Define enable_boot_cpu_mm() for the Armv8-R AArch64.
Like boot-time page table in MMU system, we need a boot-time MPU protection
region configuration in MPU system so Xen can fetch code and data from normal
memory.
To do this, Xen maps the following sections of the binary as separate regions
(with permissions) :-
1. Text (Read only at EL2, execution is permitted)
2. RO data (Read only at EL2)
3. RO after init data and RW data (Read/Write at EL2)
4. Init Text (Read only at EL2, execution is permitted)
5. Init data and BSS (Read/Write at EL2)
Before creating a region, we check if the count exceeds the number defined in
MPUIR_EL2. If so, then the boot fails.
Also we check if the region is empty or not. IOW, if the start and end address
are same, we skip mapping the region.
To map a region, Xen uses the PRBAR_EL2, PRLAR_EL2 and PRSELR_EL2 registers.
One can refer to ARM DDI 0600B.a ID062922 G1.3 "General System Control
Registers", to get the definitions of these registers. Also, refer to G1.2
"Accessing MPU memory region registers", the following
```
The MPU provides two register interfaces to program the MPU regions:
- Access to any of the MPU regions via PRSELR_ELx, PRBAR<n>_ELx, and
PRLAR<n>_ELx.
```
We use the above mechanism to create the MPU memory regions.
Also, the compiler needs the flag ("-march=armv8-r") in order to build Xen for
Armv8-R AArch64 MPU based systems. There will be no need for us to explicitly
define MPU specific registers.
Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
---
