On Mon, Oct 09, 2017 at 01:18:20PM -0600, Jason Gunthorpe wrote: > > > 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? > > I don't think this has ever come up in the context of an all-device MR > invalidate requirement. Drivers already have code to invalidate > specifc MRs, but to find all MRs that touch certain pages and then > invalidate them would be new code. The whole point is that we should not need that IFF we provide the right interface. If we have a new 'register memory with a lease', the driver (or in fact probably the umem core for the drivers using it) has the lease associated with the ib_umem structure, which will just need a backpointer from the ib_umem to the to the MR to unregister it. Which might be a good opportunity to break the user MR from the in-kernel ones and merge it with ib_umem, but that's a different story..
