[ewg] Mellanox target workaround in SRP

[Michael S. Tsirkin]

On Mon, Jan 10, 2011 at 10:51:13AM -0800, Roland Dreier wrote:
> Maybe we can use MST's current email to ask him... Michael, do you have
> any memory of the issue we worked around here?
> 
>  > I have question regarding workaround introduced in commit 559ce8f1 of
>  > the mainline tree:
>  > 
>  >     IB/srp: Work around data corruption bug on Mellanox targets
>  >     
>  >     Data corruption has been seen with Mellanox SRP targets when FMRs
>  >     create a memory region with I/O virtual address != 0.  Add a
>  >     workaround that disables FMR merging for Mellanox targets (OUI 0002c9).
>  > 
>  > I don't see how this can make a difference to the target -- it sees an
>  > address and length, and there should be no visible difference to it when
>  > it gets an FMR versus a direct-mapped region of the same space, right?
>  > And how is it different than getting a direct or indirect descriptor
>  > with a similar offset?
>  > 
>  > I could see there being a bug on the initiator HCA not liking such FMR
>  > mappings, but then it should be keyed off of the vendor of our HCA and
>  > not the target.
>  > 
>  > I'm sure this was tested and shown to fix the problem; I'm just confused
>  > as to what the problem really was and if this is still relevant. Can
>  > someone please enlighten me?


I don't recall unfortunately. Sorry.

-- 
MST