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Dear All, I am investigating whether the Arm V3AE CPU in the Nvidia AGX Thor supports the Realm Management Extension (RME).
Currently, the RME bit value for ID_AA64PFR0_EL1 on the AGX Thor is 0, indicating that RME is not supported.
According to the official documentation, this RME register value is related to the LEGACYTZEN hardware signal. I would like to know how to modify this signal. I have also raised this question with Nvidia. Since the hardware is still based on the Arm CPU, I would appreciate your insights on this matter.
Support for RME requires both the CPU and the SoC memory system to support it. CPU support alone is not sufficient. The purpose of the LEGACYTZEN signal is to allow the system manufacturer to indicate to the CPU whether their memory system is also configured to support realms. If the memory system hardware does not support it, then there is no way to enable it in software.
Whether this is configurable at boot time would need to be a question for Nvidia, as it's outside of the Arm implementation.
Kind regards, Pete