Date:   Sat, 29 Oct 2016 12:30:49 +0800
From:   Jike Song <jike.song@...el.com>
To:     Kirti Wankhede <kwankhede@...dia.com>
CC:     alex.williamson@...hat.com, pbonzini@...hat.com, kraxel@...hat.com,
        cjia@...dia.com, qemu-devel@...gnu.org, kvm@...r.kernel.org,
        kevin.tian@...el.com, bjsdjshi@...ux.vnet.ibm.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 01/19] vfio: Mediated device Core driver

On 10/27/2016 05:29 AM, Kirti Wankhede wrote:
> +int mdev_register_device(struct device *dev, const struct parent_ops *ops)
> +{
> +	int ret;
> +	struct parent_device *parent;
> +
> +	/* check for mandatory ops */
> +	if (!ops || !ops->create || !ops->remove || !ops->supported_type_groups)
> +		return -EINVAL;
> +
> +	dev = get_device(dev);
> +	if (!dev)
> +		return -EINVAL;
> +
> +	mutex_lock(&parent_list_lock);
> +
> +	/* Check for duplicate */
> +	parent = __find_parent_device(dev);
> +	if (parent) {
> +		ret = -EEXIST;
> +		goto add_dev_err;
> +	}
> +
> +	parent = kzalloc(sizeof(*parent), GFP_KERNEL);
> +	if (!parent) {
> +		ret = -ENOMEM;
> +		goto add_dev_err;
> +	}
> +
> +	kref_init(&parent->ref);
> +	mutex_init(&parent->lock);
> +
> +	parent->dev = dev;
> +	parent->ops = ops;
> +
> +	ret = parent_create_sysfs_files(parent);
> +	if (ret) {
> +		mutex_unlock(&parent_list_lock);
> +		mdev_put_parent(parent);
> +		return ret;
> +	}
> +
> +	ret = class_compat_create_link(mdev_bus_compat_class, dev, NULL);
> +	if (ret)
> +		dev_warn(dev, "Failed to create compatibility class link\n");
> +

Hi Kirti,

Like I replied to previous version:

	http://www.spinics.net/lists/kvm/msg139331.html

You can always check if mdev_bus_compat_class already registered
here, and register it if not yet. Same logic should be adopted to
mdev_init.

Current implementation will simply panic if configured as builtin,
which is rare but far from impossible.

--
Thanks,
Jike


> +	list_add(&parent->next, &parent_list);
> +	mutex_unlock(&parent_list_lock);
> +
> +	dev_info(dev, "MDEV: Registered\n");
> +	return 0;
> +
> +add_dev_err:
> +	mutex_unlock(&parent_list_lock);
> +	put_device(dev);
> +	return ret;
> +}
> +EXPORT_SYMBOL(mdev_register_device);
> +
> +/*
> + * mdev_unregister_device : Unregister a parent device
> + * @dev: device structure representing parent device.
> + *
> + * Remove device from list of registered parent devices. Give a chance to free
> + * existing mediated devices for given device.
> + */
> +
> +void mdev_unregister_device(struct device *dev)
> +{
> +	struct parent_device *parent;
> +	bool force_remove = true;
> +
> +	mutex_lock(&parent_list_lock);
> +	parent = __find_parent_device(dev);
> +
> +	if (!parent) {
> +		mutex_unlock(&parent_list_lock);
> +		return;
> +	}
> +	dev_info(dev, "MDEV: Unregistering\n");
> +
> +	list_del(&parent->next);
> +	class_compat_remove_link(mdev_bus_compat_class, dev, NULL);
> +
> +	device_for_each_child(dev, (void *)&force_remove,
> +			      mdev_device_remove_cb);
> +
> +	parent_remove_sysfs_files(parent);
> +
> +	mutex_unlock(&parent_list_lock);
> +	mdev_put_parent(parent);
> +}
> +EXPORT_SYMBOL(mdev_unregister_device);
> +
> +static void mdev_device_release(struct device *dev)
> +{
> +	struct mdev_device *mdev = to_mdev_device(dev);
> +
> +	dev_dbg(&mdev->dev, "MDEV: destroying\n");
> +	kfree(mdev);
> +}
> +
> +int mdev_device_create(struct kobject *kobj, struct device *dev, uuid_le uuid)
> +{
> +	int ret;
> +	struct mdev_device *mdev;
> +	struct parent_device *parent;
> +	struct mdev_type *type = to_mdev_type(kobj);
> +
> +	parent = mdev_get_parent(type->parent);
> +	if (!parent)
> +		return -EINVAL;
> +
> +	mutex_lock(&parent->lock);
> +
> +	/* Check for duplicate */
> +	if (mdev_device_exist(parent, uuid)) {
> +		ret = -EEXIST;
> +		goto create_err;
> +	}
> +
> +	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
> +	if (!mdev) {
> +		ret = -ENOMEM;
> +		goto create_err;
> +	}
> +
> +	memcpy(&mdev->uuid, &uuid, sizeof(uuid_le));
> +	mdev->parent = parent;
> +	kref_init(&mdev->ref);
> +
> +	mdev->dev.parent  = dev;
> +	mdev->dev.bus     = &mdev_bus_type;
> +	mdev->dev.release = mdev_device_release;
> +	dev_set_name(&mdev->dev, "%pUl", uuid.b);
> +
> +	ret = device_register(&mdev->dev);
> +	if (ret) {
> +		put_device(&mdev->dev);
> +		goto create_err;
> +	}
> +
> +	ret = mdev_device_create_ops(kobj, mdev);
> +	if (ret)
> +		goto create_failed;
> +
> +	ret = mdev_create_sysfs_files(&mdev->dev, type);
> +	if (ret) {
> +		mdev_device_remove_ops(mdev, true);
> +		goto create_failed;
> +	}
> +
> +	mdev->type_kobj = kobj;
> +	dev_dbg(&mdev->dev, "MDEV: created\n");
> +
> +	mutex_unlock(&parent->lock);
> +	return ret;
> +
> +create_failed:
> +	device_unregister(&mdev->dev);
> +
> +create_err:
> +	mutex_unlock(&parent->lock);
> +	mdev_put_parent(parent);
> +	return ret;
> +}
> +
> +int mdev_device_remove(struct device *dev, bool force_remove)
> +{
> +	struct mdev_device *mdev;
> +	struct parent_device *parent;
> +	struct mdev_type *type;
> +	int ret;
> +
> +	mdev = to_mdev_device(dev);
> +	type = to_mdev_type(mdev->type_kobj);
> +	parent = mdev->parent;
> +	mutex_lock(&parent->lock);
> +
> +	ret = mdev_device_remove_ops(mdev, force_remove);
> +	if (ret) {
> +		mutex_unlock(&parent->lock);
> +		return ret;
> +	}
> +
> +	mdev_remove_sysfs_files(dev, type);
> +	device_unregister(dev);
> +	mutex_unlock(&parent->lock);
> +	mdev_put_parent(parent);
> +	return ret;
> +}
> +
> +static int __init mdev_init(void)
> +{
> +	int ret;
> +
> +	ret = mdev_bus_register();
> +	if (ret) {
> +		pr_err("Failed to register mdev bus\n");
> +		return ret;
> +	}
> +
> +	mdev_bus_compat_class = class_compat_register("mdev_bus");
> +	if (!mdev_bus_compat_class) {
> +		mdev_bus_unregister();
> +		return -ENOMEM;
> +	}
> +
> +	/*
> +	 * Attempt to load known vfio_mdev.  This gives us a working environment
> +	 * without the user needing to explicitly load vfio_mdev driver.
> +	 */
> +	request_module_nowait("vfio_mdev");
> +
> +	return ret;
> +}
> +
> +static void __exit mdev_exit(void)
> +{
> +	class_compat_unregister(mdev_bus_compat_class);
> +	mdev_bus_unregister();
> +}

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