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[24.6.151.244]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2ff5f6a64ecsm1685585a91.0.2025.03.06.09.00.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Mar 2025 09:00:05 -0800 (PST) Date: Thu, 6 Mar 2025 09:00:02 -0800 From: Joe Damato To: Jakub Kicinski Cc: netdev@vger.kernel.org, mkarsten@uwaterloo.ca, gerhard@engleder-embedded.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, mst@redhat.com, leiyang@redhat.com, Eugenio =?iso-8859-1?Q?P=E9rez?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Paolo Abeni , "open list:VIRTIO CORE AND NET DRIVERS" , open list Subject: Re: [PATCH net-next v5 3/4] virtio-net: Map NAPIs to queues Message-ID: Mail-Followup-To: Joe Damato , Jakub Kicinski , netdev@vger.kernel.org, mkarsten@uwaterloo.ca, gerhard@engleder-embedded.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, mst@redhat.com, leiyang@redhat.com, Eugenio =?iso-8859-1?Q?P=E9rez?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Paolo Abeni , "open list:VIRTIO CORE AND NET DRIVERS" , open list References: <20250227185017.206785-1-jdamato@fastly.com> <20250227185017.206785-4-jdamato@fastly.com> <20250228182759.74de5bec@kernel.org> <20250303160355.5f8d82d8@kernel.org> <20250305182118.3d885f0d@kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250305182118.3d885f0d@kernel.org> On Wed, Mar 05, 2025 at 06:21:18PM -0800, Jakub Kicinski wrote: > On Wed, 5 Mar 2025 17:42:35 -0800 Joe Damato wrote: > > Two spots that come to mind are: > > - in virtnet_probe where all the other netdev ops are plumbed > > through, or > > - above virtnet_disable_queue_pair which I assume a future queue > > API implementor would need to call for ndo_queue_stop > > I'd put it next to some call which will have to be inspected. > Normally we change napi_disable() to napi_disable_locked() > for drivers using the instance lock, so maybe on the napi_disable() > line in the refill? Sure, that seems reasonable to me. Does this comment seem reasonable? I tried to distill what you said in your previous message (thanks for the guidance, btw): diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index d6c8fe670005..fe5f6313d422 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -2883,6 +2883,18 @@ static void refill_work(struct work_struct *work) for (i = 0; i < vi->curr_queue_pairs; i++) { struct receive_queue *rq = &vi->rq[i]; + /* + * When queue API support is added in the future and the call + * below becomes napi_disable_locked, this driver will need to + * be refactored. + * + * One possible solution would be to: + * - cancel refill_work with cancel_delayed_work (note: non-sync) + * - cancel refill_work with cancel_delayed_work_sync in + * virtnet_remove after the netdev is unregistered + * - wrap all of the work in a lock (perhaps vi->refill_lock?) + * - check netif_running() and return early to avoid a race + */