Re: [PATCH v15 10/11] qapi/s390x/cpu topology: CPU_POLARITY_CHANGE qapi event

[Markus Armbruster]

Daniel P. Berrangé <berrange@redhat.com> writes:

> On Wed, Feb 08, 2023 at 06:35:39PM +0100, Nina Schoetterl-Glausch wrote:

[...]

>> I also wonder if you should add 'feature' : [ 'unstable' ].
>> On the upside, it would mark the event as unstable, but I don't know what the
>> consequences are exactly.
>
> The intention of this flag is to allow mgmt apps to make a usage policy
> decision.
>
> Libvirt's policy is that we'll never use features marked unstable.
>
> IOW, the consequence of marking it unstable is that it'll likely
> go unused until the unstable marker gets removed.
>
> Using 'unstable' is useful if you want to get complex code merged
> before you're quite happy with the design, and then iterate on the
> impl in-tree. This is OK if there's no urgent need for apps to
> consume the feature. If you want the feature to be used for real
> though, the unstable flag is not desirable and you need to finalize
> the design.

Another use of 'unstable' is debugging aids.  Making these stable can be
plenty of pain for precious little gain.

[...]