Kyösti Mälkki has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/36288 )
Change subject: cpu/amd/mtrr: Add uma resource based on cbmem_top ......................................................................
Patch Set 31:
I think we should provide clean API for end-of-romstage resources.
Looks like nowadays we register the resources in .read_resources while the hardware programming actually has completed in late romstage? The original approach of using biosram for UMA seems to be workaround for not being able to register resources in romstage, and lazyness of creating CBMEM entry for the purpose.
Looking deeper into northbridge .read_resources, if we want to break away from legacy stuff with kernel payloads, why do we unconditionally reserve 0xa0000 VGA or 0xc0000 OPROM? Or legacy BIOS shadow just below 1MiB? I think an active device should mark those regions reserved instead.