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How to configure the Linux kernel/arch/s390

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Howto configure the Linux kernel / arch / s390


For a description of the syntax of this configuration file,
see Documentation/kbuild/kconfig-language.txt.


  • Option: MMU
    • Kernel Versions: 2.6.15.6 ...
    • (on/off)
    • default y


  • Option: RWSEM_GENERIC_SPINLOCK
    • Kernel Versions: 2.6.15.6 ...
    • (on/off)


  • Option: RWSEM_XCHGADD_ALGORITHM
    • Kernel Versions: 2.6.15.6 ...
    • (on/off)
    • default y


  • Option: GENERIC_CALIBRATE_DELAY
    • Kernel Versions: 2.6.15.6 ...
    • (on/off)
    • default y


  • Option: GENERIC_BUST_SPINLOCK
    • Kernel Versions: 2.6.15.6 ...
    • (on/off)

"Linux Kernel Configuration"


  • Option: ARCH_S390
    • Kernel Versions: 2.6.15.6 ...
    • (on/off)
    • default y


  • Option: UID16
    • Kernel Versions: 2.6.15.6 ...
    • (on/off)
    • default y
    • depends on ARCH_S390X = 'n'


Base setupEdit

"Processor type and features"


  • Option: ARCH_S390X
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) 64 bit kernel
      Select this option if you have a 64 bit IBM zSeries machine and want to use the 64 bit addressing mode.


  • Option: 64BIT
    • Kernel Versions: 2.6.15.6 ...

_bool ARCH_S390X


  • Option: ARCH_S390_31
    • Kernel Versions: 2.6.15.6 ...
    • (on/off)
    • depends on ARCH_S390X = 'n'
    • default y


  • Option: SMP
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Symmetric multi-processing support
      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.
      See also the <file:Documentation/smp.txt> and the SMP-HOWTO available at <http://www.tldp.org/docs.html#howto>.
      Even if you don't know what to do here, say Y.


  • Option: NR_CPUS
    • Kernel Versions: 2.6.15.6 ...

"Maximum number of CPUs (2-64)" 2 64

    • depends on SMP
    • default "32"
      This allows you to specify the maximum number of CPUs which this kernel will support. The maximum supported value is 64 and the minimum value which makes sense is 2.
      This is purely to save memory - each supported CPU adds approximately sixteen kilobytes to the kernel image.


  • Option: HOTPLUG_CPU
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Support for hot-pluggable CPUs
    • depends on SMP
    • select HOTPLUG
    • default n
      Say Y here to be able to turn CPUs off and on. CPUs can be controlled through /sys/devices/system/cpu/cpu#. Say N if you want to disable CPU hotplug.


  • Option: MATHEMU
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) IEEE FPU emulation
    • depends on MARCH_G5
      This option is required for IEEE compliant floating point arithmetic on older S/390 machines. Say Y unless you know your machine doesn't need this.


  • Option: S390_SUPPORT
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Kernel support for 31 bit emulation
    • depends on ARCH_S390X
      Select this option if you want to enable your system kernel to handle system-calls from ELF binaries for 31 bit ESA. This option (and some other stuff like libraries and such) is needed for executing 31 bit applications. It is safe to say "Y".


  • Option: COMPAT
    • Kernel Versions: 2.6.15.6 ...
    • (on/off)
    • depends on S390_SUPPORT
    • default y


  • Option: SYSVIPC_COMPAT
    • Kernel Versions: 2.6.15.6 ...
    • (on/off)
    • depends on COMPAT && SYSVIPC
    • default y


  • Option: BINFMT_ELF32
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Kernel support for 31 bit ELF binaries
    • depends on S390_SUPPORT
      This allows you to run 32-bit Linux/ELF binaries on your zSeries in 64 bit mode. Everybody wants this; say Y.

"Code generation options"


"Processor type"

    • default MARCH_G5


  • Option: MARCH_G5
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) S/390 model G5 and G6
    • depends on ARCH_S390_31
      Select this to build a 31 bit kernel that works on all S/390 and zSeries machines.


  • Option: MARCH_Z900
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) IBM eServer zSeries model z800 and z900
      Select this to optimize for zSeries machines. This will enable some optimizations that are not available on older 31 bit only CPUs.


  • Option: MARCH_Z990
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) IBM eServer zSeries model z890 and z990
      Select this enable optimizations for model z890/z990. This will be slightly faster but does not work on older machines such as the z900.



  • Option: PACK_STACK
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Pack kernel stack
      This option enables the compiler option -mkernel-backchain if it is available. If the option is available the compiler supports the new stack layout which dramatically reduces the minimum stack frame size. With an old compiler a non-leaf function needs a minimum of 96 bytes on 31 bit and 160 bytes on 64 bit. With -mkernel-backchain the minimum size drops to 16 byte on 31 bit and 24 byte on 64 bit.
      Say Y if you are unsure.


  • Option: SMALL_STACK
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Use 4kb/8kb for kernel stack instead of 8kb/16kb
    • depends on PACK_STACK
      If you say Y here and the compiler supports the -mkernel-backchain option the kernel will use a smaller kernel stack size. For 31 bit the reduced size is 4kb instead of 8kb and for 64 bit it is 8kb instead of 16kb. This allows to run more thread on a system and reduces the pressure on the memory management for higher order page allocations.
      Say N if you are unsure.



  • Option: CHECK_STACK
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Detect kernel stack overflow
      This option enables the compiler option -mstack-guard and -mstack-size if they are available. If the compiler supports them it will emit additional code to each function prolog to trigger an illegal operation if the kernel stack is about to overflow.
      Say N if you are unsure.


  • Option: STACK_GUARD
    • Kernel Versions: 2.6.15.6 ...

"Size of the guard area (128-1024)" 128 1024

    • depends on CHECK_STACK
    • default "256"
      This allows you to specify the size of the guard area at the lower end of the kernel stack. If the kernel stack points into the guard area on function entry an illegal operation is triggered. The size needs to be a power of 2. Please keep in mind that the size of an interrupt frame is 184 bytes for 31 bit and 328 bytes on 64 bit. The minimum size for the stack guard should be 256 for 31 bit and 512 for 64 bit.


  • Option: WARN_STACK
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Emit compiler warnings for function with broken stack usage
      This option enables the compiler options -mwarn-framesize and -mwarn-dynamicstack. If the compiler supports these options it will generate warnings for function which either use alloca or create a stack frame bigger than CONFIG_WARN_STACK_SIZE.
      Say N if you are unsure.


  • Option: WARN_STACK_SIZE
    • Kernel Versions: 2.6.15.6 ...

"Maximum frame size considered safe (128-2048)" 128 2048

    • depends on WARN_STACK
    • default "256"
      This allows you to specify the maximum frame size a function may have without the compiler complaining about it.


"I/O subsystem configuration"


  • Option: MACHCHK_WARNING
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Process warning machine checks
      Select this option if you want the machine check handler on IBM S/390 or zSeries to process warning machine checks (e.g. on power failures). If unsure, say "Y".


  • Option: QDIO
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) QDIO support
      This driver provides the Queued Direct I/O base support for the IBM S/390 (G5 and G6) and eServer zSeries (z800, z890, z900 and z990).
      For details please refer to the documentation provided by IBM at <http://www10.software.ibm.com/developerworks/opensource/linux390>
      To compile this driver as a module, choose M here: the module will be called qdio.
      If unsure, say Y.


  • Option: QDIO_PERF_STATS
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Performance statistics in /proc
    • depends on QDIO
      Say Y here to get performance statistics in /proc/qdio_perf
      If unsure, say N.


  • Option: QDIO_DEBUG
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Extended debugging information
    • depends on QDIO
      Say Y here to get extended debugging output in /proc/s390dbf/qdio... Warning: this option reduces the performance of the QDIO module.
      If unsure, say N.

"Misc"


  • Option: PREEMPT
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Preemptible Kernel
      This option reduces the latency of the kernel when reacting to real-time or interactive events by allowing a low priority process to be preempted even if it is in kernel mode executing a system call. This allows applications to run more reliably even when the system is under load.
      Say N if you are unsure.


  • Option: IPL
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Builtin IPL record support
      If you want to use the produced kernel to IPL directly from a device, you have to merge a bootsector specific to the device into the first bytes of the kernel. You will have to select the IPL device.


"IPL method generated into head.S"

    • depends on IPL
    • default IPL_TAPE
      Select "tape" if you want to IPL the image from a Tape.
      Select "vm_reader" if you are running under VM/ESA and want to IPL the image from the emulated card reader.


  • Option: IPL_TAPE
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) tape


  • Option: IPL_VM
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) vm_reader




  • Option: PROCESS_DEBUG
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Show crashed user process info
      Say Y to print all process fault locations to the console. This is a debugging option; you probably do not want to set it unless you are an S390 port maintainer.


  • Option: PFAULT
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Pseudo page fault support
      Select this option, if you want to use PFAULT pseudo page fault handling under VM. If running native or in LPAR, this option has no effect. If your VM does not support PFAULT, PAGEEX pseudo page fault handling will be used. Note that VM 4.2 supports PFAULT but has a bug in its implementation that causes some problems. Everybody who wants to run Linux under VM != VM4.2 should select this option.


  • Option: SHARED_KERNEL
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) VM shared kernel support
      Select this option, if you want to share the text segment of the Linux kernel between different VM guests. This reduces memory usage with lots of guests but greatly increases kernel size. You should only select this option if you know what you are doing and want to exploit this feature.


  • Option: CMM
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Cooperative memory management
      Select this option, if you want to enable the kernel interface to reduce the memory size of the system. This is accomplished by allocating pages of memory and put them "on hold". This only makes sense for a system running under VM where the unused pages will be reused by VM for other guest systems. The interface allows an external monitor to balance memory of many systems. Everybody who wants to run Linux under VM should select this option.


  • Option: CMM_PROC
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) /proc interface to cooperative memory management
    • depends on CMM
      Select this option to enable the /proc interface to the cooperative memory management.


  • Option: CMM_IUCV
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) IUCV special message interface to cooperative memory management
    • depends on CMM && (SMSGIUCV=y || CMM=SMSGIUCV)
      Select this option to enable the special message interface to the cooperative memory management.


  • Option: VIRT_TIMER
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Virtual CPU timer support
      This provides a kernel interface for virtual CPU timers. Default is disabled.


  • Option: VIRT_CPU_ACCOUNTING
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Base user process accounting on virtual cpu timer
    • depends on VIRT_TIMER
      Select this option to use CPU timer deltas to do user process accounting.


  • Option: APPLDATA_BASE
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Linux - VM Monitor Stream, base infrastructure
    • depends on PROC_FS && VIRT_TIMER=y
      This provides a kernel interface for creating and updating z/VM APPLDATA monitor records. The monitor records are updated at certain time intervals, once the timer is started. Writing 1 or 0 to /proc/appldata/timer starts(1) or stops(0) the timer, i.e. enables or disables monitoring on the Linux side. A custom interval value (in seconds) can be written to /proc/appldata/interval.
      Defaults are 60 seconds interval and timer off. The /proc entries can also be read from, showing the current settings.


  • Option: APPLDATA_MEM
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Monitor memory management statistics
    • depends on APPLDATA_BASE
      This provides memory management related data to the Linux - VM Monitor Stream, like paging/swapping rate, memory utilisation, etc. Writing 1 or 0 to /proc/appldata/memory creates(1) or removes(0) a z/VM APPLDATA monitor record, i.e. enables or disables monitoring this record on the z/VM side.
      Default is disabled. The /proc entry can also be read from, showing the current settings.
      This can also be compiled as a module, which will be called appldata_mem.o.


  • Option: APPLDATA_OS
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Monitor OS statistics
    • depends on APPLDATA_BASE
      This provides OS related data to the Linux - VM Monitor Stream, like CPU utilisation, etc. Writing 1 or 0 to /proc/appldata/os creates(1) or removes(0) a z/VM APPLDATA monitor record, i.e. enables or disables monitoring this record on the z/VM side.
      Default is disabled. This can also be compiled as a module, which will be called appldata_os.o.


  • Option: APPLDATA_NET_SUM
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Monitor overall network statistics
    • depends on APPLDATA_BASE
      This provides network related data to the Linux - VM Monitor Stream, currently there is only a total sum of network I/O statistics, no per-interface data. Writing 1 or 0 to /proc/appldata/net_sum creates(1) or removes(0) a z/VM APPLDATA monitor record, i.e. enables or disables monitoring this record on the z/VM side.
      Default is disabled. This can also be compiled as a module, which will be called appldata_net_sum.o.


  • Option: NO_IDLE_HZ
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) No HZ timer ticks in idle
      Switches the regular HZ timer off when the system is going idle. This helps z/VM to detect that the Linux system is idle. VM can then "swap-out" this guest which reduces memory usage. It also reduces the overhead of idle systems.
      The HZ timer can be switched on/off via /proc/sys/kernel/hz_timer. hz_timer=0 means HZ timer is disabled. hz_timer=1 means HZ timer is active.


  • Option: NO_IDLE_HZ_INIT
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) HZ timer in idle off by default
    • depends on NO_IDLE_HZ
      The HZ timer is switched off in idle by default. That means the HZ timer is already disabled at boot time.


  • Option: KEXEC
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) kexec system call (EXPERIMENTAL)
    • depends on EXPERIMENTAL
      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 is independent of hardware/microcode support.




  • Option: PCMCIA
    • Kernel Versions: 2.6.15.6 ...
    • (on/off)
    • default n












Linux Kernel Configuration

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