Memory map and type 13 (Fwd: Re: e820: Undefined type not treated as AddressRangeReserved)

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/[email protected]/
[4]: https://lore.kernel.org/all/[email protected]/

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