> From: Liu, Yi L <yi.l....@intel.com>
> Sent: Monday, February 13, 2023 11:14 PM
>
> With the introduction of vfio device cdev, userspace can get device
> access by either the legacy group path or the cdev path. For VFIO devices,
> it can only be opened by one of the group path and the cdev path at one
> time. e.g. when the device is opened via cdev path, the group path should
> be failed. Both paths will call into vfio_device_open(), so the exclusion
> is done in it.
the exclusive part between two paths is handled by the last patch.
this patch should stay with explaining single-open facet in cdev path.
>
> + /*
> + * Device cdev path cannot support multiple device open since
> + * it doesn't have a secure way for it. So a second device
> + * open attempt should be failed if the caller is from a cdev
> + * path.
> + */
remove the last sentence.
> + if (device->open_count != 0 && df->is_cdev_device)
> + return -EINVAL;
> +
> device->open_count++;
> if (device->open_count == 1) {
> ret = vfio_device_first_open(df, dev_id, pt_id);
> @@ -543,7 +552,12 @@ static int vfio_device_fops_release(struct inode
> *inode, struct file *filep)
> struct vfio_device_file *df = filep->private_data;
> struct vfio_device *device = df->device;
>
> - vfio_device_group_close(df);
> + /*
> + * group path supports multiple device open, while cdev doesn't.
> + * So use vfio_device_group_close() for !is_cdev_device case.
> + */
I don't say why multi-open is the reason to call group_close(). Isn't
it straightforward to do so in the group path? I'd just remove the comment.
> + if (!df->is_cdev_device)
> + vfio_device_group_close(df);
>
> vfio_device_put_registration(device);
>
> --
> 2.34.1
