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 ?

That would mean in many cases adding a layer of iommu, which will slow
things down a lot ... unless we create a special virtio bus which has
its own dma-ops that do a direct v:p translation that is. But anything
PCI doing dma_map_sg and co will involved emulated iommu mapping &
unmapping and will be a huge hit on performances.

Cheers,
Ben.