Re: [dpdk-dev] [PATCH v5 07/11] net/virtio: implement transmit path for packed queues

["Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>]

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Jens Freimann
> Sent: Friday, September 7, 2018 2:20 AM
> To: dev@dpdk.org
> Cc: tiwei.bie@intel.com; maxime.coquelin@redhat.com
> Subject: [dpdk-dev] [PATCH v5 07/11] net/virtio: implement transmit path
> for packed queues
>
> This implements the transmit path for devices with support for packed
> virtqueues.
>
> Add the feature bit and enable code to
> add buffers to vring and mark descriptors as available.
>
> Signed-off-by: Jens Freiman <jfreimann@redhat.com>
> ---
>  drivers/net/virtio/virtio_ethdev.c |   8 +-
>  drivers/net/virtio/virtio_ethdev.h |   2 +
>  drivers/net/virtio/virtio_rxtx.c   | 113 ++++++++++++++++++++++++++++-
>  3 files changed, 121 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio/virtio_ethdev.c
> b/drivers/net/virtio/virtio_ethdev.c
> index ad91f7f82..d2c5755bb 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -384,6 +384,8 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t
> vtpci_queue_idx)
>  vq->hw = hw;
>  vq->vq_queue_index = vtpci_queue_idx;
>  vq->vq_nentries = vq_size;
> +if (vtpci_packed_queue(hw))
> +vq->vq_ring.avail_wrap_counter = 1;
>
>  /*
>   * Reserve a memzone for vring elements @@ -1338,7 +1340,11 @@
> set_rxtx_funcs(struct rte_eth_dev *eth_dev)
>  eth_dev->rx_pkt_burst = &virtio_recv_pkts;
>  }
>
> -if (hw->use_inorder_tx) {
> +if (vtpci_packed_queue(hw)) {
> +PMD_INIT_LOG(INFO, "virtio: using virtio 1.1 Tx path on
> port %u",
> +eth_dev->data->port_id);
> +eth_dev->tx_pkt_burst = virtio_xmit_pkts_packed;
> +} else if (hw->use_inorder_tx) {
>  PMD_INIT_LOG(INFO, "virtio: using inorder Tx path on
> port %u",
>  eth_dev->data->port_id);
>  eth_dev->tx_pkt_burst = virtio_xmit_pkts_inorder; diff --git
> a/drivers/net/virtio/virtio_ethdev.h b/drivers/net/virtio/virtio_ethdev.h
> index b726ad108..04161b461 100644
> --- a/drivers/net/virtio/virtio_ethdev.h
> +++ b/drivers/net/virtio/virtio_ethdev.h
> @@ -79,6 +79,8 @@ uint16_t virtio_recv_mergeable_pkts_inorder(void
> *rx_queue,
>
>  uint16_t virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
>  uint16_t nb_pkts);
> +uint16_t virtio_xmit_pkts_packed(void *tx_queue, struct rte_mbuf
> **tx_pkts,
> +uint16_t nb_pkts);
>
>  uint16_t virtio_xmit_pkts_inorder(void *tx_queue, struct rte_mbuf
> **tx_pkts,
>  uint16_t nb_pkts);
> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
> index eb891433e..12787070e 100644
> --- a/drivers/net/virtio/virtio_rxtx.c
> +++ b/drivers/net/virtio/virtio_rxtx.c
> @@ -38,6 +38,112 @@
>  #define  VIRTIO_DUMP_PACKET(m, len) do { } while (0)  #endif
>
> +
> +/* Cleanup from completed transmits. */ static void
> +virtio_xmit_cleanup_packed(struct virtqueue *vq) {
> +uint16_t idx;
> +uint16_t size = vq->vq_nentries;
> +struct vring_desc_packed *desc = vq->vq_ring.desc_packed;
> +struct vq_desc_extra *dxp;
> +
> +idx = vq->vq_used_cons_idx;
> +while (desc_is_used(&desc[idx], &vq->vq_ring) &&
> +       vq->vq_free_cnt < size) {
> +dxp = &vq->vq_descx[idx];
> +vq->vq_free_cnt += dxp->ndescs;
> +idx = dxp->ndescs;
> +idx = idx >= size ? idx - size : idx;
> +}
> +}
> +
> +uint16_t
> +virtio_xmit_pkts_packed(void *tx_queue, struct rte_mbuf **tx_pkts,
> +     uint16_t nb_pkts)
> +{
> +struct virtnet_tx *txvq = tx_queue;
> +struct virtqueue *vq = txvq->vq;
> +uint16_t i;
> +struct vring_desc_packed *desc = vq->vq_ring.desc_packed;
> +uint16_t idx, prev;
> +struct vq_desc_extra *dxp;
> +
> +if (unlikely(nb_pkts < 1))
> +return nb_pkts;
> +
> +PMD_TX_LOG(DEBUG, "%d packets to xmit", nb_pkts);
> +
> +if (likely(vq->vq_free_cnt < vq->vq_free_thresh))
> +virtio_xmit_cleanup_packed(vq);
> +
> +for (i = 0; i < nb_pkts; i++) {
> +struct rte_mbuf *txm = tx_pkts[i];
> +struct virtio_tx_region *txr = txvq->virtio_net_hdr_mz->addr;
> +uint16_t head_idx;
> +int wrap_counter;
> +int descs_used;
> +
> +if (unlikely(txm->nb_segs + 1 > vq->vq_free_cnt)) {
> +virtio_xmit_cleanup_packed(vq);
> +
> +if (unlikely(txm->nb_segs + 1 > vq->vq_free_cnt)) {
> +PMD_TX_LOG(ERR,
> +   "No free tx descriptors to transmit");
> +break;
> +}
> +}
> +
> +txvq->stats.bytes += txm->pkt_len;
> +
> +vq->vq_free_cnt -= txm->nb_segs + 1;
> +
> +wrap_counter = vq->vq_ring.avail_wrap_counter;
> +idx = vq->vq_avail_idx;
> +head_idx = idx;
> +
> +dxp = &vq->vq_descx[idx];
> +if (dxp->cookie != NULL)
> +rte_pktmbuf_free(dxp->cookie);
> +dxp->cookie = txm;
> +
> +desc[idx].addr  = txvq->virtio_net_hdr_mem +
> +  RTE_PTR_DIFF(&txr[idx].tx_hdr, txr);
> +desc[idx].len   = vq->hw->vtnet_hdr_size;
> +desc[idx].flags = VRING_DESC_F_NEXT |
> +VRING_DESC_F_AVAIL(vq-
> >vq_ring.avail_wrap_counter) |
> +VRING_DESC_F_USED(!vq-
> >vq_ring.avail_wrap_counter);
> +descs_used = 1;
> +
> +do {
> +idx = update_pq_avail_index(vq);
> +desc[idx].addr  =
> VIRTIO_MBUF_DATA_DMA_ADDR(txm, vq);
> +desc[idx].len   = txm->data_len;
> +desc[idx].flags = VRING_DESC_F_NEXT |
> +VRING_DESC_F_AVAIL(vq-
> >vq_ring.avail_wrap_counter) |
> +VRING_DESC_F_USED(!vq-
> >vq_ring.avail_wrap_counter);

According to spec, all the flags update should be moved after the memory barriers.

> +descs_used++;
> +} while ((txm = txm->next) != NULL);
> +
> +desc[idx].flags &= ~VRING_DESC_F_NEXT;

Ditto

> +
> +rte_smp_wmb();
> +prev = (idx > 0 ? idx : vq->vq_nentries) - 1;
> +desc[prev].index = head_idx; //FIXME
> +desc[head_idx].flags =
> +(VRING_DESC_F_AVAIL(wrap_counter) |
> + VRING_DESC_F_USED(!wrap_counter));
> +
> +vq->vq_descx[head_idx].ndescs = descs_used;
> +idx = update_pq_avail_index(vq);
> +}
> +
> +txvq->stats.packets += i;
> +txvq->stats.errors  += nb_pkts - i;
> +
> +return i;
> +}
> +
>  int
>  virtio_dev_rx_queue_done(void *rxq, uint16_t offset)  { @@ -736,7 +842,12
> @@ virtio_dev_tx_queue_setup_finish(struct rte_eth_dev *dev,
>  if (hw->use_inorder_tx)
>  vq->vq_ring.desc[vq->vq_nentries - 1].next = 0;
>
> -VIRTQUEUE_DUMP(vq);
> +if (vtpci_packed_queue(hw)) {
> +vq->vq_ring.avail_wrap_counter = 1;
> +}
> +
> +if (!vtpci_packed_queue(hw))
> +VIRTQUEUE_DUMP(vq);
>
>  return 0;
>  }
> --
> 2.17.1

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