[libvirt] how to expose missing libxl APIs in xml?

libvirt lacks support for various API interfaces provided by libxl. There is probably no list to track the items not supported by libvirt. Where should such list be maintained, in libvirt.git? The specific case I have right now is this member of libxl_domain_build_info: tools/libxl/libxl_types.idl:483: ("max_grant_frames", uint32, {'init_val': 'LIBXL_MAX_GRANT_FRAMES_DEFAULT'}), How should this be exposed in the guest xml? Olaf