linux-kernel - RE: [EXTERNAL] Re: [net-next, v3] net: mana: Support HW link state events

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Message-ID:
 <SA3PR21MB3867F780F0247DD9D774ECF6CAFAA@SA3PR21MB3867.namprd21.prod.outlook.com>
Date: Wed, 29 Oct 2025 13:20:47 +0000
From: Haiyang Zhang <haiyangz@...rosoft.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Paolo Abeni <pabeni@...hat.com>, Haiyang Zhang
	<haiyangz@...ux.microsoft.com>, "linux-hyperv@...r.kernel.org"
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Subject: RE: [EXTERNAL] Re: [net-next, v3] net: mana: Support HW link state
 events



> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Tuesday, October 28, 2025 6:02 PM
> To: Haiyang Zhang <haiyangz@...rosoft.com>
> Cc: Paolo Abeni <pabeni@...hat.com>; Haiyang Zhang
> <haiyangz@...ux.microsoft.com>; linux-hyperv@...r.kernel.org;
> netdev@...r.kernel.org; Paul Rosswurm <paulros@...rosoft.com>; Dexuan Cui
> <DECUI@...rosoft.com>; KY Srinivasan <kys@...rosoft.com>;
> wei.liu@...nel.org; edumazet@...gle.com; davem@...emloft.net; Long Li
> <longli@...rosoft.com>; ssengar@...ux.microsoft.com;
> ernis@...ux.microsoft.com; dipayanroy@...ux.microsoft.com; Konstantin
> Taranov <kotaranov@...rosoft.com>; horms@...nel.org;
> shradhagupta@...ux.microsoft.com; leon@...nel.org; mlevitsk@...hat.com;
> yury.norov@...il.com; Shiraz Saleem <shirazsaleem@...rosoft.com>;
> andrew+netdev@...n.ch; linux-rdma@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [EXTERNAL] Re: [net-next, v3] net: mana: Support HW link
> state events
> 
> On Tue, 28 Oct 2025 19:36:02 +0000 Haiyang Zhang wrote:
> > > Why is  the above needed? I thought mana_link_state_handle() should
> kick
> > > and set the carrier on as needed???
> >
> > Thanks for the question -- our MANA NIC only sends out the link state
> down/up
> > messages when need to let the VM rerun DHCP client and change IP
> address...
> >
> > So, I need to add netif_carrier_on(ndev) in the probe(), otherwise the
> > /sys/class/net/ethX/operstate will remain "unknown" until it receives
> the
> > Link down/up messages which do NOT always happen.
> 
> Oh that makes the code make much more sense.
> Please add this and more detail into the commit message.

Will do.

> 
> > +			if (!netif_carrier_ok(ndev))
> > +				netif_carrier_on(ndev);
> 
> Testing carrier_ok() before calling carrier_on/off is entirely
> pointless, please see the relevant implementations.
> 
> BTW I think the ac->link_event accesses are technically racy,
> wrap them in READ_ONCE() / WRITE_ONCE() while you respin.
> (Unless mana_hwc_init_event_handler() is somehow under rtnl_lock)

I will remove the netif_carrier_ok(), and add READ/WRITE_ONCE.

Thanks,
- Haiyang