Messages in this thread | | | Date | Mon, 3 Sep 2007 10:32:42 +0200 | From | "Andreas Herrmann" <> | Subject | Re: [patches] [patch 3/5] x86: Add PCI extended config space access for AMD Barcelona |
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On Sat, Sep 01, 2007 at 12:11:52PM +0200, Andi Kleen wrote: > On Thursday 30 August 2007 19:43:14 Robert Richter wrote: > > This patch implements PCI extended configuration space access for > > AMD's Barcelona CPUs. It extends the method using CF8/CFC IO > > addresses. An x86 capability bit has been introduced that is set for > > CPUs supporting PCI extended config space accesses. > > We shouldn't need this because extended config space should work > here and Linux should use it > (especially after we added the ugly Barcelona workaround into that code)
This patch is needed for all buggy BIOSes that don't correctly set up MCFG.
> The only exception would be if the user disables MMCONFIG in CONFIG, but that's > their own fault then.
No, as you stated yourself there are two exceptions. And the more serious one is the BIOS issue.
> Ok there might be buggy BIOS around with no or no usable MCFG table, but since > extended config space is not really a critical feature that's not a big issue.
Not sure why you assume extended config space (ECS) is not critical. Ok, for a lot of stuff it does not matter. But it is needed for some devices for full functionality. E.g. for perfmon (family 0x10/extended inerrupts) extended config space access is a prerequisite.
> So I don't think we want this special case code at all and should > just rely on MMCONFIG.
Rely on something unreliable (due to buggy/incomplete BIOS)? I don't think we should do this.
IMHO it is best to try to use MMCONFIG if it's working and to use a fallback (e.g. CF8 ECS access for family 0x10) if available.
Regards,
Andreas
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