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 if CC_HAS_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_MEM_ENCRYPT
72 select ARCH_HAS_MEMBARRIER_SYNC_CORE
73 select ARCH_HAS_PMEM_API if X86_64
74 select ARCH_HAS_PTE_DEVMAP if X86_64
75 select ARCH_HAS_PTE_SPECIAL
76 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
77 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
78 select ARCH_HAS_SET_MEMORY
79 select ARCH_HAS_SET_DIRECT_MAP
80 select ARCH_HAS_STRICT_KERNEL_RWX
81 select ARCH_HAS_STRICT_MODULE_RWX
82 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
83 select ARCH_HAS_UBSAN_SANITIZE_ALL
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_WANT_DEFAULT_BPF_JIT if X86_64
97 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
98 select ARCH_WANT_HUGE_PMD_SHARE
99 select ARCH_WANTS_THP_SWAP if X86_64
100 select BUILDTIME_TABLE_SORT
102 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
103 select CLOCKSOURCE_WATCHDOG
104 select DCACHE_WORD_ACCESS
105 select EDAC_ATOMIC_SCRUB
107 select GENERIC_CLOCKEVENTS
108 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
109 select GENERIC_CLOCKEVENTS_MIN_ADJUST
110 select GENERIC_CMOS_UPDATE
111 select GENERIC_CPU_AUTOPROBE
112 select GENERIC_CPU_VULNERABILITIES
113 select GENERIC_EARLY_IOREMAP
114 select GENERIC_FIND_FIRST_BIT
116 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
117 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
118 select GENERIC_IRQ_MIGRATION if SMP
119 select GENERIC_IRQ_PROBE
120 select GENERIC_IRQ_RESERVATION_MODE
121 select GENERIC_IRQ_SHOW
122 select GENERIC_PENDING_IRQ if SMP
123 select GENERIC_SMP_IDLE_THREAD
124 select GENERIC_STRNCPY_FROM_USER
125 select GENERIC_STRNLEN_USER
126 select GENERIC_TIME_VSYSCALL
127 select GENERIC_GETTIMEOFDAY
128 select GENERIC_VDSO_TIME_NS
129 select GUP_GET_PTE_LOW_HIGH if X86_PAE
130 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
131 select HAVE_ACPI_APEI if ACPI
132 select HAVE_ACPI_APEI_NMI if ACPI
133 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
134 select HAVE_ARCH_AUDITSYSCALL
135 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
136 select HAVE_ARCH_JUMP_LABEL
137 select HAVE_ARCH_JUMP_LABEL_RELATIVE
138 select HAVE_ARCH_KASAN if X86_64
139 select HAVE_ARCH_KASAN_VMALLOC if X86_64
140 select HAVE_ARCH_KGDB
141 select HAVE_ARCH_MMAP_RND_BITS if MMU
142 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
143 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
144 select HAVE_ARCH_PREL32_RELOCATIONS
145 select HAVE_ARCH_SECCOMP_FILTER
146 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
147 select HAVE_ARCH_STACKLEAK
148 select HAVE_ARCH_TRACEHOOK
149 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
150 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
151 select HAVE_ARCH_VMAP_STACK if X86_64
152 select HAVE_ARCH_WITHIN_STACK_FRAMES
153 select HAVE_ASM_MODVERSIONS
154 select HAVE_CMPXCHG_DOUBLE
155 select HAVE_CMPXCHG_LOCAL
156 select HAVE_CONTEXT_TRACKING if X86_64
157 select HAVE_COPY_THREAD_TLS
158 select HAVE_C_RECORDMCOUNT
159 select HAVE_DEBUG_KMEMLEAK
160 select HAVE_DMA_CONTIGUOUS
161 select HAVE_DYNAMIC_FTRACE
162 select HAVE_DYNAMIC_FTRACE_WITH_REGS
163 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
165 select HAVE_EFFICIENT_UNALIGNED_ACCESS
167 select HAVE_EXIT_THREAD
169 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
170 select HAVE_FTRACE_MCOUNT_RECORD
171 select HAVE_FUNCTION_GRAPH_TRACER
172 select HAVE_FUNCTION_TRACER
173 select HAVE_GCC_PLUGINS
174 select HAVE_HW_BREAKPOINT
176 select HAVE_IOREMAP_PROT
177 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
178 select HAVE_IRQ_TIME_ACCOUNTING
179 select HAVE_KERNEL_BZIP2
180 select HAVE_KERNEL_GZIP
181 select HAVE_KERNEL_LZ4
182 select HAVE_KERNEL_LZMA
183 select HAVE_KERNEL_LZO
184 select HAVE_KERNEL_XZ
186 select HAVE_KPROBES_ON_FTRACE
187 select HAVE_FUNCTION_ERROR_INJECTION
188 select HAVE_KRETPROBES
190 select HAVE_LIVEPATCH if X86_64
191 select HAVE_MEMBLOCK_NODE_MAP
192 select HAVE_MIXED_BREAKPOINTS_REGS
193 select HAVE_MOD_ARCH_SPECIFIC
197 select HAVE_OPTPROBES
198 select HAVE_PCSPKR_PLATFORM
199 select HAVE_PERF_EVENTS
200 select HAVE_PERF_EVENTS_NMI
201 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
203 select HAVE_PERF_REGS
204 select HAVE_PERF_USER_STACK_DUMP
205 select HAVE_RCU_TABLE_FREE if PARAVIRT
206 select HAVE_REGS_AND_STACK_ACCESS_API
207 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
208 select HAVE_FUNCTION_ARG_ACCESS_API
209 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
210 select HAVE_STACK_VALIDATION if X86_64
212 select HAVE_SYSCALL_TRACEPOINTS
213 select HAVE_UNSTABLE_SCHED_CLOCK
214 select HAVE_USER_RETURN_NOTIFIER
215 select HAVE_GENERIC_VDSO
216 select HOTPLUG_SMT if SMP
217 select IRQ_FORCED_THREADING
218 select NEED_SG_DMA_LENGTH
219 select PCI_DOMAINS if PCI
220 select PCI_LOCKLESS_CONFIG if PCI
223 select RTC_MC146818_LIB
226 select SYSCTL_EXCEPTION_TRACE
227 select THREAD_INFO_IN_TASK
228 select USER_STACKTRACE_SUPPORT
230 select X86_FEATURE_NAMES if PROC_FS
231 select PROC_PID_ARCH_STATUS if PROC_FS
233 config INSTRUCTION_DECODER
235 depends on KPROBES || PERF_EVENTS || UPROBES
239 default "elf32-i386" if X86_32
240 default "elf64-x86-64" if X86_64
242 config ARCH_DEFCONFIG
244 default "arch/x86/configs/i386_defconfig" if X86_32
245 default "arch/x86/configs/x86_64_defconfig" if X86_64
247 config LOCKDEP_SUPPORT
250 config STACKTRACE_SUPPORT
256 config ARCH_MMAP_RND_BITS_MIN
260 config ARCH_MMAP_RND_BITS_MAX
264 config ARCH_MMAP_RND_COMPAT_BITS_MIN
267 config ARCH_MMAP_RND_COMPAT_BITS_MAX
273 config GENERIC_ISA_DMA
275 depends on ISA_DMA_API
280 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
282 config GENERIC_BUG_RELATIVE_POINTERS
285 config ARCH_MAY_HAVE_PC_FDC
287 depends on ISA_DMA_API
289 config GENERIC_CALIBRATE_DELAY
292 config ARCH_HAS_CPU_RELAX
295 config ARCH_HAS_CACHE_LINE_SIZE
298 config ARCH_HAS_FILTER_PGPROT
301 config HAVE_SETUP_PER_CPU_AREA
304 config NEED_PER_CPU_EMBED_FIRST_CHUNK
307 config NEED_PER_CPU_PAGE_FIRST_CHUNK
310 config ARCH_HIBERNATION_POSSIBLE
313 config ARCH_SUSPEND_POSSIBLE
316 config ARCH_WANT_GENERAL_HUGETLB
325 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
328 config KASAN_SHADOW_OFFSET
331 default 0xdffffc0000000000
333 config HAVE_INTEL_TXT
335 depends on INTEL_IOMMU && ACPI
339 depends on X86_32 && SMP
343 depends on X86_64 && SMP
345 config X86_32_LAZY_GS
347 depends on X86_32 && !STACKPROTECTOR
349 config ARCH_SUPPORTS_UPROBES
352 config FIX_EARLYCON_MEM
355 config DYNAMIC_PHYSICAL_MASK
358 config PGTABLE_LEVELS
360 default 5 if X86_5LEVEL
365 config CC_HAS_SANE_STACKPROTECTOR
367 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
368 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
370 We have to make sure stack protector is unconditionally disabled if
371 the compiler produces broken code.
373 menu "Processor type and features"
376 bool "DMA memory allocation support" if EXPERT
379 DMA memory allocation support allows devices with less than 32-bit
380 addressing to allocate within the first 16MB of address space.
381 Disable if no such devices will be used.
386 bool "Symmetric multi-processing support"
388 This enables support for systems with more than one CPU. If you have
389 a system with only one CPU, say N. If you have a system with more
392 If you say N here, the kernel will run on uni- and multiprocessor
393 machines, but will use only one CPU of a multiprocessor machine. If
394 you say Y here, the kernel will run on many, but not all,
395 uniprocessor machines. On a uniprocessor machine, the kernel
396 will run faster if you say N here.
398 Note that if you say Y here and choose architecture "586" or
399 "Pentium" under "Processor family", the kernel will not work on 486
400 architectures. Similarly, multiprocessor kernels for the "PPro"
401 architecture may not work on all Pentium based boards.
403 People using multiprocessor machines who say Y here should also say
404 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
405 Management" code will be disabled if you say Y here.
407 See also <file:Documentation/x86/i386/IO-APIC.rst>,
408 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
409 <http://www.tldp.org/docs.html#howto>.
411 If you don't know what to do here, say N.
413 config X86_FEATURE_NAMES
414 bool "Processor feature human-readable names" if EMBEDDED
417 This option compiles in a table of x86 feature bits and corresponding
418 names. This is required to support /proc/cpuinfo and a few kernel
419 messages. You can disable this to save space, at the expense of
420 making those few kernel messages show numeric feature bits instead.
425 bool "Support x2apic"
426 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
428 This enables x2apic support on CPUs that have this feature.
430 This allows 32-bit apic IDs (so it can support very large systems),
431 and accesses the local apic via MSRs not via mmio.
433 If you don't know what to do here, say N.
436 bool "Enable MPS table" if ACPI || SFI
438 depends on X86_LOCAL_APIC
440 For old smp systems that do not have proper acpi support. Newer systems
441 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
445 depends on X86_GOLDFISH
448 bool "Avoid speculative indirect branches in kernel"
450 select STACK_VALIDATION if HAVE_STACK_VALIDATION
452 Compile kernel with the retpoline compiler options to guard against
453 kernel-to-user data leaks by avoiding speculative indirect
454 branches. Requires a compiler with -mindirect-branch=thunk-extern
455 support for full protection. The kernel may run slower.
457 config X86_CPU_RESCTRL
458 bool "x86 CPU resource control support"
459 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
461 select PROC_CPU_RESCTRL if PROC_FS
463 Enable x86 CPU resource control support.
465 Provide support for the allocation and monitoring of system resources
468 Intel calls this Intel Resource Director Technology
469 (Intel(R) RDT). More information about RDT can be found in the
470 Intel x86 Architecture Software Developer Manual.
472 AMD calls this AMD Platform Quality of Service (AMD QoS).
473 More information about AMD QoS can be found in the AMD64 Technology
474 Platform Quality of Service Extensions manual.
480 bool "Support for big SMP systems with more than 8 CPUs"
483 This option is needed for the systems that have more than 8 CPUs.
485 config X86_EXTENDED_PLATFORM
486 bool "Support for extended (non-PC) x86 platforms"
489 If you disable this option then the kernel will only support
490 standard PC platforms. (which covers the vast majority of
493 If you enable this option then you'll be able to select support
494 for the following (non-PC) 32 bit x86 platforms:
495 Goldfish (Android emulator)
498 SGI 320/540 (Visual Workstation)
499 STA2X11-based (e.g. Northville)
500 Moorestown MID devices
502 If you have one of these systems, or if you want to build a
503 generic distribution kernel, say Y here - otherwise say N.
507 config X86_EXTENDED_PLATFORM
508 bool "Support for extended (non-PC) x86 platforms"
511 If you disable this option then the kernel will only support
512 standard PC platforms. (which covers the vast majority of
515 If you enable this option then you'll be able to select support
516 for the following (non-PC) 64 bit x86 platforms:
521 If you have one of these systems, or if you want to build a
522 generic distribution kernel, say Y here - otherwise say N.
524 # This is an alphabetically sorted list of 64 bit extended platforms
525 # Please maintain the alphabetic order if and when there are additions
527 bool "Numascale NumaChip"
529 depends on X86_EXTENDED_PLATFORM
532 depends on X86_X2APIC
533 depends on PCI_MMCONFIG
535 Adds support for Numascale NumaChip large-SMP systems. Needed to
536 enable more than ~168 cores.
537 If you don't have one of these, you should say N here.
541 select HYPERVISOR_GUEST
543 depends on X86_64 && PCI
544 depends on X86_EXTENDED_PLATFORM
547 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
548 supposed to run on these EM64T-based machines. Only choose this option
549 if you have one of these machines.
552 bool "SGI Ultraviolet"
554 depends on X86_EXTENDED_PLATFORM
557 depends on X86_X2APIC
560 This option is needed in order to support SGI Ultraviolet systems.
561 If you don't have one of these, you should say N here.
563 # Following is an alphabetically sorted list of 32 bit extended platforms
564 # Please maintain the alphabetic order if and when there are additions
567 bool "Goldfish (Virtual Platform)"
568 depends on X86_EXTENDED_PLATFORM
570 Enable support for the Goldfish virtual platform used primarily
571 for Android development. Unless you are building for the Android
572 Goldfish emulator say N here.
575 bool "CE4100 TV platform"
577 depends on PCI_GODIRECT
578 depends on X86_IO_APIC
580 depends on X86_EXTENDED_PLATFORM
581 select X86_REBOOTFIXUPS
583 select OF_EARLY_FLATTREE
585 Select for the Intel CE media processor (CE4100) SOC.
586 This option compiles in support for the CE4100 SOC for settop
587 boxes and media devices.
590 bool "Intel MID platform support"
591 depends on X86_EXTENDED_PLATFORM
592 depends on X86_PLATFORM_DEVICES
594 depends on X86_64 || (PCI_GOANY && X86_32)
595 depends on X86_IO_APIC
601 select MFD_INTEL_MSIC
603 Select to build a kernel capable of supporting Intel MID (Mobile
604 Internet Device) platform systems which do not have the PCI legacy
605 interfaces. If you are building for a PC class system say N here.
607 Intel MID platforms are based on an Intel processor and chipset which
608 consume less power than most of the x86 derivatives.
610 config X86_INTEL_QUARK
611 bool "Intel Quark platform support"
613 depends on X86_EXTENDED_PLATFORM
614 depends on X86_PLATFORM_DEVICES
618 depends on X86_IO_APIC
623 Select to include support for Quark X1000 SoC.
624 Say Y here if you have a Quark based system such as the Arduino
625 compatible Intel Galileo.
627 config X86_INTEL_LPSS
628 bool "Intel Low Power Subsystem Support"
629 depends on X86 && ACPI && PCI
634 Select to build support for Intel Low Power Subsystem such as
635 found on Intel Lynxpoint PCH. Selecting this option enables
636 things like clock tree (common clock framework) and pincontrol
637 which are needed by the LPSS peripheral drivers.
639 config X86_AMD_PLATFORM_DEVICE
640 bool "AMD ACPI2Platform devices support"
645 Select to interpret AMD specific ACPI device to platform device
646 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
647 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
648 implemented under PINCTRL subsystem.
651 tristate "Intel SoC IOSF Sideband support for SoC platforms"
654 This option enables sideband register access support for Intel SoC
655 platforms. On these platforms the IOSF sideband is used in lieu of
656 MSR's for some register accesses, mostly but not limited to thermal
657 and power. Drivers may query the availability of this device to
658 determine if they need the sideband in order to work on these
659 platforms. The sideband is available on the following SoC products.
660 This list is not meant to be exclusive.
665 You should say Y if you are running a kernel on one of these SoC's.
667 config IOSF_MBI_DEBUG
668 bool "Enable IOSF sideband access through debugfs"
669 depends on IOSF_MBI && DEBUG_FS
671 Select this option to expose the IOSF sideband access registers (MCR,
672 MDR, MCRX) through debugfs to write and read register information from
673 different units on the SoC. This is most useful for obtaining device
674 state information for debug and analysis. As this is a general access
675 mechanism, users of this option would have specific knowledge of the
676 device they want to access.
678 If you don't require the option or are in doubt, say N.
681 bool "RDC R-321x SoC"
683 depends on X86_EXTENDED_PLATFORM
685 select X86_REBOOTFIXUPS
687 This option is needed for RDC R-321x system-on-chip, also known
689 If you don't have one of these chips, you should say N here.
691 config X86_32_NON_STANDARD
692 bool "Support non-standard 32-bit SMP architectures"
693 depends on X86_32 && SMP
694 depends on X86_EXTENDED_PLATFORM
696 This option compiles in the bigsmp and STA2X11 default
697 subarchitectures. It is intended for a generic binary
698 kernel. If you select them all, kernel will probe it one by
699 one and will fallback to default.
701 # Alphabetically sorted list of Non standard 32 bit platforms
703 config X86_SUPPORTS_MEMORY_FAILURE
705 # MCE code calls memory_failure():
707 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
708 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
709 depends on X86_64 || !SPARSEMEM
710 select ARCH_SUPPORTS_MEMORY_FAILURE
713 bool "STA2X11 Companion Chip Support"
714 depends on X86_32_NON_STANDARD && PCI
719 This adds support for boards based on the STA2X11 IO-Hub,
720 a.k.a. "ConneXt". The chip is used in place of the standard
721 PC chipset, so all "standard" peripherals are missing. If this
722 option is selected the kernel will still be able to boot on
723 standard PC machines.
726 tristate "Eurobraille/Iris poweroff module"
729 The Iris machines from EuroBraille do not have APM or ACPI support
730 to shut themselves down properly. A special I/O sequence is
731 needed to do so, which is what this module does at
734 This is only for Iris machines from EuroBraille.
738 config SCHED_OMIT_FRAME_POINTER
740 prompt "Single-depth WCHAN output"
743 Calculate simpler /proc/<PID>/wchan values. If this option
744 is disabled then wchan values will recurse back to the
745 caller function. This provides more accurate wchan values,
746 at the expense of slightly more scheduling overhead.
748 If in doubt, say "Y".
750 menuconfig HYPERVISOR_GUEST
751 bool "Linux guest support"
753 Say Y here to enable options for running Linux under various hyper-
754 visors. This option enables basic hypervisor detection and platform
757 If you say N, all options in this submenu will be skipped and
758 disabled, and Linux guest support won't be built in.
763 bool "Enable paravirtualization code"
765 This changes the kernel so it can modify itself when it is run
766 under a hypervisor, potentially improving performance significantly
767 over full virtualization. However, when run without a hypervisor
768 the kernel is theoretically slower and slightly larger.
773 config PARAVIRT_DEBUG
774 bool "paravirt-ops debugging"
775 depends on PARAVIRT && DEBUG_KERNEL
777 Enable to debug paravirt_ops internals. Specifically, BUG if
778 a paravirt_op is missing when it is called.
780 config PARAVIRT_SPINLOCKS
781 bool "Paravirtualization layer for spinlocks"
782 depends on PARAVIRT && SMP
784 Paravirtualized spinlocks allow a pvops backend to replace the
785 spinlock implementation with something virtualization-friendly
786 (for example, block the virtual CPU rather than spinning).
788 It has a minimal impact on native kernels and gives a nice performance
789 benefit on paravirtualized KVM / Xen kernels.
791 If you are unsure how to answer this question, answer Y.
793 config X86_HV_CALLBACK_VECTOR
796 source "arch/x86/xen/Kconfig"
799 bool "KVM Guest support (including kvmclock)"
801 select PARAVIRT_CLOCK
802 select ARCH_CPUIDLE_HALTPOLL
805 This option enables various optimizations for running under the KVM
806 hypervisor. It includes a paravirtualized clock, so that instead
807 of relying on a PIT (or probably other) emulation by the
808 underlying device model, the host provides the guest with
809 timing infrastructure such as time of day, and system time
811 config ARCH_CPUIDLE_HALTPOLL
813 prompt "Disable host haltpoll when loading haltpoll driver"
815 If virtualized under KVM, disable host haltpoll.
818 bool "Support for running PVH guests"
820 This option enables the PVH entry point for guest virtual machines
821 as specified in the x86/HVM direct boot ABI.
824 bool "Enable debug information for KVM Guests in debugfs"
825 depends on KVM_GUEST && DEBUG_FS
827 This option enables collection of various statistics for KVM guest.
828 Statistics are displayed in debugfs filesystem. Enabling this option
829 may incur significant overhead.
831 config PARAVIRT_TIME_ACCOUNTING
832 bool "Paravirtual steal time accounting"
835 Select this option to enable fine granularity task steal time
836 accounting. Time spent executing other tasks in parallel with
837 the current vCPU is discounted from the vCPU power. To account for
838 that, there can be a small performance impact.
840 If in doubt, say N here.
842 config PARAVIRT_CLOCK
845 config JAILHOUSE_GUEST
846 bool "Jailhouse non-root cell support"
847 depends on X86_64 && PCI
850 This option allows to run Linux as guest in a Jailhouse non-root
851 cell. You can leave this option disabled if you only want to start
852 Jailhouse and run Linux afterwards in the root cell.
855 bool "ACRN Guest support"
857 select X86_HV_CALLBACK_VECTOR
859 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
860 a flexible, lightweight reference open-source hypervisor, built with
861 real-time and safety-criticality in mind. It is built for embedded
862 IOT with small footprint and real-time features. More details can be
863 found in https://projectacrn.org/.
865 endif #HYPERVISOR_GUEST
867 source "arch/x86/Kconfig.cpu"
871 prompt "HPET Timer Support" if X86_32
873 Use the IA-PC HPET (High Precision Event Timer) to manage
874 time in preference to the PIT and RTC, if a HPET is
876 HPET is the next generation timer replacing legacy 8254s.
877 The HPET provides a stable time base on SMP
878 systems, unlike the TSC, but it is more expensive to access,
879 as it is off-chip. The interface used is documented
880 in the HPET spec, revision 1.
882 You can safely choose Y here. However, HPET will only be
883 activated if the platform and the BIOS support this feature.
884 Otherwise the 8254 will be used for timing services.
886 Choose N to continue using the legacy 8254 timer.
888 config HPET_EMULATE_RTC
890 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
893 def_bool y if X86_INTEL_MID
894 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
896 depends on X86_INTEL_MID && SFI
898 APB timer is the replacement for 8254, HPET on X86 MID platforms.
899 The APBT provides a stable time base on SMP
900 systems, unlike the TSC, but it is more expensive to access,
901 as it is off-chip. APB timers are always running regardless of CPU
902 C states, they are used as per CPU clockevent device when possible.
904 # Mark as expert because too many people got it wrong.
905 # The code disables itself when not needed.
908 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
909 bool "Enable DMI scanning" if EXPERT
911 Enabled scanning of DMI to identify machine quirks. Say Y
912 here unless you have verified that your setup is not
913 affected by entries in the DMI blacklist. Required by PNP
917 bool "Old AMD GART IOMMU support"
920 depends on X86_64 && PCI && AMD_NB
922 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
923 GART based hardware IOMMUs.
925 The GART supports full DMA access for devices with 32-bit access
926 limitations, on systems with more than 3 GB. This is usually needed
927 for USB, sound, many IDE/SATA chipsets and some other devices.
929 Newer systems typically have a modern AMD IOMMU, supported via
930 the CONFIG_AMD_IOMMU=y config option.
932 In normal configurations this driver is only active when needed:
933 there's more than 3 GB of memory and the system contains a
934 32-bit limited device.
939 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
940 depends on X86_64 && SMP && DEBUG_KERNEL
941 select CPUMASK_OFFSTACK
943 Enable maximum number of CPUS and NUMA Nodes for this architecture.
947 # The maximum number of CPUs supported:
949 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
950 # and which can be configured interactively in the
951 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
953 # The ranges are different on 32-bit and 64-bit kernels, depending on
954 # hardware capabilities and scalability features of the kernel.
956 # ( If MAXSMP is enabled we just use the highest possible value and disable
957 # interactive configuration. )
960 config NR_CPUS_RANGE_BEGIN
962 default NR_CPUS_RANGE_END if MAXSMP
966 config NR_CPUS_RANGE_END
969 default 64 if SMP && X86_BIGSMP
970 default 8 if SMP && !X86_BIGSMP
973 config NR_CPUS_RANGE_END
976 default 8192 if SMP && CPUMASK_OFFSTACK
977 default 512 if SMP && !CPUMASK_OFFSTACK
980 config NR_CPUS_DEFAULT
983 default 32 if X86_BIGSMP
987 config NR_CPUS_DEFAULT
990 default 8192 if MAXSMP
995 int "Maximum number of CPUs" if SMP && !MAXSMP
996 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
997 default NR_CPUS_DEFAULT
999 This allows you to specify the maximum number of CPUs which this
1000 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1001 supported value is 8192, otherwise the maximum value is 512. The
1002 minimum value which makes sense is 2.
1004 This is purely to save memory: each supported CPU adds about 8KB
1005 to the kernel image.
1012 prompt "Multi-core scheduler support"
1015 Multi-core scheduler support improves the CPU scheduler's decision
1016 making when dealing with multi-core CPU chips at a cost of slightly
1017 increased overhead in some places. If unsure say N here.
1019 config SCHED_MC_PRIO
1020 bool "CPU core priorities scheduler support"
1021 depends on SCHED_MC && CPU_SUP_INTEL
1022 select X86_INTEL_PSTATE
1026 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1027 core ordering determined at manufacturing time, which allows
1028 certain cores to reach higher turbo frequencies (when running
1029 single threaded workloads) than others.
1031 Enabling this kernel feature teaches the scheduler about
1032 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1033 scheduler's CPU selection logic accordingly, so that higher
1034 overall system performance can be achieved.
1036 This feature will have no effect on CPUs without this feature.
1038 If unsure say Y here.
1042 depends on !SMP && X86_LOCAL_APIC
1045 bool "Local APIC support on uniprocessors" if !PCI_MSI
1047 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1049 A local APIC (Advanced Programmable Interrupt Controller) is an
1050 integrated interrupt controller in the CPU. If you have a single-CPU
1051 system which has a processor with a local APIC, you can say Y here to
1052 enable and use it. If you say Y here even though your machine doesn't
1053 have a local APIC, then the kernel will still run with no slowdown at
1054 all. The local APIC supports CPU-generated self-interrupts (timer,
1055 performance counters), and the NMI watchdog which detects hard
1058 config X86_UP_IOAPIC
1059 bool "IO-APIC support on uniprocessors"
1060 depends on X86_UP_APIC
1062 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1063 SMP-capable replacement for PC-style interrupt controllers. Most
1064 SMP systems and many recent uniprocessor systems have one.
1066 If you have a single-CPU system with an IO-APIC, you can say Y here
1067 to use it. If you say Y here even though your machine doesn't have
1068 an IO-APIC, then the kernel will still run with no slowdown at all.
1070 config X86_LOCAL_APIC
1072 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1073 select IRQ_DOMAIN_HIERARCHY
1074 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1078 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1080 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1081 bool "Reroute for broken boot IRQs"
1082 depends on X86_IO_APIC
1084 This option enables a workaround that fixes a source of
1085 spurious interrupts. This is recommended when threaded
1086 interrupt handling is used on systems where the generation of
1087 superfluous "boot interrupts" cannot be disabled.
1089 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1090 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1091 kernel does during interrupt handling). On chipsets where this
1092 boot IRQ generation cannot be disabled, this workaround keeps
1093 the original IRQ line masked so that only the equivalent "boot
1094 IRQ" is delivered to the CPUs. The workaround also tells the
1095 kernel to set up the IRQ handler on the boot IRQ line. In this
1096 way only one interrupt is delivered to the kernel. Otherwise
1097 the spurious second interrupt may cause the kernel to bring
1098 down (vital) interrupt lines.
1100 Only affects "broken" chipsets. Interrupt sharing may be
1101 increased on these systems.
1104 bool "Machine Check / overheating reporting"
1105 select GENERIC_ALLOCATOR
1108 Machine Check support allows the processor to notify the
1109 kernel if it detects a problem (e.g. overheating, data corruption).
1110 The action the kernel takes depends on the severity of the problem,
1111 ranging from warning messages to halting the machine.
1113 config X86_MCELOG_LEGACY
1114 bool "Support for deprecated /dev/mcelog character device"
1117 Enable support for /dev/mcelog which is needed by the old mcelog
1118 userspace logging daemon. Consider switching to the new generation
1121 config X86_MCE_INTEL
1123 prompt "Intel MCE features"
1124 depends on X86_MCE && X86_LOCAL_APIC
1126 Additional support for intel specific MCE features such as
1127 the thermal monitor.
1131 prompt "AMD MCE features"
1132 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1134 Additional support for AMD specific MCE features such as
1135 the DRAM Error Threshold.
1137 config X86_ANCIENT_MCE
1138 bool "Support for old Pentium 5 / WinChip machine checks"
1139 depends on X86_32 && X86_MCE
1141 Include support for machine check handling on old Pentium 5 or WinChip
1142 systems. These typically need to be enabled explicitly on the command
1145 config X86_MCE_THRESHOLD
1146 depends on X86_MCE_AMD || X86_MCE_INTEL
1149 config X86_MCE_INJECT
1150 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1151 tristate "Machine check injector support"
1153 Provide support for injecting machine checks for testing purposes.
1154 If you don't know what a machine check is and you don't do kernel
1155 QA it is safe to say n.
1157 config X86_THERMAL_VECTOR
1159 depends on X86_MCE_INTEL
1161 source "arch/x86/events/Kconfig"
1163 config X86_LEGACY_VM86
1164 bool "Legacy VM86 support"
1167 This option allows user programs to put the CPU into V8086
1168 mode, which is an 80286-era approximation of 16-bit real mode.
1170 Some very old versions of X and/or vbetool require this option
1171 for user mode setting. Similarly, DOSEMU will use it if
1172 available to accelerate real mode DOS programs. However, any
1173 recent version of DOSEMU, X, or vbetool should be fully
1174 functional even without kernel VM86 support, as they will all
1175 fall back to software emulation. Nevertheless, if you are using
1176 a 16-bit DOS program where 16-bit performance matters, vm86
1177 mode might be faster than emulation and you might want to
1180 Note that any app that works on a 64-bit kernel is unlikely to
1181 need this option, as 64-bit kernels don't, and can't, support
1182 V8086 mode. This option is also unrelated to 16-bit protected
1183 mode and is not needed to run most 16-bit programs under Wine.
1185 Enabling this option increases the complexity of the kernel
1186 and slows down exception handling a tiny bit.
1188 If unsure, say N here.
1192 default X86_LEGACY_VM86
1195 bool "Enable support for 16-bit segments" if EXPERT
1197 depends on MODIFY_LDT_SYSCALL
1199 This option is required by programs like Wine to run 16-bit
1200 protected mode legacy code on x86 processors. Disabling
1201 this option saves about 300 bytes on i386, or around 6K text
1202 plus 16K runtime memory on x86-64,
1206 depends on X86_16BIT && X86_32
1210 depends on X86_16BIT && X86_64
1212 config X86_VSYSCALL_EMULATION
1213 bool "Enable vsyscall emulation" if EXPERT
1217 This enables emulation of the legacy vsyscall page. Disabling
1218 it is roughly equivalent to booting with vsyscall=none, except
1219 that it will also disable the helpful warning if a program
1220 tries to use a vsyscall. With this option set to N, offending
1221 programs will just segfault, citing addresses of the form
1224 This option is required by many programs built before 2013, and
1225 care should be used even with newer programs if set to N.
1227 Disabling this option saves about 7K of kernel size and
1228 possibly 4K of additional runtime pagetable memory.
1230 config X86_IOPL_IOPERM
1231 bool "IOPERM and IOPL Emulation"
1234 This enables the ioperm() and iopl() syscalls which are necessary
1235 for legacy applications.
1237 Legacy IOPL support is an overbroad mechanism which allows user
1238 space aside of accessing all 65536 I/O ports also to disable
1239 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1240 capabilities and permission from potentially active security
1243 The emulation restricts the functionality of the syscall to
1244 only allowing the full range I/O port access, but prevents the
1245 ability to disable interrupts from user space which would be
1246 granted if the hardware IOPL mechanism would be used.
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"
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
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 mechanism, which
1519 helps to determine the effectiveness of preserving large and huge
1520 page mappings when mapping protections are changed.
1522 config AMD_MEM_ENCRYPT
1523 bool "AMD Secure Memory Encryption (SME) support"
1524 depends on X86_64 && CPU_SUP_AMD
1525 select DYNAMIC_PHYSICAL_MASK
1526 select ARCH_USE_MEMREMAP_PROT
1527 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1529 Say yes to enable support for the encryption of system memory.
1530 This requires an AMD processor that supports Secure Memory
1533 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1534 bool "Activate AMD Secure Memory Encryption (SME) by default"
1536 depends on AMD_MEM_ENCRYPT
1538 Say yes to have system memory encrypted by default if running on
1539 an AMD processor that supports Secure Memory Encryption (SME).
1541 If set to Y, then the encryption of system memory can be
1542 deactivated with the mem_encrypt=off command line option.
1544 If set to N, then the encryption of system memory can be
1545 activated with the mem_encrypt=on command line option.
1547 # Common NUMA Features
1549 bool "NUMA Memory Allocation and Scheduler Support"
1551 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1552 default y if X86_BIGSMP
1554 Enable NUMA (Non-Uniform Memory Access) support.
1556 The kernel will try to allocate memory used by a CPU on the
1557 local memory controller of the CPU and add some more
1558 NUMA awareness to the kernel.
1560 For 64-bit this is recommended if the system is Intel Core i7
1561 (or later), AMD Opteron, or EM64T NUMA.
1563 For 32-bit this is only needed if you boot a 32-bit
1564 kernel on a 64-bit NUMA platform.
1566 Otherwise, you should say N.
1570 prompt "Old style AMD Opteron NUMA detection"
1571 depends on X86_64 && NUMA && PCI
1573 Enable AMD NUMA node topology detection. You should say Y here if
1574 you have a multi processor AMD system. This uses an old method to
1575 read the NUMA configuration directly from the builtin Northbridge
1576 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1577 which also takes priority if both are compiled in.
1579 config X86_64_ACPI_NUMA
1581 prompt "ACPI NUMA detection"
1582 depends on X86_64 && NUMA && ACPI && PCI
1585 Enable ACPI SRAT based node topology detection.
1587 # Some NUMA nodes have memory ranges that span
1588 # other nodes. Even though a pfn is valid and
1589 # between a node's start and end pfns, it may not
1590 # reside on that node. See memmap_init_zone()
1592 config NODES_SPAN_OTHER_NODES
1594 depends on X86_64_ACPI_NUMA
1597 bool "NUMA emulation"
1600 Enable NUMA emulation. A flat machine will be split
1601 into virtual nodes when booted with "numa=fake=N", where N is the
1602 number of nodes. This is only useful for debugging.
1605 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1607 default "10" if MAXSMP
1608 default "6" if X86_64
1610 depends on NEED_MULTIPLE_NODES
1612 Specify the maximum number of NUMA Nodes available on the target
1613 system. Increases memory reserved to accommodate various tables.
1615 config ARCH_HAVE_MEMORY_PRESENT
1617 depends on X86_32 && DISCONTIGMEM
1619 config ARCH_FLATMEM_ENABLE
1621 depends on X86_32 && !NUMA
1623 config ARCH_DISCONTIGMEM_ENABLE
1625 depends on NUMA && X86_32
1628 config ARCH_SPARSEMEM_ENABLE
1630 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1631 select SPARSEMEM_STATIC if X86_32
1632 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1634 config ARCH_SPARSEMEM_DEFAULT
1635 def_bool X86_64 || (NUMA && X86_32)
1637 config ARCH_SELECT_MEMORY_MODEL
1639 depends on ARCH_SPARSEMEM_ENABLE
1641 config ARCH_MEMORY_PROBE
1642 bool "Enable sysfs memory/probe interface"
1643 depends on X86_64 && MEMORY_HOTPLUG
1645 This option enables a sysfs memory/probe interface for testing.
1646 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1647 If you are unsure how to answer this question, answer N.
1649 config ARCH_PROC_KCORE_TEXT
1651 depends on X86_64 && PROC_KCORE
1653 config ILLEGAL_POINTER_VALUE
1656 default 0xdead000000000000 if X86_64
1658 config X86_PMEM_LEGACY_DEVICE
1661 config X86_PMEM_LEGACY
1662 tristate "Support non-standard NVDIMMs and ADR protected memory"
1663 depends on PHYS_ADDR_T_64BIT
1665 select X86_PMEM_LEGACY_DEVICE
1668 Treat memory marked using the non-standard e820 type of 12 as used
1669 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1670 The kernel will offer these regions to the 'pmem' driver so
1671 they can be used for persistent storage.
1676 bool "Allocate 3rd-level pagetables from highmem"
1679 The VM uses one page table entry for each page of physical memory.
1680 For systems with a lot of RAM, this can be wasteful of precious
1681 low memory. Setting this option will put user-space page table
1682 entries in high memory.
1684 config X86_CHECK_BIOS_CORRUPTION
1685 bool "Check for low memory corruption"
1687 Periodically check for memory corruption in low memory, which
1688 is suspected to be caused by BIOS. Even when enabled in the
1689 configuration, it is disabled at runtime. Enable it by
1690 setting "memory_corruption_check=1" on the kernel command
1691 line. By default it scans the low 64k of memory every 60
1692 seconds; see the memory_corruption_check_size and
1693 memory_corruption_check_period parameters in
1694 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1696 When enabled with the default parameters, this option has
1697 almost no overhead, as it reserves a relatively small amount
1698 of memory and scans it infrequently. It both detects corruption
1699 and prevents it from affecting the running system.
1701 It is, however, intended as a diagnostic tool; if repeatable
1702 BIOS-originated corruption always affects the same memory,
1703 you can use memmap= to prevent the kernel from using that
1706 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1707 bool "Set the default setting of memory_corruption_check"
1708 depends on X86_CHECK_BIOS_CORRUPTION
1711 Set whether the default state of memory_corruption_check is
1714 config X86_RESERVE_LOW
1715 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1719 Specify the amount of low memory to reserve for the BIOS.
1721 The first page contains BIOS data structures that the kernel
1722 must not use, so that page must always be reserved.
1724 By default we reserve the first 64K of physical RAM, as a
1725 number of BIOSes are known to corrupt that memory range
1726 during events such as suspend/resume or monitor cable
1727 insertion, so it must not be used by the kernel.
1729 You can set this to 4 if you are absolutely sure that you
1730 trust the BIOS to get all its memory reservations and usages
1731 right. If you know your BIOS have problems beyond the
1732 default 64K area, you can set this to 640 to avoid using the
1733 entire low memory range.
1735 If you have doubts about the BIOS (e.g. suspend/resume does
1736 not work or there's kernel crashes after certain hardware
1737 hotplug events) then you might want to enable
1738 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1739 typical corruption patterns.
1741 Leave this to the default value of 64 if you are unsure.
1743 config MATH_EMULATION
1745 depends on MODIFY_LDT_SYSCALL
1746 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1748 Linux can emulate a math coprocessor (used for floating point
1749 operations) if you don't have one. 486DX and Pentium processors have
1750 a math coprocessor built in, 486SX and 386 do not, unless you added
1751 a 487DX or 387, respectively. (The messages during boot time can
1752 give you some hints here ["man dmesg"].) Everyone needs either a
1753 coprocessor or this emulation.
1755 If you don't have a math coprocessor, you need to say Y here; if you
1756 say Y here even though you have a coprocessor, the coprocessor will
1757 be used nevertheless. (This behavior can be changed with the kernel
1758 command line option "no387", which comes handy if your coprocessor
1759 is broken. Try "man bootparam" or see the documentation of your boot
1760 loader (lilo or loadlin) about how to pass options to the kernel at
1761 boot time.) This means that it is a good idea to say Y here if you
1762 intend to use this kernel on different machines.
1764 More information about the internals of the Linux math coprocessor
1765 emulation can be found in <file:arch/x86/math-emu/README>.
1767 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1768 kernel, it won't hurt.
1772 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1774 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1775 the Memory Type Range Registers (MTRRs) may be used to control
1776 processor access to memory ranges. This is most useful if you have
1777 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1778 allows bus write transfers to be combined into a larger transfer
1779 before bursting over the PCI/AGP bus. This can increase performance
1780 of image write operations 2.5 times or more. Saying Y here creates a
1781 /proc/mtrr file which may be used to manipulate your processor's
1782 MTRRs. Typically the X server should use this.
1784 This code has a reasonably generic interface so that similar
1785 control registers on other processors can be easily supported
1788 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1789 Registers (ARRs) which provide a similar functionality to MTRRs. For
1790 these, the ARRs are used to emulate the MTRRs.
1791 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1792 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1793 write-combining. All of these processors are supported by this code
1794 and it makes sense to say Y here if you have one of them.
1796 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1797 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1798 can lead to all sorts of problems, so it's good to say Y here.
1800 You can safely say Y even if your machine doesn't have MTRRs, you'll
1801 just add about 9 KB to your kernel.
1803 See <file:Documentation/x86/mtrr.rst> for more information.
1805 config MTRR_SANITIZER
1807 prompt "MTRR cleanup support"
1810 Convert MTRR layout from continuous to discrete, so X drivers can
1811 add writeback entries.
1813 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1814 The largest mtrr entry size for a continuous block can be set with
1819 config MTRR_SANITIZER_ENABLE_DEFAULT
1820 int "MTRR cleanup enable value (0-1)"
1823 depends on MTRR_SANITIZER
1825 Enable mtrr cleanup default value
1827 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1828 int "MTRR cleanup spare reg num (0-7)"
1831 depends on MTRR_SANITIZER
1833 mtrr cleanup spare entries default, it can be changed via
1834 mtrr_spare_reg_nr=N on the kernel command line.
1838 prompt "x86 PAT support" if EXPERT
1841 Use PAT attributes to setup page level cache control.
1843 PATs are the modern equivalents of MTRRs and are much more
1844 flexible than MTRRs.
1846 Say N here if you see bootup problems (boot crash, boot hang,
1847 spontaneous reboots) or a non-working video driver.
1851 config ARCH_USES_PG_UNCACHED
1857 prompt "x86 architectural random number generator" if EXPERT
1859 Enable the x86 architectural RDRAND instruction
1860 (Intel Bull Mountain technology) to generate random numbers.
1861 If supported, this is a high bandwidth, cryptographically
1862 secure hardware random number generator.
1866 prompt "Supervisor Mode Access Prevention" if EXPERT
1868 Supervisor Mode Access Prevention (SMAP) is a security
1869 feature in newer Intel processors. There is a small
1870 performance cost if this enabled and turned on; there is
1871 also a small increase in the kernel size if this is enabled.
1877 depends on CPU_SUP_INTEL || CPU_SUP_AMD
1878 prompt "User Mode Instruction Prevention" if EXPERT
1880 User Mode Instruction Prevention (UMIP) is a security feature in
1881 some x86 processors. If enabled, a general protection fault is
1882 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1883 executed in user mode. These instructions unnecessarily expose
1884 information about the hardware state.
1886 The vast majority of applications do not use these instructions.
1887 For the very few that do, software emulation is provided in
1888 specific cases in protected and virtual-8086 modes. Emulated
1891 config X86_INTEL_MPX
1892 prompt "Intel MPX (Memory Protection Extensions)"
1894 # Note: only available in 64-bit mode due to VMA flags shortage
1895 depends on CPU_SUP_INTEL && X86_64
1896 select ARCH_USES_HIGH_VMA_FLAGS
1898 MPX provides hardware features that can be used in
1899 conjunction with compiler-instrumented code to check
1900 memory references. It is designed to detect buffer
1901 overflow or underflow bugs.
1903 This option enables running applications which are
1904 instrumented or otherwise use MPX. It does not use MPX
1905 itself inside the kernel or to protect the kernel
1906 against bad memory references.
1908 Enabling this option will make the kernel larger:
1909 ~8k of kernel text and 36 bytes of data on a 64-bit
1910 defconfig. It adds a long to the 'mm_struct' which
1911 will increase the kernel memory overhead of each
1912 process and adds some branches to paths used during
1913 exec() and munmap().
1915 For details, see Documentation/x86/intel_mpx.rst
1919 config X86_INTEL_MEMORY_PROTECTION_KEYS
1920 prompt "Intel Memory Protection Keys"
1922 # Note: only available in 64-bit mode
1923 depends on CPU_SUP_INTEL && X86_64
1924 select ARCH_USES_HIGH_VMA_FLAGS
1925 select ARCH_HAS_PKEYS
1927 Memory Protection Keys provides a mechanism for enforcing
1928 page-based protections, but without requiring modification of the
1929 page tables when an application changes protection domains.
1931 For details, see Documentation/core-api/protection-keys.rst
1936 prompt "TSX enable mode"
1937 depends on CPU_SUP_INTEL
1938 default X86_INTEL_TSX_MODE_OFF
1940 Intel's TSX (Transactional Synchronization Extensions) feature
1941 allows to optimize locking protocols through lock elision which
1942 can lead to a noticeable performance boost.
1944 On the other hand it has been shown that TSX can be exploited
1945 to form side channel attacks (e.g. TAA) and chances are there
1946 will be more of those attacks discovered in the future.
1948 Therefore TSX is not enabled by default (aka tsx=off). An admin
1949 might override this decision by tsx=on the command line parameter.
1950 Even with TSX enabled, the kernel will attempt to enable the best
1951 possible TAA mitigation setting depending on the microcode available
1952 for the particular machine.
1954 This option allows to set the default tsx mode between tsx=on, =off
1955 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1958 Say off if not sure, auto if TSX is in use but it should be used on safe
1959 platforms or on if TSX is in use and the security aspect of tsx is not
1962 config X86_INTEL_TSX_MODE_OFF
1965 TSX is disabled if possible - equals to tsx=off command line parameter.
1967 config X86_INTEL_TSX_MODE_ON
1970 TSX is always enabled on TSX capable HW - equals the tsx=on command
1973 config X86_INTEL_TSX_MODE_AUTO
1976 TSX is enabled on TSX capable HW that is believed to be safe against
1977 side channel attacks- equals the tsx=auto command line parameter.
1981 bool "EFI runtime service support"
1984 select EFI_RUNTIME_WRAPPERS
1986 This enables the kernel to use EFI runtime services that are
1987 available (such as the EFI variable services).
1989 This option is only useful on systems that have EFI firmware.
1990 In addition, you should use the latest ELILO loader available
1991 at <http://elilo.sourceforge.net> in order to take advantage
1992 of EFI runtime services. However, even with this option, the
1993 resultant kernel should continue to boot on existing non-EFI
1997 bool "EFI stub support"
1998 depends on EFI && !X86_USE_3DNOW
1999 depends on $(cc-option,-mabi=ms) || X86_32
2002 This kernel feature allows a bzImage to be loaded directly
2003 by EFI firmware without the use of a bootloader.
2005 See Documentation/admin-guide/efi-stub.rst for more information.
2008 bool "EFI mixed-mode support"
2009 depends on EFI_STUB && X86_64
2011 Enabling this feature allows a 64-bit kernel to be booted
2012 on a 32-bit firmware, provided that your CPU supports 64-bit
2015 Note that it is not possible to boot a mixed-mode enabled
2016 kernel via the EFI boot stub - a bootloader that supports
2017 the EFI handover protocol must be used.
2023 prompt "Enable seccomp to safely compute untrusted bytecode"
2025 This kernel feature is useful for number crunching applications
2026 that may need to compute untrusted bytecode during their
2027 execution. By using pipes or other transports made available to
2028 the process as file descriptors supporting the read/write
2029 syscalls, it's possible to isolate those applications in
2030 their own address space using seccomp. Once seccomp is
2031 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
2032 and the task is only allowed to execute a few safe syscalls
2033 defined by each seccomp mode.
2035 If unsure, say Y. Only embedded should say N here.
2037 source "kernel/Kconfig.hz"
2040 bool "kexec system call"
2043 kexec is a system call that implements the ability to shutdown your
2044 current kernel, and to start another kernel. It is like a reboot
2045 but it is independent of the system firmware. And like a reboot
2046 you can start any kernel with it, not just Linux.
2048 The name comes from the similarity to the exec system call.
2050 It is an ongoing process to be certain the hardware in a machine
2051 is properly shutdown, so do not be surprised if this code does not
2052 initially work for you. As of this writing the exact hardware
2053 interface is strongly in flux, so no good recommendation can be
2057 bool "kexec file based system call"
2062 depends on CRYPTO_SHA256=y
2064 This is new version of kexec system call. This system call is
2065 file based and takes file descriptors as system call argument
2066 for kernel and initramfs as opposed to list of segments as
2067 accepted by previous system call.
2069 config ARCH_HAS_KEXEC_PURGATORY
2073 bool "Verify kernel signature during kexec_file_load() syscall"
2074 depends on KEXEC_FILE
2077 This option makes the kexec_file_load() syscall check for a valid
2078 signature of the kernel image. The image can still be loaded without
2079 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2080 there's a signature that we can check, then it must be valid.
2082 In addition to this option, you need to enable signature
2083 verification for the corresponding kernel image type being
2084 loaded in order for this to work.
2086 config KEXEC_SIG_FORCE
2087 bool "Require a valid signature in kexec_file_load() syscall"
2088 depends on KEXEC_SIG
2090 This option makes kernel signature verification mandatory for
2091 the kexec_file_load() syscall.
2093 config KEXEC_BZIMAGE_VERIFY_SIG
2094 bool "Enable bzImage signature verification support"
2095 depends on KEXEC_SIG
2096 depends on SIGNED_PE_FILE_VERIFICATION
2097 select SYSTEM_TRUSTED_KEYRING
2099 Enable bzImage signature verification support.
2102 bool "kernel crash dumps"
2103 depends on X86_64 || (X86_32 && HIGHMEM)
2105 Generate crash dump after being started by kexec.
2106 This should be normally only set in special crash dump kernels
2107 which are loaded in the main kernel with kexec-tools into
2108 a specially reserved region and then later executed after
2109 a crash by kdump/kexec. The crash dump kernel must be compiled
2110 to a memory address not used by the main kernel or BIOS using
2111 PHYSICAL_START, or it must be built as a relocatable image
2112 (CONFIG_RELOCATABLE=y).
2113 For more details see Documentation/admin-guide/kdump/kdump.rst
2117 depends on KEXEC && HIBERNATION
2119 Jump between original kernel and kexeced kernel and invoke
2120 code in physical address mode via KEXEC
2122 config PHYSICAL_START
2123 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2126 This gives the physical address where the kernel is loaded.
2128 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2129 bzImage will decompress itself to above physical address and
2130 run from there. Otherwise, bzImage will run from the address where
2131 it has been loaded by the boot loader and will ignore above physical
2134 In normal kdump cases one does not have to set/change this option
2135 as now bzImage can be compiled as a completely relocatable image
2136 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2137 address. This option is mainly useful for the folks who don't want
2138 to use a bzImage for capturing the crash dump and want to use a
2139 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2140 to be specifically compiled to run from a specific memory area
2141 (normally a reserved region) and this option comes handy.
2143 So if you are using bzImage for capturing the crash dump,
2144 leave the value here unchanged to 0x1000000 and set
2145 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2146 for capturing the crash dump change this value to start of
2147 the reserved region. In other words, it can be set based on
2148 the "X" value as specified in the "crashkernel=YM@XM"
2149 command line boot parameter passed to the panic-ed
2150 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2151 for more details about crash dumps.
2153 Usage of bzImage for capturing the crash dump is recommended as
2154 one does not have to build two kernels. Same kernel can be used
2155 as production kernel and capture kernel. Above option should have
2156 gone away after relocatable bzImage support is introduced. But it
2157 is present because there are users out there who continue to use
2158 vmlinux for dump capture. This option should go away down the
2161 Don't change this unless you know what you are doing.
2164 bool "Build a relocatable kernel"
2167 This builds a kernel image that retains relocation information
2168 so it can be loaded someplace besides the default 1MB.
2169 The relocations tend to make the kernel binary about 10% larger,
2170 but are discarded at runtime.
2172 One use is for the kexec on panic case where the recovery kernel
2173 must live at a different physical address than the primary
2176 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2177 it has been loaded at and the compile time physical address
2178 (CONFIG_PHYSICAL_START) is used as the minimum location.
2180 config RANDOMIZE_BASE
2181 bool "Randomize the address of the kernel image (KASLR)"
2182 depends on RELOCATABLE
2185 In support of Kernel Address Space Layout Randomization (KASLR),
2186 this randomizes the physical address at which the kernel image
2187 is decompressed and the virtual address where the kernel
2188 image is mapped, as a security feature that deters exploit
2189 attempts relying on knowledge of the location of kernel
2192 On 64-bit, the kernel physical and virtual addresses are
2193 randomized separately. The physical address will be anywhere
2194 between 16MB and the top of physical memory (up to 64TB). The
2195 virtual address will be randomized from 16MB up to 1GB (9 bits
2196 of entropy). Note that this also reduces the memory space
2197 available to kernel modules from 1.5GB to 1GB.
2199 On 32-bit, the kernel physical and virtual addresses are
2200 randomized together. They will be randomized from 16MB up to
2201 512MB (8 bits of entropy).
2203 Entropy is generated using the RDRAND instruction if it is
2204 supported. If RDTSC is supported, its value is mixed into
2205 the entropy pool as well. If neither RDRAND nor RDTSC are
2206 supported, then entropy is read from the i8254 timer. The
2207 usable entropy is limited by the kernel being built using
2208 2GB addressing, and that PHYSICAL_ALIGN must be at a
2209 minimum of 2MB. As a result, only 10 bits of entropy are
2210 theoretically possible, but the implementations are further
2211 limited due to memory layouts.
2215 # Relocation on x86 needs some additional build support
2216 config X86_NEED_RELOCS
2218 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2220 config PHYSICAL_ALIGN
2221 hex "Alignment value to which kernel should be aligned"
2223 range 0x2000 0x1000000 if X86_32
2224 range 0x200000 0x1000000 if X86_64
2226 This value puts the alignment restrictions on physical address
2227 where kernel is loaded and run from. Kernel is compiled for an
2228 address which meets above alignment restriction.
2230 If bootloader loads the kernel at a non-aligned address and
2231 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2232 address aligned to above value and run from there.
2234 If bootloader loads the kernel at a non-aligned address and
2235 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2236 load address and decompress itself to the address it has been
2237 compiled for and run from there. The address for which kernel is
2238 compiled already meets above alignment restrictions. Hence the
2239 end result is that kernel runs from a physical address meeting
2240 above alignment restrictions.
2242 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2243 this value must be a multiple of 0x200000.
2245 Don't change this unless you know what you are doing.
2247 config DYNAMIC_MEMORY_LAYOUT
2250 This option makes base addresses of vmalloc and vmemmap as well as
2251 __PAGE_OFFSET movable during boot.
2253 config RANDOMIZE_MEMORY
2254 bool "Randomize the kernel memory sections"
2256 depends on RANDOMIZE_BASE
2257 select DYNAMIC_MEMORY_LAYOUT
2258 default RANDOMIZE_BASE
2260 Randomizes the base virtual address of kernel memory sections
2261 (physical memory mapping, vmalloc & vmemmap). This security feature
2262 makes exploits relying on predictable memory locations less reliable.
2264 The order of allocations remains unchanged. Entropy is generated in
2265 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2266 configuration have in average 30,000 different possible virtual
2267 addresses for each memory section.
2271 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2272 hex "Physical memory mapping padding" if EXPERT
2273 depends on RANDOMIZE_MEMORY
2274 default "0xa" if MEMORY_HOTPLUG
2276 range 0x1 0x40 if MEMORY_HOTPLUG
2279 Define the padding in terabytes added to the existing physical
2280 memory size during kernel memory randomization. It is useful
2281 for memory hotplug support but reduces the entropy available for
2282 address randomization.
2284 If unsure, leave at the default value.
2290 config BOOTPARAM_HOTPLUG_CPU0
2291 bool "Set default setting of cpu0_hotpluggable"
2292 depends on HOTPLUG_CPU
2294 Set whether default state of cpu0_hotpluggable is on or off.
2296 Say Y here to enable CPU0 hotplug by default. If this switch
2297 is turned on, there is no need to give cpu0_hotplug kernel
2298 parameter and the CPU0 hotplug feature is enabled by default.
2300 Please note: there are two known CPU0 dependencies if you want
2301 to enable the CPU0 hotplug feature either by this switch or by
2302 cpu0_hotplug kernel parameter.
2304 First, resume from hibernate or suspend always starts from CPU0.
2305 So hibernate and suspend are prevented if CPU0 is offline.
2307 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2308 offline if any interrupt can not migrate out of CPU0. There may
2309 be other CPU0 dependencies.
2311 Please make sure the dependencies are under your control before
2312 you enable this feature.
2314 Say N if you don't want to enable CPU0 hotplug feature by default.
2315 You still can enable the CPU0 hotplug feature at boot by kernel
2316 parameter cpu0_hotplug.
2318 config DEBUG_HOTPLUG_CPU0
2320 prompt "Debug CPU0 hotplug"
2321 depends on HOTPLUG_CPU
2323 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2324 soon as possible and boots up userspace with CPU0 offlined. User
2325 can online CPU0 back after boot time.
2327 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2328 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2329 compilation or giving cpu0_hotplug kernel parameter at boot.
2335 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2336 depends on COMPAT_32
2338 Certain buggy versions of glibc will crash if they are
2339 presented with a 32-bit vDSO that is not mapped at the address
2340 indicated in its segment table.
2342 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2343 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2344 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2345 the only released version with the bug, but OpenSUSE 9
2346 contains a buggy "glibc 2.3.2".
2348 The symptom of the bug is that everything crashes on startup, saying:
2349 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2351 Saying Y here changes the default value of the vdso32 boot
2352 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2353 This works around the glibc bug but hurts performance.
2355 If unsure, say N: if you are compiling your own kernel, you
2356 are unlikely to be using a buggy version of glibc.
2359 prompt "vsyscall table for legacy applications"
2361 default LEGACY_VSYSCALL_XONLY
2363 Legacy user code that does not know how to find the vDSO expects
2364 to be able to issue three syscalls by calling fixed addresses in
2365 kernel space. Since this location is not randomized with ASLR,
2366 it can be used to assist security vulnerability exploitation.
2368 This setting can be changed at boot time via the kernel command
2369 line parameter vsyscall=[emulate|xonly|none].
2371 On a system with recent enough glibc (2.14 or newer) and no
2372 static binaries, you can say None without a performance penalty
2373 to improve security.
2375 If unsure, select "Emulate execution only".
2377 config LEGACY_VSYSCALL_EMULATE
2378 bool "Full emulation"
2380 The kernel traps and emulates calls into the fixed vsyscall
2381 address mapping. This makes the mapping non-executable, but
2382 it still contains readable known contents, which could be
2383 used in certain rare security vulnerability exploits. This
2384 configuration is recommended when using legacy userspace
2385 that still uses vsyscalls along with legacy binary
2386 instrumentation tools that require code to be readable.
2388 An example of this type of legacy userspace is running
2389 Pin on an old binary that still uses vsyscalls.
2391 config LEGACY_VSYSCALL_XONLY
2392 bool "Emulate execution only"
2394 The kernel traps and emulates calls into the fixed vsyscall
2395 address mapping and does not allow reads. This
2396 configuration is recommended when userspace might use the
2397 legacy vsyscall area but support for legacy binary
2398 instrumentation of legacy code is not needed. It mitigates
2399 certain uses of the vsyscall area as an ASLR-bypassing
2402 config LEGACY_VSYSCALL_NONE
2405 There will be no vsyscall mapping at all. This will
2406 eliminate any risk of ASLR bypass due to the vsyscall
2407 fixed address mapping. Attempts to use the vsyscalls
2408 will be reported to dmesg, so that either old or
2409 malicious userspace programs can be identified.
2414 bool "Built-in kernel command line"
2416 Allow for specifying boot arguments to the kernel at
2417 build time. On some systems (e.g. embedded ones), it is
2418 necessary or convenient to provide some or all of the
2419 kernel boot arguments with the kernel itself (that is,
2420 to not rely on the boot loader to provide them.)
2422 To compile command line arguments into the kernel,
2423 set this option to 'Y', then fill in the
2424 boot arguments in CONFIG_CMDLINE.
2426 Systems with fully functional boot loaders (i.e. non-embedded)
2427 should leave this option set to 'N'.
2430 string "Built-in kernel command string"
2431 depends on CMDLINE_BOOL
2434 Enter arguments here that should be compiled into the kernel
2435 image and used at boot time. If the boot loader provides a
2436 command line at boot time, it is appended to this string to
2437 form the full kernel command line, when the system boots.
2439 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2440 change this behavior.
2442 In most cases, the command line (whether built-in or provided
2443 by the boot loader) should specify the device for the root
2446 config CMDLINE_OVERRIDE
2447 bool "Built-in command line overrides boot loader arguments"
2448 depends on CMDLINE_BOOL
2450 Set this option to 'Y' to have the kernel ignore the boot loader
2451 command line, and use ONLY the built-in command line.
2453 This is used to work around broken boot loaders. This should
2454 be set to 'N' under normal conditions.
2456 config MODIFY_LDT_SYSCALL
2457 bool "Enable the LDT (local descriptor table)" if EXPERT
2460 Linux can allow user programs to install a per-process x86
2461 Local Descriptor Table (LDT) using the modify_ldt(2) system
2462 call. This is required to run 16-bit or segmented code such as
2463 DOSEMU or some Wine programs. It is also used by some very old
2464 threading libraries.
2466 Enabling this feature adds a small amount of overhead to
2467 context switches and increases the low-level kernel attack
2468 surface. Disabling it removes the modify_ldt(2) system call.
2470 Saying 'N' here may make sense for embedded or server kernels.
2472 source "kernel/livepatch/Kconfig"
2476 config ARCH_HAS_ADD_PAGES
2478 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2480 config ARCH_ENABLE_MEMORY_HOTPLUG
2482 depends on X86_64 || (X86_32 && HIGHMEM)
2484 config ARCH_ENABLE_MEMORY_HOTREMOVE
2486 depends on MEMORY_HOTPLUG
2488 config USE_PERCPU_NUMA_NODE_ID
2492 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2494 depends on X86_64 || X86_PAE
2496 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2498 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2500 config ARCH_ENABLE_THP_MIGRATION
2502 depends on X86_64 && TRANSPARENT_HUGEPAGE
2504 menu "Power management and ACPI options"
2506 config ARCH_HIBERNATION_HEADER
2508 depends on HIBERNATION
2510 source "kernel/power/Kconfig"
2512 source "drivers/acpi/Kconfig"
2514 source "drivers/sfi/Kconfig"
2521 tristate "APM (Advanced Power Management) BIOS support"
2522 depends on X86_32 && PM_SLEEP
2524 APM is a BIOS specification for saving power using several different
2525 techniques. This is mostly useful for battery powered laptops with
2526 APM compliant BIOSes. If you say Y here, the system time will be
2527 reset after a RESUME operation, the /proc/apm device will provide
2528 battery status information, and user-space programs will receive
2529 notification of APM "events" (e.g. battery status change).
2531 If you select "Y" here, you can disable actual use of the APM
2532 BIOS by passing the "apm=off" option to the kernel at boot time.
2534 Note that the APM support is almost completely disabled for
2535 machines with more than one CPU.
2537 In order to use APM, you will need supporting software. For location
2538 and more information, read <file:Documentation/power/apm-acpi.rst>
2539 and the Battery Powered Linux mini-HOWTO, available from
2540 <http://www.tldp.org/docs.html#howto>.
2542 This driver does not spin down disk drives (see the hdparm(8)
2543 manpage ("man 8 hdparm") for that), and it doesn't turn off
2544 VESA-compliant "green" monitors.
2546 This driver does not support the TI 4000M TravelMate and the ACER
2547 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2548 desktop machines also don't have compliant BIOSes, and this driver
2549 may cause those machines to panic during the boot phase.
2551 Generally, if you don't have a battery in your machine, there isn't
2552 much point in using this driver and you should say N. If you get
2553 random kernel OOPSes or reboots that don't seem to be related to
2554 anything, try disabling/enabling this option (or disabling/enabling
2557 Some other things you should try when experiencing seemingly random,
2560 1) make sure that you have enough swap space and that it is
2562 2) pass the "no-hlt" option to the kernel
2563 3) switch on floating point emulation in the kernel and pass
2564 the "no387" option to the kernel
2565 4) pass the "floppy=nodma" option to the kernel
2566 5) pass the "mem=4M" option to the kernel (thereby disabling
2567 all but the first 4 MB of RAM)
2568 6) make sure that the CPU is not over clocked.
2569 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2570 8) disable the cache from your BIOS settings
2571 9) install a fan for the video card or exchange video RAM
2572 10) install a better fan for the CPU
2573 11) exchange RAM chips
2574 12) exchange the motherboard.
2576 To compile this driver as a module, choose M here: the
2577 module will be called apm.
2581 config APM_IGNORE_USER_SUSPEND
2582 bool "Ignore USER SUSPEND"
2584 This option will ignore USER SUSPEND requests. On machines with a
2585 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2586 series notebooks, it is necessary to say Y because of a BIOS bug.
2588 config APM_DO_ENABLE
2589 bool "Enable PM at boot time"
2591 Enable APM features at boot time. From page 36 of the APM BIOS
2592 specification: "When disabled, the APM BIOS does not automatically
2593 power manage devices, enter the Standby State, enter the Suspend
2594 State, or take power saving steps in response to CPU Idle calls."
2595 This driver will make CPU Idle calls when Linux is idle (unless this
2596 feature is turned off -- see "Do CPU IDLE calls", below). This
2597 should always save battery power, but more complicated APM features
2598 will be dependent on your BIOS implementation. You may need to turn
2599 this option off if your computer hangs at boot time when using APM
2600 support, or if it beeps continuously instead of suspending. Turn
2601 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2602 T400CDT. This is off by default since most machines do fine without
2607 bool "Make CPU Idle calls when idle"
2609 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2610 On some machines, this can activate improved power savings, such as
2611 a slowed CPU clock rate, when the machine is idle. These idle calls
2612 are made after the idle loop has run for some length of time (e.g.,
2613 333 mS). On some machines, this will cause a hang at boot time or
2614 whenever the CPU becomes idle. (On machines with more than one CPU,
2615 this option does nothing.)
2617 config APM_DISPLAY_BLANK
2618 bool "Enable console blanking using APM"
2620 Enable console blanking using the APM. Some laptops can use this to
2621 turn off the LCD backlight when the screen blanker of the Linux
2622 virtual console blanks the screen. Note that this is only used by
2623 the virtual console screen blanker, and won't turn off the backlight
2624 when using the X Window system. This also doesn't have anything to
2625 do with your VESA-compliant power-saving monitor. Further, this
2626 option doesn't work for all laptops -- it might not turn off your
2627 backlight at all, or it might print a lot of errors to the console,
2628 especially if you are using gpm.
2630 config APM_ALLOW_INTS
2631 bool "Allow interrupts during APM BIOS calls"
2633 Normally we disable external interrupts while we are making calls to
2634 the APM BIOS as a measure to lessen the effects of a badly behaving
2635 BIOS implementation. The BIOS should reenable interrupts if it
2636 needs to. Unfortunately, some BIOSes do not -- especially those in
2637 many of the newer IBM Thinkpads. If you experience hangs when you
2638 suspend, try setting this to Y. Otherwise, say N.
2642 source "drivers/cpufreq/Kconfig"
2644 source "drivers/cpuidle/Kconfig"
2646 source "drivers/idle/Kconfig"
2651 menu "Bus options (PCI etc.)"
2654 prompt "PCI access mode"
2655 depends on X86_32 && PCI
2658 On PCI systems, the BIOS can be used to detect the PCI devices and
2659 determine their configuration. However, some old PCI motherboards
2660 have BIOS bugs and may crash if this is done. Also, some embedded
2661 PCI-based systems don't have any BIOS at all. Linux can also try to
2662 detect the PCI hardware directly without using the BIOS.
2664 With this option, you can specify how Linux should detect the
2665 PCI devices. If you choose "BIOS", the BIOS will be used,
2666 if you choose "Direct", the BIOS won't be used, and if you
2667 choose "MMConfig", then PCI Express MMCONFIG will be used.
2668 If you choose "Any", the kernel will try MMCONFIG, then the
2669 direct access method and falls back to the BIOS if that doesn't
2670 work. If unsure, go with the default, which is "Any".
2675 config PCI_GOMMCONFIG
2692 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2694 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2697 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2700 bool "Support mmconfig PCI config space access" if X86_64
2702 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2703 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2707 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2711 depends on PCI && XEN
2714 config MMCONF_FAM10H
2716 depends on X86_64 && PCI_MMCONFIG && ACPI
2718 config PCI_CNB20LE_QUIRK
2719 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2722 Read the PCI windows out of the CNB20LE host bridge. This allows
2723 PCI hotplug to work on systems with the CNB20LE chipset which do
2726 There's no public spec for this chipset, and this functionality
2727 is known to be incomplete.
2729 You should say N unless you know you need this.
2732 bool "ISA bus support on modern systems" if EXPERT
2734 Expose ISA bus device drivers and options available for selection and
2735 configuration. Enable this option if your target machine has an ISA
2736 bus. ISA is an older system, displaced by PCI and newer bus
2737 architectures -- if your target machine is modern, it probably does
2738 not have an ISA bus.
2742 # x86_64 have no ISA slots, but can have ISA-style DMA.
2744 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2747 Enables ISA-style DMA support for devices requiring such controllers.
2755 Find out whether you have ISA slots on your motherboard. ISA is the
2756 name of a bus system, i.e. the way the CPU talks to the other stuff
2757 inside your box. Other bus systems are PCI, EISA, MicroChannel
2758 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2759 newer boards don't support it. If you have ISA, say Y, otherwise N.
2762 tristate "NatSemi SCx200 support"
2764 This provides basic support for National Semiconductor's
2765 (now AMD's) Geode processors. The driver probes for the
2766 PCI-IDs of several on-chip devices, so its a good dependency
2767 for other scx200_* drivers.
2769 If compiled as a module, the driver is named scx200.
2771 config SCx200HR_TIMER
2772 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2776 This driver provides a clocksource built upon the on-chip
2777 27MHz high-resolution timer. Its also a workaround for
2778 NSC Geode SC-1100's buggy TSC, which loses time when the
2779 processor goes idle (as is done by the scheduler). The
2780 other workaround is idle=poll boot option.
2783 bool "One Laptop Per Child support"
2791 Add support for detecting the unique features of the OLPC
2795 bool "OLPC XO-1 Power Management"
2796 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2798 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2801 bool "OLPC XO-1 Real Time Clock"
2802 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2804 Add support for the XO-1 real time clock, which can be used as a
2805 programmable wakeup source.
2808 bool "OLPC XO-1 SCI extras"
2809 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2813 Add support for SCI-based features of the OLPC XO-1 laptop:
2814 - EC-driven system wakeups
2818 - AC adapter status updates
2819 - Battery status updates
2821 config OLPC_XO15_SCI
2822 bool "OLPC XO-1.5 SCI extras"
2823 depends on OLPC && ACPI
2826 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2827 - EC-driven system wakeups
2828 - AC adapter status updates
2829 - Battery status updates
2832 bool "PCEngines ALIX System Support (LED setup)"
2835 This option enables system support for the PCEngines ALIX.
2836 At present this just sets up LEDs for GPIO control on
2837 ALIX2/3/6 boards. However, other system specific setup should
2840 Note: You must still enable the drivers for GPIO and LED support
2841 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2843 Note: You have to set alix.force=1 for boards with Award BIOS.
2846 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2849 This option enables system support for the Soekris Engineering net5501.
2852 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2856 This option enables system support for the Traverse Technologies GEOS.
2859 bool "Technologic Systems TS-5500 platform support"
2861 select CHECK_SIGNATURE
2865 This option enables system support for the Technologic Systems TS-5500.
2871 depends on CPU_SUP_AMD && PCI
2874 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2876 Firmwares often provide initial graphics framebuffers so the BIOS,
2877 bootloader or kernel can show basic video-output during boot for
2878 user-guidance and debugging. Historically, x86 used the VESA BIOS
2879 Extensions and EFI-framebuffers for this, which are mostly limited
2881 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2882 framebuffers so the new generic system-framebuffer drivers can be
2883 used on x86. If the framebuffer is not compatible with the generic
2884 modes, it is advertised as fallback platform framebuffer so legacy
2885 drivers like efifb, vesafb and uvesafb can pick it up.
2886 If this option is not selected, all system framebuffers are always
2887 marked as fallback platform framebuffers as usual.
2889 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2890 not be able to pick up generic system framebuffers if this option
2891 is selected. You are highly encouraged to enable simplefb as
2892 replacement if you select this option. simplefb can correctly deal
2893 with generic system framebuffers. But you should still keep vesafb
2894 and others enabled as fallback if a system framebuffer is
2895 incompatible with simplefb.
2902 menu "Binary Emulations"
2904 config IA32_EMULATION
2905 bool "IA32 Emulation"
2907 select ARCH_WANT_OLD_COMPAT_IPC
2909 select COMPAT_BINFMT_ELF
2910 select COMPAT_OLD_SIGACTION
2912 Include code to run legacy 32-bit programs under a
2913 64-bit kernel. You should likely turn this on, unless you're
2914 100% sure that you don't have any 32-bit programs left.
2917 tristate "IA32 a.out support"
2918 depends on IA32_EMULATION
2921 Support old a.out binaries in the 32bit emulation.
2924 bool "x32 ABI for 64-bit mode"
2927 Include code to run binaries for the x32 native 32-bit ABI
2928 for 64-bit processors. An x32 process gets access to the
2929 full 64-bit register file and wide data path while leaving
2930 pointers at 32 bits for smaller memory footprint.
2932 You will need a recent binutils (2.22 or later) with
2933 elf32_x86_64 support enabled to compile a kernel with this
2938 depends on IA32_EMULATION || X86_32
2940 select OLD_SIGSUSPEND3
2944 depends on IA32_EMULATION || X86_X32
2947 config COMPAT_FOR_U64_ALIGNMENT
2950 config SYSVIPC_COMPAT
2958 config HAVE_ATOMIC_IOMAP
2962 config X86_DEV_DMA_OPS
2965 source "drivers/firmware/Kconfig"
2967 source "arch/x86/kvm/Kconfig"