This guide can also be reached under the shortlink: http://bit.ly/vt-d which may be useful once you are in your VM.
Ensure you have hardware support for VT-d and VT-x. In your host bios, set 'init display first' to 'iGPU'. Otherwise your AMD gpu will get initialized.
Follow the guide at: https://bbs.archlinux.org/viewtopic.php?id=162768