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[142.162.113.180]) by smtp.gmail.com with ESMTPSA id c126sm8706155qkd.13.2019.10.21.07.10.39 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 21 Oct 2019 07:10:39 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1iMYON-00084E-Fl; Mon, 21 Oct 2019 11:10:39 -0300 Date: Mon, 21 Oct 2019 11:10:39 -0300 From: Jason Gunthorpe To: Bart Van Assche Cc: Leon Romanovsky , Doug Ledford , linux-rdma@vger.kernel.org, "Michael J . Ruhl" , Ira Weiny , Adit Ranadive , Shiraz Saleem , Gal Pressman , Selvin Xavier Subject: Re: [PATCH 2/4] RDMA/core: Set DMA parameters correctly Message-ID: <20191021141039.GC25178@ziepe.ca> References: <20191021021030.1037-1-bvanassche@acm.org> <20191021021030.1037-3-bvanassche@acm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191021021030.1037-3-bvanassche@acm.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Sun, Oct 20, 2019 at 07:10:28PM -0700, Bart Van Assche wrote: > The effect of the dma_set_max_seg_size() call in setup_dma_device() is > as follows: > - If device->dev.dma_parms is NULL, that call has no effect at all. > - If device->dev.dma_parms is not NULL, since that pointer points at > the DMA parameters of the parent device, modify the DMA limits of the > parent device. > > Both actions are wrong. Instead of changing the DMA parameters of the > parent device, use the DMA parameters of the parent device if these > parameters are available. > > Compile-tested only. > > Cc: Michael J. Ruhl > Cc: Ira Weiny > Cc: Adit Ranadive > Cc: Shiraz Saleem > Cc: Gal Pressman > Cc: Selvin Xavier > Fixes: d10bcf947a3e ("RDMA/umem: Combine contiguous PAGE_SIZE regions in SGEs") > Signed-off-by: Bart Van Assche > drivers/infiniband/core/device.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c > index 536310fb6510..b33d684a2a99 100644 > +++ b/drivers/infiniband/core/device.c > @@ -1199,9 +1199,18 @@ static void setup_dma_device(struct ib_device *device) > WARN_ON_ONCE(!parent); > device->dma_device = parent; > } > - /* Setup default max segment size for all IB devices */ > - dma_set_max_seg_size(device->dma_device, SZ_2G); > > + if (!device->dev.dma_parms) { > + if (parent) { > + /* > + * The caller did not provide DMA parameters. Use the > + * DMA parameters of the parent device. > + */ > + device->dev.dma_parms = parent->dma_parms; > + } else { > + WARN_ON_ONCE(true); > + } > + } > } We really do want to, by default, increase the max_seg_size above 64k though, so this approach doesn't seem right either. Jason