Re: [PATCH rdma-next 01/10] RDMA: Add access flags to ib_alloc_mr() and ib_mr_pool_init()

Christoph Hellwig
2021-04-06T12:30:53Z

On Tue, Apr 06, 2021 at 09:13:12AM -0300, Jason Gunthorpe wrote:
> So we broadly have two choice
> 1) Diverge the kernel and user interfaces and make the RDMA drivers
> special case all the kernel stuff to force
> ACCESS_RELAXED_ORDERING when they are building MRs and processing
> FMR WQE's
> 2) Keep the two interfaces the same and push the
> ACCESS_RELAXED_ORDERING to a couple of places in the ULPs so the
> drivers see a consistent API
>
> They are both poor choices, but I think #2 has a greater chance of
> everyone doing their parts correctly.

No, 1 is the only sensible choice. The userspace verbs interface is
a mess and should not inflict pain on the kernel in any way. We've moved
away from a lot of the idiotic "Verbs API" concepts with things like
how we handle the global lkey, the new CQ API and the RDMA R/W
abstraction and that massively helped the kernel ecosystem.