Something very useful - find the name of the virtual NIC on the host, and run a magical tc command:
# ip l | grep vnet
47: vnet1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc htb master virbr0 state UNKNOWN mode DEFAULT group default qlen 1000
# tc class change dev vnet1 classid 1:1 root htb rate 100Mbit
Here is an example of me using it to choke Steam: