linux-kernel - Re: [PATCH v2 2/7] perf cs-etm: Use new OpenCSD consistency checks

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Message-ID: <332e0654-df8c-44b1-8e55-398aeba37b08@linaro.org>
Date: Fri, 13 Sep 2024 13:09:06 +0100
From: James Clark <james.clark@...aro.org>
To: Leo Yan <leo.yan@....com>
Cc: 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>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 "Liang, Kan" <kan.liang@...ux.intel.com>,
 Suzuki K Poulose <suzuki.poulose@....com>, Mike Leach
 <mike.leach@...aro.org>, John Garry <john.g.garry@...cle.com>,
 Will Deacon <will@...nel.org>, Leo Yan <leo.yan@...ux.dev>,
 Ben Gainey <ben.gainey@....com>, Ruidong Tian
 <tianruidong@...ux.alibaba.com>, Benjamin Gray <bgray@...ux.ibm.com>,
 Mathieu Poirier <mathieu.poirier@...aro.org>, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-perf-users@...r.kernel.org,
 gankulkarni@...amperecomputing.com, coresight@...ts.linaro.org,
 scclevenger@...amperecomputing.com
Subject: Re: [PATCH v2 2/7] perf cs-etm: Use new OpenCSD consistency checks



On 13/09/2024 12:54, Leo Yan wrote:
> On 9/12/24 16:11, James Clark wrote:>
>>
>> Previously when the incorrect binary was used for decode, Perf would
>> silently continue to generate incorrect samples. With OpenCSD 1.5.4 we
>> can enable consistency checks that do a best effort to detect a mismatch
>> in the image. When one is detected a warning is printed and sample
>> generation stops until the trace resynchronizes with a good part of the
>> image.
>>
>> Reported-by: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
>> Closes: 
>> https://lore.kernel.org/all/20240719092619.274730-1-gankulkarni@os.amperecomputing.com/
>> Signed-off-by: James Clark <james.clark@...aro.org>
>> ---
>>   tools/perf/util/cs-etm-decoder/cs-etm-decoder.c | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c 
>> b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
>> index b78ef0262135..b85a8837bddc 100644
>> --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
>> +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
>> @@ -685,9 +685,14 @@ cs_etm_decoder__create_etm_decoder(struct 
>> cs_etm_decoder_params *d_params,
>>          }
>>
>>          if (d_params->operation == CS_ETM_OPERATION_DECODE) {
>> +               int decode_flags = OCSD_CREATE_FLG_FULL_DECODER;
>> +#ifdef OCSD_OPFLG_N_UNCOND_DIR_BR_CHK
>> +               decode_flags |= OCSD_OPFLG_N_UNCOND_DIR_BR_CHK | 
>> OCSD_OPFLG_CHK_RANGE_CONTINUE |
>> +                               ETM4_OPFLG_PKTDEC_AA64_OPCODE_CHK;
>> +#endif
> 
> Looks good to me.
> 
> Just one question: should the flag ETM4_OPFLG_PKTDEC_AA64_OPCODE_CHK be set
> according to ETM version? E.g. it should be only set for ETMv4 or this is
> fine for ETE as well.
> 
> Thanks,
> Leo
> 

I asked Mike the same question about ETMv3 and he said none of the flags 
overlap and it was ok to always pass them. So I assume the same applies 
to ETE as well.