On Tue, Jan 10, 2017 at 02:42:23PM +0100, Arnd Bergmann wrote: > It's a much rarer problem for the IOMMU case though, because it only > impacts devices that are restricted to addressing of less than 32-bits. > > If you have an IOMMU enabled, the dma-mapping interface does not care > if the device can do wider than 32 bit addressing, as it will never > hand out IOVAs above 0xffffffff. That's absolutely not the case. IOMMUs can and do generate addresses larger than 32-bit. Also various platforms have modes where an IOMMU can be used when <= 32-bit addresses are used and bypassed if full 64-bit addressing is supported and I/O isolation is not explicitly requested.
