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    SubjectRe: [PATCH] iommu: Include MSI susceptibility to DMA in creating iommu groups
    * Joerg Roedel (joro@8bytes.org) wrote:
    > >From device standpoint a MSI transaction is always a DMA memory write
    > to a given address range. The IOMMU-API should export a feature flag
    > whether it supports filtering on those transaction or not. We have that
    > today with the IOMMU_CAP_INTR_REMAP. I agree that the interface to get
    > this information is ugly because a domain is needed. But the interface
    > can be fixed. While doing this I suggest to rename that feature
    > IOMMU_CAP_INTR_ISOLATION or something like that.
    > VFIO can then check for this flag on module-load and refuse to load if
    > it is not available.

    I can see that the native grouping (the typical pci bridge type) is
    really more a property of the topology.

    The isolation properties of a group (arguably the whole point of the
    group) is subtly different.

    Leaves the questions:

    What is the value of a group w/out complete isolation?
    Is there a practical problem w/ conflating the subtleties above?

    thanks,
    -chris


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