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