It is not possible that GPU in your host server will work with the PCI passthrough. Virtual machines will be unable to use hypervisor GPU configured for PCI passthrough.
For GPU to work with PCI passthrough, it should be explicitly designed for this purpose, such as AMD MxGPU or NVIDIA Grid devices.
The main reason is that the specific usage described above violates the architecture design principle where two BIOSs can claim a single device.
Another important point is that GPU sharing is not possible between the hypervisor itself and VMs.
