[PATCH v2 2/5] test/pmu: enable test

[rkudurumalla]

From: Rakesh Kudurumalla <rkudurumalla at marvell.com>

Enable test to allow users to verify basic functionality. Due to varying
configuration options across distributions and kernels user should
ensure that all requirements are satisfied before starting test.

Signed-off-by: Tomasz Duszynski <tduszynski at marvell.com>
Signed-off-by: Rakesh Kudurumalla <rkudurumalla at marvell.com>
---
 app/test/test_pmu.c | 60 ++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 54 insertions(+), 6 deletions(-)

diff --git a/app/test/test_pmu.c b/app/test/test_pmu.c
index 62ce8911fc..a73594d73d 100644
--- a/app/test/test_pmu.c
+++ b/app/test/test_pmu.c
@@ -2,10 +2,48 @@
  * Copyright(C) 2025 Marvell International Ltd.
  */
 
+#include <stdbool.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+
 #include <rte_pmu.h>
 
 #include "test.h"
 
+#define PERF_EVENT_PARANOID_PATH "/proc/sys/kernel/perf_event_paranoid"
+
+static bool perf_allowed_quirk(void)
+{
+	int level, ret;
+	FILE *fp;
+
+	fp = fopen(PERF_EVENT_PARANOID_PATH, "r");
+	if (!fp)
+		return false;
+
+	ret = fscanf(fp, "%d", &level);
+	fclose(fp);
+	if (ret != 1)
+		return false;
+
+	/* On vanilla Linux the default perf_event_paranoid level is 2, which allows non-privileged
+	 * processes to access performance counters.
+	 *
+	 * Debian / Ubuntu and their derivatives apply patches that introduce
+	 * additional paranoia levels:
+	 *
+	 * - Debian adds level 3, which restricts access to perf_event_open() for
+	 *   monitoring other processes, but still allows unprivileged self-monitoring.
+	 *   See: https://lore.kernel.org/all/1469630746-32279-1-git-send-email-jeffv@google.com/
+	 * - Ubuntu adds level 4 (which is also the default), completely disabling perf_event_open()
+	 *   for unprivileged users—effectively disabling self-monitoring.
+	 *
+	 * That said, check below should be sufficient to enable this test on most kernels.
+	 */
+	return level < 4;
+}
+
 static int
 test_pmu_read(void)
 {
@@ -24,8 +62,15 @@ test_pmu_read(void)
 		return TEST_SKIPPED;
 	}
 
-	if (rte_pmu_init() < 0)
-		return TEST_FAILED;
+	if ((getuid() != 0) && !perf_allowed_quirk()) {
+		printf("self-monitoring disabled\n");
+		return TEST_SKIPPED;
+	}
+
+	if (rte_pmu_init() < 0) {
+		printf("PMU not initialized\n");
+		return TEST_SKIPPED;
+	}
 
 	event = rte_pmu_add_event(name);
 	while (tries--)
@@ -33,7 +78,12 @@ test_pmu_read(void)
 
 	rte_pmu_fini();
 
-	return val ? TEST_SUCCESS : TEST_FAILED;
+	/* rte_pmu_read() returns zero if it can't read perf counter. Thus series of zeros doesn't
+	 * necessarily mean the counter is actually zero. It might just signal a problem with setup
+	 * itself. So skip test to avoid testing failure and leave it to user to interpret this
+	 * outcome.
+	 */
+	return val ? TEST_SUCCESS : TEST_SKIPPED;
 }
 
 static struct unit_test_suite pmu_tests = {
@@ -52,6 +102,4 @@ test_pmu(void)
 	return unit_test_suite_runner(&pmu_tests);
 }
 
-/* disabled because of reported failures, waiting for a fix
- * REGISTER_FAST_TEST(pmu_autotest, NOHUGE_OK, ASAN_OK, test_pmu);
- */
+REGISTER_FAST_TEST(pmu_autotest, NOHUGE_OK, ASAN_OK, test_pmu);
-- 
2.25.1