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    SubjectRe: [PATCH] Xen/i386 cleanups - AGP bus/phys cleanups
    Alan Cox writes:

    > On Iau, 2005-03-17 at 09:34, Paul Mackerras wrote:
    > > This code needs real physical addresses, which are not the same things
    > > as bus addresses.
    >
    > Not always. The code needs platform specific goodies. We've only never
    > been burned so far because there isn't a box with an IOMMU and AGPGART
    > where one maps through the other.

    That sounds like a good way to make AGP accesses slower. :)

    Seriously, given that AGP is a technology that is being superseded by
    PCI Express, I think it's reasonable to look at the range of current
    implementations to see what we have to cope with. So I don't think
    it's worth worrying too much about the possibility of GARTs that go
    through the IOMMU. However, the idea of having phys_to_agp/agp_to_phys
    (or virt_to_agp/agp_to_virt) sounds like it wouldn't be too much
    effort, if it would help Xen.

    Paul.
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