Hi,
I am writing this email to find out any legacy platforms supports in TF-A (upstream or downstream) which does not have any NS-EL2 component running.
Because NS-EL2 is present but unused EL3 also need to do a minimal initialization of EL2. The side effect of this is, TF-A currently has extra code in generic path (e.g. cm_prepare_el3_exit() ) to cater for these platforms which is not required for most others.
The most likely reason why TF-A introduced support for systems without NS-EL2 was because of UEFI implementation for Windows which didn't initialize NS-EL2 properly. Given that the UEFI spec has said "Use the highest 64 bit non secure privilege level available" for a long time now we are safe to assume that any UEFI implementation will handover to windows at NS-EL2. (similar to Linux)
Considering that there are very few platforms which need this code and to keep backward compatibility, we propose to introduce a macro like "INIT_UNUSED_NS_EL2" and guard the code under this[1]. Keep this flag default disabled and get rid of it( along with code) altogether in next couple of releases, if we are certain that none of the platforms using it.
Please let me know if you are aware of any such platform configuration.
[1] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/22716
Thanks Manish