[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:
> that explains why smmstore won't work for that. […]

As discussed in the leadership meeting, we don't want to pull UEFI code in for verification, and locking the store is an idea brought up on https://review.coreboot.org/c/coreboot/+/79095, which I've addressed there.

Currently, UefiPayload has code that's generic for Intel platforms, so long as it's passed the register offsets. That code is in cbtable.c. Support for AMD platforms could be added to UefiPayload, then, for the current design, we would pass the required registers. I'm already aware that one driver there needs enhancement...

Intel platforms can trigger an SMI for entering S3/S4/S5, but they don't have to. In coreboot, I believe, it's almost just a print-and-return deal. Board dependent SMI handlers aren't supported. That does make the case for sharing SMM, I'm working on that.