[ofiwg] [libfabric-users] mmap'ed kernel memory in fi_mr_reg

[Hefty, Sean]

> > The only alternative I can think of is to try a normal registration
> call, and if that fails, try again using the physical flag.  Would
> this work, or does the normal registration call succeed, but produce
> an unusable MR?
> 
> This would not work because of a subtlety of the physical memory
> registration. The reason is that actually NULL is passed as address in
> the call. Check the github link to my patch in the other E-Mail, there
> is a line that replaces the address with NULL.
> 
> If a user passes an illegal virtual address the call should fail. But
> if the libfabric call falls back to the physical address registration,
> this would then actually succeed as the address is replaced with NULL.

I looked back at the patches and related documentation.  IMO, the verbs physical memory registration interface is just weird.  There is no association between the actual pages and the region AFAICT.

- Sean