Avi Kivity summarized the kvm patches bound for the 2.6.25 kernel:
"Changes include performance and scalability improvements, completion of the portability work (though no new architectures are supported with this submission), support for new hardware features, using general userspace memory for kvm (which enables swapping guest memory as well as sharing memory among guests), as well as the usual cleanups and incremental fixes."
The Kernel-based Virtual Machine project, kvm, was started in mid-2006, and has been part of the Linux kernel since the 2.6.20 release in February of 2007. The recent changes can be browsed with gitweb.