Re: [PATCH v3] virtio_console: allocate inbufs in add_port() only if it is needed

On Tue, 2019-12-03 at 10:42 -0500, Michael S. Tsirkin wrote:

On Tue, Dec 03, 2019 at 03:46:50PM +0100, Amit Shah wrote:

quoted

On Thu, 2019-11-14 at 13:25 +0100, Laurent Vivier wrote:

quoted

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 ignore
ENOSPC
error in fill_queue(), which means queue has already been filled.

Fixes: a7a69ec0d8e4 ("virtio_console: free buffers after reset")
Cc: mst@redhat.com
Cc: stable@vger.kernel.org
Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Reviewed-by: Amit Shah <amit@kernel.org>

Thanks!

Thanks, however this has already been merged by Linus.
I can't add the tag retroactively, sorry about that.

Right, no problem - but I wanted to ensure it's on-list :)

For bugfix patches like that, I think we can reasonably
target a turn around of a couple of days, these
shouldn't really need to wait weeks for review.

Sure, thanks for picking it up fast enough.  Life happens, etc., and
it's not always possible to reply in a couple of days.  Since we had
already covered the main comments in v1 and v2, v3 wasn't going to need
much attention anyway.