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Mon, 18 Dec 2023 13:18:35 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.129]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 21CCC40C6EB9; Mon, 18 Dec 2023 13:18:35 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 35A1E21E6920; Mon, 18 Dec 2023 14:18:34 +0100 (CET) From: Markus Armbruster To: Maksim Davydov Cc: qemu-devel@nongnu.org, vsementsov@yandex-team.ru, eduardo@habkost.net, marcel.apfelbaum@gmail.com, philmd@linaro.org, wangyanan55@huawei.com, jsnow@redhat.com, crosa@redhat.com, bleal@redhat.com, eblake@redhat.com, pbonzini@redhat.com, berrange@redhat.com, alxndr@bu.edu, bsd@redhat.com, stefanha@redhat.com, thuth@redhat.com, darren.kenny@oracle.com, Qiuhao.Li@outlook.com, lvivier@redhat.com Subject: Re: [PATCH v6 2/4] qmp: add dump machine type compatible properties In-Reply-To: <63dc1069-d3e9-4fb9-b553-7ffaf7a595f4@yandex-team.ru> (Maksim Davydov's message of "Wed, 13 Dec 2023 17:46:12 +0300") References: <20231108153827.39692-1-davydov-max@yandex-team.ru> <20231108153827.39692-3-davydov-max@yandex-team.ru> <87sf4mxnem.fsf@pond.sub.org> <63dc1069-d3e9-4fb9-b553-7ffaf7a595f4@yandex-team.ru> Date: Mon, 18 Dec 2023 14:18:34 +0100 Message-ID: <87o7ensl79.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.083, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Maksim Davydov writes: > Thanks for reviewing > Sorry for replying late > > On 12/1/23 12:49, Markus Armbruster wrote: >> I apologize for the lateness of my review. >> >> Maksim Davydov writes: >> >>> To control that creating new machine type doesn't affect the previous >>> types (their compat_props) and to check complex compat_props inheritance >>> we need qmp command to print machine type compatible properties. >>> >>> This patch adds the ability to get list of all the compat_props of the >>> corresponding supported machines for their comparison via new optional >>> argument of "query-machines" command. >> >> Sounds like this is to let developers prevent unwanted change. Such >> testing interfaces need not and should not be stable interfaces. >> Thoughts? > > I'm not sure that rightly understand your idea about unstable: do you mean > that we can allow this interface to be not robust (e.g. compat-props in > MachineInfo can be not presented) or that this is new thusit can be > unstable? It's about external interface stability: incompatible change requires deprecation and a grace period. See docs/about/deprecated.rst first section. QMP is a stable external interface, except for parts marked unstable. In my review, I wondered whether the QMP interface you add needs to be stable in that sense. Does it? If no, I'll gladly show you how to mark it unstable. >>> Signed-off-by: Maksim Davydov >>> Reviewed-by: Vladimir Sementsov-Ogievskiy [...] >>> diff --git a/qapi/machine.json b/qapi/machine.json >>> index b6d634b30d..8ca0c134a2 100644 >>> --- a/qapi/machine.json >>> +++ b/qapi/machine.json [...] >>> ## >>> # @query-machines: >>> # >>> # Return a list of supported machines >>> # >>> +# @compat-props: if true return will contain information about machine type >>> +# compatible properties (since 8.2) >> >> "compatibility properties" >> >> Suppressing parts of the output makes sense only if it's fairly big. >> How much additional compat-props output do you observe? > > now, there are 61 machines types, so this qmp command generates a 450KB JSON Uff. Recommend to explain this briefly in the commit message. Something like "Since information on compatibility properties can increase the command output by a factor of 40, add an argument to enable it, default off." Does make me wonder whether we want a separate command, though. [...]