Re: [RFC PATCH v3 00/16] Core scheduling v3

From: Peter Zijlstra
Date: Wed Aug 28 2019 - 12:17:00 EST

On Wed, Aug 28, 2019 at 08:59:21AM -0700, Tim Chen wrote:
> On 8/27/19 2:50 PM, Peter Zijlstra wrote:
> > On Tue, Aug 27, 2019 at 10:14:17PM +0100, Matthew Garrett wrote:
> >> Apple have provided a sysctl that allows applications to indicate that
> >> specific threads should make use of core isolation while allowing
> >> the rest of the system to make use of SMT, and browsers (Safari, Firefox
> >> and Chrome, at least) are now making use of this. Trying to do something
> >> similar using cgroups seems a bit awkward. Would something like this be
> >> reasonable?
> >
> > Sure; like I wrote earlier; I only did the cgroup thing because I was
> > lazy and it was the easiest interface to hack on in a hurry.
> >
> > The rest of the ABI nonsense can 'trivially' be done later; if when we
> > decide to actually do this.
> >
> > And given MDS, I'm still not entirely convinced it all makes sense. If
> > it were just L1TF, then yes, but now...
> >
> For MDS, core-scheduler does prevent thread to thread
> attack between user space threads running on sibling CPU threads.
> Yes, it doesn't prevent the user to kernel attack from sibling
> which will require additional mitigation measure. However, it does
> block a major attack vector for MDS if HT is enabled.

I'm not sure what your argument is; the dike has two holes; you plug
one, you still drown.