Xen, VMware, and upstream merge
There's been a whole lot of articles about Xen, VMware, and the on going upstream merge effort. I just want to point out a couple things. The first is that a number of the articles are a bit misleading/speculative. The second is that there is much more common ground than the articles seem to suggest.
There are only a very small number of areas where VMI and Xen differ. Most of these differences are superficial. One thing to keep in mind is that neither set of patches is complete at all. Neither support SMP (fully), writable page tables, or management mode stuff. Both Zach and Chris tried to make this very clear in the initial posts.
There's a lot of work to do and a lot of hard problems to solve. In any case, even though neither set of patches is really complete, they are still way to big. Far too big to go into Linux all at once. Upstream merge is going to require a large number of small changes to incrementally add support for virtualization into Linux. That's what's going to be interesting over the next year. Once we figure out how to break things up, we'll start doing it.
The whole VMI vs. Xen thing is overrated. This is really just about what's the best interface for Linux. The actual underlying hypervisor doesn't really matter.