I have a problem about using libvirt now. 

There is a feather about HVM driver ---PV_on_HVM_drivers,  in xm configure, using flag xen_platform_pci can control the feather, but in libvirt  I can not find the flags to use pv-on-HVM drivers. So I want to find the answer if the libvirt can control the modules using xml file? thanks a lot.