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 lists.gnu.org (lists.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 9F4B7E9A04C for ; Thu, 19 Feb 2026 08:50:01 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vszip-0002LC-SZ; Thu, 19 Feb 2026 03:49:19 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vszio-0002L2-Gp for qemu-devel@nongnu.org; Thu, 19 Feb 2026 03:49:18 -0500 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 1vszim-00060f-AP for qemu-devel@nongnu.org; Thu, 19 Feb 2026 03:49:18 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1771490953; 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=FQxPdGv3vL6y6uPlT83ZP5eypFxu8NkCpR+l20z6wKs=; b=XQqLIEtIVkJyNcw0q2JYAo1uiRfPT6H6WJ0/Wt15FBUKMeb1OzczHKJ7hqhNpf1KOAsVp0 vkkx3HdC00afRhnmfSrRP0ERooK9I4cOMozaSe6aiqmlATdbzbQDNZqQ+xPO4h7Qe4x2fw mEAr0WySqiE+92O4qVEfp7M45WjtU38= Received: from mx-prod-mc-03.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-88-O7EbssunOSCsSKqZSPMC4Q-1; Thu, 19 Feb 2026 03:49:10 -0500 X-MC-Unique: O7EbssunOSCsSKqZSPMC4Q-1 X-Mimecast-MFC-AGG-ID: O7EbssunOSCsSKqZSPMC4Q_1771490949 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 177BB1956063; Thu, 19 Feb 2026 08:49:09 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.14]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6E1FB19560A7; Thu, 19 Feb 2026 08:49:08 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id E9E2821E692D; Thu, 19 Feb 2026 09:49:05 +0100 (CET) From: Markus Armbruster To: Thomas Huth Cc: qemu-devel@nongnu.org, Paolo Bonzini , Daniel P. =?utf-8?Q?Berrang=C3=A9?= , Eduardo Habkost Subject: Re: [RFC PATCH] hw/core: Avoid attaching qdevs to /machine/unattached if they have a bus In-Reply-To: <20260217164049.543975-1-thuth@redhat.com> (Thomas Huth's message of "Tue, 17 Feb 2026 17:40:49 +0100") References: <20260217164049.543975-1-thuth@redhat.com> Date: Thu, 19 Feb 2026 09:49:05 +0100 Message-ID: <874ind5da6.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 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: -13 X-Spam_score: -1.4 X-Spam_bar: - X-Spam_report: (-1.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.043, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, GB_FAKE_RF=0.754, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development 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 Thomas Huth writes: > From: Thomas Huth > > We still have a lot of devices that end up in /machine/unattached in > case the caller forgot to use object_property_add_child() to add it > to a proper location in the QOM tree. This is QOM papering over sloppy modeling. Predictably, it has enabled us to remain sloppy slobs. I think the decision to paper over sloppiness to get QOM off the ground quickly was defensible back then. It's a lot less defensible now that QOM has been off the ground for more than a decade. I believe people are by and large unaware of the need to add children. This risks further accumulation of technical debt. To really put a stop to it, we'd have to mark the existing misuses, then warn or crash on umarked misuse. None of the above is an objection to your patch. > But at least for the devices > that get realized via qdev_realize() and that have a bus specified, > we can do better: Add the device automatically as a child to the bus > device instead! This way the QOM tree looks way more logical, with > way less devices hanging around in the /machine/unattached space. > > While we're at it, use the type name as node name (instead of using > "device" like we did in the "unattached" space). But since these > entries might not be stable (they use a counting number in the square > brackets), the code also uses a "x-" prefix here to indicate that > this still might change in the course of time (once a board decides > to manually attach the device with a proper name instead). > > Signed-off-by: Thomas Huth > --- > hw/core/qdev.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/hw/core/qdev.c b/hw/core/qdev.c > index 42641c5224e..5b773d0108a 100644 > --- a/hw/core/qdev.c > +++ b/hw/core/qdev.c > @@ -266,9 +266,19 @@ bool qdev_realize(DeviceState *dev, BusState *bus, Error **errp) > assert(!dev->realized && !dev->parent_bus); > > if (bus) { > + Object *obj = OBJECT(dev); > + > if (!qdev_set_parent_bus(dev, bus, errp)) { > return false; > } > + > + if (!obj->parent) { > + static int count; > + g_autofree char *name = g_strdup_printf("x-%s[%d]", > + object_get_typename(obj), > + count++); > + object_property_add_child(OBJECT(bus), name, obj); > + } > } else { > assert(!DEVICE_GET_CLASS(dev)->bus_type); > } As a quick test, I ran $ qemu-system-x86_64 -S -display none -nodefaults -monitor stdio QEMU 10.2.50 monitor - type 'help' for more information (qemu) info qom-tree before and after. Diff of output appended. Observations: * 24 of 25 device[*] move out of /machine/unattached/. Remaining: - /device[0] (qemu64-x86_64-cpu) because it doesn't plug into a bus. - /sysbus (System) - A bunch of memory regions and irqs. Some of them smell like sloppy modeling: ide[*]. * The moved device[i] get renamed to x-type-name[j]. The number changes because the type-name[*] use their own global counter. Changing the number is fine, but I wonder whether a counter local to the parent would be better. BusClass does that for "automatically allocated bus ids". --- info-qom-tree@master 2026-02-19 08:43:03.732267517 +0100 +++ - 2026-02-19 08:43:43.562332914 +0100 @@ -37,6 +37,156 @@ /pci-conf-data[0] (memory-region) /pci-conf-idx[0] (memory-region) /pci.0 (PCI) + /x-PIIX3[2] (PIIX3) + /bus master container[0] (memory-region) + /bus master[0] (memory-region) + /dma[0] (i8257) + /dma-chan[0] (memory-region) + /dma-cont[0] (memory-region) + /dma-page[0] (memory-region) + /dma-page[1] (memory-region) + /dma[1] (i8257) + /dma-chan[0] (memory-region) + /dma-cont[0] (memory-region) + /dma-page[0] (memory-region) + /dma-page[1] (memory-region) + /ide (piix3-ide) + /bmdma[0] (memory-region) + /bmdma[1] (memory-region) + /bus master container[0] (memory-region) + /bus master[0] (memory-region) + /ide.0 (IDE) + /ide.1 (IDE) + /piix-bmdma-container[0] (memory-region) + /piix-bmdma[0] (memory-region) + /piix-bmdma[1] (memory-region) + /isa.0 (ISA) + /x-i8042[9] (i8042) + /i8042-cmd[0] (memory-region) + /i8042-data[0] (memory-region) + /ps2-kbd-input-irq[0] (irq) + /ps2-mouse-input-irq[0] (irq) + /ps2kbd (ps2-kbd) + /ps2mouse (ps2-mouse) + /x-isa-fdc[8] (isa-fdc) + /fdc[0] (memory-region) + /fdc[1] (memory-region) + /floppy-bus.0 (floppy-bus) + /x-isa-i8259[3] (isa-i8259) + /elcr[0] (memory-region) + /pic[0] (memory-region) + /unnamed-gpio-in[0] (irq) + /unnamed-gpio-in[1] (irq) + /unnamed-gpio-in[2] (irq) + /unnamed-gpio-in[3] (irq) + /unnamed-gpio-in[4] (irq) + /unnamed-gpio-in[5] (irq) + /unnamed-gpio-in[6] (irq) + /unnamed-gpio-in[7] (irq) + /x-isa-i8259[4] (isa-i8259) + /elcr[0] (memory-region) + /pic[0] (memory-region) + /unnamed-gpio-in[0] (irq) + /unnamed-gpio-in[1] (irq) + /unnamed-gpio-in[2] (irq) + /unnamed-gpio-in[3] (irq) + /unnamed-gpio-in[4] (irq) + /unnamed-gpio-in[5] (irq) + /unnamed-gpio-in[6] (irq) + /unnamed-gpio-in[7] (irq) + /x-isa-pcspk[7] (isa-pcspk) + /pcspk[0] (memory-region) + /x-isa-pit[6] (isa-pit) + /pit[0] (memory-region) + /unnamed-gpio-in[0] (irq) + /x-port92[12] (port92) + /port92[0] (memory-region) + /x-vmmouse[11] (vmmouse) + /x-vmport[10] (vmport) + /vmport[0] (memory-region) + /piix-reset-control[0] (memory-region) + /pm (PIIX4_PM) + /acpi-cnt[0] (memory-region) + /acpi-cpu-hotplug[0] (memory-region) + /acpi-evt[0] (memory-region) + /acpi-gpe0[0] (memory-region) + /acpi-pci-hotplug[0] (memory-region) + /acpi-tmr[0] (memory-region) + /apm-io[0] (memory-region) + /bus master container[0] (memory-region) + /bus master[0] (memory-region) + /i2c (i2c-bus) + /x-smbus-eeprom[13] (smbus-eeprom) + /x-smbus-eeprom[14] (smbus-eeprom) + /x-smbus-eeprom[15] (smbus-eeprom) + /x-smbus-eeprom[16] (smbus-eeprom) + /x-smbus-eeprom[17] (smbus-eeprom) + /x-smbus-eeprom[18] (smbus-eeprom) + /x-smbus-eeprom[19] (smbus-eeprom) + /x-smbus-eeprom[20] (smbus-eeprom) + /piix4-pm[0] (memory-region) + /pm-smbus[0] (memory-region) + /rtc (mc146818rtc) + /rtc-index[0] (memory-region) + /rtc[0] (memory-region) + /x-i440FX[1] (i440FX) + /bus master container[0] (memory-region) + /bus master[0] (memory-region) + /pam-pci[0] (memory-region) + /pam-pci[10] (memory-region) + /pam-pci[11] (memory-region) + /pam-pci[12] (memory-region) + /pam-pci[13] (memory-region) + /pam-pci[14] (memory-region) + /pam-pci[15] (memory-region) + /pam-pci[16] (memory-region) + /pam-pci[17] (memory-region) + /pam-pci[18] (memory-region) + /pam-pci[19] (memory-region) + /pam-pci[1] (memory-region) + /pam-pci[20] (memory-region) + /pam-pci[21] (memory-region) + /pam-pci[22] (memory-region) + /pam-pci[23] (memory-region) + /pam-pci[24] (memory-region) + /pam-pci[25] (memory-region) + /pam-pci[2] (memory-region) + /pam-pci[3] (memory-region) + /pam-pci[4] (memory-region) + /pam-pci[5] (memory-region) + /pam-pci[6] (memory-region) + /pam-pci[7] (memory-region) + /pam-pci[8] (memory-region) + /pam-pci[9] (memory-region) + /pam-ram[0] (memory-region) + /pam-ram[10] (memory-region) + /pam-ram[11] (memory-region) + /pam-ram[12] (memory-region) + /pam-ram[1] (memory-region) + /pam-ram[2] (memory-region) + /pam-ram[3] (memory-region) + /pam-ram[4] (memory-region) + /pam-ram[5] (memory-region) + /pam-ram[6] (memory-region) + /pam-ram[7] (memory-region) + /pam-ram[8] (memory-region) + /pam-ram[9] (memory-region) + /pam-rom[0] (memory-region) + /pam-rom[10] (memory-region) + /pam-rom[11] (memory-region) + /pam-rom[12] (memory-region) + /pam-rom[1] (memory-region) + /pam-rom[2] (memory-region) + /pam-rom[3] (memory-region) + /pam-rom[4] (memory-region) + /pam-rom[5] (memory-region) + /pam-rom[6] (memory-region) + /pam-rom[7] (memory-region) + /pam-rom[8] (memory-region) + /pam-rom[9] (memory-region) + /smram-low[0] (memory-region) + /smram-region[0] (memory-region) + /smram[0] (memory-region) /peripheral (container) /peripheral-anon (container) /unattached (container) @@ -46,162 +196,6 @@ /memory[0] (memory-region) /memory[1] (memory-region) /smram[0] (memory-region) - /device[10] (i8042) - /i8042-cmd[0] (memory-region) - /i8042-data[0] (memory-region) - /ps2-kbd-input-irq[0] (irq) - /ps2-mouse-input-irq[0] (irq) - /ps2kbd (ps2-kbd) - /ps2mouse (ps2-mouse) - /device[11] (vmport) - /vmport[0] (memory-region) - /device[12] (vmmouse) - /device[13] (port92) - /port92[0] (memory-region) - /device[14] (smbus-eeprom) - /device[15] (smbus-eeprom) - /device[16] (smbus-eeprom) - /device[17] (smbus-eeprom) - /device[18] (smbus-eeprom) - /device[19] (smbus-eeprom) - /device[1] (kvmvapic) - /kvmvapic[0] (memory-region) - /device[20] (smbus-eeprom) - /device[21] (smbus-eeprom) - /device[2] (i440FX) - /bus master container[0] (memory-region) - /bus master[0] (memory-region) - /pam-pci[0] (memory-region) - /pam-pci[10] (memory-region) - /pam-pci[11] (memory-region) - /pam-pci[12] (memory-region) - /pam-pci[13] (memory-region) - /pam-pci[14] (memory-region) - /pam-pci[15] (memory-region) - /pam-pci[16] (memory-region) - /pam-pci[17] (memory-region) - /pam-pci[18] (memory-region) - /pam-pci[19] (memory-region) - /pam-pci[1] (memory-region) - /pam-pci[20] (memory-region) - /pam-pci[21] (memory-region) - /pam-pci[22] (memory-region) - /pam-pci[23] (memory-region) - /pam-pci[24] (memory-region) - /pam-pci[25] (memory-region) - /pam-pci[2] (memory-region) - /pam-pci[3] (memory-region) - /pam-pci[4] (memory-region) - /pam-pci[5] (memory-region) - /pam-pci[6] (memory-region) - /pam-pci[7] (memory-region) - /pam-pci[8] (memory-region) - /pam-pci[9] (memory-region) - /pam-ram[0] (memory-region) - /pam-ram[10] (memory-region) - /pam-ram[11] (memory-region) - /pam-ram[12] (memory-region) - /pam-ram[1] (memory-region) - /pam-ram[2] (memory-region) - /pam-ram[3] (memory-region) - /pam-ram[4] (memory-region) - /pam-ram[5] (memory-region) - /pam-ram[6] (memory-region) - /pam-ram[7] (memory-region) - /pam-ram[8] (memory-region) - /pam-ram[9] (memory-region) - /pam-rom[0] (memory-region) - /pam-rom[10] (memory-region) - /pam-rom[11] (memory-region) - /pam-rom[12] (memory-region) - /pam-rom[1] (memory-region) - /pam-rom[2] (memory-region) - /pam-rom[3] (memory-region) - /pam-rom[4] (memory-region) - /pam-rom[5] (memory-region) - /pam-rom[6] (memory-region) - /pam-rom[7] (memory-region) - /pam-rom[8] (memory-region) - /pam-rom[9] (memory-region) - /smram-low[0] (memory-region) - /smram-region[0] (memory-region) - /smram[0] (memory-region) - /device[3] (PIIX3) - /bus master container[0] (memory-region) - /bus master[0] (memory-region) - /dma[0] (i8257) - /dma-chan[0] (memory-region) - /dma-cont[0] (memory-region) - /dma-page[0] (memory-region) - /dma-page[1] (memory-region) - /dma[1] (i8257) - /dma-chan[0] (memory-region) - /dma-cont[0] (memory-region) - /dma-page[0] (memory-region) - /dma-page[1] (memory-region) - /ide (piix3-ide) - /bmdma[0] (memory-region) - /bmdma[1] (memory-region) - /bus master container[0] (memory-region) - /bus master[0] (memory-region) - /ide.0 (IDE) - /ide.1 (IDE) - /piix-bmdma-container[0] (memory-region) - /piix-bmdma[0] (memory-region) - /piix-bmdma[1] (memory-region) - /isa.0 (ISA) - /piix-reset-control[0] (memory-region) - /pm (PIIX4_PM) - /acpi-cnt[0] (memory-region) - /acpi-cpu-hotplug[0] (memory-region) - /acpi-evt[0] (memory-region) - /acpi-gpe0[0] (memory-region) - /acpi-pci-hotplug[0] (memory-region) - /acpi-tmr[0] (memory-region) - /apm-io[0] (memory-region) - /bus master container[0] (memory-region) - /bus master[0] (memory-region) - /i2c (i2c-bus) - /piix4-pm[0] (memory-region) - /pm-smbus[0] (memory-region) - /rtc (mc146818rtc) - /rtc-index[0] (memory-region) - /rtc[0] (memory-region) - /device[4] (isa-i8259) - /elcr[0] (memory-region) - /pic[0] (memory-region) - /unnamed-gpio-in[0] (irq) - /unnamed-gpio-in[1] (irq) - /unnamed-gpio-in[2] (irq) - /unnamed-gpio-in[3] (irq) - /unnamed-gpio-in[4] (irq) - /unnamed-gpio-in[5] (irq) - /unnamed-gpio-in[6] (irq) - /unnamed-gpio-in[7] (irq) - /device[5] (isa-i8259) - /elcr[0] (memory-region) - /pic[0] (memory-region) - /unnamed-gpio-in[0] (irq) - /unnamed-gpio-in[1] (irq) - /unnamed-gpio-in[2] (irq) - /unnamed-gpio-in[3] (irq) - /unnamed-gpio-in[4] (irq) - /unnamed-gpio-in[5] (irq) - /unnamed-gpio-in[6] (irq) - /unnamed-gpio-in[7] (irq) - /device[6] (hpet) - /hpet[0] (memory-region) - /unnamed-gpio-in[0] (irq) - /unnamed-gpio-in[1] (irq) - /device[7] (isa-pit) - /pit[0] (memory-region) - /unnamed-gpio-in[0] (irq) - /device[8] (isa-pcspk) - /pcspk[0] (memory-region) - /device[9] (isa-fdc) - /fdc[0] (memory-region) - /fdc[1] (memory-region) - /floppy-bus.0 (floppy-bus) /ide[0] (memory-region) /ide[1] (memory-region) /ide[2] (memory-region) @@ -243,5 +237,11 @@ /pci[0] (memory-region) /ram-below-4g[0] (memory-region) /sysbus (System) + /x-hpet[5] (hpet) + /hpet[0] (memory-region) + /unnamed-gpio-in[0] (irq) + /unnamed-gpio-in[1] (irq) + /x-kvmvapic[0] (kvmvapic) + /kvmvapic[0] (memory-region) /system[0] (memory-region)