Re: [RFC PATCH] PCI MMCONFIG: add validation against ACPI motherboard resources

Stephen Hemminger
2007-05-23T23:15:23Z

On Wed, 23 May 2007 17:09:37 -0400
Jeff Garzik <jgarzik@pobox.com> wrote:

> Jesse Barnes wrote:
> > Apparently Vista will move away from using type 1 config space accesses
> > though, so if we keep using it, we'll probably run into some lame board
>
> Yep.
>
>
> > that assumes you're using mmconfig at some point in the near future.
> > But then again, we're often on that less tested path (e.g. with ACPI),
> > so maybe that doesn't matter much.
>
> One of the reasons why hardware vendors want to move away from
> traditional accesses is to be able to use the larger config space in
> PCI-Express, rather than being locked into the 256-byte legacy PCI
> config space.
>
> Several modern PCI-Express devices utilize the upper config space, but
> due to legacy reasons the registers are usually ones that do not require
> OS drivers to know about (like BIST stuff or diagnostic registers).
>
> Expect that to change, as MS shakes out the bugs (or maybe we are doing
> their job for them?).
>

On some PCI-Express boards, if you don't clear the advanced error reporting
registers on boot up, they will cause IRQ storm. The AER registers
are above 256 boundary. In fact, the AER support in Linux should depend
on MMCONFIG.

--
Stephen Hemminger <shemminger@linux-foundation.org>