if (unlikely(head == tail))
return;
+ /*
+ * We will consume all events from HW, or at least pretend to.
+ *
+ * The sequence of events from the HW is deterministic, and derived
+ * from our writes to the ELSP, with a smidgen of variability for
+ * the arrival of the asynchronous requests wrt to the inflight
+ * execution. If the HW sends an event that does not correspond with
+ * the one we are expecting, we have to abandon all hope as we lose
+ * all tracking of what the engine is actually executing. We will
+ * only detect we are out of sequence with the HW when we get an
+ * 'impossible' event because we have already drained our own
+ * preemption/promotion queue. If this occurs, we know that we likely
+ * lost track of execution earlier and must unwind and restart, the
+ * simplest way is by stop processing the event queue and force the
+ * engine to reset.
+ */
+ execlists->csb_head = tail;
+ ENGINE_TRACE(engine, "cs-irq head=%d, tail=%d\n", head, tail);
+
/*
* Hopefully paired with a wmb() in HW!
*
* we perform the READ_ONCE(*csb_write).
*/
rmb();
-
- ENGINE_TRACE(engine, "cs-irq head=%d, tail=%d\n", head, tail);
do {
bool promote;
if (promote) {
struct i915_request * const *old = execlists->active;
+ if (GEM_WARN_ON(!*execlists->pending)) {
+ execlists->error_interrupt |= ERROR_CSB;
+ break;
+ }
+
ring_set_paused(engine, 0);
/* Point active to the new ELSP; prevent overwriting */
WRITE_ONCE(execlists->pending[0], NULL);
} else {
- GEM_BUG_ON(!*execlists->active);
+ if (GEM_WARN_ON(!*execlists->active)) {
+ execlists->error_interrupt |= ERROR_CSB;
+ break;
+ }
/* port0 completed, advanced to port1 */
trace_ports(execlists, "completed", execlists->active);
}
} while (head != tail);
- execlists->csb_head = head;
set_timeslice(engine);
/*
process_csb(engine);
if (unlikely(READ_ONCE(engine->execlists.error_interrupt))) {
+ const char *msg;
+
+ /* Generate the error message in priority wrt to the user! */
+ if (engine->execlists.error_interrupt & GENMASK(15, 0))
+ msg = "CS error"; /* thrown by a user payload */
+ else if (engine->execlists.error_interrupt & ERROR_CSB)
+ msg = "invalid CSB event";
+ else
+ msg = "internal error";
+
engine->execlists.error_interrupt = 0;
- if (ENGINE_READ(engine, RING_ESR)) /* confirm the error */
- execlists_reset(engine, "CS error");
+ execlists_reset(engine, msg);
}
if (!READ_ONCE(engine->execlists.pending[0]) || timeout) {