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 12F81C3ABC0 for ; Thu, 8 May 2025 12:33:01 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uD0Ql-0004kM-OW; Thu, 08 May 2025 08:32:52 -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 1uD0Qh-0004ij-31 for qemu-devel@nongnu.org; Thu, 08 May 2025 08:32:47 -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 1uD0Qe-0003bv-Re for qemu-devel@nongnu.org; Thu, 08 May 2025 08:32:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1746707562; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qraPEFHDmnMYwxu0uhWFKpy4r4Y407C6B0MBxZZmqfs=; b=g1X1JqmXAikEjZHpQneHMex1G0lVOeQyncXAgiJVfqbvdXzazzdpaViPzAJCod/54LT0D7 K2g+hLyesyg2/sUBRCAbSD3cAPu3r/j40eqwgSTLqjCOnB2B/fA/iz4hYR6qFOafIlvSuV eN3pUZ/wr5BD0nKkwXrGpwTIs1nKpHk= Received: from mx-prod-mc-02.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-8-qk_aPeRtOBqtMkwO2PKQYQ-1; Thu, 08 May 2025 08:32:39 -0400 X-MC-Unique: qk_aPeRtOBqtMkwO2PKQYQ-1 X-Mimecast-MFC-AGG-ID: qk_aPeRtOBqtMkwO2PKQYQ_1746707554 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-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C1AB7195608B; Thu, 8 May 2025 12:32:32 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.27]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5759F19560AE; Thu, 8 May 2025 12:32:29 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 7814121E6768; Thu, 08 May 2025 14:32:26 +0200 (CEST) From: Markus Armbruster To: Zhao Liu Cc: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Paolo Bonzini , Alex =?utf-8?Q?Benn=C3=A9e?= , Mark Burton , Eduardo Habkost , Alessandro Di Federico , Alistair Francis , Anton Johansson , Brian Cain , "Daniel P. Berrange" , 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? In-Reply-To: (Zhao Liu's message of "Thu, 8 May 2025 16:47:21 +0800") References: <874iy85yx2.fsf@draig.linaro.org> <87a57ydj8y.fsf@pond.sub.org> <5ce00003-4105-40c7-954b-63336a4325d5@linaro.org> <87plgkihg4.fsf@pond.sub.org> Date: Thu, 08 May 2025 14:32:26 +0200 Message-ID: <87plgjcmg5.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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: -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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Zhao Liu writes: > On Wed, May 07, 2025 at 05:11:39PM +0200, Markus Armbruster wrote: >> Date: Wed, 07 May 2025 17:11:39 +0200 >> From: Markus Armbruster >> Subject: Re: KVM/QEMU Community call 29/04/2025 agenda items? >>=20 >> Philippe Mathieu-Daud=C3=A9 writes: >>=20 >> > On 30/4/25 12:41, Markus Armbruster wrote: >>=20 >> [...] >>=20 >> >> Pierrick's stated goal is to have no noticable differences between the >> >> single binary and the qemu-system- it covers. >> >>=20 >> >> We have two external interfaces to worry about: QMP and the command >> >> line. Let's ignore the latter for now. >> >>=20 >> >> Target-specific differences in *syntax* come from QAPI schema >> >> conditionals with target-specific conditions. Example: >> >>=20 >> >> { 'command': 'query-cpu-definitions', 'returns': ['CpuDefinition= Info'], >> >> 'if': { 'any': [ 'TARGET_PPC', >> >> 'TARGET_ARM', >> >> 'TARGET_I386', >> >> 'TARGET_S390X', >> >> 'TARGET_MIPS', >> >> 'TARGET_LOONGARCH64', >> >> 'TARGET_RISCV' ] } } >> >>=20 >> >> This command is only defined for some targets. >> >>=20 >> >> 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. >> >>=20 >> >> 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 *alway= s*. >> >> This is a noticable difference. It may break management applications >> >> that use query-qmp-schema to probe for the command. >> >>=20 >> >> Moreover, conditionals aren't limited to commands. Example: >> >>=20 >> >> { 'struct': 'CpuModelExpansionInfo', >> >> 'data': { 'model': 'CpuModelInfo', >> >> 'deprecated-props' : { 'type': ['str'], >> >> ---> 'if': 'TARGET_S390X' } }, >> >> 'if': { 'any': [ 'TARGET_S390X', >> >> 'TARGET_I386', >> >> 'TARGET_ARM', >> >> 'TARGET_LOONGARCH64', >> >> 'TARGET_RISCV' ] } } >> >>=20 >> >> Here we have a conditional member. >>=20 >> [...] >>=20 >> > IMHO conditionals should only depend on host / static configuration >> > features, not features modifiable from the command line. >>=20 >> This is how the QAPI schema works now. >>=20 >> > (I'm always >> > confused by KVM features published in the schema, but then you start >> > your binary with -accel=3Dtcg and still can run KVM specific commands >> > via QMP, returning errors). >>=20 >> Not exactly a ringing endorsement for keeping the QAPI schema work the >> way it does now, isn't it? ;) >>=20 >> The problem at hand is QAPI-generated files in a single binary. >>=20 >> Pierrick posted "[RFC PATCH 0/3] single-binary: make QAPI generated >> files common". The patches are flawed, but that's alright for RFC. >>=20 >> In review, I pointed out three possible solutions, and discussed their >> pros and cons: >>=20 >> (1) Drop target-specific conditionals. >>=20 >> (2) Replace them by run-time checks. >>=20 >> (3) Have target-specific QAPI-generated code for multiple targets >> coexist in the single binary. > > Thank you Markus for your nice summary! I also apologize to you and > Philippe if I didn't understand correctly (I tried to look at > Pierrick's and Philippe's work, but still worry about I may have wrong > understanding :-) ) > >> Both (1) and (3) keep the QAPI schema work as it does now. >>=20 >> Pierrick's patches are an incomplete attempt at (2). > > I see. > >> Daniel made a case for (1). You and I actually discussed (1) before, >> and I encouraged you to explore it. > > And I notice Philippe has 2 patches: > > (1) For QAPI, this is to drop target-specific cond: > > https://lore.kernel.org/qemu-devel/20250429100419.20427-1-philmd@linaro.o= rg/ > > I feel it's a smart way to make it optional. > > (2) Not for QAPI, but this is try to add runtime check: > > https://lore.kernel.org/qemu-devel/20250502214551.80401-5-philmd@linaro.o= rg/ > > I am thinking about how kvm-pmu-filter could be aligned with these > current efforts in mail list. > > I can drop all the target conditions for KvmPmuEventFormat: > > { 'enum': 'KvmPmuEventFormat', > 'data': ['raw', 'x86-select-umask', 'x86-masked-entry'] } This is what you need to do if we pick solution (1). > This is what you listed before and it is similar to the way in (1). But > only (1) is not enough because I can't make these formats as optional > (pls educate me if I'm wrong :-) ). > > Therefore, I think I need run-time check like Philippe did in (2), in > my kvm-pmu.c file. Do you think so? In general, not just for your KVM PMU filter work: dropping target-specific conditionals makes the formerly conditional things exist for targets where they didn't exist before. This commonly breaks the build for these targets. To fix a target's build, we can either implement things for the target, or make attempts to use them fail cleanly. > An additional question - about CONFIG_KVM - is that I see that it's all > currently focused on solving target-specific problems, and I understand > that it's not yet kvm-specific's turn. > > But kvm-pmu-filter does (or, may :-) ) need CONFIG_KVM. My initial > thought is, is it possible to remove the CONFIG_KVM condition for > kvm-pmu-filter in QAPI and use the same runtime check? But this would > require accel-info as Philippe's work on target-info in [2]). I'm afraid I don't understand your question. >> We can certainly discuss this some more, but I'd prefer to review a >> working solution instead. > > With so many options on the table, I'm a bit confused about the fate of > kvm-pmu-filter. Should this case wait for the most appropriate option to > come along, or could it move forward based on the status quo, and then > consider the refactoring later with the final optimal option? Up to you. We'll hopefully reach consensus fairly soon. You might want to wait a few days for that.