On Fri, 31 May 2019, Andy Lutomirski wrote: > 2. Put the CPU all the way to sleep by sending it an INIT IPI. > > Version 2 seems very simple and robust. Is there a reason we can't do > it? We obviously don't want to do it for normal offline because it > might be a high-power state, but a cpu in the wait-for-SIPI state is > not going to exit that state all by itself. > > The patch to implement #2 should be short and sweet as long as we are > careful to only put genuine APs to sleep like this. The only downside > I can see is that an new kernel resuming and old kernel that was > booted with nosmt is going to waste power, but I don't think that's a > showstopper.
Well, if *that* is not an issue, than the original 3-liner that just forces them to 'hlt' [1] would be good enough as well. [1] https://lore.kernel.org/lkml/nycvar.yfh.7.76.1905291230130.1...@cbobk.fhfr.pm/ Thanks, -- Jiri Kosina SUSE Labs
