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Date:   Fri, 16 Aug 2019 06:44:48 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Jason Gunthorpe <jgg@mellanox.com>
Cc:     Jerome Glisse <jglisse@redhat.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Christoph Hellwig <hch@lst.de>,
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Subject: Re: [PATCH 04/15] mm: remove the pgmap field from struct
 hmm_vma_walk
Message-ID: <20190816044448.GB4093@lst.de>
References: <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> <20190815204128.GI22970@mellanox.com> <20190815205132.GC25517@redhat.com> <20190816004303.GC9929@mellanox.com>
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On Fri, Aug 16, 2019 at 12:43:07AM +0000, Jason Gunthorpe wrote:
> On Thu, Aug 15, 2019 at 04:51:33PM -0400, Jerome Glisse wrote:
> 
> > struct page. In this case any way we can update the
> > nouveau_dmem_page() to check that page page->pgmap == the
> > expected pgmap.
> 
> I was also wondering if that is a problem.. just blindly doing a
> container_of on the page->pgmap does seem like it assumes that only
> this driver is using DEVICE_PRIVATE.
> 
> It seems like something missing in hmm_range_fault, it should be told
> what DEVICE_PRIVATE is acceptable to trigger HMM_PFN_DEVICE_PRIVATE
> and fault all others?

The whole device private handling in hmm and migrate_vma seems pretty
broken as far as I can tell, and I have some WIP patches.  Basically we
should not touch (or possibly eventually call migrate to ram eventually
in the future) device private pages not owned by the caller, where I
try to defined the caller by the dev_pagemap_ops instance.