Apply vast quantities of poison and not tell anyone to see if we fall
for the trap of using a stale RING_HEAD.
References: 42827350f75c ("drm/i915/gt: Avoid resetting ring->head outside of its timeline mutex")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Andi Shyti <andi.shyti@xxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gt/selftest_lrc.c | 75 ++++++++++++++++++++++++++
1 file changed, 75 insertions(+)
diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
index 82fa0712808e..1421dc2db7cf 100644
--- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
+++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
@@ -300,6 +300,80 @@ static int live_unlite_preempt(void *arg)
return live_unlite_restore(arg, I915_USER_PRIORITY(I915_PRIORITY_MAX));
}
+static int live_pin_rewind(void *arg)
+{
+ struct intel_gt *gt = arg;
+ struct intel_engine_cs *engine;
+ enum intel_engine_id id;
+ int err = 0;
+
+ /*
+ * We have to be careful not to trust intel_ring too much, for example
+ * ring->head is updated upon retire which is out of sync with pinning
+ * the context. Thus we cannot use ring->head to set CTX_RING_HEAD,
+ * or else we risk writing an older, stale value.
+ *
+ * To simulate this, let's apply a bit of deliberate sabotague.
+ */
+
+ for_each_engine(engine, gt, id) {
+ struct intel_context *ce;
+ struct i915_request *rq;
+ struct igt_live_test t;
+
+ if (igt_live_test_begin(&t, gt->i915, __func__, engine->name)) {
+ err = -EIO;
+ break;
+ }
+
+ ce = intel_context_create(engine);
+ if (IS_ERR(ce)) {
+ err = PTR_ERR(ce);
+ break;
+ }
+
+ err = intel_context_pin(ce);
+ if (err) {
+ intel_context_put(ce);
+ break;
+ }
+
+ /* Keep the context awake while we play games */
+ err = i915_active_acquire(&ce->active);
+ if (err) {
+ intel_context_unpin(ce);
+ intel_context_put(ce);
+ break;
+ }
+
+ /* Poison the head of the ring */
+ memset32(ce->ring->vaddr, STACK_MAGIC, 1024);
+ ce->ring->emit = 1024;
+ ce->ring->tail = 1024;
+
+ intel_context_unpin(ce);
+
+ /* Submit a simple nop request */
+ GEM_BUG_ON(intel_context_is_pinned(ce));
+ rq = intel_context_create_request(ce);
+ i915_active_release(&ce->active); /* e.g. async retire */
+ intel_context_put(ce);
+ if (IS_ERR(rq)) {
+ err = PTR_ERR(rq);
+ break;
+ }
+ i915_request_add(rq);
+
+ /* Expect not to hang! */
+ if (igt_live_test_end(&t)) {
+ err = -EIO;
+ break;
+ }
+ }
+
+ return err;
+}
+
static int live_hold_reset(void *arg)
{
struct intel_gt *gt = arg;
@@ -3616,6 +3690,7 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
SUBTEST(live_sanitycheck),
SUBTEST(live_unlite_switch),
SUBTEST(live_unlite_preempt),
+ SUBTEST(live_pin_rewind),
SUBTEST(live_hold_reset),
SUBTEST(live_error_interrupt),
SUBTEST(live_timeslice_preempt),
--
2.25.0
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