From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v4 13/25] virtio_console: enable VQs early Date: Mon, 20 Oct 2014 17:04:11 +0300 Message-ID: <20141020140410.GA10994@redhat.com> References: <1413114332-626-1-git-send-email-mst-v4@redhat.com> <1413114332-626-14-git-send-email-mst-v4@redhat.com> <20141020120750.GA18561@casper.infradead.org> <20141020144223.5655dcbc.cornelia.huck@de.ibm.com> <20141020133555.GA27111@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-scsi@vger.kernel.org, Christian Borntraeger , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Amit Shah , Greg Kroah-Hartman , Arnd Bergmann , Paolo Bonzini , Thomas Graf , v9fs-developer@lists.sourceforge.net, "David S. Miller" To: Cornelia Huck Return-path: Content-Disposition: inline In-Reply-To: <20141020133555.GA27111@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org On Mon, Oct 20, 2014 at 04:35:55PM +0300, Michael S. Tsirkin wrote: > On Mon, Oct 20, 2014 at 02:42:23PM +0200, Cornelia Huck wrote: > > On Mon, 20 Oct 2014 13:07:50 +0100 > > Thomas Graf wrote: > > > > > On 10/13/14 at 10:50am, Michael S. Tsirkin wrote: > > > > virtio spec requires drivers to set DRIVER_OK before using VQs. > > > > This is set automatically after probe returns, virtio console violated this > > > > rule by adding inbufs, which causes the VQ to be used directly within > > > > probe. > > > > > > > > To fix, call virtio_device_ready before using VQs. > > > > > > > > Signed-off-by: Michael S. Tsirkin > > > > --- > > > > drivers/char/virtio_console.c | 2 ++ > > > > 1 file changed, 2 insertions(+) > > > > > > > > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c > > > > index b585b47..6ebe8f6 100644 > > > > --- a/drivers/char/virtio_console.c > > > > +++ b/drivers/char/virtio_console.c > > > > @@ -1449,6 +1449,8 @@ static int add_port(struct ports_device *portdev, u32 id) > > > > spin_lock_init(&port->outvq_lock); > > > > init_waitqueue_head(&port->waitqueue); > > > > > > > > + virtio_device_ready(portdev->vdev); > > > > + > > > > /* Fill the in_vq with buffers so the host can send us data. */ > > > > nr_added_bufs = fill_queue(port->in_vq, &port->inbuf_lock); > > > > if (!nr_added_bufs) { > > > > > > Seems like probe and add_port() now both set VIRTIO_CONFIG_S_DRIVER_OK > > > > I think we need to set this in the probe function instead, otherwise we > > fail for multiqueue (which also wants to use the control queue early). > > > > Completely untested patch below; I can send this with proper s-o-b if > > it helps. > > > > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c > > index bfa6400..cf7a561 100644 > > --- a/drivers/char/virtio_console.c > > +++ b/drivers/char/virtio_console.c > > @@ -1449,8 +1449,6 @@ static int add_port(struct ports_device *portdev, u32 id) > > spin_lock_init(&port->outvq_lock); > > init_waitqueue_head(&port->waitqueue); > > > > - virtio_device_ready(portdev->vdev); > > - > > /* Fill the in_vq with buffers so the host can send us data. */ > > nr_added_bufs = fill_queue(port->in_vq, &port->inbuf_lock); > > if (!nr_added_bufs) { > > @@ -2026,6 +2024,8 @@ static int virtcons_probe(struct virtio_device *vdev) > > spin_lock_init(&portdev->ports_lock); > > INIT_LIST_HEAD(&portdev->ports); > > > > + virtio_device_ready(portdev->vdev); > > + > > if (multiport) { > > unsigned int nr_added_bufs; > > > > I wanted to set DRIVER_OK as late as possible, to both reduce > the chance it can fail after DRIVER_OK and to reduce the risk of > introducing a regression since old qemu might only start sending > interrupts after DRIVER_OK is set. > > So I wanted everything completely initialized before DRIVER_OK. > > You patch makes sense to me since nothing can fail, > and we won't get interrupts before we add inbufs. > > Reviewed-by: Michael S. Tsirkin > > Testig will report shortly, pls send with sob line. Sure enough, this helps: Tested-by: Michael S. Tsirkin Acked-by: Michael S. Tsirkin Pls repost as a top-level patch. > -- > MST