another thing:
How hard would it be to add an CONFIG_IOMMU_DEBUG option that forces as
many DMA requests to go via the IOMMU as possible?
This slows things down of course so it's only for debugging - but it
also makes sure that we utilize the IOMMU code to the maximum - which is
not normally the case.
Would be nice to have it .config driven (default-disabled), so that
-tip's randconfig testing can stumble upon it every now and then. I've
got GART test-systems - this way we could find certain types of IOMMU
breakages sooner.
Ingo
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