Re: [PATCH v4 0/8] mm: Rework hmm to use devm_memremap_pages and other fixes

[Dan Williams <dan.j.williams@intel.com>]

On Fri, Jul 20, 2018 at 1:17 PM Jerome Glisse <jglisse@redhat.com> wrote:
>
> On Fri, Jul 20, 2018 at 01:01:24PM -0700, Matthew Wilcox wrote:
> > On Fri, Jul 20, 2018 at 03:57:47PM -0400, Jerome Glisse wrote:
> > > On Fri, Jul 20, 2018 at 12:51:46PM -0700, Andrew Morton wrote:
> > > > Problem is, that patch is eighth in a series which we're waiting for
> > > > Jerome to review and the changelog starts with "Now that all producers
> > > > of dev_pagemap instances in the kernel are properly converted to
> > > > EXPORT_SYMBOL_GPL...".
> > >
> > > I am fine with the patchset modulo GPL, i did review it in the past
> > > but i did not formaly reply as i was opose to the GPL changes. So my
> > > only objection is with the GPL export, everything else looks fine.
> >
> > Everyone from the mm side who's looked at these patches agrees that it
> > reaches far too far into the guts of the mm to be anything other than
> > exposing internals.  It's not credible to claim that a module written that
> > uses these interfaces is anything other than a derived work of the kernel.
> >
> > I feel these patches should be merged over Jerome's objections.
>
> I feel that people do not understand how far reaching this is. It means
> that any new devices with memory supporting new system bus like CAPI or
> CCIX will need to have a GPL driver. This is a departure of current
> state of affair where we allow non GPL driver to exist.

Proprietary GPU driver vendors have done just fine without us adding
explicit new mechanisms for them to consume.

> Moreover I have argue that HMM abstract the internal mm and by doing so
> allow anyone to update the mm code without having to worried about driver
> which use HMM. Thus disproving that user of HMM are tie to mm internal.

No, HMM has has deployed a GPL-bypass shim into the kernel.

> Also to make thing perfectly clear i am a strong proponent of open
> source and i rather have a GPL driver but at the same time i do not want
> linux kernel to become second citizen because it can not support new
> devices ...

HMM diminishes the letter and the spirit of EXPORT_SYMBOL_GPL, it
grants access to and consumes GPL-only infrastructure written by me
and others.