linux-kernel - Re: [PATCH net v3] Revert ncsi: Propagate carrier gain/loss events to the NCSI controller

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Message-ID: <20231115094122.GL74656@kernel.org>
Date:   Wed, 15 Nov 2023 09:41:22 +0000
From:   Simon Horman <horms@...nel.org>
To:     Johnathan Mantey <johnathanx.mantey@...el.com>
Cc:     netdev@...r.kernel.org, sam@...dozajonas.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v3] Revert ncsi: Propagate carrier gain/loss events
 to the NCSI controller

On Tue, Nov 14, 2023 at 12:20:52PM -0800, Johnathan Mantey wrote:
> 
> Simon Horman <horms@...nel.org> writes:
> 
> > On Mon, Nov 13, 2023 at 08:30:29AM -0800, Johnathan Mantey wrote:
> > > This reverts commit 3780bb29311eccb7a1c9641032a112eed237f7e3.
> > > 
> > > The cited commit introduced unwanted behavior.
> > > 
> > > The intent for the commit was to be able to detect carrier loss/gain
> > > for just the NIC connected to the BMC. The unwanted effect is a
> > > carrier loss for auxiliary paths also causes the BMC to lose
> > > carrier. The BMC never regains carrier despite the secondary NIC
> > > regaining a link.
> > > 
> > > This change, when merged, needs to be backported to stable kernels.
> > > 5.4-stable, 5.10-stable, 5.15-stable, 6.1-stable, 6.5-stable
> > > 
> > > Fixes: 3780bb29311e ("ncsi: Propagate carrier gain/loss events to
> > > the NCSI controller")
> > > CC: stable@...r.kernel.org
> > > Signed-off-by: Johnathan Mantey <johnathanx.mantey@...el.com>
> > 
> > Hi Jonathan,
> > 
> > thanks for addressing my feedback on v2.
> > 
> > So far as addressing a regression goes, this looks good to me.
> > But I do wonder what can be done about the issue that
> > the cited commit was intended to address: will this patch regress things
> > on that front?
> 
> Unfortunately the original issue will reoccur. I'm not sure which behavior
> is worse. What's been present for the lifespan of the ncsi driver, or this
> new issue I've introduced. In both instances a cable unplug causes
> undesirable behavior. I'm going to investigate solving this for Intel's
> specific use case ATM. NCSI has numerous modes in which it can be
> configured. I don't have a good feel for how to generalize the code given
> the side effect introduced by my change.

Thanks Jonathan,

I agree that is a bit of a conundrum without a working fix available.
I would lean towards the old bug being somehow better than the new one -
better the devil you know than the one you don't.

So, FWIIW, from a pragmatic pov I'm happy with this patch.

Reviewed-by: Simon Horman <horms@...nel.org>