Re: [v4 2/3] vfio_register_notifier: also register on the group notifier

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

On Tue, 15 Nov 2016 19:35:46 +0800
Jike Song <jike.song@intel.com> wrote:

> The user of vfio_register_notifier might care about not only
> iommu events but also vfio_group events, so also register the
> notifier_block on vfio_group.
> 
> Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Jike Song <jike.song@intel.com>
> ---
>  drivers/vfio/vfio.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index b149ced..2c0eedb 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -2065,6 +2065,8 @@ int vfio_register_notifier(struct device *dev, struct notifier_block *nb)
>  	else
>  		ret = -ENOTTY;
>  
> +	vfio_group_register_notifier(group, nb);
> +
>  	up_read(&container->group_lock);
>  	vfio_group_try_dissolve_container(group);
>  
> @@ -2102,6 +2104,8 @@ int vfio_unregister_notifier(struct device *dev, struct notifier_block *nb)
>  	else
>  		ret = -ENOTTY;
>  
> +	vfio_group_unregister_notifier(group, nb);
> +
>  	up_read(&container->group_lock);
>  	vfio_group_try_dissolve_container(group);
>  

You haven't addressed the error paths, if the iommu driver returns
error and therefore the {un}register returns error, what is the caller
to expect about the group registration?