linux-kernel - Re: [PATCH 01/17] perf cs-etm: Print error for new PERF_RECORD_AUX_OUTPUT_HW

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Date: Tue, 7 May 2024 11:54:25 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: James Clark <james.clark@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>, Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>,
	Leo Yan <leo.yan@...ux.dev>, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-perf-users@...r.kernel.org,
	gankulkarni@...amperecomputing.com,
	scclevenger@...amperecomputing.com, coresight@...ts.linaro.org,
	mike.leach@...aro.org
Subject: Re: [PATCH 01/17] perf cs-etm: Print error for new
 PERF_RECORD_AUX_OUTPUT_HW_ID versions

On Tue, May 07, 2024 at 04:27:25PM +0530, Anshuman Khandual wrote:
> On 5/7/24 15:36, James Clark wrote:
> > On 07/05/2024 04:47, Anshuman Khandual wrote:
> >> On 4/29/24 20:51, James Clark wrote:
> >>> The likely fix for this is to update Perf so print a helpful message.
> >>>
> >>> Signed-off-by: James Clark <james.clark@....com>
> >>> ---
> >>>  tools/perf/util/cs-etm.c | 5 ++++-
> >>>  1 file changed, 4 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> >>> index d65d7485886c..32818bd7cd17 100644
> >>> --- a/tools/perf/util/cs-etm.c
> >>> +++ b/tools/perf/util/cs-etm.c
> >>> @@ -335,8 +335,11 @@ static int cs_etm__process_aux_output_hw_id(struct perf_session *session,
> >>>  	trace_chan_id = FIELD_GET(CS_AUX_HW_ID_TRACE_ID_MASK, hw_id);
> >>>  
> >>>  	/* check that we can handle this version */
> >>> -	if (version > CS_AUX_HW_ID_CURR_VERSION)
> >>> +	if (version > CS_AUX_HW_ID_CURR_VERSION) {
> >>> +		pr_err("CS ETM Trace: PERF_RECORD_AUX_OUTPUT_HW_ID version %d not supported. Please update Perf.\n",
> >>
> >> Is not this bit misleading ? PERF_RECORD_AUX_OUTPUT_HW_ID is just the perf record
> >> format identifier. The record version here, is derived from the platform specific
> >> hardware ID information embedded in this perf record.
> > 
> > Not sure I follow what you mean here. 'version' is something that's
> > output by the kernel. It's saved into a perf.data file, and if Perf
> > can't handle version 2 for example, you need to update Perf.
 
> Got it.
 
> >> Should not this be just s/PERF_RECORD_AUX_OUTPUT_HW_ID/hardware ID/ instead ?
> >>
> > 
> > It's just a way to go from the error message to the part of the code or
> > docs that you need to look at. "hardware ID" wouldn't lead you anywhere
> > so I don't think it would be useful.
> 
> Sure, fair enough.

I'm taking this as an Acked-by, ok?

- Arnaldo