netdev - Re: [rdma 14/16] RDMA/irdma: Add ABI definitions

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Date:   Wed, 10 Jul 2019 13:32:10 +0000
From:   Jason Gunthorpe <jgg@...lanox.com>
To:     Henry Orosco <henry.orosco@...el.com>
CC:     "Saleem, Shiraz" <shiraz.saleem@...el.com>,
        Leon Romanovsky <leon@...nel.org>,
        "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
        "dledford@...hat.com" <dledford@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "Ismail, Mustafa" <mustafa.ismail@...el.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "sassmann@...hat.com" <sassmann@...hat.com>,
        "poswald@...e.com" <poswald@...e.com>,
        "Ertman, David M" <david.m.ertman@...el.com>
Subject: Re: [rdma 14/16] RDMA/irdma: Add ABI definitions

On Tue, Jul 09, 2019 at 03:56:13PM -0500, Henry Orosco wrote:
> On Mon, Jul 08, 2019 at 02:13:39PM +0000, Jason Gunthorpe wrote:
> > On Sat, Jul 06, 2019 at 04:15:20PM +0000, Saleem, Shiraz wrote:
> > > > Subject: Re: [rdma 14/16] RDMA/irdma: Add ABI definitions
> > > > 
> > > > On Fri, Jul 05, 2019 at 04:42:19PM +0000, Saleem, Shiraz wrote:
> > > > > > Subject: Re: [rdma 14/16] RDMA/irdma: Add ABI definitions
> > > > > >
> > > > > > On Thu, Jul 04, 2019 at 10:40:21AM +0300, Leon Romanovsky wrote:
> > > > > > > On Wed, Jul 03, 2019 at 07:12:57PM -0700, Jeff Kirsher wrote:
> > > > > > > > From: Mustafa Ismail <mustafa.ismail@...el.com>
> > > > > > > >
> > > > > > > > Add ABI definitions for irdma.
> > > > > > > >
> > > > > > > > Signed-off-by: Mustafa Ismail <mustafa.ismail@...el.com>
> > > > > > > > Signed-off-by: Shiraz Saleem <shiraz.saleem@...el.com>
> > > > > > > > include/uapi/rdma/irdma-abi.h | 130
> > > > > > > > ++++++++++++++++++++++++++++++++++
> > > > > > > >  1 file changed, 130 insertions(+)  create mode 100644
> > > > > > > > include/uapi/rdma/irdma-abi.h
> > > > > > > >
> > > > > > > > diff --git a/include/uapi/rdma/irdma-abi.h
> > > > > > > > b/include/uapi/rdma/irdma-abi.h new file mode 100644 index
> > > > > > > > 000000000000..bdfbda4c829e
> > > > > > > > +++ b/include/uapi/rdma/irdma-abi.h
> > > > > > > > @@ -0,0 +1,130 @@
> > > > > > > > +/* SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause */
> > > > > > > > +/* Copyright (c) 2006 - 2019 Intel Corporation.  All rights reserved.
> > > > > > > > + * Copyright (c) 2005 Topspin Communications.  All rights reserved.
> > > > > > > > + * Copyright (c) 2005 Cisco Systems.  All rights reserved.
> > > > > > > > + * Copyright (c) 2005 Open Grid Computing, Inc. All rights reserved.
> > > > > > > > + */
> > > > > > > > +
> > > > > > > > +#ifndef IRDMA_ABI_H
> > > > > > > > +#define IRDMA_ABI_H
> > > > > > > > +
> > > > > > > > +#include <linux/types.h>
> > > > > > > > +
> > > > > > > > +/* irdma must support legacy GEN_1 i40iw kernel
> > > > > > > > + * and user-space whose last ABI ver is 5  */ #define
> > > > > > > > +IRDMA_ABI_VER
> > > > > > > > +6
> > > > > > >
> > > > > > > Can you please elaborate about it more?
> > > > > > > There is no irdma code in RDMA yet, so it makes me wonder why new
> > > > > > > define shouldn't start from 1.
> > > > > >
> > > > > > It is because they are ABI compatible with the current user space,
> > > > > > which raises the question why we even have this confusing header file..
> > > > >
> > > > > It is because we need to support current providers/i40iw user-space.
> > > > > Our user-space patch series will introduce a new provider (irdma)
> > > > > whose ABI ver. is also 6 (capable of supporting X722 and which will
> > > > > work with i40iw driver on older kernels) and removes providers/i40iw from rdma-
> > > > core.
> > > > 
> > > > Why on earth would we do that?
> > > > 
> > > A unified library providers/irdma to go in hand with the driver irdma and uses the ABI header.
> > > It can support the new network device e810 and existing x722 iWARP device. It obsoletes
> > > providers/i40iw and extends its ABI. So why keep providers/i40iw around in rdma-core?
> > 
> > Why rewrite a perfectly good userspace that is compatible with the
> > future and past kernels?
> > 
> > Is there something so wrong with the userspace provider to need this?
> >
> 
> Yes, the issue is that providers/i40iw was never designed to work with a unified driver
> which supports multiple hardware generations.

But Shiraz said it works fine with the new kernel driver.. So what is
actually the problem?

Jason