The npiv info could be loaded from the conf file during the boot of a
vm. The entry should be in the format of

npiv = [ 'vpwwn:vnwwn:autoattach:ppwwn,...', ...]
vpwwn --virtual port wwn, should be an string of 64-bit unsigned integer
vnwwn -- virtual node wwn
ppwwn ? physical port wwn
auto_attach ? '0' or '1'