linux-kernel - RE: [PATCH RESEND net] ice: Correctly deal with PFs that do not support RDMA

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Date:   Mon, 13 Sep 2021 15:49:43 +0000
From:   "Saleem, Shiraz" <shiraz.saleem@...el.com>
To:     Leon Romanovsky <leon@...nel.org>,
        "Ertman, David M" <david.m.ertman@...el.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "yongxin.liu@...driver.com" <yongxin.liu@...driver.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "jgg@...pe.ca" <jgg@...pe.ca>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "Singhai, Anjali" <anjali.singhai@...el.com>,
        "Parikh, Neerav" <neerav.parikh@...el.com>,
        "Samudrala, Sridhar" <sridhar.samudrala@...el.com>
Subject: RE: [PATCH RESEND net] ice: Correctly deal with PFs that do not
 support RDMA

> Subject: Re: [PATCH RESEND net] ice: Correctly deal with PFs that do not
> 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 to
> > 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.

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.

> 
> 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.

It's a design choice on how you carve out function(s) off your PCI core device to be
managed by auxiliary driver(s) and not a bug.

Shiraz