Re: [PATCH 10/11] IB: only keep a single key in struct ib_mr

[Sagi Grimberg <sagig-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

On 22/12/2015 15:13, Christoph Hellwig wrote:
> On Tue, Dec 22, 2015 at 11:17:54AM +0200, Sagi Grimberg wrote:
>> What makes me worried here is that the IB/RoCE specification really
>> defines different keys for local and remote access. I'm less concerned
>> about our consumers but more about our providers. We keep seeing new
>> providers come along and its not impossible that a specific HW will
>> *rely* on this distinction. In such a case we'd need to revert this
>> patch altogether in that very moment.
>>
>> I think we're better off working on proper abstractions to help ULPs
>> get it right (and simple!), without risking future devices support.
>
> With the new API in the next patch ULPs simply can't request an lkey
> and a rkey at the same time, so for kernel use it's not a problmblem at
> all.

This is why I said that the problem here is not the ULPs. But if a new
HW comes along with distinction between rkeys and lkeys it will have a
problem. For example a HW allocates two different keys, rkey and lkey.
And, it chooses to fail SEND from a rkey, or incoming READ/WRITE to a
lkey. How can such a device be supported with an API that allows a
single key per MR?
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