Xen 3.0 and the Art of Virtualization

The Xen Virtual Machine Monitor will soon be undergoing its third major release, and is maturing into a stable, secure, and full-featured virtualization solution for Linux and other operating systems.

This new release of Xen supports a number of key new features, such as: SMP guest operating systems (as well as SMP hosts); x86_64 support (with further ports to ppc and ia-64 in progress); and support for Intel's VT-x virtualization extensions, which enable Xen/Linux to host `legacy' OSes such as Windows XP.

This paper reviews the Xen hypervisor ABI, and examines the Linux 2.6 port. We follow the evolution of memory virtualization techniques supported by Xen and show how the current implementation achieves excellent performance while minimising changes to Linux. We discuss the new support for SMP guest OSes, and show how modifications to Linux`s spinlock code allow us to optimise scheduling of virtual CPUs. Finally we look at how Linux IO devices may be virtualized and exported to other virtual machines using high-performance `device-channels'.