Using UEFI runtime variables on Xavier AGX

I’m trying to set/modify some UEFI variables (specifically boot entries/ordering) at runtime after having already booted into Linux. However, this functionality isn’t working on the Xavier AGX, even though it does work on the Orin AGX (and presumably also on the Xavier NX).

I had found this document relating to the experimental version of the UEFI firmware, and it mentions that SetVariable() is not available on the Xavier AGX: https://developer.download.nvidia.com/embedded/L4T/UEFI_Readme_8.26.html
I was hoping this was just a limitation of the experimental UEFI firmware, but it looks like it’s still an issue with the Jetpack 5.0.2 GA release.

After digging into the code, it looks like FvbDxe (from edk2-nvidia/Silicon/NVIDIA/Drivers/FvbDxe) is used on the Xavier AGX, which sets RuntimeServicesSupport to PcdNoVariableRtProperties, unlike FvbNorFlashDxe which sets it to PcdVariableRtProperties. Moreover, in FvbDxe there are checks for EfiAtRuntime() which then exit with EFI_UNSUPPORTED.

I was wondering if there is something fundamental preventing the UEFI variable store from working at runtime on the Xavier AGX, or is it just an unimplemented feature? If the latter, is this on the roadmap to be fixed in the near future?

Our team will do the investigation and provide suggestions soon. Thanks