Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 28 Aug 2019 18:16:41 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Tim Chen <tim.c.chen@linux.intel.com>
Cc:     Matthew Garrett <mjg59@srcf.ucam.org>,
        Vineeth Remanan Pillai <vpillai@digitalocean.com>,
        Nishanth Aravamudan <naravamudan@digitalocean.com>,
        Julien Desfossez <jdesfossez@digitalocean.com>,
        mingo@kernel.org, tglx@linutronix.de, pjt@google.com,
        torvalds@linux-foundation.org, linux-kernel@vger.kernel.org,
        subhra.mazumdar@oracle.com, fweisbec@gmail.com,
        keescook@chromium.org, kerrnel@google.com,
        Phil Auld <pauld@redhat.com>, Aaron Lu <aaron.lwe@gmail.com>,
        Aubrey Li <aubrey.intel@gmail.com>,
        Valentin Schneider <valentin.schneider@arm.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [RFC PATCH v3 00/16] Core scheduling v3
Message-ID: <20190828161641.GJ2369@hirez.programming.kicks-ass.net>
References: <cover.1559129225.git.vpillai@digitalocean.com>
 <20190827211417.snpwgnhsu5t6u52y@srcf.ucam.org>
 <20190827215035.GH2332@hirez.programming.kicks-ass.net>
 <c005e75c-0966-63ca-bce7-05f545702688@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <c005e75c-0966-63ca-bce7-05f545702688@linux.intel.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.