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    SubjectRe: Possible issue with dangling PCI BARs
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    On Thu, 2007-12-13 at 12:04 -0800, Jesse Barnes wrote:
    >
    > Yeah, that seems like a reasonable compromise. Though in practice
    > I'd
    > expect the full disable decode approach to work fairly well too. I
    > mean, if we really end up failing to allocate space for the device
    > with
    > the root drive on it, there are probably bigger issues than just
    > failing to get a few bytes of I/O space for it...
    >

    The really bad scenario would be something like the Sil680 that Alan
    talked about setup by a BIOS that "knows" about the unused BAR when
    MMIO_EN is not set.

    If the device is behind a P2P bridge and the BIOS has set the windows of
    that bridge so tightly that there is no room to allocate the MMIO BAR,
    then a full disable/full enable would fail on a device that would
    otherwise work using only PIO.

    However, I'd be curious to see that happening in practice :-)

    But I think it's fair enough to do an IO only / MEM only approach. I've
    seen cases where IO is just not useable because of other constraints and
    so I expect the MEM-only case to be more common, especially on non-x86.

    Ben.




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