Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 19 Mar 2019 07:18:26 -0700
From:   Ira Weiny <ira.weiny@intel.com>
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     Jerome Glisse <jglisse@redhat.com>,
        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>,
        Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        Ralph Campbell <rcampbell@nvidia.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Jason Gunthorpe <jgg@mellanox.com>,
        Alex Deucher <alexander.deucher@amd.com>
Subject: Re: [PATCH 00/10] HMM updates for 5.1
Message-ID: <20190319141826.GJ7485@iweiny-DESK2.sc.intel.com>
References: <20190318170404.GA6786@redhat.com>
 <20190319094007.a47ce9222b5faacec3e96da4@linux-foundation.org>
 <20190319165802.GA3656@redhat.com>
 <20190319101249.d2076f4bacbef948055ae758@linux-foundation.org>
 <20190319171847.GC3656@redhat.com>
 <CAPcyv4iesGET_PV-QcdBbxJGgmJ_HhoGczyvb=0+SnLkFDhRuQ@mail.gmail.com>
 <20190319174552.GA3769@redhat.com>
 <CAPcyv4hFPOO0-=v3ZCNFA=LgE_QCvyFXGqF24Crveoj_NTbq0Q@mail.gmail.com>
 <20190319190528.GA4012@redhat.com>
 <CAPcyv4hg5Y_NC1iu56zcznYkCRnwg+_7bGFr==7=AC6ii=O=Ng@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAPcyv4hg5Y_NC1iu56zcznYkCRnwg+_7bGFr==7=AC6ii=O=Ng@mail.gmail.com>
User-Agent: Mutt/1.11.1 (2018-12-01)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Mar 19, 2019 at 12:13:40PM -0700, Dan Williams wrote:
> 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:

[snip]

> >
> > 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.

Just to get on the record in this thread.

+1

I think having an interface which handles the MMU notifier stuff for drivers is
awesome but we need to agree that the trajectory is to help more drivers if
possible.

Ira