Comment 3 for bug 1835839

Is the proposed patch backwards compatible (ie "old QEMU binary works with newer binfmt-misc registration" and "new QEMU binary works with older binfmt-misc registration") ? Because binfmt-misc stuff is whole-system but QEMU binaries are per-chroot, this kind of thing is awkward to change if we don't have back-compat (and typically the kernel semantics for these things often don't allow back-compat or any kind of migration-path to the new better setup :-( )