linux-kernel - Re: [PATCH v3 2/2] misc: pvpanic: introduce module parameter 'events'

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Date:   Fri, 8 Jan 2021 16:15:16 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     zhenwei pi <pizhenwei@...edance.com>, arnd@...db.de,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] misc: pvpanic: introduce module parameter 'events'

On Fri, Jan 08, 2021 at 04:04:24PM +0100, Paolo Bonzini wrote:
> On 08/01/21 15:07, Greg KH wrote:
> > >   static void __iomem *base;
> > > +static unsigned int events = PVPANIC_PANICKED | PVPANIC_CRASH_LOADED;
> > > +module_param(events, uint, 0644);
> > > +MODULE_PARM_DESC(events, "set event limitation of pvpanic device");
> > I do not understand you wanting a module parameter as well as a sysfs
> > file.  Why is this needed?  Why are you spreading this information out
> > across different apis and locations?
> 
> It can be useful to disable some functionality, for example in case you want
> to fake running on an older virtualization host.  This can be done for
> debugging reasons, or to keep uniform handling across a fleet that is
> running different versions of QEMU.

And where is this all going to be documented?

And what's wrong with just making the sysfs attribute writable?

thanks,

greg k-h