linux-kernel - Re: [PATCH 0/5] mm: rework hmm to use devm_memremap

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Message-ID: <20180524063507.GA9750@lst.de>
Date:   Thu, 24 May 2018 08:35:07 +0200
From:   Christoph Hellwig <hch@....de>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Jerome Glisse <jglisse@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable <stable@...r.kernel.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        Christoph Hellwig <hch@....de>, Michal Hocko <mhocko@...e.com>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/5] mm: rework hmm to use devm_memremap_pages

On Wed, May 23, 2018 at 08:18:11PM -0700, Dan Williams wrote:
> On Wed, May 23, 2018 at 5:10 PM, Jerome Glisse <jglisse@...hat.com> wrote:
> > On Mon, May 21, 2018 at 03:35:14PM -0700, Dan Williams wrote:
> >> Hi Andrew, please consider this series for 4.18.
> >>
> >> For maintainability, as ZONE_DEVICE continues to attract new users,
> >> it is useful to keep all users consolidated on devm_memremap_pages() as
> >> the interface for create "device pages".
> >>
> >> The devm_memremap_pages() implementation was recently reworked to make
> >> it more generic for arbitrary users, like the proposed peer-to-peer
> >> PCI-E enabling. HMM pre-dated this rework and opted to duplicate
> >> devm_memremap_pages() as hmm_devmem_pages_create().
> >>
> >> Rework HMM to be a consumer of devm_memremap_pages() directly and fix up
> >> the licensing on the exports given the deep dependencies on the mm.
> >
> > I am on PTO right now so i won't be able to quickly review it all
> > but forcing GPL export is problematic for me now. I rather have
> > device driver using "sane" common helpers than creating their own
> > crazy thing.
> 
> Sane drivers that need this level of deep integration with Linux
> memory management need to be upstream. Otherwise, HMM is an
> unprecedented departure from the norms of Linux kernel development.

Agreed.  I consider every driver using this a derived work, independ
on the marking or not.  And I'm willing to enforce this.