[Mesa-dev] [PATCH 01/17] i965/miptree: Fix handling of uninitialized MCS buffers

[Tapani Pälli]

Hi Nanley;

On 05/03/2018 10:03 PM, Nanley Chery wrote:
> Before this patch, if we failed to initialize an MCS buffer, we'd
> end up in a state in which the miptree thinks it has an MCS buffer,
> but doesn't. We also leaked the clear_color_bo if it existed.
> 
> With this patch, we now free the miptree aux buffer resources and let
> intel_miptree_alloc_mcs() know that the MCS buffer no longer exists.

I triggered this by forcing the failure (by inserting 1 instead 
unlikely(map ==NULL) to mcs buffer map condition) and following happens 
currently:

--- 8< ---
Failed to map mcs buffer into GTT
deqp-egl: ../src/intel/blorp/blorp_clear.c:313: blorp_fast_clear: 
Assertion `start_layer + num_layers <= 
MAX2(surf->aux_surf->logical_level0_px.depth >> level, 
surf->aux_surf->logical_level0_px.array_len)' failed.
Aborted (core dumped)
--- 8< ---

However even with this fix it seems we will end up in same or similar 
case (segfault happening in do_single_blorp_clear):

--- 8< ---
Failed to map mcs buffer into GTT
Segmentation fault (core dumped)
--- 8< ---

Test case used was:
    dEQP-EGL.functional.color_clears.single_context.gles2.rgba8888_window


Are we expected to survive without mcs?


> Cc: <mesa-stable at lists.freedesktop.org>
> ---
>   src/mesa/drivers/dri/i965/intel_mipmap_tree.c | 14 +++++++-------
>   1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> index b9a564552df..377efae32c9 100644
> --- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> +++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> @@ -1658,7 +1658,7 @@ intel_miptree_copy_teximage(struct brw_context *brw,
>      intel_obj->needs_validate = true;
>   }
>   
> -static void
> +static bool
>   intel_miptree_init_mcs(struct brw_context *brw,
>                          struct intel_mipmap_tree *mt,
>                          int init_value)
> @@ -1678,13 +1678,14 @@ intel_miptree_init_mcs(struct brw_context *brw,
>      void *map = brw_bo_map(brw, mt->aux_buf->bo, MAP_WRITE | MAP_RAW);
>      if (unlikely(map == NULL)) {
>         fprintf(stderr, "Failed to map mcs buffer into GTT\n");
> -      brw_bo_unreference(mt->aux_buf->bo);
> -      free(mt->aux_buf);
> -      return;
> +      intel_miptree_aux_buffer_free(mt->aux_buf);
> +      mt->aux_buf = NULL;
> +      return false;
>      }
>      void *data = map;
>      memset(data, init_value, mt->aux_buf->size);
>      brw_bo_unmap(mt->aux_buf->bo);
> +   return true;
>   }
>   
>   static struct intel_miptree_aux_buffer *
> @@ -1764,15 +1765,14 @@ intel_miptree_alloc_mcs(struct brw_context *brw,
>      const uint32_t alloc_flags = 0;
>      mt->aux_buf = intel_alloc_aux_buffer(brw, "mcs-miptree",
>                                           &temp_mcs_surf, alloc_flags, mt);
> -   if (!mt->aux_buf) {
> +   if (!mt->aux_buf ||
> +       !intel_miptree_init_mcs(brw, mt, 0xFF)) {
>         free(aux_state);
>         return false;
>      }
>   
>      mt->aux_state = aux_state;
>   
> -   intel_miptree_init_mcs(brw, mt, 0xFF);
> -
>      return true;
>   }
>   
>