linux-kernel - RE: [PATCH net,v2] hv_netvsc: fix race of netvsc and VF register

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Message-ID: <PH7PR21MB31169E4E03163358946BF95DCAA5A@PH7PR21MB3116.namprd21.prod.outlook.com>
Date:   Fri, 3 Nov 2023 22:44:08 +0000
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH net,v2] hv_netvsc: fix race of netvsc and VF
 register_netdevice



> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Thursday, November 2, 2023 1:08 AM
> To: Haiyang Zhang <haiyangz@...rosoft.com>
> Cc: linux-hyperv@...r.kernel.org; netdev@...r.kernel.org; KY Srinivasan
> <kys@...rosoft.com>; wei.liu@...nel.org; Dexuan Cui
> <decui@...rosoft.com>; edumazet@...gle.com; pabeni@...hat.com;
> davem@...emloft.net; linux-kernel@...r.kernel.org; stable@...r.kernel.org
> Subject: Re: [PATCH net,v2] hv_netvsc: fix race of netvsc and VF
> register_netdevice
> 
> 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.
> 
> Are you sure you need this? I thought the netdev notifier "replays"
> registration events (i.e. sends "fake" events for already present
> netdevs).
> 
> 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 
is not.  And we will use NETDEV_POST_INIT soon.

Also, we want to get notified by NETDEV_POST_INIT immediately from 
VF, before VF NIC shows up to upper layers. So, even if we make 
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