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Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l752i-0003rW-39; Tue, 02 Feb 2021 23:25:08 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l752f-0003qu-RU for linux-arm-kernel@lists.infradead.org; Tue, 02 Feb 2021 23:25:07 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7CB3731B; Tue, 2 Feb 2021 15:25:03 -0800 (PST) Received: from [10.57.35.108] (unknown [10.57.35.108]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BE9093F694; Tue, 2 Feb 2021 15:25:00 -0800 (PST) Subject: Re: [PATCH v2 7/7] Documentation: coresight: Add PID tracing description To: Leo Yan , Arnaldo Carvalho de Melo , Mathieu Poirier , Mike Leach , Jonathan Corbet , Alexander Shishkin , John Garry , Will Deacon , Peter Zijlstra , Ingo Molnar , Mark Rutland , Jiri Olsa , Namhyung Kim , Daniel Kiss , Denis Nikitin , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210202163842.134734-1-leo.yan@linaro.org> <20210202163842.134734-8-leo.yan@linaro.org> From: Suzuki K Poulose Message-ID: <451d58bd-e79d-5fb4-a67f-962da02a3937@arm.com> Date: Tue, 2 Feb 2021 23:24:48 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210202163842.134734-8-leo.yan@linaro.org> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210202_182506_046015_FE050968 X-CRM114-Status: GOOD ( 28.80 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2/2/21 4:38 PM, Leo Yan wrote: > After support the PID tracing for the kernel in EL1 or EL2, the usage > gets more complicated. > > This patch gives description for the PMU formats of contextID configs, > this can help users to understand how to control the knobs for PID > tracing when the kernel is in different ELs. > > Signed-off-by: Leo Yan > --- > Documentation/trace/coresight/coresight.rst | 37 +++++++++++++++++++++ > 1 file changed, 37 insertions(+) > > diff --git a/Documentation/trace/coresight/coresight.rst b/Documentation/trace/coresight/coresight.rst > index 0b73acb44efa..771558f22938 100644 > --- a/Documentation/trace/coresight/coresight.rst > +++ b/Documentation/trace/coresight/coresight.rst > @@ -512,6 +512,43 @@ The --itrace option controls the type and frequency of synthesized events > Note that only 64-bit programs are currently supported - further work is > required to support instruction decode of 32-bit Arm programs. > > +2.2) Tracing PID > + > +When the kernel is running at EL2 with Virtualization Host Extensions (VHE), > +perf records CONTEXTIDR_EL2 in the trace data and can be used as PID when > +decoding; and if the kernel is running at EL1 with nVHE, CONTEXTIDR_EL1 is > +traced for PID. > + > +To support tracing PID for the kernel runs at different exception levels, > +the PMU formats are defined as follow: > + > + "contextid1": Available on both EL1 kernel and EL2 kernel. When the > + kernel is running at EL1, "contextid1" enables the PID > + tracing; when the kernel is running at EL2, this enables > + tracing the PID of guest applications. > + > + "contextid2": Only usable when the kernel is running at EL2. When > + selected, enables PID tracing on EL2 kernel. > + > + "contextid": Will be an alias for the option that enables PID > + tracing. I.e, > + contextid == contextid1, on EL1 kernel. > + contextid == contextid2, on EL2 kernel. > + > +The perf tool automatically sets corresponding bit for the "contextid" config, > +therefore, the user doesn't have to bother which EL the kernel is running. > + > + i.e, perf record -e cs_etm/contextid/u -- uname > + or perf record -e cs_etm//u -- uname > + > +will always do the "PID" tracing, independent of the kernel EL. > + > +When the kernel is running at EL2 with VHE, if user wants to trace both the > +PIDs for both host and guest, the two configs "contextid1" and "contextid2" > +can be set at the same time: > + > + perf record -e cs_etm/contextid1,contextid2/u -- uname > + To make this case clear, we could change the command from uname to something like: perf record -e cs_etm/contextid1,contextid2/u -- vm Otherwise looks good to me. With the above fixed, Reviewed-by: Suzuki K Poulose _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel