Kyösti Mälkki has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/42208 )
Change subject: soc/amd/picasso/bootblock: Clear BSS ......................................................................
Patch Set 1:
(1 comment)
https://review.coreboot.org/c/coreboot/+/42208/1//COMMIT_MSG Commit Message:
https://review.coreboot.org/c/coreboot/+/42208/1//COMMIT_MSG@9 PS1, Line 9: The PSP does not currently reload bootblock on S3 resume. This means the
Sorry for being ignorant about the bootflow, but why would it be useful to reload the bootblock? (bo […]
It was not clear from the couple commit messages, but mentioned somewhere in the comments; future PSP will reload the bootblock.
Picasso has a very different bootflow to other x86, bootblock is not execute-in-place, and may reside "anywhere" in the SPI flash. Instead, executable is linked and loaded at a static memory location, low enough to be guaranteed to reside in DRAM and not overlap MMIO windows. As I understand it, region could only be marked as reserved from the OS, not write-protected.
It is forbidden for S3 resume path to execute code that may have been altered from the OS. So choices are reloading or creating a relocatable bootblock rmodule that would get relocated in SMRAM. Former is easier to develop, latter might have had a slightly faster S3 resume path.