Virgl just sends opengl commands to the host. And it also has to copy some buffers back and forth. So it won't be as fast as vfio. But, there is a new feature called VirtGPU DRM native contexts which eliminates some of this overhead and run at near native speeds. Unfortunately it's only implemented for adreno/msm GPUs for now.I think there is work on the way for Intel and AMD GPUs.