[S] Change in coreboot[master]: payloads/edk2: Set max variable size to 0x8000 for SMMSTORE

[Benjamin Doron (Code Review)]

Attention is currently required from: Sean Rhodes, Martin L Roth, Matt DeVillier, Stefan Reinauer.

Benjamin Doron has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/74176 )

Change subject: payloads/edk2: Set max variable size to 0x8000 for SMMSTORE
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Patch Set 3:

(2 comments)

Patchset:

PS2:
> I don't disagree there - but this is the one major patch we can't merge upstream. […]

I hope upstream merges it at some point, possibly into edk2-platforms PlatformPayloadFeature if we must, but I'm alright with the status quo until then: upstream EDK2 doesn't have SMMSTORE support, users should choose a fork that does. I worry that trying to script `git am` will risk maintaining a mess of slightly different patches per checkout...

What was upstream's rationale? Something like 'UefiPayload isn't for bootloader-specific parts?' Do we have room to push back or is PlatformPayloadFeature good enough?

Patchset:

PS3:
> pretty sure the size was set to 64k due to needing 2 32k blocks at a minimum per UEFI spec

Yeah, I recall that... Seems there's a maximum in this case too. Possibly `SMM_BLOCK_SIZE`.