Re: [PATCH] IB/mlx4: Allow to always block UD multicast loopback

[Or Gerlitz <or.gerlitz-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Tue, Apr 22, 2014 at 12:06 AM, Christoph Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org> wrote:
> On Mon, 21 Apr 2014, Or Gerlitz wrote:
>
>> > Currently, there's no way for user-space applications to specify
>> > the IB_QP_CREATE_BLOCK_MULTICAST_LOOPBACK QP creation flags
>> > defined by commit 47ee1b9 "IB/core: Add support for multicast loopback blocking".
>> > As a result, applications who send and recieve on the same QP over
>> > the same multicast group get all their packets bouncded back to them,
>> > which is bad..
>>
>> Hi Christoph, I do see your P&F (Pain and Frustration), however, this
>> patch was only meant to be bandaid (*) for the fact that whole ~six
>> years elapsed since a basically proper patch that does the task was
>> posted http://lists.openfabrics.org/pipermail/general/2008-July/053021.html
>> and we still don't have uverbs support for QP creation flags!!
>>
>> Roland, how you prefer to move on here? we can come up with quick
>> patch that just uses the reserved field of struct ib_uverbs_create_qp
>> and would allow to support upto 8 creation flags, this would not
>> require new uverbs command, OK?
>
> Urgh. So we have all these flags and we cannot use them?

Christoph, the support (kernel IB core API and HW drivers e.g mlx4 and
now also mlx5) is there for **kernel** consumers (e.g IPoIB). and
missing for **user-space** consumers whose calls are tunneled through
uverbs. The uverbs piece is the missing one.
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