Re: [patch] Ignore MCFG if the mmconfig area isn't reserved in the e820 table.

[Arjan van de Ven <arjan@linux.intel.com>]

Petr Vandrovec wrote:
> Arjan van de Ven wrote:
>> Konrad Rzeszutek wrote:
>>
>>> That is definitely a problem - and the "sanity-check" can definitly bail
>>> out on those BIOSes and not crash Linux. The other side of the coin 
>>> is that BIOSes that do implement the MCFG/E820 correctly are penalized:
>>
>> I hereby contest that it's implemented correctly if it's not marked 
>> reserved...
> 
> PCI Firmware Specification 3.0 
> (http://www.pcisig.com/members/downloads/specifications/conventional/pcifw_r3.0.pdf), 
> page 42, notes for table 4-2, paragraph 2 says that firmware must report 
> MCFG as reserved region.  Last sentence of same paragraph says that 
> resources may be optionally marked reserved by E820 or EFIGetMemoryMap, 

resources == BARs, MCFG is a whole different beast

> but must be always reported as motherboard resources through ACPI  (for 
> exact citation please see document itself, it is not freely available so 
> I'm not going to copy-paste text from it without written permission from 
> pcisig...).
> 
> So it seems to me that BIOS not reporting MMCONFIG as reserved through 
> E820 is compliant, and what matters is that MMCONFIG must be reported as 
> ACPI motherboard resource.

I think that's not the right interpretation; resources==BARs in this context.
I'll find a way to get that document and recheck to make sure...