On Thu, 2018-08-09 at 08:13 +1000, Benjamin Herrenschmidt wrote: > > For completeness, virtio could also have its own bounce buffer > > outside of DMA API one. I don't see lots of benefits to this > > though. > > Not fan of that either... To elaborate a bit ... For our secure VMs, we will need bounce buffering for everything anyway. virtio, emulated PCI, or vfio. By ensuring that we create an identity mapping in the IOMMU for the bounce buffering pool, we enable virtio "legacy/direct" to use the same mapping ops as things using the iommu. That said, we still need somewhere in arch/powerpc a set of dma ops which we'll attach to all PCI devices of a secure VM to force bouncing always, rather than just based on address (which is what the standard swiotlb ones do)... Unless we can tweak the swiotlb "threshold" for example by using an empty mask. We'll need the same set of DMA ops for VIO devices too, not just PCI. Cheers, Ben. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
