What's meaning of each bit of machine frame address for xen 64bit

Question

I'm using xen 4.30 64bit. I know that only 48bits are used to index the machine address. The last 12 bits (A0-A11) are the offset of each page, and A12-A47 are the mfn.

I remembered some two bits of the last 12 bits are used for privilege control, but cannot remember which two bits are.

In addition, I want to know how xen uses the last 12 bits to do the page control.

I really appreciate your help if you could point me to some link that explain the last 12 bits.

Thank you very much!

Answer 1

I found the file that contains such information. It's the file: "xen/include/asm-x86/mm.h"

It has all of the bit mask's definition.