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 6D9EBCA5FDD for ; Fri, 2 Oct 2026 16:19:10 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xCfxu-0007zi-Hw; Fri, 02 Oct 2026 12:18:30 -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 1xCfxM-0007kY-Ai for qemu-devel@nongnu.org; Fri, 02 Oct 2026 12:17:56 -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 1xCfxI-000572-G9 for qemu-devel@nongnu.org; Fri, 02 Oct 2026 12:17:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1790957871; 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=sD1Pa4ZbPe40FfSTDC6yco8mQNGfluxBibY7kpJmsh0=; b=GIidlt8fTCf5JYTa6DhXcHgb/zpBu3VeZOxf8c6XtpC/Cr3BPMnntPR+uB3TXMXe0hyVyr abzeZn7t64/FFYwnjtTeTHm9CIkQUie4Wz4Gk0YDs72aXuCr+jLCaJEHPuO3x6SlUvrXxy ldSNsdvBsVZVRm2DJ0HmGbvcD+hpFyc= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-342-V1pAD1yLPa25npwKhYSV1g-1; Fri, 02 Oct 2026 12:17:47 -0400 X-MC-Unique: V1pAD1yLPa25npwKhYSV1g-1 X-Mimecast-MFC-AGG-ID: V1pAD1yLPa25npwKhYSV1g_1790957862 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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 48BC81849F3D; Fri, 2 Oct 2026 16:17:37 +0000 (UTC) Received: from redhat.com (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id F303077A; Fri, 2 Oct 2026 16:17:30 +0000 (UTC) Date: Fri, 2 Oct 2026 17:17:28 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Yonggang Luo Cc: Pierrick Bouvier , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org, Chao Liu , Eric Blake , qemu-arm@nongnu.org, Paolo Bonzini , Markus Armbruster , Alistair Francis , Brian Cain , Stafford Horne , Peter Maydell , Jiaxun Yang , Fabiano Rosas , Daniel Henrique Barboza , qemu-riscv@nongnu.org, Laurent Vivier , Max Filippov , Song Gao <17746591750@163.com>, Philippe Mathieu-Daude , Palmer Dabbelt , Laurent Vivier , Weiwei Li , Zhao Liu Subject: Re: [PATCH v3 01/10] machine: allow -M name to differ from QOM type Message-ID: References: <26b0d44d-0322-4ceb-a47b-747fc52c61b7@oss.qualcomm.com> <6bf4dad5-4fa2-4df1-b6b8-d594dbd3842c@oss.qualcomm.com> <557262df-b8e7-49b5-a245-ae46b8885b30@oss.qualcomm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.4.2 (2026-08-30) X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.336, 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, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable 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 Fri, Oct 02, 2026 at 10:00:24AM +0800, Yonggang Luo wrote: > On Fri, Oct 2, 2026 at 2:56 AM Pierrick Bouvier > wrote: > > > > On 10/1/2026 11:26 AM, Daniel P. Berrangé wrote: > > > On Thu, Oct 01, 2026 at 11:08:17AM -0700, Pierrick Bouvier wrote: > > >> On 10/1/2026 10:40 AM, Daniel P. Berrangé wrote: > > >>> Even with the current per-target binaries there are countless > > >>> devices linked in which are incompatible / not usable with > > >>> certain machine types. A new multi-target binary with a union > > >>> of all devices will just be a bigger example of a scenario that > > >>> already has to be dealt with for today's binaries. > > >>> > > >>> So if we have that assumption that we don't need to do device > > >>> filtering, at that point, a --target option doesn't have as > > >>> big of a role to play. The machine type code knows what target(s) > > >>> it wants (1 or 2 targets depending on if there are 32 + 64 bit > > >>> varaints. The CPU model the user requests (if the CPU is not > > >>> hardcoded by the machine), determines 32 bit vs 64 bit. > > >>> > > >> > > >> How can we deduce this information (bitness or target for existing > > >> machines/cpus)? > > > > > > It would require that we introduce a new field in MachineClass > > > that returned that information about what target a machine is > > > associated with. > > > > > > I note the SysEmuTarget covers both 32-bit and 64-bit variants. > > > > > > It might be better use QEMU_ARCH which correlates directly to > > > the TCG targets, rather than the traditional binary target > > > names ? > > > > > > Likely the CPU class would also want to declare its list of > > > supported targets. > > > > > > > QEMU_ARCH only represents base architectures, and not variant, so > > SysEmuTarget is the right choice. > > > > So, we would need a list of SysEmuTarget for every cpu/machine that is > > target specific, since one could be available for variants of base arch? > > For this, adding TargetInfo parameter to is_avaible callback will let us get the > list of SysEmuTarget for every cpu/machine. As we can iterate on all TargetInfo > then check if that TargetInfo is present for every cpu/machine. > And indeed for devices if you want. That's what my patches are already done. > > And also I have an idea about the set is_avaiable in an easy way. As > QOM basically > is a TREE, so for example x86_32 and x86_64 can share a same "i386" > base, all children's > is_avaiable inherent from parents is_avaiable, we can ensure every QOM > object have a > is_avaiable by update children is_avaiable from parents one. > > > > > @Yonggang: can you try to provide a RFC based on this, to see what it > > could look like? No need to cover all machines/cpus, just select one of > > machine+cpu, ideally with multiple SysEmuTarget (like virt and max cpu > > for aarch64), and let's iterate from this. > > > > @Daniel: how do we deal with machines available for all targets like > > null? We would need a way to ensure all machines/cpus are tagged > > correctly, in an independent way from "available for all", without > > having to repeat all existing SysEmuTarget. > > > > >> Also, how to deal with devices that are only available for some targets, > > >> but not others, depending on various Kconfig knobs? > > > > > > IMHO just leave devices to raise an error when passed to '-device' > > > if not compatible with the requested machine. > > > > > > eg this example from x86 world: > > > > > > $ qemu-system-x86_64 -M microvm -device xen-disk > > > qemu-system-x86_64: -device xen-disk: No 'xen-bus' bus found for device 'xen-disk' > > > > > > $ qemu-system-x86_64 -M isapc -device virtio-net-pci > > > qemu-system-x86_64: -device virtio-net-pci: No 'PCI' bus found for device 'virtio-net-pci' > > > > > > Hopefully most devices have sane error reporting when they > > > find a dependancy they have is not satisfied by the machine, > > > but if some end up asserting with crashes that's not a > > > blocker. Those asserts can be turned into pretty error > > > messages at our leisure by whomever cares about improving > > > error diagnosis. > > > > > > > Fine for me. I am a bit skeptical this will be possible to catch all > > issues, but let's try! > > > > So, for existing binary: -M virt works as before. > > > > For new multi binary: > > $ qemu-system -M virt: > > Multiple machines were found, select one among: > > - aarch64-virt > > - riscv64-virt > > This would be very hard, that means QOM must be initialized. but we need > ensure the target is selected before the QOM init. We don't need to have initialized anything. We just need a single global variable, whose default initializer is true vs false, for for the separate vs multi-target binaries. That's just a pair of .o files with a single bool variable, that we choose between when linking. 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 :|