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
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.
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. If you don't know what to do here, say N.
This enables support for sparse irqs. This is useful for distro kernels that want to define a high CONFIG_NR_CPUS value but still want to have low kernel memory footprint on smaller machines. ( Sparse IRQs can also be beneficial on NUMA boxes, as they spread out the irq_desc[] array in a more NUMA-friendly way. ) If you don't know what to do here, say N.
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
This option is needed for the systems that have more than 8 CPUs
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) 32 bit x86 platforms: AMD Elan NUMAQ (IBM/Sequent) RDC R-321x SoC SGI 320/540 (Visual Workstation) Summit/EXA (IBM x440) Unisys ES7000 IA32 series Moorestown MID devices If you have one of these systems, or if you want to build a generic distribution kernel, say Y here - otherwise say N.
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) 64 bit x86 platforms: 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.
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.
This option is needed in order to support SGI Ultraviolet systems. If you don't have one of these, you should say N here.
Select this for an AMD Elan processor. Do not use this option for K6/Athlon/Opteron processors! If unsure, choose "PC-compatible" instead.
Moorestown is Intel's Low Power Intel Architecture (LPIA) based Moblin Internet Device(MID) platform. Moorestown consists of two chips: Lincroft (CPU core, graphics, and memory controller) and Langwell IOH. Unlike standard x86 PCs, Moorestown does not have many legacy devices nor standard legacy replacement devices/features. e.g. Moorestown does not contain i8259, i8254, HPET, legacy BIOS, most of the io ports.
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.
This option compiles in the NUMAQ, Summit, bigsmp, ES7000, 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.
This option is used for getting Linux to run on a NUMAQ (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 <Martin.Bligh@us.ibm.com>.
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 run on general PCs as well. See <file:Documentation/sgi-visws.txt> for details.
This option is needed for IBM systems that use the Summit/EXA chipset. In particular, it is needed for the x440.
Support for Unisys ES7000 systems. Say 'Y' here if this kernel is supposed to run on an IA32-based Unisys ES7000 system.
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".
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.
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. As of September 2009, VMware has started a phased retirement of this feature from VMware's products. Please see feature-removal-schedule.txt for details. If you are planning to enable this option, please note that you cannot live migrate a VMI enabled VM to a future VMware product, which doesn't support VMI. So if you expect your kernel to seamlessly migrate to newer VMware products, keep this disabled.
Turning on this option will allow you to run a paravirtualized clock when running over the KVM hypervisor. 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
This option enables various optimizations for running under the KVM hypervisor.
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.
Paravirtualized spinlocks allow a pvops backend to replace the spinlock implementation with something virtualization-friendly (for example, block the virtual CPU rather than spinning). Unfortunately the downside is an up to 5% performance hit on native kernels, with various workloads. If you are unsure how to answer this question, answer N.
Enable to debug paravirt_ops internals. Specifically, BUG if a paravirt_op is missing when it is called.
This option adds a kernel parameter 'memtest', which allows memtest to be set. memtest=0, mean disabled; -- default memtest=1, mean do 1 test pattern; ... memtest=4, mean do 4 test patterns. If you are unsure how to answer this question, answer N.
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_1.pdf>. 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.
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.
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.
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.
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.
With this option you can enable support for AMD IOMMU hardware in your system. An IOMMU is a hardware component which provides remapping of DMA memory accesses from devices. With an AMD IOMMU you can isolate the the DMA memory of different devices and protect the system from misbehaving device drivers or hardware. You can find out if your system has an AMD IOMMU if you look into your BIOS for an option to enable it or if you have an IVRS ACPI table.
This option enables code in the AMD IOMMU driver to collect various statistics about whats happening in the driver and exports that information to userspace via debugfs. If unsure, say N.
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.
Configure maximum number of CPUS and NUMA Nodes for this architecture. If unsure, say N.
This allows you to specify the maximum number of CPUs which this kernel will support. The maximum supported value is 512 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.
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.
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.
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.
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.
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.
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.
Additional support for intel specific MCE features such as the thermal monitor.
Additional support for AMD specific MCE features such as the DRAM Error Threshold.
Include support for machine check handling on old Pentium 5 or WinChip systems. These typically need to be enabled explicitely on the command line.
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.
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.
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.
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.
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.
If you say Y here, you will be able to update the microcode on certain Intel and AMD processors. The Intel support is for the IA32 family, e.g. Pentium Pro, Pentium II, Pentium III, Pentium 4, Xeon etc. The AMD support is for family 0x10 and 0x11 processors, e.g. Opteron, Phenom and Turion 64 Ultra. You will obviously need the actual microcode binary data itself which is not shipped with the Linux kernel. This option selects the general module only, you need to select at least one vendor specific module as well. To compile this driver as a module, choose M here: the module will be called microcode.
This options enables microcode patch loading support for Intel processors. For latest news and information on obtaining all the required Intel ingredients for this driver, check: <http://www.urbanmyth.org/microcode/>.
If you select this option, microcode patch loading support for AMD processors will be enabled.
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.
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.
If you select this option, this will provide various x86 CPUs information through debugfs.
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".
Select this if you have a 32-bit processor and between 1 and 4 gigabytes of physical RAM.
Select this if you have a 32-bit processor and more than 4 gigabytes of physical RAM.
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"
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.
Allow the kernel linear mapping to use 1GB pages on CPUs that support it. This can improve the kernel's performance a tiny bit by reducing TLB pressure. If in doubt, say "Y".
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 on (rare) 32-bit-only platforms that support NUMA topologies, such as NUMAQ / Summit, or if you boot a 32-bit kernel on a 64-bit NUMA platform. Otherwise, you should say N.
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.
Enable ACPI SRAT based node topology detection.
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.
Specify the maximum number of NUMA Nodes available on the target system. Increases memory reserved to accommodate various tables.
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.
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/kernel-parameters.txt 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.
Set whether the default state of memory_corruption_check is on or off.
Reserve the first 64K of physical RAM on BIOSes that are known to potentially corrupt that memory range. A numbers of BIOSes are known to utilize this area during suspend/resume, so it must not be used by the kernel. Set this to N if you are absolutely sure that you trust the BIOS to get all its memory reservations and usages right. If you have doubts about the BIOS (e.g. suspend/resume does not work or there's kernel crashes after certain hardware hotplug events) and it's not AMI or Phoenix, then you might want to enable X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check typical corruption patterns. Say Y if unsure.
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.
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/x86/mtrr.txt> for more information.
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.
Enable mtrr cleanup default value
mtrr cleanup spare entries default, it can be changed via mtrr_spare_reg_nr=N on the kernel command line.
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.
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 <http://elilo.sourceforge.net> 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.
This kernel feature is useful for number crunching applications that may need to compute untrusted bytecode during their execution. By using pipes or other transports made available to the process as file descriptors supporting the read/write syscalls, it's possible to isolate those applications in their own address space using seccomp. Once seccomp is enabled via prctl(PR_SET_SECCOMP), it cannot be disabled and the task is only allowed to execute a few safe syscalls defined by each seccomp mode. If unsure, say Y. Only embedded should say N here.
This option turns on the -fstack-protector GCC feature. This feature puts, at the beginning of functions, a canary value on the stack just before the return address, and validates the value just before actually returning. Stack based buffer overflows (that need to overwrite this return address) now also overwrite the canary, which gets detected and the attack is then neutralized via a kernel panic. This feature requires gcc version 4.2 or above, or a distribution gcc with the feature backported. Older versions are automatically detected and for those versions, this configuration option is ignored. (and a warning is printed during bootup)
kexec is a system call that implements the ability to shutdown your current kernel, and to start another kernel. It is like a reboot but it is independent of the system firmware. And like a reboot you can start any kernel with it, not just Linux. The name comes from the similarity to the exec system call. It is an ongoing process to be certain the hardware in a machine is properly shutdown, so do not be surprised if this code does not initially work for you. It may help to enable device hotplugging support. As of this writing the exact hardware interface is strongly in flux, so no good recommendation can be made.
Generate crash dump after being started by kexec. This should be normally only set in special crash dump kernels which are loaded in the main kernel with kexec-tools into a specially reserved region and then later executed after a crash by kdump/kexec. The crash dump kernel must be compiled to a memory address not used by the main kernel or BIOS using PHYSICAL_START, or it must be built as a relocatable image (CONFIG_RELOCATABLE=y). For more details see Documentation/kdump/kdump.txt
Jump between original kernel and kexeced kernel and invoke code in physical address mode via KEXEC
This gives the physical address where the kernel is loaded. If kernel is a 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 and will ignore above physical address. 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/kdump/kdump.txt 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.
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 ignored.
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. Don't change this unless you know what you are doing.
Say Y here to allow turning CPUs off and on. CPUs can be controlled through /sys/devices/system/cpu. ( Note: power management support will enable this option automatically on SMP systems. ) Say N if you want to disable CPU hotplug.
Map the 32-bit VDSO to the predictable old-style address too. ---help--- Say N here if you are running a sufficiently recent glibc version (2.3.3 or later), to remove the high-mapped VDSO mapping and to exclusively use the randomized VDSO. If unsure, say Y.
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 the boot arguments in CONFIG_CMDLINE. Systems with fully functional boot loaders (i.e. non-embedded) should leave this option set to 'N'.
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.
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.
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 <file:Documentation/power/pm.txt> and the
Battery Powered Linux mini-HOWTO, available from
<http://www.tldp.org/docs.html#howto>.
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 "no-hlt" 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 <http://www.bitwizard.nl/sig11/>
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.
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.
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.
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.)
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.
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.
Find out whether you have a PCI motherboard. PCI 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 ISA, EISA, MicroChannel (MCA) or VESA. If you have PCI, say Y, otherwise N.
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".
DMA remapping (DMAR) devices support enables independent address translations for Direct Memory Access (DMA) from devices. These DMA remapping devices are reported via ACPI tables and include PCI device scope covered by these DMA remapping devices.
Selecting this option will enable a DMAR device at boot time if one is found. If this option is not selected, DMAR support can be enabled by passing intel_iommu=on to the kernel. It is recommended you say N here while the DMAR code remains experimental.
Current Graphics drivers tend to use physical address for DMA and avoid using DMA APIs. Setting this config option permits the IOMMU driver to set a unity map for all the OS-visible memory. Hence the driver can continue to use physical addresses for DMA, at least until this option is removed in the 2.6.32 kernel.
Floppy disk drivers are known to bypass DMA API calls thereby failing to work when IOMMU is enabled. This workaround will setup a 1:1 mapping for the first 16MiB to make floppy (an ISA device) work.
Supports Interrupt remapping for IO-APIC and MSI devices. To use x2apic mode in the CPU's which support x2APIC enhancements or to support platforms with CPU's having > 8 bit APIC ID, say Y.
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.
The Extended Industry Standard Architecture (EISA) bus was developed as an open alternative to the IBM MicroChannel bus. The EISA bus provided some of the features of the IBM MicroChannel bus while maintaining backward compatibility with cards made for the older ISA bus. The EISA bus saw limited use between 1988 and 1995 when it was made obsolete by the PCI bus. Say Y here if you are building a kernel for an EISA-based machine. Otherwise, say N.
MicroChannel Architecture is found in some IBM PS/2 machines and laptops. It is a bus system similar to PCI or ISA. See <file:Documentation/mca.txt> (and especially the web page given there) before attempting to build an MCA bus kernel.
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.
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.
This driver provides a clock event source based on the MFGPT timer(s) in the CS5535 and CS5536 companion chip for the geode. MFGPTs have a better resolution and max interval than the generic PIT, and are suitable for use as high-res timers.
Add support for detecting the unique features of the OLPC XO hardware.
Include code to run 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.
Support old a.out binaries in the 32bit emulation.