Re: [PATCH rdma-core 2/3] mlx5: Add support for managing QP with a given source QP number

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Wed, Sep 06, 2017 at 11:50:15PM -0700, Yuval Shaia wrote:
> On Wed, Sep 06, 2017 at 06:56:29PM +0300, Yishai Hadas wrote:
> > On 9/6/2017 6:12 PM, Yuval Shaia wrote:
> > >On Wed, Sep 06, 2017 at 05:38:48PM +0300, Yishai Hadas wrote:
> > >>Add support to create a QP with source QPN (e.g. IPoIB QPN) over UD QP.
> > >
> > >Sorry, i missed the kernel patches.
> > >Is this UD limitation is for mlx5 only? Asking as i see no limitation in
> > >the verb layer (patch 1/3).
> > 
> > From API point of view as was introduced by the verbs patch there is
> > no limitation. The mlx5 driver implements the use case for UD QP to
> > accelerate IPoIB packets.
> > 
> > >If no, any plans for CM?
> > No plan for CM at the moment, however, it may be considered in the
> > future based on demand/use case.
> 
> I can give you use case - migration.

Maybe Yishai should adjust the name and description for this feature.

It creates a SEND ONLY QP that is non-exclusive to normal UD QPs using
the same QPN.

What you are asking for is a way to create a new QP of any type with a
fixed QPN so long as the QPN does not overlap with an existing
QPN.. Very different.

.. and migration needs a way to import quite alot of other state too,
so not sure a fixed QPN is really useful for that in any event.

Jason
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