Source of vfio-pci-override-vga.sh is http://vfio.blogspot.com/2015/05/
This is a simple script that makes your system ready to run a KVM/QEMU virtual machine with its own GPU.
2 GPUs are needed. One of the GPUs can be an iGPU.
For a tutorial, visit: https://youtu.be/_9W18QN26-4