From Linus Torvalds <> Date Sun, 18 Nov 2018 12:36:08 -0800 Subject STIBP by default.. Revert? This was marked for stable, and honestly, nowhere in the discussion

did I see any mention of just *how* bad the performance impact of this

was.



When performance goes down by 50% on some loads, people need to start

asking themselves whether it was worth it. It's apparently better to

just disable SMT entirely, which is what security-conscious people do

anyway.



So why do that STIBP slow-down by default when the people who *really*

care already disabled SMT?



I think we should use the same logic as for L1TF: we default to

something that doesn't kill performance. Warn once about it, and let

the crazy people say "I'd rather take a 50% performance hit than

worry about a theoretical issue".



Linus



