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Date:   Tue, 1 Sep 2020 11:53:31 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Mathieu Poirier <mathieu.poirier@linaro.org>
Cc:     Leo Yan <leo.yan@linaro.org>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Mike Leach <mike.leach@linaro.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        AAl Grant <al.grant@arm.com>
Subject: Re: [PATCH 2/2] perf intel-pt: Fix corrupt data after perf inject
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Message-ID: <20200901145331.GA1422817@kernel.org>
References: <20200819084751.17686-1-leo.yan@linaro.org>
 <20200819084751.17686-2-leo.yan@linaro.org>
 <20200831203832.GA120995@xps15>
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Em Mon, Aug 31, 2020 at 02:38:32PM -0600, Mathieu Poirier escreveu:
> On Wed, Aug 19, 2020 at 04:47:51PM +0800, Leo Yan wrote:
> > From: Al Grant <al.grant@arm.com>
> > 
> > Commit 42bbabed09ce ("perf tools: Add hw_idx in struct branch_stack")
> > changed the format of branch stacks in perf samples. When samples use
> > this new format, a flag must be set in the corresponding event.
> > Synthesized branch stacks generated from Intel PT were using the new
> > format, but not setting the event attribute, leading to consumers
> > seeing corrupt data. This patch fixes the issue by setting the event
> > attribute to indicate use of the new format.
> > 
> > Fixes: 42bbabed09ce ("perf tools: Add hw_idx in struct branch_stack")
> > Signed-off-by: Al Grant <al.grant@arm.com>
> > Signed-off-by: Leo Yan <leo.yan@linaro.org>
> 
> Arnaldo, please consider.
> 
> Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Thanks, applied, and 1/2 too.

- Arnaldo
 
> > ---
> >  tools/perf/util/intel-pt.c | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
> > index 2a8d245351e7..0af4e81c46e2 100644
> > --- a/tools/perf/util/intel-pt.c
> > +++ b/tools/perf/util/intel-pt.c
> > @@ -3017,8 +3017,15 @@ static int intel_pt_synth_events(struct intel_pt *pt,
> >  
> >  	if (pt->synth_opts.callchain)
> >  		attr.sample_type |= PERF_SAMPLE_CALLCHAIN;
> > -	if (pt->synth_opts.last_branch)
> > +	if (pt->synth_opts.last_branch) {
> >  		attr.sample_type |= PERF_SAMPLE_BRANCH_STACK;
> > +		/*
> > +		 * We don't use the hardware index, but the sample generation
> > +		 * code uses the new format branch_stack with this field,
> > +		 * so the event attributes must indicate that it's present.
> > +		 */
> > +		attr.branch_sample_type |= PERF_SAMPLE_BRANCH_HW_INDEX;
> > +	}
> >  
> >  	if (pt->synth_opts.instructions) {
> >  		attr.config = PERF_COUNT_HW_INSTRUCTIONS;
> > -- 
> > 2.17.1
> > 

-- 

- Arnaldo