Re: [PATCH] x86_64: set cfg_size for AMD Family 10h in case MMCONFIG is used

H. Peter Anvin
2007-09-13T19:31:43Z

Yinghai Lu wrote:
> On 9/13/07, H. Peter Anvin <hpa@zytor.com> wrote:
>> Yinghai Lu wrote:
>>> BIOS guys also said that fam 10h need mmconfig via eax accessing, may
>>> need OS do sth, so it is safe to stay with MCFG entry for SB like
>>> mcp55...
>>>
>>> but latest kernel already have that workaround to make mmconfig via eax...
>>>
>> This is actually a good point. Since the CPU vendor managed to
>> completely fuck up the operation of MMCONFIG itself on this CPU (it's a
>> *MEMORY REFERENCE*, guys!), it is actually to be expected and prudent
>> that BIOS vendors will drop the MCFG entry. MMCONFIG doesn't actually
>> work on this CPU for any system software which doesn't already know to
>> work around this particular piece of severe braindamage;
>> standards-complicant MMCONFIG isn't supported at all.
>
> if other mmconfig device on x86 is sick of accessing via eax, may need
> to provide one fam10h_pci_mmcfg to be assigned to raw_pci_ops instead
> and leave pci_mmcfg to default behavior ( *MEMORY REFERENCE*).
>

We already have the workaround. WE do. However, you could easily see
why a BIOS vendor would want to leave out the MCFG ACPI info, since fam
10h's mmconfig is broken.

-hpa