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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 85EADC433DB for ; Sat, 30 Jan 2021 10:54:36 +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 D453D64DD9 for ; Sat, 30 Jan 2021 10:54:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D453D64DD9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:33334 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l5nti-0006U1-N5 for qemu-devel@archiver.kernel.org; Sat, 30 Jan 2021 05:54:34 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:39948) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l5nsh-00061e-Mj for qemu-devel@nongnu.org; Sat, 30 Jan 2021 05:53:31 -0500 Received: from mx2.suse.de ([195.135.220.15]:35472) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l5nsg-0001De-2s for qemu-devel@nongnu.org; Sat, 30 Jan 2021 05:53:31 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7A939AC45; Sat, 30 Jan 2021 10:53:28 +0000 (UTC) Subject: Re: [PATCH v14 18/22] accel: introduce AccelCPUClass extending CPUClass To: Richard Henderson , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , =?UTF-8?Q?Alex_Benn=c3=a9e?= References: <20210128092814.8676-1-cfontana@suse.de> <20210128092814.8676-19-cfontana@suse.de> <64d8385c-db22-b647-2402-3840b0e0e9b5@redhat.com> <9a51a203-f6a8-686f-7859-475537b3607a@suse.de> <878s8dujj5.fsf@linaro.org> <40ed971e-a4fe-77c5-94b9-28691874ee32@redhat.com> <0943e736-6847-4b6a-8433-f28f4692a299@linaro.org> From: Claudio Fontana Message-ID: Date: Sat, 30 Jan 2021 11:53:27 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <0943e736-6847-4b6a-8433-f28f4692a299@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=195.135.220.15; envelope-from=cfontana@suse.de; helo=mx2.suse.de X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_MED=-2.3, 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: Laurent Vivier , Peter Maydell , Thomas Huth , Eduardo Habkost , qemu-devel@nongnu.org, Markus Armbruster , Roman Bolshakov , Alistair Francis , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 1/29/21 1:13 AM, Richard Henderson wrote: > On 1/28/21 6:29 AM, Philippe Mathieu-Daudé wrote: >> On 1/28/21 5:08 PM, Alex Bennée wrote: >>> >>> Claudio Fontana writes: >>> >>>> On 1/28/21 2:03 PM, Philippe Mathieu-Daudé wrote: >>>>> On 1/28/21 10:28 AM, Claudio Fontana wrote: >>> >>>>>> + >>>>>> +#define TYPE_ACCEL_CPU "accel-" CPU_RESOLVING_TYPE >>>>>> +#define ACCEL_CPU_NAME(name) (name "-" TYPE_ACCEL_CPU) >>>>>> +typedef struct AccelCPUClass AccelCPUClass; >>>>>> +DECLARE_CLASS_CHECKERS(AccelCPUClass, ACCEL_CPU, TYPE_ACCEL_CPU) >>>>>> + >>>>>> +typedef struct AccelCPUClass { >>>>>> + /*< private >*/ >>>>>> + ObjectClass parent_class; >>>>>> + /*< public >*/ >>>>>> + >>>>>> + void (*cpu_class_init)(CPUClass *cc); >>>>>> + void (*cpu_instance_init)(CPUState *cpu); >>>>>> + void (*cpu_realizefn)(CPUState *cpu, Error **errp); >>>>> >>>>> If we want callers to check errp, better have the prototype return >>>>> a boolean. >>>> >>>> Good point, the whole errp thing is worth revisiting in the series, >>>> there are many cases (which are basically reproduced in the refactoring from existing code), >>>> where errp is passed but is really unused. >>>> >>>> I am constantly internally debating whether to remove the parameter altogether, or to keep it in there. >>>> >>>> What would you suggest? >>> >>> I think it really depends on if we can expect the realizefn to usefully >>> return an error message that can be read and understood by the user. I >>> guess this comes down to how much user config is going to be checked at >>> the point we realize the CPU? >> >> cpu_realize() is were various feature checks are, isn't it? >> >> -cpu mycpu,feat1=on,feat2=off >> CPU 'mycpu' can not disable feature 'feat2' because of REASON. > > Yes. And while changing the return type of realize is probably a good idea, it > should be a separate patch. > > > r~ > To summarize: 1) accel->cpu_realizefn extends the current cpu target-specific realize functions with accelerator-specific code, which currently does not make use of errp at all (thus, the temptation to remove errp from the interface until it is actually needed by a target). 2) Regarding the target-specific cpu realize functions themselves, registered with the pattern: device_class_set_parent_realize(dc, x86_cpu_realizefn, &xcc->parent_realize); device_class_set_parent_realize(dc, arm_cpu_realizefn, &acc->parent_realize); ... etc ... these currently all return void, and the code that realizes devices (f.e. in hw/core/qdev.c) calls these callbacks like this: static void device_set_realized(...) { ... if (dc->realize) { dc->realize(dev, &local_err); if (local_err != NULL) { goto fail; } } Ie it does not expect a bool return type for realize(). So making realize return bool means changing all the realize functions for all devices in my view, which I don't think should be crammed in here.. Wdty? Thanks, Claudio