[dpdk-dev] [PATCH v5 7/9] net/virtio: support in-order Rx and Tx

[Ferruh Yigit]

On 7/2/2018 2:56 PM, Marvin Liu wrote:
> IN_ORDER Rx function depends on merge-able feature. Descriptors
> allocation and free will be done in bulk.
> 
> Virtio dequeue logic:
>     dequeue_burst_rx(burst mbufs)
>     for (each mbuf b) {
>             if (b need merge) {
>                     merge remained mbufs
>                     add merged mbuf to return mbufs list
>             } else {
>                     add mbuf to return mbufs list
>             }
>     }
>     if (last mbuf c need merge) {
>             dequeue_burst_rx(required mbufs)
>             merge last mbuf c
>     }
>     refill_avail_ring_bulk()
>     update_avail_ring()
>     return mbufs list
> 
> IN_ORDER Tx function can support offloading features. Packets which
> matched "can_push" option will be handled by simple xmit function. Those
> packets can't match "can_push" will be handled by original xmit function
> with in-order flag.
> 
> Virtio enqueue logic:
>     xmit_cleanup(used descs)
>     for (each xmit mbuf b) {
>             if (b can inorder xmit) {
>                     add mbuf b to inorder burst list
>                     continue
>             } else {
>                     xmit inorder burst list
>                     xmit mbuf b by original function
>             }
>     }
>     if (inorder burst list not empty) {
>             xmit inorder burst list
>     }
>     update_avail_ring()
> 
> Signed-off-by: Marvin Liu <yong.liu at intel.com>
> Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>

<...>

> @@ -150,6 +188,83 @@ virtio_xmit_cleanup(struct virtqueue *vq, uint16_t num)
>  	}
>  }
>  
> +/* Cleanup from completed inorder transmits. */
> +static void
> +virtio_xmit_cleanup_inorder(struct virtqueue *vq, uint16_t num)
> +{
> +	uint16_t i, used_idx, desc_idx, last_idx;


Getting following build error [1], from code it looks like false positive, but
to get rid of the build error would it be OK to set initial value to "desc_idx"?


[1]
.../dpdk/drivers/net/virtio/virtio_rxtx.c:195:24: error: ‘desc_idx’ may be used
uninitialized in this function [-Werror=maybe-uninitialized]


  uint16_t i, used_idx, desc_idx, last_idx;



                        ^~~~~~~~