linux-kernel - Re: [PATCH 3/3] Documentation: tee: Add TS-TEE driver

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Message-ID: <bbb40718-9bfa-4431-a3b0-c09d068fd6cc@infradead.org>
Date: Tue, 13 Feb 2024 13:44:45 -0800
From: Randy Dunlap <rdunlap@...radead.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 3/3] Documentation: tee: Add TS-TEE driver

Hi--

On 2/13/24 06:52, Balint Dobszay wrote:
> Add documentation for the Trusted Services TEE driver.
> 
> Signed-off-by: Balint Dobszay <balint.dobszay@....com>
> ---
>  Documentation/tee/index.rst  |  1 +
>  Documentation/tee/ts-tee.rst | 70 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 71 insertions(+)
>  create mode 100644 Documentation/tee/ts-tee.rst
> 

> diff --git a/Documentation/tee/ts-tee.rst b/Documentation/tee/ts-tee.rst
> new file mode 100644
> index 000000000000..e121ebbbfab7
> --- /dev/null
> +++ b/Documentation/tee/ts-tee.rst
> @@ -0,0 +1,70 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=================================
> +TS-TEE (Trusted Services project)
> +=================================
> +
> +This driver provides access to secure services implemented by Trusted Services.
> +
> +Trusted Services [1] is a TrustedFirmware.org project that provides a framework
> +for developing and deploying device Root of Trust services in FF-A [2] S-EL0
> +Secure Partitions. The project hosts the reference implementation of the Arm
> +Platform Security Architecture [3] for Arm A-profile devices.
> +
> +The FF-A Secure Partitions (SP) are accessible through the FF-A driver [4] which
> +provides the low level communication for this driver. On top of that the Trusted
> +Services RPC protocol is used [5]. To use the driver from user space a reference
> +implementation is provided at [6], which is part of the Trusted Services client
> +library called libts [7].
> +

Fix run-on sentences:

> +All Trusted Services (TS) SPs have the same FF-A UUID, it identifies the TS RPC

                                                    UUID. It
or
                                                    UUIT; it

> +protocol. A TS SP can host one or more services (e.g. PSA Crypto, PSA ITS, etc).
> +A service is identified by its service UUID, the same type of service cannot be

                                          UUID;

> +present twice in the same SP. During SP boot each service in the SP is assigned
> +an "interface ID", this is just a short ID to simplify message addressing.

      "interface ID." This

> +
> +The generic TEE design is to share memory at once with the TEE implementation,
> +which can then be reused to communicate with multiple TAs. However, in case of

"TA" is not defined.

> +FF-A, memory sharing works on an endpoint level, i.e. memory is shared with a
> +specific SP. User space has to be able to separately share memory with each SP
> +based on its endpoint ID, therefore a separate TEE device is registered for each

                         ID; therefore

> +discovered TS SP. Opening the SP corresponds to opening the TEE device and
> +creating a TEE context. A TS SP hosts one or more services, opening a service

                                                     services. Opening

> +corresponds to opening a session in the given tee_context.
> +
> +Overview of a system with Trusted Services components::
> +
> +   User space                  Kernel space                   Secure world
> +   ~~~~~~~~~~                  ~~~~~~~~~~~~                   ~~~~~~~~~~~~
> +   +--------+                                               +-------------+
> +   | Client |                                               | Trusted     |
> +   +--------+                                               | Services SP |
> +      /\                                                    +-------------+
> +      ||                                                          /\
> +      ||                                                          ||
> +      ||                                                          ||
> +      \/                                                          \/
> +   +-------+                +----------+--------+           +-------------+
> +   | libts |                |  TEE     | TS-TEE |           |  FF-A SPMC  |
> +   |       |                |  subsys  | driver |           |   + SPMD    |
> +   +-------+----------------+----+-----+--------+-----------+-------------+
> +   |      Generic TEE API        |     |  FF-A  |     TS RPC protocol     |
> +   |      IOCTL (TEE_IOC_*)      |     | driver |        over FF-A        |
> +   +-----------------------------+     +--------+-------------------------+
> +
> +References
> +==========
> +
> +[1] https://www.trustedfirmware.org/projects/trusted-services/
> +
> +[2] https://developer.arm.com/documentation/den0077/
> +
> +[3] https://www.arm.com/architecture/security-features/platform-security
> +
> +[4] drivers/firmware/arm_ffa/
> +
> +[5] https://trusted-services.readthedocs.io/en/v1.0.0/developer/service-access-protocols.html#abi
> +
> +[6] https://git.trustedfirmware.org/TS/trusted-services.git/tree/components/rpc/ts_rpc/caller/linux/ts_rpc_caller_linux.c?h=v1.0.0
> +
> +[7] https://git.trustedfirmware.org/TS/trusted-services.git/tree/deployments/libts/arm-linux/CMakeLists.txt?h=v1.0.0

-- 
#Randy