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[2a02:3100:a951:9501:1471:d90c:a21f:9dd7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48dfd50d080sm2455314f8f.53.2026.10.15.21.55.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Oct 2026 21:55:10 -0700 (PDT) Date: Fri, 16 Oct 2026 06:55:09 +0200 From: Karl Mehltretter To: Gerd Hoffmann , Vivek Kasireddy Cc: Sumit Semwal , Christian =?utf-8?B?S8O2bmln?= , Jason Gunthorpe , dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] udmabuf: respect the device's maximum segment size Message-ID: References: <20260929054835.94118-1-kmehltretter@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260929054835.94118-1-kmehltretter@gmail.com> On Tue, Sep 29, 2026 at 07:48:35AM +0100, Karl Mehltretter wrote: > get_sg_table() merges physically contiguous pages without accounting > for the mapping device's maximum segment size. This affects both > importer mappings and the udmabuf misc device mapping used for CPU > access. > > With DMA_API_DEBUG enabled, DMA_BUF_IOCTL_SYNC on a 64 MiB udmabuf > reports: > > DMA-API: misc udmabuf: mapping sg segment longer than device claims to > support [len=65884160] [max=65536] > > Use sg_alloc_table_from_pages_segment() with the mapping device's > maximum segment size. Return -EINVAL if the limit is smaller than > PAGE_SIZE because the page-based allocator cannot honor it. > > Before commit 5bf888673e0d ("udmabuf: Do not create malformed > scatterlists"), each entry covered one page. > > Fixes: 5bf888673e0d ("udmabuf: Do not create malformed scatterlists") > Reviewed-by: Jason Gunthorpe > Assisted-by: LLM > Signed-off-by: Karl Mehltretter Friendly ping on v2. It has Reviewed-by tags from Jason and Christian. Thanks, Karl