Re: [RFC][PATCH] perf, intel: Don't touch MSR_IA32_DEBUGCTLMSR fromNMI context

From: Stephane Eranian
Date: Wed Sep 12 2012 - 14:00:48 EST

On Wed, Sep 12, 2012 at 7:45 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Wed, 2012-09-12 at 19:37 +0200, Peter Zijlstra wrote:
>> Ah, so I do think EIO will re-enable LBR,
> OK, it does not, but the:
>> also the handler is wrapped in
>> x86_pmu::{dis,en}able_all() which does end up calling
>> intel_pmu_lbr_{dis,en}able_all().
> Thing does the re-enable for us,

>> However that leaves the MSR in the
>> exact same state on exit as it was on enter, so that's not a problem for
>> the: read-modify-write change.
> in a safe way.
Well, I think it does even when we have to stop events (x86_pmu_stop)
because the buffer is full. Looks like we always re-enable lbr. So looks
like the handler is a wash for debugctl.
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