From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH] virtio_console: allocate inbufs in add_port() only if it is needed Date: Wed, 6 Nov 2019 08:56:31 -0500 Message-ID: <20191106085548-mutt-send-email-mst@kernel.org> References: <20191018164718.15999-1-lvivier@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20191018164718.15999-1-lvivier@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 To: Laurent Vivier Cc: Greg Kroah-Hartman , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Arnd Bergmann , Amit Shah List-Id: virtualization@lists.linuxfoundation.org On Fri, Oct 18, 2019 at 06:47:18PM +0200, Laurent Vivier wrote: > When we hot unplug a virtserialport and then try to hot plug again, > it fails: > > (qemu) chardev-add socket,id=serial0,path=/tmp/serial0,server,nowait > (qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\ > chardev=serial0,id=serial0,name=serial0 > (qemu) device_del serial0 > (qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\ > chardev=serial0,id=serial0,name=serial0 > kernel error: > virtio-ports vport2p2: Error allocating inbufs > qemu error: > virtio-serial-bus: Guest failure in adding port 2 for device \ > virtio-serial0.0 > > This happens because buffers for the in_vq are allocated when the port is > added but are not released when the port is unplugged. > > They are only released when virtconsole is removed (see a7a69ec0d8e4) > > To avoid the problem and to be symmetric, we could allocate all the buffers > in init_vqs() as they are released in remove_vqs(), but it sounds like > a waste of memory. > > Rather than that, this patch changes add_port() logic to only allocate the > buffers if the in_vq has available free slots. > > Fixes: a7a69ec0d8e4 ("virtio_console: free buffers after reset") > Cc: mst@redhat.com > Signed-off-by: Laurent Vivier > --- > drivers/char/virtio_console.c | 17 +++++++++++------ > 1 file changed, 11 insertions(+), 6 deletions(-) > > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c > index 7270e7b69262..77105166fe01 100644 > --- a/drivers/char/virtio_console.c > +++ b/drivers/char/virtio_console.c > @@ -1421,12 +1421,17 @@ static int add_port(struct ports_device *portdev, u32 id) > spin_lock_init(&port->outvq_lock); > init_waitqueue_head(&port->waitqueue); > > - /* 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) { > - dev_err(port->dev, "Error allocating inbufs\n"); > - err = -ENOMEM; > - goto free_device; > + /* if the in_vq has not already been filled (the port has already been > + * used and unplugged), fill the in_vq with buffers so the host can > + * send us data. > + */ > + if (port->in_vq->num_free != 0) { > + nr_added_bufs = fill_queue(port->in_vq, &port->inbuf_lock); > + if (!nr_added_bufs) { > + dev_err(port->dev, "Error allocating inbufs\n"); > + err = -ENOMEM; > + goto free_device; > + } > } > > if (is_rproc_serial(port->portdev->vdev)) Well fill_queue will just add slots as long as it can. So on a full queue it does nothing. How does this patch help? > -- > 2.21.0