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Tue, 10 Nov 2026 09:26:27 -0800 (PST) Received: from redhat.com ([2a0d:6fc0:1511:2900:ff37:b35c:a97:952d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-498365ccbccsm6152831f8f.44.2026.11.10.09.26.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Nov 2026 09:26:26 -0800 (PST) Date: Tue, 10 Nov 2026 12:26:23 -0500 From: "Michael S. Tsirkin" To: forfortuna@naver.com Cc: Harald Mommer , Matias Ezequiel Vara Larsen , Marc Kleine-Budde , Vincent Mailhol , Mikhail Golubev-Ciuchea , Francesco Valla , virtualization@lists.linux.dev, linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, Jason Wang Subject: Re: [PATCH] can: virtio: fix virtqueue use before DRIVER_OK Message-ID: <20261110122457-mutt-send-email-mst@kernel.org> References: <20261111-virtio-can-ready-v1-1-0b4dd020af0b@naver.com> X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 In-Reply-To: <20261111-virtio-can-ready-v1-1-0b4dd020af0b@naver.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: o3cbYSiRX0NViutf-VT2gXvJIcqeDIK845CFEBoJFcw_1794331588 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Nov 11, 2026 at 02:11:13AM +0900, Seonghyeon Lim via B4 Relay wrote: > From: Seonghyeon Lim > > virtio_can_probe() and virtio_can_restore() fill the RX virtqueue and > kick it before the device is set DRIVER_OK. The virtio specification > does not allow the driver to notify the device before DRIVER_OK. > > In restore, if the interface was up, virtio_can_open() then sends a > START control message and waits for the reply. DRIVER_OK is only set > by the virtio core after restore returns, so the device may never > handle the request and the wait never completes, which hangs system > resume. In probe, an ndo_open() right after register_candev() can > likewise send the START message before DRIVER_OK. > > Call virtio_device_ready() before the first virtqueue use in both > probe and restore, as virtio-net does. > > Fixes: 083082a4e6d8 ("can: virtio: Add virtio CAN driver") > Signed-off-by: Seonghyeon Lim however, device ready means you can get callbacks: config and vq. did you audit the driver to make sure this is safe while probe did not yet populate and register the device? > --- > Tested with QEMU 8.2 + vhost-device-can: with the CAN interface up, > suspend/resume (pm_test=devices) hangs without this patch and > completes with it. No new lockdep warnings. > --- > drivers/net/can/virtio_can.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/net/can/virtio_can.c b/drivers/net/can/virtio_can.c > index f67d0bf09681..ae35a00b784b 100644 > --- a/drivers/net/can/virtio_can.c > +++ b/drivers/net/can/virtio_can.c > @@ -912,6 +912,9 @@ static int virtio_can_probe(struct virtio_device *vdev) > err = -ENOMEM; > goto on_failure; > } > + > + virtio_device_ready(vdev); > + > virtio_can_populate_rx_vq(vdev); > > err = register_virtio_can_dev(dev); > @@ -966,6 +969,9 @@ static int __maybe_unused virtio_can_restore(struct virtio_device *vdev) > virtio_can_del_vq(vdev); > return -ENOMEM; > } > + > + virtio_device_ready(vdev); > + > virtio_can_populate_rx_vq(vdev); > > if (netif_running(ndev)) { > > --- > base-commit: ddfe51b0a0f5dc9e415cc2c8ad8db17532dd426b > change-id: 20261111-virtio-can-ready-85cefff06a84 > > Best regards, > -- > Seonghyeon Lim >