lkml.org 
[lkml]   [2012]   [Aug]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH] perf/x86: fix microcode revision check for SNB-PEBS

    The following patch, relative to 3.6.0-rc3, makes
    the microcode update code path actually invoke the
    perf_check_microcode() function and thus potentially
    renabling SNB PEBS.

    By default, CONFIG_MICROCODE_OLD_INTERFACE is
    forced to Y in arch/x86/Kconfig. There is no
    way to disable this. That means that the code
    path used in arch/x86/kernel/microcode_core.c
    did not include the call to perf_check_microcode().

    Thus, even though the microcode was updated to a
    version that fixes the SNB PEBS problem, perf_event
    would still return EOPNOTSUPP when enabling precise
    sampling.

    This patch simply adds a call to perf_check_microcode()
    in the call path used when OLD_INTERFACE=y.

    Signed-off-by: Stephane Eranian <eranian@google.com>
    ---

    --- a/arch/x86/kernel/microcode_core.c
    +++ b/arch/x86/kernel/microcode_core.c
    @@ -225,6 +225,9 @@ static ssize_t microcode_write(struct file *file, const char __user *buf,
    if (do_microcode_update(buf, len) == 0)
    ret = (ssize_t)len;

    + if (ret > 0)
    + perf_check_microcode();
    +
    mutex_unlock(&microcode_mutex);
    put_online_cpus();


    \
     
     \ /
      Last update: 2012-08-24 16:21    [W:2.498 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site