Re: [PATCH 2/2] qom: use correct field name when getting/setting alias properties

[Markus Armbruster]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 20/07/21 03:00, Eric Blake wrote:
>> Deceptively simple; all the work was in the previous patch writing up
>> the forwarding visitor.  I still wonder if Kevin's QAPI aliases will
>> do this more gracefully, but if we're trying to justify this as a bug
>> fix worthy of 6.1, this is certainly a smaller approach than Kevin's.
>> Reviewed-by: Eric Blake<eblake@redhat.com>
>
> As discussed on IRC, this is unrelated to QAPI aliases; QOM alias
> properties typically target a property *on a different object*.

Yes, these are different beasts.

A QAPI alias provides an alternate name for a member.  The member may be
nested.  It's still within the same QAPI object.  Can be useful for
maintaining backwards compatibility, in particular for replacing (flat)
QemuOpts by QAPI-based dotted keys.

A QOM alias property is a proxy for a property of an *arbitrary* QOM
object.  Not limited to the alias's object and its sub-objects.
Strictly more powerful.

QOM alias properties are created at run time: creation requires the
target object.  QAPI aliases are completely defined at compile-time.

> This is a regression, so it certainly has to be fixed in 6.1 one way
> or the other.

Understood.