On 5/22/2014 3:20 PM, Bjorn Helgaas wrote:
On Thu, May 22, 2014 at 1:17 PM, Borislav Petkov <bp@xxxxxxxxx> wrote:
On Thu, May 22, 2014 at 11:56:03AM -0600, Bjorn Helgaas wrote:
I chose Fam16h (0x16) because it looks like that's the newest stuff
that's in the field. I suspect things would probably work if we
changed this patch to leave ECS disabled on some Fam16h, Fam15h, etc.,
but that would change behavior on existing systems, which obviously
adds some risk. I didn't think there was much benefit that makes the
risk worthwhile.
My goal is to stop needing CPU-specific changes in the future, not
necessarily to remove the CPU-specific code we already have.
Does that make sense? I'm not sure whether I understood your real
question.
No, you got it right. I'm just wondering why only the newest stuff.
MMCONFIG is supposed to work just fine on everything from Fam10h
onwards, I'm not sure all Fam10h supported it though. Maybe Suravee can
verify that...
Even if MMCONFIG does work fine on everything from Fam10h onwards, we
still depend on the BIOS to provide a correct MCFG table. I don't
think we can guarantee that changing from ECS to MMCONFIG on a Fam16h
box in the field is safe, because we'd then be using a feature we've
never used before.
Bjorn
At this point, family11h and later (upto 16h which is our most current
processor) should already have supports for the MCFG. However, we can't
guarantee that all the systems currently out there would not use the
ECS. So, I think it is ok to say we won't support it post 16h as Bjorn
suggests.
Suravee
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