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

[Gleb Natapov]

On Tue, Aug 06, 2013 at 01:03:34PM +0200, Andreas Färber wrote:
> Am 06.08.2013 12:44, schrieb Gleb Natapov:
> > On Tue, Aug 06, 2013 at 01:19:53PM +0300, Michael S. Tsirkin wrote:
> >>>> It's a QEMU issue, devices that are added with -device are
> >>>> documented in -device help and removed by dropping them from
> >>>> command line. Devices added by default have no way to
> >>>> be dropped from QOM except -nodefaults.
> >>>>
> >>> Are you saying that because pvpanic is added automatically QEMU -device
> >>> help does not print help about it? Why not fix that? What QEMU --help
> >>> issues has to do with deciding which devices should or should not be
> >>> present by default?
> >>
> >> No, I'm saying what I said: that there's no way to remove a device
> >> added by default except -nodefaults, and no way to
> >> find out what does -nodefaults exclude so you
> >> can add things you need back selectively.
> >>
> > And what are the rules that govern device exclusion from -nodefaults
> > list? Why -nodefaults does not create empty machine?
> 
> We have -M none to create an empty machine.
> 
> FWIW -M q35 does not create all Q35 devices, there's -readconfig
> docs/q35-chipset.cfg for the rest. The criteria certainly is not
> migratability, since ICH9 AHCI (part of -M q35) is unmigratable,
> unfortunately.
> One practical reason not to create everything via config is that we
> cannot create SysBusDevices via -device when they require MMIO mapping
> or IRQ setup. For ISADevices such as pvpanic that's not a problem.
> Anthony has proposed QOM'ifying MemoryRegions and qemu_irq as solution
> to do the wiring-up from command line or config file, but those attempts
> got stuck a long time ago.
> 
But -M creates not only things that cannot be created from a command
line, it includes some default set of devices, so what is the criteria
for those?

--
                        Gleb.