Re: [PATCH 0/2] Backport IBPB on context switch to non-dumpable process

[Greg Kroah-Hartman]

On Fri, Mar 02, 2018 at 01:32:08PM -0800, Tim Chen wrote:
> Greg,
> 
> I will like to propose backporting "x86/speculation: Use Indirect Branch
> Prediction Barrier on context switch" from commit 18bf3c3e in upstream
> to 4.9 and 4.4 stable.  The patch has already been ported to 4.14 and
> 4.15 stable.  The patch needs mm context id that Andy added in commit
> f39681ed. I have lifted the mm context id change from Andy's upstream
> patch and included it here.

What does this patch "fix" in those older kernels?  Is this a
performance improvement or something else?

thanks,

greg k-h