I've been messing around with the sources, and have been able to compile the virtio drivers, and succesfully load them into the kernel.
Everything loaded fine, and no errors where thrown, however, no virtio devices (ethernet, disk) actually work. Is this the same problem you've had before?
Why can't we compile a new zImage? I can't seem to find a tutorial anywhere? I'm guesing a simple "CROSS_COMPILE=... make zImage" won't work?
Good news!