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From: Markus Armbruster <armbru@redhat.com>
To: Christophe de Dinechin <dinechin@redhat.com>
Cc: "Kevin Wolf" <kwolf@redhat.com>,
	"Peter Maydell" <peter.maydell@linaro.org>,
	"Daniel P. Berrange" <berrange@redhat.com>,
	"Denis V. Lunev" <den@virtuozzo.com>,
	"Stefan Hajnoczi" <stefanha@gmail.com>,
	qemu-devel <qemu-devel@nongnu.org>,
	"Marc-André Lureau" <marcandre.lureau@redhat.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"John Snow" <jsnow@redhat.com>,
	"Dominik Csapak" <d.csapak@proxmox.com>
Subject: Re: Making QEMU easier for management tools and applications
Date: Wed, 15 Jan 2020 13:15:17 +0100	[thread overview]
Message-ID: <87r200zzje.fsf@dusky.pond.sub.org> (raw)
In-Reply-To: <8CF8359B-1E52-4F7A-944E-C1C14FEC4F92@redhat.com> (Christophe de Dinechin's message of "Wed, 15 Jan 2020 10:34:09 +0100")

Christophe de Dinechin <dinechin@redhat.com> writes:

> Thanks a bunch. This clarifies a number of my misconceptions about
> how this is currently used. Most notably this one:
>
>> On 15 Jan 2020, at 10:20, Markus Armbruster <armbru@redhat.com> wrote:
>> 
>>> We don’t want the QAPI to let arbitrary fields of a QOM object
>>> be modified, do we?
>> 
>> We already do: QMP command qom-set.  If it breaks your guest, you get to
>> keep the pieces.
>
> Ouch. I certainly did not expect that.
>
> "It is not what you don’t know that kills you, it is what you know that ain’t so".

Do we have a legitimate use for qom-set right now?  Hmm, let's check
libvirt... aha:

* qemuMonitorJSONSetMemoryStatsPeriod() uses it to control
  virtio-balloon's guest-stats-polling-interval property, in accordance
  with docs/virtio-balloon-stats.txt.

* qemuMonitorJSONSetIOThread() uses it to control iothread's properties
  poll-max-ns, poll-grow, poll-shrink.  Their use with -object is
  documented (in qemu-options.hx), their use with qom-set is not.

Oh well.

>>>> http://dreamsongs.com/RiseOfWorseIsBetter.html
>>> 
>>> You know that I positively hate this ;-)
>> 
>> It's been a tough lesson for me, too.
>
> Not sure I can call it a “lesson”. Much like a philosophy to fight against, IMO.

The tough lesson isn't philosophy, it's an observation: "I believe that
worse-is-better [...] has better survival characteristics than
the-right-thing".

>>> Well, I guess we can expand the schema. #ILoveJSON.
>> 
>> Basing the QAPI language on JSON was a poor choice.  Not sure that's
>> fixable at a reasonable cost.
>
> Well, at least now I have a slightly better understanding of the related costs
> and trade-offs. Thanks a lot for explaining.

You're welcome!



  reply	other threads:[~2020-01-15 12:16 UTC|newest]

Thread overview: 183+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-20 16:13 Making QEMU easier for management tools and applications Stefan Hajnoczi
2019-12-20 21:07 ` Richard W.M. Jones
2020-01-02 11:26   ` Stefan Hajnoczi
2019-12-21  9:02 ` Markus Armbruster
2019-12-23 15:04   ` Michal Prívozník
2020-01-07  9:36     ` Kevin Wolf
2020-01-07 10:55       ` Michal Privoznik
2020-01-07 12:57         ` Kevin Wolf
2020-01-07 17:53           ` Christophe de Dinechin
2019-12-24 13:41   ` Daniel P. Berrangé
2020-01-22 22:28     ` John Snow
2020-01-23  7:19       ` Markus Armbruster
2020-01-23 17:58         ` John Snow
2020-01-23 19:01           ` Daniel P. Berrangé
2020-01-23 21:07             ` John Snow
2020-01-24  7:59               ` Markus Armbruster
2020-01-24 10:27                 ` Daniel P. Berrangé
2020-01-24 14:38                   ` Kevin Wolf
2020-01-24 18:23                     ` John Snow
2020-01-24 18:30                       ` Dr. David Alan Gilbert
2020-01-24 18:48                         ` John Snow
2020-01-24 18:52                           ` Dr. David Alan Gilbert
2020-01-24 18:58                             ` John Snow
2020-01-25 10:18                     ` Markus Armbruster
2020-01-27 10:18                       ` Daniel P. Berrangé
2020-01-27 12:48                         ` Markus Armbruster
2020-01-27 11:56                       ` Kevin Wolf
2020-01-27 12:04                         ` Peter Maydell
2020-01-27 20:11                         ` John Snow
2020-01-27 22:38                           ` Paolo Bonzini
2020-01-28  0:37                             ` John Snow
2020-01-28 10:16                             ` Daniel P. Berrangé
2020-01-28 10:39                               ` Kevin Wolf
2020-01-28 15:36                                 ` Markus Armbruster
2020-01-31 12:25                                   ` Eric Blake
2020-01-28 10:28                           ` Kevin Wolf
2020-01-28 12:36                             ` Markus Armbruster
2020-01-28 12:54                               ` Kevin Wolf
2020-01-28 13:45                                 ` Gerd Hoffmann
2020-01-31  6:50                                 ` Markus Armbruster
2020-01-31  7:48                                   ` Paolo Bonzini
2020-01-31  8:09                                     ` Markus Armbruster
2020-02-03 20:07                                   ` Andrea Bolognani
2020-02-04  9:58                                     ` Markus Armbruster
2020-01-31 12:27                                 ` Eric Blake
2020-02-02  9:21                                   ` Kevin Wolf
2020-02-02 10:44                                     ` Paolo Bonzini
2020-02-03  6:20                                       ` Markus Armbruster
2020-02-03  8:48                                         ` Markus Armbruster
2020-01-27 20:12                         ` Dr. David Alan Gilbert
2020-01-24 20:34                 ` John Snow
2020-01-27  8:35                   ` Gerd Hoffmann
2020-01-27 12:13                     ` Kevin Wolf
2020-01-27 16:18                       ` Gerd Hoffmann
2020-01-24  9:50               ` Daniel P. Berrangé
2020-01-25 11:52                 ` Paolo Bonzini
2020-01-27 10:05                   ` Daniel P. Berrangé
2020-01-27  8:25                 ` Tooling to help humans use JSON (was: Making QEMU easier for management tools and applications) Markus Armbruster
2020-01-27  9:06                 ` Making QEMU easier for management tools and applications Markus Armbruster
2020-01-27 10:00                   ` Daniel P. Berrangé
2020-01-27 14:35                 ` Kevin Wolf
2020-01-27 20:29                   ` Dr. David Alan Gilbert
2020-01-28 10:59                     ` Kevin Wolf
2020-02-05 13:09                       ` Kevin Wolf
2020-02-05 19:09                         ` qmp-shell for GSoC/Outreachy? (Was: Re: Making QEMU easier for management tools and applications) John Snow
2020-02-05 19:49                           ` Dr. David Alan Gilbert
2020-02-06  9:40                             ` qmp-shell for GSoC/Outreachy? Markus Armbruster
2020-02-06 10:09                               ` Daniel P. Berrangé
2020-02-06 12:11                                 ` Markus Armbruster
2020-02-06 12:15                                   ` Daniel P. Berrangé
2020-02-06 18:02                                     ` Dr. David Alan Gilbert
2020-02-07 21:03                                   ` John Snow
2020-02-08  7:17                                     ` Markus Armbruster
2020-02-06 14:21                               ` Kevin Wolf
2020-02-06 18:26                                 ` Dr. David Alan Gilbert
2020-02-07 10:49                                   ` Kevin Wolf
2020-02-07 21:23                                 ` John Snow
2020-02-08  7:25                                   ` Markus Armbruster
2020-02-10 11:59                                     ` Kevin Wolf
2020-02-10 12:26                                   ` Kevin Wolf
2020-02-06 18:18                               ` Dr. David Alan Gilbert
2020-02-07  7:47                                 ` Markus Armbruster
2020-02-07 21:31                                 ` Eric Blake
2020-02-08  7:34                                   ` Markus Armbruster
2020-02-07 21:56                                 ` John Snow
2020-02-07 20:56                               ` John Snow
2020-01-27 20:59                   ` Making QEMU easier for management tools and applications John Snow
2020-01-28 10:16                     ` Markus Armbruster
2020-01-28 19:21                       ` John Snow
2020-01-24  6:38           ` Markus Armbruster
2020-01-25 22:34           ` Christophe de Dinechin
2020-01-25 11:55     ` Paolo Bonzini
2020-01-02 14:47   ` Stefan Hajnoczi
2020-01-16 11:03     ` Kashyap Chamarthy
2020-01-20  9:55       ` Stefan Hajnoczi
2020-01-20 13:57         ` Kashyap Chamarthy
2020-01-25 11:41         ` Paolo Bonzini
2020-01-27 19:41           ` John Snow
2020-01-02 15:05   ` Dr. David Alan Gilbert
2020-01-13 13:44     ` Markus Armbruster
2019-12-24 13:00 ` Daniel P. Berrangé
2020-01-02 14:22   ` Stefan Hajnoczi
2020-01-22 22:42   ` John Snow
2020-01-23  7:21     ` Markus Armbruster
2020-01-23 10:27     ` Daniel P. Berrangé
2020-01-23 18:13       ` John Snow
2020-01-23 19:12         ` Daniel P. Berrangé
2020-01-02 15:10 ` Dr. David Alan Gilbert
2020-01-07 17:11 ` Christophe de Dinechin
2020-01-08 10:43   ` Kevin Wolf
2020-01-08 11:40     ` Christophe de Dinechin
2020-01-08 13:38       ` Kevin Wolf
2020-01-14 13:04         ` Markus Armbruster
2020-01-14 17:31           ` Christophe de Dinechin
2020-01-15  9:20             ` Markus Armbruster
2020-01-15  9:34               ` Christophe de Dinechin
2020-01-15 12:15                 ` Markus Armbruster [this message]
2020-01-15 12:19                   ` Daniel P. Berrangé
2020-01-15 14:02                     ` Markus Armbruster
2020-01-30 21:09                       ` Improving QOM documentation [Was: Re: Making QEMU easier for management tools and applications] Kashyap Chamarthy
2020-01-31  6:11                         ` Markus Armbruster
2020-01-31  7:46                           ` Paolo Bonzini
2020-01-31 15:37                             ` Christophe de Dinechin
2020-01-31 16:28                               ` Paolo Bonzini
2020-01-31  9:50                           ` Kashyap Chamarthy
2020-01-31 10:35                           ` Peter Maydell
2020-01-31 11:02                             ` Paolo Bonzini
2020-01-31 15:22                               ` Kashyap Chamarthy
2020-01-31 17:23                                 ` Markus Armbruster
2020-02-03  8:56                                   ` Paolo Bonzini
2020-02-03  9:54                                     ` Markus Armbruster
2020-02-03 15:21                                       ` Paolo Bonzini
2020-02-04  8:42                                         ` Markus Armbruster
2020-01-31 16:39                               ` Markus Armbruster
2020-01-20 10:08                   ` Making QEMU easier for management tools and applications Stefan Hajnoczi
2020-01-21  5:42                     ` Markus Armbruster
2020-01-21 11:32                       ` Stefan Hajnoczi
2020-01-21 12:03                         ` Marc-André Lureau
2020-01-21 13:36                           ` Integrating QOM into QAPI (was: Making QEMU easier for management tools and applications) Markus Armbruster
2020-01-21 14:36                             ` Daniel P. Berrangé
2020-01-21 15:01                               ` Integrating QOM into QAPI Markus Armbruster
2020-01-21 15:11                                 ` Marc-André Lureau
2020-01-21 16:21                                   ` Peter Maydell
2020-01-22  5:16                                     ` Getting whole-tree patches reviewed and merged (was: Integrating QOM into QAPI) Markus Armbruster
2020-02-07 21:53                                       ` Getting whole-tree patches reviewed and merged Eric Blake
2020-02-10 11:26                                         ` Paolo Bonzini
2020-02-10 16:04                                           ` Markus Armbruster
2020-02-10 16:12                                             ` Peter Maydell
2020-01-22 10:50                                   ` Integrating QOM into QAPI Alex Bennée
2020-01-22 12:24                                     ` Markus Armbruster
2020-01-22 12:42                                       ` Marc-André Lureau
2020-01-22 13:28                                         ` Peter Maydell
2020-01-22 13:32                                           ` Marc-André Lureau
2020-01-23  7:37                                         ` Markus Armbruster
2020-01-24 18:32                                         ` Paolo Bonzini
2020-01-25  4:44                                           ` Marc-André Lureau
2020-01-25  9:28                                             ` Paolo Bonzini
2020-01-25 21:25                                               ` Peter Maydell
2020-01-26  8:09                                   ` Christophe de Dinechin
2020-01-26  9:11                                     ` Marc-André Lureau
2020-01-26 16:47                                       ` Paolo Bonzini
2020-01-27 19:05                                         ` Christophe de Dinechin
2020-01-27 19:05                                       ` Christophe de Dinechin
2020-01-26 15:04                                     ` Peter Maydell
2020-01-27 19:05                                       ` Christophe de Dinechin
2020-01-28  8:00                                         ` Markus Armbruster
2020-01-28 10:03                                         ` Daniel P. Berrangé
2020-01-29 12:42                                           ` Christophe de Dinechin
2020-01-15  9:35               ` Making QEMU easier for management tools and applications Marc-André Lureau
2020-01-15 12:25                 ` Markus Armbruster
2020-01-25 17:18               ` Paolo Bonzini
2020-01-27  9:30                 ` Markus Armbruster
2020-01-13 16:30   ` Stefan Hajnoczi
2020-02-04 15:54 ` Summary of " Markus Armbruster
2020-02-05  6:38   ` Markus Armbruster
2020-02-10 10:56   ` Stefan Hajnoczi
2020-02-10 11:01     ` Peter Maydell
2020-02-10 11:08       ` Daniel P. Berrangé
2020-02-10 11:29         ` Peter Maydell
2020-02-10 11:04     ` Paolo Bonzini
2020-02-10 16:43     ` Markus Armbruster
2020-02-12 13:54       ` Stefan Hajnoczi
2020-02-12 14:03         ` Daniel P. Berrangé

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