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[2603:8081:140c:1a00:b6dc:62b4:e209:78d4]) by smtp.gmail.com with ESMTPSA id j3sm1216839oij.9.2020.10.29.22.46.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Oct 2020 22:46:54 -0700 (PDT) Subject: Re: [PATCH for-next] RDMA/rxe: fix regression caused by recent patch From: Bob Pearson To: jgg@nvidia.com, zyjzyj2000@gmail.com, linux-rdma@vger.kernel.org Cc: Bob Pearson References: <20201029212545.6616-1-rpearson@hpe.com> Message-ID: <703e1658-1efa-9dbb-1803-9f7392a2439d@gmail.com> Date: Fri, 30 Oct 2020 00:46:53 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.2 MIME-Version: 1.0 In-Reply-To: <20201029212545.6616-1-rpearson@hpe.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On 10/29/20 4:25 PM, Bob Pearson wrote: > The commit referenced below performs additional checking on > devices used for DMA. Specifically it checks that > > device->dma_mask != NULL > > Rdma_rxe uses this device when pinning MR memory but did not > set the value of dma_mask. In fact rdma_rxe does not perform > any DMA operations so the value is never used but is checked. > > This patch gives dma_mask a valid value. Without this patch > rdma_rxe does not function at all. > > Fixes: f959dcd6ddfd2 ("dma-direct: Fix potential NULL pointer dereference") > Signed-off-by: Bob Pearson > --- > drivers/infiniband/sw/rxe/rxe_verbs.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c > index 7652d53af2c1..116a234e92db 100644 > --- a/drivers/infiniband/sw/rxe/rxe_verbs.c > +++ b/drivers/infiniband/sw/rxe/rxe_verbs.c > @@ -1134,8 +1134,15 @@ int rxe_register_device(struct rxe_dev *rxe, const char *ibdev_name) > dev->node_type = RDMA_NODE_IB_CA; > dev->phys_port_cnt = 1; > dev->num_comp_vectors = num_possible_cpus(); > + > + /* rdma_rxe never does real DMA but does rely on > + * pinning user memory in MRs to avoid page faults > + * in responder and completer tasklets > + */ > dev->dev.parent = rxe_dma_device(rxe); > + dev->dev.dma_mask = DMA_BIT_MASK(64); > dev->local_dma_lkey = 0; > + > addrconf_addr_eui48((unsigned char *)&dev->node_guid, > rxe->ndev->dev_addr); > dev->dev.dma_parms = &rxe->dma_parms; > Ignore this patch. It turns out it works because any nonzero number in dma_mask will stop the check that is failing and since rxe never uses DMA it won't affect anything. But, it doesn't compile cleanly because the dma_mask is a pointer to the actual dma_mask and not the mask. Somehow I missed the warning. I have a newer version that uses the function dma_coerce_mask_and_coherent() and also works. (Works means it gets to the next problem as mentioned in the prvious note.) Bob