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

Jesse Barnes
2007-05-23T23:11:44Z

On Wednesday, May 23, 2007 4:04 pm David Miller wrote:
> From: Linus Torvalds <torvalds@linux-foundation.org>
> Date: Wed, 23 May 2007 15:16:23 -0700 (PDT)
>
> > That crap should be seen for the crap it is! Dammit, how hard can
> > it be to just admit that mmconfig isn't that great?
>
> I knew mmconfig was broken conceptually the first time I started
> seeing write posting "bug fixes" for it that would do a read back
> from PCI config space via mmconfig to post the write, which of course
> has potential side-effects on the device and is absolutely illegal if
> the write just performed put the device into a PM state or whatever.

I've actually seen that specific form of posted write flushing cause
crashes on some machines, so yes, it sucks.

Unfortunately, I don't think we have any other way of getting at
extended config space on x86, unless EFI provides methods or something,
but I'm not sure that would be an improvement...

Jesse