[Mesa-stable] [Mesa-dev] [PATCH 1/3] anv/descriptor_set: Fix binding partly undefined descriptor sets

[Jason Ekstrand]

On Wed, Jul 13, 2016 at 3:34 PM, Nanley Chery <nanleychery at gmail.com> wrote:

> Section 13.2.3. of the Vulkan spec requires that implementations be able to
> bind sparsely-defined Descriptor Sets without any errors or exceptions.
>
> When binding a descriptor set that contains a dynamic buffer
> binding/descriptor,
> the driver attempts to dereference the descriptor's buffer_view field if
> it is
> non-NULL. It currently segfaults on undefined descriptors as this field is
> never
> zero-initialized. Zero undefined descriptors to avoid segfaulting. This
> solution was suggested by Jason Ekstrand.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96850
> Cc: 12.0 <mesa-stable at lists.freedesktop.org>
> Signed-off-by: Nanley Chery <nanley.g.chery at intel.com>
> ---
>  src/intel/vulkan/anv_descriptor_set.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/src/intel/vulkan/anv_descriptor_set.c
> b/src/intel/vulkan/anv_descriptor_set.c
> index 448ae0e..f06d2e4 100644
> --- a/src/intel/vulkan/anv_descriptor_set.c
> +++ b/src/intel/vulkan/anv_descriptor_set.c
> @@ -412,8 +412,8 @@ anv_descriptor_set_create(struct anv_device *device,
>     /* Go through and fill out immutable samplers if we have any */
>     struct anv_descriptor *desc = set->descriptors;
>     for (uint32_t b = 0; b < layout->binding_count; b++) {
> -      if (layout->binding[b].immutable_samplers) {
> -         for (uint32_t i = 0; i < layout->binding[b].array_size; i++) {
> +      for (uint32_t i = 0; i < layout->binding[b].array_size; i++) {
> +         if (layout->binding[b].immutable_samplers) {
>              /* The type will get changed to COMBINED_IMAGE_SAMPLER in
>               * UpdateDescriptorSets if needed.  However, if the descriptor
>               * set has an immutable sampler, UpdateDescriptorSets may
> never
> @@ -423,6 +423,11 @@ anv_descriptor_set_create(struct anv_device *device,
>                 .type = VK_DESCRIPTOR_TYPE_SAMPLER,
>                 .sampler = layout->binding[b].immutable_samplers[i],
>              };
> +         } else {
> +            /* By defining the descriptors to be zero now, we can later
> verify that
> +             * the descriptor has not been populated with user data.
> +             */
> +            zero(desc[i]);
>

I think I'd rather just zero the whole thing rather than one descriptor at
a time.  Given that the memset will use vectorized memory operations, it's
almost certainly just as fast if not faster to do so and I think it's more
clear.

--Jason


>           }
>        }
>        desc += layout->binding[b].array_size;
> --
> 2.9.0
>
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