[libvirt] XML for the "boot=on" option

Hi, there, In order to install windows 2008 using the virtio driver, I had to modify the KVM command to include the boot=on option like: -drive file=<path>/virtioWin08.raw,if=virtio,index=0,boot=on However, I haven't been able to find a corresponding libvirt XML element that can enable this "boot=on" option. Is there a way to do this? Thanks a lot. -- Shi Jin, PhD