Re: [RFC, PATCH 1/1] rpmb: add Replay Protected Memory Block (RPMB) driver

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Hi Bart,

sorry for not replying earlier, as I am very new to NVMe/UFS spec and was figuring out few details about them.

On 7/21/23 18:40, Shyam Saini wrote:
 +config RPMB
 +	tristate "RPMB partition interface"
 +	help
 +	  Unified RPMB partition interface for RPMB capable devices such as
 +          eMMC and UFS. Provides interface for in kernel security
 controllers to
 +	  access RPMB partition.
 +
 +	  If unsure, select N.

Please also mention NVMe.

Sure,
Please change the word "partition" into "unit" to avoid confusion with the concept "LBA range partition".

sure, in next iteration

 +static DEFINE_IDA(rpmb_ida);

How are accesses to this IDA serialized?

I will look into that.

 +/**
 + * rpmb_get_capacity() - returns the capacity of the rpmb device
 + * @rdev: rpmb device
 + *
 + * Return:
 + * *        capacity of the device in units of 128K, on success
 + * *        -EINVAL on wrong parameters
 + * *        -EOPNOTSUPP if device doesn't support the requested operation
 + * *        < 0 if the operation fails
 + */

Why in units of 128 KiB?

I think UFS/eMMC RPMB spec suggests size of RPMB multiple of 128K
and NVMe spec suggests RPMB Data Area to be multiple of 128K as well.

 +/**
 + * rpmb_dev_find_by_device() - retrieve rpmb device from the parent
 device
 + * @parent: parent device of the rpmb device
 + * @target: RPMB target/region within the physical device
 + *
 + * Return: NULL if there is no rpmb device associated with the parent
 device
 + */

Can an NVMe controller have multiple RPMB units? From the NVMe specification: "The controller may support multiple RPMB targets."

That we have to figure, I see NVMe device can have upto 7 RPMB
targets/units

Can rpmb_dev_find_by_device() be used if multiple RPMB units are associated with a single controller?

That's not finalised yet, but we some ideas from Optee folks on the other replies.

 +/**
 + * rpmb_dev_register - register RPMB partition with the RPMB subsystem
 + * @dev: storage device of the rpmb device
 + * @target: RPMB target/region within the physical device
 + * @ops: device specific operations
 + *
 + * Return: a pointer to rpmb device
 + */
 +struct rpmb_dev *rpmb_dev_register(struct device *dev, u8 target,
 +				   const struct rpmb_ops *ops)
 +{
 +	struct rpmb_dev *rdev;
 +	int id;
 +	int ret;
 +
 +	if (!dev || !ops)
 +		return ERR_PTR(-EINVAL);
 +
 +	if (!ops->program_key)
 +		return ERR_PTR(-EINVAL);
 +
 +	if (!ops->get_capacity)
 +		return ERR_PTR(-EINVAL);
 +
 +	if (!ops->get_write_counter)
 +		return ERR_PTR(-EINVAL);
 +
 +	if (!ops->write_blocks)
 +		return ERR_PTR(-EINVAL);
 +
 +	if (!ops->read_blocks)
 +		return ERR_PTR(-EINVAL);
 +
 +	rdev = kzalloc(sizeof(*rdev), GFP_KERNEL);
 +	if (!rdev)
 +		return ERR_PTR(-ENOMEM);
 +
 +	id = ida_simple_get(&rpmb_ida, 0, 0, GFP_KERNEL);
 +	if (id < 0) {
 +		ret = id;
 +		goto exit;
 +	}
 +
 +	mutex_init(&rdev->lock);
 +	rdev->ops = ops;
 +	rdev->id = id;
 +	rdev->target = target;
 +
 +	dev_set_name(&rdev->dev, "rpmb%d", id);
 +	rdev->dev.class = &rpmb_class;
 +	rdev->dev.parent = dev;
 +
 +	rpmb_cdev_prepare(rdev);
 +
 +	ret = device_register(&rdev->dev);
 +	if (ret)
 +		goto exit;
 +
 +	rpmb_cdev_add(rdev);
 +
 +	dev_dbg(&rdev->dev, "registered device\n");
 +
 +	return rdev;
 +
 +exit:
 +	if (id >= 0)
 +		ida_simple_remove(&rpmb_ida, id);
 +	kfree(rdev);
 +	return ERR_PTR(ret);
 +}

How is user space software supposed to map an NVMe RPMB target ID to an RPMB device name?

I am not sure, this driver aims to provide in kernel RPMB access APIs, user space support may be added later on, but i will look if the current RFC version has any implication on future user-space support.

 +MODULE_AUTHOR("Intel Corporation");

Shouldn't this be the name of a person instead of the name of a company?


Thanks, I will address that in next iteration.

Please keep posted your reviews and feedback.

Best Regards,
Shyam



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