[dpdk-dev] [PATCH] virtio: fix idx in used ring retrieved only once

[Yuanhan Liu]

On Thu, Jun 16, 2016 at 02:30:37AM +0800, Huawei Xie wrote:
> -     while (vq->vq_used_cons_idx != vq->vq_ring.used->idx) {
> +     while (VIRTQUEUE_NUSED(vq)) {
>               uint32_t idx, desc_idx, used_idx;
>               struct vring_used_elem *uep;
>  
> diff --git a/drivers/net/virtio/virtio_ring.h 
> b/drivers/net/virtio/virtio_ring.h
> index 447760a..fcecc16 100644
> --- a/drivers/net/virtio/virtio_ring.h
> +++ b/drivers/net/virtio/virtio_ring.h
> @@ -79,7 +79,7 @@ struct vring_used_elem {
>  
>  struct vring_used {
>       uint16_t flags;
> -     uint16_t idx;
> +     volatile uint16_t idx;
>       struct vring_used_elem ring[0];
>  };
>  
> diff --git a/drivers/net/virtio/virtio_rxtx_simple.c 
> b/drivers/net/virtio/virtio_rxtx_simple.c
> index 7b50119..a0ef8d2 100644
> --- a/drivers/net/virtio/virtio_rxtx_simple.c
> +++ b/drivers/net/virtio/virtio_rxtx_simple.c
> @@ -184,8 +184,7 @@ virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf 
> **rx_pkts,
>       if (unlikely(nb_pkts < RTE_VIRTIO_DESC_PER_LOOP))
>               return 0;
>  
> -     nb_used = *(volatile uint16_t *)&vq->vq_ring.used->idx -
> -             vq->vq_used_cons_idx;
> +     nb_used = vq->vq_ring.used->idx - vq->vq_used_cons_idx;

How about replacing it with VIRTQUEUE_NUSED here?

        --yliu