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Message-ID: <84e9e6ba-7903-d2d9-f09d-ba7a1a4332a9@arm.com>
Date: Fri, 23 Jul 2021 13:09:26 +0100
From: James Clark <james.clark@....com>
To: Mike Leach <mike.leach@...aro.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
Mathieu Poirier <mathieu.poirier@...aro.org>,
Coresight ML <coresight@...ts.linaro.org>,
Leo Yan <leo.yan@...aro.org>, Al Grant <al.grant@....com>,
"Suzuki K. Poulose" <suzuki.poulose@....com>,
Anshuman Khandual <anshuman.khandual@....com>,
John Garry <john.garry@...wei.com>,
Will Deacon <will@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 3/6] perf cs-etm: Save TRCDEVARCH register
On 21/07/2021 10:48, Mike Leach wrote:
> HI James,
>
> On Wed, 21 Jul 2021 at 10:07, James Clark <james.clark@....com> wrote:
>>
>> Now that the metadata has a length field we can add extra registers
>> without breaking any previous versions of perf.
>>
>> Save the TRCDEVARCH register so that it can be used to configure the ETE
>> decoder in the next commit. If the sysfs file doesn't exist then 0 will
>> be saved which is an impossible register value and can also be used to
>> signify that the file couldn't be read.
>>
>> Signed-off-by: James Clark <james.clark@....com>
>> ---
>> tools/perf/arch/arm/util/cs-etm.c | 13 ++++++++++++-
>> tools/perf/util/cs-etm.c | 1 +
>> tools/perf/util/cs-etm.h | 5 +++--
>> 3 files changed, 16 insertions(+), 3 deletions(-)
>>
>> diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
>> index 85168d87b2d7..65a863bdf5cc 100644
>> --- a/tools/perf/arch/arm/util/cs-etm.c
>> +++ b/tools/perf/arch/arm/util/cs-etm.c
>> @@ -53,6 +53,7 @@ static const char *metadata_etmv4_ro[CS_ETMV4_PRIV_MAX] = {
>> [CS_ETMV4_TRCIDR2] = "trcidr/trcidr2",
>> [CS_ETMV4_TRCIDR8] = "trcidr/trcidr8",
>> [CS_ETMV4_TRCAUTHSTATUS] = "mgmt/trcauthstatus",
>> + [CS_ETE_TRCDEVARCH] = "mgmt/trcdevarch"
>> };
>>
>> static bool cs_etm_is_etmv4(struct auxtrace_record *itr, int cpu);
>> @@ -73,7 +74,7 @@ static int cs_etm_set_context_id(struct auxtrace_record *itr,
>> if (!cs_etm_is_etmv4(itr, cpu))
>> goto out;
>>
>> - /* Get a handle on TRCIRD2 */
>> + /* Get a handle on TRCIDR2 */
>> snprintf(path, PATH_MAX, "cpu%d/%s",
>> cpu, metadata_etmv4_ro[CS_ETMV4_TRCIDR2]);
>> err = perf_pmu__scan_file(cs_etm_pmu, path, "%x", &val);
>> @@ -643,6 +644,16 @@ static void cs_etm_get_metadata(int cpu, u32 *offset,
>> cs_etm_get_ro(cs_etm_pmu, cpu,
>> metadata_etmv4_ro
>> [CS_ETMV4_TRCAUTHSTATUS]);
>> + /*
>> + * ETE uses the same registers as ETMv4 plus TRCDEVARCH. It's also backwards
>> + * compatible, so don't change the magic number otherwise that will reduce the
>> + * number of versions of perf that can open it. Just append TRCDEVARCH to the end of
>> + * the register block and allow newer versions of perf to make use. cs_etm_get_ro()
>> + * returns 0 if it couldn't be read.
>> + */
>
> ETE is a superset of ETMv4, but an old perf that only knows ETMv4
> cannot be guaranteed to decode all ETE due to new packet types.
> Therefore do we want to allow old perfs to decode only some ETE,
> possibly with errors?
>
> I think it would be better to add in a new magic number for the new
> decoder rather than have some grey overlap area were an "older" perf
> might work intermittently dependent on the packets generated in a
> particular trace run.
I did think about doing it this way and I'm also ok with adding a new
magic number. I will wait till Al's back to get his opinion before
making the change.
Thanks
James
>
> Regards
>
> Mike
>
>> + info->priv[*offset + CS_ETE_TRCDEVARCH] =
>> + cs_etm_get_ro(cs_etm_pmu, cpu,
>> + metadata_etmv4_ro[CS_ETE_TRCDEVARCH]);
>>
>> /* How much space was used */
>> increment = CS_ETMV4_PRIV_MAX;
>> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
>> index 62769a84a53f..68978f6707a8 100644
>> --- a/tools/perf/util/cs-etm.c
>> +++ b/tools/perf/util/cs-etm.c
>> @@ -2508,6 +2508,7 @@ static const char * const cs_etmv4_priv_fmts[] = {
>> [CS_ETMV4_TRCIDR2] = " TRCIDR2 %llx\n",
>> [CS_ETMV4_TRCIDR8] = " TRCIDR8 %llx\n",
>> [CS_ETMV4_TRCAUTHSTATUS] = " TRCAUTHSTATUS %llx\n",
>> + [CS_ETE_TRCDEVARCH] = " TRCDEVARCH %llx\n"
>> };
>>
>> static const char * const param_unk_fmt =
>> diff --git a/tools/perf/util/cs-etm.h b/tools/perf/util/cs-etm.h
>> index d65c7b19407d..52d82dce9d59 100644
>> --- a/tools/perf/util/cs-etm.h
>> +++ b/tools/perf/util/cs-etm.h
>> @@ -59,7 +59,7 @@ enum {
>> /* define fixed version 0 length - allow new format reader to read old files. */
>> #define CS_ETM_NR_TRC_PARAMS_V0 (CS_ETM_ETMIDR - CS_ETM_ETMCR + 1)
>>
>> -/* ETMv4 metadata */
>> +/* ETMv4 + ETE metadata */
>> enum {
>> /* Dynamic, configurable parameters */
>> CS_ETMV4_TRCCONFIGR = CS_ETM_COMMON_BLK_MAX_V1,
>> @@ -70,7 +70,8 @@ enum {
>> CS_ETMV4_TRCIDR2,
>> CS_ETMV4_TRCIDR8,
>> CS_ETMV4_TRCAUTHSTATUS,
>> - CS_ETMV4_PRIV_MAX,
>> + CS_ETE_TRCDEVARCH,
>> + CS_ETMV4_PRIV_MAX
>> };
>>
>> /* define fixed version 0 length - allow new format reader to read old files. */
>> --
>> 2.28.0
>>
>
>
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