There is a problem when it comes to Qemu and migration: according to the mailinglist (see URL) migration fails between qemu-processes with different Seabios blob size which in turn depends on the toolchain used to build the roms. In larger setups (otherwise you are probably not interested in migration) one most likely has a binhost and can assure that all seabios blobs are built with the same toolchain (and thus have the same size). Nevertheless, this may cause headaches for people testing migration on Gentoo where the Seabios blob on the different machines was built with slightly different toolchains. Qemu should therefore depend on seabios[binary] to make sure a proper and identical Seabios blob is used everywhere.
We support it and we support migration. You're using your own overlay for qemu, which doesn't contain patches to support migration. This is one of the reasons I explained to you why 1.3.x isn't in Gentoo yet and unmasked. We take the stance that if you're not using the official ROMs supported (e.g. seabios[binary] and specific version of ipxe and vgabios) you are off the reservation and migration isn't supported nor is managed save. You will get a detailed error message when using the qemu ebuilds from the tree with the patchset I maintain that tell you what went wrong and why.
I also posted a thread on -dev about the fact that we're kind of hindered on using the prebuilt binaries, which might not fit Gentoo's policies kind of like Debian. You'll also notice its impossible to migrate between Fedora/RHEL and Debian of the same version due to the fact that they build their own roms and ship them as their own rpm/deb and the result is slightly different.
mark this as UPSTREAM ? or otherwise WORKSFORME ?
there is USE=binary for seabios and vgabios
