On 10/21/19 10:44 AM, Saleem, Shiraz wrote:
diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c index a667636f74bf..a523d844ad9d 100644 --- a/drivers/infiniband/core/device.c +++ b/drivers/infiniband/core/device.c @@ -1199,9 +1199,21 @@ 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, so + * 'parent' probably represents a PCI device. The PCI + * core sets the maximum segment size to 64 + * KB. Increase this parameter to 2G. + */ + device->dev.dma_parms = parent->dma_parms; + dma_set_max_seg_size(device->dma_device, SZ_2G);Did you mean dma_set_max_seg_size(&device->dev, SZ_2G)?
Have you realized that that call has the same effect as what I proposed since both devices share the dma_parms parameter?
device->dma_device could be pointing to parent if the caller did not provide dma_ops. So wont this update the parent device dma params?
That's correct, this will update the parent device DMA parameters.
Also do we want to ensure all callers device max_seg_sz params >= threshold (=2G)? If so, perhaps we can do something similar to vb2_dma_contig_set_max_seg_size() https://elixir.bootlin.com/linux/v5.4-rc2/source/drivers/media/common/videobuf2/videobuf2-dma-contig.c#L734
It depends on what PCIe RDMA adapters support. If all PCIe RDMA adapters supported by the Linux kernel support max_segment_size >= 2G the above code is probably the easiest approach.
Thanks, Bart.
