From SemanticLab

Connect to the virtual machine

The safest way is to use vnc over an ssh tunnel. Log into the host-machine using ssh-tunneling and then connect to the guest using vnc (on your computer).

 ssh user@hostmaschine -L 5900:localhost:5900 

Afterwards enter at your machine:

 xvncviewer localhost

If you use multiple kvm instances on one host, assign different screens to them using the -vnc paramter:

 -vnc localhost:0
 -vnc localhost:1
 ...