Re: protection domain question

[Sagi Grimberg <sagi-NQWnxTmZq1alnMjI0IkVqw@public.gmane.org>]

> As far as I can tell from reading the Verbs spec the raison d'êtrefor
> protection domains is to allow associating MRs with different address
> spaces in userspace programs.

The PD number is enforced when accessing the associated MRs (via the
associated QPs). So if someone is accessing a MR that is associated
with a PD via a queue-pair that is not it will fail (its a security
thing).

> Is there any good reason to have each kernel driver create it's own PDs
> instead of simply creating one per device and sticking it into the
> ib_device structure?

There is a theoretical breach here. Say you're connected with a srp
channel to a target, and you send out rkey X to your peer. In case
there is a man-in-the-middle who sniffs it, he can theoretically
read/write to your rkey by connecting to IPoIB in RC mode (which
will connect to anyone).

The fact that srp has it's own PD prevents this from happening.
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