Re: [PATCH 3/4] x86, pci: Add interface to force mmconfig

From: Thomas Gleixner
Date: Tue Mar 14 2017 - 13:56:44 EST


On Tue, 14 Mar 2017, Andi Kleen wrote:
> The other option is to simply make it unconditional. That would
> be even simpler, but it is a bit more risky. Hmm, I suppose may
> be worth trying to find out what Windows uses. If they get away
> with MMCONFIG everywhere we should be too.

>From the PCIe spec:

The PCI 3.0 compatible Configuration Space can be accessed using either
the mechanism defined in the PCI Local Bus Specification or the PCI
Express Enhanced Configuration Access Mechanism (ECAM) described later in
this section. Accesses made using either access mechanism are
equivalent. The PCI Express Extended Configuration Space can only be
accessed by using the ECAM.

The 1.0 spec has a similar wording (s/3.0/2.3).

Definitely the best way to go.

Thanks,

tglx