Re: [PATCH 00/10] HMM updates for 5.1

[Ira Weiny]

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@xxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxx> 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