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[173.76.246.42]) by smtp.gmail.com with ESMTPSA id 14sm2832025qkf.23.2019.03.10.23.35.38 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 10 Mar 2019 23:35:39 -0700 (PDT) Date: Mon, 11 Mar 2019 02:35:37 -0400 From: "Michael S. Tsirkin" To: Pankaj Gupta Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, amit@kernel.org, arnd@arndb.de, gregkh@linuxfoundation.org, xiaohli@redhat.com, Gal Hammer Subject: Re: [PATCH] virtio_console: free unused buffers with virtio port Message-ID: <20190311023154-mutt-send-email-mst@kernel.org> References: <20190304130511.14450-1-pagupta@redhat.com> <20190304142506-mutt-send-email-mst@kernel.org> <444210313.9669582.1551769746169.JavaMail.zimbra@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <444210313.9669582.1551769746169.JavaMail.zimbra@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 05, 2019 at 02:09:06AM -0500, Pankaj Gupta wrote: > > Hello Michael, > > Thanks for your reply. > > > > > On Mon, Mar 04, 2019 at 06:35:11PM +0530, Pankaj Gupta wrote: > > > The commit a7a69ec0d8e4 ("virtio_console: free buffers after reset") > > > deffered detaching of unused buffer to virtio device unplug time. > > > > > > This causes unplug/replug of single port in virtio device with an > > > error "Error allocating inbufs\n". As we don't free the unused buffers > > > attached with the port. Re-plug the same port tries to allocate new > > > buffers in virtqueue and results in this error if queue is full. That's the basic issue, isn't it? Why aren't we reusing buffers that are already there? > > > > > > This patch removes the unused buffers in vq's when we unplug the port. > > > This is the best we can do as we cannot call device_reset because virtio > > > device is still active. This was the working behaviour before the change > > > introduced in commit b3258ff1d6. > > > > > > Reported-by: Xiaohui Li > > > Fixes: b3258ff1d6 ("virtio_console: free buffers after reset") > > > Signed-off-by: Pankaj Gupta > > > > I think if you do this you need to add support > > in the packed ring. > > o.k. I will look at the implementation details for "support > of packed ring" for virtio_console. This will take some time. > > Meanwhile "virtio_console" port hotplug/unplug is broken in upstream. > Can we accept this patch as it fixes the upstream and together > with parent patch(b3258ff1d6) does nice cleanups as well. > > Thanks, > Pankaj Sorry, no - I don't think we should fix one configuration by breaking the other. If you want to go back, then that's a spec violation, but I guess we can fix the spec to match. OK, but code-wise if you call virtqueue_detach_unused_buf without device reset then you need to teach packed ring code to support that. > > > > > --- > > > drivers/char/virtio_console.c | 14 +++++++++++--- > > > 1 file changed, 11 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c > > > index fbeb71953526..5fbf2ac73111 100644 > > > --- a/drivers/char/virtio_console.c > > > +++ b/drivers/char/virtio_console.c > > > @@ -1506,15 +1506,25 @@ static void remove_port(struct kref *kref) > > > kfree(port); > > > } > > > > > > +static void remove_unused_bufs(struct virtqueue *vq) > > > +{ > > > + struct port_buffer *buf; > > > + > > > + while ((buf = virtqueue_detach_unused_buf(vq))) > > > + free_buf(buf, true); > > > +} > > > + > > > static void remove_port_data(struct port *port) > > > { > > > spin_lock_irq(&port->inbuf_lock); > > > /* Remove unused data this port might have received. */ > > > discard_port_data(port); > > > + remove_unused_bufs(port->in_vq); > > > spin_unlock_irq(&port->inbuf_lock); > > > > > > spin_lock_irq(&port->outvq_lock); > > > reclaim_consumed_buffers(port); > > > + remove_unused_bufs(port->out_vq); > > > spin_unlock_irq(&port->outvq_lock); > > > } > > > > > > @@ -1950,11 +1960,9 @@ static void remove_vqs(struct ports_device *portdev) > > > struct virtqueue *vq; > > > > > > virtio_device_for_each_vq(portdev->vdev, vq) { > > > - struct port_buffer *buf; > > > > > > flush_bufs(vq, true); > > > - while ((buf = virtqueue_detach_unused_buf(vq))) > > > - free_buf(buf, true); > > > + remove_unused_bufs(vq); > > > } > > > portdev->vdev->config->del_vqs(portdev->vdev); > > > kfree(portdev->in_vqs); > > > -- > > > 2.20.1 > >