qemu upstream commit 4b3a4f2d458ca5a7c6c16ac36a8d9ac22cc253d6 fixes an annoying segfault due to a potential null pointer dereference. it seems to always trigger when using virtio-9p to share a tree on the host filesystem.
i've added that to 2.5.0-r3 now https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=5ffdef327ca2184359715dccb7a74373ef3d6a78