netdev - RE: [PATCH net v2 1/5] Revert "net: macsec: report real_dev features when HW offloading is enabled"

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Message-ID: <DM4PR12MB535741462D5FC1D5F4014896C9349@DM4PR12MB5357.namprd12.prod.outlook.com>
Date:   Sun, 30 Oct 2022 15:02:20 +0000
From:   Raed Salem <raeds@...dia.com>
To:     Raed Salem <raeds@...dia.com>, Leon Romanovsky <leon@...nel.org>,
        Sabrina Dubroca <sd@...asysnail.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Antoine Tenart <atenart@...nel.org>,
        Mark Starovoytov <mstarovoitov@...vell.com>,
        Igor Russkikh <irusskikh@...vell.com>
Subject: RE: [PATCH net v2 1/5] Revert "net: macsec: report real_dev features
 when HW offloading is enabled"

>>On Wed, Oct 26, 2022 at 11:56:23PM +0200, Sabrina Dubroca wrote:
>>> This reverts commit c850240b6c4132574a00f2da439277ab94265b66.
>>>
>>> That commit tried to improve the performance of macsec offload by
>>> taking advantage of some of the NIC's features, but in doing so,
>>> broke macsec offload when the lower device supports both macsec and
>>> ipsec offload, as the ipsec offload feature flags (mainly
>>> NETIF_F_HW_ESP) were copied from the real device. Since the macsec
>>> device doesn't provide xdo_* ops, the XFRM core rejects the
>>> registration of the new macsec device in xfrm_api_check.
>>>
>>> Example perf trace when running
>>>   ip link add link eni1np1 type macsec port 4 offload mac
>>>
>>>     ip   737 [003]   795.477676: probe:xfrm_dev_event__REGISTER
>>name="macsec0" features=0x1c000080014869
>>>               xfrm_dev_event+0x3a
>>>               notifier_call_chain+0x47
>>>               register_netdevice+0x846
>>>               macsec_newlink+0x25a
>>>
>>>     ip   737 [003]   795.477687:   probe:xfrm_dev_event__return
>ret=0x8002
>>(NOTIFY_BAD)
>>>              notifier_call_chain+0x47
>>>              register_netdevice+0x846
>>>              macsec_newlink+0x25a
>>>
>>> dev->features includes NETIF_F_HW_ESP (0x04000000000000), so
>>> xfrm_api_check returns NOTIFY_BAD because we don't have
>>> dev->xfrmdev_ops on the macsec device.
>>>
>>> We could probably propagate GSO and a few other features from the
>>> lower device, similar to macvlan. This will be done in a future patch.
>>>
>>> Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
>>> ---
>>>  drivers/net/macsec.c | 27 ++++-----------------------
>>>  1 file changed, 4 insertions(+), 23 deletions(-)
>>>
>>
>>It is still mystery for me why mlx5 works.
>I think it works when the offload enablement on the macsec device is done
>after the macsec netdev creation stage i.e.:
>Ip link add link eni1np1 type macsec port 4 Then ip macsec offload
>$MACSEC_IF mac I think this path skips xfrm core rejection
Further check it shows that xfrm_api_check fails in both configuration flavors,
in first method because of register_netdevice call the second method because of
netdev_update_features call, however, using the second method (that "works") masks
this error so user space is not aware of it, hence why the second method works.
>>
>>Thanks,
>>Reviewed-by: Leon Romanovsky <leonro@...dia.com>