On 10/18/2013 1:51 AM, Hefty, Sean wrote:
@@ -885,6 +901,19 @@ struct ib_send_wr {
u32 rkey;
struct ib_mw_bind_info bind_info;
} bind_mw;
+ struct {
+ struct ib_sig_attrs *sig_attrs;
+ struct ib_mr *sig_mr;
+ int access_flags;
+ /* Registered data mr */
+ struct ib_mr *data_mr;
+ u32 data_size;
+ u64 data_va;
+ /* Registered protection mr */
+ struct ib_mr *prot_mr;
+ u32 prot_size;
+ u64 prot_va;
+ } sig_handover;
At what point do we admit that this is a ridiculous structure?
If you are referring to ib_send_wr, I agree, shall we modify it to a
union of typedefs so it becomes more readable?
Help me understand what this WR is doing. Is this telling the HCA to copy data
between local MRs? What is a 'data MR' versus a 'protected MR'? (I'm not hip
on T10-DIF.)
No data copy, god forbids... :)
Let me start by giving a short intro on signature (and T10-DIF).
In signature world, data may exist with protection information which is
the guarding the data. In T10-DIF (Data Integrity Fields) for example,
these are 8-byte guards which includes CRC for each 512 bytes of data
(block).
An HCA which support signature offload, is expected to validate that the
data is intact (each block matches its guard) and send it correctly over
the wire (in T10-DIF case the data and protection should be interleaved
i.e. 512B of data followed by 8B of protection guard) or alternatively,
validate data (+ protection) coming from the wire and write it to the
associated memory areas.
In the general case, the data and the protection guards may lie in
different memory areas. SCSI mid-layer for instance, passes the
transport driver 2 buffers using 2 scatterlists.
The transport driver (or application in the general case), is expected
to register each buffer (as it normally would in order to use RDMA)
using 2 MRs.
The signature handover operation is binding all the necessary
information for the HCA together: where is the data (data_mr), where is
the protection information (prot_mr), what are the signature properties
(sig_attrs).
Once this step is taken (WR is posted), a single MR (sig_mr) describes
the signature handover operation and can be used to perform RDMA under
signature presence.
Once the HCA will perform RDMA over this MR, it will take into account
the signature context of the transaction and will follow the signature
attributes configured.
Hope this helps,
Sagi.
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