Il 03/09/2014 02:25, Benjamin Herrenschmidt ha scritto: > > But there aren't any ACPI systems with both virtio-pci and IOMMUs, > > right? So we could say that, henceforth, ACPI systems must declare > > whether virtio-pci devices live behind IOMMUs without breaking > > backward compatibility. > > I don't know for sure whether that's the case and whether we can rely on > that not happening, we'll need x86 folks opinion here. IOMMU support for x86 is going to go in this week. However, it is and likely will remain niche enough that I don't really care about performance loss from IOMMU support. If you enable it, you want it. So from the QEMU point of view we can simply add the direct-ram-access property, and have the pseries machine turn it on by default (while other machines can leave it off by default---they have no IOMMU and thus no performance cost). Paolo -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
