If you ever start up Parallels Desktop on a Mac Pro (or any Mac), and get an error/warning saying that optimization is being turn off because hardward/virtualization technology is disabled in the firmware, have no fear.
Simply exit out of Parallels Desktop, put your Mac Pro (or any Mac) to sleep, wake it back up, start up Parallels Desktop, and you are good to go until you restart the Mac (which, hopefully, is not too often). At that point, putting it to sleep again, would fix this until the next restart.
I’ve seen this mentioned several times on various forums. Apparently it’s an error that only Apple can fix with some kind of firmware upgrade. I’m not sure why sleeping the Mac Pro fixes this, but it does.