On Fri, Sep 8, 2017 at 2:43 PM, Samuel Pitoiset
<samuel.pitoi...@gmail.com> wrote:
> 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.
FWIW, this is invalid usage. The Vulkan spec states: "Descriptors in
each bound descriptor set, specified via vkCmdBindDescriptorSets, must
be
valid if they are statically used by the currently bound VkPipeline
object, specified via
vkCmdBindPipeline".
>
> 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 <pgriff...@valvesoftware.com>
> Signed-off-by: Samuel Pitoiset <samuel.pitoi...@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
>
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