On 11/26/2018 01:52 PM, Lendacky, Thomas wrote: > On 11/26/2018 02:58 PM, Thomas Gleixner wrote: >> 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. > > From an AMD standpoint, we recommend still issuing the IBPB. >
Yes, our Intel HW architect also recommends still issuing the IBPB. We're now getting approval for some additional explanations of STIBP. Those additional explanations should help clarify things. Thanks. Tim
