relying on a PIT (or probably other) emulation by the
804 underlying device model, the host provides the guest with
805 timing infrastructure such as time of day, and system time
808 bool "Support for running PVH guests"
810 This option enables the PVH entry point for guest virtual machines
811 as specified in the x86/HVM direct boot ABI.
814 bool "Enable debug information for KVM Guests in debugfs"
815 depends on KVM_GUEST && DEBUG_FS
817 This option enables collection of various statistics for KVM guest.
818 Statistics are displayed in debugfs filesystem. Enabling this option
819 may incur significant overhead.
821 config PARAVIRT_TIME_ACCOUNTING
822 bool "Paravirtual steal time accounting"
825 Select this option to enable fine granularity task steal time
826 accounting. Time spent executing other tasks in parallel with
827 the current vCPU is discounted from the vCPU power. To account for
828 that, there can be a small performance impact.
830 If in doubt, say N here.
832 config PARAVIRT_CLOCK
835 config JAILHOUSE_GUEST
836 bool "Jailhouse non-root cell support"
837 depends on X86_64 && PCI
840 This option allows to run Linux as guest in a Jailhouse non-root
841 cell. You can leave this option disabled if you only want to start
842 Jailhouse and run Linux afterwards in the root cell.
845 bool "ACRN Guest support"
847 select X86_HV_CALLBACK_VECTOR
849 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
850 a flexible, lightweight reference open-source hypervisor, built with
851 real-time and safety-criticality in mind. It is built for embedded
852 IOT with small footprint and real-time features. More details can be
853 found in https://projectacrn.org/.
855 endif #HYPERVISOR_GUEST
857 source "arch/x86/Kconfig.cpu"
861 prompt "HPET Timer Support" if X86_32
863 Use the IA-PC HPET (High Precision Event Timer) to manage
864 time in preference to the PIT and RTC, if a HPET is
866 HPET is the next generation timer replacing legacy 8254s.
867 The HPET provides a stable time base on SMP
868 systems, unlike the TSC, but it is more expensive to access,
869 as it is off-chip. The interface used is documented
870 in the HPET spec, revision 1.
872 You can safely choose Y here. However, HPET will only be
873 activated if the platform and the BIOS support this feature.
874 Otherwise the 8254 will be used for timing services.
876 Choose N to continue using the legacy 8254 timer.
878 config HPET_EMULATE_RTC
880 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
883 def_bool y if X86_INTEL_MID
884 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
886 depends on X86_INTEL_MID && SFI
888 APB timer is the replacement for 8254, HPET on X86 MID platforms.
889 The APBT provides a stable time base on SMP
890 systems, unlike the TSC, but it is more expensive to access,
891 as it is off-chip. APB timers are always running regardless of CPU
892 C states, they are used as per CPU clockevent device when possible.
894 # Mark as expert because too many people got it wrong.
895 # The code disables itself when not needed.
898 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
899 bool "Enable DMI scanning" if EXPERT
901 Enabled scanning of DMI to identify machine quirks. Say Y
902 here unless you have verified that your setup is not
903 affected by entries in the DMI blacklist. Required by PNP
907 bool "Old AMD GART IOMMU support"
910 depends on X86_64 && PCI && AMD_NB
912 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
913 GART based hardware IOMMUs.
915 The GART supports full DMA access for devices with 32-bit access
916 limitations, on systems with more than 3 GB. This is usually needed
917 for USB, sound, many IDE/SATA chipsets and some other devices.
919 Newer systems typically have a modern AMD IOMMU, supported via
920 the CONFIG_AMD_IOMMU=y config option.
922 In normal configurations this driver is only active when needed:
923 there's more than 3 GB of memory and the system contains a
924 32-bit limited device.
929 bool "IBM Calgary IOMMU support"
932 depends on X86_64 && PCI
934 Support for hardware IOMMUs in IBM's xSeries x366 and x460
935 systems. Needed to run systems with more than 3GB of memory
936 properly with 32-bit PCI devices that do not support DAC
937 (Double Address Cycle). Calgary also supports bus level
938 isolation, where all DMAs pass through the IOMMU. This
939 prevents them from going anywhere except their intended
940 destination. This catches hard-to-find kernel bugs and
941 mis-behaving drivers and devices that do not use the DMA-API
942 properly to set up their DMA buffers. The IOMMU can be
943 turned off at boot time with the iommu=off parameter.
944 Normally the kernel will make the right choice by itself.
947 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
949 prompt "Should Calgary be enabled by default?"
950 depends on CALGARY_IOMMU
952 Should Calgary be enabled by default? if you choose 'y', Calgary
953 will be used (if it exists). If you choose 'n', Calgary will not be
954 used even if it exists. If you choose 'n' and would like to use
955 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
959 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
960 depends on X86_64 && SMP && DEBUG_KERNEL
961 select CPUMASK_OFFSTACK
963 Enable maximum number of CPUS and NUMA Nodes for this architecture.
967 # The maximum number of CPUs supported:
969 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
970 # and which can be configured interactively in the
971 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
973 # The ranges are different on 32-bit and 64-bit kernels, depending on
974 # hardware capabilities and scalability features of the kernel.
976 # ( If MAXSMP is enabled we just use the highest possible value and disable
977 # interactive configuration. )
980 config NR_CPUS_RANGE_BEGIN
982 default NR_CPUS_RANGE_END if MAXSMP
986 config NR_CPUS_RANGE_END
989 default 64 if SMP && X86_BIGSMP
990 default 8 if SMP && !X86_BIGSMP
993 config NR_CPUS_RANGE_END
996 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
997 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
1000 config NR_CPUS_DEFAULT
1003 default 32 if X86_BIGSMP
1007 config NR_CPUS_DEFAULT
1010 default 8192 if MAXSMP
1015 int "Maximum number of CPUs" if SMP && !MAXSMP
1016 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1017 default NR_CPUS_DEFAULT
1019 This allows you to specify the maximum number of CPUs which this
1020 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1021 supported value is 8192, otherwise the maximum value is 512. The
1022 minimum value which makes sense is 2.
1024 This is purely to save memory: each supported CPU adds about 8KB
1025 to the kernel image.
1032 prompt "Multi-core scheduler support"
1035 Multi-core scheduler support improves the CPU scheduler's decision
1036 making when dealing with multi-core CPU chips at a cost of slightly
1037 increased overhead in some places. If unsure say N here.
1039 config SCHED_MC_PRIO
1040 bool "CPU core priorities scheduler support"
1041 depends on SCHED_MC && CPU_SUP_INTEL
1042 select X86_INTEL_PSTATE
1046 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1047 core ordering determined at manufacturing time, which allows
1048 certain cores to reach higher turbo frequencies (when running
1049 single threaded workloads) than others.
1051 Enabling this kernel feature teaches the scheduler about
1052 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1053 scheduler's CPU selection logic accordingly, so that higher
1054 overall system performance can be achieved.
1056 This feature will have no effect on CPUs without this feature.
1058 If unsure say Y here.
1062 depends on !SMP && X86_LOCAL_APIC
1065 bool "Local APIC support on uniprocessors" if !PCI_MSI
1067 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1069 A local APIC (Advanced Programmable Interrupt Controller) is an
1070 integrated interrupt controller in the CPU. If you have a single-CPU
1071 system which has a processor with a local APIC, you can say Y here to
1072 enable and use it. If you say Y here even though your machine doesn't
1073 have a local APIC, then the kernel will still run with no slowdown at
1074 all. The local APIC supports CPU-generated self-interrupts (timer,
1075 performance counters), and the NMI watchdog which detects hard
1078 config X86_UP_IOAPIC
1079 bool "IO-APIC support on uniprocessors"
1080 depends on X86_UP_APIC
1082 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1083 SMP-capable replacement for PC-style interrupt controllers. Most
1084 SMP systems and many recent uniprocessor systems have one.
1086 If you have a single-CPU system with an IO-APIC, you can say Y here
1087 to use it. If you say Y here even though your machine doesn't have
1088 an IO-APIC, then the kernel will still run with no slowdown at all.
1090 config X86_LOCAL_APIC
1092 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1093 select IRQ_DOMAIN_HIERARCHY
1094 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1098 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1100 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1101 bool "Reroute for broken boot IRQs"
1102 depends on X86_IO_APIC
1104 This option enables a workaround that fixes a source of
1105 spurious interrupts. This is recommended when threaded
1106 interrupt handling is used on systems where the generation of
1107 superfluous "boot interrupts" cannot be disabled.
1109 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1110 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1111 kernel does during interrupt handling). On chipsets where this
1112 boot IRQ generation cannot be disabled, this workaround keeps
1113 the original IRQ line masked so that only the equivalent "boot
1114 IRQ" is delivered to the CPUs. The workaround also tells the
1115 kernel to set up the IRQ handler on the boot IRQ line. In this
1116 way only one interrupt is delivered to the kernel. Otherwise
1117 the spurious second interrupt may cause the kernel to bring
1118 down (vital) interrupt lines.
1120 Only affects "broken" chipsets. Interrupt sharing may be
1121 increased on these systems.
1124 bool "Machine Check / overheating reporting"
1125 select GENERIC_ALLOCATOR
1128 Machine Check support allows the processor to notify the
1129 kernel if it detects a problem (e.g. overheating, data corruption).
1130 The action the kernel takes depends on the severity of the problem,
1131 ranging from warning messages to halting the machine.
1133 config X86_MCELOG_LEGACY
1134 bool "Support for deprecated /dev/mcelog character device"
1137 Enable support for /dev/mcelog which is needed by the old mcelog
1138 userspace logging daemon. Consider switching to the new generation
1141 config X86_MCE_INTEL
1143 prompt "Intel MCE features"
1144 depends on X86_MCE && X86_LOCAL_APIC
1146 Additional support for intel specific MCE features such as
1147 the thermal monitor.
1151 prompt "AMD MCE features"
1152 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1154 Additional support for AMD specific MCE features such as
1155 the DRAM Error Threshold.
1157 config X86_ANCIENT_MCE
1158 bool "Support for old Pentium 5 / WinChip machine checks"
1159 depends on X86_32 && X86_MCE
1161 Include support for machine check handling on old Pentium 5 or WinChip
1162 systems. These typically need to be enabled explicitly on the command
1165 config X86_MCE_THRESHOLD
1166 depends on X86_MCE_AMD || X86_MCE_INTEL
1169 config X86_MCE_INJECT
1170 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1171 tristate "Machine check injector support"
1173 Provide support for injecting machine checks for testing purposes.
1174 If you don't know what a machine check is and you don't do kernel
1175 QA it is safe to say n.
1177 config X86_THERMAL_VECTOR
1179 depends on X86_MCE_INTEL
1181 source "arch/x86/events/Kconfig"
1183 config X86_LEGACY_VM86
1184 bool "Legacy VM86 support"
1187 This option allows user programs to put the CPU into V8086
1188 mode, which is an 80286-era approximation of 16-bit real mode.
1190 Some very old versions of X and/or vbetool require this option
1191 for user mode setting. Similarly, DOSEMU will use it if
1192 available to accelerate real mode DOS programs. However, any
1193 recent version of DOSEMU, X, or vbetool should be fully
1194 functional even without kernel VM86 support, as they will all
1195 fall back to software emulation. Nevertheless, if you are using
1196 a 16-bit DOS program where 16-bit performance matters, vm86
1197 mode might be faster than emulation and you might want to
1200 Note that any app that works on a 64-bit kernel is unlikely to
1201 need this option, as 64-bit kernels don't, and can't, support
1202 V8086 mode. This option is also unrelated to 16-bit protected
1203 mode and is not needed to run most 16-bit programs under Wine.
1205 Enabling this option increases the complexity of the kernel
1206 and slows down exception handling a tiny bit.
1208 If unsure, say N here.
1212 default X86_LEGACY_VM86
1215 bool "Enable support for 16-bit segments" if EXPERT
1217 depends on MODIFY_LDT_SYSCALL
1219 This option is required by programs like Wine to run 16-bit
1220 protected mode legacy code on x86 processors. Disabling
1221 this option saves about 300 bytes on i386, or around 6K text
1222 plus 16K runtime memory on x86-64,
1226 depends on X86_16BIT && X86_32
1230 depends on X86_16BIT && X86_64
1232 config X86_VSYSCALL_EMULATION
1233 bool "Enable vsyscall emulation" if EXPERT
1237 This enables emulation of the legacy vsyscall page. Disabling
1238 it is roughly equivalent to booting with vsyscall=none, except
1239 that it will also disable the helpful warning if a program
1240 tries to use a vsyscall. With this option set to N, offending
1241 programs will just segfault, citing addresses of the form
1244 This option is required by many programs built before 2013, and
1245 care should be used even with newer programs if set to N.
1247 Disabling this option saves about 7K of kernel size and
1248 possibly 4K of additional runtime pagetable memory.
1251 tristate "Toshiba Laptop support"
1254 This adds a driver to safely access the System Management Mode of
1255 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1256 not work on models with a Phoenix BIOS. The System Management Mode
1257 is used to set the BIOS and power saving options on Toshiba portables.
1259 For information on utilities to make use of this driver see the
1260 Toshiba Linux utilities web site at:
1261 <http://www.buzzard.org.uk/toshiba/>.
1263 Say Y if you intend to run this kernel on a Toshiba portable.
1267 tristate "Dell i8k legacy laptop support"
1269 select SENSORS_DELL_SMM
1271 This option enables legacy /proc/i8k userspace interface in hwmon
1272 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1273 temperature and allows controlling fan speeds of Dell laptops via
1274 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1275 it reports also power and hotkey status. For fan speed control is
1276 needed userspace package i8kutils.
1278 Say Y if you intend to run this kernel on old Dell laptops or want to
1279 use userspace package i8kutils.
1282 config X86_REBOOTFIXUPS
1283 bool "Enable X86 board specific fixups for reboot"
1286 This enables chipset and/or board specific fixups to be done
1287 in order to get reboot to work correctly. This is only needed on
1288 some combinations of hardware and BIOS. The symptom, for which
1289 this config is intended, is when reboot ends with a stalled/hung
1292 Currently, the only fixup is for the Geode machines using
1293 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1295 Say Y if you want to enable the fixup. Currently, it's safe to
1296 enable this option even if you don't need it.
1300 bool "CPU microcode loading support"
1302 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
1327 This options enables microcode patch loading support for Intel
1330 For the current Intel microcode data package go to
1331 <https://downloadcenter.intel.com> and search for
1332 'Linux Processor Microcode Data File'.
1334 config MICROCODE_AMD
1335 bool "AMD microcode loading support"
1336 depends on MICROCODE
1339 If you select this option, microcode patch loading support for AMD
1340 processors will be enabled.
1342 config MICROCODE_OLD_INTERFACE
1343 bool "Ancient loading interface (DEPRECATED)"
1345 depends on MICROCODE
1347 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1348 which was used by userspace tools like iucode_tool and microcode.ctl.
1349 It is inadequate because it runs too late to be able to properly
1350 load microcode on a machine and it needs special tools. Instead, you
1351 should've switched to the early loading method with the initrd or
1352 builtin microcode by now: Documentation/x86/microcode.rst
1355 tristate "/dev/cpu/*/msr - Model-specific register support"
1357 This device gives privileged processes access to the x86
1358 Model-Specific Registers (MSRs). It is a character device with
1359 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1360 MSR accesses are directed to a specific CPU on multi-processor
1364 tristate "/dev/cpu/*/cpuid - CPU information support"
1366 This device gives processes access to the x86 CPUID instruction to
1367 be executed on a specific processor. It is a character device
1368 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1372 prompt "High Memory Support"
1379 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1380 However, the address space of 32-bit x86 processors is only 4
1381 Gigabytes large. That means that, if you have a large amount of
1382 physical memory, not all of it can be "permanently mapped" by the
1383 kernel. The physical memory that's not permanently mapped is called
1386 If you are compiling a kernel which will never run on a machine with
1387 more than 1 Gigabyte total physical RAM, answer "off" here (default
1388 choice and suitable for most users). This will result in a "3GB/1GB"
1389 split: 3GB are mapped so that each process sees a 3GB virtual memory
1390 space and the remaining part of the 4GB virtual memory space is used
1391 by the kernel to permanently map as much physical memory as
1394 If the machine has between 1 and 4 Gigabytes physical RAM, then
1397 If more than 4 Gigabytes is used then answer "64GB" here. This
1398 selection turns Intel PAE (Physical Address Extension) mode on.
1399 PAE implements 3-level paging on IA32 processors. PAE is fully
1400 supported by Linux, PAE mode is implemented on all recent Intel
1401 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1402 then the kernel will not boot on CPUs that don't support PAE!
1404 The actual amount of total physical memory will either be
1405 auto detected or can be forced by using a kernel command line option
1406 such as "mem=256M". (Try "man bootparam" or see the documentation of
1407 your boot loader (lilo or loadlin) about how to pass options to the
1408 kernel at boot time.)
1410 If unsure, say "off".
1415 Select this if you have a 32-bit processor and between 1 and 4
1416 gigabytes of physical RAM.
1420 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1423 Select this if you have a 32-bit processor and more than 4
1424 gigabytes of physical RAM.
1429 prompt "Memory split" if EXPERT
1433 Select the desired split between kernel and user memory.
1435 If the address range available to the kernel is less than the
1436 physical memory installed, the remaining memory will be available
1437 as "high memory". Accessing high memory is a little more costly
1438 than low memory, as it needs to be mapped into the kernel first.
1439 Note that increasing the kernel address space limits the range
1440 available to user programs, making the address space there
1441 tighter. Selecting anything other than the default 3G/1G split
1442 will also likely make your kernel incompatible with binary-only
1445 If you are not absolutely sure what you are doing, leave this
1449 bool "3G/1G user/kernel split"
1450 config VMSPLIT_3G_OPT
1452 bool "3G/1G user/kernel split (for full 1G low memory)"
1454 bool "2G/2G user/kernel split"
1455 config VMSPLIT_2G_OPT
1457 bool "2G/2G user/kernel split (for full 2G low memory)"
1459 bool "1G/3G user/kernel split"
1464 default 0xB0000000 if VMSPLIT_3G_OPT
1465 default 0x80000000 if VMSPLIT_2G
1466 default 0x78000000 if VMSPLIT_2G_OPT
1467 default 0x40000000 if VMSPLIT_1G
1473 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1476 bool "PAE (Physical Address Extension) Support"
1477 depends on X86_32 && !HIGHMEM4G
1478 select PHYS_ADDR_T_64BIT
1481 PAE is required for NX support, and furthermore enables
1482 larger swapspace support for non-overcommit purposes. It
1483 has the cost of more pagetable lookup overhead, and also
1484 consumes more pagetable space per process.
1487 bool "Enable 5-level page tables support"
1488 select DYNAMIC_MEMORY_LAYOUT
1489 select SPARSEMEM_VMEMMAP
1492 5-level paging enables access to larger address space:
1493 upto 128 PiB of virtual address space and 4 PiB of
1494 physical address space.
1496 It will be supported by future Intel CPUs.
1498 A kernel with the option enabled can be booted on machines that
1499 support 4- or 5-level paging.
1501 See Documentation/x86/x86_64/5level-paging.rst for more
1506 config X86_DIRECT_GBPAGES
1508 depends on X86_64 && !DEBUG_PAGEALLOC
1510 Certain kernel features effectively disable kernel
1511 linear 1 GB mappings (even if the CPU otherwise
1512 supports them), so don't confuse the user by printing
1513 that we have them enabled.
1515 config X86_CPA_STATISTICS
1516 bool "Enable statistic for Change Page Attribute"
1519 Expose statistics about the Change Page Attribute mechanims, which
1520 helps to determine the effectiveness of preserving large and huge
1521 page mappings when mapping protections are changed.
1523 config ARCH_HAS_MEM_ENCRYPT
1526 config AMD_MEM_ENCRYPT
1527 bool "AMD Secure Memory Encryption (SME) support"
1528 depends on X86_64 && CPU_SUP_AMD
1529 select DYNAMIC_PHYSICAL_MASK
1530 select ARCH_USE_MEMREMAP_PROT
1532 Say yes to enable support for the encryption of system memory.
1533 This requires an AMD processor that supports Secure Memory
1536 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1537 bool "Activate AMD Secure Memory Encryption (SME) by default"
1539 depends on AMD_MEM_ENCRYPT
1541 Say yes to have system memory encrypted by default if running on
1542 an AMD processor that supports Secure Memory Encryption (SME).
1544 If set to Y, then the encryption of system memory can be
1545 deactivated with the mem_encrypt=off command line option.
1547 If set to N, then the encryption of system memory can be
1548 activated with the mem_encrypt=on command line option.
1550 # Common NUMA Features
1552 bool "Numa Memory Allocation and Scheduler Support"
1554 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1555 default y if X86_BIGSMP
1557 Enable NUMA (Non Uniform Memory Access) support.
1559 The kernel will try to allocate memory used by a CPU on the
1560 local memory controller of the CPU and add some more
1561 NUMA awareness to the kernel.
1563 For 64-bit this is recommended if the system is Intel Core i7
1564 (or later), AMD Opteron, or EM64T NUMA.
1566 For 32-bit this is only needed if you boot a 32-bit
1567 kernel on a 64-bit NUMA platform.
1569 Otherwise, you should say N.
1573 prompt "Old style AMD Opteron NUMA detection"
1574 depends on X86_64 && NUMA && PCI
1576 Enable AMD NUMA node topology detection. You should say Y here if
1577 you have a multi processor AMD system. This uses an old method to
1578 read the NUMA configuration directly from the builtin Northbridge
1579 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1580 which also takes priority if both are compiled in.
1582 config X86_64_ACPI_NUMA
1584 prompt "ACPI NUMA detection"
1585 depends on X86_64 && NUMA && ACPI && PCI
1588 Enable ACPI SRAT based node topology detection.
1590 # Some NUMA nodes have memory ranges that span
1591 # other nodes. Even though a pfn is valid and
1592 # between a node's start and end pfns, it may not
1593 # reside on that node. See memmap_init_zone()
1595 config NODES_SPAN_OTHER_NODES
1597 depends on X86_64_ACPI_NUMA
1600 bool "NUMA emulation"
1603 Enable NUMA emulation. A flat machine will be split
1604 into virtual nodes when booted with "numa=fake=N", where N is the
1605 number of nodes. This is only useful for debugging.
1608 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1610 default "10" if MAXSMP
1611 default "6" if X86_64
1613 depends on NEED_MULTIPLE_NODES
1615 Specify the maximum number of NUMA Nodes available on the target
1616 system. Increases memory reserved to accommodate various tables.
1618 config ARCH_HAVE_MEMORY_PRESENT
1620 depends on X86_32 && DISCONTIGMEM
1622 config ARCH_FLATMEM_ENABLE
1624 depends on X86_32 && !NUMA
1626 config ARCH_DISCONTIGMEM_ENABLE
1628 depends on NUMA && X86_32
1631 config ARCH_SPARSEMEM_ENABLE
1633 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1634 select SPARSEMEM_STATIC if X86_32
1635 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1637 config ARCH_SPARSEMEM_DEFAULT
1638 def_bool X86_64 || (NUMA && X86_32)
1640 config ARCH_SELECT_MEMORY_MODEL
1642 depends on ARCH_SPARSEMEM_ENABLE
1644 config ARCH_MEMORY_PROBE
1645 bool "Enable sysfs memory/probe interface"
1646 depends on X86_64 && MEMORY_HOTPLUG
1648 This option enables a sysfs memory/probe interface for testing.
1649 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1650 If you are unsure how to answer this question, answer N.
1652 config ARCH_PROC_KCORE_TEXT
1654 depends on X86_64 && PROC_KCORE
1656 config ILLEGAL_POINTER_VALUE
1659 default 0xdead000000000000 if X86_64
1661 config X86_PMEM_LEGACY_DEVICE
1664 config X86_PMEM_LEGACY
1665 tristate "Support non-standard NVDIMMs and ADR protected memory"
1666 depends on PHYS_ADDR_T_64BIT
1668 select X86_PMEM_LEGACY_DEVICE
1671 Treat memory marked using the non-standard e820 type of 12 as used
1672 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1673 The kernel will offer these regions to the 'pmem' driver so
1674 they can be used for persistent storage.
1679 bool "Allocate 3rd-level pagetables from highmem"
1682 The VM uses one page table entry for each page of physical memory.
1683 For systems with a lot of RAM, this can be wasteful of precious
1684 low memory. Setting this option will put user-space page table
1685 entries in high memory.
1687 config X86_CHECK_BIOS_CORRUPTION
1688 bool "Check for low memory corruption"
1690 Periodically check for memory corruption in low memory, which
1691 is suspected to be caused by BIOS. Even when enabled in the
1692 configuration, it is disabled at runtime. Enable it by
1693 setting "memory_corruption_check=1" on the kernel command
1694 line. By default it scans the low 64k of memory every 60
1695 seconds; see the memory_corruption_check_size and
1696 memory_corruption_check_period parameters in
1697 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1699 When enabled with the default parameters, this option has
1700 almost no overhead, as it reserves a relatively small amount
1701 of memory and scans it infrequently. It both detects corruption
1702 and prevents it from affecting the running system.
1704 It is, however, intended as a diagnostic tool; if repeatable
1705 BIOS-originated corruption always affects the same memory,
1706 you can use memmap= to prevent the kernel from using that
1709 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1710 bool "Set the default setting of memory_corruption_check"
1711 depends on X86_CHECK_BIOS_CORRUPTION
1714 Set whether the default state of memory_corruption_check is
1717 config X86_RESERVE_LOW
1718 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1722 Specify the amount of low memory to reserve for the BIOS.
1724 The first page contains BIOS data structures that the kernel
1725 must not use, so that page must always be reserved.
1727 By default we reserve the first 64K of physical RAM, as a
1728 number of BIOSes are known to corrupt that memory range
1729 during events such as suspend/resume or monitor cable
1730 insertion, so it must not be used by the kernel.
1732 You can set this to 4 if you are absolutely sure that you
1733 trust the BIOS to get all its memory reservations and usages
1734 right. If you know your BIOS have problems beyond the
1735 default 64K area, you can set this to 640 to avoid using the
1736 entire low memory range.
1738 If you have doubts about the BIOS (e.g. suspend/resume does
1739 not work or there's kernel crashes after certain hardware
1740 hotplug events) then you might want to enable
1741 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1742 typical corruption patterns.
1744 Leave this to the default value of 64 if you are unsure.
1746 config MATH_EMULATION
1748 depends on MODIFY_LDT_SYSCALL
1749 prompt "Math emulation" if X86_32
1751 Linux can emulate a math coprocessor (used for floating point
1752 operations) if you don't have one. 486DX and Pentium processors have
1753 a math coprocessor built in, 486SX and 386 do not, unless you added
1754 a 487DX or 387, respectively. (The messages during boot time can
1755 give you some hints here ["man dmesg"].) Everyone needs either a
1756 coprocessor or this emulation.
1758 If you don't have a math coprocessor, you need to say Y here; if you
1759 say Y here even though you have a coprocessor, the coprocessor will
1760 be used nevertheless. (This behavior can be changed with the kernel
1761 command line option "no387", which comes handy if your coprocessor
1762 is broken. Try "man bootparam" or see the documentation of your boot
1763 loader (lilo or loadlin) about how to pass options to the kernel at
1764 boot time.) This means that it is a good idea to say Y here if you
1765 intend to use this kernel on different machines.
1767 More information about the internals of the Linux math coprocessor
1768 emulation can be found in <file:arch/x86/math-emu/README>.
1770 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1771 kernel, it won't hurt.
1775 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1777 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1778 the Memory Type Range Registers (MTRRs) may be used to control
1779 processor access to memory ranges. This is most useful if you have
1780 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1781 allows bus write transfers to be combined into a larger transfer
1782 before bursting over the PCI/AGP bus. This can increase performance
1783 of image write operations 2.5 times or more. Saying Y here creates a
1784 /proc/mtrr file which may be used to manipulate your processor's
1785 MTRRs. Typically the X server should use this.
1787 This code has a reasonably generic interface so that similar
1788 control registers on other processors can be easily supported
1791 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1792 Registers (ARRs) which provide a similar functionality to MTRRs. For
1793 these, the ARRs are used to emulate the MTRRs.
1794 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1795 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1796 write-combining. All of these processors are supported by this code
1797 and it makes sense to say Y here if you have one of them.
1799 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1800 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1801 can lead to all sorts of problems, so it's good to say Y here.
1803 You can safely say Y even if your machine doesn't have MTRRs, you'll
1804 just add about 9 KB to your kernel.
1806 See <file:Documentation/x86/mtrr.rst> for more information.
1808 config MTRR_SANITIZER
1810 prompt "MTRR cleanup support"
1813 Convert MTRR layout from continuous to discrete, so X drivers can
1814 add writeback entries.
1816 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1817 The largest mtrr entry size for a continuous block can be set with
1822 config MTRR_SANITIZER_ENABLE_DEFAULT
1823 int "MTRR cleanup enable value (0-1)"
1826 depends on MTRR_SANITIZER
1828 Enable mtrr cleanup default value
1830 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1831 int "MTRR cleanup spare reg num (0-7)"
1834 depends on MTRR_SANITIZER
1836 mtrr cleanup spare entries default, it can be changed via
1837 mtrr_spare_reg_nr=N on the kernel command line.
1841 prompt "x86 PAT support" if EXPERT
1844 Use PAT attributes to setup page level cache control.
1846 PATs are the modern equivalents of MTRRs and are much more
1847 flexible than MTRRs.
1849 Say N here if you see bootup problems (boot crash, boot hang,
1850 spontaneous reboots) or a non-working video driver.
1854 config ARCH_USES_PG_UNCACHED
1860 prompt "x86 architectural random number generator" if EXPERT
1862 Enable the x86 architectural RDRAND instruction
1863 (Intel Bull Mountain technology) to generate random numbers.
1864 If supported, this is a high bandwidth, cryptographically
1865 secure hardware random number generator.
1869 prompt "Supervisor Mode Access Prevention" if EXPERT
1871 Supervisor Mode Access Prevention (SMAP) is a security
1872 feature in newer Intel processors. There is a small
1873 performance cost if this enabled and turned on; there is
1874 also a small increase in the kernel size if this is enabled.
1878 config X86_INTEL_UMIP
1880 depends on CPU_SUP_INTEL
1881 prompt "Intel User Mode Instruction Prevention" if EXPERT
1883 The User Mode Instruction Prevention (UMIP) is a security
1884 feature in newer Intel processors. If enabled, a general
1885 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1886 or STR instructions are executed in user mode. These instructions
1887 unnecessarily expose information about the hardware state.
1889 The vast majority of applications do not use these instructions.
1890 For the very few that do, software emulation is provided in
1891 specific cases in protected and virtual-8086 modes. Emulated
1894 config X86_INTEL_MPX
1895 prompt "Intel MPX (Memory Protection Extensions)"
1897 # Note: only available in 64-bit mode due to VMA flags shortage
1898 depends on CPU_SUP_INTEL && X86_64
1899 select ARCH_USES_HIGH_VMA_FLAGS
1901 MPX provides hardware features that can be used in
1902 conjunction with compiler-instrumented code to check
1903 memory references. It is designed to detect buffer
1904 overflow or underflow bugs.
1906 This option enables running applications which are
1907 instrumented or otherwise use MPX. It does not use MPX
1908 itself inside the kernel or to protect the kernel
1909 against bad memory references.
1911 Enabling this option will make the kernel larger:
1912 ~8k of kernel text and 36 bytes of data on a 64-bit
1913 defconfig. It adds a long to the 'mm_struct' which
1914 will increase the kernel memory overhead of each
1915 process and adds some branches to paths used during
1916 exec() and munmap().
1918 For details, see Documentation/x86/intel_mpx.rst
1922 config X86_INTEL_MEMORY_PROTECTION_KEYS
1923 prompt "Intel Memory Protection Keys"
1925 # Note: only available in 64-bit mode
1926 depends on CPU_SUP_INTEL && X86_64
1927 select ARCH_USES_HIGH_VMA_FLAGS
1928 select ARCH_HAS_PKEYS
1930 Memory Protection Keys provides a mechanism for enforcing
1931 page-based protections, but without requiring modification of the
1932 page tables when an application changes protection domains.
1934 For details, see Documentation/core-api/protection-keys.rst
1939 bool "EFI runtime service support"
1942 select EFI_RUNTIME_WRAPPERS
1944 This enables the kernel to use EFI runtime services that are
1945 available (such as the EFI variable services).
1947 This option is only useful on systems that have EFI firmware.
1948 In addition, you should use the latest ELILO loader available
1949 at <http://elilo.sourceforge.net> in order to take advantage
1950 of EFI runtime services. However, even with this option, the
1951 resultant kernel should continue to boot on existing non-EFI
1955 bool "EFI stub support"
1956 depends on EFI && !X86_USE_3DNOW
1959 This kernel feature allows a bzImage to be loaded directly
1960 by EFI firmware without the use of a bootloader.
1962 See Documentation/efi-stub.txt for more information.
1965 bool "EFI mixed-mode support"
1966 depends on EFI_STUB && X86_64
1968 Enabling this feature allows a 64-bit kernel to be booted
1969 on a 32-bit firmware, provided that your CPU supports 64-bit
1972 Note that it is not possible to boot a mixed-mode enabled
1973 kernel via the EFI boot stub - a bootloader that supports
1974 the EFI handover protocol must be used.
1980 prompt "Enable seccomp to safely compute untrusted bytecode"
1982 This kernel feature is useful for number crunching applications
1983 that may need to compute untrusted bytecode during their
1984 execution. By using pipes or other transports made available to
1985 the process as file descriptors supporting the read/write
1986 syscalls, it's possible to isolate those applications in
1987 their own address space using seccomp. Once seccomp is
1988 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1989 and the task is only allowed to execute a few safe syscalls
1990 defined by each seccomp mode.
1992 If unsure, say Y. Only embedded should say N here.
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
2029 config KEXEC_VERIFY_SIG
2030 bool "Verify kernel signature during kexec_file_load() syscall"
2031 depends on KEXEC_FILE
2033 This option makes kernel signature verification mandatory for
2034 the kexec_file_load() syscall.
2036 In addition to that option, you need to enable signature
2037 verification for the corresponding kernel image type being
2038 loaded in order for this to work.
2040 config KEXEC_BZIMAGE_VERIFY_SIG
2041 bool "Enable bzImage signature verification support"
2042 depends on KEXEC_VERIFY_SIG
2043 depends on SIGNED_PE_FILE_VERIFICATION
2044 select SYSTEM_TRUSTED_KEYRING
2046 Enable bzImage signature verification support.
2049 bool "kernel crash dumps"
2050 depends on X86_64 || (X86_32 && HIGHMEM)
2052 Generate crash dump after being started by kexec.
2053 This should be normally only set in special crash dump kernels
2054 which are loaded in the main kernel with kexec-tools into
2055 a specially reserved region and then later executed after
2056 a crash by kdump/kexec. The crash dump kernel must be compiled
2057 to a memory address not used by the main kernel or BIOS using
2058 PHYSICAL_START, or it must be built as a relocatable image
2059 (CONFIG_RELOCATABLE=y).
2060 For more details see Documentation/kdump/kdump.rst
2064 depends on KEXEC && HIBERNATION
2066 Jump between original kernel and kexeced kernel and invoke
2067 code in physical address mode via KEXEC
2069 config PHYSICAL_START
2070 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2073 This gives the physical address where the kernel is loaded.
2075 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2076 bzImage will decompress itself to above physical address and
2077 run from there. Otherwise, bzImage will run from the address where
2078 it has been loaded by the boot loader and will ignore above physical
2081 In normal kdump cases one does not have to set/change this option
2082 as now bzImage can be compiled as a completely relocatable image
2083 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2084 address. This option is mainly useful for the folks who don't want
2085 to use a bzImage for capturing the crash dump and want to use a
2086 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2087 to be specifically compiled to run from a specific memory area
2088 (normally a reserved region) and this option comes handy.
2090 So if you are using bzImage for capturing the crash dump,
2091 leave the value here unchanged to 0x1000000 and set
2092 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2093 for capturing the crash dump change this value to start of
2094 the reserved region. In other words, it can be set based on
2095 the "X" value as specified in the "crashkernel=YM@XM"
2096 command line boot parameter passed to the panic-ed
2097 kernel. Please take a look at Documentation/kdump/kdump.rst
2098 for more details about crash dumps.
2100 Usage of bzImage for capturing the crash dump is recommended as
2101 one does not have to build two kernels. Same kernel can be used
2102 as production kernel and capture kernel. Above option should have
2103 gone away after relocatable bzImage support is introduced. But it
2104 is present because there are users out there who continue to use
2105 vmlinux for dump capture. This option should go away down the
2108 Don't change this unless you know what you are doing.
2111 bool "Build a relocatable kernel"
2114 This builds a kernel image that retains relocation information
2115 so it can be loaded someplace besides the default 1MB.
2116 The relocations tend to make the kernel binary about 10% larger,
2117 but are discarded at runtime.
2119 One use is for the kexec on panic case where the recovery kernel
2120 must live at a different physical address than the primary
2123 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2124 it has been loaded at and the compile time physical address
2125 (CONFIG_PHYSICAL_START) is used as the minimum location.
2127 config RANDOMIZE_BASE
2128 bool "Randomize the address of the kernel image (KASLR)"
2129 depends on RELOCATABLE
2132 In support of Kernel Address Space Layout Randomization (KASLR),
2133 this randomizes the physical address at which the kernel image
2134 is decompressed and the virtual address where the kernel
2135 image is mapped, as a security feature that deters exploit
2136 attempts relying on knowledge of the location of kernel
2139 On 64-bit, the kernel physical and virtual addresses are
2140 randomized separately. The physical address will be anywhere
2141 between 16MB and the top of physical memory (up to 64TB). The
2142 virtual address will be randomized from 16MB up to 1GB (9 bits
2143 of entropy). Note that this also reduces the memory space
2144 available to kernel modules from 1.5GB to 1GB.
2146 On 32-bit, the kernel physical and virtual addresses are
2147 randomized together. They will be randomized from 16MB up to
2148 512MB (8 bits of entropy).
2150 Entropy is generated using the RDRAND instruction if it is
2151 supported. If RDTSC is supported, its value is mixed into
2152 the entropy pool as well. If neither RDRAND nor RDTSC are
2153 supported, then entropy is read from the i8254 timer. The
2154 usable entropy is limited by the kernel being built using
2155 2GB addressing, and that PHYSICAL_ALIGN must be at a
2156 minimum of 2MB. As a result, only 10 bits of entropy are
2157 theoretically possible, but the implementations are further
2158 limited due to memory layouts.
2162 # Relocation on x86 needs some additional build support
2163 config X86_NEED_RELOCS
2165 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2167 config PHYSICAL_ALIGN
2168 hex "Alignment value to which kernel should be aligned"
2170 range 0x2000 0x1000000 if X86_32
2171 range 0x200000 0x1000000 if X86_64
2173 This value puts the alignment restrictions on physical address
2174 where kernel is loaded and run from. Kernel is compiled for an
2175 address which meets above alignment restriction.
2177 If bootloader loads the kernel at a non-aligned address and
2178 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2179 address aligned to above value and run from there.
2181 If bootloader loads the kernel at a non-aligned address and
2182 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2183 load address and decompress itself to the address it has been
2184 compiled for and run from there. The address for which kernel is
2185 compiled already meets above alignment restrictions. Hence the
2186 end result is that kernel runs from a physical address meeting
2187 above alignment restrictions.
2189 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2190 this value must be a multiple of 0x200000.
2192 Don't change this unless you know what you are doing.
2194 config DYNAMIC_MEMORY_LAYOUT
2197 This option makes base addresses of vmalloc and vmemmap as well as
2198 __PAGE_OFFSET movable during boot.
2200 config RANDOMIZE_MEMORY
2201 bool "Randomize the kernel memory sections"
2203 depends on RANDOMIZE_BASE
2204 select DYNAMIC_MEMORY_LAYOUT
2205 default RANDOMIZE_BASE
2207 Randomizes the base virtual address of kernel memory sections
2208 (physical memory mapping, vmalloc & vmemmap). This security feature
2209 makes exploits relying on predictable memory locations less reliable.
2211 The order of allocations remains unchanged. Entropy is generated in
2212 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2213 configuration have in average 30,000 different possible virtual
2214 addresses for each memory section.
2218 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2219 hex "Physical memory mapping padding" if EXPERT
2220 depends on RANDOMIZE_MEMORY
2221 default "0xa" if MEMORY_HOTPLUG
2223 range 0x1 0x40 if MEMORY_HOTPLUG
2226 Define the padding in terabytes added to the existing physical
2227 memory size during kernel memory randomization. It is useful
2228 for memory hotplug support but reduces the entropy available for
2229 address randomization.
2231 If unsure, leave at the default value.
2237 config BOOTPARAM_HOTPLUG_CPU0
2238 bool "Set default setting of cpu0_hotpluggable"
2239 depends on HOTPLUG_CPU
2241 Set whether default state of cpu0_hotpluggable is on or off.
2243 Say Y here to enable CPU0 hotplug by default. If this switch
2244 is turned on, there is no need to give cpu0_hotplug kernel
2245 parameter and the CPU0 hotplug feature is enabled by default.
2247 Please note: there are two known CPU0 dependencies if you want
2248 to enable the CPU0 hotplug feature either by this switch or by
2249 cpu0_hotplug kernel parameter.
2251 First, resume from hibernate or suspend always starts from CPU0.
2252 So hibernate and suspend are prevented if CPU0 is offline.
2254 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2255 offline if any interrupt can not migrate out of CPU0. There may
2256 be other CPU0 dependencies.
2258 Please make sure the dependencies are under your control before
2259 you enable this feature.
2261 Say N if you don't want to enable CPU0 hotplug feature by default.
2262 You still can enable the CPU0 hotplug feature at boot by kernel
2263 parameter cpu0_hotplug.
2265 config DEBUG_HOTPLUG_CPU0
2267 prompt "Debug CPU0 hotplug"
2268 depends on HOTPLUG_CPU
2270 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2271 soon as possible and boots up userspace with CPU0 offlined. User
2272 can online CPU0 back after boot time.
2274 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2275 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2276 compilation or giving cpu0_hotplug kernel parameter at boot.
2282 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2283 depends on COMPAT_32
2285 Certain buggy versions of glibc will crash if they are
2286 presented with a 32-bit vDSO that is not mapped at the address
2287 indicated in its segment table.
2289 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2290 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2291 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2292 the only released version with the bug, but OpenSUSE 9
2293 contains a buggy "glibc 2.3.2".
2295 The symptom of the bug is that everything crashes on startup, saying:
2296 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2298 Saying Y here changes the default value of the vdso32 boot
2299 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2300 This works around the glibc bug but hurts performance.
2302 If unsure, say N: if you are compiling your own kernel, you
2303 are unlikely to be using a buggy version of glibc.
2306 prompt "vsyscall table for legacy applications"
2308 default LEGACY_VSYSCALL_XONLY
2310 Legacy user code that does not know how to find the vDSO expects
2311 to be able to issue three syscalls by calling fixed addresses in
2312 kernel space. Since this location is not randomized with ASLR,
2313 it can be used to assist security vulnerability exploitation.
2315 This setting can be changed at boot time via the kernel command
2316 line parameter vsyscall=[emulate|xonly|none].
2318 On a system with recent enough glibc (2.14 or newer) and no
2319 static binaries, you can say None without a performance penalty
2320 to improve security.
2322 If unsure, select "Emulate execution only".
2324 config LEGACY_VSYSCALL_EMULATE
2325 bool "Full emulation"
2327 The kernel traps and emulates calls into the fixed vsyscall
2328 address mapping. This makes the mapping non-executable, but
2329 it still contains readable known contents, which could be
2330 used in certain rare security vulnerability exploits. This
2331 configuration is recommended when using legacy userspace
2332 that still uses vsyscalls along with legacy binary
2333 instrumentation tools that require code to be readable.
2335 An example of this type of legacy userspace is running
2336 Pin on an old binary that still uses vsyscalls.
2338 config LEGACY_VSYSCALL_XONLY
2339 bool "Emulate execution only"
2341 The kernel traps and emulates calls into the fixed vsyscall
2342 address mapping and does not allow reads. This
2343 configuration is recommended when userspace might use the
2344 legacy vsyscall area but support for legacy binary
2345 instrumentation of legacy code is not needed. It mitigates
2346 certain uses of the vsyscall area as an ASLR-bypassing
2349 config LEGACY_VSYSCALL_NONE
2352 There will be no vsyscall mapping at all. This will
2353 eliminate any risk of ASLR bypass due to the vsyscall
2354 fixed address mapping. Attempts to use the vsyscalls
2355 will be reported to dmesg, so that either old or
2356 malicious userspace programs can be identified.
2361 bool "Built-in kernel command line"
2363 Allow for specifying boot arguments to the kernel at
2364 build time. On some systems (e.g. embedded ones), it is
2365 necessary or convenient to provide some or all of the
2366 kernel boot arguments with the kernel itself (that is,
2367 to not rely on the boot loader to provide them.)
2369 To compile command line arguments into the kernel,
2370 set this option to 'Y', then fill in the
2371 boot arguments in CONFIG_CMDLINE.
2373 Systems with fully functional boot loaders (i.e. non-embedded)
2374 should leave this option set to 'N'.
2377 string "Built-in kernel command string"
2378 depends on CMDLINE_BOOL
2381 Enter arguments here that should be compiled into the kernel
2382 image and used at boot time. If the boot loader provides a
2383 command line at boot time, it is appended to this string to
2384 form the full kernel command line, when the system boots.
2386 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2387 change this behavior.
2389 In most cases, the command line (whether built-in or provided
2390 by the boot loader) should specify the device for the root
2393 config CMDLINE_OVERRIDE
2394 bool "Built-in command line overrides boot loader arguments"
2395 depends on CMDLINE_BOOL
2397 Set this option to 'Y' to have the kernel ignore the boot loader
2398 command line, and use ONLY the built-in command line.
2400 This is used to work around broken boot loaders. This should
2401 be set to 'N' under normal conditions.
2403 config MODIFY_LDT_SYSCALL
2404 bool "Enable the LDT (local descriptor table)" if EXPERT
2407 Linux can allow user programs to install a per-process x86
2408 Local Descriptor Table (LDT) using the modify_ldt(2) system
2409 call. This is required to run 16-bit or segmented code such as
2410 DOSEMU or some Wine programs. It is also used by some very old
2411 threading libraries.
2413 Enabling this feature adds a small amount of overhead to
2414 context switches and increases the low-level kernel attack
2415 surface. Disabling it removes the modify_ldt(2) system call.
2417 Saying 'N' here may make sense for embedded or server kernels.
2419 source "kernel/livepatch/Kconfig"
2423 config ARCH_HAS_ADD_PAGES
2425 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2427 config ARCH_ENABLE_MEMORY_HOTPLUG
2429 depends on X86_64 || (X86_32 && HIGHMEM)
2431 config ARCH_ENABLE_MEMORY_HOTREMOVE
2433 depends on MEMORY_HOTPLUG
2435 config USE_PERCPU_NUMA_NODE_ID
2439 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2441 depends on X86_64 || X86_PAE
2443 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2445 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2447 config ARCH_ENABLE_THP_MIGRATION
2449 depends on X86_64 && TRANSPARENT_HUGEPAGE
2451 menu "Power management and ACPI options"
2453 config ARCH_HIBERNATION_HEADER
2455 depends on HIBERNATION
2457 source "kernel/power/Kconfig"
2459 source "drivers/acpi/Kconfig"
2461 source "drivers/sfi/Kconfig"
2468 tristate "APM (Advanced Power Management) BIOS support"
2469 depends on X86_32 && PM_SLEEP
2471 APM is a BIOS specification for saving power using several different
2472 techniques. This is mostly useful for battery powered laptops with
2473 APM compliant BIOSes. If you say Y here, the system time will be
2474 reset after a RESUME operation, the /proc/apm device will provide
2475 battery status information, and user-space programs will receive
2476 notification of APM "events" (e.g. battery status change).
2478 If you select "Y" here, you can disable actual use of the APM
2479 BIOS by passing the "apm=off" option to the kernel at boot time.
2481 Note that the APM support is almost completely disabled for
2482 machines with more than one CPU.
2484 In order to use APM, you will need supporting software. For location
2485 and more information, read <file:Documentation/power/apm-acpi.txt>
2486 and the Battery Powered Linux mini-HOWTO, available from
2487 <http://www.tldp.org/docs.html#howto>.
2489 This driver does not spin down disk drives (see the hdparm(8)
2490 manpage ("man 8 hdparm") for that), and it doesn't turn off
2491 VESA-compliant "green" monitors.
2493 This driver does not support the TI 4000M TravelMate and the ACER
2494 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2495 desktop machines also don't have compliant BIOSes, and this driver
2496 may cause those machines to panic during the boot phase.
2498 Generally, if you don't have a battery in your machine, there isn't
2499 much point in using this driver and you should say N. If you get
2500 random kernel OOPSes or reboots that don't seem to be related to
2501 anything, try disabling/enabling this option (or disabling/enabling
2504 Some other things you should try when experiencing seemingly random,
2507 1) make sure that you have enough swap space and that it is
2509 2) pass the "no-hlt" option to the kernel
2510 3) switch on floating point emulation in the kernel and pass
2511 the "no387" option to the kernel
2512 4) pass the "floppy=nodma" option to the kernel
2513 5) pass the "mem=4M" option to the kernel (thereby disabling
2514 all but the first 4 MB of RAM)
2515 6) make sure that the CPU is not over clocked.
2516 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2517 8) disable the cache from your BIOS settings
2518 9) install a fan for the video card or exchange video RAM
2519 10) install a better fan for the CPU
2520 11) exchange RAM chips
2521 12) exchange the motherboard.
2523 To compile this driver as a module, choose M here: the
2524 module will be called apm.
2528 config APM_IGNORE_USER_SUSPEND
2529 bool "Ignore USER SUSPEND"
2531 This option will ignore USER SUSPEND requests. On machines with a
2532 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2533 series notebooks, it is necessary to say Y because of a BIOS bug.
2535 config APM_DO_ENABLE
2536 bool "Enable PM at boot time"
2538 Enable APM features at boot time. From page 36 of the APM BIOS
2539 specification: "When disabled, the APM BIOS does not automatically
2540 power manage devices, enter the Standby State, enter the Suspend
2541 State, or take power saving steps in response to CPU Idle calls."
2542 This driver will make CPU Idle calls when Linux is idle (unless this
2543 feature is turned off -- see "Do CPU IDLE calls", below). This
2544 should always save battery power, but more complicated APM features
2545 will be dependent on your BIOS implementation. You may need to turn
2546 this option off if your computer hangs at boot time when using APM
2547 support, or if it beeps continuously instead of suspending. Turn
2548 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2549 T400CDT. This is off by default since most machines do fine without
2554 bool "Make CPU Idle calls when idle"
2556 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2557 On some machines, this can activate improved power savings, such as
2558 a slowed CPU clock rate, when the machine is idle. These idle calls
2559 are made after the idle loop has run for some length of time (e.g.,
2560 333 mS). On some machines, this will cause a hang at boot time or
2561 whenever the CPU becomes idle. (On machines with more than one CPU,
2562 this option does nothing.)
2564 config APM_DISPLAY_BLANK
2565 bool "Enable console blanking using APM"
2567 Enable console blanking using the APM. Some laptops can use this to
2568 turn off the LCD backlight when the screen blanker of the Linux
2569 virtual console blanks the screen. Note that this is only used by
2570 the virtual console screen blanker, and won't turn off the backlight
2571 when using the X Window system. This also doesn't have anything to
2572 do with your VESA-compliant power-saving monitor. Further, this
2573 option doesn't work for all laptops -- it might not turn off your
2574 backlight at all, or it might print a lot of errors to the console,
2575 especially if you are using gpm.
2577 config APM_ALLOW_INTS
2578 bool "Allow interrupts during APM BIOS calls"
2580 Normally we disable external interrupts while we are making calls to
2581 the APM BIOS as a measure to lessen the effects of a badly behaving
2582 BIOS implementation. The BIOS should reenable interrupts if it
2583 needs to. Unfortunately, some BIOSes do not -- especially those in
2584 many of the newer IBM Thinkpads. If you experience hangs when you
2585 suspend, try setting this to Y. Otherwise, say N.
2589 source "drivers/cpufreq/Kconfig"
2591 source "drivers/cpuidle/Kconfig"
2593 source "drivers/idle/Kconfig"
2598 menu "Bus options (PCI etc.)"
2601 prompt "PCI access mode"
2602 depends on X86_32 && PCI
2605 On PCI systems, the BIOS can be used to detect the PCI devices and
2606 determine their configuration. However, some old PCI motherboards
2607 have BIOS bugs and may crash if this is done. Also, some embedded
2608 PCI-based systems don't have any BIOS at all. Linux can also try to
2609 detect the PCI hardware directly without using the BIOS.
2611 With this option, you can specify how Linux should detect the
2612 PCI devices. If you choose "BIOS", the BIOS will be used,
2613 if you choose "Direct", the BIOS won't be used, and if you
2614 choose "MMConfig", then PCI Express MMCONFIG will be used.
2615 If you choose "Any", the kernel will try MMCONFIG, then the
2616 direct access method and falls back to the BIOS if that doesn't
2617 work. If unsure, go with the default, which is "Any".
2622 config PCI_GOMMCONFIG
2639 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2641 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2644 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2647 bool "Support mmconfig PCI config space access" if X86_64
2649 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2650 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2654 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2658 depends on PCI && XEN
2661 config MMCONF_FAM10H
2663 depends on X86_64 && PCI_MMCONFIG && ACPI
2665 config PCI_CNB20LE_QUIRK
2666 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2669 Read the PCI windows out of the CNB20LE host bridge. This allows
2670 PCI hotplug to work on systems with the CNB20LE chipset which do
2673 There's no public spec for this chipset, and this functionality
2674 is known to be incomplete.
2676 You should say N unless you know you need this.
2679 bool "ISA bus support on modern systems" if EXPERT
2681 Expose ISA bus device drivers and options available for selection and
2682 configuration. Enable this option if your target machine has an ISA
2683 bus. ISA is an older system, displaced by PCI and newer bus
2684 architectures -- if your target machine is modern, it probably does
2685 not have an ISA bus.
2689 # x86_64 have no ISA slots, but can have ISA-style DMA.
2691 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2694 Enables ISA-style DMA support for devices requiring such controllers.
2702 Find out whether you have ISA slots on your motherboard. ISA is the
2703 name of a bus system, i.e. the way the CPU talks to the other stuff
2704 inside your box. Other bus systems are PCI, EISA, MicroChannel
2705 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2706 newer boards don't support it. If you have ISA, say Y, otherwise N.
2709 tristate "NatSemi SCx200 support"
2711 This provides basic support for National Semiconductor's
2712 (now AMD's) Geode processors. The driver probes for the
2713 PCI-IDs of several on-chip devices, so its a good dependency
2714 for other scx200_* drivers.
2716 If compiled as a module, the driver is named scx200.
2718 config SCx200HR_TIMER
2719 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2723 This driver provides a clocksource built upon the on-chip
2724 27MHz high-resolution timer. Its also a workaround for
2725 NSC Geode SC-1100's buggy TSC, which loses time when the
2726 processor goes idle (as is done by the scheduler). The
2727 other workaround is idle=poll boot option.
2730 bool "One Laptop Per Child support"
2737 Add support for detecting the unique features of the OLPC
2741 bool "OLPC XO-1 Power Management"
2742 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2744 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2747 bool "OLPC XO-1 Real Time Clock"
2748 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2750 Add support for the XO-1 real time clock, which can be used as a
2751 programmable wakeup source.
2754 bool "OLPC XO-1 SCI extras"
2755 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2759 Add support for SCI-based features of the OLPC XO-1 laptop:
2760 - EC-driven system wakeups
2764 - AC adapter status updates
2765 - Battery status updates
2767 config OLPC_XO15_SCI
2768 bool "OLPC XO-1.5 SCI extras"
2769 depends on OLPC && ACPI
2772 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2773 - EC-driven system wakeups
2774 - AC adapter status updates
2775 - Battery status updates
2778 bool "PCEngines ALIX System Support (LED setup)"
2781 This option enables system support for the PCEngines ALIX.
2782 At present this just sets up LEDs for GPIO control on
2783 ALIX2/3/6 boards. However, other system specific setup should
2786 Note: You must still enable the drivers for GPIO and LED support
2787 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2789 Note: You have to set alix.force=1 for boards with Award BIOS.
2792 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2795 This option enables system support for the Soekris Engineering net5501.
2798 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2802 This option enables system support for the Traverse Technologies GEOS.
2805 bool "Technologic Systems TS-5500 platform support"
2807 select CHECK_SIGNATURE
2811 This option enables system support for the Technologic Systems TS-5500.
2817 depends on CPU_SUP_AMD && PCI
2820 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2822 Firmwares often provide initial graphics framebuffers so the BIOS,
2823 bootloader or kernel can show basic video-output during boot for
2824 user-guidance and debugging. Historically, x86 used the VESA BIOS
2825 Extensions and EFI-framebuffers for this, which are mostly limited
2827 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2828 framebuffers so the new generic system-framebuffer drivers can be
2829 used on x86. If the framebuffer is not compatible with the generic
2830 modes, it is advertised as fallback platform framebuffer so legacy
2831 drivers like efifb, vesafb and uvesafb can pick it up.
2832 If this option is not selected, all system framebuffers are always
2833 marked as fallback platform framebuffers as usual.
2835 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2836 not be able to pick up generic system framebuffers if this option
2837 is selected. You are highly encouraged to enable simplefb as
2838 replacement if you select this option. simplefb can correctly deal
2839 with generic system framebuffers. But you should still keep vesafb
2840 and others enabled as fallback if a system framebuffer is
2841 incompatible with simplefb.
2848 menu "Binary Emulations"
2850 config IA32_EMULATION
2851 bool "IA32 Emulation"
2853 select ARCH_WANT_OLD_COMPAT_IPC
2855 select COMPAT_BINFMT_ELF
2856 select COMPAT_OLD_SIGACTION
2858 Include code to run legacy 32-bit programs under a
2859 64-bit kernel. You should likely turn this on, unless you're
2860 100% sure that you don't have any 32-bit programs left.
2863 tristate "IA32 a.out support"
2864 depends on IA32_EMULATION
2867 Support old a.out binaries in the 32bit emulation.
2870 bool "x32 ABI for 64-bit mode"
2873 Include code to run binaries for the x32 native 32-bit ABI
2874 for 64-bit processors. An x32 process gets access to the
2875 full 64-bit register file and wide data path while leaving
2876 pointers at 32 bits for smaller memory footprint.
2878 You will need a recent binutils (2.22 or later) with
2879 elf32_x86_64 support enabled to compile a kernel with this
2884 depends on IA32_EMULATION || X86_32
2886 select OLD_SIGSUSPEND3
2890 depends on IA32_EMULATION || X86_X32
2893 config COMPAT_FOR_U64_ALIGNMENT
2896 config SYSVIPC_COMPAT
2904 config HAVE_ATOMIC_IOMAP
2908 config X86_DEV_DMA_OPS
2911 source "drivers/firmware/Kconfig"
2913 source "arch/x86/kvm/Kconfig"