Re: [PATCH for-6.0 6/6] qapi: Deprecate 'query-kvm'

[Peter Krempa]

On Fri, Nov 27, 2020 at 15:53:16 +0000, Daniel Berrange wrote:
> On Fri, Nov 27, 2020 at 01:18:09PM +0100, Peter Krempa wrote:
> > On Fri, Nov 27, 2020 at 14:45:12 +0300, Roman Bolshakov wrote:

[...]

> IIUC, this all relies on us importing a dump of the latest QEMU
> capabilities into the libvirt test suite.
> 
> Most of the capabilities we import are the release version, but
> we also periodically import the git snapshot capabilities and
> will refresh them until GA of QEMU.
> 
> Could we arrange it so that libvirt only reports an error for use
> of deprecated interfaces when testing against the GA capabilities
> dump. If testing against QEMU git snapshot capabilities, we can
> emit a warning only.
> 
> That way, we'll have a grace period in which libvirt can see the
> warning from tests, and we would only need to add an override
> to silence it once we import the GA capabilities, at which time
> it is safe to implement the new solution too.

As I've noted in my reply to Markus, in many cases we develop features
on top of unreleased qemu features. I don't really want to throw a
spanner into that process.

While deprecating old interfaces which are changed would lead to
regression in behaviour rather than releasing a broken feature if
changes are done in the API of a new feature the situation is slightly
worse, but it's also a very rare occurence.

I want to basically just an agreement that after such a thing is done
libvirt will be notified. We'll still try to develop replacements sooner
which can actually catch problems in the new features sooner than they
are released in qemu.