Hi all,
We found the problem with FPU S16-S31 registers if FPU is enabled and compiler uses S16-S31 FPU registers on CM33 non-secure code with TZ agent. SPM doesn't save/restore S16-S31 registers properly nor by PendSV neither by FLIH SVC handler. I created a patch for this problem: https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/34202
The second problem I found is related to lazy stacking. It's possible that float point context will be stacked by MCU when FLIH is switching to/from background thread after a new boundary is applied. As result it's possible that the non-privileged code will no have access to PSP stack of suspended partition because a new MPU settings are applied. Please review a patch for this problem: https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/34203
Regards, Roman.