Il 03/09/2014 01:20, Benjamin Herrenschmidt ha scritto: > I wouldn't be so certain, as I said, the way virtio is implemented in > qemu bypass the DMA layer which is where IOMMUs sit. The fact that > currently x86 doesn't put an IOMMU there is not even garanteed, is it ? > What happens if you try to mix and match virtio and other emulated > devices that require the iommu on the same bus ?
As far as QEMU is concerned, it's trivial to add a property like "direct-ram-access" that selects whether to bypass the IOMMU or not. And it would have zero performance cost if direct RAM access is enabled, compared to the current code. If possible, I would quirk it in the PPC code. Paolo _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
