Re: [PATCH V1 3/5] vfio: detect closed container

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

On Tue,  5 Jan 2021 07:36:51 -0800
Steve Sistare <steven.sistare@oracle.com> wrote:

> Add a function that detects if an iommu_group has a valid container.
> 
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
>  drivers/vfio/vfio.c  | 12 ++++++++++++
>  include/linux/vfio.h |  1 +
>  2 files changed, 13 insertions(+)
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 262ab0e..f89ab80 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -61,6 +61,7 @@ struct vfio_container {
>  	struct vfio_iommu_driver	*iommu_driver;
>  	void				*iommu_data;
>  	bool				noiommu;
> +	bool				closed;
>  };
>  
>  struct vfio_unbound_dev {
> @@ -1223,6 +1224,7 @@ static int vfio_fops_release(struct inode *inode, struct file *filep)
>  
>  	filep->private_data = NULL;
>  
> +	container->closed = true;
>  	vfio_container_put(container);
>  
>  	return 0;
> @@ -2216,6 +2218,16 @@ void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm)
>  }
>  EXPORT_SYMBOL_GPL(vfio_group_set_kvm);
>  
> +bool vfio_iommu_group_contained(struct iommu_group *iommu_group)
> +{
> +	struct vfio_group *group = vfio_group_get_from_iommu(iommu_group);
> +	bool ret = group && group->container && !group->container->closed;
> +
> +	vfio_group_put(group);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(vfio_iommu_group_contained);

This seems like a pointless interface, the result is immediately stale.
Anything that relies on the container staying open needs to add itself
as a user.  We already have some interfaces for that, ex.
vfio_group_get_external_user().  Thanks,

Alex

> +
>  static int vfio_register_group_notifier(struct vfio_group *group,
>  					unsigned long *events,
>  					struct notifier_block *nb)
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 38d3c6a..b2724e7 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -148,6 +148,7 @@ extern int vfio_unregister_notifier(struct device *dev,
>  
>  struct kvm;
>  extern void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm);
> +extern bool vfio_iommu_group_contained(struct iommu_group *group);
>  
>  /*
>   * Sub-module helpers