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Kconfig
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# x86 configuration
mainmenu "Linux Kernel Configuration for x86"
# Select 32 or 64 bit
config 64BIT
bool "64-bit kernel" if ARCH = "x86"
default ARCH = "x86_64"
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 !64BIT
config X86_64
def_bool 64BIT
### Arch settings
config X86
def_bool y
select HAVE_OPROFILE
select HAVE_KPROBES
config GENERIC_LOCKBREAK
def_bool n
config GENERIC_TIME
def_bool y
config GENERIC_CMOS_UPDATE
def_bool y
config CLOCKSOURCE_WATCHDOG
def_bool y
config GENERIC_CLOCKEVENTS
def_bool y
config GENERIC_CLOCKEVENTS_BROADCAST
def_bool y
depends on X86_64 || (X86_32 && X86_LOCAL_APIC)
config LOCKDEP_SUPPORT
def_bool y
config STACKTRACE_SUPPORT
def_bool y
config HAVE_LATENCYTOP_SUPPORT
def_bool y
config SEMAPHORE_SLEEPERS
def_bool y
config MMU
def_bool y
config ZONE_DMA
def_bool y
config QUICKLIST
def_bool X86_32
config SBUS
bool
config GENERIC_ISA_DMA
def_bool y
config GENERIC_IOMAP
def_bool y
config GENERIC_BUG
def_bool y
depends on BUG
config GENERIC_HWEIGHT
def_bool y
config GENERIC_GPIO
def_bool n
config ARCH_MAY_HAVE_PC_FDC
def_bool y
config DMI
def_bool y
config RWSEM_GENERIC_SPINLOCK
def_bool !X86_XADD
config RWSEM_XCHGADD_ALGORITHM
def_bool X86_XADD
config ARCH_HAS_ILOG2_U32
def_bool n
config ARCH_HAS_ILOG2_U64
def_bool n
config GENERIC_CALIBRATE_DELAY
def_bool y
config GENERIC_TIME_VSYSCALL
bool
default X86_64
config HAVE_SETUP_PER_CPU_AREA
def_bool X86_64
select HAVE_KVM
config ARCH_HIBERNATION_POSSIBLE
def_bool y
depends on !SMP || !X86_VOYAGER
config ARCH_SUSPEND_POSSIBLE
def_bool y
depends on !X86_VOYAGER
config ZONE_DMA32
bool
default X86_64
config ARCH_POPULATES_NODE_MAP
def_bool y
config AUDIT_ARCH
bool
default X86_64
# Use the generic interrupt handling code in kernel/irq/:
config GENERIC_HARDIRQS
bool
default y
config GENERIC_IRQ_PROBE
bool
default y
config GENERIC_PENDING_IRQ
bool
depends on GENERIC_HARDIRQS && SMP
default y
config X86_SMP
bool
depends on SMP && ((X86_32 && !X86_VOYAGER) || X86_64)
default y
config X86_32_SMP
def_bool y
depends on X86_32 && SMP
config X86_64_SMP
def_bool y
depends on X86_64 && SMP
config X86_HT
bool
depends on SMP
depends on (X86_32 && !(X86_VISWS || X86_VOYAGER)) || (X86_64 && !MK8)
default y
config X86_BIOS_REBOOT
bool
depends on X86_32 && !(X86_VISWS || X86_VOYAGER)
default y
config X86_TRAMPOLINE
bool
depends on X86_SMP || (X86_VOYAGER && SMP)
default y
config KTIME_SCALAR
def_bool X86_32
source "init/Kconfig"
menu "Processor type and features"
source "kernel/time/Kconfig"
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, like most personal computers, say N. If
you have a system with more than one CPU, say Y.
If you say N here, the kernel will run on single 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,
singleprocessor machines. On a singleprocessor 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 <file:Documentation/i386/IO-APIC.txt>,
<file:Documentation/nmi_watchdog.txt> and the SMP-HOWTO available at
<http://www.tldp.org/docs.html#howto>.
If you don't know what to do here, say N.
choice
prompt "Subarchitecture Type"
default X86_PC
config X86_PC
bool "PC-compatible"
help
Choose this option if your computer is a standard PC or compatible.
config X86_ELAN
bool "AMD Elan"
depends on X86_32
help
Select this for an AMD Elan processor.
Do not use this option for K6/Athlon/Opteron processors!
If unsure, choose "PC-compatible" instead.
config X86_VOYAGER
bool "Voyager (NCR)"
depends on X86_32
select SMP if !BROKEN
help
Voyager is an MCA-based 32-way capable SMP architecture proprietary
to NCR Corp. Machine classes 345x/35xx/4100/51xx are Voyager-based.
*** WARNING ***
If you do not specifically know you have a Voyager based machine,
say N here, otherwise the kernel you build will not be bootable.
config X86_NUMAQ
bool "NUMAQ (IBM/Sequent)"
select SMP
select NUMA
depends on X86_32
help
This option is used for getting Linux to run on a (IBM/Sequent) NUMA
multiquad box. This changes the way that processors are bootstrapped,
and uses Clustered Logical APIC addressing mode instead of Flat Logical.
You will need a new lynxer.elf file to flash your firmware with - send
email to <[email protected]>.
config X86_SUMMIT
bool "Summit/EXA (IBM x440)"
depends on X86_32 && SMP
help
This option is needed for IBM systems that use the Summit/EXA chipset.
In particular, it is needed for the x440.
If you don't have one of these computers, you should say N here.
If you want to build a NUMA kernel, you must select ACPI.
config X86_BIGSMP
bool "Support for other sub-arch SMP systems with more than 8 CPUs"
depends on X86_32 && SMP
help
This option is needed for the systems that have more than 8 CPUs
and if the system is not of any sub-arch type above.
If you don't have such a system, you should say N here.
config X86_VISWS
bool "SGI 320/540 (Visual Workstation)"
depends on X86_32
help
The SGI Visual Workstation series is an IA32-based workstation
based on SGI systems chips with some legacy PC hardware attached.
Say Y here to create a kernel to run on the SGI 320 or 540.
A kernel compiled for the Visual Workstation will not run on PCs
and vice versa. See <file:Documentation/sgi-visws.txt> for details.
config X86_GENERICARCH
bool "Generic architecture (Summit, bigsmp, ES7000, default)"
depends on X86_32
help
This option compiles in the Summit, bigsmp, ES7000, default subarchitectures.
It is intended for a generic binary kernel.
If you want a NUMA kernel, select ACPI. We need SRAT for NUMA.
config X86_ES7000
bool "Support for Unisys ES7000 IA32 series"
depends on X86_32 && SMP
help
Support for Unisys ES7000 systems. Say 'Y' here if this kernel is
supposed to run on an IA32-based Unisys ES7000 system.
Only choose this option if you have such a system, otherwise you
should say N here.
config X86_RDC321X
bool "RDC R-321x SoC"
depends on X86_32
select M486
select X86_REBOOTFIXUPS
select GENERIC_GPIO
select LEDS_CLASS
select LEDS_GPIO
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_VSMP
bool "Support for ScaleMP vSMP"
depends on X86_64 && PCI
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.
endchoice
config SCHED_NO_NO_OMIT_FRAME_POINTER
def_bool y
prompt "Single-depth WCHAN output"
depends on X86_32
help
Calculate simpler /proc/<PID>/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 PARAVIRT_GUEST
bool "Paravirtualized guest support"
help
Say Y here to get to see options related to running Linux under
various hypervisors. This option alone does not add any kernel code.
If you say N, all options in this submenu will be skipped and disabled.
if PARAVIRT_GUEST
source "arch/x86/xen/Kconfig"
config VMI
bool "VMI Guest support"
select PARAVIRT
depends on X86_32
depends on !(X86_VISWS || X86_VOYAGER)
help
VMI provides a paravirtualized interface to the VMware ESX server
(it could be used by other hypervisors in theory too, but is not
at the moment), by linking the kernel to a GPL-ed ROM module
provided by the hypervisor.
source "arch/x86/lguest/Kconfig"
config PARAVIRT
bool "Enable paravirtualization code"
depends on !(X86_VISWS || X86_VOYAGER)
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.
endif
config ACPI_SRAT
def_bool y
depends on X86_32 && ACPI && NUMA && (X86_SUMMIT || X86_GENERICARCH)
select ACPI_NUMA
config HAVE_ARCH_PARSE_SRAT
def_bool y
depends on ACPI_SRAT
config X86_SUMMIT_NUMA
def_bool y
depends on X86_32 && NUMA && (X86_SUMMIT || X86_GENERICARCH)
config X86_CYCLONE_TIMER
def_bool y
depends on X86_32 && X86_SUMMIT || X86_GENERICARCH
config ES7000_CLUSTERED_APIC
def_bool y
depends on SMP && X86_ES7000 && MPENTIUMIII
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. You can find the HPET spec at
<http://www.intel.com/hardwaredesign/hpetspec.htm>.
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=y || RTC=m)
# Mark as embedded because too many people got it wrong.
# The code disables itself when not needed.
config GART_IOMMU
bool "GART IOMMU support" if EMBEDDED
default y
select SWIOTLB
select AGP
depends on X86_64 && PCI
help
Support for full DMA access of devices with 32bit memory access only
on systems with more than 3GB. This is usually needed for USB,
sound, many IDE/SATA chipsets and some other devices.
Provides a driver for the AMD Athlon64/Opteron/Turion/Sempron GART
based hardware IOMMU and a software bounce buffer based IOMMU used
on Intel systems and as fallback.
The code is only active when needed (enough memory and limited
device) unless CONFIG_IOMMU_DEBUG or iommu=force is specified
too.
config CALGARY_IOMMU
bool "IBM Calgary IOMMU support"
select SWIOTLB
depends on X86_64 && PCI && EXPERIMENTAL
help
Support for hardware IOMMUs in IBM's xSeries x366 and x460
systems. Needed to run systems with more than 3GB of memory
properly with 32-bit PCI devices that do not support DAC
(Double Address Cycle). Calgary also supports bus level
isolation, where all DMAs pass through the IOMMU. This
prevents them from going anywhere except their intended
destination. This catches hard-to-find kernel bugs and
mis-behaving drivers and devices that do not use the DMA-API
properly to set up their DMA buffers. The IOMMU can be
turned off at boot time with the iommu=off parameter.
Normally the kernel will make the right choice by itself.
If unsure, say Y.
config CALGARY_IOMMU_ENABLED_BY_DEFAULT
def_bool y
prompt "Should Calgary be enabled by default?"
depends on CALGARY_IOMMU
help
Should Calgary be enabled by default? if you choose 'y', Calgary
will be used (if it exists). If you choose 'n', Calgary will not be
used even if it exists. If you choose 'n' and would like to use
Calgary anyway, pass 'iommu=calgary' on the kernel command line.
If unsure, say Y.
# need this always selected by IOMMU for the VIA workaround
config SWIOTLB
bool
help
Support for software bounce buffers used on x86-64 systems
which don't have a hardware IOMMU (e.g. the current generation
of Intel's x86-64 CPUs). Using this PCI devices which can only
access 32-bits of memory can be used on systems with more than
3 GB of memory. If unsure, say Y.
config NR_CPUS
int "Maximum number of CPUs (2-255)"
range 2 255
depends on SMP
default "32" if X86_NUMAQ || X86_SUMMIT || X86_BIGSMP || X86_ES7000
default "8"
help
This allows you to specify the maximum number of CPUs which this
kernel will support. The maximum supported value is 255 and the
minimum value which makes sense is 2.
This is purely to save memory - each supported CPU adds
approximately eight kilobytes to the kernel image.
config SCHED_SMT
bool "SMT (Hyperthreading) scheduler support"
depends on (X86_64 && SMP) || (X86_32 && X86_HT)
help
SMT scheduler support improves the CPU scheduler's decision making
when dealing with Intel Pentium 4 chips with HyperThreading at a
cost of slightly increased overhead in some places. If unsure say
N here.
config SCHED_MC
def_bool y
prompt "Multi-core scheduler support"
depends on (X86_64 && SMP) || (X86_32 && X86_HT)
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.
source "kernel/Kconfig.preempt"
config X86_UP_APIC
bool "Local APIC support on uniprocessors"
depends on X86_32 && !SMP && !(X86_VISWS || X86_VOYAGER || X86_GENERICARCH)
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 || (X86_32 && (X86_UP_APIC || ((X86_VISWS || SMP) && !X86_VOYAGER) || X86_GENERICARCH))
config X86_IO_APIC
def_bool y
depends on X86_64 || (X86_32 && (X86_UP_IOAPIC || (SMP && !(X86_VISWS || X86_VOYAGER)) || X86_GENERICARCH))
config X86_VISWS_APIC
def_bool y
depends on X86_32 && X86_VISWS
config X86_MCE
bool "Machine Check Exception"
depends on !X86_VOYAGER
---help---
Machine Check Exception support allows the processor to notify the
kernel if it detects a problem (e.g. overheating, component failure).
The action the kernel takes depends on the severity of the problem,
ranging from a warning message on the console, to halting the machine.
Your processor must be a Pentium or newer to support this - check the
flags in /proc/cpuinfo for mce. Note that some older Pentium systems
have a design flaw which leads to false MCE events - hence MCE is
disabled on all P5 processors, unless explicitly enabled with "mce"
as a boot argument. Similarly, if MCE is built in and creates a
problem on some new non-standard machine, you can boot with "nomce"
to disable it. MCE support simply ignores non-MCE processors like
the 386 and 486, so nearly everyone can say Y here.
config X86_MCE_INTEL
def_bool y
prompt "Intel MCE features"
depends on X86_64 && 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_64 && X86_MCE && X86_LOCAL_APIC
help
Additional support for AMD specific MCE features such as
the DRAM Error Threshold.
config X86_MCE_NONFATAL
tristate "Check for non-fatal errors on AMD Athlon/Duron / Intel Pentium 4"
depends on X86_32 && X86_MCE
help
Enabling this feature starts a timer that triggers every 5 seconds which
will look at the machine check registers to see if anything happened.
Non-fatal problems automatically get corrected (but still logged).
Disable this if you don't want to see these messages.
Seeing the messages this option prints out may be indicative of dying
or out-of-spec (ie, overclocked) hardware.
This option only does something on certain CPUs.
(AMD Athlon/Duron and Intel Pentium 4)
config X86_MCE_P4THERMAL
bool "check for P4 thermal throttling interrupt."
depends on X86_32 && X86_MCE && (X86_UP_APIC || SMP) && !X86_VISWS
help
Enabling this feature will cause a message to be printed when the P4
enters thermal throttling.
config VM86
bool "Enable VM86 support" if EMBEDDED
default y
depends on X86_32
help
This option is required by programs like DOSEMU to run 16-bit legacy
code on X86 processors. It also may be needed by software like
XFree86 to initialize some video cards via BIOS. Disabling this
option saves about 6k.
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:
<http://www.buzzard.org.uk/toshiba/>.
Say Y if you intend to run this kernel on a Toshiba portable.
Say N otherwise.
config I8K
tristate "Dell laptop support"
depends on X86_32
---help---
This adds a driver to safely access the System Management Mode
of the CPU on the Dell Inspiron 8000. The System Management Mode
is used to read cpu temperature and cooling fan status and to
control the fans on the I8K portables.
This driver has been tested only on the Inspiron 8000 but it may
also work with other Dell laptops. You can force loading on other
models by passing the parameter `force=1' to the module. Use at
your own risk.
For information on utilities to make use of this driver see the
I8K Linux utilities web site at:
<http://people.debian.org/~dz/i8k/>
Say Y if you intend to run this kernel on a Dell Inspiron 8000.
Say N otherwise.
config X86_REBOOTFIXUPS
def_bool n
prompt "Enable X86 board specific fixups for reboot"
depends on X86_32 && X86
---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
tristate "/dev/cpu/microcode - Intel IA32 CPU microcode support"
select FW_LOADER
---help---
If you say Y here, you will be able to update the microcode on
Intel processors in the IA32 family, e.g. Pentium Pro, Pentium II,
Pentium III, Pentium 4, Xeon etc. You will obviously need the
actual microcode binary data itself which is not shipped with the
Linux kernel.
For latest news and information on obtaining all the required
ingredients for this driver, check:
<http://www.urbanmyth.org/microcode/>.
To compile this driver as a module, choose M here: the
module will be called microcode.
config MICROCODE_OLD_INTERFACE
def_bool y
depends on MICROCODE
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 if !X86_NUMAQ
default HIGHMEM64G if X86_NUMAQ
depends on X86_32
config NOHIGHMEM
bool "off"
depends on !X86_NUMAQ
---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"
depends on !X86_NUMAQ
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 !M386 && !M486
select X86_PAE
help
Select this if you have a 32-bit processor and more than 4
gigabytes of physical RAM.
endchoice
choice
depends on EXPERIMENTAL
prompt "Memory split" if EMBEDDED
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
def_bool n
prompt "PAE (Physical Address Extension) Support"
depends on X86_32 && !HIGHMEM4G
select RESOURCES_64BIT
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.
# Common NUMA Features
config NUMA
bool "Numa Memory Allocation and Scheduler Support (EXPERIMENTAL)"
depends on SMP
depends on X86_64 || (X86_32 && HIGHMEM64G && (X86_NUMAQ || (X86_SUMMIT || X86_GENERICARCH) && ACPI) && EXPERIMENTAL)
default n if X86_PC
default y if (X86_NUMAQ || X86_SUMMIT)
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 i386 this is currently highly experimental and should be only
used for kernel development. It might also cause boot failures.
For x86_64 this is recommended on all multiprocessor Opteron systems.
If the system is EM64T, you should say N unless your system is
EM64T NUMA.
comment "NUMA (Summit) requires SMP, 64GB highmem support, ACPI"
depends on X86_32 && X86_SUMMIT && (!HIGHMEM64G || !ACPI)
config K8_NUMA
def_bool y
prompt "Old style AMD Opteron NUMA detection"
depends on X86_64 && NUMA && PCI
help
Enable K8 NUMA node topology detection. You should say Y here if
you have a multi processor AMD K8 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 NUMA_EMU
bool "NUMA emulation"
depends on X86_64 && NUMA
help
Enable NUMA emulation. A flat machine will be split
into virtual nodes when booted with "numa=fake=N", where N is the
number of nodes. This is only useful for debugging.
config NODES_SHIFT
int
range 1 15 if X86_64
default "6" if X86_64
default "4" if X86_NUMAQ
default "3"
depends on NEED_MULTIPLE_NODES
config HAVE_ARCH_BOOTMEM_NODE
def_bool y
depends on X86_32 && NUMA
config ARCH_HAVE_MEMORY_PRESENT
def_bool y
depends on X86_32 && DISCONTIGMEM
config NEED_NODE_MEMMAP_SIZE
def_bool y
depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
config HAVE_ARCH_ALLOC_REMAP
def_bool y
depends on X86_32 && NUMA
config ARCH_FLATMEM_ENABLE
def_bool y
depends on X86_32 && ARCH_SELECT_MEMORY_MODEL && X86_PC && !NUMA
config ARCH_DISCONTIGMEM_ENABLE
def_bool y
depends on NUMA && X86_32
config ARCH_DISCONTIGMEM_DEFAULT
def_bool y
depends on NUMA && X86_32
config ARCH_SPARSEMEM_DEFAULT
def_bool y
depends on X86_64
config ARCH_SPARSEMEM_ENABLE
def_bool y
depends on X86_64 || NUMA || (EXPERIMENTAL && X86_PC)
select SPARSEMEM_STATIC if X86_32
select SPARSEMEM_VMEMMAP_ENABLE if X86_64
config ARCH_SELECT_MEMORY_MODEL
def_bool y
depends on ARCH_SPARSEMEM_ENABLE
config ARCH_MEMORY_PROBE
def_bool X86_64
depends on MEMORY_HOTPLUG
source "mm/Kconfig"
config HIGHPTE
bool "Allocate 3rd-level pagetables from highmem"
depends on X86_32 && (HIGHMEM4G || HIGHMEM64G)
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 MATH_EMULATION
bool
prompt "Math emulation" if X86_32
---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 <file:arch/x86/math-emu/README>.
If you are not sure, say Y; apart from resulting in a 66 KB bigger
kernel, it won't hurt.
config MTRR
bool "MTRR (Memory Type Range Register) support"
---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 <file:Documentation/mtrr.txt> for more information.
config EFI
def_bool n