On Mon, Oct 9, 2017 at 11:58 AM, Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote: > On Fri, Oct 06, 2017 at 03:35:54PM -0700, Dan Williams wrote: >> otherwise be quiesced. The need for this knowledge is driven by a need >> to make RDMA transfers to DAX mappings safe. If the DAX file's block map >> changes we need to be to reliably stop accesses to blocks that have been >> freed or re-assigned to a new file. > > If RDMA is driving this need, why not invalidate backing RDMA MRs > instead of requiring a IOMMU to do it? RDMA MR are finer grained and > do not suffer from the re-use problem David W. brought up with IOVAs.. Sounds promising. All I want in the end is to be sure that the kernel is enabled to stop any in-flight RDMA at will without asking userspace. Does this require per-RDMA driver opt-in or is there a common call that can be made? Outside of that the re-use problem is already solved by just unmapping (iommu_unmap()) the IOVA, but keeping it allocated until the eventual dma_unmap_sg() at memory un-registration time frees it.
