linux-kernel - Re: [PATCH] hyperv: make HYPERV a menuconfig to ease disabling it all

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Message-ID: <20171216095120.568fad34@xeon-e3>
Date:   Sat, 16 Dec 2017 09:51:20 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Greg KH <greg@...ah.com>,
        Vincent Legoll <vincent.legoll@...il.com>,
        devel@...uxdriverproject.org, haiyangz@...rosoft.com,
        sthemmin@...rosoft.com,
        Linux Kernel ML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] hyperv: make HYPERV a menuconfig to ease disabling it
 all

On Thu, 14 Dec 2017 09:43:48 -0800
Randy Dunlap <rdunlap@...radead.org> wrote:

> On 12/13/2017 11:51 PM, Greg KH wrote:
> > 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@...il.com> wrote:
> >>  
> >>> Hello,
> >>>
> >>> On Sun, Dec 10, 2017 at 6:50 AM, Stephen Hemminger
> >>> <stephen@...workplumber.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.  
> 
> That should work.
> 
> > 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.  
> 
> Some of us would like to be able to disable many like drivers at one time
> instead of having to go down a list of say 20-30 drivers and disable them
> one at a time.
> 

It makes sense to organize the config if you dont break old configs.
It would be more logical to group and treat all para-virtualized guest
support in same way.  Hyper-V should be next to KVM and Xen.