# SPDX-License-Identifier: GPL-2.0 # Select 32 or 64 bit config 64BIT bool "64-bit kernel" if "$(ARCH)" = "x86" default "$(ARCH)" != "i386" help Say yes to build a 64-bit kernel - formerly known as x86_64 Say no to build a 32-bit kernel - formerly known as i386 config X86_32 def_bool y depends on !64BIT # Options that are inherently 32-bit kernel only: select ARCH_WANT_IPC_PARSE_VERSION select CLKSRC_I8253 select CLONE_BACKWARDS select GENERIC_VDSO_32 select HAVE_DEBUG_STACKOVERFLOW select KMAP_LOCAL select MODULES_USE_ELF_REL select OLD_SIGACTION select ARCH_SPLIT_ARG64 config X86_64 def_bool y depends on 64BIT # Options that are inherently 64-bit kernel only: select ARCH_HAS_GIGANTIC_PAGE select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 select ARCH_SUPPORTS_PER_VMA_LOCK select ARCH_SUPPORTS_HUGE_PFNMAP if TRANSPARENT_HUGEPAGE select HAVE_ARCH_SOFT_DIRTY select MODULES_USE_ELF_RELA select NEED_DMA_MAP_STATE select SWIOTLB select ARCH_HAS_ELFCORE_COMPAT select ZONE_DMA32 select EXECMEM if DYNAMIC_FTRACE config FORCE_DYNAMIC_FTRACE def_bool y depends on X86_32 depends on FUNCTION_TRACER select DYNAMIC_FTRACE help We keep the static function tracing (!DYNAMIC_FTRACE) around in order to test the non static function tracing in the generic code, as other architectures still use it. But we only need to keep it around for x86_64. No need to keep it for x86_32. For x86_32, force DYNAMIC_FTRACE. # # Arch settings # # ( Note that options that are marked 'if X86_64' could in principle be # ported to 32-bit as well. ) # config X86 def_bool y # # Note: keep this list sorted alphabetically # select ACPI_LEGACY_TABLES_LOOKUP if ACPI select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI select ACPI_HOTPLUG_CPU if ACPI_PROCESSOR && HOTPLUG_CPU select ARCH_32BIT_OFF_T if X86_32 select ARCH_CLOCKSOURCE_INIT select ARCH_CONFIGURES_CPU_MITIGATIONS select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64 select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE) select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI select ARCH_HAS_CACHE_LINE_SIZE select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION select ARCH_HAS_CPU_FINALIZE_INIT select ARCH_HAS_CPU_PASID if IOMMU_SVA select ARCH_HAS_CURRENT_STACK_POINTER select ARCH_HAS_DEBUG_VIRTUAL select ARCH_HAS_DEBUG_VM_PGTABLE if !X86_PAE select ARCH_HAS_DEVMEM_IS_ALLOWED select ARCH_HAS_DMA_OPS if GART_IOMMU || XEN select ARCH_HAS_EARLY_DEBUG if KGDB select ARCH_HAS_ELF_RANDOMIZE select ARCH_HAS_EXECMEM_ROX if X86_64 select ARCH_HAS_FAST_MULTIPLIER select ARCH_HAS_FORTIFY_SOURCE select ARCH_HAS_GCOV_PROFILE_ALL select ARCH_HAS_KCOV if X86_64 select ARCH_HAS_KERNEL_FPU_SUPPORT select ARCH_HAS_MEM_ENCRYPT select ARCH_HAS_MEMBARRIER_SYNC_CORE select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE select ARCH_HAS_PMEM_API if X86_64 select ARCH_HAS_PREEMPT_LAZY select ARCH_HAS_PTE_DEVMAP if X86_64 select ARCH_HAS_PTE_SPECIAL select ARCH_HAS_HW_PTE_YOUNG select ARCH_HAS_NONLEAF_PMD_YOUNG if PGTABLE_LEVELS > 2 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64 select ARCH_HAS_COPY_MC if X86_64 select ARCH_HAS_SET_MEMORY select ARCH_HAS_SET_DIRECT_MAP select ARCH_HAS_STRICT_KERNEL_RWX select ARCH_HAS_STRICT_MODULE_RWX select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE select ARCH_HAS_SYSCALL_WRAPPER select ARCH_HAS_UBSAN select ARCH_HAS_DEBUG_WX select ARCH_HAS_ZONE_DMA_SET if EXPERT select ARCH_HAVE_NMI_SAFE_CMPXCHG select ARCH_HAVE_EXTRA_ELF_NOTES select ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI select ARCH_MIGHT_HAVE_PC_PARPORT select ARCH_MIGHT_HAVE_PC_SERIO select ARCH_STACKWALK select ARCH_SUPPORTS_ACPI select ARCH_SUPPORTS_ATOMIC_RMW select ARCH_SUPPORTS_DEBUG_PAGEALLOC select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096 select ARCH_SUPPORTS_CFI_CLANG if X86_64 select ARCH_USES_CFI_TRAPS if X86_64 && CFI_CLANG select ARCH_SUPPORTS_LTO_CLANG select ARCH_SUPPORTS_LTO_CLANG_THIN select ARCH_SUPPORTS_RT select ARCH_SUPPORTS_AUTOFDO_CLANG select ARCH_SUPPORTS_PROPELLER_CLANG if X86_64 select ARCH_USE_BUILTIN_BSWAP select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64 select ARCH_USE_MEMTEST select ARCH_USE_QUEUED_RWLOCKS select ARCH_USE_QUEUED_SPINLOCKS select ARCH_USE_SYM_ANNOTATIONS select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH select ARCH_WANT_DEFAULT_BPF_JIT if X86_64 select ARCH_WANTS_DYNAMIC_TASK_STRUCT select ARCH_WANTS_NO_INSTR select ARCH_WANT_GENERAL_HUGETLB select ARCH_WANT_HUGE_PMD_SHARE select ARCH_WANT_LD_ORPHAN_WARN select ARCH_WANT_OPTIMIZE_DAX_VMEMMAP if X86_64 select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP if X86_64 select ARCH_WANTS_THP_SWAP if X86_64 select ARCH_HAS_PARANOID_L1D_FLUSH select BUILDTIME_TABLE_SORT select CLKEVT_I8253 select CLOCKSOURCE_WATCHDOG # Word-size accesses may read uninitialized data past the trailing \0 # in strings and cause false KMSAN reports. select DCACHE_WORD_ACCESS if !KMSAN select DYNAMIC_SIGFRAME select EDAC_ATOMIC_SCRUB select EDAC_SUPPORT select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC) select GENERIC_CLOCKEVENTS_BROADCAST_IDLE if GENERIC_CLOCKEVENTS_BROADCAST select GENERIC_CLOCKEVENTS_MIN_ADJUST select GENERIC_CMOS_UPDATE select GENERIC_CPU_AUTOPROBE select GENERIC_CPU_DEVICES select GENERIC_CPU_VULNERABILITIES select GENERIC_EARLY_IOREMAP select GENERIC_ENTRY select GENERIC_IOMAP select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP select GENERIC_IRQ_MATRIX_ALLOCATOR if X86_LOCAL_APIC select GENERIC_IRQ_MIGRATION if SMP select GENERIC_IRQ_PROBE select GENERIC_IRQ_RESERVATION_MODE select GENERIC_IRQ_SHOW select GENERIC_PENDING_IRQ if SMP select GENERIC_PTDUMP select GENERIC_SMP_IDLE_THREAD select GENERIC_TIME_VSYSCALL select GENERIC_GETTIMEOFDAY select GENERIC_VDSO_TIME_NS select GENERIC_VDSO_OVERFLOW_PROTECT select GUP_GET_PXX_LOW_HIGH if X86_PAE select HARDIRQS_SW_RESEND select HARDLOCKUP_CHECK_TIMESTAMP if X86_64 select HAS_IOPORT select HAVE_ACPI_APEI if ACPI select HAVE_ACPI_APEI_NMI if ACPI select HAVE_ALIGNED_STRUCT_PAGE select HAVE_ARCH_AUDITSYSCALL select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE select HAVE_ARCH_HUGE_VMALLOC if X86_64 select HAVE_ARCH_JUMP_LABEL select HAVE_ARCH_JUMP_LABEL_RELATIVE select HAVE_ARCH_KASAN if X86_64 select HAVE_ARCH_KASAN_VMALLOC if X86_64 select HAVE_ARCH_KFENCE select HAVE_ARCH_KMSAN if X86_64 select HAVE_ARCH_KGDB select HAVE_ARCH_MMAP_RND_BITS if MMU select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT select HAVE_ARCH_PREL32_RELOCATIONS select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_THREAD_STRUCT_WHITELIST select HAVE_ARCH_STACKLEAK select HAVE_ARCH_TRACEHOOK select HAVE_ARCH_TRANSPARENT_HUGEPAGE select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD select HAVE_ARCH_USERFAULTFD_MINOR if X86_64 && USERFAULTFD select HAVE_ARCH_VMAP_STACK if X86_64 select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET select HAVE_ARCH_WITHIN_STACK_FRAMES select HAVE_ASM_MODVERSIONS select HAVE_CMPXCHG_DOUBLE select HAVE_CMPXCHG_LOCAL select HAVE_CONTEXT_TRACKING_USER if X86_64 select HAVE_CONTEXT_TRACKING_USER_OFFSTACK if HAVE_CONTEXT_TRACKING_USER select HAVE_C_RECORDMCOUNT select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL select HAVE_OBJTOOL_NOP_MCOUNT if HAVE_OBJTOOL_MCOUNT select HAVE_BUILDTIME_MCOUNT_SORT select HAVE_DEBUG_KMEMLEAK select HAVE_DMA_CONTIGUOUS select HAVE_DYNAMIC_FTRACE select HAVE_DYNAMIC_FTRACE_WITH_REGS select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64 select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS select HAVE_SAMPLE_FTRACE_DIRECT if X86_64 select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64 select HAVE_EBPF_JIT select HAVE_EFFICIENT_UNALIGNED_ACCESS select HAVE_EISA select HAVE_EXIT_THREAD select HAVE_GUP_FAST select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE select HAVE_FTRACE_MCOUNT_RECORD select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE) select HAVE_FUNCTION_TRACER select HAVE_GCC_PLUGINS select HAVE_HW_BREAKPOINT select HAVE_IOREMAP_PROT select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64 select HAVE_IRQ_TIME_ACCOUNTING select HAVE_JUMP_LABEL_HACK if HAVE_OBJTOOL select HAVE_KERNEL_BZIP2 select HAVE_KERNEL_GZIP select HAVE_KERNEL_LZ4 select HAVE_KERNEL_LZMA select HAVE_KERNEL_LZO select HAVE_KERNEL_XZ select HAVE_KERNEL_ZSTD select HAVE_KPROBES select HAVE_KPROBES_ON_FTRACE select HAVE_FUNCTION_ERROR_INJECTION select HAVE_KRETPROBES select HAVE_RETHOOK select HAVE_LIVEPATCH if X86_64 select HAVE_MIXED_BREAKPOINTS_REGS select HAVE_MOD_ARCH_SPECIFIC select HAVE_MOVE_PMD select HAVE_MOVE_PUD select HAVE_NOINSTR_HACK if HAVE_OBJTOOL select HAVE_NMI select HAVE_NOINSTR_VALIDATION if HAVE_OBJTOOL select HAVE_OBJTOOL if X86_64 select HAVE_OPTPROBES select HAVE_PAGE_SIZE_4KB select HAVE_PCSPKR_PLATFORM select HAVE_PERF_EVENTS select HAVE_PERF_EVENTS_NMI select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI select HAVE_PCI select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT select MMU_GATHER_MERGE_VMAS select HAVE_POSIX_CPU_TIMERS_TASK_WORK select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RELIABLE_STACKTRACE if UNWINDER_ORC || STACK_VALIDATION select HAVE_FUNCTION_ARG_ACCESS_API select HAVE_SETUP_PER_CPU_AREA select HAVE_SOFTIRQ_ON_OWN_STACK select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR select HAVE_STACK_VALIDATION if HAVE_OBJTOOL select HAVE_STATIC_CALL select HAVE_STATIC_CALL_INLINE if HAVE_OBJTOOL select HAVE_PREEMPT_DYNAMIC_CALL select HAVE_RSEQ select HAVE_RUST if X86_64 select HAVE_SYSCALL_TRACEPOINTS select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL select HAVE_UNSTABLE_SCHED_CLOCK select HAVE_USER_RETURN_NOTIFIER select HAVE_GENERIC_VDSO select VDSO_GETRANDOM if X86_64 select HOTPLUG_PARALLEL if SMP && X86_64 select HOTPLUG_SMT if SMP select HOTPLUG_SPLIT_STARTUP if SMP && X86_32 select IRQ_FORCED_THREADING select LOCK_MM_AND_FIND_VMA select NEED_PER_CPU_EMBED_FIRST_CHUNK select NEED_PER_CPU_PAGE_FIRST_CHUNK select NEED_SG_DMA_LENGTH select NUMA_MEMBLKS if NUMA select PCI_DOMAINS if PCI select PCI_LOCKLESS_CONFIG if PCI select PERF_EVENTS select RTC_LIB select RTC_MC146818_LIB select SPARSE_IRQ select SYSCTL_EXCEPTION_TRACE select THREAD_INFO_IN_TASK select TRACE_IRQFLAGS_SUPPORT select TRACE_IRQFLAGS_NMI_SUPPORT select USER_STACKTRACE_SUPPORT select HAVE_ARCH_KCSAN if X86_64 select PROC_PID_ARCH_STATUS if PROC_FS select HAVE_ARCH_NODE_DEV_GROUP if X86_SGX select FUNCTION_ALIGNMENT_16B if X86_64 || X86_ALIGNMENT_16 select FUNCTION_ALIGNMENT_4B imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE config INSTRUCTION_DECODER def_bool y depends on KPROBES || PERF_EVENTS || UPROBES config OUTPUT_FORMAT string default "elf32-i386" if X86_32 default "elf64-x86-64" if X86_64 config LOCKDEP_SUPPORT def_bool y config STACKTRACE_SUPPORT def_bool y config MMU def_bool y config ARCH_MMAP_RND_BITS_MIN default 28 if 64BIT default 8 config ARCH_MMAP_RND_BITS_MAX default 32 if 64BIT default 16 config ARCH_MMAP_RND_COMPAT_BITS_MIN default 8 config ARCH_MMAP_RND_COMPAT_BITS_MAX default 16 config SBUS bool config GENERIC_ISA_DMA def_bool y depends on ISA_DMA_API config GENERIC_CSUM bool default y if KMSAN || KASAN config GENERIC_BUG def_bool y depends on BUG select GENERIC_BUG_RELATIVE_POINTERS if X86_64 config GENERIC_BUG_RELATIVE_POINTERS bool config ARCH_MAY_HAVE_PC_FDC def_bool y depends on ISA_DMA_API config GENERIC_CALIBRATE_DELAY def_bool y config ARCH_HAS_CPU_RELAX def_bool y config ARCH_HIBERNATION_POSSIBLE def_bool y config ARCH_SUSPEND_POSSIBLE def_bool y config AUDIT_ARCH def_bool y if X86_64 config KASAN_SHADOW_OFFSET hex depends on KASAN default 0xdffffc0000000000 config HAVE_INTEL_TXT def_bool y depends on INTEL_IOMMU && ACPI config X86_64_SMP def_bool y depends on X86_64 && SMP config ARCH_SUPPORTS_UPROBES def_bool y config FIX_EARLYCON_MEM def_bool y config DYNAMIC_PHYSICAL_MASK bool config PGTABLE_LEVELS int default 5 if X86_5LEVEL default 4 if X86_64 default 3 if X86_PAE default 2 config CC_HAS_SANE_STACKPROTECTOR bool default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) $(CLANG_FLAGS)) if 64BIT default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC) $(CLANG_FLAGS)) help We have to make sure stack protector is unconditionally disabled if the compiler produces broken code or if it does not let us control the segment on 32-bit kernels. menu "Processor type and features" config SMP bool "Symmetric multi-processing support" help This enables support for systems with more than one CPU. If you have a system with only one CPU, say N. If you have a system with more than one CPU, say Y. If you say N here, the kernel will run on uni- and multiprocessor machines, but will use only one CPU of a multiprocessor machine. If you say Y here, the kernel will run on many, but not all, uniprocessor machines. On a uniprocessor machine, the kernel will run faster if you say N here. Note that if you say Y here and choose architecture "586" or "Pentium" under "Processor family", the kernel will not work on 486 architectures. Similarly, multiprocessor kernels for the "PPro" architecture may not work on all Pentium based boards. People using multiprocessor machines who say Y here should also say Y to "Enhanced Real Time Clock Support", below. The "Advanced Power Management" code will be disabled if you say Y here. See also , and the SMP-HOWTO available at . If you don't know what to do here, say N. config X86_X2APIC bool "Support x2apic" depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST) help This enables x2apic support on CPUs that have this feature. This allows 32-bit apic IDs (so it can support very large systems), and accesses the local apic via MSRs not via mmio. Some Intel systems circa 2022 and later are locked into x2APIC mode and can not fall back to the legacy APIC modes if SGX or TDX are enabled in the BIOS. They will boot with very reduced functionality without enabling this option. If you don't know what to do here, say N. config X86_POSTED_MSI bool "Enable MSI and MSI-x delivery by posted interrupts" depends on X86_64 && IRQ_REMAP help This enables MSIs that are under interrupt remapping to be delivered as posted interrupts to the host kernel. Interrupt throughput can potentially be improved by coalescing CPU notifications during high frequency bursts. If you don't know what to do here, say N. config X86_MPPARSE bool "Enable MPS table" if ACPI default y depends on X86_LOCAL_APIC help For old smp systems that do not have proper acpi support. Newer systems (esp with 64bit cpus) with acpi support, MADT and DSDT will override it config X86_CPU_RESCTRL bool "x86 CPU resource control support" depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD) select KERNFS select PROC_CPU_RESCTRL if PROC_FS help Enable x86 CPU resource control support. Provide support for the allocation and monitoring of system resources usage by the CPU. Intel calls this Intel Resource Director Technology (Intel(R) RDT). More information about RDT can be found in the Intel x86 Architecture Software Developer Manual. AMD calls this AMD Platform Quality of Service (AMD QoS). More information about AMD QoS can be found in the AMD64 Technology Platform Quality of Service Extensions manual. Say N if unsure. config X86_FRED bool "Flexible Return and Event Delivery" depends on X86_64 help When enabled, try to use Flexible Return and Event Delivery instead of the legacy SYSCALL/SYSENTER/IDT architecture for ring transitions and exception/interrupt handling if the system supports it. config X86_BIGSMP bool "Support for big SMP systems with more than 8 CPUs" depends on SMP && X86_32 help This option is needed for the systems that have more than 8 CPUs. config X86_EXTENDED_PLATFORM bool "Support for extended (non-PC) x86 platforms" default y help If you disable this option then the kernel will only support standard PC platforms. (which covers the vast majority of systems out there.) If you enable this option then you'll be able to select support for the following non-PC x86 platforms, depending on the value of CONFIG_64BIT. 32-bit platforms (CONFIG_64BIT=n): Goldfish (Android emulator) AMD Elan RDC R-321x SoC SGI 320/540 (Visual Workstation) STA2X11-based (e.g. Northville) Moorestown MID devices 64-bit platforms (CONFIG_64BIT=y): Numascale NumaChip ScaleMP vSMP SGI Ultraviolet If you have one of these systems, or if you want to build a generic distribution kernel, say Y here - otherwise say N. # This is an alphabetically sorted list of 64 bit extended platforms # Please maintain the alphabetic order if and when there are additions config X86_NUMACHIP bool "Numascale NumaChip" depends on X86_64 depends on X86_EXTENDED_PLATFORM depends on NUMA depends on SMP depends on X86_X2APIC depends on PCI_MMCONFIG help Adds support for Numascale NumaChip large-SMP systems. Needed to enable more than ~168 cores. If you don't have one of these, you should say N here. config X86_VSMP bool "ScaleMP vSMP" select HYPERVISOR_GUEST select PARAVIRT depends on X86_64 && PCI depends on X86_EXTENDED_PLATFORM depends on SMP help Support for ScaleMP vSMP systems. Say 'Y' here if this kernel is supposed to run on these EM64T-based machines. Only choose this option if you have one of these machines. config X86_UV bool "SGI Ultraviolet" depends on X86_64 depends on X86_EXTENDED_PLATFORM depends on NUMA depends on EFI depends on KEXEC_CORE depends on X86_X2APIC depends on PCI help This option is needed in order to support SGI Ultraviolet systems. If you don't have one of these, you should say N here. # Following is an alphabetically sorted list of 32 bit extended platforms # Please maintain the alphabetic order if and when there are additions config X86_GOLDFISH bool "Goldfish (Virtual Platform)" depends on X86_EXTENDED_PLATFORM help Enable support for the Goldfish virtual platform used primarily for Android development. Unless you are building for the Android Goldfish emulator say N here. config X86_INTEL_CE bool "CE4100 TV platform" depends on PCI depends on PCI_GODIRECT depends on X86_IO_APIC depends on X86_32 depends on X86_EXTENDED_PLATFORM select X86_REBOOTFIXUPS select OF select OF_EARLY_FLATTREE help Select for the Intel CE media processor (CE4100) SOC. This option compiles in support for the CE4100 SOC for settop boxes and media devices. config X86_INTEL_MID bool "Intel MID platform support" depends on X86_EXTENDED_PLATFORM depends on X86_PLATFORM_DEVICES depends on PCI depends on X86_64 || (PCI_GOANY && X86_32) depends on X86_IO_APIC select I2C select DW_APB_TIMER select INTEL_SCU_PCI help Select to build a kernel capable of supporting Intel MID (Mobile Internet Device) platform systems which do not have the PCI legacy interfaces. If you are building for a PC class system say N here. Intel MID platforms are based on an Intel processor and chipset which consume less power than most of the x86 derivatives. config X86_INTEL_QUARK bool "Intel Quark platform support" depends on X86_32 depends on X86_EXTENDED_PLATFORM depends on X86_PLATFORM_DEVICES depends on X86_TSC depends on PCI depends on PCI_GOANY depends on X86_IO_APIC select IOSF_MBI select INTEL_IMR select COMMON_CLK help Select to include support for Quark X1000 SoC. Say Y here if you have a Quark based system such as the Arduino compatible Intel Galileo. config X86_INTEL_LPSS bool "Intel Low Power Subsystem Support" depends on X86 && ACPI && PCI select COMMON_CLK select PINCTRL select IOSF_MBI help Select to build support for Intel Low Power Subsystem such as found on Intel Lynxpoint PCH. Selecting this option enables things like clock tree (common clock framework) and pincontrol which are needed by the LPSS peripheral drivers. config X86_AMD_PLATFORM_DEVICE bool "AMD ACPI2Platform devices support" depends on ACPI select COMMON_CLK select PINCTRL help Select to interpret AMD specific ACPI device to platform device such as I2C, UART, GPIO found on AMD Carrizo and later chipsets. I2C and UART depend on COMMON_CLK to set clock. GPIO driver is implemented under PINCTRL subsystem. config IOSF_MBI tristate "Intel SoC IOSF Sideband support for SoC platforms" depends on PCI help This option enables sideband register access support for Intel SoC platforms. On these platforms the IOSF sideband is used in lieu of MSR's for some register accesses, mostly but not limited to thermal and power. Drivers may query the availability of this device to determine if they need the sideband in order to work on these platforms. The sideband is available on the following SoC products. This list is not meant to be exclusive. - BayTrail - Braswell - Quark You should say Y if you are running a kernel on one of these SoC's. config IOSF_MBI_DEBUG bool "Enable IOSF sideband access through debugfs" depends on IOSF_MBI && DEBUG_FS help Select this option to expose the IOSF sideband access registers (MCR, MDR, MCRX) through debugfs to write and read register information from different units on the SoC. This is most useful for obtaining device state information for debug and analysis. As this is a general access mechanism, users of this option would have specific knowledge of the device they want to access. If you don't require the option or are in doubt, say N. config X86_RDC321X bool "RDC R-321x SoC" depends on X86_32 depends on X86_EXTENDED_PLATFORM select M486 select X86_REBOOTFIXUPS help This option is needed for RDC R-321x system-on-chip, also known as R-8610-(G). If you don't have one of these chips, you should say N here. config X86_32_NON_STANDARD bool "Support non-standard 32-bit SMP architectures" depends on X86_32 && SMP depends on X86_EXTENDED_PLATFORM help This option compiles in the bigsmp and STA2X11 default subarchitectures. It is intended for a generic binary kernel. If you select them all, kernel will probe it one by one and will fallback to default. # Alphabetically sorted list of Non standard 32 bit platforms config X86_SUPPORTS_MEMORY_FAILURE def_bool y # MCE code calls memory_failure(): depends on X86_MCE # On 32-bit this adds too big of NODES_SHIFT and we run out of page flags: # On 32-bit SPARSEMEM adds too big of SECTIONS_WIDTH: depends on X86_64 || !SPARSEMEM select ARCH_SUPPORTS_MEMORY_FAILURE config STA2X11 bool "STA2X11 Companion Chip Support" depends on X86_32_NON_STANDARD && PCI select SWIOTLB select MFD_STA2X11 select GPIOLIB help This adds support for boards based on the STA2X11 IO-Hub, a.k.a. "ConneXt". The chip is used in place of the standard PC chipset, so all "standard" peripherals are missing. If this option is selected the kernel will still be able to boot on standard PC machines. config X86_32_IRIS tristate "Eurobraille/Iris poweroff module" depends on X86_32 help The Iris machines from EuroBraille do not have APM or ACPI support to shut themselves down properly. A special I/O sequence is needed to do so, which is what this module does at kernel shutdown. This is only for Iris machines from EuroBraille. If unused, say N. config SCHED_OMIT_FRAME_POINTER def_bool y prompt "Single-depth WCHAN output" depends on X86 help Calculate simpler /proc//wchan values. If this option is disabled then wchan values will recurse back to the caller function. This provides more accurate wchan values, at the expense of slightly more scheduling overhead. If in doubt, say "Y". menuconfig HYPERVISOR_GUEST bool "Linux guest support" help Say Y here to enable options for running Linux under various hyper- visors. This option enables basic hypervisor detection and platform setup. If you say N, all options in this submenu will be skipped and disabled, and Linux guest support won't be built in. if HYPERVISOR_GUEST config PARAVIRT bool "Enable paravirtualization code" depends on HAVE_STATIC_CALL help This changes the kernel so it can modify itself when it is run under a hypervisor, potentially improving performance significantly over full virtualization. However, when run without a hypervisor the kernel is theoretically slower and slightly larger. config PARAVIRT_XXL bool config PARAVIRT_DEBUG bool "paravirt-ops debugging" depends on PARAVIRT && DEBUG_KERNEL help Enable to debug paravirt_ops internals. Specifically, BUG if a paravirt_op is missing when it is called. config PARAVIRT_SPINLOCKS bool "Paravirtualization layer for spinlocks" depends on PARAVIRT && SMP help Paravirtualized spinlocks allow a pvops backend to replace the spinlock implementation with something virtualization-friendly (for example, block the virtual CPU rather than spinning). It has a minimal impact on native kernels and gives a nice performance benefit on paravirtualized KVM / Xen kernels. If you are unsure how to answer this question, answer Y. config X86_HV_CALLBACK_VECTOR def_bool n source "arch/x86/xen/Kconfig" config KVM_GUEST bool "KVM Guest support (including kvmclock)" depends on PARAVIRT select PARAVIRT_CLOCK select ARCH_CPUIDLE_HALTPOLL select X86_HV_CALLBACK_VECTOR default y help This option enables various optimizations for running under the KVM hypervisor. It includes a paravirtualized clock, so that instead of relying on a PIT (or probably other) emulation by the underlying device model, the host provides the guest with timing infrastructure such as time of day, and system time config ARCH_CPUIDLE_HALTPOLL def_bool n prompt "Disable host haltpoll when loading haltpoll driver" help If virtualized under KVM, disable host haltpoll. config PVH bool "Support for running PVH guests" help This option enables the PVH entry point for guest virtual machines as specified in the x86/HVM direct boot ABI. config PARAVIRT_TIME_ACCOUNTING bool "Paravirtual steal time accounting" depends on PARAVIRT help Select this option to enable fine granularity task steal time accounting. Time spent executing other tasks in parallel with the current vCPU is discounted from the vCPU power. To account for that, there can be a small performance impact. If in doubt, say N here. config PARAVIRT_CLOCK bool config JAILHOUSE_GUEST bool "Jailhouse non-root cell support" depends on X86_64 && PCI select X86_PM_TIMER help This option allows to run Linux as guest in a Jailhouse non-root cell. You can leave this option disabled if you only want to start Jailhouse and run Linux afterwards in the root cell. config ACRN_GUEST bool "ACRN Guest support" depends on X86_64 select X86_HV_CALLBACK_VECTOR help This option allows to run Linux as guest in the ACRN hypervisor. ACRN is a flexible, lightweight reference open-source hypervisor, built with real-time and safety-criticality in mind. It is built for embedded IOT with small footprint and real-time features. More details can be found in https://projectacrn.org/. config INTEL_TDX_GUEST bool "Intel TDX (Trust Domain Extensions) - Guest Support" depends on X86_64 && CPU_SUP_INTEL depends on X86_X2APIC depends on EFI_STUB select ARCH_HAS_CC_PLATFORM select X86_MEM_ENCRYPT select X86_MCE select UNACCEPTED_MEMORY help Support running as a guest under Intel TDX. Without this support, the guest kernel can not boot or run under TDX. TDX includes memory encryption and integrity capabilities which protect the confidentiality and integrity of guest memory contents and CPU state. TDX guests are protected from some attacks from the VMM. endif # HYPERVISOR_GUEST source "arch/x86/Kconfig.cpu" config HPET_TIMER def_bool X86_64 prompt "HPET Timer Support" if X86_32 help Use the IA-PC HPET (High Precision Event Timer) to manage time in preference to the PIT and RTC, if a HPET is present. HPET is the next generation timer replacing legacy 8254s. The HPET provides a stable time base on SMP systems, unlike the TSC, but it is more expensive to access, as it is off-chip. The interface used is documented in the HPET spec, revision 1. You can safely choose Y here. However, HPET will only be activated if the platform and the BIOS support this feature. Otherwise the 8254 will be used for timing services. Choose N to continue using the legacy 8254 timer. config HPET_EMULATE_RTC def_bool y depends on HPET_TIMER && (RTC_DRV_CMOS=m || RTC_DRV_CMOS=y) # Mark as expert because too many people got it wrong. # The code disables itself when not needed. config DMI default y select DMI_SCAN_MACHINE_NON_EFI_FALLBACK bool "Enable DMI scanning" if EXPERT help Enabled scanning of DMI to identify machine quirks. Say Y here unless you have verified that your setup is not affected by entries in the DMI blacklist. Required by PNP BIOS code. config GART_IOMMU bool "Old AMD GART IOMMU support" select IOMMU_HELPER select SWIOTLB depends on X86_64 && PCI && AMD_NB help Provides a driver for older AMD Athlon64/Opteron/Turion/Sempron GART based hardware IOMMUs. The GART supports full DMA access for devices with 32-bit access limitations, on systems with more than 3 GB. This is usually needed for USB, sound, many IDE/SATA chipsets and some other devices. Newer systems typically have a modern AMD IOMMU, supported via the CONFIG_AMD_IOMMU=y config option. In normal configurations this driver is only active when needed: there's more than 3 GB of memory and the system contains a 32-bit limited device. If unsure, say Y. config BOOT_VESA_SUPPORT bool help If true, at least one selected framebuffer driver can take advantage of VESA video modes set at an early boot stage via the vga= parameter. config MAXSMP bool "Enable Maximum number of SMP Processors and NUMA Nodes" depends on X86_64 && SMP && DEBUG_KERNEL select CPUMASK_OFFSTACK help Enable maximum number of CPUS and NUMA Nodes for this architecture. If unsure, say N. # # The maximum number of CPUs supported: # # The main config value is NR_CPUS, which defaults to NR_CPUS_DEFAULT, # and which can be configured interactively in the # [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range. # # The ranges are different on 32-bit and 64-bit kernels, depending on # hardware capabilities and scalability features of the kernel. # # ( If MAXSMP is enabled we just use the highest possible value and disable # interactive configuration. ) # config NR_CPUS_RANGE_BEGIN int default NR_CPUS_RANGE_END if MAXSMP default 1 if !SMP default 2 config NR_CPUS_RANGE_END int depends on X86_32 default 64 if SMP && X86_BIGSMP default 8 if SMP && !X86_BIGSMP default 1 if !SMP config NR_CPUS_RANGE_END int depends on X86_64 default 8192 if SMP && CPUMASK_OFFSTACK default 512 if SMP && !CPUMASK_OFFSTACK default 1 if !SMP config NR_CPUS_DEFAULT int depends on X86_32 default 32 if X86_BIGSMP default 8 if SMP default 1 if !SMP config NR_CPUS_DEFAULT int depends on X86_64 default 8192 if MAXSMP default 64 if SMP default 1 if !SMP config NR_CPUS int "Maximum number of CPUs" if SMP && !MAXSMP range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END default NR_CPUS_DEFAULT help This allows you to specify the maximum number of CPUs which this kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum supported value is 8192, otherwise the maximum value is 512. The minimum value which makes sense is 2. This is purely to save memory: each supported CPU adds about 8KB to the kernel image. config SCHED_CLUSTER bool "Cluster scheduler support" depends on SMP default y help Cluster scheduler support improves the CPU scheduler's decision making when dealing with machines that have clusters of CPUs. Cluster usually means a couple of CPUs which are placed closely by sharing mid-level caches, last-level cache tags or internal busses. config SCHED_SMT def_bool y if SMP config SCHED_MC def_bool y prompt "Multi-core scheduler support" depends on SMP help Multi-core scheduler support improves the CPU scheduler's decision making when dealing with multi-core CPU chips at a cost of slightly increased overhead in some places. If unsure say N here. config SCHED_MC_PRIO bool "CPU core priorities scheduler support" depends on SCHED_MC select X86_INTEL_PSTATE if CPU_SUP_INTEL select X86_AMD_PSTATE if CPU_SUP_AMD && ACPI select CPU_FREQ default y help Intel Turbo Boost Max Technology 3.0 enabled CPUs have a core ordering determined at manufacturing time, which allows certain cores to reach higher turbo frequencies (when running single threaded workloads) than others. Enabling this kernel feature teaches the scheduler about the TBM3 (aka ITMT) priority order of the CPU cores and adjusts the scheduler's CPU selection logic accordingly, so that higher overall system performance can be achieved. This feature will have no effect on CPUs without this feature. If unsure say Y here. config UP_LATE_INIT def_bool y depends on !SMP && X86_LOCAL_APIC config X86_UP_APIC bool "Local APIC support on uniprocessors" if !PCI_MSI default PCI_MSI depends on X86_32 && !SMP && !X86_32_NON_STANDARD help A local APIC (Advanced Programmable Interrupt Controller) is an integrated interrupt controller in the CPU. If you have a single-CPU system which has a processor with a local APIC, you can say Y here to enable and use it. If you say Y here even though your machine doesn't have a local APIC, then the kernel will still run with no slowdown at all. The local APIC supports CPU-generated self-interrupts (timer, performance counters), and the NMI watchdog which detects hard lockups. config X86_UP_IOAPIC bool "IO-APIC support on uniprocessors" depends on X86_UP_APIC help An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an SMP-capable replacement for PC-style interrupt controllers. Most SMP systems and many recent uniprocessor systems have one. If you have a single-CPU system with an IO-APIC, you can say Y here to use it. If you say Y here even though your machine doesn't have an IO-APIC, then the kernel will still run with no slowdown at all. config X86_LOCAL_APIC def_bool y depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI select IRQ_DOMAIN_HIERARCHY config ACPI_MADT_WAKEUP def_bool y depends on X86_64 depends on ACPI depends on SMP depends on X86_LOCAL_APIC config X86_IO_APIC def_bool y depends on X86_LOCAL_APIC || X86_UP_IOAPIC config X86_REROUTE_FOR_BROKEN_BOOT_IRQS bool "Reroute for broken boot IRQs" depends on X86_IO_APIC help This option enables a workaround that fixes a source of spurious interrupts. This is recommended when threaded interrupt handling is used on systems where the generation of superfluous "boot interrupts" cannot be disabled. Some chipsets generate a legacy INTx "boot IRQ" when the IRQ entry in the chipset's IO-APIC is masked (as, e.g. the RT kernel does during interrupt handling). On chipsets where this boot IRQ generation cannot be disabled, this workaround keeps the original IRQ line masked so that only the equivalent "boot IRQ" is delivered to the CPUs. The workaround also tells the kernel to set up the IRQ handler on the boot IRQ line. In this way only one interrupt is delivered to the kernel. Otherwise the spurious second interrupt may cause the kernel to bring down (vital) interrupt lines. Only affects "broken" chipsets. Interrupt sharing may be increased on these systems. config X86_MCE bool "Machine Check / overheating reporting" select GENERIC_ALLOCATOR default y help Machine Check support allows the processor to notify the kernel if it detects a problem (e.g. overheating, data corruption). The action the kernel takes depends on the severity of the problem, ranging from warning messages to halting the machine. config X86_MCELOG_LEGACY bool "Support for deprecated /dev/mcelog character device" depends on X86_MCE help Enable support for /dev/mcelog which is needed by the old mcelog userspace logging daemon. Consider switching to the new generation rasdaemon solution. config X86_MCE_INTEL def_bool y prompt "Intel MCE features" depends on X86_MCE && X86_LOCAL_APIC help Additional support for intel specific MCE features such as the thermal monitor. config X86_MCE_AMD def_bool y prompt "AMD MCE features" depends on X86_MCE && X86_LOCAL_APIC && AMD_NB help Additional support for AMD specific MCE features such as the DRAM Error Threshold. config X86_ANCIENT_MCE bool "Support for old Pentium 5 / WinChip machine checks" depends on X86_32 && X86_MCE help Include support for machine check handling on old Pentium 5 or WinChip systems. These typically need to be enabled explicitly on the command line. config X86_MCE_THRESHOLD depends on X86_MCE_AMD || X86_MCE_INTEL def_bool y config X86_MCE_INJECT depends on X86_MCE && X86_LOCAL_APIC && DEBUG_FS tristate "Machine check injector support" help Provide support for injecting machine checks for testing purposes. If you don't know what a machine check is and you don't do kernel QA it is safe to say n. source "arch/x86/events/Kconfig" config X86_LEGACY_VM86 bool "Legacy VM86 support" depends on X86_32 help This option allows user programs to put the CPU into V8086 mode, which is an 80286-era approximation of 16-bit real mode. Some very old versions of X and/or vbetool require this option for user mode setting. Similarly, DOSEMU will use it if available to accelerate real mode DOS programs. However, any recent version of DOSEMU, X, or vbetool should be fully functional even without kernel VM86 support, as they will all fall back to software emulation. Nevertheless, if you are using a 16-bit DOS program where 16-bit performance matters, vm86 mode might be faster than emulation and you might want to enable this option. Note that any app that works on a 64-bit kernel is unlikely to need this option, as 64-bit kernels don't, and can't, support V8086 mode. This option is also unrelated to 16-bit protected mode and is not needed to run most 16-bit programs under Wine. Enabling this option increases the complexity of the kernel and slows down exception handling a tiny bit. If unsure, say N here. config VM86 bool default X86_LEGACY_VM86 config X86_16BIT bool "Enable support for 16-bit segments" if EXPERT default y depends on MODIFY_LDT_SYSCALL help This option is required by programs like Wine to run 16-bit protected mode legacy code on x86 processors. Disabling this option saves about 300 bytes on i386, or around 6K text plus 16K runtime memory on x86-64, config X86_ESPFIX32 def_bool y depends on X86_16BIT && X86_32 config X86_ESPFIX64 def_bool y depends on X86_16BIT && X86_64 config X86_VSYSCALL_EMULATION bool "Enable vsyscall emulation" if EXPERT default y depends on X86_64 help This enables emulation of the legacy vsyscall page. Disabling it is roughly equivalent to booting with vsyscall=none, except that it will also disable the helpful warning if a program tries to use a vsyscall. With this option set to N, offending programs will just segfault, citing addresses of the form 0xffffffffff600?00. This option is required by many programs built before 2013, and care should be used even with newer programs if set to N. Disabling this option saves about 7K of kernel size and possibly 4K of additional runtime pagetable memory. config X86_IOPL_IOPERM bool "IOPERM and IOPL Emulation" default y help This enables the ioperm() and iopl() syscalls which are necessary for legacy applications. Legacy IOPL support is an overbroad mechanism which allows user space aside of accessing all 65536 I/O ports also to disable interrupts. To gain this access the caller needs CAP_SYS_RAWIO capabilities and permission from potentially active security modules. The emulation restricts the functionality of the syscall to only allowing the full range I/O port access, but prevents the ability to disable interrupts from user space which would be granted if the hardware IOPL mechanism would be used. config TOSHIBA tristate "Toshiba Laptop support" depends on X86_32 help This adds a driver to safely access the System Management Mode of the CPU on Toshiba portables with a genuine Toshiba BIOS. It does not work on models with a Phoenix BIOS. The System Management Mode is used to set the BIOS and power saving options on Toshiba portables. For information on utilities to make use of this driver see the Toshiba Linux utilities web site at: . Say Y if you intend to run this kernel on a Toshiba portable. Say N otherwise. config X86_REBOOTFIXUPS bool "Enable X86 board specific fixups for reboot" depends on X86_32 help This enables chipset and/or board specific fixups to be done in order to get reboot to work correctly. This is only needed on some combinations of hardware and BIOS. The symptom, for which this config is intended, is when reboot ends with a stalled/hung system. Currently, the only fixup is for the Geode machines using CS5530A and CS5536 chipsets and the RDC R-321x SoC. Say Y if you want to enable the fixup. Currently, it's safe to enable this option even if you don't need it. Say N otherwise. config MICROCODE def_bool y depends on CPU_SUP_AMD || CPU_SUP_INTEL config MICROCODE_INITRD32 def_bool y depends on MICROCODE && X86_32 && BLK_DEV_INITRD config MICROCODE_LATE_LOADING bool "Late microcode loading (DANGEROUS)" default n depends on MICROCODE && SMP help Loading microcode late, when the system is up and executing instructions is a tricky business and should be avoided if possible. Just the sequence of synchronizing all cores and SMT threads is one fragile dance which does not guarantee that cores might not softlock after the loading. Therefore, use this at your own risk. Late loading taints the kernel unless the microcode header indicates that it is safe for late loading via the minimal revision check. This minimal revision check can be enforced on the kernel command line with "microcode.minrev=Y". config MICROCODE_LATE_FORCE_MINREV bool "Enforce late microcode loading minimal revision check" default n depends on MICROCODE_LATE_LOADING help To prevent that users load microcode late which modifies already in use features, newer microcode patches have a minimum revision field in the microcode header, which tells the kernel which minimum revision must be active in the CPU to safely load that new microcode late into the running system. If disabled the check will not be enforced but the kernel will be tainted when the minimal revision check fails. This minimal revision check can also be controlled via the "microcode.minrev" parameter on the kernel command line. If unsure say Y. config X86_MSR tristate "/dev/cpu/*/msr - Model-specific register support" help This device gives privileged processes access to the x86 Model-Specific Registers (MSRs). It is a character device with major 202 and minors 0 to 31 for /dev/cpu/0/msr to /dev/cpu/31/msr. MSR accesses are directed to a specific CPU on multi-processor systems. config X86_CPUID tristate "/dev/cpu/*/cpuid - CPU information support" help This device gives processes access to the x86 CPUID instruction to be executed on a specific processor. It is a character device with major 203 and minors 0 to 31 for /dev/cpu/0/cpuid to /dev/cpu/31/cpuid. choice prompt "High Memory Support" default HIGHMEM4G depends on X86_32 config NOHIGHMEM bool "off" help Linux can use up to 64 Gigabytes of physical memory on x86 systems. However, the address space of 32-bit x86 processors is only 4 Gigabytes large. That means that, if you have a large amount of physical memory, not all of it can be "permanently mapped" by the kernel. The physical memory that's not permanently mapped is called "high memory". If you are compiling a kernel which will never run on a machine with more than 1 Gigabyte total physical RAM, answer "off" here (default choice and suitable for most users). This will result in a "3GB/1GB" split: 3GB are mapped so that each process sees a 3GB virtual memory space and the remaining part of the 4GB virtual memory space is used by the kernel to permanently map as much physical memory as possible. If the machine has between 1 and 4 Gigabytes physical RAM, then answer "4GB" here. If more than 4 Gigabytes is used then answer "64GB" here. This selection turns Intel PAE (Physical Address Extension) mode on. PAE implements 3-level paging on IA32 processors. PAE is fully supported by Linux, PAE mode is implemented on all recent Intel processors (Pentium Pro and better). NOTE: If you say "64GB" here, then the kernel will not boot on CPUs that don't support PAE! The actual amount of total physical memory will either be auto detected or can be forced by using a kernel command line option such as "mem=256M". (Try "man bootparam" or see the documentation of your boot loader (lilo or loadlin) about how to pass options to the kernel at boot time.) If unsure, say "off". config HIGHMEM4G bool "4GB" help Select this if you have a 32-bit processor and between 1 and 4 gigabytes of physical RAM. config HIGHMEM64G bool "64GB" depends on X86_HAVE_PAE select X86_PAE help Select this if you have a 32-bit processor and more than 4 gigabytes of physical RAM. endchoice choice prompt "Memory split" if EXPERT default VMSPLIT_3G depends on X86_32 help Select the desired split between kernel and user memory. If the address range available to the kernel is less than the physical memory installed, the remaining memory will be available as "high memory". Accessing high memory is a little more costly than low memory, as it needs to be mapped into the kernel first. Note that increasing the kernel address space limits the range available to user programs, making the address space there tighter. Selecting anything other than the default 3G/1G split will also likely make your kernel incompatible with binary-only kernel modules. If you are not absolutely sure what you are doing, leave this option alone! config VMSPLIT_3G bool "3G/1G user/kernel split" config VMSPLIT_3G_OPT depends on !X86_PAE bool "3G/1G user/kernel split (for full 1G low memory)" config VMSPLIT_2G bool "2G/2G user/kernel split" config VMSPLIT_2G_OPT depends on !X86_PAE bool "2G/2G user/kernel split (for full 2G low memory)" config VMSPLIT_1G bool "1G/3G user/kernel split" endchoice config PAGE_OFFSET hex default 0xB0000000 if VMSPLIT_3G_OPT default 0x80000000 if VMSPLIT_2G default 0x78000000 if VMSPLIT_2G_OPT default 0x40000000 if VMSPLIT_1G default 0xC0000000 depends on X86_32 config HIGHMEM def_bool y depends on X86_32 && (HIGHMEM64G || HIGHMEM4G) config X86_PAE bool "PAE (Physical Address Extension) Support" depends on X86_32 && X86_HAVE_PAE select PHYS_ADDR_T_64BIT select SWIOTLB help PAE is required for NX support, and furthermore enables larger swapspace support for non-overcommit purposes. It has the cost of more pagetable lookup overhead, and also consumes more pagetable space per process. config X86_5LEVEL bool "Enable 5-level page tables support" default y select DYNAMIC_MEMORY_LAYOUT select SPARSEMEM_VMEMMAP depends on X86_64 help 5-level paging enables access to larger address space: up to 128 PiB of virtual address space and 4 PiB of physical address space. It will be supported by future Intel CPUs. A kernel with the option enabled can be booted on machines that support 4- or 5-level paging. See Documentation/arch/x86/x86_64/5level-paging.rst for more information. Say N if unsure. config X86_DIRECT_GBPAGES def_bool y depends on X86_64 help Certain kernel features effectively disable kernel linear 1 GB mappings (even if the CPU otherwise supports them), so don't confuse the user by printing that we have them enabled. config X86_CPA_STATISTICS bool "Enable statistic for Change Page Attribute" depends on DEBUG_FS help Expose statistics about the Change Page Attribute mechanism, which helps to determine the effectiveness of preserving large and huge page mappings when mapping protections are changed. config X86_MEM_ENCRYPT select ARCH_HAS_FORCE_DMA_UNENCRYPTED select DYNAMIC_PHYSICAL_MASK def_bool n config AMD_MEM_ENCRYPT bool "AMD Secure Memory Encryption (SME) support" depends on X86_64 && CPU_SUP_AMD depends on EFI_STUB select DMA_COHERENT_POOL select ARCH_USE_MEMREMAP_PROT select INSTRUCTION_DECODER select ARCH_HAS_CC_PLATFORM select X86_MEM_ENCRYPT select UNACCEPTED_MEMORY help Say yes to enable support for the encryption of system memory. This requires an AMD processor that supports Secure Memory Encryption (SME). # Common NUMA Features config NUMA bool "NUMA Memory Allocation and Scheduler Support" depends on SMP depends on X86_64 || (X86_32 && HIGHMEM64G && X86_BIGSMP) default y if X86_BIGSMP select USE_PERCPU_NUMA_NODE_ID select OF_NUMA if OF help Enable NUMA (Non-Uniform Memory Access) support. The kernel will try to allocate memory used by a CPU on the local memory controller of the CPU and add some more NUMA awareness to the kernel. For 64-bit this is recommended if the system is Intel Core i7 (or later), AMD Opteron, or EM64T NUMA. For 32-bit this is only needed if you boot a 32-bit kernel on a 64-bit NUMA platform. Otherwise, you should say N. config AMD_NUMA def_bool y prompt "Old style AMD Opteron NUMA detection" depends on X86_64 && NUMA && PCI help Enable AMD NUMA node topology detection. You should say Y here if you have a multi processor AMD system. This uses an old method to read the NUMA configuration directly from the builtin Northbridge of Opteron. It is recommended to use X86_64_ACPI_NUMA instead, which also takes priority if both are compiled in. config X86_64_ACPI_NUMA def_bool y prompt "ACPI NUMA detection" depends on X86_64 && NUMA && ACPI && PCI select ACPI_NUMA help Enable ACPI SRAT based node topology detection. config NODES_SHIFT int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP range 1 10 default "10" if MAXSMP default "6" if X86_64 default "3" depends on NUMA help Specify the maximum number of NUMA Nodes available on the target system. Increases memory reserved to accommodate various tables. config ARCH_FLATMEM_ENABLE def_bool y depends on X86_32 && !NUMA config ARCH_SPARSEMEM_ENABLE def_bool y depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD select SPARSEMEM_STATIC if X86_32 select SPARSEMEM_VMEMMAP_ENABLE if X86_64 config ARCH_SPARSEMEM_DEFAULT def_bool X86_64 || (NUMA && X86_32) config ARCH_SELECT_MEMORY_MODEL def_bool y depends on ARCH_SPARSEMEM_ENABLE && ARCH_FLATMEM_ENABLE config ARCH_MEMORY_PROBE bool "Enable sysfs memory/probe interface" depends on MEMORY_HOTPLUG help This option enables a sysfs memory/probe interface for testing. See Documentation/admin-guide/mm/memory-hotplug.rst for more information. If you are unsure how to answer this question, answer N. config ARCH_PROC_KCORE_TEXT def_bool y depends on X86_64 && PROC_KCORE config ILLEGAL_POINTER_VALUE hex default 0 if X86_32 default 0xdead000000000000 if X86_64 config X86_PMEM_LEGACY_DEVICE bool config X86_PMEM_LEGACY tristate "Support non-standard NVDIMMs and ADR protected memory" depends on PHYS_ADDR_T_64BIT depends on BLK_DEV select X86_PMEM_LEGACY_DEVICE select NUMA_KEEP_MEMINFO if NUMA select LIBNVDIMM help Treat memory marked using the non-standard e820 type of 12 as used by the Intel Sandy Bridge-EP reference BIOS as protected memory. The kernel will offer these regions to the 'pmem' driver so they can be used for persistent storage. Say Y if unsure. config HIGHPTE bool "Allocate 3rd-level pagetables from highmem" depends on HIGHMEM help The VM uses one page table entry for each page of physical memory. For systems with a lot of RAM, this can be wasteful of precious low memory. Setting this option will put user-space page table entries in high memory. config X86_CHECK_BIOS_CORRUPTION bool "Check for low memory corruption" help Periodically check for memory corruption in low memory, which is suspected to be caused by BIOS. Even when enabled in the configuration, it is disabled at runtime. Enable it by setting "memory_corruption_check=1" on the kernel command line. By default it scans the low 64k of memory every 60 seconds; see the memory_corruption_check_size and memory_corruption_check_period parameters in Documentation/admin-guide/kernel-parameters.rst to adjust this. When enabled with the default parameters, this option has almost no overhead, as it reserves a relatively small amount of memory and scans it infrequently. It both detects corruption and prevents it from affecting the running system. It is, however, intended as a diagnostic tool; if repeatable BIOS-originated corruption always affects the same memory, you can use memmap= to prevent the kernel from using that memory. config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK bool "Set the default setting of memory_corruption_check" depends on X86_CHECK_BIOS_CORRUPTION default y help Set whether the default state of memory_corruption_check is on or off. config MATH_EMULATION bool depends on MODIFY_LDT_SYSCALL prompt "Math emulation" if X86_32 && (M486SX || MELAN) help Linux can emulate a math coprocessor (used for floating point operations) if you don't have one. 486DX and Pentium processors have a math coprocessor built in, 486SX and 386 do not, unless you added a 487DX or 387, respectively. (The messages during boot time can give you some hints here ["man dmesg"].) Everyone needs either a coprocessor or this emulation. If you don't have a math coprocessor, you need to say Y here; if you say Y here even though you have a coprocessor, the coprocessor will be used nevertheless. (This behavior can be changed with the kernel command line option "no387", which comes handy if your coprocessor is broken. Try "man bootparam" or see the documentation of your boot loader (lilo or loadlin) about how to pass options to the kernel at boot time.) This means that it is a good idea to say Y here if you intend to use this kernel on different machines. More information about the internals of the Linux math coprocessor emulation can be found in . If you are not sure, say Y; apart from resulting in a 66 KB bigger kernel, it won't hurt. config MTRR def_bool y prompt "MTRR (Memory Type Range Register) support" if EXPERT help On Intel P6 family processors (Pentium Pro, Pentium II and later) the Memory Type Range Registers (MTRRs) may be used to control processor access to memory ranges. This is most useful if you have a video (VGA) card on a PCI or AGP bus. Enabling write-combining allows bus write transfers to be combined into a larger transfer before bursting over the PCI/AGP bus. This can increase performance of image write operations 2.5 times or more. Saying Y here creates a /proc/mtrr file which may be used to manipulate your processor's MTRRs. Typically the X server should use this. This code has a reasonably generic interface so that similar control registers on other processors can be easily supported as well: The Cyrix 6x86, 6x86MX and M II processors have Address Range Registers (ARRs) which provide a similar functionality to MTRRs. For these, the ARRs are used to emulate the MTRRs. The AMD K6-2 (stepping 8 and above) and K6-3 processors have two MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing write-combining. All of these processors are supported by this code and it makes sense to say Y here if you have one of them. Saying Y here also fixes a problem with buggy SMP BIOSes which only set the MTRRs for the boot CPU and not for the secondary CPUs. This can lead to all sorts of problems, so it's good to say Y here. You can safely say Y even if your machine doesn't have MTRRs, you'll just add about 9 KB to your kernel. See for more information. config MTRR_SANITIZER def_bool y prompt "MTRR cleanup support" depends on MTRR help Convert MTRR layout from continuous to discrete, so X drivers can add writeback entries. Can be disabled with disable_mtrr_cleanup on the kernel command line. The largest mtrr entry size for a continuous block can be set with mtrr_chunk_size. If unsure, say Y. config MTRR_SANITIZER_ENABLE_DEFAULT int "MTRR cleanup enable value (0-1)" range 0 1 default "0" depends on MTRR_SANITIZER help Enable mtrr cleanup default value config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT int "MTRR cleanup spare reg num (0-7)" range 0 7 default "1" depends on MTRR_SANITIZER help mtrr cleanup spare entries default, it can be changed via mtrr_spare_reg_nr=N on the kernel command line. config X86_PAT def_bool y prompt "x86 PAT support" if EXPERT depends on MTRR select ARCH_USES_PG_ARCH_2 help Use PAT attributes to setup page level cache control. PATs are the modern equivalents of MTRRs and are much more flexible than MTRRs. Say N here if you see bootup problems (boot crash, boot hang, spontaneous reboots) or a non-working video driver. If unsure, say Y. config X86_UMIP def_bool y prompt "User Mode Instruction Prevention" if EXPERT help User Mode Instruction Prevention (UMIP) is a security feature in some x86 processors. If enabled, a general protection fault is issued if the SGDT, SLDT, SIDT, SMSW or STR instructions are executed in user mode. These instructions unnecessarily expose information about the hardware state. The vast majority of applications do not use these instructions. For the very few that do, software emulation is provided in specific cases in protected and virtual-8086 modes. Emulated results are dummy. config CC_HAS_IBT # GCC >= 9 and binutils >= 2.29 # Retpoline check to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654 # Clang/LLVM >= 14 # https://github.com/llvm/llvm-project/commit/e0b89df2e0f0130881bf6c39bf31d7f6aac00e0f # https://github.com/llvm/llvm-project/commit/dfcf69770bc522b9e411c66454934a37c1f35332 def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \ (CC_IS_CLANG && CLANG_VERSION >= 140000)) && \ $(as-instr,endbr64) config X86_CET def_bool n help CET features configured (Shadow stack or IBT) config X86_KERNEL_IBT prompt "Indirect Branch Tracking" def_bool y depends on X86_64 && CC_HAS_IBT && HAVE_OBJTOOL # https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f depends on !LD_IS_LLD || LLD_VERSION >= 140000 select OBJTOOL select X86_CET help Build the kernel with support for Indirect Branch Tracking, a hardware support course-grain forward-edge Control Flow Integrity protection. It enforces that all indirect calls must land on an ENDBR instruction, as such, the compiler will instrument the code with them to make this happen. In addition to building the kernel with IBT, seal all functions that are not indirect call targets, avoiding them ever becoming one. This requires LTO like objtool runs and will slow down the build. It does significantly reduce the number of ENDBR instructions in the kernel image. config X86_INTEL_MEMORY_PROTECTION_KEYS prompt "Memory Protection Keys" def_bool y # Note: only available in 64-bit mode depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD) select ARCH_USES_HIGH_VMA_FLAGS select ARCH_HAS_PKEYS help Memory Protection Keys provides a mechanism for enforcing page-based protections, but without requiring modification of the page tables when an application changes protection domains. For details, see Documentation/core-api/protection-keys.rst If unsure, say y. config ARCH_PKEY_BITS int default 4 choice prompt "TSX enable mode" depends on CPU_SUP_INTEL default X86_INTEL_TSX_MODE_OFF help Intel's TSX (Transactional Synchronization Extensions) feature allows to optimize locking protocols through lock elision which can lead to a noticeable performance boost. On the other hand it has been shown that TSX can be exploited to form side channel attacks (e.g. TAA) and chances are there will be more of those attacks discovered in the future. Therefore TSX is not enabled by default (aka tsx=off). An admin might override this decision by tsx=on the command line parameter. Even with TSX enabled, the kernel will attempt to enable the best possible TAA mitigation setting depending on the microcode available for the particular machine. This option allows to set the default tsx mode between tsx=on, =off and =auto. See Documentation/admin-guide/kernel-parameters.txt for more details. Say off if not sure, auto if TSX is in use but it should be used on safe platforms or on if TSX is in use and the security aspect of tsx is not relevant. config X86_INTEL_TSX_MODE_OFF bool "off" help TSX is disabled if possible - equals to tsx=off command line parameter. config X86_INTEL_TSX_MODE_ON bool "on" help TSX is always enabled on TSX capable HW - equals the tsx=on command line parameter. config X86_INTEL_TSX_MODE_AUTO bool "auto" help TSX is enabled on TSX capable HW that is believed to be safe against side channel attacks- equals the tsx=auto command line parameter. endchoice config X86_SGX bool "Software Guard eXtensions (SGX)" depends on X86_64 && CPU_SUP_INTEL && X86_X2APIC depends on CRYPTO=y depends on CRYPTO_SHA256=y select MMU_NOTIFIER select NUMA_KEEP_MEMINFO if NUMA select XARRAY_MULTI help Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions that can be used by applications to set aside private regions of code and data, referred to as enclaves. An enclave's private memory can only be accessed by code running within the enclave. Accesses from outside the enclave, including other enclaves, are disallowed by hardware. If unsure, say N. config X86_USER_SHADOW_STACK bool "X86 userspace shadow stack" depends on AS_WRUSS depends on X86_64 select ARCH_USES_HIGH_VMA_FLAGS select ARCH_HAS_USER_SHADOW_STACK select X86_CET help Shadow stack protection is a hardware feature that detects function return address corruption. This helps mitigate ROP attacks. Applications must be enabled to use it, and old userspace does not get protection "for free". CPUs supporting shadow stacks were first released in 2020. See Documentation/arch/x86/shstk.rst for more information. If unsure, say N. config INTEL_TDX_HOST bool "Intel Trust Domain Extensions (TDX) host support" depends on CPU_SUP_INTEL depends on X86_64 depends on KVM_INTEL depends on X86_X2APIC select ARCH_KEEP_MEMBLOCK depends on CONTIG_ALLOC depends on !KEXEC_CORE depends on X86_MCE help Intel Trust Domain Extensions (TDX) protects guest VMs from malicious host and certain physical attacks. This option enables necessary TDX support in the host kernel to run confidential VMs. If unsure, say N. config EFI bool "EFI runtime service support" depends on ACPI select UCS2_STRING select EFI_RUNTIME_WRAPPERS select ARCH_USE_MEMREMAP_PROT select EFI_RUNTIME_MAP if KEXEC_CORE help This enables the kernel to use EFI runtime services that are available (such as the EFI variable services). This option is only useful on systems that have EFI firmware. In addition, you should use the latest ELILO loader available at in order to take advantage of EFI runtime services. However, even with this option, the resultant kernel should continue to boot on existing non-EFI platforms. config EFI_STUB bool "EFI stub support" depends on EFI select RELOCATABLE help This kernel feature allows a bzImage to be loaded directly by EFI firmware without the use of a bootloader. See Documentation/admin-guide/efi-stub.rst for more information. config EFI_HANDOVER_PROTOCOL bool "EFI handover protocol (DEPRECATED)" depends on EFI_STUB default y help Select this in order to include support for the deprecated EFI handover protocol, which defines alternative entry points into the EFI stub. This is a practice that has no basis in the UEFI specification, and requires a priori knowledge on the part of the bootloader about Linux/x86 specific ways of passing the command line and initrd, and where in memory those assets may be loaded. If in doubt, say Y. Even though the corresponding support is not present in upstream GRUB or other bootloaders, most distros build GRUB with numerous downstream patches applied, and may rely on the handover protocol as as result. config EFI_MIXED bool "EFI mixed-mode support" depends on EFI_STUB && X86_64 help Enabling this feature allows a 64-bit kernel to be booted on a 32-bit firmware, provided that your CPU supports 64-bit mode. Note that it is not possible to boot a mixed-mode enabled kernel via the EFI boot stub - a bootloader that supports the EFI handover protocol must be used. If unsure, say N. config EFI_RUNTIME_MAP bool "Export EFI runtime maps to sysfs" if EXPERT depends on EFI help Export EFI runtime memory regions to /sys/firmware/efi/runtime-map. That memory map is required by the 2nd kernel to set up EFI virtual mappings after kexec, but can also be used for debugging purposes. See also Documentation/ABI/testing/sysfs-firmware-efi-runtime-map. source "kernel/Kconfig.hz" config ARCH_SUPPORTS_KEXEC def_bool y config ARCH_SUPPORTS_KEXEC_FILE def_bool X86_64 config ARCH_SELECTS_KEXEC_FILE def_bool y depends on KEXEC_FILE select HAVE_IMA_KEXEC if IMA config ARCH_SUPPORTS_KEXEC_PURGATORY def_bool y config ARCH_SUPPORTS_KEXEC_SIG def_bool y config ARCH_SUPPORTS_KEXEC_SIG_FORCE def_bool y config ARCH_SUPPORTS_KEXEC_BZIMAGE_VERIFY_SIG def_bool y config ARCH_SUPPORTS_KEXEC_JUMP def_bool y config ARCH_SUPPORTS_CRASH_DUMP def_bool X86_64 || (X86_32 && HIGHMEM) config ARCH_DEFAULT_CRASH_DUMP def_bool y config ARCH_SUPPORTS_CRASH_HOTPLUG def_bool y config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION def_bool CRASH_RESERVE config PHYSICAL_START hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP) default "0x1000000" help This gives the physical address where the kernel is loaded. If the kernel is not relocatable (CONFIG_RELOCATABLE=n) then bzImage will decompress itself to above physical address and run from there. Otherwise, bzImage will run from the address where it has been loaded by the boot loader. The only exception is if it is loaded below the above physical address, in which case it will relocate itself there. In normal kdump cases one does not have to set/change this option as now bzImage can be compiled as a completely relocatable image (CONFIG_RELOCATABLE=y) and be used to load and run from a different address. This option is mainly useful for the folks who don't want to use a bzImage for capturing the crash dump and want to use a vmlinux instead. vmlinux is not relocatable hence a kernel needs to be specifically compiled to run from a specific memory area (normally a reserved region) and this option comes handy. So if you are using bzImage for capturing the crash dump, leave the value here unchanged to 0x1000000 and set CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux for capturing the crash dump change this value to start of the reserved region. In other words, it can be set based on the "X" value as specified in the "crashkernel=YM@XM" command line boot parameter passed to the panic-ed kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst for more details about crash dumps. Usage of bzImage for capturing the crash dump is recommended as one does not have to build two kernels. Same kernel can be used as production kernel and capture kernel. Above option should have gone away after relocatable bzImage support is introduced. But it is present because there are users out there who continue to use vmlinux for dump capture. This option should go away down the line. Don't change this unless you know what you are doing. config RELOCATABLE bool "Build a relocatable kernel" default y help This builds a kernel image that retains relocation information so it can be loaded someplace besides the default 1MB. The relocations tend to make the kernel binary about 10% larger, but are discarded at runtime. One use is for the kexec on panic case where the recovery kernel must live at a different physical address than the primary kernel. Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address it has been loaded at and the compile time physical address (CONFIG_PHYSICAL_START) is used as the minimum location. config RANDOMIZE_BASE bool "Randomize the address of the kernel image (KASLR)" depends on RELOCATABLE default y help In support of Kernel Address Space Layout Randomization (KASLR), this randomizes the physical address at which the kernel image is decompressed and the virtual address where the kernel image is mapped, as a security feature that deters exploit attempts relying on knowledge of the location of kernel code internals. On 64-bit, the kernel physical and virtual addresses are randomized separately. The physical address will be anywhere between 16MB and the top of physical memory (up to 64TB). The virtual address will be randomized from 16MB up to 1GB (9 bits of entropy). Note that this also reduces the memory space available to kernel modules from 1.5GB to 1GB. On 32-bit, the kernel physical and virtual addresses are randomized together. They will be randomized from 16MB up to 512MB (8 bits of entropy). Entropy is generated using the RDRAND instruction if it is supported. If RDTSC is supported, its value is mixed into the entropy pool as well. If neither RDRAND nor RDTSC are supported, then entropy is read from the i8254 timer. The usable entropy is limited by the kernel being built using 2GB addressing, and that PHYSICAL_ALIGN must be at a minimum of 2MB. As a result, only 10 bits of entropy are theoretically possible, but the implementations are further limited due to memory layouts. If unsure, say Y. # Relocation on x86 needs some additional build support config X86_NEED_RELOCS def_bool y depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE) config PHYSICAL_ALIGN hex "Alignment value to which kernel should be aligned" default "0x200000" range 0x2000 0x1000000 if X86_32 range 0x200000 0x1000000 if X86_64 help This value puts the alignment restrictions on physical address where kernel is loaded and run from. Kernel is compiled for an address which meets above alignment restriction. If bootloader loads the kernel at a non-aligned address and CONFIG_RELOCATABLE is set, kernel will move itself to nearest address aligned to above value and run from there. If bootloader loads the kernel at a non-aligned address and CONFIG_RELOCATABLE is not set, kernel will ignore the run time load address and decompress itself to the address it has been compiled for and run from there. The address for which kernel is compiled already meets above alignment restrictions. Hence the end result is that kernel runs from a physical address meeting above alignment restrictions. On 32-bit this value must be a multiple of 0x2000. On 64-bit this value must be a multiple of 0x200000. Don't change this unless you know what you are doing. config DYNAMIC_MEMORY_LAYOUT bool help This option makes base addresses of vmalloc and vmemmap as well as __PAGE_OFFSET movable during boot. config RANDOMIZE_MEMORY bool "Randomize the kernel memory sections" depends on X86_64 depends on RANDOMIZE_BASE select DYNAMIC_MEMORY_LAYOUT default RANDOMIZE_BASE help Randomizes the base virtual address of kernel memory sections (physical memory mapping, vmalloc & vmemmap). This security feature makes exploits relying on predictable memory locations less reliable. The order of allocations remains unchanged. Entropy is generated in the same way as RANDOMIZE_BASE. Current implementation in the optimal configuration have in average 30,000 different possible virtual addresses for each memory section. If unsure, say Y. config RANDOMIZE_MEMORY_PHYSICAL_PADDING hex "Physical memory mapping padding" if EXPERT depends on RANDOMIZE_MEMORY default "0xa" if MEMORY_HOTPLUG default "0x0" range 0x1 0x40 if MEMORY_HOTPLUG range 0x0 0x40 help Define the padding in terabytes added to the existing physical memory size during kernel memory randomization. It is useful for memory hotplug support but reduces the entropy available for address randomization. If unsure, leave at the default value. config ADDRESS_MASKING bool "Linear Address Masking support" depends on X86_64 depends on COMPILE_TEST || !CPU_MITIGATIONS # wait for LASS help Linear Address Masking (LAM) modifies the checking that is applied to 64-bit linear addresses, allowing software to use of the untranslated address bits for metadata. The capability can be used for efficient address sanitizers (ASAN) implementation and for optimizations in JITs. config HOTPLUG_CPU def_bool y depends on SMP config COMPAT_VDSO def_bool n prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)" depends on COMPAT_32 help Certain buggy versions of glibc will crash if they are presented with a 32-bit vDSO that is not mapped at the address indicated in its segment table. The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and 49ad572a70b8aeb91e57483a11dd1b77e31c4468. Glibc 2.3.3 is the only released version with the bug, but OpenSUSE 9 contains a buggy "glibc 2.3.2". The symptom of the bug is that everything crashes on startup, saying: dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! Saying Y here changes the default value of the vdso32 boot option from 1 to 0, which turns off the 32-bit vDSO entirely. This works around the glibc bug but hurts performance. If unsure, say N: if you are compiling your own kernel, you are unlikely to be using a buggy version of glibc. choice prompt "vsyscall table for legacy applications" depends on X86_64 default LEGACY_VSYSCALL_XONLY help Legacy user code that does not know how to find the vDSO expects to be able to issue three syscalls by calling fixed addresses in kernel space. Since this location is not randomized with ASLR, it can be used to assist security vulnerability exploitation. This setting can be changed at boot time via the kernel command line parameter vsyscall=[emulate|xonly|none]. Emulate mode is deprecated and can only be enabled using the kernel command line. On a system with recent enough glibc (2.14 or newer) and no static binaries, you can say None without a performance penalty to improve security. If unsure, select "Emulate execution only". config LEGACY_VSYSCALL_XONLY bool "Emulate execution only" help The kernel traps and emulates calls into the fixed vsyscall address mapping and does not allow reads. This configuration is recommended when userspace might use the legacy vsyscall area but support for legacy binary instrumentation of legacy code is not needed. It mitigates certain uses of the vsyscall area as an ASLR-bypassing buffer. config LEGACY_VSYSCALL_NONE bool "None" help There will be no vsyscall mapping at all. This will eliminate any risk of ASLR bypass due to the vsyscall fixed address mapping. Attempts to use the vsyscalls will be reported to dmesg, so that either old or malicious userspace programs can be identified. endchoice config CMDLINE_BOOL bool "Built-in kernel command line" help Allow for specifying boot arguments to the kernel at build time. On some systems (e.g. embedded ones), it is necessary or convenient to provide some or all of the kernel boot arguments with the kernel itself (that is, to not rely on the boot loader to provide them.) To compile command line arguments into the kernel, set this option to 'Y', then fill in the boot arguments in CONFIG_CMDLINE. Systems with fully functional boot loaders (i.e. non-embedded) should leave this option set to 'N'. config CMDLINE string "Built-in kernel command string" depends on CMDLINE_BOOL default "" help Enter arguments here that should be compiled into the kernel image and used at boot time. If the boot loader provides a command line at boot time, it is appended to this string to form the full kernel command line, when the system boots. However, you can use the CONFIG_CMDLINE_OVERRIDE option to change this behavior. In most cases, the command line (whether built-in or provided by the boot loader) should specify the device for the root file system. config CMDLINE_OVERRIDE bool "Built-in command line overrides boot loader arguments" depends on CMDLINE_BOOL && CMDLINE != "" help Set this option to 'Y' to have the kernel ignore the boot loader command line, and use ONLY the built-in command line. This is used to work around broken boot loaders. This should be set to 'N' under normal conditions. config MODIFY_LDT_SYSCALL bool "Enable the LDT (local descriptor table)" if EXPERT default y help Linux can allow user programs to install a per-process x86 Local Descriptor Table (LDT) using the modify_ldt(2) system call. This is required to run 16-bit or segmented code such as DOSEMU or some Wine programs. It is also used by some very old threading libraries. Enabling this feature adds a small amount of overhead to context switches and increases the low-level kernel attack surface. Disabling it removes the modify_ldt(2) system call. Saying 'N' here may make sense for embedded or server kernels. config STRICT_SIGALTSTACK_SIZE bool "Enforce strict size checking for sigaltstack" depends on DYNAMIC_SIGFRAME help For historical reasons MINSIGSTKSZ is a constant which became already too small with AVX512 support. Add a mechanism to enforce strict checking of the sigaltstack size against the real size of the FPU frame. This option enables the check by default. It can also be controlled via the kernel command line option 'strict_sas_size' independent of this config switch. Enabling it might break existing applications which allocate a too small sigaltstack but 'work' because they never get a signal delivered. Say 'N' unless you want to really enforce this check. config CFI_AUTO_DEFAULT bool "Attempt to use FineIBT by default at boot time" depends on FINEIBT default y help Attempt to use FineIBT by default at boot time. If enabled, this is the same as booting with "cfi=auto". If disabled, this is the same as booting with "cfi=kcfi". source "kernel/livepatch/Kconfig" config X86_BUS_LOCK_DETECT bool "Split Lock Detect and Bus Lock Detect support" depends on CPU_SUP_INTEL || CPU_SUP_AMD default y help Enable Split Lock Detect and Bus Lock Detect functionalities. See for more information. endmenu config CC_HAS_NAMED_AS def_bool $(success,echo 'int __seg_fs fs; int __seg_gs gs;' | $(CC) -x c - -S -o /dev/null) depends on CC_IS_GCC config CC_HAS_NAMED_AS_FIXED_SANITIZERS def_bool CC_IS_GCC && GCC_VERSION >= 130300 config USE_X86_SEG_SUPPORT def_bool y depends on CC_HAS_NAMED_AS # # -fsanitize=kernel-address (KASAN) and -fsanitize=thread # (KCSAN) are incompatible with named address spaces with # GCC < 13.3 - see GCC PR sanitizer/111736. # depends on !(KASAN || KCSAN) || CC_HAS_NAMED_AS_FIXED_SANITIZERS config CC_HAS_SLS def_bool $(cc-option,-mharden-sls=all) config CC_HAS_RETURN_THUNK def_bool $(cc-option,-mfunction-return=thunk-extern) config CC_HAS_ENTRY_PADDING def_bool $(cc-option,-fpatchable-function-entry=16,16) config FUNCTION_PADDING_CFI int default 59 if FUNCTION_ALIGNMENT_64B default 27 if FUNCTION_ALIGNMENT_32B default 11 if FUNCTION_ALIGNMENT_16B default 3 if FUNCTION_ALIGNMENT_8B default 0 # Basically: FUNCTION_ALIGNMENT - 5*CFI_CLANG # except Kconfig can't do arithmetic :/ config FUNCTION_PADDING_BYTES int default FUNCTION_PADDING_CFI if CFI_CLANG default FUNCTION_ALIGNMENT config CALL_PADDING def_bool n depends on CC_HAS_ENTRY_PADDING && OBJTOOL select FUNCTION_ALIGNMENT_16B config FINEIBT def_bool y depends on X86_KERNEL_IBT && CFI_CLANG && MITIGATION_RETPOLINE select CALL_PADDING config HAVE_CALL_THUNKS def_bool y depends on CC_HAS_ENTRY_PADDING && MITIGATION_RETHUNK && OBJTOOL config CALL_THUNKS def_bool n select CALL_PADDING config PREFIX_SYMBOLS def_bool y depends on CALL_PADDING && !CFI_CLANG menuconfig CPU_MITIGATIONS bool "Mitigations for CPU vulnerabilities" default y help Say Y here to enable options which enable mitigations for hardware vulnerabilities (usually related to speculative execution). Mitigations can be disabled or restricted to SMT systems at runtime via the "mitigations" kernel parameter. If you say N, all mitigations will be disabled. This CANNOT be overridden at runtime. Say 'Y', unless you really know what you are doing. if CPU_MITIGATIONS config MITIGATION_PAGE_TABLE_ISOLATION bool "Remove the kernel mapping in user mode" default y depends on (X86_64 || X86_PAE) help This feature reduces the number of hardware side channels by ensuring that the majority of kernel addresses are not mapped into userspace. See Documentation/arch/x86/pti.rst for more details. config MITIGATION_RETPOLINE bool "Avoid speculative indirect branches in kernel" select OBJTOOL if HAVE_OBJTOOL default y help Compile kernel with the retpoline compiler options to guard against kernel-to-user data leaks by avoiding speculative indirect branches. Requires a compiler with -mindirect-branch=thunk-extern support for full protection. The kernel may run slower. config MITIGATION_RETHUNK bool "Enable return-thunks" depends on MITIGATION_RETPOLINE && CC_HAS_RETURN_THUNK select OBJTOOL if HAVE_OBJTOOL default y if X86_64 help Compile the kernel with the return-thunks compiler option to guard against kernel-to-user data leaks by avoiding return speculation. Requires a compiler with -mfunction-return=thunk-extern support for full protection. The kernel may run slower. config MITIGATION_UNRET_ENTRY bool "Enable UNRET on kernel entry" depends on CPU_SUP_AMD && MITIGATION_RETHUNK && X86_64 default y help Compile the kernel with support for the retbleed=unret mitigation. config MITIGATION_CALL_DEPTH_TRACKING bool "Mitigate RSB underflow with call depth tracking" depends on CPU_SUP_INTEL && HAVE_CALL_THUNKS select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE select CALL_THUNKS default y help Compile the kernel with call depth tracking to mitigate the Intel SKL Return-Stack-Buffer (RSB) underflow issue. The mitigation is off by default and needs to be enabled on the kernel command line via the retbleed=stuff option. For non-affected systems the overhead of this option is marginal as the call depth tracking is using run-time generated call thunks in a compiler generated padding area and call patching. This increases text size by ~5%. For non affected systems this space is unused. On affected SKL systems this results in a significant performance gain over the IBRS mitigation. config CALL_THUNKS_DEBUG bool "Enable call thunks and call depth tracking debugging" depends on MITIGATION_CALL_DEPTH_TRACKING select FUNCTION_ALIGNMENT_32B default n help Enable call/ret counters for imbalance detection and build in a noisy dmesg about callthunks generation and call patching for trouble shooting. The debug prints need to be enabled on the kernel command line with 'debug-callthunks'. Only enable this when you are debugging call thunks as this creates a noticeable runtime overhead. If unsure say N. config MITIGATION_IBPB_ENTRY bool "Enable IBPB on kernel entry" depends on CPU_SUP_AMD && X86_64 default y help Compile the kernel with support for the retbleed=ibpb mitigation. config MITIGATION_IBRS_ENTRY bool "Enable IBRS on kernel entry" depends on CPU_SUP_INTEL && X86_64 default y help Compile the kernel with support for the spectre_v2=ibrs mitigation. This mitigates both spectre_v2 and retbleed at great cost to performance. config MITIGATION_SRSO bool "Mitigate speculative RAS overflow on AMD" depends on CPU_SUP_AMD && X86_64 && MITIGATION_RETHUNK default y help Enable the SRSO mitigation needed on AMD Zen1-4 machines. config MITIGATION_SLS bool "Mitigate Straight-Line-Speculation" depends on CC_HAS_SLS && X86_64 select OBJTOOL if HAVE_OBJTOOL default n help Compile the kernel with straight-line-speculation options to guard against straight line speculation. The kernel image might be slightly larger. config MITIGATION_GDS bool "Mitigate Gather Data Sampling" depends on CPU_SUP_INTEL default y help Enable mitigation for Gather Data Sampling (GDS). GDS is a hardware vulnerability which allows unprivileged speculative access to data which was previously stored in vector registers. The attacker uses gather instructions to infer the stale vector register data. config MITIGATION_RFDS bool "RFDS Mitigation" depends on CPU_SUP_INTEL default y help Enable mitigation for Register File Data Sampling (RFDS) by default. RFDS is a hardware vulnerability which affects Intel Atom CPUs. It allows unprivileged speculative access to stale data previously stored in floating point, vector and integer registers. See also config MITIGATION_SPECTRE_BHI bool "Mitigate Spectre-BHB (Branch History Injection)" depends on CPU_SUP_INTEL default y help Enable BHI mitigations. BHI attacks are a form of Spectre V2 attacks where the branch history buffer is poisoned to speculatively steer indirect branches. See config MITIGATION_MDS bool "Mitigate Microarchitectural Data Sampling (MDS) hardware bug" depends on CPU_SUP_INTEL default y help Enable mitigation for Microarchitectural Data Sampling (MDS). MDS is a hardware vulnerability which allows unprivileged speculative access to data which is available in various CPU internal buffers. See also config MITIGATION_TAA bool "Mitigate TSX Asynchronous Abort (TAA) hardware bug" depends on CPU_SUP_INTEL default y help Enable mitigation for TSX Asynchronous Abort (TAA). TAA is a hardware vulnerability that allows unprivileged speculative access to data which is available in various CPU internal buffers by using asynchronous aborts within an Intel TSX transactional region. See also config MITIGATION_MMIO_STALE_DATA bool "Mitigate MMIO Stale Data hardware bug" depends on CPU_SUP_INTEL default y help Enable mitigation for MMIO Stale Data hardware bugs. Processor MMIO Stale Data Vulnerabilities are a class of memory-mapped I/O (MMIO) vulnerabilities that can expose data. The vulnerabilities require the attacker to have access to MMIO. See also config MITIGATION_L1TF bool "Mitigate L1 Terminal Fault (L1TF) hardware bug" depends on CPU_SUP_INTEL default y help Mitigate L1 Terminal Fault (L1TF) hardware bug. L1 Terminal Fault is a hardware vulnerability which allows unprivileged speculative access to data available in the Level 1 Data Cache. See config MITIGATION_SPECTRE_V2 bool "Mitigate SPECTRE V2 hardware bug" default y help Enable mitigation for Spectre V2 (Branch Target Injection). Spectre V2 is a class of side channel attacks that takes advantage of indirect branch predictors inside the processor. In Spectre variant 2 attacks, the attacker can steer speculative indirect branches in the victim to gadget code by poisoning the branch target buffer of a CPU used for predicting indirect branch addresses. See also config MITIGATION_SRBDS bool "Mitigate Special Register Buffer Data Sampling (SRBDS) hardware bug" depends on CPU_SUP_INTEL default y help Enable mitigation for Special Register Buffer Data Sampling (SRBDS). SRBDS is a hardware vulnerability that allows Microarchitectural Data Sampling (MDS) techniques to infer values returned from special register accesses. An unprivileged user can extract values returned from RDRAND and RDSEED executed on another core or sibling thread using MDS techniques. See also config MITIGATION_SSB bool "Mitigate Speculative Store Bypass (SSB) hardware bug" default y help Enable mitigation for Speculative Store Bypass (SSB). SSB is a hardware security vulnerability and its exploitation takes advantage of speculative execution in a similar way to the Meltdown and Spectre security vulnerabilities. endif config ARCH_HAS_ADD_PAGES def_bool y depends on ARCH_ENABLE_MEMORY_HOTPLUG menu "Power management and ACPI options" config ARCH_HIBERNATION_HEADER def_bool y depends on HIBERNATION source "kernel/power/Kconfig" source "drivers/acpi/Kconfig" config X86_APM_BOOT def_bool y depends on APM menuconfig APM tristate "APM (Advanced Power Management) BIOS support" depends on X86_32 && PM_SLEEP help APM is a BIOS specification for saving power using several different techniques. This is mostly useful for battery powered laptops with APM compliant BIOSes. If you say Y here, the system time will be reset after a RESUME operation, the /proc/apm device will provide battery status information, and user-space programs will receive notification of APM "events" (e.g. battery status change). If you select "Y" here, you can disable actual use of the APM BIOS by passing the "apm=off" option to the kernel at boot time. Note that the APM support is almost completely disabled for machines with more than one CPU. In order to use APM, you will need supporting software. For location and more information, read and the Battery Powered Linux mini-HOWTO, available from . This driver does not spin down disk drives (see the hdparm(8) manpage ("man 8 hdparm") for that), and it doesn't turn off VESA-compliant "green" monitors. This driver does not support the TI 4000M TravelMate and the ACER 486/DX4/75 because they don't have compliant BIOSes. Many "green" desktop machines also don't have compliant BIOSes, and this driver may cause those machines to panic during the boot phase. Generally, if you don't have a battery in your machine, there isn't much point in using this driver and you should say N. If you get random kernel OOPSes or reboots that don't seem to be related to anything, try disabling/enabling this option (or disabling/enabling APM in your BIOS). Some other things you should try when experiencing seemingly random, "weird" problems: 1) make sure that you have enough swap space and that it is enabled. 2) pass the "idle=poll" option to the kernel 3) switch on floating point emulation in the kernel and pass the "no387" option to the kernel 4) pass the "floppy=nodma" option to the kernel 5) pass the "mem=4M" option to the kernel (thereby disabling all but the first 4 MB of RAM) 6) make sure that the CPU is not over clocked. 7) read the sig11 FAQ at 8) disable the cache from your BIOS settings 9) install a fan for the video card or exchange video RAM 10) install a better fan for the CPU 11) exchange RAM chips 12) exchange the motherboard. To compile this driver as a module, choose M here: the module will be called apm. if APM config APM_IGNORE_USER_SUSPEND bool "Ignore USER SUSPEND" help This option will ignore USER SUSPEND requests. On machines with a compliant APM BIOS, you want to say N. However, on the NEC Versa M series notebooks, it is necessary to say Y because of a BIOS bug. config APM_DO_ENABLE bool "Enable PM at boot time" help Enable APM features at boot time. From page 36 of the APM BIOS specification: "When disabled, the APM BIOS does not automatically power manage devices, enter the Standby State, enter the Suspend State, or take power saving steps in response to CPU Idle calls." This driver will make CPU Idle calls when Linux is idle (unless this feature is turned off -- see "Do CPU IDLE calls", below). This should always save battery power, but more complicated APM features will be dependent on your BIOS implementation. You may need to turn this option off if your computer hangs at boot time when using APM support, or if it beeps continuously instead of suspending. Turn this off if you have a NEC UltraLite Versa 33/C or a Toshiba T400CDT. This is off by default since most machines do fine without this feature. config APM_CPU_IDLE depends on CPU_IDLE bool "Make CPU Idle calls when idle" help Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop. On some machines, this can activate improved power savings, such as a slowed CPU clock rate, when the machine is idle. These idle calls are made after the idle loop has run for some length of time (e.g., 333 mS). On some machines, this will cause a hang at boot time or whenever the CPU becomes idle. (On machines with more than one CPU, this option does nothing.) config APM_DISPLAY_BLANK bool "Enable console blanking using APM" help Enable console blanking using the APM. Some laptops can use this to turn off the LCD backlight when the screen blanker of the Linux virtual console blanks the screen. Note that this is only used by the virtual console screen blanker, and won't turn off the backlight when using the X Window system. This also doesn't have anything to do with your VESA-compliant power-saving monitor. Further, this option doesn't work for all laptops -- it might not turn off your backlight at all, or it might print a lot of errors to the console, especially if you are using gpm. config APM_ALLOW_INTS bool "Allow interrupts during APM BIOS calls" help Normally we disable external interrupts while we are making calls to the APM BIOS as a measure to lessen the effects of a badly behaving BIOS implementation. The BIOS should reenable interrupts if it needs to. Unfortunately, some BIOSes do not -- especially those in many of the newer IBM Thinkpads. If you experience hangs when you suspend, try setting this to Y. Otherwise, say N. endif # APM source "drivers/cpufreq/Kconfig" source "drivers/cpuidle/Kconfig" source "drivers/idle/Kconfig" endmenu menu "Bus options (PCI etc.)" choice prompt "PCI access mode" depends on X86_32 && PCI default PCI_GOANY help On PCI systems, the BIOS can be used to detect the PCI devices and determine their configuration. However, some old PCI motherboards have BIOS bugs and may crash if this is done. Also, some embedded PCI-based systems don't have any BIOS at all. Linux can also try to detect the PCI hardware directly without using the BIOS. With this option, you can specify how Linux should detect the PCI devices. If you choose "BIOS", the BIOS will be used, if you choose "Direct", the BIOS won't be used, and if you choose "MMConfig", then PCI Express MMCONFIG will be used. If you choose "Any", the kernel will try MMCONFIG, then the direct access method and falls back to the BIOS if that doesn't work. If unsure, go with the default, which is "Any". config PCI_GOBIOS bool "BIOS" config PCI_GOMMCONFIG bool "MMConfig" config PCI_GODIRECT bool "Direct" config PCI_GOOLPC bool "OLPC XO-1" depends on OLPC config PCI_GOANY bool "Any" endchoice config PCI_BIOS def_bool y depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY) # x86-64 doesn't support PCI BIOS access from long mode so always go direct. config PCI_DIRECT def_bool y depends on PCI && (X86_64 || (PCI_GODIRECT || PCI_GOANY || PCI_GOOLPC || PCI_GOMMCONFIG)) config PCI_MMCONFIG bool "Support mmconfig PCI config space access" if X86_64 default y depends on PCI && (ACPI || JAILHOUSE_GUEST) depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG) config PCI_OLPC def_bool y depends on PCI && OLPC && (PCI_GOOLPC || PCI_GOANY) config PCI_XEN def_bool y depends on PCI && XEN config MMCONF_FAM10H def_bool y depends on X86_64 && PCI_MMCONFIG && ACPI config PCI_CNB20LE_QUIRK bool "Read CNB20LE Host Bridge Windows" if EXPERT depends on PCI help Read the PCI windows out of the CNB20LE host bridge. This allows PCI hotplug to work on systems with the CNB20LE chipset which do not have ACPI. There's no public spec for this chipset, and this functionality is known to be incomplete. You should say N unless you know you need this. config ISA_BUS bool "ISA bus support on modern systems" if EXPERT help Expose ISA bus device drivers and options available for selection and configuration. Enable this option if your target machine has an ISA bus. ISA is an older system, displaced by PCI and newer bus architectures -- if your target machine is modern, it probably does not have an ISA bus. If unsure, say N. # x86_64 have no ISA slots, but can have ISA-style DMA. config ISA_DMA_API bool "ISA-style DMA support" if (X86_64 && EXPERT) default y help Enables ISA-style DMA support for devices requiring such controllers. If unsure, say Y. if X86_32 config ISA bool "ISA support" help Find out whether you have ISA slots on your motherboard. ISA is the name of a bus system, i.e. the way the CPU talks to the other stuff inside your box. Other bus systems are PCI, EISA, MicroChannel (MCA) or VESA. ISA is an older system, now being displaced by PCI; newer boards don't support it. If you have ISA, say Y, otherwise N. config SCx200 tristate "NatSemi SCx200 support" help This provides basic support for National Semiconductor's (now AMD's) Geode processors. The driver probes for the PCI-IDs of several on-chip devices, so its a good dependency for other scx200_* drivers. If compiled as a module, the driver is named scx200. config SCx200HR_TIMER tristate "NatSemi SCx200 27MHz High-Resolution Timer Support" depends on SCx200 default y help This driver provides a clocksource built upon the on-chip 27MHz high-resolution timer. Its also a workaround for NSC Geode SC-1100's buggy TSC, which loses time when the processor goes idle (as is done by the scheduler). The other workaround is idle=poll boot option. config OLPC bool "One Laptop Per Child support" depends on !X86_PAE select GPIOLIB select OF select OF_PROMTREE select IRQ_DOMAIN select OLPC_EC help Add support for detecting the unique features of the OLPC XO hardware. config OLPC_XO1_PM bool "OLPC XO-1 Power Management" depends on OLPC && MFD_CS5535=y && PM_SLEEP help Add support for poweroff and suspend of the OLPC XO-1 laptop. config OLPC_XO1_RTC bool "OLPC XO-1 Real Time Clock" depends on OLPC_XO1_PM && RTC_DRV_CMOS help Add support for the XO-1 real time clock, which can be used as a programmable wakeup source. config OLPC_XO1_SCI bool "OLPC XO-1 SCI extras" depends on OLPC && OLPC_XO1_PM && GPIO_CS5535=y depends on INPUT=y select POWER_SUPPLY help Add support for SCI-based features of the OLPC XO-1 laptop: - EC-driven system wakeups - Power button - Ebook switch - Lid switch - AC adapter status updates - Battery status updates config OLPC_XO15_SCI bool "OLPC XO-1.5 SCI extras" depends on OLPC && ACPI select POWER_SUPPLY help Add support for SCI-based features of the OLPC XO-1.5 laptop: - EC-driven system wakeups - AC adapter status updates - Battery status updates config GEODE_COMMON bool config ALIX bool "PCEngines ALIX System Support (LED setup)" select GPIOLIB select GEODE_COMMON help This option enables system support for the PCEngines ALIX. At present this just sets up LEDs for GPIO control on ALIX2/3/6 boards. However, other system specific setup should get added here. Note: You must still enable the drivers for GPIO and LED support (GPIO_CS5535 & LEDS_GPIO) to actually use the LEDs Note: You have to set alix.force=1 for boards with Award BIOS. config NET5501 bool "Soekris Engineering net5501 System Support (LEDS, GPIO, etc)" select GPIOLIB select GEODE_COMMON help This option enables system support for the Soekris Engineering net5501. config GEOS bool "Traverse Technologies GEOS System Support (LEDS, GPIO, etc)" select GPIOLIB select GEODE_COMMON depends on DMI help This option enables system support for the Traverse Technologies GEOS. config TS5500 bool "Technologic Systems TS-5500 platform support" depends on MELAN select CHECK_SIGNATURE select NEW_LEDS select LEDS_CLASS help This option enables system support for the Technologic Systems TS-5500. endif # X86_32 config AMD_NB def_bool y depends on CPU_SUP_AMD && PCI endmenu menu "Binary Emulations" config IA32_EMULATION bool "IA32 Emulation" depends on X86_64 select ARCH_WANT_OLD_COMPAT_IPC select BINFMT_ELF select COMPAT_OLD_SIGACTION help Include code to run legacy 32-bit programs under a 64-bit kernel. You should likely turn this on, unless you're 100% sure that you don't have any 32-bit programs left. config IA32_EMULATION_DEFAULT_DISABLED bool "IA32 emulation disabled by default" default n depends on IA32_EMULATION help Make IA32 emulation disabled by default. This prevents loading 32-bit processes and access to 32-bit syscalls. If unsure, leave it to its default value. config X86_X32_ABI bool "x32 ABI for 64-bit mode" depends on X86_64 # llvm-objcopy does not convert x86_64 .note.gnu.property or # compressed debug sections to x86_x32 properly: # https://github.com/ClangBuiltLinux/linux/issues/514 # https://github.com/ClangBuiltLinux/linux/issues/1141 depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm) help Include code to run binaries for the x32 native 32-bit ABI for 64-bit processors. An x32 process gets access to the full 64-bit register file and wide data path while leaving pointers at 32 bits for smaller memory footprint. config COMPAT_32 def_bool y depends on IA32_EMULATION || X86_32 select HAVE_UID16 select OLD_SIGSUSPEND3 config COMPAT def_bool y depends on IA32_EMULATION || X86_X32_ABI config COMPAT_FOR_U64_ALIGNMENT def_bool y depends on COMPAT endmenu config HAVE_ATOMIC_IOMAP def_bool y depends on X86_32 source "arch/x86/kvm/Kconfig" source "arch/x86/Kconfig.assembler"