RE: [PATCH v6 13/24] vfio/iommufd: Split the compat_ioas attach out from vfio_iommufd_bind()

["Tian, Kevin" <kevin.tian@intel.com>]

> From: Liu, Yi L <yi.l.liu@intel.com>
> Sent: Wednesday, March 8, 2023 9:29 PM
> 
> @@ -177,7 +177,7 @@ static int vfio_device_group_open(struct
> vfio_device_file *df)
>  	mutex_lock(&device->group->group_lock);
>  	if (!vfio_group_has_iommu(device->group)) {
>  		ret = -EINVAL;
> -		goto out_unlock;
> +		goto err_unlock;
>  	}

My impression - out_xxx means go to do xxx while err_xxx means
go to do something for error xxx, though in many places the two
are mixed to both meaning 'do xxx'.

either way I don't see a need of changing it.

> -int vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx *ictx)
> +static int vfio_iommufd_device_probe_comapt_noiommu(struct vfio_device
> *vdev,
> +						    struct iommufd_ctx *ictx)

s/comapt/compat/

btw it's clearer to move this check into vfio_device_group_open().

if noiommu then pass NULL to vfio_device_open(), same as the cdev path.

> +
> +int vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx *ictx)
> +{
>  	u32 device_id;
>  	int ret;
> 
>  	lockdep_assert_held(&vdev->dev_set->lock);
> 
>  	if (vfio_device_is_noiommu(vdev)) {
> -		if (!capable(CAP_SYS_RAWIO))
> -			return -EPERM;
> -
> -		/*
> -		 * Require no compat ioas to be assigned to proceed. The
> basic
> -		 * statement is that the user cannot have done something
> that
> -		 * implies they expected translation to exist
> -		 */
> -		if (!iommufd_vfio_compat_ioas_get_id(ictx, &ioas_id))
> -			return -EPERM;
> -		return 0;
> +		ret = vfio_iommufd_device_probe_comapt_noiommu(vdev,
> ictx);
> +		if (ret)
> +			return ret;
>  	}
> 
>  	if (WARN_ON(!vdev->ops->bind_iommufd))
>  		return -ENODEV;
> 
> -	ret = vdev->ops->bind_iommufd(vdev, ictx, &device_id);
> -	if (ret)
> -		return ret;
> +	/* The legacy path has no way to return the device id */
> +	return vdev->ops->bind_iommufd(vdev, ictx, &device_id);
> +}
> 
> -	ret = iommufd_vfio_compat_ioas_get_id(ictx, &ioas_id);
> -	if (ret)
> -		goto err_unbind;
> -	ret = vdev->ops->attach_ioas(vdev, &ioas_id);
> -	if (ret)
> -		goto err_unbind;

after noiommu check and attach_ioas are moved out then this
entire function can be removed now. Just call the ops in
vfio_device_first_open().

> +int vfio_iommufd_attach_compat_ioas(struct vfio_device *vdev,
> +				    struct iommufd_ctx *ictx)
> +{
> +	u32 ioas_id;
> +	int ret;
> +
> +	lockdep_assert_held(&vdev->dev_set->lock);
> 
>  	/*
> -	 * The legacy path has no way to return the device id or the selected
> -	 * pt_id
> +	 * If the driver doesn't provide this op then it means the device does
> +	 * not do DMA at all. So nothing to do.
>  	 */
> -	return 0;
> +	if (WARN_ON(!vdev->ops->bind_iommufd))
> +		return -ENODEV;
> 
> -err_unbind:
> -	if (vdev->ops->unbind_iommufd)
> -		vdev->ops->unbind_iommufd(vdev);
> -	return ret;
> +	if (vfio_device_is_noiommu(vdev)) {
> +		if
> (WARN_ON(vfio_iommufd_device_probe_comapt_noiommu(vdev, ictx)))
> +			return -EINVAL;
> +		return 0;
> +	}

no need. let's directly call following from vfio_device_group_open().
In that case no need to do noiommu check twice in one function.

> +
> +	ret = iommufd_vfio_compat_ioas_get_id(ictx, &ioas_id);
> +	if (ret)
> +		return ret;
> +
> +	/* The legacy path has no way to return the selected pt_id */
> +	return vdev->ops->attach_ioas(vdev, &ioas_id);
>  }
>