I think I just managed to passthrough my nVidia GPU which has muxless architecture. So had to passthrough both vGPU and dGPU. Somehow its working getting more then 100 FPS using heave unigine. But the VM display is tearing a bit. Seems like looking glass can help here instead of spice display server, according to my common sense. But commonly, I found looking glass is installed in muxless setup, copying frame buffer from gpu memory. I was wondering if it will be able to copy frame buffer from vGPU (GVT-g), since dGPU has to go through iGPU in muxless setup.