Mesa (master): iris/gen12: Work around push constant corruption on context switch.

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Module: Mesa
Branch: master
Commit: 20e2c7308f67412234847fd66fb330969ae30de0
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=20e2c7308f67412234847fd66fb330969ae30de0

Author: Francisco Jerez <currojerez at riseup.net>
Date:   Mon Mar 29 12:26:41 2021 -0700

iris/gen12: Work around push constant corruption on context switch.

This has been confirmed to fix sporadic graphics corruption on Gen12
platforms for a number of workloads (including Heaven, Valley and
CS:GO among others).  Corruption seems to occur during context switch
fairly consistently, but unfortunately this problem doesn't seem to be
documented.  Until the hardware team comes up with a better
workaround, fix the problem by reemitting constants at the beginning
of each batch.

No corruption has been observed so far in GL due to preemption,
however this is a possibility to keep in mind, it may be necessary to
disable preemption in addition to this patch in order to fully address
this problem (see also 81201e461772a06ed2).

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/4412
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/4454
Cc: mesa-stable
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

---

 src/gallium/drivers/iris/iris_state.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/gallium/drivers/iris/iris_state.c b/src/gallium/drivers/iris/iris_state.c
index 6ad47bff8a7..8b1efc35b20 100644
--- a/src/gallium/drivers/iris/iris_state.c
+++ b/src/gallium/drivers/iris/iris_state.c
@@ -6584,9 +6584,25 @@ iris_upload_render_state(struct iris_context *ice,
    iris_use_pinned_bo(batch, ice->state.binder.bo, false,
                       IRIS_DOMAIN_NONE);
 
+   if (!batch->contains_draw) {
+      if (GFX_VER == 12) {
+         /* Re-emit constants when starting a new batch buffer in order to
+          * work around push constant corruption on context switch.
+          *
+          * XXX - Provide hardware spec quotation when available.
+          */
+         ice->state.stage_dirty |= (IRIS_STAGE_DIRTY_CONSTANTS_VS  |
+                                    IRIS_STAGE_DIRTY_CONSTANTS_TCS |
+                                    IRIS_STAGE_DIRTY_CONSTANTS_TES |
+                                    IRIS_STAGE_DIRTY_CONSTANTS_GS  |
+                                    IRIS_STAGE_DIRTY_CONSTANTS_FS);
+      }
+      batch->contains_draw = true;
+   }
+
    if (!batch->contains_draw_with_next_seqno) {
       iris_restore_render_saved_bos(ice, batch, draw);
-      batch->contains_draw_with_next_seqno = batch->contains_draw = true;
+      batch->contains_draw_with_next_seqno = true;
    }
 
    iris_upload_dirty_render_state(ice, batch, draw);