On Mon, 17 Dec 2018, Barry Kauler wrote: > With CONFIG_SCHED_SMT disabled, CONFIG_RETPOLINE is not needed. This is not true. Retpoline protects also against a scenario where process A posions BTB for process B that gets scheduled afterwards on the same core, irrespective of SMT. > With CONFIG_SCHED_SMT enabled, then CONFIG_RETPOLINE is required for > security reasons. This is answered by the above as well. Retpoline is needed irrespective of SMT. > Enabling CONFIG_SCHED_SMT speeds up some operations, enabling > CONFIG_RETPOLINE slows it down again. There is no 'again', as those two things are not really dependent in any way. > End result, not much speed gain, far more complicated kernel. And therefore this is bogus :) -- Jiri Kosina SUSE Labs
