netdev - RE: [PATCH 04/22] ice: Register auxiliary device to provide RDMA

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Message-ID: <ae763e223c0040259c63c1e745faa095@intel.com>
Date:   Fri, 5 Feb 2021 15:23:12 +0000
From:   "Saleem, Shiraz" <shiraz.saleem@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     "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>
Subject: RE: [PATCH 04/22] ice: Register auxiliary device to provide RDMA

> Subject: Re: [PATCH 04/22] ice: Register auxiliary device to provide RDMA
>  
> > @@ -1254,20 +1282,37 @@ int ice_init_peer_devices(struct ice_pf *pf)
> >  		 * |--> iidc_peer_obj
> >  		 * |--> *ice_peer_drv_int
> >  		 *
> > +		 * iidc_auxiliary_object (container_of parent for adev)
> > +		 * |--> auxiliary_device
> > +		 * |--> *iidc_peer_obj (pointer from internal struct)
> > +		 *
> >  		 * ice_peer_drv_int (internal only peer_drv struct)
> >  		 */
> >  		peer_obj_int = kzalloc(sizeof(*peer_obj_int), GFP_KERNEL);
> > -		if (!peer_obj_int)
> > +		if (!peer_obj_int) {
> > +			ida_simple_remove(&ice_peer_ida, id);
> >  			return -ENOMEM;
> > +		}
> 
> Why is this allocated memory with a lifetime different from the aux device?

This ice_peer_obj_int is the PCI driver internal only info about the peer_obj (not exposed externally)
like the state machine, per PF. But Dave is re-writing all of this with the feedback about getting rid
of state machine, and this peer_obj_int will likely be culled.

I think what we will end up with is an iidc_peer_obj per PF which is exported to aux driver with lifetime as described below.

/* structure layout needed for container_of's looks like:  
                  * iidc_auxiliary_dev (container_of parent for adev)
                  * |--> auxiliary_device
                  * |--> *iidc_peer_obj (pointer from peer_obj struct)
                  *
                  * The iidc_auxiliary device has a lifespan as long as it is
                  * on the bus.  Once removed it will be freed and a new
                  * one allocated if needed to re-add.
                  *
                  * The peer_obj is tied to the life of the PF, and will
                  * exist as long as the PF driver is loaded.  It will be
                  * freed in the remove flow for the PF driver.
                  */