[Intel-gfx] [PATCH v9 09/25] vfio: Add cdev_device_open_cnt to vfio_group

[Eric Auger]

Hi Yi,

On 4/1/23 17:18, Yi Liu wrote:
> 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.
>
> Reviewed-by: Kevin Tian <kevin.tian at intel.com>
> Reviewed-by: Jason Gunthorpe <jgg at nvidia.com>
> Tested-by: Terrence Xu <terrence.xu at intel.com>
> Tested-by: Nicolin Chen <nicolinc at nvidia.com>
> Tested-by: Matthew Rosato <mjrosato at linux.ibm.com>
> Tested-by: Yanting Jiang <yanting.jiang at intel.com>
> Signed-off-by: Yi Liu <yi.l.liu at intel.com>
Reviewed-by: Eric Auger <eric.auger at redhat.com>

Thanks

Eric
> ---
>  drivers/vfio/group.c | 33 +++++++++++++++++++++++++++++++++
>  drivers/vfio/vfio.h  |  3 +++
>  2 files changed, 36 insertions(+)
>
> diff --git a/drivers/vfio/group.c b/drivers/vfio/group.c
> index 71f0a9a4016e..d55ce3ca44b7 100644
> --- a/drivers/vfio/group.c
> +++ b/drivers/vfio/group.c
> @@ -383,6 +383,33 @@ static long vfio_group_fops_unl_ioctl(struct file *filep,
>  	}
>  }
>  
> +int vfio_device_block_group(struct vfio_device *device)
> +{
> +	struct vfio_group *group = device->group;
> +	int ret = 0;
> +
> +	mutex_lock(&group->group_lock);
> +	if (group->opened_file) {
> +		ret = -EBUSY;
> +		goto out_unlock;
> +	}
> +
> +	group->cdev_device_open_cnt++;
> +
> +out_unlock:
> +	mutex_unlock(&group->group_lock);
> +	return ret;
> +}
> +
> +void vfio_device_unblock_group(struct vfio_device *device)
> +{
> +	struct vfio_group *group = device->group;
> +
> +	mutex_lock(&group->group_lock);
> +	group->cdev_device_open_cnt--;
> +	mutex_unlock(&group->group_lock);
> +}
> +
>  static int vfio_group_fops_open(struct inode *inode, struct file *filep)
>  {
>  	struct vfio_group *group =
> @@ -405,6 +432,11 @@ 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.
>  	 */
> @@ -479,6 +511,7 @@ static void vfio_group_release(struct device *dev)
>  	mutex_destroy(&group->device_lock);
>  	mutex_destroy(&group->group_lock);
>  	WARN_ON(group->iommu_group);
> +	WARN_ON(group->cdev_device_open_cnt);
>  	ida_free(&vfio.group_ida, MINOR(group->dev.devt));
>  	kfree(group);
>  }
> diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
> index 854f2c97cb9a..b2f20b78a707 100644
> --- a/drivers/vfio/vfio.h
> +++ b/drivers/vfio/vfio.h
> @@ -83,8 +83,11 @@ 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_block_group(struct vfio_device *device);
> +void vfio_device_unblock_group(struct vfio_device *device);
>  int vfio_device_set_group(struct vfio_device *device,
>  			  enum vfio_group_type type);
>  void vfio_device_remove_group(struct vfio_device *device);