
%     Registration             Xen 3.0 and the Art of Virtualization          
%  [2]Register/Submit Ian Pratt (ian.pratt@cl.cam.ac.uk)                      

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.'                                      


