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
24 # Options that are inherently 64-bit kernel only:
25 select ARCH_HAS_GIGANTIC_PAGE
26 select ARCH_SUPPORTS_INT128
27 select ARCH_USE_CMPXCHG_LOCKREF
28 select HAVE_ARCH_SOFT_DIRTY
29 select MODULES_USE_ELF_RELA
30 select NEED_DMA_MAP_STATE
32 select ARCH_HAS_SYSCALL_WRAPPER
37 # ( Note that options that are marked 'if X86_64' could in principle be
38 # ported to 32-bit as well. )
43 # Note: keep this list sorted alphabetically
45 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
46 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
47 select ARCH_32BIT_OFF_T if X86_32
48 select ARCH_CLOCKSOURCE_DATA
49 select ARCH_CLOCKSOURCE_INIT
50 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
51 select ARCH_HAS_DEBUG_VIRTUAL
52 select ARCH_HAS_DEVMEM_IS_ALLOWED
53 select ARCH_HAS_ELF_RANDOMIZE
54 select ARCH_HAS_FAST_MULTIPLIER
55 select ARCH_HAS_FILTER_PGPROT
56 select ARCH_HAS_FORTIFY_SOURCE
57 select ARCH_HAS_GCOV_PROFILE_ALL
58 select ARCH_HAS_KCOV if X86_64
59 select ARCH_HAS_MEMBARRIER_SYNC_CORE
60 select ARCH_HAS_PMEM_API if X86_64
61 select ARCH_HAS_PTE_SPECIAL
62 select ARCH_HAS_REFCOUNT
63 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
64 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
65 select ARCH_HAS_SET_MEMORY
66 select ARCH_HAS_SET_DIRECT_MAP
67 select ARCH_HAS_STRICT_KERNEL_RWX
68 select ARCH_HAS_STRICT_MODULE_RWX
69 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
70 select ARCH_HAS_UBSAN_SANITIZE_ALL
71 select ARCH_HAS_ZONE_DEVICE if X86_64
72 select ARCH_HAVE_NMI_SAFE_CMPXCHG
73 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
74 select ARCH_MIGHT_HAVE_PC_PARPORT
75 select ARCH_MIGHT_HAVE_PC_SERIO
77 select ARCH_SUPPORTS_ACPI
78 select ARCH_SUPPORTS_ATOMIC_RMW
79 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
80 select ARCH_USE_BUILTIN_BSWAP
81 select ARCH_USE_QUEUED_RWLOCKS
82 select ARCH_USE_QUEUED_SPINLOCKS
83 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
84 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
85 select ARCH_WANTS_THP_SWAP if X86_64
86 select BUILDTIME_EXTABLE_SORT
88 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
89 select CLOCKSOURCE_WATCHDOG
90 select DCACHE_WORD_ACCESS
91 select EDAC_ATOMIC_SCRUB
93 select GENERIC_CLOCKEVENTS
94 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
95 select GENERIC_CLOCKEVENTS_MIN_ADJUST
96 select GENERIC_CMOS_UPDATE
97 select GENERIC_CPU_AUTOPROBE
98 select GENERIC_CPU_VULNERABILITIES
99 select GENERIC_EARLY_IOREMAP
100 select GENERIC_FIND_FIRST_BIT
102 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
103 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
104 select GENERIC_IRQ_MIGRATION if SMP
105 select GENERIC_IRQ_PROBE
106 select GENERIC_IRQ_RESERVATION_MODE
107 select GENERIC_IRQ_SHOW
108 select GENERIC_PENDING_IRQ if SMP
109 select GENERIC_SMP_IDLE_THREAD
110 select GENERIC_STRNCPY_FROM_USER
111 select GENERIC_STRNLEN_USER
112 select GENERIC_TIME_VSYSCALL
113 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
114 select HAVE_ACPI_APEI if ACPI
115 select HAVE_ACPI_APEI_NMI if ACPI
116 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
117 select HAVE_ARCH_AUDITSYSCALL
118 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
119 select HAVE_ARCH_JUMP_LABEL
120 select HAVE_ARCH_JUMP_LABEL_RELATIVE
121 select HAVE_ARCH_KASAN if X86_64
122 select HAVE_ARCH_KGDB
123 select HAVE_ARCH_MMAP_RND_BITS if MMU
124 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
125 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
126 select HAVE_ARCH_PREL32_RELOCATIONS
127 select HAVE_ARCH_SECCOMP_FILTER
128 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
129 select HAVE_ARCH_STACKLEAK
130 select HAVE_ARCH_TRACEHOOK
131 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
132 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
133 select HAVE_ARCH_VMAP_STACK if X86_64
134 select HAVE_ARCH_WITHIN_STACK_FRAMES
135 select HAVE_CMPXCHG_DOUBLE
136 select HAVE_CMPXCHG_LOCAL
137 select HAVE_CONTEXT_TRACKING if X86_64
138 select HAVE_COPY_THREAD_TLS
139 select HAVE_C_RECORDMCOUNT
140 select HAVE_DEBUG_KMEMLEAK
141 select HAVE_DMA_CONTIGUOUS
142 select HAVE_DYNAMIC_FTRACE
143 select HAVE_DYNAMIC_FTRACE_WITH_REGS
145 select HAVE_EFFICIENT_UNALIGNED_ACCESS
147 select HAVE_EXIT_THREAD
148 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
149 select HAVE_FTRACE_MCOUNT_RECORD
150 select HAVE_FUNCTION_GRAPH_TRACER
151 select HAVE_FUNCTION_TRACER
152 select HAVE_GCC_PLUGINS
153 select HAVE_HW_BREAKPOINT
155 select HAVE_IOREMAP_PROT
156 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
157 select HAVE_IRQ_TIME_ACCOUNTING
158 select HAVE_KERNEL_BZIP2
159 select HAVE_KERNEL_GZIP
160 select HAVE_KERNEL_LZ4
161 select HAVE_KERNEL_LZMA
162 select HAVE_KERNEL_LZO
163 select HAVE_KERNEL_XZ
165 select HAVE_KPROBES_ON_FTRACE
166 select HAVE_FUNCTION_ERROR_INJECTION
167 select HAVE_KRETPROBES
169 select HAVE_LIVEPATCH if X86_64
170 select HAVE_MEMBLOCK_NODE_MAP
171 select HAVE_MIXED_BREAKPOINTS_REGS
172 select HAVE_MOD_ARCH_SPECIFIC
176 select HAVE_OPTPROBES
177 select HAVE_PCSPKR_PLATFORM
178 select HAVE_PERF_EVENTS
179 select HAVE_PERF_EVENTS_NMI
180 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
182 select HAVE_PERF_REGS
183 select HAVE_PERF_USER_STACK_DUMP
184 select HAVE_RCU_TABLE_FREE if PARAVIRT
185 select HAVE_REGS_AND_STACK_ACCESS_API
186 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
187 select HAVE_FUNCTION_ARG_ACCESS_API
188 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
189 select HAVE_STACK_VALIDATION if X86_64
191 select HAVE_SYSCALL_TRACEPOINTS
192 select HAVE_UNSTABLE_SCHED_CLOCK
193 select HAVE_USER_RETURN_NOTIFIER
194 select HOTPLUG_SMT if SMP
195 select IRQ_FORCED_THREADING
196 select NEED_SG_DMA_LENGTH
197 select PCI_DOMAINS if PCI
198 select PCI_LOCKLESS_CONFIG if PCI
201 select RTC_MC146818_LIB
204 select SYSCTL_EXCEPTION_TRACE
205 select THREAD_INFO_IN_TASK
206 select USER_STACKTRACE_SUPPORT
208 select X86_FEATURE_NAMES if PROC_FS
210 config INSTRUCTION_DECODER
212 depends on KPROBES || PERF_EVENTS || UPROBES
216 default "elf32-i386" if X86_32
217 default "elf64-x86-64" if X86_64
219 config ARCH_DEFCONFIG
221 default "arch/x86/configs/i386_defconfig" if X86_32
222 default "arch/x86/configs/x86_64_defconfig" if X86_64
224 config LOCKDEP_SUPPORT
227 config STACKTRACE_SUPPORT
233 config ARCH_MMAP_RND_BITS_MIN
237 config ARCH_MMAP_RND_BITS_MAX
241 config ARCH_MMAP_RND_COMPAT_BITS_MIN
244 config ARCH_MMAP_RND_COMPAT_BITS_MAX
250 config GENERIC_ISA_DMA
252 depends on ISA_DMA_API
257 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
259 config GENERIC_BUG_RELATIVE_POINTERS
262 config GENERIC_HWEIGHT
265 config ARCH_MAY_HAVE_PC_FDC
267 depends on ISA_DMA_API
269 config GENERIC_CALIBRATE_DELAY
272 config ARCH_HAS_CPU_RELAX
275 config ARCH_HAS_CACHE_LINE_SIZE
278 config ARCH_HAS_FILTER_PGPROT
281 config HAVE_SETUP_PER_CPU_AREA
284 config NEED_PER_CPU_EMBED_FIRST_CHUNK
287 config NEED_PER_CPU_PAGE_FIRST_CHUNK
290 config ARCH_HIBERNATION_POSSIBLE
293 config ARCH_SUSPEND_POSSIBLE
296 config ARCH_WANT_HUGE_PMD_SHARE
299 config ARCH_WANT_GENERAL_HUGETLB
308 config ARCH_SUPPORTS_OPTIMIZED_INLINING
311 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
314 config KASAN_SHADOW_OFFSET
317 default 0xdffffc0000000000
319 config HAVE_INTEL_TXT
321 depends on INTEL_IOMMU && ACPI
325 depends on X86_32 && SMP
329 depends on X86_64 && SMP
331 config X86_32_LAZY_GS
333 depends on X86_32 && !STACKPROTECTOR
335 config ARCH_SUPPORTS_UPROBES
338 config FIX_EARLYCON_MEM
341 config DYNAMIC_PHYSICAL_MASK
344 config PGTABLE_LEVELS
346 default 5 if X86_5LEVEL
351 config CC_HAS_SANE_STACKPROTECTOR
353 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
354 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
356 We have to make sure stack protector is unconditionally disabled if
357 the compiler produces broken code.
359 menu "Processor type and features"
362 bool "DMA memory allocation support" if EXPERT
365 DMA memory allocation support allows devices with less than 32-bit
366 addressing to allocate within the first 16MB of address space.
367 Disable if no such devices will be used.
372 bool "Symmetric multi-processing support"
374 This enables support for systems with more than one CPU. If you have
375 a system with only one CPU, say N. If you have a system with more
378 If you say N here, the kernel will run on uni- and multiprocessor
379 machines, but will use only one CPU of a multiprocessor machine. If
380 you say Y here, the kernel will run on many, but not all,
381 uniprocessor machines. On a uniprocessor machine, the kernel
382 will run faster if you say N here.
384 Note that if you say Y here and choose architecture "586" or
385 "Pentium" under "Processor family", the kernel will not work on 486
386 architectures. Similarly, multiprocessor kernels for the "PPro"
387 architecture may not work on all Pentium based boards.
389 People using multiprocessor machines who say Y here should also say
390 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
391 Management" code will be disabled if you say Y here.
393 See also <file:Documentation/x86/i386/IO-APIC.txt>,
394 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
395 <http://www.tldp.org/docs.html#howto>.
397 If you don't know what to do here, say N.
399 config X86_FEATURE_NAMES
400 bool "Processor feature human-readable names" if EMBEDDED
403 This option compiles in a table of x86 feature bits and corresponding
404 names. This is required to support /proc/cpuinfo and a few kernel
405 messages. You can disable this to save space, at the expense of
406 making those few kernel messages show numeric feature bits instead.
411 bool "Support x2apic"
412 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
414 This enables x2apic support on CPUs that have this feature.
416 This allows 32-bit apic IDs (so it can support very large systems),
417 and accesses the local apic via MSRs not via mmio.
419 If you don't know what to do here, say N.
422 bool "Enable MPS table" if ACPI || SFI
424 depends on X86_LOCAL_APIC
426 For old smp systems that do not have proper acpi support. Newer systems
427 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
431 depends on X86_GOLDFISH
434 bool "Avoid speculative indirect branches in kernel"
436 select STACK_VALIDATION if HAVE_STACK_VALIDATION
438 Compile kernel with the retpoline compiler options to guard against
439 kernel-to-user data leaks by avoiding speculative indirect
440 branches. Requires a compiler with -mindirect-branch=thunk-extern
441 support for full protection. The kernel may run slower.
443 config X86_CPU_RESCTRL
444 bool "x86 CPU resource control support"
445 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
448 Enable x86 CPU resource control support.
450 Provide support for the allocation and monitoring of system resources
453 Intel calls this Intel Resource Director Technology
454 (Intel(R) RDT). More information about RDT can be found in the
455 Intel x86 Architecture Software Developer Manual.
457 AMD calls this AMD Platform Quality of Service (AMD QoS).
458 More information about AMD QoS can be found in the AMD64 Technology
459 Platform Quality of Service Extensions manual.
465 bool "Support for big SMP systems with more than 8 CPUs"
468 This option is needed for the systems that have more than 8 CPUs
470 config X86_EXTENDED_PLATFORM
471 bool "Support for extended (non-PC) x86 platforms"
474 If you disable this option then the kernel will only support
475 standard PC platforms. (which covers the vast majority of
478 If you enable this option then you'll be able to select support
479 for the following (non-PC) 32 bit x86 platforms:
480 Goldfish (Android emulator)
483 SGI 320/540 (Visual Workstation)
484 STA2X11-based (e.g. Northville)
485 Moorestown MID devices
487 If you have one of these systems, or if you want to build a
488 generic distribution kernel, say Y here - otherwise say N.
492 config X86_EXTENDED_PLATFORM
493 bool "Support for extended (non-PC) x86 platforms"
496 If you disable this option then the kernel will only support
497 standard PC platforms. (which covers the vast majority of
500 If you enable this option then you'll be able to select support
501 for the following (non-PC) 64 bit x86 platforms:
506 If you have one of these systems, or if you want to build a
507 generic distribution kernel, say Y here - otherwise say N.
509 # This is an alphabetically sorted list of 64 bit extended platforms
510 # Please maintain the alphabetic order if and when there are additions
512 bool "Numascale NumaChip"
514 depends on X86_EXTENDED_PLATFORM
517 depends on X86_X2APIC
518 depends on PCI_MMCONFIG
520 Adds support for Numascale NumaChip large-SMP systems. Needed to
521 enable more than ~168 cores.
522 If you don't have one of these, you should say N here.
526 select HYPERVISOR_GUEST
528 depends on X86_64 && PCI
529 depends on X86_EXTENDED_PLATFORM
532 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
533 supposed to run on these EM64T-based machines. Only choose this option
534 if you have one of these machines.
537 bool "SGI Ultraviolet"
539 depends on X86_EXTENDED_PLATFORM
542 depends on X86_X2APIC
545 This option is needed in order to support SGI Ultraviolet systems.
546 If you don't have one of these, you should say N here.
548 # Following is an alphabetically sorted list of 32 bit extended platforms
549 # Please maintain the alphabetic order if and when there are additions
552 bool "Goldfish (Virtual Platform)"
553 depends on X86_EXTENDED_PLATFORM
555 Enable support for the Goldfish virtual platform used primarily
556 for Android development. Unless you are building for the Android
557 Goldfish emulator say N here.
560 bool "CE4100 TV platform"
562 depends on PCI_GODIRECT
563 depends on X86_IO_APIC
565 depends on X86_EXTENDED_PLATFORM
566 select X86_REBOOTFIXUPS
568 select OF_EARLY_FLATTREE
570 Select for the Intel CE media processor (CE4100) SOC.
571 This option compiles in support for the CE4100 SOC for settop
572 boxes and media devices.
575 bool "Intel MID platform support"
576 depends on X86_EXTENDED_PLATFORM
577 depends on X86_PLATFORM_DEVICES
579 depends on X86_64 || (PCI_GOANY && X86_32)
580 depends on X86_IO_APIC
586 select MFD_INTEL_MSIC
588 Select to build a kernel capable of supporting Intel MID (Mobile
589 Internet Device) platform systems which do not have the PCI legacy
590 interfaces. If you are building for a PC class system say N here.
592 Intel MID platforms are based on an Intel processor and chipset which
593 consume less power than most of the x86 derivatives.
595 config X86_INTEL_QUARK
596 bool "Intel Quark platform support"
598 depends on X86_EXTENDED_PLATFORM
599 depends on X86_PLATFORM_DEVICES
603 depends on X86_IO_APIC
608 Select to include support for Quark X1000 SoC.
609 Say Y here if you have a Quark based system such as the Arduino
610 compatible Intel Galileo.
612 config X86_INTEL_LPSS
613 bool "Intel Low Power Subsystem Support"
614 depends on X86 && ACPI && PCI
619 Select to build support for Intel Low Power Subsystem such as
620 found on Intel Lynxpoint PCH. Selecting this option enables
621 things like clock tree (common clock framework) and pincontrol
622 which are needed by the LPSS peripheral drivers.
624 config X86_AMD_PLATFORM_DEVICE
625 bool "AMD ACPI2Platform devices support"
630 Select to interpret AMD specific ACPI device to platform device
631 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
632 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
633 implemented under PINCTRL subsystem.
636 tristate "Intel SoC IOSF Sideband support for SoC platforms"
639 This option enables sideband register access support for Intel SoC
640 platforms. On these platforms the IOSF sideband is used in lieu of
641 MSR's for some register accesses, mostly but not limited to thermal
642 and power. Drivers may query the availability of this device to
643 determine if they need the sideband in order to work on these
644 platforms. The sideband is available on the following SoC products.
645 This list is not meant to be exclusive.
650 You should say Y if you are running a kernel on one of these SoC's.
652 config IOSF_MBI_DEBUG
653 bool "Enable IOSF sideband access through debugfs"
654 depends on IOSF_MBI && DEBUG_FS
656 Select this option to expose the IOSF sideband access registers (MCR,
657 MDR, MCRX) through debugfs to write and read register information from
658 different units on the SoC. This is most useful for obtaining device
659 state information for debug and analysis. As this is a general access
660 mechanism, users of this option would have specific knowledge of the
661 device they want to access.
663 If you don't require the option or are in doubt, say N.
666 bool "RDC R-321x SoC"
668 depends on X86_EXTENDED_PLATFORM
670 select X86_REBOOTFIXUPS
672 This option is needed for RDC R-321x system-on-chip, also known
674 If you don't have one of these chips, you should say N here.
676 config X86_32_NON_STANDARD
677 bool "Support non-standard 32-bit SMP architectures"
678 depends on X86_32 && SMP
679 depends on X86_EXTENDED_PLATFORM
681 This option compiles in the bigsmp and STA2X11 default
682 subarchitectures. It is intended for a generic binary
683 kernel. If you select them all, kernel will probe it one by
684 one and will fallback to default.
686 # Alphabetically sorted list of Non standard 32 bit platforms
688 config X86_SUPPORTS_MEMORY_FAILURE
690 # MCE code calls memory_failure():
692 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
693 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
694 depends on X86_64 || !SPARSEMEM
695 select ARCH_SUPPORTS_MEMORY_FAILURE
698 bool "STA2X11 Companion Chip Support"
699 depends on X86_32_NON_STANDARD && PCI
700 select ARCH_HAS_PHYS_TO_DMA
705 This adds support for boards based on the STA2X11 IO-Hub,
706 a.k.a. "ConneXt". The chip is used in place of the standard
707 PC chipset, so all "standard" peripherals are missing. If this
708 option is selected the kernel will still be able to boot on
709 standard PC machines.
712 tristate "Eurobraille/Iris poweroff module"
715 The Iris machines from EuroBraille do not have APM or ACPI support
716 to shut themselves down properly. A special I/O sequence is
717 needed to do so, which is what this module does at
720 This is only for Iris machines from EuroBraille.
724 config SCHED_OMIT_FRAME_POINTER
726 prompt "Single-depth WCHAN output"
729 Calculate simpler /proc/<PID>/wchan values. If this option
730 is disabled then wchan values will recurse back to the
731 caller function. This provides more accurate wchan values,
732 at the expense of slightly more scheduling overhead.
734 If in doubt, say "Y".
736 menuconfig HYPERVISOR_GUEST
737 bool "Linux guest support"
739 Say Y here to enable options for running Linux under various hyper-
740 visors. This option enables basic hypervisor detection and platform
743 If you say N, all options in this submenu will be skipped and
744 disabled, and Linux guest support won't be built in.
749 bool "Enable paravirtualization code"
751 This changes the kernel so it can modify itself when it is run
752 under a hypervisor, potentially improving performance significantly
753 over full virtualization. However, when run without a hypervisor
754 the kernel is theoretically slower and slightly larger.
759 config PARAVIRT_DEBUG
760 bool "paravirt-ops debugging"
761 depends on PARAVIRT && DEBUG_KERNEL
763 Enable to debug paravirt_ops internals. Specifically, BUG if
764 a paravirt_op is missing when it is called.
766 config PARAVIRT_SPINLOCKS
767 bool "Paravirtualization layer for spinlocks"
768 depends on PARAVIRT && SMP
770 Paravirtualized spinlocks allow a pvops backend to replace the
771 spinlock implementation with something virtualization-friendly
772 (for example, block the virtual CPU rather than spinning).
774 It has a minimal impact on native kernels and gives a nice performance
775 benefit on paravirtualized KVM / Xen kernels.
777 If you are unsure how to answer this question, answer Y.
779 source "arch/x86/xen/Kconfig"
782 bool "KVM Guest support (including kvmclock)"
784 select PARAVIRT_CLOCK
787 This option enables various optimizations for running under the KVM
788 hypervisor. It includes a paravirtualized clock, so that instead
789 of relying on a PIT (or probably other) emulation by the
790 underlying device model, the host provides the guest with
791 timing infrastructure such as time of day, and system time
794 bool "Support for running PVH guests"
796 This option enables the PVH entry point for guest virtual machines
797 as specified in the x86/HVM direct boot ABI.
800 bool "Enable debug information for KVM Guests in debugfs"
801 depends on KVM_GUEST && DEBUG_FS
803 This option enables collection of various statistics for KVM guest.
804 Statistics are displayed in debugfs filesystem. Enabling this option
805 may incur significant overhead.
807 config PARAVIRT_TIME_ACCOUNTING
808 bool "Paravirtual steal time accounting"
811 Select this option to enable fine granularity task steal time
812 accounting. Time spent executing other tasks in parallel with
813 the current vCPU is discounted from the vCPU power. To account for
814 that, there can be a small performance impact.
816 If in doubt, say N here.
818 config PARAVIRT_CLOCK
821 config JAILHOUSE_GUEST
822 bool "Jailhouse non-root cell support"
823 depends on X86_64 && PCI
826 This option allows to run Linux as guest in a Jailhouse non-root
827 cell. You can leave this option disabled if you only want to start
828 Jailhouse and run Linux afterwards in the root cell.
830 endif #HYPERVISOR_GUEST
832 source "arch/x86/Kconfig.cpu"
836 prompt "HPET Timer Support" if X86_32
838 Use the IA-PC HPET (High Precision Event Timer) to manage
839 time in preference to the PIT and RTC, if a HPET is
841 HPET is the next generation timer replacing legacy 8254s.
842 The HPET provides a stable time base on SMP
843 systems, unlike the TSC, but it is more expensive to access,
844 as it is off-chip. The interface used is documented
845 in the HPET spec, revision 1.
847 You can safely choose Y here. However, HPET will only be
848 activated if the platform and the BIOS support this feature.
849 Otherwise the 8254 will be used for timing services.
851 Choose N to continue using the legacy 8254 timer.
853 config HPET_EMULATE_RTC
855 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
858 def_bool y if X86_INTEL_MID
859 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
861 depends on X86_INTEL_MID && SFI
863 APB timer is the replacement for 8254, HPET on X86 MID platforms.
864 The APBT provides a stable time base on SMP
865 systems, unlike the TSC, but it is more expensive to access,
866 as it is off-chip. APB timers are always running regardless of CPU
867 C states, they are used as per CPU clockevent device when possible.
869 # Mark as expert because too many people got it wrong.
870 # The code disables itself when not needed.
873 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
874 bool "Enable DMI scanning" if EXPERT
876 Enabled scanning of DMI to identify machine quirks. Say Y
877 here unless you have verified that your setup is not
878 affected by entries in the DMI blacklist. Required by PNP
882 bool "Old AMD GART IOMMU support"
885 depends on X86_64 && PCI && AMD_NB
887 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
888 GART based hardware IOMMUs.
890 The GART supports full DMA access for devices with 32-bit access
891 limitations, on systems with more than 3 GB. This is usually needed
892 for USB, sound, many IDE/SATA chipsets and some other devices.
894 Newer systems typically have a modern AMD IOMMU, supported via
895 the CONFIG_AMD_IOMMU=y config option.
897 In normal configurations this driver is only active when needed:
898 there's more than 3 GB of memory and the system contains a
899 32-bit limited device.
904 bool "IBM Calgary IOMMU support"
907 depends on X86_64 && PCI
909 Support for hardware IOMMUs in IBM's xSeries x366 and x460
910 systems. Needed to run systems with more than 3GB of memory
911 properly with 32-bit PCI devices that do not support DAC
912 (Double Address Cycle). Calgary also supports bus level
913 isolation, where all DMAs pass through the IOMMU. This
914 prevents them from going anywhere except their intended
915 destination. This catches hard-to-find kernel bugs and
916 mis-behaving drivers and devices that do not use the DMA-API
917 properly to set up their DMA buffers. The IOMMU can be
918 turned off at boot time with the iommu=off parameter.
919 Normally the kernel will make the right choice by itself.
922 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
924 prompt "Should Calgary be enabled by default?"
925 depends on CALGARY_IOMMU
927 Should Calgary be enabled by default? if you choose 'y', Calgary
928 will be used (if it exists). If you choose 'n', Calgary will not be
929 used even if it exists. If you choose 'n' and would like to use
930 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
934 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
935 depends on X86_64 && SMP && DEBUG_KERNEL
936 select CPUMASK_OFFSTACK
938 Enable maximum number of CPUS and NUMA Nodes for this architecture.
942 # The maximum number of CPUs supported:
944 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
945 # and which can be configured interactively in the
946 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
948 # The ranges are different on 32-bit and 64-bit kernels, depending on
949 # hardware capabilities and scalability features of the kernel.
951 # ( If MAXSMP is enabled we just use the highest possible value and disable
952 # interactive configuration. )
955 config NR_CPUS_RANGE_BEGIN
957 default NR_CPUS_RANGE_END if MAXSMP
961 config NR_CPUS_RANGE_END
964 default 64 if SMP && X86_BIGSMP
965 default 8 if SMP && !X86_BIGSMP
968 config NR_CPUS_RANGE_END
971 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
972 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
975 config NR_CPUS_DEFAULT
978 default 32 if X86_BIGSMP
982 config NR_CPUS_DEFAULT
985 default 8192 if MAXSMP
990 int "Maximum number of CPUs" if SMP && !MAXSMP
991 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
992 default NR_CPUS_DEFAULT
994 This allows you to specify the maximum number of CPUs which this
995 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
996 supported value is 8192, otherwise the maximum value is 512. The
997 minimum value which makes sense is 2.
999 This is purely to save memory: each supported CPU adds about 8KB
1000 to the kernel image.
1007 prompt "Multi-core scheduler support"
1010 Multi-core scheduler support improves the CPU scheduler's decision
1011 making when dealing with multi-core CPU chips at a cost of slightly
1012 increased overhead in some places. If unsure say N here.
1014 config SCHED_MC_PRIO
1015 bool "CPU core priorities scheduler support"
1016 depends on SCHED_MC && CPU_SUP_INTEL
1017 select X86_INTEL_PSTATE
1021 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1022 core ordering determined at manufacturing time, which allows
1023 certain cores to reach higher turbo frequencies (when running
1024 single threaded workloads) than others.
1026 Enabling this kernel feature teaches the scheduler about
1027 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1028 scheduler's CPU selection logic accordingly, so that higher
1029 overall system performance can be achieved.
1031 This feature will have no effect on CPUs without this feature.
1033 If unsure say Y here.
1037 depends on !SMP && X86_LOCAL_APIC
1040 bool "Local APIC support on uniprocessors" if !PCI_MSI
1042 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1044 A local APIC (Advanced Programmable Interrupt Controller) is an
1045 integrated interrupt controller in the CPU. If you have a single-CPU
1046 system which has a processor with a local APIC, you can say Y here to
1047 enable and use it. If you say Y here even though your machine doesn't
1048 have a local APIC, then the kernel will still run with no slowdown at
1049 all. The local APIC supports CPU-generated self-interrupts (timer,
1050 performance counters), and the NMI watchdog which detects hard
1053 config X86_UP_IOAPIC
1054 bool "IO-APIC support on uniprocessors"
1055 depends on X86_UP_APIC
1057 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1058 SMP-capable replacement for PC-style interrupt controllers. Most
1059 SMP systems and many recent uniprocessor systems have one.
1061 If you have a single-CPU system with an IO-APIC, you can say Y here
1062 to use it. If you say Y here even though your machine doesn't have
1063 an IO-APIC, then the kernel will still run with no slowdown at all.
1065 config X86_LOCAL_APIC
1067 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1068 select IRQ_DOMAIN_HIERARCHY
1069 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1073 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1075 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1076 bool "Reroute for broken boot IRQs"
1077 depends on X86_IO_APIC
1079 This option enables a workaround that fixes a source of
1080 spurious interrupts. This is recommended when threaded
1081 interrupt handling is used on systems where the generation of
1082 superfluous "boot interrupts" cannot be disabled.
1084 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1085 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1086 kernel does during interrupt handling). On chipsets where this
1087 boot IRQ generation cannot be disabled, this workaround keeps
1088 the original IRQ line masked so that only the equivalent "boot
1089 IRQ" is delivered to the CPUs. The workaround also tells the
1090 kernel to set up the IRQ handler on the boot IRQ line. In this
1091 way only one interrupt is delivered to the kernel. Otherwise
1092 the spurious second interrupt may cause the kernel to bring
1093 down (vital) interrupt lines.
1095 Only affects "broken" chipsets. Interrupt sharing may be
1096 increased on these systems.
1099 bool "Machine Check / overheating reporting"
1100 select GENERIC_ALLOCATOR
1103 Machine Check support allows the processor to notify the
1104 kernel if it detects a problem (e.g. overheating, data corruption).
1105 The action the kernel takes depends on the severity of the problem,
1106 ranging from warning messages to halting the machine.
1108 config X86_MCELOG_LEGACY
1109 bool "Support for deprecated /dev/mcelog character device"
1112 Enable support for /dev/mcelog which is needed by the old mcelog
1113 userspace logging daemon. Consider switching to the new generation
1116 config X86_MCE_INTEL
1118 prompt "Intel MCE features"
1119 depends on X86_MCE && X86_LOCAL_APIC
1121 Additional support for intel specific MCE features such as
1122 the thermal monitor.
1126 prompt "AMD MCE features"
1127 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1129 Additional support for AMD specific MCE features such as
1130 the DRAM Error Threshold.
1132 config X86_ANCIENT_MCE
1133 bool "Support for old Pentium 5 / WinChip machine checks"
1134 depends on X86_32 && X86_MCE
1136 Include support for machine check handling on old Pentium 5 or WinChip
1137 systems. These typically need to be enabled explicitly on the command
1140 config X86_MCE_THRESHOLD
1141 depends on X86_MCE_AMD || X86_MCE_INTEL
1144 config X86_MCE_INJECT
1145 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1146 tristate "Machine check injector support"
1148 Provide support for injecting machine checks for testing purposes.
1149 If you don't know what a machine check is and you don't do kernel
1150 QA it is safe to say n.
1152 config X86_THERMAL_VECTOR
1154 depends on X86_MCE_INTEL
1156 source "arch/x86/events/Kconfig"
1158 config X86_LEGACY_VM86
1159 bool "Legacy VM86 support"
1162 This option allows user programs to put the CPU into V8086
1163 mode, which is an 80286-era approximation of 16-bit real mode.
1165 Some very old versions of X and/or vbetool require this option
1166 for user mode setting. Similarly, DOSEMU will use it if
1167 available to accelerate real mode DOS programs. However, any
1168 recent version of DOSEMU, X, or vbetool should be fully
1169 functional even without kernel VM86 support, as they will all
1170 fall back to software emulation. Nevertheless, if you are using
1171 a 16-bit DOS program where 16-bit performance matters, vm86
1172 mode might be faster than emulation and you might want to
1175 Note that any app that works on a 64-bit kernel is unlikely to
1176 need this option, as 64-bit kernels don't, and can't, support
1177 V8086 mode. This option is also unrelated to 16-bit protected
1178 mode and is not needed to run most 16-bit programs under Wine.
1180 Enabling this option increases the complexity of the kernel
1181 and slows down exception handling a tiny bit.
1183 If unsure, say N here.
1187 default X86_LEGACY_VM86
1190 bool "Enable support for 16-bit segments" if EXPERT
1192 depends on MODIFY_LDT_SYSCALL
1194 This option is required by programs like Wine to run 16-bit
1195 protected mode legacy code on x86 processors. Disabling
1196 this option saves about 300 bytes on i386, or around 6K text
1197 plus 16K runtime memory on x86-64,
1201 depends on X86_16BIT && X86_32
1205 depends on X86_16BIT && X86_64
1207 config X86_VSYSCALL_EMULATION
1208 bool "Enable vsyscall emulation" if EXPERT
1212 This enables emulation of the legacy vsyscall page. Disabling
1213 it is roughly equivalent to booting with vsyscall=none, except
1214 that it will also disable the helpful warning if a program
1215 tries to use a vsyscall. With this option set to N, offending
1216 programs will just segfault, citing addresses of the form
1219 This option is required by many programs built before 2013, and
1220 care should be used even with newer programs if set to N.
1222 Disabling this option saves about 7K of kernel size and
1223 possibly 4K of additional runtime pagetable memory.
1226 tristate "Toshiba Laptop support"
1229 This adds a driver to safely access the System Management Mode of
1230 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1231 not work on models with a Phoenix BIOS. The System Management Mode
1232 is used to set the BIOS and power saving options on Toshiba portables.
1234 For information on utilities to make use of this driver see the
1235 Toshiba Linux utilities web site at:
1236 <http://www.buzzard.org.uk/toshiba/>.
1238 Say Y if you intend to run this kernel on a Toshiba portable.
1242 tristate "Dell i8k legacy laptop support"
1244 select SENSORS_DELL_SMM
1246 This option enables legacy /proc/i8k userspace interface in hwmon
1247 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1248 temperature and allows controlling fan speeds of Dell laptops via
1249 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1250 it reports also power and hotkey status. For fan speed control is
1251 needed userspace package i8kutils.
1253 Say Y if you intend to run this kernel on old Dell laptops or want to
1254 use userspace package i8kutils.
1257 config X86_REBOOTFIXUPS
1258 bool "Enable X86 board specific fixups for reboot"
1261 This enables chipset and/or board specific fixups to be done
1262 in order to get reboot to work correctly. This is only needed on
1263 some combinations of hardware and BIOS. The symptom, for which
1264 this config is intended, is when reboot ends with a stalled/hung
1267 Currently, the only fixup is for the Geode machines using
1268 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1270 Say Y if you want to enable the fixup. Currently, it's safe to
1271 enable this option even if you don't need it.
1275 bool "CPU microcode loading support"
1277 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1280 If you say Y here, you will be able to update the microcode on
1281 Intel and AMD processors. The Intel support is for the IA32 family,
1282 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1283 AMD support is for families 0x10 and later. You will obviously need
1284 the actual microcode binary data itself which is not shipped with
1287 The preferred method to load microcode from a detached initrd is described
1288 in Documentation/x86/microcode.txt. For that you need to enable
1289 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1290 initrd for microcode blobs.
1292 In addition, you can build the microcode into the kernel. For that you
1293 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1296 config MICROCODE_INTEL
1297 bool "Intel microcode loading support"
1298 depends on MICROCODE
1302 This options enables microcode patch loading support for Intel
1305 For the current Intel microcode data package go to
1306 <https://downloadcenter.intel.com> and search for
1307 'Linux Processor Microcode Data File'.
1309 config MICROCODE_AMD
1310 bool "AMD microcode loading support"
1311 depends on MICROCODE
1314 If you select this option, microcode patch loading support for AMD
1315 processors will be enabled.
1317 config MICROCODE_OLD_INTERFACE
1318 bool "Ancient loading interface (DEPRECATED)"
1320 depends on MICROCODE
1322 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1323 which was used by userspace tools like iucode_tool and microcode.ctl.
1324 It is inadequate because it runs too late to be able to properly
1325 load microcode on a machine and it needs special tools. Instead, you
1326 should've switched to the early loading method with the initrd or
1327 builtin microcode by now: Documentation/x86/microcode.txt
1330 tristate "/dev/cpu/*/msr - Model-specific register support"
1332 This device gives privileged processes access to the x86
1333 Model-Specific Registers (MSRs). It is a character device with
1334 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1335 MSR accesses are directed to a specific CPU on multi-processor
1339 tristate "/dev/cpu/*/cpuid - CPU information support"
1341 This device gives processes access to the x86 CPUID instruction to
1342 be executed on a specific processor. It is a character device
1343 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1347 prompt "High Memory Support"
1354 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1355 However, the address space of 32-bit x86 processors is only 4
1356 Gigabytes large. That means that, if you have a large amount of
1357 physical memory, not all of it can be "permanently mapped" by the
1358 kernel. The physical memory that's not permanently mapped is called
1361 If you are compiling a kernel which will never run on a machine with
1362 more than 1 Gigabyte total physical RAM, answer "off" here (default
1363 choice and suitable for most users). This will result in a "3GB/1GB"
1364 split: 3GB are mapped so that each process sees a 3GB virtual memory
1365 space and the remaining part of the 4GB virtual memory space is used
1366 by the kernel to permanently map as much physical memory as
1369 If the machine has between 1 and 4 Gigabytes physical RAM, then
1372 If more than 4 Gigabytes is used then answer "64GB" here. This
1373 selection turns Intel PAE (Physical Address Extension) mode on.
1374 PAE implements 3-level paging on IA32 processors. PAE is fully
1375 supported by Linux, PAE mode is implemented on all recent Intel
1376 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1377 then the kernel will not boot on CPUs that don't support PAE!
1379 The actual amount of total physical memory will either be
1380 auto detected or can be forced by using a kernel command line option
1381 such as "mem=256M". (Try "man bootparam" or see the documentation of
1382 your boot loader (lilo or loadlin) about how to pass options to the
1383 kernel at boot time.)
1385 If unsure, say "off".
1390 Select this if you have a 32-bit processor and between 1 and 4
1391 gigabytes of physical RAM.
1395 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1398 Select this if you have a 32-bit processor and more than 4
1399 gigabytes of physical RAM.
1404 prompt "Memory split" if EXPERT
1408 Select the desired split between kernel and user memory.
1410 If the address range available to the kernel is less than the
1411 physical memory installed, the remaining memory will be available
1412 as "high memory". Accessing high memory is a little more costly
1413 than low memory, as it needs to be mapped into the kernel first.
1414 Note that increasing the kernel address space limits the range
1415 available to user programs, making the address space there
1416 tighter. Selecting anything other than the default 3G/1G split
1417 will also likely make your kernel incompatible with binary-only
1420 If you are not absolutely sure what you are doing, leave this
1424 bool "3G/1G user/kernel split"
1425 config VMSPLIT_3G_OPT
1427 bool "3G/1G user/kernel split (for full 1G low memory)"
1429 bool "2G/2G user/kernel split"
1430 config VMSPLIT_2G_OPT
1432 bool "2G/2G user/kernel split (for full 2G low memory)"
1434 bool "1G/3G user/kernel split"
1439 default 0xB0000000 if VMSPLIT_3G_OPT
1440 default 0x80000000 if VMSPLIT_2G
1441 default 0x78000000 if VMSPLIT_2G_OPT
1442 default 0x40000000 if VMSPLIT_1G
1448 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1451 bool "PAE (Physical Address Extension) Support"
1452 depends on X86_32 && !HIGHMEM4G
1453 select PHYS_ADDR_T_64BIT
1456 PAE is required for NX support, and furthermore enables
1457 larger swapspace support for non-overcommit purposes. It
1458 has the cost of more pagetable lookup overhead, and also
1459 consumes more pagetable space per process.
1462 bool "Enable 5-level page tables support"
1463 select DYNAMIC_MEMORY_LAYOUT
1464 select SPARSEMEM_VMEMMAP
1467 5-level paging enables access to larger address space:
1468 upto 128 PiB of virtual address space and 4 PiB of
1469 physical address space.
1471 It will be supported by future Intel CPUs.
1473 A kernel with the option enabled can be booted on machines that
1474 support 4- or 5-level paging.
1476 See Documentation/x86/x86_64/5level-paging.txt for more
1481 config X86_DIRECT_GBPAGES
1483 depends on X86_64 && !DEBUG_PAGEALLOC
1485 Certain kernel features effectively disable kernel
1486 linear 1 GB mappings (even if the CPU otherwise
1487 supports them), so don't confuse the user by printing
1488 that we have them enabled.
1490 config X86_CPA_STATISTICS
1491 bool "Enable statistic for Change Page Attribute"
1494 Expose statistics about the Change Page Attribute mechanims, which
1495 helps to determine the effectiveness of preserving large and huge
1496 page mappings when mapping protections are changed.
1498 config ARCH_HAS_MEM_ENCRYPT
1501 config AMD_MEM_ENCRYPT
1502 bool "AMD Secure Memory Encryption (SME) support"
1503 depends on X86_64 && CPU_SUP_AMD
1504 select DYNAMIC_PHYSICAL_MASK
1505 select ARCH_USE_MEMREMAP_PROT
1507 Say yes to enable support for the encryption of system memory.
1508 This requires an AMD processor that supports Secure Memory
1511 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1512 bool "Activate AMD Secure Memory Encryption (SME) by default"
1514 depends on AMD_MEM_ENCRYPT
1516 Say yes to have system memory encrypted by default if running on
1517 an AMD processor that supports Secure Memory Encryption (SME).
1519 If set to Y, then the encryption of system memory can be
1520 deactivated with the mem_encrypt=off command line option.
1522 If set to N, then the encryption of system memory can be
1523 activated with the mem_encrypt=on command line option.
1525 # Common NUMA Features
1527 bool "Numa Memory Allocation and Scheduler Support"
1529 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1530 default y if X86_BIGSMP
1532 Enable NUMA (Non Uniform Memory Access) support.
1534 The kernel will try to allocate memory used by a CPU on the
1535 local memory controller of the CPU and add some more
1536 NUMA awareness to the kernel.
1538 For 64-bit this is recommended if the system is Intel Core i7
1539 (or later), AMD Opteron, or EM64T NUMA.
1541 For 32-bit this is only needed if you boot a 32-bit
1542 kernel on a 64-bit NUMA platform.
1544 Otherwise, you should say N.
1548 prompt "Old style AMD Opteron NUMA detection"
1549 depends on X86_64 && NUMA && PCI
1551 Enable AMD NUMA node topology detection. You should say Y here if
1552 you have a multi processor AMD system. This uses an old method to
1553 read the NUMA configuration directly from the builtin Northbridge
1554 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1555 which also takes priority if both are compiled in.
1557 config X86_64_ACPI_NUMA
1559 prompt "ACPI NUMA detection"
1560 depends on X86_64 && NUMA && ACPI && PCI
1563 Enable ACPI SRAT based node topology detection.
1565 # Some NUMA nodes have memory ranges that span
1566 # other nodes. Even though a pfn is valid and
1567 # between a node's start and end pfns, it may not
1568 # reside on that node. See memmap_init_zone()
1570 config NODES_SPAN_OTHER_NODES
1572 depends on X86_64_ACPI_NUMA
1575 bool "NUMA emulation"
1578 Enable NUMA emulation. A flat machine will be split
1579 into virtual nodes when booted with "numa=fake=N", where N is the
1580 number of nodes. This is only useful for debugging.
1583 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1585 default "10" if MAXSMP
1586 default "6" if X86_64
1588 depends on NEED_MULTIPLE_NODES
1590 Specify the maximum number of NUMA Nodes available on the target
1591 system. Increases memory reserved to accommodate various tables.
1593 config ARCH_HAVE_MEMORY_PRESENT
1595 depends on X86_32 && DISCONTIGMEM
1597 config ARCH_FLATMEM_ENABLE
1599 depends on X86_32 && !NUMA
1601 config ARCH_DISCONTIGMEM_ENABLE
1603 depends on NUMA && X86_32
1606 config ARCH_SPARSEMEM_ENABLE
1608 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1609 select SPARSEMEM_STATIC if X86_32
1610 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1612 config ARCH_SPARSEMEM_DEFAULT
1613 def_bool X86_64 || (NUMA && X86_32)
1615 config ARCH_SELECT_MEMORY_MODEL
1617 depends on ARCH_SPARSEMEM_ENABLE
1619 config ARCH_MEMORY_PROBE
1620 bool "Enable sysfs memory/probe interface"
1621 depends on X86_64 && MEMORY_HOTPLUG
1623 This option enables a sysfs memory/probe interface for testing.
1624 See Documentation/memory-hotplug.txt for more information.
1625 If you are unsure how to answer this question, answer N.
1627 config ARCH_PROC_KCORE_TEXT
1629 depends on X86_64 && PROC_KCORE
1631 config ILLEGAL_POINTER_VALUE
1634 default 0xdead000000000000 if X86_64
1636 config X86_PMEM_LEGACY_DEVICE
1639 config X86_PMEM_LEGACY
1640 tristate "Support non-standard NVDIMMs and ADR protected memory"
1641 depends on PHYS_ADDR_T_64BIT
1643 select X86_PMEM_LEGACY_DEVICE
1646 Treat memory marked using the non-standard e820 type of 12 as used
1647 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1648 The kernel will offer these regions to the 'pmem' driver so
1649 they can be used for persistent storage.
1654 bool "Allocate 3rd-level pagetables from highmem"
1657 The VM uses one page table entry for each page of physical memory.
1658 For systems with a lot of RAM, this can be wasteful of precious
1659 low memory. Setting this option will put user-space page table
1660 entries in high memory.
1662 config X86_CHECK_BIOS_CORRUPTION
1663 bool "Check for low memory corruption"
1665 Periodically check for memory corruption in low memory, which
1666 is suspected to be caused by BIOS. Even when enabled in the
1667 configuration, it is disabled at runtime. Enable it by
1668 setting "memory_corruption_check=1" on the kernel command
1669 line. By default it scans the low 64k of memory every 60
1670 seconds; see the memory_corruption_check_size and
1671 memory_corruption_check_period parameters in
1672 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1674 When enabled with the default parameters, this option has
1675 almost no overhead, as it reserves a relatively small amount
1676 of memory and scans it infrequently. It both detects corruption
1677 and prevents it from affecting the running system.
1679 It is, however, intended as a diagnostic tool; if repeatable
1680 BIOS-originated corruption always affects the same memory,
1681 you can use memmap= to prevent the kernel from using that
1684 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1685 bool "Set the default setting of memory_corruption_check"
1686 depends on X86_CHECK_BIOS_CORRUPTION
1689 Set whether the default state of memory_corruption_check is
1692 config X86_RESERVE_LOW
1693 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1697 Specify the amount of low memory to reserve for the BIOS.
1699 The first page contains BIOS data structures that the kernel
1700 must not use, so that page must always be reserved.
1702 By default we reserve the first 64K of physical RAM, as a
1703 number of BIOSes are known to corrupt that memory range
1704 during events such as suspend/resume or monitor cable
1705 insertion, so it must not be used by the kernel.
1707 You can set this to 4 if you are absolutely sure that you
1708 trust the BIOS to get all its memory reservations and usages
1709 right. If you know your BIOS have problems beyond the
1710 default 64K area, you can set this to 640 to avoid using the
1711 entire low memory range.
1713 If you have doubts about the BIOS (e.g. suspend/resume does
1714 not work or there's kernel crashes after certain hardware
1715 hotplug events) then you might want to enable
1716 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1717 typical corruption patterns.
1719 Leave this to the default value of 64 if you are unsure.
1721 config MATH_EMULATION
1723 depends on MODIFY_LDT_SYSCALL
1724 prompt "Math emulation" if X86_32
1726 Linux can emulate a math coprocessor (used for floating point
1727 operations) if you don't have one. 486DX and Pentium processors have
1728 a math coprocessor built in, 486SX and 386 do not, unless you added
1729 a 487DX or 387, respectively. (The messages during boot time can
1730 give you some hints here ["man dmesg"].) Everyone needs either a
1731 coprocessor or this emulation.
1733 If you don't have a math coprocessor, you need to say Y here; if you
1734 say Y here even though you have a coprocessor, the coprocessor will
1735 be used nevertheless. (This behavior can be changed with the kernel
1736 command line option "no387", which comes handy if your coprocessor
1737 is broken. Try "man bootparam" or see the documentation of your boot
1738 loader (lilo or loadlin) about how to pass options to the kernel at
1739 boot time.) This means that it is a good idea to say Y here if you
1740 intend to use this kernel on different machines.
1742 More information about the internals of the Linux math coprocessor
1743 emulation can be found in <file:arch/x86/math-emu/README>.
1745 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1746 kernel, it won't hurt.
1750 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1752 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1753 the Memory Type Range Registers (MTRRs) may be used to control
1754 processor access to memory ranges. This is most useful if you have
1755 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1756 allows bus write transfers to be combined into a larger transfer
1757 before bursting over the PCI/AGP bus. This can increase performance
1758 of image write operations 2.5 times or more. Saying Y here creates a
1759 /proc/mtrr file which may be used to manipulate your processor's
1760 MTRRs. Typically the X server should use this.
1762 This code has a reasonably generic interface so that similar
1763 control registers on other processors can be easily supported
1766 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1767 Registers (ARRs) which provide a similar functionality to MTRRs. For
1768 these, the ARRs are used to emulate the MTRRs.
1769 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1770 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1771 write-combining. All of these processors are supported by this code
1772 and it makes sense to say Y here if you have one of them.
1774 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1775 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1776 can lead to all sorts of problems, so it's good to say Y here.
1778 You can safely say Y even if your machine doesn't have MTRRs, you'll
1779 just add about 9 KB to your kernel.
1781 See <file:Documentation/x86/mtrr.txt> for more information.
1783 config MTRR_SANITIZER
1785 prompt "MTRR cleanup support"
1788 Convert MTRR layout from continuous to discrete, so X drivers can
1789 add writeback entries.
1791 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1792 The largest mtrr entry size for a continuous block can be set with
1797 config MTRR_SANITIZER_ENABLE_DEFAULT
1798 int "MTRR cleanup enable value (0-1)"
1801 depends on MTRR_SANITIZER
1803 Enable mtrr cleanup default value
1805 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1806 int "MTRR cleanup spare reg num (0-7)"
1809 depends on MTRR_SANITIZER
1811 mtrr cleanup spare entries default, it can be changed via
1812 mtrr_spare_reg_nr=N on the kernel command line.
1816 prompt "x86 PAT support" if EXPERT
1819 Use PAT attributes to setup page level cache control.
1821 PATs are the modern equivalents of MTRRs and are much more
1822 flexible than MTRRs.
1824 Say N here if you see bootup problems (boot crash, boot hang,
1825 spontaneous reboots) or a non-working video driver.
1829 config ARCH_USES_PG_UNCACHED
1835 prompt "x86 architectural random number generator" if EXPERT
1837 Enable the x86 architectural RDRAND instruction
1838 (Intel Bull Mountain technology) to generate random numbers.
1839 If supported, this is a high bandwidth, cryptographically
1840 secure hardware random number generator.
1844 prompt "Supervisor Mode Access Prevention" if EXPERT
1846 Supervisor Mode Access Prevention (SMAP) is a security
1847 feature in newer Intel processors. There is a small
1848 performance cost if this enabled and turned on; there is
1849 also a small increase in the kernel size if this is enabled.
1853 config X86_INTEL_UMIP
1855 depends on CPU_SUP_INTEL
1856 prompt "Intel User Mode Instruction Prevention" if EXPERT
1858 The User Mode Instruction Prevention (UMIP) is a security
1859 feature in newer Intel processors. If enabled, a general
1860 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1861 or STR instructions are executed in user mode. These instructions
1862 unnecessarily expose information about the hardware state.
1864 The vast majority of applications do not use these instructions.
1865 For the very few that do, software emulation is provided in
1866 specific cases in protected and virtual-8086 modes. Emulated
1869 config X86_INTEL_MPX
1870 prompt "Intel MPX (Memory Protection Extensions)"
1872 # Note: only available in 64-bit mode due to VMA flags shortage
1873 depends on CPU_SUP_INTEL && X86_64
1874 select ARCH_USES_HIGH_VMA_FLAGS
1876 MPX provides hardware features that can be used in
1877 conjunction with compiler-instrumented code to check
1878 memory references. It is designed to detect buffer
1879 overflow or underflow bugs.
1881 This option enables running applications which are
1882 instrumented or otherwise use MPX. It does not use MPX
1883 itself inside the kernel or to protect the kernel
1884 against bad memory references.
1886 Enabling this option will make the kernel larger:
1887 ~8k of kernel text and 36 bytes of data on a 64-bit
1888 defconfig. It adds a long to the 'mm_struct' which
1889 will increase the kernel memory overhead of each
1890 process and adds some branches to paths used during
1891 exec() and munmap().
1893 For details, see Documentation/x86/intel_mpx.txt
1897 config X86_INTEL_MEMORY_PROTECTION_KEYS
1898 prompt "Intel Memory Protection Keys"
1900 # Note: only available in 64-bit mode
1901 depends on CPU_SUP_INTEL && X86_64
1902 select ARCH_USES_HIGH_VMA_FLAGS
1903 select ARCH_HAS_PKEYS
1905 Memory Protection Keys provides a mechanism for enforcing
1906 page-based protections, but without requiring modification of the
1907 page tables when an application changes protection domains.
1909 For details, see Documentation/x86/protection-keys.txt
1914 bool "EFI runtime service support"
1917 select EFI_RUNTIME_WRAPPERS
1919 This enables the kernel to use EFI runtime services that are
1920 available (such as the EFI variable services).
1922 This option is only useful on systems that have EFI firmware.
1923 In addition, you should use the latest ELILO loader available
1924 at <http://elilo.sourceforge.net> in order to take advantage
1925 of EFI runtime services. However, even with this option, the
1926 resultant kernel should continue to boot on existing non-EFI
1930 bool "EFI stub support"
1931 depends on EFI && !X86_USE_3DNOW
1934 This kernel feature allows a bzImage to be loaded directly
1935 by EFI firmware without the use of a bootloader.
1937 See Documentation/efi-stub.txt for more information.
1940 bool "EFI mixed-mode support"
1941 depends on EFI_STUB && X86_64
1943 Enabling this feature allows a 64-bit kernel to be booted
1944 on a 32-bit firmware, provided that your CPU supports 64-bit
1947 Note that it is not possible to boot a mixed-mode enabled
1948 kernel via the EFI boot stub - a bootloader that supports
1949 the EFI handover protocol must be used.
1955 prompt "Enable seccomp to safely compute untrusted bytecode"
1957 This kernel feature is useful for number crunching applications
1958 that may need to compute untrusted bytecode during their
1959 execution. By using pipes or other transports made available to
1960 the process as file descriptors supporting the read/write
1961 syscalls, it's possible to isolate those applications in
1962 their own address space using seccomp. Once seccomp is
1963 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1964 and the task is only allowed to execute a few safe syscalls
1965 defined by each seccomp mode.
1967 If unsure, say Y. Only embedded should say N here.
1969 source "kernel/Kconfig.hz"
1972 bool "kexec system call"
1975 kexec is a system call that implements the ability to shutdown your
1976 current kernel, and to start another kernel. It is like a reboot
1977 but it is independent of the system firmware. And like a reboot
1978 you can start any kernel with it, not just Linux.
1980 The name comes from the similarity to the exec system call.
1982 It is an ongoing process to be certain the hardware in a machine
1983 is properly shutdown, so do not be surprised if this code does not
1984 initially work for you. As of this writing the exact hardware
1985 interface is strongly in flux, so no good recommendation can be
1989 bool "kexec file based system call"
1994 depends on CRYPTO_SHA256=y
1996 This is new version of kexec system call. This system call is
1997 file based and takes file descriptors as system call argument
1998 for kernel and initramfs as opposed to list of segments as
1999 accepted by previous system call.
2001 config ARCH_HAS_KEXEC_PURGATORY
2004 config KEXEC_VERIFY_SIG
2005 bool "Verify kernel signature during kexec_file_load() syscall"
2006 depends on KEXEC_FILE
2008 This option makes kernel signature verification mandatory for
2009 the kexec_file_load() syscall.
2011 In addition to that option, you need to enable signature
2012 verification for the corresponding kernel image type being
2013 loaded in order for this to work.
2015 config KEXEC_BZIMAGE_VERIFY_SIG
2016 bool "Enable bzImage signature verification support"
2017 depends on KEXEC_VERIFY_SIG
2018 depends on SIGNED_PE_FILE_VERIFICATION
2019 select SYSTEM_TRUSTED_KEYRING
2021 Enable bzImage signature verification support.
2024 bool "kernel crash dumps"
2025 depends on X86_64 || (X86_32 && HIGHMEM)
2027 Generate crash dump after being started by kexec.
2028 This should be normally only set in special crash dump kernels
2029 which are loaded in the main kernel with kexec-tools into
2030 a specially reserved region and then later executed after
2031 a crash by kdump/kexec. The crash dump kernel must be compiled
2032 to a memory address not used by the main kernel or BIOS using
2033 PHYSICAL_START, or it must be built as a relocatable image
2034 (CONFIG_RELOCATABLE=y).
2035 For more details see Documentation/kdump/kdump.txt
2039 depends on KEXEC && HIBERNATION
2041 Jump between original kernel and kexeced kernel and invoke
2042 code in physical address mode via KEXEC
2044 config PHYSICAL_START
2045 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2048 This gives the physical address where the kernel is loaded.
2050 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2051 bzImage will decompress itself to above physical address and
2052 run from there. Otherwise, bzImage will run from the address where
2053 it has been loaded by the boot loader and will ignore above physical
2056 In normal kdump cases one does not have to set/change this option
2057 as now bzImage can be compiled as a completely relocatable image
2058 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2059 address. This option is mainly useful for the folks who don't want
2060 to use a bzImage for capturing the crash dump and want to use a
2061 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2062 to be specifically compiled to run from a specific memory area
2063 (normally a reserved region) and this option comes handy.
2065 So if you are using bzImage for capturing the crash dump,
2066 leave the value here unchanged to 0x1000000 and set
2067 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2068 for capturing the crash dump change this value to start of
2069 the reserved region. In other words, it can be set based on
2070 the "X" value as specified in the "crashkernel=YM@XM"
2071 command line boot parameter passed to the panic-ed
2072 kernel. Please take a look at Documentation/kdump/kdump.txt
2073 for more details about crash dumps.
2075 Usage of bzImage for capturing the crash dump is recommended as
2076 one does not have to build two kernels. Same kernel can be used
2077 as production kernel and capture kernel. Above option should have
2078 gone away after relocatable bzImage support is introduced. But it
2079 is present because there are users out there who continue to use
2080 vmlinux for dump capture. This option should go away down the
2083 Don't change this unless you know what you are doing.
2086 bool "Build a relocatable kernel"
2089 This builds a kernel image that retains relocation information
2090 so it can be loaded someplace besides the default 1MB.
2091 The relocations tend to make the kernel binary about 10% larger,
2092 but are discarded at runtime.
2094 One use is for the kexec on panic case where the recovery kernel
2095 must live at a different physical address than the primary
2098 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2099 it has been loaded at and the compile time physical address
2100 (CONFIG_PHYSICAL_START) is used as the minimum location.
2102 config RANDOMIZE_BASE
2103 bool "Randomize the address of the kernel image (KASLR)"
2104 depends on RELOCATABLE
2107 In support of Kernel Address Space Layout Randomization (KASLR),
2108 this randomizes the physical address at which the kernel image
2109 is decompressed and the virtual address where the kernel
2110 image is mapped, as a security feature that deters exploit
2111 attempts relying on knowledge of the location of kernel
2114 On 64-bit, the kernel physical and virtual addresses are
2115 randomized separately. The physical address will be anywhere
2116 between 16MB and the top of physical memory (up to 64TB). The
2117 virtual address will be randomized from 16MB up to 1GB (9 bits
2118 of entropy). Note that this also reduces the memory space
2119 available to kernel modules from 1.5GB to 1GB.
2121 On 32-bit, the kernel physical and virtual addresses are
2122 randomized together. They will be randomized from 16MB up to
2123 512MB (8 bits of entropy).
2125 Entropy is generated using the RDRAND instruction if it is
2126 supported. If RDTSC is supported, its value is mixed into
2127 the entropy pool as well. If neither RDRAND nor RDTSC are
2128 supported, then entropy is read from the i8254 timer. The
2129 usable entropy is limited by the kernel being built using
2130 2GB addressing, and that PHYSICAL_ALIGN must be at a
2131 minimum of 2MB. As a result, only 10 bits of entropy are
2132 theoretically possible, but the implementations are further
2133 limited due to memory layouts.
2137 # Relocation on x86 needs some additional build support
2138 config X86_NEED_RELOCS
2140 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2142 config PHYSICAL_ALIGN
2143 hex "Alignment value to which kernel should be aligned"
2145 range 0x2000 0x1000000 if X86_32
2146 range 0x200000 0x1000000 if X86_64
2148 This value puts the alignment restrictions on physical address
2149 where kernel is loaded and run from. Kernel is compiled for an
2150 address which meets above alignment restriction.
2152 If bootloader loads the kernel at a non-aligned address and
2153 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2154 address aligned to above value and run from there.
2156 If bootloader loads the kernel at a non-aligned address and
2157 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2158 load address and decompress itself to the address it has been
2159 compiled for and run from there. The address for which kernel is
2160 compiled already meets above alignment restrictions. Hence the
2161 end result is that kernel runs from a physical address meeting
2162 above alignment restrictions.
2164 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2165 this value must be a multiple of 0x200000.
2167 Don't change this unless you know what you are doing.
2169 config DYNAMIC_MEMORY_LAYOUT
2172 This option makes base addresses of vmalloc and vmemmap as well as
2173 __PAGE_OFFSET movable during boot.
2175 config RANDOMIZE_MEMORY
2176 bool "Randomize the kernel memory sections"
2178 depends on RANDOMIZE_BASE
2179 select DYNAMIC_MEMORY_LAYOUT
2180 default RANDOMIZE_BASE
2182 Randomizes the base virtual address of kernel memory sections
2183 (physical memory mapping, vmalloc & vmemmap). This security feature
2184 makes exploits relying on predictable memory locations less reliable.
2186 The order of allocations remains unchanged. Entropy is generated in
2187 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2188 configuration have in average 30,000 different possible virtual
2189 addresses for each memory section.
2193 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2194 hex "Physical memory mapping padding" if EXPERT
2195 depends on RANDOMIZE_MEMORY
2196 default "0xa" if MEMORY_HOTPLUG
2198 range 0x1 0x40 if MEMORY_HOTPLUG
2201 Define the padding in terabytes added to the existing physical
2202 memory size during kernel memory randomization. It is useful
2203 for memory hotplug support but reduces the entropy available for
2204 address randomization.
2206 If unsure, leave at the default value.
2212 config BOOTPARAM_HOTPLUG_CPU0
2213 bool "Set default setting of cpu0_hotpluggable"
2214 depends on HOTPLUG_CPU
2216 Set whether default state of cpu0_hotpluggable is on or off.
2218 Say Y here to enable CPU0 hotplug by default. If this switch
2219 is turned on, there is no need to give cpu0_hotplug kernel
2220 parameter and the CPU0 hotplug feature is enabled by default.
2222 Please note: there are two known CPU0 dependencies if you want
2223 to enable the CPU0 hotplug feature either by this switch or by
2224 cpu0_hotplug kernel parameter.
2226 First, resume from hibernate or suspend always starts from CPU0.
2227 So hibernate and suspend are prevented if CPU0 is offline.
2229 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2230 offline if any interrupt can not migrate out of CPU0. There may
2231 be other CPU0 dependencies.
2233 Please make sure the dependencies are under your control before
2234 you enable this feature.
2236 Say N if you don't want to enable CPU0 hotplug feature by default.
2237 You still can enable the CPU0 hotplug feature at boot by kernel
2238 parameter cpu0_hotplug.
2240 config DEBUG_HOTPLUG_CPU0
2242 prompt "Debug CPU0 hotplug"
2243 depends on HOTPLUG_CPU
2245 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2246 soon as possible and boots up userspace with CPU0 offlined. User
2247 can online CPU0 back after boot time.
2249 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2250 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2251 compilation or giving cpu0_hotplug kernel parameter at boot.
2257 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2258 depends on COMPAT_32
2260 Certain buggy versions of glibc will crash if they are
2261 presented with a 32-bit vDSO that is not mapped at the address
2262 indicated in its segment table.
2264 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2265 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2266 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2267 the only released version with the bug, but OpenSUSE 9
2268 contains a buggy "glibc 2.3.2".
2270 The symptom of the bug is that everything crashes on startup, saying:
2271 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2273 Saying Y here changes the default value of the vdso32 boot
2274 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2275 This works around the glibc bug but hurts performance.
2277 If unsure, say N: if you are compiling your own kernel, you
2278 are unlikely to be using a buggy version of glibc.
2281 prompt "vsyscall table for legacy applications"
2283 default LEGACY_VSYSCALL_EMULATE
2285 Legacy user code that does not know how to find the vDSO expects
2286 to be able to issue three syscalls by calling fixed addresses in
2287 kernel space. Since this location is not randomized with ASLR,
2288 it can be used to assist security vulnerability exploitation.
2290 This setting can be changed at boot time via the kernel command
2291 line parameter vsyscall=[emulate|none].
2293 On a system with recent enough glibc (2.14 or newer) and no
2294 static binaries, you can say None without a performance penalty
2295 to improve security.
2297 If unsure, select "Emulate".
2299 config LEGACY_VSYSCALL_EMULATE
2302 The kernel traps and emulates calls into the fixed
2303 vsyscall address mapping. This makes the mapping
2304 non-executable, but it still contains known contents,
2305 which could be used in certain rare security vulnerability
2306 exploits. This configuration is recommended when userspace
2307 still uses the vsyscall area.
2309 config LEGACY_VSYSCALL_NONE
2312 There will be no vsyscall mapping at all. This will
2313 eliminate any risk of ASLR bypass due to the vsyscall
2314 fixed address mapping. Attempts to use the vsyscalls
2315 will be reported to dmesg, so that either old or
2316 malicious userspace programs can be identified.
2321 bool "Built-in kernel command line"
2323 Allow for specifying boot arguments to the kernel at
2324 build time. On some systems (e.g. embedded ones), it is
2325 necessary or convenient to provide some or all of the
2326 kernel boot arguments with the kernel itself (that is,
2327 to not rely on the boot loader to provide them.)
2329 To compile command line arguments into the kernel,
2330 set this option to 'Y', then fill in the
2331 boot arguments in CONFIG_CMDLINE.
2333 Systems with fully functional boot loaders (i.e. non-embedded)
2334 should leave this option set to 'N'.
2337 string "Built-in kernel command string"
2338 depends on CMDLINE_BOOL
2341 Enter arguments here that should be compiled into the kernel
2342 image and used at boot time. If the boot loader provides a
2343 command line at boot time, it is appended to this string to
2344 form the full kernel command line, when the system boots.
2346 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2347 change this behavior.
2349 In most cases, the command line (whether built-in or provided
2350 by the boot loader) should specify the device for the root
2353 config CMDLINE_OVERRIDE
2354 bool "Built-in command line overrides boot loader arguments"
2355 depends on CMDLINE_BOOL
2357 Set this option to 'Y' to have the kernel ignore the boot loader
2358 command line, and use ONLY the built-in command line.
2360 This is used to work around broken boot loaders. This should
2361 be set to 'N' under normal conditions.
2363 config MODIFY_LDT_SYSCALL
2364 bool "Enable the LDT (local descriptor table)" if EXPERT
2367 Linux can allow user programs to install a per-process x86
2368 Local Descriptor Table (LDT) using the modify_ldt(2) system
2369 call. This is required to run 16-bit or segmented code such as
2370 DOSEMU or some Wine programs. It is also used by some very old
2371 threading libraries.
2373 Enabling this feature adds a small amount of overhead to
2374 context switches and increases the low-level kernel attack
2375 surface. Disabling it removes the modify_ldt(2) system call.
2377 Saying 'N' here may make sense for embedded or server kernels.
2379 source "kernel/livepatch/Kconfig"
2383 config ARCH_HAS_ADD_PAGES
2385 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2387 config ARCH_ENABLE_MEMORY_HOTPLUG
2389 depends on X86_64 || (X86_32 && HIGHMEM)
2391 config ARCH_ENABLE_MEMORY_HOTREMOVE
2393 depends on MEMORY_HOTPLUG
2395 config USE_PERCPU_NUMA_NODE_ID
2399 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2401 depends on X86_64 || X86_PAE
2403 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2405 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2407 config ARCH_ENABLE_THP_MIGRATION
2409 depends on X86_64 && TRANSPARENT_HUGEPAGE
2411 menu "Power management and ACPI options"
2413 config ARCH_HIBERNATION_HEADER
2415 depends on HIBERNATION
2417 source "kernel/power/Kconfig"
2419 source "drivers/acpi/Kconfig"
2421 source "drivers/sfi/Kconfig"
2428 tristate "APM (Advanced Power Management) BIOS support"
2429 depends on X86_32 && PM_SLEEP
2431 APM is a BIOS specification for saving power using several different
2432 techniques. This is mostly useful for battery powered laptops with
2433 APM compliant BIOSes. If you say Y here, the system time will be
2434 reset after a RESUME operation, the /proc/apm device will provide
2435 battery status information, and user-space programs will receive
2436 notification of APM "events" (e.g. battery status change).
2438 If you select "Y" here, you can disable actual use of the APM
2439 BIOS by passing the "apm=off" option to the kernel at boot time.
2441 Note that the APM support is almost completely disabled for
2442 machines with more than one CPU.
2444 In order to use APM, you will need supporting software. For location
2445 and more information, read <file:Documentation/power/apm-acpi.txt>
2446 and the Battery Powered Linux mini-HOWTO, available from
2447 <http://www.tldp.org/docs.html#howto>.
2449 This driver does not spin down disk drives (see the hdparm(8)
2450 manpage ("man 8 hdparm") for that), and it doesn't turn off
2451 VESA-compliant "green" monitors.
2453 This driver does not support the TI 4000M TravelMate and the ACER
2454 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2455 desktop machines also don't have compliant BIOSes, and this driver
2456 may cause those machines to panic during the boot phase.
2458 Generally, if you don't have a battery in your machine, there isn't
2459 much point in using this driver and you should say N. If you get
2460 random kernel OOPSes or reboots that don't seem to be related to
2461 anything, try disabling/enabling this option (or disabling/enabling
2464 Some other things you should try when experiencing seemingly random,
2467 1) make sure that you have enough swap space and that it is
2469 2) pass the "no-hlt" option to the kernel
2470 3) switch on floating point emulation in the kernel and pass
2471 the "no387" option to the kernel
2472 4) pass the "floppy=nodma" option to the kernel
2473 5) pass the "mem=4M" option to the kernel (thereby disabling
2474 all but the first 4 MB of RAM)
2475 6) make sure that the CPU is not over clocked.
2476 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2477 8) disable the cache from your BIOS settings
2478 9) install a fan for the video card or exchange video RAM
2479 10) install a better fan for the CPU
2480 11) exchange RAM chips
2481 12) exchange the motherboard.
2483 To compile this driver as a module, choose M here: the
2484 module will be called apm.
2488 config APM_IGNORE_USER_SUSPEND
2489 bool "Ignore USER SUSPEND"
2491 This option will ignore USER SUSPEND requests. On machines with a
2492 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2493 series notebooks, it is necessary to say Y because of a BIOS bug.
2495 config APM_DO_ENABLE
2496 bool "Enable PM at boot time"
2498 Enable APM features at boot time. From page 36 of the APM BIOS
2499 specification: "When disabled, the APM BIOS does not automatically
2500 power manage devices, enter the Standby State, enter the Suspend
2501 State, or take power saving steps in response to CPU Idle calls."
2502 This driver will make CPU Idle calls when Linux is idle (unless this
2503 feature is turned off -- see "Do CPU IDLE calls", below). This
2504 should always save battery power, but more complicated APM features
2505 will be dependent on your BIOS implementation. You may need to turn
2506 this option off if your computer hangs at boot time when using APM
2507 support, or if it beeps continuously instead of suspending. Turn
2508 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2509 T400CDT. This is off by default since most machines do fine without
2514 bool "Make CPU Idle calls when idle"
2516 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2517 On some machines, this can activate improved power savings, such as
2518 a slowed CPU clock rate, when the machine is idle. These idle calls
2519 are made after the idle loop has run for some length of time (e.g.,
2520 333 mS). On some machines, this will cause a hang at boot time or
2521 whenever the CPU becomes idle. (On machines with more than one CPU,
2522 this option does nothing.)
2524 config APM_DISPLAY_BLANK
2525 bool "Enable console blanking using APM"
2527 Enable console blanking using the APM. Some laptops can use this to
2528 turn off the LCD backlight when the screen blanker of the Linux
2529 virtual console blanks the screen. Note that this is only used by
2530 the virtual console screen blanker, and won't turn off the backlight
2531 when using the X Window system. This also doesn't have anything to
2532 do with your VESA-compliant power-saving monitor. Further, this
2533 option doesn't work for all laptops -- it might not turn off your
2534 backlight at all, or it might print a lot of errors to the console,
2535 especially if you are using gpm.
2537 config APM_ALLOW_INTS
2538 bool "Allow interrupts during APM BIOS calls"
2540 Normally we disable external interrupts while we are making calls to
2541 the APM BIOS as a measure to lessen the effects of a badly behaving
2542 BIOS implementation. The BIOS should reenable interrupts if it
2543 needs to. Unfortunately, some BIOSes do not -- especially those in
2544 many of the newer IBM Thinkpads. If you experience hangs when you
2545 suspend, try setting this to Y. Otherwise, say N.
2549 source "drivers/cpufreq/Kconfig"
2551 source "drivers/cpuidle/Kconfig"
2553 source "drivers/idle/Kconfig"
2558 menu "Bus options (PCI etc.)"
2561 prompt "PCI access mode"
2562 depends on X86_32 && PCI
2565 On PCI systems, the BIOS can be used to detect the PCI devices and
2566 determine their configuration. However, some old PCI motherboards
2567 have BIOS bugs and may crash if this is done. Also, some embedded
2568 PCI-based systems don't have any BIOS at all. Linux can also try to
2569 detect the PCI hardware directly without using the BIOS.
2571 With this option, you can specify how Linux should detect the
2572 PCI devices. If you choose "BIOS", the BIOS will be used,
2573 if you choose "Direct", the BIOS won't be used, and if you
2574 choose "MMConfig", then PCI Express MMCONFIG will be used.
2575 If you choose "Any", the kernel will try MMCONFIG, then the
2576 direct access method and falls back to the BIOS if that doesn't
2577 work. If unsure, go with the default, which is "Any".
2582 config PCI_GOMMCONFIG
2599 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2601 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2604 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2607 bool "Support mmconfig PCI config space access" if X86_64
2609 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2610 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2614 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2618 depends on PCI && XEN
2621 config MMCONF_FAM10H
2623 depends on X86_64 && PCI_MMCONFIG && ACPI
2625 config PCI_CNB20LE_QUIRK
2626 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2629 Read the PCI windows out of the CNB20LE host bridge. This allows
2630 PCI hotplug to work on systems with the CNB20LE chipset which do
2633 There's no public spec for this chipset, and this functionality
2634 is known to be incomplete.
2636 You should say N unless you know you need this.
2639 bool "ISA bus support on modern systems" if EXPERT
2641 Expose ISA bus device drivers and options available for selection and
2642 configuration. Enable this option if your target machine has an ISA
2643 bus. ISA is an older system, displaced by PCI and newer bus
2644 architectures -- if your target machine is modern, it probably does
2645 not have an ISA bus.
2649 # x86_64 have no ISA slots, but can have ISA-style DMA.
2651 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2654 Enables ISA-style DMA support for devices requiring such controllers.
2662 Find out whether you have ISA slots on your motherboard. ISA is the
2663 name of a bus system, i.e. the way the CPU talks to the other stuff
2664 inside your box. Other bus systems are PCI, EISA, MicroChannel
2665 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2666 newer boards don't support it. If you have ISA, say Y, otherwise N.
2669 tristate "NatSemi SCx200 support"
2671 This provides basic support for National Semiconductor's
2672 (now AMD's) Geode processors. The driver probes for the
2673 PCI-IDs of several on-chip devices, so its a good dependency
2674 for other scx200_* drivers.
2676 If compiled as a module, the driver is named scx200.
2678 config SCx200HR_TIMER
2679 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2683 This driver provides a clocksource built upon the on-chip
2684 27MHz high-resolution timer. Its also a workaround for
2685 NSC Geode SC-1100's buggy TSC, which loses time when the
2686 processor goes idle (as is done by the scheduler). The
2687 other workaround is idle=poll boot option.
2690 bool "One Laptop Per Child support"
2697 Add support for detecting the unique features of the OLPC
2701 bool "OLPC XO-1 Power Management"
2702 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2704 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2707 bool "OLPC XO-1 Real Time Clock"
2708 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2710 Add support for the XO-1 real time clock, which can be used as a
2711 programmable wakeup source.
2714 bool "OLPC XO-1 SCI extras"
2715 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2719 Add support for SCI-based features of the OLPC XO-1 laptop:
2720 - EC-driven system wakeups
2724 - AC adapter status updates
2725 - Battery status updates
2727 config OLPC_XO15_SCI
2728 bool "OLPC XO-1.5 SCI extras"
2729 depends on OLPC && ACPI
2732 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2733 - EC-driven system wakeups
2734 - AC adapter status updates
2735 - Battery status updates
2738 bool "PCEngines ALIX System Support (LED setup)"
2741 This option enables system support for the PCEngines ALIX.
2742 At present this just sets up LEDs for GPIO control on
2743 ALIX2/3/6 boards. However, other system specific setup should
2746 Note: You must still enable the drivers for GPIO and LED support
2747 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2749 Note: You have to set alix.force=1 for boards with Award BIOS.
2752 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2755 This option enables system support for the Soekris Engineering net5501.
2758 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2762 This option enables system support for the Traverse Technologies GEOS.
2765 bool "Technologic Systems TS-5500 platform support"
2767 select CHECK_SIGNATURE
2771 This option enables system support for the Technologic Systems TS-5500.
2777 depends on CPU_SUP_AMD && PCI
2780 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2782 Firmwares often provide initial graphics framebuffers so the BIOS,
2783 bootloader or kernel can show basic video-output during boot for
2784 user-guidance and debugging. Historically, x86 used the VESA BIOS
2785 Extensions and EFI-framebuffers for this, which are mostly limited
2787 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2788 framebuffers so the new generic system-framebuffer drivers can be
2789 used on x86. If the framebuffer is not compatible with the generic
2790 modes, it is advertised as fallback platform framebuffer so legacy
2791 drivers like efifb, vesafb and uvesafb can pick it up.
2792 If this option is not selected, all system framebuffers are always
2793 marked as fallback platform framebuffers as usual.
2795 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2796 not be able to pick up generic system framebuffers if this option
2797 is selected. You are highly encouraged to enable simplefb as
2798 replacement if you select this option. simplefb can correctly deal
2799 with generic system framebuffers. But you should still keep vesafb
2800 and others enabled as fallback if a system framebuffer is
2801 incompatible with simplefb.
2808 menu "Binary Emulations"
2810 config IA32_EMULATION
2811 bool "IA32 Emulation"
2813 select ARCH_WANT_OLD_COMPAT_IPC
2815 select COMPAT_BINFMT_ELF
2816 select COMPAT_OLD_SIGACTION
2818 Include code to run legacy 32-bit programs under a
2819 64-bit kernel. You should likely turn this on, unless you're
2820 100% sure that you don't have any 32-bit programs left.
2823 tristate "IA32 a.out support"
2824 depends on IA32_EMULATION
2827 Support old a.out binaries in the 32bit emulation.
2830 bool "x32 ABI for 64-bit mode"
2833 Include code to run binaries for the x32 native 32-bit ABI
2834 for 64-bit processors. An x32 process gets access to the
2835 full 64-bit register file and wide data path while leaving
2836 pointers at 32 bits for smaller memory footprint.
2838 You will need a recent binutils (2.22 or later) with
2839 elf32_x86_64 support enabled to compile a kernel with this
2844 depends on IA32_EMULATION || X86_32
2846 select OLD_SIGSUSPEND3
2850 depends on IA32_EMULATION || X86_X32
2853 config COMPAT_FOR_U64_ALIGNMENT
2856 config SYSVIPC_COMPAT
2864 config HAVE_ATOMIC_IOMAP
2868 config X86_DEV_DMA_OPS
2871 config HAVE_GENERIC_GUP
2874 source "drivers/firmware/Kconfig"
2876 source "arch/x86/kvm/Kconfig"