iris: Disable aux as needed in iris_flush_resource

Disable compression in iris_flush_resource if the resource lacks a
modifier. When a caller wants to prepare such a resource for sharing
(via eglCreateImage for example), this change enables all reference
holders to access the resource in a common manner - without compression.

This fixes misrendering with 3D-accelerated qemu. A piglit test which
reproduces qemu's behavior, ext_image_dma_buf_import-export-tex, is also
enabled to pass.

Cc: mesa-stable
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/2678
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8663>
(cherry picked from commit 40d6b92de9)

.pick_status.json

@@ -346,7 +346,7 @@
         "description": "iris: Disable aux as needed in iris_flush_resource",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "master_sha": null,
         "because_sha": null
     },

src/gallium/drivers/iris/iris_resource.c

@@ -1165,6 +1165,20 @@ iris_flush_resource(struct pipe_context *ctx, struct pipe_resource *resource)
                                 0, INTEL_REMAINING_LAYERS,
                                 mod ? mod->aux_usage : ISL_AUX_USAGE_NONE,
                                 mod ? mod->supports_clear_color : false);
+
+   if (!res->mod_info && res->aux.usage != ISL_AUX_USAGE_NONE) {
+      /* flush_resource may be used to prepare an image for sharing external
+       * to the driver (e.g. via eglCreateImage). To account for this, make
+       * sure to get rid of any compression that a consumer wouldn't know how
+       * to handle.
+       */
+      for (int i = 0; i < IRIS_BATCH_COUNT; i++) {
+         if (iris_batch_references(&ice->batches[i], res->bo))
+            iris_batch_flush(&ice->batches[i]);
+      }
+
+      iris_resource_disable_aux(res);
+   }
 }
 
 static void