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Subject: Re: [PATCH v1 3/7] perf cs-etm: Calculate per CPU metadata array size
To:     Leo Yan <leo.yan@linaro.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Mike Leach <mike.leach@linaro.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        John Garry <john.garry@huawei.com>,
        Will Deacon <will@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Daniel Kiss <Daniel.Kiss@arm.com>,
        Denis Nikitin <denik@chromium.org>, coresight@lists.linaro.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20210109074435.626855-1-leo.yan@linaro.org>
 <20210109074435.626855-4-leo.yan@linaro.org>
From:   Suzuki K Poulose <suzuki.poulose@arm.com>
Message-ID: <96ec434e-4103-02ac-a05a-761a9ca8cb0d@arm.com>
Date:   Mon, 11 Jan 2021 07:28:55 +0000
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On 1/9/21 7:44 AM, Leo Yan wrote:
> The metadata array can be extended over time and the tool, if using the
> predefined macro (like CS_ETMV4_PRIV_MAX for ETMv4) as metadata array
> size to copy data, it can cause compatible issue within different
> versions of perf tool.
> 
> E.g. we recorded a data file with an old version tool, afterwards if
> use the new version perf tool to parse the file, since the metadata
> array has been extended and the macro CS_ETMV4_PRIV_MAX has been
> altered, if use it to parse the perf data with old format, this will
> lead to mismatch.
> 
> To maintain backward compatibility, this patch calculates per CPU
> metadata array size on the runtime, the calculation is based on the
> info stored in the data file so that it's reliable.
> 
> Signed-off-by: Leo Yan <leo.yan@linaro.org>

Looks good to me.

Acked-by: Suzuki K Poulose <suzuki.poulose@arm.com>