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From: Peter Zijlstra <peterz@infradead.org>
To: Alexander Graf <graf@amazon.com>
Cc: Joel Fernandes <joel@joelfernandes.org>,
	vpillai <vpillai@digitalocean.com>,
	Nishanth Aravamudan <naravamudan@digitalocean.com>,
	Julien Desfossez <jdesfossez@digitalocean.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	mingo@kernel.org, tglx@linutronix.de, pjt@google.com,
	torvalds@linux-foundation.org, linux-kernel@vger.kernel.org,
	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>,
	aubrey.li@linux.intel.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 00/13] Core scheduling v5
Date: Fri, 17 Apr 2020 15:08:25 +0200	[thread overview]
Message-ID: <20200417130825.GE20730@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <79529592-5d60-2a41-fbb6-4a5f8279f998@amazon.com>

On Fri, Apr 17, 2020 at 02:35:38PM +0200, Alexander Graf wrote:
> On 17.04.20 13:12, Peter Zijlstra wrote:

> If we first kick out the sibling HT for every #VMEXIT, performance will be
> abysmal, no?

I've been given to understand that people serious about virt try really
hard to avoid VMEXIT.


> > That doesn't completely solve things I think. Even if you run all
> > untrusted tasks as core exclusive, you still have a problem of them vs
> > interrupts on the other sibling.
> >
> > You need to somehow arrange all interrupts to the core happen on the
> > same sibling that runs your untrusted task, such that the VERW on
> > return-to-userspace works as intended.
> > 
> > I suppose you can try and play funny games with interrupt routing tied
> > to the force-idle state, but I'm dreading what that'll look like. Or
> > were you going to handle this from your irq_enter() thing too?
> 
> I'm not sure I follow. We have thread local interrupts (timers, IPIs) and
> device interrupts (network, block, etc).
> 
> Thread local ones shouldn't transfer too much knowledge, so I'd be inclined
> to say we can just ignore that attack vector.
> 
> Device interrupts we can easily route to HT0. If we now make "core
> exclusive" a synonym for "always run on HT0", we can guarantee that they
> always land on the same CPU, no?
> 
> Then you don't need to hook into any idle state tracking, because you always
> know which CPU the "safe" one to both schedule tasks and route interrupts to
> is.

That would come apart most mighty when someone does an explicit
sched_setaffinity() for !HT0.

While that might work for some relatively contained systems like
chromeos, it will not work in general I think.

  reply	other threads:[~2020-04-17 13:09 UTC|newest]

Thread overview: 115+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-04 16:59 [RFC PATCH 00/13] Core scheduling v5 vpillai
2020-03-04 16:59 ` [RFC PATCH 01/13] sched: Wrap rq::lock access vpillai
2020-03-04 16:59 ` [RFC PATCH 02/13] sched: Introduce sched_class::pick_task() vpillai
2020-03-04 16:59 ` [RFC PATCH 03/13] sched: Core-wide rq->lock vpillai
2020-04-01 11:42   ` [PATCH] sched/arm64: store cpu topology before notify_cpu_starting Cheng Jian
2020-04-01 13:23     ` Valentin Schneider
2020-04-01 13:23       ` Valentin Schneider
2020-04-06  8:00       ` chengjian (D)
2020-04-06  8:00         ` chengjian (D)
2020-04-09  9:59       ` Sudeep Holla
2020-04-09  9:59         ` Sudeep Holla
2020-04-09 10:32         ` Valentin Schneider
2020-04-09 10:32           ` Valentin Schneider
2020-04-09 11:08           ` Sudeep Holla
2020-04-09 11:08             ` Sudeep Holla
2020-04-09 17:54     ` Joel Fernandes
2020-04-10 13:49       ` chengjian (D)
2020-04-14 11:36   ` [RFC PATCH 03/13] sched: Core-wide rq->lock Peter Zijlstra
2020-04-14 21:35     ` Vineeth Remanan Pillai
2020-04-15 10:55       ` Peter Zijlstra
2020-04-14 14:32   ` Peter Zijlstra
2020-03-04 16:59 ` [RFC PATCH 04/13] sched/fair: Add a few assertions vpillai
2020-03-04 16:59 ` [RFC PATCH 05/13] sched: Basic tracking of matching tasks vpillai
2020-03-04 16:59 ` [RFC PATCH 06/13] sched: Update core scheduler queue when taking cpu online/offline vpillai
2020-03-04 16:59 ` [RFC PATCH 07/13] sched: Add core wide task selection and scheduling vpillai
2020-04-14 13:35   ` Peter Zijlstra
2020-04-16 23:32     ` Tim Chen
2020-04-17 10:57       ` Peter Zijlstra
2020-04-16  3:39   ` Chen Yu
2020-04-16 19:59     ` Vineeth Remanan Pillai
2020-04-17 11:18     ` Peter Zijlstra
2020-04-19 15:31       ` Chen Yu
2020-05-21 23:14   ` Joel Fernandes
2020-05-21 23:16     ` Joel Fernandes
2020-05-22  2:35     ` Joel Fernandes
2020-05-22  3:44       ` Aaron Lu
2020-05-22 20:13         ` Joel Fernandes
2020-03-04 16:59 ` [RFC PATCH 08/13] sched/fair: wrapper for cfs_rq->min_vruntime vpillai
2020-03-04 16:59 ` [RFC PATCH 09/13] sched/fair: core wide vruntime comparison vpillai
2020-04-14 13:56   ` Peter Zijlstra
2020-04-15  3:34     ` Aaron Lu
2020-04-15  4:07       ` Aaron Lu
2020-04-15 21:24         ` Vineeth Remanan Pillai
2020-04-17  9:40           ` Aaron Lu
2020-04-20  8:07             ` [PATCH updated] sched/fair: core wide cfs task priority comparison Aaron Lu
2020-04-20 22:26               ` Vineeth Remanan Pillai
2020-04-21  2:51                 ` Aaron Lu
2020-04-24 14:24                   ` [PATCH updated v2] " Aaron Lu
2020-05-06 14:35                     ` Peter Zijlstra
2020-05-08  8:44                       ` Aaron Lu
2020-05-08  9:09                         ` Peter Zijlstra
2020-05-08 12:34                           ` Aaron Lu
2020-05-14 13:02                             ` Peter Zijlstra
2020-05-14 22:51                               ` Vineeth Remanan Pillai
2020-05-15 10:38                                 ` Peter Zijlstra
2020-05-15 10:43                                   ` Peter Zijlstra
2020-05-15 14:24                                   ` Vineeth Remanan Pillai
2020-05-16  3:42                               ` Aaron Lu
2020-05-22  9:40                                 ` Aaron Lu
2020-06-08  1:41                               ` Ning, Hongyu
2020-03-04 17:00 ` [RFC PATCH 10/13] sched: Trivial forced-newidle balancer vpillai
2020-03-04 17:00 ` [RFC PATCH 11/13] sched: migration changes for core scheduling vpillai
2020-06-12 13:21   ` Joel Fernandes
2020-06-12 21:32     ` Vineeth Remanan Pillai
2020-06-13  2:25       ` Joel Fernandes
2020-06-13 18:59         ` Vineeth Remanan Pillai
2020-06-15  2:05           ` Li, Aubrey
2020-03-04 17:00 ` [RFC PATCH 12/13] sched: cgroup tagging interface " vpillai
2020-06-26 15:06   ` Vineeth Remanan Pillai
2020-03-04 17:00 ` [RFC PATCH 13/13] sched: Debug bits vpillai
2020-03-04 17:36 ` [RFC PATCH 00/13] Core scheduling v5 Tim Chen
2020-03-04 17:42   ` Vineeth Remanan Pillai
2020-04-14 14:21 ` Peter Zijlstra
2020-04-15 16:32   ` Joel Fernandes
2020-04-17 11:12     ` Peter Zijlstra
2020-04-17 12:35       ` Alexander Graf
2020-04-17 13:08         ` Peter Zijlstra [this message]
2020-04-18  2:25       ` Joel Fernandes
2020-05-09 14:35   ` Dario Faggioli
     [not found] ` <38805656-2e2f-222a-c083-692f4b113313@linux.intel.com>
2020-05-09  3:39   ` Ning, Hongyu
2020-05-14 20:51     ` FW: " Gruza, Agata
2020-05-10 23:46 ` [PATCH RFC] Add support for core-wide protection of IRQ and softirq Joel Fernandes (Google)
2020-05-11 13:49   ` Peter Zijlstra
2020-05-11 14:54     ` Joel Fernandes
2020-05-20 22:26 ` [PATCH RFC] sched: Add a per-thread core scheduling interface Joel Fernandes (Google)
2020-05-21  4:09   ` [PATCH RFC] sched: Add a per-thread core scheduling interface(Internet mail) benbjiang(蒋彪)
2020-05-21 13:49     ` Joel Fernandes
2020-05-21  8:51   ` [PATCH RFC] sched: Add a per-thread core scheduling interface Peter Zijlstra
2020-05-21 13:47     ` Joel Fernandes
2020-05-21 20:20       ` Vineeth Remanan Pillai
2020-05-22 12:59       ` Peter Zijlstra
2020-05-22 21:35         ` Joel Fernandes
2020-05-24 14:00           ` Phil Auld
2020-05-28 14:51             ` Joel Fernandes
2020-05-28 17:01             ` Peter Zijlstra
2020-05-28 18:17               ` Phil Auld
2020-05-28 18:34                 ` Phil Auld
2020-05-28 18:23               ` Joel Fernandes
2020-05-21 18:31   ` Linus Torvalds
2020-05-21 20:40     ` Joel Fernandes
2020-05-21 21:58       ` Jesse Barnes
2020-05-22 16:33         ` Linus Torvalds
2020-05-20 22:37 ` [PATCH RFC v2] Add support for core-wide protection of IRQ and softirq Joel Fernandes (Google)
2020-05-20 22:48 ` [PATCH RFC] sched: Use sched-RCU in core-scheduling balancing logic Joel Fernandes (Google)
2020-05-21 22:52   ` Paul E. McKenney
2020-05-22  1:26     ` Joel Fernandes
2020-06-25 20:12 ` [RFC PATCH 00/13] Core scheduling v5 Vineeth Remanan Pillai
2020-06-26  1:47   ` Joel Fernandes
2020-06-26 14:36     ` Vineeth Remanan Pillai
2020-06-26 15:10       ` Joel Fernandes
2020-06-26 15:12         ` Joel Fernandes
2020-06-27 16:21         ` Joel Fernandes
2020-06-30 14:11         ` Phil Auld
2020-06-29 12:33   ` Li, Aubrey
2020-06-29 19:41     ` Vineeth Remanan Pillai

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