Re: [dpdk-dev] [PATCH v6 10/15] vhost: create descriptor mapping function

[Tiwei Bie <tiwei.bie@intel.com>]

On Mon, Jul 02, 2018 at 10:16:24AM +0200, Maxime Coquelin wrote:
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/librte_vhost/virtio_net.c | 61 ++++++++++++++++++++++++++-----------------
>  1 file changed, 37 insertions(+), 24 deletions(-)
> 
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index f0e2e6a1f..64664b7de 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -292,6 +292,37 @@ virtio_enqueue_offload(struct rte_mbuf *m_buf, struct virtio_net_hdr *net_hdr)
>  	}
>  }
>  
> +static __rte_always_inline int
> +map_one_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
> +		struct buf_vector *buf_vec, uint16_t *vec_idx,
> +		uint64_t desc_iova, uint64_t desc_len, uint8_t perm)
> +{
> +	uint16_t vec_id = *vec_idx;
> +
> +	while (desc_len) {
> +		uint64_t desc_addr;
> +		uint64_t desc_chunck_len = desc_len;
> +
> +		desc_addr = vhost_iova_to_vva(dev, vq,
> +				desc_iova,
> +				&desc_chunck_len,
> +				perm);
> +		if (unlikely(!desc_addr))
> +			return -1;
> +
> +		buf_vec[vec_id].buf_iova = desc_iova;
> +		buf_vec[vec_id].buf_addr = desc_addr;
> +		buf_vec[vec_id].buf_len  = desc_chunck_len;
> +
> +		desc_len -= desc_chunck_len;
> +		desc_iova += desc_chunck_len;
> +		vec_id++;

FYI, a rebase on top of the latest "vhost: generalize
buffer vectors" series is needed to make sure that
access buf_vec[vec_id] won't cause overflow.

> +	}
> +	*vec_idx = vec_id;
> +
> +	return 0;
> +}
> +
[...]