On Mon, Jun 11, 2018 at 01:29:18PM +1000, Benjamin Herrenschmidt wrote: > At the risk of repeating myself, let's just do the first pass which is > to switch virtio over to always using the DMA API in the actual data > flow code, with a hook at initialization time that replaces the DMA ops > with some home cooked "direct" ops in the case where the IOMMU flag > isn't set. > > This will be equivalent to what we have today but avoids having 2 > separate code path all over the driver. > > Then a second stage, I think, is to replace this "hook" so that the > architecture gets a say in the matter. I don't think we can actually use dma_direct_ops. It still allows architectures to override parts of the dma setup, which virtio seems to blindly assume phys == dma and not cache flushing. I think the right way forward is to either add a new VIRTIO_F_IS_PCI_DEVICE (or redefine the existing iommu flag if deemed possible). And then make sure recent qemu always sets it. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
