I think paravirtualization just means that there are drivers installed on the guest OS that make the interaction with hardware faster (perhaps reduce the number of copies and/or interrupts) by being cooperative.
Paravirtualization is just an extension of what you think is "full virtualization"
BTW, In case this article was misleading: I think Xen already has paravirt support that VPS providers already take advantage of.
Paravirtualization is not an extension of full virtualization. If anything, it's moving in the other direction - instead of virtualizing the parts of the system that are difficult or low performance when virtualized, you instead offer up a software device. In practice, this is generally your IO devices - without SR-IOV support, your IO is quite slow through an emulated device.
Paravirtual IO drivers, you have a front end driver in the guest, and a back end driver elsewhere. In Xen, this is a dom0 or stub domain that also includes the actual hardware driver. With Xen the front end and back end are just a shared memory segment using a ring buffer. KVM does things a bit differently, but the core concept is pretty similar.
SR-IOV you have a virtual function of the device that is passed through directly to the guest, eliminating the need for the PV IO drivers at all.
Paravirtualization is just an extension of what you think is "full virtualization"
BTW, In case this article was misleading: I think Xen already has paravirt support that VPS providers already take advantage of.