tree 3e71b18560289540eab3baa74bdaf966560b0744
parent 683928a6faf9d3b2d9f864b2c22d1d9a86d74017
author Chip Davis <cdavis@codeweavers.com> 1586290909 -0500
committer Chip Davis <cdavis@codeweavers.com> 1586979074 -0500

MVKBuffer: Support texel buffers in "host-coherent" memory on Mac.

According to the Vulkan spec:

> * If `buffer` is a `VkBuffer` not created with the
>   `VK_BUFFER_CREATE_SPARSE_BINDING_BIT` bit set[...] then the
>   `memoryTypeBits` member always contains at least one bit set
>   corresponding to a `VkMemoryType` with a `propertyFlags` that has
>   both the `VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT` bit and the
>   `VK_MEMORY_PROPERTY_HOST_COHERENT_BIT` bit set. In other words,
>   mappable coherent memory **can** always be attached to these
>   objects.

There is no exception for texel buffers. Even though desktop Metal
disallows textures in shared memory, even linear textures created from a
buffer, we have to advertise host-coherent memory for texel buffers.
Some applications actually depend on this behavior, so it's not just a
theoretical concern.

To support host-coherent texel buffers, we implicitly create a managed
buffer and copy data between the device memory and the managed buffer,
just like for a linear image.

Signed-off-by: Chip Davis <cdavis@codeweavers.com>