Re: [PATCH 04/15] mm: remove the pgmap field from struct hmm_vma_walk

[Christoph Hellwig]

On Thu, Aug 15, 2019 at 04:33:06PM -0400, Jerome Glisse wrote:
> So nor HMM nor driver should dereference the struct page (i do not
> think any iommu driver would either),

Both current hmm drivers convert the hmm pfn back to a page and
eventually call dma_map_page on it.  As do the ODP patches from you.