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

[Eric Blake]

On Mon, Jul 19, 2021 at 12:40:33PM +0200, Paolo Bonzini wrote:
> Alias targets have a different name than the alias property itself
> (e.g. a machine's pflash0 might be an alias of a property named 'drive').
> When the target's getter or setter invokes the visitor, it will use
> a different name than what the caller expects, and the visitor will
> not be able to find it (or will consume erroneously).
> 
> The solution is for alias getters and setters to wrap the incoming
> visitor, and forward the sole field that the target is expecting while
> renaming it appropriately.
> 
> This bug has been there forever, but it was exposed after -M parsing
> switched from QemuOptions and StringInputVisitor to keyval and
> QObjectInputVisitor.  Before, the visitor ignored the name. Now, it
> checks "drive" against what was passed on the command line and finds
> that no such property exists.
> 
> Fixes: #484
> Reported-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  qom/object.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)

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>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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