Messages in this thread | | | From | Jesse Barnes <> | Subject | Re: [RFC PATCH] PCI MMCONFIG: add validation against ACPI motherboard resources | Date | Tue, 1 May 2007 19:41:06 -0700 |
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On Monday, April 30, 2007, Olivier Galibert wrote: > On Sun, Apr 29, 2007 at 08:14:37PM -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. This might be > > overly pessimistic - we might be able to instead verify that no > > other reserved resources (like chipset registers) are inside this > > memory range. > > I have a fundamental problem with that: you don't validate a higher > reliability information against a lower one. The chipset registers > are high reliability. Modulo unknown hardware erratas and bugs in the > code (and accepting f0000000 is in practice a bug in the code, the > docs are starting to catch up with it too), the chipset *will* decode > mmconfig at the looked up address no matter what. On the other side, > the ACPI data is bios generated, and that is well known to be horribly > unreliable. Hell, if it was reliable we could just use the MFCG ACPI > table without questions.
Now that I've read his patch closely I think you're right.
Robert, it looks like you'll trust acpi_table_parse if pci_mmcfg_check_hostbridge returns a failure. I think it should be treated with a higher priority. If pci_mmcfg_check_hostbridge returns a failure, there's no way MCFG space can work, so we should disable it unconditionally in that case (even if ACPI says "trust me, when have I ever lied to you?").
I'm testing it now on my 965...
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