Re: [PATCH net-next RFC 2/5] vhost: introduce helper to prefetch desc index

Jason Wang
2017-09-25T02:04:13Z

On 2017年09月22日 17:02, Stefan Hajnoczi wrote:
> On Fri, Sep 22, 2017 at 04:02:32PM +0800, Jason Wang wrote:
>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>> index f87ec75..8424166d 100644
>> --- a/drivers/vhost/vhost.c
>> +++ b/drivers/vhost/vhost.c
>> @@ -2437,6 +2437,61 @@ struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev,
>> }
>> EXPORT_SYMBOL_GPL(vhost_dequeue_msg);
>>
>> +int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq,
>> + struct vring_used_elem *heads,
>> + u16 num, bool used_update)
> Missing doc comment.

Will fix this.

>
>> +{
>> + int ret, ret2;
>> + u16 last_avail_idx, last_used_idx, total, copied;
>> + __virtio16 avail_idx;
>> + struct vring_used_elem __user *used;
>> + int i;
> The following variable names are a little confusing:
>
> last_avail_idx vs vq->last_avail_idx. last_avail_idx is a wrapped
> avail->ring[] index, vq->last_avail_idx is a free-running counter. The
> same for last_used_idx vs vq->last_used_idx.
>
> num argument vs vq->num. The argument could be called nheads instead to
> make it clear that this is heads[] and not the virtqueue size.
>
> Not a bug but it took me a while to figure out what was going on.

I admit the name is confusing. Let me try better ones in V2.

Thanks