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SubjectRe: [PATCH 4/4] Documentation: tee: add AMD-TEE driver details
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On 12/26/19 11:24 PM, Rijo Thomas wrote:
> Update tee.txt with AMD-TEE driver details. The driver is written
> to communicate with AMD's TEE.
>
> Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
> Co-developed-by: Devaraj Rangasamy <Devaraj.Rangasamy@amd.com>
> Signed-off-by: Devaraj Rangasamy <Devaraj.Rangasamy@amd.com>
> Signed-off-by: Rijo Thomas <Rijo-john.Thomas@amd.com>

Reviewed-by: Gary R Hook <gary.hook@amd.com>

> ---
> Documentation/tee.txt | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 81 insertions(+)
>
> diff --git a/Documentation/tee.txt b/Documentation/tee.txt
> index afacdf2..c8fad81 100644
> --- a/Documentation/tee.txt
> +++ b/Documentation/tee.txt
> @@ -112,6 +112,83 @@ kernel are handled by the kernel driver. Other RPC messages will be forwarded to
> tee-supplicant without further involvement of the driver, except switching
> shared memory buffer representation.
>
> +AMD-TEE driver
> +==============
> +
> +The AMD-TEE driver handles the communication with AMD's TEE environment. The
> +TEE environment is provided by AMD Secure Processor.
> +
> +The AMD Secure Processor (formerly called Platform Security Processor or PSP)
> +is a dedicated processor that features ARM TrustZone technology, along with a
> +software-based Trusted Execution Environment (TEE) designed to enable
> +third-party Trusted Applications. This feature is currently enabled only for
> +APUs.
> +
> +The following picture shows a high level overview of AMD-TEE::
> +
> + |
> + x86 |
> + |
> + User space (Kernel space) | AMD Secure Processor (PSP)
> + ~~~~~~~~~~ ~~~~~~~~~~~~~~ | ~~~~~~~~~~~~~~~~~~~~~~~~~~
> + |
> + +--------+ | +-------------+
> + | Client | | | Trusted |
> + +--------+ | | Application |
> + /\ | +-------------+
> + || | /\
> + || | ||
> + || | \/
> + || | +----------+
> + || | | TEE |
> + || | | Internal |
> + \/ | | API |
> + +---------+ +-----------+---------+ +----------+
> + | TEE | | TEE | AMD-TEE | | AMD-TEE |
> + | Client | | subsystem | driver | | Trusted |
> + | API | | | | | OS |
> + +---------+-----------+----+------+---------+---------+----------+
> + | Generic TEE API | | ASP | Mailbox |
> + | IOCTL (TEE_IOC_*) | | driver | Register Protocol |
> + +--------------------------+ +---------+--------------------+
> +
> +At the lowest level (in x86), the AMD Secure Processor (ASP) driver uses the
> +CPU to PSP mailbox regsister to submit commands to the PSP. The format of the
> +command buffer is opaque to the ASP driver. It's role is to submit commands to
> +the secure processor and return results to AMD-TEE driver. The interface
> +between AMD-TEE driver and AMD Secure Processor driver can be found in [6].
> +
> +The AMD-TEE driver packages the command buffer payload for processing in TEE.
> +The command buffer format for the different TEE commands can be found in [7].
> +
> +The TEE commands supported by AMD-TEE Trusted OS are:
> +* TEE_CMD_ID_LOAD_TA - loads a Trusted Application (TA) binary into
> + TEE environment.
> +* TEE_CMD_ID_UNLOAD_TA - unloads TA binary from TEE environment.
> +* TEE_CMD_ID_OPEN_SESSION - opens a session with a loaded TA.
> +* TEE_CMD_ID_CLOSE_SESSION - closes session with loaded TA
> +* TEE_CMD_ID_INVOKE_CMD - invokes a command with loaded TA
> +* TEE_CMD_ID_MAP_SHARED_MEM - maps shared memory
> +* TEE_CMD_ID_UNMAP_SHARED_MEM - unmaps shared memory
> +
> +AMD-TEE Trusted OS is the firmware running on AMD Secure Processor.
> +
> +The AMD-TEE driver registers itself with TEE subsystem and implements the
> +following driver function callbacks:
> +
> +* get_version - returns the driver implementation id and capability.
> +* open - sets up the driver context data structure.
> +* release - frees up driver resources.
> +* open_session - loads the TA binary and opens session with loaded TA.
> +* close_session - closes session with loaded TA and unloads it.
> +* invoke_func - invokes a command with loaded TA.
> +
> +cancel_req driver callback is not supported by AMD-TEE.
> +
> +The GlobalPlatform TEE Client API [5] can be used by the user space (client) to
> +talk to AMD's TEE. AMD's TEE provides a secure environment for loading, opening
> +a session, invoking commands and clossing session with TA.
> +
> References
> ==========
>
> @@ -125,3 +202,7 @@ References
>
> [5] http://www.globalplatform.org/specificationsdevice.asp look for
> "TEE Client API Specification v1.0" and click download.
> +
> +[6] include/linux/psp-tee.h
> +
> +[7] drivers/tee/amdtee/amdtee_if.h
>

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