Dear coreboot folks,
Some payloads, like GRUB [1] and formerly FILO [2], convert coreboot’s memory map(?) to E820 table, and copy the type 13. Currently, the Linux kernel does not follow the ACPI specification to treat the undefined types as AddressRangeReserved, so `cbmem` does not work, which can be worked around with `iomem=relaxed`.
I brought this up to the Linux x86 maintainers, and Ingo Molnar kindly responded [attached, 3], and asked:
Just curious: why do they mark it type 13? What semantics do they expect? It's not just some random value I suspect.
Could somebody of the experts here shed some light on this?
Thank you and kind regards,
Paul
PS: Ingo also prepared some patches to make Linux follow the ACPI specification [4].
[1]: https://ticket.coreboot.org/issues/590 [2]: https://review.coreboot.org/c/filo/+/51120 [3]: https://lore.kernel.org/all/aADkQoJE62OdWMhu@gmail.com/ [4]: https://lore.kernel.org/all/20250421185210.3372306-1-mingo@kernel.org/