[libvirt-users] <qemu:commandline> domain XML tag is not working?

Hi, I tried to enable virtio-blk data plane feature for VMs in my openstack environment, the hypervisor is ubuntu 14.04, libvirt 1.2.2 and QEMU 2.0. As nova doesn't support that parameter yet, I did belows 1. nova boot a VM with raw disk image. 2. nova stop the VM. 3. run "virsh edit <instance-id>" on the hyprvisor node, and adding below into instance xml just before </domain>. However, the <qemu:commandline> part is ignored and not saved after closing virsh edit, seems that libvirt rejected these changes. Is there any XML syntax error here? Or libvirt doesn't support <qemu:commandline> tag? <qemu:commandline> <qemu:arg value='-set'/> <qemu:arg value='device.drive-virtio-disk0.x-data-plane=on'/> </qemu:commandline> Regards, Chengyuan.