2.5. Communicating with Shared Memory

The UNIX signal model is good for delivering events quickly, but it is not enough to build a general purpose interprocess communication (IPC) mechanism. Other mechanisms, such as pipes, message queues, and shared memory exist for this purpose. Because it is possible to implement mechanisms like pipes and message queues solely from shared memory, it is not necessary for Xen—a minimalist hypervisor—to provide anything except shared memory.

Xen supports two basic interdomain operations on memory pages: sharing and transferring. A shared page is similar to a page shared with POSIX shared memory; both domains are able to access the contents. Page transfer is a coarse-grained message-passing mechanism.