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

[Richard W.M. Jones]

On Fri, Dec 06, 2013 at 05:26:58PM +0100, Pino Toscano wrote:
> 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?

Sure.  Note that we assume qemu >= 1.2 (see README) but for some
reason are only checking for qemu >= 1.0 (see configure.ac) .. a bug!

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
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