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[142.162.112.119]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8c37f4a97fesm67018585a.4.2026.01.05.17.07.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 Jan 2026 17:07:09 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vcvXR-00000001Eb9-164U; Mon, 05 Jan 2026 21:07:09 -0400 Date: Mon, 5 Jan 2026 21:07:09 -0400 From: Jason Gunthorpe To: "Zhijian Li (Fujitsu)" Cc: "linux-rdma@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "zyjzyj2000@gmail.com" , "leon@kernel.org" , Yi Zhang , Bob Pearson Subject: Re: [PATCH RFC] rxe: Fix iova-to-va conversion for MR page sizes != PAGE_SIZE Message-ID: <20260106010709.GO125261@ziepe.ca> References: <20251226095237.3047496-1-lizhijian@fujitsu.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: On Mon, Jan 05, 2026 at 06:55:22AM +0000, Zhijian Li (Fujitsu) wrote: > After digging into the behavior during the srp/012 test again, it > turns out this fix is incomplete. The current xarray page_list > approach cannot correctly map memory regions composed of two or more > scatter-gather segments. I seem to recall there are DMA API functions that can control what kinds of scatterlists the block stack will push down. For real HW we already cannot support less than 4K alignment of interior SGL segments. Maybe rxe can tell the block stack it can only support PAGE_SIZE alignment of interior SGL segments? If not then this would be the reason rxe needs mr->page_size, to support 4k. And obviously if the mr->page size is less than PAGE_SIZE the xarray datastructure does not work. You'd have to store physical addresses instead.. Jason