VGA Passtrough > VM Script

Question

I´m using Xubuntu 15.04 and i try to create a script with the following points.

1. Run your system normally
2. Use dGPU via DRI_PRIME=1
3. Stop X server
4. Unload dGPU driver
5. Pass GPU to VFIO
6. Run X server and VM
7. Pass GPU to VM
8. Stop VM
9. Stop X server
10. Unbind GPU from VFIO
11. Load driver
12. Start X server
13. Use dGPU via DRI_PRIME again

How its possible to include point 3 (Stop X server) and point 12 (Start X server)? Someone can help me?

Kind regards