[Xen-devel] Handling VT-d translation faults

[Espen Skoglund <espen.skoglund@xxxxxxxxxxxxx>]

I've been looking through the VT-d code trying to get a better grip on
what's going on internally, and I've got some questions regarding VT-d
translation faults.

 o Currently all VT-d faults are handled in the iommu_page_fault()
   handler.  This is kind of a misnomer since the fault handler must
   also be able to handle interrupt remapping faults and faults
   related to lookups for the context entry.  I assume that this
   naming is just temporary?

 o The fault handler doesn't actually do much right now.  It just
   clears out the fault queue and prints out warnings.  I can only
   suspect that some more code to handle faults more gracefully are
   somewhere in the pipeline.

The question is what the plans for dealing with DMA translation faults
are (i.e., due to accessing unmapped memory or writing to read-only
mappings).  At the very least the associated driver should have the
possibility to somehow be notified about failed transactions due to
translation faults.  Is something like this being planned for?

        eSk


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