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

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Date:	Wed, 23 May 2007 14:20:23 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Robert Hancock <hancockr@...w.ca>,
	Olivier Galibert <galibert@...ox.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...e.de>, Chuck Ebbert <cebbert@...hat.com>,
	Len Brown <lenb@...nel.org>
Subject: Re: [RFC PATCH] PCI MMCONFIG: add validation against ACPI motherboard resources

On Wednesday, May 23, 2007 1:56 pm Linus Torvalds wrote:
> > Not for systems with PCIe...  and the platforms I've been having
> > trouble with have PCIe slots, so I'd really like mmconfig to be
> > used at least on machines with PCIe bridges.  For other machines,
> > it probably doesn't matter much.  I don't know of any regular PCI
> > devices offhand that really need extended config space.
>
> Ehh. Even for PCIe, why not use the normal accesses for the first 256
> bytes? Problem solved.

Ok, this patch also works.  We still need to enable mmconfig space for 
PCIe and extended config space, but we can continue to use type 1 
accesses for legacy PCI config space cycles to avoid decode trouble 
with mmconfig based BAR sizing.

Assuming Robert's and my patches to enable mmconfig space go in, we'd 
want a similar patch to the i386 mmconfig code.

Jesse

diff --git a/arch/x86_64/pci/mmconfig.c b/arch/x86_64/pci/mmconfig.c
index 65d8273..5052f80 100644
--- a/arch/x86_64/pci/mmconfig.c
+++ b/arch/x86_64/pci/mmconfig.c
@@ -61,7 +61,7 @@ static int pci_mmcfg_read(unsigned int seg, unsigned 
int bus,
 	}
 
 	addr = pci_dev_base(seg, bus, devfn);
-	if (!addr)
+	if (!addr || reg < 256) /* Use type 1 for non-extended access */
 		return pci_conf1_read(seg,bus,devfn,reg,len,value);
 
 	switch (len) {
@@ -89,7 +89,7 @@ static int pci_mmcfg_write(unsigned int seg, unsigned 
int bus,
 		return -EINVAL;
 
 	addr = pci_dev_base(seg, bus, devfn);
-	if (!addr)
+	if (!addr || reg < 256) /* Use type 1 for non-extended access */
 		return pci_conf1_write(seg,bus,devfn,reg,len,value);
 
 	switch (len) {
-
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