On Mon, 26 Nov 2018, Andrea Arcangeli wrote: > Hello, > > On Sun, Nov 25, 2018 at 11:28:59PM +0100, Thomas Gleixner wrote: > > Indeed. Just checked the documentation again, it's also not clear whether > > IBPB is required if STIPB is in use. > > I tried to ask this question too earlier: > > https://lkml.kernel.org/r/20181119234528.gj29...@redhat.com > > If the BTB mistraining in SECCOMP context with STIBP set in SPEC_CTRL, > can still influence the hyperthreading sibling after STIBP is cleared, > IBPB is needed before clearing STIBP. Otherwise it's not. Unless told > otherwise, it'd be safe to assume IBPB is needed in such case.
IBPB is still issued. I won't change that before we have clarification. But I doubt it's necessary. STIBP seems to be a rather big hammer. Thanks, tglx