They’re fig leafing a hardware security bug in software. Obfuscation maneuvers drive down the risk of known ways to run exploits and that’s about it.
Looking at Apple’s description of it, I wonder what sent the world’s computer scientists to sleep with Rip Van Winkle.
Yeah, I totally agree. Actually the entire thread is very entertaining if you like watching software bake. Woodhouse also commented on HackerNews that he wasn't offended at all. Later in the thread Woodhouse also rebutted some of objections by pointing out that Linus was mistaken about the context. Also he doesn't work for Intel any more, but obviously has a close relationship still.
But I have to say it's very disturbing to think that that a microcode change could also silently invalidate the retpoline approach. Now I'm having paranoid fantasies of secret NSA microcode updates that render systems open kimono and we can't even tell the difference!
There has also been criticism that implies this an emergent property of bashing the X86 architecture into the VM server era. However I recall similar bugs from the mainframe and minicomputer eras, e.g. amusing race conditions that could allow executing code to exceed the scope of a virtual environment. So even purpose built vm hardware from past generations had similar problems.
Unfortunately many people think that computing is very deterministic and newtonian. But in fact it's built on quantum mechanics and full of Gödelian gotchas. Thus I predict there will always be exploits and since our technological civilization is completely dependent on computing, it will continue to be worth the trouble of sniffing these things out, no matter how obscure they may seem.