I guess he is talking about the disk device not the network one.
You can edit the .conf file of the VM and change idex to virtiox for the disk you want ( after a total shutdown
of the VM changes takes effect )
However you should note that this will change from /dev/sda to /dev/vda so any references to this naming
has to be changed inside your VM. For a test you can do this and boot in single mode to see if it mounts rootfs
properly..