Re: [PATCH RFC v2 0/8] tee: optee: add RPMI backend support on RISC-V

[Amirreza Zarrabi <amirreza.zarrabi@oss.qualcomm.com>]

Hi Jens,

On 10/8/2026 5:15 PM, Jens Wiklander wrote:
> Hi Amir,
> 
> On Tue, Oct 6, 2026 at 2:39 AM Amirreza Zarrabi
> <amirreza.zarrabi@oss.qualcomm.com> wrote:
>>
>> This series adds an RPMI backend to the OP-TEE driver for RISC-V.
>> It builds on the separately posted RPMI TEE transport series [1],
>> which provides service discovery, synchronous calls, memory parcels
>> and asynchronous signals.
>>
>> This revision is effectively a full rewrite of the original RFC.
>> The generic RPMI transport has been separated from the OP-TEE backend,
>> and the backend has been reworked around the service bus and a new
>> OP-TEE control ABI.
>>
>> Unlike v1, the OP-TEE backend no longer manages SBI MPXY mailbox
>> channels or implements RPMI TEE service-group operations directly.
>> It binds to the OP-TEE service UUID on the RPMI TEE bus and uses the
>> transport's public operations. No additional OP-TEE device-tree node
>> is required.
>>
>> The backend reuses the common OP-TEE session, shared-memory, argument
>> cache, call queue and RPC infrastructure. Shared memory is represented
>> by RPMI parcel IDs and nonces. Yielding calls pass command and RPC
>> buffer ranges within a parcel and resume suspended execution using
>> an opaque token returned by OP-TEE.
>>
>> The OP-TEE control ABI uses fixed-width little-endian messages carried
>> in TEE_CALL payloads rather than reproducing FF-A's register-based
>> message layout. Asynchronous notifications use an allocated TEE-to-REE
>> signal as a bottom-half doorbell, while ordinary logical notifications
>> continue through the common RPC path.
>>
>> Matching OP-TEE OS support for this ABI has not yet been implemented.
>> This remains an RFC for review of the backend integration and the
>> Linux-to-OP-TEE protocol.
>>
>> [1] RPMI TEE transport dependency:
>> https://lore.kernel.org/op-tee/20260928-riscv-rpmi-tee-abi-v1-0-04908b81d885@oss.qualcomm.com/
>>
>> Signed-off-by: Amirreza Zarrabi <amirreza.zarrabi@oss.qualcomm.com>
>> ---
>> Changes in v2:
>> - Effectively rewrite the backend around the separately posted RPMI
>>   TEE transport and a new OP-TEE control ABI.
>> - Remove backend-owned per-hart mailbox channels and the OP-TEE-specific
>>   device-tree binding.
>> - Replace the register-like control payload with fixed-width messages,
>>   explicit command/RPC buffer ranges and opaque resume tokens.
>> - Add a parcel-reference parameter layout carrying the parcel ID,
>>   nonce, and 64-bit offset and size without changing parameter size.
>> - Make argument-offset support part of the baseline ABI and retain
>>   the common shared argument cache.
>> - Use a transport-allocated signal for asynchronous bottom-half
>>   notifications.
>> - Link to v1: https://lore.kernel.org/r/20260912-rpmi-tee-service-grp-dev-v1-0-1d1d35c2a859@oss.qualcomm.com
>>
>> ---
>> Amirreza Zarrabi (8):
>>       tee: optee: allow RPMI transport builds on RISC-V
>>       tee: optee: define the RPMI control and parcel-reference ABI
>>       tee: optee: add RPMI shared-memory and parameter support
>>       tee: optee: add RPMI dynamic shared-memory pool
>>       tee: optee: add RPMI RPC handling
>>       tee: optee: execute yielding RPMI calls
>>       tee: optee: bind RPMI services and negotiate backend capabilities
>>       tee: optee: support RPMI asynchronous notification doorbells
>>
>>  drivers/tee/Kconfig               |    3 +-
>>  drivers/tee/optee/Kconfig         |    3 +-
>>  drivers/tee/optee/Makefile        |    1 +
>>  drivers/tee/optee/call.c          |    2 +
>>  drivers/tee/optee/core.c          |   10 +-
>>  drivers/tee/optee/optee_msg.h     |   38 +-
>>  drivers/tee/optee/optee_private.h |   54 +-
>>  drivers/tee/optee/optee_rpmi.h    |  234 ++++++++
>>  drivers/tee/optee/rpmi_abi.c      | 1059 +++++++++++++++++++++++++++++++++++++
>>  9 files changed, 1389 insertions(+), 15 deletions(-)
> 
> The rpmi changes in the optee driver harmonize quite well with the
> rest of the driver, but there are two things I'd like fixed:
> - avoid <linux/cleanup.h> macros. They are distracting.
> - use rc for the trivial int ERRNO values.
> 

I'll make these changes.

> I would be great with a QEMU-based end-to-end prototype to demonstrate
> that the ABI works.
> 

The OP-TEE side implementation is nearly complete. I'll incorporate your
comments here and update the OP-TEE code accordingly. I haven't started
the OpenSBI changes yet. Getting a QEMU-based end-to-end prototype working
is my first priority before moving the series out of RFC.

Apologies for the obvious oversights and bugs in this version. So far,
I've only compile-tested the code; it still needs end-to-end validation.

> More comments to come in the individual patches.

Thanks, Jens, for the early comments and feedback. They are very helpful
in shaping the final code and guiding the direction of the implementation.

Best regards,
Amir

> 
> Cheers,
> Jens