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 GENERIC_VDSO_32
18 select HAVE_DEBUG_STACKOVERFLOW
20 select MODULES_USE_ELF_REL
22 select ARCH_SPLIT_ARG64
27 # Options that are inherently 64-bit kernel only:
28 select ARCH_HAS_GIGANTIC_PAGE
29 select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
30 select ARCH_USE_CMPXCHG_LOCKREF
31 select HAVE_ARCH_SOFT_DIRTY
32 select MODULES_USE_ELF_RELA
33 select NEED_DMA_MAP_STATE
35 select ARCH_HAS_ELFCORE_COMPAT
38 config FORCE_DYNAMIC_FTRACE
41 depends on FUNCTION_TRACER
44 We keep the static function tracing (!DYNAMIC_FTRACE) around
45 in order to test the non static function tracing in the
46 generic code, as other architectures still use it. But we
47 only need to keep it around for x86_64. No need to keep it
48 for x86_32. For x86_32, force DYNAMIC_FTRACE.
52 # ( Note that options that are marked 'if X86_64' could in principle be
53 # ported to 32-bit as well. )
58 # Note: keep this list sorted alphabetically
60 select ACPI_LEGACY_TABLES_LOOKUP if ACPI
61 select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
62 select ARCH_32BIT_OFF_T if X86_32
63 select ARCH_CLOCKSOURCE_INIT
64 select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
65 select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
66 select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
67 select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
68 select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE)
69 select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
70 select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
71 select ARCH_HAS_CACHE_LINE_SIZE
72 select ARCH_HAS_CURRENT_STACK_POINTER
73 select ARCH_HAS_DEBUG_VIRTUAL
74 select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE
75 select ARCH_HAS_DEVMEM_IS_ALLOWED
76 select ARCH_HAS_EARLY_DEBUG if KGDB
77 select ARCH_HAS_ELF_RANDOMIZE
78 select ARCH_HAS_FAST_MULTIPLIER
79 select ARCH_HAS_FILTER_PGPROT
80 select ARCH_HAS_FORTIFY_SOURCE
81 select ARCH_HAS_GCOV_PROFILE_ALL
82 select ARCH_HAS_KCOV if X86_64
83 select ARCH_HAS_MEM_ENCRYPT
84 select ARCH_HAS_MEMBARRIER_SYNC_CORE
85 select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
86 select ARCH_HAS_PMEM_API if X86_64
87 select ARCH_HAS_PTE_DEVMAP if X86_64
88 select ARCH_HAS_PTE_SPECIAL
89 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
90 select ARCH_HAS_COPY_MC if X86_64
91 select ARCH_HAS_SET_MEMORY
92 select ARCH_HAS_SET_DIRECT_MAP
93 select ARCH_HAS_STRICT_KERNEL_RWX
94 select ARCH_HAS_STRICT_MODULE_RWX
95 select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
96 select ARCH_HAS_SYSCALL_WRAPPER
97 select ARCH_HAS_UBSAN_SANITIZE_ALL
98 select ARCH_HAS_DEBUG_WX
99 select ARCH_HAS_ZONE_DMA_SET if EXPERT
100 select ARCH_HAVE_NMI_SAFE_CMPXCHG
101 select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
102 select ARCH_MIGHT_HAVE_PC_PARPORT
103 select ARCH_MIGHT_HAVE_PC_SERIO
104 select ARCH_STACKWALK
105 select ARCH_SUPPORTS_ACPI
106 select ARCH_SUPPORTS_ATOMIC_RMW
107 select ARCH_SUPPORTS_DEBUG_PAGEALLOC
108 select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64
109 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
110 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
111 select ARCH_SUPPORTS_LTO_CLANG
112 select ARCH_SUPPORTS_LTO_CLANG_THIN
113 select ARCH_USE_BUILTIN_BSWAP
114 select ARCH_USE_MEMTEST
115 select ARCH_USE_QUEUED_RWLOCKS
116 select ARCH_USE_QUEUED_SPINLOCKS
117 select ARCH_USE_SYM_ANNOTATIONS
118 select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
119 select ARCH_WANT_DEFAULT_BPF_JIT if X86_64
120 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
121 select ARCH_WANTS_NO_INSTR
122 select ARCH_WANT_GENERAL_HUGETLB
123 select ARCH_WANT_HUGE_PMD_SHARE
124 select ARCH_WANT_LD_ORPHAN_WARN
125 select ARCH_WANTS_RT_DELAYED_SIGNALS
126 select ARCH_WANTS_THP_SWAP if X86_64
127 select ARCH_HAS_PARANOID_L1D_FLUSH
128 select BUILDTIME_TABLE_SORT
130 select CLOCKSOURCE_VALIDATE_LAST_CYCLE
131 select CLOCKSOURCE_WATCHDOG
132 select DCACHE_WORD_ACCESS
133 select DYNAMIC_SIGFRAME
134 select EDAC_ATOMIC_SCRUB
136 select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
137 select GENERIC_CLOCKEVENTS_MIN_ADJUST
138 select GENERIC_CMOS_UPDATE
139 select GENERIC_CPU_AUTOPROBE
140 select GENERIC_CPU_VULNERABILITIES
141 select GENERIC_EARLY_IOREMAP
144 select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
145 select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC
146 select GENERIC_IRQ_MIGRATION if SMP
147 select GENERIC_IRQ_PROBE
148 select GENERIC_IRQ_RESERVATION_MODE
149 select GENERIC_IRQ_SHOW
150 select GENERIC_PENDING_IRQ if SMP
151 select GENERIC_PTDUMP
152 select GENERIC_SMP_IDLE_THREAD
153 select GENERIC_TIME_VSYSCALL
154 select GENERIC_GETTIMEOFDAY
155 select GENERIC_VDSO_TIME_NS
156 select GUP_GET_PTE_LOW_HIGH if X86_PAE
157 select HARDIRQS_SW_RESEND
158 select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
159 select HAVE_ACPI_APEI if ACPI
160 select HAVE_ACPI_APEI_NMI if ACPI
161 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
162 select HAVE_ARCH_AUDITSYSCALL
163 select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
164 select HAVE_ARCH_HUGE_VMALLOC if X86_64
165 select HAVE_ARCH_JUMP_LABEL
166 select HAVE_ARCH_JUMP_LABEL_RELATIVE
167 select HAVE_ARCH_KASAN if X86_64
168 select HAVE_ARCH_KASAN_VMALLOC if X86_64
169 select HAVE_ARCH_KFENCE
170 select HAVE_ARCH_KGDB
171 select HAVE_ARCH_MMAP_RND_BITS if MMU
172 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
173 select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
174 select HAVE_ARCH_PREL32_RELOCATIONS
175 select HAVE_ARCH_SECCOMP_FILTER
176 select HAVE_ARCH_THREAD_STRUCT_WHITELIST
177 select HAVE_ARCH_STACKLEAK
178 select HAVE_ARCH_TRACEHOOK
179 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
180 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
181 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD
182 select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD
183 select HAVE_ARCH_VMAP_STACK if X86_64
184 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
185 select HAVE_ARCH_WITHIN_STACK_FRAMES
186 select HAVE_ASM_MODVERSIONS
187 select HAVE_CMPXCHG_DOUBLE
188 select HAVE_CMPXCHG_LOCAL
189 select HAVE_CONTEXT_TRACKING if X86_64
190 select HAVE_CONTEXT_TRACKING_OFFSTACK if HAVE_CONTEXT_TRACKING
191 select HAVE_C_RECORDMCOUNT
192 select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION
193 select HAVE_BUILDTIME_MCOUNT_SORT
194 select HAVE_DEBUG_KMEMLEAK
195 select HAVE_DMA_CONTIGUOUS
196 select HAVE_DYNAMIC_FTRACE
197 select HAVE_DYNAMIC_FTRACE_WITH_REGS
198 select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
199 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
200 select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
201 select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
203 select HAVE_EFFICIENT_UNALIGNED_ACCESS
205 select HAVE_EXIT_THREAD
207 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
208 select HAVE_FTRACE_MCOUNT_RECORD
209 select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
210 select HAVE_FUNCTION_TRACER
211 select HAVE_GCC_PLUGINS
212 select HAVE_HW_BREAKPOINT
213 select HAVE_IOREMAP_PROT
214 select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
215 select HAVE_IRQ_TIME_ACCOUNTING
216 select HAVE_KERNEL_BZIP2
217 select HAVE_KERNEL_GZIP
218 select HAVE_KERNEL_LZ4
219 select HAVE_KERNEL_LZMA
220 select HAVE_KERNEL_LZO
221 select HAVE_KERNEL_XZ
222 select HAVE_KERNEL_ZSTD
224 select HAVE_KPROBES_ON_FTRACE
225 select HAVE_FUNCTION_ERROR_INJECTION
226 select HAVE_KRETPROBES
228 select HAVE_LIVEPATCH if X86_64
229 select HAVE_MIXED_BREAKPOINTS_REGS
230 select HAVE_MOD_ARCH_SPECIFIC
234 select HAVE_OPTPROBES
235 select HAVE_PCSPKR_PLATFORM
236 select HAVE_PERF_EVENTS
237 select HAVE_PERF_EVENTS_NMI
238 select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
240 select HAVE_PERF_REGS
241 select HAVE_PERF_USER_STACK_DUMP
242 select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT
243 select HAVE_POSIX_CPU_TIMERS_TASK_WORK
244 select HAVE_REGS_AND_STACK_ACCESS_API
245 select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
246 select HAVE_FUNCTION_ARG_ACCESS_API
247 select HAVE_SETUP_PER_CPU_AREA
248 select HAVE_SOFTIRQ_ON_OWN_STACK
249 select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
250 select HAVE_STACK_VALIDATION if X86_64
251 select HAVE_STATIC_CALL
252 select HAVE_STATIC_CALL_INLINE if HAVE_STACK_VALIDATION
253 select HAVE_PREEMPT_DYNAMIC_CALL
255 select HAVE_SYSCALL_TRACEPOINTS
256 select HAVE_UNSTABLE_SCHED_CLOCK
257 select HAVE_USER_RETURN_NOTIFIER
258 select HAVE_GENERIC_VDSO
259 select HOTPLUG_SMT if SMP
260 select IRQ_FORCED_THREADING
261 select NEED_PER_CPU_EMBED_FIRST_CHUNK
262 select NEED_PER_CPU_PAGE_FIRST_CHUNK
263 select NEED_SG_DMA_LENGTH
264 select PCI_DOMAINS if PCI
265 select PCI_LOCKLESS_CONFIG if PCI
268 select RTC_MC146818_LIB
271 select STACK_VALIDATION if HAVE_STACK_VALIDATION && (HAVE_STATIC_CALL_INLINE || RETPOLINE)
272 select SYSCTL_EXCEPTION_TRACE
273 select THREAD_INFO_IN_TASK
274 select TRACE_IRQFLAGS_SUPPORT
275 select USER_STACKTRACE_SUPPORT
277 select HAVE_ARCH_KCSAN if X86_64
278 select X86_FEATURE_NAMES if PROC_FS
279 select PROC_PID_ARCH_STATUS if PROC_FS
280 select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX
281 imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
283 config INSTRUCTION_DECODER
285 depends on KPROBES || PERF_EVENTS || UPROBES
289 default "elf32-i386" if X86_32
290 default "elf64-x86-64" if X86_64
292 config LOCKDEP_SUPPORT
295 config STACKTRACE_SUPPORT
301 config ARCH_MMAP_RND_BITS_MIN
305 config ARCH_MMAP_RND_BITS_MAX
309 config ARCH_MMAP_RND_COMPAT_BITS_MIN
312 config ARCH_MMAP_RND_COMPAT_BITS_MAX
318 config GENERIC_ISA_DMA
320 depends on ISA_DMA_API
325 select GENERIC_BUG_RELATIVE_POINTERS if X86_64
327 config GENERIC_BUG_RELATIVE_POINTERS
330 config ARCH_MAY_HAVE_PC_FDC
332 depends on ISA_DMA_API
334 config GENERIC_CALIBRATE_DELAY
337 config ARCH_HAS_CPU_RELAX
340 config ARCH_HAS_FILTER_PGPROT
343 config ARCH_HIBERNATION_POSSIBLE
348 default 1024 if X86_64
351 config ARCH_SUSPEND_POSSIBLE
357 config KASAN_SHADOW_OFFSET
360 default 0xdffffc0000000000
362 config HAVE_INTEL_TXT
364 depends on INTEL_IOMMU && ACPI
368 depends on X86_32 && SMP
372 depends on X86_64 && SMP
374 config ARCH_SUPPORTS_UPROBES
377 config FIX_EARLYCON_MEM
380 config DYNAMIC_PHYSICAL_MASK
383 config PGTABLE_LEVELS
385 default 5 if X86_5LEVEL
390 config CC_HAS_SANE_STACKPROTECTOR
392 default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
393 default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
395 We have to make sure stack protector is unconditionally disabled if
396 the compiler produces broken code or if it does not let us control
397 the segment on 32-bit kernels.
399 menu "Processor type and features"
402 bool "Symmetric multi-processing support"
404 This enables support for systems with more than one CPU. If you have
405 a system with only one CPU, say N. If you have a system with more
408 If you say N here, the kernel will run on uni- and multiprocessor
409 machines, but will use only one CPU of a multiprocessor machine. If
410 you say Y here, the kernel will run on many, but not all,
411 uniprocessor machines. On a uniprocessor machine, the kernel
412 will run faster if you say N here.
414 Note that if you say Y here and choose architecture "586" or
415 "Pentium" under "Processor family", the kernel will not work on 486
416 architectures. Similarly, multiprocessor kernels for the "PPro"
417 architecture may not work on all Pentium based boards.
419 People using multiprocessor machines who say Y here should also say
420 Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
421 Management" code will be disabled if you say Y here.
423 See also <file:Documentation/x86/i386/IO-APIC.rst>,
424 <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO available at
425 <http://www.tldp.org/docs.html#howto>.
427 If you don't know what to do here, say N.
429 config X86_FEATURE_NAMES
430 bool "Processor feature human-readable names" if EMBEDDED
433 This option compiles in a table of x86 feature bits and corresponding
434 names. This is required to support /proc/cpuinfo and a few kernel
435 messages. You can disable this to save space, at the expense of
436 making those few kernel messages show numeric feature bits instead.
441 bool "Support x2apic"
442 depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
444 This enables x2apic support on CPUs that have this feature.
446 This allows 32-bit apic IDs (so it can support very large systems),
447 and accesses the local apic via MSRs not via mmio.
449 If you don't know what to do here, say N.
452 bool "Enable MPS table" if ACPI
454 depends on X86_LOCAL_APIC
456 For old smp systems that do not have proper acpi support. Newer systems
457 (esp with 64bit cpus) with acpi support, MADT and DSDT will override it
461 depends on X86_GOLDFISH
464 bool "Avoid speculative indirect branches in kernel"
467 Compile kernel with the retpoline compiler options to guard against
468 kernel-to-user data leaks by avoiding speculative indirect
469 branches. Requires a compiler with -mindirect-branch=thunk-extern
470 support for full protection. The kernel may run slower.
473 def_bool $(cc-option,-mharden-sls=all)
476 bool "Mitigate Straight-Line-Speculation"
477 depends on CC_HAS_SLS && X86_64
480 Compile the kernel with straight-line-speculation options to guard
481 against straight line speculation. The kernel image might be slightly
484 config X86_CPU_RESCTRL
485 bool "x86 CPU resource control support"
486 depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
488 select PROC_CPU_RESCTRL if PROC_FS
490 Enable x86 CPU resource control support.
492 Provide support for the allocation and monitoring of system resources
495 Intel calls this Intel Resource Director Technology
496 (Intel(R) RDT). More information about RDT can be found in the
497 Intel x86 Architecture Software Developer Manual.
499 AMD calls this AMD Platform Quality of Service (AMD QoS).
500 More information about AMD QoS can be found in the AMD64 Technology
501 Platform Quality of Service Extensions manual.
507 bool "Support for big SMP systems with more than 8 CPUs"
510 This option is needed for the systems that have more than 8 CPUs.
512 config X86_EXTENDED_PLATFORM
513 bool "Support for extended (non-PC) x86 platforms"
516 If you disable this option then the kernel will only support
517 standard PC platforms. (which covers the vast majority of
520 If you enable this option then you'll be able to select support
521 for the following (non-PC) 32 bit x86 platforms:
522 Goldfish (Android emulator)
525 SGI 320/540 (Visual Workstation)
526 STA2X11-based (e.g. Northville)
527 Moorestown MID devices
529 If you have one of these systems, or if you want to build a
530 generic distribution kernel, say Y here - otherwise say N.
534 config X86_EXTENDED_PLATFORM
535 bool "Support for extended (non-PC) x86 platforms"
538 If you disable this option then the kernel will only support
539 standard PC platforms. (which covers the vast majority of
542 If you enable this option then you'll be able to select support
543 for the following (non-PC) 64 bit x86 platforms:
548 If you have one of these systems, or if you want to build a
549 generic distribution kernel, say Y here - otherwise say N.
551 # This is an alphabetically sorted list of 64 bit extended platforms
552 # Please maintain the alphabetic order if and when there are additions
554 bool "Numascale NumaChip"
556 depends on X86_EXTENDED_PLATFORM
559 depends on X86_X2APIC
560 depends on PCI_MMCONFIG
562 Adds support for Numascale NumaChip large-SMP systems. Needed to
563 enable more than ~168 cores.
564 If you don't have one of these, you should say N here.
568 select HYPERVISOR_GUEST
570 depends on X86_64 && PCI
571 depends on X86_EXTENDED_PLATFORM
574 Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is
575 supposed to run on these EM64T-based machines. Only choose this option
576 if you have one of these machines.
579 bool "SGI Ultraviolet"
581 depends on X86_EXTENDED_PLATFORM
584 depends on KEXEC_CORE
585 depends on X86_X2APIC
588 This option is needed in order to support SGI Ultraviolet systems.
589 If you don't have one of these, you should say N here.
591 # Following is an alphabetically sorted list of 32 bit extended platforms
592 # Please maintain the alphabetic order if and when there are additions
595 bool "Goldfish (Virtual Platform)"
596 depends on X86_EXTENDED_PLATFORM
598 Enable support for the Goldfish virtual platform used primarily
599 for Android development. Unless you are building for the Android
600 Goldfish emulator say N here.
603 bool "CE4100 TV platform"
605 depends on PCI_GODIRECT
606 depends on X86_IO_APIC
608 depends on X86_EXTENDED_PLATFORM
609 select X86_REBOOTFIXUPS
611 select OF_EARLY_FLATTREE
613 Select for the Intel CE media processor (CE4100) SOC.
614 This option compiles in support for the CE4100 SOC for settop
615 boxes and media devices.
618 bool "Intel MID platform support"
619 depends on X86_EXTENDED_PLATFORM
620 depends on X86_PLATFORM_DEVICES
622 depends on X86_64 || (PCI_GOANY && X86_32)
623 depends on X86_IO_APIC
628 Select to build a kernel capable of supporting Intel MID (Mobile
629 Internet Device) platform systems which do not have the PCI legacy
630 interfaces. If you are building for a PC class system say N here.
632 Intel MID platforms are based on an Intel processor and chipset which
633 consume less power than most of the x86 derivatives.
635 config X86_INTEL_QUARK
636 bool "Intel Quark platform support"
638 depends on X86_EXTENDED_PLATFORM
639 depends on X86_PLATFORM_DEVICES
643 depends on X86_IO_APIC
648 Select to include support for Quark X1000 SoC.
649 Say Y here if you have a Quark based system such as the Arduino
650 compatible Intel Galileo.
652 config X86_INTEL_LPSS
653 bool "Intel Low Power Subsystem Support"
654 depends on X86 && ACPI && PCI
659 Select to build support for Intel Low Power Subsystem such as
660 found on Intel Lynxpoint PCH. Selecting this option enables
661 things like clock tree (common clock framework) and pincontrol
662 which are needed by the LPSS peripheral drivers.
664 config X86_AMD_PLATFORM_DEVICE
665 bool "AMD ACPI2Platform devices support"
670 Select to interpret AMD specific ACPI device to platform device
671 such as I2C, UART, GPIO found on AMD Carrizo and later chipsets.
672 I2C and UART depend on COMMON_CLK to set clock. GPIO driver is
673 implemented under PINCTRL subsystem.
676 tristate "Intel SoC IOSF Sideband support for SoC platforms"
679 This option enables sideband register access support for Intel SoC
680 platforms. On these platforms the IOSF sideband is used in lieu of
681 MSR's for some register accesses, mostly but not limited to thermal
682 and power. Drivers may query the availability of this device to
683 determine if they need the sideband in order to work on these
684 platforms. The sideband is available on the following SoC products.
685 This list is not meant to be exclusive.
690 You should say Y if you are running a kernel on one of these SoC's.
692 config IOSF_MBI_DEBUG
693 bool "Enable IOSF sideband access through debugfs"
694 depends on IOSF_MBI && DEBUG_FS
696 Select this option to expose the IOSF sideband access registers (MCR,
697 MDR, MCRX) through debugfs to write and read register information from
698 different units on the SoC. This is most useful for obtaining device
699 state information for debug and analysis. As this is a general access
700 mechanism, users of this option would have specific knowledge of the
701 device they want to access.
703 If you don't require the option or are in doubt, say N.
706 bool "RDC R-321x SoC"
708 depends on X86_EXTENDED_PLATFORM
710 select X86_REBOOTFIXUPS
712 This option is needed for RDC R-321x system-on-chip, also known
714 If you don't have one of these chips, you should say N here.
716 config X86_32_NON_STANDARD
717 bool "Support non-standard 32-bit SMP architectures"
718 depends on X86_32 && SMP
719 depends on X86_EXTENDED_PLATFORM
721 This option compiles in the bigsmp and STA2X11 default
722 subarchitectures. It is intended for a generic binary
723 kernel. If you select them all, kernel will probe it one by
724 one and will fallback to default.
726 # Alphabetically sorted list of Non standard 32 bit platforms
728 config X86_SUPPORTS_MEMORY_FAILURE
730 # MCE code calls memory_failure():
732 # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags:
733 # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH:
734 depends on X86_64 || !SPARSEMEM
735 select ARCH_SUPPORTS_MEMORY_FAILURE
738 bool "STA2X11 Companion Chip Support"
739 depends on X86_32_NON_STANDARD && PCI
744 This adds support for boards based on the STA2X11 IO-Hub,
745 a.k.a. "ConneXt". The chip is used in place of the standard
746 PC chipset, so all "standard" peripherals are missing. If this
747 option is selected the kernel will still be able to boot on
748 standard PC machines.
751 tristate "Eurobraille/Iris poweroff module"
754 The Iris machines from EuroBraille do not have APM or ACPI support
755 to shut themselves down properly. A special I/O sequence is
756 needed to do so, which is what this module does at
759 This is only for Iris machines from EuroBraille.
763 config SCHED_OMIT_FRAME_POINTER
765 prompt "Single-depth WCHAN output"
768 Calculate simpler /proc/<PID>/wchan values. If this option
769 is disabled then wchan values will recurse back to the
770 caller function. This provides more accurate wchan values,
771 at the expense of slightly more scheduling overhead.
773 If in doubt, say "Y".
775 menuconfig HYPERVISOR_GUEST
776 bool "Linux guest support"
778 Say Y here to enable options for running Linux under various hyper-
779 visors. This option enables basic hypervisor detection and platform
782 If you say N, all options in this submenu will be skipped and
783 disabled, and Linux guest support won't be built in.
788 bool "Enable paravirtualization code"
789 depends on HAVE_STATIC_CALL
791 This changes the kernel so it can modify itself when it is run
792 under a hypervisor, potentially improving performance significantly
793 over full virtualization. However, when run without a hypervisor
794 the kernel is theoretically slower and slightly larger.
799 config PARAVIRT_DEBUG
800 bool "paravirt-ops debugging"
801 depends on PARAVIRT && DEBUG_KERNEL
803 Enable to debug paravirt_ops internals. Specifically, BUG if
804 a paravirt_op is missing when it is called.
806 config PARAVIRT_SPINLOCKS
807 bool "Paravirtualization layer for spinlocks"
808 depends on PARAVIRT && SMP
810 Paravirtualized spinlocks allow a pvops backend to replace the
811 spinlock implementation with something virtualization-friendly
812 (for example, block the virtual CPU rather than spinning).
814 It has a minimal impact on native kernels and gives a nice performance
815 benefit on paravirtualized KVM / Xen kernels.
817 If you are unsure how to answer this question, answer Y.
819 config X86_HV_CALLBACK_VECTOR
822 source "arch/x86/xen/Kconfig"
825 bool "KVM Guest support (including kvmclock)"
827 select PARAVIRT_CLOCK
828 select ARCH_CPUIDLE_HALTPOLL
829 select X86_HV_CALLBACK_VECTOR
832 This option enables various optimizations for running under the KVM
833 hypervisor. It includes a paravirtualized clock, so that instead
834 of relying on a PIT (or probably other) emulation by the
835 underlying device model, the host provides the guest with
836 timing infrastructure such as time of day, and system time
838 config ARCH_CPUIDLE_HALTPOLL
840 prompt "Disable host haltpoll when loading haltpoll driver"
842 If virtualized under KVM, disable host haltpoll.
845 bool "Support for running PVH guests"
847 This option enables the PVH entry point for guest virtual machines
848 as specified in the x86/HVM direct boot ABI.
850 config PARAVIRT_TIME_ACCOUNTING
851 bool "Paravirtual steal time accounting"
854 Select this option to enable fine granularity task steal time
855 accounting. Time spent executing other tasks in parallel with
856 the current vCPU is discounted from the vCPU power. To account for
857 that, there can be a small performance impact.
859 If in doubt, say N here.
861 config PARAVIRT_CLOCK
864 config JAILHOUSE_GUEST
865 bool "Jailhouse non-root cell support"
866 depends on X86_64 && PCI
869 This option allows to run Linux as guest in a Jailhouse non-root
870 cell. You can leave this option disabled if you only want to start
871 Jailhouse and run Linux afterwards in the root cell.
874 bool "ACRN Guest support"
876 select X86_HV_CALLBACK_VECTOR
878 This option allows to run Linux as guest in the ACRN hypervisor. ACRN is
879 a flexible, lightweight reference open-source hypervisor, built with
880 real-time and safety-criticality in mind. It is built for embedded
881 IOT with small footprint and real-time features. More details can be
882 found in https://projectacrn.org/.
884 endif #HYPERVISOR_GUEST
886 source "arch/x86/Kconfig.cpu"
890 prompt "HPET Timer Support" if X86_32
892 Use the IA-PC HPET (High Precision Event Timer) to manage
893 time in preference to the PIT and RTC, if a HPET is
895 HPET is the next generation timer replacing legacy 8254s.
896 The HPET provides a stable time base on SMP
897 systems, unlike the TSC, but it is more expensive to access,
898 as it is off-chip. The interface used is documented
899 in the HPET spec, revision 1.
901 You can safely choose Y here. However, HPET will only be
902 activated if the platform and the BIOS support this feature.
903 Otherwise the 8254 will be used for timing services.
905 Choose N to continue using the legacy 8254 timer.
907 config HPET_EMULATE_RTC
909 depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y)
911 # Mark as expert because too many people got it wrong.
912 # The code disables itself when not needed.
915 select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
916 bool "Enable DMI scanning" if EXPERT
918 Enabled scanning of DMI to identify machine quirks. Say Y
919 here unless you have verified that your setup is not
920 affected by entries in the DMI blacklist. Required by PNP
924 bool "Old AMD GART IOMMU support"
928 depends on X86_64 && PCI && AMD_NB
930 Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron
931 GART based hardware IOMMUs.
933 The GART supports full DMA access for devices with 32-bit access
934 limitations, on systems with more than 3 GB. This is usually needed
935 for USB, sound, many IDE/SATA chipsets and some other devices.
937 Newer systems typically have a modern AMD IOMMU, supported via
938 the CONFIG_AMD_IOMMU=y config option.
940 In normal configurations this driver is only active when needed:
941 there's more than 3 GB of memory and the system contains a
942 32-bit limited device.
947 bool "Enable Maximum number of SMP Processors and NUMA Nodes"
948 depends on X86_64 && SMP && DEBUG_KERNEL
949 select CPUMASK_OFFSTACK
951 Enable maximum number of CPUS and NUMA Nodes for this architecture.
955 # The maximum number of CPUs supported:
957 # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT,
958 # and which can be configured interactively in the
959 # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range.
961 # The ranges are different on 32-bit and 64-bit kernels, depending on
962 # hardware capabilities and scalability features of the kernel.
964 # ( If MAXSMP is enabled we just use the highest possible value and disable
965 # interactive configuration. )
968 config NR_CPUS_RANGE_BEGIN
970 default NR_CPUS_RANGE_END if MAXSMP
974 config NR_CPUS_RANGE_END
977 default 64 if SMP && X86_BIGSMP
978 default 8 if SMP && !X86_BIGSMP
981 config NR_CPUS_RANGE_END
984 default 8192 if SMP && CPUMASK_OFFSTACK
985 default 512 if SMP && !CPUMASK_OFFSTACK
988 config NR_CPUS_DEFAULT
991 default 32 if X86_BIGSMP
995 config NR_CPUS_DEFAULT
998 default 8192 if MAXSMP
1003 int "Maximum number of CPUs" if SMP && !MAXSMP
1004 range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
1005 default NR_CPUS_DEFAULT
1007 This allows you to specify the maximum number of CPUs which this
1008 kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
1009 supported value is 8192, otherwise the maximum value is 512. The
1010 minimum value which makes sense is 2.
1012 This is purely to save memory: each supported CPU adds about 8KB
1013 to the kernel image.
1015 config SCHED_CLUSTER
1016 bool "Cluster scheduler support"
1020 Cluster scheduler support improves the CPU scheduler's decision
1021 making when dealing with machines that have clusters of CPUs.
1022 Cluster usually means a couple of CPUs which are placed closely
1023 by sharing mid-level caches, last-level cache tags or internal
1031 prompt "Multi-core scheduler support"
1034 Multi-core scheduler support improves the CPU scheduler's decision
1035 making when dealing with multi-core CPU chips at a cost of slightly
1036 increased overhead in some places. If unsure say N here.
1038 config SCHED_MC_PRIO
1039 bool "CPU core priorities scheduler support"
1040 depends on SCHED_MC && CPU_SUP_INTEL
1041 select X86_INTEL_PSTATE
1045 Intel Turbo Boost Max Technology 3.0 enabled CPUs have a
1046 core ordering determined at manufacturing time, which allows
1047 certain cores to reach higher turbo frequencies (when running
1048 single threaded workloads) than others.
1050 Enabling this kernel feature teaches the scheduler about
1051 the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the
1052 scheduler's CPU selection logic accordingly, so that higher
1053 overall system performance can be achieved.
1055 This feature will have no effect on CPUs without this feature.
1057 If unsure say Y here.
1061 depends on !SMP && X86_LOCAL_APIC
1064 bool "Local APIC support on uniprocessors" if !PCI_MSI
1066 depends on X86_32 && !SMP && !X86_32_NON_STANDARD
1068 A local APIC (Advanced Programmable Interrupt Controller) is an
1069 integrated interrupt controller in the CPU. If you have a single-CPU
1070 system which has a processor with a local APIC, you can say Y here to
1071 enable and use it. If you say Y here even though your machine doesn't
1072 have a local APIC, then the kernel will still run with no slowdown at
1073 all. The local APIC supports CPU-generated self-interrupts (timer,
1074 performance counters), and the NMI watchdog which detects hard
1077 config X86_UP_IOAPIC
1078 bool "IO-APIC support on uniprocessors"
1079 depends on X86_UP_APIC
1081 An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
1082 SMP-capable replacement for PC-style interrupt controllers. Most
1083 SMP systems and many recent uniprocessor systems have one.
1085 If you have a single-CPU system with an IO-APIC, you can say Y here
1086 to use it. If you say Y here even though your machine doesn't have
1087 an IO-APIC, then the kernel will still run with no slowdown at all.
1089 config X86_LOCAL_APIC
1091 depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
1092 select IRQ_DOMAIN_HIERARCHY
1093 select PCI_MSI_IRQ_DOMAIN if PCI_MSI
1097 depends on X86_LOCAL_APIC || X86_UP_IOAPIC
1099 config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
1100 bool "Reroute for broken boot IRQs"
1101 depends on X86_IO_APIC
1103 This option enables a workaround that fixes a source of
1104 spurious interrupts. This is recommended when threaded
1105 interrupt handling is used on systems where the generation of
1106 superfluous "boot interrupts" cannot be disabled.
1108 Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
1109 entry in the chipset's IO-APIC is masked (as, e.g. the RT
1110 kernel does during interrupt handling). On chipsets where this
1111 boot IRQ generation cannot be disabled, this workaround keeps
1112 the original IRQ line masked so that only the equivalent "boot
1113 IRQ" is delivered to the CPUs. The workaround also tells the
1114 kernel to set up the IRQ handler on the boot IRQ line. In this
1115 way only one interrupt is delivered to the kernel. Otherwise
1116 the spurious second interrupt may cause the kernel to bring
1117 down (vital) interrupt lines.
1119 Only affects "broken" chipsets. Interrupt sharing may be
1120 increased on these systems.
1123 bool "Machine Check / overheating reporting"
1124 select GENERIC_ALLOCATOR
1127 Machine Check support allows the processor to notify the
1128 kernel if it detects a problem (e.g. overheating, data corruption).
1129 The action the kernel takes depends on the severity of the problem,
1130 ranging from warning messages to halting the machine.
1132 config X86_MCELOG_LEGACY
1133 bool "Support for deprecated /dev/mcelog character device"
1136 Enable support for /dev/mcelog which is needed by the old mcelog
1137 userspace logging daemon. Consider switching to the new generation
1140 config X86_MCE_INTEL
1142 prompt "Intel MCE features"
1143 depends on X86_MCE && X86_LOCAL_APIC
1145 Additional support for intel specific MCE features such as
1146 the thermal monitor.
1150 prompt "AMD MCE features"
1151 depends on X86_MCE && X86_LOCAL_APIC && AMD_NB
1153 Additional support for AMD specific MCE features such as
1154 the DRAM Error Threshold.
1156 config X86_ANCIENT_MCE
1157 bool "Support for old Pentium 5 / WinChip machine checks"
1158 depends on X86_32 && X86_MCE
1160 Include support for machine check handling on old Pentium 5 or WinChip
1161 systems. These typically need to be enabled explicitly on the command
1164 config X86_MCE_THRESHOLD
1165 depends on X86_MCE_AMD || X86_MCE_INTEL
1168 config X86_MCE_INJECT
1169 depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS
1170 tristate "Machine check injector support"
1172 Provide support for injecting machine checks for testing purposes.
1173 If you don't know what a machine check is and you don't do kernel
1174 QA it is safe to say n.
1176 source "arch/x86/events/Kconfig"
1178 config X86_LEGACY_VM86
1179 bool "Legacy VM86 support"
1182 This option allows user programs to put the CPU into V8086
1183 mode, which is an 80286-era approximation of 16-bit real mode.
1185 Some very old versions of X and/or vbetool require this option
1186 for user mode setting. Similarly, DOSEMU will use it if
1187 available to accelerate real mode DOS programs. However, any
1188 recent version of DOSEMU, X, or vbetool should be fully
1189 functional even without kernel VM86 support, as they will all
1190 fall back to software emulation. Nevertheless, if you are using
1191 a 16-bit DOS program where 16-bit performance matters, vm86
1192 mode might be faster than emulation and you might want to
1195 Note that any app that works on a 64-bit kernel is unlikely to
1196 need this option, as 64-bit kernels don't, and can't, support
1197 V8086 mode. This option is also unrelated to 16-bit protected
1198 mode and is not needed to run most 16-bit programs under Wine.
1200 Enabling this option increases the complexity of the kernel
1201 and slows down exception handling a tiny bit.
1203 If unsure, say N here.
1207 default X86_LEGACY_VM86
1210 bool "Enable support for 16-bit segments" if EXPERT
1212 depends on MODIFY_LDT_SYSCALL
1214 This option is required by programs like Wine to run 16-bit
1215 protected mode legacy code on x86 processors. Disabling
1216 this option saves about 300 bytes on i386, or around 6K text
1217 plus 16K runtime memory on x86-64,
1221 depends on X86_16BIT && X86_32
1225 depends on X86_16BIT && X86_64
1227 config X86_VSYSCALL_EMULATION
1228 bool "Enable vsyscall emulation" if EXPERT
1232 This enables emulation of the legacy vsyscall page. Disabling
1233 it is roughly equivalent to booting with vsyscall=none, except
1234 that it will also disable the helpful warning if a program
1235 tries to use a vsyscall. With this option set to N, offending
1236 programs will just segfault, citing addresses of the form
1239 This option is required by many programs built before 2013, and
1240 care should be used even with newer programs if set to N.
1242 Disabling this option saves about 7K of kernel size and
1243 possibly 4K of additional runtime pagetable memory.
1245 config X86_IOPL_IOPERM
1246 bool "IOPERM and IOPL Emulation"
1249 This enables the ioperm() and iopl() syscalls which are necessary
1250 for legacy applications.
1252 Legacy IOPL support is an overbroad mechanism which allows user
1253 space aside of accessing all 65536 I/O ports also to disable
1254 interrupts. To gain this access the caller needs CAP_SYS_RAWIO
1255 capabilities and permission from potentially active security
1258 The emulation restricts the functionality of the syscall to
1259 only allowing the full range I/O port access, but prevents the
1260 ability to disable interrupts from user space which would be
1261 granted if the hardware IOPL mechanism would be used.
1264 tristate "Toshiba Laptop support"
1267 This adds a driver to safely access the System Management Mode of
1268 the CPU on Toshiba portables with a genuine Toshiba BIOS. It does
1269 not work on models with a Phoenix BIOS. The System Management Mode
1270 is used to set the BIOS and power saving options on Toshiba portables.
1272 For information on utilities to make use of this driver see the
1273 Toshiba Linux utilities web site at:
1274 <http://www.buzzard.org.uk/toshiba/>.
1276 Say Y if you intend to run this kernel on a Toshiba portable.
1279 config X86_REBOOTFIXUPS
1280 bool "Enable X86 board specific fixups for reboot"
1283 This enables chipset and/or board specific fixups to be done
1284 in order to get reboot to work correctly. This is only needed on
1285 some combinations of hardware and BIOS. The symptom, for which
1286 this config is intended, is when reboot ends with a stalled/hung
1289 Currently, the only fixup is for the Geode machines using
1290 CS5530A and CS5536 chipsets and the RDC R-321x SoC.
1292 Say Y if you want to enable the fixup. Currently, it's safe to
1293 enable this option even if you don't need it.
1297 bool "CPU microcode loading support"
1299 depends on CPU_SUP_AMD || CPU_SUP_INTEL
1301 If you say Y here, you will be able to update the microcode on
1302 Intel and AMD processors. The Intel support is for the IA32 family,
1303 e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The
1304 AMD support is for families 0x10 and later. You will obviously need
1305 the actual microcode binary data itself which is not shipped with
1308 The preferred method to load microcode from a detached initrd is described
1309 in Documentation/x86/microcode.rst. For that you need to enable
1310 CONFIG_BLK_DEV_INITRD in order for the loader to be able to scan the
1311 initrd for microcode blobs.
1313 In addition, you can build the microcode into the kernel. For that you
1314 need to add the vendor-supplied microcode to the CONFIG_EXTRA_FIRMWARE
1317 config MICROCODE_INTEL
1318 bool "Intel microcode loading support"
1319 depends on MICROCODE
1322 This options enables microcode patch loading support for Intel
1325 For the current Intel microcode data package go to
1326 <https://downloadcenter.intel.com> and search for
1327 'Linux Processor Microcode Data File'.
1329 config MICROCODE_AMD
1330 bool "AMD microcode loading support"
1331 depends on MICROCODE
1333 If you select this option, microcode patch loading support for AMD
1334 processors will be enabled.
1336 config MICROCODE_OLD_INTERFACE
1337 bool "Ancient loading interface (DEPRECATED)"
1339 depends on MICROCODE
1341 DO NOT USE THIS! This is the ancient /dev/cpu/microcode interface
1342 which was used by userspace tools like iucode_tool and microcode.ctl.
1343 It is inadequate because it runs too late to be able to properly
1344 load microcode on a machine and it needs special tools. Instead, you
1345 should've switched to the early loading method with the initrd or
1346 builtin microcode by now: Documentation/x86/microcode.rst
1349 tristate "/dev/cpu/*/msr - Model-specific register support"
1351 This device gives privileged processes access to the x86
1352 Model-Specific Registers (MSRs). It is a character device with
1353 major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr.
1354 MSR accesses are directed to a specific CPU on multi-processor
1358 tristate "/dev/cpu/*/cpuid - CPU information support"
1360 This device gives processes access to the x86 CPUID instruction to
1361 be executed on a specific processor. It is a character device
1362 with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to
1366 prompt "High Memory Support"
1373 Linux can use up to 64 Gigabytes of physical memory on x86 systems.
1374 However, the address space of 32-bit x86 processors is only 4
1375 Gigabytes large. That means that, if you have a large amount of
1376 physical memory, not all of it can be "permanently mapped" by the
1377 kernel. The physical memory that's not permanently mapped is called
1380 If you are compiling a kernel which will never run on a machine with
1381 more than 1 Gigabyte total physical RAM, answer "off" here (default
1382 choice and suitable for most users). This will result in a "3GB/1GB"
1383 split: 3GB are mapped so that each process sees a 3GB virtual memory
1384 space and the remaining part of the 4GB virtual memory space is used
1385 by the kernel to permanently map as much physical memory as
1388 If the machine has between 1 and 4 Gigabytes physical RAM, then
1391 If more than 4 Gigabytes is used then answer "64GB" here. This
1392 selection turns Intel PAE (Physical Address Extension) mode on.
1393 PAE implements 3-level paging on IA32 processors. PAE is fully
1394 supported by Linux, PAE mode is implemented on all recent Intel
1395 processors (Pentium Pro and better). NOTE: If you say "64GB" here,
1396 then the kernel will not boot on CPUs that don't support PAE!
1398 The actual amount of total physical memory will either be
1399 auto detected or can be forced by using a kernel command line option
1400 such as "mem=256M". (Try "man bootparam" or see the documentation of
1401 your boot loader (lilo or loadlin) about how to pass options to the
1402 kernel at boot time.)
1404 If unsure, say "off".
1409 Select this if you have a 32-bit processor and between 1 and 4
1410 gigabytes of physical RAM.
1414 depends on !M486SX && !M486 && !M586 && !M586TSC && !M586MMX && !MGEODE_LX && !MGEODEGX1 && !MCYRIXIII && !MELAN && !MWINCHIPC6 && !MWINCHIP3D && !MK6
1417 Select this if you have a 32-bit processor and more than 4
1418 gigabytes of physical RAM.
1423 prompt "Memory split" if EXPERT
1427 Select the desired split between kernel and user memory.
1429 If the address range available to the kernel is less than the
1430 physical memory installed, the remaining memory will be available
1431 as "high memory". Accessing high memory is a little more costly
1432 than low memory, as it needs to be mapped into the kernel first.
1433 Note that increasing the kernel address space limits the range
1434 available to user programs, making the address space there
1435 tighter. Selecting anything other than the default 3G/1G split
1436 will also likely make your kernel incompatible with binary-only
1439 If you are not absolutely sure what you are doing, leave this
1443 bool "3G/1G user/kernel split"
1444 config VMSPLIT_3G_OPT
1446 bool "3G/1G user/kernel split (for full 1G low memory)"
1448 bool "2G/2G user/kernel split"
1449 config VMSPLIT_2G_OPT
1451 bool "2G/2G user/kernel split (for full 2G low memory)"
1453 bool "1G/3G user/kernel split"
1458 default 0xB0000000 if VMSPLIT_3G_OPT
1459 default 0x80000000 if VMSPLIT_2G
1460 default 0x78000000 if VMSPLIT_2G_OPT
1461 default 0x40000000 if VMSPLIT_1G
1467 depends on X86_32 && (HIGHMEM64G || HIGHMEM4G)
1470 bool "PAE (Physical Address Extension) Support"
1471 depends on X86_32 && !HIGHMEM4G
1472 select PHYS_ADDR_T_64BIT
1475 PAE is required for NX support, and furthermore enables
1476 larger swapspace support for non-overcommit purposes. It
1477 has the cost of more pagetable lookup overhead, and also
1478 consumes more pagetable space per process.
1481 bool "Enable 5-level page tables support"
1483 select DYNAMIC_MEMORY_LAYOUT
1484 select SPARSEMEM_VMEMMAP
1487 5-level paging enables access to larger address space:
1488 upto 128 PiB of virtual address space and 4 PiB of
1489 physical address space.
1491 It will be supported by future Intel CPUs.
1493 A kernel with the option enabled can be booted on machines that
1494 support 4- or 5-level paging.
1496 See Documentation/x86/x86_64/5level-paging.rst for more
1501 config X86_DIRECT_GBPAGES
1505 Certain kernel features effectively disable kernel
1506 linear 1 GB mappings (even if the CPU otherwise
1507 supports them), so don't confuse the user by printing
1508 that we have them enabled.
1510 config X86_CPA_STATISTICS
1511 bool "Enable statistic for Change Page Attribute"
1514 Expose statistics about the Change Page Attribute mechanism, which
1515 helps to determine the effectiveness of preserving large and huge
1516 page mappings when mapping protections are changed.
1518 config X86_MEM_ENCRYPT
1519 select ARCH_HAS_FORCE_DMA_UNENCRYPTED
1520 select DYNAMIC_PHYSICAL_MASK
1521 select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
1524 config AMD_MEM_ENCRYPT
1525 bool "AMD Secure Memory Encryption (SME) support"
1526 depends on X86_64 && CPU_SUP_AMD
1527 select DMA_COHERENT_POOL
1528 select ARCH_USE_MEMREMAP_PROT
1529 select INSTRUCTION_DECODER
1530 select ARCH_HAS_CC_PLATFORM
1531 select X86_MEM_ENCRYPT
1533 Say yes to enable support for the encryption of system memory.
1534 This requires an AMD processor that supports Secure Memory
1537 config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
1538 bool "Activate AMD Secure Memory Encryption (SME) by default"
1539 depends on AMD_MEM_ENCRYPT
1541 Say yes to have system memory encrypted by default if running on
1542 an AMD processor that supports Secure Memory Encryption (SME).
1544 If set to Y, then the encryption of system memory can be
1545 deactivated with the mem_encrypt=off command line option.
1547 If set to N, then the encryption of system memory can be
1548 activated with the mem_encrypt=on command line option.
1550 # Common NUMA Features
1552 bool "NUMA Memory Allocation and Scheduler Support"
1554 depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP)
1555 default y if X86_BIGSMP
1556 select USE_PERCPU_NUMA_NODE_ID
1558 Enable NUMA (Non-Uniform Memory Access) support.
1560 The kernel will try to allocate memory used by a CPU on the
1561 local memory controller of the CPU and add some more
1562 NUMA awareness to the kernel.
1564 For 64-bit this is recommended if the system is Intel Core i7
1565 (or later), AMD Opteron, or EM64T NUMA.
1567 For 32-bit this is only needed if you boot a 32-bit
1568 kernel on a 64-bit NUMA platform.
1570 Otherwise, you should say N.
1574 prompt "Old style AMD Opteron NUMA detection"
1575 depends on X86_64 && NUMA && PCI
1577 Enable AMD NUMA node topology detection. You should say Y here if
1578 you have a multi processor AMD system. This uses an old method to
1579 read the NUMA configuration directly from the builtin Northbridge
1580 of Opteron. It is recommended to use X86_64_ACPI_NUMA instead,
1581 which also takes priority if both are compiled in.
1583 config X86_64_ACPI_NUMA
1585 prompt "ACPI NUMA detection"
1586 depends on X86_64 && NUMA && ACPI && PCI
1589 Enable ACPI SRAT based node topology detection.
1592 bool "NUMA emulation"
1595 Enable NUMA emulation. A flat machine will be split
1596 into virtual nodes when booted with "numa=fake=N", where N is the
1597 number of nodes. This is only useful for debugging.
1600 int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP
1602 default "10" if MAXSMP
1603 default "6" if X86_64
1607 Specify the maximum number of NUMA Nodes available on the target
1608 system. Increases memory reserved to accommodate various tables.
1610 config ARCH_FLATMEM_ENABLE
1612 depends on X86_32 && !NUMA
1614 config ARCH_SPARSEMEM_ENABLE
1616 depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
1617 select SPARSEMEM_STATIC if X86_32
1618 select SPARSEMEM_VMEMMAP_ENABLE if X86_64
1620 config ARCH_SPARSEMEM_DEFAULT
1621 def_bool X86_64 || (NUMA && X86_32)
1623 config ARCH_SELECT_MEMORY_MODEL
1625 depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE
1627 config ARCH_MEMORY_PROBE
1628 bool "Enable sysfs memory/probe interface"
1629 depends on MEMORY_HOTPLUG
1631 This option enables a sysfs memory/probe interface for testing.
1632 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
1633 If you are unsure how to answer this question, answer N.
1635 config ARCH_PROC_KCORE_TEXT
1637 depends on X86_64 && PROC_KCORE
1639 config ILLEGAL_POINTER_VALUE
1642 default 0xdead000000000000 if X86_64
1644 config X86_PMEM_LEGACY_DEVICE
1647 config X86_PMEM_LEGACY
1648 tristate "Support non-standard NVDIMMs and ADR protected memory"
1649 depends on PHYS_ADDR_T_64BIT
1651 select X86_PMEM_LEGACY_DEVICE
1652 select NUMA_KEEP_MEMINFO if NUMA
1655 Treat memory marked using the non-standard e820 type of 12 as used
1656 by the Intel Sandy Bridge-EP reference BIOS as protected memory.
1657 The kernel will offer these regions to the 'pmem' driver so
1658 they can be used for persistent storage.
1663 bool "Allocate 3rd-level pagetables from highmem"
1666 The VM uses one page table entry for each page of physical memory.
1667 For systems with a lot of RAM, this can be wasteful of precious
1668 low memory. Setting this option will put user-space page table
1669 entries in high memory.
1671 config X86_CHECK_BIOS_CORRUPTION
1672 bool "Check for low memory corruption"
1674 Periodically check for memory corruption in low memory, which
1675 is suspected to be caused by BIOS. Even when enabled in the
1676 configuration, it is disabled at runtime. Enable it by
1677 setting "memory_corruption_check=1" on the kernel command
1678 line. By default it scans the low 64k of memory every 60
1679 seconds; see the memory_corruption_check_size and
1680 memory_corruption_check_period parameters in
1681 Documentation/admin-guide/kernel-parameters.rst to adjust this.
1683 When enabled with the default parameters, this option has
1684 almost no overhead, as it reserves a relatively small amount
1685 of memory and scans it infrequently. It both detects corruption
1686 and prevents it from affecting the running system.
1688 It is, however, intended as a diagnostic tool; if repeatable
1689 BIOS-originated corruption always affects the same memory,
1690 you can use memmap= to prevent the kernel from using that
1693 config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
1694 bool "Set the default setting of memory_corruption_check"
1695 depends on X86_CHECK_BIOS_CORRUPTION
1698 Set whether the default state of memory_corruption_check is
1701 config MATH_EMULATION
1703 depends on MODIFY_LDT_SYSCALL
1704 prompt "Math emulation" if X86_32 && (M486SX || MELAN)
1706 Linux can emulate a math coprocessor (used for floating point
1707 operations) if you don't have one. 486DX and Pentium processors have
1708 a math coprocessor built in, 486SX and 386 do not, unless you added
1709 a 487DX or 387, respectively. (The messages during boot time can
1710 give you some hints here ["man dmesg"].) Everyone needs either a
1711 coprocessor or this emulation.
1713 If you don't have a math coprocessor, you need to say Y here; if you
1714 say Y here even though you have a coprocessor, the coprocessor will
1715 be used nevertheless. (This behavior can be changed with the kernel
1716 command line option "no387", which comes handy if your coprocessor
1717 is broken. Try "man bootparam" or see the documentation of your boot
1718 loader (lilo or loadlin) about how to pass options to the kernel at
1719 boot time.) This means that it is a good idea to say Y here if you
1720 intend to use this kernel on different machines.
1722 More information about the internals of the Linux math coprocessor
1723 emulation can be found in <file:arch/x86/math-emu/README>.
1725 If you are not sure, say Y; apart from resulting in a 66 KB bigger
1726 kernel, it won't hurt.
1730 prompt "MTRR (Memory Type Range Register) support" if EXPERT
1732 On Intel P6 family processors (Pentium Pro, Pentium II and later)
1733 the Memory Type Range Registers (MTRRs) may be used to control
1734 processor access to memory ranges. This is most useful if you have
1735 a video (VGA) card on a PCI or AGP bus. Enabling write-combining
1736 allows bus write transfers to be combined into a larger transfer
1737 before bursting over the PCI/AGP bus. This can increase performance
1738 of image write operations 2.5 times or more. Saying Y here creates a
1739 /proc/mtrr file which may be used to manipulate your processor's
1740 MTRRs. Typically the X server should use this.
1742 This code has a reasonably generic interface so that similar
1743 control registers on other processors can be easily supported
1746 The Cyrix 6x86, 6x86MX and M II processors have Address Range
1747 Registers (ARRs) which provide a similar functionality to MTRRs. For
1748 these, the ARRs are used to emulate the MTRRs.
1749 The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
1750 MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
1751 write-combining. All of these processors are supported by this code
1752 and it makes sense to say Y here if you have one of them.
1754 Saying Y here also fixes a problem with buggy SMP BIOSes which only
1755 set the MTRRs for the boot CPU and not for the secondary CPUs. This
1756 can lead to all sorts of problems, so it's good to say Y here.
1758 You can safely say Y even if your machine doesn't have MTRRs, you'll
1759 just add about 9 KB to your kernel.
1761 See <file:Documentation/x86/mtrr.rst> for more information.
1763 config MTRR_SANITIZER
1765 prompt "MTRR cleanup support"
1768 Convert MTRR layout from continuous to discrete, so X drivers can
1769 add writeback entries.
1771 Can be disabled with disable_mtrr_cleanup on the kernel command line.
1772 The largest mtrr entry size for a continuous block can be set with
1777 config MTRR_SANITIZER_ENABLE_DEFAULT
1778 int "MTRR cleanup enable value (0-1)"
1781 depends on MTRR_SANITIZER
1783 Enable mtrr cleanup default value
1785 config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
1786 int "MTRR cleanup spare reg num (0-7)"
1789 depends on MTRR_SANITIZER
1791 mtrr cleanup spare entries default, it can be changed via
1792 mtrr_spare_reg_nr=N on the kernel command line.
1796 prompt "x86 PAT support" if EXPERT
1799 Use PAT attributes to setup page level cache control.
1801 PATs are the modern equivalents of MTRRs and are much more
1802 flexible than MTRRs.
1804 Say N here if you see bootup problems (boot crash, boot hang,
1805 spontaneous reboots) or a non-working video driver.
1809 config ARCH_USES_PG_UNCACHED
1815 prompt "x86 architectural random number generator" if EXPERT
1817 Enable the x86 architectural RDRAND instruction
1818 (Intel Bull Mountain technology) to generate random numbers.
1819 If supported, this is a high bandwidth, cryptographically
1820 secure hardware random number generator.
1824 prompt "Supervisor Mode Access Prevention" if EXPERT
1826 Supervisor Mode Access Prevention (SMAP) is a security
1827 feature in newer Intel processors. There is a small
1828 performance cost if this enabled and turned on; there is
1829 also a small increase in the kernel size if this is enabled.
1835 prompt "User Mode Instruction Prevention" if EXPERT
1837 User Mode Instruction Prevention (UMIP) is a security feature in
1838 some x86 processors. If enabled, a general protection fault is
1839 issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are
1840 executed in user mode. These instructions unnecessarily expose
1841 information about the hardware state.
1843 The vast majority of applications do not use these instructions.
1844 For the very few that do, software emulation is provided in
1845 specific cases in protected and virtual-8086 modes. Emulated
1848 config X86_INTEL_MEMORY_PROTECTION_KEYS
1849 prompt "Memory Protection Keys"
1851 # Note: only available in 64-bit mode
1852 depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
1853 select ARCH_USES_HIGH_VMA_FLAGS
1854 select ARCH_HAS_PKEYS
1856 Memory Protection Keys provides a mechanism for enforcing
1857 page-based protections, but without requiring modification of the
1858 page tables when an application changes protection domains.
1860 For details, see Documentation/core-api/protection-keys.rst
1865 prompt "TSX enable mode"
1866 depends on CPU_SUP_INTEL
1867 default X86_INTEL_TSX_MODE_OFF
1869 Intel's TSX (Transactional Synchronization Extensions) feature
1870 allows to optimize locking protocols through lock elision which
1871 can lead to a noticeable performance boost.
1873 On the other hand it has been shown that TSX can be exploited
1874 to form side channel attacks (e.g. TAA) and chances are there
1875 will be more of those attacks discovered in the future.
1877 Therefore TSX is not enabled by default (aka tsx=off). An admin
1878 might override this decision by tsx=on the command line parameter.
1879 Even with TSX enabled, the kernel will attempt to enable the best
1880 possible TAA mitigation setting depending on the microcode available
1881 for the particular machine.
1883 This option allows to set the default tsx mode between tsx=on, =off
1884 and =auto. See Documentation/admin-guide/kernel-parameters.txt for more
1887 Say off if not sure, auto if TSX is in use but it should be used on safe
1888 platforms or on if TSX is in use and the security aspect of tsx is not
1891 config X86_INTEL_TSX_MODE_OFF
1894 TSX is disabled if possible - equals to tsx=off command line parameter.
1896 config X86_INTEL_TSX_MODE_ON
1899 TSX is always enabled on TSX capable HW - equals the tsx=on command
1902 config X86_INTEL_TSX_MODE_AUTO
1905 TSX is enabled on TSX capable HW that is believed to be safe against
1906 side channel attacks- equals the tsx=auto command line parameter.
1910 bool "Software Guard eXtensions (SGX)"
1911 depends on X86_64 && CPU_SUP_INTEL
1913 depends on CRYPTO_SHA256=y
1916 select NUMA_KEEP_MEMINFO if NUMA
1919 Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
1920 that can be used by applications to set aside private regions of code
1921 and data, referred to as enclaves. An enclave's private memory can
1922 only be accessed by code running within the enclave. Accesses from
1923 outside the enclave, including other enclaves, are disallowed by
1929 bool "EFI runtime service support"
1932 select EFI_RUNTIME_WRAPPERS
1933 select ARCH_USE_MEMREMAP_PROT
1935 This enables the kernel to use EFI runtime services that are
1936 available (such as the EFI variable services).
1938 This option is only useful on systems that have EFI firmware.
1939 In addition, you should use the latest ELILO loader available
1940 at <http://elilo.sourceforge.net> in order to take advantage
1941 of EFI runtime services. However, even with this option, the
1942 resultant kernel should continue to boot on existing non-EFI
1946 bool "EFI stub support"
1948 depends on $(cc-option,-mabi=ms) || X86_32
1951 This kernel feature allows a bzImage to be loaded directly
1952 by EFI firmware without the use of a bootloader.
1954 See Documentation/admin-guide/efi-stub.rst for more information.
1957 bool "EFI mixed-mode support"
1958 depends on EFI_STUB && X86_64
1960 Enabling this feature allows a 64-bit kernel to be booted
1961 on a 32-bit firmware, provided that your CPU supports 64-bit
1964 Note that it is not possible to boot a mixed-mode enabled
1965 kernel via the EFI boot stub - a bootloader that supports
1966 the EFI handover protocol must be used.
1970 source "kernel/Kconfig.hz"
1973 bool "kexec system call"
1976 kexec is a system call that implements the ability to shutdown your
1977 current kernel, and to start another kernel. It is like a reboot
1978 but it is independent of the system firmware. And like a reboot
1979 you can start any kernel with it, not just Linux.
1981 The name comes from the similarity to the exec system call.
1983 It is an ongoing process to be certain the hardware in a machine
1984 is properly shutdown, so do not be surprised if this code does not
1985 initially work for you. As of this writing the exact hardware
1986 interface is strongly in flux, so no good recommendation can be
1990 bool "kexec file based system call"
1995 depends on CRYPTO_SHA256=y
1997 This is new version of kexec system call. This system call is
1998 file based and takes file descriptors as system call argument
1999 for kernel and initramfs as opposed to list of segments as
2000 accepted by previous system call.
2002 config ARCH_HAS_KEXEC_PURGATORY
2006 bool "Verify kernel signature during kexec_file_load() syscall"
2007 depends on KEXEC_FILE
2010 This option makes the kexec_file_load() syscall check for a valid
2011 signature of the kernel image. The image can still be loaded without
2012 a valid signature unless you also enable KEXEC_SIG_FORCE, though if
2013 there's a signature that we can check, then it must be valid.
2015 In addition to this option, you need to enable signature
2016 verification for the corresponding kernel image type being
2017 loaded in order for this to work.
2019 config KEXEC_SIG_FORCE
2020 bool "Require a valid signature in kexec_file_load() syscall"
2021 depends on KEXEC_SIG
2023 This option makes kernel signature verification mandatory for
2024 the kexec_file_load() syscall.
2026 config KEXEC_BZIMAGE_VERIFY_SIG
2027 bool "Enable bzImage signature verification support"
2028 depends on KEXEC_SIG
2029 depends on SIGNED_PE_FILE_VERIFICATION
2030 select SYSTEM_TRUSTED_KEYRING
2032 Enable bzImage signature verification support.
2035 bool "kernel crash dumps"
2036 depends on X86_64 || (X86_32 && HIGHMEM)
2038 Generate crash dump after being started by kexec.
2039 This should be normally only set in special crash dump kernels
2040 which are loaded in the main kernel with kexec-tools into
2041 a specially reserved region and then later executed after
2042 a crash by kdump/kexec. The crash dump kernel must be compiled
2043 to a memory address not used by the main kernel or BIOS using
2044 PHYSICAL_START, or it must be built as a relocatable image
2045 (CONFIG_RELOCATABLE=y).
2046 For more details see Documentation/admin-guide/kdump/kdump.rst
2050 depends on KEXEC && HIBERNATION
2052 Jump between original kernel and kexeced kernel and invoke
2053 code in physical address mode via KEXEC
2055 config PHYSICAL_START
2056 hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
2059 This gives the physical address where the kernel is loaded.
2061 If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
2062 bzImage will decompress itself to above physical address and
2063 run from there. Otherwise, bzImage will run from the address where
2064 it has been loaded by the boot loader and will ignore above physical
2067 In normal kdump cases one does not have to set/change this option
2068 as now bzImage can be compiled as a completely relocatable image
2069 (CONFIG_RELOCATABLE=y) and be used to load and run from a different
2070 address. This option is mainly useful for the folks who don't want
2071 to use a bzImage for capturing the crash dump and want to use a
2072 vmlinux instead. vmlinux is not relocatable hence a kernel needs
2073 to be specifically compiled to run from a specific memory area
2074 (normally a reserved region) and this option comes handy.
2076 So if you are using bzImage for capturing the crash dump,
2077 leave the value here unchanged to 0x1000000 and set
2078 CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
2079 for capturing the crash dump change this value to start of
2080 the reserved region. In other words, it can be set based on
2081 the "X" value as specified in the "crashkernel=YM@XM"
2082 command line boot parameter passed to the panic-ed
2083 kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
2084 for more details about crash dumps.
2086 Usage of bzImage for capturing the crash dump is recommended as
2087 one does not have to build two kernels. Same kernel can be used
2088 as production kernel and capture kernel. Above option should have
2089 gone away after relocatable bzImage support is introduced. But it
2090 is present because there are users out there who continue to use
2091 vmlinux for dump capture. This option should go away down the
2094 Don't change this unless you know what you are doing.
2097 bool "Build a relocatable kernel"
2100 This builds a kernel image that retains relocation information
2101 so it can be loaded someplace besides the default 1MB.
2102 The relocations tend to make the kernel binary about 10% larger,
2103 but are discarded at runtime.
2105 One use is for the kexec on panic case where the recovery kernel
2106 must live at a different physical address than the primary
2109 Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
2110 it has been loaded at and the compile time physical address
2111 (CONFIG_PHYSICAL_START) is used as the minimum location.
2113 config RANDOMIZE_BASE
2114 bool "Randomize the address of the kernel image (KASLR)"
2115 depends on RELOCATABLE
2118 In support of Kernel Address Space Layout Randomization (KASLR),
2119 this randomizes the physical address at which the kernel image
2120 is decompressed and the virtual address where the kernel
2121 image is mapped, as a security feature that deters exploit
2122 attempts relying on knowledge of the location of kernel
2125 On 64-bit, the kernel physical and virtual addresses are
2126 randomized separately. The physical address will be anywhere
2127 between 16MB and the top of physical memory (up to 64TB). The
2128 virtual address will be randomized from 16MB up to 1GB (9 bits
2129 of entropy). Note that this also reduces the memory space
2130 available to kernel modules from 1.5GB to 1GB.
2132 On 32-bit, the kernel physical and virtual addresses are
2133 randomized together. They will be randomized from 16MB up to
2134 512MB (8 bits of entropy).
2136 Entropy is generated using the RDRAND instruction if it is
2137 supported. If RDTSC is supported, its value is mixed into
2138 the entropy pool as well. If neither RDRAND nor RDTSC are
2139 supported, then entropy is read from the i8254 timer. The
2140 usable entropy is limited by the kernel being built using
2141 2GB addressing, and that PHYSICAL_ALIGN must be at a
2142 minimum of 2MB. As a result, only 10 bits of entropy are
2143 theoretically possible, but the implementations are further
2144 limited due to memory layouts.
2148 # Relocation on x86 needs some additional build support
2149 config X86_NEED_RELOCS
2151 depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
2153 config PHYSICAL_ALIGN
2154 hex "Alignment value to which kernel should be aligned"
2156 range 0x2000 0x1000000 if X86_32
2157 range 0x200000 0x1000000 if X86_64
2159 This value puts the alignment restrictions on physical address
2160 where kernel is loaded and run from. Kernel is compiled for an
2161 address which meets above alignment restriction.
2163 If bootloader loads the kernel at a non-aligned address and
2164 CONFIG_RELOCATABLE is set, kernel will move itself to nearest
2165 address aligned to above value and run from there.
2167 If bootloader loads the kernel at a non-aligned address and
2168 CONFIG_RELOCATABLE is not set, kernel will ignore the run time
2169 load address and decompress itself to the address it has been
2170 compiled for and run from there. The address for which kernel is
2171 compiled already meets above alignment restrictions. Hence the
2172 end result is that kernel runs from a physical address meeting
2173 above alignment restrictions.
2175 On 32-bit this value must be a multiple of 0x2000. On 64-bit
2176 this value must be a multiple of 0x200000.
2178 Don't change this unless you know what you are doing.
2180 config DYNAMIC_MEMORY_LAYOUT
2183 This option makes base addresses of vmalloc and vmemmap as well as
2184 __PAGE_OFFSET movable during boot.
2186 config RANDOMIZE_MEMORY
2187 bool "Randomize the kernel memory sections"
2189 depends on RANDOMIZE_BASE
2190 select DYNAMIC_MEMORY_LAYOUT
2191 default RANDOMIZE_BASE
2193 Randomizes the base virtual address of kernel memory sections
2194 (physical memory mapping, vmalloc & vmemmap). This security feature
2195 makes exploits relying on predictable memory locations less reliable.
2197 The order of allocations remains unchanged. Entropy is generated in
2198 the same way as RANDOMIZE_BASE. Current implementation in the optimal
2199 configuration have in average 30,000 different possible virtual
2200 addresses for each memory section.
2204 config RANDOMIZE_MEMORY_PHYSICAL_PADDING
2205 hex "Physical memory mapping padding" if EXPERT
2206 depends on RANDOMIZE_MEMORY
2207 default "0xa" if MEMORY_HOTPLUG
2209 range 0x1 0x40 if MEMORY_HOTPLUG
2212 Define the padding in terabytes added to the existing physical
2213 memory size during kernel memory randomization. It is useful
2214 for memory hotplug support but reduces the entropy available for
2215 address randomization.
2217 If unsure, leave at the default value.
2223 config BOOTPARAM_HOTPLUG_CPU0
2224 bool "Set default setting of cpu0_hotpluggable"
2225 depends on HOTPLUG_CPU
2227 Set whether default state of cpu0_hotpluggable is on or off.
2229 Say Y here to enable CPU0 hotplug by default. If this switch
2230 is turned on, there is no need to give cpu0_hotplug kernel
2231 parameter and the CPU0 hotplug feature is enabled by default.
2233 Please note: there are two known CPU0 dependencies if you want
2234 to enable the CPU0 hotplug feature either by this switch or by
2235 cpu0_hotplug kernel parameter.
2237 First, resume from hibernate or suspend always starts from CPU0.
2238 So hibernate and suspend are prevented if CPU0 is offline.
2240 Second dependency is PIC interrupts always go to CPU0. CPU0 can not
2241 offline if any interrupt can not migrate out of CPU0. There may
2242 be other CPU0 dependencies.
2244 Please make sure the dependencies are under your control before
2245 you enable this feature.
2247 Say N if you don't want to enable CPU0 hotplug feature by default.
2248 You still can enable the CPU0 hotplug feature at boot by kernel
2249 parameter cpu0_hotplug.
2251 config DEBUG_HOTPLUG_CPU0
2253 prompt "Debug CPU0 hotplug"
2254 depends on HOTPLUG_CPU
2256 Enabling this option offlines CPU0 (if CPU0 can be offlined) as
2257 soon as possible and boots up userspace with CPU0 offlined. User
2258 can online CPU0 back after boot time.
2260 To debug CPU0 hotplug, you need to enable CPU0 offline/online
2261 feature by either turning on CONFIG_BOOTPARAM_HOTPLUG_CPU0 during
2262 compilation or giving cpu0_hotplug kernel parameter at boot.
2268 prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
2269 depends on COMPAT_32
2271 Certain buggy versions of glibc will crash if they are
2272 presented with a 32-bit vDSO that is not mapped at the address
2273 indicated in its segment table.
2275 The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a
2276 and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and
2277 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is
2278 the only released version with the bug, but OpenSUSE 9
2279 contains a buggy "glibc 2.3.2".
2281 The symptom of the bug is that everything crashes on startup, saying:
2282 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
2284 Saying Y here changes the default value of the vdso32 boot
2285 option from 1 to 0, which turns off the 32-bit vDSO entirely.
2286 This works around the glibc bug but hurts performance.
2288 If unsure, say N: if you are compiling your own kernel, you
2289 are unlikely to be using a buggy version of glibc.
2292 prompt "vsyscall table for legacy applications"
2294 default LEGACY_VSYSCALL_XONLY
2296 Legacy user code that does not know how to find the vDSO expects
2297 to be able to issue three syscalls by calling fixed addresses in
2298 kernel space. Since this location is not randomized with ASLR,
2299 it can be used to assist security vulnerability exploitation.
2301 This setting can be changed at boot time via the kernel command
2302 line parameter vsyscall=[emulate|xonly|none].
2304 On a system with recent enough glibc (2.14 or newer) and no
2305 static binaries, you can say None without a performance penalty
2306 to improve security.
2308 If unsure, select "Emulate execution only".
2310 config LEGACY_VSYSCALL_EMULATE
2311 bool "Full emulation"
2313 The kernel traps and emulates calls into the fixed vsyscall
2314 address mapping. This makes the mapping non-executable, but
2315 it still contains readable known contents, which could be
2316 used in certain rare security vulnerability exploits. This
2317 configuration is recommended when using legacy userspace
2318 that still uses vsyscalls along with legacy binary
2319 instrumentation tools that require code to be readable.
2321 An example of this type of legacy userspace is running
2322 Pin on an old binary that still uses vsyscalls.
2324 config LEGACY_VSYSCALL_XONLY
2325 bool "Emulate execution only"
2327 The kernel traps and emulates calls into the fixed vsyscall
2328 address mapping and does not allow reads. This
2329 configuration is recommended when userspace might use the
2330 legacy vsyscall area but support for legacy binary
2331 instrumentation of legacy code is not needed. It mitigates
2332 certain uses of the vsyscall area as an ASLR-bypassing
2335 config LEGACY_VSYSCALL_NONE
2338 There will be no vsyscall mapping at all. This will
2339 eliminate any risk of ASLR bypass due to the vsyscall
2340 fixed address mapping. Attempts to use the vsyscalls
2341 will be reported to dmesg, so that either old or
2342 malicious userspace programs can be identified.
2347 bool "Built-in kernel command line"
2349 Allow for specifying boot arguments to the kernel at
2350 build time. On some systems (e.g. embedded ones), it is
2351 necessary or convenient to provide some or all of the
2352 kernel boot arguments with the kernel itself (that is,
2353 to not rely on the boot loader to provide them.)
2355 To compile command line arguments into the kernel,
2356 set this option to 'Y', then fill in the
2357 boot arguments in CONFIG_CMDLINE.
2359 Systems with fully functional boot loaders (i.e. non-embedded)
2360 should leave this option set to 'N'.
2363 string "Built-in kernel command string"
2364 depends on CMDLINE_BOOL
2367 Enter arguments here that should be compiled into the kernel
2368 image and used at boot time. If the boot loader provides a
2369 command line at boot time, it is appended to this string to
2370 form the full kernel command line, when the system boots.
2372 However, you can use the CONFIG_CMDLINE_OVERRIDE option to
2373 change this behavior.
2375 In most cases, the command line (whether built-in or provided
2376 by the boot loader) should specify the device for the root
2379 config CMDLINE_OVERRIDE
2380 bool "Built-in command line overrides boot loader arguments"
2381 depends on CMDLINE_BOOL && CMDLINE != ""
2383 Set this option to 'Y' to have the kernel ignore the boot loader
2384 command line, and use ONLY the built-in command line.
2386 This is used to work around broken boot loaders. This should
2387 be set to 'N' under normal conditions.
2389 config MODIFY_LDT_SYSCALL
2390 bool "Enable the LDT (local descriptor table)" if EXPERT
2393 Linux can allow user programs to install a per-process x86
2394 Local Descriptor Table (LDT) using the modify_ldt(2) system
2395 call. This is required to run 16-bit or segmented code such as
2396 DOSEMU or some Wine programs. It is also used by some very old
2397 threading libraries.
2399 Enabling this feature adds a small amount of overhead to
2400 context switches and increases the low-level kernel attack
2401 surface. Disabling it removes the modify_ldt(2) system call.
2403 Saying 'N' here may make sense for embedded or server kernels.
2405 config STRICT_SIGALTSTACK_SIZE
2406 bool "Enforce strict size checking for sigaltstack"
2407 depends on DYNAMIC_SIGFRAME
2409 For historical reasons MINSIGSTKSZ is a constant which became
2410 already too small with AVX512 support. Add a mechanism to
2411 enforce strict checking of the sigaltstack size against the
2412 real size of the FPU frame. This option enables the check
2413 by default. It can also be controlled via the kernel command
2414 line option 'strict_sas_size' independent of this config
2415 switch. Enabling it might break existing applications which
2416 allocate a too small sigaltstack but 'work' because they
2417 never get a signal delivered.
2419 Say 'N' unless you want to really enforce this check.
2421 source "kernel/livepatch/Kconfig"
2425 config ARCH_HAS_ADD_PAGES
2427 depends on ARCH_ENABLE_MEMORY_HOTPLUG
2429 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
2432 menu "Power management and ACPI options"
2434 config ARCH_HIBERNATION_HEADER
2436 depends on HIBERNATION
2438 source "kernel/power/Kconfig"
2440 source "drivers/acpi/Kconfig"
2447 tristate "APM (Advanced Power Management) BIOS support"
2448 depends on X86_32 && PM_SLEEP
2450 APM is a BIOS specification for saving power using several different
2451 techniques. This is mostly useful for battery powered laptops with
2452 APM compliant BIOSes. If you say Y here, the system time will be
2453 reset after a RESUME operation, the /proc/apm device will provide
2454 battery status information, and user-space programs will receive
2455 notification of APM "events" (e.g. battery status change).
2457 If you select "Y" here, you can disable actual use of the APM
2458 BIOS by passing the "apm=off" option to the kernel at boot time.
2460 Note that the APM support is almost completely disabled for
2461 machines with more than one CPU.
2463 In order to use APM, you will need supporting software. For location
2464 and more information, read <file:Documentation/power/apm-acpi.rst>
2465 and the Battery Powered Linux mini-HOWTO, available from
2466 <http://www.tldp.org/docs.html#howto>.
2468 This driver does not spin down disk drives (see the hdparm(8)
2469 manpage ("man 8 hdparm") for that), and it doesn't turn off
2470 VESA-compliant "green" monitors.
2472 This driver does not support the TI 4000M TravelMate and the ACER
2473 486/DX4/75 because they don't have compliant BIOSes. Many "green"
2474 desktop machines also don't have compliant BIOSes, and this driver
2475 may cause those machines to panic during the boot phase.
2477 Generally, if you don't have a battery in your machine, there isn't
2478 much point in using this driver and you should say N. If you get
2479 random kernel OOPSes or reboots that don't seem to be related to
2480 anything, try disabling/enabling this option (or disabling/enabling
2483 Some other things you should try when experiencing seemingly random,
2486 1) make sure that you have enough swap space and that it is
2488 2) pass the "no-hlt" option to the kernel
2489 3) switch on floating point emulation in the kernel and pass
2490 the "no387" option to the kernel
2491 4) pass the "floppy=nodma" option to the kernel
2492 5) pass the "mem=4M" option to the kernel (thereby disabling
2493 all but the first 4 MB of RAM)
2494 6) make sure that the CPU is not over clocked.
2495 7) read the sig11 FAQ at <http://www.bitwizard.nl/sig11/>
2496 8) disable the cache from your BIOS settings
2497 9) install a fan for the video card or exchange video RAM
2498 10) install a better fan for the CPU
2499 11) exchange RAM chips
2500 12) exchange the motherboard.
2502 To compile this driver as a module, choose M here: the
2503 module will be called apm.
2507 config APM_IGNORE_USER_SUSPEND
2508 bool "Ignore USER SUSPEND"
2510 This option will ignore USER SUSPEND requests. On machines with a
2511 compliant APM BIOS, you want to say N. However, on the NEC Versa M
2512 series notebooks, it is necessary to say Y because of a BIOS bug.
2514 config APM_DO_ENABLE
2515 bool "Enable PM at boot time"
2517 Enable APM features at boot time. From page 36 of the APM BIOS
2518 specification: "When disabled, the APM BIOS does not automatically
2519 power manage devices, enter the Standby State, enter the Suspend
2520 State, or take power saving steps in response to CPU Idle calls."
2521 This driver will make CPU Idle calls when Linux is idle (unless this
2522 feature is turned off -- see "Do CPU IDLE calls", below). This
2523 should always save battery power, but more complicated APM features
2524 will be dependent on your BIOS implementation. You may need to turn
2525 this option off if your computer hangs at boot time when using APM
2526 support, or if it beeps continuously instead of suspending. Turn
2527 this off if you have a NEC UltraLite Versa 33/C or a Toshiba
2528 T400CDT. This is off by default since most machines do fine without
2533 bool "Make CPU Idle calls when idle"
2535 Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
2536 On some machines, this can activate improved power savings, such as
2537 a slowed CPU clock rate, when the machine is idle. These idle calls
2538 are made after the idle loop has run for some length of time (e.g.,
2539 333 mS). On some machines, this will cause a hang at boot time or
2540 whenever the CPU becomes idle. (On machines with more than one CPU,
2541 this option does nothing.)
2543 config APM_DISPLAY_BLANK
2544 bool "Enable console blanking using APM"
2546 Enable console blanking using the APM. Some laptops can use this to
2547 turn off the LCD backlight when the screen blanker of the Linux
2548 virtual console blanks the screen. Note that this is only used by
2549 the virtual console screen blanker, and won't turn off the backlight
2550 when using the X Window system. This also doesn't have anything to
2551 do with your VESA-compliant power-saving monitor. Further, this
2552 option doesn't work for all laptops -- it might not turn off your
2553 backlight at all, or it might print a lot of errors to the console,
2554 especially if you are using gpm.
2556 config APM_ALLOW_INTS
2557 bool "Allow interrupts during APM BIOS calls"
2559 Normally we disable external interrupts while we are making calls to
2560 the APM BIOS as a measure to lessen the effects of a badly behaving
2561 BIOS implementation. The BIOS should reenable interrupts if it
2562 needs to. Unfortunately, some BIOSes do not -- especially those in
2563 many of the newer IBM Thinkpads. If you experience hangs when you
2564 suspend, try setting this to Y. Otherwise, say N.
2568 source "drivers/cpufreq/Kconfig"
2570 source "drivers/cpuidle/Kconfig"
2572 source "drivers/idle/Kconfig"
2577 menu "Bus options (PCI etc.)"
2580 prompt "PCI access mode"
2581 depends on X86_32 && PCI
2584 On PCI systems, the BIOS can be used to detect the PCI devices and
2585 determine their configuration. However, some old PCI motherboards
2586 have BIOS bugs and may crash if this is done. Also, some embedded
2587 PCI-based systems don't have any BIOS at all. Linux can also try to
2588 detect the PCI hardware directly without using the BIOS.
2590 With this option, you can specify how Linux should detect the
2591 PCI devices. If you choose "BIOS", the BIOS will be used,
2592 if you choose "Direct", the BIOS won't be used, and if you
2593 choose "MMConfig", then PCI Express MMCONFIG will be used.
2594 If you choose "Any", the kernel will try MMCONFIG, then the
2595 direct access method and falls back to the BIOS if that doesn't
2596 work. If unsure, go with the default, which is "Any".
2601 config PCI_GOMMCONFIG
2618 depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
2620 # x86-64 doesn't support PCI BIOS access from long mode so always go direct.
2623 depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG))
2626 bool "Support mmconfig PCI config space access" if X86_64
2628 depends on PCI && (ACPI || JAILHOUSE_GUEST)
2629 depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
2633 depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY)
2637 depends on PCI && XEN
2639 config MMCONF_FAM10H
2641 depends on X86_64 && PCI_MMCONFIG && ACPI
2643 config PCI_CNB20LE_QUIRK
2644 bool "Read CNB20LE Host Bridge Windows" if EXPERT
2647 Read the PCI windows out of the CNB20LE host bridge. This allows
2648 PCI hotplug to work on systems with the CNB20LE chipset which do
2651 There's no public spec for this chipset, and this functionality
2652 is known to be incomplete.
2654 You should say N unless you know you need this.
2657 bool "ISA bus support on modern systems" if EXPERT
2659 Expose ISA bus device drivers and options available for selection and
2660 configuration. Enable this option if your target machine has an ISA
2661 bus. ISA is an older system, displaced by PCI and newer bus
2662 architectures -- if your target machine is modern, it probably does
2663 not have an ISA bus.
2667 # x86_64 have no ISA slots, but can have ISA-style DMA.
2669 bool "ISA-style DMA support" if (X86_64 && EXPERT)
2672 Enables ISA-style DMA support for devices requiring such controllers.
2680 Find out whether you have ISA slots on your motherboard. ISA is the
2681 name of a bus system, i.e. the way the CPU talks to the other stuff
2682 inside your box. Other bus systems are PCI, EISA, MicroChannel
2683 (MCA) or VESA. ISA is an older system, now being displaced by PCI;
2684 newer boards don't support it. If you have ISA, say Y, otherwise N.
2687 tristate "NatSemi SCx200 support"
2689 This provides basic support for National Semiconductor's
2690 (now AMD's) Geode processors. The driver probes for the
2691 PCI-IDs of several on-chip devices, so its a good dependency
2692 for other scx200_* drivers.
2694 If compiled as a module, the driver is named scx200.
2696 config SCx200HR_TIMER
2697 tristate "NatSemi SCx200 27MHz High-Resolution Timer Support"
2701 This driver provides a clocksource built upon the on-chip
2702 27MHz high-resolution timer. Its also a workaround for
2703 NSC Geode SC-1100's buggy TSC, which loses time when the
2704 processor goes idle (as is done by the scheduler). The
2705 other workaround is idle=poll boot option.
2708 bool "One Laptop Per Child support"
2716 Add support for detecting the unique features of the OLPC
2720 bool "OLPC XO-1 Power Management"
2721 depends on OLPC && MFD_CS5535=y && PM_SLEEP
2723 Add support for poweroff and suspend of the OLPC XO-1 laptop.
2726 bool "OLPC XO-1 Real Time Clock"
2727 depends on OLPC_XO1_PM && RTC_DRV_CMOS
2729 Add support for the XO-1 real time clock, which can be used as a
2730 programmable wakeup source.
2733 bool "OLPC XO-1 SCI extras"
2734 depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y
2738 Add support for SCI-based features of the OLPC XO-1 laptop:
2739 - EC-driven system wakeups
2743 - AC adapter status updates
2744 - Battery status updates
2746 config OLPC_XO15_SCI
2747 bool "OLPC XO-1.5 SCI extras"
2748 depends on OLPC && ACPI
2751 Add support for SCI-based features of the OLPC XO-1.5 laptop:
2752 - EC-driven system wakeups
2753 - AC adapter status updates
2754 - Battery status updates
2757 bool "PCEngines ALIX System Support (LED setup)"
2760 This option enables system support for the PCEngines ALIX.
2761 At present this just sets up LEDs for GPIO control on
2762 ALIX2/3/6 boards. However, other system specific setup should
2765 Note: You must still enable the drivers for GPIO and LED support
2766 (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs
2768 Note: You have to set alix.force=1 for boards with Award BIOS.
2771 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)"
2774 This option enables system support for the Soekris Engineering net5501.
2777 bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)"
2781 This option enables system support for the Traverse Technologies GEOS.
2784 bool "Technologic Systems TS-5500 platform support"
2786 select CHECK_SIGNATURE
2790 This option enables system support for the Technologic Systems TS-5500.
2796 depends on CPU_SUP_AMD && PCI
2801 menu "Binary Emulations"
2803 config IA32_EMULATION
2804 bool "IA32 Emulation"
2806 select ARCH_WANT_OLD_COMPAT_IPC
2808 select COMPAT_OLD_SIGACTION
2810 Include code to run legacy 32-bit programs under a
2811 64-bit kernel. You should likely turn this on, unless you're
2812 100% sure that you don't have any 32-bit programs left.
2815 tristate "IA32 a.out support"
2816 depends on IA32_EMULATION
2819 Support old a.out binaries in the 32bit emulation.
2822 bool "x32 ABI for 64-bit mode"
2825 Include code to run binaries for the x32 native 32-bit ABI
2826 for 64-bit processors. An x32 process gets access to the
2827 full 64-bit register file and wide data path while leaving
2828 pointers at 32 bits for smaller memory footprint.
2830 You will need a recent binutils (2.22 or later) with
2831 elf32_x86_64 support enabled to compile a kernel with this
2836 depends on IA32_EMULATION || X86_32
2838 select OLD_SIGSUSPEND3
2842 depends on IA32_EMULATION || X86_X32
2845 config COMPAT_FOR_U64_ALIGNMENT
2848 config SYSVIPC_COMPAT
2856 config HAVE_ATOMIC_IOMAP
2860 source "arch/x86/kvm/Kconfig"
2862 source "arch/x86/Kconfig.assembler"