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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id y206sm4461898wmd.34.2020.10.23.09.08.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 23 Oct 2020 09:08:20 -0700 (PDT) To: Markus Armbruster , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= References: <20201023101222.250147-1-kwolf@redhat.com> <20201023103603.GG445638@redhat.com> <87blgtoybe.fsf@dusky.pond.sub.org> From: Paolo Bonzini Subject: Re: [PATCH 0/6] qemu-storage-daemon: QAPIfy --chardev Message-ID: Date: Fri, 23 Oct 2020 18:08:19 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <87blgtoybe.fsf@dusky.pond.sub.org> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/23 02:46:25 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] 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=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.108, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: Kevin Wolf , marcandre.lureau@redhat.com, qemu-devel@nongnu.org, qemu-block@nongnu.org, Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 23/10/20 15:40, Markus Armbruster wrote: >> >> The benefit of the user creatable object approach is that we dont >> have to add custom CLI args for different types of object, nor write >> code to populate QOM from QAPI. The downside is that we're divorced >> from the QAPI schema, so loose introspection, and have a different >> type of tedious boilerplate code to write. > Loss of QAPI introspection is the killer. > > We have QOM introspection, but it's far too weak to serve as > replacement. Besides, two introspection facilities is one too many. Wouldn't Eduardo+Kevin's work on object-add provide that too? > Nevertheless, we need Kevin's work now to get a decent storage daemon > CLI while that's still easy to do. We'll have to promise stability > soon, and then changes get much harder. I think we haven't answered the question of whether qsd needs a CLI at all. I looked recently at qemu_init and it struck me that, in principle, the only _really_ necessary command line options for QEMU are -sandbox, -name and possibly -trace (only to be able to trace the monitor). For everything else, one could use LISTEN_FDS socket activation mechanism, or if there's no LISTEN_FDS environment variable open a QMP socket on stdin/stdout. For qemu-standard-daemon, that would be _really_ true and not just in principle I understand that having a command-line can be useful to developers as it's less unwieldy than JSON, but why does it have to be stable? Could we default to only 2-3 command-line options in the same fashion, and only accept --blockdev and friends if the user starts the command line with "qemu-storage-daemon --i-am-not-a-script"? Paolo