On 11/18/2018 02:36 PM, Linus Torvalds wrote: > On Sun, Nov 18, 2018 at 2:17 PM Jiri Kosina <jikos@xxxxxxxxxx> wrote: >> Which gets us back to Tim's fixup patch. Do you still prefer the revert, >> given the existence of that? > > I don't think the code needs to be reverted, but the *behavior* of > just unconditionally enabling STIBP needs to be reverted. Yes, in the patchset I proposed on top of Jiri's, the default will be enabling STIBP only for tasks that ask for STIBP via prctl or those that are non-dumpable, like sshd. > > Because it was clearly way more expensive than people were told. I did realize the performance implications of making STIBP on for all tasks. Here's to recap performance impact of STIBP when I posted my patchset: "...leaving STIBP on all the time is expensive for certain applications that have frequent indirect branches. One such application is perlbench in the SpecInt Rate 2006 test suite which shows a 21% reduction in throughput." I think if we include Jiri's patchset for 4.20, we should have my patchset also included to avoid the performance impact on regular tasks but still allow admin and applications to turn on STIBP if needed. Thanks. Tim
