linux-kernel - Re: [PATCH 15/15] amdgpu: remove CONFIG_DRM_AMDGPU_USERPTR

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Message-ID: <CADnq5_Puv-N=FVpNXhv7gOWZ8=tgBD2VjrKpVzEE0imWqJdD1A@mail.gmail.com>
Date:   Tue, 6 Aug 2019 14:58:58 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     "Kuehling, Felix" <Felix.Kuehling@....com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>, Christoph Hellwig <hch@....de>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        Ralph Campbell <rcampbell@...dia.com>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        Ben Skeggs <bskeggs@...hat.com>
Subject: Re: [PATCH 15/15] amdgpu: remove CONFIG_DRM_AMDGPU_USERPTR

On Tue, Aug 6, 2019 at 1:51 PM Kuehling, Felix <Felix.Kuehling@....com> wrote:
>
> On 2019-08-06 13:44, Jason Gunthorpe wrote:
> > On Tue, Aug 06, 2019 at 07:05:53PM +0300, Christoph Hellwig wrote:
> >> The option is just used to select HMM mirror support and has a very
> >> confusing help text.  Just pull in the HMM mirror code by default
> >> instead.
> >>
> >> Signed-off-by: Christoph Hellwig <hch@....de>
> >> ---
> >>   drivers/gpu/drm/Kconfig                 |  2 ++
> >>   drivers/gpu/drm/amd/amdgpu/Kconfig      | 10 ----------
> >>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c |  6 ------
> >>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h | 12 ------------
> >>   4 files changed, 2 insertions(+), 28 deletions(-)
> > Felix, was this an effort to avoid the arch restriction on hmm or
> > something? Also can't see why this was like this.
>
> This option predates KFD's support of userptrs, which in turn predates
> HMM. Radeon has the same kind of option, though it doesn't affect HMM in
> that case.
>
> Alex, Christian, can you think of a good reason to maintain userptr
> support as an option in amdgpu? I suspect it was originally meant as a
> way to allow kernels with amdgpu without MMU notifiers. Now it would
> allow a kernel with amdgpu without HMM or MMU notifiers. I don't know if
> this is a useful thing to have.

Right.  There were people that didn't have MMU notifiers that wanted
support for the GPU.  For a lot of older APIs, a lack of userptr
support was not a big deal (it just disabled some optimizations and
API extensions), but as it becomes more relevant it may make sense to
just make it a requirement.

Alex

>
> Regards,
>    Felix
>
> >
> > Reviewed-by: Jason Gunthorpe <jgg@...lanox.com>
> >
> > Jason
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx

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