[libvirt] pvspinlock not accepted by libvirt

[bancfc at openmailbox.org]

Hello, I have been experimenting with the various options to squeeze out 
the last bit of performance gains so I added the <pvspinlock/> feature 
to my machines. However when saving the xml, libvirt complains and 
refuses to accept this tag. AFAIK this is a feature that can be used by 
KVM too. My guests are Linux of course. So what am I doing wrong here?