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Re: [libvirt] [RFC PATCH 19/19] qapi: Implement -compat deprecated-outpu
From: |
Daniel P . Berrangé |
Subject: |
Re: [libvirt] [RFC PATCH 19/19] qapi: Implement -compat deprecated-output=hide for events |
Date: |
Thu, 24 Oct 2019 15:16:58 +0100 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
On Thu, Oct 24, 2019 at 02:34:58PM +0200, Markus Armbruster wrote:
> This policy suppresses deprecated events, and thus permits "testing
> the future".
One thing that occurs to me is that this is a fairly passive impact
on libvirt. eg it may well be not at all obvious if libvirt is behaving
in a broken way due to an event not being emitted, as the code in
question simply won't be triggered.
With the current QMP this situation is unavoidable since QEMU doesn't
know which events the client (libvirt) is actually using. QEMU just
unconditionally emits all events.
I've often wondered if we should have the client explicitly tell
QEMU which events it wants to receive as part of the QMP greeting
handshake.
ie, libvirt knows which events it can handle. QEMU knows which
events it can emit, and reports this via capabilities which
libvirt probes.
So on connecting libvirt can tell QEMU exactly which evnets it
wants to get back. QEMU is now able to explicitly tell libvirt
it has asked for a deprecated event, and so the logic from the
"deprecated-input" option can take effect.
We'd not need "deprecated-output" at that point.
Regards,
Daniel
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- [RFC PATCH 02/19] tests/test-qmp-cmds: Check responses more thoroughly, (continued)
- [RFC PATCH 02/19] tests/test-qmp-cmds: Check responses more thoroughly, Markus Armbruster, 2019/10/24
- [RFC PATCH 03/19] tests/test-qmp-cmds: Simplify test data setup, Markus Armbruster, 2019/10/24
- [RFC PATCH 04/19] tests/test-qmp-event: Simplify test data setup, Markus Armbruster, 2019/10/24
- [RFC PATCH 01/19] tests/test-qmp-cmds: Factor out qmp_dispatch() test helpers, Markus Armbruster, 2019/10/24
- [RFC PATCH 12/19] qapi: Replace qmp_dispatch()'s TODO comment by an explanation, Markus Armbruster, 2019/10/24
- [RFC PATCH 15/19] qapi: Mark deprecated QMP commands with feature 'deprecated', Markus Armbruster, 2019/10/24
- [RFC PATCH 18/19] qapi: Include a warning in the response to a deprecated command, Markus Armbruster, 2019/10/24
- [RFC PATCH 19/19] qapi: Implement -compat deprecated-output=hide for events, Markus Armbruster, 2019/10/24
- Re: [libvirt] [RFC PATCH 19/19] qapi: Implement -compat deprecated-output=hide for events,
Daniel P . Berrangé <=
- [RFC PATCH 17/19] qapi: Implement -compat deprecated-input=crash for commands, Markus Armbruster, 2019/10/24
- [RFC PATCH 13/19] qapi: New special feature flag "deprecated", Markus Armbruster, 2019/10/24
- [RFC PATCH 05/19] tests/test-qmp-event: Use qobject_is_equal(), Markus Armbruster, 2019/10/24
- [RFC PATCH 14/19] qemu-options: New -compat to set policy for "funny" interfaces, Markus Armbruster, 2019/10/24
- [RFC PATCH 09/19] qapi: Inline do_qmp_dispatch() into qmp_dispatch(), Markus Armbruster, 2019/10/24
- [RFC PATCH 11/19] qapi: Simplify how qmp_dispatch() gets the request ID, Markus Armbruster, 2019/10/24
- [RFC PATCH 16/19] qapi: Implement -compat deprecated-input=reject for commands, Markus Armbruster, 2019/10/24
- [RFC PATCH 06/19] tests/test-qmp-event: Check event is actually emitted, Markus Armbruster, 2019/10/24
- [RFC PATCH 10/19] qapi: Simplify how qmp_dispatch() deals with QCO_NO_SUCCESS_RESP, Markus Armbruster, 2019/10/24