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References: <87tv0vzrwj.fsf@dusky.pond.sub.org> <6fc8633a-6d91-b83a-e6cd-5f714ccaf9ea@redhat.com> Date: Tue, 05 May 2020 18:03:25 +0200 In-Reply-To: <6fc8633a-6d91-b83a-e6cd-5f714ccaf9ea@redhat.com> (Paolo Bonzini's message of "Mon, 4 May 2020 16:58:54 +0200") Message-ID: <875zda8j3m.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=207.211.31.120; envelope-from=armbru@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/05 00:37:38 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: "Daniel P. Berrange" , Markus Armbruster , Eduardo Habkost , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Paolo Bonzini writes: > On 04/05/20 16:38, Markus Armbruster wrote: >> makes no progreess because OBJECT(dev)->parent is still null, and >> therefore object_unparent() does nothing. >>=20 >> Possible culprit: qdev_try_create() calls qdev_set_parent_bus(), which >> adds the device to the bus, but leaves ->parent null. If this isn't >> wrong outright, it's at least a dangerous state. >>=20 >> Work-around: call qdev_set_id(dev, NULL) right after qdev_create(). >> This sets ->parent. > > That's a good one, and especially a safe one, since it matches > qdev_device_add. It has the disadvantage of having to touch all > qdev_create() calls. Also, it moves onboard devices from /machine/unattached/ to /machine/peripheral-anon/. I really regard it as a work-around, not a proper solution. > Even better however would be to move the bus argument (and thus > qdev_set_parent_bus) to qdev_init, and likewise in qdev_device_add move > qdev_set_id after qemu_opt_foreach. I looked at the property setters > and couldn't find anything suspicious (somewhat to my surprise), but I > haven't honestly tried. Thus, we satisfy bus_unparent()'s precondition "bus children have a QOM parent"[*] by moving "add to parent bus" next to the place where we ensure "has QOM parent" by putting orphans under /machine/unattached/. Makes sense. If we add to the bus first, the precondition ceases to hold until we realize. Ugly, but harmless unless we manage to actually call the function then. I suspect we can't realize first, because the realize method may want to use the parent bus. We could lift putting orphans under /machine/unattached from device_set_realized() into those callers that don't already assign a QOM parent. Possibly hundreds of places, hmm. We could factor it out into a helper, and call it right before we add to the parent bus. Orphans with a parent bus would get adopted ealier, orphans without one would still get adopted at realize time. I'll play with it. [*] Confusing terminology; two separate parent-child relationships