Normal World-Realm World and RME-RMM architecture

Hi everyone,

  I'm trying to understand the architecture underneath normal world and realm world.

  So in FVP, I can boot the normal world first, then boot the realm world to run application in it. But by doing so, I can't debug the application since I can only do it in Arm DS.

  If I want to create a realm VM, I will need to invoke libraries from RME(RMM) to create a realm world VM and then it counts as running an application in realm world.

  My question is:

  what's the difference between running an application in realm world in FVP and writing a C++ program using RME libraries but I run the application in normal world in FVP.

  Do they count as all running applications in realm world or not?

Much appreciated if anyone can help me!