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

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Message-ID: <de635db0-6510-452f-91be-4fc5f7fdf671@arm.com>
Date: Tue, 7 May 2024 11:06:47 +0100
From: James Clark <james.clark@....com>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: 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>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 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,
 suzuki.poulose@....com, mike.leach@...aro.org
Subject: Re: [PATCH 01/17] perf cs-etm: Print error for new
 PERF_RECORD_AUX_OUTPUT_HW_ID versions



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.

> 
> 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.

>> +		       version);
>>  		return -EINVAL;
>> +	}
>>  
>>  	/* get access to the etm metadata */
>>  	etm = container_of(session->auxtrace, struct cs_etm_auxtrace, auxtrace);
>