Re: [v4 1/3] vfio: add vfio_group_notify support

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

On Tue, 15 Nov 2016 19:35:45 +0800
Jike Song <jike.song@intel.com> wrote:

> A vfio_group may be or may not be attached to a KVM instance,
> if it is, the user of vfio_group might also want to know which
> KVM instance it is attached to, and when it will detach. In VFIO
> there are already external APIs for KVM to get/put vfio_group,
> by providing a similar vfio_group_notify, KVM can notify the
> vfio_group about attaching events.
> 
> 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  | 30 ++++++++++++++++++++++++++++++
>  include/linux/vfio.h |  4 ++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 0afb58e..b149ced 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -86,6 +86,8 @@ struct vfio_group {
>  	struct mutex			unbound_lock;
>  	atomic_t			opened;
>  	bool				noiommu;
> +	struct kvm			*kvm;
> +	struct blocking_notifier_head	notifier;
>  };
>  
>  struct vfio_device {
> @@ -1015,6 +1017,34 @@ static long vfio_ioctl_check_extension(struct vfio_container *container,
>  	return ret;
>  }
>  
> +void vfio_group_notify(struct vfio_group *group, struct kvm *kvm)
> +{
> +	group->kvm = kvm;
> +	blocking_notifier_call_chain(&group->notifier,
> +				VFIO_GROUP_NOTIFY_SET_KVM, kvm);
> +}
> +EXPORT_SYMBOL_GPL(vfio_group_notify);

This shouldn't be called vfio_group_notify() if it's specific to kvm.
vfio_group_set_kvm() perhaps.

> +
> +static void vfio_group_register_notifier(struct vfio_group *group,
> +					 struct notifier_block *nb)
> +{
> +	blocking_notifier_chain_register(&group->notifier, nb);
> +
> +	/*
> +	 * The attaching of kvm and vfio_group might already happen, so
> +	 * here we replay once on registration.
> +	 */
> +	if (group->kvm)
> +		blocking_notifier_call_chain(&group->notifier,
> +					VFIO_GROUP_NOTIFY_SET_KVM, group->kvm);
> +}
> +
> +static void vfio_group_unregister_notifier(struct vfio_group *group,
> +					 struct notifier_block *nb)
> +{
> +	blocking_notifier_chain_unregister(&group->notifier, nb);
> +}
> +
>  /* hold write lock on container->group_lock */
>  static int __vfio_container_attach_groups(struct vfio_container *container,
>  					  struct vfio_iommu_driver *driver,
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index d4ce14d..ec9f74f 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -100,6 +100,9 @@ extern void vfio_unregister_iommu_driver(
>  extern long vfio_external_check_extension(struct vfio_group *group,
>  					  unsigned long arg);
>  
> +struct kvm;
> +extern void vfio_group_notify(struct vfio_group *group, struct kvm *kvm);
> +
>  /*
>   * Sub-module helpers
>   */
> @@ -149,6 +152,7 @@ extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn,
>  			    int npage);
>  
>  #define VFIO_IOMMU_NOTIFY_DMA_UNMAP	1
> +#define VFIO_GROUP_NOTIFY_SET_KVM	2
>  
>  extern int vfio_register_notifier(struct device *dev,
>  				  struct notifier_block *nb);