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 2E52FC624D3 for ; Fri, 4 Sep 2026 11:41:06 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x2SHb-000615-GK; Fri, 04 Sep 2026 07:40:35 -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 1x2SHa-0005zV-Jr for qemu-arm@nongnu.org; Fri, 04 Sep 2026 07:40:34 -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 1x2SHY-0008JC-Qn for qemu-arm@nongnu.org; Fri, 04 Sep 2026 07:40:34 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788522032; 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=R38LyZZ4K3QaJ25ZD439ymOxvz60UecUM1qk9A8ZK7U=; b=EAe+V36u+1j6e/y2kdxy+w/5TYi6sixZuO02WfDwpZhPeC3PE2LPpuGVkxtdihwaX4UVug arCb9GOmXJSbtzMmcIyGwNVtLomwR9+ApVLiBmCc8eYqm1oaGj0M0r2Ocmx4fKPVLRlc3v FmqS8+6jRh6chQEj92xt1H7T6lrM9cM= Received: from mx-prod-mc-08.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-588-SACnOwuKPjGbtx6UtIH1IA-1; Fri, 04 Sep 2026 07:40:26 -0400 X-MC-Unique: SACnOwuKPjGbtx6UtIH1IA-1 X-Mimecast-MFC-AGG-ID: SACnOwuKPjGbtx6UtIH1IA_1788522024 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 961E518C0FC3; Fri, 4 Sep 2026 11:40:24 +0000 (UTC) Received: from redhat.com (headnet03.pony-001.prod.iad2.dc.redhat.com [10.2.32.114]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A810E1955F70; Fri, 4 Sep 2026 11:40:21 +0000 (UTC) Date: Fri, 4 Sep 2026 12:40:18 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: Peter Maydell , Markus Armbruster , Bernhard Beschow , Bin Meng , Pierrick Bouvier , Daniel Henrique Barboza , Bin Meng , QEMU , Paolo Bonzini , qemu-arm@nongnu.org, Yonggang Luo , Anton Johansson Subject: Re: [PATCH 02/33] hw/arm: Add basic Phytium Pi machine Message-ID: References: <20260903112532.3276678-1-bin.meng@processmission.com> <20260903112532.3276678-3-bin.meng@processmission.com> <0795176d-4580-4acc-a3cf-c40f8d221661@oss.qualcomm.com> <881be57e-5496-41f2-af0b-e21087fa5e54@oss.qualcomm.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.4.0 (2026-06-19) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Mimecast-MFC-PROC-ID: FD05OC86wbw0AnfZRF3V0rBc_fESB7DL9c-LXvq9ayE_1788522024 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit 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: -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_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-arm@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org Sender: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org On Fri, Sep 04, 2026 at 01:24:35PM +0200, Philippe Mathieu-Daudé wrote: > On 4/9/26 12:47, Peter Maydell wrote: > > On Fri, 4 Sept 2026 at 11:36, Daniel P. Berrangé wrote: > > > > > > On Fri, Sep 04, 2026 at 11:28:35AM +0100, Peter Maydell wrote: > > > > On Fri, 4 Sept 2026 at 11:25, Daniel P. Berrangé wrote: > > > > > We need to use QAPI MachineInfo / MachineClass to report to mgmt apps > > > > > whether a machine is capable of using hardware acceleration or not in > > > > > response to "query-machines". > > > > > > > > > > Currently if a target supports HW accel, then apps assume that all > > > > > machines in that target can use acceleration. This was a convenient > > > > > short cut assumption, but this new machine suggests we can no make > > > > > do with that assumption, and need to explicitly report it per-machine. > > > > > > > > That assumption has never been true for Arm; this new machine > > > > type is no different to any of our existing boards in that regard. > > > > Support for KVM etc is only present for the 'virt' machine type and > > > > one or two others. Most of the rest don't work with KVM because they > > > > create a specific CPU type (not 'host' or 'max') and that won't work > > > > with KVM, or (as with sbsa-ref) because they want EL3 support and > > > > KVM doesn't provide that. > > > > > > Oh, then the problem is already way worse than I realized which > > > really makes we think we should consider exposing whether > > > machines can use HW acceleration or not. > > > > It also depends on the options to the machine, so for instance > > this should always work with any of the hw accelerators: > > qemu-system-aarch64 -M virt -cpu host > > but this wants nested virt, so only works with a hw accel > > that supports that and a host kernel that has the KVM side support: > > qemu-system-aarch64 -M virt,virtualization=on -cpu host > > and this wants EL3, which won't work in any hw accelerator > > qemu-system-aarch64 -M virt,secure=on -cpu host > > > > Similarly the interrupt controller choice matters, so this: > > qemu-system-aarch64 -M virt,gic-version=2 -cpu host > > may or may not work depending on whether the host CPU has the > > GICv2 back-compat support; and this: > > qemu-system-aarch64 -M virt,gic-version=x-5 -cpu host > > is currently TCG-only. (But also it's experimental so you kind > > of know you're off-piste here ;-)) > > > > If you try the things that won't work with -enable-kvm then they > > should wind up causing QEMU to exit with a hopefully more or less > > informative error message, but I don't think we have any mechanism > > for introspection of the form "if I try this particular set of > > QEMU options is it going to work?" short of actually trying. > > I recall some discussion with Markus / Paolo when brainstorming > declarative dynamic machines, we'd need another MachinePhase > iterating on all selected types to instantiate and check whether > they can be instantiated, and returning impossible config error; > way before a property is evaluated on an instance at Realize time. Mmm, yes, that is getting into quite alot of work for probably not enough benefit. > Here IMO accelerators should report whether a CPU model class > requested is accelerable or not (then later we can double check > with features updated on the model instances). > The machine deciding is a shortcut, not scalable and hard to maintain. Yeah, I think you're right - the machine does look like a facade around the CPU for accelerator runnability. So it probably better fits the QMP commands for querying CPU runnability. 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 :|