از طریق ssh was wondering how to connect to a SSH server running on a guest computer with QEmu. There wasn't really an obvious way to do that, until I looked at the help text a bit closer:
-redir [tcp|udp]:host-port:[guest-host]:guest-port
redirect TCP or UDP connections from host to guest [-net user]
So starting QEmu with the following parameters did the trick:
$ qemu ... -redir tcp:2222::22 &
Now connecting is a piece of cake:
$ ssh -p 2222 localhost