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 7C6ECC5DF6D for ; Wed, 19 Aug 2026 13:03:13 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wwfwc-0001P6-Ga; Wed, 19 Aug 2026 09:03:02 -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 1wwfwa-0001Oo-Pe for qemu-devel@nongnu.org; Wed, 19 Aug 2026 09:03:00 -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 1wwfwV-0001fr-Ld for qemu-devel@nongnu.org; Wed, 19 Aug 2026 09:02:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1787144574; 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=i9+0IFLBWxGj9Sd5nF/8JOZKM8gUz/+gGD0zkzKterY=; b=F67AGJL7B2m6yfrdusUhzNc10nMVrewfu7Gk1GJPjqD8Rsrv4tMESQw5VQSXbqsjtgjJva LDcny94PKdvj2rKW8dVNkg8vehIB9UwlxLTER2fLYwj7O8/vU0vr1v9a1LfjkVVBN2Nkz9 8rxTpNDJ1YPl/ldw9xHfI3zDQrQALHk= 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-629-ubxxC0rROFu_3f4PeyVAPw-1; Wed, 19 Aug 2026 09:02:50 -0400 X-MC-Unique: ubxxC0rROFu_3f4PeyVAPw-1 X-Mimecast-MFC-AGG-ID: ubxxC0rROFu_3f4PeyVAPw_1787144569 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 9F0F31800643; Wed, 19 Aug 2026 13:02:48 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.44.22.12]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 155451800346; Wed, 19 Aug 2026 13:02:48 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 9A21F21E6920; Wed, 19 Aug 2026 15:02:45 +0200 (CEST) From: Markus Armbruster To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: Peter Maydell , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , qemu-devel@nongnu.org, Thomas Huth , qemu-s390x@nongnu.org, qemu-ppc@nongnu.org, Christian Borntraeger , Corey Minyard , Paolo Bonzini , Richard Henderson Subject: Re: [PATCH 4/4] hw/nmi: Remove @cpu_index argument from nmi_trigger() In-Reply-To: ("Philippe =?utf-8?Q?Mathieu-Daud=C3=A9=22's?= message of "Tue, 11 Aug 2026 12:17:19 +0200") References: <20240220150833.13674-1-philmd@linaro.org> <20240220150833.13674-5-philmd@linaro.org> Date: Wed, 19 Aug 2026 15:02:45 +0200 Message-ID: <87tsoq5klm.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 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.341, 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_H2=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development 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 Philippe Mathieu-Daud=C3=A9 writes: > On 20/3/24 14:34, Peter Maydell wrote: >> On Tue, 20 Feb 2024 at 15:09, Philippe Mathieu-Daud=3DC3=3DA9 org> wrote: >>> >>> nmi_monitor_handle() is not related to the monitor, >>> rename it as nmi_trigger(). Return boolean value >>> indicating success / failure. The 'cpu_index' argument >>> is not used, remove it. >>> >>> Signed-off-by: Philippe Mathieu-Daud=3DC3=3DA9 [...] >>> diff --git a/include/hw/nmi.h b/include/hw/nmi.h >>> index c70db941c9..32b27067f2 100644 >>> --- a/include/hw/nmi.h >>> +++ b/include/hw/nmi.h >>> @@ -49,6 +49,17 @@ struct NMIClass { >>> bool (*nmi_handler)(NMIState *n, Error **errp); >>> }; >>> >>> -void nmi_monitor_handle(int cpu_index, Error **errp); >>> +/** >>> + * nmi_trigger: Trigger a NMI. >>> + * >>> + * @errp: pointer to error object >>> + * >>> + * Iterate over all objects implementing the TYPE_NMI interface >>> + * and deliver NMI to them. [...] >>> + * >>> + * On success, return %true. >>> + * On failure, store an error through @errp and return %false. >>> + */ >>> +bool nmi_trigger(Error **errp); >> >> Why return a bool here? None of the callsites looks at the >> return value. > > Indeed, but again this is the style *recommended* by the Error API > since commit e3fe3988d7 ("error: Document Error API usage rules"). Correct: * - Whenever practical, also return a value that indicates success / * failure. This can make the error checking more concise, and can * avoid useless error object creation and destruction. Note that * we still have many functions returning void. We recommend * =E2=80=A2 bool-valued functions return true on success / false on fail= ure, * =E2=80=A2 pointer-valued functions return non-null / null pointer, and * =E2=80=A2 integer-valued functions return non-negative / negative. > > Callers providing a non-NULL errp should check the return value, > but the QMP handlers generated by gen_command_decl() like > qmp_inject_nmi() here don't return anything. qmp_inject_nmi() passes the error to its caller. That's fine. ipmi_do_hw_op() and watchdog_perform_action() ignore the error. Also fine. > Markus, what would be your preference? I prefer sticking to the rule whenever practical. Example for a defensible exception: a callback that's implemented many more times than it's called. There the effort of returning something can exceed the benefit of making the calls more concise. In a case like nmi_trigger(), what could possibly be gained by deviating from the rule is dwarved many times over by having to consider the tradeoffs and justifying them in review. And if a caller shows up that could use a return value, we'll waste some more time. Not worth it.