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Today I was browsing the ACPI spec and found this interesting description of E820 limitations https://uefi.org/specs/ACPI/6.4/15_Syst ... tions.html

15.2. E820 Assumptions and Limitations
The platform boot firmware returns address ranges describing baseboard memory.

The platform boot firmware does not return a range description for the memory mapping of PCI devices, ISA Option ROMs, and ISA Plug and Play cards because the OS has mechanisms available to detect them.

What is it trying to say in the second point? Are PCI BARs reported as free memory? Does that mean you have to scan the entire PCI tree and manually mark BARs as allocated memory?
Or does it simply not report them at all (either allocated or free)?

Thanks

It doesn't report them at all.

Octocontrabass wrote:It doesn't report them at all.

Thank you, just wanted to double check.