[libvirt] How can I attach a network interface to KVM machine

[Anton Protopopov <aspsk2 gmail com>]

Hi.

When I am trying to attach an interface
    <interface type='bridge'>
      <mac address='52:54:00:db:1a:bb'/>
      <source bridge='mkvebr0'/>
    </interface>
libvirt reports me, that
     libvirt.libvirtError: this function is not supported by the hypervisor: this device type cannot be attached

Is there a legal way to attach a network interface to QEMU/KVM machine?