Ping again.
On Tue, 10 Oct 2023 at 14:23, Sun Feng <loyo...@gmail.com> wrote:
>
> With commit d4c19cde("virtio-serial: add missing virtio_detach_element()
> call"),
> when virtio serial is throttled and closed by host, port->elem should be
> discard with virtqueue_push,
> otherwise virtqueue will not rewind, guest will blocked finally and cannot
> write anymore data.
>
> It can be reproduced with following steps:
> Create a vm with virtio-serial device through libvirt:
>
> <channel type='unix'>
> <source mode='bind' path='/tmp/test'/>
> <target type='virtio' name='com.test.channel.0'/>
> <address type='virtio-serial' controller='0' bus='0' port='1'/>
> </channel>
>
> Host run:
> watch -n0.5 'timeout 0.5 nc -U /tmp/test'
>
> Guest run:
> hexdump -C -v /dev/zero > /dev/vport1p1
>
> After sometime, guest can not write any data to serial.
> We can see vq->last_avail_idx - vq->used_idx = 128 with gdb.
>
> (gdb) p *(struct VirtQueue *) 0x565161c5c788
> $4 = {vring = {num = 128, num_default = 128, align = 4096, desc = 4316049408,
> avail = 4316051456, used = 4316051776,
> caches = 0x7fc530067e60}, used_elems = 0x565161c88dc0, last_avail_idx =
> 7929, last_avail_wrap_counter = true,
> shadow_avail_idx = 7929, shadow_avail_wrap_counter = true, used_idx = 7801,
> used_wrap_counter = true, signalled_used = 7801,
> signalled_used_valid = true, notification = true, queue_index = 5, inuse =
> 0, vector = 1,
> handle_output = 0x56515da8aea0 <handle_output>, handle_aio_output = 0x0,
> vdev = 0x565161c54e30, guest_notifier = {rfd = 0,
> wfd = 0}, host_notifier = {rfd = 74, wfd = 74}, host_notifier_enabled =
> true, node = {le_next = 0x565161c5c6f0,
> le_prev = 0x565161c5c8a8}}
>
> Fixes: d4c19cde("virtio-serial: add missing virtio_detach_element() call")
> Signed-off-by: Sun Feng <loyo...@gmail.com>
> ---
> hw/char/virtio-serial-bus.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
> index dd619f0..30b00a4 100644
> --- a/hw/char/virtio-serial-bus.c
> +++ b/hw/char/virtio-serial-bus.c
> @@ -151,7 +151,7 @@ static void discard_vq_data(VirtQueue *vq, VirtIODevice
> *vdev)
> static void discard_throttle_data(VirtIOSerialPort *port)
> {
> if (port->elem) {
> - virtqueue_detach_element(port->ovq, port->elem, 0);
> + virtqueue_push(port->ovq, port->elem, 0);
> g_free(port->elem);
> port->elem = NULL;
> }
> --
> 2.7.4
>
