• Heiko Carstens's avatar
    [S390] Standby cpu activation/deactivation. · 08d07968
    Heiko Carstens authored
    
    
    Add a new interface so that cpus can be put into standby state and
    configured state.
    Only offline cpus can be put into standby state or configured state.
    For that the new percpu sysfs attribute "configure" must be used.
    To put a cpu in standby state a "0" must be written to the attribute.
    In order to switch it into configured state a "1" must be written to
    the attribute.
    Only cpus in configured state can be brought online.
    In addition this patch introduces a static mapping of physical to
    logical cpus. As a result only the sysfs directories of present cpus
    will be created. To scan for new cpus the new sysfs attribute "rescan"
    must be used.
    Writing to /sys/devices/system/cpu/rescan will trigger a rescan of
    cpus and will create directories for new cpus.
    
    On IPL only configured cpus will be used. And on reboot/shutdown all
    cpus will remain in their current state (configured/standby).
    Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
    Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
    08d07968