Messages in this thread | | | Date | Fri, 24 Aug 2012 18:08:38 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] perf/x86: fix microcode revision check for SNB-PEBS |
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On Fri, Aug 24, 2012 at 03:34:34PM +0200, Stephane Eranian wrote: > > 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.
Ok, so c93dc84cbe324 added calls to perf_check_microcode but it looks like you're updating the microcode from /dev/cpu/microcode, correct?
And if so, the old interface got missed.
Oh well, as long as we have to support it, we might as well add that perf call there - it will go when the interface goes anyway so until then:
Acked-by: Borislav Petkov <borislav.petkov@amd.com>
> > 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(µcode_mutex); > put_online_cpus(); > >
Thanks.
-- Regards/Gruss, Boris.
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