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@xxxxxxxxxx
> Signed-off-by: Laurent Vivier <lvivier@xxxxxxxxxx>
> ---
> 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
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