[dpdk-dev] [PATCH v6 04/13] vhost: add packed ring batch enqueue

[Gavin Hu (Arm Technology China)]

Hi Marvin,

> -----Original Message-----
> From: Marvin Liu <yong.liu at intel.com>
> Sent: Wednesday, October 16, 2019 12:08 AM
> To: maxime.coquelin at redhat.com; tiwei.bie at intel.com;
> zhihong.wang at intel.com; stephen at networkplumber.org; Gavin Hu (Arm
> Technology China) <Gavin.Hu at arm.com>
> Cc: dev at dpdk.org; Marvin Liu <yong.liu at intel.com>
> Subject: [PATCH v6 04/13] vhost: add packed ring batch enqueue
> 
> Batch enqueue function will first check whether descriptors are cache
> aligned. It will also check prerequisites in the beginning. Batch
> enqueue function do not support chained mbufs, single packet enqueue
> function will handle it.
> 
> Signed-off-by: Marvin Liu <yong.liu at intel.com>
> Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
> 
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index 142c14e04..a8130dc06 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -881,6 +881,76 @@ virtio_dev_rx_split(struct virtio_net *dev, struct
> vhost_virtqueue *vq,
>  	return pkt_idx;
>  }
> 
> +static __rte_unused int
> +virtio_dev_rx_batch_packed(struct virtio_net *dev,
> +			   struct vhost_virtqueue *vq,
> +			   struct rte_mbuf **pkts)
> +{
> +	bool wrap_counter = vq->avail_wrap_counter;
> +	struct vring_packed_desc *descs = vq->desc_packed;
> +	uint16_t avail_idx = vq->last_avail_idx;
> +	uint64_t desc_addrs[PACKED_BATCH_SIZE];
> +	struct virtio_net_hdr_mrg_rxbuf *hdrs[PACKED_BATCH_SIZE];
> +	uint32_t buf_offset = dev->vhost_hlen;
> +	uint64_t lens[PACKED_BATCH_SIZE];
> +	uint16_t i;
> +
> +	if (unlikely(avail_idx & PACKED_BATCH_MASK))
> +		return -1;
> +
> +	if (unlikely((avail_idx + PACKED_BATCH_SIZE) > vq->size))
> +		return -1;
> +
> +	for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
> +		if (unlikely(pkts[i]->next != NULL))
> +			return -1;
> +		if (unlikely(!desc_is_avail(&descs[avail_idx + i],
> +					    wrap_counter)))
> +			return -1;
> +	}
> +
> +	rte_smp_rmb();
> +
> +	for_each_try_unroll(i, 0, PACKED_BATCH_SIZE)
> +		lens[i] = descs[avail_idx + i].len;
> +
> +	for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
> +		if (unlikely(pkts[i]->pkt_len > (lens[i] - buf_offset)))
> +			return -1;
> +	}
> +
> +	for_each_try_unroll(i, 0, PACKED_BATCH_SIZE)
> +		desc_addrs[i] = vhost_iova_to_vva(dev, vq,
> +						  descs[avail_idx + i].addr,
> +						  &lens[i],
> +						  VHOST_ACCESS_RW);
> +
> +	for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
> +		if (unlikely(lens[i] != descs[avail_idx + i].len))
> +			return -1;
> +	}
> +
> +	for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
> +		rte_prefetch0((void *)(uintptr_t)desc_addrs[i]);
> +		hdrs[i] = (struct virtio_net_hdr_mrg_rxbuf *)
> +					(uintptr_t)desc_addrs[i];
> +		lens[i] = pkts[i]->pkt_len + dev->vhost_hlen;
> +	}
> +
> +	for_each_try_unroll(i, 0, PACKED_BATCH_SIZE)
> +		virtio_enqueue_offload(pkts[i], &hdrs[i]->hdr);
> +
> +	vq_inc_last_avail_packed(vq, PACKED_BATCH_SIZE);

Is the last_avail_idx a shared variable? Why is updated before the following payload copy? 
This will cause the other side get earlier-than-arrival data? 
/Gavin
> +
> +	for_each_try_unroll(i, 0, PACKED_BATCH_SIZE) {
> +		rte_memcpy((void *)(uintptr_t)(desc_addrs[i] + buf_offset),
> +			   rte_pktmbuf_mtod_offset(pkts[i], void *, 0),
> +			   pkts[i]->pkt_len);
> +	}
> +
> +	return 0;
> +}
> +
>  static __rte_unused int16_t
>  virtio_dev_rx_single_packed(struct virtio_net *dev,
>  			    struct vhost_virtqueue *vq,
> --
> 2.17.1