> -----Original Message-----
> From: Michael S. Tsirkin [mailto:m...@redhat.com]
> Sent: Sunday, December 27, 2020 7:21 PM
> To: wangyunjian <wangyunj...@huawei.com>
> Cc: netdev@vger.kernel.org; jasow...@redhat.com;
> willemdebruijn.ker...@gmail.com; virtualizat...@lists.linux-foundation.org;
> Lilijun (Jerry) <jerry.lili...@huawei.com>; chenchanghu
> <chenchan...@huawei.com>; xudingke <xudin...@huawei.com>; huangbin (J)
> <brian.huang...@huawei.com>
> Subject: Re: [PATCH net v5 2/2] vhost_net: fix tx queue stuck when sendmsg
> fails
>
> On Fri, Dec 25, 2020 at 03:24:33PM +0800, wangyunjian wrote:
> > From: Yunjian Wang <wangyunj...@huawei.com>
> >
> > Currently the driver doesn't drop a packet which can't be sent by tun
> > (e.g bad packet). In this case, the driver will always process the
> > same packet lead to the tx queue stuck.
>
> So not making progress on a bad packet has some advantages, e.g. this is
> easier to debug.
> When is it important to drop the packet and continue?
In the case, the VM will not be able to send packets persistently. Services of
VM
are affected.
Thanks
>
>
> > To fix this issue:
> > 1. in the case of persistent failure (e.g bad packet), the driver
> > can skip this descriptor by ignoring the error.
> > 2. in the case of transient failure (e.g -ENOBUFS, -EAGAIN and -ENOMEM),
> > the driver schedules the worker to try again.
> >
> > Fixes: 3a4d5c94e959 ("vhost_net: a kernel-level virtio server")
>
> I'd just drop this tag, looks more like a feature than a bug ...
OK
>
>
> > Signed-off-by: Yunjian Wang <wangyunj...@huawei.com>
> > Acked-by: Willem de Bruijn <will...@google.com>
> > ---
> > drivers/vhost/net.c | 16 ++++++++--------
> > 1 file changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index
> > c8784dfafdd7..01558fb2c552 100644
> > --- a/drivers/vhost/net.c
> > +++ b/drivers/vhost/net.c
> > @@ -827,14 +827,13 @@ static void handle_tx_copy(struct vhost_net *net,
> struct socket *sock)
> > msg.msg_flags &= ~MSG_MORE;
> > }
> >
> > - /* TODO: Check specific error and bomb out unless ENOBUFS? */
> > err = sock->ops->sendmsg(sock, &msg, len);
> > - if (unlikely(err < 0)) {
> > + if (unlikely(err == -EAGAIN || err == -ENOMEM || err ==
> > -ENOBUFS))
> > +{
> > vhost_discard_vq_desc(vq, 1);
> > vhost_net_enable_vq(net, vq);
> > break;
> > }
> > - if (err != len)
> > + if (err >= 0 && err != len)
> > pr_debug("Truncated TX packet: len %d != %zd\n",
> > err, len);
> > done:
> > @@ -922,7 +921,6 @@ static void handle_tx_zerocopy(struct vhost_net
> *net, struct socket *sock)
> > msg.msg_flags &= ~MSG_MORE;
> > }
> >
> > - /* TODO: Check specific error and bomb out unless ENOBUFS? */
> > err = sock->ops->sendmsg(sock, &msg, len);
> > if (unlikely(err < 0)) {
> > if (zcopy_used) {
> > @@ -931,11 +929,13 @@ static void handle_tx_zerocopy(struct vhost_net
> *net, struct socket *sock)
> > nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
> > % UIO_MAXIOV;
> > }
> > - vhost_discard_vq_desc(vq, 1);
> > - vhost_net_enable_vq(net, vq);
> > - break;
> > + if (err == -EAGAIN || err == -ENOMEM || err ==
> > -ENOBUFS) {
> > + vhost_discard_vq_desc(vq, 1);
> > + vhost_net_enable_vq(net, vq);
> > + break;
> > + }
> > }
> > - if (err != len)
> > + if (err >= 0 && err != len)
> > pr_debug("Truncated TX packet: "
> > " len %d != %zd\n", err, len);
> > if (!zcopy_used)
> > --
> > 2.23.0
