One other thing I'm noticing -- the GUI installation program does not recognize the "virtio" disks used for KVM. While the installation program works if I set up the IDE disks available with KVM, that's a separate option. Even then, it's as if the virtio KVM disks aren't even there.
FWIW, while you may be correct about a lack of a driver, the KVM that I'm using (on RHEL 6) does not support paravirtualization. In any case, I've also tried the qemu-kvm-sparc package without success.