Last week, the release candidate of Linux 3.0 was released, after being approved by Linus Torvalds. The final release is expected in seven to nine weeks. From a virtualization point of view, the interesting news is that this release now contains full Xen guest and management domain support the Xen hypervisor in the mainline kernel, which means that from now on, each Linux kernel from 2.6.39 and onwards can serve as guest or host in the case of KVM, which was already included or as Domain 0(host) or Domain U(guest) in the case of Xen.
Until now, there was a substantial Linux kernel patch which had to be applied in order to transform a Linux OS into a Xen host, the paravirtualized drivers for running Linux as a Xen host, were already part of the codebase. Xen itself uses Linux as its Management OS.
Update: We were contacted by Todd Deshane, who corrected a couple of things, this mainly has to do with the fact that Xen is a so called Type-1 hypervisor, and therefore it can’t be included in Linux because it runs under the OS, where KVM is a Type-2 hypervisor which runs in the OS.