The basic of concept of separate page tables for user land and kernel is well known. It's how sparc64 is implemented from the very beginning. But knowing this is the objective is almost meaningless to actually accomplishing it. The devil is in the details, of which there are many, and they aren't necessarily shared.

I mean... if you want to be really pedantic, there are technically some silver linings. But the disadvantages outweigh that stretch of a silver lining by so many orders of magnitude that it's almost insulting.

It would be like telling a mugging victim: "Hey, at least now you can justify buying a new purse!"

If you're downvoting, I'd love to know why.

I asked an honest question, made no statements to which I can imagine people disagreeing with, and went out of my way to make sure it couldn't be taken in a bad way...

In this case not really. The OpenBSD impl. looks very costly and is still incomplete. You may wonder why they didn't add a benchmark number to the commit. I suspect there's a lot of pagetable cache trashing going on, with two complete separate pages.

See https://news.ycombinator.com/item?id=16441341