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[159.2.239.150]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-91260a60f21sm68476d6.19.2026.09.18.09.53.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Sep 2026 09:53:16 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1x7bpr-00000001yyx-21Yo; Fri, 18 Sep 2026 13:53:15 -0300 Date: Fri, 18 Sep 2026 13:53:15 -0300 From: Jason Gunthorpe To: Christian =?utf-8?B?S8O2bmln?= Cc: Catalin Marinas , "Aneesh Kumar K.V (Arm)" , linux-coco@lists.linux.dev, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, Marc Zyngier , Marek Szyprowski , Robin Murphy , Steven Price , Suzuki K Poulose , Thomas Gleixner , Will Deacon , Sumit Semwal , "T.J. Mercier" Subject: Re: [PATCH v6 7/9] dma-buf: system_heap: Enforce shared-granule alignment for cc-shared buffers Message-ID: <20260918165315.GF11599@ziepe.ca> References: <97c30fce-9bda-4c61-b1b9-10297b89c8d9@amd.com> <20260918153642.GD11599@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260918_095318_383118_2F9C4D4D X-CRM114-Status: GOOD ( 11.48 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Sep 18, 2026 at 05:39:55PM +0200, Christian König wrote: > > Arch code can figure out how to do it. If some ARM configs only give > > order 4 folios or whatever then dmabuf heap doesn't care. > > The fundamental problem is that DMA allocations are highly > architecture and device specific while Linux memory allocation APIs > are generic. This isn't a dma allocation, this is a memory allocation. We made things so the CC shared folios are DMA mappable through the DMA API. From the heap perspective the only difference is passing an additional DMA_ATTR_CC_SHARED when DMA mapping the folio. Jason