Re: [dpdk-dev] [PATCH v1] vhost: add sanity check for resubmiting reqs in split ring

[Li Feng <fengli@smartx.com>]

Thank you for your response.

On Thu, Oct 14, 2021 at 4:17 PM Maxime Coquelin
<maxime.coquelin@redhat.com> wrote:
>
> Hi Li,
>
> Adding Jin Yu who introduced this function.
>
> On 8/27/21 07:12, Li Feng wrote:
> > When getting reqs from the avail ring, the id may exceed inflight
> > queue size. Then the dpdk will crash forever.
>
> You need to add Fixes tag and Cc stable@dpdk.org so that it can be
> backported.
OK, I will send the v2 version.

>
> > Signed-off-by: Li Feng <fengli@smartx.com>
> > ---
> >   lib/vhost/vhost_user.c | 10 ++++++++--
> >   1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
> > index 29a4c9af60..f09d0f6a48 100644
> > --- a/lib/vhost/vhost_user.c
> > +++ b/lib/vhost/vhost_user.c
> > @@ -1823,8 +1823,14 @@ vhost_check_queue_inflights_split(struct virtio_net *dev,
> >       last_io = inflight_split->last_inflight_io;
> >
> >       if (inflight_split->used_idx != used->idx) {
> > -             inflight_split->desc[last_io].inflight = 0;
> > -             rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
> > +             if (unlikely(last_io >= inflight_split->desc_num)) {
> > +                     VHOST_LOG_CONFIG(ERR, "last_inflight_io '%"PRIu16"' exceeds inflight "
> > +                             "queue size (%"PRIu16").\n", last_io,
> > +                             inflight_split->desc_num);
>
> If such error happens, shouldn't we return RTE_VHOST_MSG_RESULT_ERR
> instead of just logging an error?
I think ignoring the error is ok. No one could handle this error correctly.
At this time the guest virtio driver of this virtqueue may be in an
incorrect state.

>
> > +             } else {
> > +                     inflight_split->desc[last_io].inflight = 0;
> > +                     rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
> > +             }
> >               inflight_split->used_idx = used->idx;
> >       }
> >
> >
>
> Regards,
> Maxime
>