Re: [dpdk-dev] [PATCH] lib/librte_vhost: remove redundant logic judgement

[Yuanhan Liu <yliu@fridaylinux.org>]

On Mon, Dec 25, 2017 at 05:16:17PM +0800, Zhiyong Yang wrote:
> At the beginning of vring_translate, the code
> if(!(dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))) already judges
> if IOMMU_PLATFORM is supported. The function vhost_iova_to_vva always
> repeats the logic, __vhost_iova_to_vva can be used directly to avoid it
> here.
> 
> Signed-off-by: Zhiyong Yang <zhiyong.yang@intel.com>
> ---
>  lib/librte_vhost/vhost.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
> index 4f8b73a09..bb615fd2a 100644
> --- a/lib/librte_vhost/vhost.c
> +++ b/lib/librte_vhost/vhost.c
> @@ -157,7 +157,7 @@ vring_translate(struct virtio_net *dev, struct vhost_virtqueue *vq)
>  		goto out;
>  
>  	size = sizeof(struct vring_desc) * vq->size;
> -	vq->desc = (struct vring_desc *)(uintptr_t)vhost_iova_to_vva(dev, vq,
> +	vq->desc = (struct vring_desc *)(uintptr_t)__vhost_iova_to_vva(dev, vq,
>  						vq->ring_addrs.desc_user_addr,
>  						size, VHOST_ACCESS_RW);


I don't see strong reason to bother doing the change. It's not in the
datapath after all. I'd like to keep the code as it is, to keep it simpler:
user just has to call vhost_iova_to_vva() and let it to handle the details.

	--yliu


>  	if (!vq->desc)
> @@ -165,7 +165,8 @@ vring_translate(struct virtio_net *dev, struct vhost_virtqueue *vq)
>  
>  	size = sizeof(struct vring_avail);
>  	size += sizeof(uint16_t) * vq->size;
> -	vq->avail = (struct vring_avail *)(uintptr_t)vhost_iova_to_vva(dev, vq,
> +	vq->avail = (struct vring_avail *)(uintptr_t)__vhost_iova_to_vva(dev,
> +						vq,
>  						vq->ring_addrs.avail_user_addr,
>  						size, VHOST_ACCESS_RW);
>  	if (!vq->avail)
> @@ -173,7 +174,7 @@ vring_translate(struct virtio_net *dev, struct vhost_virtqueue *vq)
>  
>  	size = sizeof(struct vring_used);
>  	size += sizeof(struct vring_used_elem) * vq->size;
> -	vq->used = (struct vring_used *)(uintptr_t)vhost_iova_to_vva(dev, vq,
> +	vq->used = (struct vring_used *)(uintptr_t)__vhost_iova_to_vva(dev, vq,
>  						vq->ring_addrs.used_user_addr,
>  						size, VHOST_ACCESS_RW);
>  	if (!vq->used)
> -- 
> 2.13.3