netdev - Re: [net-next 1/2] xen-netback: add module parameter to disable ctrl-ring

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Date:   Sun, 14 Mar 2021 12:04:18 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     "Hsu, Chiahao" <andyhsu@...zon.com>, netdev@...r.kernel.org,
        wei.liu@...nel.org, paul@....org, davem@...emloft.net,
        kuba@...nel.org, xen-devel@...ts.xenproject.org
Subject: Re: [net-next 1/2] xen-netback: add module parameter to disable
 ctrl-ring

On Fri, Mar 12, 2021 at 09:36:59PM +0100, Andrew Lunn wrote:
> On Fri, Mar 12, 2021 at 04:18:02PM +0100, Hsu, Chiahao wrote:
> >
> > Andrew Lunn 於 2021/3/12 15:52 寫道:
> > > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
> > >
> > >
> > >
> > > On Thu, Mar 11, 2021 at 10:59:44PM +0000, ChiaHao Hsu wrote:
> > > > In order to support live migration of guests between kernels
> > > > that do and do not support 'feature-ctrl-ring', we add a
> > > > module parameter that allows the feature to be disabled
> > > > at run time, instead of using hardcode value.
> > > > The default value is enable.
> > > Hi ChiaHao
> > >
> > > There is a general dislike for module parameters. What other mechanisms
> > > have you looked at? Would an ethtool private flag work?
> > >
> > >       Andrew
> >
> >
> > Hi Andrew,
> >
> > I can survey other mechanisms, however before I start doing that,
> >
> > could you share more details about what the problem is with using module
> > parameters? thanks.
>
> It is not very user friendly. No two kernel modules use the same
> module parameters. Often you see the same name, but different
> meaning. There is poor documentation, you often need to read the
> kernel sources it figure out what it does, etc.

+1, It is also global parameter to whole system/devices that use this
module, which is rarely what users want.

Thanks