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From:   Haiyang Zhang <haiyangz@microsoft.com>
To:     Jakub Kicinski <kuba@kernel.org>
CC:     "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        KY Srinivasan <kys@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        Dexuan Cui <decui@microsoft.com>,
        "edumazet@google.com" <edumazet@google.com>,
        "pabeni@redhat.com" <pabeni@redhat.com>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [PATCH net,v2] hv_netvsc: fix race of netvsc and VF
 register_netdevice
Thread-Topic: [PATCH net,v2] hv_netvsc: fix race of netvsc and VF
 register_netdevice
Thread-Index: AQHaCFKpKET2UnWjhkeRl4AacA94KLBmhFAAgAK2PJA=
Date:   Fri, 3 Nov 2023 22:44:08 +0000
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References: <1698355354-12869-1-git-send-email-haiyangz@microsoft.com>
 <20231101220730.2b7cc7d1@kernel.org>
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> -----Original Message-----
> From: Jakub Kicinski <kuba@kernel.org>
> Sent: Thursday, November 2, 2023 1:08 AM
> To: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: linux-hyperv@vger.kernel.org; netdev@vger.kernel.org; KY Srinivasan
> <kys@microsoft.com>; wei.liu@kernel.org; Dexuan Cui
> <decui@microsoft.com>; edumazet@google.com; pabeni@redhat.com;
> davem@davemloft.net; linux-kernel@vger.kernel.org; stable@vger.kernel.org
> Subject: Re: [PATCH net,v2] hv_netvsc: fix race of netvsc and VF
> register_netdevice
>=20
> On Thu, 26 Oct 2023 14:22:34 -0700 Haiyang Zhang wrote:
> > And, move register_netdevice_notifier() earlier, so the call back
> > function is set before probing.
>=20
> Are you sure you need this? I thought the netdev notifier "replays"
> registration events (i.e. sends "fake" events for already present
> netdevs).
>=20
> If I'm wrong this should still be a separate patch from the rtnl
> reorder.

I tested, NETDEV_REGISTER is indeed replayed, but NETDEV_POST_INIT=20
is not.  And we will use NETDEV_POST_INIT soon.

Also, we want to get notified by NETDEV_POST_INIT immediately from=20
VF, before VF NIC shows up to upper layers. So, even if we make=20
NETDEV_POST_INIT to be replayed, that may be too late.

I will put the register_netdevice_notifier() change to a separate patch.

Thanks,
- Haiyang