[ofa-general] [PATCH RFC v3 1/2] RDMA/Core:MEM_MGT_EXTENSIONS support

[Talpey, Thomas]

At 02:40 PM 5/27/2008, Steve Wise wrote:
>Talpey, Thomas wrote:
>> At 12:58 PM 5/27/2008, Felix Marti wrote:
>>   
>>> RDMA Read with Local Invalidate does not affect the wire. The 'must
>>> invalidate' state is kept in the RNIC that issues the RDMA Read
>>> Request...
>>>     
>>
>> Aha, okay that was not clear to me. What information does the RNIC use
>> to line up the arrival of the RDMA Read response with the "must invalidate"
>> state? 
>
>The rnic already tracks outstanding read requests.  It now also will 
>track the local stag to invalidate when the read completes.

Ah - okay, so the stag that actually gets invalidated was provided with
the RDMA Read request posting, and is not necessarily the stag that
arrived in the peer's RDMA Read response. That helps.

What happens if the upper layer gives up and invalidates the stag itself,
and the peer's RDMA Read response arrives later? Nothing bad, I assume,
and the peer's response is denied?

>
>> Also, how does the RNIC signal whether the invalidation actually
>> occurred, so the upper layer can defend itself from attack?
>>
>>   
>
>The stag is guaranteed to be in the invalid state by the time the app 
>reaps the read-inv-local work completion...

Ok, given my correct understanding of the source of the stag above.

Tom.