The distinction I was trying to make was the above commenters thinking that the kernel is now checking page permissions instead of the CPU doing it - IE. Doing

The distinction I was trying to make was the above commenters thinking that the kernel is now checking page permissions instead of the CPU doing it - IE. Doing privileged checks in software. That's not what's happening, the kernel is just unmapping itself when usercode is run so the kernel can't be seen at all. Then the privileged checks (which are now broken) don't matter because there is no kernel memory to read. All your points are right though. Page access times will in general be slower because of all the extra TLB flushes, leading to more TLB misses when accessing memory.