i965: add identifier BO

A buffer added to all execbufs so that we can attribute a batch that
caused a hang to a particular driver.

v2: Reuse workaround BO

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3203>

1 files changed, 11 insertions, 1 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
index 96b7edd3f75..6cf3769c9a3 100644
--- a/src/mesa/drivers/dri/i965/brw_context.h
+++ b/src/mesa/drivers/dri/i965/brw_context.h
@@ -723,7 +723,17 @@ struct brw_context
 
    uint32_t hw_ctx;
 
-   /** BO for post-sync nonzero writes for gen6 workaround. */
+   /**
+    * BO for post-sync nonzero writes for gen6 workaround.
+    *
+    * This buffer also contains a marker + description of the driver. This
+    * buffer is added to all execbufs syscalls so that we can identify the
+    * driver that generated a hang by looking at the content of the buffer in
+    * the error state.
+    *
+    * Read/write should go at workaround_bo_offset in that buffer to avoid
+    * overriding the debug data.
+    */
    struct brw_bo *workaround_bo;
    uint32_t workaround_bo_offset;
    uint8_t pipe_controls_since_last_cs_stall;