Calling vkGetPhysicalDeviceExternalSemaphoreProperties with VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_SYNC_FD_BIT parameter doesn’t return the VK_EXTERNAL_SEMAPHORE_FEATURE_IMPORTABLE_BIT flag.
The Vulkan Virgl driver (Venus) requires the VK_EXTERNAL_SEMAPHORE_FEATURE_IMPORTABLE_BIT flag to be able to run Vulkan graphical applications inside a KVM virtual machine:
src/virtio/vulkan/vn_physical_device.c · 49a47f187e1de48794a9641821ab1e952814969c · Mesa / mesa · GitLab and src/virtio/vulkan/vn_physical_device.c · 49a47f187e1de48794a9641821ab1e952814969c · Mesa / mesa · GitLab