On Fri, Nov 11, 2016 at 09:05:43AM -0700, Alex Williamson wrote: > On Fri, 11 Nov 2016 08:50:56 -0700 > Alex Williamson <alex.williamson@xxxxxxxxxx> wrote: > > > > It's really just a happenstance that we don't map RAM over the x86 MSI > > range though. That property really can't be guaranteed once we mix > > architectures, such as running an aarch64 VM on x86 host via TCG. > > AIUI, the MSI range is actually handled differently than other DMA > > ranges, so a iommu_map() overlapping a range that the iommu cannot map > > should fail just like an attempt to map beyond the address width of the > > iommu. > > (clarification, this is x86 specific, the MSI controller - interrupt > remapper - is embedded in the iommu AIUI, so the iommu is actually not > able to provide DMA translation for this range. Right, on x86 the MSI range can be covered by page-tables, but those are ignored by the IOMMU hardware. But what I am trying to say is, that checking for these ranges happens already on a higher level (in the dma-api implementations by marking these regions as allocted) so that there is no need to check for them again in the iommu_map/unmap path. Joerg -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
