To simplify I/O, a separate domain can be used just to handle a device (perhaps running at a lower privilege level, but not at user level; e.g. level 1) - sometimes called a "driver domain".
(In Xen, "domain" == virtual machine)
- Driver domains run physical device drivers
- Regular guest domains use simple virtual drivers and communicate with driver domains or the standard domain (how?).
- Data is exchanged between guest and driver domains by page remapping; that is, no copying of data.