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

Jesse Barnes
2007-05-23T21:20:52Z

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) {