This is a very serious paravirt_ops slowdown affecting the native kernel's performance to the tune of 5-10% in certain workloads.
It's been about 2 years ago that paravirt_ops went upstream, when you told us that something like this would never happen, that paravirt_ops is designed so flexibly that it will never hinder the native kernel - and if it does it will be easy to fix it. Now is the time to fulfill that promise.