Re: [RFC 08/14] vfio/nvgrace-egm: Expose EGM region as char device

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Sep 04, 2025 at 04:08:22AM +0000, ankita@nvidia.com wrote:
> +static struct chardev *
> +setup_egm_chardev(struct nvgrace_egm_dev *egm_dev)
> +{
> +	struct chardev *egm_chardev;
> +	int ret;
> +
> +	egm_chardev = kvzalloc(sizeof(*egm_chardev), GFP_KERNEL);
> +	if (!egm_chardev)
> +		goto create_err;
> +
> +	device_initialize(&egm_chardev->device);
> +
> +	/*
> +	 * Use the proximity domain number as the device minor
> +	 * number. So the EGM corresponding to node X would be
> +	 * /dev/egmX.
> +	 */
> +	egm_chardev->device.devt = MKDEV(MAJOR(dev), egm_dev->egmpxm);
> +	egm_chardev->device.class = class;
> +	egm_chardev->device.release = egm_chardev_release;
> +	egm_chardev->device.parent = &egm_dev->aux_dev.dev;
> +	cdev_init(&egm_chardev->cdev, &file_ops);
> +	egm_chardev->cdev.owner = THIS_MODULE;
> +
> +	ret = dev_set_name(&egm_chardev->device, "egm%lld", egm_dev->egmpxm);
> +	if (ret)
> +		goto error_exit;
> +
> +	ret = cdev_device_add(&egm_chardev->cdev, &egm_chardev->device);
> +	if (ret)
> +		goto error_exit;
> +
> +	return egm_chardev;
> +
> +error_exit:
> +	kvfree(egm_chardev);

After calling init you have to use put_device not kvfree.

Why kvalloc anyhow? Struct chardev is not big

>  static void egm_driver_remove(struct auxiliary_device *aux_dev)
>  {
> +	struct nvgrace_egm_dev *egm_dev =
> +		container_of(aux_dev, struct nvgrace_egm_dev, aux_dev);
> +	struct chardev *egm_chardev = xa_erase(&egm_chardevs, egm_dev->egmpxm);
> +
> +	if (!egm_chardev)
> +		return;
> +
> +	del_egm_chardev(egm_chardev);
>  }

This proceeds even if files are left open which is not going to be any
good..

Jason