[Mesa-dev] [PATCH] radv: fix possible GPU hangs by zeroing the descriptor set

[Samuel Pitoiset]

when an application doesn't update the contents of a descriptor
set object, it contains random values and this might end up with
GPU VM faults if a shader tries to access that descriptor.

The Vulkan spec doesn't state what a driver should do when
a descriptor is unset, but zeroing the contents seems to be
a safe solution.

This fixes a GPU hang with Unity because a pixel shader tries
to access a descriptor that is unset by the application.
Though, maybe that descriptor load should have been DCE'd.

Cc: Pierre-Loup A. Griffais <pgriffais at valvesoftware.com>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
---
 src/amd/vulkan/radv_descriptor_set.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/amd/vulkan/radv_descriptor_set.c b/src/amd/vulkan/radv_descriptor_set.c
index 260bfbc12b..6271f9d06e 100644
--- a/src/amd/vulkan/radv_descriptor_set.c
+++ b/src/amd/vulkan/radv_descriptor_set.c
@@ -327,6 +327,12 @@ radv_descriptor_set_create(struct radv_device *device,
 			list_add(&set->vram_list, prev);
 		} else
 			return vk_error(VK_ERROR_OUT_OF_POOL_MEMORY_KHR);
+
+		/* Initialize the descriptor set to zero in order to avoid GPU
+		 * VM faults when an application doesn't update the contents of
+		 * a descriptor set object.
+		 */
+		memset(set->mapped_ptr, 0, layout->size);
 	}
 
 	for (unsigned i = 0; i < layout->binding_count; ++i) {
-- 
2.14.1