Re: [tip:x86/platform] x86/PCI/mmcfg: Switch to ECAM config mode if possible

[Ivan Kokshaysky]

On Fri, Jun 30, 2017 at 10:16:15AM -0700, Linus Torvalds wrote:
> On Fri, Jun 30, 2017 at 7:30 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> >> But MCFG problems were a long time ago and noone uses these systems anymore,
> >> so perhaps he is right.
> >
> > The obvious solution to this is to force type 1 for older machines, i.e. <=
> > K8. Some day we should stop supporting 15+ years old crap just because we
> > can.
> 
> No.
> 
> The fact is, type 1 is the *good* thing.  It's the standard thing that
> has worked pretty much forever, and that is not just tested, but has
> good semantics.

Fully agreed.

Also, config space accesses supposed to be *safe* rather than *fast*.

There was quite a heated discussion on this very subject back in 2008.
Thought that I have a full copy of that, but no, surprisingly...
Google still gives a sufficient part of that:

http://linux-kernel.2935.n7.nabble.com/Patch-v2-Make-PCI-extended-config-space-MMCONFIG-a-driver-opt-in-td243861i60.html

Ivan.