On Mon, 2015-11-09 at 21:35 -0800, Andy Lutomirski wrote: > > We could do it the other way around: on powerpc, if a PCI device is in > that range and doesn't have the "bypass" property at all, then it's > assumed to bypass the IOMMU. This means that everything that > currently works continues working. If someone builds a physical > virtio device or uses another system in PCIe target mode speaking > virtio, then it won't work until they upgrade their firmware to set > bypass=0. Meanwhile everyone using hypothetical new QEMU also gets > bypass=0 and no ambiguity. > > vfio will presumably notice the bypass and correctly refuse to map any > current virtio devices. > > Would that work? That would be extremely strange from a platform perspective. Any device in that vendor/device range would bypass the iommu unless some new property "actually-works-like-a-real-pci-device" happens to exist in the device-tree, which we would then need to define somewhere and handle accross at least 3 different platforms who get their device-tree from widly different places. Also if tomorrow I create a PCI device that implements virtio-net and put it in a machine running IBM proprietary firmware (or Apple's or Sun's), it won't have that property... This is not hypothetical. People are using virtio to do point-to-point communication between machines via PCIe today. Cheers, Ben. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
