perf test 6: Fix missing kvm module load for s390

Command

   # perf test -Fv 6

fails with error

   running test 100 'kvm-s390:kvm_s390_create_vm' failed to parse
    event 'kvm-s390:kvm_s390_create_vm', err -1, str 'unknown tracepoint'
    event syntax error: 'kvm-s390:kvm_s390_create_vm'
                         \___ unknown tracepoint

when the kvm module is not loaded or not built in.

Fix this by adding a valid function which tests if the module
is loaded. Loaded modules (or builtin KVM support) have a
directory named
  /sys/kernel/debug/tracing/events/kvm-s390
for this tracepoint.

Check for existence of this directory.
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20190604053504.43073-1-tmricht@linux.ibm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/parse-events.c

@@ -18,6 +18,32 @@
 #define PERF_TP_SAMPLE_TYPE (PERF_SAMPLE_RAW | PERF_SAMPLE_TIME | \
 			     PERF_SAMPLE_CPU | PERF_SAMPLE_PERIOD)
 
+#if defined(__s390x__)
+/* Return true if kvm module is available and loaded. Test this
+ * and retun success when trace point kvm_s390_create_vm
+ * exists. Otherwise this test always fails.
+ */
+static bool kvm_s390_create_vm_valid(void)
+{
+	char *eventfile;
+	bool rc = false;
+
+	eventfile = get_events_file("kvm-s390");
+
+	if (eventfile) {
+		DIR *mydir = opendir(eventfile);
+
+		if (mydir) {
+			rc = true;
+			closedir(mydir);
+		}
+		put_events_file(eventfile);
+	}
+
+	return rc;
+}
+#endif
+
 static int test__checkevent_tracepoint(struct perf_evlist *evlist)
 {
 	struct perf_evsel *evsel = perf_evlist__first(evlist);
@@ -1642,6 +1668,7 @@ static struct evlist_test test__events[] = {
 	{
 		.name  = "kvm-s390:kvm_s390_create_vm",
 		.check = test__checkevent_tracepoint,
+		.valid = kvm_s390_create_vm_valid,
 		.id    = 100,
 	},
 #endif