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From:   "Ertman, David M" <david.m.ertman@intel.com>
To:     "Saleem, Shiraz" <shiraz.saleem@intel.com>,
        Leon Romanovsky <leon@kernel.org>
CC:     "davem@davemloft.net" <davem@davemloft.net>,
        "kuba@kernel.org" <kuba@kernel.org>,
        "yongxin.liu@windriver.com" <yongxin.liu@windriver.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@intel.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Brandeburg, Jesse" <jesse.brandeburg@intel.com>,
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        "jgg@ziepe.ca" <jgg@ziepe.ca>,
        "Williams, Dan J" <dan.j.williams@intel.com>,
        "Singhai, Anjali" <anjali.singhai@intel.com>,
        "Parikh, Neerav" <neerav.parikh@intel.com>,
        "Samudrala, Sridhar" <sridhar.samudrala@intel.com>
Subject: RE: [PATCH RESEND net] ice: Correctly deal with PFs that do not
 support RDMA
Thread-Topic: [PATCH RESEND net] ice: Correctly deal with PFs that do not
 support RDMA
Thread-Index: AQHXpcrM4iqti0YqkUWIoEY3yjGYRauc/j0AgAUkHYCAAAOgcA==
Date:   Mon, 13 Sep 2021 16:07:28 +0000
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References: <20210909151223.572918-1-david.m.ertman@intel.com>
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> -----Original Message-----
> From: Saleem, Shiraz <shiraz.saleem@intel.com>
> Sent: Monday, September 13, 2021 8:50 AM
> To: Leon Romanovsky <leon@kernel.org>; Ertman, David M
> <david.m.ertman@intel.com>
> Cc: davem@davemloft.net; kuba@kernel.org; yongxin.liu@windriver.com;
> Nguyen, Anthony L <anthony.l.nguyen@intel.com>;
> netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Brandeburg, Jesse
> <jesse.brandeburg@intel.com>; intel-wired-lan@lists.osuosl.org; linux-
> rdma@vger.kernel.org; jgg@ziepe.ca; Williams, Dan J
> <dan.j.williams@intel.com>; Singhai, Anjali <anjali.singhai@intel.com>;
> Parikh, Neerav <neerav.parikh@intel.com>; Samudrala, Sridhar
> <sridhar.samudrala@intel.com>
> Subject: RE: [PATCH RESEND net] ice: Correctly deal with PFs that do not
> support RDMA
>=20
> > Subject: Re: [PATCH RESEND net] ice: Correctly deal with PFs that do no=
t
> > support RDMA
> >
> > On Thu, Sep 09, 2021 at 08:12:23AM -0700, Dave Ertman wrote:
> > > There are two cases where the current PF does not support RDMA
> > > functionality.  The first is if the NVM loaded on the device is set t=
o
> > > not support RDMA (common_caps.rdma is false).  The second is if the
> > > kernel bonding driver has included the current PF in an active link
> > > aggregate.
> > >
> > > When the driver has determined that this PF does not support RDMA,
> > > then auxiliary devices should not be created on the auxiliary bus.
> >
> > This part is wrong, auxiliary devices should always be created, in your=
 case it
> will
> > be one eth device only without extra irdma device.
>=20
> It is worth considering having an eth aux device/driver but is it a hard-=
and-
> fast rule?
> In this case, the RDMA-capable PCI network device spawns an auxiliary
> device for RDMA
> and the core driver is a network driver.
>=20
> >
> > Your "bug" is that you mixed auxiliary bus devices with "regular" ones =
and
> created
> > eth device not as auxiliary one. This is why you are calling to
> auxiliary_device_init()
> > for RDMA only and fallback to non-auxiliary mode.
>=20
> It's a design choice on how you carve out function(s) off your PCI core d=
evice
> to be
> managed by auxiliary driver(s) and not a bug.
>=20
> Shiraz

Also, regardless of whether netdev functionality is carved out into an auxi=
liary device or not, this code would still be necessary.

We don't want to carve out an auxiliary device to support a functionality t=
hat the base PCI device does not support.  Not having
the RDMA auxiliary device for an auxiliary driver to bind to is how we diff=
erentiate between devices that support RDMA and those
that don't.

Thanks,
DaveE