Re: [v5 1/3] vfio: vfio_register_notifier: classify iommu notfier

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

On Thu, 17 Nov 2016 20:57:09 +0800
Jike Song <jike.song@intel.com> wrote:

> Currently vfio_register_notifier assumes that there is only one
> notifier chain, which is in vfio_iommu. However, the user might
> also be interested in events other than vfio_iommu, for example,
> vfio_group. Refactor vfio_{un}register_notifier implementation
> to make it feasible.
> 
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Kirti Wankhede <kwankhede@nvidia.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com>
> Signed-off-by: Jike Song <jike.song@intel.com>
> ---
>  drivers/vfio/vfio.c  | 88 +++++++++++++++++++++++++++++++++++++++-------------
>  include/linux/vfio.h | 16 ++++++++--
>  2 files changed, 79 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index c815067..819c7f9 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -2007,23 +2007,25 @@ int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn, int npage)
>  }
>  EXPORT_SYMBOL(vfio_unpin_pages);
>  
> -int vfio_register_notifier(struct device *dev, struct notifier_block *nb)
> +static int vfio_register_iommu_notifier(struct vfio_group *group,
> +					unsigned long *events,
> +					struct notifier_block *nb)
>  {
>  	struct vfio_container *container;
> -	struct vfio_group *group;
>  	struct vfio_iommu_driver *driver;
>  	int ret;
>  
> -	if (!dev || !nb)
> -		return -EINVAL;
> +	/* clear known events */
> +	if (*events & VFIO_IOMMU_NOTIFY_DMA_UNMAP)

This test is unnecessary.

> +		*events &= ~VFIO_IOMMU_NOTIFY_DMA_UNMAP;
>  
> -	group = vfio_group_get_from_dev(dev);
> -	if (IS_ERR(group))
> -		return PTR_ERR(group);
> +	/* refuse to register if still events remaining */
> +	if (*events)
> +		return -EINVAL;
>  
>  	ret = vfio_group_add_container_user(group);
>  	if (ret)
> -		goto err_register_nb;
> +		return -EINVAL;
>  
>  	container = group->container;
>  	down_read(&container->group_lock);
> @@ -2037,29 +2039,19 @@ int vfio_register_notifier(struct device *dev, struct notifier_block *nb)
>  	up_read(&container->group_lock);
>  	vfio_group_try_dissolve_container(group);
>  
> -err_register_nb:
> -	vfio_group_put(group);
>  	return ret;
>  }
> -EXPORT_SYMBOL(vfio_register_notifier);
>  
> -int vfio_unregister_notifier(struct device *dev, struct notifier_block *nb)
> +static int vfio_unregister_iommu_notifier(struct vfio_group *group,
> +					  struct notifier_block *nb)
>  {
>  	struct vfio_container *container;
> -	struct vfio_group *group;
>  	struct vfio_iommu_driver *driver;
>  	int ret;
>  
> -	if (!dev || !nb)
> -		return -EINVAL;
> -
> -	group = vfio_group_get_from_dev(dev);
> -	if (IS_ERR(group))
> -		return PTR_ERR(group);
> -
>  	ret = vfio_group_add_container_user(group);
>  	if (ret)
> -		goto err_unregister_nb;
> +		return -EINVAL;
>  
>  	container = group->container;
>  	down_read(&container->group_lock);
> @@ -2074,7 +2066,59 @@ int vfio_unregister_notifier(struct device *dev, struct notifier_block *nb)
>  	up_read(&container->group_lock);
>  	vfio_group_try_dissolve_container(group);
>  
> -err_unregister_nb:
> +	return ret;
> +}
> +
> +int vfio_register_notifier(struct device *dev, vfio_notify_type_t type,
> +			   unsigned long *events,
> +			   struct notifier_block *nb)
> +{
> +	struct vfio_group *group;
> +	int ret;
> +
> +	if (!dev || !nb)
> +		return -EINVAL;
> +	if (!events || *events == 0)
> +		return -EINVAL;
> +
> +	group = vfio_group_get_from_dev(dev);
> +	if (IS_ERR(group))
> +		return PTR_ERR(group);
> +
> +	switch (type) {
> +	case VFIO_IOMMU_NOTIFY:
> +		ret = vfio_register_iommu_notifier(group, events, nb);
> +		break;
> +	default:
> +		ret = EINVAL;
> +	}
> +
> +	vfio_group_put(group);
> +	return ret;
> +}
> +EXPORT_SYMBOL(vfio_register_notifier);
> +
> +int vfio_unregister_notifier(struct device *dev, vfio_notify_type_t type,
> +			     struct notifier_block *nb)
> +{
> +	struct vfio_group *group;
> +	int ret;
> +
> +	if (!dev || !nb)
> +		return -EINVAL;
> +
> +	group = vfio_group_get_from_dev(dev);
> +	if (IS_ERR(group))
> +		return PTR_ERR(group);
> +
> +	switch (type) {
> +	case VFIO_IOMMU_NOTIFY:
> +		ret = vfio_unregister_iommu_notifier(group, nb);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
> +
>  	vfio_group_put(group);
>  	return ret;
>  }
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 15ff042..6f3ff31 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -107,14 +107,24 @@ extern int vfio_pin_pages(struct device *dev, unsigned long *user_pfn,
>  extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn,
>  			    int npage);
>  
> -#define VFIO_IOMMU_NOTIFY_DMA_UNMAP	(1)
> -
> +typedef unsigned short vfio_notify_type_t;
>  extern int vfio_register_notifier(struct device *dev,
> +				  vfio_notify_type_t type,
> +				  unsigned long *required_events,
>  				  struct notifier_block *nb);
> -
>  extern int vfio_unregister_notifier(struct device *dev,
> +				    vfio_notify_type_t type,
>  				    struct notifier_block *nb);
>  
> +/* each type has independent events */
> +enum vfio_notify_type {
> +	VFIO_IOMMU_NOTIFY = (__force vfio_notify_type_t)0,
> +};
> +
> +/* events for VFIO_IOMMU_NOTIFY */
> +#define VFIO_IOMMU_NOTIFY_DMA_UNMAP	BIT(0)
> +
> +
>  /*
>   * Sub-module helpers
>   */