tree c9805ac3a3f4de3eec699c1b2838aedf2e8799c8
parent c635acdfba3da241cf106580a90ceb9d2e043802
author Brian Ho <hob@chromium.org> 1626889760 +0000
committer Dawn LUCI CQ <dawn-scoped@luci-project-accounts.iam.gserviceaccount.com> 1626889760 +0000

Vulkan: Export VkSemaphores as SYNC_FDs instead of OPAQUE_FDs

For Dawn/Chrome interop, Chrome OS differs from Linux as it uses the
NativePixmap-based SharedImageBacking which stores image memory as
dma-bufs as opposed to opaque FDs. Likewise, for synchronization,
Chrome OS wants to use sync obj FDs as opposed to opaque FDs for
more flexibility.

The motivating difference between sync obj FDs and their opaque
counterparts is how they are created. As their name suggests, Opaque
FDs are mostly meaningless outside of the Vulkan ecosystem and must
be created from a VkDevice. As a result, Linux’s
ExternalVkImageBacking needs the Vulkan implementation to create the
FD even when accessing the SharedImage as a GL texture [1]. On Chrome
OS, however, we don’t guarantee Vulkan outside of Dawn, so we aren’t
able to create the opaque FD directly in Chrome.

Instead, we are always able to create sync objs (e.g. via a
fence [2]) which can be imported as VkSemaphores by simply changing
VkImportSemaphoreFdInfoKHR::handleType. Similarly, we can export
signal VkSemaphores as sync objs as well by updating
VkSemaphoreGetFdInfoKHR::handleType.

This CL adds conditional support for using SYNC_FDs on Chrome OS
when importing/exporting VkSemaphores and renames
SemaphoreServiceOpaqueFD accordingly. With this, we can properly
wait on reads/writes on a GL SharedImage representation before
accessing the same memory in Dawn [3].

[1] https://source.chromium.org/chromium/chromium/src/+/main:gpu/command_buffer/service/external_vk_image_gl_representation.cc;l=75;drc=f887797b3b527feabd5dfe9b3f2cc7f6deade49f
[2] https://source.chromium.org/chromium/chromium/src/+/main:gpu/command_buffer/service/shared_image_backing_gl_image.cc;l=681;drc=f887797b3b527feabd5dfe9b3f2cc7f6deade49f
[3] https://chromium-review.googlesource.com/c/chromium/src/+/3042460

BUG=b:172208313
Change-Id: I5357847fea40e41d1b982054e3573d363e17530c
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/59080
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Brian Ho <hob@chromium.org>