The dust has yet to settle from the recent announcements that Linux will switch it's process scheduler, but we're already bombarded with interesting news that the upcoming 2.6.23 kernel release will also feature no less than two new virtualization frameworks.

The smaller one is called lguest, "a simple hypervisor for Linux on Linux. Unlike kvm it doesn't need VT/SVM hardware. Unlike Xen it's simply 'modprobe and go'. Unlike both, it's 5000 lines and self-contained.". The lguest patches are written and maintained by Rusty Russell who explains, "lguest is designed to be a minimal hypervisor for the Linux kernel, for Linux developers and users to experiment with virtualization with the minimum of complexity. Nonetheless, it should have sufficient features to make it useful for specific tasks, and, of course, you are encouraged to fork and enhance it.". (commit)

The other one, merged at almost the same time, is popular Xen, "a virtual machine monitor (VMM) for x86-compatible computers. Xen can securely execute multiple virtual machines, each running its own OS, on a single physical system with close-to-native performance.". The project was originally started as a research project at the University of Cambridge, today it is one of the most popular virtualization frameworks in the world, also backed up with commercial support from XenSource. (commit)

A little bit of history: in 2.6.20 Linus merged Kernel-based Virtual Machine (kvm), and the initial support for paravirtualization (which later got improved in 2.6.21 to full featured Virtual Machine Interface (VMI)).

Feel free to share your opinion, but if you ask me, kernel development has never been faster and more interesting than these days. I just hope 2.6 series will keep it's stability after all those new code gets in, but Linus has stated many times that he considers odd numbered kernels to include more "unstable" material, where even ones try to stabilize a bit. Which, if true, would give you some incentive to wait for 2.6.24, if you prefer stability over (r)evolution. :)

Learn more about virtualization on Linux.