Re: [Qemu-devel] [PATCH v10 01/19] vfio: Mediated device Core driver

[Jike Song]

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();
> +}