[igt-dev] [PATCH i-g-t 6/9] tests/perf_pmu: PMU enable race test

[Tvrtko Ursulin <tursulin@ursulin.net>]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Test that the PMU can be safely enabled in face of interrupt-heavy load on
an engine.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 tests/perf_pmu.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/tests/perf_pmu.c b/tests/perf_pmu.c
index 27f32b8a1602..de0a1c7d936c 100644
--- a/tests/perf_pmu.c
+++ b/tests/perf_pmu.c
@@ -1221,6 +1221,51 @@ test_rc6(int gem_fd)
 	assert_within_epsilon(busy - prev, 0.0, tolerance);
 }
 
+static void
+test_enable_race(int gem_fd, const struct intel_execution_engine2 *e)
+{
+	uint64_t config = I915_PMU_ENGINE_BUSY(e->class, e->instance);
+	struct igt_helper_process engine_load = { };
+	const uint32_t bbend = MI_BATCH_BUFFER_END;
+	struct drm_i915_gem_exec_object2 obj = { };
+	struct drm_i915_gem_execbuffer2 eb = { };
+	int fd;
+
+	igt_require(intel_gen(intel_get_drm_devid(gem_fd)) >= 8);
+	igt_require(gem_has_engine(gem_fd, e->class, e->instance));
+
+	obj.handle = gem_create(gem_fd, 4096);
+	gem_write(gem_fd, obj.handle, 0, &bbend, sizeof(bbend));
+
+	eb.buffer_count = 1;
+	eb.buffers_ptr = to_user_pointer(&obj);
+	eb.flags = e2ring(gem_fd, e);
+
+	/*
+	 * Defeat the busy stats delayed disable, we need to guarantee we are
+	 * the first user.
+	 */
+	sleep(2);
+
+	/* Apply interrupt-heavy load on the engine. */
+	igt_fork_helper(&engine_load) {
+		for (;;)
+			gem_execbuf(gem_fd, &eb);
+	}
+
+	/* Wait a bit to allow engine load to start. */
+	usleep(500e3);
+
+	/* Enable the PMU. */
+	fd = open_pmu(config);
+
+	/* Cleanup. */
+	igt_stop_helper(&engine_load);
+	close(fd);
+	gem_close(gem_fd, obj.handle);
+	gem_quiescent_gpu(gem_fd);
+}
+
 igt_main
 {
 	const unsigned int num_other_metrics =
@@ -1343,6 +1388,13 @@ igt_main
 		 */
 		igt_subtest_f("busy-double-start-%s", e->name)
 			busy_double_start(fd, e);
+
+		/**
+		 * Check that the PMU can be safely enabled in face of
+		 * interrupt-heavy engine load.
+		 */
+		igt_subtest_f("enable-race-%s", e->name)
+			test_enable_race(fd, e);
 	}
 
 	/**
-- 
2.14.1

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