Re: [PATCH v2 3/4] iommu/dma-iommu: Use the dev->coherent_dma_mask

[Christoph Hellwig]

On Tue, Apr 30, 2019 at 12:27:02PM +0100, Robin Murphy wrote:
> > Hmm, I don't think we need the DMA mask for the MSI mapping, this
> > should probably always use a 64-bit mask.
> 
> If that were true then we wouldn't need DMA masks for regular mappings
> either. If we have to map the MSI doorbell at all, then we certainly have to
> place it at an IOVA that the relevant device is actually capable of
> addressing.

Well, as shown by the patch below we don't even look at the DMA mask
for the MSI page - we just allocate from bottom to top.