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

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Message-ID: <20260121101421.GZ13201@unreal>
Date: Wed, 21 Jan 2026 12:14:21 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Christian König <christian.koenig@....com>
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 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.

Thanks

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