Re: [Qemu-devel] [PATCH v3 2/4] GlobalProperty: Display warning about unused -global

[Paolo Bonzini]

Il 18/04/2014 11:21, Andreas Färber ha scritto:
> Improving this is greatly appreciated, thanks.
>
> Now, I can see two ways things can go wrong: a) Mistyping or later
> refactoring devices, or b) user typos or thinkos.
> And four ways to set globals: -global, config file (I hope?), legacy
> command line options (vl.c) and machine .compat_props.
>
> If a property does not exist on the instance of an existing type,
> object_property_parse() will raise an Error and we will abort in
> device_post_init().
>
> What we are silently missing is if a type is misspelled; for that we can
> probably add an Error **errp to the two qdev_prop_register_global*()
> functions - assuming QOM types are already registered at that point.
> qom-test would help us catch any such mistake by instantiating each machine.

Even then, I suspect sooner or later machines other than PC and Q35 will 
be versioned.  At that point we'll probably want QEMU-global 
compat_props that automatically apply to all machines, even if a type is 
not missing.  I think we should already approximate this behavior by 
allowing machine .compat_props where the type doesn't exist.

Paolo

> I note that your proposed check is not failing, but still, with hot-add
> of e.g. PCI devices we might well get a global property default for a
> type that is not instantiated immediately but possibly used later on.