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Date: Thu, 14 Dec 2017 08:51:32 +0100
From: Greg KH <greg@kroah.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: Vincent Legoll <vincent.legoll@gmail.com>,
        devel@linuxdriverproject.org, haiyangz@microsoft.com,
        sthemmin@microsoft.com, Linux Kernel ML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] hyperv: make HYPERV a menuconfig to ease disabling it all
Message-ID: <20171214075132.GB31378@kroah.com>
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On Wed, Dec 13, 2017 at 01:23:38PM -0800, Stephen Hemminger wrote:
> On Wed, 13 Dec 2017 09:54:19 +0100
> Vincent Legoll <vincent.legoll@gmail.com> wrote:
> 
> > Hello,
> > 
> > On Sun, Dec 10, 2017 at 6:50 AM, Stephen Hemminger
> > <stephen@networkplumber.org> wrote:
> > > Will this break existing configs?  
> > 
> > I don't think so. Last time I did some similar changes, the kbuild
> > test robot found some warnings on some configurations, I hope
> > it will find problems (if any) for that series too (this one is not alone,
> > I've got a bunch of other similar patches in-flight)
> > 
> > Thanks
> 
> NAK
> 
> Let me give a concrete example of how this will break users.
> 
> 1. Assume user has a working .config file in their kernel build directory
> which builds a kernel that works on Hyper-V.
> 
> 2. Add your patch (or assume it makes into a later version).
> 
> 3. User then does
> 
> $ make oldconfig
> scripts/kconfig/conf  --oldconfig Kconfig
> *
> * Restart config...
> *
> *
> * Microsoft Hyper-V guest support
> *
> Microsoft Hyper-V guest support (HYPERV_MENU) [N/y] (NEW) 
> 
> If they hit return, the default value is not enabling HyperV and they
> will then go on to build a kernel that will not boot on your system.
> 
> The default MUST be set to Yes.

Or you can just not take these types of odd and silly changes to the
Kconfig files, and leave it as-is.  I have yet to see the good reason
why these are needed at all.

thanks,

greg k-h