[M] Change in coreboot[main]: cpu/x86: Support SMBASE relocation-only use-case

[Benjamin Doron (Code Review)]

Attention is currently required from: Angel Pons, Dinesh Gehlot, Eran Mitrani, Felix Held, Fred Reitberger, Jason Glenesk, Kapil Porwal, Martin L Roth, Matt DeVillier, Matt DeVillier, Maulik Vaghela, Raul Rangel, Subrata Banik, Tarun, Tarun Tuli, ron minnich.

Benjamin Doron has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/70376?usp=email )

Change subject: cpu/x86: Support SMBASE relocation-only use-case
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Patch Set 7:

(1 comment)

Patchset:

PS7:
> ah, ok, that special hob being within smram/tseg and not just being a regular hob makes me a bit les […]

In this instance, we want to enable secure boot properly, which depends on the integrity of its variables. So, verifying and performing a SPI write should be performed together (which is why we can't use SMMSTORE).

I guess it'd be possible for someone to include proprietary code in SMM, but as I see it, I'm only concerned with the open-source implementation of UefiPayload (as far as I'm aware at this time, we don't have any SMM we're keeping closed at 9elements), and if the user and/or platform builder want to add binaries they can't verify, that's their responsibility.

Ah. Unfortunately I have university classes at 1pm EST. I might be able to make it one of these weeks anyway though.