[libvirt] Hyervisor Features elements

Hello. Under Hypevisor Features for Domain elements, I noticed new features being added like <kvm> <hidden state='on'/> </kvm> Probably more will be added later I am guessing. -Is this a performance feature? -Can it also be applied to qemu only machine templates? (I don't use qemu only, but maintain templates for both that's the reason for asking)