Re: [PATCH v11 10/23] vfio-iommufd: Move noiommu compat probe out of vfio_iommufd_bind()

[Alex Williamson <alex.williamson@redhat.com>]

On Sat, 13 May 2023 06:28:14 -0700
Yi Liu <yi.l.liu@intel.com> wrote:

> into vfio_device_group_open(). This is more consistent with what will
> be done in vfio device cdev path.

Same comment regarding flowing commit subject into body on this series.

> 
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Tested-by: Terrence Xu <terrence.xu@intel.com>
> Tested-by: Nicolin Chen <nicolinc@nvidia.com>
> Tested-by: Yanting Jiang <yanting.jiang@intel.com>
> Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> ---
>  drivers/vfio/group.c   |  6 ++++++
>  drivers/vfio/iommufd.c | 32 +++++++++++++++++++-------------
>  drivers/vfio/vfio.h    |  9 +++++++++
>  3 files changed, 34 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/vfio/group.c b/drivers/vfio/group.c
> index a17584e8be15..cfd0b9254bbc 100644
> --- a/drivers/vfio/group.c
> +++ b/drivers/vfio/group.c
> @@ -192,6 +192,12 @@ static int vfio_device_group_open(struct vfio_device_file *df)
>  		vfio_device_group_get_kvm_safe(device);
>  
>  	df->iommufd = device->group->iommufd;
> +	if (df->iommufd && vfio_device_is_noiommu(device) && device->open_count == 0) {
> +		ret = vfio_iommufd_compat_probe_noiommu(device,
> +							df->iommufd);
> +		if (ret)
> +			goto out_put_kvm;
> +	}
>  
>  	ret = vfio_device_open(df);
>  	if (ret) {
> diff --git a/drivers/vfio/iommufd.c b/drivers/vfio/iommufd.c
> index a18e920be164..7a654a1437f0 100644
> --- a/drivers/vfio/iommufd.c
> +++ b/drivers/vfio/iommufd.c
> @@ -46,6 +46,24 @@ static void vfio_iommufd_noiommu_unbind(struct vfio_device *vdev)
>  	}
>  }
>  
> +int vfio_iommufd_compat_probe_noiommu(struct vfio_device *device,
> +				      struct iommufd_ctx *ictx)
> +{
> +	u32 ioas_id;
> +
> +	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;
> +}

I think the purpose of this function is to keep the iommufd namespace
out of the group, but we're muddying it as a general grab bag of
noiommu validation.  What if the caller retained the RAWIO test and
comment, and this function simply became a wrapper around the iommufd
function, ex:

bool vfio_iommufd_device_has_compat_ioas(struct vfio_device *device,
					 struct iommufd_ctx *ictx)
{
	u32 ioas_id;

	return !iommufd_vfio_compat_ioas_get_id(ictx, &ioas_id));
}

Thanks,
Alex

> +
>  int vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx *ictx)
>  {
>  	u32 ioas_id;
> @@ -54,20 +72,8 @@ int vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx *ictx)
>  
>  	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;
> -
> +	if (vfio_device_is_noiommu(vdev))
>  		return vfio_iommufd_noiommu_bind(vdev, ictx, &device_id);
> -	}
>  
>  	ret = vdev->ops->bind_iommufd(vdev, ictx, &device_id);
>  	if (ret)
> diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
> index 785afc40ece8..8884b557fb26 100644
> --- a/drivers/vfio/vfio.h
> +++ b/drivers/vfio/vfio.h
> @@ -234,9 +234,18 @@ static inline void vfio_container_cleanup(void)
>  #endif
>  
>  #if IS_ENABLED(CONFIG_IOMMUFD)
> +int vfio_iommufd_compat_probe_noiommu(struct vfio_device *device,
> +				      struct iommufd_ctx *ictx);
>  int vfio_iommufd_bind(struct vfio_device *device, struct iommufd_ctx *ictx);
>  void vfio_iommufd_unbind(struct vfio_device *device);
>  #else
> +static inline int
> +vfio_iommufd_compat_probe_noiommu(struct vfio_device *device,
> +				  struct iommufd_ctx *ictx)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
>  static inline int vfio_iommufd_bind(struct vfio_device *device,
>  				    struct iommufd_ctx *ictx)
>  {