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 3A711C3ABBE for ; Thu, 8 May 2025 14:10:52 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uD1xL-00035C-FK; Thu, 08 May 2025 10:10:35 -0400 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 1uD1xJ-00031r-JL for qemu-devel@nongnu.org; Thu, 08 May 2025 10:10:33 -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 1uD1xH-0000Lt-9V for qemu-devel@nongnu.org; Thu, 08 May 2025 10:10:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1746713425; 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=FLCDMHa14a32Sk0pqdB3/vFUzLcHBco+wmsb/NHdj8Y=; b=QiitBr7ycmipG3N6EPmnLwwYCEHQe8shszxX/tjc+7kVQfZba5oIWBD4tcu0mGfNEkj79n NwkAVTYFAo5QDhlTm4X7opvV9ONUKa0dBdgyBIQjfptY38YPdGSoRD5fbxF955WlVEaeoD K6Zo0vaTF2wIh9MmNsQjSWeDcCnmEZ4= 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-679-N8LlvmSfPnmTS-Gk0SqKWA-1; Thu, 08 May 2025 10:10:21 -0400 X-MC-Unique: N8LlvmSfPnmTS-Gk0SqKWA-1 X-Mimecast-MFC-AGG-ID: N8LlvmSfPnmTS-Gk0SqKWA_1746713417 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (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 60A261955BCC; Thu, 8 May 2025 14:10:14 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.138]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A509B19560B3; Thu, 8 May 2025 14:09:57 +0000 (UTC) Date: Thu, 8 May 2025 15:09:54 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Cc: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Paolo Bonzini , Alex =?utf-8?Q?Benn=C3=A9e?= , Zhao Liu , Mark Burton , Eduardo Habkost , Alessandro Di Federico , Alistair Francis , Anton Johansson , Brian Cain , Chao Peng , Neo Jia , =?utf-8?Q?C=C3=A9dric?= Le Goater , "Wedgwood, Chris" , dhedde@kalrayinc.com, Eric Blake , eblot@rivosinc.com, "Edgar E. Iglesias" , Elena Ufimtseva , Auger Eric , Felipe Franciosi , iggy@theiggy.com, Warner Losh , Jan Kiszka , Jason Gunthorpe , Jidong Xiao , Jim Shu , Joao Martins , Konrad Rzeszutek Wilk , Luc Michel , Manos Pitsidianakis , Max Chou , Meirav Dean , mimu@linux.vnet.ibm.com, "Ho, Nelson" , Paul Walmsley , Peter Maydell , QEMU Developers , Roberto Campesato , Richard Henderson , Shameerali Kolothum Thodi , Bernhard Beschow , Stefan Hajnoczi , Thomas Huth , Wei Wang , z.huo@139.com, LIU Zhiwei , "Wu, Zhiyong" Subject: Re: KVM/QEMU Community call 29/04/2025 agenda items? Message-ID: References: <874iy85yx2.fsf@draig.linaro.org> <87a57ydj8y.fsf@pond.sub.org> <5ce00003-4105-40c7-954b-63336a4325d5@linaro.org> <87plgkihg4.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87plgkihg4.fsf@pond.sub.org> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 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: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.416, 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_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_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@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-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, May 07, 2025 at 05:11:39PM +0200, Markus Armbruster wrote: > Philippe Mathieu-Daudé writes: > > > On 30/4/25 12:41, Markus Armbruster wrote: > > [...] > > >> Pierrick's stated goal is to have no noticable differences between the > >> single binary and the qemu-system- it covers. > >> > >> We have two external interfaces to worry about: QMP and the command > >> line. Let's ignore the latter for now. > >> > >> Target-specific differences in *syntax* come from QAPI schema > >> conditionals with target-specific conditions. Example: > >> > >> { 'command': 'query-cpu-definitions', 'returns': ['CpuDefinitionInfo'], > >> 'if': { 'any': [ 'TARGET_PPC', > >> 'TARGET_ARM', > >> 'TARGET_I386', > >> 'TARGET_S390X', > >> 'TARGET_MIPS', > >> 'TARGET_LOONGARCH64', > >> 'TARGET_RISCV' ] } } > >> > >> This command is only defined for some targets. > >> > >> The value of query-qmp-schema reflects this: it has > >> query-cpu-definitions exactly when the condition is satisfied. The > >> condition is evaluated at compile-time, because that's how QAPI schema > >> 'if' works. > >> > >> Say we drop the condition and instead add an equivalent run-time > >> condition to command registration. This preserves behavior of command > >> execution. But query-qmp-schema now has query-cpu-definitions *always*. > >> This is a noticable difference. It may break management applications > >> that use query-qmp-schema to probe for the command. > >> > >> Moreover, conditionals aren't limited to commands. Example: > >> > >> { 'struct': 'CpuModelExpansionInfo', > >> 'data': { 'model': 'CpuModelInfo', > >> 'deprecated-props' : { 'type': ['str'], > >> ---> 'if': 'TARGET_S390X' } }, > >> 'if': { 'any': [ 'TARGET_S390X', > >> 'TARGET_I386', > >> 'TARGET_ARM', > >> 'TARGET_LOONGARCH64', > >> 'TARGET_RISCV' ] } } > >> > >> Here we have a conditional member. > > [...] > > > IMHO conditionals should only depend on host / static configuration > > features, not features modifiable from the command line. > > This is how the QAPI schema works now. > > > (I'm always > > confused by KVM features published in the schema, but then you start > > your binary with -accel=tcg and still can run KVM specific commands > > via QMP, returning errors). > > Not exactly a ringing endorsement for keeping the QAPI schema work the > way it does now, isn't it? ;) > > The problem at hand is QAPI-generated files in a single binary. > > Pierrick posted "[RFC PATCH 0/3] single-binary: make QAPI generated > files common". The patches are flawed, but that's alright for RFC. > > In review, I pointed out three possible solutions, and discussed their > pros and cons: > > (1) Drop target-specific conditionals. > > (2) Replace them by run-time checks. > > (3) Have target-specific QAPI-generated code for multiple targets > coexist in the single binary. > > Both (1) and (3) keep the QAPI schema work as it does now. > > Pierrick's patches are an incomplete attempt at (2). > > Daniel made a case for (1). You and I actually discussed (1) before, > and I encouraged you to explore it. > > We can certainly discuss this some more, but I'd prefer to review a > working solution instead. I've posted a minimal effort PoC for (1). It addresses the QAPI side of the problem, but doesn't magically make "single binary" buildable as is. It just removes QAPI from being a blocker for "single binary", and so the remaining work is more of the boring refactoring to introduce virtual methods on machines, so the QMP cmd impl behaviour switches at runtime based on what is configured & being run. https://lists.nongnu.org/archive/html/qemu-devel/2025-05/msg01915.html With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|