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    SubjectRe: [PATCH 00/10] HMM updates for 5.1
    On Tue, Mar 19, 2019 at 12:05 PM Jerome Glisse <jglisse@redhat.com> wrote:
    >
    > On Tue, Mar 19, 2019 at 11:42:00AM -0700, Dan Williams wrote:
    > > On Tue, Mar 19, 2019 at 10:45 AM Jerome Glisse <jglisse@redhat.com> wrote:
    > > >
    > > > On Tue, Mar 19, 2019 at 10:33:57AM -0700, Dan Williams wrote:
    > > > > On Tue, Mar 19, 2019 at 10:19 AM Jerome Glisse <jglisse@redhat.com> wrote:
    > > > > >
    > > > > > On Tue, Mar 19, 2019 at 10:12:49AM -0700, Andrew Morton wrote:
    > > > > > > On Tue, 19 Mar 2019 12:58:02 -0400 Jerome Glisse <jglisse@redhat.com> wrote:
    > > > > [..]
    > > > > > > Also, the discussion regarding [07/10] is substantial and is ongoing so
    > > > > > > please let's push along wth that.
    > > > > >
    > > > > > I can move it as last patch in the serie but it is needed for ODP RDMA
    > > > > > convertion too. Otherwise i will just move that code into the ODP RDMA
    > > > > > code and will have to move it again into HMM code once i am done with
    > > > > > the nouveau changes and in the meantime i expect other driver will want
    > > > > > to use this 2 helpers too.
    > > > >
    > > > > I still hold out hope that we can find a way to have productive
    > > > > discussions about the implementation of this infrastructure.
    > > > > Threatening to move the code elsewhere to bypass the feedback is not
    > > > > productive.
    > > >
    > > > I am not threatening anything that code is in ODP _today_ with that
    > > > patchset i was factering it out so that i could also use it in nouveau.
    > > > nouveau is built in such way that right now i can not use it directly.
    > > > But i wanted to factor out now in hope that i can get the nouveau
    > > > changes in 5.2 and then convert nouveau in 5.3.
    > > >
    > > > So when i said that code will be in ODP it just means that instead of
    > > > removing it from ODP i will keep it there and it will just delay more
    > > > code sharing for everyone.
    > >
    > > The point I'm trying to make is that the code sharing for everyone is
    > > moving the implementation closer to canonical kernel code and use
    > > existing infrastructure. For example, I look at 'struct hmm_range' and
    > > see nothing hmm specific in it. I think we can make that generic and
    > > not build up more apis and data structures in the "hmm" namespace.
    >
    > Right now i am trying to unify driver for device that have can support
    > the mmu notifier approach through HMM. Unify to a superset of driver
    > that can not abide by mmu notifier is on my todo list like i said but
    > it comes after. I do not want to make the big jump in just one go. So
    > i doing thing under HMM and thus in HMM namespace, but once i tackle
    > the larger set i will move to generic namespace what make sense.
    >
    > This exact approach did happen several time already in the kernel. In
    > the GPU sub-system we did it several time. First do something for couple
    > devices that are very similar then grow to a bigger set of devices and
    > generalise along the way.
    >
    > So i do not see what is the problem of me repeating that same pattern
    > here again. Do something for a smaller set before tackling it on for
    > a bigger set.

    All of that is fine, but when I asked about the ultimate trajectory
    that replaces hmm_range_dma_map() with an updated / HMM-aware GUP
    implementation, the response was that hmm_range_dma_map() is here to
    stay. The issue is not with forking off a small side effort, it's the
    plan to absorb that capability into a common implementation across
    non-HMM drivers where possible.

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