Matthew Wilcox wrote:
> On Thu, Mar 18, 2010 at 12:09:21PM -0700, Joyce Yu wrote:
>>> Does your Linux machine with its PCIe card have MMCONFIG enabled?
>>> Check your dmesg to find out. If not, Linux can't access the extended
>>> config space.
>>>
>>> Need more information before we go any further down this decision tree.
>> It is a PCIe card running on Linux. But I didn't find anything with
>> MMCONFIG in the system. I also couldn't find it in the
>> 2.6.16/2.6.18/2.6.22/2.6.24/2.4.26 linux kernel tree.
>
> My laptop reports this in dmesg:
>
> [ 0.188307] PCI: MMCONFIG for domain 0000 [bus 00-3f] at [mem 0xf8000000-0xfbffffff] (base 0xf8000000)
> [ 0.188325] PCI: MMCONFIG at [mem 0xf8000000-0xfbffffff] reserved in E820
> [ 0.188450] PCI: Using MMCONFIG for extended config space
> [ 0.188572] PCI: Using configuration type 1 for base access
>
> and it gets access to extended config space.
>
> Support for extended config space was added before 2.6.12, but I don't
> think it was ever supported by 2.4.
>
> So we need to figure out why your machine doesn't support extended
> config space. What chipset does it use? Is there a BIOS update available
> for it? What does it report in dmesg for config space accesses?
>
In addition to having MMCONFIG enabled on the system (hw & kernel),
you also need to be root because of this snippet in drivers/pci/pci-sysfs.c,
pci_read_config():
unsigned int size = 64;
loff_t init_off = off;
u8 *data = (u8*) buf;
/* Several chips lock up trying to read undefined config space */
if (capable(CAP_SYS_ADMIN)) {
size = dev->cfg_size;
} else if (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
size = 128;
}
which will truncate the read to 1st 64-bytes, so unpriv user can't
crash a system that has badly behaving PCI(e) config space.
IMO, the CAP_SYS_ADMIN ought to be replaced w/a quirk check
for badly-behaving devices &/or chip sets.
- Don
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
