The qemu-1.2.2-r1 backports tarball (qemu-kvm-1.2.0-9489a8c0.tar.xz) contains an empty directory qemu-kvm-1.2.0/patches and the actual patches directly in qemu-kvm-1.2.0/*.patch. The patches are applied using EPATCH_SOURCE="${S}/patches", which happily applies 0 patches. Compare "ebuild /path/to/qemu-1.2.2.ebuild prepare" to "ebuild /path/to/qemu-1.2.2-r1.ebuild prepare" to see what I mean. Net result is a mostly unpatched qemu-1.2.0. I'm considering masking the package temporarily as this seems like a bit of a large (and confusing) downgrade.
I've masked 1.2.2-r1.
Thanks for spotting that. I'll re-release the tarball and create -r2.
Should be in the tree. Give it a whirl.