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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Mon, 18 Mar 2019 11:30:15 -0700
Message-ID: <CAPcyv4geu34vgZszALiDxJWR8itK+A3qSmpR+_jOq29whGngNg@mail.gmail.com>
Subject: Re: [PATCH 00/10] HMM updates for 5.1
To:     Jerome Glisse <jglisse@redhat.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linux MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Felix Kuehling <Felix.Kuehling@amd.com>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        Ralph Campbell <rcampbell@nvidia.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Jason Gunthorpe <jgg@mellanox.com>
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On Mon, Mar 18, 2019 at 10:04 AM Jerome Glisse <jglisse@redhat.com> wrote:
>
> On Wed, Mar 13, 2019 at 09:10:04AM -0700, Andrew Morton wrote:
> > On Tue, 12 Mar 2019 21:27:06 -0400 Jerome Glisse <jglisse@redhat.com> wrote:
> >
> > > Andrew you will not be pushing this patchset in 5.1 ?
> >
> > I'd like to.  It sounds like we're converging on a plan.
> >
> > It would be good to hear more from the driver developers who will be
> > consuming these new features - links to patchsets, review feedback,
> > etc.  Which individuals should we be asking?  Felix, Christian and
> > Jason, perhaps?
> >
>
> So i am guessing you will not send this to Linus ? Should i repost ?
> This patchset has 2 sides, first side is just reworking the HMM API
> to make something better in respect to process lifetime. AMD folks
> did find that helpful [1]. This rework is also necessary to ease up
> the convertion of ODP to HMM [2] and Jason already said that he is
> interested in seing that happening [3]. By missing 5.1 it means now
> that i can not push ODP to HMM in 5.2 and it will be postpone to 5.3
> which is also postoning other work ...
>
> The second side is it adds 2 new helper dma map and dma unmap both
> are gonna be use by ODP and latter by nouveau (after some other
> nouveau changes are done). This new functions just do dma_map ie:
>     hmm_dma_map() {
>         existing_hmm_api()
>         for_each_page() {
>             dma_map_page()
>         }
>     }
>
> Do you want to see anymore justification than that ?

Yes, why does hmm needs its own dma mapping apis? It seems to
perpetuate the perception that hmm is something bolted onto the side
of the core-mm rather than a native capability.