> -----Original Message-----
> From: Maxime Coquelin <maxime.coque...@redhat.com>
> Sent: Monday, May 17, 2021 03:38 PM
> To: Balazs Nemeth <bnem...@redhat.com>; dev@dpdk.org; Ling, WeiX
> <weix.l...@intel.com>
> Subject: Re: [dpdk-dev] [PATCH] vhost: fix invalid use of stored last used
> index
>
> Hi Ling,
>
>
> On 5/14/21 6:02 PM, Balazs Nemeth wrote:
> > The optimization introduced by commit d18db8049c7c ("vhost: read last
> > used index once") didn't account for the fact that
> > vhost_flush_enqueue_shadow_packed increments the last_used_idx. For
> > this reason, store last_used_idx after the potential call to
> > vhost_flush_enqueue_shadow_packed.
> >
> > Fixes: d18db8049c7c ("vhost: read last used index once")
> > Signed-off-by: Balazs Nemeth <bnem...@redhat.com>
> > ---
> > lib/vhost/virtio_net.c | 7 +++++--
> > 1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index
> > abfd67d38c..8da8a86a10 100644
> > --- a/lib/vhost/virtio_net.c
> > +++ b/lib/vhost/virtio_net.c
> > @@ -218,14 +218,17 @@ vhost_flush_enqueue_batch_packed(struct
> > virtio_net *dev, {
> > uint16_t i;
> > uint16_t flags;
> > - uint16_t last_used_idx = vq->last_used_idx;
> > - struct vring_packed_desc *desc_base = &vq-
> >desc_packed[last_used_idx];
> > + uint16_t last_used_idx;
> > + struct vring_packed_desc *desc_base;
> >
> > if (vq->shadow_used_idx) {
> > do_data_copy_enqueue(dev, vq);
> > vhost_flush_enqueue_shadow_packed(dev, vq);
> > }
> >
> > + last_used_idx = vq->last_used_idx;
> > + desc_base = &vq->desc_packed[last_used_idx];
> > +
> > flags = PACKED_DESC_ENQUEUE_USED_FLAG(vq-
> >used_wrap_counter);
> >
> > vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
> >
>
> Could you please confirm the patch fixes the issue you reported?
>
> Thanks,
> Maxime
Hi Maxime,
Apply your patch
https://patches.dpdk.org/project/dpdk/patch/83fa6253725a7bc69bccb7897f380422354a2898.1621008025.git.bnem...@redhat.com/
based on DPDK-21.05-rc3(7989b7e7da9b), tested PASSED.
Regards,
Ling Wei
