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

Greg Kroah-Hartman
2018-11-21T18:15:17Z

On Wed, Nov 21, 2018 at 09:47:48AM -0800, Tim Chen wrote:
> On 11/21/2018 05:56 AM, Greg Kroah-Hartman wrote:
> > On Wed, Nov 21, 2018 at 02:21:15PM +0100, Jiri Kosina wrote:
> >> On Sun, 11 Nov 2018, Greg Kroah-Hartman wrote:
> >>
> >>> 4.19-stable review patch. If anyone has any objections, please let me know.
> >>
> >> Greg, please drop this patch from all -stable for now. Version that
> >> wouldn't have such performance impact is being worked on.
> >
> > 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.

Ok, now reverted, thanks.

greg k-h