BigSur (openCore) can't start with only VFIO-GPU (bootable with additional QXL)

Hi all, Here is my situation:

I'm running an AMD3900x + Nvidia GT710 GPU with ClearLinux as Host OS, BigSur - OpenCore as KVM guest. Even with some experience in hackintosh/kvm/vfio with Catalina, i'm quite new in OpenCore. I followed this article as starting point and get bigsur running without VFIO-GPU-PT firstly.

After start bigsur with QXL (emulated GPU) on host OS, i switched to VFIO-GPU-PT like what I've done with Catalina (my catalina is with Clover not OC). If the VM only has one GPU-PT (without additional QXL GPU), it won't starts. The `sudo virsh start myBigSur` succeeded, and `sudo virsh list` shows it's running, but screen is blank and VM is not discoverable on network by other Mac.

The QXL line determines if the guest is bootable is this

<video> <model type="qxl" ram="65536" vram="65536" vgamem="16384" heads="1" primary="yes"/> </video> 

When I keep this emulated QXL, the guest OS will show two GPUs and two displays (proof by ScreenShare from my MBP). In this case, the GT710 GPU just works like how it's working in Catalina (without QXL, only one GPU and one physical display).

I guess there is something in OpenCore configuration or NVRAM. Could you help me pointing where I should look. Thanks alot.