selftests/resctrl: Open perf fd before start & add error handling

Perf fd (pe_fd) is opened, reset, and enabled during every test the CAT
selftest runs. Also, ioctl(pe_fd, ...) calls are not error checked even
if ioctl() could return an error.

Open perf fd only once before the tests and only reset and enable the
counter within the test loop. Add error checking to pe_fd ioctl()
calls.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/resctrl/cache.c

@@ -22,10 +22,19 @@ void perf_event_attr_initialize(struct perf_event_attr *pea, __u64 config)
 }
 
 /* Start counters to log values */
-static void perf_event_reset_enable(int pe_fd)
+int perf_event_reset_enable(int pe_fd)
 {
-	ioctl(pe_fd, PERF_EVENT_IOC_RESET, 0);
-	ioctl(pe_fd, PERF_EVENT_IOC_ENABLE, 0);
+	int ret;
+
+	ret = ioctl(pe_fd, PERF_EVENT_IOC_RESET, 0);
+	if (ret < 0)
+		return ret;
+
+	ret = ioctl(pe_fd, PERF_EVENT_IOC_ENABLE, 0);
+	if (ret < 0)
+		return ret;
+
+	return 0;
 }
 
 void perf_event_initialize_read_format(struct perf_event_read *pe_read)
@@ -129,7 +138,9 @@ int perf_event_measure(int pe_fd, struct perf_event_read *pe_read,
 	int ret;
 
 	/* Stop counters after one span to get miss rate */
-	ioctl(pe_fd, PERF_EVENT_IOC_DISABLE, 0);
+	ret = ioctl(pe_fd, PERF_EVENT_IOC_DISABLE, 0);
+	if (ret < 0)
+		return ret;
 
 	ret = read(pe_fd, pe_read, sizeof(*pe_read));
 	if (ret == -1) {

tools/testing/selftests/resctrl/cat_test.c

@@ -145,6 +145,9 @@ static int cat_test(struct resctrl_val_param *param, size_t span)
 
 	perf_event_attr_initialize(&pea, PERF_COUNT_HW_CACHE_MISSES);
 	perf_event_initialize_read_format(&pe_read);
+	pe_fd = perf_open(&pea, bm_pid, param->cpu_no);
+	if (pe_fd < 0)
+		return pe_fd;
 
 	/* Test runs until the callback setup() tells the test to stop. */
 	while (1) {
@@ -155,11 +158,10 @@ static int cat_test(struct resctrl_val_param *param, size_t span)
 		}
 		if (ret < 0)
 			break;
-		pe_fd = perf_open(&pea, bm_pid, param->cpu_no);
-		if (pe_fd < 0) {
-			ret = -1;
-			break;
-		}
+
+		ret = perf_event_reset_enable(pe_fd);
+		if (ret)
+			goto pe_close;
 
 		if (run_fill_buf(span, memflush, operation, true)) {
 			fprintf(stderr, "Error-running fill buffer\n");
@@ -171,8 +173,6 @@ static int cat_test(struct resctrl_val_param *param, size_t span)
 		ret = perf_event_measure(pe_fd, &pe_read, param->filename, bm_pid);
 		if (ret)
 			goto pe_close;
-
-		close(pe_fd);
 	}
 
 	return ret;

tools/testing/selftests/resctrl/resctrl.h

@@ -122,6 +122,7 @@ int get_core_sibling(int cpu_no);
 void perf_event_attr_initialize(struct perf_event_attr *pea, __u64 config);
 void perf_event_initialize_read_format(struct perf_event_read *pe_read);
 int perf_open(struct perf_event_attr *pea, pid_t pid, int cpu_no);
+int perf_event_reset_enable(int pe_fd);
 int perf_event_measure(int pe_fd, struct perf_event_read *pe_read,
 		       const char *filename, int bm_pid);
 int measure_llc_resctrl(const char *filename, int bm_pid);