[openib-general] FMR and how they work

[Fab Tillier]

When you deregister a FMR, what information from that FMR can the HCA cache
- just the MTTs or also the MPTs?  Can an incoming RDMA transfer access the
pages previously referenced by that FMR?  If so, for how long?  When is it
safe to unpin the pages?

What about when you modify the FMR?  How long are previous mappings "at
risk" of transfers?

I'm kinda confused because the Mellanox docs indicate that the HCA can cache
stuff and that the pages can't be unpinned until the cache is flushed.  If
that's true, I don't see how FMRs can be used because they could be suspect
to malicious use by a remote host.

Help?

- Fab