Last week, Linux kernel father Linus Torvalds announced the release of version 3.0 of the Linux Kernel. This release does not introduce any binary incompatibility neither major changes.
Virtualization.info already covered the 3.0 release with regards to the integration of both KVM and Xen in the mainline tree of the kernel sources.
For Xen, this release means no more patches to the Linux kernel in order to make Linux virtual machines run as guests. In fact, Xen is a Type-1 hypervisor, so hosted operating systems need to have proper support built-in to run smoothly on virtualized hardware. Until now, a substantial Linux kernel patch had to be applied in order to add this support in the linux guest.
KVM, instead, is a Type-2 hypervisor, which runs itself on top of and operating system.
A full list of Xen related changes in the Linux kernel can be found here on the Xen wiki.