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    SubjectRe: PCI memory allocation bug with CONFIG_HIGHMEM

    On Wed, 7 Jan 2004, Eric W. Biederman wrote:
    > However insert_resource does not quite match what I think needs to
    > happen. After a pci quirk applies insert_resource I will get
    > something like:
    > fff0000-ffffffff : BIOS ROM Window
    > ffff0000-ffffffff : reserved
    > With the reserved region still present and marked as BUSY.

    I would suggest ignoring it. Not only because being overly complicated is
    bad, but simply because nobody should care.

    At some point adding extra regions is _purely_ for "documentation"
    reasons, and while that may be nice, it's not worth worrying about. The
    only thing you really want from a _correctness_ standpoint is to make sure
    that nobody else will try to allocate their stuff in that area, and your
    "BIOS ROM Window" resource should do that already.

    > Would it be reasonable to write a variant of request_resource that just
    > drops BIOS resources.

    It would not be impossible to just have a "force_resource()" that would
    simply override _any_ existing resource, but quite frankly, I'd be more
    nervous about that.

    We could also mark the e820 non-RAM resources with some special
    IORESOURCE_TENTATIVE flag, and allow just overriding those.

    But even the simple "insert_resource()" has some potential problems: if
    the BIOS has allocated the minimal window for itself (64kB at 0xffff0000),
    and has allocated some _other_ chip at 0xfffe0000 that the kernel doesn't
    know about yet, your insert_resource() would do the wrong thing and claim
    the whole area for the BIOS writing.

    Maybe that doesn't happen, but it's something to think about.

    At some point, the _correct_ answer may be: don't do complex things, and
    write a bootable floppy (without any OS at all, or a really minimal one)
    to do BIOS rom updates.

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      Last update: 2009-11-18 23:46    [W:0.019 / U:150.772 seconds]
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