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[119.244.79.106]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-231d4eba4bcsm125491825ad.182.2025.05.23.08.56.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 23 May 2025 08:56:10 -0700 (PDT) Message-ID: <56b45ad5-b3ae-40f2-bf3f-d0718e3d26c7@gmail.com> Date: Sat, 24 May 2025 00:56:07 +0900 Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/hmm: Allow hmm_dma_map_alloc() to tolerate NULL device To: Christoph Hellwig Cc: linux-rdma@vger.kernel.org, linux-mm@kvack.org, leon@kernel.org, jgg@ziepe.ca, akpm@linux-foundation.org, jglisse@redhat.com, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, zyjzyj2000@gmail.com References: <20250523143537.10362-1-dskmtsd@gmail.com> <63702a66-4cc6-4562-89f4-857fe3f044e8@gmail.com> Content-Language: en-US From: Daisuke Matsuda In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/05/24 0:42, Christoph Hellwig wrote: > Thank you very much, but I know rxe very well. And given your apparent > knowledge of the rdma subsystem you should also know pretty well that > it does not otherwise call into the dma mapping core for virtual devices > because calling into the dma mapping code is not valid for the virtual > devices. > > Please fix the rdma core to not call into the hmm dma mapping helpers > for the ib_uses_virt_dma() case. > Thank you for the clarification and guidance. I'll look into updating the RDMA core to avoid calling hmm_dma_map_alloc() when ib_uses_virt_dma() is true. That should help keep the layering and responsibilities properly separated. Thanks again, Daisuke