On Sun, Jan 29, 2023 at 03:28:28PM +0800, Xuan Zhuo wrote:
> On Sun, 29 Jan 2023 02:25:43 -0500, "Michael S. Tsirkin" <m...@redhat.com>
> wrote:
> > On Sun, Jan 29, 2023 at 10:51:50AM +0800, Xuan Zhuo wrote:
> > > Check whether it is per-queue reset state in virtio_net_flush_tx().
> > >
> > > Before per-queue reset, we need to recover async tx resources. At this
> > > time, virtio_net_flush_tx() is called, but we should not try to send
> > > new packets, so virtio_net_flush_tx() should check the current
> > > per-queue reset state.
> >
> >
> > What does "at this time" mean here?
> > Do you in fact mean it's called from flush_or_purge_queued_packets?
>
> Yes
>
> virtio_queue_reset
> k->queue_reset
> virtio_net_queue_reset
> flush_or_purge_queued_packets
> qemu_flush_or_purge_queued_packets
> .....
> (callback) virtio_net_tx_complete
> virtio_net_flush_tx <-- here
> send new packet. We need stop it.
>
>
> Because it is inside the callback, I can't pass information through the
> stack. I
> originally thought it was a general situation, so I wanted to put it in
> struct VirtQueue.
>
> If it is not very suitable, it may be better to put it in VirtIONetQueue.
>
> Thanks.
Hmm maybe. Another idea: isn't virtio_net_tx_complete called
with length 0 here? Are there other cases where length is 0?
> > What does the call stack look like?
> >
> > If yes introducing a vq state just so virtio_net_flush_tx
> > knows we are in the process of reset would be a bad idea.
> > We want something much more local, ideally on stack even ...
> >
> >
> > >
> > > Fixes: 7dc6be52 ("virtio-net: support queue reset")
> > > Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1451
> > > Reported-by: Alexander Bulekov <alx...@bu.edu>
> > > Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
> > > ---
> > > hw/net/virtio-net.c | 3 ++-
> > > 1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> > > index 3ae909041a..fba6451a50 100644
> > > --- a/hw/net/virtio-net.c
> > > +++ b/hw/net/virtio-net.c
> > > @@ -2627,7 +2627,8 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue
> > > *q)
> > > VirtQueueElement *elem;
> > > int32_t num_packets = 0;
> > > int queue_index = vq2q(virtio_get_queue_index(q->tx_vq));
> > > - if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
> > > + if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) ||
> > > + virtio_queue_reset_state(q->tx_vq)) {
btw this sounds like you are asking it to reset some state.
> > > return num_packets;
and then
ret = virtio_net_flush_tx(q);
if (ret >= n->tx_burst)
will reschedule automatically won't it?
also why check in virtio_net_flush_tx and not virtio_net_tx_complete?
> > > }
> > >
> > > --
> > > 2.32.0.3.g01195cf9f
> >
