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 X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB488C433DB for ; Mon, 11 Jan 2021 22:36:41 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 4A5F722288 for ; Mon, 11 Jan 2021 22:36:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4A5F722288 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:48844 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kz5nj-0000Xd-Uv for qemu-devel@archiver.kernel.org; Mon, 11 Jan 2021 17:36:39 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:38578) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kz5mq-000058-2k for qemu-devel@nongnu.org; Mon, 11 Jan 2021 17:35:44 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:50105) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kz5mn-0000hl-6V for qemu-devel@nongnu.org; Mon, 11 Jan 2021 17:35:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610404538; 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: in-reply-to:in-reply-to:references:references; bh=HqPxIPXsQenwU+vCDjXl8eb5ElD2cGps4OdbzWe64bw=; b=U5jUPUsI/UWuJfzTax7NtHqgmkVU3AK3etdcubpndvHUcF4kbYmHAd/GemLDAf/6jhbuux suL6yq9wUC6jCddPPBraAALe2Bcm69dUmHEbZWUJu2dTQ+V7Vin1RZm+rcbLAR41P30b/v cBOfvH/IF4MZH5Ke5tMkBUm3WusHxQQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-219-kpapKDSlNti20ROwo1ZjfQ-1; Mon, 11 Jan 2021 17:35:36 -0500 X-MC-Unique: kpapKDSlNti20ROwo1ZjfQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E553A51F0; Mon, 11 Jan 2021 22:35:33 +0000 (UTC) Received: from localhost (ovpn-119-212.rdu2.redhat.com [10.10.119.212]) by smtp.corp.redhat.com (Postfix) with ESMTP id E42B360C5B; Mon, 11 Jan 2021 22:35:29 +0000 (UTC) Date: Mon, 11 Jan 2021 17:35:29 -0500 From: Eduardo Habkost To: Claudio Fontana Subject: Re: [RFC v6 10/11] accel: introduce AccelCPUClass extending CPUClass Message-ID: <20210111223529.GA4161@habkost.net> References: <20201126223218.31480-1-cfontana@suse.de> <20201126223218.31480-11-cfontana@suse.de> <6cbd508c-b24b-3219-3302-196dfefaa8f7@redhat.com> <51838c6c-8a44-afef-1acf-b8acb3eada19@redhat.com> <050bc10b-861c-f463-18e1-c4d1aa0c301e@suse.de> <4bca1b60-ceeb-4b99-dd92-77dac07e9064@suse.de> <343846ce-12ba-23d6-4832-4aa16cb22f9d@suse.de> <2f50e4f3-dd13-bbd4-1963-daf695bbe428@suse.de> <28d06da1-296d-3b2b-bb58-e41faed6fd16@suse.de> MIME-Version: 1.0 In-Reply-To: <28d06da1-296d-3b2b-bb58-e41faed6fd16@suse.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=ehabkost@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=ehabkost@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paul Durrant , Jason Wang , qemu-devel@nongnu.org, Peter Xu , haxm-team@intel.com, Colin Xu , Olaf Hering , Stefano Stabellini , Bruce Rogers , "Emilio G . Cota" , Anthony Perard , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Laurent Vivier , Thomas Huth , Richard Henderson , Cameron Esfahani , Dario Faggioli , Roman Bolshakov , Sunil Muthuswamy , Marcelo Tosatti , Wenchao Wang , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Jan 11, 2021 at 05:13:27PM +0100, Claudio Fontana wrote: > Happy new year, Hi! > > picking up this topic again, i am looking at at now a different aspect of this problem, of setting the right tcg ops for the right cpu class. > > This issue I am highlighting is present because different targets behave differently in this regard. > > Ie, we have targets for which we always initialize all cpu classes, as a result of different machine definitions. > > This is the case of arm, for example where we end up with backtraces like: > > arm_v7m_class_init > type_initialize > object_class_foreach_tramp > g_hash_table_foreach () > object_class_foreach > object_class_get_list > select_machine () > qemu_init > main > > with the arm_v7m_class_init called even if we are just going to use an aarch64 cpu (so the class initializer for arm_v7m is called even for unused cpus classes), > > while in other cases we have the target explicitly relying on the fact that only the right cpu class is initialized, for example in cris we have code like: This shouldn't matter at all, because class_init is not supposed to have any side effects outside the corresponding ObjectClass struct. So, I don't understand what you mean below: > > target/cris/cpu.c: > > static void crisv9_cpu_class_init(ObjectClass *oc, void *data) > { > CPUClass *cc = CPU_CLASS(oc); > CRISCPUClass *ccc = CRIS_CPU_CLASS(oc); > > ccc->vr = 9; > cc->do_interrupt = crisv10_cpu_do_interrupt; > cc->gdb_read_register = crisv10_cpu_gdb_read_register; > cc->tcg_initialize = cris_initialize_crisv10_tcg; > } > > where the class initialization of the cpu is explicitly setting the methods of CPUClass, therefore implicitly relying on the fact that no other class initializer screws things up. I don't see the problem here. Having all other class initializers being called should be completely OK, because each class has its own ObjectClass struct. > > Given this context, which one of these methods is "right"? > Should we rework things so that only used cpu classes are actually initialized? This option wouldn't make sense. class_init is supposed to be called on demand on class lookup, and can be triggered by object_class_get_list(), object_class_by_name(), or similar functions. This is by design. > Or should we maybe not do these settings in cpu class_init at all, but rather at cpu initfn time, or at cpu realize time? If you are talking about initializing ObjectClass/CPUClass/...Class fields, they can always be safely initialized in class_init. If you are talking about touching anything outside the class struct (like in CPUState), class_init is not the right place to do it. -- Eduardo