On Mon, 2014-09-01 at 10:39 -0700, Andy Lutomirski wrote: > Changes from v1: > - Using the DMA API is optional now. It would be nice to improve the > DMA API to the point that it could be used unconditionally, but s390 > proves that we're not there yet. > - Includes patch 4, which fixes DMA debugging warnings from virtio_net. I'm not sure if you saw my reply on the other thread but I have a few comments based on the above "it would be nice if ..." So here we have both a yes and a no :-) It would be nice to avoid those if () games all over and indeed just use the DMA API, *however* we most certainly don't want to actually create IOMMU mappings for the KVM virio case. This would be a massive loss in performances on several platforms and generally doesn't make much sense. However, we can still use the API without that on any architecture where the dma mapping API ends up calling the generic dma_map_ops, it becomes just a matter of virtio setting up some special "nop" ops when needed. The difficulty here resides in the fact that we have never completely made the dma_map_ops generic. The ops themselves are defined generically as are the dma_map_* interfaces based on them, but the location of the ops pointer is still more/less arch specific and some architectures still chose not to use that indirection at all I believe. Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
