From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jason Wang <jasowang@redhat.com>
Subject: Re: [PATCH 07/14] net/virtio: implement transmit path
 for packed queues
Date: Mon, 12 Feb 2018 21:16:27 +0800
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References: <20180129141143.13437-1-jfreimann@redhat.com>
 <20180129141143.13437-8-jfreimann@redhat.com>
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Cc: tiwei.bie@intel.com, yliu@fridaylinux.org, maxime.coquelin@redhat.com,
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To: Jens Freimann <jfreimann@redhat.com>, dev@dpdk.org
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On 2018年01月29日 22:11, Jens Freimann wrote:
> +/* Cleanup from completed transmits. */
> +static void
> +virtio_xmit_cleanup(struct virtqueue *vq)
> +{
> +	uint16_t idx;
> +	uint16_t size = vq->vq_nentries;
> +	struct vring_desc_1_1 *desc = vq->vq_ring.desc_1_1;
> +
> +	idx = vq->vq_used_cons_idx & (size - 1);
> +	while (desc_is_used(&desc[idx]) &&
> +	       vq->vq_free_cnt < size) {
> +		while (desc[idx].flags & VRING_DESC_F_NEXT) {
> +			vq->vq_free_cnt++;
> +			idx = ++vq->vq_used_cons_idx & (size - 1);
> +		}
> +		vq->vq_free_cnt++;
> +		idx = ++vq->vq_used_cons_idx & (size - 1);
> +	}
> +}

This looks like a violation of the spec. In 2.6.6 Next Flag: Descriptor 
Chaining. It said:

"VIRTQ_DESC_F_NEXT is reserved in used descriptors, and should be 
ignored by drivers."

(Looking at the device implementation, it was in fact an in order device 
which is said to be no in the cover).

Thanks