Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [patches] [patch 3/5] x86: Add PCI extended config space access for AMD Barcelona | Date | Mon, 3 Sep 2007 14:48:41 +0200 |
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On Monday 03 September 2007 13:27, Robert Richter wrote:
> On 03.09.07 12:15:03, Andi Kleen wrote: > > > But it is needed for some devices for full functionality. > > > > Examples? I can only think of PCI express error reporting, which > > few drivers implement anyways and isn't really a show stopper > > if it doesn't work. Besides I would be surprised if it even works > > on the cheap desktop boards which have MCFG less BIOS. > > As you say, there are BIOSs that do not support MMCONFIG. Thus, CF8 > access is not only a workaround to boot a system.
We're talking about accessing the extended part of config spaces. I'm not aware of any case where that is required to boot a system.
> Recent (10h) and upcomming CPU families make heavy use of PCI ext cfg > space for certain CPU features. Setup of the extended interupt local > vector table for IBS (used with Perfmon2) is one example. CPU > designers do not take care anymore if a feature is in the base or > extended config space. So access to PCI ECS is essential.
I don't think it's a big issue if IBS doesn't work on a few buggy BIOS (which should hopefully become fewer anyways because Vista is out which actually uses MCFG)
> > > 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. > > > > We only put in workarounds if there is a serious problem otherwise (e.g. > > not booting etc.). I just don't see this here. > > As said above, I do not see CF8 access as a workaround. I expect my > system to work in the same way also if MMCONFIG is not available.
It should boot sure, but exotic stuff not working is not a major issue
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