Re: [PATCH 6/9] ib_uverbs: Avoid vendor specific masking of attributes in query_qp

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On Fri, Sep 02, 2016 at 06:45:52AM +0200, Knut Omang wrote:
> On Thu, 2016-09-01 at 20:13 -0600, Jason Gunthorpe wrote:
> > On Fri, Sep 02, 2016 at 02:09:26AM +0200, Knut Omang wrote:
> > > This commit removes the implementation and use of the modify_qp_mask
> > > helper function from the generic OFED implementation and into individual
> > > device drivers.
> > > 
> > > Like with use of the ib_modify_qp_is_ok function it should be up to
> > > each device driver how to handle bits set in the attribute masks.
> > > 
> > > With the modify_qp_mask function applied in the generic code,
> > > drivers would not see the bits that the user process actually sets.
> > > 
> > > The restrictions imposed by the filter are also beyond what
> > > is imposed by the Infiniband standard, and would also limit
> > > future drivers or hardware from checking for unsupported or
> > > invalid settings.
> > 
> > I'm not excited about this direction. It is not OK for different
> > drivers to use different mask algorithms, they must all behave the
> > same.
> 
> The problem I am solving here is that SIF expects (and requires) some of 
> the bits that the user correctly sets, but that Mellanox either ignore or need to
> be 0. So when that mask is applied to the user input, the value that reaches
> the SIF driver is not correct from SIFs perspective. 
> If the values goes through as the ULP sets them, then all is fine.

I guess I still don't understand. SIF and mlx cannot have different
behavior here. How is the application writer to know what to do?

Can you give a concrete example of the problem?

Jason
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