On Wed, Sep 05, 2007 at 06:58:58AM +0100, H. Peter Anvin wrote:
> Well, they don't add any functionality, do they?
They allow CF8/CFC to access ECS in cases where mmcfg is not working.
> As such, I would agree with Andi -- we only
> need one method which can (correctly) access the full configuration space,
Right, we need to be able to "correctly access the full config space".
> since it'll look the same on the bus anyway.
Sure, on the bus we should only see pci configuration requests in both
cases.
To summarize it:
- mmcfg needs support by BIOS ("PCI services in ACPI")
- CF8/CFC ECS access does not have that dependency
- For base configuration space access we already have two methods -
type 1 and mmcfg (type1 as fallback if there is no mmcfg).
- So what's the benefit in not allowing CF8/CFC ECS access ("extended type1")
if the hardware supports it and if mmcfg is not suitable?
One thing that comes out of that fruitless discussion:
For IBS Robert might have to implement CF8/CFC ECS access directly in the IBS
code, or in a new driver for ECS access of NB functions. Just to ensure that
IBS is working if there is no mmcfg. And this is kind of ugly.
Regards,
Andreas
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