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Thu, 14 May 2020 05:37:34 -0700 (PDT) Subject: Re: proposal: deprecate -readconfig/-writeconfig To: =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= References: <7599153e-89a2-9a86-16ad-4a3c6a107b18@redhat.com> <20200514085622.GB1280939@redhat.com> From: Paolo Bonzini Message-ID: <1287b3b8-9fd0-04d5-1dd2-66b695dace5d@redhat.com> Date: Thu, 14 May 2020 14:37:34 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200514085622.GB1280939@redhat.com> Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=207.211.31.120; envelope-from=pbonzini@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/13 22:25:46 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, 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_H2=-0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , John Snow , qemu-devel , Markus Armbruster Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 14/05/20 10:56, Daniel P. Berrangé wrote: > On Thu, May 14, 2020 at 10:09:21AM +0200, Paolo Bonzini wrote: >> IMHO configuration files are in general a failed experiment. In >> practice, they do not add much value over just a shell script because >> they don't allow configuring all QEMU options, they are very much fixed >> (by their nature). I think it's more or less agreed that they are not >> solving any problem for higher-level management stacks as well; those >> would prefer to configure the VM via QMP or another API. >> >> So, any objections to deprecating -readconfig and -writeconfig? > > Libvirt would like to have a config file for QEMU, but it would have > to be one that actually covers all the config options QEMU supports, > and ideally using a data format in common with that used for runtime > changes. So for libvirt's needs the current readconfig is entirely > useless. Yes, this is what I was thinking about. > For a less general purpose mgmt app, that targets some specific use > cases I could imagine people might have used readconfig. [...] > If we deprecate them, the only alternative users have right now is > to go back to passing CLI args. [...] We'd be deciding to kill the > feature with no direct replacement, even though it is potentially > useful in some limited scenarios. > > If we have a general strategy to eliminate QemuOpts and move entirely > to QAPI based config, then I can see -readcofig/-writeconfig may be > creating a burden of back compatibility on maintainers. I don't see QemuOpts going away anytime soon, but I do see more QMP/QAPI and less command line in the future as far as management tools are concerned. QemuOpts and HMP will remain for direct usage, for the foreseeable future. So I guess we can keep -readconfig but deprecate, or even remove, -writeconfig. Paolo