Re: [PATCH 2/8] vhost: add helper to check if a vq has been setup

[Jason Wang <jasowang@redhat.com>]

On 2020/9/22 上午2:23, Mike Christie wrote:
> This adds a helper check if a vq has been setup. The next patches
> will use this when we move the vhost scsi cmd preallocation from per
> session to per vq. In the per vq case, we only want to allocate cmds
> for vqs that have actually been setup and not for all the possible
> vqs.
>
> Signed-off-by: Mike Christie <michael.christie@oracle.com>
> ---
>   drivers/vhost/vhost.c | 9 +++++++++
>   drivers/vhost/vhost.h | 1 +
>   2 files changed, 10 insertions(+)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index b45519c..5dd9eb1 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -305,6 +305,15 @@ static void vhost_vring_call_reset(struct vhost_vring_call *call_ctx)
>   	spin_lock_init(&call_ctx->ctx_lock);
>   }
>   
> +bool vhost_vq_is_setup(struct vhost_virtqueue *vq)
> +{
> +	if (vq->avail && vq->desc && vq->used && vhost_vq_access_ok(vq))
> +		return true;
> +	else
> +		return false;
> +}
> +EXPORT_SYMBOL_GPL(vhost_vq_is_setup);


This is probably ok but I wonder maybe we should have something like 
what vDPA did (VHOST_SET_VRING_ENABLE) to match virtio 1.0 device 
definition.

Thanks


> +
>   static void vhost_vq_reset(struct vhost_dev *dev,
>   			   struct vhost_virtqueue *vq)
>   {
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 9032d3c..3d30b3d 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -190,6 +190,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *,
>   		      struct vhost_log *log, unsigned int *log_num);
>   void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
>   
> +bool vhost_vq_is_setup(struct vhost_virtqueue *vq);
>   int vhost_vq_init_access(struct vhost_virtqueue *);
>   int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len);
>   int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads,