1 # SPDX-License-Identifier: GPL-2.0
4 bool "64-bit kernel" if "$(ARCH)" = "x86"
5 default "$(ARCH)" != "i386"
7 Say yes to build a 64-bit kernel - formerly known as x86_64
8 Say no to build a 32-bit kernel - formerly known as i386
13 # Options that are inherently 32-bit kernel only:
14 select ARCH_WANT_IPC_PARSE_VERSION
16 select CLONE_BACKWARDS
17 select HAVE_DEBUG_STACKOVERFLOW
18 select MODULES_USE_ELF_REL
20 select GENERIC_VDSO_32
25 # Options that are inherently 64-bit kernel only:
26 select ARCH_HAS_GIGANTIC_PAGE
27 select ARCH_SUPPORTS_INT128
28 select ARCH_USE_CMPXCHG_LOCKREF
29 select HAVE_ARCH_SOFT_DIRTY
30 select MODULES_USE_ELF_RELA
31 select NEED_DMA_MAP_STATE
33 select ARCH_HAS_SYSCALL_WRAPPER
35 config FORCE_DYNAMIC_FTRACE
38 depends on FUNCTION_TRACER
41 We keep the static function tracing (!DYNAMIC_FTRACE) around
42 in order to test the non static function tracing in the
43 generic code, as other architectures still use it. But we
44 only need to keep it around for x86_64. No need to keep it
45 for x86_32. For x86_32, force DYNAMIC_FTRACE.
49 # ( Note that options that are marked 'if X86_64' could in principle be
50 # ported to 32-bit as well. )
55 # Note: keep this list sorted alphabetically
57 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
58 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
59 select ARCH_32BIT_OFF_T if X86_32
60 select ARCH_CLOCKSOURCE_DATA
61 select ARCH_CLOCKSOURCE_INIT
62 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
63 select ARCH_HAS_DEBUG_VIRTUAL
64 select ARCH_HAS_DEVMEM_IS_ALLOWED
65 select ARCH_HAS_ELF_RANDOMIZE
66 select ARCH_HAS_FAST_MULTIPLIER
67 select ARCH_HAS_FILTER_PGPROT
68 select ARCH_HAS_FORTIFY_SOURCE
69 select ARCH_HAS_GCOV_PROFILE_ALL
70 select ARCH_HAS_KCOV if X86_64
71 select ARCH_HAS_MEMBARRIER_SYNC_CORE
72 select ARCH_HAS_PMEM_API if X86_64
73 select ARCH_HAS_PTE_SPECIAL
74 select ARCH_HAS_REFCOUNT
75 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
76 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
77 select ARCH_HAS_SET_MEMORY
78 select ARCH_HAS_SET_DIRECT_MAP
79 select ARCH_HAS_STRICT_KERNEL_RWX
80 select ARCH_HAS_STRICT_MODULE_RWX
81 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
82 select ARCH_HAS_UBSAN_SANITIZE_ALL
83 select ARCH_HAS_ZONE_DEVICE if X86_64
84 select ARCH_HAVE_NMI_SAFE_CMPXCHG
85 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
86 select ARCH_MIGHT_HAVE_PC_PARPORT
87 select ARCH_MIGHT_HAVE_PC_SERIO
89 select ARCH_SUPPORTS_ACPI
90 select ARCH_SUPPORTS_ATOMIC_RMW
91 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
92 select ARCH_USE_BUILTIN_BSWAP
93 select ARCH_USE_QUEUED_RWLOCKS
94 select ARCH_USE_QUEUED_SPINLOCKS
95 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
96 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
97 select ARCH_WANTS_THP_SWAP if X86_64
98 select BUILDTIME_EXTABLE_SORT
100 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
101 select CLOCKSOURCE_WATCHDOG
102 select DCACHE_WORD_ACCESS
103 select EDAC_ATOMIC_SCRUB
105 select GENERIC_CLOCKEVENTS
106 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
107 select GENERIC_CLOCKEVENTS_MIN_ADJUST
108 select GENERIC_CMOS_UPDATE
109 select GENERIC_CPU_AUTOPROBE
110 select GENERIC_CPU_VULNERABILITIES
111 select GENERIC_EARLY_IOREMAP
112 select GENERIC_FIND_FIRST_BIT
114 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
115 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
116 select GENERIC_IRQ_MIGRATION if SMP
117 select GENERIC_IRQ_PROBE
118 select GENERIC_IRQ_RESERVATION_MODE
119 select GENERIC_IRQ_SHOW
120 select GENERIC_PENDING_IRQ if SMP
121 select GENERIC_SMP_IDLE_THREAD
122 select GENERIC_STRNCPY_FROM_USER
123 select GENERIC_STRNLEN_USER
124 select GENERIC_TIME_VSYSCALL
125 select GENERIC_GETTIMEOFDAY
126 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
127 select HAVE_ACPI_APEI if ACPI
128 select HAVE_ACPI_APEI_NMI if ACPI
129 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
130 select HAVE_ARCH_AUDITSYSCALL
131 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
132 select HAVE_ARCH_JUMP_LABEL
133 select HAVE_ARCH_JUMP_LABEL_RELATIVE
134 select HAVE_ARCH_KASAN if X86_64
135 select HAVE_ARCH_KGDB
136 select HAVE_ARCH_MMAP_RND_BITS if MMU
137 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
138 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
139 select HAVE_ARCH_PREL32_RELOCATIONS
140 select HAVE_ARCH_SECCOMP_FILTER
141 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
142 select HAVE_ARCH_STACKLEAK
143 select HAVE_ARCH_TRACEHOOK
144 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
145 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
146 select HAVE_ARCH_VMAP_STACK if X86_64
147 select HAVE_ARCH_WITHIN_STACK_FRAMES
148 select HAVE_CMPXCHG_DOUBLE
149 select HAVE_CMPXCHG_LOCAL
150 select HAVE_CONTEXT_TRACKING if X86_64
151 select HAVE_COPY_THREAD_TLS
152 select HAVE_C_RECORDMCOUNT
153 select HAVE_DEBUG_KMEMLEAK
154 select HAVE_DMA_CONTIGUOUS
155 select HAVE_DYNAMIC_FTRACE
156 select HAVE_DYNAMIC_FTRACE_WITH_REGS
158 select HAVE_EFFICIENT_UNALIGNED_ACCESS
160 select HAVE_EXIT_THREAD
161 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
162 select HAVE_FTRACE_MCOUNT_RECORD
163 select HAVE_FUNCTION_GRAPH_TRACER
164 select HAVE_FUNCTION_TRACER
165 select HAVE_GCC_PLUGINS
166 select HAVE_HW_BREAKPOINT
168 select HAVE_IOREMAP_PROT
169 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
170 select HAVE_IRQ_TIME_ACCOUNTING
171 select HAVE_KERNEL_BZIP2
172 select HAVE_KERNEL_GZIP
173 select HAVE_KERNEL_LZ4
174 select HAVE_KERNEL_LZMA
175 select HAVE_KERNEL_LZO
176 select HAVE_KERNEL_XZ
178 select HAVE_KPROBES_ON_FTRACE
179 select HAVE_FUNCTION_ERROR_INJECTION
180 select HAVE_KRETPROBES
182 select HAVE_LIVEPATCH if X86_64
183 select HAVE_MEMBLOCK_NODE_MAP
184 select HAVE_MIXED_BREAKPOINTS_REGS
185 select HAVE_MOD_ARCH_SPECIFIC
189 select HAVE_OPTPROBES
190 select HAVE_PCSPKR_PLATFORM
191 select HAVE_PERF_EVENTS
192 select HAVE_PERF_EVENTS_NMI
193 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
195 select HAVE_PERF_REGS
196 select HAVE_PERF_USER_STACK_DUMP
197 select HAVE_RCU_TABLE_FREE if PARAVIRT
198 select HAVE_REGS_AND_STACK_ACCESS_API
199 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
200 select HAVE_FUNCTION_ARG_ACCESS_API
201 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
202 select HAVE_STACK_VALIDATION if X86_64
204 select HAVE_SYSCALL_TRACEPOINTS
205 select HAVE_UNSTABLE_SCHED_CLOCK
206 select HAVE_USER_RETURN_NOTIFIER
207 select HAVE_GENERIC_VDSO
208 select HOTPLUG_SMT if SMP
209 select IRQ_FORCED_THREADING
210 select NEED_SG_DMA_LENGTH
211 select PCI_DOMAINS if PCI
212 select PCI_LOCKLESS_CONFIG if PCI
215 select RTC_MC146818_LIB
218 select SYSCTL_EXCEPTION_TRACE
219 select THREAD_INFO_IN_TASK
220 select USER_STACKTRACE_SUPPORT
222 select X86_FEATURE_NAMES if PROC_FS
223 select PROC_PID_ARCH_STATUS if PROC_FS
225 config INSTRUCTION_DECODER
227 depends on KPROBES || PERF_EVENTS || UPROBES
231 default "elf32-i386" if X86_32
232 default "elf64-x86-64" if X86_64
234 config ARCH_DEFCONFIG
236 default "arch/x86/configs/i386_defconfig" if X86_32
237 default "arch/x86/configs/x86_64_defconfig" if X86_64
239 config LOCKDEP_SUPPORT
242 config STACKTRACE_SUPPORT
248 config ARCH_MMAP_RND_BITS_MIN
252 config ARCH_MMAP_RND_BITS_MAX
256 config ARCH_MMAP_RND_COMPAT_BITS_MIN
259 config ARCH_MMAP_RND_COMPAT_BITS_MAX
265 config GENERIC_ISA_DMA
267 depends on ISA_DMA_API
272 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
274 config GENERIC_BUG_RELATIVE_POINTERS
277 config ARCH_MAY_HAVE_PC_FDC
279 depends on ISA_DMA_API
281 config GENERIC_CALIBRATE_DELAY
284 config ARCH_HAS_CPU_RELAX
287 config ARCH_HAS_CACHE_LINE_SIZE
290 config ARCH_HAS_FILTER_PGPROT
293 config HAVE_SETUP_PER_CPU_AREA
296 config NEED_PER_CPU_EMBED_FIRST_CHUNK
299 config NEED_PER_CPU_PAGE_FIRST_CHUNK
302 config ARCH_HIBERNATION_POSSIBLE
305 config ARCH_SUSPEND_POSSIBLE
308 config ARCH_WANT_HUGE_PMD_SHARE
311 config ARCH_WANT_GENERAL_HUGETLB
320 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
323 config KASAN_SHADOW_OFFSET
326 default 0xdffffc0000000000
328 config HAVE_INTEL_TXT
330 depends on INTEL_IOMMU && ACPI
334 depends on X86_32 && SMP
338 depends on X86_64 && SMP
340 config X86_32_LAZY_GS
342 depends on X86_32 && !STACKPROTECTOR
344 config ARCH_SUPPORTS_UPROBES
347 config FIX_EARLYCON_MEM
350 config DYNAMIC_PHYSICAL_MASK
353 config PGTABLE_LEVELS
355 default 5 if X86_5LEVEL
360 config CC_HAS_SANE_STACKPROTECTOR
362 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
363 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
365 We have to make sure stack protector is unconditionally disabled if
366 the compiler produces broken code.
368 menu "Processor type and features"
371 bool "DMA memory allocation support" if EXPERT
374 DMA memory allocation support allows devices with less than 32-bit
375 addressing to allocate within the first 16MB of address space.
376 Disable if no such devices will be used.
381 bool "Symmetric multi-processing support"
383 This enables support for systems with more than one CPU. If you have
384 a system with only one CPU, say N. If you have a system with more
387 If you say N here, the kernel will run on uni- and multiprocessor
388 machines, but will use only one CPU of a multiprocessor machine. If
389 you say Y here, the kernel will run on many, but not all,
390 uniprocessor machines. On a uniprocessor machine, the kernel
391 will run faster if you say N here.
393 Note that if you say Y here and choose architecture "586" or
394 "Pentium" under "Processor family", the kernel will not work on 486
395 architectures. Similarly, multiprocessor kernels for the "PPro"
396 architecture may not work on all Pentium based boards.
398 People using multiprocessor machines who say Y here should also say
399 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
400 Management" code will be disabled if you say Y here.
402 See also <file:Documentation/x86/i386/IO-APIC.rst>,
403 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
404 <http://www.tldp.org/docs.html#howto>.
406 If you don't know what to do here, say N.
408 config X86_FEATURE_NAMES
409 bool "Processor feature human-readable names" if EMBEDDED
412 This option compiles in a table of x86 feature bits and corresponding
413 names. This is required to support /proc/cpuinfo and a few kernel
414 messages. You can disable this to save space, at the expense of
415 making those few kernel messages show numeric feature bits instead.
420 bool "Support x2apic"
421 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
423 This enables x2apic support on CPUs that have this feature.
425 This allows 32-bit apic IDs (so it can support very large systems),
426 and accesses the local apic via MSRs not via mmio.
428 If you don't know what to do here, say N.
431 bool "Enable MPS table" if ACPI || SFI
433 depends on X86_LOCAL_APIC
435 For old smp systems that do not have proper acpi support. Newer systems
436 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
440 depends on X86_GOLDFISH
443 bool "Avoid speculative indirect branches in kernel"
445 select STACK_VALIDATION if HAVE_STACK_VALIDATION
447 Compile kernel with the retpoline compiler options to guard against
448 kernel-to-user data leaks by avoiding speculative indirect
449 branches. Requires a compiler with -mindirect-branch=thunk-extern
450 support for full protection. The kernel may run slower.
452 config X86_CPU_RESCTRL
453 bool "x86 CPU resource control support"
454 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
457 Enable x86 CPU resource control support.
459 Provide support for the allocation and monitoring of system resources
462 Intel calls this Intel Resource Director Technology
463 (Intel(R) RDT). More information about RDT can be found in the
464 Intel x86 Architecture Software Developer Manual.
466 AMD calls this AMD Platform Quality of Service (AMD QoS).
467 More information about AMD QoS can be found in the AMD64 Technology
468 Platform Quality of Service Extensions manual.
474 bool "Support for big SMP systems with more than 8 CPUs"
477 This option is needed for the systems that have more than 8 CPUs
479 config X86_EXTENDED_PLATFORM
480 bool "Support for extended (non-PC) x86 platforms"
483 If you disable this option then the kernel will only support
484 standard PC platforms. (which covers the vast majority of
487 If you enable this option then you'll be able to select support
488 for the following (non-PC) 32 bit x86 platforms:
489 Goldfish (Android emulator)
492 SGI 320/540 (Visual Workstation)
493 STA2X11-based (e.g. Northville)
494 Moorestown MID devices
496 If you have one of these systems, or if you want to build a
497 generic distribution kernel, say Y here - otherwise say N.
501 config X86_EXTENDED_PLATFORM
502 bool "Support for extended (non-PC) x86 platforms"
505 If you disable this option then the kernel will only support
506 standard PC platforms. (which covers the vast majority of
509 If you enable this option then you'll be able to select support
510 for the following (non-PC) 64 bit x86 platforms:
515 If you have one of these systems, or if you want to build a
516 generic distribution kernel, say Y here - otherwise say N.
518 # This is an alphabetically sorted list of 64 bit extended platforms
519 # Please maintain the alphabetic order if and when there are additions
521 bool "Numascale NumaChip"
523 depends on X86_EXTENDED_PLATFORM
526 depends on X86_X2APIC
527 depends on PCI_MMCONFIG
529 Adds support for Numascale NumaChip large-SMP systems. Needed to
530 enable more than ~168 cores.
531 If you don't have one of these, you should say N here.
535 select HYPERVISOR_GUEST
537 depends on X86_64 && PCI
538 depends on X86_EXTENDED_PLATFORM
541 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
542 supposed to run on these EM64T-based machines. Only choose this option
543 if you have one of these machines.
546 bool "SGI Ultraviolet"
548 depends on X86_EXTENDED_PLATFORM
551 depends on X86_X2APIC
554 This option is needed in order to support SGI Ultraviolet systems.
555 If you don't have one of these, you should say N here.
557 # Following is an alphabetically sorted list of 32 bit extended platforms
558 # Please maintain the alphabetic order if and when there are additions
561 bool "Goldfish (Virtual Platform)"
562 depends on X86_EXTENDED_PLATFORM
564 Enable support for the Goldfish virtual platform used primarily
565 for Android development. Unless you are building for the Android
566 Goldfish emulator say N here.
569 bool "CE4100 TV platform"
571 depends on PCI_GODIRECT
572 depends on X86_IO_APIC
574 depends on X86_EXTENDED_PLATFORM
575 select X86_REBOOTFIXUPS
577 select OF_EARLY_FLATTREE
579 Select for the Intel CE media processor (CE4100) SOC.
580 This option compiles in support for the CE4100 SOC for settop
581 boxes and media devices.
584 bool "Intel MID platform support"
585 depends on X86_EXTENDED_PLATFORM
586 depends on X86_PLATFORM_DEVICES
588 depends on X86_64 || (PCI_GOANY && X86_32)
589 depends on X86_IO_APIC
595 select MFD_INTEL_MSIC
597 Select to build a kernel capable of supporting Intel MID (Mobile
598 Internet Device) platform systems which do not have the PCI legacy
599 interfaces. If you are building for a PC class system say N here.
601 Intel MID platforms are based on an Intel processor and chipset which
602 consume less power than most of the x86 derivatives.
604 config X86_INTEL_QUARK
605 bool "Intel Quark platform support"
607 depends on X86_EXTENDED_PLATFORM
608 depends on X86_PLATFORM_DEVICES
612 depends on X86_IO_APIC
617 Select to include support for Quark X1000 SoC.
618 Say Y here if you have a Quark based system such as the Arduino
619 compatible Intel Galileo.
621 config X86_INTEL_LPSS
622 bool "Intel Low Power Subsystem Support"
623 depends on X86 && ACPI && PCI
628 Select to build support for Intel Low Power Subsystem such as
629 found on Intel Lynxpoint PCH. Selecting this option enables
630 things like clock tree (common clock framework) and pincontrol
631 which are needed by the LPSS peripheral drivers.
633 config X86_AMD_PLATFORM_DEVICE
634 bool "AMD ACPI2Platform devices support"
639 Select to interpret AMD specific ACPI device to platform device
640 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
641 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
642 implemented under PINCTRL subsystem.
645 tristate "Intel SoC IOSF Sideband support for SoC platforms"
648 This option enables sideband register access support for Intel SoC
649 platforms. On these platforms the IOSF sideband is used in lieu of
650 MSR's for some register accesses, mostly but not limited to thermal
651 and power. Drivers may query the availability of this device to
652 determine if they need the sideband in order to work on these
653 platforms. The sideband is available on the following SoC products.
654 This list is not meant to be exclusive.
659 You should say Y if you are running a kernel on one of these SoC's.
661 config IOSF_MBI_DEBUG
662 bool "Enable IOSF sideband access through debugfs"
663 depends on IOSF_MBI && DEBUG_FS
665 Select this option to expose the IOSF sideband access registers (MCR,
666 MDR, MCRX) through debugfs to write and read register information from
667 different units on the SoC. This is most useful for obtaining device
668 state information for debug and analysis. As this is a general access
669 mechanism, users of this option would have specific knowledge of the
670 device they want to access.
672 If you don't require the option or are in doubt, say N.
675 bool "RDC R-321x SoC"
677 depends on X86_EXTENDED_PLATFORM
679 select X86_REBOOTFIXUPS
681 This option is needed for RDC R-321x system-on-chip, also known
683 If you don't have one of these chips, you should say N here.
685 config X86_32_NON_STANDARD
686 bool "Support non-standard 32-bit SMP architectures"
687 depends on X86_32 && SMP
688 depends on X86_EXTENDED_PLATFORM
690 This option compiles in the bigsmp and STA2X11 default
691 subarchitectures. It is intended for a generic binary
692 kernel. If you select them all, kernel will probe it one by
693 one and will fallback to default.
695 # Alphabetically sorted list of Non standard 32 bit platforms
697 config X86_SUPPORTS_MEMORY_FAILURE
699 # MCE code calls memory_failure():
701 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
702 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
703 depends on X86_64 || !SPARSEMEM
704 select ARCH_SUPPORTS_MEMORY_FAILURE
707 bool "STA2X11 Companion Chip Support"
708 depends on X86_32_NON_STANDARD && PCI
709 select ARCH_HAS_PHYS_TO_DMA
714 This adds support for boards based on the STA2X11 IO-Hub,
715 a.k.a. "ConneXt". The chip is used in place of the standard
716 PC chipset, so all "standard" peripherals are missing. If this
717 option is selected the kernel will still be able to boot on
718 standard PC machines.
721 tristate "Eurobraille/Iris poweroff module"
724 The Iris machines from EuroBraille do not have APM or ACPI support
725 to shut themselves down properly. A special I/O sequence is
726 needed to do so, which is what this module does at
729 This is only for Iris machines from EuroBraille.
733 config SCHED_OMIT_FRAME_POINTER
735 prompt "Single-depth WCHAN output"
738 Calculate simpler /proc/<PID>/wchan values. If this option
739 is disabled then wchan values will recurse back to the
740 caller function. This provides more accurate wchan values,
741 at the expense of slightly more scheduling overhead.
743 If in doubt, say "Y".
745 menuconfig HYPERVISOR_GUEST
746 bool "Linux guest support"
748 Say Y here to enable options for running Linux under various hyper-
749 visors. This option enables basic hypervisor detection and platform
752 If you say N, all options in this submenu will be skipped and
753 disabled, and Linux guest support won't be built in.
758 bool "Enable paravirtualization code"
760 This changes the kernel so it can modify itself when it is run
761 under a hypervisor, potentially improving performance significantly
762 over full virtualization. However, when run without a hypervisor
763 the kernel is theoretically slower and slightly larger.
768 config PARAVIRT_DEBUG
769 bool "paravirt-ops debugging"
770 depends on PARAVIRT && DEBUG_KERNEL
772 Enable to debug paravirt_ops internals. Specifically, BUG if
773 a paravirt_op is missing when it is called.
775 config PARAVIRT_SPINLOCKS
776 bool "Paravirtualization layer for spinlocks"
777 depends on PARAVIRT && SMP
779 Paravirtualized spinlocks allow a pvops backend to replace the
780 spinlock implementation with something virtualization-friendly
781 (for example, block the virtual CPU rather than spinning).
783 It has a minimal impact on native kernels and gives a nice performance
784 benefit on paravirtualized KVM / Xen kernels.
786 If you are unsure how to answer this question, answer Y.
788 config X86_HV_CALLBACK_VECTOR
791 source "arch/x86/xen/Kconfig"
794 bool "KVM Guest support (including kvmclock)"
796 select PARAVIRT_CLOCK
799 This option enables various optimizations for running under the KVM
800 hypervisor. It includes a paravirtualized clock, so that instead
801 of relying on a PIT (or probably other) emulation by the
802 underlying device model, the host provides the guest with
803 timing infrastructure such as time of day, and system time
806 bool "Support for running PVH guests"
808 This option enables the PVH entry point for guest virtual machines
809 as specified in the x86/HVM direct boot ABI.
812 bool "Enable debug information for KVM Guests in debugfs"
813 depends on KVM_GUEST && DEBUG_FS
815 This option enables collection of various statistics for KVM guest.
816 Statistics are displayed in debugfs filesystem. Enabling this option
817 may incur significant overhead.
819 config PARAVIRT_TIME_ACCOUNTING
820 bool "Paravirtual steal time accounting"
823 Select this option to enable fine granularity task steal time
824 accounting. Time spent executing other tasks in parallel with
825 the current vCPU is discounted from the vCPU power. To account for
826 that, there can be a small performance impact.
828 If in doubt, say N here.
830 config PARAVIRT_CLOCK
833 config JAILHOUSE_GUEST
834 bool "Jailhouse non-root cell support"
835 depends on X86_64 && PCI
838 This option allows to run Linux as guest in a Jailhouse non-root
839 cell. You can leave this option disabled if you only want to start
840 Jailhouse and run Linux afterwards in the root cell.
843 bool "ACRN Guest support"
845 select X86_HV_CALLBACK_VECTOR
847 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
848 a flexible, lightweight reference open-source hypervisor, built with
849 real-time and safety-criticality in mind. It is built for embedded
850 IOT with small footprint and real-time features. More details can be
851 found in https://projectacrn.org/.
853 endif #HYPERVISOR_GUEST
855 source "arch/x86/Kconfig.cpu"
859 prompt "HPET Timer Support" if X86_32
861 Use the IA-PC HPET (High Precision Event Timer) to manage
862 time in preference to the PIT and RTC, if a HPET is
864 HPET is the next generation timer replacing legacy 8254s.
865 The HPET provides a stable time base on SMP
866 systems, unlike the TSC, but it is more expensive to access,
867 as it is off-chip. The interface used is documented
868 in the HPET spec, revision 1.
870 You can safely choose Y here. However, HPET will only be
871 activated if the platform and the BIOS support this feature.
872 Otherwise the 8254 will be used for timing services.
874 Choose N to continue using the legacy 8254 timer.
876 config HPET_EMULATE_RTC
878 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
881 def_bool y if X86_INTEL_MID
882 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
884 depends on X86_INTEL_MID && SFI
886 APB timer is the replacement for 8254, HPET on X86 MID platforms.
887 The APBT provides a stable time base on SMP
888 systems, unlike the TSC, but it is more expensive to access,
889 as it is off-chip. APB timers are always running regardless of CPU
890 C states, they are used as per CPU clockevent device when possible.
892 # Mark as expert because too many people got it wrong.
893 # The code disables itself when not needed.
896 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
897 bool "Enable DMI scanning" if EXPERT
899 Enabled scanning of DMI to identify machine quirks. Say Y
900 here unless you have verified that your setup is not
901 affected by entries in the DMI blacklist. Required by PNP
905 bool "Old AMD GART IOMMU support"
908 depends on X86_64 && PCI && AMD_NB
910 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
911 GART based hardware IOMMUs.
913 The GART supports full DMA access for devices with 32-bit access
914 limitations, on systems with more than 3 GB. This is usually needed
915 for USB, sound, many IDE/SATA chipsets and some other devices.
917 Newer systems typically have a modern AMD IOMMU, supported via
918 the CONFIG_AMD_IOMMU=y config option.
920 In normal configurations this driver is only active when needed:
921 there's more than 3 GB of memory and the system contains a
922 32-bit limited device.
927 bool "IBM Calgary IOMMU support"
930 depends on X86_64 && PCI
932 Support for hardware IOMMUs in IBM's xSeries x366 and x460
933 systems. Needed to run systems with more than 3GB of memory
934 properly with 32-bit PCI devices that do not support DAC
935 (Double Address Cycle). Calgary also supports bus level
936 isolation, where all DMAs pass through the IOMMU. This
937 prevents them from going anywhere except their intended
938 destination. This catches hard-to-find kernel bugs and
939 mis-behaving drivers and devices that do not use the DMA-API
940 properly to set up their DMA buffers. The IOMMU can be
941 turned off at boot time with the iommu=off parameter.
942 Normally the kernel will make the right choice by itself.
945 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
947 prompt "Should Calgary be enabled by default?"
948 depends on CALGARY_IOMMU
950 Should Calgary be enabled by default? if you choose 'y', Calgary
951 will be used (if it exists). If you choose 'n', Calgary will not be
952 used even if it exists. If you choose 'n' and would like to use
953 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
957 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
958 depends on X86_64 && SMP && DEBUG_KERNEL
959 select CPUMASK_OFFSTACK
961 Enable maximum number of CPUS and NUMA Nodes for this architecture.
965 # The maximum number of CPUs supported:
967 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
968 # and which can be configured interactively in the
969 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
971 # The ranges are different on 32-bit and 64-bit kernels, depending on
972 # hardware capabilities and scalability features of the kernel.
974 # ( If MAXSMP is enabled we just use the highest possible value and disable
975 # interactive configuration. )
978 config NR_CPUS_RANGE_BEGIN
980 default NR_CPUS_RANGE_END if MAXSMP
984 config NR_CPUS_RANGE_END
987 default 64 if SMP && X86_BIGSMP
988 default 8 if SMP && !X86_BIGSMP
991 config NR_CPUS_RANGE_END
994 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
995 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
998 config NR_CPUS_DEFAULT
1001 default 32 if X86_BIGSMP
1005 config NR_CPUS_DEFAULT
1008 default 8192 if MAXSMP
1013 int "Maximum number of CPUs" if SMP && !MAXSMP
1014 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1015 default NR_CPUS_DEFAULT
1017 This allows you to specify the maximum number of CPUs which this
1018 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1019 supported value is 8192, otherwise the maximum value is 512. The
1020 minimum value which makes sense is 2.
1022 This is purely to save memory: each supported CPU adds about 8KB
1023 to the kernel image.
1030 prompt "Multi-core scheduler support"
1033 Multi-core scheduler support improves the CPU scheduler's decision
1034 making when dealing with multi-core CPU chips at a cost of slightly
1035 increased overhead in some places. If unsure say N here.
1037 config SCHED_MC_PRIO
1038 bool "CPU core priorities scheduler support"
1039 depends on SCHED_MC && CPU_SUP_INTEL
1040 select X86_INTEL_PSTATE
1044 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1045 core ordering determined at manufacturing time, which allows
1046 certain cores to reach higher turbo frequencies (when running
1047 single threaded workloads) than others.
1049 Enabling this kernel feature teaches the scheduler about
1050 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1051 scheduler's CPU selection logic accordingly, so that higher
1052 overall system performance can be achieved.
1054 This feature will have no effect on CPUs without this feature.
1056 If unsure say Y here.
1060 depends on !SMP && X86_LOCAL_APIC
1063 bool "Local APIC support on uniprocessors" if !PCI_MSI
1065 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1067 A local APIC (Advanced Programmable Interrupt Controller) is an
1068 integrated interrupt controller in the CPU. If you have a single-CPU
1069 system which has a processor with a local APIC, you can say Y here to
1070 enable and use it. If you say Y here even though your machine doesn't
1071 have a local APIC, then the kernel will still run with no slowdown at
1072 all. The local APIC supports CPU-generated self-interrupts (timer,
1073 performance counters), and the NMI watchdog which detects hard
1076 config X86_UP_IOAPIC
1077 bool "IO-APIC support on uniprocessors"
1078 depends on X86_UP_APIC
1080 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1081 SMP-capable replacement for PC-style interrupt controllers. Most
1082 SMP systems and many recent uniprocessor systems have one.
1084 If you have a single-CPU system with an IO-APIC, you can say Y here
1085 to use it. If you say Y here even though your machine doesn't have
1086 an IO-APIC, then the kernel will still run with no slowdown at all.
1088 config X86_LOCAL_APIC
1090 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1091 select IRQ_DOMAIN_HIERARCHY
1092 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1096 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1098 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1099 bool "Reroute for broken boot IRQs"
1100 depends on X86_IO_APIC
1102 This option enables a workaround that fixes a source of
1103 spurious interrupts. This is recommended when threaded
1104 interrupt handling is used on systems where the generation of
1105 superfluous "boot interrupts" cannot be disabled.
1107 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1108 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1109 kernel does during interrupt handling). On chipsets where this
1110 boot IRQ generation cannot be disabled, this workaround keeps
1111 the original IRQ line masked so that only the equivalent "boot
1112 IRQ" is delivered to the CPUs. The workaround also tells the
1113 kernel to set up the IRQ handler on the boot IRQ line. In this
1114 way only one interrupt is delivered to the kernel. Otherwise
1115 the spurious second interrupt may cause the kernel to bring
1116 down (vital) interrupt lines.
1118 Only affects "broken" chipsets. Interrupt sharing may be
1119 increased on these systems.
1122 bool "Machine Check / overheating reporting"
1123 select GENERIC_ALLOCATOR
1126 Machine Check support allows the processor to notify the
1127 kernel if it detects a problem (e.g. overheating, data corruption).
1128 The action the kernel takes depends on the severity of the problem,
1129 ranging from warning messages to halting the machine.
1131 config X86_MCELOG_LEGACY
1132 bool "Support for deprecated /dev/mcelog character device"
1135 Enable support for /dev/mcelog which is needed by the old mcelog
1136 userspace logging daemon. Consider switching to the new generation
1139 config X86_MCE_INTEL
1141 prompt "Intel MCE features"
1142 depends on X86_MCE && X86_LOCAL_APIC
1144 Additional support for intel specific MCE features such as
1145 the thermal monitor.
1149 prompt "AMD MCE features"
1150 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1152 Additional support for AMD specific MCE features such as
1153 the DRAM Error Threshold.
1155 config X86_ANCIENT_MCE
1156 bool "Support for old Pentium 5 / WinChip machine checks"
1157 depends on X86_32 && X86_MCE
1159 Include support for machine check handling on old Pentium 5 or WinChip
1160 systems. These typically need to be enabled explicitly on the command
1163 config X86_MCE_THRESHOLD
1164 depends on X86_MCE_AMD || X86_MCE_INTEL
1167 config X86_MCE_INJECT
1168 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1169 tristate "Machine check injector support"
1171 Provide support for injecting machine checks for testing purposes.
1172 If you don't know what a machine check is and you don't do kernel
1173 QA it is safe to say n.
1175 config X86_THERMAL_VECTOR
1177 depends on X86_MCE_INTEL
1179 source "arch/x86/events/Kconfig"
1181 config X86_LEGACY_VM86
1182 bool "Legacy VM86 support"
1185 This option allows user programs to put the CPU into V8086
1186 mode, which is an 80286-era approximation of 16-bit real mode.
1188 Some very old versions of X and/or vbetool require this option
1189 for user mode setting. Similarly, DOSEMU will use it if
1190 available to accelerate real mode DOS programs. However, any
1191 recent version of DOSEMU, X, or vbetool should be fully
1192 functional even without kernel VM86 support, as they will all
1193 fall back to software emulation. Nevertheless, if you are using
1194 a 16-bit DOS program where 16-bit performance matters, vm86
1195 mode might be faster than emulation and you might want to
1198 Note that any app that works on a 64-bit kernel is unlikely to
1199 need this option, as 64-bit kernels don't, and can't, support
1200 V8086 mode. This option is also unrelated to 16-bit protected
1201 mode and is not needed to run most 16-bit programs under Wine.
1203 Enabling this option increases the complexity of the kernel
1204 and slows down exception handling a tiny bit.
1206 If unsure, say N here.
1210 default X86_LEGACY_VM86
1213 bool "Enable support for 16-bit segments" if EXPERT
1215 depends on MODIFY_LDT_SYSCALL
1217 This option is required by programs like Wine to run 16-bit
1218 protected mode legacy code on x86 processors. Disabling
1219 this option saves about 300 bytes on i386, or around 6K text
1220 plus 16K runtime memory on x86-64,
1224 depends on X86_16BIT && X86_32
1228 depends on X86_16BIT && X86_64
1230 config X86_VSYSCALL_EMULATION
1231 bool "Enable vsyscall emulation" if EXPERT
1235 This enables emulation of the legacy vsyscall page. Disabling
1236 it is roughly equivalent to booting with vsyscall=none, except
1237 that it will also disable the helpful warning if a program
1238 tries to use a vsyscall. With this option set to N, offending
1239 programs will just segfault, citing addresses of the form
1242 This option is required by many programs built before 2013, and
1243 care should be used even with newer programs if set to N.
1245 Disabling this option saves about 7K of kernel size and
1246 possibly 4K of additional runtime pagetable memory.
1249 tristate "Toshiba Laptop support"
1252 This adds a driver to safely access the System Management Mode of
1253 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1254 not work on models with a Phoenix BIOS. The System Management Mode
1255 is used to set the BIOS and power saving options on Toshiba portables.
1257 For information on utilities to make use of this driver see the
1258 Toshiba Linux utilities web site at:
1259 <http://www.buzzard.org.uk/toshiba/>.
1261 Say Y if you intend to run this kernel on a Toshiba portable.
1265 tristate "Dell i8k legacy laptop support"
1267 select SENSORS_DELL_SMM
1269 This option enables legacy /proc/i8k userspace interface in hwmon
1270 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1271 temperature and allows controlling fan speeds of Dell laptops via
1272 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1273 it reports also power and hotkey status. For fan speed control is
1274 needed userspace package i8kutils.
1276 Say Y if you intend to run this kernel on old Dell laptops or want to
1277 use userspace package i8kutils.
1280 config X86_REBOOTFIXUPS
1281 bool "Enable X86 board specific fixups for reboot"
1284 This enables chipset and/or board specific fixups to be done
1285 in order to get reboot to work correctly. This is only needed on
1286 some combinations of hardware and BIOS. The symptom, for which
1287 this config is intended, is when reboot ends with a stalled/hung
1290 Currently, the only fixup is for the Geode machines using
1291 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1293 Say Y if you want to enable the fixup. Currently, it's safe to
1294 enable this option even if you don't need it.
1298 bool "CPU microcode loading support"
1300 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1303 If you say Y here, you will be able to update the microcode on
1304 Intel and AMD processors. The Intel support is for the IA32 family,
1305 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1306 AMD support is for families 0x10 and later. You will obviously need
1307 the actual microcode binary data itself which is not shipped with
1310 The preferred method to load microcode from a detached initrd is described
1311 in Documentation/x86/microcode.rst. For that you need to enable
1312 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1313 initrd for microcode blobs.
1315 In addition, you can build the microcode into the kernel. For that you
1316 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1319 config MICROCODE_INTEL
1320 bool "Intel microcode loading support"
1321 depends on MICROCODE
1325 This options enables microcode patch loading support for Intel
1328 For the current Intel microcode data package go to
1329 <https://downloadcenter.intel.com> and search for
1330 'Linux Processor Microcode Data File'.
1332 config MICROCODE_AMD
1333 bool "AMD microcode loading support"
1334 depends on MICROCODE
1337 If you select this option, microcode patch loading support for AMD
1338 processors will be enabled.
1340 config MICROCODE_OLD_INTERFACE
1341 bool "Ancient loading interface (DEPRECATED)"
1343 depends on MICROCODE
1345 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1346 which was used by userspace tools like iucode_tool and microcode.ctl.
1347 It is inadequate because it runs too late to be able to properly
1348 load microcode on a machine and it needs special tools. Instead, you
1349 should've switched to the early loading method with the initrd or
1350 builtin microcode by now: Documentation/x86/microcode.rst
1353 tristate "/dev/cpu/*/msr - Model-specific register support"
1355 This device gives privileged processes access to the x86
1356 Model-Specific Registers (MSRs). It is a character device with
1357 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1358 MSR accesses are directed to a specific CPU on multi-processor
1362 tristate "/dev/cpu/*/cpuid - CPU information support"
1364 This device gives processes access to the x86 CPUID instruction to
1365 be executed on a specific processor. It is a character device
1366 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1370 prompt "High Memory Support"
1377 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1378 However, the address space of 32-bit x86 processors is only 4
1379 Gigabytes large. That means that, if you have a large amount of
1380 physical memory, not all of it can be "permanently mapped" by the
1381 kernel. The physical memory that's not permanently mapped is called
1384 If you are compiling a kernel which will never run on a machine with
1385 more than 1 Gigabyte total physical RAM, answer "off" here (default
1386 choice and suitable for most users). This will result in a "3GB/1GB"
1387 split: 3GB are mapped so that each process sees a 3GB virtual memory
1388 space and the remaining part of the 4GB virtual memory space is used
1389 by the kernel to permanently map as much physical memory as
1392 If the machine has between 1 and 4 Gigabytes physical RAM, then
1395 If more than 4 Gigabytes is used then answer "64GB" here. This
1396 selection turns Intel PAE (Physical Address Extension) mode on.
1397 PAE implements 3-level paging on IA32 processors. PAE is fully
1398 supported by Linux, PAE mode is implemented on all recent Intel
1399 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1400 then the kernel will not boot on CPUs that don't support PAE!
1402 The actual amount of total physical memory will either be
1403 auto detected or can be forced by using a kernel command line option
1404 such as "mem=256M". (Try "man bootparam" or see the documentation of
1405 your boot loader (lilo or loadlin) about how to pass options to the
1406 kernel at boot time.)
1408 If unsure, say "off".
1413 Select this if you have a 32-bit processor and between 1 and 4
1414 gigabytes of physical RAM.
1418 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1421 Select this if you have a 32-bit processor and more than 4
1422 gigabytes of physical RAM.
1427 prompt "Memory split" if EXPERT
1431 Select the desired split between kernel and user memory.
1433 If the address range available to the kernel is less than the
1434 physical memory installed, the remaining memory will be available
1435 as "high memory". Accessing high memory is a little more costly
1436 than low memory, as it needs to be mapped into the kernel first.
1437 Note that increasing the kernel address space limits the range
1438 available to user programs, making the address space there
1439 tighter. Selecting anything other than the default 3G/1G split
1440 will also likely make your kernel incompatible with binary-only
1443 If you are not absolutely sure what you are doing, leave this
1447 bool "3G/1G user/kernel split"
1448 config VMSPLIT_3G_OPT
1450 bool "3G/1G user/kernel split (for full 1G low memory)"
1452 bool "2G/2G user/kernel split"
1453 config VMSPLIT_2G_OPT
1455 bool "2G/2G user/kernel split (for full 2G low memory)"
1457 bool "1G/3G user/kernel split"
1462 default 0xB0000000 if VMSPLIT_3G_OPT
1463 default 0x80000000 if VMSPLIT_2G
1464 default 0x78000000 if VMSPLIT_2G_OPT
1465 default 0x40000000 if VMSPLIT_1G
1471 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1474 bool "PAE (Physical Address Extension) Support"
1475 depends on X86_32 && !HIGHMEM4G
1476 select PHYS_ADDR_T_64BIT
1479 PAE is required for NX support, and furthermore enables
1480 larger swapspace support for non-overcommit purposes. It
1481 has the cost of more pagetable lookup overhead, and also
1482 consumes more pagetable space per process.
1485 bool "Enable 5-level page tables support"
1486 select DYNAMIC_MEMORY_LAYOUT
1487 select SPARSEMEM_VMEMMAP
1490 5-level paging enables access to larger address space:
1491 upto 128 PiB of virtual address space and 4 PiB of
1492 physical address space.
1494 It will be supported by future Intel CPUs.
1496 A kernel with the option enabled can be booted on machines that
1497 support 4- or 5-level paging.
1499 See Documentation/x86/x86_64/5level-paging.rst for more
1504 config X86_DIRECT_GBPAGES
1506 depends on X86_64 && !DEBUG_PAGEALLOC
1508 Certain kernel features effectively disable kernel
1509 linear 1 GB mappings (even if the CPU otherwise
1510 supports them), so don't confuse the user by printing
1511 that we have them enabled.
1513 config X86_CPA_STATISTICS
1514 bool "Enable statistic for Change Page Attribute"
1517 Expose statistics about the Change Page Attribute mechanims, which
1518 helps to determine the effectiveness of preserving large and huge
1519 page mappings when mapping protections are changed.
1521 config ARCH_HAS_MEM_ENCRYPT
1524 config AMD_MEM_ENCRYPT
1525 bool "AMD Secure Memory Encryption (SME) support"
1526 depends on X86_64 && CPU_SUP_AMD
1527 select DYNAMIC_PHYSICAL_MASK
1528 select ARCH_USE_MEMREMAP_PROT
1530 Say yes to enable support for the encryption of system memory.
1531 This requires an AMD processor that supports Secure Memory
1534 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1535 bool "Activate AMD Secure Memory Encryption (SME) by default"
1537 depends on AMD_MEM_ENCRYPT
1539 Say yes to have system memory encrypted by default if running on
1540 an AMD processor that supports Secure Memory Encryption (SME).
1542 If set to Y, then the encryption of system memory can be
1543 deactivated with the mem_encrypt=off command line option.
1545 If set to N, then the encryption of system memory can be
1546 activated with the mem_encrypt=on command line option.
1548 # Common NUMA Features
1550 bool "Numa Memory Allocation and Scheduler Support"
1552 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1553 default y if X86_BIGSMP
1555 Enable NUMA (Non Uniform Memory Access) support.
1557 The kernel will try to allocate memory used by a CPU on the
1558 local memory controller of the CPU and add some more
1559 NUMA awareness to the kernel.
1561 For 64-bit this is recommended if the system is Intel Core i7
1562 (or later), AMD Opteron, or EM64T NUMA.
1564 For 32-bit this is only needed if you boot a 32-bit
1565 kernel on a 64-bit NUMA platform.
1567 Otherwise, you should say N.
1571 prompt "Old style AMD Opteron NUMA detection"
1572 depends on X86_64 && NUMA && PCI
1574 Enable AMD NUMA node topology detection. You should say Y here if
1575 you have a multi processor AMD system. This uses an old method to
1576 read the NUMA configuration directly from the builtin Northbridge
1577 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1578 which also takes priority if both are compiled in.
1580 config X86_64_ACPI_NUMA
1582 prompt "ACPI NUMA detection"
1583 depends on X86_64 && NUMA && ACPI && PCI
1586 Enable ACPI SRAT based node topology detection.
1588 # Some NUMA nodes have memory ranges that span
1589 # other nodes. Even though a pfn is valid and
1590 # between a node's start and end pfns, it may not
1591 # reside on that node. See memmap_init_zone()
1593 config NODES_SPAN_OTHER_NODES
1595 depends on X86_64_ACPI_NUMA
1598 bool "NUMA emulation"
1601 Enable NUMA emulation. A flat machine will be split
1602 into virtual nodes when booted with "numa=fake=N", where N is the
1603 number of nodes. This is only useful for debugging.
1606 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1608 default "10" if MAXSMP
1609 default "6" if X86_64
1611 depends on NEED_MULTIPLE_NODES
1613 Specify the maximum number of NUMA Nodes available on the target
1614 system. Increases memory reserved to accommodate various tables.
1616 config ARCH_HAVE_MEMORY_PRESENT
1618 depends on X86_32 && DISCONTIGMEM
1620 config ARCH_FLATMEM_ENABLE
1622 depends on X86_32 && !NUMA
1624 config ARCH_DISCONTIGMEM_ENABLE
1626 depends on NUMA && X86_32
1629 config ARCH_SPARSEMEM_ENABLE
1631 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1632 select SPARSEMEM_STATIC if X86_32
1633 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1635 config ARCH_SPARSEMEM_DEFAULT
1636 def_bool X86_64 || (NUMA && X86_32)
1638 config ARCH_SELECT_MEMORY_MODEL
1640 depends on ARCH_SPARSEMEM_ENABLE
1642 config ARCH_MEMORY_PROBE
1643 bool "Enable sysfs memory/probe interface"
1644 depends on X86_64 && MEMORY_HOTPLUG
1646 This option enables a sysfs memory/probe interface for testing.
1647 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1648 If you are unsure how to answer this question, answer N.
1650 config ARCH_PROC_KCORE_TEXT
1652 depends on X86_64 && PROC_KCORE
1654 config ILLEGAL_POINTER_VALUE
1657 default 0xdead000000000000 if X86_64
1659 config X86_PMEM_LEGACY_DEVICE
1662 config X86_PMEM_LEGACY
1663 tristate "Support non-standard NVDIMMs and ADR protected memory"
1664 depends on PHYS_ADDR_T_64BIT
1666 select X86_PMEM_LEGACY_DEVICE
1669 Treat memory marked using the non-standard e820 type of 12 as used
1670 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1671 The kernel will offer these regions to the 'pmem' driver so
1672 they can be used for persistent storage.
1677 bool "Allocate 3rd-level pagetables from highmem"
1680 The VM uses one page table entry for each page of physical memory.
1681 For systems with a lot of RAM, this can be wasteful of precious
1682 low memory. Setting this option will put user-space page table
1683 entries in high memory.
1685 config X86_CHECK_BIOS_CORRUPTION
1686 bool "Check for low memory corruption"
1688 Periodically check for memory corruption in low memory, which
1689 is suspected to be caused by BIOS. Even when enabled in the
1690 configuration, it is disabled at runtime. Enable it by
1691 setting "memory_corruption_check=1" on the kernel command
1692 line. By default it scans the low 64k of memory every 60
1693 seconds; see the memory_corruption_check_size and
1694 memory_corruption_check_period parameters in
1695 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1697 When enabled with the default parameters, this option has
1698 almost no overhead, as it reserves a relatively small amount
1699 of memory and scans it infrequently. It both detects corruption
1700 and prevents it from affecting the running system.
1702 It is, however, intended as a diagnostic tool; if repeatable
1703 BIOS-originated corruption always affects the same memory,
1704 you can use memmap= to prevent the kernel from using that
1707 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1708 bool "Set the default setting of memory_corruption_check"
1709 depends on X86_CHECK_BIOS_CORRUPTION
1712 Set whether the default state of memory_corruption_check is
1715 config X86_RESERVE_LOW
1716 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1720 Specify the amount of low memory to reserve for the BIOS.
1722 The first page contains BIOS data structures that the kernel
1723 must not use, so that page must always be reserved.
1725 By default we reserve the first 64K of physical RAM, as a
1726 number of BIOSes are known to corrupt that memory range
1727 during events such as suspend/resume or monitor cable
1728 insertion, so it must not be used by the kernel.
1730 You can set this to 4 if you are absolutely sure that you
1731 trust the BIOS to get all its memory reservations and usages
1732 right. If you know your BIOS have problems beyond the
1733 default 64K area, you can set this to 640 to avoid using the
1734 entire low memory range.
1736 If you have doubts about the BIOS (e.g. suspend/resume does
1737 not work or there's kernel crashes after certain hardware
1738 hotplug events) then you might want to enable
1739 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1740 typical corruption patterns.
1742 Leave this to the default value of 64 if you are unsure.
1744 config MATH_EMULATION
1746 depends on MODIFY_LDT_SYSCALL
1747 prompt "Math emulation" if X86_32
1749 Linux can emulate a math coprocessor (used for floating point
1750 operations) if you don't have one. 486DX and Pentium processors have
1751 a math coprocessor built in, 486SX and 386 do not, unless you added
1752 a 487DX or 387, respectively. (The messages during boot time can
1753 give you some hints here ["man dmesg"].) Everyone needs either a
1754 coprocessor or this emulation.
1756 If you don't have a math coprocessor, you need to say Y here; if you
1757 say Y here even though you have a coprocessor, the coprocessor will
1758 be used nevertheless. (This behavior can be changed with the kernel
1759 command line option "no387", which comes handy if your coprocessor
1760 is broken. Try "man bootparam" or see the documentation of your boot
1761 loader (lilo or loadlin) about how to pass options to the kernel at
1762 boot time.) This means that it is a good idea to say Y here if you
1763 intend to use this kernel on different machines.
1765 More information about the internals of the Linux math coprocessor
1766 emulation can be found in <file:arch/x86/math-emu/README>.
1768 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1769 kernel, it won't hurt.
1773 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1775 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1776 the Memory Type Range Registers (MTRRs) may be used to control
1777 processor access to memory ranges. This is most useful if you have
1778 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1779 allows bus write transfers to be combined into a larger transfer
1780 before bursting over the PCI/AGP bus. This can increase performance
1781 of image write operations 2.5 times or more. Saying Y here creates a
1782 /proc/mtrr file which may be used to manipulate your processor's
1783 MTRRs. Typically the X server should use this.
1785 This code has a reasonably generic interface so that similar
1786 control registers on other processors can be easily supported
1789 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1790 Registers (ARRs) which provide a similar functionality to MTRRs. For
1791 these, the ARRs are used to emulate the MTRRs.
1792 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1793 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1794 write-combining. All of these processors are supported by this code
1795 and it makes sense to say Y here if you have one of them.
1797 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1798 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1799 can lead to all sorts of problems, so it's good to say Y here.
1801 You can safely say Y even if your machine doesn't have MTRRs, you'll
1802 just add about 9 KB to your kernel.
1804 See <file:Documentation/x86/mtrr.rst> for more information.
1806 config MTRR_SANITIZER
1808 prompt "MTRR cleanup support"
1811 Convert MTRR layout from continuous to discrete, so X drivers can
1812 add writeback entries.
1814 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1815 The largest mtrr entry size for a continuous block can be set with
1820 config MTRR_SANITIZER_ENABLE_DEFAULT
1821 int "MTRR cleanup enable value (0-1)"
1824 depends on MTRR_SANITIZER
1826 Enable mtrr cleanup default value
1828 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1829 int "MTRR cleanup spare reg num (0-7)"
1832 depends on MTRR_SANITIZER
1834 mtrr cleanup spare entries default, it can be changed via
1835 mtrr_spare_reg_nr=N on the kernel command line.
1839 prompt "x86 PAT support" if EXPERT
1842 Use PAT attributes to setup page level cache control.
1844 PATs are the modern equivalents of MTRRs and are much more
1845 flexible than MTRRs.
1847 Say N here if you see bootup problems (boot crash, boot hang,
1848 spontaneous reboots) or a non-working video driver.
1852 config ARCH_USES_PG_UNCACHED
1858 prompt "x86 architectural random number generator" if EXPERT
1860 Enable the x86 architectural RDRAND instruction
1861 (Intel Bull Mountain technology) to generate random numbers.
1862 If supported, this is a high bandwidth, cryptographically
1863 secure hardware random number generator.
1867 prompt "Supervisor Mode Access Prevention" if EXPERT
1869 Supervisor Mode Access Prevention (SMAP) is a security
1870 feature in newer Intel processors. There is a small
1871 performance cost if this enabled and turned on; there is
1872 also a small increase in the kernel size if this is enabled.
1876 config X86_INTEL_UMIP
1878 depends on CPU_SUP_INTEL
1879 prompt "Intel User Mode Instruction Prevention" if EXPERT
1881 The User Mode Instruction Prevention (UMIP) is a security
1882 feature in newer Intel processors. If enabled, a general
1883 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1884 or STR instructions are executed in user mode. These instructions
1885 unnecessarily expose information about the hardware state.
1887 The vast majority of applications do not use these instructions.
1888 For the very few that do, software emulation is provided in
1889 specific cases in protected and virtual-8086 modes. Emulated
1892 config X86_INTEL_MPX
1893 prompt "Intel MPX (Memory Protection Extensions)"
1895 # Note: only available in 64-bit mode due to VMA flags shortage
1896 depends on CPU_SUP_INTEL && X86_64
1897 select ARCH_USES_HIGH_VMA_FLAGS
1899 MPX provides hardware features that can be used in
1900 conjunction with compiler-instrumented code to check
1901 memory references. It is designed to detect buffer
1902 overflow or underflow bugs.
1904 This option enables running applications which are
1905 instrumented or otherwise use MPX. It does not use MPX
1906 itself inside the kernel or to protect the kernel
1907 against bad memory references.
1909 Enabling this option will make the kernel larger:
1910 ~8k of kernel text and 36 bytes of data on a 64-bit
1911 defconfig. It adds a long to the 'mm_struct' which
1912 will increase the kernel memory overhead of each
1913 process and adds some branches to paths used during
1914 exec() and munmap().
1916 For details, see Documentation/x86/intel_mpx.rst
1920 config X86_INTEL_MEMORY_PROTECTION_KEYS
1921 prompt "Intel Memory Protection Keys"
1923 # Note: only available in 64-bit mode
1924 depends on CPU_SUP_INTEL && X86_64
1925 select ARCH_USES_HIGH_VMA_FLAGS
1926 select ARCH_HAS_PKEYS
1928 Memory Protection Keys provides a mechanism for enforcing
1929 page-based protections, but without requiring modification of the
1930 page tables when an application changes protection domains.
1932 For details, see Documentation/core-api/protection-keys.rst
1937 bool "EFI runtime service support"
1940 select EFI_RUNTIME_WRAPPERS
1942 This enables the kernel to use EFI runtime services that are
1943 available (such as the EFI variable services).
1945 This option is only useful on systems that have EFI firmware.
1946 In addition, you should use the latest ELILO loader available
1947 at <http://elilo.sourceforge.net> in order to take advantage
1948 of EFI runtime services. However, even with this option, the
1949 resultant kernel should continue to boot on existing non-EFI
1953 bool "EFI stub support"
1954 depends on EFI && !X86_USE_3DNOW
1957 This kernel feature allows a bzImage to be loaded directly
1958 by EFI firmware without the use of a bootloader.
1960 See Documentation/efi-stub.txt for more information.
1963 bool "EFI mixed-mode support"
1964 depends on EFI_STUB && X86_64
1966 Enabling this feature allows a 64-bit kernel to be booted
1967 on a 32-bit firmware, provided that your CPU supports 64-bit
1970 Note that it is not possible to boot a mixed-mode enabled
1971 kernel via the EFI boot stub - a bootloader that supports
1972 the EFI handover protocol must be used.
1978 prompt "Enable seccomp to safely compute untrusted bytecode"
1980 This kernel feature is useful for number crunching applications
1981 that may need to compute untrusted bytecode during their
1982 execution. By using pipes or other transports made available to
1983 the process as file descriptors supporting the read/write
1984 syscalls, it's possible to isolate those applications in
1985 their own address space using seccomp. Once seccomp is
1986 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1987 and the task is only allowed to execute a few safe syscalls
1988 defined by each seccomp mode.
1990 If unsure, say Y. Only embedded should say N here.
1992 source "kernel/Kconfig.hz"
1995 bool "kexec system call"
1998 kexec is a system call that implements the ability to shutdown your
1999 current kernel, and to start another kernel. It is like a reboot
2000 but it is independent of the system firmware. And like a reboot
2001 you can start any kernel with it, not just Linux.
2003 The name comes from the similarity to the exec system call.
2005 It is an ongoing process to be certain the hardware in a machine
2006 is properly shutdown, so do not be surprised if this code does not
2007 initially work for you. As of this writing the exact hardware
2008 interface is strongly in flux, so no good recommendation can be
2012 bool "kexec file based system call"
2017 depends on CRYPTO_SHA256=y
2019 This is new version of kexec system call. This system call is
2020 file based and takes file descriptors as system call argument
2021 for kernel and initramfs as opposed to list of segments as
2022 accepted by previous system call.
2024 config ARCH_HAS_KEXEC_PURGATORY
2027 config KEXEC_VERIFY_SIG
2028 bool "Verify kernel signature during kexec_file_load() syscall"
2029 depends on KEXEC_FILE
2031 This option makes kernel signature verification mandatory for
2032 the kexec_file_load() syscall.
2034 In addition to that option, you need to enable signature
2035 verification for the corresponding kernel image type being
2036 loaded in order for this to work.
2038 config KEXEC_BZIMAGE_VERIFY_SIG
2039 bool "Enable bzImage signature verification support"
2040 depends on KEXEC_VERIFY_SIG
2041 depends on SIGNED_PE_FILE_VERIFICATION
2042 select SYSTEM_TRUSTED_KEYRING
2044 Enable bzImage signature verification support.
2047 bool "kernel crash dumps"
2048 depends on X86_64 || (X86_32 && HIGHMEM)
2050 Generate crash dump after being started by kexec.
2051 This should be normally only set in special crash dump kernels
2052 which are loaded in the main kernel with kexec-tools into
2053 a specially reserved region and then later executed after
2054 a crash by kdump/kexec. The crash dump kernel must be compiled
2055 to a memory address not used by the main kernel or BIOS using
2056 PHYSICAL_START, or it must be built as a relocatable image
2057 (CONFIG_RELOCATABLE=y).
2058 For more details see Documentation/kdump/kdump.rst
2062 depends on KEXEC && HIBERNATION
2064 Jump between original kernel and kexeced kernel and invoke
2065 code in physical address mode via KEXEC
2067 config PHYSICAL_START
2068 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2071 This gives the physical address where the kernel is loaded.
2073 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2074 bzImage will decompress itself to above physical address and
2075 run from there. Otherwise, bzImage will run from the address where
2076 it has been loaded by the boot loader and will ignore above physical
2079 In normal kdump cases one does not have to set/change this option
2080 as now bzImage can be compiled as a completely relocatable image
2081 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2082 address. This option is mainly useful for the folks who don't want
2083 to use a bzImage for capturing the crash dump and want to use a
2084 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2085 to be specifically compiled to run from a specific memory area
2086 (normally a reserved region) and this option comes handy.
2088 So if you are using bzImage for capturing the crash dump,
2089 leave the value here unchanged to 0x1000000 and set
2090 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2091 for capturing the crash dump change this value to start of
2092 the reserved region. In other words, it can be set based on
2093 the "X" value as specified in the "crashkernel=YM@XM"
2094 command line boot parameter passed to the panic-ed
2095 kernel. Please take a look at Documentation/kdump/kdump.rst
2096 for more details about crash dumps.
2098 Usage of bzImage for capturing the crash dump is recommended as
2099 one does not have to build two kernels. Same kernel can be used
2100 as production kernel and capture kernel. Above option should have
2101 gone away after relocatable bzImage support is introduced. But it
2102 is present because there are users out there who continue to use
2103 vmlinux for dump capture. This option should go away down the
2106 Don't change this unless you know what you are doing.
2109 bool "Build a relocatable kernel"
2112 This builds a kernel image that retains relocation information
2113 so it can be loaded someplace besides the default 1MB.
2114 The relocations tend to make the kernel binary about 10% larger,
2115 but are discarded at runtime.
2117 One use is for the kexec on panic case where the recovery kernel
2118 must live at a different physical address than the primary
2121 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2122 it has been loaded at and the compile time physical address
2123 (CONFIG_PHYSICAL_START) is used as the minimum location.
2125 config RANDOMIZE_BASE
2126 bool "Randomize the address of the kernel image (KASLR)"
2127 depends on RELOCATABLE
2130 In support of Kernel Address Space Layout Randomization (KASLR),
2131 this randomizes the physical address at which the kernel image
2132 is decompressed and the virtual address where the kernel
2133 image is mapped, as a security feature that deters exploit
2134 attempts relying on knowledge of the location of kernel
2137 On 64-bit, the kernel physical and virtual addresses are
2138 randomized separately. The physical address will be anywhere
2139 between 16MB and the top of physical memory (up to 64TB). The
2140 virtual address will be randomized from 16MB up to 1GB (9 bits
2141 of entropy). Note that this also reduces the memory space
2142 available to kernel modules from 1.5GB to 1GB.
2144 On 32-bit, the kernel physical and virtual addresses are
2145 randomized together. They will be randomized from 16MB up to
2146 512MB (8 bits of entropy).
2148 Entropy is generated using the RDRAND instruction if it is
2149 supported. If RDTSC is supported, its value is mixed into
2150 the entropy pool as well. If neither RDRAND nor RDTSC are
2151 supported, then entropy is read from the i8254 timer. The
2152 usable entropy is limited by the kernel being built using
2153 2GB addressing, and that PHYSICAL_ALIGN must be at a
2154 minimum of 2MB. As a result, only 10 bits of entropy are
2155 theoretically possible, but the implementations are further
2156 limited due to memory layouts.
2160 # Relocation on x86 needs some additional build support
2161 config X86_NEED_RELOCS
2163 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2165 config PHYSICAL_ALIGN
2166 hex "Alignment value to which kernel should be aligned"
2168 range 0x2000 0x1000000 if X86_32
2169 range 0x200000 0x1000000 if X86_64
2171 This value puts the alignment restrictions on physical address
2172 where kernel is loaded and run from. Kernel is compiled for an
2173 address which meets above alignment restriction.
2175 If bootloader loads the kernel at a non-aligned address and
2176 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2177 address aligned to above value and run from there.
2179 If bootloader loads the kernel at a non-aligned address and
2180 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2181 load address and decompress itself to the address it has been
2182 compiled for and run from there. The address for which kernel is
2183 compiled already meets above alignment restrictions. Hence the
2184 end result is that kernel runs from a physical address meeting
2185 above alignment restrictions.
2187 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2188 this value must be a multiple of 0x200000.
2190 Don't change this unless you know what you are doing.
2192 config DYNAMIC_MEMORY_LAYOUT
2195 This option makes base addresses of vmalloc and vmemmap as well as
2196 __PAGE_OFFSET movable during boot.
2198 config RANDOMIZE_MEMORY
2199 bool "Randomize the kernel memory sections"
2201 depends on RANDOMIZE_BASE
2202 select DYNAMIC_MEMORY_LAYOUT
2203 default RANDOMIZE_BASE
2205 Randomizes the base virtual address of kernel memory sections
2206 (physical memory mapping, vmalloc & vmemmap). This security feature
2207 makes exploits relying on predictable memory locations less reliable.
2209 The order of allocations remains unchanged. Entropy is generated in
2210 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2211 configuration have in average 30,000 different possible virtual
2212 addresses for each memory section.
2216 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2217 hex "Physical memory mapping padding" if EXPERT
2218 depends on RANDOMIZE_MEMORY
2219 default "0xa" if MEMORY_HOTPLUG
2221 range 0x1 0x40 if MEMORY_HOTPLUG
2224 Define the padding in terabytes added to the existing physical
2225 memory size during kernel memory randomization. It is useful
2226 for memory hotplug support but reduces the entropy available for
2227 address randomization.
2229 If unsure, leave at the default value.
2235 config BOOTPARAM_HOTPLUG_CPU0
2236 bool "Set default setting of cpu0_hotpluggable"
2237 depends on HOTPLUG_CPU
2239 Set whether default state of cpu0_hotpluggable is on or off.
2241 Say Y here to enable CPU0 hotplug by default. If this switch
2242 is turned on, there is no need to give cpu0_hotplug kernel
2243 parameter and the CPU0 hotplug feature is enabled by default.
2245 Please note: there are two known CPU0 dependencies if you want
2246 to enable the CPU0 hotplug feature either by this switch or by
2247 cpu0_hotplug kernel parameter.
2249 First, resume from hibernate or suspend always starts from CPU0.
2250 So hibernate and suspend are prevented if CPU0 is offline.
2252 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2253 offline if any interrupt can not migrate out of CPU0. There may
2254 be other CPU0 dependencies.
2256 Please make sure the dependencies are under your control before
2257 you enable this feature.
2259 Say N if you don't want to enable CPU0 hotplug feature by default.
2260 You still can enable the CPU0 hotplug feature at boot by kernel
2261 parameter cpu0_hotplug.
2263 config DEBUG_HOTPLUG_CPU0
2265 prompt "Debug CPU0 hotplug"
2266 depends on HOTPLUG_CPU
2268 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2269 soon as possible and boots up userspace with CPU0 offlined. User
2270 can online CPU0 back after boot time.
2272 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2273 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2274 compilation or giving cpu0_hotplug kernel parameter at boot.
2280 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2281 depends on COMPAT_32
2283 Certain buggy versions of glibc will crash if they are
2284 presented with a 32-bit vDSO that is not mapped at the address
2285 indicated in its segment table.
2287 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2288 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2289 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2290 the only released version with the bug, but OpenSUSE 9
2291 contains a buggy "glibc 2.3.2".
2293 The symptom of the bug is that everything crashes on startup, saying:
2294 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2296 Saying Y here changes the default value of the vdso32 boot
2297 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2298 This works around the glibc bug but hurts performance.
2300 If unsure, say N: if you are compiling your own kernel, you
2301 are unlikely to be using a buggy version of glibc.
2304 prompt "vsyscall table for legacy applications"
2306 default LEGACY_VSYSCALL_XONLY
2308 Legacy user code that does not know how to find the vDSO expects
2309 to be able to issue three syscalls by calling fixed addresses in
2310 kernel space. Since this location is not randomized with ASLR,
2311 it can be used to assist security vulnerability exploitation.
2313 This setting can be changed at boot time via the kernel command
2314 line parameter vsyscall=[emulate|xonly|none].
2316 On a system with recent enough glibc (2.14 or newer) and no
2317 static binaries, you can say None without a performance penalty
2318 to improve security.
2320 If unsure, select "Emulate execution only".
2322 config LEGACY_VSYSCALL_EMULATE
2323 bool "Full emulation"
2325 The kernel traps and emulates calls into the fixed vsyscall
2326 address mapping. This makes the mapping non-executable, but
2327 it still contains readable known contents, which could be
2328 used in certain rare security vulnerability exploits. This
2329 configuration is recommended when using legacy userspace
2330 that still uses vsyscalls along with legacy binary
2331 instrumentation tools that require code to be readable.
2333 An example of this type of legacy userspace is running
2334 Pin on an old binary that still uses vsyscalls.
2336 config LEGACY_VSYSCALL_XONLY
2337 bool "Emulate execution only"
2339 The kernel traps and emulates calls into the fixed vsyscall
2340 address mapping and does not allow reads. This
2341 configuration is recommended when userspace might use the
2342 legacy vsyscall area but support for legacy binary
2343 instrumentation of legacy code is not needed. It mitigates
2344 certain uses of the vsyscall area as an ASLR-bypassing
2347 config LEGACY_VSYSCALL_NONE
2350 There will be no vsyscall mapping at all. This will
2351 eliminate any risk of ASLR bypass due to the vsyscall
2352 fixed address mapping. Attempts to use the vsyscalls
2353 will be reported to dmesg, so that either old or
2354 malicious userspace programs can be identified.
2359 bool "Built-in kernel command line"
2361 Allow for specifying boot arguments to the kernel at
2362 build time. On some systems (e.g. embedded ones), it is
2363 necessary or convenient to provide some or all of the
2364 kernel boot arguments with the kernel itself (that is,
2365 to not rely on the boot loader to provide them.)
2367 To compile command line arguments into the kernel,
2368 set this option to 'Y', then fill in the
2369 boot arguments in CONFIG_CMDLINE.
2371 Systems with fully functional boot loaders (i.e. non-embedded)
2372 should leave this option set to 'N'.
2375 string "Built-in kernel command string"
2376 depends on CMDLINE_BOOL
2379 Enter arguments here that should be compiled into the kernel
2380 image and used at boot time. If the boot loader provides a
2381 command line at boot time, it is appended to this string to
2382 form the full kernel command line, when the system boots.
2384 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2385 change this behavior.
2387 In most cases, the command line (whether built-in or provided
2388 by the boot loader) should specify the device for the root
2391 config CMDLINE_OVERRIDE
2392 bool "Built-in command line overrides boot loader arguments"
2393 depends on CMDLINE_BOOL
2395 Set this option to 'Y' to have the kernel ignore the boot loader
2396 command line, and use ONLY the built-in command line.
2398 This is used to work around broken boot loaders. This should
2399 be set to 'N' under normal conditions.
2401 config MODIFY_LDT_SYSCALL
2402 bool "Enable the LDT (local descriptor table)" if EXPERT
2405 Linux can allow user programs to install a per-process x86
2406 Local Descriptor Table (LDT) using the modify_ldt(2) system
2407 call. This is required to run 16-bit or segmented code such as
2408 DOSEMU or some Wine programs. It is also used by some very old
2409 threading libraries.
2411 Enabling this feature adds a small amount of overhead to
2412 context switches and increases the low-level kernel attack
2413 surface. Disabling it removes the modify_ldt(2) system call.
2415 Saying 'N' here may make sense for embedded or server kernels.
2417 source "kernel/livepatch/Kconfig"
2421 config ARCH_HAS_ADD_PAGES
2423 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2425 config ARCH_ENABLE_MEMORY_HOTPLUG
2427 depends on X86_64 || (X86_32 && HIGHMEM)
2429 config ARCH_ENABLE_MEMORY_HOTREMOVE
2431 depends on MEMORY_HOTPLUG
2433 config USE_PERCPU_NUMA_NODE_ID
2437 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2439 depends on X86_64 || X86_PAE
2441 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2443 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2445 config ARCH_ENABLE_THP_MIGRATION
2447 depends on X86_64 && TRANSPARENT_HUGEPAGE
2449 menu "Power management and ACPI options"
2451 config ARCH_HIBERNATION_HEADER
2453 depends on HIBERNATION
2455 source "kernel/power/Kconfig"
2457 source "drivers/acpi/Kconfig"
2459 source "drivers/sfi/Kconfig"
2466 tristate "APM (Advanced Power Management) BIOS support"
2467 depends on X86_32 && PM_SLEEP
2469 APM is a BIOS specification for saving power using several different
2470 techniques. This is mostly useful for battery powered laptops with
2471 APM compliant BIOSes. If you say Y here, the system time will be
2472 reset after a RESUME operation, the /proc/apm device will provide
2473 battery status information, and user-space programs will receive
2474 notification of APM "events" (e.g. battery status change).
2476 If you select "Y" here, you can disable actual use of the APM
2477 BIOS by passing the "apm=off" option to the kernel at boot time.
2479 Note that the APM support is almost completely disabled for
2480 machines with more than one CPU.
2482 In order to use APM, you will need supporting software. For location
2483 and more information, read <file:Documentation/power/apm-acpi.txt>
2484 and the Battery Powered Linux mini-HOWTO, available from
2485 <http://www.tldp.org/docs.html#howto>.
2487 This driver does not spin down disk drives (see the hdparm(8)
2488 manpage ("man 8 hdparm") for that), and it doesn't turn off
2489 VESA-compliant "green" monitors.
2491 This driver does not support the TI 4000M TravelMate and the ACER
2492 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2493 desktop machines also don't have compliant BIOSes, and this driver
2494 may cause those machines to panic during the boot phase.
2496 Generally, if you don't have a battery in your machine, there isn't
2497 much point in using this driver and you should say N. If you get
2498 random kernel OOPSes or reboots that don't seem to be related to
2499 anything, try disabling/enabling this option (or disabling/enabling
2502 Some other things you should try when experiencing seemingly random,
2505 1) make sure that you have enough swap space and that it is
2507 2) pass the "no-hlt" option to the kernel
2508 3) switch on floating point emulation in the kernel and pass
2509 the "no387" option to the kernel
2510 4) pass the "floppy=nodma" option to the kernel
2511 5) pass the "mem=4M" option to the kernel (thereby disabling
2512 all but the first 4 MB of RAM)
2513 6) make sure that the CPU is not over clocked.
2514 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2515 8) disable the cache from your BIOS settings
2516 9) install a fan for the video card or exchange video RAM
2517 10) install a better fan for the CPU
2518 11) exchange RAM chips
2519 12) exchange the motherboard.
2521 To compile this driver as a module, choose M here: the
2522 module will be called apm.
2526 config APM_IGNORE_USER_SUSPEND
2527 bool "Ignore USER SUSPEND"
2529 This option will ignore USER SUSPEND requests. On machines with a
2530 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2531 series notebooks, it is necessary to say Y because of a BIOS bug.
2533 config APM_DO_ENABLE
2534 bool "Enable PM at boot time"
2536 Enable APM features at boot time. From page 36 of the APM BIOS
2537 specification: "When disabled, the APM BIOS does not automatically
2538 power manage devices, enter the Standby State, enter the Suspend
2539 State, or take power saving steps in response to CPU Idle calls."
2540 This driver will make CPU Idle calls when Linux is idle (unless this
2541 feature is turned off -- see "Do CPU IDLE calls", below). This
2542 should always save battery power, but more complicated APM features
2543 will be dependent on your BIOS implementation. You may need to turn
2544 this option off if your computer hangs at boot time when using APM
2545 support, or if it beeps continuously instead of suspending. Turn
2546 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2547 T400CDT. This is off by default since most machines do fine without
2552 bool "Make CPU Idle calls when idle"
2554 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2555 On some machines, this can activate improved power savings, such as
2556 a slowed CPU clock rate, when the machine is idle. These idle calls
2557 are made after the idle loop has run for some length of time (e.g.,
2558 333 mS). On some machines, this will cause a hang at boot time or
2559 whenever the CPU becomes idle. (On machines with more than one CPU,
2560 this option does nothing.)
2562 config APM_DISPLAY_BLANK
2563 bool "Enable console blanking using APM"
2565 Enable console blanking using the APM. Some laptops can use this to
2566 turn off the LCD backlight when the screen blanker of the Linux
2567 virtual console blanks the screen. Note that this is only used by
2568 the virtual console screen blanker, and won't turn off the backlight
2569 when using the X Window system. This also doesn't have anything to
2570 do with your VESA-compliant power-saving monitor. Further, this
2571 option doesn't work for all laptops -- it might not turn off your
2572 backlight at all, or it might print a lot of errors to the console,
2573 especially if you are using gpm.
2575 config APM_ALLOW_INTS
2576 bool "Allow interrupts during APM BIOS calls"
2578 Normally we disable external interrupts while we are making calls to
2579 the APM BIOS as a measure to lessen the effects of a badly behaving
2580 BIOS implementation. The BIOS should reenable interrupts if it
2581 needs to. Unfortunately, some BIOSes do not -- especially those in
2582 many of the newer IBM Thinkpads. If you experience hangs when you
2583 suspend, try setting this to Y. Otherwise, say N.
2587 source "drivers/cpufreq/Kconfig"
2589 source "drivers/cpuidle/Kconfig"
2591 source "drivers/idle/Kconfig"
2596 menu "Bus options (PCI etc.)"
2599 prompt "PCI access mode"
2600 depends on X86_32 && PCI
2603 On PCI systems, the BIOS can be used to detect the PCI devices and
2604 determine their configuration. However, some old PCI motherboards
2605 have BIOS bugs and may crash if this is done. Also, some embedded
2606 PCI-based systems don't have any BIOS at all. Linux can also try to
2607 detect the PCI hardware directly without using the BIOS.
2609 With this option, you can specify how Linux should detect the
2610 PCI devices. If you choose "BIOS", the BIOS will be used,
2611 if you choose "Direct", the BIOS won't be used, and if you
2612 choose "MMConfig", then PCI Express MMCONFIG will be used.
2613 If you choose "Any", the kernel will try MMCONFIG, then the
2614 direct access method and falls back to the BIOS if that doesn't
2615 work. If unsure, go with the default, which is "Any".
2620 config PCI_GOMMCONFIG
2637 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2639 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2642 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2645 bool "Support mmconfig PCI config space access" if X86_64
2647 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2648 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2652 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2656 depends on PCI && XEN
2659 config MMCONF_FAM10H
2661 depends on X86_64 && PCI_MMCONFIG && ACPI
2663 config PCI_CNB20LE_QUIRK
2664 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2667 Read the PCI windows out of the CNB20LE host bridge. This allows
2668 PCI hotplug to work on systems with the CNB20LE chipset which do
2671 There's no public spec for this chipset, and this functionality
2672 is known to be incomplete.
2674 You should say N unless you know you need this.
2677 bool "ISA bus support on modern systems" if EXPERT
2679 Expose ISA bus device drivers and options available for selection and
2680 configuration. Enable this option if your target machine has an ISA
2681 bus. ISA is an older system, displaced by PCI and newer bus
2682 architectures -- if your target machine is modern, it probably does
2683 not have an ISA bus.
2687 # x86_64 have no ISA slots, but can have ISA-style DMA.
2689 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2692 Enables ISA-style DMA support for devices requiring such controllers.
2700 Find out whether you have ISA slots on your motherboard. ISA is the
2701 name of a bus system, i.e. the way the CPU talks to the other stuff
2702 inside your box. Other bus systems are PCI, EISA, MicroChannel
2703 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2704 newer boards don't support it. If you have ISA, say Y, otherwise N.
2707 tristate "NatSemi SCx200 support"
2709 This provides basic support for National Semiconductor's
2710 (now AMD's) Geode processors. The driver probes for the
2711 PCI-IDs of several on-chip devices, so its a good dependency
2712 for other scx200_* drivers.
2714 If compiled as a module, the driver is named scx200.
2716 config SCx200HR_TIMER
2717 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2721 This driver provides a clocksource built upon the on-chip
2722 27MHz high-resolution timer. Its also a workaround for
2723 NSC Geode SC-1100's buggy TSC, which loses time when the
2724 processor goes idle (as is done by the scheduler). The
2725 other workaround is idle=poll boot option.
2728 bool "One Laptop Per Child support"
2735 Add support for detecting the unique features of the OLPC
2739 bool "OLPC XO-1 Power Management"
2740 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2742 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2745 bool "OLPC XO-1 Real Time Clock"
2746 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2748 Add support for the XO-1 real time clock, which can be used as a
2749 programmable wakeup source.
2752 bool "OLPC XO-1 SCI extras"
2753 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2757 Add support for SCI-based features of the OLPC XO-1 laptop:
2758 - EC-driven system wakeups
2762 - AC adapter status updates
2763 - Battery status updates
2765 config OLPC_XO15_SCI
2766 bool "OLPC XO-1.5 SCI extras"
2767 depends on OLPC && ACPI
2770 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2771 - EC-driven system wakeups
2772 - AC adapter status updates
2773 - Battery status updates
2776 bool "PCEngines ALIX System Support (LED setup)"
2779 This option enables system support for the PCEngines ALIX.
2780 At present this just sets up LEDs for GPIO control on
2781 ALIX2/3/6 boards. However, other system specific setup should
2784 Note: You must still enable the drivers for GPIO and LED support
2785 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2787 Note: You have to set alix.force=1 for boards with Award BIOS.
2790 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2793 This option enables system support for the Soekris Engineering net5501.
2796 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2800 This option enables system support for the Traverse Technologies GEOS.
2803 bool "Technologic Systems TS-5500 platform support"
2805 select CHECK_SIGNATURE
2809 This option enables system support for the Technologic Systems TS-5500.
2815 depends on CPU_SUP_AMD && PCI
2818 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2820 Firmwares often provide initial graphics framebuffers so the BIOS,
2821 bootloader or kernel can show basic video-output during boot for
2822 user-guidance and debugging. Historically, x86 used the VESA BIOS
2823 Extensions and EFI-framebuffers for this, which are mostly limited
2825 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2826 framebuffers so the new generic system-framebuffer drivers can be
2827 used on x86. If the framebuffer is not compatible with the generic
2828 modes, it is advertised as fallback platform framebuffer so legacy
2829 drivers like efifb, vesafb and uvesafb can pick it up.
2830 If this option is not selected, all system framebuffers are always
2831 marked as fallback platform framebuffers as usual.
2833 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2834 not be able to pick up generic system framebuffers if this option
2835 is selected. You are highly encouraged to enable simplefb as
2836 replacement if you select this option. simplefb can correctly deal
2837 with generic system framebuffers. But you should still keep vesafb
2838 and others enabled as fallback if a system framebuffer is
2839 incompatible with simplefb.
2846 menu "Binary Emulations"
2848 config IA32_EMULATION
2849 bool "IA32 Emulation"
2851 select ARCH_WANT_OLD_COMPAT_IPC
2853 select COMPAT_BINFMT_ELF
2854 select COMPAT_OLD_SIGACTION
2856 Include code to run legacy 32-bit programs under a
2857 64-bit kernel. You should likely turn this on, unless you're
2858 100% sure that you don't have any 32-bit programs left.
2861 tristate "IA32 a.out support"
2862 depends on IA32_EMULATION
2865 Support old a.out binaries in the 32bit emulation.
2868 bool "x32 ABI for 64-bit mode"
2871 Include code to run binaries for the x32 native 32-bit ABI
2872 for 64-bit processors. An x32 process gets access to the
2873 full 64-bit register file and wide data path while leaving
2874 pointers at 32 bits for smaller memory footprint.
2876 You will need a recent binutils (2.22 or later) with
2877 elf32_x86_64 support enabled to compile a kernel with this
2882 depends on IA32_EMULATION || X86_32
2884 select OLD_SIGSUSPEND3
2888 depends on IA32_EMULATION || X86_X32
2891 config COMPAT_FOR_U64_ALIGNMENT
2894 config SYSVIPC_COMPAT
2902 config HAVE_ATOMIC_IOMAP
2906 config X86_DEV_DMA_OPS
2909 config HAVE_GENERIC_GUP
2912 source "drivers/firmware/Kconfig"
2914 source "arch/x86/kvm/Kconfig"