Messages in this thread | | | Date | Mon, 26 Nov 2018 21:58:27 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode |
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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.GJ29258@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
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