netdev - RE: [PATCH 07/22] RDMA/irdma: Register an auxiliary driver and implement private channel OPs

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Date:   Sat, 30 Jan 2021 01:19:15 +0000
From:   "Saleem, Shiraz" <shiraz.saleem@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     "Keller, Jacob E" <jacob.e.keller@...el.com>,
        Leon Romanovsky <leon@...nel.org>,
        "dledford@...hat.com" <dledford@...hat.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Ertman, David M" <david.m.ertman@...el.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        "Ismail, Mustafa" <mustafa.ismail@...el.com>,
        "jiri@...dia.com" <jiri@...dia.com>,
        "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Subject: RE: [PATCH 07/22] RDMA/irdma: Register an auxiliary driver and
 implement private channel OPs

> Subject: Re: [PATCH 07/22] RDMA/irdma: Register an auxiliary driver and
> implement private channel OPs
> 
> On Wed, Jan 27, 2021 at 12:42:09AM +0000, Saleem, Shiraz wrote:
> 
> > > It does, the PCI driver is not supposed to spawn any aux devices for
> > > RDMA at all if RDMA is disabled.
> > >
> > > For an iWarp driver I would consider ENABLE_ROCE to really be a
> > > general ENABLE_RDMA.
> >
> > Well the driver supports iWARP and RoCE for E810 device.
> > Are you saying that this generic enable_roce devlink param really is
> > an enable 'rdma' traffic or not param?
> 
> I've thought of it that way, that is what it was created for at least.
> 
> Overloading it to be a iwarp not roce switch feels wrong

OK.

> 
> > > Are you sure you need to implement this?
> >
> > What we are after is some mechanism for user to switch the protocols
> > iWARP vs RoCE [default the device comes up as an iWARP dev]. The
> > protocol info is really needed early-on in the RDMA driver.probe(). i.e. when the
> rdma admin queue is created.
> 
> This needs to be a pci devlink at least, some kind of mode switch seems
> appropriate
> 
> > The same goes with the other param resource_limits_selector. It's a
> > profile selector that a user can chose to different # of max QP, CQs,
> > MRs etc.
> 
> And it must be done at init time? Also seems like pci devlink

Yes.

> 
> Generally speaking anything that requires the rdma driver to be reloaded should
> remove/restore the aux device.
> 
> Mode switch from roce to/from iwarp should create aux devices of different names
> which naturally triggers the right kind of sequences in the driver core
> 

OK we will move devlink out of aux rdma driver to PCI driver.

About separate aux dev names for iWARP, RoCE, that sounds reasonable.