Backends and Frontends

The basic architecture to facilitate paravirtualized device I/O is the backend/frontend architecture, illustrated in Figure 9.1. The backend driver runs in the privileged domain, and frontend drivers run in the unprivileged guests. In particular, the unprivileged guest issues a generic device request to its frontend driver. The frontend driver then communicates this request to the backend driver running in the privileged domain. The privileged domain then queues up the request and eventually issues the request to the actual underlying hardware.

Figure 9.1. The split-driver model