On Mon, Jan 08, 2018 at 12:01:16PM -0700, Jason Gunthorpe wrote: > > So I very much disagree about where to place that workaround - the > > RDMA code is exactly the right place. > > But why? RDMA is using core code to do this. It uses dma_ops in struct > device and it uses normal dma_map SG. How is it RDMA's problem that > some PCI drivers provide strange DMA ops? Because RDMA uses the dma_virt_ops to pretend a device does DMA when in fact it doesn't - at least not for the exact data mapped, or as far as I can tell often not all - e.g. the QIB/HFI devices might do mmio access for data mapped. This whole problem only exist because a few RDMA HCA drivers lie with the help of the RDMA core.
