[PATCH v3 11/15] vfio: Add cdev_device_open_cnt to vfio_group

[Tian, Kevin]

> From: Liu, Yi L <yi.l.liu at intel.com>
> Sent: Monday, February 13, 2023 11:14 PM
> 
> for counting the devices that are opened via the cdev path. This count
> is increased and decreased by the cdev path. The group path checks it
> to achieve exclusion with the cdev path. With this, only one path (group
> path or cdev path) will claim DMA ownership. This avoids scenarios in
> which devices within the same group may be opened via different paths.

please move vfio_device_claim/release_group() from patch 14 into
this patch to make the exclusiveness part complete.

> 
> Signed-off-by: Yi Liu <yi.l.liu at intel.com>
> ---
>  drivers/vfio/group.c | 5 +++++
>  drivers/vfio/vfio.h  | 1 +
>  2 files changed, 6 insertions(+)
> 
> diff --git a/drivers/vfio/group.c b/drivers/vfio/group.c
> index 9f3f6f0e4942..f3f5f4589cdd 100644
> --- a/drivers/vfio/group.c
> +++ b/drivers/vfio/group.c
> @@ -403,6 +403,11 @@ static int vfio_group_fops_open(struct inode *inode,
> struct file *filep)
>  		goto out_unlock;
>  	}
> 
> +	if (group->cdev_device_open_cnt) {
> +		ret = -EBUSY;
> +		goto out_unlock;
> +	}
> +
>  	/*
>  	 * Do we need multiple instances of the group open?  Seems not.
>  	 */
> diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
> index 6f063e31d08a..7a77fb12bd2c 100644
> --- a/drivers/vfio/vfio.h
> +++ b/drivers/vfio/vfio.h
> @@ -84,6 +84,7 @@ struct vfio_group {
>  	struct blocking_notifier_head	notifier;
>  	struct iommufd_ctx		*iommufd;
>  	spinlock_t			kvm_ref_lock;
> +	unsigned int			cdev_device_open_cnt;
>  };
> 
>  int vfio_device_set_group(struct vfio_device *device,
> --
> 2.34.1