Re: [dpdk-stable] [PATCH 19.11] net/virtio: fix refill order in packed ring datapath

[Christian Ehrhardt <christian.ehrhardt@canonical.com>]

On Tue, Aug 17, 2021 at 4:30 AM Marvin Liu <yong.liu@intel.com> wrote:
>
> [ upstream commit 2d91b28730a945def257bc372a525c9b5dbf181c ]

Thanks, applied

> The front-end should refill the descriptor with the mbuf indicated by
> the buff_id rather then the index of used descriptor. Back-end may
> return buffers out of order if async copy mode is enabled.
>
> When initializing rxq, refill the descriptors in order as buff_id is
> not available at that time.
>
> Fixes: a76290c8f1cf ("net/virtio: implement Rx path for packed queues")
>
> Signed-off-by: Marvin Liu <yong.liu@intel.com>
> Signed-off-by: Cheng Jiang <cheng1.jiang@intel.com>
> Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>
> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
> index 5211736d2..421e4847e 100644
> --- a/drivers/net/virtio/virtio_rxtx.c
> +++ b/drivers/net/virtio/virtio_rxtx.c
> @@ -474,13 +474,35 @@ virtqueue_enqueue_recv_refill(struct virtqueue *vq, struct rte_mbuf **cookie,
>         return 0;
>  }
>
> +static inline void
> +virtqueue_refill_single_packed(struct virtqueue *vq,
> +                              struct vring_packed_desc *dp,
> +                              struct rte_mbuf *cookie)
> +{
> +       uint16_t flags = vq->vq_packed.cached_flags;
> +       struct virtio_hw *hw = vq->hw;
> +
> +       dp->addr = VIRTIO_MBUF_ADDR(cookie, vq) +
> +                       RTE_PKTMBUF_HEADROOM - hw->vtnet_hdr_size;
> +       dp->len = cookie->buf_len -
> +               RTE_PKTMBUF_HEADROOM + hw->vtnet_hdr_size;
> +
> +       virtqueue_store_flags_packed(dp, flags,
> +                                    hw->weak_barriers);
> +
> +       if (++vq->vq_avail_idx >= vq->vq_nentries) {
> +               vq->vq_avail_idx -= vq->vq_nentries;
> +               vq->vq_packed.cached_flags ^=
> +                       VRING_PACKED_DESC_F_AVAIL_USED;
> +               flags = vq->vq_packed.cached_flags;
> +       }
> +}
> +
>  static inline int
> -virtqueue_enqueue_recv_refill_packed(struct virtqueue *vq,
> +virtqueue_enqueue_recv_refill_packed_init(struct virtqueue *vq,
>                                      struct rte_mbuf **cookie, uint16_t num)
>  {
>         struct vring_packed_desc *start_dp = vq->vq_packed.ring.desc;
> -       uint16_t flags = vq->vq_packed.cached_flags;
> -       struct virtio_hw *hw = vq->hw;
>         struct vq_desc_extra *dxp;
>         uint16_t idx;
>         int i;
> @@ -496,24 +518,34 @@ virtqueue_enqueue_recv_refill_packed(struct virtqueue *vq,
>                 dxp->cookie = (void *)cookie[i];
>                 dxp->ndescs = 1;
>
> -               start_dp[idx].addr = VIRTIO_MBUF_ADDR(cookie[i], vq) +
> -                               RTE_PKTMBUF_HEADROOM - hw->vtnet_hdr_size;
> -               start_dp[idx].len = cookie[i]->buf_len - RTE_PKTMBUF_HEADROOM
> -                                       + hw->vtnet_hdr_size;
> +               virtqueue_refill_single_packed(vq, &start_dp[idx], cookie[i]);
> +       }
> +       vq->vq_free_cnt = (uint16_t)(vq->vq_free_cnt - num);
> +       return 0;
> +}
>
> -               vq->vq_desc_head_idx = dxp->next;
> -               if (vq->vq_desc_head_idx == VQ_RING_DESC_CHAIN_END)
> -                       vq->vq_desc_tail_idx = vq->vq_desc_head_idx;
> +static inline int
> +virtqueue_enqueue_recv_refill_packed(struct virtqueue *vq,
> +                                    struct rte_mbuf **cookie, uint16_t num)
> +{
> +       struct vring_packed_desc *start_dp = vq->vq_packed.ring.desc;
> +       struct vq_desc_extra *dxp;
> +       uint16_t idx, did;
> +       int i;
>
> -               virtqueue_store_flags_packed(&start_dp[idx], flags,
> -                                            hw->weak_barriers);
> +       if (unlikely(vq->vq_free_cnt == 0))
> +               return -ENOSPC;
> +       if (unlikely(vq->vq_free_cnt < num))
> +               return -EMSGSIZE;
>
> -               if (++vq->vq_avail_idx >= vq->vq_nentries) {
> -                       vq->vq_avail_idx -= vq->vq_nentries;
> -                       vq->vq_packed.cached_flags ^=
> -                               VRING_PACKED_DESC_F_AVAIL_USED;
> -                       flags = vq->vq_packed.cached_flags;
> -               }
> +       for (i = 0; i < num; i++) {
> +               idx = vq->vq_avail_idx;
> +               did = start_dp[idx].id;
> +               dxp = &vq->vq_descx[did];
> +               dxp->cookie = (void *)cookie[i];
> +               dxp->ndescs = 1;
> +
> +               virtqueue_refill_single_packed(vq, &start_dp[idx], cookie[i]);
>         }
>         vq->vq_free_cnt = (uint16_t)(vq->vq_free_cnt - num);
>         return 0;
> @@ -1022,7 +1054,7 @@ virtio_dev_rx_queue_setup_finish(struct rte_eth_dev *dev, uint16_t queue_idx)
>
>                         /* Enqueue allocated buffers */
>                         if (vtpci_packed_queue(vq->hw))
> -                               error = virtqueue_enqueue_recv_refill_packed(vq,
> +                               error = virtqueue_enqueue_recv_refill_packed_init(vq,
>                                                 &m, 1);
>                         else
>                                 error = virtqueue_enqueue_recv_refill(vq,
> --
> 2.17.1
>


-- 
Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd