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
34 config FORCE_DYNAMIC_FTRACE
37 depends on FUNCTION_TRACER
40 We keep the static function tracing (!DYNAMIC_FTRACE) around
41 in order to test the non static function tracing in the
42 generic code, as other architectures still use it. But we
43 only need to keep it around for x86_64. No need to keep it
44 for x86_32. For x86_32, force DYNAMIC_FTRACE.
48 # ( Note that options that are marked 'if X86_64' could in principle be
49 # ported to 32-bit as well. )
54 # Note: keep this list sorted alphabetically
56 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
57 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
58 select ARCH_32BIT_OFF_T if X86_32
59 select ARCH_CLOCKSOURCE_DATA
60 select ARCH_CLOCKSOURCE_INIT
61 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
62 select ARCH_HAS_DEBUG_VIRTUAL
63 select ARCH_HAS_DEVMEM_IS_ALLOWED
64 select ARCH_HAS_ELF_RANDOMIZE
65 select ARCH_HAS_FAST_MULTIPLIER
66 select ARCH_HAS_FILTER_PGPROT
67 select ARCH_HAS_FORTIFY_SOURCE
68 select ARCH_HAS_GCOV_PROFILE_ALL
69 select ARCH_HAS_KCOV if X86_64
70 select ARCH_HAS_MEMBARRIER_SYNC_CORE
71 select ARCH_HAS_PMEM_API if X86_64
72 select ARCH_HAS_PTE_SPECIAL
73 select ARCH_HAS_REFCOUNT
74 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
75 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
76 select ARCH_HAS_SET_MEMORY
77 select ARCH_HAS_SET_DIRECT_MAP
78 select ARCH_HAS_STRICT_KERNEL_RWX
79 select ARCH_HAS_STRICT_MODULE_RWX
80 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
81 select ARCH_HAS_UBSAN_SANITIZE_ALL
82 select ARCH_HAS_ZONE_DEVICE if X86_64
83 select ARCH_HAVE_NMI_SAFE_CMPXCHG
84 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
85 select ARCH_MIGHT_HAVE_PC_PARPORT
86 select ARCH_MIGHT_HAVE_PC_SERIO
88 select ARCH_SUPPORTS_ACPI
89 select ARCH_SUPPORTS_ATOMIC_RMW
90 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
91 select ARCH_USE_BUILTIN_BSWAP
92 select ARCH_USE_QUEUED_RWLOCKS
93 select ARCH_USE_QUEUED_SPINLOCKS
94 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
95 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
96 select ARCH_WANTS_THP_SWAP if X86_64
97 select BUILDTIME_EXTABLE_SORT
99 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
100 select CLOCKSOURCE_WATCHDOG
101 select DCACHE_WORD_ACCESS
102 select EDAC_ATOMIC_SCRUB
104 select GENERIC_CLOCKEVENTS
105 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
106 select GENERIC_CLOCKEVENTS_MIN_ADJUST
107 select GENERIC_CMOS_UPDATE
108 select GENERIC_CPU_AUTOPROBE
109 select GENERIC_CPU_VULNERABILITIES
110 select GENERIC_EARLY_IOREMAP
111 select GENERIC_FIND_FIRST_BIT
113 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
114 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
115 select GENERIC_IRQ_MIGRATION if SMP
116 select GENERIC_IRQ_PROBE
117 select GENERIC_IRQ_RESERVATION_MODE
118 select GENERIC_IRQ_SHOW
119 select GENERIC_PENDING_IRQ if SMP
120 select GENERIC_SMP_IDLE_THREAD
121 select GENERIC_STRNCPY_FROM_USER
122 select GENERIC_STRNLEN_USER
123 select GENERIC_TIME_VSYSCALL
124 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
125 select HAVE_ACPI_APEI if ACPI
126 select HAVE_ACPI_APEI_NMI if ACPI
127 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
128 select HAVE_ARCH_AUDITSYSCALL
129 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
130 select HAVE_ARCH_JUMP_LABEL
131 select HAVE_ARCH_JUMP_LABEL_RELATIVE
132 select HAVE_ARCH_KASAN if X86_64
133 select HAVE_ARCH_KGDB
134 select HAVE_ARCH_MMAP_RND_BITS if MMU
135 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
136 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
137 select HAVE_ARCH_PREL32_RELOCATIONS
138 select HAVE_ARCH_SECCOMP_FILTER
139 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
140 select HAVE_ARCH_STACKLEAK
141 select HAVE_ARCH_TRACEHOOK
142 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
143 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
144 select HAVE_ARCH_VMAP_STACK if X86_64
145 select HAVE_ARCH_WITHIN_STACK_FRAMES
146 select HAVE_CMPXCHG_DOUBLE
147 select HAVE_CMPXCHG_LOCAL
148 select HAVE_CONTEXT_TRACKING if X86_64
149 select HAVE_COPY_THREAD_TLS
150 select HAVE_C_RECORDMCOUNT
151 select HAVE_DEBUG_KMEMLEAK
152 select HAVE_DMA_CONTIGUOUS
153 select HAVE_DYNAMIC_FTRACE
154 select HAVE_DYNAMIC_FTRACE_WITH_REGS
156 select HAVE_EFFICIENT_UNALIGNED_ACCESS
158 select HAVE_EXIT_THREAD
159 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
160 select HAVE_FTRACE_MCOUNT_RECORD
161 select HAVE_FUNCTION_GRAPH_TRACER
162 select HAVE_FUNCTION_TRACER
163 select HAVE_GCC_PLUGINS
164 select HAVE_HW_BREAKPOINT
166 select HAVE_IOREMAP_PROT
167 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
168 select HAVE_IRQ_TIME_ACCOUNTING
169 select HAVE_KERNEL_BZIP2
170 select HAVE_KERNEL_GZIP
171 select HAVE_KERNEL_LZ4
172 select HAVE_KERNEL_LZMA
173 select HAVE_KERNEL_LZO
174 select HAVE_KERNEL_XZ
176 select HAVE_KPROBES_ON_FTRACE
177 select HAVE_FUNCTION_ERROR_INJECTION
178 select HAVE_KRETPROBES
180 select HAVE_LIVEPATCH if X86_64
181 select HAVE_MEMBLOCK_NODE_MAP
182 select HAVE_MIXED_BREAKPOINTS_REGS
183 select HAVE_MOD_ARCH_SPECIFIC
187 select HAVE_OPTPROBES
188 select HAVE_PCSPKR_PLATFORM
189 select HAVE_PERF_EVENTS
190 select HAVE_PERF_EVENTS_NMI
191 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
193 select HAVE_PERF_REGS
194 select HAVE_PERF_USER_STACK_DUMP
195 select HAVE_RCU_TABLE_FREE if PARAVIRT
196 select HAVE_REGS_AND_STACK_ACCESS_API
197 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
198 select HAVE_FUNCTION_ARG_ACCESS_API
199 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
200 select HAVE_STACK_VALIDATION if X86_64
202 select HAVE_SYSCALL_TRACEPOINTS
203 select HAVE_UNSTABLE_SCHED_CLOCK
204 select HAVE_USER_RETURN_NOTIFIER
205 select HOTPLUG_SMT if SMP
206 select IRQ_FORCED_THREADING
207 select NEED_SG_DMA_LENGTH
208 select PCI_DOMAINS if PCI
209 select PCI_LOCKLESS_CONFIG if PCI
212 select RTC_MC146818_LIB
215 select SYSCTL_EXCEPTION_TRACE
216 select THREAD_INFO_IN_TASK
217 select USER_STACKTRACE_SUPPORT
219 select X86_FEATURE_NAMES if PROC_FS
221 config INSTRUCTION_DECODER
223 depends on KPROBES || PERF_EVENTS || UPROBES
227 default "elf32-i386" if X86_32
228 default "elf64-x86-64" if X86_64
230 config ARCH_DEFCONFIG
232 default "arch/x86/configs/i386_defconfig" if X86_32
233 default "arch/x86/configs/x86_64_defconfig" if X86_64
235 config LOCKDEP_SUPPORT
238 config STACKTRACE_SUPPORT
244 config ARCH_MMAP_RND_BITS_MIN
248 config ARCH_MMAP_RND_BITS_MAX
252 config ARCH_MMAP_RND_COMPAT_BITS_MIN
255 config ARCH_MMAP_RND_COMPAT_BITS_MAX
261 config GENERIC_ISA_DMA
263 depends on ISA_DMA_API
268 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
270 config GENERIC_BUG_RELATIVE_POINTERS
273 config GENERIC_HWEIGHT
276 config ARCH_MAY_HAVE_PC_FDC
278 depends on ISA_DMA_API
280 config GENERIC_CALIBRATE_DELAY
283 config ARCH_HAS_CPU_RELAX
286 config ARCH_HAS_CACHE_LINE_SIZE
289 config ARCH_HAS_FILTER_PGPROT
292 config HAVE_SETUP_PER_CPU_AREA
295 config NEED_PER_CPU_EMBED_FIRST_CHUNK
298 config NEED_PER_CPU_PAGE_FIRST_CHUNK
301 config ARCH_HIBERNATION_POSSIBLE
304 config ARCH_SUSPEND_POSSIBLE
307 config ARCH_WANT_HUGE_PMD_SHARE
310 config ARCH_WANT_GENERAL_HUGETLB
319 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
322 config KASAN_SHADOW_OFFSET
325 default 0xdffffc0000000000
327 config HAVE_INTEL_TXT
329 depends on INTEL_IOMMU && ACPI
333 depends on X86_32 && SMP
337 depends on X86_64 && SMP
339 config X86_32_LAZY_GS
341 depends on X86_32 && !STACKPROTECTOR
343 config ARCH_SUPPORTS_UPROBES
346 config FIX_EARLYCON_MEM
349 config DYNAMIC_PHYSICAL_MASK
352 config PGTABLE_LEVELS
354 default 5 if X86_5LEVEL
359 config CC_HAS_SANE_STACKPROTECTOR
361 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
362 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
364 We have to make sure stack protector is unconditionally disabled if
365 the compiler produces broken code.
367 menu "Processor type and features"
370 bool "DMA memory allocation support" if EXPERT
373 DMA memory allocation support allows devices with less than 32-bit
374 addressing to allocate within the first 16MB of address space.
375 Disable if no such devices will be used.
380 bool "Symmetric multi-processing support"
382 This enables support for systems with more than one CPU. If you have
383 a system with only one CPU, say N. If you have a system with more
386 If you say N here, the kernel will run on uni- and multiprocessor
387 machines, but will use only one CPU of a multiprocessor machine. If
388 you say Y here, the kernel will run on many, but not all,
389 uniprocessor machines. On a uniprocessor machine, the kernel
390 will run faster if you say N here.
392 Note that if you say Y here and choose architecture "586" or
393 "Pentium" under "Processor family", the kernel will not work on 486
394 architectures. Similarly, multiprocessor kernels for the "PPro"
395 architecture may not work on all Pentium based boards.
397 People using multiprocessor machines who say Y here should also say
398 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
399 Management" code will be disabled if you say Y here.
401 See also <file:Documentation/x86/i386/IO-APIC.txt>,
402 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
403 <http://www.tldp.org/docs.html#howto>.
405 If you don't know what to do here, say N.
407 config X86_FEATURE_NAMES
408 bool "Processor feature human-readable names" if EMBEDDED
411 This option compiles in a table of x86 feature bits and corresponding
412 names. This is required to support /proc/cpuinfo and a few kernel
413 messages. You can disable this to save space, at the expense of
414 making those few kernel messages show numeric feature bits instead.
419 bool "Support x2apic"
420 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
422 This enables x2apic support on CPUs that have this feature.
424 This allows 32-bit apic IDs (so it can support very large systems),
425 and accesses the local apic via MSRs not via mmio.
427 If you don't know what to do here, say N.
430 bool "Enable MPS table" if ACPI || SFI
432 depends on X86_LOCAL_APIC
434 For old smp systems that do not have proper acpi support. Newer systems
435 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
439 depends on X86_GOLDFISH
442 bool "Avoid speculative indirect branches in kernel"
444 select STACK_VALIDATION if HAVE_STACK_VALIDATION
446 Compile kernel with the retpoline compiler options to guard against
447 kernel-to-user data leaks by avoiding speculative indirect
448 branches. Requires a compiler with -mindirect-branch=thunk-extern
449 support for full protection. The kernel may run slower.
451 config X86_CPU_RESCTRL
452 bool "x86 CPU resource control support"
453 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
456 Enable x86 CPU resource control support.
458 Provide support for the allocation and monitoring of system resources
461 Intel calls this Intel Resource Director Technology
462 (Intel(R) RDT). More information about RDT can be found in the
463 Intel x86 Architecture Software Developer Manual.
465 AMD calls this AMD Platform Quality of Service (AMD QoS).
466 More information about AMD QoS can be found in the AMD64 Technology
467 Platform Quality of Service Extensions manual.
473 bool "Support for big SMP systems with more than 8 CPUs"
476 This option is needed for the systems that have more than 8 CPUs
478 config X86_EXTENDED_PLATFORM
479 bool "Support for extended (non-PC) x86 platforms"
482 If you disable this option then the kernel will only support
483 standard PC platforms. (which covers the vast majority of
486 If you enable this option then you'll be able to select support
487 for the following (non-PC) 32 bit x86 platforms:
488 Goldfish (Android emulator)
491 SGI 320/540 (Visual Workstation)
492 STA2X11-based (e.g. Northville)
493 Moorestown MID devices
495 If you have one of these systems, or if you want to build a
496 generic distribution kernel, say Y here - otherwise say N.
500 config X86_EXTENDED_PLATFORM
501 bool "Support for extended (non-PC) x86 platforms"
504 If you disable this option then the kernel will only support
505 standard PC platforms. (which covers the vast majority of
508 If you enable this option then you'll be able to select support
509 for the following (non-PC) 64 bit x86 platforms:
514 If you have one of these systems, or if you want to build a
515 generic distribution kernel, say Y here - otherwise say N.
517 # This is an alphabetically sorted list of 64 bit extended platforms
518 # Please maintain the alphabetic order if and when there are additions
520 bool "Numascale NumaChip"
522 depends on X86_EXTENDED_PLATFORM
525 depends on X86_X2APIC
526 depends on PCI_MMCONFIG
528 Adds support for Numascale NumaChip large-SMP systems. Needed to
529 enable more than ~168 cores.
530 If you don't have one of these, you should say N here.
534 select HYPERVISOR_GUEST
536 depends on X86_64 && PCI
537 depends on X86_EXTENDED_PLATFORM
540 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
541 supposed to run on these EM64T-based machines. Only choose this option
542 if you have one of these machines.
545 bool "SGI Ultraviolet"
547 depends on X86_EXTENDED_PLATFORM
550 depends on X86_X2APIC
553 This option is needed in order to support SGI Ultraviolet systems.
554 If you don't have one of these, you should say N here.
556 # Following is an alphabetically sorted list of 32 bit extended platforms
557 # Please maintain the alphabetic order if and when there are additions
560 bool "Goldfish (Virtual Platform)"
561 depends on X86_EXTENDED_PLATFORM
563 Enable support for the Goldfish virtual platform used primarily
564 for Android development. Unless you are building for the Android
565 Goldfish emulator say N here.
568 bool "CE4100 TV platform"
570 depends on PCI_GODIRECT
571 depends on X86_IO_APIC
573 depends on X86_EXTENDED_PLATFORM
574 select X86_REBOOTFIXUPS
576 select OF_EARLY_FLATTREE
578 Select for the Intel CE media processor (CE4100) SOC.
579 This option compiles in support for the CE4100 SOC for settop
580 boxes and media devices.
583 bool "Intel MID platform support"
584 depends on X86_EXTENDED_PLATFORM
585 depends on X86_PLATFORM_DEVICES
587 depends on X86_64 || (PCI_GOANY && X86_32)
588 depends on X86_IO_APIC
594 select MFD_INTEL_MSIC
596 Select to build a kernel capable of supporting Intel MID (Mobile
597 Internet Device) platform systems which do not have the PCI legacy
598 interfaces. If you are building for a PC class system say N here.
600 Intel MID platforms are based on an Intel processor and chipset which
601 consume less power than most of the x86 derivatives.
603 config X86_INTEL_QUARK
604 bool "Intel Quark platform support"
606 depends on X86_EXTENDED_PLATFORM
607 depends on X86_PLATFORM_DEVICES
611 depends on X86_IO_APIC
616 Select to include support for Quark X1000 SoC.
617 Say Y here if you have a Quark based system such as the Arduino
618 compatible Intel Galileo.
620 config X86_INTEL_LPSS
621 bool "Intel Low Power Subsystem Support"
622 depends on X86 && ACPI && PCI
627 Select to build support for Intel Low Power Subsystem such as
628 found on Intel Lynxpoint PCH. Selecting this option enables
629 things like clock tree (common clock framework) and pincontrol
630 which are needed by the LPSS peripheral drivers.
632 config X86_AMD_PLATFORM_DEVICE
633 bool "AMD ACPI2Platform devices support"
638 Select to interpret AMD specific ACPI device to platform device
639 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
640 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
641 implemented under PINCTRL subsystem.
644 tristate "Intel SoC IOSF Sideband support for SoC platforms"
647 This option enables sideband register access support for Intel SoC
648 platforms. On these platforms the IOSF sideband is used in lieu of
649 MSR's for some register accesses, mostly but not limited to thermal
650 and power. Drivers may query the availability of this device to
651 determine if they need the sideband in order to work on these
652 platforms. The sideband is available on the following SoC products.
653 This list is not meant to be exclusive.
658 You should say Y if you are running a kernel on one of these SoC's.
660 config IOSF_MBI_DEBUG
661 bool "Enable IOSF sideband access through debugfs"
662 depends on IOSF_MBI && DEBUG_FS
664 Select this option to expose the IOSF sideband access registers (MCR,
665 MDR, MCRX) through debugfs to write and read register information from
666 different units on the SoC. This is most useful for obtaining device
667 state information for debug and analysis. As this is a general access
668 mechanism, users of this option would have specific knowledge of the
669 device they want to access.
671 If you don't require the option or are in doubt, say N.
674 bool "RDC R-321x SoC"
676 depends on X86_EXTENDED_PLATFORM
678 select X86_REBOOTFIXUPS
680 This option is needed for RDC R-321x system-on-chip, also known
682 If you don't have one of these chips, you should say N here.
684 config X86_32_NON_STANDARD
685 bool "Support non-standard 32-bit SMP architectures"
686 depends on X86_32 && SMP
687 depends on X86_EXTENDED_PLATFORM
689 This option compiles in the bigsmp and STA2X11 default
690 subarchitectures. It is intended for a generic binary
691 kernel. If you select them all, kernel will probe it one by
692 one and will fallback to default.
694 # Alphabetically sorted list of Non standard 32 bit platforms
696 config X86_SUPPORTS_MEMORY_FAILURE
698 # MCE code calls memory_failure():
700 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
701 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
702 depends on X86_64 || !SPARSEMEM
703 select ARCH_SUPPORTS_MEMORY_FAILURE
706 bool "STA2X11 Companion Chip Support"
707 depends on X86_32_NON_STANDARD && PCI
708 select ARCH_HAS_PHYS_TO_DMA
713 This adds support for boards based on the STA2X11 IO-Hub,
714 a.k.a. "ConneXt". The chip is used in place of the standard
715 PC chipset, so all "standard" peripherals are missing. If this
716 option is selected the kernel will still be able to boot on
717 standard PC machines.
720 tristate "Eurobraille/Iris poweroff module"
723 The Iris machines from EuroBraille do not have APM or ACPI support
724 to shut themselves down properly. A special I/O sequence is
725 needed to do so, which is what this module does at
728 This is only for Iris machines from EuroBraille.
732 config SCHED_OMIT_FRAME_POINTER
734 prompt "Single-depth WCHAN output"
737 Calculate simpler /proc/<PID>/wchan values. If this option
738 is disabled then wchan values will recurse back to the
739 caller function. This provides more accurate wchan values,
740 at the expense of slightly more scheduling overhead.
742 If in doubt, say "Y".
744 menuconfig HYPERVISOR_GUEST
745 bool "Linux guest support"
747 Say Y here to enable options for running Linux under various hyper-
748 visors. This option enables basic hypervisor detection and platform
751 If you say N, all options in this submenu will be skipped and
752 disabled, and Linux guest support won't be built in.
757 bool "Enable paravirtualization code"
759 This changes the kernel so it can modify itself when it is run
760 under a hypervisor, potentially improving performance significantly
761 over full virtualization. However, when run without a hypervisor
762 the kernel is theoretically slower and slightly larger.
767 config PARAVIRT_DEBUG
768 bool "paravirt-ops debugging"
769 depends on PARAVIRT && DEBUG_KERNEL
771 Enable to debug paravirt_ops internals. Specifically, BUG if
772 a paravirt_op is missing when it is called.
774 config PARAVIRT_SPINLOCKS
775 bool "Paravirtualization layer for spinlocks"
776 depends on PARAVIRT && SMP
778 Paravirtualized spinlocks allow a pvops backend to replace the
779 spinlock implementation with something virtualization-friendly
780 (for example, block the virtual CPU rather than spinning).
782 It has a minimal impact on native kernels and gives a nice performance
783 benefit on paravirtualized KVM / Xen kernels.
785 If you are unsure how to answer this question, answer Y.
787 source "arch/x86/xen/Kconfig"
790 bool "KVM Guest support (including kvmclock)"
792 select PARAVIRT_CLOCK
795 This option enables various optimizations for running under the KVM
796 hypervisor. It includes a paravirtualized clock, so that instead
797 of relying on a PIT (or probably other) emulation by the
798 underlying device model, the host provides the guest with
799 timing infrastructure such as time of day, and system time
802 bool "Support for running PVH guests"
804 This option enables the PVH entry point for guest virtual machines
805 as specified in the x86/HVM direct boot ABI.
808 bool "Enable debug information for KVM Guests in debugfs"
809 depends on KVM_GUEST && DEBUG_FS
811 This option enables collection of various statistics for KVM guest.
812 Statistics are displayed in debugfs filesystem. Enabling this option
813 may incur significant overhead.
815 config PARAVIRT_TIME_ACCOUNTING
816 bool "Paravirtual steal time accounting"
819 Select this option to enable fine granularity task steal time
820 accounting. Time spent executing other tasks in parallel with
821 the current vCPU is discounted from the vCPU power. To account for
822 that, there can be a small performance impact.
824 If in doubt, say N here.
826 config PARAVIRT_CLOCK
829 config JAILHOUSE_GUEST
830 bool "Jailhouse non-root cell support"
831 depends on X86_64 && PCI
834 This option allows to run Linux as guest in a Jailhouse non-root
835 cell. You can leave this option disabled if you only want to start
836 Jailhouse and run Linux afterwards in the root cell.
838 endif #HYPERVISOR_GUEST
840 source "arch/x86/Kconfig.cpu"
844 prompt "HPET Timer Support" if X86_32
846 Use the IA-PC HPET (High Precision Event Timer) to manage
847 time in preference to the PIT and RTC, if a HPET is
849 HPET is the next generation timer replacing legacy 8254s.
850 The HPET provides a stable time base on SMP
851 systems, unlike the TSC, but it is more expensive to access,
852 as it is off-chip. The interface used is documented
853 in the HPET spec, revision 1.
855 You can safely choose Y here. However, HPET will only be
856 activated if the platform and the BIOS support this feature.
857 Otherwise the 8254 will be used for timing services.
859 Choose N to continue using the legacy 8254 timer.
861 config HPET_EMULATE_RTC
863 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
866 def_bool y if X86_INTEL_MID
867 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
869 depends on X86_INTEL_MID && SFI
871 APB timer is the replacement for 8254, HPET on X86 MID platforms.
872 The APBT provides a stable time base on SMP
873 systems, unlike the TSC, but it is more expensive to access,
874 as it is off-chip. APB timers are always running regardless of CPU
875 C states, they are used as per CPU clockevent device when possible.
877 # Mark as expert because too many people got it wrong.
878 # The code disables itself when not needed.
881 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
882 bool "Enable DMI scanning" if EXPERT
884 Enabled scanning of DMI to identify machine quirks. Say Y
885 here unless you have verified that your setup is not
886 affected by entries in the DMI blacklist. Required by PNP
890 bool "Old AMD GART IOMMU support"
893 depends on X86_64 && PCI && AMD_NB
895 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
896 GART based hardware IOMMUs.
898 The GART supports full DMA access for devices with 32-bit access
899 limitations, on systems with more than 3 GB. This is usually needed
900 for USB, sound, many IDE/SATA chipsets and some other devices.
902 Newer systems typically have a modern AMD IOMMU, supported via
903 the CONFIG_AMD_IOMMU=y config option.
905 In normal configurations this driver is only active when needed:
906 there's more than 3 GB of memory and the system contains a
907 32-bit limited device.
912 bool "IBM Calgary IOMMU support"
915 depends on X86_64 && PCI
917 Support for hardware IOMMUs in IBM's xSeries x366 and x460
918 systems. Needed to run systems with more than 3GB of memory
919 properly with 32-bit PCI devices that do not support DAC
920 (Double Address Cycle). Calgary also supports bus level
921 isolation, where all DMAs pass through the IOMMU. This
922 prevents them from going anywhere except their intended
923 destination. This catches hard-to-find kernel bugs and
924 mis-behaving drivers and devices that do not use the DMA-API
925 properly to set up their DMA buffers. The IOMMU can be
926 turned off at boot time with the iommu=off parameter.
927 Normally the kernel will make the right choice by itself.
930 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
932 prompt "Should Calgary be enabled by default?"
933 depends on CALGARY_IOMMU
935 Should Calgary be enabled by default? if you choose 'y', Calgary
936 will be used (if it exists). If you choose 'n', Calgary will not be
937 used even if it exists. If you choose 'n' and would like to use
938 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
942 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
943 depends on X86_64 && SMP && DEBUG_KERNEL
944 select CPUMASK_OFFSTACK
946 Enable maximum number of CPUS and NUMA Nodes for this architecture.
950 # The maximum number of CPUs supported:
952 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
953 # and which can be configured interactively in the
954 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
956 # The ranges are different on 32-bit and 64-bit kernels, depending on
957 # hardware capabilities and scalability features of the kernel.
959 # ( If MAXSMP is enabled we just use the highest possible value and disable
960 # interactive configuration. )
963 config NR_CPUS_RANGE_BEGIN
965 default NR_CPUS_RANGE_END if MAXSMP
969 config NR_CPUS_RANGE_END
972 default 64 if SMP && X86_BIGSMP
973 default 8 if SMP && !X86_BIGSMP
976 config NR_CPUS_RANGE_END
979 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
980 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
983 config NR_CPUS_DEFAULT
986 default 32 if X86_BIGSMP
990 config NR_CPUS_DEFAULT
993 default 8192 if MAXSMP
998 int "Maximum number of CPUs" if SMP && !MAXSMP
999 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1000 default NR_CPUS_DEFAULT
1002 This allows you to specify the maximum number of CPUs which this
1003 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1004 supported value is 8192, otherwise the maximum value is 512. The
1005 minimum value which makes sense is 2.
1007 This is purely to save memory: each supported CPU adds about 8KB
1008 to the kernel image.
1015 prompt "Multi-core scheduler support"
1018 Multi-core scheduler support improves the CPU scheduler's decision
1019 making when dealing with multi-core CPU chips at a cost of slightly
1020 increased overhead in some places. If unsure say N here.
1022 config SCHED_MC_PRIO
1023 bool "CPU core priorities scheduler support"
1024 depends on SCHED_MC && CPU_SUP_INTEL
1025 select X86_INTEL_PSTATE
1029 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1030 core ordering determined at manufacturing time, which allows
1031 certain cores to reach higher turbo frequencies (when running
1032 single threaded workloads) than others.
1034 Enabling this kernel feature teaches the scheduler about
1035 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1036 scheduler's CPU selection logic accordingly, so that higher
1037 overall system performance can be achieved.
1039 This feature will have no effect on CPUs without this feature.
1041 If unsure say Y here.
1045 depends on !SMP && X86_LOCAL_APIC
1048 bool "Local APIC support on uniprocessors" if !PCI_MSI
1050 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1052 A local APIC (Advanced Programmable Interrupt Controller) is an
1053 integrated interrupt controller in the CPU. If you have a single-CPU
1054 system which has a processor with a local APIC, you can say Y here to
1055 enable and use it. If you say Y here even though your machine doesn't
1056 have a local APIC, then the kernel will still run with no slowdown at
1057 all. The local APIC supports CPU-generated self-interrupts (timer,
1058 performance counters), and the NMI watchdog which detects hard
1061 config X86_UP_IOAPIC
1062 bool "IO-APIC support on uniprocessors"
1063 depends on X86_UP_APIC
1065 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1066 SMP-capable replacement for PC-style interrupt controllers. Most
1067 SMP systems and many recent uniprocessor systems have one.
1069 If you have a single-CPU system with an IO-APIC, you can say Y here
1070 to use it. If you say Y here even though your machine doesn't have
1071 an IO-APIC, then the kernel will still run with no slowdown at all.
1073 config X86_LOCAL_APIC
1075 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1076 select IRQ_DOMAIN_HIERARCHY
1077 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1081 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1083 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1084 bool "Reroute for broken boot IRQs"
1085 depends on X86_IO_APIC
1087 This option enables a workaround that fixes a source of
1088 spurious interrupts. This is recommended when threaded
1089 interrupt handling is used on systems where the generation of
1090 superfluous "boot interrupts" cannot be disabled.
1092 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1093 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1094 kernel does during interrupt handling). On chipsets where this
1095 boot IRQ generation cannot be disabled, this workaround keeps
1096 the original IRQ line masked so that only the equivalent "boot
1097 IRQ" is delivered to the CPUs. The workaround also tells the
1098 kernel to set up the IRQ handler on the boot IRQ line. In this
1099 way only one interrupt is delivered to the kernel. Otherwise
1100 the spurious second interrupt may cause the kernel to bring
1101 down (vital) interrupt lines.
1103 Only affects "broken" chipsets. Interrupt sharing may be
1104 increased on these systems.
1107 bool "Machine Check / overheating reporting"
1108 select GENERIC_ALLOCATOR
1111 Machine Check support allows the processor to notify the
1112 kernel if it detects a problem (e.g. overheating, data corruption).
1113 The action the kernel takes depends on the severity of the problem,
1114 ranging from warning messages to halting the machine.
1116 config X86_MCELOG_LEGACY
1117 bool "Support for deprecated /dev/mcelog character device"
1120 Enable support for /dev/mcelog which is needed by the old mcelog
1121 userspace logging daemon. Consider switching to the new generation
1124 config X86_MCE_INTEL
1126 prompt "Intel MCE features"
1127 depends on X86_MCE && X86_LOCAL_APIC
1129 Additional support for intel specific MCE features such as
1130 the thermal monitor.
1134 prompt "AMD MCE features"
1135 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1137 Additional support for AMD specific MCE features such as
1138 the DRAM Error Threshold.
1140 config X86_ANCIENT_MCE
1141 bool "Support for old Pentium 5 / WinChip machine checks"
1142 depends on X86_32 && X86_MCE
1144 Include support for machine check handling on old Pentium 5 or WinChip
1145 systems. These typically need to be enabled explicitly on the command
1148 config X86_MCE_THRESHOLD
1149 depends on X86_MCE_AMD || X86_MCE_INTEL
1152 config X86_MCE_INJECT
1153 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1154 tristate "Machine check injector support"
1156 Provide support for injecting machine checks for testing purposes.
1157 If you don't know what a machine check is and you don't do kernel
1158 QA it is safe to say n.
1160 config X86_THERMAL_VECTOR
1162 depends on X86_MCE_INTEL
1164 source "arch/x86/events/Kconfig"
1166 config X86_LEGACY_VM86
1167 bool "Legacy VM86 support"
1170 This option allows user programs to put the CPU into V8086
1171 mode, which is an 80286-era approximation of 16-bit real mode.
1173 Some very old versions of X and/or vbetool require this option
1174 for user mode setting. Similarly, DOSEMU will use it if
1175 available to accelerate real mode DOS programs. However, any
1176 recent version of DOSEMU, X, or vbetool should be fully
1177 functional even without kernel VM86 support, as they will all
1178 fall back to software emulation. Nevertheless, if you are using
1179 a 16-bit DOS program where 16-bit performance matters, vm86
1180 mode might be faster than emulation and you might want to
1183 Note that any app that works on a 64-bit kernel is unlikely to
1184 need this option, as 64-bit kernels don't, and can't, support
1185 V8086 mode. This option is also unrelated to 16-bit protected
1186 mode and is not needed to run most 16-bit programs under Wine.
1188 Enabling this option increases the complexity of the kernel
1189 and slows down exception handling a tiny bit.
1191 If unsure, say N here.
1195 default X86_LEGACY_VM86
1198 bool "Enable support for 16-bit segments" if EXPERT
1200 depends on MODIFY_LDT_SYSCALL
1202 This option is required by programs like Wine to run 16-bit
1203 protected mode legacy code on x86 processors. Disabling
1204 this option saves about 300 bytes on i386, or around 6K text
1205 plus 16K runtime memory on x86-64,
1209 depends on X86_16BIT && X86_32
1213 depends on X86_16BIT && X86_64
1215 config X86_VSYSCALL_EMULATION
1216 bool "Enable vsyscall emulation" if EXPERT
1220 This enables emulation of the legacy vsyscall page. Disabling
1221 it is roughly equivalent to booting with vsyscall=none, except
1222 that it will also disable the helpful warning if a program
1223 tries to use a vsyscall. With this option set to N, offending
1224 programs will just segfault, citing addresses of the form
1227 This option is required by many programs built before 2013, and
1228 care should be used even with newer programs if set to N.
1230 Disabling this option saves about 7K of kernel size and
1231 possibly 4K of additional runtime pagetable memory.
1234 tristate "Toshiba Laptop support"
1237 This adds a driver to safely access the System Management Mode of
1238 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1239 not work on models with a Phoenix BIOS. The System Management Mode
1240 is used to set the BIOS and power saving options on Toshiba portables.
1242 For information on utilities to make use of this driver see the
1243 Toshiba Linux utilities web site at:
1244 <http://www.buzzard.org.uk/toshiba/>.
1246 Say Y if you intend to run this kernel on a Toshiba portable.
1250 tristate "Dell i8k legacy laptop support"
1252 select SENSORS_DELL_SMM
1254 This option enables legacy /proc/i8k userspace interface in hwmon
1255 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1256 temperature and allows controlling fan speeds of Dell laptops via
1257 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1258 it reports also power and hotkey status. For fan speed control is
1259 needed userspace package i8kutils.
1261 Say Y if you intend to run this kernel on old Dell laptops or want to
1262 use userspace package i8kutils.
1265 config X86_REBOOTFIXUPS
1266 bool "Enable X86 board specific fixups for reboot"
1269 This enables chipset and/or board specific fixups to be done
1270 in order to get reboot to work correctly. This is only needed on
1271 some combinations of hardware and BIOS. The symptom, for which
1272 this config is intended, is when reboot ends with a stalled/hung
1275 Currently, the only fixup is for the Geode machines using
1276 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1278 Say Y if you want to enable the fixup. Currently, it's safe to
1279 enable this option even if you don't need it.
1283 bool "CPU microcode loading support"
1285 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1288 If you say Y here, you will be able to update the microcode on
1289 Intel and AMD processors. The Intel support is for the IA32 family,
1290 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1291 AMD support is for families 0x10 and later. You will obviously need
1292 the actual microcode binary data itself which is not shipped with
1295 The preferred method to load microcode from a detached initrd is described
1296 in Documentation/x86/microcode.txt. For that you need to enable
1297 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1298 initrd for microcode blobs.
1300 In addition, you can build the microcode into the kernel. For that you
1301 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1304 config MICROCODE_INTEL
1305 bool "Intel microcode loading support"
1306 depends on MICROCODE
1310 This options enables microcode patch loading support for Intel
1313 For the current Intel microcode data package go to
1314 <https://downloadcenter.intel.com> and search for
1315 'Linux Processor Microcode Data File'.
1317 config MICROCODE_AMD
1318 bool "AMD microcode loading support"
1319 depends on MICROCODE
1322 If you select this option, microcode patch loading support for AMD
1323 processors will be enabled.
1325 config MICROCODE_OLD_INTERFACE
1326 bool "Ancient loading interface (DEPRECATED)"
1328 depends on MICROCODE
1330 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1331 which was used by userspace tools like iucode_tool and microcode.ctl.
1332 It is inadequate because it runs too late to be able to properly
1333 load microcode on a machine and it needs special tools. Instead, you
1334 should've switched to the early loading method with the initrd or
1335 builtin microcode by now: Documentation/x86/microcode.txt
1338 tristate "/dev/cpu/*/msr - Model-specific register support"
1340 This device gives privileged processes access to the x86
1341 Model-Specific Registers (MSRs). It is a character device with
1342 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1343 MSR accesses are directed to a specific CPU on multi-processor
1347 tristate "/dev/cpu/*/cpuid - CPU information support"
1349 This device gives processes access to the x86 CPUID instruction to
1350 be executed on a specific processor. It is a character device
1351 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1355 prompt "High Memory Support"
1362 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1363 However, the address space of 32-bit x86 processors is only 4
1364 Gigabytes large. That means that, if you have a large amount of
1365 physical memory, not all of it can be "permanently mapped" by the
1366 kernel. The physical memory that's not permanently mapped is called
1369 If you are compiling a kernel which will never run on a machine with
1370 more than 1 Gigabyte total physical RAM, answer "off" here (default
1371 choice and suitable for most users). This will result in a "3GB/1GB"
1372 split: 3GB are mapped so that each process sees a 3GB virtual memory
1373 space and the remaining part of the 4GB virtual memory space is used
1374 by the kernel to permanently map as much physical memory as
1377 If the machine has between 1 and 4 Gigabytes physical RAM, then
1380 If more than 4 Gigabytes is used then answer "64GB" here. This
1381 selection turns Intel PAE (Physical Address Extension) mode on.
1382 PAE implements 3-level paging on IA32 processors. PAE is fully
1383 supported by Linux, PAE mode is implemented on all recent Intel
1384 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1385 then the kernel will not boot on CPUs that don't support PAE!
1387 The actual amount of total physical memory will either be
1388 auto detected or can be forced by using a kernel command line option
1389 such as "mem=256M". (Try "man bootparam" or see the documentation of
1390 your boot loader (lilo or loadlin) about how to pass options to the
1391 kernel at boot time.)
1393 If unsure, say "off".
1398 Select this if you have a 32-bit processor and between 1 and 4
1399 gigabytes of physical RAM.
1403 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1406 Select this if you have a 32-bit processor and more than 4
1407 gigabytes of physical RAM.
1412 prompt "Memory split" if EXPERT
1416 Select the desired split between kernel and user memory.
1418 If the address range available to the kernel is less than the
1419 physical memory installed, the remaining memory will be available
1420 as "high memory". Accessing high memory is a little more costly
1421 than low memory, as it needs to be mapped into the kernel first.
1422 Note that increasing the kernel address space limits the range
1423 available to user programs, making the address space there
1424 tighter. Selecting anything other than the default 3G/1G split
1425 will also likely make your kernel incompatible with binary-only
1428 If you are not absolutely sure what you are doing, leave this
1432 bool "3G/1G user/kernel split"
1433 config VMSPLIT_3G_OPT
1435 bool "3G/1G user/kernel split (for full 1G low memory)"
1437 bool "2G/2G user/kernel split"
1438 config VMSPLIT_2G_OPT
1440 bool "2G/2G user/kernel split (for full 2G low memory)"
1442 bool "1G/3G user/kernel split"
1447 default 0xB0000000 if VMSPLIT_3G_OPT
1448 default 0x80000000 if VMSPLIT_2G
1449 default 0x78000000 if VMSPLIT_2G_OPT
1450 default 0x40000000 if VMSPLIT_1G
1456 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1459 bool "PAE (Physical Address Extension) Support"
1460 depends on X86_32 && !HIGHMEM4G
1461 select PHYS_ADDR_T_64BIT
1464 PAE is required for NX support, and furthermore enables
1465 larger swapspace support for non-overcommit purposes. It
1466 has the cost of more pagetable lookup overhead, and also
1467 consumes more pagetable space per process.
1470 bool "Enable 5-level page tables support"
1471 select DYNAMIC_MEMORY_LAYOUT
1472 select SPARSEMEM_VMEMMAP
1475 5-level paging enables access to larger address space:
1476 upto 128 PiB of virtual address space and 4 PiB of
1477 physical address space.
1479 It will be supported by future Intel CPUs.
1481 A kernel with the option enabled can be booted on machines that
1482 support 4- or 5-level paging.
1484 See Documentation/x86/x86_64/5level-paging.txt for more
1489 config X86_DIRECT_GBPAGES
1491 depends on X86_64 && !DEBUG_PAGEALLOC
1493 Certain kernel features effectively disable kernel
1494 linear 1 GB mappings (even if the CPU otherwise
1495 supports them), so don't confuse the user by printing
1496 that we have them enabled.
1498 config X86_CPA_STATISTICS
1499 bool "Enable statistic for Change Page Attribute"
1502 Expose statistics about the Change Page Attribute mechanims, which
1503 helps to determine the effectiveness of preserving large and huge
1504 page mappings when mapping protections are changed.
1506 config ARCH_HAS_MEM_ENCRYPT
1509 config AMD_MEM_ENCRYPT
1510 bool "AMD Secure Memory Encryption (SME) support"
1511 depends on X86_64 && CPU_SUP_AMD
1512 select DYNAMIC_PHYSICAL_MASK
1513 select ARCH_USE_MEMREMAP_PROT
1515 Say yes to enable support for the encryption of system memory.
1516 This requires an AMD processor that supports Secure Memory
1519 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1520 bool "Activate AMD Secure Memory Encryption (SME) by default"
1522 depends on AMD_MEM_ENCRYPT
1524 Say yes to have system memory encrypted by default if running on
1525 an AMD processor that supports Secure Memory Encryption (SME).
1527 If set to Y, then the encryption of system memory can be
1528 deactivated with the mem_encrypt=off command line option.
1530 If set to N, then the encryption of system memory can be
1531 activated with the mem_encrypt=on command line option.
1533 # Common NUMA Features
1535 bool "Numa Memory Allocation and Scheduler Support"
1537 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1538 default y if X86_BIGSMP
1540 Enable NUMA (Non Uniform Memory Access) support.
1542 The kernel will try to allocate memory used by a CPU on the
1543 local memory controller of the CPU and add some more
1544 NUMA awareness to the kernel.
1546 For 64-bit this is recommended if the system is Intel Core i7
1547 (or later), AMD Opteron, or EM64T NUMA.
1549 For 32-bit this is only needed if you boot a 32-bit
1550 kernel on a 64-bit NUMA platform.
1552 Otherwise, you should say N.
1556 prompt "Old style AMD Opteron NUMA detection"
1557 depends on X86_64 && NUMA && PCI
1559 Enable AMD NUMA node topology detection. You should say Y here if
1560 you have a multi processor AMD system. This uses an old method to
1561 read the NUMA configuration directly from the builtin Northbridge
1562 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1563 which also takes priority if both are compiled in.
1565 config X86_64_ACPI_NUMA
1567 prompt "ACPI NUMA detection"
1568 depends on X86_64 && NUMA && ACPI && PCI
1571 Enable ACPI SRAT based node topology detection.
1573 # Some NUMA nodes have memory ranges that span
1574 # other nodes. Even though a pfn is valid and
1575 # between a node's start and end pfns, it may not
1576 # reside on that node. See memmap_init_zone()
1578 config NODES_SPAN_OTHER_NODES
1580 depends on X86_64_ACPI_NUMA
1583 bool "NUMA emulation"
1586 Enable NUMA emulation. A flat machine will be split
1587 into virtual nodes when booted with "numa=fake=N", where N is the
1588 number of nodes. This is only useful for debugging.
1591 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1593 default "10" if MAXSMP
1594 default "6" if X86_64
1596 depends on NEED_MULTIPLE_NODES
1598 Specify the maximum number of NUMA Nodes available on the target
1599 system. Increases memory reserved to accommodate various tables.
1601 config ARCH_HAVE_MEMORY_PRESENT
1603 depends on X86_32 && DISCONTIGMEM
1605 config ARCH_FLATMEM_ENABLE
1607 depends on X86_32 && !NUMA
1609 config ARCH_DISCONTIGMEM_ENABLE
1611 depends on NUMA && X86_32
1614 config ARCH_SPARSEMEM_ENABLE
1616 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1617 select SPARSEMEM_STATIC if X86_32
1618 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1620 config ARCH_SPARSEMEM_DEFAULT
1621 def_bool X86_64 || (NUMA && X86_32)
1623 config ARCH_SELECT_MEMORY_MODEL
1625 depends on ARCH_SPARSEMEM_ENABLE
1627 config ARCH_MEMORY_PROBE
1628 bool "Enable sysfs memory/probe interface"
1629 depends on X86_64 && MEMORY_HOTPLUG
1631 This option enables a sysfs memory/probe interface for testing.
1632 See Documentation/memory-hotplug.txt for more information.
1633 If you are unsure how to answer this question, answer N.
1635 config ARCH_PROC_KCORE_TEXT
1637 depends on X86_64 && PROC_KCORE
1639 config ILLEGAL_POINTER_VALUE
1642 default 0xdead000000000000 if X86_64
1644 config X86_PMEM_LEGACY_DEVICE
1647 config X86_PMEM_LEGACY
1648 tristate "Support non-standard NVDIMMs and ADR protected memory"
1649 depends on PHYS_ADDR_T_64BIT
1651 select X86_PMEM_LEGACY_DEVICE
1654 Treat memory marked using the non-standard e820 type of 12 as used
1655 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1656 The kernel will offer these regions to the 'pmem' driver so
1657 they can be used for persistent storage.
1662 bool "Allocate 3rd-level pagetables from highmem"
1665 The VM uses one page table entry for each page of physical memory.
1666 For systems with a lot of RAM, this can be wasteful of precious
1667 low memory. Setting this option will put user-space page table
1668 entries in high memory.
1670 config X86_CHECK_BIOS_CORRUPTION
1671 bool "Check for low memory corruption"
1673 Periodically check for memory corruption in low memory, which
1674 is suspected to be caused by BIOS. Even when enabled in the
1675 configuration, it is disabled at runtime. Enable it by
1676 setting "memory_corruption_check=1" on the kernel command
1677 line. By default it scans the low 64k of memory every 60
1678 seconds; see the memory_corruption_check_size and
1679 memory_corruption_check_period parameters in
1680 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1682 When enabled with the default parameters, this option has
1683 almost no overhead, as it reserves a relatively small amount
1684 of memory and scans it infrequently. It both detects corruption
1685 and prevents it from affecting the running system.
1687 It is, however, intended as a diagnostic tool; if repeatable
1688 BIOS-originated corruption always affects the same memory,
1689 you can use memmap= to prevent the kernel from using that
1692 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1693 bool "Set the default setting of memory_corruption_check"
1694 depends on X86_CHECK_BIOS_CORRUPTION
1697 Set whether the default state of memory_corruption_check is
1700 config X86_RESERVE_LOW
1701 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1705 Specify the amount of low memory to reserve for the BIOS.
1707 The first page contains BIOS data structures that the kernel
1708 must not use, so that page must always be reserved.
1710 By default we reserve the first 64K of physical RAM, as a
1711 number of BIOSes are known to corrupt that memory range
1712 during events such as suspend/resume or monitor cable
1713 insertion, so it must not be used by the kernel.
1715 You can set this to 4 if you are absolutely sure that you
1716 trust the BIOS to get all its memory reservations and usages
1717 right. If you know your BIOS have problems beyond the
1718 default 64K area, you can set this to 640 to avoid using the
1719 entire low memory range.
1721 If you have doubts about the BIOS (e.g. suspend/resume does
1722 not work or there's kernel crashes after certain hardware
1723 hotplug events) then you might want to enable
1724 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1725 typical corruption patterns.
1727 Leave this to the default value of 64 if you are unsure.
1729 config MATH_EMULATION
1731 depends on MODIFY_LDT_SYSCALL
1732 prompt "Math emulation" if X86_32
1734 Linux can emulate a math coprocessor (used for floating point
1735 operations) if you don't have one. 486DX and Pentium processors have
1736 a math coprocessor built in, 486SX and 386 do not, unless you added
1737 a 487DX or 387, respectively. (The messages during boot time can
1738 give you some hints here ["man dmesg"].) Everyone needs either a
1739 coprocessor or this emulation.
1741 If you don't have a math coprocessor, you need to say Y here; if you
1742 say Y here even though you have a coprocessor, the coprocessor will
1743 be used nevertheless. (This behavior can be changed with the kernel
1744 command line option "no387", which comes handy if your coprocessor
1745 is broken. Try "man bootparam" or see the documentation of your boot
1746 loader (lilo or loadlin) about how to pass options to the kernel at
1747 boot time.) This means that it is a good idea to say Y here if you
1748 intend to use this kernel on different machines.
1750 More information about the internals of the Linux math coprocessor
1751 emulation can be found in <file:arch/x86/math-emu/README>.
1753 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1754 kernel, it won't hurt.
1758 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1760 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1761 the Memory Type Range Registers (MTRRs) may be used to control
1762 processor access to memory ranges. This is most useful if you have
1763 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1764 allows bus write transfers to be combined into a larger transfer
1765 before bursting over the PCI/AGP bus. This can increase performance
1766 of image write operations 2.5 times or more. Saying Y here creates a
1767 /proc/mtrr file which may be used to manipulate your processor's
1768 MTRRs. Typically the X server should use this.
1770 This code has a reasonably generic interface so that similar
1771 control registers on other processors can be easily supported
1774 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1775 Registers (ARRs) which provide a similar functionality to MTRRs. For
1776 these, the ARRs are used to emulate the MTRRs.
1777 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1778 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1779 write-combining. All of these processors are supported by this code
1780 and it makes sense to say Y here if you have one of them.
1782 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1783 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1784 can lead to all sorts of problems, so it's good to say Y here.
1786 You can safely say Y even if your machine doesn't have MTRRs, you'll
1787 just add about 9 KB to your kernel.
1789 See <file:Documentation/x86/mtrr.txt> for more information.
1791 config MTRR_SANITIZER
1793 prompt "MTRR cleanup support"
1796 Convert MTRR layout from continuous to discrete, so X drivers can
1797 add writeback entries.
1799 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1800 The largest mtrr entry size for a continuous block can be set with
1805 config MTRR_SANITIZER_ENABLE_DEFAULT
1806 int "MTRR cleanup enable value (0-1)"
1809 depends on MTRR_SANITIZER
1811 Enable mtrr cleanup default value
1813 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1814 int "MTRR cleanup spare reg num (0-7)"
1817 depends on MTRR_SANITIZER
1819 mtrr cleanup spare entries default, it can be changed via
1820 mtrr_spare_reg_nr=N on the kernel command line.
1824 prompt "x86 PAT support" if EXPERT
1827 Use PAT attributes to setup page level cache control.
1829 PATs are the modern equivalents of MTRRs and are much more
1830 flexible than MTRRs.
1832 Say N here if you see bootup problems (boot crash, boot hang,
1833 spontaneous reboots) or a non-working video driver.
1837 config ARCH_USES_PG_UNCACHED
1843 prompt "x86 architectural random number generator" if EXPERT
1845 Enable the x86 architectural RDRAND instruction
1846 (Intel Bull Mountain technology) to generate random numbers.
1847 If supported, this is a high bandwidth, cryptographically
1848 secure hardware random number generator.
1852 prompt "Supervisor Mode Access Prevention" if EXPERT
1854 Supervisor Mode Access Prevention (SMAP) is a security
1855 feature in newer Intel processors. There is a small
1856 performance cost if this enabled and turned on; there is
1857 also a small increase in the kernel size if this is enabled.
1861 config X86_INTEL_UMIP
1863 depends on CPU_SUP_INTEL
1864 prompt "Intel User Mode Instruction Prevention" if EXPERT
1866 The User Mode Instruction Prevention (UMIP) is a security
1867 feature in newer Intel processors. If enabled, a general
1868 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1869 or STR instructions are executed in user mode. These instructions
1870 unnecessarily expose information about the hardware state.
1872 The vast majority of applications do not use these instructions.
1873 For the very few that do, software emulation is provided in
1874 specific cases in protected and virtual-8086 modes. Emulated
1877 config X86_INTEL_MPX
1878 prompt "Intel MPX (Memory Protection Extensions)"
1880 # Note: only available in 64-bit mode due to VMA flags shortage
1881 depends on CPU_SUP_INTEL && X86_64
1882 select ARCH_USES_HIGH_VMA_FLAGS
1884 MPX provides hardware features that can be used in
1885 conjunction with compiler-instrumented code to check
1886 memory references. It is designed to detect buffer
1887 overflow or underflow bugs.
1889 This option enables running applications which are
1890 instrumented or otherwise use MPX. It does not use MPX
1891 itself inside the kernel or to protect the kernel
1892 against bad memory references.
1894 Enabling this option will make the kernel larger:
1895 ~8k of kernel text and 36 bytes of data on a 64-bit
1896 defconfig. It adds a long to the 'mm_struct' which
1897 will increase the kernel memory overhead of each
1898 process and adds some branches to paths used during
1899 exec() and munmap().
1901 For details, see Documentation/x86/intel_mpx.txt
1905 config X86_INTEL_MEMORY_PROTECTION_KEYS
1906 prompt "Intel Memory Protection Keys"
1908 # Note: only available in 64-bit mode
1909 depends on CPU_SUP_INTEL && X86_64
1910 select ARCH_USES_HIGH_VMA_FLAGS
1911 select ARCH_HAS_PKEYS
1913 Memory Protection Keys provides a mechanism for enforcing
1914 page-based protections, but without requiring modification of the
1915 page tables when an application changes protection domains.
1917 For details, see Documentation/x86/protection-keys.txt
1922 bool "EFI runtime service support"
1925 select EFI_RUNTIME_WRAPPERS
1927 This enables the kernel to use EFI runtime services that are
1928 available (such as the EFI variable services).
1930 This option is only useful on systems that have EFI firmware.
1931 In addition, you should use the latest ELILO loader available
1932 at <http://elilo.sourceforge.net> in order to take advantage
1933 of EFI runtime services. However, even with this option, the
1934 resultant kernel should continue to boot on existing non-EFI
1938 bool "EFI stub support"
1939 depends on EFI && !X86_USE_3DNOW
1942 This kernel feature allows a bzImage to be loaded directly
1943 by EFI firmware without the use of a bootloader.
1945 See Documentation/efi-stub.txt for more information.
1948 bool "EFI mixed-mode support"
1949 depends on EFI_STUB && X86_64
1951 Enabling this feature allows a 64-bit kernel to be booted
1952 on a 32-bit firmware, provided that your CPU supports 64-bit
1955 Note that it is not possible to boot a mixed-mode enabled
1956 kernel via the EFI boot stub - a bootloader that supports
1957 the EFI handover protocol must be used.
1963 prompt "Enable seccomp to safely compute untrusted bytecode"
1965 This kernel feature is useful for number crunching applications
1966 that may need to compute untrusted bytecode during their
1967 execution. By using pipes or other transports made available to
1968 the process as file descriptors supporting the read/write
1969 syscalls, it's possible to isolate those applications in
1970 their own address space using seccomp. Once seccomp is
1971 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1972 and the task is only allowed to execute a few safe syscalls
1973 defined by each seccomp mode.
1975 If unsure, say Y. Only embedded should say N here.
1977 source "kernel/Kconfig.hz"
1980 bool "kexec system call"
1983 kexec is a system call that implements the ability to shutdown your
1984 current kernel, and to start another kernel. It is like a reboot
1985 but it is independent of the system firmware. And like a reboot
1986 you can start any kernel with it, not just Linux.
1988 The name comes from the similarity to the exec system call.
1990 It is an ongoing process to be certain the hardware in a machine
1991 is properly shutdown, so do not be surprised if this code does not
1992 initially work for you. As of this writing the exact hardware
1993 interface is strongly in flux, so no good recommendation can be
1997 bool "kexec file based system call"
2002 depends on CRYPTO_SHA256=y
2004 This is new version of kexec system call. This system call is
2005 file based and takes file descriptors as system call argument
2006 for kernel and initramfs as opposed to list of segments as
2007 accepted by previous system call.
2009 config ARCH_HAS_KEXEC_PURGATORY
2012 config KEXEC_VERIFY_SIG
2013 bool "Verify kernel signature during kexec_file_load() syscall"
2014 depends on KEXEC_FILE
2016 This option makes kernel signature verification mandatory for
2017 the kexec_file_load() syscall.
2019 In addition to that option, you need to enable signature
2020 verification for the corresponding kernel image type being
2021 loaded in order for this to work.
2023 config KEXEC_BZIMAGE_VERIFY_SIG
2024 bool "Enable bzImage signature verification support"
2025 depends on KEXEC_VERIFY_SIG
2026 depends on SIGNED_PE_FILE_VERIFICATION
2027 select SYSTEM_TRUSTED_KEYRING
2029 Enable bzImage signature verification support.
2032 bool "kernel crash dumps"
2033 depends on X86_64 || (X86_32 && HIGHMEM)
2035 Generate crash dump after being started by kexec.
2036 This should be normally only set in special crash dump kernels
2037 which are loaded in the main kernel with kexec-tools into
2038 a specially reserved region and then later executed after
2039 a crash by kdump/kexec. The crash dump kernel must be compiled
2040 to a memory address not used by the main kernel or BIOS using
2041 PHYSICAL_START, or it must be built as a relocatable image
2042 (CONFIG_RELOCATABLE=y).
2043 For more details see Documentation/kdump/kdump.txt
2047 depends on KEXEC && HIBERNATION
2049 Jump between original kernel and kexeced kernel and invoke
2050 code in physical address mode via KEXEC
2052 config PHYSICAL_START
2053 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2056 This gives the physical address where the kernel is loaded.
2058 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2059 bzImage will decompress itself to above physical address and
2060 run from there. Otherwise, bzImage will run from the address where
2061 it has been loaded by the boot loader and will ignore above physical
2064 In normal kdump cases one does not have to set/change this option
2065 as now bzImage can be compiled as a completely relocatable image
2066 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2067 address. This option is mainly useful for the folks who don't want
2068 to use a bzImage for capturing the crash dump and want to use a
2069 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2070 to be specifically compiled to run from a specific memory area
2071 (normally a reserved region) and this option comes handy.
2073 So if you are using bzImage for capturing the crash dump,
2074 leave the value here unchanged to 0x1000000 and set
2075 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2076 for capturing the crash dump change this value to start of
2077 the reserved region. In other words, it can be set based on
2078 the "X" value as specified in the "crashkernel=YM@XM"
2079 command line boot parameter passed to the panic-ed
2080 kernel. Please take a look at Documentation/kdump/kdump.txt
2081 for more details about crash dumps.
2083 Usage of bzImage for capturing the crash dump is recommended as
2084 one does not have to build two kernels. Same kernel can be used
2085 as production kernel and capture kernel. Above option should have
2086 gone away after relocatable bzImage support is introduced. But it
2087 is present because there are users out there who continue to use
2088 vmlinux for dump capture. This option should go away down the
2091 Don't change this unless you know what you are doing.
2094 bool "Build a relocatable kernel"
2097 This builds a kernel image that retains relocation information
2098 so it can be loaded someplace besides the default 1MB.
2099 The relocations tend to make the kernel binary about 10% larger,
2100 but are discarded at runtime.
2102 One use is for the kexec on panic case where the recovery kernel
2103 must live at a different physical address than the primary
2106 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2107 it has been loaded at and the compile time physical address
2108 (CONFIG_PHYSICAL_START) is used as the minimum location.
2110 config RANDOMIZE_BASE
2111 bool "Randomize the address of the kernel image (KASLR)"
2112 depends on RELOCATABLE
2115 In support of Kernel Address Space Layout Randomization (KASLR),
2116 this randomizes the physical address at which the kernel image
2117 is decompressed and the virtual address where the kernel
2118 image is mapped, as a security feature that deters exploit
2119 attempts relying on knowledge of the location of kernel
2122 On 64-bit, the kernel physical and virtual addresses are
2123 randomized separately. The physical address will be anywhere
2124 between 16MB and the top of physical memory (up to 64TB). The
2125 virtual address will be randomized from 16MB up to 1GB (9 bits
2126 of entropy). Note that this also reduces the memory space
2127 available to kernel modules from 1.5GB to 1GB.
2129 On 32-bit, the kernel physical and virtual addresses are
2130 randomized together. They will be randomized from 16MB up to
2131 512MB (8 bits of entropy).
2133 Entropy is generated using the RDRAND instruction if it is
2134 supported. If RDTSC is supported, its value is mixed into
2135 the entropy pool as well. If neither RDRAND nor RDTSC are
2136 supported, then entropy is read from the i8254 timer. The
2137 usable entropy is limited by the kernel being built using
2138 2GB addressing, and that PHYSICAL_ALIGN must be at a
2139 minimum of 2MB. As a result, only 10 bits of entropy are
2140 theoretically possible, but the implementations are further
2141 limited due to memory layouts.
2145 # Relocation on x86 needs some additional build support
2146 config X86_NEED_RELOCS
2148 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2150 config PHYSICAL_ALIGN
2151 hex "Alignment value to which kernel should be aligned"
2153 range 0x2000 0x1000000 if X86_32
2154 range 0x200000 0x1000000 if X86_64
2156 This value puts the alignment restrictions on physical address
2157 where kernel is loaded and run from. Kernel is compiled for an
2158 address which meets above alignment restriction.
2160 If bootloader loads the kernel at a non-aligned address and
2161 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2162 address aligned to above value and run from there.
2164 If bootloader loads the kernel at a non-aligned address and
2165 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2166 load address and decompress itself to the address it has been
2167 compiled for and run from there. The address for which kernel is
2168 compiled already meets above alignment restrictions. Hence the
2169 end result is that kernel runs from a physical address meeting
2170 above alignment restrictions.
2172 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2173 this value must be a multiple of 0x200000.
2175 Don't change this unless you know what you are doing.
2177 config DYNAMIC_MEMORY_LAYOUT
2180 This option makes base addresses of vmalloc and vmemmap as well as
2181 __PAGE_OFFSET movable during boot.
2183 config RANDOMIZE_MEMORY
2184 bool "Randomize the kernel memory sections"
2186 depends on RANDOMIZE_BASE
2187 select DYNAMIC_MEMORY_LAYOUT
2188 default RANDOMIZE_BASE
2190 Randomizes the base virtual address of kernel memory sections
2191 (physical memory mapping, vmalloc & vmemmap). This security feature
2192 makes exploits relying on predictable memory locations less reliable.
2194 The order of allocations remains unchanged. Entropy is generated in
2195 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2196 configuration have in average 30,000 different possible virtual
2197 addresses for each memory section.
2201 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2202 hex "Physical memory mapping padding" if EXPERT
2203 depends on RANDOMIZE_MEMORY
2204 default "0xa" if MEMORY_HOTPLUG
2206 range 0x1 0x40 if MEMORY_HOTPLUG
2209 Define the padding in terabytes added to the existing physical
2210 memory size during kernel memory randomization. It is useful
2211 for memory hotplug support but reduces the entropy available for
2212 address randomization.
2214 If unsure, leave at the default value.
2220 config BOOTPARAM_HOTPLUG_CPU0
2221 bool "Set default setting of cpu0_hotpluggable"
2222 depends on HOTPLUG_CPU
2224 Set whether default state of cpu0_hotpluggable is on or off.
2226 Say Y here to enable CPU0 hotplug by default. If this switch
2227 is turned on, there is no need to give cpu0_hotplug kernel
2228 parameter and the CPU0 hotplug feature is enabled by default.
2230 Please note: there are two known CPU0 dependencies if you want
2231 to enable the CPU0 hotplug feature either by this switch or by
2232 cpu0_hotplug kernel parameter.
2234 First, resume from hibernate or suspend always starts from CPU0.
2235 So hibernate and suspend are prevented if CPU0 is offline.
2237 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2238 offline if any interrupt can not migrate out of CPU0. There may
2239 be other CPU0 dependencies.
2241 Please make sure the dependencies are under your control before
2242 you enable this feature.
2244 Say N if you don't want to enable CPU0 hotplug feature by default.
2245 You still can enable the CPU0 hotplug feature at boot by kernel
2246 parameter cpu0_hotplug.
2248 config DEBUG_HOTPLUG_CPU0
2250 prompt "Debug CPU0 hotplug"
2251 depends on HOTPLUG_CPU
2253 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2254 soon as possible and boots up userspace with CPU0 offlined. User
2255 can online CPU0 back after boot time.
2257 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2258 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2259 compilation or giving cpu0_hotplug kernel parameter at boot.
2265 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2266 depends on COMPAT_32
2268 Certain buggy versions of glibc will crash if they are
2269 presented with a 32-bit vDSO that is not mapped at the address
2270 indicated in its segment table.
2272 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2273 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2274 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2275 the only released version with the bug, but OpenSUSE 9
2276 contains a buggy "glibc 2.3.2".
2278 The symptom of the bug is that everything crashes on startup, saying:
2279 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2281 Saying Y here changes the default value of the vdso32 boot
2282 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2283 This works around the glibc bug but hurts performance.
2285 If unsure, say N: if you are compiling your own kernel, you
2286 are unlikely to be using a buggy version of glibc.
2289 prompt "vsyscall table for legacy applications"
2291 default LEGACY_VSYSCALL_EMULATE
2293 Legacy user code that does not know how to find the vDSO expects
2294 to be able to issue three syscalls by calling fixed addresses in
2295 kernel space. Since this location is not randomized with ASLR,
2296 it can be used to assist security vulnerability exploitation.
2298 This setting can be changed at boot time via the kernel command
2299 line parameter vsyscall=[emulate|none].
2301 On a system with recent enough glibc (2.14 or newer) and no
2302 static binaries, you can say None without a performance penalty
2303 to improve security.
2305 If unsure, select "Emulate".
2307 config LEGACY_VSYSCALL_EMULATE
2310 The kernel traps and emulates calls into the fixed
2311 vsyscall address mapping. This makes the mapping
2312 non-executable, but it still contains known contents,
2313 which could be used in certain rare security vulnerability
2314 exploits. This configuration is recommended when userspace
2315 still uses the vsyscall area.
2317 config LEGACY_VSYSCALL_NONE
2320 There will be no vsyscall mapping at all. This will
2321 eliminate any risk of ASLR bypass due to the vsyscall
2322 fixed address mapping. Attempts to use the vsyscalls
2323 will be reported to dmesg, so that either old or
2324 malicious userspace programs can be identified.
2329 bool "Built-in kernel command line"
2331 Allow for specifying boot arguments to the kernel at
2332 build time. On some systems (e.g. embedded ones), it is
2333 necessary or convenient to provide some or all of the
2334 kernel boot arguments with the kernel itself (that is,
2335 to not rely on the boot loader to provide them.)
2337 To compile command line arguments into the kernel,
2338 set this option to 'Y', then fill in the
2339 boot arguments in CONFIG_CMDLINE.
2341 Systems with fully functional boot loaders (i.e. non-embedded)
2342 should leave this option set to 'N'.
2345 string "Built-in kernel command string"
2346 depends on CMDLINE_BOOL
2349 Enter arguments here that should be compiled into the kernel
2350 image and used at boot time. If the boot loader provides a
2351 command line at boot time, it is appended to this string to
2352 form the full kernel command line, when the system boots.
2354 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2355 change this behavior.
2357 In most cases, the command line (whether built-in or provided
2358 by the boot loader) should specify the device for the root
2361 config CMDLINE_OVERRIDE
2362 bool "Built-in command line overrides boot loader arguments"
2363 depends on CMDLINE_BOOL
2365 Set this option to 'Y' to have the kernel ignore the boot loader
2366 command line, and use ONLY the built-in command line.
2368 This is used to work around broken boot loaders. This should
2369 be set to 'N' under normal conditions.
2371 config MODIFY_LDT_SYSCALL
2372 bool "Enable the LDT (local descriptor table)" if EXPERT
2375 Linux can allow user programs to install a per-process x86
2376 Local Descriptor Table (LDT) using the modify_ldt(2) system
2377 call. This is required to run 16-bit or segmented code such as
2378 DOSEMU or some Wine programs. It is also used by some very old
2379 threading libraries.
2381 Enabling this feature adds a small amount of overhead to
2382 context switches and increases the low-level kernel attack
2383 surface. Disabling it removes the modify_ldt(2) system call.
2385 Saying 'N' here may make sense for embedded or server kernels.
2387 source "kernel/livepatch/Kconfig"
2391 config ARCH_HAS_ADD_PAGES
2393 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2395 config ARCH_ENABLE_MEMORY_HOTPLUG
2397 depends on X86_64 || (X86_32 && HIGHMEM)
2399 config ARCH_ENABLE_MEMORY_HOTREMOVE
2401 depends on MEMORY_HOTPLUG
2403 config USE_PERCPU_NUMA_NODE_ID
2407 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2409 depends on X86_64 || X86_PAE
2411 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2413 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2415 config ARCH_ENABLE_THP_MIGRATION
2417 depends on X86_64 && TRANSPARENT_HUGEPAGE
2419 menu "Power management and ACPI options"
2421 config ARCH_HIBERNATION_HEADER
2423 depends on HIBERNATION
2425 source "kernel/power/Kconfig"
2427 source "drivers/acpi/Kconfig"
2429 source "drivers/sfi/Kconfig"
2436 tristate "APM (Advanced Power Management) BIOS support"
2437 depends on X86_32 && PM_SLEEP
2439 APM is a BIOS specification for saving power using several different
2440 techniques. This is mostly useful for battery powered laptops with
2441 APM compliant BIOSes. If you say Y here, the system time will be
2442 reset after a RESUME operation, the /proc/apm device will provide
2443 battery status information, and user-space programs will receive
2444 notification of APM "events" (e.g. battery status change).
2446 If you select "Y" here, you can disable actual use of the APM
2447 BIOS by passing the "apm=off" option to the kernel at boot time.
2449 Note that the APM support is almost completely disabled for
2450 machines with more than one CPU.
2452 In order to use APM, you will need supporting software. For location
2453 and more information, read <file:Documentation/power/apm-acpi.txt>
2454 and the Battery Powered Linux mini-HOWTO, available from
2455 <http://www.tldp.org/docs.html#howto>.
2457 This driver does not spin down disk drives (see the hdparm(8)
2458 manpage ("man 8 hdparm") for that), and it doesn't turn off
2459 VESA-compliant "green" monitors.
2461 This driver does not support the TI 4000M TravelMate and the ACER
2462 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2463 desktop machines also don't have compliant BIOSes, and this driver
2464 may cause those machines to panic during the boot phase.
2466 Generally, if you don't have a battery in your machine, there isn't
2467 much point in using this driver and you should say N. If you get
2468 random kernel OOPSes or reboots that don't seem to be related to
2469 anything, try disabling/enabling this option (or disabling/enabling
2472 Some other things you should try when experiencing seemingly random,
2475 1) make sure that you have enough swap space and that it is
2477 2) pass the "no-hlt" option to the kernel
2478 3) switch on floating point emulation in the kernel and pass
2479 the "no387" option to the kernel
2480 4) pass the "floppy=nodma" option to the kernel
2481 5) pass the "mem=4M" option to the kernel (thereby disabling
2482 all but the first 4 MB of RAM)
2483 6) make sure that the CPU is not over clocked.
2484 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2485 8) disable the cache from your BIOS settings
2486 9) install a fan for the video card or exchange video RAM
2487 10) install a better fan for the CPU
2488 11) exchange RAM chips
2489 12) exchange the motherboard.
2491 To compile this driver as a module, choose M here: the
2492 module will be called apm.
2496 config APM_IGNORE_USER_SUSPEND
2497 bool "Ignore USER SUSPEND"
2499 This option will ignore USER SUSPEND requests. On machines with a
2500 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2501 series notebooks, it is necessary to say Y because of a BIOS bug.
2503 config APM_DO_ENABLE
2504 bool "Enable PM at boot time"
2506 Enable APM features at boot time. From page 36 of the APM BIOS
2507 specification: "When disabled, the APM BIOS does not automatically
2508 power manage devices, enter the Standby State, enter the Suspend
2509 State, or take power saving steps in response to CPU Idle calls."
2510 This driver will make CPU Idle calls when Linux is idle (unless this
2511 feature is turned off -- see "Do CPU IDLE calls", below). This
2512 should always save battery power, but more complicated APM features
2513 will be dependent on your BIOS implementation. You may need to turn
2514 this option off if your computer hangs at boot time when using APM
2515 support, or if it beeps continuously instead of suspending. Turn
2516 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2517 T400CDT. This is off by default since most machines do fine without
2522 bool "Make CPU Idle calls when idle"
2524 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2525 On some machines, this can activate improved power savings, such as
2526 a slowed CPU clock rate, when the machine is idle. These idle calls
2527 are made after the idle loop has run for some length of time (e.g.,
2528 333 mS). On some machines, this will cause a hang at boot time or
2529 whenever the CPU becomes idle. (On machines with more than one CPU,
2530 this option does nothing.)
2532 config APM_DISPLAY_BLANK
2533 bool "Enable console blanking using APM"
2535 Enable console blanking using the APM. Some laptops can use this to
2536 turn off the LCD backlight when the screen blanker of the Linux
2537 virtual console blanks the screen. Note that this is only used by
2538 the virtual console screen blanker, and won't turn off the backlight
2539 when using the X Window system. This also doesn't have anything to
2540 do with your VESA-compliant power-saving monitor. Further, this
2541 option doesn't work for all laptops -- it might not turn off your
2542 backlight at all, or it might print a lot of errors to the console,
2543 especially if you are using gpm.
2545 config APM_ALLOW_INTS
2546 bool "Allow interrupts during APM BIOS calls"
2548 Normally we disable external interrupts while we are making calls to
2549 the APM BIOS as a measure to lessen the effects of a badly behaving
2550 BIOS implementation. The BIOS should reenable interrupts if it
2551 needs to. Unfortunately, some BIOSes do not -- especially those in
2552 many of the newer IBM Thinkpads. If you experience hangs when you
2553 suspend, try setting this to Y. Otherwise, say N.
2557 source "drivers/cpufreq/Kconfig"
2559 source "drivers/cpuidle/Kconfig"
2561 source "drivers/idle/Kconfig"
2566 menu "Bus options (PCI etc.)"
2569 prompt "PCI access mode"
2570 depends on X86_32 && PCI
2573 On PCI systems, the BIOS can be used to detect the PCI devices and
2574 determine their configuration. However, some old PCI motherboards
2575 have BIOS bugs and may crash if this is done. Also, some embedded
2576 PCI-based systems don't have any BIOS at all. Linux can also try to
2577 detect the PCI hardware directly without using the BIOS.
2579 With this option, you can specify how Linux should detect the
2580 PCI devices. If you choose "BIOS", the BIOS will be used,
2581 if you choose "Direct", the BIOS won't be used, and if you
2582 choose "MMConfig", then PCI Express MMCONFIG will be used.
2583 If you choose "Any", the kernel will try MMCONFIG, then the
2584 direct access method and falls back to the BIOS if that doesn't
2585 work. If unsure, go with the default, which is "Any".
2590 config PCI_GOMMCONFIG
2607 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2609 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2612 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2615 bool "Support mmconfig PCI config space access" if X86_64
2617 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2618 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2622 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2626 depends on PCI && XEN
2629 config MMCONF_FAM10H
2631 depends on X86_64 && PCI_MMCONFIG && ACPI
2633 config PCI_CNB20LE_QUIRK
2634 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2637 Read the PCI windows out of the CNB20LE host bridge. This allows
2638 PCI hotplug to work on systems with the CNB20LE chipset which do
2641 There's no public spec for this chipset, and this functionality
2642 is known to be incomplete.
2644 You should say N unless you know you need this.
2647 bool "ISA bus support on modern systems" if EXPERT
2649 Expose ISA bus device drivers and options available for selection and
2650 configuration. Enable this option if your target machine has an ISA
2651 bus. ISA is an older system, displaced by PCI and newer bus
2652 architectures -- if your target machine is modern, it probably does
2653 not have an ISA bus.
2657 # x86_64 have no ISA slots, but can have ISA-style DMA.
2659 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2662 Enables ISA-style DMA support for devices requiring such controllers.
2670 Find out whether you have ISA slots on your motherboard. ISA is the
2671 name of a bus system, i.e. the way the CPU talks to the other stuff
2672 inside your box. Other bus systems are PCI, EISA, MicroChannel
2673 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2674 newer boards don't support it. If you have ISA, say Y, otherwise N.
2677 tristate "NatSemi SCx200 support"
2679 This provides basic support for National Semiconductor's
2680 (now AMD's) Geode processors. The driver probes for the
2681 PCI-IDs of several on-chip devices, so its a good dependency
2682 for other scx200_* drivers.
2684 If compiled as a module, the driver is named scx200.
2686 config SCx200HR_TIMER
2687 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2691 This driver provides a clocksource built upon the on-chip
2692 27MHz high-resolution timer. Its also a workaround for
2693 NSC Geode SC-1100's buggy TSC, which loses time when the
2694 processor goes idle (as is done by the scheduler). The
2695 other workaround is idle=poll boot option.
2698 bool "One Laptop Per Child support"
2705 Add support for detecting the unique features of the OLPC
2709 bool "OLPC XO-1 Power Management"
2710 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2712 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2715 bool "OLPC XO-1 Real Time Clock"
2716 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2718 Add support for the XO-1 real time clock, which can be used as a
2719 programmable wakeup source.
2722 bool "OLPC XO-1 SCI extras"
2723 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2727 Add support for SCI-based features of the OLPC XO-1 laptop:
2728 - EC-driven system wakeups
2732 - AC adapter status updates
2733 - Battery status updates
2735 config OLPC_XO15_SCI
2736 bool "OLPC XO-1.5 SCI extras"
2737 depends on OLPC && ACPI
2740 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2741 - EC-driven system wakeups
2742 - AC adapter status updates
2743 - Battery status updates
2746 bool "PCEngines ALIX System Support (LED setup)"
2749 This option enables system support for the PCEngines ALIX.
2750 At present this just sets up LEDs for GPIO control on
2751 ALIX2/3/6 boards. However, other system specific setup should
2754 Note: You must still enable the drivers for GPIO and LED support
2755 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2757 Note: You have to set alix.force=1 for boards with Award BIOS.
2760 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2763 This option enables system support for the Soekris Engineering net5501.
2766 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2770 This option enables system support for the Traverse Technologies GEOS.
2773 bool "Technologic Systems TS-5500 platform support"
2775 select CHECK_SIGNATURE
2779 This option enables system support for the Technologic Systems TS-5500.
2785 depends on CPU_SUP_AMD && PCI
2788 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2790 Firmwares often provide initial graphics framebuffers so the BIOS,
2791 bootloader or kernel can show basic video-output during boot for
2792 user-guidance and debugging. Historically, x86 used the VESA BIOS
2793 Extensions and EFI-framebuffers for this, which are mostly limited
2795 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2796 framebuffers so the new generic system-framebuffer drivers can be
2797 used on x86. If the framebuffer is not compatible with the generic
2798 modes, it is advertised as fallback platform framebuffer so legacy
2799 drivers like efifb, vesafb and uvesafb can pick it up.
2800 If this option is not selected, all system framebuffers are always
2801 marked as fallback platform framebuffers as usual.
2803 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2804 not be able to pick up generic system framebuffers if this option
2805 is selected. You are highly encouraged to enable simplefb as
2806 replacement if you select this option. simplefb can correctly deal
2807 with generic system framebuffers. But you should still keep vesafb
2808 and others enabled as fallback if a system framebuffer is
2809 incompatible with simplefb.
2816 menu "Binary Emulations"
2818 config IA32_EMULATION
2819 bool "IA32 Emulation"
2821 select ARCH_WANT_OLD_COMPAT_IPC
2823 select COMPAT_BINFMT_ELF
2824 select COMPAT_OLD_SIGACTION
2826 Include code to run legacy 32-bit programs under a
2827 64-bit kernel. You should likely turn this on, unless you're
2828 100% sure that you don't have any 32-bit programs left.
2831 tristate "IA32 a.out support"
2832 depends on IA32_EMULATION
2835 Support old a.out binaries in the 32bit emulation.
2838 bool "x32 ABI for 64-bit mode"
2841 Include code to run binaries for the x32 native 32-bit ABI
2842 for 64-bit processors. An x32 process gets access to the
2843 full 64-bit register file and wide data path while leaving
2844 pointers at 32 bits for smaller memory footprint.
2846 You will need a recent binutils (2.22 or later) with
2847 elf32_x86_64 support enabled to compile a kernel with this
2852 depends on IA32_EMULATION || X86_32
2854 select OLD_SIGSUSPEND3
2858 depends on IA32_EMULATION || X86_X32
2861 config COMPAT_FOR_U64_ALIGNMENT
2864 config SYSVIPC_COMPAT
2872 config HAVE_ATOMIC_IOMAP
2876 config X86_DEV_DMA_OPS
2879 config HAVE_GENERIC_GUP
2882 source "drivers/firmware/Kconfig"
2884 source "arch/x86/kvm/Kconfig"