On Wed, 2018-06-13 at 22:25 +1000, Benjamin Herrenschmidt wrote: > On Wed, 2018-06-13 at 00:41 -0700, Christoph Hellwig wrote: > > 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. > > By direct ops I didn't mean *the* dma_direct_ops but a virtio-local > variants that effectively reproduces the existing expectations (ie, > virtio-dma-legacy-ops or something). Actually ... the stuff in lib/dma-direct.c seems to be just it, no ? There's no cache flushing and there's no architecture hooks that I can see other than the AMD security stuff which is probably fine. Or am I missing something ? Cheers, Ben. > > > 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. > > Ben. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
