RE: [PATCH v2 11/14] vfio: Make vfio_device_open() exclusive between group path and device cdev path

Tian, Kevin
2023-02-07T06:25:05Z

> From: Liu, Yi L <yi.l.liu@intel.com>
> Sent: Monday, February 6, 2023 5:05 PM
>
> struct vfio_device_file *
> -vfio_allocate_device_file(struct vfio_device *device)
> +vfio_allocate_device_file(struct vfio_device *device, bool is_cdev_device)
> {
> struct vfio_device_file *df;
>
> @@ -407,6 +407,7 @@ vfio_allocate_device_file(struct vfio_device *device)
> return ERR_PTR(-ENOMEM);
>
> df->device = device;
> + df->is_cdev_device = is_cdev_device;

You missed Alex's comment that the one caller can open code the
assignment instead of introducing an unmemorable Boolean arg here.

>
> + /*
> + * 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 or the device has already been opened by a cdev path.
> + */
> + if (device->open_count != 0 &&
> + (df->is_cdev_device || device->single_open))
> + return -EINVAL;
> +

If we are gonna handle the exclusive open via dma ownership, then
here we don't need a new single_open flag inside vfio_device since
only one interface (cdev or group) could be used to open this device.

Just preventing multi-open in cdev is sufficient here.