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 E3808CD98C5 for ; Mon, 15 Jun 2026 08:35:36 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wZ2mt-0004En-1U; Mon, 15 Jun 2026 04:35:19 -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 1wZ2mq-0004Dm-TS for qemu-devel@nongnu.org; Mon, 15 Jun 2026 04:35:16 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wZ2mo-0008VD-NL for qemu-devel@nongnu.org; Mon, 15 Jun 2026 04:35:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1781512513; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=iwTJDQ9ivMhJViccX27NLDlwqfHfU1ixgeZ+ookWGt0=; b=OCmTZGTSII5QaHqh6jKm43XGTkayrPk5atKxrXJ375vQumQ+d699MXa0Uy4l6gogSA7Z/l rSJzasNaLcnUIew69PMpzJ70uf5Si58mBvS85AMCWw/ZCuYUThWo+i2hxemdFE9QZBULrz 7MLxZk3WvhkmUTKpcvj3SIr1UcJ3LB8= Received: from mx-prod-mc-01.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-93-XJRfNw-MP1SaAdxaDnOGvw-1; Mon, 15 Jun 2026 04:35:10 -0400 X-MC-Unique: XJRfNw-MP1SaAdxaDnOGvw-1 X-Mimecast-MFC-AGG-ID: XJRfNw-MP1SaAdxaDnOGvw_1781512509 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 66CB51956064; Mon, 15 Jun 2026 08:35:08 +0000 (UTC) Received: from redhat.com (unknown [10.44.49.222]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 187A630001A1; Mon, 15 Jun 2026 08:35:02 +0000 (UTC) Date: Mon, 15 Jun 2026 09:34:59 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Maydell Cc: Akihiko Odaki , qemu-devel@nongnu.org, Paolo Bonzini , Manos Pitsidianakis , qemu-rust@nongnu.org, Peter Xu , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Alberto Garcia , Kevin Wolf , Hanna Reitz , qemu-block@nongnu.org Subject: Re: [PATCH 2/2] qom: Manage references to embedded child objects Message-ID: References: <20260615-embedded-v1-0-bb0c65bf126c@rsg.ci.i.u-tokyo.ac.jp> <20260615-embedded-v1-2-bb0c65bf126c@rsg.ci.i.u-tokyo.ac.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.3.2 (2026-04-26) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@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_H3=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-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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Jun 15, 2026 at 09:31:36AM +0100, Peter Maydell wrote: > On Mon, 15 Jun 2026 at 09:13, Daniel P. Berrangé wrote: > > Do we know how many examples we have of embedding objects inside > > another ? > > It is an extremely common pattern for device and SoC model > implementations; we've been recommending it for years. > > > I would much prefer if we forbid the embedding of objects. It is > > horrible design practice to have some QOM objects which can be > > freed via reference count and some which cannot. > > That would be a very large amount of code to rewrite to the > new paradigm. I don't object inherently ("you have pointers to > your child objects" works better when they might be implemented > in Rust and might play better with being able to create > machines and wire them up on the command line); I'm just > noting how much work it would be if you wanted to make > embedding forbidden. Would it be a more tractable problem to "fix" object structure only incrementally as they gain a need to be managed/reference from Rust code, or does the Rust usage already implicitly extend too broadly With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|