Re: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes

[Thomas Gleixner]

On Mon, 19 Nov 2018, Tim Chen wrote:
> On 11/19/2018 12:55 PM, Jiri Kosina wrote:
> > On Mon, 19 Nov 2018, Thomas Gleixner wrote:
> > 
> >>
> >> So before that change IBPB was usable without STIBP, now not longer. What's
> >> the rationale?
> >>
> >> This patch changes a gazillion things at once and is completely
> >> unreviewable.
> > 
> > The patchset actually ties together IBPB and STIBP pretty closely, which 
> > is IMO a good thing; there is no good reason why anone would want just one 
> > of those (or each in a different mode), at least before this magical 
> > coscheduling exists.
> > 
> > But I guess this fact should be documented somewhere.
> > 
> 
> Yes, it wouldn't make sense for having just one of those if a task
> is worried about attack from user space.
> 
> I'll document it.

What? IBPB makes tons of sense even without STIBP.

Thanks,

	tglx