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From:   Christoph Hellwig <hch@lst.de>
To:     Jerome Glisse <jglisse@redhat.com>
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        Jason Gunthorpe <jgg@mellanox.com>,
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Subject: Re: [PATCH 04/15] mm: remove the pgmap field from struct
 hmm_vma_walk
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References: <20190808065933.GA29382@lst.de> <CAPcyv4hMUzw8vyXFRPe2pdwef0npbMm9tx9wiZ9MWkHGhH1V6w@mail.gmail.com> <20190814073854.GA27249@lst.de> <20190814132746.GE13756@mellanox.com> <CAPcyv4g8usp8prJ+1bMtyV1xuedp5FKErBp-N8+KzR=rJ-v0QQ@mail.gmail.com> <20190815180325.GA4920@redhat.com> <CAPcyv4g4hzcEA=TPYVTiqpbtOoS30ahogRUttCvQAvXQbQjfnw@mail.gmail.com> <20190815194339.GC9253@redhat.com> <CAPcyv4jid8_=-8hBpn_Qm=c4S8BapL9B9RGT7e9uu303yH=Yqw@mail.gmail.com> <20190815203306.GB25517@redhat.com>
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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.