Hi Achin,
On 18/03/2019 21:04, Achin Gupta wrote:
On Mon, Mar 18, 2019 at 03:49:12PM +0000, Julien Grall wrote:
(+ Achin)
On 07/03/2019 21:04, Volodymyr Babchuk wrote:
From: Volodymyr Babchuk vlad.babchuk@gmail.com
This enumeration controls TEE type for a domain. Currently there is two possible options: either 'none' or 'native'.
'none' is the default value and it basically disables TEE support at all.
'native' enables access to a "real" TEE installed on a platform.
I am aware I made that suggestion. But I think the naming is not ideal between the user and the toolstack. The question is how this is going to fit with the S-EL2 feature where multiple TEE can run together?
I have CCed Achin to see he has any vision how this could be interfaced.
Thanks.
Multiple TEEs (or rather Trusted OSs) can coexist on Armv8.3 and earlier. They will not be isolated but play along nicely.
That's interesting. So, in the current case (i.e without SPCI), how do you communicate with a specific Trusted OS?
The intent is that prior to S-EL2 and multiple TOSs, each TOS will migrate to using the SPCI spec. At this stage, there should be no need for a TOS specific mediator in the Hypervisor. IOW, there should be a "generic" SPCI mediator. Maybe, we can add a TEE type 'generic' later to enable access to any TEE through this generic interface?
Yes, that's probably a good option to add later. So maybe renaming 'native' to 'optee'(or 'op-tee') would be more suitable here. This avoid the ambiguity of 'native'.
Support for multiple TOSs has raised other questions that we are trying to address e.g. dependencies between them or on guests in Nwd, impact on scheduling decisions made by Nwd etc. Support for OP-TEE in this patch stack does not need to answer these just yet it seems. It is more likely that we will have to tackle support for multiple TEEs afresh rather than treating it as an extension of support for a specific TOS.
I totally agree. SPCI is a separate topic, although I wanted to get a more suitable name for the config so we can avoid introduce a new option later on.
Happy to discuss further and I hope this helps in some way.
Thank you for the feedback!
Cheers,