Hi Bertrand, On 24/03/2025 13:53, Bertrand Marquis wrote:
When VM to VM support is activated and there is no suitable FF-A support in the firmware, enable FF-A support for VMs to allow using it for VM to VM communications.
tee/ and the callbacks associated are meant to be used for mediatiors. My current interpretation ist this is only meant to interpose between a guest and physical resources. Here you are extending the meaning to "virtual TEE". I am sort of ok with that but ...
If there is OP-TEE running in the secure world and using the non FF-A communication system, having CONFIG_FFA_VM_TO_VM could be non functional (if optee is probed first) or OP-TEE could be non functional (if FF-A is probed first) so it is not recommended to activate the configuration option for such systems.
... this part is concerning me. You should be able to build with CONFIG_FFA_VM_TO_VM and still boot when OP-TEE is present on the system. This is not too critical now as this is tech preview but this is definitely a blocker for making FFA supported. Can this be mentioned at the top of the ffa.c file (which already contains existing blocker)?
Also, given this would expose a fully virtual TEE, we should be able to have a system where you have some VMs talking FFA and some using the physical OPTEE (or another TEE). Whether we want to support it is a different question but this design would prevent it. Is this intended?
Cheers, -- Julien Grall
