Messages in this thread | | | Date | Mon, 04 Jun 2007 08:35:06 -0600 | From | Robert Hancock <> | Subject | Re: [PATCH -mm] 1/2: MMCONFIG: validate against ACPI motherboard resources |
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Olivier Galibert wrote: > On Tue, May 29, 2007 at 10:03:32PM -0600, Robert Hancock wrote: >> -Validate that the area is reserved even if we read it from the >> chipset directly and not from the MCFG table. This catches the case >> where the BIOS didn't set the location properly in the chipset and >> has mapped it over other things it shouldn't have. > > Just for the record, I still fundamentally disagree with that part. > You're not catching what you think you're catching, since the chipset > tells you what it is going to decode as mmconfig, no matter what is > connected to it.
But we don't - not in the case where it's overlapped some other area with the MMCONFIG region. We saw a case of this on some of the Intel boards, where the MMCONFIG is a 128MB area at 0xf0000000, and when sizing the BARs on a PCI Express video device with a 256MB region, it ended up being located momentarily at f0000000-ffffffff, which overlapped the MMCONFIG area. That caused MMCONFIG to stop working, so apparently on that chipset, PCI Express devices connected to the northbridge have a higher decode priority than the MMCONFIG area.
If the BIOS is so screwed up that this becomes an issue, I don't think we can sanely try to use the table, since we can't anticipate all the potential problems that might result.
-- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from hancockr@nospamshaw.ca Home Page: http://www.roberthancock.com/
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