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    SubjectRe: [GIT PULL] AMD IOMMU updates for 2.6.28-rc5
    On Wed, 19 Nov 2008 14:57:50 +0200
    Muli Ben-Yehuda <> wrote:

    > > device isolation is not free; e.g. use more memory rather than
    > > sharing a protection domain. I guess that more people prefer sharing
    > > a protection domain by default.
    > I doubt it, why use an isolation-capable IOMMU at all if not for the
    > increased reliability? The majority of modern devices---those that you
    > are likely to find on machines with an IOMMU---don't have DMA
    > limitations.

    I guess that there are still some modern SATA HBAs that are not
    capable of 64bit DMA. You might be right though.

    > > It had been the default option for AMD IOMMU until you hit the
    > > bugs. IIRC, VT-d also shares a protection domain by default. It
    > > would be nice to avoid surprising users if the two virtualization
    > > IOMMUs works in the similar way.
    > Calgary has a per-bus protection domain, both on x86 and PPC.

    I see. Then it might be better to change VT-d to use a separate
    protection domain by default.

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