> As for the log in the guest, how wold I copy and paste it ?

There's a stdio feature in qemu:

qemu-system-x86_64 -enable-kvm -hda Q -serial stdio -m 1G
                                      ^^^^^^^^^^^^^

So if you start qemu in a terminal, you can log into the guest from that terminal (at least when you pass (kernel-arguments '("console=ttyS0")) to the guest.

You can copy & paste normally from that terminal.