linux-kernel - Re: [PATCH 2/3] tee: tstee: Add Trusted Services TEE driver

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Message-ID: <ed8aaee7-be14-43ab-981c-d2ac04f4fc71@kernel.org>
Date: Thu, 15 Feb 2024 09:59:50 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Balint Dobszay <balint.dobszay@....com>,
 op-tee@...ts.trustedfirmware.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc: jens.wiklander@...aro.org, sumit.garg@...aro.org, corbet@....net,
 sudeep.holla@....com, gyorgy.szing@....com
Subject: Re: [PATCH 2/3] tee: tstee: Add Trusted Services TEE driver

On 13/02/2024 15:52, Balint Dobszay wrote:
> The Trusted Services project provides a framework for developing and
> deploying device Root of Trust services in FF-A Secure Partitions. The
> FF-A SPs are accessible through the FF-A driver, but this doesn't
> provide a user space interface. The goal of this TEE driver is to make
> Trusted Services SPs accessible for user space clients.
> 
> All TS SPs have the same FF-A UUID, it identifies the RPC protocol used
> by TS. A TS SP can host one or more services, a service is identified by
> its service UUID. The same type of service cannot be present twice in
> the same SP. During SP boot each service in an SP is assigned an
> interface ID, this is just a short ID to simplify message addressing.
> There is 1:1 mapping between TS SPs and TEE devices, i.e. a separate TEE
> device is registered for each TS SP. This is required since contrary to
> the generic TEE design where memory is shared with the whole TEE
> implementation, in case of FF-A, memory is shared with a specific SP. A
> user space client has to be able to separately share memory with each SP
> based on its endpoint ID.
> 
> Signed-off-by: Balint Dobszay <balint.dobszay@....com>
> ---


> +static int tstee_probe(struct ffa_device *ffa_dev)
> +{
> +	struct tstee *tstee;
> +	int rc;
> +
> +	ffa_dev->ops->msg_ops->mode_32bit_set(ffa_dev);
> +
> +	if (!tstee_check_rpc_compatible(ffa_dev))
> +		return -EINVAL;
> +
> +	tstee = kzalloc(sizeof(*tstee), GFP_KERNEL);
> +	if (!tstee)
> +		return -ENOMEM;
> +
> +	tstee->ffa_dev = ffa_dev;
> +
> +	tstee->pool = tstee_create_shm_pool();
> +	if (IS_ERR(tstee->pool)) {
> +		rc = PTR_ERR(tstee->pool);
> +		tstee->pool = NULL;
> +		goto err;

Is it logically correct to call here tee_device_unregister()?

> +	}
> +
> +	tstee->teedev = tee_device_alloc(&tstee_desc, NULL, tstee->pool, tstee);
> +	if (IS_ERR(tstee->teedev)) {
> +		rc = PTR_ERR(tstee->teedev);
> +		tstee->teedev = NULL;
> +		goto err;
> +	}
> +
> +	rc = tee_device_register(tstee->teedev);
> +	if (rc)
> +		goto err;
> +
> +	ffa_dev_set_drvdata(ffa_dev, tstee);
> +
> +	pr_info("driver initialized for endpoint 0x%x\n", ffa_dev->vm_id);

Don't print simple probe success messages. Anyway all prints in device
context should be dev_*.

> +
> +	return 0;
> +
> +err:
> +	tstee_deinit_common(tstee);
> +	return rc;
> +}
> +
> +static void tstee_remove(struct ffa_device *ffa_dev)
> +{
> +	tstee_deinit_common(ffa_dev->dev.driver_data);
> +}
> +
> +static const struct ffa_device_id tstee_device_ids[] = {
> +	/* TS RPC protocol UUID: bdcd76d7-825e-4751-963b-86d4f84943ac */
> +	{ TS_RPC_UUID },
> +	{}
> +};
> +
> +static struct ffa_driver tstee_driver = {
> +	.name = "arm_tstee",
> +	.probe = tstee_probe,
> +	.remove = tstee_remove,
> +	.id_table = tstee_device_ids,
> +};
> +
> +static int __init mod_init(void)
> +{
> +	return ffa_register(&tstee_driver);
> +}
> +module_init(mod_init)
> +
> +static void __exit mod_exit(void)
> +{
> +	ffa_unregister(&tstee_driver);
> +}
> +module_exit(mod_exit)
> +
> +MODULE_ALIAS("arm-tstee");

Why do you need this alias? I don't see MODULE_DEVICE_TABLE, so how this
bus handles module loading?


Best regards,
Krzysztof