Inquiry About When OP-TEE OS Runs in M Mode on RISC-V

[HuangBorong]

Hello,

I would like to inquire about the scenarios in which OP-TEE OS runs in M mode.

Thank you for your help!

[gagachang]

@maroueneboubakri Do you have the use case?

[maroueneboubakri]

Hi @gagachang, @HuangBorong,

A use-case is when dedicating a core to OP-TEE (a trusted hart) that may have only M+U modes. M-Mode for OP-TEE OS and U-Mode for TA.
Other cores running Linux for example my interact with OP-TEE using mailbox-like mechanism or other.

We are still investigating this in our side, probably will remove this from the code-base in future.

Best
Maro

[gagachang]

Thanks @maroueneboubakri

M-Mode for OP-TEE OS and U-Mode for TA.

In case there is no S-mode and virtual memory system, how do you construct isolation between TAs ?
Do you configure PMP before every TA execution ?

[HuangBorong]

Thanks!

[maroueneboubakri]

Thanks @maroueneboubakri

M-Mode for OP-TEE OS and U-Mode for TA.

In case there is no S-mode and virtual memory system, how do you construct isolation between TAs ? Do you configure PMP before every TA execution ?

That's correct.