On 10/22/2013 7:41 PM, Hefty, Sean wrote:
I don't think so,
Signature MR simply describes a "signature associated" memory region
i.e. it is a memory region that
also defines some signature operation offload aside from normal RDMA
(for example validate & strip).
SGL are used to publish several rkeys for the server/target/peer to
perform RDMA on each.
In this case the user previously registered each MR which he wishes it's
peer to RDMA over.
Same story here, if user has several signature associated MRs, where he
wish his peer to RDMA over (in a protected manner),
he can use these rkeys to construct SGL.
Why are the signature properties separate from the protection
information?
Well,
Protection information is the actual protection block guards of the data
(i.e. CRCs, XORs, DIFs etc..), while the signature properties
structure is the descriptor telling the HCA how to
treat/validate/generate the protection information.
Note that signature support requires the HCA to be able to support
INSERT operations.
This means that there is no protection information and the HCA is asked
to generate it and add it to the data stream
(which may be incoming or outgoing...),
Would we lose anything making this a new operation for the QP, versus trying to
hook it into the existing ib_post_send call?
If I understand correctly you are suggesting making it a verb? Well this
operation is a fast-path operation - so I guess we will loose it in this
case.
Take SCSI for example, for each IO operation submitted by SCSI
mid-layer, transport layer should perform any protection policy that
SCSI asked for.
From this point of view, signature operation resembles fast
registration (since the transport does not own the IOP data buffers, so
it uses fast registration methods).
That is why we are hooking into ib_post_send.
Hope this helps.
Sagi.
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