domiftune domain interface-device [[--config] [--live] | [--current]] [--inbound average,peak,burst] [--outbound average,peak,burst]
Set or query the domain's network interface's bandwidth parameters. interface-device can be the interface's target name (<target dev='name'/>), or the MAC address.
If no --inbound or --outbound is specified, this command will query and show the bandwidth settings. Otherwise, it will set the inbound or outbound bandwidth. average,peak,burst is the same as in command attach-interface.
If --live is specified, affect a running guest. If --config is specified, affect the next boot of a persistent guest. If --current is specified, affect the current guest state. Both --live and --current flags may be given, but --current is exclusive. If no flag is specified, behavior is different depending on hypervisor.
I'm gonna try it.