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
34 config FORCE_DYNAMIC_FTRACE
37 depends on FUNCTION_TRACER
40 We keep the static function tracing (!DYNAMIC_FTRACE) around
41 in order to test the non static function tracing in the
42 generic code, as other architectures still use it. But we
43 only need to keep it around for x86_64. No need to keep it
44 for x86_32. For x86_32, force DYNAMIC_FTRACE.
48 # ( Note that options that are marked 'if X86_64' could in principle be
49 # ported to 32-bit as well. )
54 # Note: keep this list sorted alphabetically
56 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
57 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
58 select ARCH_32BIT_OFF_T if X86_32
59 select ARCH_CLOCKSOURCE_INIT
60 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
61 select ARCH_HAS_DEBUG_VIRTUAL
62 select ARCH_HAS_DEVMEM_IS_ALLOWED
63 select ARCH_HAS_EARLY_DEBUG if KGDB
64 select ARCH_HAS_ELF_RANDOMIZE
65 select ARCH_HAS_FAST_MULTIPLIER
66 select ARCH_HAS_FILTER_PGPROT
67 select ARCH_HAS_FORTIFY_SOURCE
68 select ARCH_HAS_GCOV_PROFILE_ALL
69 select ARCH_HAS_KCOV if X86_64
70 select ARCH_HAS_MEM_ENCRYPT
71 select ARCH_HAS_MEMBARRIER_SYNC_CORE
72 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
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_SYSCALL_WRAPPER
84 select ARCH_HAS_UBSAN_SANITIZE_ALL
85 select ARCH_HAVE_NMI_SAFE_CMPXCHG
86 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
87 select ARCH_MIGHT_HAVE_PC_PARPORT
88 select ARCH_MIGHT_HAVE_PC_SERIO
90 select ARCH_SUPPORTS_ACPI
91 select ARCH_SUPPORTS_ATOMIC_RMW
92 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
93 select ARCH_USE_BUILTIN_BSWAP
94 select ARCH_USE_QUEUED_RWLOCKS
95 select ARCH_USE_QUEUED_SPINLOCKS
96 select ARCH_USE_SYM_ANNOTATIONS
97 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
98 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
99 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
100 select ARCH_WANT_HUGE_PMD_SHARE
101 select ARCH_WANTS_THP_SWAP if X86_64
102 select BUILDTIME_TABLE_SORT
104 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
105 select CLOCKSOURCE_WATCHDOG
106 select DCACHE_WORD_ACCESS
107 select EDAC_ATOMIC_SCRUB
109 select GENERIC_CLOCKEVENTS
110 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
111 select GENERIC_CLOCKEVENTS_MIN_ADJUST
112 select GENERIC_CMOS_UPDATE
113 select GENERIC_CPU_AUTOPROBE
114 select GENERIC_CPU_VULNERABILITIES
115 select GENERIC_EARLY_IOREMAP
116 select GENERIC_FIND_FIRST_BIT
118 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
119 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
120 select GENERIC_IRQ_MIGRATION if SMP
121 select GENERIC_IRQ_PROBE
122 select GENERIC_IRQ_RESERVATION_MODE
123 select GENERIC_IRQ_SHOW
124 select GENERIC_PENDING_IRQ if SMP
125 select GENERIC_PTDUMP
126 select GENERIC_SMP_IDLE_THREAD
127 select GENERIC_STRNCPY_FROM_USER
128 select GENERIC_STRNLEN_USER
129 select GENERIC_TIME_VSYSCALL
130 select GENERIC_GETTIMEOFDAY
131 select GENERIC_VDSO_TIME_NS
132 select GUP_GET_PTE_LOW_HIGH if X86_PAE
133 select HARDIRQS_SW_RESEND
134 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
135 select HAVE_ACPI_APEI if ACPI
136 select HAVE_ACPI_APEI_NMI if ACPI
137 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
138 select HAVE_ARCH_AUDITSYSCALL
139 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
140 select HAVE_ARCH_JUMP_LABEL
141 select HAVE_ARCH_JUMP_LABEL_RELATIVE
142 select HAVE_ARCH_KASAN if X86_64
143 select HAVE_ARCH_KASAN_VMALLOC if X86_64
144 select HAVE_ARCH_KGDB
145 select HAVE_ARCH_MMAP_RND_BITS if MMU
146 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
147 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
148 select HAVE_ARCH_PREL32_RELOCATIONS
149 select HAVE_ARCH_SECCOMP_FILTER
150 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
151 select HAVE_ARCH_STACKLEAK
152 select HAVE_ARCH_TRACEHOOK
153 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
154 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
155 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
156 select HAVE_ARCH_VMAP_STACK if X86_64
157 select HAVE_ARCH_WITHIN_STACK_FRAMES
158 select HAVE_ASM_MODVERSIONS
159 select HAVE_CMPXCHG_DOUBLE
160 select HAVE_CMPXCHG_LOCAL
161 select HAVE_CONTEXT_TRACKING if X86_64
162 select HAVE_COPY_THREAD_TLS
163 select HAVE_C_RECORDMCOUNT
164 select HAVE_DEBUG_KMEMLEAK
165 select HAVE_DMA_CONTIGUOUS
166 select HAVE_DYNAMIC_FTRACE
167 select HAVE_DYNAMIC_FTRACE_WITH_REGS
168 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
170 select HAVE_EFFICIENT_UNALIGNED_ACCESS
172 select HAVE_EXIT_THREAD
174 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
175 select HAVE_FTRACE_MCOUNT_RECORD
176 select HAVE_FUNCTION_GRAPH_TRACER
177 select HAVE_FUNCTION_TRACER
178 select HAVE_GCC_PLUGINS
179 select HAVE_HW_BREAKPOINT
181 select HAVE_IOREMAP_PROT
182 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
183 select HAVE_IRQ_TIME_ACCOUNTING
184 select HAVE_KERNEL_BZIP2
185 select HAVE_KERNEL_GZIP
186 select HAVE_KERNEL_LZ4
187 select HAVE_KERNEL_LZMA
188 select HAVE_KERNEL_LZO
189 select HAVE_KERNEL_XZ
191 select HAVE_KPROBES_ON_FTRACE
192 select HAVE_FUNCTION_ERROR_INJECTION
193 select HAVE_KRETPROBES
195 select HAVE_LIVEPATCH if X86_64
196 select HAVE_MEMBLOCK_NODE_MAP
197 select HAVE_MIXED_BREAKPOINTS_REGS
198 select HAVE_MOD_ARCH_SPECIFIC
202 select HAVE_OPTPROBES
203 select HAVE_PCSPKR_PLATFORM
204 select HAVE_PERF_EVENTS
205 select HAVE_PERF_EVENTS_NMI
206 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
208 select HAVE_PERF_REGS
209 select HAVE_PERF_USER_STACK_DUMP
210 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
211 select HAVE_REGS_AND_STACK_ACCESS_API
212 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
213 select HAVE_FUNCTION_ARG_ACCESS_API
214 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
215 select HAVE_STACK_VALIDATION if X86_64
217 select HAVE_SYSCALL_TRACEPOINTS
218 select HAVE_UNSTABLE_SCHED_CLOCK
219 select HAVE_USER_RETURN_NOTIFIER
220 select HAVE_GENERIC_VDSO
221 select HOTPLUG_SMT if SMP
222 select IRQ_FORCED_THREADING
223 select NEED_SG_DMA_LENGTH
224 select PCI_DOMAINS if PCI
225 select PCI_LOCKLESS_CONFIG if PCI
228 select RTC_MC146818_LIB
231 select SYSCTL_EXCEPTION_TRACE
232 select THREAD_INFO_IN_TASK
233 select USER_STACKTRACE_SUPPORT
235 select X86_FEATURE_NAMES if PROC_FS
236 select PROC_PID_ARCH_STATUS if PROC_FS
237 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
239 config INSTRUCTION_DECODER
241 depends on KPROBES || PERF_EVENTS || UPROBES
245 default "elf32-i386" if X86_32
246 default "elf64-x86-64" if X86_64
248 config LOCKDEP_SUPPORT
251 config STACKTRACE_SUPPORT
257 config ARCH_MMAP_RND_BITS_MIN
261 config ARCH_MMAP_RND_BITS_MAX
265 config ARCH_MMAP_RND_COMPAT_BITS_MIN
268 config ARCH_MMAP_RND_COMPAT_BITS_MAX
274 config GENERIC_ISA_DMA
276 depends on ISA_DMA_API
281 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
283 config GENERIC_BUG_RELATIVE_POINTERS
286 config ARCH_MAY_HAVE_PC_FDC
288 depends on ISA_DMA_API
290 config GENERIC_CALIBRATE_DELAY
293 config ARCH_HAS_CPU_RELAX
296 config ARCH_HAS_CACHE_LINE_SIZE
299 config ARCH_HAS_FILTER_PGPROT
302 config HAVE_SETUP_PER_CPU_AREA
305 config NEED_PER_CPU_EMBED_FIRST_CHUNK
308 config NEED_PER_CPU_PAGE_FIRST_CHUNK
311 config ARCH_HIBERNATION_POSSIBLE
314 config ARCH_SUSPEND_POSSIBLE
317 config ARCH_WANT_GENERAL_HUGETLB
326 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
329 config KASAN_SHADOW_OFFSET
332 default 0xdffffc0000000000
334 config HAVE_INTEL_TXT
336 depends on INTEL_IOMMU && ACPI
340 depends on X86_32 && SMP
344 depends on X86_64 && SMP
346 config X86_32_LAZY_GS
348 depends on X86_32 && !STACKPROTECTOR
350 config ARCH_SUPPORTS_UPROBES
353 config FIX_EARLYCON_MEM
356 config DYNAMIC_PHYSICAL_MASK
359 config PGTABLE_LEVELS
361 default 5 if X86_5LEVEL
366 config CC_HAS_SANE_STACKPROTECTOR
368 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
369 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
371 We have to make sure stack protector is unconditionally disabled if
372 the compiler produces broken code.
374 menu "Processor type and features"
377 bool "DMA memory allocation support" if EXPERT
380 DMA memory allocation support allows devices with less than 32-bit
381 addressing to allocate within the first 16MB of address space.
382 Disable if no such devices will be used.
387 bool "Symmetric multi-processing support"
389 This enables support for systems with more than one CPU. If you have
390 a system with only one CPU, say N. If you have a system with more
393 If you say N here, the kernel will run on uni- and multiprocessor
394 machines, but will use only one CPU of a multiprocessor machine. If
395 you say Y here, the kernel will run on many, but not all,
396 uniprocessor machines. On a uniprocessor machine, the kernel
397 will run faster if you say N here.
399 Note that if you say Y here and choose architecture "586" or
400 "Pentium" under "Processor family", the kernel will not work on 486
401 architectures. Similarly, multiprocessor kernels for the "PPro"
402 architecture may not work on all Pentium based boards.
404 People using multiprocessor machines who say Y here should also say
405 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
406 Management" code will be disabled if you say Y here.
408 See also <file:Documentation/x86/i386/IO-APIC.rst>,
409 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
410 <http://www.tldp.org/docs.html#howto>.
412 If you don't know what to do here, say N.
414 config X86_FEATURE_NAMES
415 bool "Processor feature human-readable names" if EMBEDDED
418 This option compiles in a table of x86 feature bits and corresponding
419 names. This is required to support /proc/cpuinfo and a few kernel
420 messages. You can disable this to save space, at the expense of
421 making those few kernel messages show numeric feature bits instead.
426 bool "Support x2apic"
427 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
429 This enables x2apic support on CPUs that have this feature.
431 This allows 32-bit apic IDs (so it can support very large systems),
432 and accesses the local apic via MSRs not via mmio.
434 If you don't know what to do here, say N.
437 bool "Enable MPS table" if ACPI || SFI
439 depends on X86_LOCAL_APIC
441 For old smp systems that do not have proper acpi support. Newer systems
442 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
446 depends on X86_GOLDFISH
449 bool "Avoid speculative indirect branches in kernel"
451 select STACK_VALIDATION if HAVE_STACK_VALIDATION
453 Compile kernel with the retpoline compiler options to guard against
454 kernel-to-user data leaks by avoiding speculative indirect
455 branches. Requires a compiler with -mindirect-branch=thunk-extern
456 support for full protection. The kernel may run slower.
458 config X86_CPU_RESCTRL
459 bool "x86 CPU resource control support"
460 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
462 select PROC_CPU_RESCTRL if PROC_FS
464 Enable x86 CPU resource control support.
466 Provide support for the allocation and monitoring of system resources
469 Intel calls this Intel Resource Director Technology
470 (Intel(R) RDT). More information about RDT can be found in the
471 Intel x86 Architecture Software Developer Manual.
473 AMD calls this AMD Platform Quality of Service (AMD QoS).
474 More information about AMD QoS can be found in the AMD64 Technology
475 Platform Quality of Service Extensions manual.
481 bool "Support for big SMP systems with more than 8 CPUs"
484 This option is needed for the systems that have more than 8 CPUs.
486 config X86_EXTENDED_PLATFORM
487 bool "Support for extended (non-PC) x86 platforms"
490 If you disable this option then the kernel will only support
491 standard PC platforms. (which covers the vast majority of
494 If you enable this option then you'll be able to select support
495 for the following (non-PC) 32 bit x86 platforms:
496 Goldfish (Android emulator)
499 SGI 320/540 (Visual Workstation)
500 STA2X11-based (e.g. Northville)
501 Moorestown MID devices
503 If you have one of these systems, or if you want to build a
504 generic distribution kernel, say Y here - otherwise say N.
508 config X86_EXTENDED_PLATFORM
509 bool "Support for extended (non-PC) x86 platforms"
512 If you disable this option then the kernel will only support
513 standard PC platforms. (which covers the vast majority of
516 If you enable this option then you'll be able to select support
517 for the following (non-PC) 64 bit x86 platforms:
522 If you have one of these systems, or if you want to build a
523 generic distribution kernel, say Y here - otherwise say N.
525 # This is an alphabetically sorted list of 64 bit extended platforms
526 # Please maintain the alphabetic order if and when there are additions
528 bool "Numascale NumaChip"
530 depends on X86_EXTENDED_PLATFORM
533 depends on X86_X2APIC
534 depends on PCI_MMCONFIG
536 Adds support for Numascale NumaChip large-SMP systems. Needed to
537 enable more than ~168 cores.
538 If you don't have one of these, you should say N here.
542 select HYPERVISOR_GUEST
544 depends on X86_64 && PCI
545 depends on X86_EXTENDED_PLATFORM
548 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
549 supposed to run on these EM64T-based machines. Only choose this option
550 if you have one of these machines.
553 bool "SGI Ultraviolet"
555 depends on X86_EXTENDED_PLATFORM
558 depends on X86_X2APIC
561 This option is needed in order to support SGI Ultraviolet systems.
562 If you don't have one of these, you should say N here.
564 # Following is an alphabetically sorted list of 32 bit extended platforms
565 # Please maintain the alphabetic order if and when there are additions
568 bool "Goldfish (Virtual Platform)"
569 depends on X86_EXTENDED_PLATFORM
571 Enable support for the Goldfish virtual platform used primarily
572 for Android development. Unless you are building for the Android
573 Goldfish emulator say N here.
576 bool "CE4100 TV platform"
578 depends on PCI_GODIRECT
579 depends on X86_IO_APIC
581 depends on X86_EXTENDED_PLATFORM
582 select X86_REBOOTFIXUPS
584 select OF_EARLY_FLATTREE
586 Select for the Intel CE media processor (CE4100) SOC.
587 This option compiles in support for the CE4100 SOC for settop
588 boxes and media devices.
591 bool "Intel MID platform support"
592 depends on X86_EXTENDED_PLATFORM
593 depends on X86_PLATFORM_DEVICES
595 depends on X86_64 || (PCI_GOANY && X86_32)
596 depends on X86_IO_APIC
602 select MFD_INTEL_MSIC
604 Select to build a kernel capable of supporting Intel MID (Mobile
605 Internet Device) platform systems which do not have the PCI legacy
606 interfaces. If you are building for a PC class system say N here.
608 Intel MID platforms are based on an Intel processor and chipset which
609 consume less power than most of the x86 derivatives.
611 config X86_INTEL_QUARK
612 bool "Intel Quark platform support"
614 depends on X86_EXTENDED_PLATFORM
615 depends on X86_PLATFORM_DEVICES
619 depends on X86_IO_APIC
624 Select to include support for Quark X1000 SoC.
625 Say Y here if you have a Quark based system such as the Arduino
626 compatible Intel Galileo.
628 config X86_INTEL_LPSS
629 bool "Intel Low Power Subsystem Support"
630 depends on X86 && ACPI && PCI
635 Select to build support for Intel Low Power Subsystem such as
636 found on Intel Lynxpoint PCH. Selecting this option enables
637 things like clock tree (common clock framework) and pincontrol
638 which are needed by the LPSS peripheral drivers.
640 config X86_AMD_PLATFORM_DEVICE
641 bool "AMD ACPI2Platform devices support"
646 Select to interpret AMD specific ACPI device to platform device
647 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
648 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
649 implemented under PINCTRL subsystem.
652 tristate "Intel SoC IOSF Sideband support for SoC platforms"
655 This option enables sideband register access support for Intel SoC
656 platforms. On these platforms the IOSF sideband is used in lieu of
657 MSR's for some register accesses, mostly but not limited to thermal
658 and power. Drivers may query the availability of this device to
659 determine if they need the sideband in order to work on these
660 platforms. The sideband is available on the following SoC products.
661 This list is not meant to be exclusive.
666 You should say Y if you are running a kernel on one of these SoC's.
668 config IOSF_MBI_DEBUG
669 bool "Enable IOSF sideband access through debugfs"
670 depends on IOSF_MBI && DEBUG_FS
672 Select this option to expose the IOSF sideband access registers (MCR,
673 MDR, MCRX) through debugfs to write and read register information from
674 different units on the SoC. This is most useful for obtaining device
675 state information for debug and analysis. As this is a general access
676 mechanism, users of this option would have specific knowledge of the
677 device they want to access.
679 If you don't require the option or are in doubt, say N.
682 bool "RDC R-321x SoC"
684 depends on X86_EXTENDED_PLATFORM
686 select X86_REBOOTFIXUPS
688 This option is needed for RDC R-321x system-on-chip, also known
690 If you don't have one of these chips, you should say N here.
692 config X86_32_NON_STANDARD
693 bool "Support non-standard 32-bit SMP architectures"
694 depends on X86_32 && SMP
695 depends on X86_EXTENDED_PLATFORM
697 This option compiles in the bigsmp and STA2X11 default
698 subarchitectures. It is intended for a generic binary
699 kernel. If you select them all, kernel will probe it one by
700 one and will fallback to default.
702 # Alphabetically sorted list of Non standard 32 bit platforms
704 config X86_SUPPORTS_MEMORY_FAILURE
706 # MCE code calls memory_failure():
708 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
709 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
710 depends on X86_64 || !SPARSEMEM
711 select ARCH_SUPPORTS_MEMORY_FAILURE
714 bool "STA2X11 Companion Chip Support"
715 depends on X86_32_NON_STANDARD && PCI
720 This adds support for boards based on the STA2X11 IO-Hub,
721 a.k.a. "ConneXt". The chip is used in place of the standard
722 PC chipset, so all "standard" peripherals are missing. If this
723 option is selected the kernel will still be able to boot on
724 standard PC machines.
727 tristate "Eurobraille/Iris poweroff module"
730 The Iris machines from EuroBraille do not have APM or ACPI support
731 to shut themselves down properly. A special I/O sequence is
732 needed to do so, which is what this module does at
735 This is only for Iris machines from EuroBraille.
739 config SCHED_OMIT_FRAME_POINTER
741 prompt "Single-depth WCHAN output"
744 Calculate simpler /proc/<PID>/wchan values. If this option
745 is disabled then wchan values will recurse back to the
746 caller function. This provides more accurate wchan values,
747 at the expense of slightly more scheduling overhead.
749 If in doubt, say "Y".
751 menuconfig HYPERVISOR_GUEST
752 bool "Linux guest support"
754 Say Y here to enable options for running Linux under various hyper-
755 visors. This option enables basic hypervisor detection and platform
758 If you say N, all options in this submenu will be skipped and
759 disabled, and Linux guest support won't be built in.
764 bool "Enable paravirtualization code"
766 This changes the kernel so it can modify itself when it is run
767 under a hypervisor, potentially improving performance significantly
768 over full virtualization. However, when run without a hypervisor
769 the kernel is theoretically slower and slightly larger.
774 config PARAVIRT_DEBUG
775 bool "paravirt-ops debugging"
776 depends on PARAVIRT && DEBUG_KERNEL
778 Enable to debug paravirt_ops internals. Specifically, BUG if
779 a paravirt_op is missing when it is called.
781 config PARAVIRT_SPINLOCKS
782 bool "Paravirtualization layer for spinlocks"
783 depends on PARAVIRT && SMP
785 Paravirtualized spinlocks allow a pvops backend to replace the
786 spinlock implementation with something virtualization-friendly
787 (for example, block the virtual CPU rather than spinning).
789 It has a minimal impact on native kernels and gives a nice performance
790 benefit on paravirtualized KVM / Xen kernels.
792 If you are unsure how to answer this question, answer Y.
794 config X86_HV_CALLBACK_VECTOR
797 source "arch/x86/xen/Kconfig"
800 bool "KVM Guest support (including kvmclock)"
802 select PARAVIRT_CLOCK
803 select ARCH_CPUIDLE_HALTPOLL
806 This option enables various optimizations for running under the KVM
807 hypervisor. It includes a paravirtualized clock, so that instead
808 of relying on a PIT (or probably other) emulation by the
809 underlying device model, the host provides the guest with
810 timing infrastructure such as time of day, and system time
812 config ARCH_CPUIDLE_HALTPOLL
814 prompt "Disable host haltpoll when loading haltpoll driver"
816 If virtualized under KVM, disable host haltpoll.
819 bool "Support for running PVH guests"
821 This option enables the PVH entry point for guest virtual machines
822 as specified in the x86/HVM direct boot ABI.
825 bool "Enable debug information for KVM Guests in debugfs"
826 depends on KVM_GUEST && DEBUG_FS
828 This option enables collection of various statistics for KVM guest.
829 Statistics are displayed in debugfs filesystem. Enabling this option
830 may incur significant overhead.
832 config PARAVIRT_TIME_ACCOUNTING
833 bool "Paravirtual steal time accounting"
836 Select this option to enable fine granularity task steal time
837 accounting. Time spent executing other tasks in parallel with
838 the current vCPU is discounted from the vCPU power. To account for
839 that, there can be a small performance impact.
841 If in doubt, say N here.
843 config PARAVIRT_CLOCK
846 config JAILHOUSE_GUEST
847 bool "Jailhouse non-root cell support"
848 depends on X86_64 && PCI
851 This option allows to run Linux as guest in a Jailhouse non-root
852 cell. You can leave this option disabled if you only want to start
853 Jailhouse and run Linux afterwards in the root cell.
856 bool "ACRN Guest support"
858 select X86_HV_CALLBACK_VECTOR
860 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
861 a flexible, lightweight reference open-source hypervisor, built with
862 real-time and safety-criticality in mind. It is built for embedded
863 IOT with small footprint and real-time features. More details can be
864 found in https://projectacrn.org/.
866 endif #HYPERVISOR_GUEST
868 source "arch/x86/Kconfig.cpu"
872 prompt "HPET Timer Support" if X86_32
874 Use the IA-PC HPET (High Precision Event Timer) to manage
875 time in preference to the PIT and RTC, if a HPET is
877 HPET is the next generation timer replacing legacy 8254s.
878 The HPET provides a stable time base on SMP
879 systems, unlike the TSC, but it is more expensive to access,
880 as it is off-chip. The interface used is documented
881 in the HPET spec, revision 1.
883 You can safely choose Y here. However, HPET will only be
884 activated if the platform and the BIOS support this feature.
885 Otherwise the 8254 will be used for timing services.
887 Choose N to continue using the legacy 8254 timer.
889 config HPET_EMULATE_RTC
891 depends on HPET_TIMER && (RTC=y || RTC=m || RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
894 def_bool y if X86_INTEL_MID
895 prompt "Intel MID APB Timer Support" if X86_INTEL_MID
897 depends on X86_INTEL_MID && SFI
899 APB timer is the replacement for 8254, HPET on X86 MID platforms.
900 The APBT provides a stable time base on SMP
901 systems, unlike the TSC, but it is more expensive to access,
902 as it is off-chip. APB timers are always running regardless of CPU
903 C states, they are used as per CPU clockevent device when possible.
905 # Mark as expert because too many people got it wrong.
906 # The code disables itself when not needed.
909 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
910 bool "Enable DMI scanning" if EXPERT
912 Enabled scanning of DMI to identify machine quirks. Say Y
913 here unless you have verified that your setup is not
914 affected by entries in the DMI blacklist. Required by PNP
918 bool "Old AMD GART IOMMU support"
921 depends on X86_64 && PCI && AMD_NB
923 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
924 GART based hardware IOMMUs.
926 The GART supports full DMA access for devices with 32-bit access
927 limitations, on systems with more than 3 GB. This is usually needed
928 for USB, sound, many IDE/SATA chipsets and some other devices.
930 Newer systems typically have a modern AMD IOMMU, supported via
931 the CONFIG_AMD_IOMMU=y config option.
933 In normal configurations this driver is only active when needed:
934 there's more than 3 GB of memory and the system contains a
935 32-bit limited device.
940 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
941 depends on X86_64 && SMP && DEBUG_KERNEL
942 select CPUMASK_OFFSTACK
944 Enable maximum number of CPUS and NUMA Nodes for this architecture.
948 # The maximum number of CPUs supported:
950 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
951 # and which can be configured interactively in the
952 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
954 # The ranges are different on 32-bit and 64-bit kernels, depending on
955 # hardware capabilities and scalability features of the kernel.
957 # ( If MAXSMP is enabled we just use the highest possible value and disable
958 # interactive configuration. )
961 config NR_CPUS_RANGE_BEGIN
963 default NR_CPUS_RANGE_END if MAXSMP
967 config NR_CPUS_RANGE_END
970 default 64 if SMP && X86_BIGSMP
971 default 8 if SMP && !X86_BIGSMP
974 config NR_CPUS_RANGE_END
977 default 8192 if SMP && CPUMASK_OFFSTACK
978 default 512 if SMP && !CPUMASK_OFFSTACK
981 config NR_CPUS_DEFAULT
984 default 32 if X86_BIGSMP
988 config NR_CPUS_DEFAULT
991 default 8192 if MAXSMP
996 int "Maximum number of CPUs" if SMP && !MAXSMP
997 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
998 default NR_CPUS_DEFAULT
1000 This allows you to specify the maximum number of CPUs which this
1001 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1002 supported value is 8192, otherwise the maximum value is 512. The
1003 minimum value which makes sense is 2.
1005 This is purely to save memory: each supported CPU adds about 8KB
1006 to the kernel image.
1013 prompt "Multi-core scheduler support"
1016 Multi-core scheduler support improves the CPU scheduler's decision
1017 making when dealing with multi-core CPU chips at a cost of slightly
1018 increased overhead in some places. If unsure say N here.
1020 config SCHED_MC_PRIO
1021 bool "CPU core priorities scheduler support"
1022 depends on SCHED_MC && CPU_SUP_INTEL
1023 select X86_INTEL_PSTATE
1027 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1028 core ordering determined at manufacturing time, which allows
1029 certain cores to reach higher turbo frequencies (when running
1030 single threaded workloads) than others.
1032 Enabling this kernel feature teaches the scheduler about
1033 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1034 scheduler's CPU selection logic accordingly, so that higher
1035 overall system performance can be achieved.
1037 This feature will have no effect on CPUs without this feature.
1039 If unsure say Y here.
1043 depends on !SMP && X86_LOCAL_APIC
1046 bool "Local APIC support on uniprocessors" if !PCI_MSI
1048 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1050 A local APIC (Advanced Programmable Interrupt Controller) is an
1051 integrated interrupt controller in the CPU. If you have a single-CPU
1052 system which has a processor with a local APIC, you can say Y here to
1053 enable and use it. If you say Y here even though your machine doesn't
1054 have a local APIC, then the kernel will still run with no slowdown at
1055 all. The local APIC supports CPU-generated self-interrupts (timer,
1056 performance counters), and the NMI watchdog which detects hard
1059 config X86_UP_IOAPIC
1060 bool "IO-APIC support on uniprocessors"
1061 depends on X86_UP_APIC
1063 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1064 SMP-capable replacement for PC-style interrupt controllers. Most
1065 SMP systems and many recent uniprocessor systems have one.
1067 If you have a single-CPU system with an IO-APIC, you can say Y here
1068 to use it. If you say Y here even though your machine doesn't have
1069 an IO-APIC, then the kernel will still run with no slowdown at all.
1071 config X86_LOCAL_APIC
1073 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1074 select IRQ_DOMAIN_HIERARCHY
1075 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1079 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1081 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1082 bool "Reroute for broken boot IRQs"
1083 depends on X86_IO_APIC
1085 This option enables a workaround that fixes a source of
1086 spurious interrupts. This is recommended when threaded
1087 interrupt handling is used on systems where the generation of
1088 superfluous "boot interrupts" cannot be disabled.
1090 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1091 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1092 kernel does during interrupt handling). On chipsets where this
1093 boot IRQ generation cannot be disabled, this workaround keeps
1094 the original IRQ line masked so that only the equivalent "boot
1095 IRQ" is delivered to the CPUs. The workaround also tells the
1096 kernel to set up the IRQ handler on the boot IRQ line. In this
1097 way only one interrupt is delivered to the kernel. Otherwise
1098 the spurious second interrupt may cause the kernel to bring
1099 down (vital) interrupt lines.
1101 Only affects "broken" chipsets. Interrupt sharing may be
1102 increased on these systems.
1105 bool "Machine Check / overheating reporting"
1106 select GENERIC_ALLOCATOR
1109 Machine Check support allows the processor to notify the
1110 kernel if it detects a problem (e.g. overheating, data corruption).
1111 The action the kernel takes depends on the severity of the problem,
1112 ranging from warning messages to halting the machine.
1114 config X86_MCELOG_LEGACY
1115 bool "Support for deprecated /dev/mcelog character device"
1118 Enable support for /dev/mcelog which is needed by the old mcelog
1119 userspace logging daemon. Consider switching to the new generation
1122 config X86_MCE_INTEL
1124 prompt "Intel MCE features"
1125 depends on X86_MCE && X86_LOCAL_APIC
1127 Additional support for intel specific MCE features such as
1128 the thermal monitor.
1132 prompt "AMD MCE features"
1133 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1135 Additional support for AMD specific MCE features such as
1136 the DRAM Error Threshold.
1138 config X86_ANCIENT_MCE
1139 bool "Support for old Pentium 5 / WinChip machine checks"
1140 depends on X86_32 && X86_MCE
1142 Include support for machine check handling on old Pentium 5 or WinChip
1143 systems. These typically need to be enabled explicitly on the command
1146 config X86_MCE_THRESHOLD
1147 depends on X86_MCE_AMD || X86_MCE_INTEL
1150 config X86_MCE_INJECT
1151 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1152 tristate "Machine check injector support"
1154 Provide support for injecting machine checks for testing purposes.
1155 If you don't know what a machine check is and you don't do kernel
1156 QA it is safe to say n.
1158 config X86_THERMAL_VECTOR
1160 depends on X86_MCE_INTEL
1162 source "arch/x86/events/Kconfig"
1164 config X86_LEGACY_VM86
1165 bool "Legacy VM86 support"
1168 This option allows user programs to put the CPU into V8086
1169 mode, which is an 80286-era approximation of 16-bit real mode.
1171 Some very old versions of X and/or vbetool require this option
1172 for user mode setting. Similarly, DOSEMU will use it if
1173 available to accelerate real mode DOS programs. However, any
1174 recent version of DOSEMU, X, or vbetool should be fully
1175 functional even without kernel VM86 support, as they will all
1176 fall back to software emulation. Nevertheless, if you are using
1177 a 16-bit DOS program where 16-bit performance matters, vm86
1178 mode might be faster than emulation and you might want to
1181 Note that any app that works on a 64-bit kernel is unlikely to
1182 need this option, as 64-bit kernels don't, and can't, support
1183 V8086 mode. This option is also unrelated to 16-bit protected
1184 mode and is not needed to run most 16-bit programs under Wine.
1186 Enabling this option increases the complexity of the kernel
1187 and slows down exception handling a tiny bit.
1189 If unsure, say N here.
1193 default X86_LEGACY_VM86
1196 bool "Enable support for 16-bit segments" if EXPERT
1198 depends on MODIFY_LDT_SYSCALL
1200 This option is required by programs like Wine to run 16-bit
1201 protected mode legacy code on x86 processors. Disabling
1202 this option saves about 300 bytes on i386, or around 6K text
1203 plus 16K runtime memory on x86-64,
1207 depends on X86_16BIT && X86_32
1211 depends on X86_16BIT && X86_64
1213 config X86_VSYSCALL_EMULATION
1214 bool "Enable vsyscall emulation" if EXPERT
1218 This enables emulation of the legacy vsyscall page. Disabling
1219 it is roughly equivalent to booting with vsyscall=none, except
1220 that it will also disable the helpful warning if a program
1221 tries to use a vsyscall. With this option set to N, offending
1222 programs will just segfault, citing addresses of the form
1225 This option is required by many programs built before 2013, and
1226 care should be used even with newer programs if set to N.
1228 Disabling this option saves about 7K of kernel size and
1229 possibly 4K of additional runtime pagetable memory.
1231 config X86_IOPL_IOPERM
1232 bool "IOPERM and IOPL Emulation"
1235 This enables the ioperm() and iopl() syscalls which are necessary
1236 for legacy applications.
1238 Legacy IOPL support is an overbroad mechanism which allows user
1239 space aside of accessing all 65536 I/O ports also to disable
1240 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1241 capabilities and permission from potentially active security
1244 The emulation restricts the functionality of the syscall to
1245 only allowing the full range I/O port access, but prevents the
1246 ability to disable interrupts from user space which would be
1247 granted if the hardware IOPL mechanism would be used.
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"
1488 select DYNAMIC_MEMORY_LAYOUT
1489 select SPARSEMEM_VMEMMAP
1492 5-level paging enables access to larger address space:
1493 upto 128 PiB of virtual address space and 4 PiB of
1494 physical address space.
1496 It will be supported by future Intel CPUs.
1498 A kernel with the option enabled can be booted on machines that
1499 support 4- or 5-level paging.
1501 See Documentation/x86/x86_64/5level-paging.rst for more
1506 config X86_DIRECT_GBPAGES
1510 Certain kernel features effectively disable kernel
1511 linear 1 GB mappings (even if the CPU otherwise
1512 supports them), so don't confuse the user by printing
1513 that we have them enabled.
1515 config X86_CPA_STATISTICS
1516 bool "Enable statistic for Change Page Attribute"
1519 Expose statistics about the Change Page Attribute mechanism, which
1520 helps to determine the effectiveness of preserving large and huge
1521 page mappings when mapping protections are changed.
1523 config AMD_MEM_ENCRYPT
1524 bool "AMD Secure Memory Encryption (SME) support"
1525 depends on X86_64 && CPU_SUP_AMD
1526 select DYNAMIC_PHYSICAL_MASK
1527 select ARCH_USE_MEMREMAP_PROT
1528 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1530 Say yes to enable support for the encryption of system memory.
1531 This requires an AMD processor that supports Secure Memory
1534 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1535 bool "Activate AMD Secure Memory Encryption (SME) by default"
1537 depends on AMD_MEM_ENCRYPT
1539 Say yes to have system memory encrypted by default if running on
1540 an AMD processor that supports Secure Memory Encryption (SME).
1542 If set to Y, then the encryption of system memory can be
1543 deactivated with the mem_encrypt=off command line option.
1545 If set to N, then the encryption of system memory can be
1546 activated with the mem_encrypt=on command line option.
1548 # Common NUMA Features
1550 bool "NUMA Memory Allocation and Scheduler Support"
1552 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1553 default y if X86_BIGSMP
1555 Enable NUMA (Non-Uniform Memory Access) support.
1557 The kernel will try to allocate memory used by a CPU on the
1558 local memory controller of the CPU and add some more
1559 NUMA awareness to the kernel.
1561 For 64-bit this is recommended if the system is Intel Core i7
1562 (or later), AMD Opteron, or EM64T NUMA.
1564 For 32-bit this is only needed if you boot a 32-bit
1565 kernel on a 64-bit NUMA platform.
1567 Otherwise, you should say N.
1571 prompt "Old style AMD Opteron NUMA detection"
1572 depends on X86_64 && NUMA && PCI
1574 Enable AMD NUMA node topology detection. You should say Y here if
1575 you have a multi processor AMD system. This uses an old method to
1576 read the NUMA configuration directly from the builtin Northbridge
1577 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1578 which also takes priority if both are compiled in.
1580 config X86_64_ACPI_NUMA
1582 prompt "ACPI NUMA detection"
1583 depends on X86_64 && NUMA && ACPI && PCI
1586 Enable ACPI SRAT based node topology detection.
1588 # Some NUMA nodes have memory ranges that span
1589 # other nodes. Even though a pfn is valid and
1590 # between a node's start and end pfns, it may not
1591 # reside on that node. See memmap_init_zone()
1593 config NODES_SPAN_OTHER_NODES
1595 depends on X86_64_ACPI_NUMA
1598 bool "NUMA emulation"
1601 Enable NUMA emulation. A flat machine will be split
1602 into virtual nodes when booted with "numa=fake=N", where N is the
1603 number of nodes. This is only useful for debugging.
1606 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1608 default "10" if MAXSMP
1609 default "6" if X86_64
1611 depends on NEED_MULTIPLE_NODES
1613 Specify the maximum number of NUMA Nodes available on the target
1614 system. Increases memory reserved to accommodate various tables.
1616 config ARCH_FLATMEM_ENABLE
1618 depends on X86_32 && !NUMA
1620 config ARCH_SPARSEMEM_ENABLE
1622 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1623 select SPARSEMEM_STATIC if X86_32
1624 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1626 config ARCH_SPARSEMEM_DEFAULT
1627 def_bool X86_64 || (NUMA && X86_32)
1629 config ARCH_SELECT_MEMORY_MODEL
1631 depends on ARCH_SPARSEMEM_ENABLE
1633 config ARCH_MEMORY_PROBE
1634 bool "Enable sysfs memory/probe interface"
1635 depends on X86_64 && MEMORY_HOTPLUG
1637 This option enables a sysfs memory/probe interface for testing.
1638 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1639 If you are unsure how to answer this question, answer N.
1641 config ARCH_PROC_KCORE_TEXT
1643 depends on X86_64 && PROC_KCORE
1645 config ILLEGAL_POINTER_VALUE
1648 default 0xdead000000000000 if X86_64
1650 config X86_PMEM_LEGACY_DEVICE
1653 config X86_PMEM_LEGACY
1654 tristate "Support non-standard NVDIMMs and ADR protected memory"
1655 depends on PHYS_ADDR_T_64BIT
1657 select X86_PMEM_LEGACY_DEVICE
1658 select NUMA_KEEP_MEMINFO if NUMA
1661 Treat memory marked using the non-standard e820 type of 12 as used
1662 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1663 The kernel will offer these regions to the 'pmem' driver so
1664 they can be used for persistent storage.
1669 bool "Allocate 3rd-level pagetables from highmem"
1672 The VM uses one page table entry for each page of physical memory.
1673 For systems with a lot of RAM, this can be wasteful of precious
1674 low memory. Setting this option will put user-space page table
1675 entries in high memory.
1677 config X86_CHECK_BIOS_CORRUPTION
1678 bool "Check for low memory corruption"
1680 Periodically check for memory corruption in low memory, which
1681 is suspected to be caused by BIOS. Even when enabled in the
1682 configuration, it is disabled at runtime. Enable it by
1683 setting "memory_corruption_check=1" on the kernel command
1684 line. By default it scans the low 64k of memory every 60
1685 seconds; see the memory_corruption_check_size and
1686 memory_corruption_check_period parameters in
1687 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1689 When enabled with the default parameters, this option has
1690 almost no overhead, as it reserves a relatively small amount
1691 of memory and scans it infrequently. It both detects corruption
1692 and prevents it from affecting the running system.
1694 It is, however, intended as a diagnostic tool; if repeatable
1695 BIOS-originated corruption always affects the same memory,
1696 you can use memmap= to prevent the kernel from using that
1699 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1700 bool "Set the default setting of memory_corruption_check"
1701 depends on X86_CHECK_BIOS_CORRUPTION
1704 Set whether the default state of memory_corruption_check is
1707 config X86_RESERVE_LOW
1708 int "Amount of low memory, in kilobytes, to reserve for the BIOS"
1712 Specify the amount of low memory to reserve for the BIOS.
1714 The first page contains BIOS data structures that the kernel
1715 must not use, so that page must always be reserved.
1717 By default we reserve the first 64K of physical RAM, as a
1718 number of BIOSes are known to corrupt that memory range
1719 during events such as suspend/resume or monitor cable
1720 insertion, so it must not be used by the kernel.
1722 You can set this to 4 if you are absolutely sure that you
1723 trust the BIOS to get all its memory reservations and usages
1724 right. If you know your BIOS have problems beyond the
1725 default 64K area, you can set this to 640 to avoid using the
1726 entire low memory range.
1728 If you have doubts about the BIOS (e.g. suspend/resume does
1729 not work or there's kernel crashes after certain hardware
1730 hotplug events) then you might want to enable
1731 X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
1732 typical corruption patterns.
1734 Leave this to the default value of 64 if you are unsure.
1736 config MATH_EMULATION
1738 depends on MODIFY_LDT_SYSCALL
1739 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1741 Linux can emulate a math coprocessor (used for floating point
1742 operations) if you don't have one. 486DX and Pentium processors have
1743 a math coprocessor built in, 486SX and 386 do not, unless you added
1744 a 487DX or 387, respectively. (The messages during boot time can
1745 give you some hints here ["man dmesg"].) Everyone needs either a
1746 coprocessor or this emulation.
1748 If you don't have a math coprocessor, you need to say Y here; if you
1749 say Y here even though you have a coprocessor, the coprocessor will
1750 be used nevertheless. (This behavior can be changed with the kernel
1751 command line option "no387", which comes handy if your coprocessor
1752 is broken. Try "man bootparam" or see the documentation of your boot
1753 loader (lilo or loadlin) about how to pass options to the kernel at
1754 boot time.) This means that it is a good idea to say Y here if you
1755 intend to use this kernel on different machines.
1757 More information about the internals of the Linux math coprocessor
1758 emulation can be found in <file:arch/x86/math-emu/README>.
1760 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1761 kernel, it won't hurt.
1765 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1767 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1768 the Memory Type Range Registers (MTRRs) may be used to control
1769 processor access to memory ranges. This is most useful if you have
1770 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1771 allows bus write transfers to be combined into a larger transfer
1772 before bursting over the PCI/AGP bus. This can increase performance
1773 of image write operations 2.5 times or more. Saying Y here creates a
1774 /proc/mtrr file which may be used to manipulate your processor's
1775 MTRRs. Typically the X server should use this.
1777 This code has a reasonably generic interface so that similar
1778 control registers on other processors can be easily supported
1781 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1782 Registers (ARRs) which provide a similar functionality to MTRRs. For
1783 these, the ARRs are used to emulate the MTRRs.
1784 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1785 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1786 write-combining. All of these processors are supported by this code
1787 and it makes sense to say Y here if you have one of them.
1789 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1790 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1791 can lead to all sorts of problems, so it's good to say Y here.
1793 You can safely say Y even if your machine doesn't have MTRRs, you'll
1794 just add about 9 KB to your kernel.
1796 See <file:Documentation/x86/mtrr.rst> for more information.
1798 config MTRR_SANITIZER
1800 prompt "MTRR cleanup support"
1803 Convert MTRR layout from continuous to discrete, so X drivers can
1804 add writeback entries.
1806 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1807 The largest mtrr entry size for a continuous block can be set with
1812 config MTRR_SANITIZER_ENABLE_DEFAULT
1813 int "MTRR cleanup enable value (0-1)"
1816 depends on MTRR_SANITIZER
1818 Enable mtrr cleanup default value
1820 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1821 int "MTRR cleanup spare reg num (0-7)"
1824 depends on MTRR_SANITIZER
1826 mtrr cleanup spare entries default, it can be changed via
1827 mtrr_spare_reg_nr=N on the kernel command line.
1831 prompt "x86 PAT support" if EXPERT
1834 Use PAT attributes to setup page level cache control.
1836 PATs are the modern equivalents of MTRRs and are much more
1837 flexible than MTRRs.
1839 Say N here if you see bootup problems (boot crash, boot hang,
1840 spontaneous reboots) or a non-working video driver.
1844 config ARCH_USES_PG_UNCACHED
1850 prompt "x86 architectural random number generator" if EXPERT
1852 Enable the x86 architectural RDRAND instruction
1853 (Intel Bull Mountain technology) to generate random numbers.
1854 If supported, this is a high bandwidth, cryptographically
1855 secure hardware random number generator.
1859 prompt "Supervisor Mode Access Prevention" if EXPERT
1861 Supervisor Mode Access Prevention (SMAP) is a security
1862 feature in newer Intel processors. There is a small
1863 performance cost if this enabled and turned on; there is
1864 also a small increase in the kernel size if this is enabled.
1870 prompt "User Mode Instruction Prevention" if EXPERT
1872 User Mode Instruction Prevention (UMIP) is a security feature in
1873 some x86 processors. If enabled, a general protection fault is
1874 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1875 executed in user mode. These instructions unnecessarily expose
1876 information about the hardware state.
1878 The vast majority of applications do not use these instructions.
1879 For the very few that do, software emulation is provided in
1880 specific cases in protected and virtual-8086 modes. Emulated
1883 config X86_INTEL_MEMORY_PROTECTION_KEYS
1884 prompt "Memory Protection Keys"
1886 # Note: only available in 64-bit mode
1887 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1888 select ARCH_USES_HIGH_VMA_FLAGS
1889 select ARCH_HAS_PKEYS
1891 Memory Protection Keys provides a mechanism for enforcing
1892 page-based protections, but without requiring modification of the
1893 page tables when an application changes protection domains.
1895 For details, see Documentation/core-api/protection-keys.rst
1900 prompt "TSX enable mode"
1901 depends on CPU_SUP_INTEL
1902 default X86_INTEL_TSX_MODE_OFF
1904 Intel's TSX (Transactional Synchronization Extensions) feature
1905 allows to optimize locking protocols through lock elision which
1906 can lead to a noticeable performance boost.
1908 On the other hand it has been shown that TSX can be exploited
1909 to form side channel attacks (e.g. TAA) and chances are there
1910 will be more of those attacks discovered in the future.
1912 Therefore TSX is not enabled by default (aka tsx=off). An admin
1913 might override this decision by tsx=on the command line parameter.
1914 Even with TSX enabled, the kernel will attempt to enable the best
1915 possible TAA mitigation setting depending on the microcode available
1916 for the particular machine.
1918 This option allows to set the default tsx mode between tsx=on, =off
1919 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1922 Say off if not sure, auto if TSX is in use but it should be used on safe
1923 platforms or on if TSX is in use and the security aspect of tsx is not
1926 config X86_INTEL_TSX_MODE_OFF
1929 TSX is disabled if possible - equals to tsx=off command line parameter.
1931 config X86_INTEL_TSX_MODE_ON
1934 TSX is always enabled on TSX capable HW - equals the tsx=on command
1937 config X86_INTEL_TSX_MODE_AUTO
1940 TSX is enabled on TSX capable HW that is believed to be safe against
1941 side channel attacks- equals the tsx=auto command line parameter.
1945 bool "EFI runtime service support"
1948 select EFI_RUNTIME_WRAPPERS
1950 This enables the kernel to use EFI runtime services that are
1951 available (such as the EFI variable services).
1953 This option is only useful on systems that have EFI firmware.
1954 In addition, you should use the latest ELILO loader available
1955 at <http://elilo.sourceforge.net> in order to take advantage
1956 of EFI runtime services. However, even with this option, the
1957 resultant kernel should continue to boot on existing non-EFI
1961 bool "EFI stub support"
1962 depends on EFI && !X86_USE_3DNOW
1963 depends on $(cc-option,-mabi=ms) || X86_32
1966 This kernel feature allows a bzImage to be loaded directly
1967 by EFI firmware without the use of a bootloader.
1969 See Documentation/admin-guide/efi-stub.rst for more information.
1972 bool "EFI mixed-mode support"
1973 depends on EFI_STUB && X86_64
1975 Enabling this feature allows a 64-bit kernel to be booted
1976 on a 32-bit firmware, provided that your CPU supports 64-bit
1979 Note that it is not possible to boot a mixed-mode enabled
1980 kernel via the EFI boot stub - a bootloader that supports
1981 the EFI handover protocol must be used.
1987 prompt "Enable seccomp to safely compute untrusted bytecode"
1989 This kernel feature is useful for number crunching applications
1990 that may need to compute untrusted bytecode during their
1991 execution. By using pipes or other transports made available to
1992 the process as file descriptors supporting the read/write
1993 syscalls, it's possible to isolate those applications in
1994 their own address space using seccomp. Once seccomp is
1995 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
1996 and the task is only allowed to execute a few safe syscalls
1997 defined by each seccomp mode.
1999 If unsure, say Y. Only embedded should say N here.
2001 source "kernel/Kconfig.hz"
2004 bool "kexec system call"
2007 kexec is a system call that implements the ability to shutdown your
2008 current kernel, and to start another kernel. It is like a reboot
2009 but it is independent of the system firmware. And like a reboot
2010 you can start any kernel with it, not just Linux.
2012 The name comes from the similarity to the exec system call.
2014 It is an ongoing process to be certain the hardware in a machine
2015 is properly shutdown, so do not be surprised if this code does not
2016 initially work for you. As of this writing the exact hardware
2017 interface is strongly in flux, so no good recommendation can be
2021 bool "kexec file based system call"
2026 depends on CRYPTO_SHA256=y
2028 This is new version of kexec system call. This system call is
2029 file based and takes file descriptors as system call argument
2030 for kernel and initramfs as opposed to list of segments as
2031 accepted by previous system call.
2033 config ARCH_HAS_KEXEC_PURGATORY
2037 bool "Verify kernel signature during kexec_file_load() syscall"
2038 depends on KEXEC_FILE
2041 This option makes the kexec_file_load() syscall check for a valid
2042 signature of the kernel image. The image can still be loaded without
2043 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2044 there's a signature that we can check, then it must be valid.
2046 In addition to this option, you need to enable signature
2047 verification for the corresponding kernel image type being
2048 loaded in order for this to work.
2050 config KEXEC_SIG_FORCE
2051 bool "Require a valid signature in kexec_file_load() syscall"
2052 depends on KEXEC_SIG
2054 This option makes kernel signature verification mandatory for
2055 the kexec_file_load() syscall.
2057 config KEXEC_BZIMAGE_VERIFY_SIG
2058 bool "Enable bzImage signature verification support"
2059 depends on KEXEC_SIG
2060 depends on SIGNED_PE_FILE_VERIFICATION
2061 select SYSTEM_TRUSTED_KEYRING
2063 Enable bzImage signature verification support.
2066 bool "kernel crash dumps"
2067 depends on X86_64 || (X86_32 && HIGHMEM)
2069 Generate crash dump after being started by kexec.
2070 This should be normally only set in special crash dump kernels
2071 which are loaded in the main kernel with kexec-tools into
2072 a specially reserved region and then later executed after
2073 a crash by kdump/kexec. The crash dump kernel must be compiled
2074 to a memory address not used by the main kernel or BIOS using
2075 PHYSICAL_START, or it must be built as a relocatable image
2076 (CONFIG_RELOCATABLE=y).
2077 For more details see Documentation/admin-guide/kdump/kdump.rst
2081 depends on KEXEC && HIBERNATION
2083 Jump between original kernel and kexeced kernel and invoke
2084 code in physical address mode via KEXEC
2086 config PHYSICAL_START
2087 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2090 This gives the physical address where the kernel is loaded.
2092 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2093 bzImage will decompress itself to above physical address and
2094 run from there. Otherwise, bzImage will run from the address where
2095 it has been loaded by the boot loader and will ignore above physical
2098 In normal kdump cases one does not have to set/change this option
2099 as now bzImage can be compiled as a completely relocatable image
2100 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2101 address. This option is mainly useful for the folks who don't want
2102 to use a bzImage for capturing the crash dump and want to use a
2103 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2104 to be specifically compiled to run from a specific memory area
2105 (normally a reserved region) and this option comes handy.
2107 So if you are using bzImage for capturing the crash dump,
2108 leave the value here unchanged to 0x1000000 and set
2109 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2110 for capturing the crash dump change this value to start of
2111 the reserved region. In other words, it can be set based on
2112 the "X" value as specified in the "crashkernel=YM@XM"
2113 command line boot parameter passed to the panic-ed
2114 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2115 for more details about crash dumps.
2117 Usage of bzImage for capturing the crash dump is recommended as
2118 one does not have to build two kernels. Same kernel can be used
2119 as production kernel and capture kernel. Above option should have
2120 gone away after relocatable bzImage support is introduced. But it
2121 is present because there are users out there who continue to use
2122 vmlinux for dump capture. This option should go away down the
2125 Don't change this unless you know what you are doing.
2128 bool "Build a relocatable kernel"
2131 This builds a kernel image that retains relocation information
2132 so it can be loaded someplace besides the default 1MB.
2133 The relocations tend to make the kernel binary about 10% larger,
2134 but are discarded at runtime.
2136 One use is for the kexec on panic case where the recovery kernel
2137 must live at a different physical address than the primary
2140 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2141 it has been loaded at and the compile time physical address
2142 (CONFIG_PHYSICAL_START) is used as the minimum location.
2144 config RANDOMIZE_BASE
2145 bool "Randomize the address of the kernel image (KASLR)"
2146 depends on RELOCATABLE
2149 In support of Kernel Address Space Layout Randomization (KASLR),
2150 this randomizes the physical address at which the kernel image
2151 is decompressed and the virtual address where the kernel
2152 image is mapped, as a security feature that deters exploit
2153 attempts relying on knowledge of the location of kernel
2156 On 64-bit, the kernel physical and virtual addresses are
2157 randomized separately. The physical address will be anywhere
2158 between 16MB and the top of physical memory (up to 64TB). The
2159 virtual address will be randomized from 16MB up to 1GB (9 bits
2160 of entropy). Note that this also reduces the memory space
2161 available to kernel modules from 1.5GB to 1GB.
2163 On 32-bit, the kernel physical and virtual addresses are
2164 randomized together. They will be randomized from 16MB up to
2165 512MB (8 bits of entropy).
2167 Entropy is generated using the RDRAND instruction if it is
2168 supported. If RDTSC is supported, its value is mixed into
2169 the entropy pool as well. If neither RDRAND nor RDTSC are
2170 supported, then entropy is read from the i8254 timer. The
2171 usable entropy is limited by the kernel being built using
2172 2GB addressing, and that PHYSICAL_ALIGN must be at a
2173 minimum of 2MB. As a result, only 10 bits of entropy are
2174 theoretically possible, but the implementations are further
2175 limited due to memory layouts.
2179 # Relocation on x86 needs some additional build support
2180 config X86_NEED_RELOCS
2182 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2184 config PHYSICAL_ALIGN
2185 hex "Alignment value to which kernel should be aligned"
2187 range 0x2000 0x1000000 if X86_32
2188 range 0x200000 0x1000000 if X86_64
2190 This value puts the alignment restrictions on physical address
2191 where kernel is loaded and run from. Kernel is compiled for an
2192 address which meets above alignment restriction.
2194 If bootloader loads the kernel at a non-aligned address and
2195 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2196 address aligned to above value and run from there.
2198 If bootloader loads the kernel at a non-aligned address and
2199 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2200 load address and decompress itself to the address it has been
2201 compiled for and run from there. The address for which kernel is
2202 compiled already meets above alignment restrictions. Hence the
2203 end result is that kernel runs from a physical address meeting
2204 above alignment restrictions.
2206 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2207 this value must be a multiple of 0x200000.
2209 Don't change this unless you know what you are doing.
2211 config DYNAMIC_MEMORY_LAYOUT
2214 This option makes base addresses of vmalloc and vmemmap as well as
2215 __PAGE_OFFSET movable during boot.
2217 config RANDOMIZE_MEMORY
2218 bool "Randomize the kernel memory sections"
2220 depends on RANDOMIZE_BASE
2221 select DYNAMIC_MEMORY_LAYOUT
2222 default RANDOMIZE_BASE
2224 Randomizes the base virtual address of kernel memory sections
2225 (physical memory mapping, vmalloc & vmemmap). This security feature
2226 makes exploits relying on predictable memory locations less reliable.
2228 The order of allocations remains unchanged. Entropy is generated in
2229 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2230 configuration have in average 30,000 different possible virtual
2231 addresses for each memory section.
2235 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2236 hex "Physical memory mapping padding" if EXPERT
2237 depends on RANDOMIZE_MEMORY
2238 default "0xa" if MEMORY_HOTPLUG
2240 range 0x1 0x40 if MEMORY_HOTPLUG
2243 Define the padding in terabytes added to the existing physical
2244 memory size during kernel memory randomization. It is useful
2245 for memory hotplug support but reduces the entropy available for
2246 address randomization.
2248 If unsure, leave at the default value.
2254 config BOOTPARAM_HOTPLUG_CPU0
2255 bool "Set default setting of cpu0_hotpluggable"
2256 depends on HOTPLUG_CPU
2258 Set whether default state of cpu0_hotpluggable is on or off.
2260 Say Y here to enable CPU0 hotplug by default. If this switch
2261 is turned on, there is no need to give cpu0_hotplug kernel
2262 parameter and the CPU0 hotplug feature is enabled by default.
2264 Please note: there are two known CPU0 dependencies if you want
2265 to enable the CPU0 hotplug feature either by this switch or by
2266 cpu0_hotplug kernel parameter.
2268 First, resume from hibernate or suspend always starts from CPU0.
2269 So hibernate and suspend are prevented if CPU0 is offline.
2271 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2272 offline if any interrupt can not migrate out of CPU0. There may
2273 be other CPU0 dependencies.
2275 Please make sure the dependencies are under your control before
2276 you enable this feature.
2278 Say N if you don't want to enable CPU0 hotplug feature by default.
2279 You still can enable the CPU0 hotplug feature at boot by kernel
2280 parameter cpu0_hotplug.
2282 config DEBUG_HOTPLUG_CPU0
2284 prompt "Debug CPU0 hotplug"
2285 depends on HOTPLUG_CPU
2287 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2288 soon as possible and boots up userspace with CPU0 offlined. User
2289 can online CPU0 back after boot time.
2291 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2292 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2293 compilation or giving cpu0_hotplug kernel parameter at boot.
2299 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2300 depends on COMPAT_32
2302 Certain buggy versions of glibc will crash if they are
2303 presented with a 32-bit vDSO that is not mapped at the address
2304 indicated in its segment table.
2306 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2307 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2308 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2309 the only released version with the bug, but OpenSUSE 9
2310 contains a buggy "glibc 2.3.2".
2312 The symptom of the bug is that everything crashes on startup, saying:
2313 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2315 Saying Y here changes the default value of the vdso32 boot
2316 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2317 This works around the glibc bug but hurts performance.
2319 If unsure, say N: if you are compiling your own kernel, you
2320 are unlikely to be using a buggy version of glibc.
2323 prompt "vsyscall table for legacy applications"
2325 default LEGACY_VSYSCALL_XONLY
2327 Legacy user code that does not know how to find the vDSO expects
2328 to be able to issue three syscalls by calling fixed addresses in
2329 kernel space. Since this location is not randomized with ASLR,
2330 it can be used to assist security vulnerability exploitation.
2332 This setting can be changed at boot time via the kernel command
2333 line parameter vsyscall=[emulate|xonly|none].
2335 On a system with recent enough glibc (2.14 or newer) and no
2336 static binaries, you can say None without a performance penalty
2337 to improve security.
2339 If unsure, select "Emulate execution only".
2341 config LEGACY_VSYSCALL_EMULATE
2342 bool "Full emulation"
2344 The kernel traps and emulates calls into the fixed vsyscall
2345 address mapping. This makes the mapping non-executable, but
2346 it still contains readable known contents, which could be
2347 used in certain rare security vulnerability exploits. This
2348 configuration is recommended when using legacy userspace
2349 that still uses vsyscalls along with legacy binary
2350 instrumentation tools that require code to be readable.
2352 An example of this type of legacy userspace is running
2353 Pin on an old binary that still uses vsyscalls.
2355 config LEGACY_VSYSCALL_XONLY
2356 bool "Emulate execution only"
2358 The kernel traps and emulates calls into the fixed vsyscall
2359 address mapping and does not allow reads. This
2360 configuration is recommended when userspace might use the
2361 legacy vsyscall area but support for legacy binary
2362 instrumentation of legacy code is not needed. It mitigates
2363 certain uses of the vsyscall area as an ASLR-bypassing
2366 config LEGACY_VSYSCALL_NONE
2369 There will be no vsyscall mapping at all. This will
2370 eliminate any risk of ASLR bypass due to the vsyscall
2371 fixed address mapping. Attempts to use the vsyscalls
2372 will be reported to dmesg, so that either old or
2373 malicious userspace programs can be identified.
2378 bool "Built-in kernel command line"
2380 Allow for specifying boot arguments to the kernel at
2381 build time. On some systems (e.g. embedded ones), it is
2382 necessary or convenient to provide some or all of the
2383 kernel boot arguments with the kernel itself (that is,
2384 to not rely on the boot loader to provide them.)
2386 To compile command line arguments into the kernel,
2387 set this option to 'Y', then fill in the
2388 boot arguments in CONFIG_CMDLINE.
2390 Systems with fully functional boot loaders (i.e. non-embedded)
2391 should leave this option set to 'N'.
2394 string "Built-in kernel command string"
2395 depends on CMDLINE_BOOL
2398 Enter arguments here that should be compiled into the kernel
2399 image and used at boot time. If the boot loader provides a
2400 command line at boot time, it is appended to this string to
2401 form the full kernel command line, when the system boots.
2403 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2404 change this behavior.
2406 In most cases, the command line (whether built-in or provided
2407 by the boot loader) should specify the device for the root
2410 config CMDLINE_OVERRIDE
2411 bool "Built-in command line overrides boot loader arguments"
2412 depends on CMDLINE_BOOL && CMDLINE != ""
2414 Set this option to 'Y' to have the kernel ignore the boot loader
2415 command line, and use ONLY the built-in command line.
2417 This is used to work around broken boot loaders. This should
2418 be set to 'N' under normal conditions.
2420 config MODIFY_LDT_SYSCALL
2421 bool "Enable the LDT (local descriptor table)" if EXPERT
2424 Linux can allow user programs to install a per-process x86
2425 Local Descriptor Table (LDT) using the modify_ldt(2) system
2426 call. This is required to run 16-bit or segmented code such as
2427 DOSEMU or some Wine programs. It is also used by some very old
2428 threading libraries.
2430 Enabling this feature adds a small amount of overhead to
2431 context switches and increases the low-level kernel attack
2432 surface. Disabling it removes the modify_ldt(2) system call.
2434 Saying 'N' here may make sense for embedded or server kernels.
2436 source "kernel/livepatch/Kconfig"
2440 config ARCH_HAS_ADD_PAGES
2442 depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
2444 config ARCH_ENABLE_MEMORY_HOTPLUG
2446 depends on X86_64 || (X86_32 && HIGHMEM)
2448 config ARCH_ENABLE_MEMORY_HOTREMOVE
2450 depends on MEMORY_HOTPLUG
2452 config USE_PERCPU_NUMA_NODE_ID
2456 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
2458 depends on X86_64 || X86_PAE
2460 config ARCH_ENABLE_HUGEPAGE_MIGRATION
2462 depends on X86_64 && HUGETLB_PAGE && MIGRATION
2464 config ARCH_ENABLE_THP_MIGRATION
2466 depends on X86_64 && TRANSPARENT_HUGEPAGE
2468 menu "Power management and ACPI options"
2470 config ARCH_HIBERNATION_HEADER
2472 depends on HIBERNATION
2474 source "kernel/power/Kconfig"
2476 source "drivers/acpi/Kconfig"
2478 source "drivers/sfi/Kconfig"
2485 tristate "APM (Advanced Power Management) BIOS support"
2486 depends on X86_32 && PM_SLEEP
2488 APM is a BIOS specification for saving power using several different
2489 techniques. This is mostly useful for battery powered laptops with
2490 APM compliant BIOSes. If you say Y here, the system time will be
2491 reset after a RESUME operation, the /proc/apm device will provide
2492 battery status information, and user-space programs will receive
2493 notification of APM "events" (e.g. battery status change).
2495 If you select "Y" here, you can disable actual use of the APM
2496 BIOS by passing the "apm=off" option to the kernel at boot time.
2498 Note that the APM support is almost completely disabled for
2499 machines with more than one CPU.
2501 In order to use APM, you will need supporting software. For location
2502 and more information, read <file:Documentation/power/apm-acpi.rst>
2503 and the Battery Powered Linux mini-HOWTO, available from
2504 <http://www.tldp.org/docs.html#howto>.
2506 This driver does not spin down disk drives (see the hdparm(8)
2507 manpage ("man 8 hdparm") for that), and it doesn't turn off
2508 VESA-compliant "green" monitors.
2510 This driver does not support the TI 4000M TravelMate and the ACER
2511 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2512 desktop machines also don't have compliant BIOSes, and this driver
2513 may cause those machines to panic during the boot phase.
2515 Generally, if you don't have a battery in your machine, there isn't
2516 much point in using this driver and you should say N. If you get
2517 random kernel OOPSes or reboots that don't seem to be related to
2518 anything, try disabling/enabling this option (or disabling/enabling
2521 Some other things you should try when experiencing seemingly random,
2524 1) make sure that you have enough swap space and that it is
2526 2) pass the "no-hlt" option to the kernel
2527 3) switch on floating point emulation in the kernel and pass
2528 the "no387" option to the kernel
2529 4) pass the "floppy=nodma" option to the kernel
2530 5) pass the "mem=4M" option to the kernel (thereby disabling
2531 all but the first 4 MB of RAM)
2532 6) make sure that the CPU is not over clocked.
2533 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2534 8) disable the cache from your BIOS settings
2535 9) install a fan for the video card or exchange video RAM
2536 10) install a better fan for the CPU
2537 11) exchange RAM chips
2538 12) exchange the motherboard.
2540 To compile this driver as a module, choose M here: the
2541 module will be called apm.
2545 config APM_IGNORE_USER_SUSPEND
2546 bool "Ignore USER SUSPEND"
2548 This option will ignore USER SUSPEND requests. On machines with a
2549 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2550 series notebooks, it is necessary to say Y because of a BIOS bug.
2552 config APM_DO_ENABLE
2553 bool "Enable PM at boot time"
2555 Enable APM features at boot time. From page 36 of the APM BIOS
2556 specification: "When disabled, the APM BIOS does not automatically
2557 power manage devices, enter the Standby State, enter the Suspend
2558 State, or take power saving steps in response to CPU Idle calls."
2559 This driver will make CPU Idle calls when Linux is idle (unless this
2560 feature is turned off -- see "Do CPU IDLE calls", below). This
2561 should always save battery power, but more complicated APM features
2562 will be dependent on your BIOS implementation. You may need to turn
2563 this option off if your computer hangs at boot time when using APM
2564 support, or if it beeps continuously instead of suspending. Turn
2565 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2566 T400CDT. This is off by default since most machines do fine without
2571 bool "Make CPU Idle calls when idle"
2573 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2574 On some machines, this can activate improved power savings, such as
2575 a slowed CPU clock rate, when the machine is idle. These idle calls
2576 are made after the idle loop has run for some length of time (e.g.,
2577 333 mS). On some machines, this will cause a hang at boot time or
2578 whenever the CPU becomes idle. (On machines with more than one CPU,
2579 this option does nothing.)
2581 config APM_DISPLAY_BLANK
2582 bool "Enable console blanking using APM"
2584 Enable console blanking using the APM. Some laptops can use this to
2585 turn off the LCD backlight when the screen blanker of the Linux
2586 virtual console blanks the screen. Note that this is only used by
2587 the virtual console screen blanker, and won't turn off the backlight
2588 when using the X Window system. This also doesn't have anything to
2589 do with your VESA-compliant power-saving monitor. Further, this
2590 option doesn't work for all laptops -- it might not turn off your
2591 backlight at all, or it might print a lot of errors to the console,
2592 especially if you are using gpm.
2594 config APM_ALLOW_INTS
2595 bool "Allow interrupts during APM BIOS calls"
2597 Normally we disable external interrupts while we are making calls to
2598 the APM BIOS as a measure to lessen the effects of a badly behaving
2599 BIOS implementation. The BIOS should reenable interrupts if it
2600 needs to. Unfortunately, some BIOSes do not -- especially those in
2601 many of the newer IBM Thinkpads. If you experience hangs when you
2602 suspend, try setting this to Y. Otherwise, say N.
2606 source "drivers/cpufreq/Kconfig"
2608 source "drivers/cpuidle/Kconfig"
2610 source "drivers/idle/Kconfig"
2615 menu "Bus options (PCI etc.)"
2618 prompt "PCI access mode"
2619 depends on X86_32 && PCI
2622 On PCI systems, the BIOS can be used to detect the PCI devices and
2623 determine their configuration. However, some old PCI motherboards
2624 have BIOS bugs and may crash if this is done. Also, some embedded
2625 PCI-based systems don't have any BIOS at all. Linux can also try to
2626 detect the PCI hardware directly without using the BIOS.
2628 With this option, you can specify how Linux should detect the
2629 PCI devices. If you choose "BIOS", the BIOS will be used,
2630 if you choose "Direct", the BIOS won't be used, and if you
2631 choose "MMConfig", then PCI Express MMCONFIG will be used.
2632 If you choose "Any", the kernel will try MMCONFIG, then the
2633 direct access method and falls back to the BIOS if that doesn't
2634 work. If unsure, go with the default, which is "Any".
2639 config PCI_GOMMCONFIG
2656 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2658 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2661 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2664 bool "Support mmconfig PCI config space access" if X86_64
2666 depends on PCI && (ACPI || SFI || JAILHOUSE_GUEST)
2667 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2671 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2675 depends on PCI && XEN
2678 config MMCONF_FAM10H
2680 depends on X86_64 && PCI_MMCONFIG && ACPI
2682 config PCI_CNB20LE_QUIRK
2683 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2686 Read the PCI windows out of the CNB20LE host bridge. This allows
2687 PCI hotplug to work on systems with the CNB20LE chipset which do
2690 There's no public spec for this chipset, and this functionality
2691 is known to be incomplete.
2693 You should say N unless you know you need this.
2696 bool "ISA bus support on modern systems" if EXPERT
2698 Expose ISA bus device drivers and options available for selection and
2699 configuration. Enable this option if your target machine has an ISA
2700 bus. ISA is an older system, displaced by PCI and newer bus
2701 architectures -- if your target machine is modern, it probably does
2702 not have an ISA bus.
2706 # x86_64 have no ISA slots, but can have ISA-style DMA.
2708 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2711 Enables ISA-style DMA support for devices requiring such controllers.
2719 Find out whether you have ISA slots on your motherboard. ISA is the
2720 name of a bus system, i.e. the way the CPU talks to the other stuff
2721 inside your box. Other bus systems are PCI, EISA, MicroChannel
2722 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2723 newer boards don't support it. If you have ISA, say Y, otherwise N.
2726 tristate "NatSemi SCx200 support"
2728 This provides basic support for National Semiconductor's
2729 (now AMD's) Geode processors. The driver probes for the
2730 PCI-IDs of several on-chip devices, so its a good dependency
2731 for other scx200_* drivers.
2733 If compiled as a module, the driver is named scx200.
2735 config SCx200HR_TIMER
2736 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2740 This driver provides a clocksource built upon the on-chip
2741 27MHz high-resolution timer. Its also a workaround for
2742 NSC Geode SC-1100's buggy TSC, which loses time when the
2743 processor goes idle (as is done by the scheduler). The
2744 other workaround is idle=poll boot option.
2747 bool "One Laptop Per Child support"
2755 Add support for detecting the unique features of the OLPC
2759 bool "OLPC XO-1 Power Management"
2760 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2762 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2765 bool "OLPC XO-1 Real Time Clock"
2766 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2768 Add support for the XO-1 real time clock, which can be used as a
2769 programmable wakeup source.
2772 bool "OLPC XO-1 SCI extras"
2773 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2777 Add support for SCI-based features of the OLPC XO-1 laptop:
2778 - EC-driven system wakeups
2782 - AC adapter status updates
2783 - Battery status updates
2785 config OLPC_XO15_SCI
2786 bool "OLPC XO-1.5 SCI extras"
2787 depends on OLPC && ACPI
2790 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2791 - EC-driven system wakeups
2792 - AC adapter status updates
2793 - Battery status updates
2796 bool "PCEngines ALIX System Support (LED setup)"
2799 This option enables system support for the PCEngines ALIX.
2800 At present this just sets up LEDs for GPIO control on
2801 ALIX2/3/6 boards. However, other system specific setup should
2804 Note: You must still enable the drivers for GPIO and LED support
2805 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2807 Note: You have to set alix.force=1 for boards with Award BIOS.
2810 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2813 This option enables system support for the Soekris Engineering net5501.
2816 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2820 This option enables system support for the Traverse Technologies GEOS.
2823 bool "Technologic Systems TS-5500 platform support"
2825 select CHECK_SIGNATURE
2829 This option enables system support for the Technologic Systems TS-5500.
2835 depends on CPU_SUP_AMD && PCI
2838 bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
2840 Firmwares often provide initial graphics framebuffers so the BIOS,
2841 bootloader or kernel can show basic video-output during boot for
2842 user-guidance and debugging. Historically, x86 used the VESA BIOS
2843 Extensions and EFI-framebuffers for this, which are mostly limited
2845 This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
2846 framebuffers so the new generic system-framebuffer drivers can be
2847 used on x86. If the framebuffer is not compatible with the generic
2848 modes, it is advertised as fallback platform framebuffer so legacy
2849 drivers like efifb, vesafb and uvesafb can pick it up.
2850 If this option is not selected, all system framebuffers are always
2851 marked as fallback platform framebuffers as usual.
2853 Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
2854 not be able to pick up generic system framebuffers if this option
2855 is selected. You are highly encouraged to enable simplefb as
2856 replacement if you select this option. simplefb can correctly deal
2857 with generic system framebuffers. But you should still keep vesafb
2858 and others enabled as fallback if a system framebuffer is
2859 incompatible with simplefb.
2866 menu "Binary Emulations"
2868 config IA32_EMULATION
2869 bool "IA32 Emulation"
2871 select ARCH_WANT_OLD_COMPAT_IPC
2873 select COMPAT_BINFMT_ELF
2874 select COMPAT_OLD_SIGACTION
2876 Include code to run legacy 32-bit programs under a
2877 64-bit kernel. You should likely turn this on, unless you're
2878 100% sure that you don't have any 32-bit programs left.
2881 tristate "IA32 a.out support"
2882 depends on IA32_EMULATION
2885 Support old a.out binaries in the 32bit emulation.
2888 bool "x32 ABI for 64-bit mode"
2891 Include code to run binaries for the x32 native 32-bit ABI
2892 for 64-bit processors. An x32 process gets access to the
2893 full 64-bit register file and wide data path while leaving
2894 pointers at 32 bits for smaller memory footprint.
2896 You will need a recent binutils (2.22 or later) with
2897 elf32_x86_64 support enabled to compile a kernel with this
2902 depends on IA32_EMULATION || X86_32
2904 select OLD_SIGSUSPEND3
2908 depends on IA32_EMULATION || X86_X32
2911 config COMPAT_FOR_U64_ALIGNMENT
2914 config SYSVIPC_COMPAT
2922 config HAVE_ATOMIC_IOMAP
2926 source "drivers/firmware/Kconfig"
2928 source "arch/x86/kvm/Kconfig"
2930 source "arch/x86/Kconfig.assembler"