[Libguestfs] Use of qemu-kvm command line arguments in libguestfs (was: Re: Fwd: ...)

[Pino Toscano]

On Monday 02 December 2013 09:09:44 Richard W.M. Jones wrote:
> On Mon, Dec 02, 2013 at 01:17:09AM +0100, Pino Toscano wrote:
> > On Friday 29 November 2013 18:53:38 you wrote:
> > > > > I'm marking options with NONE (not used at all), or M (used in
> > > > > master) and/or RH7 (used in rhel-7.0).
> > > > > 
> > > > > > * -nographic
> > > > > 
> > > > > M + RH7
> > > > > I guess that could be changed into (roughly)
> > > > > 
> > > > >   if (qemu_supports (g, data, "-display"))
> > > > >   { ADD_CMDLINE ("-display"); ADD_CMDLINE ("none"); }
> > > > >   else
> > > > >   
> > > > >     ADD_CMDLINE ("-nographic");
> > > > 
> > > > Yup, something like that should work.  Did you have a look at
> > > > the
> > > > qemu code to find out what other side-effects -nographic has? 
> > > > Are
> > > > they important side-effects?
> > 
> > It seems most of the effects are related to the default devices
> > (serial, parallel, vrtcon, etc) that are added; OTOH, we always use
> > -nodefaults so those are not added, so at least there should be no
> > difference from this p.o.v.
> > 
> > The other changes related to the use of nographics are in few
> > target-
> > related places:
> > - in lm32 hardware (milkymist-tmu2), no display device is created
> > when> 
> >   the display type is "nographics" (but it is when the type is
> >   "none"?
> >   hmm..)
> > 
> > - in nvram support, the FW_CFG_NOGRAPHIC bit is set to 1 if the
> > display> 
> >   is "nographics", while 0 otherwise
> > 
> > - in sparc (not sparc64 though, it seems), the ESCC serial device is
> > 
> >   created disabled if the display type is "nographics", while
> >   enabled
> >   otherwise
> > 
> > I'm not totally sure about these architecture-specific bits, but at
> > least from a quick glance it could be relatively safe to make
> > "-display none" preferred over -nographics, at it seems more like
> > "device graphics is enabled (as if it was SDL, curses, etc), just
> > with no output at all)".
> 
> It sounds fine, as long as qemu 1.2 had "-display none".

It seems like this feature was added in commit
4171d32e6eea47bf2cd160ace0ec3639e10b3aa9, which is available in
qemu >= 0.15.0.

It is not easy to check for it in qemu's --help text, as the help bits 
for -display span over multiple lines, so I guess it could be just 
switched altogether.

I tried switching it locally, and the unit tests still passed. 
(Currently using qemu 1.4.2, as shipped in f19.)
Would it be acceptable to do this change in master, to gather more 
feedback about it?

-- 
Pino Toscano