[coreboot-gerrit] Change in coreboot[master]: arch/x86: Reserve some CAR memory for FSP single stack requirement

[Aaron Durbin (Code Review)]

Aaron Durbin has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/35165 )

Change subject: arch/x86: Reserve some CAR memory for FSP single stack requirement
......................................................................

Patch Set 10:

(1 comment)

https://review.coreboot.org/c/coreboot/+/35165/9/src/arch/x86/car.ld 
File src/arch/x86/car.ld:

https://review.coreboot.org/c/coreboot/+/35165/9/src/arch/x86/car.ld@94 
PS9, Line 94: #if CONFIG(FSP_USES_CB_STACK)
> yes, agree the ordering is important hence i have added the layout diagram to call out where FSP heap should exist. i hope that helps. Now as you said, will guard with ENV_ROMSTAGE to make it explicit. but i need to check in case of FSP-T usecase do FSP need to have heap region reversed as well  (i hope that would be the case as well), right not chrome doesn't use FSP_t but there are some user for FSp-T as well.

If this reservation is needed for FSP-T then I think the FSP spec should be fixed. It has no mention of this in the spec, and I don't see why it would. If that is the case this allocation would have to be allocated and fixed in location (higher up this file). With my current understanding there's no reason to put this directly in the linker when we can put it in the .bss. If you are concerned about quality then just add a comment on top of variable.