Dmitry Osipenko of Collabora authored the merge request to relax the requirements around cross-device functionality so that this Venus driver can work under QEMU. Osipenko explained in the patch:
Cross-device is a virtio-gpu feature that enables sharing host blob dma-bufs with other virtio devices, like virtio-wl or virtio-video. This feature is mainly used by ChromeOS and not required if there is no dma-buf sharing. Venus has a hard requirement for the cross-device feature.
Qemu doesn't support cross-device. Relax cross-device feature requirement by making it optional, allowing Venus to work on Qemu.
Mesa's Venus driver is a VirtIO-GPU protocol for Vulkan command serialization that works with the Virglrenderer. This change will be part of next quarter's Mesa 24.2 release.