linux-kernel - Re: [PATCH v3 00/14] Adding GAUDI NIC code to habanalabs driver

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Date:   Sat, 19 Sep 2020 16:22:35 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Oded Gabbay <oded.gabbay@...il.com>,
        Leon Romanovsky <leon@...nel.org>,
        Gal Pressman <galpress@...zon.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        netdev@...r.kernel.org, SW_Drivers <SW_Drivers@...ana.ai>,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        linux-rdma@...r.kernel.org
Subject: Re: [PATCH v3 00/14] Adding GAUDI NIC code to habanalabs driver

On Sat, Sep 19, 2020 at 07:27:30PM +0200, Greg Kroah-Hartman wrote:
> > It's probably heresy, but why do I need to integrate into the RDMA subsystem ?
> > I understand your reasoning about networking (Ethernet) as the driver
> > connects to the kernel networking stack (netdev), but with RDMA the
> > driver doesn't use or connect to anything in that stack. If I were to
> > support IBverbs and declare that I support it, then of course I would
> > need to integrate to the RDMA subsystem and add my backend to
> > rdma-core.
> 
> IBverbs are horrid and I would not wish them on anyone.  Seriously.

I'm curious what drives this opinion? Did you have it since you
reviewed the initial submission all those years ago?

> I think the general rdma apis are the key here, not the userspace api.

Are you proposing that habana should have uAPI in drivers/misc and
present a standard rdma-core userspace for it? This is the only
userspace programming interface for RoCE HW. I think that would be
much more work.

If not, what open source userspace are you going to ask them to
present to merge the kernel side into misc?

> Note, I do not know exactly what they are, but no, IBverbs are not ok.

Should we stop merging new drivers and abandon the RDMA subsystem? Is
there something you'd like to see fixed?

Don't really understand your position, sorry.

Jason