On Wed, Jan 11, 2012 at 9:10 AM, Benjamin Herrenschmidt <b...@kernel.crashing.org> wrote: > On Wed, 2012-01-11 at 08:47 +0000, Stefan Hajnoczi wrote: >> >> This is also an opportunity to stop using CPU physical addresses in >> the ring and instead perform DMA like a normal PCI device (use bus >> addresses). > > Euh why ?
Because it's a paravirt hack that ends up hitting corner cases. It's not possible to do virtio-pci passthrough under nested virtualization unless we use an IOMMU. Imagine passing virtio-net from L0 into the L2 guest (i.e. PCI-passthrough). If virtio-pci is really "PCI" this should be possible but it's not when we use physical addresses instead of bus addresses. Stefan _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
