On Tue, Apr 02, 2024 at 12:51:09PM +0800, Yajun Wu wrote: > When vhost-user or vhost-kernel is handling virtio net datapath, qemu > should not touch used ring. > > But with vhost-user socket reconnect scenario, in a very rare case (has > pending kick event). VRING_USED_F_NO_NOTIFY is set by qemu in > following code path: > > #0 virtio_queue_split_set_notification (vq=0x7ff5f4c920a8, enable=0) > at ../hw/virtio/virtio.c:511 > #1 0x0000559d6dbf033b in virtio_queue_set_notification > (vq=0x7ff5f4c920a8, enable=0) at ../hw/virtio/virtio.c:576 > #2 0x0000559d6dbbbdbc in virtio_net_handle_tx_bh (vdev=0x559d703a6aa0, > vq=0x7ff5f4c920a8) at ../hw/net/virtio-net.c:2801 > #3 0x0000559d6dbf4791 in virtio_queue_notify_vq (vq=0x7ff5f4c920a8) at > ../hw/virtio/virtio.c:2248 > #4 0x0000559d6dbf79da in virtio_queue_host_notifier_read > (n=0x7ff5f4c9211c) at ../hw/virtio/virtio.c:3525 > #5 0x0000559d6d9a5814 in virtio_bus_cleanup_host_notifier > (bus=0x559d703a6a20, n=1) at ../hw/virtio/virtio-bus.c:321 > #6 0x0000559d6dbf83c9 in virtio_device_stop_ioeventfd_impl > (vdev=0x559d703a6aa0) at ../hw/virtio/virtio.c:3774 > #7 0x0000559d6d9a55c8 in virtio_bus_stop_ioeventfd > (bus=0x559d703a6a20) at ../hw/virtio/virtio-bus.c:259 > #8 0x0000559d6d9a53e8 in virtio_bus_grab_ioeventfd > (bus=0x559d703a6a20) at ../hw/virtio/virtio-bus.c:199 > #9 0x0000559d6dbf841c in virtio_device_grab_ioeventfd > (vdev=0x559d703a6aa0) at ../hw/virtio/virtio.c:3783 > #10 0x0000559d6d9bde18 in vhost_dev_enable_notifiers > (hdev=0x559d707edd70, vdev=0x559d703a6aa0) at ../hw/virtio/vhost.c:1592 > #11 0x0000559d6d89a0b8 in vhost_net_start_one (net=0x559d707edd70, > dev=0x559d703a6aa0) at ../hw/net/vhost_net.c:266 > #12 0x0000559d6d89a6df in vhost_net_start (dev=0x559d703a6aa0, > ncs=0x559d7048d890, data_queue_pairs=31, cvq=0) at ../hw/net/vhost_net.c:412 > #13 0x0000559d6dbb5b89 in virtio_net_vhost_status (n=0x559d703a6aa0, > status=15 '\017') at ../hw/net/virtio-net.c:311 > #14 0x0000559d6dbb5e34 in virtio_net_set_status (vdev=0x559d703a6aa0, > status=15 '\017') at ../hw/net/virtio-net.c:392 > #15 0x0000559d6dbb60d8 in virtio_net_set_link_status > (nc=0x559d7048d890) at ../hw/net/virtio-net.c:455 > #16 0x0000559d6da64863 in qmp_set_link (name=0x559d6f0b83d0 "hostnet1", > up=true, errp=0x7ffdd76569f0) at ../net/net.c:1459 > #17 0x0000559d6da7226e in net_vhost_user_event (opaque=0x559d6f0b83d0, > event=CHR_EVENT_OPENED) at ../net/vhost-user.c:301 > #18 0x0000559d6ddc7f63 in chr_be_event (s=0x559d6f2ffea0, > event=CHR_EVENT_OPENED) at ../chardev/char.c:62 > #19 0x0000559d6ddc7fdc in qemu_chr_be_event (s=0x559d6f2ffea0, > event=CHR_EVENT_OPENED) at ../chardev/char.c:82 > > This issue causes guest kernel stop kicking device and traffic stop. > > Add vhost_started check in virtio_net_handle_tx_bh to fix this wrong > VRING_USED_F_NO_NOTIFY set. > > Signed-off-by: Yajun Wu <yaj...@nvidia.com> > Reviewed-by: Jiri Pirko <j...@nvidia.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com> > --- > hw/net/virtio-net.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > index a6ff000cd9..8035e01fdf 100644 > --- a/hw/net/virtio-net.c > +++ b/hw/net/virtio-net.c > @@ -2865,6 +2865,10 @@ static void virtio_net_handle_tx_bh(VirtIODevice > *vdev, VirtQueue *vq) > VirtIONet *n = VIRTIO_NET(vdev); > VirtIONetQueue *q = &n->vqs[vq2q(virtio_get_queue_index(vq))]; > > + if (n->vhost_started) { > + return; > + } > + > if (unlikely((n->status & VIRTIO_NET_S_LINK_UP) == 0)) { > virtio_net_drop_tx_queue_data(vdev, vq); > return; > -- > 2.27.0