1 # SPDX-License-Identifier: GPL-2.0
4 bool "64-bit kernel" if "$(ARCH)" = "x86"
5 default "$(ARCH)" != "i386"
7 Say yes to build a 64-bit kernel - formerly known as x86_64
8 Say no to build a 32-bit kernel - formerly known as i386
13 # Options that are inherently 32-bit kernel only:
14 select ARCH_WANT_IPC_PARSE_VERSION
16 select CLONE_BACKWARDS
17 select HAVE_DEBUG_STACKOVERFLOW
18 select MODULES_USE_ELF_REL
20 select GENERIC_VDSO_32
25 # Options that are inherently 64-bit kernel only:
26 select ARCH_HAS_GIGANTIC_PAGE
27 select ARCH_SUPPORTS_INT128
28 select ARCH_USE_CMPXCHG_LOCKREF
29 select HAVE_ARCH_SOFT_DIRTY
30 select MODULES_USE_ELF_RELA
31 select NEED_DMA_MAP_STATE
33 select ARCH_HAS_SYSCALL_WRAPPER
35 config FORCE_DYNAMIC_FTRACE
38 depends on FUNCTION_TRACER
41 We keep the static function tracing (!DYNAMIC_FTRACE) around
42 in order to test the non static function tracing in the
43 generic code, as other architectures still use it. But we
44 only need to keep it around for x86_64. No need to keep it
45 for x86_32. For x86_32, force DYNAMIC_FTRACE.
49 # ( Note that options that are marked 'if X86_64' could in principle be
50 # ported to 32-bit as well. )
55 # Note: keep this list sorted alphabetically
57 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
58 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
59 select ARCH_32BIT_OFF_T if X86_32
60 select ARCH_CLOCKSOURCE_DATA
61 select ARCH_CLOCKSOURCE_INIT
62 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
63 select ARCH_HAS_DEBUG_VIRTUAL
64 select ARCH_HAS_DEVMEM_IS_ALLOWED
65 select ARCH_HAS_ELF_RANDOMIZE
66 select ARCH_HAS_FAST_MULTIPLIER
67 select ARCH_HAS_FILTER_PGPROT
68 select ARCH_HAS_FORTIFY_SOURCE
69 select ARCH_HAS_GCOV_PROFILE_ALL
70 select ARCH_HAS_KCOV if X86_64
71 select ARCH_HAS_MEMBARRIER_SYNC_CORE
72 select ARCH_HAS_PMEM_API if X86_64
73 select ARCH_HAS_PTE_SPECIAL
74 select ARCH_HAS_REFCOUNT
75 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
76 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
77 select ARCH_HAS_SET_MEMORY
78 select ARCH_HAS_SET_DIRECT_MAP
79 select ARCH_HAS_STRICT_KERNEL_RWX
80 select ARCH_HAS_STRICT_MODULE_RWX
81 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
82 select ARCH_HAS_UBSAN_SANITIZE_ALL
83 select ARCH_HAS_ZONE_DEVICE if X86_64
84 select ARCH_HAVE_NMI_SAFE_CMPXCHG
85 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
86 select ARCH_MIGHT_HAVE_PC_PARPORT
87 select ARCH_MIGHT_HAVE_PC_SERIO
89 select ARCH_SUPPORTS_ACPI
90 select ARCH_SUPPORTS_ATOMIC_RMW
91 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
92 select ARCH_USE_BUILTIN_BSWAP
93 select ARCH_USE_QUEUED_RWLOCKS
94 select ARCH_USE_QUEUED_SPINLOCKS
95 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
96 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
97 select ARCH_WANTS_THP_SWAP if X86_64
98 select BUILDTIME_EXTABLE_SORT
100 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
101 select CLOCKSOURCE_WATCHDOG
102 select DCACHE_WORD_ACCESS
103 select EDAC_ATOMIC_SCRUB
105 select GENERIC_CLOCKEVENTS
106 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
107 select GENERIC_CLOCKEVENTS_MIN_ADJUST
108 select GENERIC_CMOS_UPDATE
109 select GENERIC_CPU_AUTOPROBE
110 select GENERIC_CPU_VULNERABILITIES
111 select GENERIC_EARLY_IOREMAP
112 select GENERIC_FIND_FIRST_BIT
114 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
115 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
116 select GENERIC_IRQ_MIGRATION if SMP
117 select GENERIC_IRQ_PROBE
118 select GENERIC_IRQ_RESERVATION_MODE
119 select GENERIC_IRQ_SHOW
120 select GENERIC_PENDING_IRQ if SMP
121 select GENERIC_SMP_IDLE_THREAD
122 select GENERIC_STRNCPY_FROM_USER
123 select GENERIC_STRNLEN_USER
124 select GENERIC_TIME_VSYSCALL
125 select GENERIC_GETTIMEOFDAY
126 select GUP_GET_PTE_LOW_HIGH if X86_PAE
127 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
128 select HAVE_ACPI_APEI if ACPI
129 select HAVE_ACPI_APEI_NMI if ACPI
130 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
131 select HAVE_ARCH_AUDITSYSCALL
132 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
133 select HAVE_ARCH_JUMP_LABEL
134 select HAVE_ARCH_JUMP_LABEL_RELATIVE
135 select HAVE_ARCH_KASAN if X86_64
136 select HAVE_ARCH_KGDB
137 select HAVE_ARCH_MMAP_RND_BITS if MMU
138 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
139 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
140 select HAVE_ARCH_PREL32_RELOCATIONS
141 select HAVE_ARCH_SECCOMP_FILTER
142 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
143 select HAVE_ARCH_STACKLEAK
144 select HAVE_ARCH_TRACEHOOK
145 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
146 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
147 select HAVE_ARCH_VMAP_STACK if X86_64
148 select HAVE_ARCH_WITHIN_STACK_FRAMES
149 select HAVE_CMPXCHG_DOUBLE
150 select HAVE_CMPXCHG_LOCAL
151 select HAVE_CONTEXT_TRACKING if X86_64
152 select HAVE_COPY_THREAD_TLS
153 select HAVE_C_RECORDMCOUNT
154 select HAVE_DEBUG_KMEMLEAK
155 select HAVE_DMA_CONTIGUOUS
156 select HAVE_DYNAMIC_FTRACE
157 select HAVE_DYNAMIC_FTRACE_WITH_REGS
159 select HAVE_EFFICIENT_UNALIGNED_ACCESS
161 select HAVE_EXIT_THREAD
162 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
163 select HAVE_FTRACE_MCOUNT_RECORD
164 select HAVE_FUNCTION_GRAPH_TRACER
165 select HAVE_FUNCTION_TRACER
166 select HAVE_GCC_PLUGINS
167 select HAVE_HW_BREAKPOINT
169 select HAVE_IOREMAP_PROT
170 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
171 select HAVE_IRQ_TIME_ACCOUNTING
172 select HAVE_KERNEL_BZIP2
173 select HAVE_KERNEL_GZIP
174 select HAVE_KERNEL_LZ4
175 select HAVE_KERNEL_LZMA
176 select HAVE_KERNEL_LZO
177 select HAVE_KERNEL_XZ
179 select HAVE_KPROBES_ON_FTRACE
180 select HAVE_FUNCTION_ERROR_INJECTION
181 select HAVE_KRETPROBES
183 select HAVE_LIVEPATCH if X86_64
184 select HAVE_MEMBLOCK_NODE_MAP
185 select HAVE_MIXED_BREAKPOINTS_REGS
186 select HAVE_MOD_ARCH_SPECIFIC
190 select HAVE_OPTPROBES
191 select HAVE_PCSPKR_PLATFORM
192 select HAVE_PERF_EVENTS
193 select HAVE_PERF_EVENTS_NMI
194 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
196 select HAVE_PERF_REGS
197 select HAVE_PERF_USER_STACK_DUMP
198 select HAVE_RCU_TABLE_FREE if PARAVIRT
199 select HAVE_REGS_AND_STACK_ACCESS_API
200 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
201 select HAVE_FUNCTION_ARG_ACCESS_API
202 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
203 select HAVE_STACK_VALIDATION if X86_64
205 select HAVE_SYSCALL_TRACEPOINTS
206 select HAVE_UNSTABLE_SCHED_CLOCK
207 select HAVE_USER_RETURN_NOTIFIER
208 select HAVE_GENERIC_VDSO
209 select HOTPLUG_SMT if SMP
210 select IRQ_FORCED_THREADING
211 select NEED_SG_DMA_LENGTH
212 select PCI_DOMAINS if PCI
213 select PCI_LOCKLESS_CONFIG if PCI
216 select RTC_MC146818_LIB
219 select SYSCTL_EXCEPTION_TRACE
220 select THREAD_INFO_IN_TASK
221 select USER_STACKTRACE_SUPPORT
223 select X86_FEATURE_NAMES if PROC_FS
224 select PROC_PID_ARCH_STATUS if PROC_FS
226 config INSTRUCTION_DECODER
228 depends on KPROBES || PERF_EVENTS || UPROBES
232 default "elf32-i386" if X86_32
233 default "elf64-x86-64" if X86_64
235 config ARCH_DEFCONFIG
237 default "arch/x86/configs/i386_defconfig" if X86_32
238 default "arch/x86/configs/x86_64_defconfig" if X86_64
240 config LOCKDEP_SUPPORT
243 config STACKTRACE_SUPPORT
249 config ARCH_MMAP_RND_BITS_MIN
253 config ARCH_MMAP_RND_BITS_MAX
257 config ARCH_MMAP_RND_COMPAT_BITS_MIN
260 config ARCH_MMAP_RND_COMPAT_BITS_MAX
266 config GENERIC_ISA_DMA
268 depends on ISA_DMA_API
273 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
275 config GENERIC_BUG_RELATIVE_POINTERS
278 config ARCH_MAY_HAVE_PC_FDC
280 depends on ISA_DMA_API
282 config GENERIC_CALIBRATE_DELAY
285 config ARCH_HAS_CPU_RELAX
288 config ARCH_HAS_CACHE_LINE_SIZE
291 config ARCH_HAS_FILTER_PGPROT
294 config HAVE_SETUP_PER_CPU_AREA
297 config NEED_PER_CPU_EMBED_FIRST_CHUNK
300 config NEED_PER_CPU_PAGE_FIRST_CHUNK
303 config ARCH_HIBERNATION_POSSIBLE
306 config ARCH_SUSPEND_POSSIBLE
309 config ARCH_WANT_HUGE_PMD_SHARE
312 config ARCH_WANT_GENERAL_HUGETLB
321 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
324 config KASAN_SHADOW_OFFSET
327 default 0xdffffc0000000000
329 config HAVE_INTEL_TXT
331 depends on INTEL_IOMMU && ACPI
335 depends on X86_32 && SMP
339 depends on X86_64 && SMP
341 config X86_32_LAZY_GS
343 depends on X86_32 && !STACKPROTECTOR
345 config ARCH_SUPPORTS_UPROBES
348 config FIX_EARLYCON_MEM
351 config DYNAMIC_PHYSICAL_MASK
354 config PGTABLE_LEVELS
356 default 5 if X86_5LEVEL
361 config CC_HAS_SANE_STACKPROTECTOR
363 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
364 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
366 We have to make sure stack protector is unconditionally disabled if
367 the compiler produces broken code.
369 menu "Processor type and features"
372 bool "DMA memory allocation support" if EXPERT
375 DMA memory allocation support allows devices with less than 32-bit
376 addressing to allocate within the first 16MB of address space.
377 Disable if no such devices will be used.
382 bool "Symmetric multi-processing support"
384 This enables support for systems with more than one CPU. If you have
385 a system with only one CPU, say N. If you have a system with more
388 If you say N here, the kernel will run on uni- and multiprocessor
389 machines, but will use only one CPU of a multiprocessor machine. If
390 you say Y here, the kernel will run on many, but not all,
391 uniprocessor machines. On a uniprocessor machine, the kernel
392 will run faster if you say N here.
394 Note that if you say Y here and choose architecture "586" or
395 "Pentium" under "Processor family", the kernel will not work on 486
396 architectures. Similarly, multiprocessor kernels for the "PPro"
397 architecture may not work on all Pentium based boards.
399 People using multiprocessor machines who say Y here should also say
400 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
401 Management" code will be disabled if you say Y here.
403 See also <file:Documentation/x86/i386/IO-APIC.rst>,
404 <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
405 <http://www.tldp.org/docs.html#howto>.
407 If you don't know what to do here, say N.
409 config X86_FEATURE_NAMES
410 bool "Processor feature human-readable names" if EMBEDDED
413 This option compiles in a table of x86 feature bits and corresponding
414 names. This is required to support /proc/cpuinfo and a few kernel
415 messages. You can disable this to save space, at the expense of
416 making those few kernel messages show numeric feature bits instead.
421 bool "Support x2apic"
422 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
424 This enables x2apic support on CPUs that have this feature.
426 This allows 32-bit apic IDs (so it can support very large systems),
427 and accesses the local apic via MSRs not via mmio.
429 If you don't know what to do here, say N.
432 bool "Enable MPS table" if ACPI || SFI
434 depends on X86_LOCAL_APIC
436 For old smp systems that do not have proper acpi support. Newer systems
437 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
441 depends on X86_GOLDFISH
444 bool "Avoid speculative indirect branches in kernel"
446 select STACK_VALIDATION if HAVE_STACK_VALIDATION
448 Compile kernel with the retpoline compiler options to guard against
449 kernel-to-user data leaks by avoiding speculative indirect
450 branches. Requires a compiler with -mindirect-branch=thunk-extern
451 support for full protection. The kernel may run slower.
453 config X86_CPU_RESCTRL
454 bool "x86 CPU resource control support"
455 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
458 Enable x86 CPU resource control support.
460 Provide support for the allocation and monitoring of system resources
463 Intel calls this Intel Resource Director Technology
464 (Intel(R) RDT). More information about RDT can be found in the
465 Intel x86 Architecture Software Developer Manual.
467 AMD calls this AMD Platform Quality of Service (AMD QoS).
468 More information about AMD QoS can be found in the AMD64 Technology
469 Platform Quality of Service Extensions manual.
475 bool "Support for big SMP systems with more than 8 CPUs"
478 This option is needed for the systems that have more than 8 CPUs
480 config X86_EXTENDED_PLATFORM
481 bool "Support for extended (non-PC) x86 platforms"
484 If you disable this option then the kernel will only support
485 standard PC platforms. (which covers the vast majority of
488 If you enable this option then you'll be able to select support
489 for the following (non-PC) 32 bit x86 platforms:
490 Goldfish (Android emulator)
493 SGI 320/540 (Visual Workstation)
494 STA2X11-based (e.g. Northville)
495 Moorestown MID devices
497 If you have one of these systems, or if you want to build a
498 generic distribution kernel, say Y here - otherwise say N.
502 config X86_EXTENDED_PLATFORM
503 bool "Support for extended (non-PC) x86 platforms"
506 If you disable this option then the kernel will only support
507 standard PC platforms. (which covers the vast majority of
510 If you enable this option then you'll be able to select support
511 for the following (non-PC) 64 bit x86 platforms:
516 If you have one of these systems, or if you want to build a
517 generic distribution kernel, say Y here - otherwise say N.
519 # This is an alphabetically sorted list of 64 bit extended platforms
520 # Please maintain the alphabetic order if and when there are additions
522 bool "Numascale NumaChip"
524 depends on X86_EXTENDED_PLATFORM
527 depends on X86_X2APIC
528 depends on PCI_MMCONFIG
530 Adds support for Numascale NumaChip large-SMP systems. Needed to
531 enable more than ~168 cores.
532 If you don't have one of these, you should say N here.
536 select HYPERVISOR_GUEST
538 depends on X86_64 && PCI
539 depends on X86_EXTENDED_PLATFORM
542 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
543 supposed to run on these EM64T-based machines. Only choose this option
544 if you have one of these machines.
547 bool "SGI Ultraviolet"
549 depends on X86_EXTENDED_PLATFORM
552 depends on X86_X2APIC
555 This option is needed in order to support SGI Ultraviolet systems.
556 If you don't have one of these, you should say N here.
558 # Following is an alphabetically sorted list of 32 bit extended platforms
559 # Please maintain the alphabetic order if and when there are additions
562 bool "Goldfish (Virtual Platform)"
563 depends on X86_EXTENDED_PLATFORM
565 Enable support for the Goldfish virtual platform used primarily
566 for Android development. Unless you are building for the Android
567 Goldfish emulator say N here.
570 bool "CE4100 TV platform"
572 depends on PCI_GODIRECT
573 depends on X86_IO_APIC
575 depends on X86_EXTENDED_PLATFORM
576 select X86_REBOOTFIXUPS
578 select OF_EARLY_FLATTREE
580 Select for the Intel CE media processor (CE4100) SOC.
581 This option compiles in support for the CE4100 SOC for settop
582 boxes and media devices.
585 bool "Intel MID platform support"
586 depends on X86_EXTENDED_PLATFORM
587 depends on X86_PLATFORM_DEVICES
589 depends on X86_64 || (PCI_GOANY && X86_32)
590 depends on X86_IO_APIC
596 select MFD_INTEL_MSIC
598 Select to build a kernel capable of supporting Intel MID (Mobile
599 Internet Device) platform systems which do not have the PCI legacy
600 interfaces. If you are building for a PC class system say N here.
602 Intel MID platforms are based on an Intel processor and chipset which
603 consume less power than most of the x86 derivatives.
605 config X86_INTEL_QUARK
606 bool "Intel Quark platform support"
608 depends on X86_EXTENDED_PLATFORM
609 depends on X86_PLATFORM_DEVICES
613 depends on X86_IO_APIC
618 Select to include support for Quark X1000 SoC.
619 Say Y here if you have a Quark based system such as the Arduino
620 compatible Intel Galileo.
622 config X86_INTEL_LPSS
623 bool "Intel Low Power Subsystem Support"
624 depends on X86 && ACPI && PCI
629 Select to build support for Intel Low Power Subsystem such as
630 found on Intel Lynxpoint PCH. Selecting this option enables
631 things like clock tree (common clock framework) and pincontrol
632 which are needed by the LPSS peripheral drivers.
634 config X86_AMD_PLATFORM_DEVICE
635 bool "AMD ACPI2Platform devices support"
640 Select to interpret AMD specific ACPI device to platform device
641 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
642 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
643 implemented under PINCTRL subsystem.
646 tristate "Intel SoC IOSF Sideband support for SoC platforms"
649 This option enables sideband register access support for Intel SoC
650 platforms. On these platforms the IOSF sideband is used in lieu of
651 MSR's for some register accesses, mostly but not limited to thermal
652 and power. Drivers may query the availability of this device to
653 determine if they need the sideband in order to work on these
654 platforms. The sideband is available on the following SoC products.
655 This list is not meant to be exclusive.
660 You should say Y if you are running a kernel on one of these SoC's.
662 config IOSF_MBI_DEBUG
663 bool "Enable IOSF sideband access through debugfs"
664 depends on IOSF_MBI && DEBUG_FS
666 Select this option to expose the IOSF sideband access registers (MCR,
667 MDR, MCRX) through debugfs to write and read register information from
668 different units on the SoC. This is most useful for obtaining device
669 state information for debug and analysis. As this is a general access
670 mechanism, users of this option would have specific knowledge of the
671 device they want to access.
673 If you don't require the option or are in doubt, say N.
676 bool "RDC R-321x SoC"
678 depends on X86_EXTENDED_PLATFORM
680 select X86_REBOOTFIXUPS
682 This option is needed for RDC R-321x system-on-chip, also known
684 If you don't have one of these chips, you should say N here.
686 config X86_32_NON_STANDARD
687 bool "Support non-standard 32-bit SMP architectures"
688 depends on X86_32 && SMP
689 depends on X86_EXTENDED_PLATFORM
691 This option compiles in the bigsmp and STA2X11 default
692 subarchitectures. It is intended for a generic binary
693 kernel. If you select them all, kernel will probe it one by
694 one and will fallback to default.
696 # Alphabetically sorted list of Non standard 32 bit platforms
698 config X86_SUPPORTS_MEMORY_FAILURE
700 # MCE code calls memory_failure():
702 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
703 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
704 depends on X86_64 || !SPARSEMEM
705 select ARCH_SUPPORTS_MEMORY_FAILURE
708 bool "STA2X11 Companion Chip Support"
709 depends on X86_32_NON_STANDARD && PCI
710 select ARCH_HAS_PHYS_TO_DMA
715 This adds support for boards based on the STA2X11 IO-Hub,
716 a.k.a. "ConneXt". The chip is used in place of the standard
717 PC chipset, so all "standard" peripherals are missing. If this
718 option is selected the kernel will still be able to boot on
719 standard PC machines.
722 tristate "Eurobraille/Iris poweroff module"
725 The Iris machines from EuroBraille do not have APM or ACPI support
726 to shut themselves down properly. A special I/O sequence is
727 needed to do so, which is what this module does at
730 This is only for Iris machines from EuroBraille.
734 config SCHED_OMIT_FRAME_POINTER
736 prompt "Single-depth WCHAN output"
739 Calculate simpler /proc/<PID>/wchan values. If this option
740 is disabled then wchan values will recurse back to the
741 caller function. This provides more accurate wchan values,
742 at the expense of slightly more scheduling overhead.
744 If in doubt, say "Y".
746 menuconfig HYPERVISOR_GUEST
747 bool "Linux guest support"
749 Say Y here to enable options for running Linux under various hyper-
750 visors. This option enables basic hypervisor detection and platform
753 If you say N, all options in this submenu will be skipped and
754 disabled, and Linux guest support won't be built in.
759 bool "Enable paravirtualization code"
761 This changes the kernel so it can modify itself when it is run
762 under a hypervisor, potentially improving performance significantly
763 over full virtualization. However, when run without a hypervisor
764 the kernel is theoretically slower and slightly larger.
769 config PARAVIRT_DEBUG
770 bool "paravirt-ops debugging"
771 depends on PARAVIRT && DEBUG_KERNEL
773 Enable to debug paravirt_ops internals. Specifically, BUG if
774 a paravirt_op is missing when it is called.
776 config PARAVIRT_SPINLOCKS
777 bool "Paravirtualization layer for spinlocks"
778 depends on PARAVIRT && SMP
780 Paravirtualized spinlocks allow a pvops backend to replace the
781 spinlock implementation with something virtualization-friendly
782 (for example, block the virtual CPU rather than spinning).
784 It has a minimal impact on native kernels and gives a nice performance
785 benefit on paravirtualized KVM / Xen kernels.
787 If you are unsure how to answer this question, answer Y.
789 config X86_HV_CALLBACK_VECTOR
792 source "arch/x86/xen/Kconfig"
795 bool "KVM Guest support (including kvmclock)"
797 select PARAVIRT_CLOCK
800 This option enables various optimizations for running under the KVM
801 hypervisor. It includes a paravirtualized clock, so that instead
802 of relying on a PIT (or probably other) emulation by the
803 underlying device model, the host provides the guest with
804 timing infrastructure such as time of day, and system time
807 bool "Support for running PVH guests"
809 This option enables the PVH entry point for guest virtual machines
810 as specified in the x86/HVM direct boot ABI.
813 bool "Enable debug information for KVM Guests in debugfs"
814 depends on KVM_GUEST && DEBUG_FS
816 This option enables collection of various statistics for KVM guest.
817 Statistics are displayed in debugfs filesystem. Enabling this option
818 may incur significant overhead.
820 config PARAVIRT_TIME_ACCOUNTING
821 bool "Paravirtual steal time accounting"
824 Select this option to enable fine granularity task steal time
825 accounting. Time spent executing other tasks in parallel with
826 the current vCPU is discounted from the vCPU power. To account for
827 that, there can be a small performance impact.
829 If in doubt, say N here.
831 config PARAVIRT_CLOCK
834 config JAILHOUSE_GUEST
835 bool "Jailhouse non-root cell support"
836 depends on X86_64 && PCI
839 This option allows to run Linux as guest in a Jailhouse non-root
840 cell. You can leave this option disabled if you only want to start
841 Jailhouse and run Linux afterwards in the root cell.
844 bool "ACRN Guest support"
846 select X86_HV_CALLBACK_VECTOR
848 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
849 a flexible, lightweight reference open-source hypervisor, built with
850 real-time and safety-criticality in mind. It is built for embedded
851 IOT with small footprint and real-time features. More details can be
852 found in https://projectacrn.org/.
854 endif #HYPERVISOR_GUEST
856 source "arch/x86/Kconfig.cpu"
860 prompt "HPET Timer Support" if X86_32
862 Use the IA-PC HPET (High Precision Event Timer) to manage
863 time in preference to the PIT and RTC, if a HPET is
865 HPET is the next generation timer replacing legacy 8254s.
866 The HPET provides a stable time base on SMP
867 systems, unlike the TSC, but it is more expensive to access,
868 as it is off-chip. The interface used is documented
869 in the HPET spec, revision 1.
871 You can safely choose Y here. However, HPET will only be
872 activated if the platform and the BIOS support this feature.
873 Otherwise the 8254 will be used for timing services.
875 Choose N to continue using the legacy 8254 timer.
877 config HPET_EMULATE_RTC
879 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
882 def_bool y if X86_INTEL_MID
883 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
885 depends on X86_INTEL_MID && SFI
887 APB timer is the replacement for 8254, HPET on X86 MID platforms.
888 The APBT provides a stable time base on SMP
889 systems, unlike the TSC, but it is more expensive to access,
890 as it is off-chip. APB timers are always running regardless of CPU
891 C states, they are used as per CPU clockevent device when possible.
893 # Mark as expert because too many people got it wrong.
894 # The code disables itself when not needed.
897 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
898 bool "Enable DMI scanning" if EXPERT
900 Enabled scanning of DMI to identify machine quirks. Say Y
901 here unless you have verified that your setup is not
902 affected by entries in the DMI blacklist. Required by PNP
906 bool "Old AMD GART IOMMU support"
909 depends on X86_64 && PCI && AMD_NB
911 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
912 GART based hardware IOMMUs.
914 The GART supports full DMA access for devices with 32-bit access
915 limitations, on systems with more than 3 GB. This is usually needed
916 for USB, sound, many IDE/SATA chipsets and some other devices.
918 Newer systems typically have a modern AMD IOMMU, supported via
919 the CONFIG_AMD_IOMMU=y config option.
921 In normal configurations this driver is only active when needed:
922 there's more than 3 GB of memory and the system contains a
923 32-bit limited device.
928 bool "IBM Calgary IOMMU support"
931 depends on X86_64 && PCI
933 Support for hardware IOMMUs in IBM's xSeries x366 and x460
934 systems. Needed to run systems with more than 3GB of memory
935 properly with 32-bit PCI devices that do not support DAC
936 (Double Address Cycle). Calgary also supports bus level
937 isolation, where all DMAs pass through the IOMMU. This
938 prevents them from going anywhere except their intended
939 destination. This catches hard-to-find kernel bugs and
940 mis-behaving drivers and devices that do not use the DMA-API
941 properly to set up their DMA buffers. The IOMMU can be
942 turned off at boot time with the iommu=off parameter.
943 Normally the kernel will make the right choice by itself.
946 config CALGARY_IOMMU_ENABLED_BY_DEFAULT
948 prompt "Should Calgary be enabled by default?"
949 depends on CALGARY_IOMMU
951 Should Calgary be enabled by default? if you choose 'y', Calgary
952 will be used (if it exists). If you choose 'n', Calgary will not be
953 used even if it exists. If you choose 'n' and would like to use
954 Calgary anyway, pass 'iommu=calgary' on the kernel command line.
958 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
959 depends on X86_64 && SMP && DEBUG_KERNEL
960 select CPUMASK_OFFSTACK
962 Enable maximum number of CPUS and NUMA Nodes for this architecture.
966 # The maximum number of CPUs supported:
968 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
969 # and which can be configured interactively in the
970 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
972 # The ranges are different on 32-bit and 64-bit kernels, depending on
973 # hardware capabilities and scalability features of the kernel.
975 # ( If MAXSMP is enabled we just use the highest possible value and disable
976 # interactive configuration. )
979 config NR_CPUS_RANGE_BEGIN
981 default NR_CPUS_RANGE_END if MAXSMP
985 config NR_CPUS_RANGE_END
988 default 64 if SMP && X86_BIGSMP
989 default 8 if SMP && !X86_BIGSMP
992 config NR_CPUS_RANGE_END
995 default 8192 if SMP && ( MAXSMP || CPUMASK_OFFSTACK)
996 default 512 if SMP && (!MAXSMP && !CPUMASK_OFFSTACK)
999 config NR_CPUS_DEFAULT
1002 default 32 if X86_BIGSMP
1006 config NR_CPUS_DEFAULT
1009 default 8192 if MAXSMP
1014 int "Maximum number of CPUs" if SMP && !MAXSMP
1015 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1016 default NR_CPUS_DEFAULT
1018 This allows you to specify the maximum number of CPUs which this
1019 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1020 supported value is 8192, otherwise the maximum value is 512. The
1021 minimum value which makes sense is 2.
1023 This is purely to save memory: each supported CPU adds about 8KB
1024 to the kernel image.
1031 prompt "Multi-core scheduler support"
1034 Multi-core scheduler support improves the CPU scheduler's decision
1035 making when dealing with multi-core CPU chips at a cost of slightly
1036 increased overhead in some places. If unsure say N here.
1038 config SCHED_MC_PRIO
1039 bool "CPU core priorities scheduler support"
1040 depends on SCHED_MC && CPU_SUP_INTEL
1041 select X86_INTEL_PSTATE
1045 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1046 core ordering determined at manufacturing time, which allows
1047 certain cores to reach higher turbo frequencies (when running
1048 single threaded workloads) than others.
1050 Enabling this kernel feature teaches the scheduler about
1051 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1052 scheduler's CPU selection logic accordingly, so that higher
1053 overall system performance can be achieved.
1055 This feature will have no effect on CPUs without this feature.
1057 If unsure say Y here.
1061 depends on !SMP && X86_LOCAL_APIC
1064 bool "Local APIC support on uniprocessors" if !PCI_MSI
1066 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1068 A local APIC (Advanced Programmable Interrupt Controller) is an
1069 integrated interrupt controller in the CPU. If you have a single-CPU
1070 system which has a processor with a local APIC, you can say Y here to
1071 enable and use it. If you say Y here even though your machine doesn't
1072 have a local APIC, then the kernel will still run with no slowdown at
1073 all. The local APIC supports CPU-generated self-interrupts (timer,
1074 performance counters), and the NMI watchdog which detects hard
1077 config X86_UP_IOAPIC
1078 bool "IO-APIC support on uniprocessors"
1079 depends on X86_UP_APIC
1081 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1082 SMP-capable replacement for PC-style interrupt controllers. Most
1083 SMP systems and many recent uniprocessor systems have one.
1085 If you have a single-CPU system with an IO-APIC, you can say Y here
1086 to use it. If you say Y here even though your machine doesn't have
1087 an IO-APIC, then the kernel will still run with no slowdown at all.
1089 config X86_LOCAL_APIC
1091 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1092 select IRQ_DOMAIN_HIERARCHY
1093 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1097 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1099 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1100 bool "Reroute for broken boot IRQs"
1101 depends on X86_IO_APIC
1103 This option enables a workaround that fixes a source of
1104 spurious interrupts. This is recommended when threaded
1105 interrupt handling is used on systems where the generation of
1106 superfluous "boot interrupts" cannot be disabled.
1108 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1109 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1110 kernel does during interrupt handling). On chipsets where this
1111 boot IRQ generation cannot be disabled, this workaround keeps
1112 the original IRQ line masked so that only the equivalent "boot
1113 IRQ" is delivered to the CPUs. The workaround also tells the
1114 kernel to set up the IRQ handler on the boot IRQ line. In this
1115 way only one interrupt is delivered to the kernel. Otherwise
1116 the spurious second interrupt may cause the kernel to bring
1117 down (vital) interrupt lines.
1119 Only affects "broken" chipsets. Interrupt sharing may be
1120 increased on these systems.
1123 bool "Machine Check / overheating reporting"
1124 select GENERIC_ALLOCATOR
1127 Machine Check support allows the processor to notify the
1128 kernel if it detects a problem (e.g. overheating, data corruption).
1129 The action the kernel takes depends on the severity of the problem,
1130 ranging from warning messages to halting the machine.
1132 config X86_MCELOG_LEGACY
1133 bool "Support for deprecated /dev/mcelog character device"
1136 Enable support for /dev/mcelog which is needed by the old mcelog
1137 userspace logging daemon. Consider switching to the new generation
1140 config X86_MCE_INTEL
1142 prompt "Intel MCE features"
1143 depends on X86_MCE && X86_LOCAL_APIC
1145 Additional support for intel specific MCE features such as
1146 the thermal monitor.
1150 prompt "AMD MCE features"
1151 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1153 Additional support for AMD specific MCE features such as
1154 the DRAM Error Threshold.
1156 config X86_ANCIENT_MCE
1157 bool "Support for old Pentium 5 / WinChip machine checks"
1158 depends on X86_32 && X86_MCE
1160 Include support for machine check handling on old Pentium 5 or WinChip
1161 systems. These typically need to be enabled explicitly on the command
1164 config X86_MCE_THRESHOLD
1165 depends on X86_MCE_AMD || X86_MCE_INTEL
1168 config X86_MCE_INJECT
1169 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1170 tristate "Machine check injector support"
1172 Provide support for injecting machine checks for testing purposes.
1173 If you don't know what a machine check is and you don't do kernel
1174 QA it is safe to say n.
1176 config X86_THERMAL_VECTOR
1178 depends on X86_MCE_INTEL
1180 source "arch/x86/events/Kconfig"
1182 config X86_LEGACY_VM86
1183 bool "Legacy VM86 support"
1186 This option allows user programs to put the CPU into V8086
1187 mode, which is an 80286-era approximation of 16-bit real mode.
1189 Some very old versions of X and/or vbetool require this option
1190 for user mode setting. Similarly, DOSEMU will use it if
1191 available to accelerate real mode DOS programs. However, any
1192 recent version of DOSEMU, X, or vbetool should be fully
1193 functional even without kernel VM86 support, as they will all
1194 fall back to software emulation. Nevertheless, if you are using
1195 a 16-bit DOS program where 16-bit performance matters, vm86
1196 mode might be faster than emulation and you might want to
1199 Note that any app that works on a 64-bit kernel is unlikely to
1200 need this option, as 64-bit kernels don't, and can't, support
1201 V8086 mode. This option is also unrelated to 16-bit protected
1202 mode and is not needed to run most 16-bit programs under Wine.
1204 Enabling this option increases the complexity of the kernel
1205 and slows down exception handling a tiny bit.
1207 If unsure, say N here.
1211 default X86_LEGACY_VM86
1214 bool "Enable support for 16-bit segments" if EXPERT
1216 depends on MODIFY_LDT_SYSCALL
1218 This option is required by programs like Wine to run 16-bit
1219 protected mode legacy code on x86 processors. Disabling
1220 this option saves about 300 bytes on i386, or around 6K text
1221 plus 16K runtime memory on x86-64,
1225 depends on X86_16BIT && X86_32
1229 depends on X86_16BIT && X86_64
1231 config X86_VSYSCALL_EMULATION
1232 bool "Enable vsyscall emulation" if EXPERT
1236 This enables emulation of the legacy vsyscall page. Disabling
1237 it is roughly equivalent to booting with vsyscall=none, except
1238 that it will also disable the helpful warning if a program
1239 tries to use a vsyscall. With this option set to N, offending
1240 programs will just segfault, citing addresses of the form
1243 This option is required by many programs built before 2013, and
1244 care should be used even with newer programs if set to N.
1246 Disabling this option saves about 7K of kernel size and
1247 possibly 4K of additional runtime pagetable memory.
1250 tristate "Toshiba Laptop support"
1253 This adds a driver to safely access the System Management Mode of
1254 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1255 not work on models with a Phoenix BIOS. The System Management Mode
1256 is used to set the BIOS and power saving options on Toshiba portables.
1258 For information on utilities to make use of this driver see the
1259 Toshiba Linux utilities web site at:
1260 <http://www.buzzard.org.uk/toshiba/>.
1262 Say Y if you intend to run this kernel on a Toshiba portable.
1266 tristate "Dell i8k legacy laptop support"
1268 select SENSORS_DELL_SMM
1270 This option enables legacy /proc/i8k userspace interface in hwmon
1271 dell-smm-hwmon driver. Character file /proc/i8k reports bios version,
1272 temperature and allows controlling fan speeds of Dell laptops via
1273 System Management Mode. For old Dell laptops (like Dell Inspiron 8000)
1274 it reports also power and hotkey status. For fan speed control is
1275 needed userspace package i8kutils.
1277 Say Y if you intend to run this kernel on old Dell laptops or want to
1278 use userspace package i8kutils.
1281 config X86_REBOOTFIXUPS
1282 bool "Enable X86 board specific fixups for reboot"
1285 This enables chipset and/or board specific fixups to be done
1286 in order to get reboot to work correctly. This is only needed on
1287 some combinations of hardware and BIOS. The symptom, for which
1288 this config is intended, is when reboot ends with a stalled/hung
1291 Currently, the only fixup is for the Geode machines using
1292 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1294 Say Y if you want to enable the fixup. Currently, it's safe to
1295 enable this option even if you don't need it.
1299 bool "CPU microcode loading support"
1301 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1304 If you say Y here, you will be able to update the microcode on
1305 Intel and AMD processors. The Intel support is for the IA32 family,
1306 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1307 AMD support is for families 0x10 and later. You will obviously need
1308 the actual microcode binary data itself which is not shipped with
1311 The preferred method to load microcode from a detached initrd is described
1312 in Documentation/x86/microcode.rst. For that you need to enable
1313 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1314 initrd for microcode blobs.
1316 In addition, you can build the microcode into the kernel. For that you
1317 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1320 config MICROCODE_INTEL
1321 bool "Intel microcode loading support"
1322 depends on MICROCODE
1326 This options enables microcode patch loading support for Intel
1329 For the current Intel microcode data package go to
1330 <https://downloadcenter.intel.com> and search for
1331 'Linux Processor Microcode Data File'.
1333 config MICROCODE_AMD
1334 bool "AMD microcode loading support"
1335 depends on MICROCODE
1338 If you select this option, microcode patch loading support for AMD
1339 processors will be enabled.
1341 config MICROCODE_OLD_INTERFACE
1342 bool "Ancient loading interface (DEPRECATED)"
1344 depends on MICROCODE
1346 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1347 which was used by userspace tools like iucode_tool and microcode.ctl.
1348 It is inadequate because it runs too late to be able to properly
1349 load microcode on a machine and it needs special tools. Instead, you
1350 should've switched to the early loading method with the initrd or
1351 builtin microcode by now: Documentation/x86/microcode.rst
1354 tristate "/dev/cpu/*/msr - Model-specific register support"
1356 This device gives privileged processes access to the x86
1357 Model-Specific Registers (MSRs). It is a character device with
1358 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1359 MSR accesses are directed to a specific CPU on multi-processor
1363 tristate "/dev/cpu/*/cpuid - CPU information support"
1365 This device gives processes access to the x86 CPUID instruction to
1366 be executed on a specific processor. It is a character device
1367 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1371 prompt "High Memory Support"
1378 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1379 However, the address space of 32-bit x86 processors is only 4
1380 Gigabytes large. That means that, if you have a large amount of
1381 physical memory, not all of it can be "permanently mapped" by the
1382 kernel. The physical memory that's not permanently mapped is called
1385 If you are compiling a kernel which will never run on a machine with
1386 more than 1 Gigabyte total physical RAM, answer "off" here (default
1387 choice and suitable for most users). This will result in a "3GB/1GB"
1388 split: 3GB are mapped so that each process sees a 3GB virtual memory
1389 space and the remaining part of the 4GB virtual memory space is used
1390 by the kernel to permanently map as much physical memory as
1393 If the machine has between 1 and 4 Gigabytes physical RAM, then
1396 If more than 4 Gigabytes is used then answer "64GB" here. This
1397 selection turns Intel PAE (Physical Address Extension) mode on.
1398 PAE implements 3-level paging on IA32 processors. PAE is fully
1399 supported by Linux, PAE mode is implemented on all recent Intel
1400 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1401 then the kernel will not boot on CPUs that don't support PAE!
1403 The actual amount of total physical memory will either be
1404 auto detected or can be forced by using a kernel command line option
1405 such as "mem=256M". (Try "man bootparam" or see the documentation of
1406 your boot loader (lilo or loadlin) about how to pass options to the
1407 kernel at boot time.)
1409 If unsure, say "off".
1414 Select this if you have a 32-bit processor and between 1 and 4
1415 gigabytes of physical RAM.
1419 depends on !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !WINCHIP3D && !MK6
1422 Select this if you have a 32-bit processor and more than 4
1423 gigabytes of physical RAM.
1428 prompt "Memory split" if EXPERT
1432 Select the desired split between kernel and user memory.
1434 If the address range available to the kernel is less than the
1435 physical memory installed, the remaining memory will be available
1436 as "high memory". Accessing high memory is a little more costly
1437 than low memory, as it needs to be mapped into the kernel first.
1438 Note that increasing the kernel address space limits the range
1439 available to user programs, making the address space there
1440 tighter. Selecting anything other than the default 3G/1G split
1441 will also likely make your kernel incompatible with binary-only
1444 If you are not absolutely sure what you are doing, leave this
1448 bool "3G/1G user/kernel split"
1449 config VMSPLIT_3G_OPT
1451 bool "3G/1G user/kernel split (for full 1G low memory)"
1453 bool "2G/2G user/kernel split"
1454 config VMSPLIT_2G_OPT
1456 bool "2G/2G user/kernel split (for full 2G low memory)"
1458 bool "1G/3G user/kernel split"
1463 default 0xB0000000 if VMSPLIT_3G_OPT
1464 default 0x80000000 if VMSPLIT_2G
1465 default 0x78000000 if VMSPLIT_2G_OPT
1466 default 0x40000000 if VMSPLIT_1G
1472 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1475 bool "PAE (Physical Address Extension) Support"
1476 depends on X86_32 && !HIGHMEM4G
1477 select PHYS_ADDR_T_64BIT
1480 PAE is required for NX support, and furthermore enables
1481 larger swapspace support for non-overcommit purposes. It
1482 has the cost of more pagetable lookup overhead, and also
1483 consumes more pagetable space per process.
1486 bool "Enable 5-level page tables support"
1487 select DYNAMIC_MEMORY_LAYOUT
1488 select SPARSEMEM_VMEMMAP
1491 5-level paging enables access to larger address space:
1492 upto 128 PiB of virtual address space and 4 PiB of
1493 physical address space.
1495 It will be supported by future Intel CPUs.
1497 A kernel with the option enabled can be booted on machines that
1498 support 4- or 5-level paging.
1500 See Documentation/x86/x86_64/5level-paging.rst for more
1505 config X86_DIRECT_GBPAGES
1507 depends on X86_64 && !DEBUG_PAGEALLOC
1509 Certain kernel features effectively disable kernel
1510 linear 1 GB mappings (even if the CPU otherwise
1511 supports them), so don't confuse the user by printing
1512 that we have them enabled.
1514 config X86_CPA_STATISTICS
1515 bool "Enable statistic for Change Page Attribute"
1518 Expose statistics about the Change Page Attribute mechanims, which
1519 helps to determine the effectiveness of preserving large and huge
1520 page mappings when mapping protections are changed.
1522 config ARCH_HAS_MEM_ENCRYPT
1525 config AMD_MEM_ENCRYPT
1526 bool "AMD Secure Memory Encryption (SME) support"
1527 depends on X86_64 && CPU_SUP_AMD
1528 select DYNAMIC_PHYSICAL_MASK
1529 select ARCH_USE_MEMREMAP_PROT
1531 Say yes to enable support for the encryption of system memory.
1532 This requires an AMD processor that supports Secure Memory
1535 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1536 bool "Activate AMD Secure Memory Encryption (SME) by default"
1538 depends on AMD_MEM_ENCRYPT
1540 Say yes to have system memory encrypted by default if running on
1541 an AMD processor that supports Secure Memory Encryption (SME).
1543 If set to Y, then the encryption of system memory can be
1544 deactivated with the mem_encrypt=off command line option.
1546 If set to N, then the encryption of system memory can be
1547 activated with the mem_encrypt=on command line option.
1549 # Common NUMA Features
1551 bool "Numa Memory Allocation and Scheduler Support"
1553 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1554 default y if X86_BIGSMP
1556 Enable NUMA (Non Uniform Memory Access) support.
1558 The kernel will try to allocate memory used by a CPU on the
1559 local memory controller of the CPU and add some more
1560 NUMA awareness to the kernel.
1562 For 64-bit this is recommended if the system is Intel Core i7
1563 (or later), AMD Opteron, or EM64T NUMA.
1565 For 32-bit this is only needed if you boot a 32-bit
1566 kernel on a 64-bit NUMA platform.
1568 Otherwise, you should say N.
1572 prompt "Old style AMD Opteron NUMA detection"
1573 depends on X86_64 && NUMA && PCI
1575 Enable AMD NUMA node topology detection. You should say Y here if
1576 you have a multi processor AMD system. This uses an old method to
1577 read the NUMA configuration directly from the builtin Northbridge
1578 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1579 which also takes priority if both are compiled in.
1581 config X86_64_ACPI_NUMA
1583 prompt "ACPI NUMA detection"
1584 depends on X86_64 && NUMA && ACPI && PCI
1587 Enable ACPI SRAT based node topology detection.
1589 # Some NUMA nodes have memory ranges that span
1590 # other nodes. Even though a pfn is valid and
1591 # between a node's start and end pfns, it may not
1592 # reside on that node. See memmap_init_zone()
1594 config NODES_SPAN_OTHER_NODES
1596 depends on X86_64_ACPI_NUMA
1599 bool "NUMA emulation"
1602 Enable NUMA emulation. A flat machine will be split
1603 into virtual nodes when booted with "numa=fake=N", where N is the
1604 number of nodes. This is only useful for debugging.
1607 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1609 default "10" if MAXSMP
1610 default "6" if X86_64
1612 depends on NEED_MULTIPLE_NODES
1614 Specify the maximum number of NUMA Nodes available on the target
1615 system. Increases memory reserved to accommodate various tables.
1617 config ARCH_HAVE_MEMORY_PRESENT
1619 depends on X86_32 && DISCONTIGMEM
1621 config ARCH_FLATMEM_ENABLE
1623 depends on X86_32 && !NUMA
1625 config ARCH_DISCONTIGMEM_ENABLE
1627 depends on NUMA && X86_32
1630 config ARCH_SPARSEMEM_ENABLE
1632 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1633 select SPARSEMEM_STATIC if X86_32
1634 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1636 config ARCH_SPARSEMEM_DEFAULT
1637 def_bool X86_64 || (NUMA && X86_32)
1639 config ARCH_SELECT_MEMORY_MODEL
1641 depends on ARCH_SPARSEMEM_ENABLE
1643 config ARCH_MEMORY_PROBE
1644 bool "Enable sysfs memory/probe interface"
1645 depends on X86_64 && MEMORY_HOTPLUG
1647 This option enables a sysfs memory/probe interface for testing.
1648 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1649 If you are unsure how to answer this question, answer N.
1651 config ARCH_PROC_KCORE_TEXT
1653 depends on X86_64 && PROC_KCORE
1655 config ILLEGAL_POINTER_VALUE
1658 default 0xdead000000000000 if X86_64
1660 config X86_PMEM_LEGACY_DEVICE
1663 config X86_PMEM_LEGACY
1664 tristate "Support non-standard NVDIMMs and ADR protected memory"
1665 depends on PHYS_ADDR_T_64BIT
1667 select X86_PMEM_LEGACY_DEVICE
1670 Treat memory marked using the non-standard e820 type of 12 as used
1671 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1672 The kernel will offer these regions to the 'pmem' driver so
1673 they can be used for persistent storage.
1678 bool "Allocate 3rd-level pagetables from highmem"
1681 The VM uses one page table entry for each page of physical memory.
1682 For systems with a lot of RAM, this can be wasteful of precious
1683 low memory. Setting this option will put user-space page table
1684 entries in high memory.
1686 config X86_CHECK_BIOS_CORRUPTION
1687 bool "Check for low memory corruption"
1689 Periodically check for memory corruption in low memory, which
1690 is suspected to be caused by BIOS. Even when enabled in the
1691 configuration, it is disabled at runtime. Enable it by
1692 setting "memory_corruption_check=1" on the kernel command
1693 line. By default it scans the low 64k of memory every 60
1694 seconds; see the memory_corruption_check_size and
1695 memory_corruption_check_period parameters in
1696 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1698 When enabled with the default parameters, this option has
1699 almost no overhead, as it reserves a relatively small amount
1700 of memory and scans it infrequently. It both detects corruption
1701 and prevents it from affecting the running system.
1703 It is, however, intended as a diagnostic tool; if repeatable
1704 BIOS-originated corruption always affects the same memory,
1705 you can use memmap= to prevent the kernel from using that
1708 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1709 bool "Set the default setting of memory_corruption_check"
1710 depends on X86_CHECK_BIOS_CORRUPTION
1713 Set whether the default state of memory_corruption_check is
1716 config X86_RESERVE_LOW
1717 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1721 Specify the amount of low memory to reserve for the BIOS.
1723 The first page contains BIOS data structures that the kernel
1724 must not use, so that page must always be reserved.
1726 By default we reserve the first 64K of physical RAM, as a
1727 number of BIOSes are known to corrupt that memory range
1728 during events such as suspend/resume or monitor cable
1729 insertion, so it must not be used by the kernel.
1731 You can set this to 4 if you are absolutely sure that you
1732 trust the BIOS to get all its memory reservations and usages
1733 right. If you know your BIOS have problems beyond the
1734 default 64K area, you can set this to 640 to avoid using the
1735 entire low memory range.
1737 If you have doubts about the BIOS (e.g. suspend/resume does
1738 not work or there's kernel crashes after certain hardware
1739 hotplug events) then you might want to enable
1740 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1741 typical corruption patterns.
1743 Leave this to the default value of 64 if you are unsure.
1745 config MATH_EMULATION
1747 depends on MODIFY_LDT_SYSCALL
1748 prompt "Math emulation" if X86_32
1750 Linux can emulate a math coprocessor (used for floating point
1751 operations) if you don't have one. 486DX and Pentium processors have
1752 a math coprocessor built in, 486SX and 386 do not, unless you added
1753 a 487DX or 387, respectively. (The messages during boot time can
1754 give you some hints here ["man dmesg"].) Everyone needs either a
1755 coprocessor or this emulation.
1757 If you don't have a math coprocessor, you need to say Y here; if you
1758 say Y here even though you have a coprocessor, the coprocessor will
1759 be used nevertheless. (This behavior can be changed with the kernel
1760 command line option "no387", which comes handy if your coprocessor
1761 is broken. Try "man bootparam" or see the documentation of your boot
1762 loader (lilo or loadlin) about how to pass options to the kernel at
1763 boot time.) This means that it is a good idea to say Y here if you
1764 intend to use this kernel on different machines.
1766 More information about the internals of the Linux math coprocessor
1767 emulation can be found in <file:arch/x86/math-emu/README>.
1769 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1770 kernel, it won't hurt.
1774 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1776 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1777 the Memory Type Range Registers (MTRRs) may be used to control
1778 processor access to memory ranges. This is most useful if you have
1779 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1780 allows bus write transfers to be combined into a larger transfer
1781 before bursting over the PCI/AGP bus. This can increase performance
1782 of image write operations 2.5 times or more. Saying Y here creates a
1783 /proc/mtrr file which may be used to manipulate your processor's
1784 MTRRs. Typically the X server should use this.
1786 This code has a reasonably generic interface so that similar
1787 control registers on other processors can be easily supported
1790 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1791 Registers (ARRs) which provide a similar functionality to MTRRs. For
1792 these, the ARRs are used to emulate the MTRRs.
1793 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1794 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1795 write-combining. All of these processors are supported by this code
1796 and it makes sense to say Y here if you have one of them.
1798 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1799 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1800 can lead to all sorts of problems, so it's good to say Y here.
1802 You can safely say Y even if your machine doesn't have MTRRs, you'll
1803 just add about 9 KB to your kernel.
1805 See <file:Documentation/x86/mtrr.rst> for more information.
1807 config MTRR_SANITIZER
1809 prompt "MTRR cleanup support"
1812 Convert MTRR layout from continuous to discrete, so X drivers can
1813 add writeback entries.
1815 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1816 The largest mtrr entry size for a continuous block can be set with
1821 config MTRR_SANITIZER_ENABLE_DEFAULT
1822 int "MTRR cleanup enable value (0-1)"
1825 depends on MTRR_SANITIZER
1827 Enable mtrr cleanup default value
1829 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1830 int "MTRR cleanup spare reg num (0-7)"
1833 depends on MTRR_SANITIZER
1835 mtrr cleanup spare entries default, it can be changed via
1836 mtrr_spare_reg_nr=N on the kernel command line.
1840 prompt "x86 PAT support" if EXPERT
1843 Use PAT attributes to setup page level cache control.
1845 PATs are the modern equivalents of MTRRs and are much more
1846 flexible than MTRRs.
1848 Say N here if you see bootup problems (boot crash, boot hang,
1849 spontaneous reboots) or a non-working video driver.
1853 config ARCH_USES_PG_UNCACHED
1859 prompt "x86 architectural random number generator" if EXPERT
1861 Enable the x86 architectural RDRAND instruction
1862 (Intel Bull Mountain technology) to generate random numbers.
1863 If supported, this is a high bandwidth, cryptographically
1864 secure hardware random number generator.
1868 prompt "Supervisor Mode Access Prevention" if EXPERT
1870 Supervisor Mode Access Prevention (SMAP) is a security
1871 feature in newer Intel processors. There is a small
1872 performance cost if this enabled and turned on; there is
1873 also a small increase in the kernel size if this is enabled.
1877 config X86_INTEL_UMIP
1879 depends on CPU_SUP_INTEL
1880 prompt "Intel User Mode Instruction Prevention" if EXPERT
1882 The User Mode Instruction Prevention (UMIP) is a security
1883 feature in newer Intel processors. If enabled, a general
1884 protection fault is issued if the SGDT, SLDT, SIDT, SMSW
1885 or STR instructions are executed in user mode. These instructions
1886 unnecessarily expose information about the hardware state.
1888 The vast majority of applications do not use these instructions.
1889 For the very few that do, software emulation is provided in
1890 specific cases in protected and virtual-8086 modes. Emulated
1893 config X86_INTEL_MPX
1894 prompt "Intel MPX (Memory Protection Extensions)"
1896 # Note: only available in 64-bit mode due to VMA flags shortage
1897 depends on CPU_SUP_INTEL && X86_64
1898 select ARCH_USES_HIGH_VMA_FLAGS
1900 MPX provides hardware features that can be used in
1901 conjunction with compiler-instrumented code to check
1902 memory references. It is designed to detect buffer
1903 overflow or underflow bugs.
1905 This option enables running applications which are
1906 instrumented or otherwise use MPX. It does not use MPX
1907 itself inside the kernel or to protect the kernel
1908 against bad memory references.
1910 Enabling this option will make the kernel larger:
1911 ~8k of kernel text and 36 bytes of data on a 64-bit
1912 defconfig. It adds a long to the 'mm_struct' which
1913 will increase the kernel memory overhead of each
1914 process and adds some branches to paths used during
1915 exec() and munmap().
1917 For details, see Documentation/x86/intel_mpx.rst
1921 config X86_INTEL_MEMORY_PROTECTION_KEYS
1922 prompt "Intel Memory Protection Keys"
1924 # Note: only available in 64-bit mode
1925 depends on CPU_SUP_INTEL && X86_64
1926 select ARCH_USES_HIGH_VMA_FLAGS
1927 select ARCH_HAS_PKEYS
1929 Memory Protection Keys provides a mechanism for enforcing
1930 page-based protections, but without requiring modification of the
1931 page tables when an application changes protection domains.
1933 For details, see Documentation/core-api/protection-keys.rst
1938 bool "EFI runtime service support"
1941 select EFI_RUNTIME_WRAPPERS
1943 This enables the kernel to use EFI runtime services that are
1944 available (such as the EFI variable services).
1946 This option is only useful on systems that have EFI firmware.
1947 In addition, you should use the latest ELILO loader available
1948 at <http://elilo.sourceforge.net> in order to take advantage
1949 of EFI runtime services. However, even with this option, the
1950 resultant kernel should continue to boot on existing non-EFI
1954 bool "EFI stub support"
1955 depends on EFI && !X86_USE_3DNOW
1958 This kernel feature allows a bzImage to be loaded directly
1959 by EFI firmware without the use of a bootloader.
1961 See Documentation/efi-stub.txt for more information.
1964 bool "EFI mixed-mode support"
1965 depends on EFI_STUB && X86_64
1967 Enabling this feature allows a 64-bit kernel to be booted
1968 on a 32-bit firmware, provided that your CPU supports 64-bit
1971 Note that it is not possible to boot a mixed-mode enabled
1972 kernel via the EFI boot stub - a bootloader that supports
1973 the EFI handover protocol must be used.
1979 prompt "Enable seccomp to safely compute untrusted bytecode"
1981 This kernel feature is useful for number crunching applications
1982 that may need to compute untrusted bytecode during their
1983 execution. By using pipes or other transports made available to
1984 the process as file descriptors supporting the read/write
1985 syscalls, it's possible to isolate those applications in
1986 their own address space using seccomp. Once seccomp is
1987 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1988 and the task is only allowed to execute a few safe syscalls
1989 defined by each seccomp mode.
1991 If unsure, say Y. Only embedded should say N here.
1993 source "kernel/Kconfig.hz"
1996 bool "kexec system call"
1999 kexec is a system call that implements the ability to shutdown your
2000 current kernel, and to start another kernel. It is like a reboot
2001 but it is independent of the system firmware. And like a reboot
2002 you can start any kernel with it, not just Linux.
2004 The name comes from the similarity to the exec system call.
2006 It is an ongoing process to be certain the hardware in a machine
2007 is properly shutdown, so do not be surprised if this code does not
2008 initially work for you. As of this writing the exact hardware
2009 interface is strongly in flux, so no good recommendation can be
2013 bool "kexec file based system call"
2018 depends on CRYPTO_SHA256=y
2020 This is new version of kexec system call. This system call is
2021 file based and takes file descriptors as system call argument
2022 for kernel and initramfs as opposed to list of segments as
2023 accepted by previous system call.
2025 config ARCH_HAS_KEXEC_PURGATORY
2028 config KEXEC_VERIFY_SIG
2029 bool "Verify kernel signature during kexec_file_load() syscall"
2030 depends on KEXEC_FILE
2032 This option makes kernel signature verification mandatory for
2033 the kexec_file_load() syscall.
2035 In addition to that option, you need to enable signature
2036 verification for the corresponding kernel image type being
2037 loaded in order for this to work.
2039 config KEXEC_BZIMAGE_VERIFY_SIG
2040 bool "Enable bzImage signature verification support"
2041 depends on KEXEC_VERIFY_SIG
2042 depends on SIGNED_PE_FILE_VERIFICATION
2043 select SYSTEM_TRUSTED_KEYRING
2045 Enable bzImage signature verification support.
2048 bool "kernel crash dumps"
2049 depends on X86_64 || (X86_32 && HIGHMEM)
2051 Generate crash dump after being started by kexec.
2052 This should be normally only set in special crash dump kernels
2053 which are loaded in the main kernel with kexec-tools into
2054 a specially reserved region and then later executed after
2055 a crash by kdump/kexec. The crash dump kernel must be compiled
2056 to a memory address not used by the main kernel or BIOS using
2057 PHYSICAL_START, or it must be built as a relocatable image
2058 (CONFIG_RELOCATABLE=y).
2059 For more details see Documentation/kdump/kdump.rst
2063 depends on KEXEC && HIBERNATION
2065 Jump between original kernel and kexeced kernel and invoke
2066 code in physical address mode via KEXEC
2068 config PHYSICAL_START
2069 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2072 This gives the physical address where the kernel is loaded.
2074 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2075 bzImage will decompress itself to above physical address and
2076 run from there. Otherwise, bzImage will run from the address where
2077 it has been loaded by the boot loader and will ignore above physical
2080 In normal kdump cases one does not have to set/change this option
2081 as now bzImage can be compiled as a completely relocatable image
2082 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2083 address. This option is mainly useful for the folks who don't want
2084 to use a bzImage for capturing the crash dump and want to use a
2085 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2086 to be specifically compiled to run from a specific memory area
2087 (normally a reserved region) and this option comes handy.
2089 So if you are using bzImage for capturing the crash dump,
2090 leave the value here unchanged to 0x1000000 and set
2091 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2092 for capturing the crash dump change this value to start of
2093 the reserved region. In other words, it can be set based on
2094 the "X" value as specified in the "crashkernel=YM@XM"
2095 command line boot parameter passed to the panic-ed
2096 kernel. Please take a look at Documentation/kdump/kdump.rst
2097 for more details about crash dumps.
2099 Usage of bzImage for capturing the crash dump is recommended as
2100 one does not have to build two kernels. Same kernel can be used
2101 as production kernel and capture kernel. Above option should have
2102 gone away after relocatable bzImage support is introduced. But it
2103 is present because there are users out there who continue to use
2104 vmlinux for dump capture. This option should go away down the
2107 Don't change this unless you know what you are doing.
2110 bool "Build a relocatable kernel"
2113 This builds a kernel image that retains relocation information
2114 so it can be loaded someplace besides the default 1MB.
2115 The relocations tend to make the kernel binary about 10% larger,
2116 but are discarded at runtime.
2118 One use is for the kexec on panic case where the recovery kernel
2119 must live at a different physical address than the primary
2122 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2123 it has been loaded at and the compile time physical address
2124 (CONFIG_PHYSICAL_START) is used as the minimum location.
2126 config RANDOMIZE_BASE
2127 bool "Randomize the address of the kernel image (KASLR)"
2128 depends on RELOCATABLE
2131 In support of Kernel Address Space Layout Randomization (KASLR),
2132 this randomizes the physical address at which the kernel image
2133 is decompressed and the virtual address where the kernel
2134 image is mapped, as a security feature that deters exploit
2135 attempts relying on knowledge of the location of kernel
2138 On 64-bit, the kernel physical and virtual addresses are
2139 randomized separately. The physical address will be anywhere
2140 between 16MB and the top of physical memory (up to 64TB). The
2141 virtual address will be randomized from 16MB up to 1GB (9 bits
2142 of entropy). Note that this also reduces the memory space
2143 available to kernel modules from 1.5GB to 1GB.
2145 On 32-bit, the kernel physical and virtual addresses are
2146 randomized together. They will be randomized from 16MB up to
2147 512MB (8 bits of entropy).
2149 Entropy is generated using the RDRAND instruction if it is
2150 supported. If RDTSC is supported, its value is mixed into
2151 the entropy pool as well. If neither RDRAND nor RDTSC are
2152 supported, then entropy is read from the i8254 timer. The
2153 usable entropy is limited by the kernel being built using
2154 2GB addressing, and that PHYSICAL_ALIGN must be at a
2155 minimum of 2MB. As a result, only 10 bits of entropy are
2156 theoretically possible, but the implementations are further
2157 limited due to memory layouts.
2161 # Relocation on x86 needs some additional build support
2162 config X86_NEED_RELOCS
2164 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2166 config PHYSICAL_ALIGN
2167 hex "Alignment value to which kernel should be aligned"
2169 range 0x2000 0x1000000 if X86_32
2170 range 0x200000 0x1000000 if X86_64
2172 This value puts the alignment restrictions on physical address
2173 where kernel is loaded and run from. Kernel is compiled for an
2174 address which meets above alignment restriction.
2176 If bootloader loads the kernel at a non-aligned address and
2177 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2178 address aligned to above value and run from there.
2180 If bootloader loads the kernel at a non-aligned address and
2181 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2182 load address and decompress itself to the address it has been
2183 compiled for and run from there. The address for which kernel is
2184 compiled already meets above alignment restrictions. Hence the
2185 end result is that kernel runs from a physical address meeting
2186 above alignment restrictions.
2188 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2189 this value must be a multiple of 0x200000.
2191 Don't change this unless you know what you are doing.
2193 config DYNAMIC_MEMORY_LAYOUT
2196 This option makes base addresses of vmalloc and vmemmap as well as
2197 __PAGE_OFFSET movable during boot.
2199 config RANDOMIZE_MEMORY
2200 bool "Randomize the kernel memory sections"
2202 depends on RANDOMIZE_BASE
2203 select DYNAMIC_MEMORY_LAYOUT
2204 default RANDOMIZE_BASE
2206 Randomizes the base virtual address of kernel memory sections
2207 (physical memory mapping, vmalloc & vmemmap). This security feature
2208 makes exploits relying on predictable memory locations less reliable.
2210 The order of allocations remains unchanged. Entropy is generated in
2211 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2212 configuration have in average 30,000 different possible virtual
2213 addresses for each memory section.
2217 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2218 hex "Physical memory mapping padding" if EXPERT
2219 depends on RANDOMIZE_MEMORY
2220 default "0xa" if MEMORY_HOTPLUG
2222 range 0x1 0x40 if MEMORY_HOTPLUG
2225 Define the padding in terabytes added to the existing physical
2226 memory size during kernel memory randomization. It is useful
2227 for memory hotplug support but reduces the entropy available for
2228 address randomization.
2230 If unsure, leave at the default value.
2236 config BOOTPARAM_HOTPLUG_CPU0
2237 bool "Set default setting of cpu0_hotpluggable"
2238 depends on HOTPLUG_CPU
2240 Set whether default state of cpu0_hotpluggable is on or off.
2242 Say Y here to enable CPU0 hotplug by default. If this switch
2243 is turned on, there is no need to give cpu0_hotplug kernel
2244 parameter and the CPU0 hotplug feature is enabled by default.
2246 Please note: there are two known CPU0 dependencies if you want
2247 to enable the CPU0 hotplug feature either by this switch or by
2248 cpu0_hotplug kernel parameter.
2250 First, resume from hibernate or suspend always starts from CPU0.
2251 So hibernate and suspend are prevented if CPU0 is offline.
2253 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2254 offline if any interrupt can not migrate out of CPU0. There may
2255 be other CPU0 dependencies.
2257 Please make sure the dependencies are under your control before
2258 you enable this feature.
2260 Say N if you don't want to enable CPU0 hotplug feature by default.
2261 You still can enable the CPU0 hotplug feature at boot by kernel
2262 parameter cpu0_hotplug.
2264 config DEBUG_HOTPLUG_CPU0
2266 prompt "Debug CPU0 hotplug"
2267 depends on HOTPLUG_CPU
2269 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2270 soon as possible and boots up userspace with CPU0 offlined. User
2271 can online CPU0 back after boot time.
2273 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2274 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2275 compilation or giving cpu0_hotplug kernel parameter at boot.
2281 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2282 depends on COMPAT_32
2284 Certain buggy versions of glibc will crash if they are
2285 presented with a 32-bit vDSO that is not mapped at the address
2286 indicated in its segment table.
2288 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2289 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2290 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2291 the only released version with the bug, but OpenSUSE 9
2292 contains a buggy "glibc 2.3.2".
2294 The symptom of the bug is that everything crashes on startup, saying:
2295 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2297 Saying Y here changes the default value of the vdso32 boot
2298 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2299 This works around the glibc bug but hurts performance.
2301 If unsure, say N: if you are compiling your own kernel, you
2302 are unlikely to be using a buggy version of glibc.
2305 prompt "vsyscall table for legacy applications"
2307 default LEGACY_VSYSCALL_XONLY
2309 Legacy user code that does not know how to find the vDSO expects
2310 to be able to issue three syscalls by calling fixed addresses in
2311 kernel space. Since this location is not randomized with ASLR,
2312 it can be used to assist security vulnerability exploitation.
2314 This setting can be changed at boot time via the kernel command
2315 line parameter vsyscall=[emulate|xonly|none].
2317 On a system with recent enough glibc (2.14 or newer) and no
2318 static binaries, you can say None without a performance penalty
2319 to improve security.
2321 If unsure, select "Emulate execution only".
2323 config LEGACY_VSYSCALL_EMULATE
2324 bool "Full emulation"
2326 The kernel traps and emulates calls into the fixed vsyscall
2327 address mapping. This makes the mapping non-executable, but
2328 it still contains readable known contents, which could be
2329 used in certain rare security vulnerability exploits. This
2330 configuration is recommended when using legacy userspace
2331 that still uses vsyscalls along with legacy binary
2332 instrumentation tools that require code to be readable.
2334 An example of this type of legacy userspace is running
2335 Pin on an old binary that still uses vsyscalls.
2337 config LEGACY_VSYSCALL_XONLY
2338 bool "Emulate execution only"
2340 The kernel traps and emulates calls into the fixed vsyscall
2341 address mapping and does not allow reads. This
2342 configuration is recommended when userspace might use the
2343 legacy vsyscall area but support for legacy binary
2344 instrumentation of legacy code is not needed. It mitigates
2345 certain uses of the vsyscall area as an ASLR-bypassing
2348 config LEGACY_VSYSCALL_NONE
2351 There will be no vsyscall mapping at all. This will
2352 eliminate any risk of ASLR bypass due to the vsyscall
2353 fixed address mapping. Attempts to use the vsyscalls
2354 will be reported to dmesg, so that either old or
2355 malicious userspace programs can be identified.
2360 bool "Built-in kernel command line"
2362 Allow for specifying boot arguments to the kernel at
2363 build time. On some systems (e.g. embedded ones), it is
2364 necessary or convenient to provide some or all of the
2365 kernel boot arguments with the kernel itself (that is,
2366 to not rely on the boot loader to provide them.)
2368 To compile command line arguments into the kernel,
2369 set this option to 'Y', then fill in the
2370 boot arguments in CONFIG_CMDLINE.
2372 Systems with fully functional boot loaders (i.e. non-embedded)
2373 should leave this option set to 'N'.
2376 string "Built-in kernel command string"
2377 depends on CMDLINE_BOOL
2380 Enter arguments here that should be compiled into the kernel
2381 image and used at boot time. If the boot loader provides a
2382 command line at boot time, it is appended to this string to
2383 form the full kernel command line, when the system boots.
2385 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2386 change this behavior.
2388 In most cases, the command line (whether built-in or provided
2389 by the boot loader) should specify the device for the root
2392 config CMDLINE_OVERRIDE
2393 bool "Built-in command line overrides boot loader arguments"
2394 depends on CMDLINE_BOOL
2396 Set this option to 'Y' to have the kernel ignore the boot loader
2397 command line, and use ONLY the built-in command line.
2399 This is used to work around broken boot loaders. This should
2400 be set to 'N' under normal conditions.
2402 config MODIFY_LDT_SYSCALL
2403 bool "Enable the LDT (local descriptor table)" if EXPERT
2406 Linux can allow user programs to install a per-process x86
2407 Local Descriptor Table (LDT) using the modify_ldt(2) system
2408 call. This is required to run 16-bit or segmented code such as
2409 DOSEMU or some Wine programs. It is also used by some very old
2410 threading libraries.
2412 Enabling this feature adds a small amount of overhead to
2413 context switches and increases the low-level kernel attack
2414 surface. Disabling it removes the modify_ldt(2) system call.
2416 Saying 'N' here may make sense for embedded or server kernels.
2418 source "kernel/livepatch/Kconfig"
2422 config ARCH_HAS_ADD_PAGES
2424 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2426 config ARCH_ENABLE_MEMORY_HOTPLUG
2428 depends on X86_64 || (X86_32 && HIGHMEM)
2430 config ARCH_ENABLE_MEMORY_HOTREMOVE
2432 depends on MEMORY_HOTPLUG
2434 config USE_PERCPU_NUMA_NODE_ID
2438 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2440 depends on X86_64 || X86_PAE
2442 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2444 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2446 config ARCH_ENABLE_THP_MIGRATION
2448 depends on X86_64 && TRANSPARENT_HUGEPAGE
2450 menu "Power management and ACPI options"
2452 config ARCH_HIBERNATION_HEADER
2454 depends on HIBERNATION
2456 source "kernel/power/Kconfig"
2458 source "drivers/acpi/Kconfig"
2460 source "drivers/sfi/Kconfig"
2467 tristate "APM (Advanced Power Management) BIOS support"
2468 depends on X86_32 && PM_SLEEP
2470 APM is a BIOS specification for saving power using several different
2471 techniques. This is mostly useful for battery powered laptops with
2472 APM compliant BIOSes. If you say Y here, the system time will be
2473 reset after a RESUME operation, the /proc/apm device will provide
2474 battery status information, and user-space programs will receive
2475 notification of APM "events" (e.g. battery status change).
2477 If you select "Y" here, you can disable actual use of the APM
2478 BIOS by passing the "apm=off" option to the kernel at boot time.
2480 Note that the APM support is almost completely disabled for
2481 machines with more than one CPU.
2483 In order to use APM, you will need supporting software. For location
2484 and more information, read <file:Documentation/power/apm-acpi.txt>
2485 and the Battery Powered Linux mini-HOWTO, available from
2486 <http://www.tldp.org/docs.html#howto>.
2488 This driver does not spin down disk drives (see the hdparm(8)
2489 manpage ("man 8 hdparm") for that), and it doesn't turn off
2490 VESA-compliant "green" monitors.
2492 This driver does not support the TI 4000M TravelMate and the ACER
2493 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2494 desktop machines also don't have compliant BIOSes, and this driver
2495 may cause those machines to panic during the boot phase.
2497 Generally, if you don't have a battery in your machine, there isn't
2498 much point in using this driver and you should say N. If you get
2499 random kernel OOPSes or reboots that don't seem to be related to
2500 anything, try disabling/enabling this option (or disabling/enabling
2503 Some other things you should try when experiencing seemingly random,
2506 1) make sure that you have enough swap space and that it is
2508 2) pass the "no-hlt" option to the kernel
2509 3) switch on floating point emulation in the kernel and pass
2510 the "no387" option to the kernel
2511 4) pass the "floppy=nodma" option to the kernel
2512 5) pass the "mem=4M" option to the kernel (thereby disabling
2513 all but the first 4 MB of RAM)
2514 6) make sure that the CPU is not over clocked.
2515 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2516 8) disable the cache from your BIOS settings
2517 9) install a fan for the video card or exchange video RAM
2518 10) install a better fan for the CPU
2519 11) exchange RAM chips
2520 12) exchange the motherboard.
2522 To compile this driver as a module, choose M here: the
2523 module will be called apm.
2527 config APM_IGNORE_USER_SUSPEND
2528 bool "Ignore USER SUSPEND"
2530 This option will ignore USER SUSPEND requests. On machines with a
2531 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2532 series notebooks, it is necessary to say Y because of a BIOS bug.
2534 config APM_DO_ENABLE
2535 bool "Enable PM at boot time"
2537 Enable APM features at boot time. From page 36 of the APM BIOS
2538 specification: "When disabled, the APM BIOS does not automatically
2539 power manage devices, enter the Standby State, enter the Suspend
2540 State, or take power saving steps in response to CPU Idle calls."
2541 This driver will make CPU Idle calls when Linux is idle (unless this
2542 feature is turned off -- see "Do CPU IDLE calls", below). This
2543 should always save battery power, but more complicated APM features
2544 will be dependent on your BIOS implementation. You may need to turn
2545 this option off if your computer hangs at boot time when using APM
2546 support, or if it beeps continuously instead of suspending. Turn
2547 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2548 T400CDT. This is off by default since most machines do fine without
2553 bool "Make CPU Idle calls when idle"
2555 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2556 On some machines, this can activate improved power savings, such as
2557 a slowed CPU clock rate, when the machine is idle. These idle calls
2558 are made after the idle loop has run for some length of time (e.g.,
2559 333 mS). On some machines, this will cause a hang at boot time or
2560 whenever the CPU becomes idle. (On machines with more than one CPU,
2561 this option does nothing.)
2563 config APM_DISPLAY_BLANK
2564 bool "Enable console blanking using APM"
2566 Enable console blanking using the APM. Some laptops can use this to
2567 turn off the LCD backlight when the screen blanker of the Linux
2568 virtual console blanks the screen. Note that this is only used by
2569 the virtual console screen blanker, and won't turn off the backlight
2570 when using the X Window system. This also doesn't have anything to
2571 do with your VESA-compliant power-saving monitor. Further, this
2572 option doesn't work for all laptops -- it might not turn off your
2573 backlight at all, or it might print a lot of errors to the console,
2574 especially if you are using gpm.
2576 config APM_ALLOW_INTS
2577 bool "Allow interrupts during APM BIOS calls"
2579 Normally we disable external interrupts while we are making calls to
2580 the APM BIOS as a measure to lessen the effects of a badly behaving
2581 BIOS implementation. The BIOS should reenable interrupts if it
2582 needs to. Unfortunately, some BIOSes do not -- especially those in
2583 many of the newer IBM Thinkpads. If you experience hangs when you
2584 suspend, try setting this to Y. Otherwise, say N.
2588 source "drivers/cpufreq/Kconfig"
2590 source "drivers/cpuidle/Kconfig"
2592 source "drivers/idle/Kconfig"
2597 menu "Bus options (PCI etc.)"
2600 prompt "PCI access mode"
2601 depends on X86_32 && PCI
2604 On PCI systems, the BIOS can be used to detect the PCI devices and
2605 determine their configuration. However, some old PCI motherboards
2606 have BIOS bugs and may crash if this is done. Also, some embedded
2607 PCI-based systems don't have any BIOS at all. Linux can also try to
2608 detect the PCI hardware directly without using the BIOS.
2610 With this option, you can specify how Linux should detect the
2611 PCI devices. If you choose "BIOS", the BIOS will be used,
2612 if you choose "Direct", the BIOS won't be used, and if you
2613 choose "MMConfig", then PCI Express MMCONFIG will be used.
2614 If you choose "Any", the kernel will try MMCONFIG, then the
2615 direct access method and falls back to the BIOS if that doesn't
2616 work. If unsure, go with the default, which is "Any".
2621 config PCI_GOMMCONFIG
2638 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2640 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2643 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2646 bool "Support mmconfig PCI config space access" if X86_64
2648 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2649 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2653 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2657 depends on PCI && XEN
2660 config MMCONF_FAM10H
2662 depends on X86_64 && PCI_MMCONFIG && ACPI
2664 config PCI_CNB20LE_QUIRK
2665 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2668 Read the PCI windows out of the CNB20LE host bridge. This allows
2669 PCI hotplug to work on systems with the CNB20LE chipset which do
2672 There's no public spec for this chipset, and this functionality
2673 is known to be incomplete.
2675 You should say N unless you know you need this.
2678 bool "ISA bus support on modern systems" if EXPERT
2680 Expose ISA bus device drivers and options available for selection and
2681 configuration. Enable this option if your target machine has an ISA
2682 bus. ISA is an older system, displaced by PCI and newer bus
2683 architectures -- if your target machine is modern, it probably does
2684 not have an ISA bus.
2688 # x86_64 have no ISA slots, but can have ISA-style DMA.
2690 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2693 Enables ISA-style DMA support for devices requiring such controllers.
2701 Find out whether you have ISA slots on your motherboard. ISA is the
2702 name of a bus system, i.e. the way the CPU talks to the other stuff
2703 inside your box. Other bus systems are PCI, EISA, MicroChannel
2704 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2705 newer boards don't support it. If you have ISA, say Y, otherwise N.
2708 tristate "NatSemi SCx200 support"
2710 This provides basic support for National Semiconductor's
2711 (now AMD's) Geode processors. The driver probes for the
2712 PCI-IDs of several on-chip devices, so its a good dependency
2713 for other scx200_* drivers.
2715 If compiled as a module, the driver is named scx200.
2717 config SCx200HR_TIMER
2718 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2722 This driver provides a clocksource built upon the on-chip
2723 27MHz high-resolution timer. Its also a workaround for
2724 NSC Geode SC-1100's buggy TSC, which loses time when the
2725 processor goes idle (as is done by the scheduler). The
2726 other workaround is idle=poll boot option.
2729 bool "One Laptop Per Child support"
2736 Add support for detecting the unique features of the OLPC
2740 bool "OLPC XO-1 Power Management"
2741 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2743 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2746 bool "OLPC XO-1 Real Time Clock"
2747 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2749 Add support for the XO-1 real time clock, which can be used as a
2750 programmable wakeup source.
2753 bool "OLPC XO-1 SCI extras"
2754 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2758 Add support for SCI-based features of the OLPC XO-1 laptop:
2759 - EC-driven system wakeups
2763 - AC adapter status updates
2764 - Battery status updates
2766 config OLPC_XO15_SCI
2767 bool "OLPC XO-1.5 SCI extras"
2768 depends on OLPC && ACPI
2771 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2772 - EC-driven system wakeups
2773 - AC adapter status updates
2774 - Battery status updates
2777 bool "PCEngines ALIX System Support (LED setup)"
2780 This option enables system support for the PCEngines ALIX.
2781 At present this just sets up LEDs for GPIO control on
2782 ALIX2/3/6 boards. However, other system specific setup should
2785 Note: You must still enable the drivers for GPIO and LED support
2786 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2788 Note: You have to set alix.force=1 for boards with Award BIOS.
2791 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2794 This option enables system support for the Soekris Engineering net5501.
2797 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2801 This option enables system support for the Traverse Technologies GEOS.
2804 bool "Technologic Systems TS-5500 platform support"
2806 select CHECK_SIGNATURE
2810 This option enables system support for the Technologic Systems TS-5500.
2816 depends on CPU_SUP_AMD && PCI
2819 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2821 Firmwares often provide initial graphics framebuffers so the BIOS,
2822 bootloader or kernel can show basic video-output during boot for
2823 user-guidance and debugging. Historically, x86 used the VESA BIOS
2824 Extensions and EFI-framebuffers for this, which are mostly limited
2826 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2827 framebuffers so the new generic system-framebuffer drivers can be
2828 used on x86. If the framebuffer is not compatible with the generic
2829 modes, it is advertised as fallback platform framebuffer so legacy
2830 drivers like efifb, vesafb and uvesafb can pick it up.
2831 If this option is not selected, all system framebuffers are always
2832 marked as fallback platform framebuffers as usual.
2834 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2835 not be able to pick up generic system framebuffers if this option
2836 is selected. You are highly encouraged to enable simplefb as
2837 replacement if you select this option. simplefb can correctly deal
2838 with generic system framebuffers. But you should still keep vesafb
2839 and others enabled as fallback if a system framebuffer is
2840 incompatible with simplefb.
2847 menu "Binary Emulations"
2849 config IA32_EMULATION
2850 bool "IA32 Emulation"
2852 select ARCH_WANT_OLD_COMPAT_IPC
2854 select COMPAT_BINFMT_ELF
2855 select COMPAT_OLD_SIGACTION
2857 Include code to run legacy 32-bit programs under a
2858 64-bit kernel. You should likely turn this on, unless you're
2859 100% sure that you don't have any 32-bit programs left.
2862 tristate "IA32 a.out support"
2863 depends on IA32_EMULATION
2866 Support old a.out binaries in the 32bit emulation.
2869 bool "x32 ABI for 64-bit mode"
2872 Include code to run binaries for the x32 native 32-bit ABI
2873 for 64-bit processors. An x32 process gets access to the
2874 full 64-bit register file and wide data path while leaving
2875 pointers at 32 bits for smaller memory footprint.
2877 You will need a recent binutils (2.22 or later) with
2878 elf32_x86_64 support enabled to compile a kernel with this
2883 depends on IA32_EMULATION || X86_32
2885 select OLD_SIGSUSPEND3
2889 depends on IA32_EMULATION || X86_X32
2892 config COMPAT_FOR_U64_ALIGNMENT
2895 config SYSVIPC_COMPAT
2903 config HAVE_ATOMIC_IOMAP
2907 config X86_DEV_DMA_OPS
2910 config HAVE_GENERIC_GUP
2913 source "drivers/firmware/Kconfig"
2915 source "arch/x86/kvm/Kconfig"