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

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Date:   Tue, 6 Aug 2019 17:51:42 +0000
From:   "Kuehling, Felix" <Felix.Kuehling@....com>
To:     Jason Gunthorpe <jgg@...pe.ca>, Christoph Hellwig <hch@....de>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>
CC:     Jérôme Glisse <jglisse@...hat.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 15/15] amdgpu: remove CONFIG_DRM_AMDGPU_USERPTR

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.

Regards,
   Felix

>
> Reviewed-by: Jason Gunthorpe <jgg@...lanox.com>
>
> Jason