Re: [PATCH] perf cs-etm: Improve version detection and error reporting

From: James Clark
Date: Wed May 01 2024 - 04:23:32 EST

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On 30/04/2024 17:22, Ian Rogers wrote:
> On Tue, Apr 30, 2024 at 6:32 AM James Clark <james.clark@xxxxxxx> wrote:
>>
>> When the config validation functions are warning about ETMv3, they do it
>> based on "not ETMv4". If the drivers aren't all loaded or the hardware
>> doesn't support Coresight it will appear as "not ETMv4" and then Perf
>> will print the error message "... not supported in ETMv3 ..." which is
>> wrong and confusing.
>>
>> cs_etm_is_etmv4() is also misnamed because it also returns true for
>> ETE because ETE has a superset of the ETMv4 metadata files. Although
>> this was always done in the correct order so it wasn't a bug.
>>
>> Improve all this by making a single get version function which also
>> handles not present as a separate case. Change the ETMv3 error message
>> to only print when ETMv3 is detected, and add a new error message for
>> the not present case.
>>
>> Signed-off-by: James Clark <james.clark@xxxxxxx>
>> ---
>> tools/perf/arch/arm/util/cs-etm.c | 64 +++++++++++++++++++++++--------
>> 1 file changed, 48 insertions(+), 16 deletions(-)
>>
>> diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
>> index 07be32d99805..2763c6758b91 100644
>> --- a/tools/perf/arch/arm/util/cs-etm.c
>> +++ b/tools/perf/arch/arm/util/cs-etm.c
>> @@ -66,9 +66,25 @@ static const char * const metadata_ete_ro[] = {
>> [CS_ETE_TS_SOURCE] = "ts_source",
>> };
>>
>> -static bool cs_etm_is_etmv4(struct auxtrace_record *itr, int cpu);
>> +enum cs_etm_version { CS_NOT_PRESENT, CS_ETMV3, CS_ETMV4, CS_ETE };
>> +
>> +static bool cs_etm_pmu_file_present(struct auxtrace_record *itr, int cpu,
>> + const char *file);
>> static bool cs_etm_is_ete(struct auxtrace_record *itr, int cpu);
>>
>> +static enum cs_etm_version cs_etm_get_version(struct auxtrace_record *itr,
>> + int cpu)
>
> nit: perhaps use "struct perf_cpu" rather than "int cpu" for a little
> bit of type safety. Fwiw, most of the tool uses an index into a CPU
> map but then have labelled that index "cpu" which is confusing
> particularly in the uncore case, whilst a perf_cpu is never an index.
>
> Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>
>
> Thanks,
> Ian
>

Yeah I will make that change. There are quite a few early conversions
from the struct to the int that can be pushed all the way down to file open.

>> +{
>> + if (cs_etm_is_ete(itr, cpu))
>> + return CS_ETE;
>> + else if (cs_etm_pmu_file_present(itr, cpu, metadata_etmv4_ro[CS_ETMV4_TRCIDR0]))
>> + return CS_ETMV4;
>> + else if (cs_etm_pmu_file_present(itr, cpu, metadata_etmv3_ro[CS_ETM_ETMCCER]))
>> + return CS_ETMV3;
>> +
>> + return CS_NOT_PRESENT;
>> +}
>> +
>> static int cs_etm_validate_context_id(struct auxtrace_record *itr,
>> struct evsel *evsel, int cpu)
>> {
>> @@ -87,7 +103,7 @@ static int cs_etm_validate_context_id(struct auxtrace_record *itr,
>> return 0;
>>
>> /* Not supported in etmv3 */
>> - if (!cs_etm_is_etmv4(itr, cpu)) {
>> + if (cs_etm_get_version(itr, cpu) == CS_ETMV3) {
>> pr_err("%s: contextid not supported in ETMv3, disable with %s/contextid=0/\n",
>> CORESIGHT_ETM_PMU_NAME, CORESIGHT_ETM_PMU_NAME);
>> return -EINVAL;
>> @@ -154,7 +170,7 @@ static int cs_etm_validate_timestamp(struct auxtrace_record *itr,
>> perf_pmu__format_bits(cs_etm_pmu, "timestamp")))
>> return 0;
>>
>> - if (!cs_etm_is_etmv4(itr, cpu)) {
>> + if (cs_etm_get_version(itr, cpu) == CS_ETMV3) {
>> pr_err("%s: timestamp not supported in ETMv3, disable with %s/timestamp=0/\n",
>> CORESIGHT_ETM_PMU_NAME, CORESIGHT_ETM_PMU_NAME);
>> return -EINVAL;
>> @@ -218,6 +234,11 @@ static int cs_etm_validate_config(struct auxtrace_record *itr,
>> }
>>
>> perf_cpu_map__for_each_cpu_skip_any(cpu, idx, intersect_cpus) {
>> + if (cs_etm_get_version(itr, cpu.cpu) == CS_NOT_PRESENT) {
>> + pr_err("%s: Not found on CPU %d. Check hardware and firmware support and that all Coresight drivers are loaded\n",
>> + CORESIGHT_ETM_PMU_NAME, cpu.cpu);
>> + return -EINVAL;
>> + }
>> err = cs_etm_validate_context_id(itr, evsel, cpu.cpu);
>> if (err)
>> break;
>> @@ -548,13 +569,13 @@ cs_etm_info_priv_size(struct auxtrace_record *itr __maybe_unused,
>> /* Event can be "any" CPU so count all online CPUs. */
>> intersect_cpus = perf_cpu_map__new_online_cpus();
>> }
>> + /* Count number of each type of ETM. Don't count if that CPU has CS_NOT_PRESENT. */
>> perf_cpu_map__for_each_cpu_skip_any(cpu, idx, intersect_cpus) {
>> - if (cs_etm_is_ete(itr, cpu.cpu))
>> - ete++;
>> - else if (cs_etm_is_etmv4(itr, cpu.cpu))
>> - etmv4++;
>> - else
>> - etmv3++;
>> + enum cs_etm_version v = cs_etm_get_version(itr, cpu.cpu);
>> +
>> + ete += v == CS_ETE;
>> + etmv4 += v == CS_ETMV4;
>> + etmv3 += v == CS_ETMV3;
>> }
>> perf_cpu_map__put(intersect_cpus);
>>
>> @@ -564,7 +585,8 @@ cs_etm_info_priv_size(struct auxtrace_record *itr __maybe_unused,
>> (etmv3 * CS_ETMV3_PRIV_SIZE));
>> }
>>
>> -static bool cs_etm_is_etmv4(struct auxtrace_record *itr, int cpu)
>> +static bool cs_etm_pmu_file_present(struct auxtrace_record *itr, int cpu,
>> + const char *file)
>> {
>> bool ret = false;
>> char path[PATH_MAX];
>> @@ -574,9 +596,7 @@ static bool cs_etm_is_etmv4(struct auxtrace_record *itr, int cpu)
>> container_of(itr, struct cs_etm_recording, itr);
>> struct perf_pmu *cs_etm_pmu = ptr->cs_etm_pmu;
>>
>> - /* Take any of the RO files for ETMv4 and see if it present */
>> - snprintf(path, PATH_MAX, "cpu%d/%s",
>> - cpu, metadata_etmv4_ro[CS_ETMV4_TRCIDR0]);
>> + snprintf(path, PATH_MAX, "cpu%d/%s", cpu, file);
>> scan = perf_pmu__scan_file(cs_etm_pmu, path, "%x", &val);
>>
>> /* The file was read successfully, we have a winner */
>> @@ -735,21 +755,26 @@ static void cs_etm_get_metadata(int cpu, u32 *offset,
>> struct perf_pmu *cs_etm_pmu = ptr->cs_etm_pmu;
>>
>> /* first see what kind of tracer this cpu is affined to */
>> - if (cs_etm_is_ete(itr, cpu)) {
>> + switch (cs_etm_get_version(itr, cpu)) {
>> + case CS_ETE:
>> magic = __perf_cs_ete_magic;
>> cs_etm_save_ete_header(&info->priv[*offset], itr, cpu);
>>
>> /* How much space was used */
>> increment = CS_ETE_PRIV_MAX;
>> nr_trc_params = CS_ETE_PRIV_MAX - CS_ETM_COMMON_BLK_MAX_V1;
>> - } else if (cs_etm_is_etmv4(itr, cpu)) {
>> + break;
>> +
>> + case CS_ETMV4:
>> magic = __perf_cs_etmv4_magic;
>> cs_etm_save_etmv4_header(&info->priv[*offset], itr, cpu);
>>
>> /* How much space was used */
>> increment = CS_ETMV4_PRIV_MAX;
>> nr_trc_params = CS_ETMV4_PRIV_MAX - CS_ETMV4_TRCCONFIGR;
>> - } else {
>> + break;
>> +
>> + case CS_ETMV3:
>> magic = __perf_cs_etmv3_magic;
>> /* Get configuration register */
>> info->priv[*offset + CS_ETM_ETMCR] = cs_etm_get_config(itr);
>> @@ -767,6 +792,13 @@ static void cs_etm_get_metadata(int cpu, u32 *offset,
>> /* How much space was used */
>> increment = CS_ETM_PRIV_MAX;
>> nr_trc_params = CS_ETM_PRIV_MAX - CS_ETM_ETMCR;
>> + break;
>> +
>> + default:
>> + case CS_NOT_PRESENT:
>> + /* Unreachable, CPUs already validated in cs_etm_validate_config() */
>> + assert(true);
>> + return;
>> }
>>
>> /* Build generic header portion */
>> --
>> 2.34.1
>>

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