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[156.34.48.30]) by smtp.gmail.com with ESMTPSA id d20sm2167345qkj.49.2020.11.05.16.08.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Nov 2020 16:08:51 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kapJD-000Yst-1D; Thu, 05 Nov 2020 20:08:51 -0400 Date: Thu, 5 Nov 2020 20:08:51 -0400 From: Jason Gunthorpe To: Jianxin Xiong Cc: linux-rdma@vger.kernel.org, dri-devel@lists.freedesktop.org, Doug Ledford , Leon Romanovsky , Sumit Semwal , Christian Koenig , Daniel Vetter Subject: Re: [PATCH v8 1/5] RDMA/umem: Support importing dma-buf as user memory region Message-ID: <20201106000851.GK36674@ziepe.ca> References: <1604616489-69267-1-git-send-email-jianxin.xiong@intel.com> <1604616489-69267-2-git-send-email-jianxin.xiong@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1604616489-69267-2-git-send-email-jianxin.xiong@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Thu, Nov 05, 2020 at 02:48:05PM -0800, Jianxin Xiong wrote: > + /* modify the sgl in-place to match umem address and length */ > + > + start = ALIGN_DOWN(umem_dmabuf->umem.address, PAGE_SIZE); > + end = ALIGN(umem_dmabuf->umem.address + umem_dmabuf->umem.length, > + PAGE_SIZE); > + cur = 0; > + nmap = 0; > + for_each_sgtable_dma_sg(sgt, sg, i) { > + if (cur >= end) > + break; > + if (cur + sg_dma_len(sg) <= start) { > + cur += sg_dma_len(sg); > + continue; > + } This seems like a strange way to compute interesections if (cur <= start && start < cur + sg_dma_len(sg)) > + if (cur <= start) { > + unsigned long offset = start - cur; > + > + umem_dmabuf->first_sg = sg; > + umem_dmabuf->first_sg_offset = offset; > + sg_dma_address(sg) += offset; > + sg_dma_len(sg) -= offset; > + if (&sg_dma_len(sg) != &sg->length) > + sg->length -= offset; We don't need to adjust sg->length, only dma_len, so no reason for this surprising if. > + cur += offset; > + } > + if (cur + sg_dma_len(sg) >= end) { Same logic here > + unsigned long trim = cur + sg_dma_len(sg) - end; > + > + umem_dmabuf->last_sg = sg; > + umem_dmabuf->last_sg_trim = trim; > + sg_dma_len(sg) -= trim; > + if (&sg_dma_len(sg) != &sg->length) > + sg->length -= trim; break, things are done here > + } > + cur += sg_dma_len(sg); > + nmap++; > + } > + > + umem_dmabuf->umem.sg_head.sgl = umem_dmabuf->first_sg; > + umem_dmabuf->umem.sg_head.nents = nmap; > + umem_dmabuf->umem.nmap = nmap; > + umem_dmabuf->sgt = sgt; > + > + page_size = ib_umem_find_best_pgsz(&umem_dmabuf->umem, PAGE_SIZE, > + umem_dmabuf->umem.iova); > + > + if (WARN_ON(cur != end || page_size != PAGE_SIZE)) { Looks like nothing prevents this warn on to tigger The user could specify a length that is beyond the dma buf, can the dma buf length be checked during get? Also page_size can be 0 because iova is not OK. iova should be checked for alignment during get as well: iova & (PAGE_SIZE-1) == umem->addr & (PAGE_SIZE-1) But yes, this is the right idea Jason