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    SubjectRe: [PATCH 5/5] PNP: HP nx6325 fixup: reserve unreported resources
    On 12/15/2010 10:18 AM, Bjorn Helgaas wrote:
    >
    > ACPI devices tend to be at high addresses, so allocating top-down
    > is definitely more dangerous unless we explicitly avoid them. I
    > should have realized that and done something like patches 1-3 of
    > this series before the top-down patches.
    >
    > Doing it bottom-up would very likely work better than the "top-down
    > without avoiding ACPI regions" model we currently have, at least in
    > the short term. We *would* have to do something to avoid E820
    > reservations to fix this:
    > https://bugzilla.kernel.org/show_bug.cgi?id=16228,
    > but that's doable.
    >
    > So here's my proposal for .37:
    > - Keep the current state of _CRS enabled by default (for 2008
    > and newer machines).
    > - Allocate bottom-up always
    > - Avoid E820 reservations
    >
    > That should fix all the regressions I'm aware of. I'll work on
    > the patches this afternoon.
    >

    At the same time, I would like to see a few things done as a matter of
    course:

    a) reserve the top 2 MiB of the 32-bit address space. There *will* be
    ROM at the top of the 32-bit address space; it's a fact of the
    architecture, and on at least older systems it was common to have a
    shadow 1 MiB below.

    b) we may want to consider doing special things in the 0xFExxxxxx memory
    range, which is used by the CPU-APIC-MSI system in recent processors.

    -hpa

    --
    H. Peter Anvin, Intel Open Source Technology Center
    I work for Intel. I don't speak on their behalf.



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