[M] Change in coreboot[master]: arch/arm64: Add EL1/EL2/EL3 support for arm64

[David Milosevic (Code Review)]

Attention is currently required from: Julius Werner.

Hello build bot (Jenkins), Julius Werner,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/74798

to look at the new patch set (#4).

Change subject: arch/arm64: Add EL1/EL2/EL3 support for arm64
......................................................................

arch/arm64: Add EL1/EL2/EL3 support for arm64

Currently, arch/arm64 requires coreboot to run on EL3 due
to EL3 register access. This might be an issue when, for example,
one boots into TF-A first and drops into EL2 for coreboot afterwards.

This patch aims at making arch/arm64 more versatile by removing the
current EL3 constraint and allowing arm64 coreboot to run on EL1,
EL2 and EL3.

The strategy here, is to read coreboot's current EL via the
'currentel' register and choose the appropriate ELx register. So,
for example, when running coreboot on EL1, we would not access
vbar_el3 or vbar_el2 but instead vbar_el1. This way, we don't
generate faults when accessing higher-EL registers.

Currently only tested on the qemu-aarch64 target. Exceptions were
tested by enabling FATAL_ASSERTS.

Signed-off-by: David Milosevic 
Change-Id: Iae1c57f0846c8d0585384f7e54102a837e701e7e
---
M src/arch/arm64/armv8/cache.c
M src/arch/arm64/armv8/exception.c
M src/arch/arm64/armv8/mmu.c
M src/arch/arm64/include/armv8/arch/cache.h
M src/arch/arm64/include/armv8/arch/lib_helpers.h
M src/arch/arm64/ramdetect.c
M src/arch/arm64/transition.c
M src/arch/arm64/transition_asm.S
8 files changed, 145 insertions(+), 26 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/98/74798/4