Re: [Qemu-devel] [SeaBIOS] [PATCH] don't expose pvpanic device in the UI

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Aug 06, 2013 at 11:56:11AM +0200, Markus Armbruster wrote:
> Andreas Färber <afaerber@suse.de> writes:
> 
> > Am 06.08.2013 10:36, schrieb Gleb Natapov:
> >> On Tue, Aug 06, 2013 at 11:33:10AM +0300, Michael S. Tsirkin wrote:
> >>> On Tue, Aug 06, 2013 at 10:21:52AM +0300, Gleb Natapov wrote:
> >>>>> If you see a mouse in a room, how likely is it that there's
> >>>>> a single mouse there?
> >>>>>
> >>>>> This is a PV technology which to me looks like it was
> >>>>> rushed through and not only set on by default, but
> >>>>> without a way to disable it - apparently on the assumption
> >>>>> there's 0 chance it can cause any damage. Now that
> >>>>> we do know the chance it's not there, why not go back
> >>>>> to the standard interface, and why not give
> >>>>> users a chance to enable/disable it?
> >>>> You should be able to disable it with: -device pvpanic,ioport=0
> >>>
> >>> Doesn't work for me.
> >> Bug that should be fixed. With this command line _STA should return
> >> zero.
> >> 
> >>> Besides, both -device pvpanic and use of ioport=0 to disable it
> >>> are completely undocumented.
> >>>
> >> Not the only undocumented thing in QEMU command line :)
> > [snip]
> >
> > I disagree: -device adds a device, not removes one. It will still be
> > present.
> >
> > I am neutral as to whether qemu-system-x86_64 should have it enabled by
> > default or not.
> 
> Me too.

In general, me neither.
But we have -device to add a device, it's nicely self-documenting,
We don't have -nodevice to remove a device except the big -nodefaults,
and -nodefaults is not self-documenting, and it's not clear
how it can be made self-documenting.