• Balbir Singh's avatar
    powerpc/mm: Flush cache on memory hot(un)plug · fb5924fd
    Balbir Singh authored
    This patch adds support for flushing potentially dirty cache lines
    when memory is hot-plugged/hot-un-plugged. The support is currently
    limited to 64 bit systems.
    
    The bug was exposed when mappings for a device were actually
    hot-unplugged and plugged in back later. A similar issue was observed
    during the development of memtrace, but memtrace does it's own
    flushing of region via a custom routine.
    
    These patches do a flush both on hotplug/unplug to clear any stale
    data in the cache w.r.t mappings, there is a small race window where a
    clean cache line may be created again just prior to tearing down the
    mapping.
    
    The patches were tested by disabling the flush routines in memtrace
    and doing I/O on the trace file. The system immediately
    checkstops (quite reliablly if prior to the hot-unplug of the memtrace
    region, we memset the regions we are about to hot unplug). After these
    patches no custom flushing is needed in the memtrace code.
    
    Fixes: 9d5171a8 ("powerpc/powernv: Enable removal of memory for in memory tracing")
    Cc: stable@vger.kernel.org # v4.14+
    Signed-off-by: default avatarBalbir Singh <bsingharora@gmail.com>
    Acked-by: default avatarReza Arbab <arbab@linux.ibm.com>
    Reviewed-by: default avatarRashmica Gupta <rashmica.g@gmail.com>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    fb5924fd
mem.c 15.3 KB