1. Install a full virtualized guest (eg. Gentoo, Debian)
2. After installation, make another small disk image, about 100M, for new /boot partition
3. Copy all the /boot content to the new virtual disk, this will be the full virtualized disk
4. Install paravirtualized I/O driver for block device and network device
5. Remake the initial ramdisk to include to PV I/O driver
6. Modify grub's menu.lst to use the PV device name,eg /dev/xvda1
7. Power off the virtualized guest
8. Edit the configuration file for the guest, change the root disk to tap:aio:/var/lib/xen/images/xxx.img instead of file:/var/lib/xen/images/xxx.img, and use xvda instead of hda
9. Add the small disk image as hda for boot up
10. Remove ioemu configuration of vnif network configuration
11. Boot it up, it should be running in full virtualized with PV I/O driver for better performance
