[PATCH i-g-t 1/2] tests: Exercise remote request vs barrier handling race

[Janusz Krzysztofik]

Users reported oopses on list corruptions when using i915 perf with a
number of concurrently running graphics applications.  That indicates we
are currently missing some important tests for such scenarios.  Cover
that gap.

Root cause analysis pointed out to an issue in barrier processing code and
its interaction with perf replacing kernel contexts' active barriers with
its own requests.

Add a new test intended for exercising intentionally racy barrier tasks
list processing and its interaction with other i915 subsystems.  As a
first subtest, add one that exercises the interaction of remote requests
with barrier tasks list handling, especially barrier preallocate / acquire
operations performed during context first pin / last unpin.

The code is partially inspired by Chris Wilson's igt at perf@open-race
subtest, which I was not able to get an Ack for from upstream.

v4: fix typo in test description and make it generic so it will not need
    to be changed soon (Kamil),
  - rename workload functions instead of providing name wrappers (Kamil),
  - no need for all physical engines to be tested (Kamil).
v3: don't add the new subtest to gem_ctx_exec which occurred blocklisted,
    create a new test hosting the new subtest, update commit descripion,
  - prepare parameters for perf open still in the main thread to avoid
    test failures on platforms with no perf support (will skip now),
  - call perf open with OA buffer reports disabled, this will make sure
    that the perf API doesn't unnecessarily enable the OA unit, while the
    test still runs the targeted code (Umesh),
  - replace additional code for OA exponent calculations with a reasonable
    hardcoded value (Umesh).
v2: convert to a separate subtest, not a variant of another one (that has
    been dropped from the series),
  - move the subtest out of tests/i915/perf.c (Ashutosh), add it to
    tests/i915/gem_ctx_exec.c,
  - don't touch lib/i915/perf.c (Umesh, Ashutosh), duplicate reused code
    from tests/i915/perf.c in tests/i915/gem_ctx_exec.c.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/6333
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
Cc: Chris Wilson <chris.p.wilson at intel.com>
Cc: Kamil Konieczny <kamil.konieczny at linux.intel.com>
Cc: Ashutosh Dixit <ashutosh.dixit at intel.com>
Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
---
 tests/i915/gem_barrier_race.c | 153 ++++++++++++++++++++++++++++++++++
 tests/meson.build             |   8 ++
 2 files changed, 161 insertions(+)
 create mode 100644 tests/i915/gem_barrier_race.c

diff --git a/tests/i915/gem_barrier_race.c b/tests/i915/gem_barrier_race.c
new file mode 100644
index 0000000000..594a043c16
--- /dev/null
+++ b/tests/i915/gem_barrier_race.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright(c) 2023 Intel Corporation. All rights reserved.
+ */
+
+#include <stdint.h>
+
+#include "drmtest.h"
+#include "igt_aux.h"
+#include "igt_core.h"
+#include "igt_gt.h"
+#include "intel_chipset.h"
+#include "intel_reg.h"
+#include "ioctl_wrappers.h"
+
+#include "i915/gem.h"
+#include "i915/gem_create.h"
+#include "i915/gem_engine_topology.h"
+#include "i915/perf.h"
+
+IGT_TEST_DESCRIPTION("Exercise engine barriers and their interaction with other subsystems");
+
+static void remote_request_workload(int fd, int *done)
+{
+	/*
+	 * Use DRM_IOCTL_I915_PERF_OPEN / close as
+	 * intel_context_prepare_remote_request() workload
+	 *
+	 * Based on code patterns found in tests/i915/perf.c
+	 */
+	struct intel_perf_metric_set *metric_set = NULL, *metric_set_iter;
+	struct intel_perf *intel_perf = intel_perf_for_fd(fd);
+	uint64_t properties[] = {
+		DRM_I915_PERF_PROP_SAMPLE_OA, true,
+		DRM_I915_PERF_PROP_OA_METRICS_SET, 0,
+		DRM_I915_PERF_PROP_OA_FORMAT, 0,
+		DRM_I915_PERF_PROP_OA_EXPONENT, 5,
+	};
+	struct drm_i915_perf_open_param param = {
+		.flags = I915_PERF_FLAG_FD_CLOEXEC | I915_PERF_FLAG_DISABLED,
+		.num_properties = sizeof(properties) / 16,
+		.properties_ptr = to_user_pointer(properties),
+	};
+	uint32_t devid = intel_get_drm_devid(fd);
+
+	igt_require(intel_perf);
+	intel_perf_load_perf_configs(intel_perf, fd);
+
+	igt_require(devid);
+	igt_list_for_each_entry(metric_set_iter, &intel_perf->metric_sets, link) {
+		if (!strcmp(metric_set_iter->symbol_name,
+			    IS_HASWELL(devid) ? "RenderBasic" : "TestOa")) {
+			metric_set = metric_set_iter;
+			break;
+		}
+	}
+	igt_require(metric_set);
+	igt_require(metric_set->perf_oa_metrics_set);
+	properties[3] = metric_set->perf_oa_metrics_set;
+	properties[5] = metric_set->perf_oa_format;
+
+	intel_perf_free(intel_perf);
+
+	igt_fork(child, 1) {
+		do {
+			int stream = igt_ioctl(fd, DRM_IOCTL_I915_PERF_OPEN, &param);
+
+			igt_assert_fd(stream);
+			close(stream);
+
+		} while (!READ_ONCE(*done));
+	}
+}
+
+/* Copied from tests/i915/gem_ctx_exec.c */
+static int exec(int fd, uint32_t handle, int ring, int ctx_id)
+{
+	struct drm_i915_gem_exec_object2 obj = { .handle = handle };
+	struct drm_i915_gem_execbuffer2 execbuf = {
+		.buffers_ptr = to_user_pointer(&obj),
+		.buffer_count = 1,
+		.flags = ring,
+	};
+
+	i915_execbuffer2_set_context_id(execbuf, ctx_id);
+
+	return __gem_execbuf(fd, &execbuf);
+}
+
+static void intel_context_first_pin_last_unpin_loop(int fd, uint64_t engine, int *done)
+{
+	/*
+	 * Use gem_create -> gem_write -> gem_execbuf -> gem_sync -> gem_close
+	 * as intel context first pin / last unpin intensive workload
+	 */
+	const uint32_t batch[2] = { 0, MI_BATCH_BUFFER_END };
+
+	fd = gem_reopen_driver(fd);
+
+	do {
+		uint32_t handle = gem_create(fd, 4096);
+
+		gem_write(fd, handle, 0, batch, sizeof(batch));
+		igt_assert_eq(exec(fd, handle, engine, 0), 0);
+
+		gem_sync(fd, handle);
+		gem_close(fd, handle);
+
+	} while (!READ_ONCE(*done));
+}
+
+static void test_remote_request(int fd, uint64_t engine, unsigned int timeout)
+{
+	int *done = mmap(0, 4096, PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
+
+	igt_assert(done != MAP_FAILED);
+
+	remote_request_workload(fd, done);
+
+	igt_fork(child, sysconf(_SC_NPROCESSORS_ONLN))
+		intel_context_first_pin_last_unpin_loop(fd, engine, done);
+
+	sleep(timeout);
+	*done = 1;
+	igt_waitchildren();
+	munmap(done, 4096);
+}
+
+igt_main
+{
+	int fd;
+
+	igt_fixture {
+		fd = drm_open_driver_render(DRIVER_INTEL);
+		igt_require_gem(fd);
+	}
+
+	igt_describe("Race intel_context_prepare_remote_request against intel_context_active_acquire/release");
+	igt_subtest_with_dynamic("remote-request") {
+		struct intel_execution_engine2 *e;
+
+		for_each_physical_engine(fd, e) {
+			if (e->class != I915_ENGINE_CLASS_RENDER)
+				continue;
+
+			igt_dynamic(e->name)
+				test_remote_request(fd, e->flags, 5);
+
+			/* We assume no need for all physical engines to be tested */
+			break;
+		}
+	}
+}
diff --git a/tests/meson.build b/tests/meson.build
index 6fb1bb86c9..5670712ae8 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -389,6 +389,14 @@ test_executables += executable('i915_pm_rc6_residency',
 	   install : true)
 test_list += 'i915_pm_rc6_residency'
 
+test_executables += executable('gem_barrier_race',
+	   join_paths('i915', 'gem_barrier_race.c'),
+	   dependencies : test_deps + [ lib_igt_i915_perf ],
+	   install_dir : libexecdir,
+	   install_rpath : libexecdir_rpathdir,
+	   install : true)
+test_list += 'gem_barrier_race'
+
 test_executables += executable('perf_pmu',
 	   join_paths('i915', 'perf_pmu.c'),
 	   dependencies : test_deps + [ lib_igt_perf ],
-- 
2.25.1