perf: Skip and warn on unknown format 'configN' attrs

If the kernel exposes a new perf_event_attr field in a format attr, perf
will return an error stating the specified PMU can't be found. For
example, a format attr with 'config3:0-63' causes an error as config3 is
unknown to perf. This causes a compatibility issue between a newer
kernel with older perf tool.

Before this change with a kernel adding 'config3' I get:

  $ perf record -e arm_spe// -- true
  event syntax error: 'arm_spe//'
                       \___ Cannot find PMU `arm_spe'. Missing kernel support?
  Run 'perf list' for a list of valid events

   Usage: perf record [<options>] [<command>]
      or: perf record [<options>] -- <command> [<options>]

      -e, --event <event>   event selector. use 'perf list' to list
  available events

After this change, I get:

  $ perf record -e arm_spe// -- true
  WARNING: 'arm_spe_0' format 'inv_event_filter' requires 'perf_event_attr::config3' which is not supported by this version of perf!
  [ perf record: Woken up 2 times to write data ]
  [ perf record: Captured and wrote 0.091 MB perf.data ]

To support unknown configN formats, rework the YACC implementation to
pass any config[0-9]+ format to perf_pmu__new_format() to handle with a
warning.

Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Tested-by: Leo Yan <leo.yan@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220914-arm-perf-tool-spe1-2-v2-v4-1-83c098e6212e@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 74a2cafb4e8d..03284059175f 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -1005,6 +1005,23 @@ err:
 	return NULL;
 }
 
+void perf_pmu__warn_invalid_formats(struct perf_pmu *pmu)
+{
+	struct perf_pmu_format *format;
+
+	/* fake pmu doesn't have format list */
+	if (pmu == &perf_pmu__fake)
+		return;
+
+	list_for_each_entry(format, &pmu->format, list)
+		if (format->value >= PERF_PMU_FORMAT_VALUE_CONFIG_END) {
+			pr_warning("WARNING: '%s' format '%s' requires 'perf_event_attr::config%d'"
+				   "which is not supported by this version of perf!\n",
+				   pmu->name, format->name, format->value);
+			return;
+		}
+}
+
 static struct perf_pmu *pmu_find(const char *name)
 {
 	struct perf_pmu *pmu;