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What is different between AF & AP? I understand AP = permission access as read/write/readonly/no access but what is AF?
Simply do only map memory which you want to use. Any other access generates a data abort.
AF is used for the OS. With AF == 0 you will get a data abort. Then the OS will know that the user process wants to use this memory, and takes action, like loading the data from external memory. Or doing a copy on write.
Thanks again. I don't find good document that describe memory attributes. I also have question on Indx(MAIR_ELn) too. Do you any good reference doc?
You seem to talk about ARMv8-A. So check out:
DEN0024A - ARMv8 Programmer GuideDDI0478C_A - ARMv8 Reference Manualand
https://developer.arm.com/architectures/learn-the-architecture