[Intel-gfx] [PATCH] drm/i915/execlists: Verify we don't submit two identical tags

[Chris Wilson]

Check that we do not submit two contexts into ELSP with the same tag
[upper portion of the descriptor].

References: https://gitlab.freedesktop.org/drm/intel/-/issues/1793
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_lrc.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index d68a04f2a9d5..7226b6c915ec 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1621,6 +1621,7 @@ assert_pending_valid(const struct intel_engine_execlists *execlists,
 	struct i915_request * const *port, *rq;
 	struct intel_context *ce = NULL;
 	bool sentinel = false;
+	u32 tag = -1;
 
 	trace_ports(execlists, msg, execlists->pending);
 
@@ -1654,6 +1655,14 @@ assert_pending_valid(const struct intel_engine_execlists *execlists,
 		}
 		ce = rq->context;
 
+		if (tag == upper_32_bits(ce->lrc_desc)) {
+			GEM_TRACE_ERR("Dup tag:%x context:%llx in pending[%zd]\n",
+				      tag, ce->timeline->fence_context,
+				      port - execlists->pending);
+			return false;
+		}
+		tag = upper_32_bits(ce->lrc_desc);
+
 		/*
 		 * Sentinels are supposed to be lonely so they flush the
 		 * current exection off the HW. Check that they are the
-- 
2.20.1