This is never going to happen though. Not because Windows PV is not possible. Windows was ported to Xen PV in the distant past because Cambridge University had a Windows source license.
The reason it's not going to happen is because with the latest chips and 64 bit, hardware full virtualization is faster than paravirt. Paravirt on x86-64 can't use the i386 segmentation trick, because x86-64 (long mode) doesn't have full support for segment registers. So it has to use some other trick which is slower.
This is never going to happen though. Not because Windows PV is not possible. Windows was ported to Xen PV in the distant past because Cambridge University had a Windows source license.
The reason it's not going to happen is because with the latest chips and 64 bit, hardware full virtualization is faster than paravirt. Paravirt on x86-64 can't use the i386 segmentation trick, because x86-64 (long mode) doesn't have full support for segment registers. So it has to use some other trick which is slower.