Re: [PATCH 4.19 041/361] x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation

Jiri Kosina
2018-11-21T18:21:37Z

On Wed, 21 Nov 2018, Tim Chen wrote:

> > Is it reverted in Linus's tree? If not, then anything that comes "later
> > on" will not apply here, right?
> >
> > I see the thread asking about this, but I got really conflicting
> > messages here, and now it's in all of the latest releases, and no
> > testing seems to have uncovered issues. Is it just a "slow down"
> > problem?
>
> Greg,
>
> It could be a big slow down in excess of 20% for some applications.
> And cross sibling Spectre v2 attack is quite hard to pull off.
>
> So till we have the accompanying patchset that only apply STIBP on processes
> that really need it instead of universally, it should be withheld from
> stable.

Agreed; it will be trivially reintroduced with the rest, once it's ready.
It's being built on top of that patch.

Thanks,

--
Jiri Kosina
SUSE Labs