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

["Andreas Färber" <afaerber@suse.de>]

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.

Andreas

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