krtld: failed to open '/platform/i86xpv/kernel/amd64/unix'
Then you've probably given the wrong combination of unix and microroot.
By the way, in my previous entry, I mentioned we were working on upstreaming our virt-install changes. During the Xen 3.3 work (more on which soon), I updated to the latest versions and got the needed parts into the upstream version. We've still some ZFS changes to push, but if you're running a recent enough version of Xen on Linux, you may well be able to use virt-install and skip all this horrible hacking!