anv: Enable MCS init with ISL_AUX_OP_AMBIGUATE

Up until now, we have been initializing MCS with fast clears. This is
mostly safe, but there's a corner case that can be an issue.

The issue is with a workaround for MCS that requires the sampler not see
any fast-cleared blocks for certain surfaces (14013111325). Even though
we have been initializing MCS with fast clears, we expect most
applications to be safe because we expect that they would only sample
the samples they've rendered to previously (and the render would've
removed the fast-cleared blocks). In other words we don't expect that
apps would transition from VK_IMAGE_LAYOUT_UNDEFINED to
VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL and start sampling immediately.

If an application took the unexpected path of sampling undefined
samples, it's possible they'd hit the issue described in the workaround.

Fix this corner case by using an ambiguate to initialize MCS.

Reviewed-by: Ivan Briano <ivan.briano@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22545>

diff --git a/src/intel/vulkan/anv_blorp.c b/src/intel/vulkan/anv_blorp.c
index 9e941fe..c596729 100644 (file)
--- a/src/intel/vulkan/anv_blorp.c
+++ b/src/intel/vulkan/anv_blorp.c
@@ -1349,8 +1349,10 @@ exec_mcs_op(struct anv_cmd_buffer *cmd_buffer,
       blorp_mcs_partial_resolve(batch, &surf, format,
                                 base_layer, layer_count);
       break;
-   case ISL_AUX_OP_FULL_RESOLVE:
    case ISL_AUX_OP_AMBIGUATE:
+      blorp_mcs_ambiguate(batch, &surf, base_layer, layer_count);
+      break;
+   case ISL_AUX_OP_FULL_RESOLVE:
    default:
       unreachable("Unsupported MCS operation");
    }

diff --git a/src/intel/vulkan/genX_cmd_buffer.c b/src/intel/vulkan/genX_cmd_buffer.c
index c15b62d..3fa7a61 100644 (file)
--- a/src/intel/vulkan/genX_cmd_buffer.c
+++ b/src/intel/vulkan/genX_cmd_buffer.c
@@ -1096,8 +1096,9 @@ transition_color_buffer(struct anv_cmd_buffer *cmd_buffer,
        * with the MCS referring to an invalid plane because not all bits of
        * the MCS value are actually used.  Even though we've never seen issues
        * in the wild, it's best to play it safe and initialize the MCS.  We
-       * can use a fast-clear for MCS because we only ever touch from render
-       * and texture (no image load store).
+       * could use a fast-clear for MCS because we only ever touch from render
+       * and texture (no image load store). However, due to WA 14013111325,
+       * we choose to ambiguate MCS as well.
        */
       if (image->vk.samples == 1) {
          for (uint32_t l = 0; l < level_count; l++) {
@@ -1144,7 +1145,7 @@ transition_color_buffer(struct anv_cmd_buffer *cmd_buffer,
                           image->planes[plane].primary_surface.isl.format,
                           ISL_SWIZZLE_IDENTITY,
                           aspect, base_layer, layer_count,
-                          ISL_AUX_OP_FAST_CLEAR, NULL, false);
+                          ISL_AUX_OP_AMBIGUATE, NULL, false);
       }
       return;
    }