From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2A09DC43458 for ; Fri, 10 Jul 2026 08:03:58 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wi6D9-00077f-UG; Fri, 10 Jul 2026 04:03:51 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wi6D8-00076r-Kz for qemu-arm@nongnu.org; Fri, 10 Jul 2026 04:03:50 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wi6D7-00051x-1E for qemu-arm@nongnu.org; Fri, 10 Jul 2026 04:03:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1783670628; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=HnAu3sO/3EXcDRs1eSZBrA68B3yp/C/99tGMAFnBno4=; b=JtMVATQDIkxmsQ1YH/1gqMjinUCtBkfRvMlgMEDEd4IB0W01jdnlDy3a3mO0IRAwQtdcGL 4WTSO/Sjtrlsn25NoMxaFoF3Fnuc20Pt6bEgZozmrYPxKW/6vLS2P6rONVUhaBC6+hzMxh UX/6bbvwGcSBaP4pne6+LWFj51xnV7g= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-470-_4-tgnmAOvqWWuzmjMClsw-1; Fri, 10 Jul 2026 04:03:40 -0400 X-MC-Unique: _4-tgnmAOvqWWuzmjMClsw-1 X-Mimecast-MFC-AGG-ID: _4-tgnmAOvqWWuzmjMClsw_1783670615 Received: from mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.95]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8162E1956055; Fri, 10 Jul 2026 08:03:33 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.44.22.4]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7380A1771; Fri, 10 Jul 2026 08:03:29 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 1859121E6920; Fri, 10 Jul 2026 10:03:27 +0200 (CEST) From: Markus Armbruster To: "Graf (AWS), Alexander" Cc: BALATON Zoltan , "qemu-devel@nongnu.org" , Aditya Gupta , "Alexandre Iooss" , Alexey Kardashevskiy , "Alistair Francis" , Alistair Francis , Antony Pavlov , "Artyom Tarasenko" , Bernhard Beschow , "Bibo Mao" , Brian Cain , Chao Liu , Christian Borntraeger , =?utf-8?Q?Cl=C3=A9ment?= Chigot , =?utf-8?Q?C=C3=A9dric?= Le Goater , Dorjoy Chowdhury , "Edgar E. Iglesias" , Eric Farman , Farhan Ali , Felipe Balbi , Francisco Iglesias , Frederic Konrad , Gaurav Sharma , Gautam Gala , Glenn Miles , Halil Pasic , Hao Wu , Harsh Prateek Bora , "Helge Deller" , Hendrik Brueckner , =?utf-8?Q?Herv=C3=A9?= Poussineau , Huacai Chen , Jan Kiszka , Jared Rossi , Joel Stanley , Laurent Vivier , Manos Pitsidianakis , Mark Cave-Ayland , Matthew Rosato , Max Filippov , Michael Rolnik , "Michael S. Tsirkin" , Nicholas Piggin , Niek Linnenbank , "Palmer Dabbelt" , Paolo Bonzini , "Peter Maydell" , Philippe =?utf-8?Q?Mathieu-?= =?utf-8?Q?Daud=C3=A9?= , "Pierrick Bouvier" , Ran Wang , Richard Henderson , Sai Pavan Boddu , Samuel Tardieu , Sergio Lopez , Song Gao <17746591750@163.com>, Stafford Horne , Subbaraya Sundeep , Thomas Huth , Tyrone Ting , "qemu-arm@nongnu.org" , "qemu-ppc@nongnu.org" , "qemu-riscv@nongnu.org" , "qemu-s390x@nongnu.org" Subject: Re: Call to clean up QOM onboard devices lacking a parent In-Reply-To: (Graf Alexander's message of "Fri, 10 Jul 2026 07:38:07 +0000") References: <87se5scipx.fsf@pond.sub.org> <17c7f91b-8935-8ebf-a982-f91df755af81@eik.bme.hu> <87h5m7xsxi.fsf@pond.sub.org> Date: Fri, 10 Jul 2026 10:03:27 +0200 Message-ID: <87jyr3w9tc.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 X-Mimecast-MFC-PROC-ID: MLx8IDm8tqPZFdHVsWf5gKe9sPO5vT2rymEy1zv6bDI_1783670615 X-Mimecast-Originator: redhat.com Content-Type: text/plain 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: 8 X-Spam_score: 0.8 X-Spam_bar: / X-Spam_report: (0.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-arm@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-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org Sender: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org "Graf (AWS), Alexander" writes: > On 10.07.26 08:25, Markus Armbruster wrote: >> "Graf (AWS), Alexander" writes: >> >>> Hi Markus, >> [...] >> >>> I'm also curious on whether there is anything that makes sysbus device >>> spawns both easy (as they are today) and at the same time fully QOM >>> parent compliant. >>> >>> I had a quick look at the vmapple machine and most of the offenders are >>> sysbus devices I spawn via qdev_new(). Would you want all of these to >>> get their parent declared via object_property_add_child()? If that's the >>> case, why don't we introduce a new qdev_new_child() which does that >>> automatically? >> >> We do have such convenience functions at the QOM layer: object_new() and >> object_property_add_child() etc., are basic building blocks, and >> object_new_with_props() etc. combine them in useful ways. >> >> We don't have such convenience functions at the qdev layer. Can't see >> why we couldn't add them. >> >> Number of orphaned device types I see by bus_type: >> >> 69 busless >> 15 ISA >> 33 PCI >> 11 SSI >> 209 System >> 2 apple-desktop-bus >> 23 i2c-bus >> 2 sd-bus >> 1 spapr-vio-bus >> 2 usb-bus >> >> Again, not a problem with the device types, but the code that creates >> and realizes them. >> >> Bus types commonly provide a layer above qdev for that. Perhaps these >> layers could also use convenience functions to more easily deal with >> setting the QOM parent. > > > I think the crux of the problem is that we ended up inheriting creation > APIs that didn't necessarily express a clear parent/child relationship, > so we end up orphaning these type of objects in the QOM tree. So the > *real* answer IMHO is to rebuild all these APIs into something that > enforces that. This way we also won't have new offenders sneaking in. The appended trivial patch will keep new offenders out. Drawback: it breaks almost everything due to existing offenders ;) Kidding aside, the code it deletes was a mistake. We likely added it for quicker initial conversions. The technical debt's compound interest has been piling up ever since. > I won't be able to spend the weeks it requires to do this by hand, but I > can have a stab at it with AI - which is likely much more reliable at > getting this done correctly than me too :). I can post it as RFC and > then we decide whether we want to take it or leave it. The part that requires actual thought is the hardware modeling: what's part of what. diff --git a/hw/core/qdev.c b/hw/core/qdev.c index e2aab3d1fc..058f89fa55 100644 --- a/hw/core/qdev.c +++ b/hw/core/qdev.c @@ -493,15 +493,6 @@ static void device_set_realized(Object *obj, bool value, Error **errp) goto fail; } - if (!obj->parent) { - gchar *name = g_strdup_printf("device[%d]", unattached_count++); - - object_property_add_child(machine_get_container("unattached"), - name, obj); - unattached_parent = true; - g_free(name); - } - hotplug_ctrl = qdev_get_hotplug_handler(dev); if (hotplug_ctrl) { hotplug_handler_pre_plug(hotplug_ctrl, dev, &local_err);