Change in coreboot[master]: cpu/x86/entry16.S: Make Intel CBnT TOCTOU safe

[Arthur Heymans (Code Review)]

Attention is currently required from: Christian Walter, Angel Pons, Kyösti Mälkki, Patrick Rudolph.
Hello Christian Walter, Angel Pons, Kyösti Mälkki, Patrick Rudolph,

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

https://review.coreboot.org/c/coreboot/+/54010

to look at the new patch set (#2).

Change subject: cpu/x86/entry16.S: Make Intel CBnT TOCTOU safe
......................................................................

cpu/x86/entry16.S: Make Intel CBnT TOCTOU safe

Intel CBnT (and Boot Guard) makes the chain of trust TOCTOU safe by
setting up NEM (non eviction mode) in the ACM. The CBnT IBB (Initial
BootBlock) therefore should not disable caching.

Sidenote: the MSR macros are taken from the slimbootloader project.

TESTED: ocp/Deltalake boot with and without CBnT and also a broken
CBnT setup.

Change-Id: Id2031e4e406655e14198e45f137ba152f8b6f567
Signed-off-by: Arthur Heymans 
---
M src/cpu/x86/entry16.S
M src/include/cpu/intel/msr.h
2 files changed, 22 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/10/54010/2