Re: [PATCH 2/2] perf intel-pt: Fix corrupt data after perf inject from

From: Adrian Hunter <adrian.hunter@intel.com>
To: Leo Yan <leo.yan@linaro.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mathieu Poirier <mathieu.poirier@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>,
	Andi Kleen <ak@linux.intel.com>,
	Kan Liang <kan.liang@linux.intel.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Cc: Al Grant <al.grant@arm.com>
Subject: Re: [PATCH 2/2] perf intel-pt: Fix corrupt data after perf inject from
Date: Mon, 24 Aug 2020 15:41:13 +0300	[thread overview]
Message-ID: <b957484e-19f0-4a7c-c67e-38f9d81fa879@intel.com> (raw)
In-Reply-To: <20200819084751.17686-2-leo.yan@linaro.org>

On 19/08/20 11:47 am, 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>

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

> ---
>  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;
>