Re: [dpdk-dev] [PATCH v2 08/16] vhost: add flush function for burst enqueue

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

Hi Marvin,

One typo and one comment about the barrier.

/Gavin

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Marvin Liu
> Sent: Friday, September 20, 2019 12:37 AM
> To: maxime.coquelin@redhat.com; tiwei.bie@intel.com;
> zhihong.wang@intel.com
> Cc: dev@dpdk.org; Marvin Liu <yong.liu@intel.com>
> Subject: [dpdk-dev] [PATCH v2 08/16] vhost: add flush function for burst
> enqueue
> 
> Flush used flags when burst enqueue function is finished. Descriptor's
> flags are pre-calculated as them will be reset by vhost.
s/them/they

> 
> Signed-off-by: Marvin Liu <yong.liu@intel.com>
> 
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 000648dd4..9c42c7db0 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -39,6 +39,9 @@
> 
>  #define VHOST_LOG_CACHE_NR 32
> 
> +#define VIRTIO_RX_USED_FLAG  (0ULL | VRING_DESC_F_AVAIL |
> VRING_DESC_F_USED \
> +				| VRING_DESC_F_WRITE)
> +#define VIRTIO_RX_USED_WRAP_FLAG (VRING_DESC_F_WRITE)
>  #define PACKED_DESCS_BURST (RTE_CACHE_LINE_SIZE / \
>  			    sizeof(struct vring_packed_desc))
> 
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index e2787b72e..8e4036204 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -169,6 +169,51 @@ update_shadow_packed(struct vhost_virtqueue
> *vq,
>  	vq->shadow_used_packed[i].count = count;
>  }
> 
> +static __rte_always_inline void
> +flush_burst_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
> +	uint64_t *lens, uint16_t *ids, uint16_t flags)
> +{
> +	uint16_t i;
> +
> +	UNROLL_PRAGMA(PRAGMA_PARAM)
> +	for (i = 0; i < PACKED_DESCS_BURST; i++) {
> +		vq->desc_packed[vq->last_used_idx + i].id = ids[i];
> +		vq->desc_packed[vq->last_used_idx + i].len = lens[i];
> +	}
> +
> +	UNROLL_PRAGMA(PRAGMA_PARAM)
> +	for (i = 0; i < PACKED_DESCS_BURST; i++) {
> +		rte_smp_wmb();
Should this rte_smp_wmb() be moved above the loop? It guarantees the orderings of updates of id, len happens before the flags,
But all the flags of different descriptors should not be ordered. 

> +		vq->desc_packed[vq->last_used_idx + i].flags = flags;
> +	}
> +
> +	vhost_log_cache_used_vring(dev, vq, vq->last_used_idx *
> +				   sizeof(struct vring_packed_desc),
> +				   sizeof(struct vring_packed_desc) *
> +				   PACKED_DESCS_BURST);
> +	vhost_log_cache_sync(dev, vq);
> +
> +	vq->last_used_idx += PACKED_DESCS_BURST;
> +	if (vq->last_used_idx >= vq->size) {
> +		vq->used_wrap_counter ^= 1;
> +		vq->last_used_idx -= vq->size;
> +	}
> +}
> +
> +static __rte_always_inline void
> +flush_enqueue_burst_packed(struct virtio_net *dev, struct
> vhost_virtqueue *vq,
> +	uint64_t *lens, uint16_t *ids)
> +{
> +	uint16_t flags = 0;
> +
> +	if (vq->used_wrap_counter)
> +		flags = VIRTIO_RX_USED_FLAG;
> +	else
> +		flags = VIRTIO_RX_USED_WRAP_FLAG;
> +
> +	flush_burst_packed(dev, vq, lens, ids, flags);
> +}
> +
>  static __rte_always_inline void
>  update_enqueue_shadow_packed(struct vhost_virtqueue *vq, uint16_t
> desc_idx,
>  	uint32_t len, uint16_t count)
> @@ -950,6 +995,7 @@ virtio_dev_rx_burst_packed(struct virtio_net *dev,
> struct vhost_virtqueue *vq,
>  	struct virtio_net_hdr_mrg_rxbuf *hdrs[PACKED_DESCS_BURST];
>  	uint32_t buf_offset = dev->vhost_hlen;
>  	uint64_t lens[PACKED_DESCS_BURST];
> +	uint16_t ids[PACKED_DESCS_BURST];
> 
>  	uint16_t i;
> 
> @@ -1013,6 +1059,12 @@ virtio_dev_rx_burst_packed(struct virtio_net
> *dev, struct vhost_virtqueue *vq,
>  			   pkts[i]->pkt_len);
>  	}
> 
> +	UNROLL_PRAGMA(PRAGMA_PARAM)
> +	for (i = 0; i < PACKED_DESCS_BURST; i++)
> +		ids[i] = descs[avail_idx + i].id;
> +
> +	flush_enqueue_burst_packed(dev, vq, lens, ids);
> +
>  	return 0;
>  }
> 
> --
> 2.17.1