On Wed, Jun 12, 2019 at 04:35:22PM +1000, Oliver O'Halloran wrote: > Setting a 48 bit DMA mask doesn't work today because we only allocate > IOMMU tables to cover the 0..2GB range of PCI bus addresses.
I don't think that is true upstream, and if it is we need to fix bug in the powerpc code. powerpc should be falling back treating a 48-bit dma mask like a 32-bit one at least, that is use dynamic iommu mappings instead of using the direct mapping. And from my reding of arch/powerpc/kernel/dma-iommu.c that is exactly what it does.
