Re: [PATCH 12/21] vhost-vdpa: introduce uAPI to get the number of virtqueue groups

[Eli Cohen]

On Wed, Dec 16, 2020 at 02:48:09PM +0800, Jason Wang wrote:
> Follows the vDPA support for multiple address spaces, this patch
> introduce uAPI for the userspace to know the number of virtqueue
> groups supported by the vDPA device.

Can you explain what exactly you mean be userspace? Is it just qemu or
is it destined to the virtio_net driver run by the qemu process?
Also can you say for what purpose?

> 
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
>  drivers/vhost/vdpa.c       | 4 ++++
>  include/uapi/linux/vhost.h | 3 +++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 060d5b5b7e64..1ba5901b28e7 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -536,6 +536,10 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
>  	case VHOST_VDPA_GET_VRING_NUM:
>  		r = vhost_vdpa_get_vring_num(v, argp);
>  		break;
> +	case VHOST_VDPA_GET_GROUP_NUM:
> +		r = copy_to_user(argp, &v->vdpa->ngroups,
> +				 sizeof(v->vdpa->ngroups));
> +		break;
>  	case VHOST_SET_LOG_BASE:
>  	case VHOST_SET_LOG_FD:
>  		r = -ENOIOCTLCMD;
> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> index 59c6c0fbaba1..8a4e6e426bbf 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -145,4 +145,7 @@
>  /* Get the valid iova range */
>  #define VHOST_VDPA_GET_IOVA_RANGE	_IOR(VHOST_VIRTIO, 0x78, \
>  					     struct vhost_vdpa_iova_range)
> +/* Get the number of virtqueue groups. */
> +#define VHOST_VDPA_GET_GROUP_NUM	_IOR(VHOST_VIRTIO, 0x79, unsigned int)
> +
>  #endif
> -- 
> 2.25.1
>