iris: 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>

src/gallium/drivers/iris/iris_batch.c

@@ -398,6 +398,11 @@ iris_batch_reset(struct iris_batch *batch)
 
    iris_cache_sets_clear(batch);
 
+   /* Always add the workaround BO, it contains a driver identifier at the
+    * beginning quite helpful to debug error states.
+    */
+   iris_use_pinned_bo(batch, screen->workaround_bo, false);
+
    iris_batch_maybe_noop(batch);
 }
 

src/gallium/drivers/iris/iris_screen.c

@@ -663,6 +663,27 @@ iris_detect_kernel_features(struct iris_screen *screen)
       screen->kernel_features |= KERNEL_HAS_WAIT_FOR_SUBMIT;
 }
 
+static bool
+iris_init_identifier_bo(struct iris_screen *screen)
+{
+   void *bo_map;
+
+   bo_map = iris_bo_map(NULL, screen->workaround_bo, MAP_READ | MAP_WRITE);
+   if (!bo_map)
+      return false;
+
+   screen->workaround_bo->kflags |= EXEC_OBJECT_CAPTURE;
+   screen->workaround_address = (struct iris_address) {
+      .bo = screen->workaround_bo,
+      .offset = ALIGN(
+         intel_debug_write_identifiers(bo_map, 4096, "Iris") + 8, 8),
+   };
+
+   iris_bo_unmap(screen->workaround_bo);
+
+   return true;
+}
+
 struct pipe_screen *
 iris_screen_create(int fd, const struct pipe_screen_config *config)
 {
@@ -718,10 +739,8 @@ iris_screen_create(int fd, const struct pipe_screen_config *config)
    if (!screen->workaround_bo)
       return NULL;
 
-   screen->workaround_address = (struct iris_address) {
-      .bo = screen->workaround_bo,
-      .offset = 0,
-   };
+   if (!iris_init_identifier_bo(screen))
+      return NULL;
 
    brw_process_intel_debug_variable();
 

src/gallium/drivers/iris/iris_screen.h

@@ -192,8 +192,12 @@ struct iris_screen {
    const struct gen_l3_config *l3_config_cs;
 
    /**
-    * A buffer containing nothing useful, for hardware workarounds that
-    * require scratch writes or reads from some unimportant memory.
+    * A buffer containing 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. It is also used for hardware workarounds that require scratch
+    * writes or reads from some unimportant memory. To avoid overriding the
+    * debug data, use the workaround_address field for workarounds.
     */
    struct iris_bo *workaround_bo;
    struct iris_address workaround_address;