The PV drivers should be native. No need to load then. I believe they have been incorporated in most Xen kernels since 2.6.32.x I don't see why OEL 6 would be any different.... but I am not 100 percent sure if the OEL kernel fork has them or not. I don't see why they wouldn't.
Keep in mind that when running Oracle products on Oracle VM guests.... you must use PVM guests to get support. I haven't check all the requirements of every app but I know several that require PVM guests. RAC is only supported on PVM.