perf jevents: Add test for arch std events

Recently there was an undetected breakage for std arch event support.

Add support in "PMU events" testcase to detect such breakages.

For this, the "test" arch needs has support added to process std arch
events. And a test event is added for the test, ifself.

Also add a few code comments to help understand the code a bit better.

Committer testing:

Before:

  # perf test -vv pmu  |& grep l3_cache_rd
  #

After:

  # perf test -vv pmu  |& grep l3_cache_rd
  testing event table l3_cache_rd: pass
  testing aliases PMU cpu: matched event l3_cache_rd
  #
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-By: Kajol Jain<kjain@linux.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/1603364547-197086-3-git-send-email-john.garry@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/pmu-events/arch/test/arch-std-events.json

+[
+    {
+        "PublicDescription": "Attributable Level 3 cache access, read",
+        "EventCode": "0x40",
+        "EventName": "L3_CACHE_RD",
+        "BriefDescription": "L3 cache access, read"
+    }
+]

tools/perf/pmu-events/arch/test/test_cpu/cache.json

+[
+    {
+	 "ArchStdEvent": "L3_CACHE_RD"
+    }
+]
\ No newline at end of file

tools/perf/pmu-events/jevents.c

@@ -1162,6 +1162,10 @@ int main(int argc, char *argv[])
 
 	sprintf(ldirname, "%s/test", start_dirname);
 
+	rc = nftw(ldirname, preprocess_arch_std_files, maxfds, 0);
+	if (rc)
+		goto err_processing_std_arch_event_dir;
+
 	rc = nftw(ldirname, process_one_file, maxfds, 0);
 	if (rc)
 		goto err_processing_dir;

tools/perf/tests/pmu-events.c

@@ -14,8 +14,10 @@
 #include "util/parse-events.h"
 
 struct perf_pmu_test_event {
+	/* used for matching against events from generated pmu-events.c */
 	struct pmu_event event;
 
+	/* used for matching against event aliases */
 	/* extra events for aliases */
 	const char *alias_str;
 
@@ -78,6 +80,17 @@ static struct perf_pmu_test_event test_cpu_events[] = {
 		.alias_str = "umask=0,(null)=0x30d40,event=0x3a",
 		.alias_long_desc = "Number of Enhanced Intel SpeedStep(R) Technology (EIST) transitions",
 	},
+	{
+		.event = {
+			.name = "l3_cache_rd",
+			.event = "event=0x40",
+			.desc = "L3 cache access, read",
+			.long_desc = "Attributable Level 3 cache access, read",
+			.topic = "cache",
+		},
+		.alias_str = "event=0x40",
+		.alias_long_desc = "Attributable Level 3 cache access, read",
+	},
 	{ /* sentinel */
 		.event = {
 			.name = NULL,
@@ -357,6 +370,7 @@ static int __test__pmu_event_aliases(char *pmu_name, int *count)
 }
 
 
+/* Test that aliases generated are as expected */
 static int test_aliases(void)
 {
 	struct perf_pmu *pmu = NULL;