Michael Niewöhner has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/35799 )
Change subject: soc/intel/sgx: make SGX a Kconfig option ......................................................................
Patch Set 2:
(1 comment)
https://review.coreboot.org/c/coreboot/+/35799/2/src/soc/intel/apollolake/me... File src/soc/intel/apollolake/memmap.c:
https://review.coreboot.org/c/coreboot/+/35799/2/src/soc/intel/apollolake/me... PS2, Line 41: PrmrrSize
I find it weird that this is an FSP-M parameter, but sgx_enable isn't. […]
Correct,it is "just ram" but as soon as PRMRR gets enabled and locked, any access to it will be simply dropped by the CPU. Coreboot enables PRMRR only, when SGX is enabled. I'll add a comment on this.
I don't know what FSP-M really does but it does not lock/enable the range because we wouldn't be able to set and enable it after locking. I guess it just needs it for calculation of other ranges.