linux-kernel - Re: [PATCH v3 2/7] dma-buf: Always build with DMABUF_MOVE

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Message-ID: <693f302b-e859-47a3-ab00-626ced35ee78@amd.com>
Date: Wed, 21 Jan 2026 11:57:45 +0100
From: Christian König <christian.koenig@....com>
To: Leon Romanovsky <leon@...nel.org>
Cc: Sumit Semwal <sumit.semwal@...aro.org>,
 Alex Deucher <alexander.deucher@....com>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Gerd Hoffmann <kraxel@...hat.com>,
 Dmitry Osipenko <dmitry.osipenko@...labora.com>,
 Gurchetan Singh <gurchetansingh@...omium.org>, Chia-I Wu
 <olvaffe@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Lucas De Marchi <lucas.demarchi@...el.com>,
 Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
 Rodrigo Vivi <rodrigo.vivi@...el.com>, Jason Gunthorpe <jgg@...pe.ca>,
 Kevin Tian <kevin.tian@...el.com>, Joerg Roedel <joro@...tes.org>,
 Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
 Felix Kuehling <Felix.Kuehling@....com>, Alex Williamson <alex@...zbot.org>,
 Ankit Agrawal <ankita@...dia.com>,
 Vivek Kasireddy <vivek.kasireddy@...el.com>, linux-media@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
 linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
 virtualization@...ts.linux.dev, intel-xe@...ts.freedesktop.org,
 linux-rdma@...r.kernel.org, iommu@...ts.linux.dev, kvm@...r.kernel.org
Subject: Re: [PATCH v3 2/7] dma-buf: Always build with DMABUF_MOVE_NOTIFY

On 1/21/26 11:14, Leon Romanovsky wrote:
> On Wed, Jan 21, 2026 at 09:55:38AM +0100, Christian König wrote:
>> On 1/20/26 15:07, Leon Romanovsky wrote:
>>> From: Leon Romanovsky <leonro@...dia.com>
>>>
>>> DMABUF_MOVE_NOTIFY was introduced in 2018 and has been marked as
>>> experimental and disabled by default ever since. Six years later,
>>> all new importers implement this callback.
>>>
>>> It is therefore reasonable to drop CONFIG_DMABUF_MOVE_NOTIFY and
>>> always build DMABUF with support for it enabled.
>>>
>>> Suggested-by: Christian König <christian.koenig@....com>
>>> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
>>> ---
>>>  drivers/dma-buf/Kconfig                     | 12 ------------
>>>  drivers/dma-buf/dma-buf.c                   | 12 ++----------
>>>  drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 10 +++-------
>>>  drivers/gpu/drm/amd/amdkfd/Kconfig          |  2 +-
>>>  drivers/gpu/drm/xe/tests/xe_dma_buf.c       |  3 +--
>>>  drivers/gpu/drm/xe/xe_dma_buf.c             | 12 ++++--------
>>>  6 files changed, 11 insertions(+), 40 deletions(-)
>>>
>>> diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
>>> index b46eb8a552d7..84d5e9b24e20 100644
>>> --- a/drivers/dma-buf/Kconfig
>>> +++ b/drivers/dma-buf/Kconfig
>>> @@ -40,18 +40,6 @@ config UDMABUF
>>>  	  A driver to let userspace turn memfd regions into dma-bufs.
>>>  	  Qemu can use this to create host dmabufs for guest framebuffers.
>>>  
>>> -config DMABUF_MOVE_NOTIFY
>>> -	bool "Move notify between drivers (EXPERIMENTAL)"
>>> -	default n
>>> -	depends on DMA_SHARED_BUFFER
>>> -	help
>>> -	  Don't pin buffers if the dynamic DMA-buf interface is available on
>>> -	  both the exporter as well as the importer. This fixes a security
>>> -	  problem where userspace is able to pin unrestricted amounts of memory
>>> -	  through DMA-buf.
>>> -	  This is marked experimental because we don't yet have a consistent
>>> -	  execution context and memory management between drivers.
>>> -
>>>  config DMABUF_DEBUG
>>>  	bool "DMA-BUF debug checks"
>>>  	depends on DMA_SHARED_BUFFER
>>> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
>>> index 59cc647bf40e..cd3b60ce4863 100644
>>> --- a/drivers/dma-buf/dma-buf.c
>>> +++ b/drivers/dma-buf/dma-buf.c
>>> @@ -837,18 +837,10 @@ static void mangle_sg_table(struct sg_table *sg_table)
>>>  
>>>  }
>>>  
>>> -static inline bool
>>> -dma_buf_attachment_is_dynamic(struct dma_buf_attachment *attach)
>>
>> I would rather like to keep the wrapper and even add some explanation what it means when true is returned.
> 
> We have different opinion here. I don't like single line functions which
> are called only twice. I'll keep this function to ensure progress the
> series.

Yeah, I agree with that but I like to have the opportunity to document things.

Especially since the meaning changed over time.

Thanks,
Christian.

> 
> Thanks
> 
>>
>> Apart from that looks good to me.
>>
>> Regards,
>> Christian.