netdev - Re: [RFC PATCH net-next 10/16] mlxsw: spectrum_switchdev: Add support for locked FDB notifications

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Date:   Fri, 4 Nov 2022 00:54:39 +0200
From:   Ido Schimmel <idosch@...dia.com>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bridge@...ts.linux-foundation.org" 
        <bridge@...ts.linux-foundation.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "jiri@...dia.com" <jiri@...dia.com>,
        "petrm@...dia.com" <petrm@...dia.com>,
        "ivecera@...hat.com" <ivecera@...hat.com>,
        "roopa@...dia.com" <roopa@...dia.com>,
        "razor@...ckwall.org" <razor@...ckwall.org>,
        "netdev@...io-technology.com" <netdev@...io-technology.com>,
        "mlxsw@...dia.com" <mlxsw@...dia.com>
Subject: Re: [RFC PATCH net-next 10/16] mlxsw: spectrum_switchdev: Add
 support for locked FDB notifications

On Thu, Nov 03, 2022 at 10:31:52PM +0000, Vladimir Oltean wrote:
> Hi Ido,
> 
> On Mon, Oct 31, 2022 at 10:32:10AM +0200, Vladimir Oltean wrote:
> > On Sun, Oct 30, 2022 at 10:23:07AM +0200, Ido Schimmel wrote:
> > > Right. I'm quite reluctant to add the MAB flag to
> > > BR_PORT_FLAGS_HW_OFFLOAD as part of this patchset for the simple reason
> > > that it is not really needed. I'm not worried about someone adding it
> > > later when it is actually needed. We will probably catch the omission
> > > during code review. Worst case, we have a selftest that will break,
> > > notifying us that a bug fix is needed.
> > 
> > For drivers which don't emit SWITCHDEV_FDB_ADD_TO_BRIDGE but do offload
> > BR_PORT_LOCKED (like mv88e6xxx), things will not work correctly on day 1
> > of BR_PORT_MAB because they are not told MAB is enabled, so they have no
> > way of rejecting it until things work properly with the offload in place.
> > 
> > It's the same reason for which we have BR_HAIRPIN_MODE | BR_ISOLATED |
> > BR_MULTICAST_TO_UNICAST in BR_PORT_FLAGS_HW_OFFLOAD, even if nobody acts
> > upon them.
> 
> Do you have any comment on this?

Sorry, forgot to reply... I added a patch (see below) to the offload
set. If the bridge patches are accepted and we have disagreements on the
offload part I can always split out this patch and send it separately so
that mv88e6xxx rejects MAB in 6.2.

commit ebdd7363f8c1802af63c35f74d6922b727617a7d
Author: Ido Schimmel <idosch@...dia.com>
Date:   Mon Oct 31 19:36:36 2022 +0200

    bridge: switchdev: Reflect MAB bridge port flag to device drivers
    
    Reflect the 'BR_PORT_MAB' flag to device drivers so that:
    
    * Drivers that support MAB could act upon the flag being toggled.
    * Drivers that do not support MAB will prevent MAB from being enabled.
    
    Signed-off-by: Ido Schimmel <idosch@...dia.com>

Notes:
    v1:
    * New patch.

diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c
index 8a0abe35137d..7eb6fd5bb917 100644
--- a/net/bridge/br_switchdev.c
+++ b/net/bridge/br_switchdev.c
@@ -71,7 +71,7 @@ bool nbp_switchdev_allowed_egress(const struct net_bridge_port *p,
 }
 
 /* Flags that can be offloaded to hardware */
-#define BR_PORT_FLAGS_HW_OFFLOAD (BR_LEARNING | BR_FLOOD | \
+#define BR_PORT_FLAGS_HW_OFFLOAD (BR_LEARNING | BR_FLOOD | BR_PORT_MAB | \
                                  BR_MCAST_FLOOD | BR_BCAST_FLOOD | BR_PORT_LOCKED | \
                                  BR_HAIRPIN_MODE | BR_ISOLATED | BR_MULTICAST_TO_UNICAST)