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    SubjectRe: pci-disable-decode-of-io-memory-during-bar-sizing.patch
    Date
    On Tuesday, October 30, 2007 3:22 pm Linus Torvalds wrote:
    > On Tue, 30 Oct 2007, Jesse Barnes wrote:
    > > The per-device flag is fine with me, but I should make something
    > > clear:
    > >
    > > MMCONFIG IS NOT BROKEN!
    >
    > Trust me, it is.
    >
    > The particular problem _you_ had with it is only a small small part
    > of the bugs we have had.
    >
    > > What's broken is our PCI probing with certain address space layouts
    > > that include MMCONFIG space.
    >
    > No. You really don't see the big picture. There's been tons of
    > problems with MMCONFIG. Like the fact that other devices have their
    > IO regions registered on top of it, because the MMCONFIG thing was
    > done as a hidden resource. Or the fact that the area claimed was too
    > small. Or too large. Or not listed at all.

    Yeah, that's definitely a problem, and would be a firmware bug. There's
    no doubt that firmwares have had trouble with this in the past, but
    given that Vista now relies on this stuff working, it's a lot more
    likely to be reliable in current and future systems.

    > The whole thing is a total disaster. I told Intel engineers literally
    > *years* ago to not do that idiotic "hidden IO resources that are
    > described by firmware that then inevitably gets things wrong", and
    > yet what happens? Every single time.

    I don't disagree there. I'm just saying the actual mechanism is fine
    (as illustrated by the numerous non-PC ports of Linux), and this
    particular problem, at least, isn't really specific to how MMCONFIG is
    described or configured by the firmware and OS, it's simply a Linux
    problem.

    But like I said, the per-device flag Arjan suggested is fine with me...

    Jesse
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