WRT to LLVM and Linux, at the time that I spoke at the conference, Xen/KVM weren't working, but they're in much better shape now. You can't build a vanilla kernel, yes, but an allmodconfig works. E.g., you could build the default config of, say, the Debian kernel. Source code is available at github.com/lll-project. We're putting together .deb packages, soon, as well.