From: Paolo Bonzini <pbonzini@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>,
Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
kvm@vger.kernel.org, Alex Williamson <alex.williamson@redhat.com>
Subject: Re: [PATCH v2 1/2] sched/wait: Add add_wait_queue_priority()
Date: Fri, 6 Nov 2020 11:17:21 +0100 [thread overview]
Message-ID: <f0901be7-1526-5b6a-90cb-6489e53cb92f@redhat.com> (raw)
In-Reply-To: <ef4660dba8135ca5a1dc7e854babcf65d8cef46f.camel@infradead.org>
On 04/11/20 10:35, David Woodhouse wrote:
> On Wed, 2020-10-28 at 15:35 +0100, Peter Zijlstra wrote:
>> On Tue, Oct 27, 2020 at 02:39:43PM +0000, David Woodhouse wrote:
>>> From: David Woodhouse <dwmw@amazon.co.uk>
>>>
>>> This allows an exclusive wait_queue_entry to be added at the head of the
>>> queue, instead of the tail as normal. Thus, it gets to consume events
>>> first without allowing non-exclusive waiters to be woken at all.
>>>
>>> The (first) intended use is for KVM IRQFD, which currently has
>>> inconsistent behaviour depending on whether posted interrupts are
>>> available or not. If they are, KVM will bypass the eventfd completely
>>> and deliver interrupts directly to the appropriate vCPU. If not, events
>>> are delivered through the eventfd and userspace will receive them when
>>> polling on the eventfd.
>>>
>>> By using add_wait_queue_priority(), KVM will be able to consistently
>>> consume events within the kernel without accidentally exposing them
>>> to userspace when they're supposed to be bypassed. This, in turn, means
>>> that userspace doesn't have to jump through hoops to avoid listening
>>> on the erroneously noisy eventfd and injecting duplicate interrupts.
>>>
>>> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
>>
>> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>
> Thanks. Paolo, the conclusion was that you were going to take this set
> through the KVM tree, wasn't it?
>
Queued, except for patch 2/3 in the eventfd series which Alex hasn't
reviewed/acked yet.
Paolo
next prev parent reply other threads:[~2020-11-06 10:17 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-26 17:53 [RFC PATCH 1/2] sched/wait: Add add_wait_queue_priority() David Woodhouse
2020-10-26 17:53 ` [RFC PATCH 2/2] kvm/eventfd: Use priority waitqueue to catch events before userspace David Woodhouse
2020-10-27 8:01 ` Paolo Bonzini
2020-10-27 10:15 ` David Woodhouse
2020-10-27 13:55 ` [PATCH 0/3] Allow in-kernel consumers to drain events from eventfd David Woodhouse
2020-10-27 13:55 ` [PATCH 1/3] eventfd: Export eventfd_ctx_do_read() David Woodhouse
2020-10-27 13:55 ` [PATCH 2/3] vfio/virqfd: Drain events from eventfd in virqfd_wakeup() David Woodhouse
2020-11-06 23:29 ` Alex Williamson
2020-11-08 9:17 ` Paolo Bonzini
2020-10-27 13:55 ` [PATCH 3/3] kvm/eventfd: Drain events from eventfd in irqfd_wakeup() David Woodhouse
2020-10-27 18:41 ` kernel test robot
2020-10-27 18:41 ` kernel test robot
2020-10-27 21:42 ` kernel test robot
2020-10-27 21:42 ` kernel test robot
2020-10-27 23:13 ` kernel test robot
2020-10-27 23:13 ` kernel test robot
2020-10-27 14:39 ` [PATCH v2 0/2] Allow KVM IRQFD to consistently intercept events David Woodhouse
2020-10-27 14:39 ` [PATCH v2 1/2] sched/wait: Add add_wait_queue_priority() David Woodhouse
2020-10-27 19:09 ` Peter Zijlstra
2020-10-27 19:27 ` David Woodhouse
2020-10-27 20:30 ` Peter Zijlstra
2020-10-27 20:49 ` David Woodhouse
2020-10-27 21:32 ` David Woodhouse
2020-10-28 14:20 ` Peter Zijlstra
2020-10-28 14:44 ` Paolo Bonzini
2020-10-28 14:35 ` Peter Zijlstra
2020-11-04 9:35 ` David Woodhouse
2020-11-04 11:25 ` Paolo Bonzini
2020-11-06 10:17 ` Paolo Bonzini [this message]
2020-11-06 16:32 ` Alex Williamson
2020-11-06 17:18 ` David Woodhouse
2020-10-27 14:39 ` [PATCH v2 2/2] kvm/eventfd: Use priority waitqueue to catch events before userspace David Woodhouse
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