Re: [PATCH v2 8/8] ib_uverbs: Support for kernel implementation of XRC

[Knut Omang <knut.omang@oracle.com>]

On Fri, 2016-09-16 at 13:31 -0600, Jason Gunthorpe wrote:
> On Fri, Sep 16, 2016 at 08:31:19PM +0200, Knut Omang wrote:
> > +++ b/include/uapi/rdma/ib_user_verbs.h
> > @@ -725,6 +725,8 @@ struct ib_uverbs_send_wr {
> >  			__u32 reserved;
> >  		} ud;
> >  	} wr;
> > +	__u32 xrc_remote_srq_num;
> > +	__u32 reserved;
> >  };
> 
> You still need to discuss why this is OK...
> 
> Are you doing all this just to be able to use the existing post_send user
> space path in the common code? Is there a kernel XRC user planned?

Yes, with this patch, the SIF user level provider library is able to 
use either kernel verbs or user verbs on a per QP basis. This is a
very useful capability that the verbs API neatly lends itself almost 
completely to, except for this particular missing piece.

> Another approach would be to implement post_send in your driver and
> not rely on this common code path.

I agree this would be possible, but that would have been
to implement a generic feature which seems a natural completion
of what is already in there in provider specific code, something 
I would have thought from other discussions here is considered bad 
practice?

Thanks,
Knut

> 
> Jason